GB1263875A - Speed dictation apparatus for elevator motor control system - Google Patents

Abstract

1,263,875. Automatic control of lifts. OTIS ELEVATOR CO. Jan.20, 1970 [Feb. 3, 1969j, No.2798/70. Heading G3R. A high-speed lift car is operated by a hoist motor controlled by a speed regulator which receives a time-dependent signal during acceleration of the car. On receipt of a signal requiring the car to stop at a landing, the time-dependent signal changes to a deceleration command, and the manner of deceleration is brought into conformity with a distance-dependent signal generated by a landing selector mechanism. In the system shown, a lift car 10 is driven by a motor 14 which also drives a tachogenerator 17 to provide a voltage proportional to the speed of the car. The motor is supplied through a control 15. A tape 19 drives the shaft 694 of a landing selector device 22, the shaft being connected by way of gears GB1-3 with switch-controlling cams AFDC, HXC, and with sliders of potentiometers POT1-2. One input to the motor control 15 is provided by an integrating operational amplifier MIA, which in turn receives a time-controlled signal through function generators connected to a capacitive circuit in series with input resistor DAR1, Fig.2 (not shown). Logic diagrams and corresponding NAND circuits are described with reference to Figs.3a, 3b and 4 (not shown). In operation, when a start signal 13 received, an acceleration function generator charges the capacitive circuit and the lift 13 caused to move with increasing acceleration until a desired acceleration is reached. This 13 held cbnstant until the desired maximum velocity is approached. This is signalled by a comparator circuit embodying a fixed reference voltage. Subsequently, the car speed is clamped at this desired maximum. When the car reaches a point a predetermined distance away from the desired stop, a decelerating function generator takes over, but before the car is halted, a further comparator circuit operates to bring in a distance-dependent signal defined by the drive of the cams and potentiometers by gears GB1-3. This signal forces the amplifier MIA to provide an output to the control 15 which ensures stable deceleration of the car until it is close to the selected landing, at which point contacts HXA1 are opened and contacts HXA2 are closed, so that control is removed from the amplifier MIA and transferred directly to the potentiometer POT2 which brings the car rapidly and accurately to the landing level. In the case of a short journey, the car is prevented from reaching its full rated speed since it could not be stopped in the required distance with the normal deceleration rates. In this situation, the rate of change of acceleration is constrained to a negative value when the car is still in the accelerating phase.