Development Of FPGA-based Active Magnetic Bearing Amplifier And Research On Adaptive PI Parameter Tuning

Active magnetic bearings use controlled electromagnetic forces to achieve rotor levitation and active control of shaft position.They are non-contact bearings with advantages such as high environmental adaptability,high efficiency,high speed and active control.The power amplifier,as part of the actuator of the active magnetic bearing system,realises the control command signal of the position loop without static difference and quickly follows it,and its dynamic characteristics directly affect the performance of the active magnetic levitation bearing system.The actuator load coils of the active magnetically levitated bearing system are inductive loads and require high current and electromagnetic control force response speeds,thus requiring amplifiers specifically designed to match the active magnetic bearing system.However,the existing two-level modulated analogue switching amplifier,control system integration is low,current control parameters and current control algorithm adjustment is inconvenient,and at the same time cannot solve the contradiction between increasing the power circuit bus voltage to improve the dynamic performance of the amplifier system and increasing the output current ripple,which greatly limits the dynamic characteristics of the active magnetic levitation bearing improvement and urgently needs to be studied and solved.The main work of this paper is as follows.(1)A mathematical model of a three-level digital switching amplifier is established based on the Fourier series expansion method.The effect of natural frequency and damping ratio on the step response characteristics of the closed-loop transfer function of the switching amplifier system is studied under the condition that the bandwidth requirement is met,providing a th eoretical basis for the adjustment of PI current control parameters.To study the main performance parameters of three-level switching power amplifiers including loss,amplifier system bandwidth,current ripple,current response speed,electromagnetic force response speed and their influencing factors,to provide a theoretical basis for the study of ways to improve the dynamic characteristics of switching power amplifiers.(2)Development of a three-level PWM digital switching power amplifier based on FPGA.The hardware circuit section investigates the modular design of the hardware power circuit including the main power circuit,the optocoupler isolation and drive circuit,the current sensor feedback and sampling circuit,the AD conversion control circuit,etc.The software current control section investigates the implementation of AD conversion control,PI current control,triangular wave comparison method PWM threelevel pulse width modulation,phase shift and other algorithms in FPGAs and functional timing simulations.(3)Study the adaptive PI control algorithm based on a single neuron to rectify the PI control parameters of a digital switching power amplifier system.Improves the adaptive algorithm PI weight coefficient learning rules,builds simulation models and compares the digital PI step response output results.Stability analysis of the adaptive algorithm rectified PI parameters to verify the feasibility of the single neuron adaptive PI control rectified control parameters applied to a digital switching amplifier system system.(4)A magnetic bearing power amplifier performance test system was built to test the developed digital switching amplifier static current output characteristic curves,step response and sinusoidal response dynamic characteristic curves and system amplitude and frequency characteristic curves.Based on the existing copley analogue amplifier,the step response output performance is compared with the designed FPGA digital amplifier to verify the performance and reliability of the developed digital switching amplifier system.The research work in this paper can be based on the simulation of the adaptive amplifier system model to achieve PI parameter self-tuning,which is a reference value for improving the integration of the amplifier system,as well as improving the dynamic characteristics of the active magnetic levitation bearing system.