Self-validating sensors with application to a flexible link control system

For the satisfying performance of a control system, design of a controller for the system which meets the required specifications, and the role of its supporting hardware that keeps functioning are equally important. Therefore it is inevitable to keep track of accurate and reliable sensor readings for good controller performance. Among the hardware of a control system sensors are most vulnerable to malfunction. Thus it is necessary to provide physical and analytical redundancy for the sensor measurement outputs to increase reliability against sensor failures. In general the task of detection, identification, and accommodation of sensor failures is widely pursued for this need. In case of sensor faults, they are detected by examining the sensor output values and the correlated or relevant values of the system. And then the types of the faults are identified by the analysis of symptoms of faults. If necessary self-validating sensor values are synthesized according to the types of faults, and then they are used for the controller instead of the raw data. In this paper, a self-validating sensor is applied to the control of a flexible link system with the sensor fault problems in the light sensor module for exact positioning to show the applicability. It is shown that the digital controller can provide a satisfactory loop performance even when the sensor faults occur.