Novel robust control of a 7-DOF exoskeleton robot

Area of Science:

• Robotics
• Control Systems Engineering
• Mechatronics

Background:

• 7-DOF exoskeleton robots face instability due to external disturbances like friction, mass variations, backlash, and input saturation.
• Existing controllers like Fractional PID (FPID) offer good trajectory tracking but lack robustness.
• New fractional sliding mode controllers (NFSMC) provide robustness but may not optimize trajectory tracking.

Purpose of the Study:

• To develop a novel robust control method for 7-DOF exoskeleton robots.
• To enhance trajectory tracking accuracy while maintaining robustness against uncertainties and disturbances.
• To address the limitations of existing control strategies in complex robotic systems.

Main Methods:

• Design of a New Fractional Sliding Mode Controller (NFSMC) for disturbance rejection.
• Integration of NFSMC with a Fractional PID controller (FPID) to create a compound controller (NCFPIDSMC).
• Stability analysis using Lyapunov theory and validation through random noise injection.

Main Results:

• The proposed compound fractional PID sliding mode controller (NCFPIDSMC) effectively enhances trajectory tracking.
• The NCFPIDSMC demonstrates significant robustness against external disturbances and unknown dynamics.
• Stability of the control method is rigorously verified through theoretical analysis and simulation.

Conclusions:

• The NCFPIDSMC offers a superior control solution for 7-DOF exoskeleton robots, balancing trajectory tracking and robustness.
• This novel approach addresses critical challenges in exoskeleton robot control, paving the way for more reliable applications.
• The method's effectiveness is confirmed, suggesting its potential for real-world implementation in assistive and rehabilitation robotics.