Elevator absolute landing position sensor using infrared interrupter and MEMS accelerometer

Absolute encoder is a common solution to detect the position of elevator cabin in a reliable way, yet it require extra cabling and chain to accomplish the work. The installation and maintenance cost is the main trade-off. However, absolute position is only required by certain cases such as re-leveling. This is a situation where loading of the elevator cabin changes makes the elevator steel rope extends. The worst situation for a high-rise building may have more than 10 mm shifting in the elevator cabin platform. Such an offset between the cabin platform and floor level can stumble passenger boarding or disembarking. In this proposed design, a linear position sensor detecting the position of landing zone vane is targeted to provide position sensing resolution up to 0.01 mm with maximum of 1mm error, using traditional infrared interrupter and new MEMS accelerometer. The device can help to improve motion control of the elevator with its high resolution and high accuracy to prevent position overshooting and steady state error. Kalman filter is employed to fusion the detected position and acceleration signal and outputting a clean and reliable position reading to the elevator motion control system.