Underactuated Path Tracking Control of Mole Drilling Robot

Mole drilling robots have garnered considerable attention to overcome the effect by the complex composition of the regolith on the moon and other celestial bodies, especially for the explorations deeper than 5 meters. Due to the underactuated configuration of the robot and the uncertainty of the soil resistance, path tracking control of the robot aiming to round the obstacles becomes a key issue. In this paper, an effective and robust controller based on the backstepping control and the sliding mode control is investigated. Firstly, a simplified dynamic model of the mole drilling robot is derived. Subsequently, a control-oriented error dynamics equation is established in the Serret-Frenet coordinate system and the kinematic controller is designed by introducing the approach angle based on the backstepping method. Undisturbed and disturbed dynamic controllers are respectively given by the Lyapunov stability theory and the sliding mode method. Finally, the dynamic response of the control system and the control input are experimentally verified along a typical straight-circle path. The effect of the uncertainty of the soil resistant is discussed and the reliability are compared between the undisturbed and disturbed controllers.