Wearable and legged robot designers face multiple challenges when choosing actuation. Traditional fully actuated designs using electric motors are multifunctional but oversized and inefficient for bearing conservative loads and for being backdrivable. Alternatively, quasi-passive and underactuated designs reduce the amount of motorization and energy storage, but are often designed for specific tasks. Designers of versatile and stronger wearable robots will face these challenges unless future actuators become very torque-dense, backdrivable and efficient This paper explores a design paradigm for addressing this issue: reconfigurable hydrostatics. We show that a hydrostatic actuator can integrate a passive force mechanism and a sharing mechanism in the fluid domain and still be multifunctional. First, an analytical study compares the effect of these two mechanisms on the motorization requirements in the context of a load-bearing exoskeleton. Then, the hydrostatic concept integrating these two mechanisms using hydraulic components is presented. A case study analysis shows the mass/efficiency/inertia benefits of the concept over a fully actuated one. Then, experiments are conducted on robotic legs to demonstrate that the actuator concept can meet the expected performance in terms of force tracking, versatility, and efficiency under controlled conditions. The proof-of-concept can track the vertical ground reaction force (GRF) profiles of walking, running, squatting, and jumping, and the energy consumption is 4.8x lower for walking. The transient force behaviors due to switching from one leg to the other are also analyzed along with some mitigation to improve them.

翻译：可穿戴与足式机器人的设计者在选择驱动方式时面临多重挑战。传统采用电机的全驱动设计虽功能多样，但体积过大，且在承载保守载荷和实现反向驱动时效率低下。相反，准被动与欠驱动设计减少了电机化程度和能量存储需求，但通常仅针对特定任务设计。除非未来执行器能实现极高的扭矩密度、反向驱动能力和效率，否则多功能、高承载能力的可穿戴机器人设计者将持续面临这些难题。本文探讨了一种解决该问题的设计范式：可重构流体静力学。我们证明，流体静力执行器可在流体域中集成被动力机制与共享机制，同时保持多功能性。首先，通过解析研究比较了这两种机制在承载外骨骼场景下对电机化需求的影响。随后，提出了利用液压元件集成这两种机制的流体静力学概念。案例研究表明，该概念在质量、效率、惯性方面均优于全驱动方案。进一步在机器人腿部开展实验，验证了该执行器概念在受控条件下能满足力跟踪、多功能性与效率方面的预期性能。原理样机能够跟踪行走、奔跑、下蹲和跳跃时的垂直地面反作用力（GRF）曲线，其中行走工况的能耗降低至4.8倍。研究还分析了双腿切换导致的瞬态力行为，并提出了若干改善措施。