Novel Bio-Inspired 'Smart' Joint for Prosthetics and Robotics Lower Limbs

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At present there are over 90,000 new cases of knee replacements and leg amputations every year in the UK alone. This is equivalent to approximately one every six minutes. Currently between 5 - 6,000 major limb amputations are performed in the UK each year and trauma accounts for approximately 55% of them. Lower limb amputation has a profound effect on activities of daily living and not all amputees are able to tolerate or use a prosthesis. Therefore, it is essential that the prosthesis is comfortable and adapted to be used by patients in order to enhance their daily activities. Artificial knee joints are important medical devices that enable many people to maintain walking and running functions. In working towards this target, researchers have repeatedly missed the key role held by the correlation between the soft tissues (ligaments) and the structure (bones) in human-like locomotion. Biological joints demonstrate multi-functionality by integrating high conformity, compactness and low friction. These functions are crucial when designing a functional and robust joint by including this separation of functions at the conceptual stage.Though there is still little known about the exact implications and mechanisms involved while performing human movement, recent engineering research into the mechanics of the ligaments and the analysis of the knee joint in compression has produced models and simulations that have shed light on some of the possible roles of the human knee features. Therefore, we believe that this separation of functions into the design process of prosthetic joint is essential to facilitate design optimisation.Researchers are actively engaged in developing wearable devices including prosthetics that are increasingly embedding control and electronics sub-systems making them more autonomous and 'smarter'. On the other hand, limitations on space and power mean that artificial limb joints (for robots or prosthetics) must be highly optimised for mechanical performance in areas such as stiffness, strength, friction, mechanical advantage, backlash and endurance.Current trends in the design of artificial lower limbs, ranging from robotic articulations to prostheses for lower limb amputees, favour the utilisation of engineered joints, which typically are composed of a pin joint containing a hinge-pin and ball bearings. Particular prosthetic knee joints (polycentric) contain four-bar mechanisms in order to produce a moving centre of rotation as is the case with the human knee. There are two main categories of control for prosthetic knee joints - microprocessor control (use of an electronic unit, evaluating and making internal adjustments to control the motion) and mechanical control (use of a mechanical hinge, automatically controlled by the mechanism).The main purpose of this work is to further the state-of-the-art in prosthetics design and lower robotic limbs for transfemoral (above knee) amputees and humanoids robots in areas relevant to artificial devices and their uses for locomotion including walking, climbing stairs, squatting and also stability. This research will combine the relationship between three areas: the technological advancements of lower robotic limbs, knee implant design for total knee replacement, and the emergence of 'smart' prosthetics.In this two-year programme, we will investigate the feasibility and development of a novel bio-inspired prosthetic joint that will exploit the key and beneficial features of human knee joint. This research will be achieved by featuring a progressive bottom up approach towards the design and test of the bio-inspired 'smart' joint. A comparative investigation with respect to human performance (energy consumption and gait efficiency) between the novel bio-inspired joint against current prosthetics provided by the industrial partners will be undertaken with the contribution of a para-triathlete gold medallist in the Rio Paralympics 2016.