Development of a Robotic Assembly for Analyzing the Instantaneous Axis of Rotation of the Foot Ankle Complex

Figure 5

Kinematic and load control strategy. (a) Kinematic coordinate frames of the foot and ankle defined by the NTT and extended tool tip (ETT) of the RTP. The ETT (orange dot) represents the initial prescribed IAR of the foot located at the center of the talus and was a negative offset from the NTT. The coordinate frame of the load cell was initially located at the center of the load cell and transformed to the origin of the moving joint center, that is, the ETT. (b) An angular input of ankle rotation was given every 0.5 degrees, during which the loading protocol reduced the ankle moment due to off-axis forces by minimizing the distance () between the pARA (upper) and the true ARA (lower), thus creating a “pure moment” condition.

(a)

(b)