Obstacle Detection for Power Folding Seats

In the past years the automotive industry has equipped it's vehicles with more and more automated power driven functions. Starting with the “express up/down ” functions for power windows and “easy entry/exit” functions of memory seats, automated power movements have also been introduced into power sliding doors as well as power liftgates. In contrast to “press & hold” switch activated movement, where the operator takes responsibility for the movement, the control unit of the “automated” or “one-touch” movement has to provide some sort of obstacle detection or pinch protection.

This paper deals with the adaptation of a pinch protection algorithm for linear movements like power windows or memory seat applications to the rotational movement of power folding seats. With the considerable weight of a seat that is involved the motor torque changes along the travel of the seat, sometimes even reaching negative values in those positions where obstacles would most likely need to be detected. On the other hand, obstacle detection must be less sensitive in areas where the seat needs to be moved against gravity and where complex seat mechanics introduce non-linear torque requirements. The paper addresses these issues and describes basic functionality, such as how to obtain a voltage compensated torque equivalent signal from a hall sensor speed signal. It also describes the challenges that arise from rotational movement.