Research Of Active Measurement Method For Dynamical Balance Based On Dynamic Electromagnetic Force

While identifying the imbalance of the workpiece with large eccentric mass,grave error would be produced due to failing to guarantee the linearity of both the balance machine and measuring system.A method was present to improve the measurement accuracy of imbalance identification.It utilized a controllable electromagnet that generated the controllable electromagnetic force to attenuate the unbalance vibration synchronously,so as to avoid the vibration signal exceeding the liner range.This paper first introduced the measuring principle of the traditional dynamic balancing machine,whose measurement accuracy strongly depend on the linearity of the vibration system of the supporting structure.However,the linearity will be weakened due to the oversized vibration while identifying the imbalance of some special workpiece with large unbalance mass.Then the active measurement principle of dynamic unbalabce based on dynamic electromagnetic force was presented.Secondly,in order to generate the dynamic electromagnetic force with the same frequency of the centrifugal exciting force caused by the mass unbalance,E-type magnet was designed and appropriate parameters have been chosen,such as the size and material of the magnet and the turns and the diameter of the coil.Model of equivalent magnetic circuit of the electromagnet was established,and the relationship between the coil current and the dynamic electromagnetic force was analyzed by finite element modeling.The influence on the electromagnetic force of some factors such as temperature and air gap was investigated.Then,the hardware circuit of the control system of the magnet was designed.The main circuit of the control system was composed of DC chopping circuit.The exciting current of the coil,the temperature of the magnet and the residual vibration of the spring plate can be monitored through the signal acquisition circuit.To realize the on-off control of IGBT,PWM signals were generated by the EV module of the TMS320F2812.Besides,the related software system was also designed,including the signal acquisition module and the PWM signal generator module.Finally,the test rig was built and multiple dynamic balance measurement experiments were conducted.Through the processing of those repeated experimental data,it can be concluded that the scatter of the measurement results is small and with high repeatability and smaller measurement error,which verify the feasibility of this active measurement method for large imbalance measurement.