Abstract
Single-rod electrohydraulic system is widely applied in industrial production due to high power-to-weight ratio, but it generally has a low energy efficiency and has many system states which need to be measured. Therefore, an output feedback controller with energy saving is proposed in this paper. The designed controller only needs a displacement sensor to detect the position of the single-rod cylinder; the other states of the system are estimated by extended state observer (ESO). Besides, a nonlinear disturbance observer (NDO) is introduced to estimate the external mismatched disturbance. The output feedback controller based on extended state observer and nonlinear disturbance observer has a better tracking performance compared with other controllers. In addition, a proportional relief valve (PRV) is introduced to control the supply pressure of the system. The variable supply pressure reduces the energy of throttling loss and overflow loss, which achieves energy saving of about 54% according to the simulation results. Meanwhile, the tracking error of the energy saving controller is stable at 0.1 mm. In a word, the proposed controller not only achieves energy saving but also has a satisfactory trajectory tracking performance.
Highlights
Electrohydraulic systems are widely used in industrial equipment and mobile applications such as excavator, crane, robot manipulator, and hydraulic press [1,2,3,4]
An output feedback controller based on extended state observer and nonlinear disturbance observer with energy saving is proposed
For a single-rod electrohydraulic system with only displacement signal output, the extended state observer (ESO) is used to estimate all the states of system and the nonlinear disturbance observer (NDO) is used to estimate the external disturbance. e simulation results show that the observers have a satisfactory observation effect in this system
Summary
Electrohydraulic systems are widely used in industrial equipment and mobile applications such as excavator, crane, robot manipulator, and hydraulic press [1,2,3,4]. A nonlinear backstepping control algorithm was designed in the single-rod system with variable supply pressure for position tracking and energy saving [19]. Most energy saving control method with variable supply pressure required speed, pressure, and even force sensors of the load for state feedback, but in many cases, only the output of the hydraulic system is measurable. Erefore, the complete hydraulic system is introduced, where variable supply pressure control method is to realize the energy saving based on PRV and output feedback control strategy is to realize high performance position tracking based on PDV. E PDV control signal u1 is used to change the actuator flow Q1 and Q2 to improve position tracking performance, and the PRV control signal output u2 is used to change the supply pressure ps to reduce energy loss. |pL| is smaller than ps, since p1 and p2 are both bounded by ps and pr in practical hydraulic systems
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