Abstract
This paper proposes a novel robust control scheme for tip trajectory tracking of a lightweight flexible single-link arm. The developed control scheme deals with the influence of tip payload changes and disturbances during the working process of the flexible arm, thus realizing the accurate tracking for the tip reference trajectory. The robust control scheme is composed of an inner loop and an outer loop. The inner loop adopts the traditional PD control, and an active disturbance rejection control (ADRC) with a sliding mode (SM) compensation is designed in the outer loop. Moreover, the sliding mode compensation is mainly used to cope with the disturbance estimation error from the extended state observer (ESO), by which the insensitivity to tip payload variations and strong disturbance resistance is achieved. Finally, some numerical simulations are performed to support the theoretical analysis. The results show that the system is more robust to the tip mass variations of the arm and more resistant to the external torque after adding the sliding mode robustness term to the ADRC.
Highlights
Robot technology has made great progress in the past decade
The research on lightweight flexible arm robots has become a hot spot in recent years for the demand for high-speed robots in the manufacturing industry and the control of the weight of the robotic arm in order to save energy in the aerospace field
Compared with traditional rigid manipulators, the inertia of flexible manipulators is smaller, which means the high speed in the operating space and less energy consumption
Summary
Robot technology has made great progress in the past decade. robots with high speed, high precision, heavy load, and large-self weight ratio are increasingly concerned in the field of industry and aerospace. In the literature [18], the nonlinear ESO was used to estimate the nonlinear uncertainty term of the flexible doublelinked robotic arm and the feedback control law was designed using the backstepping method to achieve accurate tracking of the reference trajectory. The robustness and disturbance rejection of the control law with ESO estimates as feedback is limited because the estimation error of ESO in estimating disturbance cannot be avoided For this shortcoming of ADRC, the most straightforward solution is to use the accurate model of flexible link. [23,24], the method of adaptive estimation of disturbance upper bound is adopted in the design of sliding gain, which can effectively suppress chattering Another approach to the ESO estimation error is to introduce adaptive control law. (3) and (6) are the dynamic model of a single-link flexible arm driven by a DC motor with the tip external force disturbance
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