Application of 32-bit MCU in servo motor

In the servo system, AC permanent magnet synchronous motor has become the mainstream choice of servo system because of its excellent low-speed performance, weak magnetic high-speed control, wide speed regulation range, high dynamic characteristics and efficiency. At present, permanent magnet synchronous AC servo technology has become one of the supporting technologies of industrial automation.

This article takes Renesas Electronics' 32-bit variable frequency MCU V850E/IX3 UPD70F3454 as an example to explain its application in AC servo system.

About Renesas Electronics UPD70F3454

UPD70F3454 is a 32-bit high-performance MCU for variable frequency control developed by Renesas Electronics. It uses V850 core, RISC architecture, 5-stage pipeline, built-in DSP function, maximum 64MHZ, built-in 256K flash ROM and related peripheral functions, such as DMA controller, timer/counter, serial interface UART, SPI, IIC, A/D, bus controller, low voltage detection, on-chip debugging, etc. For variable frequency control, UPD70F3454 provides 2 groups of six-phase PWM outputs, two groups of independent 12-bit AD converters, built-in comparators and op amps, two groups of encoder input counters, highly integrated peripherals required for servo motor control, and can use one MCU to control two servo motors.

System Principle

1. System Hardware Structure:

The hardware of the servo control system based on UPD70F3454 is as shown in the figure below. It mainly includes:

⑴, MCU UPD70F3454 and its peripheral circuits, 3454 is the core controller, receives external signals, judges the working mode of the system, and converts it into the switching signal output of the inverter, drives IPM after isolation, and EEPROM is used to save parameters and store user information. The RS232 module is responsible for communicating with the host computer, or directly sending speed and direction control information through the host computer; programming and debugging can be done through MINICUBE, MINICUBE2, PG-FP5.

⑵, IPM drive circuit, MCU outputs 6-phase PWM signals, which are transmitted through optocoupler isolation and IPM full-bridge inverter output to drive the strong power circuit of the servo motor.

⑶. Current sampling. The system needs to sample at least two-phase currents, such as Ia and Ic. The signal of the sampling circuit is converted to digital after the operational amplifier and comparator of the AD module inside 3454.

⑷. Rotor position detection. The orthogonal encoding signals A, B, and Z output by the incremental photoelectric encoder are input to the TMT module of the MCU to determine the position of the motor rotor and the motor speed signal.

⑸. Sensor signal input, including pulse input, analog input, switch input, etc. and communication with other MCUs.


Figure: Renesas Electronics UPD70F3454 Servo Control Hardware Structure Diagram

2. Features and advantages:

①. Precise full digital control. Adopting Renesas Electronics 32-bit dedicated frequency conversion MCU, 64MHZ CPU and PWM operation clock, high-precision frequency output.

②. Low system cost. UPD70F3454 is equipped with rich peripheral resources such as power-on reset, voltage detection, voltage regulator, 4 operational amplifiers, 8 comparators, encoder interface, etc.

③. Rich peripheral functions. 5V single power supply, external bus, DMA controller.

④. Provide a safe and secure high-end variable frequency motor evaluation system. There are software reference codes for each module of the system, such as PWM, AD, TMT and other modules. Users can easily carry out secondary development on the original system. And there is a strong support team for the motor group.

In addition to high-speed real-time response and single clock instructions, UPD70F3454 also supports multiplication instructions, saturation operations, bit operations and other instructions optimized for digital servo control systems. The servo control system based on UPD70F3454 in this article makes full use of the internal resources of MCU, with simple circuit design and few peripheral devices, meets the real-time requirements of vector control, and realizes full digital control of servo. The low-cost and high-performance MCU control characteristics make the system have a good application prospect.

At present, UPD70F3454 has been widely used in customers' general servos, textile machinery, and sewing machines. For detailed product information and technical support, please contact Shiqiang Telecom, an authorized agent of Renesas Electronics.