New Publication on Designing Active Assistance for Gait With Hip Weakness via Predictive Simulation
KTH's Promobilia Moveability Lab and the Robot Design Lab contribute to computational design of assistive strategies for gait rehabilitation, published in IEEE Transactions on Neural Systems and Rehabilitation Engineering
Hip abductor weakness is a common impairment associated with altered gait patterns, reduced stability, and increased risk of falls. Individuals with such deficits often rely on compensatory strategies, including excessive trunk lean and pelvic motion, which can increase metabolic cost and compromise balance. In this work, we investigated these mechanisms and explored how active assistance can restore more natural gait patterns using predictive simulation. By leveraging a full-body musculoskeletal model and optimal control framework, the study systematically analyzed how varying levels of muscle weakness affected gait kinematics, kinetics, and balance-related metrics.
To design effective assistance strategies, we introduced a bilevel optimization framework that separates gait prediction from assistive torque design. Three assistive profiles of increasing complexity, step, trapezoidal, and biologically inspired patterns, were parameterized and optimized to minimize deviations from healthy gait. The simulations showed that hip abduction assistance substantially reduced compensatory trunk motion, improved balance-related measures such as margin of stability, and normalized energy expenditure. Among the tested profiles, trapezoidal torque patterns achieved a favorable trade-off between performance and simplicity, closely matching the effectiveness of more complex biological profiles while remaining more practical for implementation.
Overall, this work demonstrates how predictive simulation and optimization can be used to systematically design assistive strategies for wearable robotics. The results provide insight into the relationship between muscle weakness, compensation mechanisms, and assistive control, offering a principled foundation for the development of personalized exoskeletons aimed at improving gait stability and efficiency in clinical populations.