| 摘要 |
1,198,053. Position-finding. NATIONAL RESEARCH DEVELOPMENT CORP. 26 July, 1967 [26 July, 1966], No. 33634/66. Heading H4D. [Also in Division G3] In a system for causing a vehicle to follow a physical contour, the contour is detected by repeated scanning transversely to the direction of travel and the point in the scan at which the contour occurs is utilized to control the vehicle steering automatically. As applied to the automatic guidance of an agricultural tractor to follow one furrow edge when ploughing another parallel to it, the output of a high frequency oscillator 55, pulsed by a generator 51 and amplified at 59, is applied to an ultrasonic transmitter 45 which together with an associated receiver 47 is directed downwardly and continuously reciprocated on the tractor transversely to the direction of travel so that when the tractor is in a desired position relative to the previously ploughed furrow the latter is below the centre of reciprocation. Each pulse from generator 51, after delay at 77, also operates a flip-flop 75 which is later re-set by the signal reflected from the ground received at 47 and amplified, demodulated and shaped by stages 63, 65, 69 and 73. Flip-flop 75 is thus operated for a period corresponding to the reflection distance and charges a condenser in a Transistor circuit 81 to a corresponding voltage so that a pulse of corresponding amplitude is produced by a differentiating circuit 82. Pulses exceeding an amplitude determined by the setting of a potentiometer 85A biasing a diode 87, corresponding to the increased distance to the bottom of the furrow, are applied to a logic circuit AGA which also receives pulses from a switch 95 operated when the ultrasonic transmitter passes the centre of reciprocation. The logic circuit determines whether the furrow is to the right or left of the centre of reciprocation and energizes the appropriate solenoid SA or SB to operate an hydraulic steering motor 121 in such sense and for such a time that the tractor is brought to its correct position. Mechanical feedback may be arranged between the steering mechanism and the ultrasonic transmitter to prevent overshoot. Undue incorrect operation of the steering if a reflected pulse is not received is prevented by applying the pulses from generator 51, without delay, to re-set flip-flop 75. Instead of reciprocating the ultrasonic transmitter and receiver, a plurality of fixed transmitters and receivers, operating at the same or different frequencies, may be arranged across the vehicle and switched into operation in succession. |
