Attitude Control With Sensors on a Mining Vehicle

This invention relates generally to vehicles, such as model airplanes, pilotless surveillance airplanes, helicopters, space vehicles and submersibles. Such vehicles require a command guidance system and a servo mechanism built into the vehicle which may be controlled by devices on the vehicle or from a remote signalling station.

In recent years control systems of various kinds have been used to control flying vehicles or other vehicles moving through a wave transmitting fluid such as radiation being transmitted through the air or sound being transmitted through water. Examples of such control devices for use in flying vehicles are shown by the U.S. Pat. No. 3,162,764 to Haviland which utilizes a number of heat sensors which are aimed at a reference body such as the sun, which is much warmer than the adjacent free space. These heat sensors, properly aimed are used to operate thrust devices to control the orientation of the vehicle.

The U.S. Pat. No. 3,571,572 to Falbel utilizes infra red heat sensors which are designed to receive radiation only from a thin strip of the earth's horizon.

The U.S. Pat. No. 2,828,930 to Herbold is somewhat similar in that it employs infra red heat detectors and uses the horizon as a reference plane.

The U.S. Pat. No. 3,472,468 to Strafford also employs thermal or infra red heat detectors to use the discontinuity in temperature between a reference body and the surrounding space, as an aid to keep the space vehicle stabilized.

The U.S. Pat. No. 3,496,367 to Eckermann utilizes a number of light sensitive elements to determine when light falling on the vehicle is within a predetermined small angle of incidence, and uses this information for controlling the attitude of the space vehicle.

The U.S. Pat. No. 3,020,407 to Merlen uses infra red sensors to produce a signal which indicates the orientation of the space vehicle.

The U.S. Pat. No. 2,740,961 to Slater relates to a stable reference apparatus using lens focussed infra red radiation detectors mounted on gimbals as part of a reference apparatus for a flying vehicle.

The U.S. Pat. No. 4,223,214 to Dorian relates to a solar tracking device designed to direct a solar energy collector toward the sun and has a mechanism for tracking the sun with some safeguards to prevent overheating.

All of the above described patents are designed for control systems in situations where cost is not a factor, and they are not practical for model or pilotless aircraft.

The invention disclosed herein is based on the phenomenon that radiation from the sun, such as ultraviolet light is scattered strongly by the atmosphere and is absorbed strongly by solid objects such as the ground. This means that an ultra violet light sensor directed at the sky would respond strongly, whereas the same sensor directed at the ground would have very little response. This invention utilizes this phenomenon by using photocells of the kind whose resistance changes in accordance with the intensity of the radiation falling on it. The photocells are filtered by suitable means so only ultra violet light falls on them so they function as ultra violet light sensors. They may be used as part of an automatic pilot mechanism for aircraft, or on missiles, pilotless aircraft, or model airplanes, etc. These photo cells are connected together at a junction to form a voltage divider which produces a ratio signal whose magnitude is directly related to the attitude of the vehicle. In the embodiment shown in the drawing the sensors are mounted on the sides of the fuselage of a model aircraft, although it is understood that the drawing is for illustrative purposes only.

Referring to a model aircraft, or to a pilotless surveillance aircraft, if the aircraft is banking, one ultra violet light sensor is directed at the ground and as a result it will sense very little signal. The other ultra violet light sensor directed at the sky, will sense a strong signal. If the aircraft is flying horizontally, and the sensors are connected in series, both sensors will receive the same intensity of signal so the output signal would be one half of the voltage supply.

Because of this, the difference in intensity between both sensor is functionally related to the bank angle of the flying vehicle. Similarly if ultra violet sensors are positioned at the front and rear of the flying vehicle, and if the aircraft climbs or dives, one ultra violet light sensor directed at the sky will sense a strong signal, while the other ultra violet light sensor directed at the ground will receive a lessor signal. The difference voltage at the junction of the ultraviolet light sensors will be functionally related to the attitude of the aircraft.

An electric circuit connected between the ultra violet light sensors and a servo mechanism mounted in the flying vehicle would operate the control surfaces of the flying vehicle in accordance with a command attitude signal which could be mounted on the vehicle or could be transmitted from a remote place by a radio station on the ground.

Since ultra violet light sensors are very much cheaper than infra red sensors, the cost of such a control system would be well within the reach of even model airplane flyers.

For the most part to this point, this invention relates to vehicles which utilize the ultra violet light in the sky as illuminated from the sun as the source of radiation. It is contemplated, however that the principles of this invention could be practiced by other kinds of vehicles, such as submersibles, where instead of radiation, sensors detect ultra high frequency sound used to maintain a submerged pilotless vehicle at a command attitude, where the source of the high frequency sound may be at a considerable distance from the vehicle.

What is needed therefore and comprises an important object of this invention is to provide a control system for flying vehicles which is simple to make, economical, and reliable.

These and other objects of this invention will become more apparent when better understood in the light of the accompanying drawings and specification wherein:

FIG. 1 is a perspective view of a model airplane with ultraviolet light sensors positioned on opposite sides of the fuselage of the aircraft and showing a radio transmitter sending a command signal to the model airplane.

FIG. 2 is an elevational view of the sky and the horizon showing an aircraft flying in the sky with both wings level, and showing the ultraviolet light scattered by the earth's atmosphere.

FIG. 3 is a view similar to FIG. 2 except that the airplane is banking and the ultra violet light sensor directed toward the ground receives low intensity ultra violet light, while the ultra violet light sensor directed toward the sky receives much more intense ultra violet light.

FIG. 4 is a block diagram depicting the electrical components in the form of blocks and showing their connection to the ultra violet light sensors.

FIG. 5 is a plan view of a photo-responsive cell modified for use as an ultraviolet light sensor.

FIG. 6 is a cross sectional view of the photo-responsive cell taken on the line 6--6 of FIG. 5 and showing the ultra violet light filter in front of the photo-responsive cell.

FIG. 7 shows the schematic electricl diagram of the control system for the aircraft.

Referring now to FIG. 1 of the drawing, a pilotless aircraft indicated generally by the reference numeral 10 is shown in perspective view with left and right uv sensors 13 and 14 mounted on each side of the nose portion of the aircraft. The control surfaces (not shown) on the aircraft are controlled by the radio transmitter 12 on the ground which transmits a command signal to the aircraft. This compares the signals from the ultra violet light sensors 13 and 14 and causes the electric circuit 22, see FIG. 4 to control the servo mechanism in accordance with the requirements of the command signal.

As shown in FIGS. 5 and 6, the ultra violet light sensors 13 and 14 are formed from a pair of photo-responsive cells such as photo-conductive or photo-electric cells 38 (hereafter referred to as photo-cells) which are connected together to form a voltage divider. Light from the sun, falling on the respective photo-cells cells changes their respective responses in accordance with the light intensity. Consequently the voltage at the junction 15 between the sensors is a ratio signal having a magnitude which is a function of the attitude of the vehicle, see FIGS. 4 and 7.

These photo-cells are covered by a special glass 40 such as Shott glass UG-11 which acts as an ultra violet light filter. With the filter 4 mm thick, the only radiation transmitted has a wavelength of less than 410 nm. These photo cells are mounted securely on supports 46 and 48, see FIG. 6.

As stated above, the ultra violet light from the sun is scattered over the upper atmosphere particularly during overcast conditions, while the ground reflects only a tiny portion of the ultra violet light. Accordingly, if the plane is level, as shown in FIG. 2 both sensors 13 and 14 receive an equal amount of ultra violet light, and since the sensors are connected in series and their resistances are equal, the output of the sensors at terminal 15 is one-half of the power supply voltage.

However if the aircraft is banked, as shown in FIG. 3, one ultra violet light sensor directed at the sky receives a strong signal, while the opposite sensor directed at the ground receives a lesser signal.

With this arrangement, a current will flow from terminal 15 to the inverting amplifier 30, see FIGS. 4 and 7. This current flows through the 160K resistor R21 and through the bypass 100K resistor R22 to the output terminal 50. These voltages must be amplified to a level comparable to the DC output voltage from the inverting amplifier 28. To do this the circuit power supply Vcc is connected through the 100K resistor R23 and the grounded 125K resistor R24 to the input of the inverting amplifier 30. This increases the voltage level at terminal 50 so it can be more easily matched with the voltage ouput of inverting amplifier 28 at terminal 52. This also requires that the power supply Vcc be connected through the 425K resistor R11 and the grounded 100K resistor R12 to the positive input of inverting amplifier 28.

The transmitter 12 from the ground sends out square wave pulses which represent the command bank angle. These pulses are filtered by a network comprising the 160K R2 resistor, the grounded 47K R3 resistor, the 27K R4 resistor, and the 0.1 uf by pass capacitor C2 and the grounded 0.1 uf capacitor C1 all connected to the operational amplifier U1 which comprise the low pass filter 24 at output terminal 55.

The signal at terminal 55 is further filtered by the operational amplifier U2 which is connected to the 160K resistor R5 and the 160K resistor R6 and the grounded 47K resistor R7 which is in series with the 27K Resistor R8. As in the low pass filter 24, a by pass 0.1 uf capacitor C4 and a grounded 0.1 uf capacitor C3 form the second filter at the output terminal 57. The smoothed signal at terminal 57 is amplified by the inverting amplifier 28. This amplifier comprises the operational amplifier U3, a network comprising a 100K resistor R9, a by pass 229K Resistor R10, and a voltage supply VCC connected to the inverting amplifier to the the 425K resistor R11 and the grounded resistor R12. The junction of resistors R11 and R12 are connected to the positive input of the operational amplifier U3. The output voltage of the operational amplifier U3 at terminal 52 is proportional to the width of the square wave pulses.

Terminal 52 is connected through the 100K resistor R13 to the negative input of the inverting amplifier 32. The 100K resistors R 13, 14, 15, and 16 are chosen so the output of the inverting amplifier at terminal 54 is a voltage equal to the difference between the voltages 50 and 52 which are functionally related to the bank of the aircraft and the commanded bank angle respectively.

A servo mechanism (not shown) is connected to the control surfaces (not shown) of the aircraft 10 and is designed to operate when it receives signals with the correct pulse width and frequency. The nominal pulse width at terminal 60 is controlled by the 25K resistor R18 and the grounded 0.1 uf capacitor C5. The variation in pulse width is controlled by the output of the 1000 ohm resistor R17 at terminal 61. The astable multi-vibrator 36 powered by the voltage VCC which is connected to the 7.1K resistor R19 and the 271K Resistor R20 and the grounded 0.1 uf capacitors C6 the output of which at terminal 56 controls the frequency of the pulse width. This terminal is connected to the input terminal 58 of the monostable multi-vibrator 34. The output terminal 60 of the mono-stable multi vibrator 34 with pulses of the correct width and frequency are connected to the servo mechanism which guides the airplane.