Shin'ichiro Nakaoka

Cybernetic human HRP-4C

The development of cybernetic human HRP-4C is presented in this paper. The word “Cybernetic Human” is a coinage for us to explain a humanoid robot with a realistic head and a realistic figure of a human being. HRP-4C stands for Humanoid Robotics Platform-4 (Cybernetic human). Standing 158 [cm] tall and weighting 43 [kg] (including batteries), with the joints and dimensions set to average values for young Japanese females, HRP-4C looks very human-like. This paper introduces the design process, mechanical features, and electrical features with specifications of HRP-4C.

Task model of lower body motion for a biped humanoid robot to imitate human dances

The goal of this study is developing a biped humanoid robot that can observe a human dance performance and imitate it. To achieve this goal, we propose a task model of lower body motion, which consists of task primitives (what to do) and skill parameters (how to do it). Based on this model, a sequence of task primitives and their skill parameters are detected from human motion, and robot motion is regenerated from the detected result under constraints of a robot. This model can generate human-like lower body motion including various waist motions as well as various stepping motions of the legs. Generated motions can be performed stably on an actual robot supported by its own legs. We used improved robot hardware HRP-2, which has superior features in body weight, actuators, and DOF of the waist. By using the proposed method and HRP-2, we have realized a dance performance of Japanese folk dance by the robot, which is synchronized with a performance of a human grand master on the same stage.

ZMP-based Biped Running Enhanced by Toe Springs

We discuss a ZMP-based running pattern generation for a biped robot equipped with toe springs. Our biped robot HRP-2LT has twelve active DoFs for its legs and two passive DoFs for its toes. The trajectory of the center of mass is designed to realize the specified running motion and the foot trajectories are determined to get proper spring action at lift off phases. They are interpreted into joint angles by using the resolved momentum control. By the simulation and the preliminary experiment, it is shown that the toe springs are effectively used for running and hopping.

Constraint-based dynamics simulator for humanoid robots with shock absorbing mechanisms

We propose a simulation system that achieves realistic and efficient simulations of humanoid robots. This paper focuses on a constraint-based contact force solver and virtual spring-damper joints from among the components of the system. The contact force solver can accurately simulate contacts between rigid bodies including articulated rigid bodies. LCP-like formulation of constraint conditions is solved by an iterative calculation method that extends the Gauss-Seidel method. This paper clarifies how to integrate existing methods to implement a robust and efficient solver. Virtual spring-damper joints are proposed to simulate a shock absorbing mechanism that many biped humanoid robots have in their feet to increase the stability of walking motion. The combination of the rigid contact model and the elastic virtual joints can improve the accuracy of the simulation. The simulation system was verified by experiments using humanoid robot HRP-2, and the results shows the validity of the system.

A Pattern Generator of Humanoid Robots Walking on a Rough Terrain

This paper presents a biped humanoid robot that is able to walk on a rough terrain while touching a handrail. The contact wrench sum (CWS for short) is used as the criterion to judge if the contact between the robot and the environment is strongly stable under the sufficient friction assumption, where the contact points are not coplanar and the normal vectors at the points are not identical. It is confirmed that the proposed pattern generator can make the robot walk as desired in dynamics simulations and experiments, and the motions can be improved by a hand position control and using waist joints.

Leg motion primitives for a dancing humanoid robot

The goal of the study described In this work is to develop a total technology for archiving human dance motions. A key feature of this technology is a dance replay by a humanoid robot. Although human dance motions can be acquired by a motion capture system, a robot cannot exactly follow the captured data because of different body structure and physical properties between the human and the robot. In particular, leg motions are too constrained to be converted from the captured data because the legs must interact with the floor and keep dynamic balance within the mechanical constraints of current robots. To solve this problem, we have designed a symbolic description of leg motion primitives in a dance performance. Human dance actions are recognized as a sequence of primitives and the same actions of the robot can be regenerated from them. This framework is more reasonable than modifying the original motion to adapt the robot constraints. We have developed a system to generate feasible robot motions from a human performance, and realized a dance performance by the robot HRP-1S.

A Biped Pattern Generation Allowing Immediate Modification of Foot Placement in Real-time

This paper proposes a method of a real-time gait planning for biped robots which can change stride immediately at every step. Based on an analytical solution of an inverted pendulum model, the trajectories of COG (center of gravity) and ZMP (zero-moment point) are parameterized by polynomials. Since their coefficients can be efficiently computed with given boundary conditions, this framework can provide a real-time walking pattern generator for biped robots. To handle the unexpected result caused by immediate changes of foot placement, we made single support periods as an additional trajectory parameter. The effectiveness of our method is shown by simulations of the humanoid robot HRP-2

Experimentation of Humanoid Walking Allowing Immediate Modification of Foot Place Based on Analytical Solution

This paper proposes a method of a real-time gait planning for humanoid robots which can change stride immediately at every step. Based on an analytical solution of an inverted pendulum model, the trajectories of the COG (center of gravity) and the ZMP (zero-moment point) are parameterized by polynomials. Since their coefficients can be efficiently computed with given boundary conditions, this framework can provide a real-time walking pattern generator for humanoid robots. To handle the unexpected result caused by immediate changes of foot placement, we made single support periods as an additional trajectory parameter and the ZMP fluctuation was suppressed by mixing the opposite phase of the ZMP error. The effectiveness of our method is shown by experiments of the humanoid robot HRP-2.

Towards an Optimal Falling Motion for a Humanoid Robot

This paper studies an optimal planning of falling motions of a human-sized humanoid robot to reduce the damage of the robot. We developed a human-sized robot HRP-2FX which has a simplified humanoid robot shape with seven d.o.f. and can emulate motions in the sagittal plane of a humanoid robot. We simulated falling motions of HRP-2FX which generated by using an optimal control method to minimize a performance index, and verified the optimality

Intuitive and flexible user interface for creating whole body motions of biped humanoid robots

This paper proposes a novel user interface for creating whole body motions of biped humanoid robots just by giving key poses. Although such an interface is popular for CG character animation, there have not been any practical systems that can appropriately handle the kinematic and dynamic conditions required for moving actual biped robots stably without falling down. In our interface, every time a key pose is created, modified or removed, the system immediately processes automatic trajectory adjustment of the feet and the waist so that the key poses and the interpolated motion can always meet the conditions. This enables a user to edit variety of motions in an intuitive and flexible way without paying attention to the conditions. We implemented the interface and confirmed that characteristic whole body motions of a realistic humanoid robot HRP-4C were easily created with it and the actual HRP-4C successfully performed them.