Relative position monitoring apparatus

Abstract

A relative position derivation, sensing and indicator system primarily adapted for conventional elevators. The system displays elevator position and travel direction at each floor with a relatively old fashioned appearing indicator apparatus including an "antique" faceplate and a simple rotatable pointer arm driven by a stepper motor assembly. Electronic solid state digital circuitry is employed to derive suitable control signals for driving the associated stepper motors which rotate the pointer arms associated with each position displayed. A plurality of vanes vertically aligned within the hoistway are provided with parallel, offset rows of perforations. A generally U-shaped vane reader traveling with the elevator car establishes a pair of rapidly pulsed, oppositely directed infrared light beams across a void-like channel formed between its sides. Suitable photoresponsive elements in the vane reader may receive and interpret the light pulses to sense the presence or absence of interposed vanes (and vane perforations) to derive digital data during car movement. Correlation means in the vane reader are provided to output two pairs of control signals, which are delivered to an associated drive circuit for correlating and generating a pair of complementary clock signals and a pair of complementary direction signals. A stepper motor processor correlates and processes the last mentioned signals for ultimately controlling associated stepper motor actuation circuits associated with the multiple stepper motors employed in conjunction with the indicator apparatus disposed at each floor.