Abstract
In this paper, an adaptive robust control is investigated in order to deal with the unmatched and matched uncertainties in the manipulator dynamics and the actuator dynamics, respectively. Because these uncertainties usually include smooth and unsmooth functions, two adaptive mechanisms were investigated. First, an adaptive mechanism based on radial basis function neural network (RBFNN) was used to estimate the smooth functions. Based on the Taylor series expansion, adaptive laws derive for not only the weighting vector of the RBFNN, but also for the means and standard derivatives of the RBFs. The second one was the adaptive robust laws, which is designed to estimate the boundary of the unsmooth function. The robust gains will increase when the sliding variable leave the predefined region. Conversely, they will significantly decrease when the variable approaches the region. So, when these adaptive mechanisms are derived with the backstepping technique and sliding mode control, the proposed controller will compensate the uncertainties to improve the accuracy. In order to prove stability and robustness of the controlled system, the Lyapunov approach, based on backstepping technique, was used. Some simulation and experimental results of the proposed methodology in the electrohydraulic manipulator were presented and compared to other control to show the effectiveness of the proposed control.
Highlights
Due to advantages such as high load efficiency, small size-to-power ratio, and fast response, hydraulic actuators have been widely investigated in construction [1,2], aerospace [3], motion simulator [4], as well as robotic area [5,6,7]
In previous studies [14,15,17], the adaptive backstepping sliding mode control was applied to a manipulator including electric actuator dynamics for position control problem
Based on the works mentioned above, this paper presents an adaptive backstepping sliding mode control for position tracking control of a hydraulic manipulator including actuator dynamics
Summary
Due to advantages such as high load efficiency, small size-to-power ratio, and fast response, hydraulic actuators have been widely investigated in construction [1,2], aerospace [3], motion simulator [4], as well as robotic area [5,6,7]. Sci. 2019, 9, 1265 dynamics which were expressed by taking derivative of the acceleration variable of the manipulator to including the actuator dynamics [10,11,12,13] Their results proved the effectiveness of this approach. In previous studies [14,15,17], the adaptive backstepping sliding mode control was applied to a manipulator including electric actuator dynamics for position control problem. The adaptive mechanism were developed based on linear regressor method [14,17], and least square-support vector machine [15] Their results proved that these controllers dealt well with the uncertainties and disturbances. Based on the works mentioned above, this paper presents an adaptive backstepping sliding mode control for position tracking control of a hydraulic manipulator including actuator dynamics. The appendixes present the definitions of some matrices and vectors
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