Two-DOF Anthropomorphic Test Devices Reproducing Human Rider Motion Intent for the Evaluation of Dynamic Stability and Safety of Unicycle Robots

Safety and stability of the unicycle robots are critical for their operation, and hence they must be tested for such aspects. However, the objectivity and repeatability of the tests cannot be guaranteed with human operators, and some tests under certain conditions cannot even be run at all due to the safety of the operator. To solve this problem, we propose an ATD (anthropomorphic test device) capable of reproducing the human rider's behavior on the unicycle robot. An ATD is designed to have two prismatic joints to implement the change of center of gravity of the human operator in forward/backward and lateral direction. The reference profiles for two prismatic joints of the ATD that guarantee the same dynamic effect with the human rider's behavior are designed using a cascade control loop in consideration of dynamic interaction between the reference trajectories and the unicycle robot dynamics. A sliding mode controller was designed and implemented to control the prismatic joints such that ATD mimics the human rider's motion intent accurately and thereby the unicycle robot could be driven by the ATD as human operator drives. Feasibility of the proposed ATD was verified through computer simulations.