Research On The Motion Performance Of Wheel-legged Robot Based On 3-CUR Parallel Mechanism

In order to improve the post-disaster environment and reduce the harm caused by rescue,this paper proposes a wheel-legged robot based on 3-CUR parallel mechanism for post-disaster rescue.In this paper,the 3-CUR parallel mechanism is used as the leg structure of the wheel-legged robot,which greatly enhances the load capacity of the robot.The wheel-legged robot will be applied to environments which are complicated and dangerous for the tasks of detection and rescue instead human.Firstly,the paper proposes the whole structure of 3-CUR parallel wheel-legged mobile robot,which includes the design of the leg structure,the wheel transmission and the wheel-leg switching device.Four identical and independent wheel-leg systems are adopted.Each leg is controlled by three servo motors while walking,and the legs can realize the movements such as lift,swing and drop while moving forward.The working principles of 3-CUR parallel wheel-legged mobile robot in different modes are also described.Secondly,the paper takes the leg mechanism of 3-CUR parallel wheel-legged mobile robot as the research object,and establishs the branch screw system of the 3-CUR parallel mechanism by screw theory.The degree of freedom of the 3-CUR parallel mechanism is calculated.The linkage coordinate system for the mechanism is established through D-H method and the inverse position solution is analyzed.Using three-dimensional dynamic method and numerical search method,the working space of 3-CUR parallel mechanism is obtained and elaborated.Thirdly,the stability of the 3-CUR parallel wheel-legged mobile is determined by static stability principle and dynamic stability principle during four-footed gait.From the motion space demand and the maximum stability margin in forward direction of the four-legged mobile robot,a suitable gait for the 3-CUR parallel wheel-legged mobile robot is selected.Finally,the 3-CUR parallel wheel-legged mobile robot is simulated in a given gait mode using Solidworks software.The step size,the step height and the curve of the center of the robot during walking in this gait are obtained.Then,the motions of the robot climbing the boss and crossing the ditch are simulated.The maximum height of boss and the maximum width of ditch the robot could cross are obtained.Also the changes of mass center when crossing the boss and the ditch and the forces of the motor of each leg during the movement are analyzed.