Passive running can run by interaction between machine dynamics and environment only. It has the important feature that a stable limit cycle exists. Many studies of passive running are theory and simulation. However, its mechanism is not understood well. It is important for understanding the mechanism of passive running to simplify analysis and experimental model. Therefore, we focus on the passive running of rimless wheel with springs. In this paper, first, we experimentally demonstrate that it can generate the running phenomenon, and show the characteristics of running motion. Secondly, we show the existence of fixed point in a passive running. Finally, we derive its stability by the eigenvalue of Jacobian matrix.
