Abstract: An elevator moves through a hoistway with one or more sensors positioned so that they pass by one or more targets that are in fixed positions relative to the hoistway. As they pass, an inductive current is generated, giving the elevator's control circuitry precise information as to the vertical position of the elevator car. The control system adjusts the raising and/or lowering of the elevator car based on that position information and any discrepancy between it and the supposed position at which the control system had believed the car was. Discrepancies are accumulated over time as an indication of cable stretch, and when the stretch exceeds a particular threshold, an alarm is raised for maintenance. The control system also defines a “door zone” around each landing where, based on the precise height measurement achieved herein, it is safe under the circumstances to open the doors of the car.

Abstract: An elevator moves through a hoistway with one or more sensors positioned so that they pass by one or more targets that are in fixed positions relative to the hoistway. As they pass, an inductive current is generated, giving the elevator's control circuitry precise information as to the vertical position of the elevator car. The control system adjusts the raising and/or lowering of the elevator car based on that position information and any discrepancy between it and the supposed position at which the control system had believed the car was. Discrepancies are accumulated over time as an indication of cable stretch, and when the stretch exceeds a particular threshold, an alarm is raised for maintenance. The control system also defines a “door zone” around each landing where, based on the precise height measurement achieved herein, it is safe under the circumstances to open the doors of the car.