Frictional compliance model development and experiments for snake robot climbing

Abstract-Intelligently utilizing the frictional contact between a robot and its environment can prevent slip, maintain balance, and provide stability during a robot's motion. A contact model is first needed to enable robot control achieving these goals. The model should be both accurate and simple enough to allow further system analysis. In this paper we propose a simple parametric contact model, based on the form of the Hertz-Walton model. We experimentally demonstrate that this contact model can be effectively used to predict contact forces for linear and near-linear loading paths. Finally, we briefly discuss the applicability of the presented contact model for snake robot climbing. The control of the snake robot is based on stabilizing a sequence of set points

Motion control of a snake robot moving between two non-parallel planes

A control method that makes the head of a snake robot follow an arbitrary trajectory on two non-parallel planes, including coexisting sloped and flat planes, is presented. We clarify an appropriate condition of contact between the robot and planes and design a controller for the part of the robot connecting the two planes that satisfies the contact condition. Assuming that the contact condition is satisfied, we derive a simplified model of the robot and design a controller for trajectory tracking of the robot’s head. The controller uses kinematic redundancy to avoid violating the limit of the joint angle and a collision between the robot and the edge of a plane. The effectiveness of the proposed method is demonstrated in experiments using an actual robot

Frictional Compliance Model Development and Experiments for Snake Robot Climbing

Abstract — Intelligently utilizing the frictional contact between a robot and its environment can prevent slip, maintain balance, and provide stability during a robot’s motion. A contact model is first needed to enable robot control achieving these goals. The model should be both accurate and simple enough to allow further system analysis. In this paper we propose a simple parametric contact model, based on the form of the Hertz-Walton model. We experimentally demonstrate that this contact model can be effectively used to predict contact forces for linear and near-linear loading paths. Finally, we briefly discuss the applicability of the presented contact model for snake robot climbing. The control of the snake robot is based on stabilizing a sequence of set points. I

Snake and Snake Robot Locomotion in Complex, 3-D Terrain

Snakes are able to traverse almost all types of environments by bending their elongate bodies in three dimensions to interact with the terrain. Similarly, a snake robot is a promising platform to perform critical tasks in various environments. Understanding how 3-D body bending effectively interacts with the terrain for propulsion and stability can not only inform how snakes move through natural environments, but also inspire snake robots to achieve similar performance to facilitate humans. How snakes and snake robots move on flat surfaces has been understood relatively well in previous studies. However, such ideal terrain is rare in natural environments and little was understood about how to generate propulsion and maintain stability when large height variations occur, except for some qualitative descriptions of arboreal snake locomotion and a few robots using geometric planning. To bridge this knowledge gap, in this dissertation research we integrated animal experiments and robotic studies in three representative environments: a large smooth step, an uneven arena of blocks of large height variation, and large bumps. We discovered that vertical body bending induces stability challenges but can generate large propulsion. When traversing a large smooth step, a snake robot is challenged by roll instability that increases with larger vertical body bending because of a higher center of mass. The instability can be reduced by body compliance that statistically increases surface contact. Despite the stability challenge, vertical body bending can potentially allow snakes to push against terrain for propulsion similar to lateral body bending, as demonstrated by corn snakes traversing an uneven arena. This ability to generate large propulsion was confirmed on a robot if body-terrain contact is well maintained. Contact feedback control can help the strategy accommodate perturbations such as novel terrain geometry or excessive external forces by helping the body regain lost contact. Our findings provide insights into how snakes and snake robots can use vertical body bending for efficient and versatile traversal of the three-dimensional world while maintaining stability