Phase Plane-based Model for Steady-state Metabolic Cost Estimation

The use of steady-state metabolic cost is prevalent in evaluating the performance of wearable exoskeleton devices, particularly in providing personalized assistance to the user. Metabolic cost serves as an objective cost function for assessing the device’s assistance performance. However, conventional metabolic cost estimation methods are time-consuming in estimating steady-state metabolic time. Therefore, we adopted an improved phase plane estimation (PPE) method to reduce the estimation time of steady-state metabolic cost by optimizing the transient data. We applied this method to both normal individuals and individuals assisted by exoskeletons. By comparing walking with slowly varying intensity of movement in our experiments and those with exoskeleton-assisted walking, we found that the method can effectively reduce the time needed to estimate steady-state metabolic values and provide accurate results. The method is also feasible in the low-energy state of exoskeleton-assisted walking. These findings may support the personalized control of rehabilitation devices.