Failure Modes and Probabilities of a High Redundancy Actuator

A high redundancy actuator (HRA) is composed of a high number of actuation elements, increasing both the travel and the force over the power of an individual element. This provides inherent fault tolerance, because when an element fails, the capabilities of the actuator may be reduced, but it does not become dysfunctional. This paper analyses the likelihood of different reductions in capabilities, based on the reliability of the actuation elements used. The result is a probability distribution that quantifies the capability of the high redundancy actuator. Together with the required capabilities, this determines the fault tolerance of the actuator.