The OmniTread serpentine robot with pneumatic joint actuation

This paper describes the design of a pneumatic joint actuation system for the OmniTread serpentine robot, developed at the University of Michigan. Serpentine robots are mobile robots with one unique characteristic: they have a very large ratio of length to diameter. To implement this unique shape, they usually have multiple segments connected by joints. Some serpentine robots provide legged, wheeled, or tracked propulsion, and, in addition, actuation for the joints. In this paper we present a detailed analysis of pneumatic integrated joint actuators (IJA) invented and built especially for serpentine robots. The IJA combines advantages of pneumatic bellows-like actuators with our proportional position and stiffness (PPS) control algorithm. Controllable stiffness is of crucial importance in serpentine robots, which require stiff joints to cross gaps and compliant joints to conform to rough terrain for effective propulsion. The paper also includes results of tests performed at the Southwest Research Institute.