A walking and climbing quadruped robot capable of ground-wall transition: design, mobility analysis and gait planning

We present WCQR-III, an untethered bioinspired climbing robot capable of versatile locomotion, including ground walking, wall climbing and ground-to-wall transition. Inspired by gecko lizards, WCQR-III features a structure comprising four feet and one tail. The foot design incorporates a switching mechanism to seamlessly transition between walking and climbing modes. A spiny claw provides wall adhesion, while a rubber pad offers friction and cushioning for ground walking. Leveraging the screw theory, we establish a kinematic model to analyze the robot's mobility and transition ability. In the walking mode, a trotting gait is adopted, while the climbing mode introduces a detaching angle, pause, and backswing movement of spiny toes, facilitating easy detachment from surfaces. An offline search algorithm optimizes the motion trajectory. Mobility analysis of different configurations confirms that a crouched posture is necessary for successful ground-to-wall transition. Experimental verification on WCQR-III demonstrates a maximum speed of 0.46 m/s on horizontal ground, 0.23 m/s on vertical walls, and successful achievement of ground-to-wall transition.