Introduction With the development of power electronics technology, microelectronics technology and AC servo control theory, AC servo drives have performance comparable to DC servo drives, and AC servo drive technology has been widely used in industries such as printing, CNC machine tools, food packaging, textiles, plastics, and electronic semiconductors [1]. The motors of AC servo drive systems are generally divided into AC permanent magnet synchronous motors and squirrel-cage AC asynchronous motors. AC permanent magnet synchronous servo systems have certain advantages in the small power range, but in high power servo systems, squirrel-cage asynchronous motors are widely used due to their simple structure, easy manufacturing, low price, wide application range, and large overcurrent capacity [3]. The author developed a squirrel-cage three-phase asynchronous motor servo system based on ASIPM, field programmable gate array (FPGA) and dedicated digital signal processor (DSP). This paper introduces the system control principle, hardware and software design, and verifies it through experiments. 1 System Control Principle The vector control of the induction motor is usually oriented according to the stator flux linkage Ψs, rotor flux linkage Ψr and air gap flux linkage Ψm[6]; according to the different flux linkage position detection methods, vector control can be divided into direct vector control and indirect vector control. This system adopts indirect vector control oriented to the rotor flux linkage Ψr and uses the slip relationship to estimate the position of the flux linkage relative to the rotor, and achieves decoupling of the stator current of the motor by using coordinate transformation; it adopts current model estimation that can be used in any speed range, that is, using speed signal and current signal to estimate the rotor flux linkage component[2]. The system control block diagram is shown in Figure 1. 2 Hardware Design of Control System The servo system hardware with DSP as the core is shown in Figure 3. The core of the control circuit of the whole system is composed of DSP + FPGA. 2.1 Main Control Circuit Among them, the FPGA is Xilinx XC3S400, which is mainly used for signal logic control and output control of switch drive signals, etc. The DSP, model TMS320F2812, serves as the control core. It receives external signals, controls the servo system's operating parameters, and converts them into inverter switching signals. These signals, after isolation, directly control the ASIPM module to power the motor. 2.2 Power Circuit: The main circuit first undergoes uncontrolled rectification, then full-bridge inverter output. The power conversion circuit uses Mitsubishi's integrated intelligent power module (ASIPM) PS12036. This module uses 15A, 1200V power transistors, integrates driver circuitry, and incorporates fault detection and protection circuits for short circuits, overcurrent, and undervoltage. The system power supply uses a transformer-based step-down isolation diode rectifier and filter, followed by a linear regulated power supply and a switching power supply to power various components, including the DSP and FPGA, current sampling and processing circuits, photoelectric encoder interface circuit, 7-channel PWM signal drive power supply, serial port circuit, and protection circuit. 2.3 Current Sampling Circuit The system design requires sampling three-phase current. The sampling circuit uses a Hall sensor and limits the voltage range to 0V~3.0V via an AD analog circuit before sending it to the DSP's AD converter. 2.4 Rotor Speed ​​and Position Detection Circuit The motor feedback uses an incremental photoelectric encoder with a resolution of 2000 lines/revolution. It outputs pulse signals A, B, and Z. Signals A and B are 90° out of phase (electrical angle). The DSP determines the motor's direction and speed by judging the phase and number of A and B signals. The Z signal appears once per revolution and is used for position signal reset. The photoelectric encoder pulse signal is isolated and level-converted by the interface circuit before being sent to the DSP. The internal QEP circuit quadruples the frequency, resulting in 8000 pulses per revolution. 3 System Software Implementation Scheme The system software can be structurally divided into a main program and a PWM interrupt service subroutine. The main program only completes the initialization tasks of the system hardware and software and then enters a waiting state. The complete field-oriented real-time vector control algorithm is implemented in the T1 timer underflow interrupt service routine. The sampling of position and speed uses the QEP unit of DSP. In order to stabilize the motor speed, variable period sampling is adopted, and the sampling period of different speed segments is different. Current sampling uses the AD conversion module built into TMS320F2812, and digital filtering is performed on the signal at the same time. The current loop and speed loop use PID regulators; in order to achieve fast position tracking and no overshoot, the position loop uses a variable proportional regulator. Space vector PWM (SVPWM) divides the rotor magnetic field space into 6 regions according to the switching logic of the inverter. The stator voltage vector is decomposed in each region to obtain the parameters required to generate the actual PWM waveform. In order to improve the digital representation range and the accuracy of the operation, and enhance the portability of the program, the operation quantity is normalized, that is, the operation quantity is compared with its maximum value or rated value. In this way, the operation quantity is converted into a decimal. In order to meet the requirements of fixed-point operation of TMS320F2812, the decimal can be converted into an integer form using _iq() in the IQmath program library, that is, the Q format of the decimal[5]. In this way, floating-point operation is converted into a much faster integer operation. 4. Experimental Results and Conclusions The ASIPM used in this experiment was the Mitsubishi PS12036. The experimental motor had a rated power of 2.2kW, a rated line voltage of 380V, a rated frequency of 50Hz, a rated current of 4A, and a Y-connection. The carrier frequency of the SVPWM wave was 10kHz. The experimental waveforms are shown in Figures 7 and 8. These waveforms verified the correctness of the SVPWM, and the reduction in harmonic components of the inverter output current indicates that the system has high control accuracy and good dynamic and static characteristics. 5. Conclusion The AC servo system studied in this paper fully utilizes the peripheral circuits and control interfaces of DSP and FPGA, simplifying the hardware design. Simultaneously, the modular approach in the software design facilitates the writing of complex programs. The experimental results show that the system has good control performance. With the ever-increasing demand for high precision and high reliability in industrial production, the application of AC servo systems will become increasingly widespread. References: [1] Zhang Hao, Xu Mingjin, Yang Mei. High-voltage high-power AC variable frequency speed regulation technology [M]. Beijing: Machinery Industry Press, 2006. [2] Bose B K. Modern Power Electronics and AC Drives [M]. Beijing: Machinery Industry Press, 2003. [3] Mashimo T, Ohishi K, Dohmeki N. High speed positioning system considering load torque for servo motor [J]. The Papers of Technical Meeting on Industrial Instrumentation and Control, IEE Japan, 2003, IIC-03-27:69-74. [4] Zhao Jin, Yang Lu, Yu Gaoming, et al. AC servo system based on IPM squirrel-cage motor [J]. Power Electronics Technology, 2000, (5): 18-19. [5] Wang Xiaoming. DSP control of electric motor - TI company DSP application [M]. Beijing: Beijing University of Aeronautics and Astronautics Press, 2004. [6] Doncker De RW, Ovotny DW. The universal field oriented controller [J]. IEEE IAS Annu. Meet.Conf.Rec.1998:450～456. [7] Jiang Zhongming. Design of a fully digital servo system based on a three-phase asynchronous motor [J]. Servo Technology.2007:26～28. Mailing address: P.O. Box 38, Graduate Department, No. 25 Xinghua North Road, Daxing District, Beijing Mobile phone: 15101084190 About the authors: Long Chengyuan (1983-) Male, Master's student, research direction is power electronics technology, AC servo control. Zhang Hao (1968-) Male, Associate Professor, currently mainly engaged in teaching and research on high voltage frequency conversion, solar power generation, wind power generation, power electronics and AC drive. Xu Mingjin (1970-) Male, Lecturer, currently mainly engaged in teaching and research on electrical drive and control, frequency conversion speed regulation technology.