Stabilizing control apparatus for robtic or remotely controlled flying platform

[0002] This application claims the benefit of provisional application Serial No. 60/111,843, filed Dec. 11, 1998.

[0003] The present invention relates generally to a flying platform which may be robotic or remotely controlled, and particularly to apparatus for controlling the attitude of a platform in flight employing positionable trough shaped air deflectors.

[0004] A flying platform is disclosed in U.S. Pat. No. 4,795,111 by Moller including one or more ducted fans, each duct having adjustable vanes oriented generally in a vertical direction. Adjustable spoilers are shown positioned between vanes and provide for control of pitch and roll. The vanes are adjustable so as to direct the air flow in a sideways direction providing impetus for horizontal flight. The overall configuration of this invention provides a relatively narrow profile having low aerodynamic drag, which is desirable for horizontal flight operations. However, the spoilers cause a reduction in the air flow which reduces the lift capacity.

[0005] A design that optimizes the efficiency in stationary hovering and low speed lateral motion would be highly desirable. Also, the mechanical control mechanism employed is complex, employing a combination of multiple spoilers for pitch and roll control with separate vanes for yaw control. A simpler design could substantially reduce production cost and increase reliability.

[0006] It is therefore an object of the present invention to provide an efficient attitude control apparatus for a flying platform.

[0007] It is a further object of the present invention to provide a flying platform with an attitude control apparatus having reduced mechanical complexity.

[0008] It is a still further object of the present invention to provide a flying platform with an attitude control apparatus having substantial control redundancy.

[0009] Briefly, a preferred embodiment of the present invention includes a flying platform constructed from an air duct with an air intake on the top and an exhaust at the bottom, having supported therein a clockwise rotating fan and a counter-clockwise rotating fan. Directly below the perimeter of the air duct exhaust are mounted a plurality of trough shaped air deflection assemblies each including a rotatably adjustable deflector of half trough shape for selectively scooping a portion of the drive air, and an adjacent stationary deflector of half trough shape for receiving the scooped drive air and redirecting it outward and upward from the air duct. A centrally positioned plate has a plurality of rods, each pivotably connected between the plate and a corresponding lever associated with each of the adjustable deflectors so as to couple the adjustable deflectors in or out of the drive air stream according to the position of the plate, thereby providing control over the pitch and roll of the flying platform. The plate is driven by first and second motors responding to input control signals. The control signals also direct the yaw of the flying platform by selectively providing independent speed control to each of the clockwise and counter clockwise fan motors resulting in duct rotation in a clock wise or counter clockwise direction accordingly.

[0010] An advantage of the present invention is that the improved control apparatus results in reduced drag presented to the drive air flow resulting in increased lift efficiency.

[0011] A further advantage of the present invention is that the reduction of mechanical complexity reduces production cost and increases reliability.

[0012] A still further advantage of the present invention is the provision of a substantial control redundancy resulting in a reduction in the probability of catastrophic failure.

[0013] FIG. 1 is an illustration of a VTOL aircraft with multiple adjustable air deflector assemblies;

[0014] FIG. 2 shows the detail of a deflector control assembly driven by two servo motors;

[0015] FIG. 3 is a more detailed illustration of the deflector control assembly of FIG. 2;

[0016] FIG. 4 illustrates the use of a half toroidal shaped trough as an air deflector, and

[0017] FIG. 5 illustrates the use of individual servo motors for each of a plurality of air deflector assemblies as shown in FIG. 1.

[0018] Referring now to FIG. 1 of the drawing there is shown a vertical take-off and landing (VTOL) aircraft 10 having an air duct 12 with an intake 14 on the top and an exhaust 16 on the bottom. A plurality of landing supports 13 are shown attached to the duct. A first motor 18 and second motor 20 are mounted coaxially within the duct 12 for driving first and second fans 22 and 24 respectively. The motors 18 and 20 are suspended by engine supports 26 connected between the duct 12 and the motors 18 and 20. The first fan 22 has a plurality of fan blades 28 which are shown configured so as to pull “drive” air from the intake 14 and expel it out the exhaust 16 when empowered by the first motor 18. Similarly, the second fan 24 has a plurality of blades 30 which are configured to pull “drive” air from the intake 14 and expel it out the exhaust 16 when driven by the second motor in a counter clockwise direction.

[0019] A number of adjustable trough shaped air deflector assemblies 32 are shown mounted in a circular array below the duct wall 34. Each assembly 22 has a stationary deflector 36 having a quarter cylinder shaped bottom 38 with quarter disk shaped ends 40, shown mounted with brackets 42 to the bottom of the wall 34. A similarly shaped adjustable deflector 44 is shown mounted pivotably at locations such as 46 to each of the stationary deflectors 36.

[0020] The adjustable deflectors are positioned by a deflector control assembly 50 shown in FIGS. 2 and 3 or by individual servo motors for each adjustable assembly 32 shown in FIG. 5.

[0021] The adjustment of the deflector assemblies 32 achieve control of “roll” and “pitch” of the VTOL aircraft, and control of the speed and relative speed of fans 22 and 24 control “lift” and “yaw”. There is a flight computer 52 which converts input signals to control signals for driving the first and second motors 18 and 20 and the deflector assemblies 32. The flight computer 52 receives and processes input from attitude sensor 54, and/or input can be received from a remote transmitter (not shown) by antenna 56, which is then converted by receiver 58 for input to computer 52. Alternatively, an electrical tether cable 60 can be used to pass input signals from a remotely located operator (not shown) to the computer 52.

[0022] The VTOL aircraft is propelled by the two ducted fans 22 and 24 which pull air into the duct from the top intake 14 and propel it downward to the exhaust 16 with sufficient thrust to exceed the weight of the VTOL aircraft and thereby cause it to rise. Yaw control i.e., around a vertical axis coincident with the axis of the duct 12 and motors 18 and 20 and fans 22 and 24, is provided by the independent differential control of the two motors (or engines) 18 and 20 and their respective fans 22 and 24. This allows an operator to achieve differential torque in either direction around the vertical axis, causing the vehicle to rotate, while maintaining the necessary thrust to achieve the commanded rate of climb or descent, or to maintain altitude.

[0023] Referring now to both FIGS. 1 and 2, pitch and roll are controlled by the air deflector assemblies 32 at the bottom exhaust end of the duct. Each assembly 32 has a length somewhat less than the duct circumference divided by the number of assemblies 32. The adjustable deflector 44 is positionable from a fully deployed position (as shown at 62 in FIG. 2) protruding into the interior of the duct so as to intercept and deflect a maximum of drive air passing therethrough, to a position fully retracted into the stationary deflector intercepting no drive air, such as at the dotted line 64 in FIG. 2. A leading lip 66 of the adjustable deflector is extended as shown from the cylindrical diameter 67 for the purpose of assuring that the airflow separates from the back side (such as at 68) of the adjustable deflector 44. The lip 66 keeps the line of separation of air flow from changing in an unpredictable manner as the deflector 44 moves which would cause the effective air thrust to change inconsistently, thus creating a stability problem. The function of the stationary deflectors 36 is to continue the turning of the air, which was begun by the adjustable deflector 44, to an angle of approximately 170 degrees (arrow A, FIG. 1) from the original downward direction (arrow B, FIG. 1). The air does not have to be turned a full 180 degrees, since the “moment” that is exerted on the duct 12 is almost at a maximum using approximately 170 degrees of turning. It is desirable, however, for the angle of turning of the airflow to be as large as possible. If the airflow were to be diverted outward, and not redirected upward, there would be a lateral force on the aircraft which would cause the aircraft to be vectored laterally, rather than to have only a controlling torque generated about its center of gravity. In this system, the drive air is not only diverted from exiting in a downward manner, it is exited upward, which further enhances the control torque available. This aspect of the invention will be more fully described in relation to the description of FIG. 3.

[0024] Yaw control is provided by the independent control of the two fan motors 18 and 20. The first fan 22 creates a circumferential swirling motion in the air which is then removed by the second fan 24 under normal flight circumstances. If the speeds of the fans are such that this swirl is not completely eliminated before the air is exhausted out of the duct 12, the aircraft will have a yaw moment. This effect is exploited by the flight control computer 52 to react to operator commands for yaw control by supplying the necessary control signals to drive the motors 18 and 20. A further advantage of the use of two motors is added safety, in that if one motor fails, the other motor has the capacity to bring the VTOL aircraft down in a controlled, automatically stabilized manner, avoiding a catastrophic free-fall landing. With only one motor operating, there is an unbalanced yaw torque applied to the aircraft, but the rotational inertia of the aircraft, in conjunction with a tail rudder (not shown), will limit the rotational velocity of the aircraft during descent.

[0025] Referring again to FIG. 2, there is an illustration of a deflector control assembly 50, referred to but not described in relation to FIG. 1. The figure shows the air duct 12 and deflector assemblies 32, omitting the other parts shown in FIG. 1 for clarity of illustration. Each deflector assembly 32 is shown to have a pivot rod 70 with a lever arm 72 mounted thereon. The assembly 50 has a plate 74 interconnected with the deflector assemblies 32 by push-pull rods 76 connected by ball joints 78 and 80 to the plate 74 and the end of each lever arm 72. The plate 74 has two slots 82 and 84 therein, orthogonally oriented to each other providing guidance for pins 86 and 88, each connected at one end of arms 90 and 92 being driven at an opposite end by drive shafts 94 and 96 of servo motors 98 and 100. The servo motors 98 and 100 are mounted to a bearing plate (item 112 in FIG. 3) upon which the plate 74 slides, and to a support assembly 102 with support arms 104 suspending the assembly 50 from the duct walls 34.

[0026] The servo motors 98 and 100 selectively rotate the arms 90 and 92 to position the plate 74 relative to the air duct wall 34, causing the push-pull rods 76 to either push on a lever arm 72 resulting in an adjustable deflector to rotate inward and upward to collect more drive air, or pull on a lever arm 72 causing the deflector to rotate down and outward into the stationary deflector away from the air stream.

[0027] FIG. 3 is a cross sectional view such as B—B of FIG. 2 showing two opposing push-pull rods 106 and 108, and illustrating a bearing assembly 110 between plate 74 and the bearing plate 112 attached to the motors 98 and 100. With push-pull rod 106 and 108 in positions 1 and 1′, the two adjustable deflectors 114 and 116 are at equal extensions as shown in positions 1 and 1′. In this position the aircraft would not experience any control force causing roll or pitch. With the plate 74 in a second position (not shown), the rods 106 and 108 would be in a second position 2′, causing the deflector 114 to be fully extended and 116 to be fully retracted resulting in a strong drag due to deflector 114 reducing the lift power at side A relative to side B forcing side B upward relative to side A causing a pitch or roll of the aircraft. Because of a non-linear relationship between the angle of the adjustable deflector 114, 116 or 44 (in general) and the amount of air deflected, the optimum position for the adjustable deflectors with the plate 76 in a centered position is at an angle D equal to about 30 degrees from fully retracted. The dashed lines 117 indicate an alternative placement of supports for the bearing plate and motors 98 and 100 attached thereto.

[0028] FIG. 4 shows an alternative embodiment using a single adjustable deflector 118 in the shape of a half torus (a hollow half donut shape), suspended below the wall 34 of the duct 12 by cables 120 shown attached to the duct wall 34 by anchorages 122, the cables shown passing under the torus 118. Again, the fans 22 and 24, motors 18 and 20 and miscellaneous other parts shown in FIG. 1 are not shown in FIG. 4 for ease of illustration, but are included in the operational aircraft. Of course, the deflector 118 of FIG. 4 replaces the deflectors 32 of FIG. 1 for purposes of the FIG. 4 embodiment. The deflector control assembly 50 is connected to the torus 118 by the push-pull rods 76 and serves to position the torus relative to the duct wall 34 in any direction within the toroidal plane so as to intercept greater or lessor portions of the drive air at a selected position around the duct wall and thereby providing roll and pitch control of the aircraft. The servo motors 98 and 100, bearing plate, etc. are supported by supports 124 extending from the interior duct wall.

[0029] FIG. 5 serves to illustrate an important embodiment of the present invention wherein a deflector control assembly is defined to include individual servo motors 126 positioning the adjustable deflectors 44. Although the figure is drawn to show only the air duct 12, deflector assemblies 32 and motors 126 for ease of illustration, the other parts shown and discussed relative to FIG. 1 are also to be included in the operational aircraft.

[0030] The use of an independent servo motor for each deflector assembly is an important feature in that unlike the embodiments of FIGS. 2-4, all of the adjustable deflectors 44 can be retracted at the same time allowing maximum drive air for vertical propulsion. Separate control over each deflector can then result in the minimum of air deflection necessary for a given required maneuver. The motors 126 are all connected to the flight computer 52 for receiving control signals through lines 128. An added benefit of individual motors 126 for each deflector assembly 34 is a redundancy of control, providing an added safety feature.

[0031] The above discussed embodiments including descriptions of certain construction methods are given by way of illustration, but many other ways of fabricating the various parts such as servo motors, linkages, supports, etc will be apparent to those skilled in those arts. It is therefore intended that the following claims be interpreted as covering all such alterations and modifications as fall within the true spirit and scope of the invention.