Patent GB-1410653-A (GB)
Title: Systems for surveying and concreting trajectories
IPC: G01S13/933
Filed: 1972-05-26
Abstract: 1410653 Navigational simulators SOC FRANCAISE D'EQUIPEMENTS POUR LA NAVIGATION AERIENNE 26 May 1972 [27 May 1971 (2)] 24845/72 Heading G4G In an avoidance (or co-incidence) system, a moving object M carries apparatus which simulates trajectories T 1 , T 2 , T 3  &c. divergent from its actual (but simulated) trajectory T 0  until the computed passing distance for a particular trajectory T exceeds (or falls below) a prescribed distance S from a stationary or moving target M i , upon which the apparatus passes a command signal to modify the speed and heading of the object M. As applied to an aircraft avoidance system, the A/C carrying the apparatus may respond to a series of other A/C's and fixed obstacles, and the trajectories of the other A/C's may also be simulated by the apparatus from bearing, speed and distance data. The trajectory simulator 11, Fig. 1, is supplied with signals corresponding to initial co-ordinates x 0 , y 0 , and initial heading # 0 . In addition signals corresponding to initial velocity V 0  and initial heading rate #<SP>1</SP> 0  (first time derivative of #), are supplied under command of monostable circuit 12. A trajectory simulator 15 for a relevant target M i  is connected to a converter 16 which receives initial values a i0  and γ i0  of distance and bearing and transforms them into the coordinates x i0  and y i0  of the target M i . In addition. simulator 15 receives signal # i0  representing initial course and, under control of monostable 12, signals V i0  and #<SP>1</SP> i0  representing initial speed and angular speed. When commanded by monostable 12, the simulators 11, 15 generate trajectories of M and M i  to the same time base and two subtracting devices 18, 19 determine X i  = (x i -x) and Y i  = (y i -y). From these signals, circuits 21, 22, 23, 24 calculate the simulated distance between the trajectories The signal a is  is compared to a reference distance S in comparator 26 which emits a pulse I depending upon the sign of (a is -S). Also, a differentiation circuit 27 and pulse generator 28 produce pulses A, B dependent upon the sign of the derivative a<SP>1</SP> is . For avoidance, when B corresponds to negative a<SP>1</SP> is , a voltage generator 31 emits an incremental signal ##<SP>1</SP> upon receiving pulse I which is only generated when (a is -S) becomes negative. At the same time, monopulse 12 is triggered by a signal (I+B) produced in the adder 32. If no pulse I is received during the time that a<SP>1</SP> is  takes to become positive, signal B corresponding to positive a<SP>1</SP> is  causes the voltage generator 31 to return to zero. Signal A controls a blocking circuit 33 which allows signal C to be supplied to the controls of the A/C when A corresponds to positive a<SP>1</SP> is . Signal C depends upon increment ##<SP>1</SP>. When a is  is greater than S and a is  is positive, no further simulation is carried out. In other circumstances, incremental signal ##<SP>1</SP> is added to signal #<SP>1</SP> 0  in adder 13 and fed to simulator 11 which carries out a simulation using angular speed (#<SP>1</SP> 0  + ##<SP>1</SP>) under command of monostable 12. The increment ##<SP>1</SP> may assume successively the values of the terms of an alternating progression, e.g. 0, c, - c, 2c, - 2c, 3c &c. When simulation stops and control signal C has been sent to the A/C controls, voltage generator 31 returns to zero and monostable 12 is triggered to cause the device to deal with a new target M i . Since the initial simulator distance a is  is much greater than the value at which simulation ceased for the previous trajectory, the value of a<SP>1</SP> is  becomes momentarily positive, a state of affairs which normally would result in a new control command C. To prevent this, the control signal from the monostable 12 is fed via line 121 to a blocking input of the pulse generator 28. When used in the "approach" mode, the circuit is modified so that comparator 26 only produces pulse I when signal (a is -S) is positive, and voltage generator 31 sends increment ##<SP>1</SP> to adder 13 only when I is emitted and B represents positive a<SP>1</SP> is . The mode of operation is otherwise analogous to the "avoidance" operational mode described above. In addition to signals ##<SP>1</SP> corresponding to incremental angular velocity, the pulse generator 31 may be modified to supply signals #V of incremental linear velocity for addition to the initial speed signal V 0 . Further, a command corresponding to #V may be sent to the A/C controls. In a modification of the circuit of Fig. 1 (Fig. 4, not shown), two additional simulators (43, 44) give outputs corresponding to the actual trajectories of the target and A/C, and these trajectories are displaced on a multiple-trace oscilloscope (45). The existing simulators 11, 15 operate on a timebase about twenty-five times faster than the additional simulators and receive signals corresponding (as before) to incremental angular and linear velocities. The rapidly simulated hypothetical trajectories are displayed on the same screen as the actual trajectories. The Specification gives detailed circuitry for the simulators, distance calculators and logic circuits.