Abstract
The output feedback signal of the electro-hydraulic valve system (EHVS) affects the activation of its right or left envelope function; thus, even weak measurement noise can cause high-frequency switching between the two envelope functions, leading to chattering in the control input. Consequently, feedforward and feedback controllers in a cascaded configuration generate undesirable chattering in the output signal. We propose a practical and reliable control approach for an EHVS actuated by a proportional control valve. The proposed controller has a parallel structure comprising an inverse generalized Prandtl–Ishlinskii (P–I) model-based feedforward controller, with both hydraulic dead-zone and flow saturation limits, for compensating asymmetric hysteretic behavior. Further, the proposed controller comprises a robust proportional-integral-derivative (PID) feedback controller for achieving robustness against disturbances and noises. The proposed parallel structure is independent of the output feedback of the EHVS. Moreover, the proposed robust PID feedback controller guarantees EHVS stability by precisely selecting the cutoff frequency for the sensitivity and complementary sensitivity functions based on the amplitude spectrum of the inverse-model-based feedforward compensation error. The results verify the high reliability of the proposed EHVS control scheme for the precise control of an EHVS actuated by a proportional control valve in practice.
Highlights
Electro-hydraulic valve systems (EHVSs) have been extensively applied to heavy industrial machinery, robot manipulators, tunnel boring machines, mobile systems, and different machine tools, owing to their characteristics such as high power-to-weight ratio, appropriate stiffness, self-cooling, rapid response, and high positioning ability
The experimental results demonstrate that the proposed method can improve the tracking performance and robustness of an EHVS actuated by a proportional control valve
We propose a feedforward controller using an inverse model to compensate for nonlinearities and a robust PID controller to enhance robustness against disturbances and noise for an EHVS actuated by a proportional control valve
Summary
Electro-hydraulic valve systems (EHVSs) have been extensively applied to heavy industrial machinery, robot manipulators, tunnel boring machines, mobile systems, and different machine tools, owing to their characteristics such as high power-to-weight ratio, appropriate stiffness, self-cooling, rapid response, and high positioning ability. We evaluate the practical necessity of adopting the parallel implementation of the feedforward controller using the inverse generalized P–I model to an EHVS compensated by a robust PID controller in the closed-loop system. We experimentally demonstrate that the feedforward control using the inverse hysteresis model plus robust PID feedback control in cascade connection does not provide sufficient robustness against output EHVS noise.
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