Multiphase permanent magnet synchronous motor (PMSM) has better performance than traditional motor. Its redundancy makes PMSM keep running after phase-out or phase-out. In this paper, a multi-phase permanent magnet synchronous motor controller based on TMS320F28335 is designed. The design method of minimum system and peripheral circuit of DSP is given. A 50W power supply is designed for the controller. In recent years, with the increasing demand for the reliability of speed control system in industrial field and the rapid development of material technology and power electronics technology, it is possible to realize high-performance multi-phase frequency speed control system.
Its advantages and application scope have been further improved and expanded, especially in military application field.
In important industrial fields, the stability and reliability of high performance multi-phase motor speed control system is an important guarantee for the system operation. With the development of industrial technology, the advantages of multi-phase motor speed control system are more and more obvious. It is widely used in military and civil fields, such as aerospace, surface warships, submarines, and electric vehicles. TMS320F28335 Digital Signal Processor TI Company’s a series of floating-point DSP controller of TMS320C28X. Compared with the previous fixed-point DSP, thermostatic element the device has high precision, low cost, low power consumption, high performance, high peripheral integration, large data and program storage, and A/D conversion is more accurate and fast. Therefore, this system takes DSP28335 as the core, and designs a multi-phase permanent magnet synchronous motor controller [1]. TMS320F28335 is a floating-point digital signal processor developed by TI company in recent years, which has greatly improved the performance of C2000 series of DSPs. It has powerful digital signal processing capability. Secondly, it integrates a large number of peripherals for control and use. It also has the function of microcontroller, as well as improved Harvard structure, cyclic addressing and the execution speed of DSP [3]. The control system of DSP includes minimum system and peripheral circuit. The minimum system consists of power supply, reset, clock and JTAG circuit. The peripheral circuit is designed according to the actual needs. Its overall structure is shown in Figure 1.
The power supply of DSP chip adopts TPS767D301, which is a power supply chip specially designed by TI company for DSP. It can output two voltage channels: one output 3.3V, and one output voltage can be adjusted. Because the DSP28335 chip is powered by 3.
3V and 1.9V dual power supply, the second power supply is needed to output 1.9V stable voltage.
The power supply schematic diagram of DSP is shown in Figure 2. With the I/O port of the DSP, the DSP can output six complementary PWM signals. Because of the limited I/O output capability of the DSP, the PWM signal is very vulnerable to external interference, which affects the control circuit behind. Therefore, it is necessary to isolate the PWM signal from the external circuit. In this paper, 74LVX3245 driver chip and 6N136 isolator chip are used, and the driving circuit is as follows. In this paper, LEM-HAS50 current sensor is used to detect each phase current of six-phase permanent magnet synchronous motor. The sensor adopts Hall effect measurement principle. The primary and secondary circuits are separated by transformers. The isolation voltage is 3000V. It is small, easy to install and saves space. It has strong anti-jamming ability with a precision of 1%. The input current INP=50A is transmitted. Output Voltage VOUT= 4V. Fig. 5 is a current sampling schematic diagram, which converts IC1 current signal to 0 ~ 3V voltage signal and inputs it to ADC pin of DSP. In this paper, an external active 30MHz crystal oscillator is used, connected with X1 and X2 pins, and processed by internal frequency division of DSP to 150 MHz. The system reset circuit uses TPS3823-3.
3 chip provided by TI company and connects with XRST pin. The speed and direction of the motor need to be measured in real time, so the system uses OIH-48-2500P4-L6-5V encoder. The encoder consists of a central axis photoelectric code disc with circular through and dark notches, a photoelectric transmitter and a receiver reading and acquiring four sets of sinusoidal wave signals, which are combined into A, B, C and D. Each sinusoidal wave has a 90 degree phase difference (360 degrees relative to a cycle wave). The C and D signals are reversed and superimposed on A and B phases to enhance the stable signal. Another Z-phase pulse is output to represent the zero reference bit. Because the encoder is directly connected with the motor, if the encoder signal is sent directly to the DSP, the interference signal will also enter the DSP, affecting the normal operation of the system.
Therefore, the output signal of the encoder is optically coupled to the DSP. There is an enhanced orthogonal encoding module (eQEP) in the DSP. When the motor is running, the eQEP module cooperates with the photoelectric encoder. The speed and position information of the motor can be obtained. The physical object of the controller is shown in Figure 6.
Switching power supply is a kind of power supply which uses modern power electronic technology to control the time ratio of switching on and off and maintain stable output voltage. It is generally composed of pulse width modulation (PWM) control IC and MOSFET. With the development and innovation of power electronics technology, switching power supply technology is constantly innovating. At present, switching power supply is widely used in almost all electronic devices because of its small size, light weight and high efficiency.
It is an indispensable power supply mode for the rapid development of the electronic information industry. The stability of power supply circuit is related to the stability of control circuit and signal acquisition circuit, so power supply circuit should have good anti-overvoltage and over-current ability. The switching power supply with flyback topology is adopted in this paper. Its input voltage is 220 VAC ( 10% fluctuation), and its output power is two 24V/300mA, one 15V/600mA and one 5V/2A, so the output power is 50W. Np = 75 turns, Ns1 = 10 turns, Ns2 = 15 turns, Ns3 = 17 turns. The main function of RCD circuit is to absorb reflection voltage and leakage voltage and protect MOSFET, which can be omitted when high voltage MOSFET is selected. Note that RCD parameters should be determined during commissioning. The calculated values are only a rough range. The accurate values should be determined under full load. The purpose is to weaken the peak voltage, make the voltage waveform approximate square wave and protect MOSFET. After debugging, R = 102K and C = 2.2nF are obtained. The drain-to-ground voltage waveform of MOSFET is shown in Figure 7. The software is programmed in the environment of CCS (Code Composer Studio). CCS is an integrated development environment for the series of TMS320 DSPs. It uses graphical interface under Windows operating system to provide environment configuration, source file editing, program debugging, tracking and analysis tools. CCS integrates many functions of code editing, compiling, linking and debugging, and supports mixed programming of C/C and assembly. The main program first initializes all the hardware in the system, and then AD collects all the signals in the system. When the system works properly and the start-up is confirmed, the program first detects the encoder information, determines the position and direction of the motor rotor, speed and other information, and then carries out PI regulation of the speed loop and current loop, PARK transformation, SVPWM control in turn. In summary, this paper designs a six-phase permanent magnet synchronous motor controller based on TMS320F28335, and improves it to further improve the control progress and anti-interference.