Abstract
In electro-hydraulic system (EHS), uncertain nonlinearities such as some hydraulic parametric uncertainties and external load disturbance often degrade the output dynamic performance. To address this problem, a prescribed performance constraint (PPC) control method is adopted in EHS to restrict the tracking position error of the cylinder position to a prescribed accuracy and guarantee the dynamic and steady position response in a required boundedness under these uncertain nonlinearities. Furthermore, a dynamic surface is designed to avoid the explosion of complexity due to the repeatedly calculated differentiations of the virtual control variables derived in backstepping. The effectiveness of the proposed controller has been verified by a comparative results.
Highlights
Electro-hydraulic systems are currently widely used in mechatronic control engineering as they have a superior load efficiency
The controller based on prescribed performance constraint has the steady tracking errors ∆x1 = 0.01 mm in low frequency demand and ∆x1 = 0.05 mm in high frequency demand respectively, which is better than the PI controller
To verify the dynamic response performance of the proposed prescribed performance constraint controller, the frequency of the cylinder position demands and the initial states are same to Section 4.1
Summary
Electro-hydraulic systems are currently widely used in mechatronic control engineering as they have a superior load efficiency. These high-order derivatives will magnify noise and uncertainty in the actual control signals which results into violent control and chatter response [32,36] To solve this problem, the dynamic surface control (DSC) has been proposed to design a stabilizing function instead of the repeatedly calculated derivative of virtual control. Different from the constraint holding technique of BLF, the PPC employed a weighted performance function to design an adjustable time-varying output-constraint and improve the system stable margin and dynamic performance By this controller, all the signals of the single-rod EHS are uniformly bounded and the tracking error of the cylinder position can converge to a small compact set without violating the constraints.
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