Hydraulic Diaphragm Flexible Servo Mechanism And Its Application In Non-circular Pin Hole

The piston is one of the core of automotive engine parts,with the constant improvement of the performance requirements of engine,the conventional image of the "bell" piston pin hole structure has been difficult to meet the requirements of high power motors,by the piston pin hole for irregular oval cross section design can improve the bearing capacity of the piston,prolong its service life,However,the existing boring machine can not realize the high speed tool radial compensation motion,so the non-circular hole cannot be processed.Therefore,a piston non-round pin hole machining system based on Hydraulic Diaphragm Actuator(HDA)is designed in this paper.The system includes high frequency ring motor direct drive servo valve(VCM-DDV)and membrane flexible variable body.Firstly,the thesis analyzes VCM-DDV,and focuses on the study of hydraulic force and flow characteristics.Through the research on the hydraulic system and the rigidity of membrane flexible deformable body,the feasibility of machining non-round pin holes with the flexible mechanism of hydraulic diaphragm is demonstrated.In view of the boring tool rod vibration problems appeared in the process of experiment,design a new type of composite structure boring bar,and through the optimization of structural parameters theory analysis and optimization design based on Ansys the damping properties of the boring bar for further optimization,and finally to 40 cr boring bar and carbide boring bar processing experiment was carried out comparative analysis,proved the superiority of boring bar system design.Through the analysis of the hydraulic servo system,the HDA system model is established,the frequency response method is used to identify the transfer function of the system,and the structural parameters of the system are determined.High displacement control accuracy and frequency response characteristics are required in HDA system to realize high speed boring of non-circular pin holes.However,the traditional system based on VCM-DDV is difficult to achieve high frequency response and high precision in piston pin hole machining.In this paper,the pressure feedback control is added on the basis of the closed loop control of the valve core displacement,so as to realize the high frequency and high precision boring of the non-circular pin hole.In the process of boring,the cutting impact and elastic hysteresis of the film deformable body lead to the nonlinear compensation of tool displacement,which affects the machining accuracy of non-round pin holes.So traditional PID and fuzzy adaptive algorithm is proposed with the combination of double closed loop control method,realized the position control the inner ring and outer ring of pressure control parameter self-tuning,finally and single closed-loop control for the position response contrast,the results show that under the 80 hz follow error rate from 20.2%to 3.5%,the superiority of the proposed control algorithm is verified.Finally,the experimental platform was built and the processing experiment was verified.The experimental results show that the designed hydraulic diaphragm flexible mechanism and control strategy are reasonable,which provides a basis for the piston non-round pin hole processing.