Design And Implementation Of Single-Legged System For Motor-Driven Quadruped Robot

Quadruped robots have always been a research hotspot in the field of mobile robots.With the development of technology and economy,the quadruped robot has predictable commercial application scenarios,such as power inspection of substations and earthquake rescue.However,in order to achieve the application of the scenarios,it is necessary to develop a quadruped robot capable of adapting to various uneven terrains,crossing obstacles,and climbing stairs.Therefore,it is crucial to develop high-performance and flexible quadruped robots.The single leg is the basis of the quadruped robot,so it is important to study the high-performance and flexible single-leg system.To this end,this thesis analyzes,studies and experimentally validates the single-leg mechanical system,control system,and compliance strategy.The main contents are as follows:(1)Mechanical system:for the mechanical system,this thesis analyzes the mechanical design of the quadruped robot with excellent performance at home and abroad,and summarizes the five principles of mechanical design of high-performance single-leg:high torque density joint,low inertial legs,low mechanical impedance legs,large working space,high energy efficiency.And found that different design goals lead to different design methods.This thesis proposes to design a quadruped robot with good backdrivability performance and high flexibility,so it is necessary to follow the principle of large working space and low inertia,while taking into account low mechanical impedance and high torque density.Therefore,for a single joint,a quasi-direct-drive actuators with planetary reducer of a small reduction ratio is used.Both the pitch hip and the pitch knee motors are mounted at the hip joint to reduce the inertia of the leg.Using a belt with teeth drives the knee joint.(2)Control system:For the design of the control system,this thesis follows the principles of stability,clear timing,strong real-time and certain fault tolerance.These principles are realized by hardware and software.PCM-3362 military-grade industrial computer,QNX operating system,ELMO Gold series high-performance driver and CANopen bus are selecting about hardware.The communication module that is most suitable for the system is designed by analyzing the real-time performance of the CANopen module.System stability and real-time are ensured by task assignment to the CPU,using multi-threading technology,setting priority,and non-blocking driver program.(3)Compliant algorithm:For the compliance strategy,this thesis analyzes the advantages and disadvantages of passive compliance and active compliance,as well as the advantages and disadvantages of the three mainstream active compliances,and finally adopts the compliance method of joint torque control based on virtual model.In order to reduce damage to the system,the physical experimental validations are implemented after simulation analysis.Firstly,the relationship of torque and current of the motor is calibrated.Then the active compliance of the single joint and the single leg is realized.The damping coefficient of the system is adaptively adjusted by using fuzzy control,and the system performance is greatly improved.In order to solve the problem of strong fluctuation of foot speed,this thesis uses kalman filter to estimate the optimal foot speed.For the one-leg jump,this thesis divides it into three stages of buffer-bounce-fly,and realizes the ground detection and the three-stage accurate switching based on the foot position detection and time statistics without using the foot sensor.Finally,the experimental validation of the physical prototype is implemented,and the rationality and effectiveness of the design of the single-leg system are verified by the experimental results.