Moyuru Yamada

Point-contact type foot with springs and posture control for biped walking on rough terrain

This paper proposes a new foot system to achieve stable biped walking on rough terrain. The new foot system, which is named point-contact type foot with springs (PCFS), has four passive joints each of which equips a spring and a sensor. The proposed foot system has the following advantages: 1) The geometrical adaptability to rough terrain. 2) The measurability of the posture of the robot. 3) The absorption of the influence of disturbances. The index of stability like ZMP and the posture of the robot can be estimated from the displacement of each spring. The foot system can also absorb not only the impact at the foot landing but also the influence of irregularities on the ground and unexpected disturbances. However, because the biped walking by use of the foot with springs corresponds to walking on a soft ground, posture control is indispensable. Therefore we consider an appropriate walking pattern generation and present feedback control for the proposed foot system. The effectiveness of the proposed foot system is demonstrated by simulation results.

Design of point-contact type foot with springs for biped robot

This paper presents a new foot system for biped walking on rough terrain and its design flow. To achieve the stable biped walking on rough terrain, the following functions are required. 1) Stabilization of contact states between foot and ground. 2) Landing to unknown terrain. The conventional rigid and flat foot changes its contact states and is separated from the ground easily. In addition, the impulsive impact force at landing on rough terrain must be suppressed. We propose a point-contact type foot with springs (PCFS). The proposed foot has the following advantages. 1) Stabilization of contact state. 2) Estimation of stability index, and 3) Absorption of landing impact. A design method of primary parameters for PCFS is presented to increase the stability of the robot and reduce the impact force at the landing. The validity of the proposed design method is shown experimentally.

Landing Control of Foot with Springs for Walking Robots on Rough Terrain

Landing control is one of the important issues for biped walking robot, because robots are expected to walk on not only known flat surfaces but also unknown and uneven terrain for working at various fields. This paper presents a new controller design for a robotic foot to land on unknown terrain. The robotic foot considered in this study equips springs to reduce the impact force at the foot landing. There are two objectives in the landing control; achieving the desired ground reaction force and positioning the foot on unknown terrain. To achieve these two objectives simultaneously by adjusting the foot position, we propose a PI force controller with a desired foot position, which guarantees the robust stability of control system with respect to terrain variance, and exact positioning of the foot to unknown terrain. Simulation results using the Open Dynamics Engine demonstrate the effectiveness of the proposed controller.

Verification of biped robot using point-contact type foot with springs for walking on rough terrain

This study introduces a biped robot designed with a point-contact type foot with springs (PCFS) and proposes a control method for stable walking on rough terrain. Realizing stable walking on rough terrain is important because biped robots are expected to assist humans not only in flat and known environments but also on rough ground surfaces with unknown terrain variances. The PCFS is a new foot system that was proposed in our previous study, which realizes stability on complex ground surfaces and suppresses impact force during foot landing. To adjust a foot position and posture in response to the declination between the predicted and actual ground surfaces, we proposed a landing controller for uncertain rough terrain. In this study, we also propose a dynamic walking pattern for the biped robot and demonstrate the effectiveness of the proposed method via simulation results.

Point-contact type foot with springs and landing control for biped walking on rough terrain

This paper proposes a biped robot with a point-contact type foot with springs (PCFS) and its control method for stable locomotion on rough terrain. PCFS is a new foot system that was proposed in our previous study. Realizing stable walking on rough terrain is important, because biped robots are expected to assist humans in not only a flat known environment but also on rough ground surfaces with terrain variances while maintaining their usefulness. PCFS realizes stability on complex ground surfaces and suppresses the impact force at the foot landing. To adjust a foot position and posture in response to the declination between the predicted ground surface and the actual ground surface, we propose a landing controller for uncertain rough terrain. This proposed controller provides exact positioning to the actual ground without excessive reaction force and robust stability with respect to terrain variance. The biped robot implements these proposed approaches, and their effectiveness is demonstrated by simulation and experimental results.