A robust variable-structure LQI controller for under-actuated systems via flexible online adaptation of...

Area of Science:

• Control Systems Engineering
• Robotics
• Nonlinear Dynamics

Background:

• Under-actuated rotary pendulum systems present challenges in control due to limited actuators.
• Traditional Linear-Quadratic-Integral (LQI) controllers may lack adaptability to external disturbances.
• Optimizing control performance requires flexible adjustment of system parameters.

Purpose of the Study:

• To develop flexible online adaptation strategies for performance-index weights in an LQI controller.
• To enhance the adaptability of LQI controllers for under-actuated rotary pendulum systems.
• To improve disturbance rejection and energy efficiency while maintaining closed-loop stability.

Main Methods:

• Augmenting a standard LQI controller with an online weight adaptation law.
• Formulating the adaptation law based on dissipative, anti-dissipative, and model-reference tracking terms.
• Utilizing adjusted state weighting factors in the Riccati equation to derive time-varying state-compensator gains.

Main Results:

• The proposed controller demonstrates flexible online adaptation of performance-index weights.
• Effective rejection of bounded exogenous disturbances is achieved.
• Control stiffness is manipulated to economize control energy expenditure while preserving system stability.

Conclusions:

• The developed adaptive LQI controller offers enhanced flexibility and robustness for under-actuated rotary pendulum systems.
• The online weight adaptation strategy effectively balances performance, stability, and energy efficiency.
• This approach provides a viable solution for real-world applications requiring adaptive control in dynamic environments.