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jrl-umi3218 / lipm_walking_controller

Walking controller based on linear inverted pendulum tracking
BSD 2-Clause "Simplified" License
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Why ankle torque minimization in wrench distribution? #44

Open shbang91 opened 2 years ago

shbang91 commented 2 years ago

Hello,

Thank you for your effort in maintaining this nice repo!

I have a question regarding the ankle torque minimization (Eq.(13)) in II-C. Contact Wrench Distribution on your stair climbing stabilization paper.

First of all, what is the benefit of minimizing ankle torque minimization (Eq.(13)) over minimizing the contact wrench in each sole center frame (lc_W_left, rc_W_right)? (I believe the position of the sole center frame(lc, rc) is in the bottom center of the foot which directly contacts with the ground while the ankle frame is located in the same planer surface offset along x and y axis of the sole center frame based on the discussion in https://github.com/stephane-caron/lipm_walking_controller/discussions/69. Please correct me if I am wrong).

Secondly, looking at the lipm_walking_controller/src/Stabilizer.cpp, I wonder why you weighted more on the taux and tauy. Is this because you don't want to generate tilting motions in the x and y local ankle frame (By minimizing the external wrench applied on the ankle joint through Eq.(13), you would expect the ankle joint to execute small torque command)?

Finally, do the sole center frame and ankle frame share the same orientation in your definition?

Thank you, Seung Hyeon

stephane-caron commented 2 years ago

Hi @shbang91, I've posted some answers to your questions at https://github.com/stephane-caron/lipm_walking_controller/discussions/77. Hoping this helps!