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中文版 | English Version

Project Introduction

0. Robot Display

Bilibili Video Link

Show.mp4

1. File Description

  • Mechanical: The file 平衡步兵-原型机-总装 v17.f3z is the 3D model of the robot, modeled using Fusion
  • Electrical control: The tool chain is STM32CubeMX + arm-none-eabi-gcc + OpenOCD + VSCode + Makefile
  • Balance algorithm: Use serial PID, "bench model"

2. Mechanical Part (Body Parameters)

  • Joint motor upper swing angle = +20.0°
  • Joint motor lower swing angle = -80.0°
  • Development-Board-C distance from Body center distance (used for acceleration correction code not used)
  #define CENTER_IMU_W 0.11f        Gyroscope to Body center distance in X direction?  
  #define CENTER_IMU_L 0.074f       Gyroscope to Body center distance in Y direction?  
  #define CENTER_IMU_H 0.060f       Gyroscope to Body center height
Part Weight kg Length mm
Total mass 8.235
Main body 5.215
Main body center to simplified joint z direction distance -14.5mm
Leg total weight (one side) 1.5
Drive leg 0.2 150mm
Passive leg 0.3 270mm
Xiaomi motor 0.317
Wheel 0.183 62.2mm radius

3. Electrical Control Part

The tasks.json file has 2 tasks:

  • buildEmbeddedTargets task is used as a Prelaunchtask in lanuch.json, to compile files before debugging, more convenient
  • Download to STM task is used to burn the program, the method is to enter openocd -c in the terminal to burn the .hex file

3.1 Motor Selection

  • Joint motor: Unitree A1
    • Communication method: RS485 (need to use TTL to RS485 module driver)
    • Maximum series connection: 3 (so the left and right legs use 2+2, that is, one side of the leg is connected in series with two joint motors)
    • Single encoder (need to use mechanical limit, pull the leg back to zero every time it is powered on, hit the mechanical limit as zero)
  • Hub motor: XIAOMI Cyber Gear
    • Communication method: CAN
    • Maximum series connection: very many
    • Single encoder

3.2 Opened peripherals

Peripheral Description
UART1 Unitree A1 motor (mounted on APB? peripheral clock) (enable DMA)
UART6 Unitree A1 motor (mounted on APB? peripheral clock) (enable DMA)
CAN1 Control Xiaomi motor (mounted on APB? peripheral clock)
UART3 Remote control reception
I2C2 OLED
TIM4 PWM buzzer (mounted on APB2 peripheral clock)
TIM10 BMI088 PWM heating
SPI1 BMI088 inertial measurement unit
I2C3 IST8310 magnetometer

3.3 FreeRTOS

task description
OLED_Task Display OLED + receive remote control
Motor_A1_Task Control A1 motor
Motor_MI_Task Control MI motor
INS_task Posture calculation (DJI original program)
Robot_task Balance control algorithm

3.4 Motor Wiring and ID

  • About A1 motor signal line
    • let the XT30 port face up, from left to right are GND A B
    • The connection for RS485 is A to A, B to B, GND to GND

3.5 Remote Control Operation Instructions

  • Left joystick
    • Control the leg length up and down, pull down to lengthen the leg, pull up to shorten the leg
  • Right joystick
    • Control forward and backward
  • Left Trigger
    • UP = leg locked at zero position
    • MIDDLE = leg position mode
  • Right Trigger
    • UP = laying-down + remote control mode
    • MIDDLE = balancing + remote control mode
    • DOWN = balancing + tracking mode
  • Attention: the tracking algorithm is not in this repository

4. Acknowledgements

  • Thanks to night8858 for the open source A1 motor control code
  • Thanks to 是小企鹅呀 for the open source Xiaomi micro motor control code
  • Thanks to Dongguan University of Technology for sharing the electronic control document
  • Thanks to HUNAN UNIVERSITY for the open source code of simulation and control
  • Thanks to SHANGHAI JIAOTONG UNIVERSITY for the open source mechanical design
  • Thanks to HARBIN INSTITUTE OF TECHNOLOGY for balancing algorithm instructions