Control System And Multi-gait Control Method Of Motor-driven Quadruped Robot

With the rapid development of bio-inspired robots,the application fields of them become wider.With respect to different functional requirements,various of bio-inspired robots are presented to the public.According to their different ways of movement,they can be divided into wheeled robots,tracked robots and legged robots.Compared to other types of robots,legged robots have a huge advantage in operating in natural environment due to the flexibility of the leg-foot mechanism.Nowadays,imitating the movement of quadruped mammals,many research teams have carried out research on quadruped robots.Among them,due to the advantages of simple control and convenient maintenance,motor-driven quadruped robots have become a research hotspot recently.To realize their application in different scenarios,it is essential to develop high-performance control systems and study control algorithms for various gaits.To this end,based on the open source robot simulation software Webots and the motor-driven quadruped robot prototype independently developed by Shandong University Center of Robotics,this thesis reports a new kind of control system of the quadruped robot,studies the control method of various gaits,and conducts experimental verification.The main contents are as follows.(1)The single-leg testing platform is introduced.The single-leg joint coordinate system of the quadruped robot is constructed and the kinematics and dynamics of the single leg are calculated.Tests including the free fall and the continuous bounce of the single leg based on the single-leg virtual model are carried on.Through multiple experiments and parameter adjustments,the feasibility of the single leg platform is verified on the platform.(2)A high-frequency,real-time,stable control system is designed.In this thesis,through the combination of software and hardware,and following the principles of real-time,stability and certian tolerance of error,a robot control system with the frequency of 1KHz is realized.For the hardware,the Kontron industrial computer ECX-BDW-U equipped with QNX operating system,ELMO Gold series high-performance drivers,and EtherCAT bus are chosen.In terms of the software,tasks are assigned to the CPU by binding the cores and multi-threading technology is applied,which can achieve error tolerance and high frequency of the control system.The threads include data recording thread,CoE mailbox thread,quadruped robot control algorithm thread,and TCP/IP thread.In addition,the driving program are set to non-blocking mode to ensure the real-time and strong stability of the system.(3)Based on model predictive control,the optimal foot force is calculated to achieve multi-gait control and gait switching methods.A gait scheduler is designed to realize various gaits of the quadruped robot,such as walk,trot,pronk,bound etc.According to the simplified quadruped robot model,the robot state space equation is constructed,and the current phase of the robot is judged according to the desired gait period.If the current time is in the swing phase,the single-leg swing control is performed and if in the stand phase,the model predictive control is transformed to quadratic programming to calculate the optimal foot force and finally the multi-gait control and gait switching of the quadruped robot is realized.In the open source dynamics simulation software Webots,the above method is verified by simulation experiments.