| With the broaching widely applied in the forming complex surface in the field of aero engine,marine turbine,automobile break system and so on,the point has become one of focus that is how to improve broaching performance.Especially,the nonlinear force caused by the coupling effect of broach motion should be reduced.Meanwhile,the vibration-assisted broaching(VAB)technique has a huge developing potential in improving the stability,precision and efficiency of broaching process,because of the pulse characteristics of broaching force.Therefore,in order to realize the industrialization development of VAB,the influence of broach motion on dynamic characteristics of broaching process is used to analysis.And the variation rules of exciting parameters and broaching force can be obtained,combining with important research target in the project.However,there are some problems on the dynamic characteristics of electro-hydraulic VAB at present.The first one is the dynamic characteristics of the electro-hydraulic exciter.The second one is the dynamic characteristics of multi-tooth broaching process.The last one is the coupling dynamics of the exciter and broaching system.Aiming at the above problems,this study focus on establishing the dynamic model of dual-valve electro-hydraulic VAB system by introducing the hydraulic fluid mechanics,the model of valve controlled asymmetric cylinder,empirical formula model and shear angle theory,broach motion equation,three variable control(TVC),inverse model control(IMC),iterative learning control(ILC)and fuzzy-PID control method.And then,the dynamic characteristics of VAB system was studied based on the simulation results by MATLAB/Simulink and experimental data.The main research contents and results are as follows.(1)The novel dual-valve electro-hydraulic VAB system was designed with the analysis on the main factors affecting the VAB performance.In order to determine the VAB system scheme,the principle and performance of broaching also had been analyzed in detail.And then,the key components of VAB system were chosen by the calculation,such as exciter cylinder and servo valve.(2)The mathematical model of dual-valve electro-hydraulic vibrator was built.And then,the stability and dynamic response of exciter was studied through the MATLAB/Simulink simulation model.Moreover,the output performance of exciter with external force was been analyzed.The simulation results with varying excitation parameters show that the parallel dual-valve can effectively increase the output amplitude.However,the maximum amplitude gain was 80% because of the limiting effect of the sink flow.The excitation frequency and the opening of the valve directly affect the pressure characteristics of the cylinder and the displacement output amplitude,while the external load would aggravate the disturbance of the output displacement and the amplitude of output force.Therefore,the pressure characteristics of the exciting cylinder varied greatly when the broaching force transient,which would lead to the drift of the balance position of the displacement waveform.(3)The dynamic model of dual valve VAB system was built.First of all,the mathematic model of broaching was built.And the relationship of broach motion,the time-domain characteristics of broaching area and the dynamic characteristics of broaching were analyzed by simulation model.And the influence of coupling characteristics on dynamic broaching force were also researched.The simulation results show that the main factor that causes the difference on the dynamic characteristics of vibratory broaching force and the broaching is the time domain characteristics of broaching area.And the excitation frequency is the main factor which affects the performance of VAB.And the average broaching force is obviously decreased because of the pulse characteristics of broaching force.Based on the different vibration frequency,its decline rate is about 49.6% to 67.6%;but under the influence of system coupling,the average value of the VAB force actually decreased by 15% to 27.4%.Therefore,in order to achieve better broaching performance,the exciting parameters should be adjusted in real-time during the process to change the output characteristics of the exciting system.(4)The stability control strategy for dual-valve electro-hydraulic VAB system were proposed.The FFIM-TVC controller was designed for improving the stability excitator without load based on the TVC principle and inverse system theory.The simulation results show that FFIM-TVC controller is not only to improve the frequency response characteristics of vibration system,but also make the system easier to replicate position instruction,compared with the open-loop control.And the ILC-FPID controller was designed for improving the stability excitatory with load based on the ILC theory and the fuzzy PID control theory.It can closed-loop feedback control of the stabilization waveform of the excitation system by iterative learning and training.The simulation results show that the ILC-FPID controller can make the output waveform under the broaching force stabilize gradually,and also can correct the offset of the output waveform.(5)The experiments were carried out for investigating the performance of dual-valve electro-hydraulic VAB system.By comparing the measured data with the simulation results,on the one hand,the validity of the established dynamic model is verified.On the other hand,it shows that the VAB process has beneficial effects on the broaching performance. |
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