Reliable control using vector-valued majority decision

Recently control system safety against device faults, especially sensor faults, has attracted widespread attention. This paper is based on redundancy of truly important information for device fault tolerance, and introduces a new decision rule on the information. To put the assertion more concretely, this paper considers the state of a plant as the truly important information. To obtain redundancy of the information, it uses three redundant subsystems, where each subsystem consists of a sensor set and an observer. Only the estimated state adopted by an analogue and vector-valued decision rule is used for state feedback. In a sensor fault case the rule almost always adopts a correct state estimated by a normal observer just like majority decision, so that the total system has the sensor fault tolerance.