Fixed-time fractional second-order sliding mode control for robotic systems with actuator faults

Area of Science:

• Robotics
• Control Systems Engineering
• Nonlinear Control Theory

Background:

• Actuator faults in robotic systems can degrade performance and lead to instability.
• Existing fault-tolerant control (FTC) methods may not guarantee fixed-time convergence or effectively handle complex fault dynamics.
• Sliding mode control (SMC) offers robustness but can suffer from chattering and limitations in convergence time.

Purpose of the Study:

• To propose a novel active fault-tolerant control (FTC) scheme for robotic systems subject to actuator faults.
• To achieve fixed-time convergence of position tracking errors despite actuator faults.
• To enhance fault compensation, tracking accuracy, and system response speed while mitigating chattering.

Main Methods:

• Development of a fixed-time fault observer for estimating actuator faults.
• Design of a fixed-time fractional-order sliding mode surface with a double-power reaching law.
• Implementation of an adaptive law to address fault estimation errors.
• Mathematical proof of fixed-time convergence for position tracking error.

Main Results:

• The proposed control scheme ensures fixed-time convergence of the position tracking error.
• Simulations demonstrate superior fault compensation ability compared to integer-order finite-time SMC.
• The scheme improves tracking accuracy and accelerates system response within a fixed time.
• Effective mitigation of chattering is achieved.

Conclusions:

• The proposed fixed-time fractional-order sliding mode active FTC scheme is effective for robotic systems with actuator faults.
• This approach offers significant advantages in fault compensation, tracking performance, and response time.
• The method provides a robust solution for enhancing the reliability and performance of robotic systems under fault conditions.