Caption: Figure 2: Typical parallel ankle robot designs with or without aligned rotation center
between the robot and the ankle joint: (a) misaligned rotation center
, (b) can be programed to have aligned rotation center
but will sacrifice workspace, and (c) aligned rotation center
without sacrificing workspace.
Distance R' between O and instantaneous rotation center
[O.sub.p]' is defined with [V.sub.[GGAMMA]] and [V.sub.s] in Eq.
The ilium thickness and width reached its peak 25 mm above the rotation center
, approximately at the acetabular dome, and decreased quickly to approximately, especially 2 cm above the doom.
[v.sub.1] and [v.sub.2] are the speed of the left and right drive motors, respectively, [r.sub.1] and [r.sub.2] are the distance of the left drive unit and right drive unit, respectively, from the rotation center
. Therefore, the robot rotation center
will not depend on the robot gravity center and the position of drive units in the robot.
Through examining the existing robots for ankle rehabilitation, a few improvements could still be identified as follows: (1) the rotation center
of the foot pedal should easily point to the rotation center
of the ankle joint via mechanical configuration; (2) the robot should be friendly and stimulate the patient to participate in ankle training, encouraging the patient to self-balance both their ankle joints during exercise; and (3) maintainability and modularity might be improved.
The accuracy of the bored lens arrays is dependent on the accuracy of the diamond tool geometry and the exact position of the diamond tool in relation to the rotation center
of the spindle.
One problem associated with this design is the misalignment between the rotation center
of the end-effector and the actual rotation center
of the pelvis.
This robotic platform consists of two three-DOF symmetric layer-stacking mechanisms, which can execute ankle internal/external rotation, dorsiflexion/plantarflexion, and inversion/eversion exercises while the rotation center
of the distal end of the robotic platform always coincides with patient's ankle pivot center.