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Researchers Yuki Asano, Kei Okada, and Masayuki Inaba from the Department of Mechano-Informatics, Graduate School of Information Science and Technology at the University of Tokyo wanted to create a “human mimetic humanoid with an unprecedented degree of anatomical fidelity to the human musculoskeletal structure” to address the systems and mechanics of the human body that have yet to be fully understood.
“A limitation of conventional humanoids is that they have been designed on the basis of the theories of conventional engineering, mechanics, electronics, and informatics,” the researchers pointed out, “by contrast, our intent is to design a humanoid based on human systems—including the musculoskeletal structure, sensory nervous system, and methods of information processing in the brain—to support science-oriented goals, such as gaining a deeper understanding of the internal mechanisms of humans.”
The researchers used human statistical data from previous humanoid research data to give Kenshiro and Kengoro more humanoid proportions.
“In our case, the design priority was to achieve bone lengths and limb shapes similar to those of humans,” the researchers added. “The skeletal structure of the human mimetic humanoid was designed to imitate the skeletal shape, joint structure, and joint DOFs of humans.”
To evaluate Kenshiro and Kengoro’s body proportions, the researchers conducted a comparison of the mass distribution properties between them and an average human, “[They] exhibited an average of 115 and 116% of the mass of an average human.”
A skeletal structure evaluation was also conducted, comparing the number of degrees of freedom between Kenshiro and Kengoro, and several humanoids. They found that humans have 548 joint DOFs. Humanoids with actuators at their joints were found to have 27 to 35 joint DOFs while humanoids with human-inspired musculoskeletal structures and tendons have 55 to 114 joint DOFs.
Kenshiro has multiple spine joints that are structured like a human’s S-curve and a yaw rotation DOF in the knee, giving it 64 DOFs. Meanwhile, Kengoro’s hands have multiple DOFs and end effectors, giving it 174 DOFs.
“The use of multiple spine joints is one of the most important factors required to approach the flexibility of a human, and the number of DOFs of current humanoids is limited by whether the humanoid has spinal flexibility,” the researchers noted.
The researchers believe that incorporating these kinds of humanoid characteristics could help reveal the inner workings of the human bodies which would, in turn, help find better ways to prevent and treat illnesses or injuries.
“One research group has suggested the possibility that a musculoskeletal humanoid can be used in medicine, such as to grow tissue grafts,” the researchers pointed out, “If a humanoid can replicate human movements, then the resulting muscle contribution analysis or sensory data obtained during motion will benefit athletes or sports trainers.”