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. Author manuscript; available in PMC: 2021 Mar 2.
Published in final edited form as: IEEE Trans Neural Syst Rehabil Eng. 2021 Mar 1;29:262–272. doi: 10.1109/TNSRE.2020.3045003

Fig. 1.

Fig. 1.

Definitions of subject coordinates: the angles of the thigh (θth) and foot (θf) segments are defined relative to the world frame, and the knee (θk) and ankle (θa) angles are defined in the frame of the proximal limb segment. All angles are zero when the subject is standing upright.