[Reading Science] The Evolution of Exoskeleton Robots Resembling Humans

[Asia Economy Reporter Kim Bong-su] "It is becoming more human-like." Wearable exoskeleton robots that assist and support human strength and endurance are evolving. They are developing to be easier for humans to wear, lighter, yet capable of exerting more complex forces. It is similar to the upgrade in movies from the ‘Terminator’ robot ‘T-600,’ which looked human on the outside but was a mechanical device inside, to the ‘T-1000,’ which is difficult to detect and can freely change shape. Exoskeleton robots are not a distant story. They are already changing our lives in various ways, such as preventing musculoskeletal disorders in various industrial sites, enabling patients with lower limb paralysis to walk, and being used for military purposes. Especially, they can supplement the declining physical abilities of humans due to aging, emerging as an important complementary tool in the labor market in the era of population aging.

Types of Exoskeletons

There are passive exoskeletons that use elastic structures without actuators to store energy when the human body moves and assist specific movements. On the other hand, there are active exoskeletons that use actuators (motors) powered by electricity, hydraulics, compressed air, etc., and operate by exchanging signals with the human body such as brain waves and electromyography. According to the ‘Exoskeleton Research and Development Trend Report’ published by the Korea Research Foundation’s ICT Convergence Research Group on the 30th of last month, exoskeletons reduce the use of human spinal erector muscles by 10 to 57%, reducing the load on the lower back and decreasing upper body bending sensitivity, helping perform tasks effectively and safely.

Especially in tasks that require bending the waist, which workers feel relatively burdensome, the effect of wearing exoskeletons is greater. Accordingly, they have begun to be used as a preventive measure against musculoskeletal disorders commonly occurring in industrial sites. Musculoskeletal disorders caused by excessive muscle use, improper posture, excessive force, and repetitive movements account for the largest portion of industrial accident compensation costs in major countries such as the United States and Korea.

By wearing exoskeletons to increase endurance or support posture, the risk of musculoskeletal disorders for workers is significantly reduced. They reduce biomechanical stress on major body parts and the risk of injury, contributing to productivity improvement. Especially, by enhancing the physical abilities of workers that decline due to aging, they prevent the side effects of an aging labor market. This is why exoskeletons are being actively introduced in various fields such as automobiles, ships, manufacturing, aviation, space, military, and healthcare.

Exoskeletons Entering Daily Life

Exoskeletons are already widely used domestically and internationally. Ford Motor Company in the U.S. has developed an exoskeleton called ExsoVest and provides it to workers. When worn on the upper body, it allows lifting up to 7 kg with one arm without feeling the weight, significantly reducing the force workers need to exert when lifting their arms above the shoulder to perform tasks.

Japan’s ActiveLink developed an industrial exoskeleton robot using 18 motors that can lift heavy objects up to 110 kg. Also, a research team from Lockheed Martin and the University of California, Berkeley developed a wearable robot (HULC) using lithium polymer batteries and fuel cells that allows soldiers to carry heavy military gear weighing up to 90 kg and run at a peak speed of 16 km/h. In healthcare, the Rewalk Personal lower limb exoskeleton suit by U.S. company Rewalk stands out. It helps patients with lower limb paralysis walk using only upper body movements. Japan’s Cyberdyne also developed a wearable robot that recognizes user intent by analyzing electromyography signals.

Wearable Robot Developed by Hyundai Motor Group

In Korea, fundamental technologies for wearable robots are actively researched but still in the early stages. They are active in industrial and rehabilitation fields, and various attempts are underway to introduce them into production lines by companies. Hyundai Rotem developed industrial wearable exoskeleton robots VEX (upper body) and CEX (lower body) in 2019, and in 2020 introduced the wearable strength-assist robot ‘H-Frame’ in production sites to prevent musculoskeletal disorders. Hankook Tire also protects workers’ lower backs involved in tire loading tasks by using the exoskeleton wearable robot ‘StepUp.’ Samsung Electronics’ lower limb wearable robot for elderly and disabled people, GEMS, attracted attention for being lightweight and easy to wear.

However, challenges remain. The costs of purchasing, managing, and utilizing exoskeletons are enormous. Above all, workers avoid them because putting them on and taking them off is inconvenient and time-consuming compared to the benefits gained. Wearing exoskeletons also makes it difficult to perform other actions such as moving outside the task, operating devices, or driving, which hinders their utilization.

Hyundai Kia Motors researchers wearing wearable robots and demonstrating them

Become More Human-Like

Exoskeletons and wearable robots are now advancing to a stage where they not only improve wearing comfort but also enhance interaction with humans, allowing users to utilize them as if they were their own bodies and perform complex, high-level movements with ease. First, research on Human-Robot Interaction (HRI) is active. In the U.S., 16 government agencies, 56 companies, 13 universities, and 10 national research institutes have participated extensively to develop the military wearable robot ‘Strategic Assault Lightweight Operational Suit,’ actively researching and applying physical interaction between humans and robots and user biosensing technologies. In Europe, the PHRIENDS (Physical Human-Robot Interaction: depENDability and Safety) project is underway with the main goal of ensuring interaction and safety between humans and robots. A representative case is the University of Mainz in Germany studying pain perceived by humans at human-machine contact points to research safety requirements for collaborative robots that do not harm the human body. In Japan, development of assistive exoskeleton robots that operate using biosignals from elderly and disabled people is active in response to the super-aged society. Microsoft is also researching an innovative wearable environment that recognizes user movements, voice, and face through cameras and sensors to command robots.

In Korea, development of human-like exoskeleton robots is accelerating through AI, big data, and advanced material technologies. A representative example is the ‘Hercules-class’ artificial muscle material developed by Professor Kim Sang-wook’s research team at KAIST’s Department of Materials Science and Engineering, announced on the 5th. Unlike existing exoskeletons and wearable robots that use machines such as hydraulic devices to generate force, this artificial muscle is similar to human muscles, highly practical, and can exert more than 17 times the strength of a human muscle, receiving high praise.

Professor Kim explained, "Existing artificial muscle materials only bend sideways or require preliminary actions like winding and unwinding to obtain power. The artificial muscle developed this time is made of soft fiber bundles like human muscles, contracts in length to exert force, and can contract infinitely repeatedly. The only difference is that human muscles move by electrical signals, but this operates by light."

Especially, Professor Kim’s artificial muscle is highly evaluated for its practicality due to its various applications. He said, "Existing robotics are hydraulic or mechanical, but with this artificial muscle development, when creating future synthetic life forms like avatars or Hulk, synthetic tissues similar to human muscles can be used instead of machines. It can be immediately applied to human augmentation that humans can wear and use, and can also be used as artificial muscles implantable inside the human body connected to nerves."

He added, "This is the first development of artificial muscles that outperform living organisms in all performances through artificial actuators, including speed, deformation, energy, and strength. It can be used in the robot industry and various wearable devices and will greatly contribute to non-face-to-face science and technology in the Fourth Industrial Revolution."