We introduce a new method of a biped walking pattern generation by using a preview control of the zero-moment point (ZMP). First, the dynamics of a biped robot is modeled as a running cart on a table which gives a convenient representation to treat ZMP. After reviewing conventional methods of ZMP based pattern generation, we formalize the problem as the design of a ZMP tracking servo controller. It is shown that we can realize such controller by adopting the preview control theory that uses the future reference. It is also shown that a preview controller can be used to compensate the ZMP error caused by the difference between a simple model and the precise multibody model. The effectiveness of the proposed method is demonstrated by a simulation of walking on spiral stairs.

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Biped walking pattern generation by using preview control of zero-moment point

This paper is devoted to the permanence of the concept of Zero-Moment Point, widelyknown by the acronym ZMP. Thirty-five years have elapsed since its implicit presentation (actually before being named ZMP) to the scientific community and thirty-three years since it was explicitly introduced and clearly elaborated, initially in the leading journals published in English. Its first practical demonstration took place in Japan in 1984, at Waseda University, Laboratory of Ichiro Kato, in the first dynamically balanced robot WL-10RD of the robotic family WABOT. The paper gives an in-depth discussion of source results concerning ZMP, paying particular attention to some delicate issues that may lead to confusion if this method is applied in a mechanistic manner onto irregular cases of artificial gait, i.e. in the case of loss of dynamic balance of a humanoid robot. After a short survey of the history of the origin of ZMP a very detailed elaboration of ZMP notion is given, with a special review concerning “boundary cases” when the ZMP is close to the edge of the support polygon and “fictious cases” when the ZMP should be outside the support polygon. In addition, the difference between ZMP and the center of pressure is pointed out. Finally, some unresolved or insufficiently treated phenomena that may yield a significant improvement in robot performance are considered.

https://www.techfak.uni-bielefeld.de/~rhaschke/lehre/WS04/humanoids/papers/zmp-review.pdf

Zero-moment point — thirty five years of its life

For 3D walking control of a biped robot we analyze the dynamics of a 3D inverted pendulum in which motion is constrained to move along an arbitrarily defined plane. This analysis yields a simple linear dynamics, the 3D linear inverted pendulum mode (3D-LIPM). Geometric nature of trajectories under the 3D-LIPM and a method for walking pattern generation are discussed. A simulation result of a walking control using a 12-DOF biped robot model is also shown.

The 3D linear inverted pendulum mode: a simple modeling for a biped walking pattern generation

Bipedal locomotion is among the most difficult challenges in control engineering. Most books treat the subject from a quasi-static perspective, overlooking the hybrid nature of bipedal mechanics. Feedback Control of Dynamic Bipedal Robot Locomotion is the first book to present a comprehensive and mathematically sound treatment of feedback design for achieving stable, agile, and efficient locomotion in bipedal robots.In this unique and groundbreaking treatise, expert authors lead you systematically through every step of the process, including:Mathematical modeling of walking and running gaits in planar robotsAnalysis of periodic orbits in hybrid systemsDesign and analysis of feedback systems for achieving stable periodic motionsAlgorithms for synthesizing feedback controllersDetailed simulation examplesExperimental implementations on two bipedal test bedsThe elegance of the authors' approach is evident in the marriage of control theory and mechanics, uniting control-based presentation and mathematical custom with a mechanics-based approach to the problem and computational rendering. Concrete examples and numerous illustrations complement and clarify the mathematical discussion. A supporting Web site offers links to videos of several experiments along with MATLAB® code for several of the models. This one-of-a-kind book builds a solid understanding of the theoretical and practical aspects of truly dynamic locomotion in planar bipedal robots.

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Feedback Control of Dynamic Bipedal Robot Locomotion

A humanoid robot is expected to be a rational form of machine to act in the real human environment and support people through interaction with them. Current humanoid robots, however, lack in adaptability, agility, or high-mobility enough to meet the expectations. In order to enhance high-mobility, the humanoid motion should be generated in real-time in accordance with the dynamics, which commonly requires a large amount of computation and has not been implemented so far. We have developed a real-time motion generation method that controls the center of gravity (COG) by indirect manipulation of the zero moment point (ZMP). The real-time response of the method provides humanoid robots with high-mobility. In the paper, the algorithm is presented. It consists of four parts, namely, the referential ZMP planning, the ZMP manipulation, the COG velocity decomposition to joint angles, and local control of joint angles. An advantage of the algorithm lies in its applicability to humanoids with a lot of degrees of freedom. The effectiveness of the proposed method is verified by computer simulations.

Real-time humanoid motion generation through ZMP manipulation based on inverted pendulum control

The authors have focused on the bipedal humanoid robot expected to play an active role in human living space, through studies on an anthropomorphic biped walking robot. As the first stage of developing a bipedal humanoid robot, the authors developed the human-size 35 active DOF bipedal humanoid robot "WABIAN" and the human-size 41 active DOF bipedal humanoid robot "WABIAN-R". The authors also proposed a basic control method of whole body cooperative dynamic biped walking that uses trunk or trunk-waist cooperative motion to compensate for three-axis (pitch, roll and yaw-axis) moment generated not only by the motion of the lower-limbs planned arbitrarily but by the time trajectory of the hands planned arbitrarily. Using these systems and the control method, normal biped walking (forward and backward), dynamic dance, waving arms and hip, dynamic carrying of a load using its arms, and trunk-waist cooperative dynamic walking are achieved.

/pdf/development-of-a-bipedal-humanoid-robot-control-method-of-3as69cmfnv.pdf

Development of a bipedal humanoid robot-control method of whole body cooperative dynamic biped walking

The authors proposed the construction of a bipedal humanoid robot that has a head system with visual sensors, two hand-arm systems, 3-DOF trunk and antagonistic driven joints using the nonlinear spring mechanism, on the basis of WL-13. And we really designed and built it. In addition, as the first step to realize the dynamic cooperative motion of limbs and 3-DOF trunk, the authors developed the control algorithm and the simulation program that generates the trajectory of 3-DOF trunk for stable biped walking pattern even if the trajectories of upper and lower limbs are arbitrarily set for locomotion and manipulation respectively. Using this preset walking pattern with variable muscle tension references correspond to swing phase and stance phase, the authors performed walking experiment of dynamic walking forward and backward dynamic dance with 3-DOF trunk motion and carrying, on a flat level surface (1.28 s/step with a 0.15 m step length). As a result, the efficiency of our walking control algorithm and robot system was proved. In this paper, the mechanism of WABIAN and its control method are introduced.

Development of a bipedal humanoid robot having antagonistic driven joints and three DOF trunk

This research is aimed at the development of bipedal humanoid robots working in a human living space, with a focus on its physical construction and motion control method. At the first stage, we developed the bipedal humanoid robot WABIAN (Waseda bipedal humanoid), and proposed a control method for dynamic cooperative biped walking. In this paper, we present a follow-walking control method with a switching patterns technique for a bipedal humanoid robot to follow human motion by hand contact. By a combination of both algorithms, the robot is able to perform dynamic stepping and walking forward and backward in a continuous time while someone is pushing or pulling its hand. In this paper, the authors describe the control methods for the realization of physical interaction between a human and a bipedal humanoid robot.

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Physical interaction between human and a bipedal humanoid robot-realization of human-follow walking

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.

Experimental development of a foot mechanism with shock absorbing material for acquisition of landing surface position information and stabilization of dynamic biped walking

The authors introduce a life-size biped walking robot having antagonistic driven joints using a nonlinear spring mechanism and a dynamic biped walking control method using these joints. In the current research concerning a biped walking robot, there is no developed example of a life-size biped walking robot with antagonistically driven joints by which the human musculo-skeletal system is imitated in lower limbs. Humans are considered to walk efficiently using the inertial energy and the potential energy of the lower limbs effectively, walk smoothly with less impact force when a foot lands and cope flexibly with the outside environment. The human joint is driven by two or more muscle groups. Humans can vary the joint stiffness, using nonlinear spring characteristics possessed by the muscles themselves. These functions are indispensable for a humanoid. However, the biped walking robots developed previously have been unable to walk in this way. Therefore, the authors developed a biped walking robot having antagonistic driven joints, and proposed a walking control method for dynamic biped walking that uses antagonistic driven joints to vary joint stiffness. The authors performed walking experiments using the biped walking robot and the control method. As a result, dynamic biped walking varying the joint stiffness using antagonistic driven joints was realized.

Jin'ichi Yamaguchi

Papers

Development of a bipedal humanoid robot-control method of whole body cooperative dynamic biped walking

Development of a bipedal humanoid robot having antagonistic driven joints and three DOF trunk

Physical interaction between human and a bipedal humanoid robot-realization of human-follow walking

Experimental development of a foot mechanism with shock absorbing material for acquisition of landing surface position information and stabilization of dynamic biped walking

Realization of dynamic biped walking varying joint stiffness using antagonistic driven joints