Finite-time sliding surface constrained control for a robot manipulator with an unknown deadzone and disturbance

Area of Science:

• Robotics
• Control Systems Engineering
• Nonlinear Control Theory

Background:

• Robot manipulators often face challenges with input nonlinearities like unknown deadzones.
• External disturbances can significantly degrade positioning accuracy.
• Existing control methods may require complex parameter identification or lack robustness.

Purpose of the Study:

• To develop a robust finite-time sliding mode control (FSMC) for robot manipulators.
• To address positioning inaccuracies caused by unknown deadzones and external disturbances.
• To achieve predefined tracking error and sliding surface constraints.

Main Methods:

• An assumed model feedforward FSMC was designed for faster response and to bypass parameter identification.
• Two constraint switching control functions were integrated, based on tracking error and finite-time sliding surface.
• The controller was validated through simulations and experiments on an articulated robot manipulator.

Main Results:

• The proposed FSMC effectively suppressed tracking errors within predefined boundaries, even with unknown deadzones and disturbances.
• Performance was achieved by simply tuning the gain of the constraint switching function, without extra compensators.
• The sliding surface constraint indirectly guaranteed tracking error constraints with improved stability compared to direct tracking error control.

Conclusions:

• The developed constraint controller offers a simpler structure than conventional methods.
• The FSMC with constraint functions provides robust and stable positioning for robot manipulators.
• The approach simplifies control design while maintaining high performance in the presence of uncertainties.