SLIP-Model-Based Dynamic Gait Generation in a Leg-Wheel Transformable Robot With Force Control

We report on the model-based development of the pronking and trotting behaviors of a leg-wheel transformable robot. The spring-loaded inverted pendulum (SLIP) model serves as the motion template; its stable running motion is investigated, and the parameters and state conditions suitable for implementation in the robot are selected. Mapping between the SLIP model and the robot is conducted so that the running of the SLIP model can be transformed into the robot's pronking and trotting behaviors. The spring effect of the leg-wheel is achieved using force control with motor current feedback. The robot was operated to initiate four different dynamic behaviors with variations in stiffness and gait based on four different fixed-point trajectories of the SLIP model. The experimental results confirm that the proposed strategy is effective in initiating the dynamic behaviors.