In this study, a command smoothing-disturbance observer-based proxy sliding mode control (CS-DPSMC) method is proposed for a class of hydraulic servo systems with structural flexibility. First, to alleviate the influence of residual vibration due to structural flexibility, command smoothing method (CS) is used to modify the desired trajectory; Then, a nonlinear disturbance observer-based proxy sliding mode controller (DPSMC) is developed so as to make the hydraulic actuator track the desired trajectory. Besides, the control signal is continuous because the discontinuous sign function is theoretically canceled. Therefore, high-frequency unmodeled dynamics of flexible structures will not be excited. According to the passivity theory and Lyapunov theory, the stability of the control system is proven. The effectiveness of the proposed algorithm is verified by comparative numerical analysis.

Command smoothing-proxy sliding mode control of hydraulic servo system considering structural flexibility

In this study, active vibration control of a single-link flexible manipulator has been performed. Residual vibrations affect the end-point positioning accuracy of the manipulator. To control residual vibration amplitudes, closed loop control scheme has been effectuated. Velocity feedback of the desired endpoint has been carried out and traditional proportional-integral (PI) Control has been applied. The mathematical model of the flexible manipulator has been established by the finite element method (FEM). The FEM results in modal analysis have been verified by the experimental results and then, the transient analysis has been realized by the Newmark method. Different velocity profiles have been applied to the manipulator to demonstrate the effect of PI controller on vibration amplitudes. The root mean square values and steady-state time have been calculated presented for different cases. It is observed from the results that the residual vibration amplitudes of the manipulators are successfully suppressed by the proportional-integral control gains. 

Active Vibration Control of a Flexible Manipulator With Velocity Feedback

There are three motion stages for an industrial robot manipulator, including the acceleration stage, the constant velocity stage, and the deceleration stage. Aiming at reducing the residual vibration of the manipulator after the movement of the deceleration, a new method is proposed by configuring the movement parameters of the flexible manipulator. Firstly, we conduct experiments to verify a numerical vibration model of the manipulator, and then, we analyze the vibration suppression effect under different conditions based on the numerical model. The results show that in the range of one movement, the residual vibration can be well suppressed when the acceleration and deceleration time are set as a positive integer to the natural period of the manipulator operation; otherwise, the vibration suppression effect is not obvious and proportional to the difference between the acceleration/deceleration time and the manipulator natural period.

https://journals.sagepub.com/doi/pdf/10.1177/14613484221094982

Ruiqiang Xia

Papers

An active control method for vibration reduction of a single-link flexible manipulator