Lower-limb exoskeletons require actuation systems that can provide accurate joint torque control while preserving low mass and encumbrance. Conventional architectures often rely on independently actuated joints and joint-level torque sensors, increasing system complexity and weight. This paper presents a novel differential actuation architecture for hip-knee flexion/extension, enabling cooperative torque sharing between two motors via a linear differential mapping between motor and joint. To compensate for transmission losses, a model-based friction estimation strategy is developed and experimentally implemented, allowing accurate joint torque estimation without the need for torque sensors. The proposed solution is validated on a physical prototype, demonstrating the feasibility of sensorless torque estimation in a differentially actuated hip-knee module of a lower-limb exoskeleton.

翻译：下肢外骨骼需要具备低质量、低负担且能提供精确关节力矩控制的致动系统。传统架构通常依赖独立驱动的关节和关节级力矩传感器，增加了系统复杂性和重量。本文提出了一种用于髋-膝关节屈伸的新型差分致动架构，通过电机与关节之间的线性差分映射，实现两个电机间的协同力矩分配。为补偿传动损耗，开发并实验验证了一种基于模型的摩擦估计策略，无需力矩传感器即可实现精确的关节力矩估计。该方案在物理样机上得到验证，证明了在下肢外骨骼差分致动的髋-膝模块中实现无传感器力矩估计的可行性。