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sugarsweetrobotics / python_pepper_kinematics

Forward/Inverse kinematics model for SoftBank Pepper.
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question of inverse_kinematics.py #2

Open kbeom9307 opened 5 years ago

kbeom9307 commented 5 years ago

May I ask the meaning of epsilon and the sum_old in inverse_kinematics?

I think epsilon is kind of tolerance but I cannot understand the meaning of sum_old.

best regards.

sugarsweetrobotics commented 5 years ago

I am very sorry for my poor English, but please do not hesitate to ask me if you had any question.

In this library, the inverse kinematics is solved by repeated calculation and Pseudo inverse matrix calculation(singular value decomposition). sum_old: sum is the sum of error values. sum_old is the sum in the previous calculation step. If the sum is increased from the previous, the inverse kinematics function returns error (None). In this case, the start posture of the inverse kinematics calculation must be changed (or can not be solved anyway).

epsilon: The epsilon is the threshold of singular value. If the arm posture is near the singular point posture, the sigma contains relatively large value. When the singular value is higher than epsilon, the value is set to zero to ignore it.