Development of dual-mode precision current source for macro–microcomposite actuator based on field programmable gate array

Abstract

To meet the requirements of variable input current forms, microstep adjustment, low error coefficient, high output linearity, and the low ripple of macro–microcomposite actuators developed by combining voice coil motors and a giant magnetostrictive actuator, in this study, a design scheme of dual-mode precise programmable current sources based on a field programmable gate array (FPGA) was proposed. First, according to the working principle and control characteristics of macro–microcomposite drivers, an overall circuit system model of a driving power supply was established. Second, based on the circuit operational amplifier principle, an output current equation of the power supply was obtained, and a current switching circuit and a dual-mode current sampling circuit were designed. Finally, an FPGA was used as the current control core, and an incremental PI algorithm was introduced to compensate for the current feedback. The experimental results showed that the precision current source can output two current modes (positive current 0–5 A and positive and negative current −5 to 5 A) under the FPGA control. The average current error coefficient of the output in the two current output modes was ε ≦ 0.006, the maximum nonlinearity was η_max ≦ 0.005, and the error between the current adjusting step value and the preset value was less than 1%.