Observer-based fault tolerant control of shape memory alloy actuator

Area of Science:

• Robotics and Control Systems
• Materials Science
• Fault-Tolerant Control

Background:

• Shape Memory Alloy (SMA) actuators are crucial for robotic manipulators due to their unique properties.
• Ensuring reliable operation of SMA actuators in robotic systems is challenging due to potential faults and uncertainties.
• Existing fault-tolerant control strategies may lack robustness against unmodeled dynamics and actuator faults.

Purpose of the Study:

• To design and experimentally implement a nonlinear fault-tolerant control (FTC) scheme for SMA actuators in robotic manipulators.
• To develop a robust control system capable of handling actuator faults and unmodeled dynamics.
• To improve the overall reliability and performance of robotic manipulators utilizing SMA actuators.

Main Methods:

• A super-twisting sliding mode controller (ST-SMC) was developed as a baseline controller.
• A nonlinear observer was introduced to estimate system perturbations and detect actuator faults.
• A decision mechanism was implemented to reconfigure the controller upon fault detection, utilizing observer data.
• Lyapunov stability analysis was employed to demonstrate controller stability under input constraints.

Main Results:

• The baseline ST-SMC demonstrated robustness against uncertainties and unmodeled dynamics in fault-free conditions.
• The nonlinear observer successfully estimated perturbations and enabled effective fault detection.
• The fault-tolerant scheme successfully compensated for actuator faults, uncertainties, and unmodeled dynamics.
• Experimental results showed superior performance compared to a passive fault-tolerant controller.

Conclusions:

• The proposed nonlinear FTC scheme provides robust control for SMA actuators in robotic manipulators.
• The integrated fault detection and compensation mechanism enhances system reliability and simplifies control architecture.
• The experimental validation confirms the effectiveness and superiority of the developed fault-tolerant control strategy.