Difference: BiomechanicalBipeds (4 vs. 5)

Revision 52009-03-11 - PhilippeBeaudoin

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Real-time Control of Walking for Biomechanical Models of Bipeds

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Discussion

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Discovering muscle activation from torque-based simbicon

One idea I have for this would be to linearize the torque-->muscle function around the steady state of a torque-based simbicon controller. Then we can simply run our torque-based controller (given the current character state) and use our linear relationship to get muscle activations. Since linearization is around steady-state, it can be precomputed. Some remaining questions are:

What to do outside steady state?
How far can we take our linear model?
Do we have to linearize on-the-fly when the character state is far from what we know?
Do we want to skip the "torque" stage and directly get muscle activations (or forces?) from the target angles (i.e. some kind of muscle-PD-controller)?

Also note that the "character state" is higher dimensional here than in torque-based Simbicon. This is because muscles are generally modeled as dynamical systems (using an ODE), so the "past state" of the muscle has an influence on the activation-->force function. Linearizing around steady-state eschew this problem, but it can appear again during perturbations. Can we build a simple model of the force-->activation function? Then we still have the problem of torque-->force, but this requires a lower-dimensional character state (only angles? or angular velocities too?).

-- PhilippeBeaudoin - 04 Feb 2009

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