Joint sensor fault detection for fault tolerant parallel manipulators

Abstract

Parallel manipulators with redundant joint displacement sensing can be exploited to develop fault tolerant implementations. This is possible since fundamental problems of the associated kinematics can still be solved after the elimination of faulty sensor readings. The ability of detecting faulty sensor readings is a requirement of any fault tolerant implementation scheme. A sensor fault detection method is presented for redundantly sensed parallel manipulators. A broad class of three-branch manipulators is considered where each branch consists of three main-arm joints and supports a common payload through respective passive spherical joints. The detection method is based on the comparison of forward displacement solutions for different cases of joint sensor readings. The existence of common solutions based on the branches–sensors considered, is used to effectively identify the existence of a failed sensor. Once a faulty sensor is identified, continued (fault tolerant) operation is possible using a forward displacement solution based on the readings of the accurate sensors. The detection method is implemented in a computer simulation of a calibrated three-branch parallel manipulator. © 2000 John Wiley & Sons, Inc.