Takuma Shirai

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.

Design methodology for the thorax and shoulder of human mimetic musculoskeletal humanoid Kenshiro -a thorax structure with rib like surface -

To design a robot with humanlike body structure, this paper presents a design methodology for a humanoid upper limb by tendon driven system. We newly designed an upper limb and rib cage like thorax for a musculoskeletal humanoid robot, based on the knowledge of anatomy. The robot consists of muscle, bone, and joint structure based on human and is expected to move flexibly and dynamically. This paper describes how to design such an upper limb and proposes the key mechanical design points, which is “rib surface thorax”, “muscle cushion”, “planar muscle”, and “open type ball joint”. To show that these mechanisms is effective in making a musculoskeletal humanoid robot, we examine the motion range of the robot. One of our goals is to enable robots to do the same movements as humans do through mimicking the human body structure, finding some important elements of human nature. This robots explained in this paper is the prototype for a new life size robot “Kenshiro” project.

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.

Design of upper limb by adhesion of muscles and bones — Detail human mimetic musculoskeletal humanoid kenshiro

This paper presents a design methodology for humanoid upper limb based on human anatomy. Kenshiro is a full body tendon driven humanoid robot and is designed from the data of average 14 year old Japanese boy. The design of his upper limb is realizing detail features of muscles, bones and the adhesive relation of the two. Human mimetic design is realized by focusing on the fact that joints are being stabled by muscles winding around the bones, and by accurately mimicking the bone shape this was enabled. In this paper we also introduce details of mechanical specifications of the upper limb. By having muscles, bones, and joint structures based on human anatomy, Kenshiro can move flexibly. The use as human body simulator can be expected by measuring sensor data which can correspond to biological data.

A sensor-driver integrated muscle module with high-tension measurability and flexibility for tendon-driven robots

We propose a sensor-driver integrated muscle module by integrating necessarily components for tendon-driven robot which is likely to complicate. The module has abilities of high-tension measurability and flexible tension control. In order to achieve flexible tension control, we developed the new tension measurement mechanism with high-tension measurability and the new motor driver which enables current based motor control. We demonstrate the tension control ability of the module by several experiments. Furthermore, utilizing the module advantage of design facilitation, we made two types of tendon-driven robots and confirmed effectiveness of the module.

Learning nonlinear muscle-joint state mapping toward geometric model-free tendon driven musculoskeletal robots

To control a musculoskeletal tendon-driven robot we propose a novel method to learn musculoskeletal nonlinear bidirectional mapping between muscle length and posture (joint angle) from a real musculoskeletal robot. We show the nonlinear musculoskeletal mapping from joint angle to muscle length can be learned as a linear combination of simple nonlinear functions. This formulation can be extended to posture estimation (mapping from muscle length to joint angle) by EKF (Extened Kalman Filter) and torque estimation by differentiation in a musculoskeletal robot. In this paper, we applied the method to tendon driven musculoskeletal robots and verified the validity.

Whole body adapting behavior with muscle level stiffness control of tendon-driven multijoint robot

A tendon-driven multijoint robot is a humanlike robot which is driven by a tendon-driven actuator. One of the problems is that the complexity of the tendon-driven multijoint robot body structure. The complexity makes it difficult to control body by commonly used methods which are based on a dynamics computation of a physical robot model. We proposed a appropriate control method for tendon-driven actuators. In this control method, we defined an ideal reaction model that is based on a physical motion equation. This equation includes an elastic term, inertia term and a friction term. The control method then calculates target rotational velocity of the actuator from the motion equation. Finally, the motor driver of the actuator outputs voltage to follow the target velocity through a basic PID control. Our control method enables the tendon-driven actuator to act as a mechanical spring. Through this, the tendon-driven multijoint robot can attain the flexibility to adapt to external forces applied by collision with objects without using a precise dynamics computation. Moreover, our control method enables the tendon-driven multijoint robot to adjust its stiffness and flexibility depending on the purpose of its given tasks. We tested this control method by using KOJIRO, and showed the control method works as declared.

Skeletal structure with artificial perspiration for cooling by latent heat for musculoskeletal humanoid Kengoro

In this paper we propose a novel method to utilize the skeletal structure not only for supporting force but for releasing heat by latent heat.

Development of musculoskeletal spine structure that fulfills great force requirements in upper body kinematics

The main goal of this paper is to design and evaluate a spine structure which withstands various motions. The structure around the neck has a prevailing importance since it is involved in various motions of the upper half of the body. The new design method we introduce essentially shows how to design all 7 cervical vertebrae (the part of spine in the neck) in a limited space, actuated by the wires winded around the motors. Then we show the muscle arrangements around the upper half of the spine. More specifically, we make use of a so called planar muscle mechanism. An abduction experiment which requires great force around the spine is made to show its stability. Finally, we show a variable stiffness system which enables the spine to resist an impulsive force. We have tested the system in the situation of whiplash injury which is a case of extreme external forces which can occur in car crash accidents. As such we have evaluated the strength of the design and the viability of our robot to act as a human body simulator.

Motion generation of redundant musculoskeletal humanoid based on robot-model error compensation by muscle load sharing and interactive control device

Musculoskeletal humanoid has robot-model errors because of muscle elasticity or elongation. This leads to low accuracy and repeatability in joint position control. In particular, this is a serious problem during high-load motions. In this paper, we propose and implement its compensation methods for generating motions in the presence of robot-model errors. One of the control methods presented is a muscle-load sharing method utilizing redundant muscle arrangement which is specific in musculoskeletal humanoid. The other is an interactive control system enabling interactive joint position modification by using human physical or visual information. Finally, we tested several motions by integrating the two systems.