On Thu, 20 Dec 2012, Viesturs L?cis wrote:
Date: Thu, 20 Dec 2012 17:23:07 +0200
From: "[UTF-8] Viesturs L?cis" <[email protected]>
Reply-To: "Enhanced Machine Controller (EMC)"
<[email protected]>
To: "Enhanced Machine Controller (EMC)" <[email protected]>
Subject: Re: [Emc-users] Pid saturated, was: Servo error
2012/12/20 Andrew <[email protected]>:
2012/12/20 Viesturs L??cis <[email protected]>
I discovered that there is a pid.n.saturated pin that is "true" at the
moment when I thought that motor is running away. For that joint I
increased max output from 0.5 to 0.67 and at least jogging up to
5m/min is fine. So I managed to get PID parameters that keep following
error within 0.02 mm which I find acceptable for plasma table.
I don't understand why you limit MAX_OUTPUT to 0.5 or so.
Usually MAX_OUTPUT 10 corresponds to max velocity of motor.
Thus 0.5 is only 1/20 of max motor rpm!
You limit it then PID gets saturated but the motor can't catch up the jog
speed that you want.
Just increase it
I have 7i39LV as servodrives and MotionKing servos that have 8.7A
rated current (now I understand that it is not a good match). 7i39 has
10A limit for current. I thought that this limit applies to each
motor, but since there is 10A fuse soldered right next to motor power
input on card, it applies also to whole card. As I have 2 such motors
attached to each of two 7i39 cards in the machine, I am limiting the
pid output because I do not want to reach limits of the servo drive
and blow the fuse or whatever. I just brought it to error (one of
error LEDs turned on) with max_output = 0.9 and attempts to move only
one motor.
The Max_output value alone does not tell much, it should be considered
together with output_scale value, which is 1.0 or -1.0 for all joints.
--
Viesturs
If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto
The 7I39 is a voltage output device. You should not limit the maximum PID
value or this will limit the maximum speed (but max PID should be limited to
about 95% for bootstrap gate drive reasons)
Overcurrent and fault conditions should be handled by having a reasonable
ferror setting (a motor in current limit will cause a stall thats is
detectable as a ferror)
Peter Wallace
Mesa Electronics
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(='.'=) This is Bunny. Copy and paste bunny into your
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