Implementation of complete AC Servo control in a low cost FPGA and subsequent ASSP conversion

Abstract

A process of creating AC servo drives without software programming has been created using FPGA technology At the core of this design is a flexible motion control engine, designed using Verilog HDL language and implemented on an industry standard FPGA. The resulting portable design is converted into a unique servo-on-a-chip ASSP (application specific standard product) for use in cost sensitive applications. Functionality includes field orientation control (FOC), closed loop velocity control, (optionally) closed loop position control with notch filter/feedforward functions, incremental encoder, space vector modulation (SVM), and host communication modules. The system also supports direct digital interface to high voltage (600 V) bus systems by utilizing monolithic gate driving and current sensing ICs which are insensitive to high common mode offset and dV/dT. The FOC executes quickly in dedicated parallel hardware without the timing overhead penalty of a serial processor core. Fast control update is thus achieved which yields high bandwidth torque control exceeding 5 kHz at -3dB. The focus of this paper is efficient use of hardware (FPGA) resources to create a powerful, yet open architecture for AC servo control development, including performance analysis and comparison against conventional software based solutions. Test results based on 1 kW servo system are discussed, which are included for system verification.