Patent GB-1436742-A (GB)
Title: Elevator system
IPC: B66B1/28
Filed: 1973-05-02
Abstract: 1436742 Elevator speed pattern generation WESTINGHOUSE ELECTRIC CORP 2 May 1973 [17 May 1972] 20909/73 Heading B8L In a speed pattern generator for an elevator motor control system, the speed pattern signal is derived by two successive integrations, in time ramp generator 542, of a "jerk" signal controllably switched between positive and negative voltage levels, preset, using potentiometers 584, 586, Fig. 14, to represent a chosen tolerable value of jerk. Switch 587, controlling jerk signal switching, is controlled by a speed feedback loop connected from the output of integrator 596, and positive, and negative acceleration loops connected from integrator 594 so that, during constant or zero acceleration stages, the jerk signal is switched between positive and negative values at a higher rate than the elevator response time, so that its nett-effect is zero, see stages I, III, V, VII, Fig. 15A (not shown), representing respectively, zero, positive, zero, and negative constant values of acceleration. For stages II, IV, VI, VIII of changing acceleration, switch 587 remains closed, or open in dependence on the sense of acceleration change, the amplitude of the jerk stepped waveform (587, Fig. 15A) defining the amount of jerk present. Transfer of the system from stage I, (Fig. 15A) [car at rest] opens the production of a signal ACC, stopping switching of switch 587 in the closed position to produce progressively increasing acceleration (II) until comparator 644, Fig. 14, detects that the acceleration has attained the desired level preset in the acceleration demand circuit, whence switching restarts III, until comparator 600 detects attainment of a preset speed set in demand unit 614, whence switch 587 remains open to provide acceleration decreasing to zero (IV) as the highest car speed is reached at zero acceleration where switching restarts (V). Coupling 653 between speed and acceleration feedback loops is provided to stop the car overshooting the maximum preset speed. The deceleration pattern VI-VIII is similarly developed for lower car speeds, comparator 668 detecting when the preset car deceleration is reached. For higher speeds, signal MINA indicating attainment of maximum deceleration causes the control to switch from time ramp generator 542 to a deceleration characteristic controlled by unit 546, dependent upon the distance to go to the landing. Distance dependent slowdown, 546, see Fig. 17 (not shown).-Reversible counter 544 is counted up during car acceleration, the counting; under control of pulses developed by optical or magnetic detector (30), Fig. 1 (not shown), co-operating with a perforated pulley (26) driven by the car; being stopped at attainment of maximum speed. During deceleration, as the counter is counted down to binary twenty, its output, via D/A converter (960) controls circuit (964) whose analogue output, in view of multiplier (984) in the feedback of amplifier (982) is proportional to the square root of the count, leading to constant, distance dependent deceleration. A logic circuit ensures that D/A (960) receives the count twenty should the actual count fall below this. The deceleration signal is fed to output DSAN, whose lowest value is preset at point (1014) and communicated during acceleration to capacitor (1028) to be passed from there to terminal DSAN during distance dependent car deceleration to control the car at lower speeds, thus reducing accuracy requirements for the analogue circuit. Deceleration characteristic is preset in unit (976. 1000). Attainment of the minimum output of counter 544 causes car control to switch over to hatch transducer circuit 554, Fig. 12, controlling the last part of car movement to a landing. Control of car speed profiling overall is performed by driver 552, see Fig. 21 (not shown), controlling analogue switches 548, 550, 556 and 560, the latter being switched discontinuously, or providing a blend of signals TRAN/DSAN; DSAN/HTAN during a switchover period. The Specification discloses a terminal slowdown device, described and claimed in Specification 1,436,741. Features of the floor selector disclosed herein are described and claimed in Specification 1,436,743.