Mori MVJR Build Log

Progress Report

I have power to the servos now with one axis motor disconnected from the screw for testing.
I tried the manual jog in AXIS and the motor turned about 1/2 turn then started vibrating.
(I have to admit it was exciting to see something move on that machine!)

From reading the following in PID tuning, I guess this means the P is too high or I should increase I next.

'"Simple method

If the system must remain on line, one tuning method is to first set the I and D values to zero. Increase the P until the output of the loop oscillates. Then increase I until oscillation stops. Finally, increase D until the loop is acceptably quick to reach its reference. A fast PID loop tuning usually overshoots slightly to reach the set point more quickly; however, some systems cannot accept overshoot."

I am not clear what "increase P until the output of the loop oscillates" means.

Does it mean the same as the drive motor vibrating?

If so, does it mean that it would:
1. Start to osculate just from increasing the P without jogging it?
2. Start to osculate just from increasing the P after jogging it?
3. Something else?

I guess the next thing to do is start tuning the rest of INI file.

The default value DEADBAND in my INI = 0.000015; I don't know what resolution my encoder has but I would be surprised to hear that it was that close, maybe that number should be more like 0.0002"?

Here is what I have now, if anyone sees something out of line can you set me straight?

[TRAJ]

AXES = 3
# COORDINATES = X Y Z
COORDINATES = X Y Z
# HOME = 0 0 0 0
HOME = 0 0 0
LINEAR_UNITS = inch
ANGULAR_UNITS = degree
CYCLE_TIME = 0.010
DEFAULT_VELOCITY = 1.00
MAX_VELOCITY = 6.567
DEFAULT_ACCELERATION = 6.0
MAX_ACCELERATION = 10.0

[AXIS_0]

TYPE = LINEAR
MAX_VELOCITY = 6.567
MAX_ACCELERATION = 10
BACKLASH = 0.000
FERROR = .5
MIN_FERROR = .5

INPUT_SCALE = -25400

# PID tuning params
DEADBAND = 0.000015
P = 10
I = 0
D = 0
FF0 = 0
FF1 = 0
FF2 = 0
BIAS = 0

Hmmmm, maybe my procedure is off then.

I removed my drive motor thinking I would need to adjust the speed first.

But now I find this osculation problem shows up first.

So what should I do first?

Reconnect the motor to tune PID, or get it roughed-in while it is disconnected first?

Have you seen the wonderful and clear explanations on PID and FFn on this forum?

I'm not sure, I found some reading, but don't feel confident that I know what I am doing.

I would leave it connected, the tuning will be quite different for bare motors than when they are connected to the ballscrews/linear_motion_parts

You also may need to tune the drives velocity loop (outside of EMC, for older drives this may be a potentiometer adjustment)

After a reboot python problem went away

Major progress today, I set the P (in PID) to 1.0 now all the axis can move smoothly.

My motors do have brushes.

With P set to 1, I was able to send

"unlinkp hm2_5i23.0.pwmgen.00.value"
"setp hm2_5i23.0.pwmgen.00.value .1"

the motor ran smoothly

I stepped it up to:
"setp hm2_5i23.0.pwmgen.00.value .5"

It still runs smooth but a little more than twice as fast as i expected so I will probably start adjusting the pots tonight. Is it correct to do this before PID have been established, or will I need to come back and do that again later?

I thought I had read an explanation of a procedure to adjust PID using halscope but I can't find it now.
Does anyone know of a doc on that?