In this paper, the authors introduce an anthropomorphic dynamic biped walking robot adapting to the humans' living floor. The robot has two systems: 1) a special foot system to obtain the position relative to a landing surface and the gradient of the surface during its dynamic walking; 2) an adaptive walking control system to adapt to the path surfaces with unknown shapes by utilising the information of landing surface, obtained by the foot system. Two units of the foot system WAF-3 have been developed: a biped walking robot WL-12RVII that has the foot system and the adaptive walking control system installed inside it. A walking experiment with the WL-12RVII was performed. As a result, dynamic biped walking adapting to humans' living floor with unknown shape was realised. The maximum walking speed was 1.28 s/step with a 0.3 m step length, and the adaptable deviation range was from -16 to 16 mm/step in the vertical direction, and from -3 to +3/spl deg/ in the tilt angle.

As the first stage of dynamic biped walking adapting to an unknown uneven surface using an anthropomorphic biped walking robot, this paper introduces a special foot mechanism with shock-absorbing material that stabilizes dynamic biped walking and acquires position information on the landing surface. The new foot has three functions: (1) a function to obtain information on the position relative to a landing surface; (2) a function to absorb the shock of the foot landing; and (3) a function to stabilize changes in the support leg. Two units of the foot mechanism were produced, a biped walking robot WL-12RVI that had the foot mechanism installed inside it was developed and a walking experiment with WL-12RVI was performed. As a result, decreased vibration around the pitch axis, decreased torque demands on ankle actuators on the pitch axis, increased dynamic biped walking success probability, and acquired landing surface information were achieved.

Many future applications of robotic systems will require that manipulators perform operations while being carried by moving vehicles. However, such a vehicle mounted mobile manipulator can be unstable or even tip over. Previous work on stability control hardly considered the dynamics and environmental disturbances. The stability of a mobile manipulator has a close relation with the vehicle motion, manipulator motion and posture, and end-effector force. To evaluate the stability for a mobile manipulator, the concepts about stability, such as the stability degree and the valid stable region based on the zero moment point (ZMP) criterion have already been proposed. In this paper, as a control scheme for maintaining or recovering stability, the method of ZMP path planning by a stability potential field is presented, in which the concepts of the goal state and prohibitive state of stability are outlined. A motion planning algorithm is then formulated, which controls the manipulator in order to maintain the stability of the whole system while the vehicle is moving along a given trajectory.>

In this paper, as the first stage of biped walking adapting to an uneven surface using an anthropomorphic biped walking robot, the authors introduce a biped walking control method for adapting to a surface that is called a horizontally composed (HC) plane whose step height is unknown, and a special foot mechanism which is capable of shock absorbtion. The authors developed an anthropomorphic biped walking robot with a foot mechanism and performed walking experiments with the robot using the control method. As a result, adaptive dynamic biped walking over a step of unknown height was realized. The maximum walking speed was 0.96 sec per step with a 0.3 m step length, and the greatest step height was 12 mm. The authors believe that the adaptability is integral to an anthropomorphic robot that will support human living in the near future. The authors call the robot Humanoid.>

The authors propose learning control methods for compensative trunk motion for a biped walking robot that has a trunk, based on the ZMP (zero moment point) stability criterion, for the cases of the ZMP being inside the stable region and outside the stable region, respectively. They have developed a biped walking robot with a ZMP measurement system and a support device. The results of computer simulation and learning control experiments confirm the convergence of the learning methods and the change of the convergence rate with the change of the weight coefficient. The learning control experiments for the case of the ZMP being outside the stable region show that even though the walking state of the robot itself changes, with the support of a human and by its learning with the ZMP and the support force, stable walking even without the support of a human ultimately is realized.

Many future applications of robotic systems will require manipulators to operate from moving vehicles. However, vehicle-mounted mobile manipulators might be unstable and even tip over. The authors assume that the stability of such a mobile manipulator has a close relationship with the vehicle's motion, the manipulator's posture and motion, and the endpoint's force. They present the concepts of the stability degree and the valid stable region based on the ZMP zero moment point criterion, which can be used as effective stability criteria in controlling mobile manipulators. Finally, the concepts are illustrated by computer simulation.

The authors have been using the ZMP (zero moment point) as a criterion to distinguish the stability of walking for a biped walking robot which has a trunk. The authors introduce a control method of dynamic biped walking for a biped walking robot to compensate for the three-axis (pitch, roll and yaw-axis) moment on an arbitrary planned ZMP by trunk motion. The authors developed a biped walking robot and performed a walking experiment with the robot using the control method. The result was a fast dynamic biped walking at the walking speed of 0.54 s/step with a 0.3 m step on a flat floor. This walking speed is about 50% faster than that with the robot which compensates for only the two-axis (pitch and roll-axis) moment by trunk motion.

The authors have been using the ZMP (Zero Mo- ment Point) as a criterion to distinguish the stability of walk- ing for a biped walking robot that has a trunk. In this paper, the authors propose a learning control algorithm of the com- pensative trunk motion that makes the actual ZMP get closer to the desired ZMP. The convergency of the algorithm is con- firmed by computer simulation and learning experiments with the biped robot. The change of the convergence rate with the change of the weight coefficient multiplied to the errors be- tween the measured ZMP and the desired ZMP is confirmed by the simulation and the experiments. And also the reasons are discussed.

Concerns the use of the zero moment point (ZMP) as a criterion in order to distinguish the stability of walking for a biped walking robot. If the ZMP during walking can be measured, it is possible for a biped walking robot to realize stabler walking by a control method that makes use of the measured ZMP. A method of measuring the ZMP throughout the whole walking phase is proposed, and a newly developed biped walking robot that has a ZMP measurement system using two universal force-moment sensors is explained. The accuracy of the ZMP measurement system is experimentally confirmed, and the ZMP throughout the whole walking phase is measured.>