Unified Control of a Powered Knee-Ankle Prosthesis Enables Walking, Stairs, Transitions, and Other Daily Ambulation Activities

Conventional passive prostheses for lower limb amputees lack active assistance and cannot replicate the natural energy dynamics of healthy limbs, resulting in compromised mobility and diminished quality of life. Powered lower-limb prostheses can theoretically replicate the biomechanical function of healthy limbs during ambulation. However, existing powered prostheses fall short of fully restoring mobility for individuals with above-knee amputations. This limitation is mainly due to existing controllers, which struggle to coordinate their assistance with the user's movements across a variety of activities in a natural manner. This paper proposes a novel unified controller for powered knee and ankle prostheses that enables multiple activities and adapts to users and the environment. The proposed controller enables natural ambulation without requiring explicit measurements of the environmental characteristics or classification of the intended ambulation task. In experiments with three amputee subjects, the proposed controller enabled walking on level, inclined, and uneven ground, ascending/descending stairs, sitting and standing, and seamless transitions between these activities. This work presents the first implementation of a unified, task-agnostic control strategy for continuous ambulation across everyday ambulation activities for powered knee and ankle prostheses.