A tugging controller that maximizes lateral resistive force by mounding sandy terrain

Abstract: “Sandy environments present challenges for robotic space rovers and systems due to reduced traction, limiting mobility and tugging force. This paper presents an anchoring method that utilizes a winching system to create a sand mound in front of a mobile agent dragged through the media. The proposed controller is designed to consistently achieve realtime capture of close-to-maximal lateral sand mound resistive force, even when applied to varied uneven terrains, like holes or waves. Notably, tugging is non-reversible, so suitable peaks should be captured before breakdown and without necessarily knowing the global optimum a priori. The controller logic tracks both tugging force and agent pitch gradients to detect terrain conditions and peak force trends. Results show that the controller captures an average 92% of the maximum forces, within the previously winched workspace tested, across three different granular media with four varying structured terrain features. The controller achieves higher resistive force peaks on terrains with geometric features, as opposed to flat sand. We conclude that sand mounding through tugging is a viable means to generate robotic resistive forces for unknown sandy terrains, a simple yet effective anchoring mechanism.”