Redundant Structure-Based Multimotor Servo System Fuzzy Adaptive Fault-Tolerant Control via Unbalanced Torque Compensation

A novel observer-based fuzzy adaptive fault-tolerant control approach is proposed for multi-motor synchronously driving servo systems in the situation of a single-motor malfunction. Different from most existing fault-tolerant control strategies based on analytical redundancy, this paper leverages inherent hardware advantages of multi-motor systems and develops a structural redundancy-based fault-tolerant control by directly turning off the faulty motor, which enhances the reliability of the remaining healthy motors driving the asymmetric system. To further address the unknown nonlinearities and measurement inaccuracies introduced by the unbalanced faulty system, a fuzzy logic system is developed to identify the state-based unbalanced torque and additional friction dynamics, and a state observer is then designed to estimate the load speed. Moreover, the command-filtered backstepping technique is utilized in the control design process to reduce the computational complexity caused by the repeated signal derivations. After stability analysis, an experiment on the multi-motor prototype is implemented to show the effectiveness of the designed fault-tolerant control approach.