Method and system for automatic pointing stabilization and aiming control device

[0001] This is a regular application of provisional application No. 60/731,541 filed on Oct. 29, 2005 and is a Continuation-In-Part application of application Ser. No. 11/212,062 filed on Aug. 24, 2005.

[0002] 1. Field of the Present Invention

[0003] There is an urgent need for bypassing the operator for the tracking task and this is done by a video tracker, automatically. The operator will execute the initial target acquisition task which is more appropriate for human intervention.

[0004] The present invention relates to a controlling method and system for automatic positioning stabilization and aiming control allowing platform stabilization and pointing in a given direction so as to effect remote viewing of objects of interest and execution of object interdiction commands without exposing the operator to danger.

[0005] The present invention also relates to a controlling method and system for positioning measurement, and more particularly to a method and system for automatic stabilization and pointing control of a device that needs to be pointed at a determined direction, wherein output data of an IMU (Inertial Measurement Unit) installed in the device and target information date are processed to compute a platform rotation command to an actuator; the actuator rotates and stabilizes the device into the determined direction according to the platform rotation commands; a visual and voice device provide a user with visualization and voice indication of the automatic stabilization and pointing control procedure of the device.

[0006] The present invention relates to an innovative design of the automatic stabilization and pointing control of a device based on the MEMS technology, which is small enough and has acceptable accuracy to be integrated into many application systems, such as, laser pointing systems, telescopic systems, imaging systems, and optical communication systems. The stabilization mechanism configuration design is based on utilization of AGNC commercial products, the coremicro IMU and the coremicro AHRS/INS/GPS Integration Unit. The coremicro AHRS/INS/GPS Integration Unit is used as the processing platform core for the design of the MEMS coremicro IMU based automatic stabilization and pointing control of a device.

[0007] 2. Description of Related Arts

[0008] In many applications, a user needs to command a device to be pointed and stabilized with specified orientation. For example, an antenna or a transmitter and receiver beam in a mobile communication system carried in a vehicle needs to be pointed at a communication satellite in orbit in dynamic environments. Or, a gun turret or a sniper rifle in the hands of a warrior of an Army elite sniper team needs to be pointed at a hostile target in a complex environment. A measurement device in a land survey system needs to be pointed at a specific direction with precision and stabilized.

[0009] Conventional systems for automatic stabilization and pointing control of a device are usually bigger, heavier, use more power, are more costly, and are used only in large military weapon systems, or commercial equipment, which systems use conventional expensive, large, heavy, and high power consumption spinning iron wheel gyros and accelerometers as motion sensing devices. The platform body of the systems must be large enough and strong enough to accommodate the gyros (and sometimes the accelerometers as well), so large gimbals with large moments of inertia must be used to support the platform. This in turn requires powerful torque motors to drive the gimbals. The result is that we have gimbaled systems for automatic stabilization and pointing control of a device whose cost, size, and power prohibit them from use in the emerging commercial applications, including phased array antennas for mobile communication systems. This is mostly due to the size and weight of the inertial sensors in the gimbaled systems for automatic stabilization and pointing control of a device.

[0010] Conventional gyros and accelerometers, which are commonly used in inertial systems to sense rotation and translation motion of a carrier, include: Floated Integrating Gyros (FIG), Dynamically-Tuned Gyros (DTG), Ring Laser Gyros (RLG), Fiber-Optic Gyros (FOG), Electrostatic Gyros (ESG), Josephson Junction Gyros (JJG), Hemisperical Resonating Gyros (HRG), Pulsed Integrating Pendulous Accelerometer (PIPA), Pendulous Integrating Gyro Accelerometer (PIGA), etc.

[0011] New horizons are opening up for inertial sensor technologies. MEMS (MicroElectronicMechanicalSystem) inertial sensors offer tremendous cost, size, and reliability improvements for imaging guidance, navigation, tracking, pointing stabilization and control systems, compared with conventional inertial sensors. It is well known that the silicon revolution began over three decades ago, with the introduction of the first integrated circuit. The integrated circuit has changed virtually every aspect of our lives. The hallmark of the integrated circuit industry over the past three decades has been the exponential increase in the number of transistors incorporated onto a single piece of silicon. This rapid advance in the number of transistors per chip leads to integrated circuits with continuously increasing capability and performance. As time has progressed, large, expensive, complex systems have been replaced by small, high performance, inexpensive integrated circuits. While the growth in the functionality of microelectronic circuits has been truly phenomenal, for the most part, this growth has been limited to the processing power of the chip.

[0012] MEMS, or, as stated more simply, micromachines, are considered the next logical step in the silicon revolution. It is believed that this next step will be different, and more important than simply packing more transistors onto silicon. The hallmark of the next thirty years of the silicon revolution will be the incorporation of new types of functionality onto the chip structures, which will enable the chip to, not only think, but to sense, act, and communicate as well.

[0013] MEMS exploits the existing microelectronics infrastructure to create complex machines with micron feature sizes. These machines can have many functions, including sensing, communication, and actuation. Extensive applications for these devices exist in a wide variety of commercial systems.

[0014] Micromachining utilizes process technology developed by the integrated circuit industry to fabricate tiny sensors and actuators on silicon chips. In addition to shrinking the sensor size by several orders of magnitude, integrated electronics can be added to the same chip, creating an entire system on a chip. This instrument will result in, not only the redesign of conventional military products, but also new commercial applications that could not have existed without small, inexpensive inertial sensors.

[0015] Recent advances in the solid-state MEMS technology make it possible to build a very small, light-weight, low-power, and inexpensive IMU. The coremicro IMU patented product employs the MEMS technology to provide angle increments (i.e., rotation rates), velocity increments (i.e., accelerations), a time base (sync) in three axes and is capable of withstanding high vibration and acceleration. The coremicro IMU is a low-cost, high-performance motion sensing device (made up of 3 gyros and 3 accelerometers) measuring rotation rates and accelerations in body-fixed axes.

[0016] Therefore, it is possible to develop an automatic stabilization and pointing control of a device incorporating the MEMS IMU technologies that create a lightweight miniature gimbaled system for a physical inertially-stable platform. When mounted on a vehicle, the platform points to a fixed direction in inertial space, that is, the motion of the vehicle is isolated from the platform. In practice, a two-axis pointing stabilization mechanism has two coupled servo control loops.

[0017] The main objective of the present invention is to provide a method and system for pointing and stabilizing a device which needs to be pointed and stabilized with a determined orientation, wherein output signals of an inertial measurement unit and the desired direction information are processed to compute platform rotation commands to an actuator; the actuator rotates and stabilizes the device at the desired direction according to the platform rotation commands.

[0018] Another objective of the present invention is to provide a method and system for pointing and stabilizing a device, which needs to be pointed and stabilized at a desired orientation, wherein a visual and voice device is attached to provide a user with visualization and voice indications of targets and the pointing and stabilization operational procedure.

[0019] Another objective of the present invention is to provide a method and system for pointing and stabilizing a device which needs to be pointed and stabilized with a determined orientation, wherein the pointing and stabilization system has increased accuracy that an increase in the system's ability to reproduce faithfully the output pointing direction dictated by the desirable direction.

[0020] Another objective of the present invention is to provide a method and system for pointing and stabilizing a device, which can reduce sensitivity to disturbance, wherein the fluctuation in the relationship of system output pointing direction to the input desirable direction caused by changes within the system are reduced. The values of system components change constantly through their lifetime, but using the self-correcting aspect of feedback, the effects of these changes can be minimized. The device to be pointed is often subjected to undesired disturbances resulting from structural and thermal excitations. To aggravate the problem, disturbance profiles throughout the mission may have different characteristics.

[0021] Another objective of the present invention is to provide a method and system for pointing and stabilizing a device, which is more smoothing and filtering that the undesired effects of noise and distortion within the system are reduced.

[0022] Another objective of the present invention is to provide a method and system for pointing and stabilizing a device, which can increase bandwidth that the bandwidth of the system is defined as a range of frequencies or changes to the input desired direction to which the system will respond satisfactorily.

[0023] Another objective of the present invention is to provide a method and system for pointing and stabilizing a device, wherein the pointed and stabilized device may be very diverse, including:

• • [0024] (a) Antennas for a wireless communication system,
  • [0025] (b) Radar beams,
  • [0026] (c) Laser beam, leaser pointing system,
  • [0027] (d) Gun barrels, including gun turret, mortar, artillery, sniper rifles, machine guns,
  • [0028] (e) Measurement devices for a land survey.
  • [0029] (f) Optical pointing camera
  • [0030] (g) Optical communication devices.
  • [0031] (h) Telescopic systems,
  • [0032] (i) Imaging systems,
  • [0033] (j) Optical communication systems.

[0034] Another specific objective of the present invention is to provide a method and system for an innovative design of the automatic stabilization and pointing control of a device based on the MEMS IMU technology, which is small enough and has acceptable accuracy to be integrated into many application systems. The automatic stabilization and pointing control configuration design is based on utilization of AGNC commercial products, the coremicro IMU and the coremicro AHRS/INS/GPS Integration Unit. The coremicro AHRS/INS/GPS Integration Unit is used as the processing platform core for the design of the MEMS coremicro IMU based stabilization mechanism.

[0035] Another specific objective of the present invention is to provide a method and system for innovative Intelligent Remotely Controlled Weapon Station with Automated Target Hand-Off. The purpose of the Intelligent Remotely Controlled Weapon Station is to get the gunner out of the turret where he is exposed to enemy fire and fragments, and position him inside the vehicle for protection. The Shooter Detection System can be considered as a function augmentation to the coremicro® Palm Navigator (CPN). With this augmentation, using the CPN provided absolute position and the shooter detector determined relative bullet trajectory and position of the shooter (sniper), the CPN can determine the absolute position of the shooter and hand off the target to the fire control system by reporting the shooter's position to the local Intelligent Remotely Controlled Weapon Station. This is an automated hand-off situation for an individual unit of the Intelligent Remotely Controlled Weapon Station with a Shooter Detection System. Furthermore, multiple units of the Intelligent Remotely Controlled Weapon Station with a Shooter Detection System can be networked by a RF data link and they can also be linked to the CDAS and/or other C3 or C4 systems centers for battlefield awareness enhancement, decision aiding and coordinated fire control. The target acquired by a unit can be handed off to other units or C3/C4 systems centers. In this way a powerful distributed fire control system is established.

[0048] Referring to FIGS. 1 to 9, a method and system for pointing and stabilizing a device, which needs to be pointed and stabilized at a determined orientation, according to a preferred embodiment of the present invention is illustrated.

[0049] Rapid advance in MEMS technologies makes it possible to fabricate low cost, lightweight, miniaturized size, and low power gyros and accelerometers. “MEMS” stands for “MicroElectroMechanical Systems”, or small integrated electrical/mechanical devices. MEMS devices involve creating controllable mechanical and movable structures using IC (Integrated Circuit) technologies. MEMS includes the concepts of integration of Microelectronics and Micromachining. Examples of successful MEMS devices include inkjet-printer cartridges, accelerometers that deploy car airbags, and miniature robots.

[0050] Microelectronics, the development of electronic circuitry on silicon chips, is a very well developed and sophisticated technology. Micromachining utilizes process technology developed by the integrated circuit industry to fabricate tiny sensors and actuators on silicon chips. In addition to shrinking the sensor size by several orders of magnitude, integrated electronics can be placed on the same chip, creating an entire system on a chip. This instrument will result in, not only a revolution in conventional military and commercial products, but also new commercial applications that could not have existed without small, inexpensive inertial sensors.

[0051] MEMS (MicroElectronicMechanicalSystem) inertial sensors offer tremendous cost, size, reliability improvements for guidance, navigation, and control systems, compared with conventional inertial sensors.

[0052] American GNC Corporation (AGNC), Simi Valley, Calif., invented MEMS angular rate sensors and MEMS IMUs (Inertial Measurement Units), referring to US patents, “MicroElectroMechanical System for Measuring Angular Rate”, U.S. Pat. No. 6,508,122; “Processing Method for Motion Measurement”, U.S. Pat. No. 6,473,713; “Angular Rate Producer with MicroElectroMechanical System Technology”, Ser. No. 6,311,555; “Micro Inertial Measurement Unit”, Ser. No. 6,456,939. Either the micro IMU or the coremicro IMU is “The world's smallest” IMU, and is based on the combination of solid state MicroElectroMechanical Systems (MEMS) inertial sensors and Application Specific Integrated Circuits (ASIC) implementation. The coremicro IMU is a fully self contained motion-sensing unit. It provides angle increments, velocity increments, a time base (sync) in three axes and is capable of withstanding high vibration and acceleration. The coremicro IMU is opening versatile commercial applications, in which conventional IMUs can not be applied. They include land navigation, automobiles, personal hand-held navigators, robotics, marine users and unmanned air users, various communication, instrumentation, guidance, navigation, and control applications.

[0053] The coremicro IMU makes it possible to build a low-cost, low-weight, and small-size automatic stabilization and pointing control of a device.

[0054] It is worth to mention that although the coremicro IMU is preferred for the present invention, the present invention is not limited to the coremicro IMU. Any IMU device with such specifications can be used in the system of the present invention.

[0055] Referring to FIG. 1A, the automatic stabilization and pointing control system of the present invention for a device comprises an attitude producer 5, a target coordinate producer 8, a pointing controller 7, an actuator 6, and a visual and voice device 9.

[0056] The attitude producer 5 includes an IMU/AHRS (Inertial Measurement Unit/Attitude and Heading Reference System) device or GPS (Global Positioning System) attitude receiver for determining current attitude and attitude rate measurements of a device 1.

[0057] The target coordinate producer 8 is adapted for measuring the desired point direction of the device 1 by capturing and tracking a target.

[0058] The pointing controller 7 is adapted for computing platform rotation commands to an actuator 6 using the desired pointing direction of the device and the current attitude measurement of the device 1 to rotate the device 1.

[0059] The actuator 6 is adapted for rotating the device 1 to the desired pointing direction.

[0060] The visual and voice device 9, which can be a hand-held or head-up device or others, is adapted for providing the operator with audio and visual means to improve his/her decision, including displaying the desired pointing direction and current attitude of the device, target trajectory, and producing a voice representing the pointing procedure.

[0061] The automatic stabilization and pointing control system of the present invention is a feedback control system. The operator uses the target coordinate producer 8 to capture and track a target to measure the desired point direction of the pointed device 1. The IMU/AHRS 5 is used to measure the current attitude of the pointed device 1. Using errors between the desired point direction and current direction of the pointed device 1, the pointing controller 7 determines platform rotation commands to the actuator 6. The actuator 6 changes the current attitude of the pointed device 1 to bring it into closer correspondence with the desired orientation.

[0062] Since arbitrary disturbances and unwanted fluctuations can occur at various points in the system of the present invention, the system of the present invention must be able to reject or filter out these fluctuations and perform its task with the prescribed accuracy, while producing as faithful a representation of the desirable pointing direction as feasible. This function of the filtering and smoothing is achieved by the above mentioned pointing controller with different types of feedback approaches, namely:

[0063] (a) Angle position feedback,

[0064] (b) Angular rate and acceleration feedback.

[0065] As shown in FIG. 1B the target coordinate producer 8 comprises of eye tracker 81 and viewing sensor 82. The target coordinate producer 8 using eye tracker measuring a desired pointing direction for the remote controlled weapon-firing of said device by capturing and tracking a target comprises a platform on which reside a viewing sensor 82 and a weapon 1 such as a gun, a gun turret, a mortar, an artillery, etc.

[0066] There is an operator system that is remotely monitoring the scene on a display as viewed by the viewing sensor. The goal of the operator system is to acquire and track a selected target according to the scanning motion of the eyes of the object and the locking point at a selected target of the eyes. The operator system can therefore subsequently track the target according to the eye motion of an object.

[0067] The movement of the object's eyes is followed by a dual camera sensor of the eye tracker 81 that the operator is looking into. This sensor is monitoring the object's eyesight motion while the object simultaneously monitors the external viewing sensor's scene, locking and tracking with his eyesight some selected target.

[0068] The goal is to translate the display coordinates of the target, the operator system has selected and is tracking, to point the weapon on the external platform so that the object can fire at the target when he so desires.

[0069] The problem is thus summarized as one of controlling the weapon pointing, movement and firing on a target that has been selected and is tracked by the eyes of an operator viewing a display.

[0070] The viewing sensor 82 includes an Infrared sensor (IR), RF (Radio Frequency) radar, Laser radar (LADAR), and CCD (Charge Couple Devices) camera, or a multisensor data fusion system. Multisensor data fusion is an evolving technology that is analogous to the cognitive process used by humans to integrate data from their senses (sights, sounds, smells, tastes, and touch) continuously and make inferences about the external world.

[0071] In general, the benefit of employing multisensor data fusion system includes:

[0072] (1) Robust operational performance

[0073] (2) Extended spatial coverage

[0074] (3) Extended temporal coverage

[0075] (4) Increased confidence

[0076] (5) Improved ambiguity

[0077] (6) Improved detection performance

[0078] (7) Enhanced spatial resolution

[0079] (8) Improved system operational reliability

[0080] In the preferred gun turret smart machine gun application of the present invention, referring to FIG. 2, the user identifies the coordinates of a target by the use of the target coordinate producer 8, including a radar and laser rangefinder. The coordinates of a target are electronically relayed to the pointing controller 7 through the visual and voice device 9. The actuator 6, including a machine gunner, slews the gun barrel boresight toward the precise coordinates of the target so that it is ready to start laying down fire. The visual and voice device 9 shows the location of the target and the pointing procedure. After the user selects the target from the display, the target coordinates are automatically relayed to the pointing controller 7, as well as current attitude of the device 1 from the IMU/AHRS 5. The actuator 6 (the machine gunner) interacts with the pointing controller 7 to implement the fire control mission.

[0081] The gun turret smart machine gun application of the present invention is required to perform its missions in the presence of disturbances, parametric uncertainces and malfunctions, and to account for undesired vibrations. The system of the present invention integrates the techniques of signal/image processing, pattern classification, control system modeling, analysis and synthesis. The system of the present invention balances and optimizes tightly coupled signal processing and control strategies, algorithms and procedures.

[0082] Referring to FIG. 3, the pointing controller 7 further comprises:

[0083] a measurement data processing module 71, for transforming the target positioning measurements, measured by the target coordinate producer 8 and corrupted with measurement noise, from the target coordinate producer body coordinates to local level coordinates;

[0084] a target position estimator 72, for yielding the current target state including target position estimation using the target positioning measurements;

[0085] a target position predictor 73, for predicting the future target trajectory and calculating the interception position and time of a projectile launched by the gun turret and the target;

[0086] a fire control solution module 74, for producing the gun turret azimuth and elevation required for launch of the projectile; and

[0087] a device control command computation module 75, for producing control commands to the actuator 6 using the required gun turret azimuth and elevation and current attitude and attitude rate data of the gun turret 1 from the IMU/AHRS 5 to stabilize and implement the required gun turret azimuth and elevation with disturbance rejection.

[0088] Generally, radar measurements include the target range, range rate, azimuth, azimuth rate, elevation and elevation rate. The relationship between the target position and velocity, and the radar measurements can be expressed as:

[0089] $r_m=\sqrt{x_T^2+y_T^2+z_T^2}+w_1$ ${\theta }_m={\tan }^{-1}\left(\frac{-z_T}{\sqrt{x_T^2+y_T^2}}\right)+w_2$ ${\phi }_m={\tan }^{-1}\left(\frac{y_T}{x_T}\right)+w_3$ ${\stackrel{.}{r}}_m=\frac{{\stackrel{.}{x}}_T{x}_T+{\stackrel{.}{y}}_T{y}_T+{\stackrel{.}{z}}_T{z}_T}{\sqrt{x_T^2+y_T^2+z_T^2}}+w_4$ ${\stackrel{.}{\theta }}_m=\frac{z\left({\stackrel{.}{x}}_T{x}_T+{\stackrel{.}{y}}_T{y}_T\right)-\stackrel{.}{z}\left(x_T^2+y_T^2\right)}{\left(x_T^2+y_T^2+z_T^2\right)\sqrt{x_T^2+y_T^2}}+w_5$ ${\stackrel{.}{\phi }}_m=\frac{{\stackrel{.}{y}}_T{x}_T-{\stackrel{.}{x}}_T{y}_T}{x_T^2+y_T^2}+w_6$

[0090] where

[0091] (x_T,y_T,z_T)=real target position;

[0092] ({dot over (x)}_T,{dot over (y)}_T,ż_T)=real target velocity;

[0093] (r_m,{dot over (r)}_m)=measured target line of sight (LOS) range and range rate;

[0094] (θ_m,{dot over (θ)}_m)=measured target LOS elevation and elevation rate;

[0095] (φ_m,{dot over (φ)}_m)=measured target LOS azimuth and azimuth rate;

[0096] The radar measurements are expressed in radar antenna coordinates. The target position estimator 72 is embodied as a Kalman filter 72. In order to simplify the software design of the Kalman filter 72, the radar measurements are transferred back into local level orthogonal coordinates. The measurement data processing module 71 maps nonlinearly the radar measurements presented in radar antenna coordinates into those presented in the local level orthogonal coordinates. The relationship between the input and output of the measurement data processing module 71 are:
x_mT=r_m cos(θ_m)cos(φ_m)
y_mT=r_m cos(θ_m)sin(φ_m)
z_mT=r_m sin(φ_m)
{dot over (x)}_mT={dot over (r)}_m cos(θ_m)cos(φ_m)−r_m sin(θ_m)cos(φ_m){dot over (θ)}_m−r_m cos(θ_m)sin(φ_m){dot over (φ)}_m
{dot over (y)}_mT={dot over (r)}_m cos(θ_m)sin(φ_m)−r_m cos(θ_m)sin(φ_m){dot over (θ)}_m+r_m cos(θ_m)cos(φ_m){dot over (φ)}_m
ż_mT=−{dot over (r)}_m sin θ_m)−r_m cos(θ_m){dot over (θ)}_m

[0097] where

[0098] (x_mT,y_mT,z_mT)=transformed target position measurement;

[0099] (x_mT,y_mT,z_mT)=transformed target velocity;

[0100] For a successful engagement, the future target trajectory needs to be predicted accurately. Then the intercept position and time can be solved rapidly in terms of predicted target trajectory and the projectile flight dynamics. The inputs to the target position predictor 73 are the currently estimated target states, including target position and velocity, from the target position estimator 72, while the outputs the target position predictor 73 are the predicted intercept and intercept time.

[0101] Referring to FIG. 4, the target position predictor 73 further comprises a target position extrapolation module 731, a projectile flight time calculation 732, and an interception position and time determination 733.

[0102] The target position extrapolation module 731 is adapted for extrapolating the future trajectory of the projectile using the current target state including the target position estimation and system dynamic matrix:
X(t_k+j)=ΦX(t_k+j−1)

[0103] where

[0104] X(t_k) is the current target state estimating from the target position estimator 72. X(t_k+j) is predicted target state vector at time t_k+j=t_k+δt*j, where δt is chosen much less than the Kalman filtering step δT=t_k+1−t_k.

[0105] The projectile flight time calculation module 732 is adapted for computing the time of the projectile to fly from the gun turret to the interception position. As a preliminary design of the projectile flight time calculation module 732, the projectile flight time is approximately calculated by the LOS distance divided by a constant projectile speed.

[0106] The interception position and time determination module 733 is adapted for computing the interception position and time using the predicted future projectile trajectory and projectile flight time. Once the predicted target trajectory is determined, the time t₁, for the projectile to fly from the gun turret to each point of the predicted target trajectory and the time t₂ for the target to fly to the point can be calculated. Then the interception position can be determined, since for the interception point, the time t₁ should be equal to the time t₂.

[0107] The fire control solution module 74 gives the required gun turret azimuth and elevation by means of the given interception time and position from the target position predictor 72. Once the interception position is known, the gun tip elevation and azimuth can be accurately determined by using the fire control solution algorithms. The desired device tip azimuth φ_gun^d and elevation θ_gum^d are calculated by

[0108] ${\phi }_{\mathrm{gun}}^d={\tan }^{-1}\left(\frac{y_{\mathrm{Tp}}}{x_{\mathrm{TP}}}\right)$ ${\theta }_{\mathrm{gun}}^d={\tan }^{-1}\left(\frac{-z_{\mathrm{Tp}}}{\sqrt{x_{\mathrm{Tp}}^2+y_{\mathrm{Tp}}^2}}\right)$

[0109] where (x_mT,y_mT,z_mT)=the predicted interception position.

[0110] The device control command computation module 75 computes the platform rotation commands to the actuator 6 using the desired device tip azimuth and the elevation from the fire control solution module and the current attitude and attitude rate data from the IMU/AHRS 5 to place the gun tip to the desired position and stabilize the gun tip at the desired position with any disturbance rejection.

[0111] The device control command computation module 75 is a digital controller and definitely essential to isolate the gun turret from vibrations while maintaining precision stabilization and pointing performance.

[0112] As a preferred embodiment of the visual and voice device 9, the visual and voice device 9 is designed to display the target of the field of view of the gun turret motion, the projectile and target flight trajectories during the interception process.

[0113] Referring to FIGS. 1 to 4, the automatic stabilization and pointing control method according to the above preferred embodiment of the present invention comprises the steps of:

[0114] (1) identifying a desired pointing direction of a device by providing coordinates of a target by a means, including a target coordinate producer 8;

[0115] (2) determining a current attitude measurement of the device by a means, including an inertial measurement unit;

[0116] (3) computing platform rotation commands of the device using the desired pointing direction of the device and the current attitude measurements of the device by a means, including a pointing controller 7;

[0117] (4) rotating the device to the desired pointing direction by a means, including an actuator 6.

[0118] (5) visualizing the targets and desired pointing direction and current direction of the device; and

[0119] (6) producing a voice representing the pointing procedure.

[0120] According to the preferred embodiment of the present invention, the step (3) further comprises the steps of,

[0121] 3.1 transforming the target positioning measurements, measured by the target coordinate producer 8 and corrupted with measurement noise, from the target coordinate producer body coordinates to local level coordinates;

[0122] 3.2 yielding the current target state including target position estimation using target positioning measurements measured by the target coordinate producer 8;

[0123] 3.3 predicting the future target trajectory and calculating interception position and time of a projectile launched by the gun turret and the target;

[0124] 3.4 producing gun turret azimuth and elevation required for launch of the projectile; and

[0125] 3.5 producing control commands to the actuator using the gun turret azimuth and elevation and the current attitude and attitude rate data of the gun turret from the IMU/AHRS to stabilize and implement the gun turret azimuth and elevation with disturbance rejection.

[0126] Also, the step (3.3) further comprises the steps of:

[0127] 3.3.1 extrapolating the future trajectory of the projectile using the current target state, including the current target position estimation and system dynamic matrix;

[0128] 3.3.2 computing time of the projectile to fly from the gun turret to interception position; and

[0129] 3.3.3 computing interception position and time using the predicted future projectile trajectory and projectile flight time.

[0130] The preferred IMU/AHRS 5 is a micro MEMS IMU in which a position and attitude processor is built in. The IMU/AHRS 5 is disclosed as follows.

[0131] Generally, an inertial measurement unit (IMU) is employed to determine the motion of a carrier. In principle, an inertial measurement unit relies on three orthogonally mounted inertial angular rate producers and three orthogonally mounted acceleration producers to obtain three-axis angular rate and acceleration measurement signals. The three orthogonally mounted inertial angular rate producers and three orthogonally mounted acceleration producers with additional supporting mechanical structure and electronic devices are conventionally called an Inertial Measurement Unit (IMU). The conventional IMUs may be cataloged into Platform IMU and Strapdown IMU.

[0132] In the platform IMU, angular rate producers and acceleration producers are installed on a stabilized platform. Attitude measurements can be directly picked off from the platform structure. But attitude rate measurements can not be directly obtained from the platform. Moreover, there are highly accurate feedback control loops associated with the platform.

[0133] Compared with the platform IMU, in the strapdown IMU, angular rate producers and acceleration producers are directly strapped down with the carrier and move with the carrier. The output signals of the strapdown rate producers and acceleration producers are expressed in the carrier body frame. The attitude and attitude rate measurements can be obtained by means of a series of computations.

[0134] A conventional IMU uses a variety of inertial angular rate producers and acceleration producers. Conventional inertial angular rate producers include iron spinning wheel gyros and optical gyros, such as Floated Integrating Gyros (FIG), Dynamically Tuned Gyros (DTG), Ring Laser Gyros (RLG), Fiber-Optic Gyros (FOG), Electrostatic Gyros (ESG), Josephson Junction Gyros (JJG), Hemisperical Resonating Gyros (HRG), etc. Conventional acceleration producers include Pulsed Integrating Pendulous Accelerometer (PIPA), Pendulous Integrating Gyro Accelerometer (PIGA), etc.

[0135] The processing method, mechanical supporting structures, and electronic circuitry of conventional IMUs vary with the type of gyros and accelerometers employed in the IMUs. Because conventional gyros and accelerometers have a large size, high power consumption, and moving mass, complex feedback control loops are required to obtain stable motion measurements. For example, dynamic-tuned gyros and accelerometers need force-rebalance loops to create a moving mass idle position. There are often pulse modulation force-rebalance circuits associated with dynamic-tuned gyros and accelerometer based IMUs. Therefore, conventional IMUs commonly have the following features:

[0136] 1. High cost,

[0137] 2. Large bulk (volume, mass, large weight),

[0138] 3. High power consumption,

[0139] 4. Limited lifetime, and

[0140] 5. Long turn-on time.

[0141] These present deficiencies of conventional IMUs prohibit them from use in the emerging commercial applications, such as phased array antennas for mobile communications, automotive navigation, and handheld equipment.

[0142] New horizons are opening up for inertial sensor device technologies. MEMS (MicroElectronicMechanicalSystem) inertial sensors offer tremendous cost, size, and reliability improvements for guidance, navigation, and control systems, compared with conventional inertial sensors.

[0143] MEMS, or, as stated more simply, micromachines, are considered as the next logical step in the silicon revolution. It is believed that this coming step will be different, and more important than simply packing more transistors onto silicon. The hallmark of the next thirty years of the silicon revolution will be the incorporation of new types of functionality onto the chip structures, which will enable the chip to, not only think, but to sense, act, and communicate as well.

[0144] Prolific MEMS angular rate sensor approaches have been developed to meet the need for inexpensive yet reliable angular rate sensors in fields ranging from automotive to consumer electronics. Single input axis MEMS angular rate sensors are based on either translational resonance, such as tuning forks, or structural mode resonance, such as vibrating rings. Moreover, dual input axis MEMS angular rate sensors may be based on angular resonance of a rotating rigid rotor suspended by torsional springs. Current MEMS angular rate sensors are primarily based on an electronically-driven tuning fork method.

[0145] More accurate MEMS accelerometers are the force rebalance type that use closed-loop capacitive sensing and electrostatic forcing. Draper's micromechnical accelerometer is a typical example, where the accelerometer is a monolithic silicon structure consisting of a torsional pendulum with capacitive readout and electrostatic torquer. Analog Device's MEMS accelerometer has an integrated polysilicon capacitive structure fabricated with on-chip BiMOS process to include a precision voltage reference, local oscillators, amplifiers, demodulators, force rebalance loop and self-test functions.

[0146] Although the MEMS angular rate sensors and MEMS accelerometers are available commercially and have achieved micro chip-size and low power consumption, however, there is not yet available high performance, small size, and low power consumption IMUs.

[0147] Currently, MEMS exploits the existing microelectronics infrastructure to create complex machines with micron feature sizes. These machines can have many functions, including sensing, communication, and actuation. Extensive applications for these devices exist in a wide variety of commercial systems.

[0148] The difficulties for building a micro IMU is the achievement of the following hallmark using existing low cost and low accuracy angular rate sensors and accelerometers:

[0149] 1. Low cost,

[0150] 2. Micro size

[0151] 3. Lightweight

[0152] 4. Low power consumption

[0153] 5. No wear/extended lifetime

[0154] 6. Instant turn-on

[0155] 7. Large dynamic range

[0156] 8. High sensitivity

[0157] 9. High stability

[0158] 10. High accuracy

[0159] To achieve the high degree of performance mentioned above, a number of problems need to be addressed:

[0160] (1) Micro-size angular rate sensors and accelerometers need to be obtained. Currently, the best candidate angular rate sensor and accelerometer to meet the micro size are MEMS angular rate sensors and MEMS accelerometers.

[0161] (2) Associated mechanical structures need to be designed.

[0162] (3) Associated electronic circuitry needs to be designed.

[0163] (4) Associated thermal requirements design need to be met to compensate the MEMS sensor's thermal effects.

[0164] (5) The size and power of the associated electronic circuitry needs to be reduced.

[0165] The micro inertial measurement unit of the present invention is preferred to employ with the angular rate producer, such as MEMS angular rate device array or gyro array, that provides three-axis angular rate measurement signals of a carrier, and the acceleration producer, such as MEMS acceleration device array or accelerometer array, that provides three-axis acceleration measurement signals of the carrier, wherein the motion measurements of the carrier, such as attitude and heading angles, are achieved by means of processing procedures of the three-axis angular rate measurement signals from the angular rate producer and the three-axis acceleration measurement signals from the acceleration producer.

[0166] In the present invention, output signals of the angular rate producer and acceleration producer are processed to obtain digital highly accurate angular rate increment and velocity increment measurements of the carrier, and are further processed to obtain highly accurate position, velocity, attitude and heading measurements of the carrier under dynamic environments.

[0167] Referring to FIG. 5, the micro inertial measurement unit of the present invention comprises an angular rate producer c5 for producing three-axis (X axis, Y axis and Z axis) angular rate signals; an acceleration producer c10 for producing three-axis (X-axis, Y axis and Z axis) acceleration signals; and an angular increment and velocity increment producer c6 for converting the three-axis angular rate signals into digital angular increments and for converting the input three-axis acceleration signals into digital velocity increments.

[0168] Moreover, a position and attitude processor c80 is adapted to further connect with the micro IMU of the present invention to compute position, attitude and heading angle measurements using the three-axis digital angular increments and three-axis velocity increments to provide a user with a rich motion measurement to meet diverse needs.

[0169] The position, attitude and heading processor c80 further comprises two optional running modules:

[0170] (1) Attitude and Heading Module c81, producing attitude and heading angle only; and

[0171] (2) Position, Velocity, Attitude, and Heading Module c82, producing position, velocity, and attitude angles.

[0172] Referring to FIG. 5, the digital three-axis angular increment voltage values or real values and three-axis digital velocity increment voltage values or real values are produced and outputted from the angular increment and velocity increment producer c6.

[0173] FIG. 6 is another embodiment of the detailed block diagram of System for Automatic Stabilization and Pointing Control of a Device in which the pointed device 1 in FIG. 1, 2, is specifically referred to as the platform 1 or platform body 1 or gimbaled platform and the pointing controller 7 and the actuator 6 are further broken down into sublevels. With the application of the MEMS IMU, the design of the servo controller 76 is a key technical issue in this invention. The servo controller 76 signals are amplified by an amplifier 77. The stability and anti-interference performance of the automatic stabilization and pointing control of a device is mostly determined by the servo loop design. The characteristics of the MEMS gyro also impact the control loop design.

[0174] The stability and anti-interference performance of the pointing stabilization mechanism is mostly determined by the servo loop design. It is often difficult to determine the controller parameters that can satisfy different application environments. The system model has platform rates or platform angles as outputs, and three inputs, platform rotation command, interference torque, and gyro drift. The performance of the servo system can be described by the response of the platform 1 to the system inputs.

[0175] The platform 1 of the automatic stabilization and pointing control of a device can rotate with respect to inertial space if there is a command input. In the automatic stabilization and pointing control of a device, the command function can be used to reset or initialize the attitude system pointing direction. Because gyro drift exists, the platform of the attitude system needs to be reset periodically. In this invent, however, the major objective of the servo loop design is to eliminate the effect of short-term interference torque acting on the platform. The interference torque is induced by attitude changes of the vehicle, the elastic deformation of the platform and gimbals, and vehicle vibration. The frequency range of interest is from about one third of a hertz to 10 Khz. The design of the servo controller C(s) is the key issue in this task. After the hardware of the servo system is implemented, the performance of the servo system is mostly determined by the servo controller design. But the following factors make it difficult to design a servo controller that can satisfy requirements under different application conditions:

[0176] (A) The coupling between the two servo control channels of the pointing stabilization mechanism. In the servo controller design we can ignore it, but in practice the coupling can affect the system performance.

[0177] (B) The existence of non-linearity. The platform-gimbals system 1 is actually a nonlinear system that can be described by two interacting rigid bodies. The dry friction between the platform and gimbals is also nonlinear.

[0178] (C) The vibration models of the vehicle, gamble, and mirror are often unknown. Since in the gimbaled pointing stabilization mechanism the vibration induced interference torque to the platform is of special concern, the vibration model is needed in the servo controller design.

[0179] FIG. 7 is depicts a simplified mechanical system model of the gimbaled platform 1.

[0180] FIG. 8 depicts the system configuration of the experimental automatic stabilization and pointing control of a device.

[0181] Referring to FIGS. 1 to 8, the automatic stabilization and pointing control method according to the above preferred embodiment of the present invention comprises the steps of:

[0182] (1) identifying a desired pointing direction of a device by providing coordinates of a target by a means, including a target coordinate producer 8;

[0183] (2) determining a current attitude measurement of the device by a means, including an inertial measurement unit;

[0184] (3) computing platform rotation commands of the device using the desired pointing direction of the device and the current attitude measurements of the device 5 by a means, including measurement data processing module 71, target position estimator 72, target position predictor 73, fire control solution module 74, gun control command computation module 75;

[0185] (4) combining the computed platform rotation commands with the feedback signals from the coremicro IMU 5;

[0186] (5) computing the automatic stabilization and pointing control signal by with the servo controller 76;

[0187] (7) amplifying the servo controller 76 signals by an amplifier 77;

[0188] (8) sending the amplified the servo controller 76 signals to the actuator 6;

[0189] (9) the actuator 6—torque motors—converts the electric signals to torques and the torque exerted on the platform body 10 to eliminate interference to the platform body 10;

[0190] (10) sensing the motion of the platform body 10 by coremicro IMU 5 and feedback the sensor signal to the servo controller 76;

[0191] (11) visualizing the targets and desired pointing direction and current direction of the device; and

[0192] (12) producing a voice representing the pointing procedure.

[0193] The present invention also provides a first alternative method for Automatic Pointing Stabilization and Aiming Control Device comprising the steps of:

[0194] (1) receiving platform rotation commands of said device using said desired pointing direction of said device and said current attitude measurement of said device;

[0195] (2) combining the computed platform rotation commands with the feedback signals from the coremicro IMU 5;

[0196] (3) computing the automatic stabilization and pointing control signal by with the servo controller 76;

[0197] (4) amplifying the servo controller 76 signals by an amplifier 77;

[0198] (5) sending the amplified the servo controller 76 signals to the actuator 6;

[0199] (6) the actuator 6—torque motors—converts the electric signals to torques and the torque exerted on the platform body 10 to eliminate interference to the platform body 10; and

[0200] (7) sensing the motion of the platform body 10 by coremicro IMU 5 and feedback the sensor signal to the servo controller 76.

[0201] According to the present invention, a second alternative of the present invention comprises the steps of:

[0202] (1) identifying a desired pointing direction of a device by providing coordinates of a target by a means;

[0203] (2) determining a current attitude measurement of the device by a means, including an inertial measurement unit;

[0204] (3) computing platform rotation commands of the device using the desired pointing direction of the device and the current attitude measurements of the device 5;

[0205] (4) combining the computed platform rotation commands with the feedback signals from the coremicro IMU 5;

[0206] (5) computing the automatic stabilization and pointing control signal by with the servo controller 76;

[0207] (7) amplifying the servo controller 76 signals by an amplifier 77;

[0208] (8) sending the amplified the servo controller 76 signals to the actuator 6;

[0209] (9) the actuator 6—torque motors—converts the electric signals to torques and the torque exerted on the platform body 10 to eliminate interference to the platform body 10; and

[0210] (10) sensing the motion of the platform body 10 by coremicro IMU 5 and feedback the sensor signal to the servo controller 76.

[0211] Referring to FIG. 7, the pointed device is usually a gambled two-degree-of-freedom platform body 10. Now we analyze the motion model of the gimbaled platform. A simplified mechanical system model of the gimbaled platform is depicted. It consists of 3 objects: a base that is stationary or fixed to a carrier, an outer gimbal, and the inner gimbal or platform. To describe the motion and establish a mathematical model for the gimbaled platform, we define 3 systems of coordinates (frames):

[0212] (I) Frame 0, OX₀Y₀Z₀—fixed to the base.

[0213] (II) Frame 1, OX₁Y₁Z₁—fixed to the outer gimbal.

[0214] (III) Frame 2 or B, OX₂Y₂Z₂/OX_bY_bZ_b—fixed to the inner gimbal or platform.

[0215] FIG. 7 depicts the directions definition of the above 3 frames. The angular position of the platform can be described by the relative position of the frame B/2 with respective to the frame 0, which is determined by two gimbal angles along the two gimbal axes, α and β.

[0216] Using a directional cosine matrix (DCM) to describe the relative angular position, the frame 1 angular position with respective to frame 0 is expressed as:

[0217] $C_0^1=\left[\begin{array}{ccc}1& 0& 0\\ 0& \cos \alpha & \sin \alpha \\ 0& -\sin \alpha & \cos \alpha \end{array}\right]$

[0218] Similarly, the frame 2/B angular position with respective to frame 1 is expressed as:

[0219] $C_1^2=\left[\begin{array}{ccc}\cos \beta & 0& -\sin \beta \\ 0& 1& 0\\ \sin \beta & 0& \cos \beta \end{array}\right]$

[0220] The angular velocity of the gimbaled platform is determined by the vector equation:
ω={dot over (α)}+{dot over (β)}

[0221] Expressing it in component form and in the frame 2/B, we obtain:

[0222] ${\omega }^b=C_1^2\left[\begin{array}{c}\stackrel{.}{\alpha }\\ 0\\ 0\end{array}\right]+\left[\begin{array}{c}0\\ \stackrel{.}{\beta }\\ 0\end{array}\right]$

[0223] Or:
ω_x={dot over (α)} cos β
ω_y={dot over (β)}
ω_z={dot over (α)} sin β

[0224] The external torques applied on the gimbaled platform 1 are transferred from the outer gimbal. They can be expressed in the 3 axes directions of the frame 1:

• [0225] (i) Torque from motor in the OX₁ direction, M_α.
• [0226] (ii) Torque from motor in the OY₁ direction, M_β.
• [0227] (iii) Torque from the base in the OZ₁ direction, M_z.

[0228] In addition, there are also external torques caused by friction and elastic properties of the gimbals. We consider them as external interference torques in the analysis and simulation.

[0229] The external torques transferred to the frame 2/B, the gimbaled platform 1, and expressed in the frame 2/B are:

[0230] $M^b=C_1^2\left[\begin{array}{c}{M}_{\alpha }\\ M_{\beta }\\ M_z\end{array}\right]$

[0231] Or in components:
M_x=M_α cos β−M_z sin β
M_y=M_β
M_z=M_α sin β+M_z cos β

[0232] At first, we consider the gimbaled platform 1 as a rigid body and the dynamic motion can be described by the so-called Euler Equations:
{dot over (H)}=[I^b]{dot over (ω)}+ω×H=M^b

[0233] where H is the angular relative momentum of the gimbaled platform 1 and
H=└I^b┘ω

[0234] where └I^b┘ is the inertia matrix of the gimbaled platform 1 with respect to frame 2/B.

[0235] The Euler Equations in component form is:
I_x{dot over (ω)}_x+(I_z−I_y)ω_zω_y=M_x
I_y{dot over (ω)}_y+(I_x−I_z)ω_xω_z=M_y
I_z{dot over (ω)}_z+(I_y−I_x)ω_yω_x=M_z

[0236] where I_x, I_y, I_z, are the moments of inertia of the gimbaled platform 1 with respect to the axes of the frame 2/B.

[0237] Combining the angular velocity equations and torque equations into the Euler Equations, we can obtain the dynamic mathematical model of the gimbaled platform 1:
I_x({umlaut over (α)} cos β−{dot over (α)}{dot over (β)} sin β)+(I_z−I_y){dot over (α)}{dot over (β)} sin β=M_α cos β−M_z sin β
I_y{umlaut over (β)}+(I_x−I_z){dot over (α)}² cos β sin β=M_β
I_z({umlaut over (α)} sin β+{dot over (α)}{dot over (β)} cos β)+(I_y−I_x){dot over (α)}{dot over (β)} cos β=M_α sin β+M_z cos β

[0238] In the above 3 equations, M_α, M_β are controlling torques from the motors, while M_z is a reaction torque from the base. Therefore, the first 2 equations are useful for control system analysis design and the third equation is a torque relation for the gimbaled system.

[0239] Referring to FIG. 6, the actuator 6 is usually a set of DC motors. A generic DC motor model can be expressed as:
V_in=iR+L di/dt+K_bω
M=K_ti

[0240] where:

[0241] V_in—motor input voltage;

[0242] i—motor armature coil current;

[0243] R—motor armature coil resistance;

[0244] L—motor armature coil inductance;

[0245] K_b—motor back electromotive force (EMF) constant;

[0246] ω—motor shaft angular velocity;

[0247] M.—motor shaft torque;

[0248] K_t—motor torque constant.

[0249] Applying this model to the two motors to control the motion of the gimbaled platform 1 in the two axes, OX₁ and OY₁, respectively, we obtain two sets of motor equations:

[0250] $V_{\mathrm{inx}}=i_{x}R+L\frac{d{i}_x}{dt}+K_b\stackrel{.}{\alpha }$ $M_{\alpha }=K_t{i}_x$ $V_{\mathrm{iny}}=i_{y}R+L\frac{d{i}_y}{dt}+K_b\stackrel{.}{\beta }$ $M_{\beta }=K_t{i}_y$

[0251] Combined together, the dynamic model of the motor-gimbaled platform system is expressed as follows:

[0252] $I_x\left(\ddot{\alpha }\cos \beta -\stackrel{.}{\alpha }\stackrel{.}{\beta }\sin \beta \right)+\left(I_x-I_y\right)\stackrel{.}{\alpha }\stackrel{.}{\beta }\sin \beta =K_t{i}_x\cos \beta -M_z\sin \beta$ $i_{x}R+L\frac{d{i}_x}{dt}+K_b\stackrel{.}{\alpha }=V_{\mathrm{inx}}$ $I_y\ddot{\beta }+\left(I_x-I_z\right){\stackrel{.}{\alpha }}^2\cos \beta \sin \beta =K_t{i}_y$ $i_{y}R+L\frac{d{i}_y}{dt}+K_b\stackrel{.}{\beta }=V_{\mathrm{iny}}$

[0253] The inputs of the system are V_inx, V_iny, and outputs are α and β.

[0254] Two direct drive, brushless dc motors are used in the two-axis gimbals system for the experimental inertial pointing and stabilization mechanism. We need to have a motor controller circuit module to control the two direct drive, brushless dc motors. When making a DC brushless motor controller choice, there are several issues that have to be addressed so that the proper device is selected for the system.

[0255] In the two-axis gimbals system, the direction of the motor needs to be changed. This has to be taken into account in the controller selection. And the torque needs to be controlled, so a controller with a current loop control needs to be specified. Also, if the two-axis gimbals system control calls for a high bandwidth servo control loop, a full four-quadrant controller must be chosen.

[0256] There are four possible modes or quadrants of operation using a DC motor, brushless or otherwise. In an X-Y plot of speed versus torque, Quadrant I is forward speed and forward torque. The torque is rotating the motor in the forward direction. Conversely, Quadrant III is reverse speed and reverse torque. Now the motor is rotating in the reverse direction, spinning backwards with the reverse torque. Quadrant II is where the motor is spinning in the forward direction, but torque is being applied in reverse. Torque is being used to “brake” the motor, and the motor is now generating power as a result. Finally, Quadrant IV is exactly the opposite. The motor is spinning in the reverse direction, but the torque is being applied in the forward direction. Again, torque is being applied to attempt to slow the motor and change its direction to forward again. Once again, the motor is generating power.

[0257] A one-quadrant motor controller will drive the motor in one direction only. An example of this would be a small fan or blower, such as the brushless fans used on some PC power supplies. A small pump that only needs to run in one direction can also use such a controller. A two-quadrant controller has the capability of reversing the direction of the motor. If the pump needs to be backed up, this would be the controller to use. A four-quadrant controller can control the motor torque both in the forward and the reverse direction regardless of the direction of the motor. A servo control system needs just this kind of control.

[0258] In order to have complete control of torque, the feedback loop has to allow the amplifier to maintain control of the torque at all times. A missile fin actuator or antenna pointing system needs to have complete control of motor torque at all times in order to satisfy the system requirements. Examining what happens during the PWM sequence will reveal the difference in controllers.

[0259] Pulse width modulation, or PWM is the method by which all class D amplifiers operate. By turning the supply voltage on and off at a high rate to a load and letting the characteristics of the load smooth out the current spikes, a much more efficient means of varying the power to the load is achieved. A switch is placed between one end of a DC motor and the supply and another switch between the other end of the motor and the return to the supply. Modulating the on-off duty cycle of one or both of the switches results in the proportional control of power to the motor, in one direction only. This is how one quadrant operation is achieved.

[0260] Adding a second pair of switches to the first pair, basically making two totem pole half bridges, is how a two-quadrant controller is constructed. Modulating one or both of the second pair of switches will result in controlling the motor in the opposite direction. This is operation in quadrant three.

[0261] The construction of a four-quadrant controller is exactly the same as the two-quadrant controller. The difference is in the modulation of the four switches. By modulating the opposite pairs of switches together in a complementary fashion, there is modulation control occurring at all times. In the two-quadrant case, as the motor either stops or changes direction, the modulation decreases to zero and starts backing up the opposite way. The control loop is out of the control influence during the time the modulation is stopped.

[0262] With a four-quadrant controller, modulation is occurring at a 50 percent duty cycle when the motor is not turning. The controller maintains control as the motor speed passes through zero. The net result is tighter control without any discontinuity at zero, and the bandwidth capability of the control system is doubled because, in effect, double the supply voltage is being utilized at all times.

[0263] Using this concept in a three-phase brushless DC motor controller, another half bridge is added. The pairs of half bridges are controlled by the Hall sensors, as they electrically commutate the motor with the three half bridges. At any given time, only two of the half bridges are being used, but they are modulated exactly as previously discussed.

[0264] The selected three-phase brushless DC motor controller is a full four-quadrant DC brushless motor control “torque amplifier.” It is designed to provide closed loop current control of a brushless motor by sensing the current through the motor, thereby controlling the torque output of the motor. In a DC motor, torque is proportional to current. Enough torque produces speed, and the controller is used as the inner loop of a servo speed control system. By controlling torque directly instead of speed, better control of a motor in a servo system is realized. In other controllers, the loop control is lost as the controller passes through zero torque. This is not acceptable in most servo control systems. This discontinuity will disrupt the control system in many cases.

[0265] To stabilize the gimbaled platform 1 with respect to the stationary base or the inertial space, a coremicro IMU is mounted on the platform to sense its motion. If, on the platform, the IMU's sensing axes are identical to those of the frame 2/B, respectively, the measurement model of the IMU can be expressed as:

[0266] ${\omega }_{\mathrm{out}}={\omega }_{\mathrm{bi}}^b+\varepsilon =C_1^2\left[\begin{array}{c}\stackrel{.}{\alpha }\\ 0\\ 0\end{array}\right]+\left[\begin{array}{c}0\\ \stackrel{.}{\beta }\\ 0\end{array}\right]+C_0^2{\omega }_{0i}^0+\varepsilon$

[0267] where ε is the total gyro drift, and ω_0i⁰ is the base angular velocity with respect to inertial space.

[0268] Referring to FIG. 8, the system configuration of the experimental automatic stabilization and pointing control system of a device. The experimental automatic stabilization and pointing control system consists of an AGNC coremicro AHRS/INS/GPS Integration Unit 5, a COTS 2-axis gimbals system 10, a 2-channel platform controller 76 and amplifier 77. Referring to FIG. 8 the amplifier 77 further comprises:

• • [0269] a motor controller circuits module 771 producing a suite of PWM control pulses (usually 4 channels) according to the data or signals from the platform controller 76. The produced signals control the PWM amplifier 772;
  • [0270] a PWM amplifier 772 to drive the gimbal motor in different operation modes, such as forward, backward, brake, lock, etc. The PWM amplifier 772 consists of a set of high speed high power semi-conductor switches, such as GTR, VMOS, or IGBT. Under the control of pulses from the motor controller circuits 771, the PWM amplifier 772 generates PWM voltages and currents to the motors; and
  • [0271] a DC power supply 773. The electric power is from the DC power supply 773, which rectifies the AC to produce a 28V DC power.

[0272] The coremicro AHRS/INS/GPS Integration Unit 5 is embedded in the 2-axis gimbals platform 1 to measure the platform motion with respect to inertial space. The computation capability of the coremicro AHRS/INS/GPS Integration Unit 5 is also used to implement the 2-channel gimbals platform controller 76.

[0273] The two-axis gimbals system selected for the experimental inertial pointing and stabilization mechanism is a COTS gimbals meeting challenging performance demands for pointing various payloads at high degrees of accuracy and in extreme environments. These gimbals accommodate diverse payloads, including mirror flats, laser transponders, optical telescopes, and science instrument packages This two-axis gimbals system can be designed to meet specific needs. It combines direct drive, brushless dc motors, precision bearings, angular position transducers, and signal transfer devices with a lightweight, stiff structure. The gimbals system can be modified to embed the coremicro AHRS/INS/GPS Integration Unit with its structure.

[0274] The gimbals system utilizes a vacuum lubrication process to protect contacting surfaces. Wet or dry vacuum lubrication process offers very low outgassing lubrication options chosen based on life, temperature, contamination, or radiation requirements. This gimbals system and specialized lubrication have been integrated into some of the most precise pointing systems for ground, aircraft, and space-based applications.

[0275] The gimbals can be operated in either the position mode or the stabilization mode.

[0276] In the position mode, the gimbal control loop holds the gimbal in a given position with respect to the vehicle. An angle-measuring resolver is used as the loop feedback element.

[0277] In the stabilization mode, the gimbal control loop holds the gimbal in a given orientation in inertial space. This is realized because of the use of the coremicro AHRS/INS/GPS Integration Unit.

[0278] The coremicro AHRS/INS/GPS Integration Unit is used as the loop feedback element in the stabilization mode. In either mode, the gimbal controller sends a torque command signal to the motor current loop closed by the motor controller.

[0279] Referring to FIG. 9, the Intelligent Remotely Controlled Weapon can be mounted on top of a vehicle and controlled from a command center within it. In an Intelligent Remotely Controlled Weapon Station equipped vehicle, the gunner sits safely inside the armored vehicle, looks at a computer screen and controls the weapon with the use of a joystick or other kind of user interface device, such as gaze tracking. In addition, the Intelligent Remotely Controlled Weapon Station is equipped with a powerful color camera, forward-looking infrared camera, a laser range finder, and other EO/IR/radar/Laser sensors, which make it possible to realize an automatic target tracking and fire control system. Once a target has been identified the computer builds a ballistic solution, taking into account distance, elevation and the type of weapon. All the gunner has to do now is to lock onto the target, tell the computer to fire the weapon and the computer executes the rest of the action.

[0280] Furthermore, the Intelligent Remotely Controlled Weapon Station has two types of user interfaces mounted inside the vehicle, allowing operation from within the vehicle's ballistic protection. 1) The first type of user interface is a video-mechanical system. Its main components include a display unit, switch panel unit, and hand controller joystick). The control user interface provides full remote control of the weapon system via on-screen menus presented on the display, and by the switches and joystick. 2) The second type of user interface is a video-eye tracker system. The switch panel unit and hand controller joystick) is replaced by an eye tracker. The operator is remotely monitoring the scene on a display as viewed by a viewing sensor. The goal of the operator is to acquire and track a selected target. The operator does this by scanning the scene with his eyes and locking his eyesight onto a selected target. The operator subsequently tracks the target with his eyes. The movement of the operator's eyes is followed by a dual camera sensor that the operator is looking into. This sensor is monitoring the operator's eyesight motion while the operator simultaneously monitors the external viewing sensor's scene, locking and tracking with his eyesight some selected target. The goal is to translate the display coordinates of the target, the operator has selected and is tracking, to point the weapon on the external platform so that the operator can fire at the target when he so desires. A user eye controlled target tracking system is thus realized. This type of user interface can significantly reduce the operator's workload.

[0281] A typical Intelligent Remotely Controlled Weapon Station with a Shooter Detection System comprises the following main subsystems:

• • [0282] The gun and its mechanical supporting weapon cradle that form a two-degrees-of-freedom gun turret platform.
  • [0283] Electric motors for two-degrees-of-freedom gun turret traverse and elevation drives, including two channel motor servo control system based on microcontroller or microcomputer.
  • [0284] Weapon interface.
  • [0285] Weapon remote charger.
  • [0286] Ammunition feed system.
  • [0287] Viewing and sighting sensors and their stabilization unit.
  • [0288] Remote control user interface.
  • [0289] Fire control computer.
  • [0290] Acoustic sensors for the Shooter Detection System.
  • [0291] coremicro® Palm Navigator (CPN) for navigation and Shooter Detection processing.
  • [0292] Shooter position indicator or display, etc.

[0293] A remotely operated weapon station has been built for the US military, called Stabilized Remotely operated Weapon Station (SRWS) or Common Remotely Operated Weapon Station (CROWS). However, it only provides the basic functions for remote operation and fire control. For example, the CROWS has no automatic target tracking function and its two-axis stabilization is with respect to the base or the vehicle. If the vehicle is in motion, the pointing direction of the gun turret will move with the vehicle. This makes it difficult for locking onto targets and tracking them in motion. The object of this invention is to add more advanced stabilization, control, shooter detection, and target tracking and hand-off functions to the existing weapon stations.

[0294] For the complete Intelligent Remotely Controlled Weapon Station system configuration, a basis is provided by the inertial two-degree-of-freedom gun turret stabilization and control system based on the application of AGNC's coremicro Palm Navigator. Based on the stabilization and control system, next comes the automatic moving target tracking system and the user eye controlled target tracking. The following is a detailed description of the inertial two-degree-of-freedom gun turret stabilization and control system.

[0295] Referring to FIG. 6, Inertial stabilization systems are widely used in navigation, control, tracking, pointing, imaging, and stabilization systems. In this invention, we use a gimbaled system for a physical inertially-stable platform—gun turret, as a reference object model. When mounted on a vehicle, the gun turret is capable to point in a fixed direction in inertial space or with respect to ground in a short time period, that is, the motion of the vehicle is isolated from the platform. In practice, a two-axis pointing stabilization mechanism has two coupled servo control loops. In the analysis of the system, however, the two loops can be decoupled and regarded as independent. The automatic stabilization and pointing control system of the present invention is a feedback control system. The operator uses the target coordinates producer to capture and track a target to measure the desired pointing direction of the pointed device. The CPN (IMU/AHRS) is used to measure the current attitude of the gun turret. Using errors between the desired pointing direction and the current direction of the gun turret, the pointing controller determines platform rotation commands to the actuator. The actuator changes the current attitude of the pointed device to bring it into closer correspondence with the desired orientation.

[0296] The weapon turret smart machine weapon application is required to perform its missions in the presence of disturbances, parametric uncertainces and malfunctions, and to account for undesired vibrations. The Gun Turret Inertial Automatic Stabilization and Pointing system integrates the techniques of signal/image processing, pattern classification, control system modeling, analysis and synthesis. The system balances and optimizes tightly coupled signal processing and control strategies, algorithms and procedures. The Gun Turret Inertial Automatic Stabilization and Pointing controller further comprises:

• • [0297] a measurement data processing module, for transforming the target positioning measurements, measured by the target coordinate producer and corrupted with measurement noise, from the target coordinate producer body coordinates to local level coordinates;
  • [0298] a target position estimator, for yielding the current target state including target position estimation using the target positioning measurements;
  • [0299] a target position predictor, for predicting the future target trajectory and calculating the interception position and time of a projectile launched by the weapon turret and the target;
  • [0300] a fire control solution module, for producing the weapon turret azimuth and elevation required for launch of the projectile; and
  • [0301] a device control command computation module, for producing control commands to the actuator using the required weapon turret azimuth and elevation and current attitude and attitude rate data of the weapon turret from the CPN (IMU/AHRS) to stabilize and implement the required weapon turret azimuth and elevation with disturbance rejection.

[0302] The coremicro® Palm Navigator embedded with the coremicro IMU employs the MEMS technology to provide angle increments (i.e., rotation rates), velocity increments (i.e., accelerations), a time base (sync) in three axes and is capable of withstanding high vibration and acceleration. The coremicro IMU is a low-cost, high-performance motion sensing device (made up of 3 gyros and 3 accelerometers) measuring rotation rates and accelerations in body-fixed axes. The coremicro IMU based coremicro® Palm Navigator (CPN) is used as motion sensors for implementation of the intelligent remotely controlled weapon station with automated target hand-off.

[0303] Referring to FIG. 10, a shooter/sniper detection system determines relative shooter azimuth, range, and elevation from incoming weapons fire. Currently, there are several different approaches for detecting weapons fire:

• • [0304] Acoustic approach to detect the muzzle blast and/or the supersonic acoustic shock wave;
  • [0305] IR imaging approach to detect bullets in flight;
  • [0306] Optical approach to detect muzzle flash;
  • [0307] Optics Laser reflection approach.

[0308] At present, most successful sniper-detecting systems today are based on acoustic measurements. But there are still many problems in the practical field applications. Based on the inventors past experience, we will mainly follow the acoustic approach for the shooter detection system.

[0309] The shooter detection can be regarded as a function augmentation for the CPN. With this function augmentation, based on the CPN provided absolute position and the shooter detector determined relative position of the shooter (sniper), the CPN can determine the absolute position of the shooter and report the shooter position to the CDAS and/or other C3 or C4 systems for battlefield awareness enhancement, decision aiding and fire control.

[0310] When a shooting is detected, the shooter/sniper position and the bullet trajectory is indicated and displayed in different media, such as:

• • [0311] Indicate the relative position (heading/bearing) of the sniper on the local unit's screen or LED/LCD array;
  • [0312] Mark the sniper position on the local CDAS map;
  • [0313] Display the bullet trajectory on the local CDAS map;
  • [0314] Through the RF data link, the sniper position and bullet trajectory is displayed on all individual units engaged in the mission;
  • [0315] Through the RF data link, the sniper position and bullet trajectory is reported to other remote C3/C4 stations and command center.

[0316] Using AGNC's existing products and technology, the shooter detection system is wirelessly networked to AGNC's 4D GIS system, map system, CDAS, and other C3 or C4 systems.

[0317] In summary, the present invention provides a method and system for an innovative design of the automatic stabilization and pointing control of a device based on the MEMS technology, which is small enough and has acceptable accuracy to be integrated into many application systems, such as, laser pointing systems, telescopic systems, imaging systems, and optical communication systems. The stabilization mechanism configuration design is based on utilization of AGNC commercial products, the coremicro IMU and the coremicro AHRS/INS/GPS Integration Unit. The coremicro AHRS/INS/GPS Integration Unit is used as the processing platform core for the design of the MEMS coremicro IMU based stabilization mechanism.

[0318] A platform is utilized on which reside a viewing sensor and a pointing system/weapon (e.g. gun, gun turret, mortar, artillery, communication system, etc.). There is an operator that is remotely monitoring the scene on a display as viewed by the viewing sensor. The operator gazes, acquires and tracks targets by scanning the scene with his eyes and locking his eyesight onto a selected target. The operator subsequently tracks the target with his eyes. The system further comprises a dual camera sensor the operator is looking into that follows the operator's eyes. This sensor is monitoring the operator's eyesight motion while the operator simultaneously monitors the external viewing sensor's scene, locking and tracking with his eyesight some selected target. The display coordinates of the target, the operator has selected and is tracking, are utilized to point the pointing system/weapon on the external platform so that the operator can fire at the target when he so desires. The problem is thus summarized as one of controlling the weapon pointing, movement and firing on a target that has been selected and is tracked by the eyes of an operator viewing a display.

[0319] The present invention also provides a method and system for innovative Intelligent Remotely Controlled Weapon Station with Automated Target Hand-Off. The purpose of the Intelligent Remotely Controlled Weapon Station is to get the gunner out of the turret where he is exposed to enemy fire and fragments, and position him inside the vehicle for protection. The Shooter Detection System can be considered as a function augmentation to the coremicro® Palm Navigator (CPN). With this augmentation, using the CPN provided absolute position and the shooter detector determined relative bullet trajectory and position of the shooter (sniper), the CPN can determine the absolute position of the shooter and hand off the target to the fire control system by reporting the shooter's position to the local Intelligent Remotely Controlled Weapon Station. This is an automated hand-off situation for an individual unit of the Intelligent Remotely Controlled Weapon Station with a Shooter Detection System. The target acquired by a unit can be handed off to other units or C3/C4 systems centers.

[0320] As shown in FIGS. 1A and 1B, a target coordinate producer 8 using eye tracker measuring a desired pointing direction for the remote controlled weapon-firing of the device by capturing and tracking a target comprises a platform on which reside a viewing sensor 82 and a weapon 1 such as a gun, a gun turret, a mortar, an artillery, etc.

[0321] There is an operator system that is remotely monitoring the scene on a display as viewed by the viewing sensor. The goal of the operator system is to acquire and track a selected target by scanning the scene and locking onto a selected target according to the motion of the eyesight of an object. The operator system subsequently tracks the target.

[0322] The movement of the object's eyes is followed by a dual camera sensor of the eye tracker 81 that the object is looking into. This sensor is monitoring the object's eyesight motion while the object simultaneously monitors the external viewing sensor's scene, locking and tracking with his eyesight some selected target.

[0323] The goal is to translate the display coordinates of the target, the object has selected and is tracking, to point the weapon on the external platform so that the object can fire at the target when he so desires by using the operator system.

[0324] The problem is thus summarized as one of controlling the weapon pointing, movement and firing on a target that has been selected and is tracked by the eyes of an object viewing a display.

[0325] The external viewing sensor and the weapon are close to each other on an external platform. The operator can slew the platform to gaze at and search a large field of regard. The control achieves a smooth and accurate following of the target so that the weapon can successfully and rapidly engage the target. The viewing coordinates are translated to weapon pointing azimuth and elevation motion which accurately follows the target.

[0326] The design is general with a baseline that can be formulated and modified to take care of specific needs. For example, one can select eye tracking units that are already commercially available and COTS displays. One can select a platform and size it for a viewing sensor that can be useful for nominal target acquisition distances and select a machine gun that is already there, for shooting at objects, such as, helicopters.

[0327] As shown in FIG. 1C the operator can remotely monitor the scene on a display as viewed by the camera/telescope. The operator gazes at, acquires and tracks a selected target by scanning the scene with his eyes and locking his eyesight onto a selected target. The movement of the operator's eyes is followed by a dual camera sensor that the operator is looking into. This sensor is monitoring the operator's eyesight motion while the operator simultaneously monitors the external camera/telescope's scene, locking and tracking with his eyesight some selected targets. The display coordinates of the target that the operator has selected are translated to point the weapon on the external platform so that the operator can fire at the target when he desires.

[0328] The use of an autotracker is deemed to be of maximum benefit to the operator of a remotely controlled weapon system since, following initial designation by the operator, multiple targets can be autonomously tracked simultaneously, until the operator decides to engage them, Even in the single target case an autotracker can significantly alleviate the operator's monitoring workload.