Resources

Added by J. Simmons over 11 years ago

There are two projects that I think might help us sort out how to get started with data collection.


Replies (53)

RE: Resources - Added by J. Simmons over 11 years ago

I had a lunch meeting last week with Rick Wills of UDART, and he said these sites might be useful to us:
  • www.jamesyawn.com - This site has the signal conditioning circuit that UDART built for their test stand.
  • www.comedi.org - Comedi Linux control and measurement device interface: These are drivers for a number of different DAQ cards. It's mostly command line type interface. There are some fairly low cost A/D packages that come with a simple DAQ software as well.

RE: Resources - Added by J. Simmons over 11 years ago

Here are some technical details about using the Arduino as a ADC (all based on material in Practical Arduino). First, the analog inputs have a resolution of 10 bits, and a default read speed of 111 microseconds. While this is not very good performance, the read speed can be decreased to about 16 microseconds with "reasonably good accuracy." This is accomplished by adjusting the ADC clock rate through the Arduino source code. The source code (GPL 3.0) provided with the Practical Arduino oscilloscope project includes the appropriate lines in the setup() function. I think we should start with this as our approach, modifying the Arduino sketch to only use the two analog channels we need right now (force and temperature measurements). This will require us to change the licensing for the project's source code from Apache 2.0 to GPL 3.0.

The other half of the input processing is the data capture/display on the computer. The oscilloscope project in Practical Arduino is compatible with the Arduionscope GUI written in Processing. This software project is a ready made GUI for the Arduino sketch above, and includes a "scope" class to make it easy to create custom GUIs. It also has the ability to save the data to csv files. Note, it is also licensed under the GPL 3.0. My thoughts are we start by using the shipping build of the Arduinoscope software (this gets us going very quickly), then look at embedding the scope functionality into a custom GUI for the teststand. Ultimately, I think it would be cool if the custom GUI controlled the ignition and data collection so all of that was appropriately timed.

RE: Resources - Added by Ben Barnett over 11 years ago

Intro: I am an old analog circuit design engineer, and I have a machine shop in my basement. My most challenging signal-conditioning design was to present a 12-bit ADC with a signal of 0-5VDC from an optical signal of 0-13pW of light at 535nm. I am an old ADHD kid that took two changes of school system to get through the 8th grade. For those not familiar, ADHD is Attention Deficit Hyperactivity Disorder (the "H" fell off about 15 years ago) so I am totally scattered and highly creative. J. will have a tough time getting me to think "inside the box". I have an Associate in Electrical Engineering Technology (Sinclair College 1968, with honors) and 40+ years experience in signal conditioning for electrical, mechanical, and chemical sensors. My wife and I are both dealing with significant physical challenges, so my time-on-project may be somewhat limited.

Do we have a Mechanical Engineer on the project? ..or is it me?

I have been thinking about low-cost test stand designs. It looks like the biggest trade-off is between material cost and off-the-shelf components. The more we use off-the-shelf components, the higher the cost. If shop time is fee, materials get really cheap. In general, analog signal processing can be cheaper than digital, and it needs no software :-)

Please arrange the following in order of priority:
Keep it cheap.
Minimize custom-made parts.
Keep it simple.
Low-mass engine mount.
Low-cost force sensor (cheap coil spring?)

Note that a low-mass engine mount means better resolution, lower hysteresis, and more custom-made parts. Using a dirt-cheap coil spring for a force sensor takes a fair amount of analog circuitry to get to a DC voltage signal. OTOH, a frequency measurement with sufficient resolution (about 20 bits?) is all that is needed for digital signal processing.

Ben

RE: Resources - Added by J. Simmons over 11 years ago

I just left a somewhat lengthy post over in the process thread, which I think informs some of my opinions about the order of priority. Here is my proposed order, but I'd like to hear from Greg as well.

  1. Keep it cheap - We have a hard ceiling of $200 for this project. The project is not meant to develop the best possible test stand for Estes motors, but to get us some live lessons for design, and operation of a test stand. The real bucks will come with future test stands for larger engines. Note, I think this implies low cost sensors and ADC (thrust and temperature).
  2. Keep it simple - Our requirements are pretty simple, so I want to make sure our design is as well. See above about the real investment comes later. I think simplicity is also going to help make sure the test stand is reliable and can be built or added on to by others (both important qualities in open source projects). Note, I think this implies minimizing custom-made parts, but in balance to make it cheap. So, let's first always look into COTS components, and replace them with custom ones when they are too expensive.
  3. Low-mass engine mount - Alright, here is the place I am beginning to think is going to be the real kicker. If we have a quality engine mount, we can come back in another revision of the test stand and upgrade the sensors or ADC and get improved performance. It is also I am guessing, going to be one of those items that there will be few, if any COTS solutions. Note, we should still take a look around our resource links and on google to make sure about that assumption, but if that is the case, it is also something that could be a real contribution to the existing base of designs.

Finally, to answer the question about Mech Eng, I am certainly not one. And right now, it is just you, me, and Greg. Greg, can you remind us about your experience in Mech Eng? I know you have spent most of your professional time in Systems Eng, but you seem much more mechanically inclined than me.

RE: Resources "COTS" ? - Added by Ben Barnett over 11 years ago

Please remind me what "COTS" means. Is it "O-T-S" with "cheap" as its primary value?
Thanks,
Ben

RE: Resources - Added by J. Simmons over 11 years ago

COTS = Commercial Off The Shelf

So, in my comment above, I just meant that using existing commercial products as components over custom made ones will drive us to a simpler solution (one that is easier to build and document).

RE: Resources - Added by Greg Moran over 11 years ago

So i guess it's time for me to introduce myself. My name is Greg, and I'm an with an emphasis on rocket/space systems, structures, and propulsion. I did my undergrad at TX A&M where I (we) designed, built, and tested a custom sounding rocket. As part of the testing team, we integrated the custom hybrid engine onto the existing test stand and verified the thrust profile of our new design. If memory serves, we were going for a 100 lb thrust for 10 seconds. Probably a bit extreme for this project, but informative nonetheless.

My masters degrees from AFIT are in astro- and systems- engineering which is why I'd like to emphasize the process as much as the final product. We were taught that space systems (of which rocket engines are a piece) projects are more successful if a rigorous Systems Engineering (SE) methodology is applied. On projects like this test stand it shouldn't take a very long time, but it can potentially save LOTS of time down the road.

RE: Resources - Added by J. Simmons over 11 years ago

Hey guys,

Just got a note from another AFIT student about this journal article on a 5N class test stand. Looks like they cover their design pretty well. I think it is worth our time to review this paper.

Greg, any reflections on process vs FIST?

-J

RE: Resources - Test Stand Paper - Added by Ben Barnett over 11 years ago

First, things have been a bit hectic with trying to get ready to escape from Sinus Valley for the rest of the ragweed season, so I have not read the paper for mechanical detail. The principle is simple but the implementation looks like it uses mostly custom-made parts. While laser position Sensors are COTS items, I think that one might consume your whole project budget. Do you have contacts in the local Sales-Rep community that can get prices on the Micro-Epsilon position sensor or a similar device from Keyence:
http://www.keyence.com/products/measure/laser/laser.php
I suspect that the Keyence sensors will be less expensive.

You might also want to consider a force-balance system with the voice-coil of a high-powered (car-stereo) speaker to apply the balancing force. The feedback loop is simple and cheap, but would need a bit of electronic tweaking to adjust the frequency response to eliminate mechanical resonance. The current in the voice coil at zero displacement is directly proportional to force. "Zero displacement" is easy to sense with a small LED, a photodiode, and something like a razor-blade in the gap between the LED and the diode. GE used to make cheap analog gap sensors where the sensor current decreased as the edge of a thin object entered the gap. I had a drawer full of them in my goody cabinet back when I was working for YSI.

I find it interesting that the torsion element was listed only as "stainless steel". 304 SS makes really bad springs. 316 is better, and 440 makes good springs, but is very sensitive to heat-treatment. I wonder why they didn't use ordinary carbon steel spring stock.

Ben

RE: Resources - Added by J. Simmons about 11 years ago

Just capturing a link I found that looks interesting:

http://ryanjmclaughlin.com/wiki/Arduino_Thermocouple_Shield

RE: Resources - Added by Greg Moran about 11 years ago

I'll have to take a closer read through the whole paper, but from my scan of the abstract it sounds like a cool project. The driving requirement here is the extreme time resolution and very sensitive force measurements needed to collect relevant data. I couldnt get a read on the FISTy-ness of the project.

J. Simmons wrote:

Hey guys,

Just got a note from another AFIT student about this journal article on a 5N class test stand. Looks like they cover their design pretty well. I think it is worth our time to review this paper.

Greg, any reflections on process vs FIST?

-J

RE: Resources - Added by Jeremy Wright almost 11 years ago

I need to get up to speed on Mach 30's engineering procedures ("Use of the formal systems engineering process" discussion) before I post too much, but I thought I would add this link to test out my new account. The link has a lot of pictures of test stands that other groups/people have built.

http://www.aeroconsystems.com/cart/ts-pics

RE: Resources - Added by J. Simmons almost 11 years ago

I think this is a great find. Lots of examples with good variation in design. Should make for a good start on the overall design of the Shepard Test Stand. And I just posted a follow up on the process thread with links to the Amanda Wozniak talk on engineering design process, which I hope will get us pointed in the right direction on the process front.

RE: Resources - Added by Jeremy Wright almost 11 years ago

Here are a few links that were given to me by the head of the NAR (National Association of Rocketry) Standards Testing Committee.

Here's a motor testing manual from the NAR Standards and Testing Committee: http://www.nar.org/SandT/docs/ST-MotorTestingManual.pdf

This link has information on rocket motor certification, and software that can be used to analyze collected motor data. http://www.thrustcurve.org/

NFPA (National Fire Protection Association) 1125 is what the NAR follows for motor testing. http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=1125&cookie_test=1

RE: Resources - Added by Jeremy Wright almost 11 years ago

Here is the NAR "Standards & Testing Committee Motor Testing Manual", in which they deal with procedures for test stands: http://www.nar.org/SandT/docs/ST-MotorTestingManual.pdf

RE: Resources - Added by J. Simmons over 10 years ago

This looks like a good find. I am particularly interested in sections 8.5 (Test Stand Requirements), 8.6 (Thermal Testing Requirements), and all of part 9 (Data Reduction Procedures and Standards).

RE: Resources - Added by J. Simmons over 10 years ago

A higher power embedded system board (running Linux) that I hope we won't need in phase 1, but might be something to consider for future test stands.

http://beagleboard.org/bone

RE: Resources - Added by Jeremy Wright over 10 years ago

Here's an interesting resource to go along with that (the Beagle Bone) too.

http://www.gigamegablog.com/2012/01/22/beaglebone-coding-101-using-the-serial-and-analog-pins/

RE: Resources - Added by Jeremy Wright over 10 years ago

Interesting document on the mathematics behind test stand thrust measurements.

http://chrisanddee.com/science/HS%20Rocketry/Rocketry%20&%20Calculus.pdf

RE: Resources - Added by Jeremy Wright over 10 years ago

Here are 3 videos where a guy builds and operates his own small motor test stand. The part 3 video clearly shows how the igniter acts during a static test. You can also see what happens with the C and D motors when the parachute charge goes off. He also goes through lessons learned at the end of part 3. Not very high tech, but it works.

Part 1
http://www.youtube.com/watch?v=KduDTol9GmM&context=C4151c75ADvjVQa1PpcFNnCEkjiNd0uOdpkTAC6drr_D1JsfSkVMo=

Part 2
http://www.youtube.com/watch?v=3lIT6Nh2RFo&context=C4da0444ADvjVQa1PpcFNnCEkjiNd0uLK43mPRoHbE3BDHaKXxtqE=

Part 3
http://www.youtube.com/watch?v=Rs7BsWkNPMU&context=C4fd5bd0ADvjVQa1PpcFNnCEkjiNd0uJFz63Y18CourHQeeqbTj9Y=

RE: Resources - Added by Jeremy Wright over 10 years ago

It turns out that Pasco Scientific (http://www.pasco.com) has a motor test clamp that will work with A through D Estes motors for $45. It's specifically designed to work with their own force sensor (CI-6537 for $210). They're too expensive for our budget, but that's an interesting design on the clamp. The document also includes some decent safety guidelines, so I'll be posting this link to the safety discussion as well.

ftp://www.pasco.com/Support/Documents/English/ME/ME-6617/012-06418A.pdf

http://www.pasco.com/prodCatalog/ME/ME-6617_rocket-engine-test-bracket/index.cfm
http://www.pasco.com/prodCatalog/CI/CI-6537_force-sensor/

RE: Resources - Added by Jeremy Wright over 10 years ago

This stand was built using galvanized Unistrut: http://www.ukrocketman.com/rocketry/statictest.shtml

There's some interesting information for v2.0 of Shepard too. The acquisition system on the stand can "accomodate thermocouples, pressure sensors, an acoustic sensor, and a vibration sensor." I hadn't thought of acoustic and vibration sensors. He also mentions a "bulletcam". I'm guessing the following is what he's talking about. http://www.electroflip.com/bulletcam-weather-friendly-sportscam.html

The base website (ukrocketman.com) seems to be a pretty good rocketry resource in general.

RE: Resources - Added by Jeremy Wright over 10 years ago

This test stand is an interesting vertical tripod design - http://www.nakka-rocketry.net/kdx002f.html

Here's a whole NAR article in Sport Rocketry about test stands - http://www.nar.org/pdf/S%26T%20Sport%20Rocketry%20Article%20(Nov%2010).pdf

A quote from that article talks about the WRASP data format:
"http://www.nar.org/SandT/NARenglist.shtml. Note that the PDF contains an average thrust/time curve in WRASP format, which is the format used by rocket flight simulators."

RE: Resources - Added by J. Simmons over 10 years ago

These are great resources, Jeremy. Posting videos (especially ones that include test firings) is always cool. And this is the perfect opportunity to show case an ODE feature, Embedded YouTube Videos.

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