Comparative Study of two Biomechanics Frameworks for Upper Limb Exoskeleton Simulations

The development of wearable assistive devices calls for advanced predictive simulation tools capable of modelling musculoskeletal systems incorporating closed kinematic loops, such as upper-limb exoskeletons. This study focuses on simulating arm movement with a shoulder exoskeleton in two scenarios: a forward dynamics simulation and an optimal control problem to determine the optimal muscle excitations and motor torque inputs required for a desired motion.
Two computational frameworks are employed and compared: The first is OpenSim, which benefits from existing biomechanical models and optimal control capabilities with MOCO. The second framework is Odin, a state-of-the-art multibody simulation software in which biomechanics capabilities were integrated for this study.
The comparison highlights the strengths and limitations of each tool in simulating biomechanical systems with complex kinematic topologies. While results were successfully obtained in OpenSim, challenges were encountered due to the presence of kinematic closed loops. In contrast, Odin’s general multibody framework simplifies the definition and numerical simulation of closed kinematic loops, demonstrating significant potential for future applications in exoskeleton design and analysis.