Motion Control Design

I am looking at building a relatively low cost mo-co rig....probably four channels. Skateboard dolly with toothed track-one channel. Geared head conversion - two channels. Focus - one channel. I am looking for a little advice on the use of steppers over servos or vsv. I am particularly interested in how to ascertain ratings of torque and required speed etc.

Has anyone fabricated such a device out of relatively cheap process control equipment?

I am really looking at cobbling together a system for an upcoming doco and beyond. I will eventually have on board a robotics guy and several electrical engineering friends but at present they all have little idea of the particulars of film requirements.

Any takers?

Nick Paton
Film & Digital Cinematography
www.npdop.com

Nick Paton wrote :

>will eventually have on board a robotics guy and several electrical >engineering friends but at present they all have little idea of the >particulars of film requirements.

Nick,

My advice is, Don't. There have been many who have thought they could build a motion control and ended up wasting a lot of time and money. As near twenty year veteran of the industry, I have seen it again and again.

Having said that, here is a moko building primer.

There are three main components to a system. First is the mechanical part. The physical machine that moves objects like cameras via motors attached to gears and belts. Many a grip or mechanic has looked at a motion control rig and said "I could make one of those". I now just inwardly chuckle. The trick is to make a repeatable machine that can do MANY differently things rather than just one expensive rig that can only do one type of shot. As it is, the most flexible of the rigs that are manufactured for use by the film industry cannot do it all. There is not any one repeatable machine that sets up quickly, goes super fast, is ultra quiet, has a long reach, fits through a standard doorway and also shoots time-lapse and stop motion miniatures.

The Second component is the driver electronics. This unit translates the incremental and directional signals from the computer into power units to move the motors. This technology has been made quite easy in the last ten years. There are now many companies selling modules that make building this component a near plug-and-play operation.

Third is the development of programming software. Here is where I say don't! As a systems consultant on a few "in-house" systems, I would say the number one problem software designers have is that they are not camera people. The control of the camera is so separate in it's needs that programmers need to end up making TWO motion control programs within one seamless interface.

Unless you want the ultra simplest of operations, you should buy a Kuper system. Industrial Light and Magic had a team of software designers working over a year trying to develop their own Apple based program. After a reputed 1 million dollars was spent on the own in-house motion control system they pulled the plug and bought a Kuper system for (then) $3,500.00 US.

Beside buying a Kuper system for the card and software, I would recommend looking at what your primary shooting is going to be (remember, NO RIG WILL DO IT ALL) and look at buying a used rig. They come up for sale often from closing effects houses. Unless you have a very special need like shooting underwater, your money is best spent adapting a rig that someone else has spent years debugging.

Last month Disney closed their Visual Effects division called The Secret Lab. They sold all of the Moko gear they had. It was all the equipment that had been developed and refined at Dream Quest. The mouse had bought out the two decade old company and dumped it after only a year or two of operation.

Lastly, if you are still going to scratch build your own system, talk to the film industry Motion Control suppliers about what wiring standards are already in place. There are thousand of connectors and wiring schemes possible and if you want to rent a device like a simple rotator for a two day shoot, it's as easy as making a phone call and sending it back with a check.

Believe me, you do not want to be cutting wires, making adapters and totally rewiring both ends of the system while on-set. The same goes for mounting plates and hole patterns. Standards are great, let's just not have so many of 'em.

Cheers,

Eric Swenson
VizFxDp On-Set Super
http://www.ericvfx.com
IATSE Local 600 Dp and Supervisor

Disclaimer: I do not work for Kuper Controls nor am I paid any money by them for my recommendations. In fact, I don't think I have paid THEM enough for the help I have gotten from over the years.

Thanks, Eric.

I'm doing some research before committing. There seems to be systems out there and I am only looking at a field portable unit with pan, tilt, focus and dolly action. This is to be backed up with laptop or dedicated controller...preference for a system that allows movement capture so that we can work a shot then scale the movement on replay. Ring any bells...who makes a cheapish version?

Nick Paton
Film & Digital Cinematography

Nick Paton wrote :

>Thanks, Eric. I'm doing some research before committing. There seems >to be systems out there and I am only looking at a field portable unit >with pan, tilt, focus and dolly action

For the pan, tilt, and focus part you might want to look at Hot Gears.

You can find information at

www.hotgears.com

Miran Salamati developed that system and is a good guy to deal with.

Mike Most
VFX Supervisor
IATSE Local 600
Los Angeles

When I first saw this post, my reaction was the same as Eric said about hearing a grip or machinist say "I could build one of those..." I inwardly chuckled.

As another with 20+ years experience with all aspects of motion control, I recommend you read and re-read Eric's post. I have nothing to add, I simply post this for emphasis.

I was particularly drawn to comment by Eric's disclaimer about how he doesn't feel he's paid enough for the help he's gotten from Kuper. I agree totally with this statement, as I would wager every motion control operator in the world would...even those who don't regularly use Kuper.

An interesting development in Motion Control is Arri's new "ArriMotion" equipment (I'm not sure whether it really exists yet). It will be interesting to see if they can get it right where so many others have failed, including, as Eric pointed out, the grand-daddy of visual effects, ILM.

Arri's system is totally new hardware and software system, apparently build from the ground up to work with some new, some existing hardware. Time will tell if it will work, if it will be cost effective, and if it will be accepted.

If so, it might be just the thing for Nick's project...if it ever becomes more than vapourware.

Don Canfield
Gear+Rose Motion Control
NYC
www.gearandrose.com

Nick

Get in touch with Maxim Ford who has a couple of simple rigs using steppers, including a tracking system with toothed track. It is(or was) controlled with the little Psion computers and is an ideal field rig, although perhaps more of a time-lapse/repeat move rig rather than accurate moko.

I don't have his details to hand but a web search should find his site.

Chris Plevin

Thanks all for your information on motion control.

I've been put onto a few companies stateside by the kins readers here and will most probably use existing technology with the addition of some customisation. There seems to exist a few people around the place who are very knowledgeable and prepared to do custom rigs with small dollars.

Nick Paton
Film & Digital Cinematography