[rirazvan]

Hello,

I did built a gantry CNC 1500x1300mm as in picture:
LinuxCNC :: Topic: Step or velocity control for servo gantry (1/4)

4 x MR-J2S-40A, LinuxCNC 2.6.4, Mesa 5i25+ 7i77/7i85S

On Y1 and Y2 axis I use MR-J2S-40A drivers with compatible 400W motor with pulley axis driver 2:1. I also use linear scale for secondary feedback on all axis (including y master and slave).
The motors are in velocity control mode. That introduce a problem on Y axis because the system is unstable and sometimes after a software update slave axis did not move.
That is the reason we decided to master slave y amplifiers instead of doing it in software .

As far as I understand there are two options :

1. Using pulse output from the master to connect to pulse input of the slave and in this case slave will follow the master pulse and the master will receive the SON and Velocity signal.
2. Using master -slave RS422 communications between amplifiers according to the following document:
ftp://81.105.173.212/SERVO/Legacy%20...B32110-018.pdf

The document refers to amplifiers produces starting 2004. The ones we use are built in 2008 so there should have this feature.

The problem is that I do not have access to parameter 106 as per document. This parameter should be in optional parameters.

How can I access optional parameters on MR-J2S-A?

I would appreciate any ideas, I relay want to finish the machine.

[dm17ry]

have a look at page 13 of the document you posted. did you set parameter No.19 (parameter block) to 00AB?

[rirazvan]

have a look at page 13 of the document you posted. did you set parameter No.19 (parameter block) to 00AB?

Hello,
I missed that part, both me and my colleague
00AB unlock until parameter 124 , thank you. I will test if the setup master -slave woks without a position controller from Mitsubishi.

How can I change the parameter 183 to use smaller motors? I noticed that you wrote about that.

Thank you,
Razvan

[dm17ry]

param 19=ABCD unlocks all 255 params. 183=1 to bypass motor/amp capacity match check - any combination should work

[rirazvan]

Thank you, I will check wit 100W motors, I still have a few.

Do you know if there is a closed-loop setup for MR-J2S-A? Ideal would be to input the linear scale directly to the amplifier and close the servo loop in the amplifier instead of doing it in LinuxCNC.

Razvan

[dm17ry]

there is, but i haven't touch one myself. it's MR-J2S-A-PY091 i believe. its firrmware is different from MR-J2S-A and it doesn't support speed/torque control and absolute positioning for obvious reasons...
here's a manual: ftp://81.105.173.212/SERVO/Legacy%20...10-011_PDF.pdf

[rirazvan]

Did test my setup in master - slave config . Only works in torque mode . Master sends torque command to salve . I believe that is for application that use two motors connected at one shaft or two motors on the same belt....
It is not a solution for tandem axis or gantry setup.
I have to find a solution for tandem control.
Any ideas?

[dm17ry]

Did test my setup in master - slave config . Only works in torque mode . Master sends torque command to salve . I believe that is for application that use two motors connected at one shaft or two motors on the same belt....
It is not a solution for tandem axis or gantry setup.
I have to find a solution for tandem control.
Any ideas?

i see. thanks for sharing...
how about switching slave amp to position control and feed it with the master's encoder pulse train?

master -> slave
LA -> PP
LAR -> PG
LB -> NP
LBR -> NG
LG -> LG

[rirazvan]

That is correct.
The problem is that the same internal encoder output from master (rotary PID) I use for first part of PID control in LinuxCNC, The second part of PID that i use is linear PID that is form the linear scale. The linear scale (5um) does not offer enough pulses to do the PID alone on one axis.
In fact at the first setup we use linear scale alone as PID and we got a huge forward error because LinuxCnc did not has enough pulses to close the loop.
I need to split encoder output pulse differential line driver type to Mesa 7I85S differential line driver input and slave amplifier pulse input, differential line driver also. I avoided this setup until now. The output pulse driver in amplifier can handle max 35mA.
At 7i85S in RS-422 input we have an 120 Ohm termination resistor and a 26LS32 RS-422 differential receiver. So will have one RS422TX (master) and two RS422 RX (slave and Mesa). Should work.

Razvan


Razvan