Force tracking in robotic control systems using an online work object stiffness hybrid impedance PI control approach

Abstract

This study presents an advanced control strategy for robotic contact force tracking, integrating an Online Work-Object Stiffness PI Force (OWSPIF) impedance controller to achieve highly accurate contact position and force. The contact between the robot end and its work object is modeled as a second-order system. A position-based PI-impedance controller processes a force signal correction to maintain a desired force and ensuring precise tracking of both the target contact force and the reference trajectory. The OWPSIF approach dynamically generates an inverse signal to compensate for force errors and effectively reduce them to zero. Stability is analyzed using the Lyapunov direct method. Simulation studies on virtual ramps, curved, and complex surfaces are performed to validate the proposed methodology. The results are compared against a single impedance controller and two recent controllers from the literature, showcasing the effectiveness of the proposed approach. An experimental validation on 7DOF and 6DOF robotic manipulators demonstrates the method's effectiveness for force tracking and polishing processes, respectively, where a real-time trajectory is generated using an NURBS interpolation curve. The results show a clear correlation between the PI-generated signal and the force tracking error, indicating an improvement in force accuracy and a reduction in computational processing. • Position and force tracking are curical for accuracy and efficiency in robotic contact tasks. • For this issue, the paper uses a hybrid impedance-PI controller with online object stiffness. • Position and force tracking simulations are conducted on work objects with virual surfaces. • For validation, an experimens are conducted using tracking technology and polishing process. • Results show improved force accuracy and reduced computational load with PI signal tracking.