A Novel Servovalve Pilot Stage Actuated by a Piezo-electric Ring Bender: A Numerical and Experimental Analysis

Abstract

Electrohydraulic servovalves are widely used for precise motion control in aerospace and other industries due to their high accuracy and speed of response. However, commercial two-stage servovalves have several undesirable characteristics, such as the power consumption caused by the quiescent flow (internal leakage) in the pilot stage, and the complexity and high number of parts of the torque motor assembly, which affect the cost and the speed of manufacture. The solution to these problems can help to reduce costs, weight and power consumption, and enhance the reliability and reproducibility as well as the performance of these valves. For these reasons, this paper proposes a novel configuration for the pilot stage: it is composed of two normally closed two-way two-position (2/2) valves actuated by two piezo-electric ring benders; the opening and closing of the two piezo-valves can generate a differential pressure to be used to control the displacement of the main spool. In this way, there is negligible quiescent flow when the main stage is at rest; in addition, the torque motor and all its components are removed. To assess the performance of this novel pilot stage concept, a prototype of the piezo-valve has been constructed and tested. The experimental results indicate that the response speed of the new piezo-valve is very high. Furthermore, a numerical model is employed to show that, by adjusting specific parameters, the performance of the piezo-valve can be further improved, so that the valve can be fully opened or closed in less than 5 ms.

Stiffness Model of the Armature Assembly in a Jet Pipe Pressure Servo Valve

“…In addition, we can calculate the stiffness constants based on Eqs. (1) ~ (11) in MATLAB and also determine the load-displacement relationship, which is regarded as the theoretical analysis result. Fig.…”

“…In [7], magnetic fluids are filled in the air gap of a torque motor to suppress the vibration and noise. Besides studying the torque motor, scholars have devised some innovative electro-mechanical converters, such as piezoelectric actuator [8], piezoelectric ring benders [9][10][11], and giant magnetostrictive actuators [12,13] to pursue higher dynamic performance. The common pre-stage hydraulic amplifiers in TSPSVs are spool valves [14], single nozzle flapper valves [15], double nozzle flapper valves [16], jet pipe valves [17] and deflector jet valves [18][19][20].…”

Feasibility study of using amplified piezo-stack actuators for the actuation of direct drive servovalves

“…The most common piezo electric actuators available on the market are ring benders, rectangular benders, piezo-stacks, and amplified piezo-stacks [1]. In previous studies, we demonstrated that ring benders and rectangular benders are suitable for the actuation of the pilot stages of servovalves [4][5][6][7][8]. Concerning ring benders, two of them, mounted in tandem to provide redundancy, were proposed in [4] to actuate, in place of the torque motor, a double nozzle flapper pilot stage; the feasibility of this architecture was assessed using a detailed Simulink model of the hydraulic, mechanical and electrical parts [4].…”

“…Concerning ring benders, two of them, mounted in tandem to provide redundancy, were proposed in [4] to actuate, in place of the torque motor, a double nozzle flapper pilot stage; the feasibility of this architecture was assessed using a detailed Simulink model of the hydraulic, mechanical and electrical parts [4]. In [5,6], we proposed and studied a novel pilot stage configuration composed of two normally closed two-way twoposition (2/2) valves actuated by two piezo-electric ring benders, achieving very good step and frequency response in addition to minimizing the internal leakage. Again, a Simulink model was instrumental in assessing this novel architecture [5,6]; the comparison between the results of the simulations and the experimental data showed that this simulation approach provides very good accuracy [5].…”

“…In [5,6], we proposed and studied a novel pilot stage configuration composed of two normally closed two-way twoposition (2/2) valves actuated by two piezo-electric ring benders, achieving very good step and frequency response in addition to minimizing the internal leakage. Again, a Simulink model was instrumental in assessing this novel architecture [5,6]; the comparison between the results of the simulations and the experimental data showed that this simulation approach provides very good accuracy [5]. Concerning rectangular benders, there are some examples, provided by us and by other authors, of rectangular benders applied to the actuation of deflector jet pilot stages and to the actuation of double nozzle flapper pilot stages [8][9][10][11].…”