Integrated joint actuator for serpentine robots

Serpentine robots, also sometimes called "snake robots," are slender, multisegmented vehicles designed to provide greater mobility than conventional wheeled or tracked robots. Serpentine robots are typically comprised of three or more rigid segments connected by two or three degrees of freedom joints. The segments typically have powered wheels, tracks, or legs to propel the vehicle forward; the joints may be powered or unpowered. We have developed a joint actuator system that is highly optimized for use in serpentine robots. This article first presents an analysis of the particular requirements for joint actuators in serpentine robots. We then compare existing actuators against those requirements and show that pneumatic bellows are ideally suited for this application. Following this analysis, this paper introduces our fully functional, pneumatically operated actuation system that is efficiently integrated in the space occupied by a joint. This system, which we call an "integrated joint actuator," also allows simultaneous proportional control of position and stiffness of the joint. The key advantages of our design over other joint actuation methods are its great strength combined with controllable compliance and minimal space requirements.