Implementation of a control system with dual structure in processor module and I/O modules

The authors´ experience of implementing a fault tolerant control system is reported. The dual structure is used to enhance the reliability of the control system, and its hardware and software for fault detection and location are described along with backup schemes. More specifically, fault detection of processor modules is accomplished by conducting self test, comparison test of calculated controller output values and test of exception errors. Fault detection in I/O modules is done by diagnosis of processor modules. The proposed control system can also backup faulty units in a more flexible manner, i.e. cross backup is possible. The primary processor module can acquire data from the secondary I/O module when the primary I/O module is faulty, or vice versa. Implementation results are presented