Torsion adapters in lower limb prostheses aim to increase comfort, mobility and health
of users by allowing rotation in the transversal plane. A preliminary study with two
transtibial amputees indicated correlations between torsional stiffness and foot alignment
to increase comfort and stability of the user depending on the gait situation and
velocity. This paper presents the design and proof-of-concept of an active, bio-inspired
prosthetic shank adapter and a novel approach to create a user-specific human-machine
interaction through adapting the device’s properties. To provide adequate support, load
data and subjective feedback of subjects are recorded and analyzed regarding defined
gait situations. The results are merged to an user individual preference-setting matrix
to select optimal parameters for each gait situation and velocity. A control strategy
is implemented to render the specified desired torsional stiffness and transversal foot
alignment values to achieve situation-dependent adaptation based on the input of
designed gait detection algorithms. The proposed parallel elastic drive train mimics the
functions of bones and muscles in the human shank. It is designed to provide the desired
physical human-machine interaction properties along with optimized actuator energy
consumption. Following test bench verification, trials with five participants with lower
limb amputation at different levels are performed for basic validation. The results suggest
improved movement support in turning maneuvers. Subjective user feedback confirmed
a noticeable reduction of load at the stump and improved ease of turning