Development Of Driver Card Of Distributed Multi-axis AC Servo Motion Control System

Motion control is the core of CNC and Robots. Permanent Magnet Synchronous AC Motors (PMAC) are widely used in modern motion control system for its outstanding performance. With the improvement in the performance of digital signal processor (DSP) and field programmable gate array (FPGA), more and more functions are implemented in the lower level of the control system. The motion control technology is developing towards network and distributed structure. In this dissertation, a multi-axis distributed AC servo system is studied. The control principle, power stage and its interface are extensively discussed. The main works are listed as follows:1. A distributed multi-axis motion control system, based on DSP and FPGA techniques, is proposed. The system integrates the functions of motion controller and motor driver. The system is assembled in one processor board and 3 driver boards and can offer the functions of 1 motion controller and 6 motor drivers.2. A drive board, which implements the power stage for motor control and interface for analog and digital signals, for distributed motion control system is designed. The driver board is designed after the requirements for the interface to motor are studied. FPGA is used as interface between the DSP and the encoder, pulse command and power module. The latest intelligent power module (IPM) is used to provide the function of power stage. Most chips in the circuit are the latest IC that can offer more functions with fewer components. Both the performance and reliability are improved.3. Based on DSP and FPGA, a new space vector pulse width modulation (SVPWM) scheme is proposed. The traditional realization methods of SVPWM can't be used in the new system because the multi-axis character of the new system. In the new approach, the pulse width is calculated by DSP software and PWM generator is constructed by FPGA. The hardware and software resources are fully utilized and system structure is simplified.4. The FPGA interface to a novel current sensing circuit is designed. A high voltage integrated circuit (HVIC) is used to measure the motor phase current. The interface of the circuit is implemented with FPGA. Simulation results show that the design can work as expected.5. The vector control software for PMAC motor is developed. The vector control algorithm is the most time-critical part in PMAC control. So the algorithm is written in assemble language. The data are represented in fix point format. Forward CLARK, forward PARK, reverse PARK transform and 2 PI control loops are implemented with this data format. Simulation results show the calculation precision is satisfactory.6. The designed system is tested. The PMAC motor made by Sanyo Denki is controlled. The control precision and response speed are tested. Test results are shown and analyzed. Experiments show that the system can run smoothly with high position tracking precision and fast response speed.