Development of a Spherical Wheel-legged Composite Mobile Robot with Multimodal Motion Capabilities

In this paper, we present a spherical wheel-legged mobile robot, aiming to meet the demands of adaptability to complex terrains and high maneuverability. It consists of a spherical main body and five-bar linkage parallel wheel-legged mechanisms. It can switch between legged and spherical modes by extending and retracting its legs according to the demands of the actual environment, thereby enhancing the overall mobility of the robot. By designing the Linear Quadratic Regulator (LQR) controller, we achieve the impact-resistant leg balancing motion and autonomous pitch adjustment for the robot on inclined surfaces in the legged configuration. For the rolling control in the spherical configuration, a hierarchical sliding mode control method and Proportional-Integral-Derivative controller (PID) are employed to control the rolling and turning of the robot. We verify the robustness of the robot in wheel-legged configuration against disturbances and the stability of its motion in spherical configuration.