Abstract: The wheel-legged self-balancing robot has both the high speed and efficiency of the wheeled type and the ground adaptability of the legged type. When facing unstructured terrain, it can overcome obstacles by jumping. According to the degree of freedom of the legs, it can be divided into single-degree-of-freedom type and two-degree-of-freedom type. Among them, the single-degree-of-freedom type has a simpler structure, lighter weight and less difficult to control. However, on the problem of jump trajectory planning, on the one hand, the leg structure has a higher demand for the output of the hip joint, which limits the maximum obstacle height that can be achieved by using the two-mass linear spring model trajectory planning method; On the other hand, the overall center of mass will move in the x-direction during the height adjustment process, which will affect the accuracy and stability of jumping. A research on the jumping problem of a single-degree-of-freedom wheel-legged self-balancing robot is carried out. Firstly, in order to ensure the stability of jumping, a wheel control algorithm is proposed to control the pitch attitude of the fuselage during the whole jumping process. After that, a trajectory planning method based on a two-mass nonlinear spring model is proposed and proved to be more flexible and powerful comparing with the planning method based on the two-mass linear-spring model. Then, a method of long jump in situ is designed by using the wheel control algorithm furtherly, so that the robot can achieve the same jumping distance in a shorter takeoff time and distance. The three-dimensional model of the robot is established, as well as its kinematics, single-leg statics and aerial dynamics models. The jump trajectory planning and tracking algorithms proposed in this paper is realized in the Simulink-Adams simulation and proved to be feasible.

Key words: wheel-legged self-balancing robot, trajectory planning, jumping algorithm, nonlinear spring