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Piezoelectric hydraulic pumps play a pivotal role in more electric aircraft and all-electric aircraft utilizing power-by-wire technology, owing to their high power density and reliability. The cantilever reed valve (CRV) serves as a crucial component within these pumps, and its dynamic behavior within the fluid directly impacts the pumps' output power. A precise mathematical model of the CRV is essential for understanding its motion mechanisms. However, existing models for the CRV inadequately capture its dynamics and fail to explain the observed motion phenomena. Further exploration into dynamic modeling of the CRV is warranted. This paper employs finite element analysis to investigate CRV's dynamics, revealing the significant impact of squeeze flow on CRV's dynamics and identifying the cause of slow closure. Based on this, a novel lumped parameter model incorporating squeeze force is proposed to accurately depict CRV's dynamics, particularly focusing on the phenomenon of slow closure. To validate the proposed model's accuracy, an experimental system capable of independently driving the CRV is constructed to eliminate interference resulting from integrating the CRV into the pumps. The results show that the dynamic response during closure, as predicted by the proposed model, is in good agreement with the outcomes from finite element analysis. Notably, the proposed model exhibits an 11.11% higher prediction accuracy for experimental closing times compared to the traditional model that neglects squeeze forces. This study offers guidance for optimizing CRV's dynamics and improving the performance of piezoelectric hydraulic pumps in future applications. [ABSTRACT FROM AUTHOR]

The average flow rate of a high speed on/off valve (HSV) is usually obtained by a flow sensor, which leads to pressure loss, structural complexity, and long test time. This paper proposes a rapid flow measurement for HSV based on the coil current derivative. The average flow rate is calculated by the effective opening time, which is solved by the critical moving time according to the proposed flow models. To estimate the critical moving time in real-time, an analytical model between the coil current derivative and the valve's displacement is derived. Experiments indicate that the error between the linear and nonlinear flow model is small when the frequency is smaller than 50 Hz. Moreover, compared to the linear flow model, the average error of the nonlinear flow model decreases from 0.21 L/min to 0.12 L/min under 100 Hz. The proposed flow measurement method has advantages of rapid measurement, structural simplicity, non-contact, and easy to implement intelligence. [ABSTRACT FROM AUTHOR]

High speed on/off valves (HSV) have often been used to control flow or pressure in digital hydraulic systems due to higher switching frequency. However, the dynamic performance and energy efficiency are highly affected by the supply pressure and the carrier frequency. In this paper, a new adaptive PWM control method for HSV based on software is proposed. The proposed adaptive PWM consists of a reference PWM, an excitation PWM, a high frequency PWM, and a reverse PWM. First, the nonlinear model of the HSV was established, and the structural composition and working principle of the proposed adaptive PWM control strategy were presented. Secondly, individual feedback controllers for the excitation PWM, the high frequency PWM, and the reverse PWM were designed, respectively; and each of the individual feedback controllers was experimentally verified. Finally, the comparative experimental results demonstrated that, with the proposed adaptive PWM control, the rising delay time of the control pressure drastically reduces by 84.6 % (from 13 ms to 2 ms), the duty cycle's effective range remains large (12 %-85 %) even with high carrier frequency (100 Hz), and the temperature rise of the valve's coil shell is reduced by 61.5 %, compared to the three-voltage control. In addition, the dynamic performance and the energy efficiency of the HSV are not affected by the supply pressures and carrier frequencies, which proves that the proposed control strategy can improve the robustness and stability of the valve system. [ABSTRACT FROM AUTHOR]

• Wedge erosion greatly affects the performance of jet pipe servo valve. • The change of the flow field of the jet amplifier after wedge erosion is the fundamental reason for the performance degradation of the jet pipe servo valve. • The relationship between the erosion degree of the wedge and the performance degradation of jet pipe servo valve is nonlinear. • Experiments verify the method proposed in this study to be feasible to evaluate the performance degradation of jet pipe servo valve. Due to the erosion of solid particles in contaminated oil, the material of the wedge of the jet amplifier falls off, and the wedge structure deforms, which inevitably leads to irreversible performance degradation and even failure of the jet pipe servo valve (JPSV). In this study, the experimental analysis of the performance of the JPSV before and after wedge erosion is carried out. According to the physical object of wedge erosion, the three-dimensional model of the jet amplifier after wedge erosion is reconstructed. Based on computational fluid dynamics (CFD) simulation, the comparison results of the flow field of the jet amplifier before and after wedge erosion are analyzed to explain the performance degradation of the JPSV. Furthermore, the relationship between the erosion degree of the wedge and the performance deterioration of the JPSV is investigated. The experimental and simulation results indicate that the dynamic behavior of the JPSV will gradually degrade with the increase of the erosion degree of the wedge, and the degradation process is nonlinear. Additionally, through CFD simulation, it is revealed that the critical factor causing the dynamic performance deterioration of the JPSV is that after wedge erosion, the shunting effect of the wedge is weakened, and the flow field of the jet amplifier changes significantly. This paper provides a new reference and practical method for studying and predicting the performance degradation of the JPSV caused by wedge erosion. [ABSTRACT FROM AUTHOR]

The use of smart materials-based high speed on/off valve has exhibited the potential to replace traditional servo and proportional valves in fluid power systems. In this paper, a novel pneumatic high speed on/off valve driven by a piezoelectric stack actuator is developed and its dynamics are studied. For an upstream gauge pressure of 0.5 MPa, the valve exhibited a large flow rate of up to 86 L/min. Furthermore, to study the ability of this novel high speed on/off valve to be applied in closed-loop control systems, a real-time position control system is realized using a PID controller. In order to prove its feasibility and effectiveness, a number of closed-loop trajectory tracking experiments are conducted on a pneumatic cylinder. The system is proved feasible and the results demonstrate good tracking performance. [ABSTRACT FROM AUTHOR]