Yoshito Ikemata

A physical principle of gait generation and its stabilization derived from mechanism of fixed point

Passive walker with knees can walk down shallow slope in a natural gait and can exhibit a stable limit cycle. Though the passive walker is mechanically simple, it is a sort of hybrid system that combines the continuous dynamics of leg-swing motion and the discrete event of leg-exchange. In this paper, we focus on the mechanism of fixed point. We demonstrate a physical principle of gait generation and its stabilization derived from the mechanism of fixed point. Based on the principle, we made a simple improvement on passive walker with knees. The passive walker could have high stability, and could walk on treadmill for 4010 steps

A study of the leg-swing motion of passive walking

In our earlier work, we showed that high stability of passive walking can be achieved by the global stabilization principle of fixed point. The principle has been established, providing that the state just after heel-strike exists at the next step. However, this condition may not always hold. The passive walker with knees can execute the leg-swing motion with no control, only by gravity effect. Unfortunately, while the walker takes a step forward, the swing leg may strike its toe on the slope at unsuitable point. Therefore, understanding of the mechanism of leg-swing motion is very important for assuring the next step. In this paper, we focus on the leg-swing motion of passive walking, and demonstrate the mechanism of the flexion and extension of knee joint of swing leg.

Dynamic effects of arc feet on the leg motion of passive walker

The passive walker with knees can naturally execute the leg motion by the dynamics of legs under the gravity only. Circular arc foot is very important for the leg motion. In this paper, the dynamical effects of the arc foot, which can keep the knee joint of stance leg straight only by the stopper and can enhance the flexion of knee joint of swing leg, are discussed. Also, its geometrical negative effect is examined. Finally, the desired arc foot is designed and the actual effects are confirmed by a walking experiment.

Generation and Local Stabilization of Fixed Point Based on a Stability Mechanism of Passive Walking

A passive walker with knees can walk down gentle slope in a natural gait and can exhibit a stable limit cycle. Though the passive walker is simple, it is a sort of hybrid system which combines the continuous dynamics of leg-swing motion and the discrete event of leg-exchange. We focus on the mechanisms of generation and stabilization of a fixed point of passive walking. We propose a generation method of fixed point based on its physical structure. We derive the local stabilization control method from a stability mechanism of a fixed point of passive walking.

A study of bouncing rod dynamics aiming at passive running

Passive running robot can run down shallow slope with no energy source without gravity. The robot can generate a stable limit cycle. Dynamics of passive running is very interesting target and important for developing the robot and understanding the human locomotion. By the way, running high jumper can jump very high. The point of jumping is to transfer horizontal velocity into lifting momentum through the hinged-movement. In this paper, we demonstrate the experimental passive running based on the hinged-movement. Moreover, we derive the fixed point of the passive running, and analyze its stability.

Stabilization of Passive Walking Based on a Stability Mechanism of Fixed Point

Passive walker can walk down shallow slope without actuator and control. Though mechanical system of passive walker is simple, it is a sort of hybrid system that combines the continuous dynamics of leg-swing motion and the discrete event of leg-exchange. Passive walker can exhibit a stable limit cycle. In this paper, we demonstrate a global stabilization principle of fixed point from a simple passive walker with knees. And, the validity of stabilization principle is confirmed by walking experiment