Design And Research Of A Transformable Wheel-Legged Robot

Transformable wheel-legged robots combine the high mobility of wheeled mobile robots and the high obstacle-crossing performance of legged mobile robots,which can adapt to work in both flat and complex terrain and have broad application prospects.In this paper,we propose a new design of deformable wheel-legged robot with the practical needs and development requirements of deformable wheel-legged robots,and address the shortcomings of current deformable wheel-legged robots in unstructured terrain in terms of obstacle-crossing capability and terrain adaptability.Firstly,a three-phase double-rocker deformable wheel-leg mechanism is proposed based on the phenomenon of variable folding and extension of parallelogram in a circle,whose deformation ratio(ratio of leg mode radius to wheel mode radius)is 2.575 and the theoretical overrun ratio(ratio of theoretical overrun height to wheel radius)is 4.46.The kinematic analysis of the deformable wheel-leg mechanism is carried out by using the closed vector equation method,and the kinematic curves solved by MATLAB and the Solid Works Motion Simulation Module are compared.The theoretical kinematic curves solved by MATLAB and the kinematic curves of Solid Works Motion simulation module,the correctness of the kinematic theoretical analysis and the rationality of the deformable wheel-leg mechanism were verified.By establishing the mechanical model of the deformable wheel-leg mechanism for overrunning,the required deformation torque and the overrunning process are analyzed.At the same time,the design of the deformable wheel-leg robot with symmetrical distribution of the left and right wheels and the tailstock bar is proposed.Secondly,the kinematic model of deformable wheel-legged robot in wheel mode is established to analyze its motion characteristics;the kinematic and dynamic models of deformable wheel-legged robot in leg mode are established by Lagrange’s equation method to solve the forces and moments of the robot in each direction.Finally,Solid Works Motion simulation module is used to simulate the deformable wheel-legged robot in different terrain and analyze the linear displacement curve in each direction and linear velocity curve in each direction.The simulation analysis includes forward/reverse,differential steering and single step crossing in wheel mode;forward/reverse,single step crossing,irregular terrain crossing,stair climbing and continuous up and down step crossing in leg mode.3D printing technology was used to print the parts,build the physical test prototype and conduct the test analysis.In the wheeled mode,the in-situ steering test was conducted;in the leg mode,the single-step overrun test,the irregular rough terrain overrun test,the soil slope overrun test,the grass overrun test and the stair climbing test were conducted.The simulation and test results verify the feasibility and motion stability of the deformable wheel-legged robot,and show that the deformable wheel-legged robot has good obstacle crossing ability and can climb through obstacles with 3.41 times the height of wheel radius;it has high adaptability and can adapt to different terrain environments for climbing and crossing obstacles.