Mobility Characterization and Control of a Spherical Multi-Legged Robot

Abstract

Mobility in rough terrain has long been a hindrance in ground-based robotic exploration. Historically, such tasks have been approached with wheeled platforms, which have difficulty surmounting obstacles of even moderate height, or with legged robots that can step over obstacles but require complex foot-placement planning and posture control. In this thesis, I present the latest Robotic All-Terrain Surveyor (RATS) prototype as a unique approach to locomotion in varied terrain through the ability to emulate multiple mobility modes using a single type of actuator. The novel robot has a spherical body roughly the size of a soccer ball with 12 legs symmetrically distributed around its surface. Each leg is a single-DOF pneumatic linear actuator, oriented normal to the spherical body. Thorough investigation of this prototype’s mobility and actuation behavior has demonstrated the feasibility of achiev- ing tipping, hopping, and prolonged rolling behavior without the need for controlling body posture. Here I summarize the experimental results of this characterization and present an understanding of the system’s performance limitations in an effort to draw insight for con- trolling its movements. I also discuss the initial control strategies that have been developed to achieve multi-modal RATS locomotion, both in simulation and with the prototype. This paper concludes with a discussion of the numerous areas for future development to improve on the robot’s mobility performance and implement more sophisticated control techniques for locomotion.