Jason Newton, Michael Hays,
Jonathan Clark, and William Oates
Department of Mechanical Engineering
Florida State University
Tallahassee, FL, 32310
Legged robotics exhibit unique mobility over complex terrains that overcome many of the challenges experienced with wheeled robots. This includes the ability to climb over rough terrains and in some robotic platforms, climb walls. It is known from bio-locomotion research that humans and other animals adjust the stiffness of their muscles to accommodate differences in the terrain. Methods to implement this on a legged robotic platform have included thermally induced modulus changes in shape memory polymers or geometric changes to the leg structure with complex mechanical linkages and gears. Both of these cases are limited in their dynamic response and efficiency. As an alternative, we have developed a leg module that changes its stiffness by an electric field. This is achieved by applying a large voltage to the dielectric elastomer VHB. Up to a 92% stiffness reduction has been demonstrated under an electric field in a previous study. The goal of the current research is to identify electromechanical dynamic responses to understand limits in adaptibility from abrupt changes in terrain. We will quantify the structural dynamic behavior and electromechanical limits governing rapid stiffness changes in our legged VHB module. Structural vibration characterization will be presented to illustrate transient dynamic changes when the VHB material is exposed to a step input voltage change. The results will be anaylzed and compared to the system dynamics required for the iSprawl legged robot.