As one of dynamics-based control of biped walking, some researchers presented the control method to take advantage of robot dynamics directly by use of point-contact state between a robot and the ground. We proposed passive dynamic autonomous control (PDAC) previously (2004) as one of point-contact methods. PDAC expresses the robot dynamics as a 1-dimensional autonomous system based on the two concepts: 1) point-contact 2) virtual constraint (proposed by Grizzle et al. (2001) and Westervelt et al. (2004)). We actually realized 3D dynamic walking by means of proposed method, however stability is not proved and the convergence domain is not clear. Thus, this paper finds the convergence domain of the previously proposed controller and proves the stability by the Liapunov theory. Finally, the correctness of stability proof is confirmed by the numerical simulation.

This paper proposes the control method of biped walking with heel-off motion. Heel-off motion made it possible to avoid the problem for the impact shock at foot-contact to break the stabilization of walking. The 3D motion is separated into lateral and sagittal motion and each motion is designed individually under the assumption that each motion is possible to be treated independently each other. We adopt the approximate 1-mass model in both planes and derive the dynamics based on these models. It is assumed that the lateral motion is relevant to heel-off motion. On the other hand, in the sagittal plane, there are two phases: 1) the center of rotation (contact point) is ankle joint. 2) the center of rotation is toe. In phase 2), heel-off motion is designed to diminish the impact shock at foot-contact. By applying PDAC to the dynamics, phase around the contact point can be derived. By means of this phase of dynamics, it is possible to inspect heel-off motion analytically. We design the stabilizing controller for each plane and confirm the convergency of dynamics with the numerical simulation

We propose an energy-based control method for a multilocomotion robot to improve the stability of continuous brachiation. The target continuous brachiation is an effective locomotion from one bar to another exchanging a kinetic energy with potential energy like a pendulum. Our control strategy for the continuous brachiation is to control the swing-back action so that the robot pumps up the feasible energy to grasp a target bar, and then the locomotion action is designed based on the symmetric motion of a pendulum in order to conserve the total energy: summation of the kinetic and potential energy. The proposed controller is implemented on a new type of mobile multilocomotion robot named “Gorilla Robot III” whose dimensions are mimicking those of a gorilla. Continuous brachiation on various uniform ladders is experimentally achieved with this robot. The experimental results show the validity of our control algorithm. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 1025–1043, 2006.

In this paper, we develop the lateral motion control based on Passive Dynamic Autonomous Control (PDAC) in order to solve two following problem in previous paper: 1) the step-length control in the sagittal plane results in the delay of one step cycle since walking period is not controlled taking the sagittal control effect into consideration 2) error of the lateral dynamics is big since the effect of the sagittal motion on the lateral dynamics is neglected. At first, the walking period is controlled, by adjusting the amplitude of side-to-side rocking motion. Secondly, the value to lengthen the lateral inverted pendulum is decided according to the sagittal motion effect on it. By means of this new lateral control in addition to sagittal step-length control, the 3-dimensional stable dynamic walking based on the robot inherent dynamics is realized.

In this paper, we present a control method to realize continuous brachiation. The target brachiation is basically divided into two actions: a swing action and a locomotion action. In order to realize the continuous brachiation effectively and stably, it is necessary to control these actions according to the total energy of the system. Because brachiation has been modeled as a pendulum-like motion and the amplitude of the oscillation determines whether the robot can grasp the target bar or not. In consideration of this point, an energy based control method is proposed and introduced into the swing action controller. The purpose of this method is to control the angular velocity of the swing action in order to satisfy the desired energy evaluated by the distance of bars. Experimental results show that the robot can successfully achieve smooth, continuous brachiation.

In this paper, the new control method to realize 3D natural dynamic walking based on the 3D robot inherent dynamics is proposed. The proposed method describes robot dynamics by use of a 3D inverted pendulum model and applies passive dynamic autonomous control (PDAC) to it. By utilizing the polar coordinate system to express the robot state around the contact-point between robot and the ground and applying PDAC, it is possible to express the 3-dimensional dynamics as 1-dimensional autonomous system. Due to autonomy, this 1D dynamics has the conservative quantity named PDAC constant. We build the stabilizing controller by means of PDAC constant and analyze the walking based on the 1D dynamics. Finally the proposed method is tested by experiment.

This paper proposes passive trajectory control (PTC), a new control method of Acrobot, and discusses its application to biped walking robots. PTC makes the first joint passive and makes the point contact between the whole robot system and the ground, then actuates other joints according to the motion of the passive joint. Due to this interlock, the whole robot system becomes autonomous and the controller is independent of time. Hence, PTC makes it possible to design the robot motion based on not the trajectory of time, but the dynamics around the contact point. In this paper, we design the lateral motion of bipedal walking by means of PTC and realize the dynamic stable motion.

The goal of our research is to achieve a dynamic and skillful motion by a real robot. We have previously developed a brachiation controller that can achieve two kinds of brachiation: overhand and side-hand motions. In this paper, we redesign behavior controllers in order to achieve a stable continuous brachiation without a break. We make the behavior controllers that can be controlled by the angle around a catching bar because the angle is the most dominant parameters of the brachiation motions. In addition, we introduce the action of bending elbow joints in order to realize a pendulum motion and to reduce the impact of the moment of catching a bar. Finally, we show the experimental results that the robot could successfully achieve continuous brachiation.