Falls are the leading cause of injury related hospitalization and mortality among older adults. Consequently, mitigating age-related declines in gait stability and reducing fall risk during walking is a critical goal for assistive devices. Lower-limb exoskeletons have the potential to support users in maintaining stability during walking. However, most exoskeleton controllers are optimized to reduce the energetic cost of walking rather than to improve stability. While some studies report stability benefits with assistance, the effects of specific parameters, such as assistance magnitude and duration, remain unexplored. To address this gap, we systematically modulated the magnitude and duration of torque provided by a bilateral hip exoskeleton during slip perturbations in eight healthy adults, quantifying stability using whole-body angular momentum (WBAM). WBAM responses were governed by a significant interaction between assistance magnitude and duration, with duration determining whether exoskeleton assistance was stabilizing or destabilizing relative to not wearing the exoskeleton device. Compared to an existing energy-optimized controller, experimentally identified stability-optimal parameters reduced WBAM range by 25.7% on average. Notably, substantial inter-subject variability was observed in the parameter combinations that minimized WBAM during perturbations. We found that optimizing exoskeleton assistance for energetic outcomes alone is insufficient for improving reactive stability during gait perturbations. Stability-focused exoskeleton control should prioritize temporal assistance parameters and include user-specific personalization. This study represents an important step toward personalized, stability-focused exoskeleton control, with direct implications for improving stability and reducing fall risk in older adults.

翻译：跌倒是导致老年人受伤住院和死亡的首要原因。因此，缓解与年龄相关的步态稳定性下降并降低行走过程中的跌倒风险，是辅助设备的一个关键目标。下肢外骨骼有潜力在使用者行走时帮助其维持稳定性。然而，大多数外骨骼控制器的优化目标是降低行走的能量消耗，而非提高稳定性。尽管一些研究报告了辅助带来的稳定性益处，但具体参数（如辅助幅度和持续时间）的影响仍未得到探索。为填补这一空白，我们在八名健康成年人经历滑移扰动时，系统性地调节了双侧髋关节外骨骼提供的扭矩幅度和持续时间，并使用全身角动量来量化稳定性。WBAM响应受辅助幅度和持续时间之间显著交互作用的支配，其中持续时间决定了外骨骼辅助相对于不穿戴设备时是起稳定作用还是失稳作用。与现有的能量优化控制器相比，通过实验确定的稳定性最优参数平均将WBAM范围降低了25.7%。值得注意的是，在扰动期间最小化WBAM的参数组合中观察到了显著的受试者间差异。我们发现，仅针对能量结果优化外骨骼辅助不足以改善步态扰动期间的响应稳定性。以稳定性为重点的外骨骼控制应优先考虑时间辅助参数，并包含针对用户的个性化设置。本研究代表了迈向个性化、以稳定性为重点的外骨骼控制的重要一步，对提高老年人稳定性和降低跌倒风险具有直接意义。