Currently, stepper motors are widely used in industrial applications such as automatic wire stripping machines, industrial robots, engraving machines, and flocking machine workbenches, where precise positioning is required. Common stepper motor control systems consist of a drive module and a controller module. The drive module amplifies power, while the controller module generates control signals for motor rotation. This control method consumes significant resources from the control core, impacting the real-time performance and flexibility of the control system. The stepper motor driver designed in this paper integrates the control circuit and drive module circuitry into a single module, reducing the burden on the main control core, improving the system's real-time performance and reliability, and making system design more flexible and convenient.
1. Design of CAN Repeater Hardware
1.1 System Hardware Structure
The block diagram of the integrated two-phase stepper motor driver system based on the CAN bus designed in this paper is shown in Figure 1. It includes a CAN transceiver L9616, an STM32F103C6 MCU, optocouplers, an SLA7033M driver chip, a temperature sensor, and a D/A converter. After receiving the frame data packets sent by the main control core, the CAN transceiver L9616 sends the data packets to the MCU. The STM32F103C6 is the core of the integrated stepper motor driver. It parses data packets transmitted from the L9616 CAN transceiver, performs corresponding operations, and generates the appropriate drive signals and rotation direction. On the other hand, the MCU controls a high-precision D/A converter. The voltage output from the D/A converter is sent to the SLA7033M driver chip to maintain a constant output current. A sampling resistor is added to the output of the SLA7033M, and the MCU monitors the output current in real time. When the output current exceeds a threshold, the drive signal is shut off to protect the SLA7033M chip. Additionally, the MCU monitors the temperature of the heatsink connected to the SLA7033M chip in real time. When the temperature on the heatsink exceeds a preset value, the drive signal is shut off, further protecting the SLA7033M. The MCU's sampling of the SLA7033M's output current and real-time temperature monitoring effectively protect the SLA7033M, extending its lifespan and ensuring more stable operation. Since the signal output by the MCU is a weak signal, while the signal output by the SLA7033M is a high-voltage and high-current signal, optocoupler isolation is used to ensure the normal operation of the MCU, so that the control signal and the drive signal are separated. At the same time, the control and drive circuits are powered by independent power supplies, so they do not interfere with each other, and the signals are transmitted through optocouplers.
1.2 STM32F105 Microcontroller
The STM32F105 is a 32-bit flash microcontroller based on the latest ARMv7.0 Cortex-M3 core. This core is specifically developed for embedded applications and features PWM output for motor control, making it particularly suitable for motor control applications. The STM32F10 has a built-in CAN transceiver FIFO, which can reduce the cost of using an external CAN controller and improve system stability. The STM32F103 has a large capacity of FLASH and RAM, as well as rich peripherals, so using the STM32F103 as the main control chip can easily implement CAN data transmission and reception, A/D conversion, D/A conversion, PWM output, etc.
1.3 CAN Transceiver Circuit
The CAN transceiver uses STMicroelectronics' L9616. The terminating resistors are provided via jumpers for user selection during installation. Transient voltage suppressor diodes are connected in parallel on the differential signal lines to protect the L9616's I/O. The opto-isolation section uses the high-speed optocoupler 6N137 with a maximum slew rate of 10 Mbit/s, and resistors R2 and R5 limit current. VCC5_1 is a 5V voltage generated separately by the DC/DC isolated power supply.
1.4 Power Supply Circuit
The stepper motor uses a 5V power supply. The traditional three-stage voltage regulator is replaced by the LM2596 switching regulator integrated chip, requiring very few external components to form a highly efficient voltage regulation circuit without the need for a heatsink. The 5V voltage generated by the LM2576 supplies the motor driver chip, while the 3.3V voltage required for the main control CPU is generated by the LM1117-3.3 LDO chip. The DC/DC circuit with a separate power supply for the CAN transceiver circuit uses an isolated power supply module, ensuring complete electrical isolation between the driver and the CAN bus interface.
