Design Of Joint Drive And Motion Control System Of The Mammal-reptile Quadruped Robot

Compared with wheeled robots and crawler robots,the leg-foot featured quadruped robot shows outstanding advantages in terms of flexible locomotion,terrain adaptability,and climbing obstacles,and has become a hot topic in the field of robotics research in recent years.According to the different forms of locomotion,quadruped robots can be divided into mammal-like quadruped robots and reptile-like quadruped robots.The mammal-like quadruped robot has the characteristics of flexible movement and good dynamic stability,but its center of mass is high,and the static stability is poor;the reptile-like quadruped robot adopts the limbs abduction structure,which results that its center of mass is low and its movement is stable,but the robot moving speed slow.In order to integrate the motion characteristics of these two bionic quadruped robots,Center for Robotics,Shandong University,designs a bionic quadruped robot with a mammal-reptile fusion.This paper takes the mammal-reptile quadruped robot as the research object,and designs a high-torque and high-performance joint drive unit and a high-real-time and high reliability motion control system for it.The main research contents are as follows:(1)Design of joint drive unit.In order to realize the servo control of the leg joints of the quadruped robot,this paper uses a three-phase brushless DC motor to drive the leg joints,designs a joint driver that integrates a motor,a reducer and a driver board,and completes the design of the hardware circuit and software system of the joint driver.In order to verify the servo performance of the joint driver,a joint drive experiment platform based on a magnetic powder dynamometer is designed,and experiments are carried out from three aspects:position servo,velocity servo and torque servo.The experimental results show that the joint servo system has good position,velocity and torque servo performance,and meets the joint control requirements of the mammal-reptile quadruped robot.(2)Design of motion control system.A modular approach is adopted to design the overall framework of the robot real-time control system in this paper,and completes the design of the hardware and software of each module.Firstly,this paper designs the motion controller and uses NI's sbRIO-9629 real-time controller to complete the planning of various control tasks for the robot;Secondly,in order to meet the communication requirements between the motion controller and the joint driver,this paper uses the NI 9853E CAN card to expand the CAN bus in order to ensure that each single leg of the robot occupies a CAN bus,and designs the execution process of the CAN communication program.Thirdly,this paper designs a robot attitude information acquisition system which uses IMU to collect attitude data including pitch angle,yaw angle and roll angle of the robot;Fourthly,in view of the robot remote control problem,by redefining the button and joystick functions of the wireless controller,this paper realizes the control of the robot forward and backward,stand up and squat and posture adjustment;Finally,in order to facilitate the control of the robot's power supply and supply power to the various components of the control system,based on the analysis of the working conditions of each device,a power management system with functions such as switching,step-down,current and voltage detection and protection is designed.(3)Mammal-reptile quadruped robot physical prototype integration and experiment.Firstly,this paper analyzes the mammal-reptile quadruped robot prototype from single-leg joint structure,trunk structure and bionic mechanism.Secondly,For the anti-parallelogram structure of the roll hip joint and the pitch knee joint,this paper derives the angle transmission relationship and the torque transmission relationship between the joint and the motor output shaft.Thirdly,the control system designed in the early stage is integrated into the physical prototype of the robot,and the construction of the robot's underlying hardware is completed.Finally,the CAN bus communication experiment and the robot movement experiment are designed,and the CAN bus communication rate and the robot's movement performance are tested.The experimental results show that the CAN bus communication frequency can reach 1 kHz,which meets the requirements of the mammal-reptile quadruped robot for the communication rate between the motion controller and the joint driver;the robot control system is reliable and effective,and the mammal-reptile quadruped robot can move with the trot gait at a step frequency of 1.5Hz.