Study On Chopper Driving Electromagnet And Its Force Control System

The application of electromagnet in many areas involves the problem of the closed-loop control. Although the purpose for the suction maglev system is to make the air-gap stable by controlling the force and the electromagnetic vibration exciter is to make the object vibrate with a designated frequency and amplitude, the realizing methods and control strategies are basically the same. Therefore, this article introduces the applition of the maglev system force control technology in the electromagnetic vibration system, including the related theoretical and experimental researches.Firstly, the system plan of the electromagnetic vibration exciter is reseached according to the need of the bow net arc mechanism research test for simulating the bow net pressure or clearance control. Though the analysis and calculation, the air gap for the electromagnetic vibration exciter to work stablely and the range of the corresponding exciter current is obtained. On the basis of the analysis of the electromagnetic vibration mechanics and control system characteristics, the article explores the design of the controller with the current feedback loop. The analysis shows that the current loop can overcome the inductance influence and make the current reach the expected value fast. This approves the response speed greatly.Secondly, the characteristic and parameters of the H bridge chopper are studied. The main circuit of the electromagnetic vibration exciter is designed. The detection schemes of the current, the inductance, the bit displacement and the acceleration are designed. Choose the DSP2812 as the MPU, expend the A/D conversion module, build the electromagnetic vibration control platform, and make the program of the A/D conversion, the asynchronous serial communication, the PWM output and the closed-loop control.Finally, the combined debugging of the software and hardware is finished on the platform of the experimental study, and the experimental results are analyzed. Test results show that the current loop can reduce the effect of the electromagnet inductance and improve the system of dynamic response speed. In the condition of constant exciter current amplitude, the higher the exciter current frequency is, the smaller the vibration amplitude is. But the waveform has large distortion in low-frequency vibration, and adding the current closed-loop control can obviously improve the low-frequency vibration waveform.