Fast Wheeled Driving to Legged Leaping Onto a Step in a Leg-Wheel Transformable Robot

The leg-wheel transformable robot has the advantage of smooth, fast, and power-efficient motion on flat terrain and negotiability on rough terrain. This study presents a highly dynamic maneuver of the robot to leap onto a step using its legged form from its original form of wheeled driving, taking full advantage of the rapid switching capabilities of the leg-wheel design of the robot. The robot motion is designed based on a reduced-order model and is planned using an optimization method with multiple constraints. In addition, both position and impedance control strategies are investigated. The proposed strategy is experimentally evaluated. The results show that the robot can leap onto a step higher than itself and then smoothly transition back to the wheeled mode after leaping. The dynamic driving-to-leaping maneuver endows the robot with an alternative and time-efficient approach to negotiate the step obstacles.