Junichi Urata

An advanced musculoskeletal humanoid Kojiro

We have been promoting a project of musculoskeletal humanoids. The project aims at the long-term goal of human-symbiotic robots as well as the mid-term goal of necessary design and control concepts for musculoskeletal robots. This paper presents the concepts and aim of the project and also shows the outline of our latest results about development of new musculoskeletal humanoid Kojiro, which is the succeeding version of our previous Kotaro.

Online decision of foot placement using singular LQ preview regulation

In this paper, we introduce an online decision method of foot placement for legged robots that manages unknown external forces. It consists of a fast trajectory generation method and an optimization method of foot placement. The fast trajectory generation method is based on an explicit solution for singular LQ preview regulation problem of an inverted pendulum model. By using the regulator problem, the conditions of target ZMP trajectory that will not make the COM trajectory diverge and a fast generation method of the COM trajectory which satisfies the target ZMP trajectory are obtained. An online optimization of foot placement is realized by using the fast trajectory generation method. An experiment of the online decision method of foot placement that manages unknown external force shows the performance of the proposed method.

Design of high torque and high speed leg module for high power humanoid

The high power ability of humanoid is desired for application of nursing or running or jumping motions. Achievement of the actuator of light and powerful equivalent to humans is required. In this paper, we propose a method to extract inherent performance from motors by an active temperature control. The method safely improves the output of motors. The active temperature control is achieved by combining the estimation of an internal temperature of the motor with the forced cooling by liquid. We also developed high power motor drivers for the proposed method. An experiment of a high power joint test bench is shown. In this paper, we show a high power prototype biped robot for application of nursing, running or jumping motions. High power actuator system and robust internal body network are developed for high power robot. Basic demonstration experiments of high power motion are shown.

Design concept of detail musculoskeletal humanoid “Kenshiro” - Toward a real human body musculoskeletal simulator

We have developed and studied musculoskeletal humanoids. Our goal is to realize a more human-like humanoid as a real human simulator, which has the same muscle and joint arrangements as humans and can do natural and dynamic motions as well as humans. Especially, it is very challenging to design musculoskeletal structure which can contain a large number of high powered muscles. Now, we design new fullbody musculoskeletal humanoid Kenshiro. This paper presents the concepts of this new robot and also shows the outline of our latest results Kenshiro, which is the succeeding version of our previous robot Kojiro.

Thermal control of electrical motors for high-power humanoid robots

High physical ability of humanoid robots is desired for application to nursing care. Light and powerful actuators are required to realize the high-power performance. In this paper, we propose a method to bring out maximum performance of electric motors aggressively. The technique of motor core temperature estimation and control improves the motor power performance dramatically but safely without motor burnout. We have developed high power motor driver modules for the proposed method and equipped them into our humanoid robot and prototype jumping robot. High-power performance experiments with the robots demonstrate our method.

Online walking pattern generation for push recovery and minimum delay to commanded change of direction and speed

A walking biped robot is required to change its walking direction and speed with minimal delay and not to tip off even when subjected to an unexpected external force. A major drawback of Zero Moment Point (ZMP) based online walking pattern generation methods is that arbitrary ZMPs cannot be achieved without divergence of the Conter of Mass (CoM). In this paper, we propose a new online walking trajectory generation method that utilizes nondivergence conditions of ZMP-CoM in a successive manner. This method enables changes in the walking direction and speed of a robot and push recovery under an unknown external force in unifie form. Experiments confir walking change of up to 4.05 km/h in the speed and changes in the walking direction with minimum delay and successful push recovery under an implse of 22 Ns.

Development of muscle-driven flexible-spine humanoids

Aiming at opening up a new stage of humanoid robotics, we have been studying on the mechanically soft structure for humanoids and have developed a full-body muscle-driven flexible-spine humanoid robots. In this paper, we discuss body structure of humanoids, describing the advantages of musculoskeletal flexible body and briefly introducing the previous works on constructing hardware and software of flexible spine robots. This paper also presents the design and development of a novel musculoskeletal humanoid named Kotaro

Development and verification of life-size humanoid with high-output actuation system

Life-size humanoids which have the same joint arrangement as humans are expected to help in the living environment. In this case, they require high load operations such as gripping and conveyance of heavy load, and holding people at the care spot. However, these operations are difficult for existing humanoids because of their low joint output. Therefore, the purpose of this study is to develop the highoutput life-size humanoid robot. We first designed a motor driver for humanoid with featuring small, water-cooled, and high output, and it performed higher joint output than existing humanoids utilizing. In this paper, we describe designed humanoid arm and leg with this motor driver. The arm is featuring the designed 2-axis unit and the leg is featuring the water-cooled double motor system. We demonstrated the arms high torque and high velocity experiment and the legs high performance experiment based on water-cooled double motor compared with air-cooled and single motor. Then we designed and developed a life-size humanoid with these arms and legs. We demonstrated some humanoids experiment operating high load to find out the arm and legs validity.

Lower thigh design of detailed musculoskeletal humanoid “Kenshiro”

In order to know human dynamics, humanoid as a human body simulator is increasing its importance. Such humanoid is expected to have human musculoskeletal structure as close as possible. From this viewpoint, we are trying to create new musculoskeletal humanoid which has detailed human imitating structure, such as bi-articular muscle, muscle arrangement, joint structure and so on. In this paper, we address the design of lower thigh. The concepts of the thigh include leg configuration, new knee joint and link, and artificial muscle arrangements, especially knee joint structure imitating human flexible motion. The knee joint has yaw axis DOF and its locking mechanism which is usually simplified in robotics. Finally, we conduct extension, flexion and rotation as basic experiment to confirm the joint characteristics. Also, we conduct rotation experiment in the ground state to confirm the contribution of yaw axis DOF for human-like motion.

Design Approach of Biologically-Inspired Musculoskeletal Humanoids

In order to realize more natural and various motions like humans, humanlike musculoskeletal tendon-driven humanoids have been studied. Especially, it is very challenging to design musculoskeletal body structure which consists of complicated bones, redundant powerful and flexible muscles, and large number of distributed sensors. In addition, it is very challenging to reveal humanlike intelligence to manage these complicated musculoskeletal body structure. This paper sums up life-sized musculoskeletal humanoids Kenta, Kotaro, Kenzoh and Kenshiro which we have developed so far, and describes key technologies to develop and control these robots.