Research On Design And Characteristics Of Servovalve Actuated By Piezoelectric Ceramics

Compared with other control systems,hydraulic servo control systems are widely used in military and aerospace industries due to their fast response capability,high control accuracy,and large power-to-weight ratio.But in the past 50 years,as a key component of the hydraulic servo control system,the design of the servovalve has not changed.With the development of smart materials,the use of new materials to drive servovalves has become a new direction for people to explore servovalves.At present,piezoelectric ceramics have become the material of choice for driving servovalves because of their superior piezoelectric performance,fast response and good durability.In this paper,the mathematical model is established for the designed servovalve and the control strategy is proposed,then the simulation analysis is carried out.Finally,the effectiveness of the proposed control strategy is verified by experiments.This paper analyzes the working principle of piezoelectric ceramic actuators.According to the output force and displacement characteristics and resonant frequency characteristics of current piezoelectric ceramic actuators,the types of piezoelectric ceramic actuators that can meet the requirements of servovalve driving are selected.The selected piezoelectric ceramic ring benders are analyzed,and the static characteristics are simulated by finite element analysis to obtain a simplified mathematical model of the piezoelectric ceramic ring benders.Then the installation factors that affect the output characteristics of the piezoelectric ceramics are researched,and the installation and connection methods with better output performance are obtained.According to the improved design requirements of the servovalve,the designed servovalve is selected as the pilot valve and forms a two-stage servovalve with the slide valve for amplification.Then the corresponding mathematical model and simulation model are established.The dynamic and static characteristics of the piezoelectric drive servovalve are simulated and analyzed,and the related factors affecting the dynamic characteristics of the servovalve are researched.According to the specific requirements of the servovalve output characteristics,some key parameters of the valve are calculated,and the three-dimensional structure of the servovalve is designed.Aiming at the inherent hysteresis characteristics of piezoelectric ceramics,this paper establishes a dynamic Bouc-Wen hysteresis model to describe it.According to the relationship between the input voltage and the output displacement,the Parameter Estimation module in simulink is used to identify the unknown parameters in the hysteresis model.The corresponding feedforward voltage compensation control strategy is proposed.In order to improve the control precision,the PI control method is added,and finally the hysteresis of the piezoelectric ceramic output displacement is effectively improved.Based on the theoretical analysis,the experimental prototype of the piezoelectric ceramic driver was established.The output characteristics and control strategy of the driver were verified by the experiment,and the causes of the error were analyzed.