Research On The Control Technology Of Water Jet For The Auxiliary Support Of Low-rigidity Parts

Low-rigidity parts are mostly characterized by complicated structure,high requirement of precision and relatively low stiffness.In CNC machining,they are vulnerable to the coupling effect of cutting force,cutting heat,residual stress,clamping conditions and other factors,resulting in machining deformation and cutting vibration,ultimately reducing machining precision and surface quality,and severe cases can cause parts scrapped.Up to now,the research of water jet is mainly for the application of water jet in industrial cutting,drilling and rock breaking,the goal of which is how to effectively destroy the impacted object,how to enlarge the erosion pressure,and how to enlarge the damage to the material.However,it ignores that controllable water jet within a certain range will have broader application fields and application prospects,such as auxiliary support,machining,surface polishing and so on.This paper was closely around the jet control technology to start.The impact characteristics of water jet and the effect of water jet on workpiece were studied.An intelligent precision servo direct drive pressure regulator was developed,due to the several defects of typical water jet generation system.An appropriate control strategy was selected for this new type of pressure source,then the dynamic and static performance of the whole system was analyzed by the joint simulation technology.These would undoubtedly have an important role in the study of jet support technology and jet technology.First of all,the background of this research was briefly introduced,as well as the current situation and development trend.The difficulties in stability,accuracy and rapid response of jet-assisted supporting process were discussed.After summarizing and analyzing,the research direction of jet control technology was put forward and established.Additionally,in order to make better use of water jet technology,the theoretical basis and the related characteristics behind the water jet technology were introduced.Secondly,the process of water jet assisted supporting workpiece was simulated by using ANSYS/LS-DYNA based on the algorithm of Smoothed Particle Hydrodynamics(SPH)coupled with Finite Element Method(FEM).The effects of water jet pressure,nozzle diameter,stand-off distance,impact angle and head structure on jet impact force were studied.The radial flow characteristics and the damage of workpiece under jet impact were discussed,which provided an important theoretical reference for real-time follow-up control of jet impact force.Additionally,the effects of water jet pressure,impact angle and stand-off distance on jet impact force were verified by means of experiment.Morever,the overall design of servo direct drive pressure regulator was performed from the mechanical-hydraulic part and the electrical control part.The key components were selected and designed by calculation.The mathematical model of servo direct drive pressure regulation system was established in the form of subsystem.The open-loop stability and the control characteristics of the system were studied by means of frequency domain analysis,which provided a theoretical guidance for the follow-up control strategy research and system performance analysis.Lastly,a three closed loop control scheme of "pressure loop + speed loop + current loop" was proposed according to the characteristics of the controlled object,and the fuzzy adaptive PID control algorithm was applied to the pressure control system of this new type of pressure source.And then this research used the advantages of AMESim and MATLAB/Simulink to establish the joint simulation model.The dynamic and static performance of the whole system under different control algorithms and different test signals was analyzed.It was proved that the fuzzy adaptive PID control algorithm could meet the control requirements such as small pressure fluctuation,good follow-up effect,fast response and strong anti-interference ability.