SMA Actuator-Based Nonlinear Fault Tolerant Control for A Flexible Arm with Active Compensating Unit

This paper provides an interactive shape memory alloy (SMA) actuator-based nonlinear fault tolerant control (FTC) for the flexible arm with an active compensating unit. In control system structure, two SMA wires in parallel are unified an interactive actuator to govern the arm vibration displacement. SMA actuator-based nonlinear FTC system is designed by using operator-theoretic approach. Meanwhile, multiple feedback loops (MFLs) with an active compensation unit is to obtain the desired tracking performance, which the compensation unit is to eliminate the effect of non-invertible hysteresis factor from SMA actuator. The robust stability of the designed control system can be guaranteed with robust stabilization condition. When the unknown fault behavior of the actuator occurs, the fault tolerant characteristics can ensure the safety and reliability of the control system. Finally, the simulation cases verify the effectiveness of the proposed scheme under the normal and faulty states of the actuator. The results show that even if the one-sided actuator loses the input signal, the designed control system can still remain stable the arm vibration displacement, as well as has a good fault-tolerant characteristics for actuator faults. Compared with the classic Proportional-Derivative (PD) controller, the proposed method not only can quickly the vibration suppression with less time but also with lower input energy. The effectiveness and reliability of the SMA actuator-based FTC system is confirmed in case of actuator faults.