Engineers develop prosthetic that mimics the human ankle

Dr David Moser, a biomechatronics engineer at Blatchford, explained to The Engineer that if a prosthetic does not interact with the ground in a smooth manner then the body will have to compensate in some way, which can cause discomfort to the user.

Due for release in December, the élan uses two microprocessors to redistribute weight and resistance around the artificial ankle joint so that it replicates how a human ankle works and allows amputees to walk with relative ease on inclines. The microprocessors work in tandem with the hydraulic ankle, which sits on top of carbon-fibre foot springs.

Moser said: ‘By adapting the hydraulic ankle module, you can adjust how much mechanical energy goes in and out of the foot springs.’

The élan is reportedly able to detect the outside environment through intelligent sensors that are built into the device.

Moser explained: ‘Somehow this system needs to know how the prosthesis has been fitted to the amputee, what springs are being used, and how that amputee walks. It also needs to understand the environment that the amputee is walking in.

‘From an electronics point of view, the challenge was sensing the environment in a robust and reliable manner. It’s really very difficult because the ground outside is just so variable.’

To program the device, the patient simply conducts three 78-step walks. The élan captures this data and uses it to configure the prosthetic to the individual amputee’s walking style.

Rechargeable batteries currently provide the élan with power but they have to be recharged on a daily basis.

Moser said: ‘I’d quite like to see microprocessor-controlled limbs generate their own power. It’s an interesting observation that human muscles actually spend a lot of time absorbing energy.’

Meanwhile, technical director Saeed Zahedi has even bigger plans.

He said: ‘By having microprocessor-controlled knee joints and microprocessor-controlled ankles, we know the performance of the ankle and the knee have independently increased. When we combine the two we are actually seeing a much larger-scale effect.’