RoboticsConnection User Forum / Serializer Robot Controller Support / RoboticsConnection Hardware Support / How configure PID ? / Latest Posts

RE: How configure PID ?

jsummerour — Mon, 28 Apr 2008 10:08:55 GMT

I think Ringo confused you a few posts back, when he referred to using a floating PID parameter. The firmware doesn't support a floating parameter, and is integer based only.

He was talking about possibly adding it to a future release of the firmware. :) I apologize for the confusion.

Sounds like you're making good progress! The PID stuff just takes some trial runs to get it set exactly like you want it.

Best Regards!

RE: How configure PID ?

n at mime — Sat, 26 Apr 2008 17:41:57 GMT

ok, here is the process that I have used to configure my vpid and dpid
1- first off all, configure vpid
(as developped in my previous message)
you have to find the right curve that increases well (without oscillation and vibration, without jerk, something like a cumulative chi-square distribution. (using vpid and mogo)
2- configure dpid
set the dpid and use digo

so, one main question remains:
currently, VPID are explained with float values
(vpid with 0.1 for V, 0 for P, 0 for I and 10 for D, that is corresponding to 10 div regulation according to coders)
P defines approximatively the starting slope
BUT, in the serializer doc, pids are available with integer arguments ?
so when you are at 1 for P value, how to divide P again?

(ps: contrary to my previous message, CFG ENC works as mentionned in the doc but nothing is different between simple and quadric modes.
I have tested all this using two differents motors, and the one with 512 div per wheel circonference needs to start slower (jerking at start with P = 1) , so it needs a smaller P value, but once again, how to fix P at 0.1)

RE: How configure PID ?

n at mime — Thu, 24 Apr 2008 02:54:13 GMT

Dear Rigo, many thanks for your interesting reply.

I have tried vpid with following steps:
(serializer reply are mentionned under stars)
-------------------
getFirmware
* 1.5.1> *
vpid 1:0:5:2
* ACK> *
clrenc 1 2
* ACK> *
getenc
* 0 0> *
mogo 1: 20 2:20
* ACK> *
%%%%% wait 1 sec to release the mogo
getenc
* 6169 6206> *
setStopMotor
* ACK> *
-------------------

so it seems to work well
vpid works but dpid is more interesting

from now, few problems appeared:
1) sometimes, the first command doesn't work (i.e. replies * NACK> * )
2) cfg enc seems to be different than the doc
-------------------
cfg enc 0
* ACK> *

cfg enc 1
* ACK> *

%%%%%% but both reply
cfg enc
* ACK> *
%%%%%% (that is different from the doc,
%%%%%% serializer WL 2.1, p22 ??? )
-------------------

is there anybody who has same problems?

So, I will try dpid today and report it soon
Does anybody can show me a good dpid sequence?

RE: How configure PID ?

Arnaud — Wed, 23 Apr 2008 22:52:58 GMT

Thanks for informations

But can you said me which parameters are float (vpid,dpid,mogo,digo)? because in you document i d'ont find anything about float

RE: How configure PID ?

ringo — Wed, 23 Apr 2008 06:05:01 GMT

The ramping down function will be tied to the P parameter, If you P is too high then it may stop abruptly. We have tested this extensively with the stinger and traxter, and a little with a couple home-brew robots. Every setup is different however. I don;t think we coul d show the code without publishing just about the entire Serializer code because it is so linked with everythign else but i can try to explain how we did it.

the VPID parameters are pretty straightforward. this is what MOGO uses. It works to maintain a constant velocity for each wheel.

The way the DIGO command works is it is sort of a wrapper around the VPID stuff.

If you call DIGO and tell it to go 1000 ticks at a speed of 50 with an accelleration of 5, then Digo is going to ramp up the speed variable that MOGO uses until it reaches 50. So MOGO is maintaining the 50. Then as the counters approach 1000, the DIGO command start decreasing the speed variable the MOGO uses untill the distance is reached. That is why the VPID parameters must be tuned before the DPID ones are.

So try playing with the P in DPID. If you cannot get it low enough then we may need to make a change so it can be fractional or somethig like that. You may need a P of 0.1 or somehting depending on your setup. The math is there and it works, we jsut need to feed it the right constants.

Ringo

RE: How configure PID ?

n at mime — Tue, 22 Apr 2008 19:48:12 GMT

Dear Arnaud, I have the same problem. Motors controlled by the serializer using the pid over a fixed distance brutally stop when this fixed distance has been reached. Each motor seems to stop independantly. No decelerating ramp seems to be calculated in the serializer (and so on, no trapezoid control). When doing this, the robot shifts forward, left or right, and this pid command becomes useless.
Maybe jsummerour could show us how the pid control has been done?
Does anyone have successfully use the dpid command? (without drift due to stop)
Is there a way to see the whole code used here to implement dpid (I mean the serializer class)?

RE: How configure PID ?

Arnaud — Tue, 22 Apr 2008 12:56:42 GMT

I have configure Vpid and dpid but can you say me the form of your pid

Half trapezoidal , trapezoidal ??

Please!!!!!

Arnaud

RE: How configure PID ?

Arnaud — Tue, 22 Apr 2008 04:01:11 GMT

When i read the doc, i read "you must also configure the VPID and DPID parameters" p26

inside digo command.

And you say me the parameters are independants ?(i don't understand)

Regards

Arnaud

RE: How configure PID ?

Arnaud — Mon, 21 Apr 2008 23:36:01 GMT

Inside pour PID algo :

The cmd form are trapezoidal ?(start low speed (acceleration),middle1 max speed, middle2 max speed, end low speed(deceleration) ) ????

Because when i test the pid i have only acceleration to max speed and stop ??? i don't saw the deceleration.

Thanks

RE: How configure PID ?

jsummerour — Mon, 21 Apr 2008 13:10:08 GMT

VPID sets the Velocity PID parameters, and DPID sets the Distance PID Parameters.

Digo command the Serializer to run the motors, based on the DPID parameters a specified distance. Mogo commands the Serializer the drive the motors at a specified velocity, based on the VPID parameters.

It's all documented in the User Guide. Just read it.

Best Regards,

RE: How configure PID ?

Arnaud — Sun, 20 Apr 2008 23:49:09 GMT

Thanks,

I have seen your articles, but VPID and DPID are independant ?

If there are independant when i read DPID article, the digo cmd modifie the vpid values ?

The cmd form are trapezoidal ?(start low speed (acceleration),middle1 max speed, middle2 max speed, end low speed(deceleration) )

What is the use of restore ? (factory default settings ? reset all card ?)

Thanks

Arnaud

RE: How configure PID ?

jsummerour — Sun, 20 Apr 2008 07:03:49 GMT

Hi Arnaud,

We have a section in the Serializer User's Guide dedicated to explaining how to configure the PID settings for your robot. Read and work thru that, and if you have any specific questions, please don't hesitate to post.

Best Regards!

How configure PID ?

Arnaud — Sat, 19 Apr 2008 15:10:17 GMT

I want to configure PID for my robot with serializer but i don't find anything for calculate vpid and dpid values.

if you have calculate personnal values can you help me

Thanks

Arnaud