Tolerance Towards Sensor Faults: An Application to a Flexible Arm Manipulator

Chee Pin Tan,Maki K Habib

doi:10.5772/5720

Abstract

As more engineering operations become automatic, the need for robustness towards faults increases. Hence, a fault tolerant control (FTC) scheme is a valuable asset. This paper presents a robust sensor fault FTC scheme implemented on a flexible arm manipulator, which has many applications in automation. Sensor faults affect the system's performance in the closed loop when the faulty sensor readings are used to generate the control input. In this paper, the non-faulty sensors are used to reconstruct the faults on the potentially faulty sensors. The reconstruction is subtracted from the faulty sensors to form a compensated ‘virtual sensor’ and this signal (instead of the normally used faulty sensor output) is then used to generate the control input. A design method is also presented in which the FTC scheme is made insensitive to any system uncertainties. Two fault conditions are tested; total failure and incipient faults. Then the scheme robustness is tested by implementing the flexible joint's FTC scheme on a flexible link, which has different parameters. Excellent results have been obtained for both cases (joint and link); the FTC scheme caused the system performance is almost identical to the fault-free scenario, whilst providing an indication that a fault is present, even for simultaneous faults.

Highlights

Fault tolerant control (FTC) is a really valuable asset for any system, and perhaps even an essential one
This paper is concerned with the application of an FTC scheme on a flexible joint and flexible link system, which can be a single DOF robotic manipulator
There has been a lot of work done in the area of FTC applied to robotic manipulators

Summary

Introduction

Fault tolerant control (FTC) is a really valuable asset for any system, and perhaps even an essential one. Izumikawa et al (Izumikawa, Y. et al, 2002) presented a flexible joint FTC scheme for sensor faults; when a certain. These faults will affect the process if the sensor measurements are used to generate the input control signal. A reconstruction of the sensor fault is obtained by subtracting a function of the estimated states from the measured outputs, and the result is multiplied by a scaling matrix. Habib / Tolerance towards sensor faults; An application to a flexible arm manipulator where xe ∈ \n is an estimate for the state x and L ∈ \n×( p−q) is a design matrix such that A − LC1 is stable.

Test results

Conclusion