Engineering an intelligent prosthetic with joints that communicate

Categories: Design

17 November 2016

Author: Nadine Stech



The Paralympic Games in London in 2012, and then in Rio this year, have propelled more disabled athletes into the limelight than any games before. This summer we watched some astonishing success stories, resulting in the biggest medal haul of the Paralympic Games to date.

For me, the most fascinating events featured lower limb amputees running on composite blades. The speed afforded by the prosthetics was amazing. The blades used in the Paralympic Games are designed with extreme sports in mind, but they are not ideal for the numerous challenging situations of daily life. Amputees must instead change between different prosthetic limbs for different purposes.

At Blatchford, our research focus lies in overcoming these everyday challenges. During the course of a typical day, a person takes a huge variety of different steps, makes numerous small movements and undertakes hundreds of complex tasks. When it comes to developing a device that can replace a missing lower limb, every motion must be considered.

We have developed an integrated prosthetic limb called ‘Linx’, designed for people with amputations above the knee. The robotic limb has both a knee joint and a foot joint that are controlled by microcontrollers. The Linx limb is unique, because both the knee and the foot can ‘talk’ to each other. In all previous prosthetics, knee and foot joints were developed separately and worked in isolation.

The biggest challenge we faced was developing a system that would allow the joints to communicate. Let’s imagine, for example, that one speaks English and the other speaks French. To make them work together, we needed to develop a ’translator’ that could understand both languages. One of my core tasks on this project was to develop the translator that holds the whole system together, and then develop additional limb functionalities.

Linx is the first commercially available system which features communication between its joints. By communicating as a whole, the limb can react in a coordinated way to changes in gait. This offers the wearer greater stability when descending a ramp and while standing still.

During ramp descent, typically our muscles absorb more energy than they generate. A person with a lower-leg amputation must take more stress on their other leg in order to keep themselves descending at a controlled pace. This often causes discomfort when wearing a conventional prosthetic. With Linx, we created a special ramp descent mode. Both the prosthetic knee and the foot brake together when walking downhill; which can relieve the additional stress on the other leg.

In 2016, the Linx limb won the Royal Academy of Engineering’s prestigious MacRobert Award. The award highlights the uniqueness and potential of our approach, and marks the Linx as an innovation that many people can benefit from. While winning has been a huge honour for the team, seeing the big smile on peoples’ faces when they realise the full capability of the limb has been the best reward!

At Blatchford, we are now looking into the future of prosthetics and how we can develop assistive technology further. Besides prosthetics, we are currently involved in an EU project MovAiD, investigating the potential of technology and additive manufacturing in orthotics.

Nadine and the team at Blatchford won the 2016 MacRobert Award for the Linx intelligent prosthetic limb.

The MacRobert Award, first presented in 1969, is the UK's longest running and most prestigious national prize for engineering innovation. It is presented annually by the Royal Academy of Engineering, with support from the Worshipful Company of Engineers.

Applications are now open for the 2017 MacRobert Award. You can keep up-to-date with the latest MacRobert Award news on Twitter at @RAEngMacRobert

More on the author, Nadine Stech

Senior Control Design Engineer, Blatchford

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