Wheeled Motion Analysis And Locomotion Mode Switching Of Biped Wheel-legged Robot

Hybrid wheel-legged robot,as the name suggested,is capable of achieving both wheeling and walking locomotion.Combining advantages of both locomotion mode while avoiding their drawbacks,hybrid wheel-legged robot is able to attain high speed,strong robust and efficiently overcome obstacles.The academic community has studied this problem extensively and has already development a few systems,however,most of them incline to multiple robot rather than a biped one.Although biped robot exhibits its adaptability towards complex environment and has a simpler structure,its poor motion stability increases the control difficulty tremendously,which lead to an enormous challenge of effectively and reliably locomotion mode switch between wheeling and walking.Combining both advantage of biped robot and wheeled robot,a redundant degree-offreedom module biped wheel-legged robot is proposed in this paper.The mechanism of switching between wheeling locomotion m ode with walking locomotion mode has been studied deeply and systematically in this paper,main contributions are as follows:(1)According to the application requirements,a modular biped wheel-legged robot is designed and implemented.Its kinematics in both wheeling locomotion mode as well as walking locomotion mode are analyzed based on D-H method.(2)Movement of the robot under wheeling locomotion mode is analyzed.Based on the character of the configuration of the robot and the wheeling kinematic constraints,a two-wheel differential motion and a wheel-track-changing or wheel-direction-changing motion mathematical model is presented.(3)A motion planning algorithm of wheeling-walking locomotion mode switch is presented.According to the requirements of stability,a foot–wheel hybrid gait is presented.The reversible switching process consists of two steps: left foot-wheel module from walking to wheeled and right foot-wheel module from walking to wheeled.(4)The ADAMS simulation environment is set up and simulations are conducted for wheeling locomotion and the locomotion mode switching process.A series of experimental evaluations are conducted in our self-developed robot system,which proves the correction of the motion analysis and verifies the motion planning algorithm of locomotion mode switch we proposed.In this paper,we leverage modular robot joint to develop a biped wheel-legged robot with simple structure,and assembly and convenient transportation.By changing wheel track and direction under the wheeling motion mode,the robot can moving flexibly in the plane.It is also capable of crossing obstacle in the uneven plane by switching to walking locomotion mode.We show that attaining flexibly switch between two locomotion mode greatly improves the mobility and robustness of the robot.