Motion controller recommendation?

[cnczoner]

Hi all,

I am looking for a device (which I believe is a motion controller) that will let me control stepper motors from a PC. I will be using this with custom software, and would like to tell the device to move to some X,Y,Z (possibly X,Y,Z,A) coordinate, and the device will generate the *simultaneous* step/dir signals to send to the drivers ( for a smooth diagonal path).

Yes, I can have the PC and custom SW generate the correct pulse trains for the motors, but being able to do this with an external device would be nice, as it would save me from having to piddle around with real-time extensions to the OS (I'll be using C on Linux).

I can also build my own device to do this (using a microcontroller), but being able to purchase a ready-to-go device will save me lots of time, which is an issue nowadays.

Google got me a device called the SmoothStepper, which I think will do what I need, but it seems to be in development still -- there's a lack of detailed info and the manual states that some sections are pending. It also talks about working with Mach3 only, and does not explain how to control it direcly. I'd prefer a mature, proven product.

Any other ideas? I don't need it to have stepper drivers, as I can get those separately. And BTW, is it really a "motion controller" that I'm looking for?

Cheers,
-Neil.

[Al_The_Man]

Could you not go with Mach direct from PP port to stepper drive, as is usually the basic method with Mach.
Al.

[cnczoner]

Not using Mach3 -- will be linux OS with custom code in C. The code will have to control a number of other things, which won't be easy with any other generic machine controller program anyway. This is for a homebrew PnP system, BTW.

[Al_The_Man]

You could design around a Galil Motion card, there are several options with their products, also libraries and s/w for design in VB or C++.
Built in vector or interpolated motion.
Plus PLC options and servo's or stepper option.
Al.

[Andre' B]

You could also give the people at Mesa a call.
http://www.mesanet.com/index.html

Edit:
http://www.mesanet.com/motioncardinfo.html
Quote:
The SoftDMC firmware converts any of our FPGA based I/O cardsto a high performance DSP based motion control system. The SoftDMC system supports up to 8 axis simultaneous motion. Features include Position and Velocity control modes, trapezoidal motion profiles, cubic motion profiles, 32 bit position range, 32 bit acceleration and velocity parameters, high sample rates (>60 KHz for 4 axis, >30 KHz for 8), two quadrature encoder inputs per axis for dual feedback systems, 32 bit gearing, velocity, acceleration and friction feed forward terms in PID loop, breakpoint/event logic for flexible real time (within one sample period) handling of internal and external events (such as limit switches), efficient FIFOed host interface with multichannel command queueing, and much more. SoftDMC supports Brush motors, 2 phase stepper motors in closed loop and open loop modes, and 3 phase AC and DC brushless motors in closed and open loop modes. The SoftDMC firmware is included free with all Mesa FPGA based cards and can be licensed for a nominal charge for non-Mesa cards and embedded FPGA designs. SoftDMC is an ideal replacement for LM629 and other ASIC based motion controllers, assuring long term availability and ease of modification due to its open FPGA based design.
End Quote:

[H.O]

Hi,
Have you looked at EMC2? It is for Linux what Mach3 is for Windows - and more in some respects. It can use the LPT-port directly (for step- and direction) or talk to various hardware boards available. It's open source and seeing you are a C programmer perhaps you can make it do what you want, if it doesn't already do it.

There are several low-ish cost boards available from MESA (EMC2 has drivers for a few of them a believe) perhaps one of those might do the trick if you're writing software from scratch. Also, have a look at the boards from Dynomtion, on their downloadpage they have what they call a KMotion Coordinated Motion and Trajectory Planner Library (Includes Source code).

Regarding the Smoothstepper. It was designed specifically for use with Mach3 and it's protocol is not available. But AFAIK it does not work the way you want anyway, it's pretty much 6 frequency generators at the end of the USB-cable and it's up to the PC to plan and calculate axis velocities and send it to the Smoothstepper which then updates it's "step generators" with the info from the PC at a rate of 1000-4000times/second thus generating motion. All the interpolation stuff etc is handled by the PC.

/Henrik.

[cnczoner]

Found Galil -- will need to read/research. Also found these, but also need to read/research to see what control-API details are provided...
http://deskcnc.com/gen2.pdf
http://www.arcus-technology.com/pmx-...621776bfbbce59

Andre -- funny, I have seen the Mesanet website in the past, but never thought they had anything to do with steppers -- just servos. Will contact them.

Thanks,
-Neil.

[cnczoner]

Henrik,

I spent a good part of last week trying to get EMC2 to run on my PC (Mini-ITX w/CLE chipset), but it seems Ubuntu just does not like this. But EMC2 won't be my final answer anyway, because of the other requirements of the software (need to integrate a camera later for accurate positioning).

My requirements are fairly basic, btw. I don't mind having the PC calculate the positions, but really want to relieve the PC from having to generate the accurate pulsetrains. Acceleration will be tricky with something basic though, as the PC will need to update the controller quickly, and in a timely basis until constant speed is achieved, so any of the cards that handles acceleration will be preferred.

Ideally, I want the PC to calculate the offset distance (or number of X,Y,Z steps) to the destination, and I can specify max speed and acceleration values, and then let the controller handle the simultaneous pulsetrains to smoothly accelerate, move to, then decelerate to the destination point. The only thing I'd need after that is a signal back from the controller that the destination has been reached.

Cheers,
-Neil.

[Al_The_Man]

The problem you may run into with steppers is there is no closed loop, so no confirmation back to the controller, you could add encoders, then it would be feasible to go with servo control, with the Galil card you can constantly read the position, or just be advised when the position has been reached.
Also a nice feature is the Gearing and Electronic Cam functions, these allow one or more motors to be geared of another's encoder, with varying gear ratios on the fly if needed.
As far as position commands, these can be issued in absolute or incremental.
Al.

[cnczoner]

Correctamundo. I've thought about adding encoders, but figured I'd deal with that later, as I'd really consider linear encoders to verify accuracy.

FWIW, I spoke with Galil an hour ago and they've got a few products that would serve my purposes incredibly well, including the ability to verify against encoders. But any of these that meet my specs are in the $1000-$2000 range... ack!

[Al_The_Man]

There is always ebay, I have picked up incredible deals, especially for the legacy cards, which perform equally as well.
Although lately some of the prices asked are unreal, but obviously they do not end up being sold.
Al.

[RomanLini]

I think your earlier idea of coding your own with a microcontroller sounds best.

PNP is one of the easier motion control apps, you wont have complex toolpaths like cutting text (or even curves!) it's basically a 2D format that only needs some basic XY coding.

Rolling your own will have other benefits, as you will probably want to customise some special features like you might want to add a paste dot dispenser with specific timing, temperature compensation or special vacuum pickup timing etc.

It's a MUCH less demanding app than writing an indexer for 3D cutting, you don't even need exact tool speed or an exact linear path.