A day in the life of a PhD candidate

Lower limb prostheses: optimal human-in-the-loop co-adaptation

In this series, HTRIC PhD candidates will give a little insight in there life during there PhD. Chengxiang, who also goes by the name of Oran, is one of our PhD candidates and currently 6 months into his HTRIC PhD. In this blog, he will tell you all about his project and take you through some of his day-to-day experiences.

Let ‘s begin with an introduction of my PhD project: The optimal transfemoral amputee-prosthesis co-adaptation (Co-adapt). The project proposes to enhance the user-prothesis interaction from the perspective of co-adaptation, which takes into account the reciprocal nature of this process. The proposed approach combines the complexity and inherent unpredictability of the behavior of the user’s musculoskeletal and motor control systems.

This way, the prosthesis can incorporate the input of the amputee to find optimal control and mechanical settings for the correct human movement. Furthermore, this project aims to provide solutions to optimize the function of the powered prosthesis. With the realization of this objective, people with lower limb amputation will better accept the prosthesis, their quality of life will improve, their social contacts will be enlarged, and their (re-)integration in society and the labor market will be facilitated.

The project is based on a previous project, MyLeg (awarded by the European Union in Horizon 2020 in 2018). Hence, we have the complete mechanical structure of the prosthesis, and most of the electronic systems are ready. The rest of the work mainly focuses on control scheme development, clinical experiments, and validation.

In the past six months, I mainly worked on developing a leg prosthesis to track a predefined trajectory and tune critical parameters between the interface and the user. Further work will explore the stiffness and equilibrium effect on walking performance measured by metabolic energy and asymmetric and step length variability. After that, the user’s response to the prosthesis’ settings/parameters will be continuously assessed during gait, and iterative adaptations to these settings/parameters will be made to optimize defined cost functions related to gait performance.

Developing a prosthesis leg can sometimes be tedious and cause many setbacks. Sometimes, to fix a bug, you must spend several days going through thousands of lines of code and checking dozens of cable connections. More frustratingly, more bugs may pop out after one bug is solved. Nevertheless, when bugs are solved, the feelings of joy and reward are also with you, and the prosthesis leg works as expected. Below you can find a photo of me wearing the prosthesis leg with an adaptor.

In conclusion, I am excited about what I am doing and how the potential contribution may be made to improve the daily life quality of amputees. Please feel free to reach me if you are interested in more details about my journey in developing the prosthesis leg!