Motorless foot prosthesis mimics human foot
Foot prostheses are usually inflexible, which prevents natural walking. Italian researchers have developed a prosthesis that adapts to the ground.
The foot prosthesis automatically adapts to any shape of surface.
(Image: IIT)
Scientists at the Instituto Italiano de Tecnologia (IIT) in Genoa, Italy, have developed a motorless, flexible, waterproof prosthetic foot that is modeled on the anatomy of the human foot and can adapt to different surfaces. This happens completely without any controls. The prosthesis, known as SoftFoot Pro, is particularly suitable for people with limb loss, but could also have a positive impact on the locomotion of robots.
"What prostheses and today's humanoid robots have in common is the characteristic of having flat or less compliant feet, designed to provide maximum stability but unable to adapt to changes in terrain contour, slope and different positions such as kneeling or bending," Manuel G. Catalano explains, researcher in the Soft Robotics for Human Cooperation and Rehabilitation Lab at IIT about the approach of the prosthetic foot.
Imitation of the human foot
The SoftFoot Pro weighs around 450 g and can support a weight of up to 100 kg. Two feet can handle 200 kg, making them suitable for heavy people and humanoid robots. The artificial foot comprises a movable arch mechanism made of titanium, the ends of which are connected to each other by five high-strength plastic chains arranged in parallel. They simulate the plantar fascia of the human foot.
The chain is traversed lengthwise by a 210 mm long, mechanically non-stretchable high-performance cable, which is connected to the heel. The individual modules of the chain are connected with elastomer connecting links.
Together, the arch system and the elastic chains artificially mimic the human foot, which consists of the tarsus, metatarsus and phalanges. The structure of the artificial foot imitates the so-called Windlass mechanism. This stiffens the plantar fascia when walking and distributes the force exerted on the ground evenly. This enables wearers of such a prosthetic foot to overcome obstacles more efficiently. The researchers promise that this improves forward propulsion and energy efficiency. At the same time, the foot adapts to the ground independently. The prosthetic foot can absorb around 10 to 50 percent of the impact force.
The foot's adaptability also enables more natural locomotion and stabilizes the wearer's gait. In addition, the prosthesis adapts to everyday movements, such as kneeling and tying a shoe or picking up objects. According to the research team, this also makes climbing stairs easier.
The artificial foot is waterproof and can therefore be used for outdoor activities. It is therefore suitable for outdoor use in meadows, on beaches and on slippery surfaces.
Tests with humans and robots
Independent tests at the Hannover Medical School (MHH) and the Medical University of Vienna have shown good effectiveness in people with unilateral lower limb amputations. Tests were also carried out on robots. The Swiss Federal Institute of Technology in Zurich (ETH Zurich) tested them on the four-legged robot Anymal, while the University of Tokyo tested them on the humanoid robot HRP-4.
(olb)