Patent GB-912737-A (GB)
Title: Improvements in or relating to automatic vehicle control arrangements
IPC: B61L17/02
Filed: 1961-01-27
Abstract: 912,737. Doppler radar. TELEFUNKEN G.m.b.H. Jan. 27, 1961 [Jan. 30, 1960], No. 3248/61. Class 40 (7). [Also in Group XXX] Relates to a railway vehicle shunting system in which a Doppler radar 1, Fig. 1, produces an output voltage u t , Fig. 6, corresponding to the speed of a shunted vehicle and the rail brakes are automatically released when said voltage falls below a predetermined reference value corresponding to a predetermined speed. According to the present invention the brakes are only released if the speed voltage u t  remain below said predetermined value for a predetermined minimum period of time T p , thereby preventing release of the brakes in response to a transient reduction T in u t  such as caused by variations in the reflection characteristics of the vehicle. Means are also described for compensating for the effect of (1) the delay time T p  and (2) the reaction time Tr between initiation of the brake release signal and the actual brake release. As shown in Fig. 1, the speed voltage u t  and a reference voltage from a source 4 are applied to an amplitude comparator 3 coupled to a bi-stable trigger circuit 5 which produces an output of predetermined amplitude as long as the amplitude of the speed voltage u t  is less than that of the reference voltage and the output from the trigger circuit is applied to an AND circuit 61 (1) directly and (2) through a delay line 6<SP>11</SP> producing a delay T p , the output from the AND circuit being used as the brake release signal. If the speed at which it is required to release the brake is v a  then the amplitude of the reference voltage is set at (u a + # u ) corresponding to a speed v a + #v, where #v=T p <SP>b</SP>max and b max  is the maximum deceleration of the vehicle. The output, Fig. 6b, from the trigger circuit 5 then comprises an unwanted component 9 due to the transient T and the wanted component 10 and the output control signal 11, Fig. 6c, from the AND circuit 6<SP>1</SP> corresponds to the wanted signal 10 delayed by T p . If the actual deceleration of the vehicle is less than b max  then as shown in Fig. 6 the brake release signal 11 is initiated slightly before the speed v t  has reduced to v a  and in order to prevent this voltages u t  and u a  are applied to an additional computer and trigger circuit, Fig. 2 (not shown), producing an output, Fig. 6d, which is applied together with the signal 11, Fig. 6c, to a further AND circuit to produce a control signal 16, Fig. 6e. In the Fig. 2 arrangement the voltages u t  and u a  may also be applied to the first comparator corresponding to comparator 3 in Fig. 1, the comparator being set to produce an output when u t  is less than u a + #u. When there is a delay T r  between initiation of the brake release signal 16 Fig. 6e, and the actual brake release this may be compensated in the Fig. 2 arrangement by automatically controlling the amplitude of the reference voltage ua by means of a computer, Fig. 3 (not shown), in accordance with the equation where u e  corresponds to the vehicle speed v e  at which the brake should be released. The value Tr is set into the computer manually and the value u e  may be set in manually or automatically by means which take account of the running characteristics of the vehicle. Similarly in the Fig. 1 arrangement utilizing a single comparator 3 the effects of the reaction time T r  and the delay time T  p may be compensated, Fig. 4 (not shown), by controlling the amplitude of the reference voltage u<SP>1</SP> a  in accordance with the equation Additional means may be provided, Fig. 5 (not shown), for preventing initiation of the brake release signal in the absence of the signals indicative of required operating conditions.