Yotaro Motegi

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.

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.

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.

Achievement of twist squat by musculoskeletal humanoid with screw-home mechanism

Human knee joint has a yaw-axis rotational DOF and a locking mechanism called screw-home mechanism. We focus on this mechanism and implement it to a musculoskeletal humanoid through hardware design. The importance of developing a knee joint with screw-home mechanism is that such a joint is capable of working yaw-axis properly and generating enough pitch joint torque for supporting whole body motion. In this paper, as an evaluation of our developed knee joint, we first checked the moment arm of the yaw rotational axis of the knee. Moreover, we also checked the yaw angle displacement during squat motion. From these results, we confirmed that the mechanism worked properly. Second, in order to check whether enough pitch joint torque is generated during movement, we conducted several experiments with whole body motions such as squatting. Lastly, as unique and integrated motions that involve the use of yaw DOF derived from the mechanism, we tested knee joint Open-Close, Right-to-Left and whole body twist squat motion. Our results demonstrated the feasibility of musculoskeletal humanoids with screw-home mechanism and showed that we have achieved humanlike twisting motion.

Dual connected Bi-Copter with new wall trace locomotion feasibility that can fly at arbitrary tilt angle

We have developed a robot with a new control mechanism in order to collect information on flying robots in multiple fields. We aimed for a function that could rotate the tilt angle continuously and without limit and a function for flying maintaining any desired tilt angle with a structure that could efficiently use the thrust generated by the propellers. We devised a mechanism that connected two bicopter modules, each of which combines two of the four propellers into one set and named this mechanism the “Bi2 Copter”. This mechanism provided movements including landing, take-off, and flying with any desired tilt angle. This ability of this mechanism to fly walls with continuously changing surface angles and full 360° spherical coverage makes possible applications in investigation, measurement, etc. This report covers the design concepts of this flying robot, the structure design, basic control and operations verification.

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.

Muscle-tendon complex control by “Tension controlled Muscle” and “Non-linear Spring Ligament” for real world musculoskeletal body simulator Kenshiro

This paper presents a control approach to express muscle-tendon complex in a musculoskeletal humanoid robot. Kenshiro is a full body tendon driven humanoid robot and is designed from the data of average 14 year old Japanese boy. By winding wires by motors we can express the contraction of muscles, and in this paper we introduce novel actuation system realized by integrating “Tension controlled Muscle(TCM)” and “Non-linear Spring Ligament(NSL)”. Combination of active and passive compliance control is explained in this paper to realize the behavior of muscle-tendon complex(MTC). This enables flexible behavior of Kenshiro, and mimic joint trajectory of human when external force is applied. At the same time the tension data of the load cells can be regarded as muscle tension. In this way it becomes possible to use musculoskeletal humanoid robots for measuring biological data quantitatively. Application of Kenshiro as actively movable car crash simulation mannequin is illustrated by an example as a future work.

Controlling tendon driven humanoids with a wearable device with Direct-Mapping Method

In this paper we propose a “Direct-Mapping Method” and describe a wearable device which has a similar muscle arrangement as a tendon-driven humanoid robot. This device has linear-encoders as many as the muscles of the robot to control, and they are arranged like the robots muscle alignment. Tendon-driven humanoids have advantages of their human size, multiple Degrees of freedoms and their musclo-skeletal structure, therefore they are able to make more human-like poses than shaft-driven humanoid robots. If we can teach human poses to them, they become more human-like so that we feel a sense of familiarity with robots. However, because of their complex structure, sometimes they make incorrect poses. There must be a feedback system to control their bones in detail. To make human-like pose naturally and to make precise motion by feed back to the user, the best way may be a wearable device. With this device, we can control tendon-driven humanoids without making their simulation model in the computer. We discuss the hardware settings of the device and the controlling system in this paper. Experiments of controlling a tendon-driven humanoid were conducted to demonstrate the effectiveness of the device. When controlling the robot, a situation that some muscles are loose or too tight occured. However, this devices behavior-teaching framework contributes to detailed robotic movement in the future.

Implementation of Human Mimetic Knee Joint with Screw-Home Mechanism and Achievement of Motion under Environment Contact by Musculoskeletal Humanoid

Human knee joint has a yaw-axis rotational DOF and a locking mechanism called screw-home mechanism(SHM). We focus on this mechanism and implement it to a musculoskeletal humanoid through hardware design. In this paper, we first explained human knee characteristic of SHM and joint range of motion. Next, we explained hardware design and implementation method of the mechanism. As an evaluation of our developed knee joint, we checked the function of SHM from viewpoint of moment arm of the yaw rotational axis and the yaw angle displacement during squat motion. Lastly, as unique and integrated motions that involve the use of yaw DOF derived from SHM, we made several motion achievement including humanlike twisting squat, heel move motion and switch pedals, under a condition of contacting environment. This result demonstrates human mimetic rotational DOF of knee contributes motion achievement.