Patent GB-647724-A (GB)
Title: Improvements in or relating to navigation and vehicle control systems
IPC: G01S13/935
Filed: 1947-08-01
Abstract: 647,724. Automatic control systems for radio navigation. SPERRY GYROSCOPE CO., Inc. Aug. 1, 1947, No. 21031. Convention date, March 31, 1943. [Class 38 (iv)] [Also in Group XL (c)] Obstacle detection apparatus on a vehicle provided with a device controlling its motion comprises means for radiating electromagnetic energy into a sector of space and receiving echo signals reflected from objects in the said sector, means for producing an electrical output in response to signals from only'those of the said objects that are at less than a predetermined range, and means for controlling the motion control device in response to the electrical output. In the pulse system described a pulse transmitting and receiving system T, including a narrow beam spirally scanning aerial system of the spin and nod type, radiates pulses under the control of pulse generator 12. Echo signals are received by receiver R and displayed by intensity modulation on the screen of a cathoderay tube 24 which is scanned spirally under the control sweep circuit 26 in synchronism with the movement of the antenna. To adjust the automatic control device to avoid objects within a certain solid angle in front of the vehicle carrying the apparatus a second cathode-ray tube 42 is scanned similarly to tube 24 and has an electrode 47 disposed on its screen. Whenever an echo signal appears on the electrode area of the screen 46 a current flows in line 52. Amplifier 45 having adjustable amplification, and also imposing adjustable bias, is connected in the deflection leads to the tube 42 so that the effective shape and position of the area of view scanned which corresponds to electrode 47 may be altered. To render the alarm or control effective only when echo signals within the desired solid angle are returned from objects within a certain distance a further cathode-ray tube is scanned horizontally by a saw-tooth sweep generator 67 triggered by the pulse generator 12. Echo signals direct from receiver R are arranged to cause vertical deflections of the trace which is normally biassed so as to be below the level of electrode 66 mounted to one side of the tube screen. Echo indications occurring within the area of electrode 47 of tube 42 serve to brighten the trace of tube 61 at the moment of their occurrence and providing they are within the range covered by electrode 66 a signal is obtained over line 74. An alternative to the use of the tube 42 is indicated at 75 and comprises an onverload relay which only completes the circuit for the echo signals to reach tube 61 when the deflection potential from one of the outputs of the sweep circuit is below a certain value. The range tube may be replaced by a gate circuit (Fig. 2, not shown) and the maximum range from which echo signals are effective may be adjusted according to the velocity of the craft. Switch segments, 84 and 85, Fig. 1, effective during each scanning period of the antenna system may be used, to switch on the beam of the cathode-ray tube 61 when the antenna is directed downwards at a certain angle (e.g. 45 degrees) from an aircraft and in the vertical fore-and-aft plane of the craft so that if the ground comes with a given distance the automatic pilot is adjusted to direct the craft upwards and, if required, a warning given. An arrangement for maintaining an aircraft at a suitable height above ground is shown at Fig. 4. Normally the elevation control 57 of the automatic pilot 58 is set to a desired value and barometric device 99 serves to maintain the craft on a horizontal course. However, when there is a pulse signal output from ground clearance meter 116, which may correspond to Fig. 1, the output being that of line 74 thereof, relay 111 is operated to break the barometric control circuit and to complete the circuit from battery 128 through relays 111 and 122 and thermostat switch winding 132. Relay 122 draws rack 118 down against the tension of spring 124 so rotating pinion 119 to re-adjust the elevation control of the pilot device 58 through slip clutch 121 and cause the craft to rise. After a delay time determined by the bimetallic strip the circuit through relays 111 and 122 is broken and the barometric control of the craft recommenced. If the ground clearance meter continues to detect the presence of an obstacle in the danger area relay 111 is re-energized and the cycle of operations repeated until the obstacle is no longer a danger. The sensitivity of the relay 111 is controlled by resistor 137 and capacitor 138 the constants of the system being arranged so that a single moving object, for example another craft crossing the flight path, will not operate the relay. Specification 525,617, [Group XXXIII], is referred to.