Hironori Mizoguchi

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.

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.

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.

Biomimetic design of musculoskeletal humanoid knee joint with patella and screw-home mechanism

We are trying to create a novel musculoskeletal humanoid robot which has a humanlike structure. In this paper, we present a new knee joint which is usually simplified in robotics for high controllability. The knee joint has three human mimetic points, patella, screw-home mechanism and four-linked linkage. Patella is for a longer moment arm. Screw-home mechanism is for locking knee joint. Four-linked linkage is for making humanlike motion. Furthermore, we confirmed those performances by three experiments.

Design of humanoid body trunk with “multiple spine structure” and “planar-muscle-driven” system for achievement of humanlike powerful and lithe motion

In recent years, humanlike robots have recieved a lot of attension. For making humanlike robots, a muscu-loskeletal humanoid is an effective approach. However, many musculoskeletal humanoids have not yet been equipped with really humanlike bones and muscles, especially for the body trunk, which is the core of the robot. For making a powerful and lithe humanoid body trunk with really humanlike bones and muscles, we think an enhanced “planar-muscle-driven” system and “multiple spine” structure were keys. Planar-muscle-driven systems move several wires simultaneously by using two moving-pulley bars per motor, while the prior linear-muscle-driven system moved only one wire per motor. Using the planar-muscle-driven system, we were able to simplify prior complex composition and control systems. On the other hand, we proposed a multiple spine structure, which has an S-curve alignment like the human spine. In human, the S-curve is important for upper body stability while walking and shock relaxation of heavy human head. This paper describes the “planar muscle” unit and the “multiple spine” structures, and then the body trunk containing both elements. Using the model, we performed experiments to show the efficacy of those elements.

Biomimetic design and implementation of muscle arrangement around hip joint for musculoskeletal humanoid

Our laboratory has tackled the composition theory approach of clarifying the structure in the human body by imitating it. Focusing on the hip joint, which has many complex muscle groups, we estimated and implemented 15 muscles to restrict the hip joint. However, it was difficult to implement such a quantity muscles to musculoskeletal humanoid because motor space is limited and the frame must have strength. In this paper, we propose new design and implementation methodology of musculoskeletal humanoids. First, we propose the biomimetic design of the hybrid pelvis, which uses metal and resin. Second, to arrange the muscles in a way similar to a human, we propose the human mimetic muscle arrangement by using the internal organ space. As a result, we developed the high-strength and biologically inspired pelvis, and achieved human-like muscle attachment layout and muscle arrangement.

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.