Speaker
Description
The development of patient-specific lower limb prosthetics is highly important. Recent advances in additive manufacturing have paved the way for cost-effective, rapid, and customized prosthetic design. In order to ensure the safety and comfort of the wearer, a versatile testing method that can be used from the early stages of development is required. It is important that this method not only considers the mechanical properties of the prosthesis, but also the dynamic interaction between the prosthesis and the wearer. We believe that Real-Time Hybrid Substructuring (RTHS) is a promising approach to achieve this. In this method, a system is divided into substructures, some of which are simulated numerically and some of which are tested experimentally. Compatibility and equilibrium conditions at the interfaces of the substructures are satisfied in real-time using actuators and sensors. Thus, the dynamics of the complete coupled system can be replicated based on the hybrid set of substructures. When applying this approach to the testing of lower limb prostheses, the wearer is modeled using a numerical gait model, while a prototype of the prosthesis is built and tested experimentally. The motion and forces at the interface between the numerical gait model and the prosthesis are exchanged in real-time using a robotic actuator and a force-torque sensor. This technique offers the possibility to analyze the performance of the prosthetic device as well as the whole system of the amputee wearing the prosthesis and the interplay between the wearer and the prosthesis. It avoids the use of a test subject and numerical modeling of the prosthesis. In this talk, we will present the method of using RTHS to test prostheses itself, our current state of research, and give an outlook on future research with the intent of establishing a novel testing standard for prostheses. Our research has shown that alternating contact RTHS testing is particularly challenging because imperfect interface synchronization endangers system stability. To address this, we developed a control framework to ensure stable and high-fidelity contact RTHS testing, which was tested on two different hardware setups, namely a custom-built Stewart platform and a KUKA robotic arm. While our approach showed great performance on the Stewart platform, it could not yet reach its full potential on the KUKA robot. This is currently under investigation. We also present an initial proof-of-concept experiment using a life-size foot prosthesis.
