Landing Motion Planning for a Moving Wheeled Quadruped Robot Based on Virtual Model Control

The Wheeled Quadruped Robot (WQR) combines the agility of wheels with the stability of legs for precise landings from elevated platforms. However., achieving a fast and stable descent remains a key challenge. This paper presents a novel method for landing motion planning of a moving WQR from a platform using Virtual Model Control (VMC). The proposed Motion Planning VMC (MPVMC) approach utilizes kinematic principles to ensure a desired descent. During landing., the front legs are controlled by VMC., while the hind legs switch control strategies based on feedback from contact sensors in the wheels. When the front legs detach and the hind legs remain in contact with the platform., the ideal distance between the hind wheels and the torso is adjusted based on the pitch angle from the inertial measurement unit mounted in the torso. Once all wheels are off the platform., the hind legs use PD control in joint space to maximize torque for stabilizing the WQR. As the torso's pitch angle decreases to a desired value., the hind legs switch to VMC in Cartesian space for a soft landing. Simulations confirm the effectiveness of this method., advancing motion planning and control strategies for WQRs in various challenging environments.