Research On Micro-displacement Actuator Based On Hydraulic Expansion

In order to solve the problem of micro displacement driving in precision machining,this paper proposes a new micro displacement actuator based on the principle of static pressure expansion.A hydraulic displacement actuator is designed on the basis of theoretical analysis.The main research contents include using finite element method to analyze its main performance and carrying out some relevant experimental researches on the actuator.Firstly,a simplified analytical model of a thin circular plate which is subjected to static pressure is established.Through deriving the relation between the maximum displacement of the thin circular plate and the main structural parameters according to the differential equation of the elastic thin plate,this paper has provide the initial parameter choice basis for structure design.Based on correlation analysis,a cylindrical cavity hydraulic micro displacement actuator is designed.Secondly,through the finite element analysis of the hydraulic micro displacement actuator,including the displacement output characteristics and the contact stiffness characteristics,this paper got a linear relationship between the output displacement and the size of cavity pressure through the analysis of the cylindrical cavity drive unit.Based on this type of cavity,several improved structures of the cavity are put forward,and also found that a kind of long cylindrical internal cavity has a better performance in the output characteristic and the stress distribution after analysis and comparison.In addition,with the analysis of the two different cavities through the establishment of stiffness analysis finite element model,the projuct has got the changing law of contact stiffness and its relationship with the liquid pressure.In order to obtain the optimal output performance of the micro-displacement actuator,a optimal design of the micro-displacement actuator on the basis of the preliminary is designed.With a sensitivity analysis of the main parameters which influence on the drive unit features,several parameters have been got which have have more effect on the performance.Then this paper analyzed the relationship between the output characteristics and the main parameters one by one,which provide the basis for how to improve the output characteristics by adjusting the cavity size.By establishing the optimization model to optimize the drive unit,a set of optimized parameters has been got which can improvethe overall performance of the micro displacement actuator.Finally,a test rig is designed to do some experimental studies on the micro displacement actuator.The results show that the output displacement has a linear relation with the pressure and the contact stiffness test results has a high consistency with the theoretical analysis results,which verified the rationality of theoretical analysis.For the output displacement accuracy problem caused by the limited contact stiffness,a set of micro-displacement closed-loop feedback control system is designed,using PID control algorithm based on PLC to adjust the output displacement.After continuous parameter tuning and testing,the performance of the control system had achieved the expected goal.A large number of theoretical analysis and experiment show that the output displacement of hydraulic micro displacement actuator can be controlled.It has high precision,high repeatability and high stiffness.The output precision and dynamic characteristic are guaranteed due to the micro displacement closed-loop control system.In general,the micro-displacement actuator which is based on static pressure expansion is feasible.