GB1493191A - Controlled mechanical system - Google Patents

Abstract

1493191 Change-speed control TEXAS INSTRUMENTS Ltd 2 Jan 1975 34/74 Heading F2D A controlled mechanical system comprises a control system and a mechanism, such as an automatic transmission on a motor-vehicle, or a chemical process plant, which is required to assume a number of different states at different times, the control system, shown as electronic, including a number of stages A, B, C corresponding to the respective states and each having set and re-set conditions, and a control unit 1 for setting a selected stage only when that stage is adjacent to a stage already set and for thereby initiating a corresponding change of state of the mechanism, and for re-setting a previously set stage in response to such setting, and a verification unit 9 for comparing an indication of the state of the mechanism with the control system stage which is set and for inhibiting operation of the control unit if they do not correspond. The control is described with reference to an automatic transmission only. The upper part of Fig. 1 represents the electronic control system having three stages A, B, C, and the lower part the mechanical system capable of assuming three corresponding states A<SP>1</SP>, B<SP>1</SP>, C<SP>1</SP>, coupled by elements 5 ... 8, controlled by signals a<SP>1</SP>b<SP>1</SP>... c<SP>1</SP>b<SP>1</SP> from the control unit 1 at 4, and producing the change of state (i.e. ratio shift) by operating mechanical valves, switches or solenoids. The electronic stages A, B, C are connected by various AND and OR gates shown, which receive corresponding input signals ab ... cb from the control unit 1 at 3, to set and re-set the respective stages. In operation, assuming that the stage A is set, the mechanical system is in state A<SP>1</SP>, e.g. first ratio, and the control is to initiate a change to mechanical state B<SP>1</SP>, e.g. second ratio. In the established first ratio condition stages B and C will be re-set (i.e. disestablished) so that the verification unit 9 will receive from the electronic and mechanical systems signals which are in correspondence, causing it to issue an enabling signal 23 to the control unit 1, which receives input signals 2 representing output speed and engine throttle angle. When these require the 1-2 upshift, the control unit 1 issues ab and a<SP>1</SP>b<SP>1</SP> signals to the electronic and mechanical systems respectively, the former taking effect first due to time lag in the mechanical system. The ab electronic signal is applied to an AND circuit 10 along with a signal from the stage A, indicating that the latter is set, which activates the AND circuit 10 and a following OR circuit 12 to set the stage B, which then activates AND and OR gates 13, 14 to re-set (i.e. disestablish) the stage A. With stages A and B now signalling the verification unit 9 re-set and set respectively, there is lack of correspondence with the lagging mechanical signals, causing the unit 9 to erase the enabling signal 23 to the control unit 1, which is now unable to command any further shift, until after the time lag necessary for the mechanical a<SP>1</SP>b<SP>1</SP> signal to change from stage A<SP>1</SP> to B<SP>1</SP> (1-2 upshift), thereby restoring correspondence in the verification unit 9, which then again issues the enabling signal 23 to the control unit ready for the next shift. Should correspondence not be obtained within the predetermined time, the verification unit 9 would issue an alarm at 24. Further, since one input to the AND circuit 10 is the output of stage A when set, the shift to B cannot occur unless A is initially set. The remaining AND and OR circuits act similarly for the 2-3 upshift and the downshifts. Fig. 4, not shown, is a block diagram of a control system for three forward and one reverse ratios, neutral and park, established by four hydraulic cylinders or solenoids (a ... d, not related to the signals above described), all of which are de-energized in high ratio; two (bc) energized in intermediate ratio; two (b, d) energized for manual low; two (ad) for reverse; one (a) for neutral and park; and one (b) for automatic low. A delay condition is provided to smooth the shift between intermediate and high, with one (c) energized above. During shift from reverse to manual low, high ratio is temporarily established. The energization sequences are tabulated in Fig. 3, not shown. The input to the control unit is from a manual selector lever (201), a throttle angle potentiometer (203) and a proximity pick-up speed sensor (205). Signals representing the mechanical state are produced by microswitches operated by the ratio actuators. Pulses from a clock generator (206) control operation of the system.