This robot can move around like a human and even eat a Cheeto. (Image Credit: Suzumori Endo Robotics Laboratory)
Developing human-like robots is not an easy feat. For starters, they would need to be designed exactly like a human body, which has 206 bones and 650 muscles. Back in 2016, scientists at the Suzumori Endo Robotics Laboratory in Tokyo built a musculoskeletal robot driven by multifilament artificial muscles, allowing it to move exactly like a human. The robot used a walking auxiliary instrument to walk and OpenSim to obtain a walking pattern.
The team also used McKibben muscles, which are comprised of a silicone tube. The outer sleeve yarn is made out of Tetoron mono-filament. Measuring 1.8mm, the McKibben muscles were designed with an 18° braiding angle, and it contains 24 outer fibers. Each multifilament muscle has a tendon made of Dyneema (high-density polyethylene) fibers at each end that attaches to a skeleton. It also has a heat-shrink plastic air supply port.
The structure of a multifilament muscle consists of an air supply tube, a tendon on each end, heat shrink plastic, and thin McKibben muscles. (Image Credit: Suzumori Endo Robotics Laboratory) 
Each multifilament muscle, which contains 60 McKibben muscles measuring 310 mm long, functions as a contracting linear actuator. The contracting force is almost similar to the number of muscles. Meanwhile, the contraction ratio is equal to a thin McKibben muscle. This allows the team to design a muscle with that property. The actuator is fairly robust. If some of the McKibben muscles become damaged, then the multifilament muscle still functions with minimal air leakage. It can easily be fixed and sealed. These actuators were designed and developed to function as human muscles.
The bands of multifilament muscles are controlled by an electric current, causing the fibers to contract and expand like real muscles in a human body. Even the robot's head can move around. However, it's not very strong or fast. "I am trying something new every day," the robot says in the video. It can even take a bite out of a Cheetos and kick a basketball, two activities that humans normally perform.
The robot can't support itself, but its legs have the same number of muscles that humans use to walk. The scientists hope that it can balance itself and walk on its own, much like the ATLAS robot. The team also concluded that they need to improve the opening area of valves and the length of air.
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