About 25 million years after our ancestors traded theirs for an upright stance, a research team at Keio University Graduate School of Media Design gave our long-lost tails a comeback tour. The prototype, dubbed Arque, was a meter-long wearable robot designed to help elderly users with balance problems.
For most vertebrate animals, tail plays an important role for their body, providing variant functions to expand their mobility. In this work, Arque, we propose an artificial biomimicry-inspired anthropomorphic tail to allow us to alter our body momentum for assistive and haptic feedback applications.
The pitch is biomimicry. Cheetahs flick their tails to corner at full sprint. Monkeys use theirs as a counterweight in the canopy. Arque, the Keio team says, can do the same for us when crossing a slick kitchen floor. When the wearer leans one way, the tail swings the other, acting as a pendulum to nudge the body's center of mass back over its feet.
Mechanically, it's an articulated stack of vertebra-like plates strapped to the lower back via a harness. Four pneumatic artificial muscles, driven by compressed air, move the appendage in eight directions. Sensors read the wearer's posture and weight shifts, then fire the muscles in response. The result, in the team's demo videos, is unsettlingly organic: the tail twitches, coils and corrects in real time.
The project debuted at SIGGRAPH 2019's Emerging Technologies showcase and has lingered in the press ever since, because the "fossil yet furry" imagery is straight-up incredible and because the underlying problem isn't going away. Japan has the world's oldest population — close to 30% of residents are 65 or older — and falls remain a leading cause of injury. Canes and walkers aren't enough.
Lead researcher Junichi Nabeshima floated VR and heavy-lifting applications too (cf. "Get away from her, you bitch") but the trail seems cold since the SIGGRAPH paper, authored by Nabeshima with Yamen Saraiji and Kouta Minamizawa of Keio's Embodied Media lab. It hasn't apparently been further developed, let alone put to clinical trials or productized. All I could find in English since is recap journalism, like this!
But search results show a team in the U.K. has picked up the ball: led by Ildar Farkhatdinov at Queen Mary University of London, researchers there and at King's College are studying the practicality of balance-assistance tails.
Taking inspiration from the natural world, where some animals utilise tails for balance, this paper presents a Supernumerary Robotic Limb (SRL), in this case a wearable robotic tail, to support human balance. We showcase the modelling, design, manufacturing, and testing of the tail. It is mounted to a wearable harness, allowing for fast setup and easy don and doffing, i.e. attachment and removal. The tail's rotation is determined by the distance of a carried load from the user's body, with actuating motors serving the dual purpose of controlling the tail and acting as the counterbalance. This characteristic gives a higher counterweight to overall weight ratio when compared to related devices. Testing has demonstrated an accuracy of 89 % in position control and a rapid 57 ms response time. In trials with a healthy human participant, the system assists with balance, resulting in a 59 % smaller displacement of Centre of Pressure (CoP) when lifting a weight, contributing to better balance and safer posture. Wearable robotic systems such as this tail have the potential to be used in industries where manual labour often involves lifting heavy objects or adopting awkward postures.
If the robot tail concept has remained niche, the Queen Mary group shows the idea yet has… legs.
