Composite nonlinear disturbance observer-based practical prescribed time control for nonlinear systems with matched...

Area of Science:

• Control Systems Engineering
• Nonlinear Dynamics
• Robotics

Background:

• Nonlinear strict-feedback systems often face challenges with matched and mismatched disturbances.
• Achieving precise control within a finite, predetermined time is crucial for many applications.
• Existing control methods may struggle with complexity or disturbance rejection.

Purpose of the Study:

• To develop a practical prescribed-time control (PPTC) scheme for nonlinear strict-feedback systems.
• To ensure prescribed transient and steady-state performances within a specified time frame.
• To effectively handle both matched and mismatched disturbances.

Main Methods:

• A novel error transformation mechanism using a prescribed-time constraining function and tanh(⋅).
• Design of a composite nonlinear disturbance observer (CNDO) for fast disturbance estimation.
• Implementation of a nonlinear filter to prevent "explosion of complexity".
• Backstepping method combined with CNDO estimates and nonlinear filter for controller design.

Main Results:

• The proposed scheme ensures system output satisfies constraints within the prescribed time.
• Disturbance estimation is fast and accurate, improving control performance.
• Control cost is reduced while maintaining desired performance.
• Theoretical analysis and experimental results validate the effectiveness on a turntable servo system.

Conclusions:

• The composite nonlinear disturbance observer-based PPTC scheme effectively controls nonlinear systems under disturbances within a prescribed time.
• The method achieves desired transient and steady-state performance, handles complexity, and reduces control effort.
• Validated through simulations and experiments, demonstrating practical applicability.