Those Delta Computer Systems guys sure get around

I was going through the latest issue of Control Engineering magazine and what do I see but an article by Peter Nachtwey. Delta Computer Systems supplied motion controllers to a company that makes chassis test stands for NASCAR racing teams. It was a good article too, although a little light on detail compared to what Peter does in Hydraulic and Pneumatic magazine. It's a pretty good read.

Several years ago they also supplied motion controllers to the movie industry for the motion of the ship in Master and Commander. They do play with the fun stuff, those Delta guys.

Keith

kamenges said:

I was going through the latest issue of Control Engineering magazine and what do I see but an article by Peter Nachtwey. Delta Computer Systems supplied motion controllers to a company that makes chassis test stands for NASCAR racing teams. It was a good article too, although a little light on detail compared to what Peter does in Hydraulic and Pneumatic magazine. It's a pretty good read.

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It is light on detail because the customer that makes the test stand doesn't want others to copy what they have done.

Several years ago they also supplied motion controllers to the movie industry for the motion of the ship in Master and Commander. They do play with the fun stuff, those Delta guys.
Keith

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We don't do the 'fun' stuff. The integrators do it. We only go out when things get tough and it isn't fun anymore. How about Fort McMurry in the winter when it is -30 below to set up a rock crusher. Same with dropping simulated mars probes out of helicopters. That required some that can simulate a falling object using non-linear differential equation for the simulation. Another of our guys went to Qatar ( HOT! ) to set up a controller in a steel mill. The system wasn't working so it must be the controllers fault even if it isn't wired up correctly.

Round, round, round, round, we get a round.

More to come. There is a new program called Prototype this. It is on the discovery channel Wednesday night for me. One of the episodes will have their proto type project controlled by our controller. I think it will be obvious when you see the program but right now I don't see the project we were involved in the schedule.

http://dsc.discovery.com/tv/prototype-this/prototype-this.html

One of our people was down at Treasure Island where the program is filmed and made the system go. It took about two weeks to get the project we were involved in to work. Our engineer that was there is wondering how many seconds of time he will get on TV. He also said that Zoz, the programmer, was able to build a Java interface to our controller very quickly. Our engineer was impressed with Zoz's ability and that takes a lot.

If you like geek engineering then this is a program for you.

BTW, the press at the Orange County Choppers uses one of our controllers too. We weren't involved by the press OEM is. However, it just a piece of equipment in the job.

Tonight the water slide is on Prototype This

Tonight's episode is about a circular water slide. Our controller controls the motion of the water slide. I am interested in how many seconds of TV time our engineer gets on the show. This is the same engineer that worked on the Phoenix lander landing simulator using the helicopter.

Hopefully we get some publicity out of this. I was very upset at the amount of time it took our engineer to get this system to go. Our engineer did well and probably saved the project. It took just about every trick we know to make the system controllable. A typical motion controller would not be able to do this project because of the poor hydraulic design There was a lot of hose between the valves and the actuators. The valves were not linear, they had a dead band. I was not happy. We weren't getting paid for this. 3 days is OK. 8 days and two plane trips has me upset and it wasn't our fault. It those @#$% hydraulic and mechanical guys, again.

BTW, if you saw the last episode with the 6 legged vehicle you saw that fail. We could have made that go easily. There were two main problems. The big one is that there wasn't enough power. The vehicle had to have enough power to lift itself up with just 3 legs, not 6. One can see by watching that every step it took using three legs the vehicle started sinking close to the ground. This in turn causes the required torque to hold it up to increase. Eventually the drives overloaded. The other was with the controller. Obviously it wasn't industrial grade. We can easily program in the cam profiles for the legs and make them smoother. It would have been better if there where more legs on each axles. Then the legs wouldn't need to whip around the tops fast to be in position. The problem is that the legs would then hit those on the axle in front and behind unless there was an offset. The cam profiles on either side can be geared to a virtual master. Then the vehicle can be steered using the relative speed of the left and right virtual masters.

Peter, looking forward to tonight.

I also enjoy the series Time Warp with the slow motion photography. The episode that broke the bottom out of the beer bottle was very revealing to me. They did not use beer but a amber colored liquid. Leaving a generous air gap at the top of the bottle they slammed their palm to the open bootle top. This created a pressure wave that rebounded off the bottom of the bottle. It was the rebounding pressure wave that caused the liquid to cavitate (beer just forms bubbles/foam) as the cavitation bubbles collapsed the pressure differential caused the fluid to rush to the bottom again. It was at this point the bottom broke out.

This episode confirmed for me all your talk about the compressibility of oil, pressure differential and resulting flow. I just needed an example in a media I was familiar with to make me a believer.

milldrone said:

This episode confirmed for me all your talk about the compressibility of oil, pressure differential and resulting flow. I just needed an example in a media I was familiar with to make me a believer.

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You have brought up another hydraulic topic that bothers me. At this time I assume the pressure in a cylinder is the same on each side of the piston. Now we know it takes time for those pressure waves to travel. In oil the pressure waves travel at the speed of sound in oil. The long hoses I complain about not only make the system hard to control because the system is more compliant or springy, it also takes more time for the pressure waves to go from the valves to the piston. In this case and extra 50ft of hose will cause about a 10 millisecond dead time. That doesn't seem long for a temperature control system but that is an eternity for a motion control system. That dead time makes the motion control difficult. BTW, the speed of sound is determined by the bulk modulus.
http://en.wikipedia.org/wiki/Speed_of_sound
The wiki page uses C for the bulk modulus of oil.
Now you see and believe.

Peter Nachtwey said:

...There was a lot of hose between the valves and the actuators. The valves were not linear, they had a dead band. I was not happy...

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Which brings up the system that I currently have under design. Seven axis and thanks to the bean counters I cannot have seperate manifolds for each acutator as originally designed. They said "too expensive, eat our shorts, its not happening" no matter how much yeah-buting I did. Grrrr. But I did absolutely insist that we were not using any hose - hell no no way. It will be steel pipe. Unfortunately I have between 3' and about 6' of pipe to each actuator. Does that mean different a response for each actuator? Will it be significantly different?
Hopefully the one saving thing is that the actuators are 22" in diameter and max V is about .3 in/s.

I have it set in my Tivo.

When working with long hoses and small cylinders it seems like you could easily have more oil in the lines than in the cylinder. What keeps the oil from getting hot in the cylinder and taking out the seals?

I know of a machine that had a 24" double rod cylinder and a small jack cylinder for the fast moves. They put in a bypass valve that would move oil from the top to the bottom of the large cylinder when moving with the small cylinder. They kept loosing the seals in the big cylinder from heat. They didn't have enough oil transfer in the cylinder to get rid of the heat. I think this could be a problem with long hoses?

This brings up another question. How does oil temp change a servo system?

Peter I just finished watching the show. It looks like another great project. Probably not the plug you wanted but it may lead to a few jobs.

It is good enough

Dennis got about 20 seconds and 1 sentence and he didn't screw up. He also wore his white Delta shirt at the show time. We can point to this program and other movie projects.

Splashtacular supplied the video and the motion profile which was a series of points. Dennis had to calibrate the water wheel so its coordinate system was similar to the splashtacular data so the motion profile would match image on the water spray. This wasn't too hard.
http://www.splashtacular.com/

Zoz wrote a small interface between the graphics and our motion controller. He used Omron's FINS protocol because is is one of the simplest to implement. I was told Zoz wrote the interface in java in just a few minutes.

The motion controller and the video was tested out using our software simulator so the confidence in the controls was high until they tried moving the wheel. It didn't take long to down load the very long cam table data using Ethernet but a few points did need to be edited because they would cause the hydraulics to move faster than what it was capable of doing.

The biggest problem was the hose and the dead band in the valves but that wasn't an issue on the TV program because Dennis got the system tuned.
The tuning required using a second derivative and a jerk feed forward and an output filter to smooth out the rough control signal.

I stayed up and watched the show on the Discovery channel late second showing. It was pretty interesting - but I had to wonder, how much of the engineering was actually done by the four guys on the show and how much was done by others behind the scenes. Its a cool project though. I spoke with Peter this morning and heard more about it, sounds like a fun one despite the problems with the hydraulic system desing.

Peter Nachtwey said:

The biggest problem was the hose and the dead band in the valves but that wasn't an issue on the TV program because Dennis got the system tuned.
The tuning required using a second derivative and a jerk feed forward and an output filter to smooth out the rough control signal.

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The magic of editing! If only we had the opportunity to go back and edit our own startups - instead the smelly stuff usually hits the fan right in front of management when the project is already late before the control guy gets a crack at it, and its not usually the control guy's fault. But that is not what management remembers and there is no film to edit.

It was pretty interesting - but I had to wonder, how much of the engineering was actually done by the four guys on the show and how much was done by others behind the scenes.

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I had the same thoughts. However sometimes the hardest part is getting the right people for the job.