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Submitted by Phoebus on Sat, 04/07/2007 - 23:57

Which automatic tuning can I get a good result for Hexapod robots? And about the complex dynamic of such robots? Can I just define the PID variables for one leg and use these for the others? How will I define the max AC/DC/SP values that suit better for a fast robot? :confused:

Comments 1

Galil_AndyH on 04/09/2007 - 09:08

There is not one method that stands out as a better option than the others. I would try Auto Crossover and General Tuning, and then use the storage scopes to determine which method is producing the best results.

Because of the non-standard mechanics of the hexapod robot, you will probably achieve the best performance if you manually tune the system. See the link below for the manual tuning application note.
http://www.galilmc.com/support/appnotes/optima/note3413.pdf

Whether or not you can tune one motor and apply those parameters to the axes will depend on a few things.
1) Your system requirements - You should find that there are tuning parameters that work pretty well for all axes that are similar in mechanics, but you will also find that you can more tightly tune each axis separately. So if your system requirements fall into the performance that you achieve with tuned down settings on all axes, then use those.
2) Your mechanics - If your mechanics and mechanical design provide near identical loads and responses for each axis, then your tuning parameters will be similar for all the axes.

AC/DC/SP parameters all come down to mechanical design and loading. What can your mechanics handle? Try setting the parameters to the max speeds and accel/decel that you would like to achieve, and tune with those values. If your mechanics can't handle those parameters, lower them.

You should also use the TL, TK, ER and OE settings to make sure you do not over-torque your mechanics or cause damage if you accidentally set your system unstable while tuning. These settings are again determined by your mechanics and system requirements, and with TL and TK, your amplifier gain and motor constants.