To address the challenges encountered in precise motion control of the boom, this paper proposes a class of order-reduced adaptive backstepping disturbance rejection controllers. In the control scheme, the low gain state observer is used to suppress measurement noise and a nonlinear disturbance observer is combined to estimate composite disturbances in real time for compensation. Furthermore, fuzzy and neural network systems are used to approximate uncertain nonlinear functions and adaptive laws are designed to handle parameter uncertainties. Compared with conventionally designed backstepping controllers based on the full order model of the electro-hydraulic system, the design process of the proposed controller is greatly simplified and the control parameters are effectively reduced. In addition, the control scheme verily cuts the control cost, because it only requires the output position state and the control input without the precise model and the strict feedback form of the system. Comparative results show that the proposed order-reduced adaptive backstepping controller has an excellent position tracking performance and strong robustness for electro-hydraulic system.
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