Novel observer based friction estimation and control methods for simple nonlinear mechanical systems

Abstract

Friction is a common nonlinear phenomenon in inertial mechanical systems, often leading to undesirable effects such as stick-slip motion, hysteresis, and reduced tracking accuracy. Effective friction compensation is essential for enhancing robustness and achieving high precision in controlling such systems. Both model-based and non-model-based approaches have been widely utilized for friction compensation, with friction observers playing a significant role in estimating the friction acting on the system. This study focuses on observer-based adaptive estimation techniques, specifically employing the Friedland-Park observer to estimate the parameters of a friction model in an inertial system. The proposed approach aims to mitigate stick-slip motion and enhance tracking performance. The research evaluates various applications of the Friedland-Park observer for friction compensation and its implementation in high-order systems. Both two-state and single-state observers are examined, alongside different system models and controllers, to ensure the robustness of the proposed methods. Performance metrics include velocity reference tracking accuracy and the compensator's responsiveness during velocity sign reversals, assessed under diverse reference input conditions. Simulation results demonstrate a significant improvement in velocity tracking accuracy, with up to a 65% reduction in tracking error. The proposed friction compensation methods effectively handle varying friction conditions, ensuring system robustness and precision. This study contributes a comprehensive approach to friction compensation, offering various design options for inertial mechanical systems. Future work will extend this research by incorporating a gyroscope model to address the noisy nature of inertial sensors and performing the hardware implementation of the proposed methodology on gyro-stabilized platforms to validate its practical applicability. This work can also be extended within the scope of system identification by developing a novel approach for estimating plant parameters through the adaptation of Friedland-Park observer equations.