Robust Vibration Control Based on Rigid-Body State Observer for Modular Joints

Abstract

The vibration caused by resonance modes frequently occurs during acceleration and deceleration of the modular joint integrated with flexible harmonic drive. The conventional equivalent rigid-body velocity method with observer can suppress the residual vibration induced by resonant frequency but has poor robustness to model uncertainties and external disturbances. Moreover, it cannot eliminate the torque ripple caused by the harmonic drive during low-speed uniform motion, reducing the velocity tracking accuracy. Hence, a velocity controller with a rigid-body state observer and an adjustable damper is designed to improve the robust performance and velocity tracking accuracy. The designed rigid-body state observer allows a higher gain so that the bandwidth of the observer can increase, and the equivalent rigid-body velocity can be acquired more accurately. Notably, the high gain observer reduces the sensitivity to model uncertainties and exotic disturbances, especially near the resonant frequency. In addition, the observer combined with an adjustable damper can suppress the residual vibration and torque ripple simultaneously. The proposed method is compared experimentally with a PI method and two other rigid-body velocity methods, such as the conventional equivalent rigid-body observer method and the self-resonance cancellation method, to verify its advantages.

Mitigation of Torsional Vibrations in a Modular Drivetrain with Interleaving Control

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Decoupling Vibration Control for a Two-Link Manipulator

“…When the Damperi is designed as a negative proportional gain, the system damping of the decoupled flexible jointi can be increased. Then the vibrations can be damped by the increased system damping [16].…”

“…The RBSO aims to depress vibrations of the TITO system in a decentralized structure, which contains a state observer (SOB) and a Damper. The SOB aims to observe a rigid-body velocity, which is designed to be more robust to external disturbances and model uncertainties than traditional methods that are theoretically proven in our previous work [16]. The Damper feeds back the error between the observed rigid-body velocity and link velocity to a proportional-integral controller, adding system damping to achieve vibration suppression.…”

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