Integrated control system design of magnetic bearings for flywheel based on FPGA

In order to reduce the volume and power consumption of the control system for magnetically suspended flywheel,an integrated controller for 4-axis flywheel magnetic bearings and its field programmable gate array(FPGA) implementation were proposed.The integrated controller optimizes the signal conditioning,the position controller and the power amplifier as a whole,using a single FPGA chip to implement the rotor position control with unbalance compensation,current control,and the three-level PWM algorithms.The calculation tasks were implemented by means of reusing floating-point IP cores in timepieces.In order to balance the calculation speed and logic resources consumption,a method to select the precision of the A/D converter and the word length of the floating-point IP cores in the control algorithms was proposed.An incremental algorithm was proposed to calculate the trigonometric function online,using only multipliers,accumulators,and lookup tables.The FPGA solution of the three-level PWM and an auto calibration method for the rotor position signals were proposed.Experiment results show that the maximum radial position error at the rotation speeds of 0～7 000 r/min is less than 10% of the protection gap.The conclusion is that all the control task for 4-axis flywheel magnetic bearings can be implemented on a single FPGA with less than 0.2 million equivalent logic gates.