-- SanjayDastoor - 28 Apr 2006
Moved Muscle stuff to ArtificialMuscles? (private)
--MarkCutkosky 21 Mar06
Starting a New Page on ArtificialMuscleIntegration issues
--MarkCutkosky 15 Mar 2006
Here are some slides & link to a movie that illustrate one advantage of having tunable leg stiffness for stable open-loop trotting. Values of mass, stiffness, damping are chosen to be similar to those of Sprawlita.
Second simulation that has a maximum spring extension:
Results:
-- JonathanKarpick - 08 Mar 2006
Running some sims - realize that we should really be looking at max foot height per stride versus body height per stride. With a weak spring and the same actuator force, the body can get pretty far off the ground while the foot is still on the ground...
ss_var_fn.pdf - Hopping height vs. Activation Frequency for a variety of hopper natural frequencies.
Without a maximum leg extension, the hopper hops higher with lower natural frequencies - the spring extends a lot until the foot lifts off of the ground.
In other words, without a max leg extension, there's no optimal stiffness in terms of hopping height for a given force level and a given damping ratio.
Changing the natural frequency of the hopper does change when the hopper enters and leaves period-2 hopping. The lower the natural frequency, the earlier (in terms of actuation frequency) the hopper goes to period-2 (and the earlier it returns to period-1).
Code is attached in the zip file here: HopperSim.zip (updated 7pm 3/8/06)
Description of contents:
-- JonathanKarpick - 01 Mar 2006
I found some of Jorge's old dashpod Matlab code, and have modified it for an even simpler hopper. (Jorge had limits on the extension of the spring/damper/actuator, and some modeling of actuator dynamics).
NOTE:
Working on:
-- JonathanKarpick - 02 Mar 2006
Initial change in hopping height vs. frequency with varying k: