Looking for different communication possibilities.

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06 Apr 2017 12:12 #90968 by dab77
Hi all, I need to interface LCNC (pre 2.8) to 4 big winches with non trivial kins (something similar to a spidercam..).
Those winches are moved by big servo motors (between 1,5 and 2,5kW), but they still don't have the driver part. the company who is building those winches is going to buy inverters/plc in these days, and I need to know eventual suggestions to interface with LinuxCNC.
Do you have some advice on what protocol to use?
- is Step/Dir a possibility?
- is it possible using some ModBus/CanBus to drive in realtime such a kinematic?
- maybe ethernet?
- is there any other performing communication usual in Industrial CNC which can be implemented in LinuxCNC?

Thanks for any advice.
Davide.

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09 Apr 2017 01:30 #91066 by tommylight
Yes, step/dir is a posibility.
Yes you can use modbus to control VFD, i doubt it can do any kins and i read that it is a userspace component, not realtime.
Ethernet can be used with Mesa cards or Beckhoff devices, have a look at ethercat.
Parallel port is an option, realtime, can controll machines easily but limited for IO, 12 outputs and 5 inputs per port, adding add on PCI cards is also possible. It can control step/dir drives, do PWM, used for 5 inputs ( 9 inputs in X mode, limiting ouptuts to 8 ). In most cases can do up to 20.000 pulses per second, some computers will do more ( i have an older xeon workstation that does 50.000 easily ).
Usualy winches are not very diferent from CNC machines as they do forward/backward, left/right and up/down. Using Linuxcnc to controll it, it becomes a huge pick and place machine. Hmmm nice idea. :)

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09 Apr 2017 15:58 #91088 by dab77
I've spoken with the seller, and the inverter is a Rexroth hcs02. They can put in different modules to communicate. Now there's a simple 0-10v to control position, just to setup the machine.the seller suggest using profibus. Is there already made drivers for this bus? He says profibus is the most performing on this inverter as fast as 500uS per transmission, which i think is enough. The winches are going to move not more than 100cm/s with a 1/25 reduction and 50cm diameter drum. He also spoke about ethercat, but less performing.
The winch is going to have an on-board plc to manipulate a bunch of security sensors (belts, load, brakes, temp, current and 2 couple of endstops) and (i think) the pc is going to communicate with the plc.
I really don't know if its going to work with Lcnc or if I have to code a new software to make them run...
So let's face one step. What about profibus? In case I have to write a new driver, how they are written for lcnc? Python? Is there any example/codelines to follow?

Thanks you for helping..

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12 Apr 2017 10:40 #91234 by andypugh
I think writing a Profibus driver would be too much work.
0-10V _position_ control is also a bad idea, but +/-10V _velocity_ control with encoder feedback and a position loop closed in LinuxCNC would work well.

There is an existing profibus _userspace_ driver for LinuxCNC, but that would not be suitable for motion-control because it is userspace (nothing that uses Python will work in the realtime layer).

Is CAN bus an option? General Mechatronics seem to be well set up for LinuxCNC + CAN

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12 Apr 2017 12:25 - 12 Apr 2017 13:05 #91242 by dab77
Do Mesa have such a board? I mean -10+10 vel and enc in?

I think CanBus can be a possibility. But for what I know Canbus is not implemented same way from every productor. (I mean different data on different packets) Is the LCNC driver open to be corrected in case? So canbus is not run in userspace?
Thanks for the info.
Last edit: 12 Apr 2017 13:05 by dab77.

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12 Apr 2017 13:12 #91245 by andypugh

Do Mesa have such a board? I mean -10+10 vel and enc in?

Several of them. From the classic 7i33TA to the 7i77.

I think CanBus can be a possibility. But for what I know Canbus is not implemented same way from every productor. (I mean different data on different packets) Is the LCNC driver open to be corrected in case?


I don't know, I have never tried to use a General Mechatronics card.

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12 Apr 2017 17:20 - 12 Apr 2017 17:23 #91261 by bkt
use mesa 7i77 ... +/-10V and enc .... modbus is never rtai ... all plc have modbus module .. but modbus is not a rt protocol. .... nobody will certify a safety chain based on Modbus (for shure I'm in UE) .... and I have not seen around many security modules canbus ... why? Other question for you: if it is not good for security can be good to drive a motor? There is some difference between make sure to run a thing and make sure it's a sure thing.
Apologize if I seem rude ... the fact is that I do not speak English well.


Regards
giorgio
Last edit: 12 Apr 2017 17:23 by bkt.

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12 Apr 2017 18:02 #91263 by dab77
Grazie Giorgio, tranquillo. I think we speak the same english. I agree on the modbus.
Other problem: winches can be 20-30mt from the pc, and the same distance one to the other.. so i think i should go ethernet or rs485 to mesa analog drivers, which are each close to its motor. What about that?

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12 Apr 2017 22:32 - 12 Apr 2017 22:39 #91273 by bkt
ok dab77 .... not understand very well your problem about distances .... probabily because I'm not familiar with all winches mechanical design. With 7i77 I make cartesian paletizer with 45mt of cable for "a" axis, 40mt for "y" , 35mt for "z" & 28mt for "x" ..... motor x-z axis of 2.5kw, y 1000w & a 200w. For electrical part I think winches and paletizing robot (cartesian type) is not so different.... x = 5500mm Z = 3400mm Y = 2400 mm all to 60mt/min max vel ....

If you use ethernet/serial mesa cards, you must make an electrical box near every motor ... I understand well your ideas?
In these case consider the difference between cable cost and electrical box ... I think cable is better. If your spidercam is a spider delta robot I think cable is suitable. If your spidercam have usual late/mill velocity (15mt/min max) you can use for shure ethernet cable and mesa ethernet or serial card. I not love the surprise, and in my experience EtherCAT also suffer if you fly too many axes with high dynamics. I talk about close ethercat not open version. ;) ....
Now I work of imagination and imagine that you have many inputs and outputs associated with each axis .... pressure, tension cables, brake winch, temperature control and other ... In these case you have 3 option: 1) your ideas (mesa ethernet: motion control + io near interesting point) ... 2) You can have 3 cables for motion control (motor power, encoder cable cable) + can bus/ethercat for remote plc io (+power cable for remote io) .... 3) as option 2) but with multipolar cable or bus cable for junction box for io (no remote plc module but juntion box). These structure request Lcnc + pc for motion control and HMI & std plc for io control + emergency chain. More respectful of the regulations for industrial environment than use only Lcnc for pilot all. Plc has its certification, and Nobody care who pilot servomotor if the emergency controls and safety are related to the safety plc.

But other can have ideas better than mine.

regards
Giorgio
Last edit: 12 Apr 2017 22:39 by bkt.

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12 Apr 2017 23:46 #91276 by tommylight
Winch? We are talking about overhead cranes right?
Then usualy they are for all intents and purposes a 3 axis cnc and they have the same layout, long non moving rails on both sides ( call it Y axis ), a gantry that moves on those rails ( call it X axis ), and the winch that is moving on that gantry with the up/down part.
If that is the case, the controll box is always mounted on one side of that gantry. I would put the control box next to that electrical box as all the cabling will go from there. In that box should be relays or servo drives with Mesa boards ( if you choose Mesa, i know i would ), so i would have to add a single ethernet cable up to the control box. Cat6 ethernet cables can go up to 100 meters easily, so can shielded Cat5 ( named STP or shielded twisted pair ). There is also the posibilty of lowering the singal speed through ethernet cable as all network cards can be set to work in all these modes: 10 Mb half duplex, 10 Mb full duplex, 100 Mb half duplex, 100 Mb full duplex, and new ones at 1000 Mb half and full duplex.
For Mesa boards the half duplex can not be used, but full duplex will most probably work properly even at 10Mbit.
These seting are awailable and functional in most Linux distros on network managers, can also be set through terminal in any Linux.
This is the most eficient way of doing it as the cables will remain short.

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