Research On Quadruped Robot Motion Plan And Control In Rough Terrain

Quadruped robot has much more advantage than conventional wheeled robot in rough terrain,such as uneven plane,large scale obstacle,stairs ans slope and so on,but also has brong much more complexity in motion plan and control to ensure its stable locomotion.In this work,an approach for quadruped robot's motion plan and control was proposed,and a software system was built to do experiment on both simulated robot and real robot in order to control a quadruped robot moving stablely and flexibly.According to the design requirments of locomotion and task operation,the approach of motion plan and control has divided into two parts,legs and the base.For the motion plan of single leg,a Hermite interpolation was applied to generate the end effector of single leg;and for base motion plan,a method for static base pose optimization using Sequence Quadratic Program(SQP)and for dynamic base Co M trajectory generate using the weights curves of swing and stance legs.For the control problem,the single swing leg was controlled by an operation space Inverse Dynamic PD single leg controller(SLC)to follow the end effector trajectory,and the base pose command was controlled by a Vitual Modle Controller(VMC)with contact force distribution calculated by a Quadratic Program(QP)optimization.Based on the proposed plan and control method,the locomotion was achieved by dynamic and static gaits: according to gaits schedule and contact detection,the dynamic gait generate footholds using desired and actual base velocity,the static gait generate foothold only use velocity command and optimize the foothold with terrian preception and score using depth camera;for the task operation,the planer will conbined the leg and base command given by the operator,and call the corresponding methods for leg motion plan and base pose optimization and base Co M trajectory generation.Both the SLC and VMC output the joint torque command for the 12 leg joints.In order to meet the requirement of the implementation of the proposed plan and control method and easily debugging,a software system on Ubuntu and ROS was designed and verified both on real robot and a simulate robot in Gazebo.The software system has five layer: the Graphic User Interface(GUI)layer send to user's command to the Motion Plan(MP)layer,the MP layer use the poporsed motion plan method generate the base and legs commands and send to the Real-Time Control(RTC)layer,and the RTC layer calculate the joint torque command with SLC and VMC and send to the Hareware Interface(HI)layer,the HI layer has two type fot real and simulation.In the real robot,a Intel NUC is used for running the software system,a Nivdia Jetson TX 2 with ZED binocular camera for terrain perception,a pressure based contact sensor fot contact detection,a IMU for orientation and inertia sensing,a Ether CAT bus communication is used for high frequece and high synchronization torque control.With this software and hardware system,we have done the experiment such as terrain perception,leg and base motion,combined task opertion,dynamic and in plat terrain and static walk in rough terrain.The results shows the poposred methon achieved the locomotion and task operation in rough terrain and meet the design reqirements.