Jerk limiting in elevator rescue system
Abstract:
An elevator rescue system allows an elevator car of an elevator to be moved in an emergency situation. The elevator includes an elevator motor acting on hoisting ropes by which the elevator car is suspended including at least one electro-mechanical brake and an encoder outputting a signal corresponding to its speed. The rescue system includes a back-up power source, a jerk monitoring circuit connected to the encoder and including a memory storing an upper threshold value for the derivative of car acceleration, a brake feed circuit controlled by the jerk monitoring circuit, and a release switch connected to the jerk monitoring circuit and/or to the brake feed circuit. The release switch activates the brake feed circuit to release the brake, and initiate the jerk monitoring circuit to compare the derivative of car acceleration derived from the encoder signal with the stored first upper threshold value, and forwards a control signal to the brake feed circuit to initiate/stop braking depending on the comparison result.
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