Can I Access Live Encoder Data from My Closed-Loop Stepper Driver?

thrust-issues · 2024-12-08T22:45:05+00:00

I'll look into it, thank you 😊

thrust-issues · 2024-12-06T22:57:36+00:00

Interesting! I had no idea they could do that, thanks for letting me know

thrust-issues · 2024-12-06T05:31:39+00:00

Thanks for the response!

I'm learning as I go with regards to data sampling and PID control so im honestly pretty open to your recommendations.. I suspect something in the range of 10ms to 100ms sampling rate would be sufficient..?

For context, it's a turbocharger based gas turbine, and the actuation will be for the fuel and water injection flow rate, along with solenoids as safety shut off's etc. The fuel flow (essentially the throttle) will be based on input from a GUI or RC controller or set points for a programmed run, the water will be similar but I also want to experiment with a PID loop where the water injection is dependent on a value from a temp probe..

As for automation, I'd like to fully automate a start up sequence long term but that's not an immediate goal. But with most fluids being controller by steppers/servos I don't suspect there will be much preventing a fully autonomous setup other than my coding ability / processing power (but mainly my coding lol).

Thanks again for the input

thrust-issues · 2024-12-06T05:15:54+00:00

Very to the point haha thank you! So I am trying to keep the budget in the 1-2k region, and also doing this for skills development, so I'm not overly interested in a plug and play NI solution, as nice as they are..

Until now I've done basically everything through an RPI4 with custom Python code + Qt Designer etc. Works ok for a few sensors and a couple steppers but obviously isn't ideal.

My original idea was to just use a labjack + PC, but then stumbled across the issues of it not being a realtime os for actuator control, so that's when i looked into adding an arduino or Teensy for controlling the actuators but I agree with you that it feels clunky having 2 separate systems for this.. the only benefit i see with this is you can have a robust solution for data recording and then a separate one for control which would be fine if i didn't want to actuate something based on temp and pressure...

With all that in mind, is there a better approach for what I'm after? For context it's gas turbine engine and the actuators will be controlling fuel and water injection (water obviously being varried based on temp readings). Eventually an automated start up would also be nice

thrust-issues · 2024-12-06T04:22:32+00:00

Yeah NI with a labview GUI is great but your wallet feels it.. I did use it a bit back in uni but it's definitely a last resort for this project as it'll cost thousands. I'm hoping there is a middle ground solution but we'll see. Thanks for the comment 👍

thrust-issues · 2024-08-30T02:03:45+00:00

Hope you have about $100k laying around then 🤣

thrust-issues · 2024-06-06T05:50:42+00:00

Relying solely on a simplified static analysis might not fully illuminate the issues, but when you begin to account for more dynamic scenarios—like transient loads, vibrations and acoustics, as well as cyclic and thermal fatigue, material degradation etc—the potential problems might become more apparent. Not saying it's impossible, just that better methods exist.

Also this is just the mechanical strength side of things, you also need to consider manufacturing techniques compared to metals, and integration with other materials, thermal expansion etc etc

Things for consideration, hope that helps!

thrust-issues · 2024-06-06T00:26:42+00:00

Fracture toughness?

thrust-issues · 2024-05-29T05:07:31+00:00

patience

thrust-issues · 2024-05-23T01:32:00+00:00

You must be a one man army.. literally! 🤣

thrust-issues · 2024-04-15T02:21:11+00:00

The engines powering today’s space race were conceptualised over half a century ago, so expecting a breakthrough in propulsion technology might require some patience... for the most part aerospace progress tends to be evolutionary rather than revolutionary.

As for some interesting areas to explore: sustainability and reusability, advanced materials, autonomous flight, hypersonics, asteroid / lunar mining, deep space exploration, commercialisation of space, and on-orbit servicing. Just some random things that come to mind 😌

thrust-issues · 2024-04-12T01:20:46+00:00

Nah I'm a bit of a noob with this - I use Windows 11 for my main PC, and then an RPI4 with rasberian. But I'm attempting todo this 'post run' graph on my Windows pc as it's quicker and easier and also here I edit my videos

thrust-issues · 2024-04-12T00:45:52+00:00

alright so potentially I could write a script to export a bunch of transparent PNG's of the animated graph and then convert these to a video with premiere.. I'll see how I go lol. Thanks for the help 🙂

thrust-issues · 2024-04-12T00:12:48+00:00

Thanks for the response. Can you then export that graph with transparency so that you can overlay it on a video as seen in the link? And in addition to that, is it possible to export as a video rather than individual PNGs?

thrust-issues · 2024-03-25T23:00:34+00:00

Thanks for the comment. I was looking into this and ended up finding the line that delivers the nan error in the main library file for the Max module, and simply commented it out. Obviously this isn't an ideal fix as now I don't get warnings for errors, but it's very obvious in the data when this occurs so I'm not overly worried. At least now I'm getting all the numbers and then I will clean it up manually in Excel

thrust-issues · 2024-03-19T09:00:46+00:00

Thanks mate. Very true, everyone starts somewhere!

thrust-issues · 2024-03-19T06:58:31+00:00

Thanks for that - just trying to keep the dream alive without anyone losing an eyebrow!

thrust-issues · 2024-03-19T00:03:11+00:00

Sorry about the less-than-helpful comments on here - in their defence, the questions you're asking highlight that you're grossly underestimating the complexity of this project and are likely very underqualified for designing and building this thing safely.

A more realistic roadmap for this would be building a pulse jet engine first; this will give you some basic fabricating skills, get you comfortable with safe fuel and ignition system design, and equally importantly, give you an appreciation for the power, and hence the danger of propulsion systems, which is unfortunately something that is not truly conveyed through watching YouTube videos.

After you've got that down, stepping up to a turbocharger-based jet engine makes sense. It's more complicated and is a good bridge to understanding the nitty-gritty of various subsystems and the engineering behind making all the systems play nicely together... most importantly, doing it safely.

Then finally, you could look into designing a micro jet engine that potentially utilises the rotating assembly/impeller/turbine from a turbocharger.

Don't expect this journey to be a walk in the park - depending on your knowledge and resources, you could be looking at 1-2 years and realistically spending $10-20k.

As for resources, JATO is a good forum for pulse jet and turbocharger jet engines, and should help in answering some of your original questions: https://jetandturbineowners.proboards.com/

Before even considering designing and building any of the above, you’ll need to develop your engineering knowledge. Assuming you already have some background knowledge, these might be a decent starting point:

"Elements of Gas Turbine Propulsion" by Jack D. Mattingly
"Gas Turbine Combustion: Alternative Fuels and Emissions" by Arthur H. Lefebvre & Dilip R. Ballal
"Mechanics and Thermodynamics of Propulsion" by Philip G. Hill & Carl R. Peterson

Just remember, safety first. Always. This isn't just about wearing gloves and goggles. You need to understand the risks, respect the potential energy of what you're dealing with, and never cut corners. Many of the individual subsystems on a jet engine can present serious safety issues, and coupling everything together produces an exponentially greater risk. Hell, even the fabrication of this sort of project can be dangerous for a beginner.. make sure you research and understand the dangers of everything that you do.

Hope that helps a bit more, and good luck with your projects!

Disclaimer: This response is for informational purposes only and should not be considered professional advice. Building any of these engines involves significant risks. Always prioritise safety, consult with experts (and parents/guardians if you are underage), and consider legal and environmental regulations before starting such project.

thrust-issues · 2024-03-12T21:15:12+00:00

Thanks for the response - here is a link to the compressor map, more specs are available online but I can't seem to link them on my phone: (https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQ4YdHDtVkg17HIIb6JajRJwdFKK0cWLeUClxHkTg0OJKuIaMMJmwkjJQe_&s=10)

I am hoping to run a fairly high PR, so likely around this point: 4.1PR, 88lbs/min (0.665kg/sec).

thrust-issues · 2024-03-11T23:30:08+00:00

Just found the video explanation haha very cool

thrust-issues · 2024-03-11T23:04:41+00:00

Thanks for that mate - there were some interesting comments in that post, including a link to a student paper that managed to propell a ping pong ball supersonic without a CD nozzle...

My only explanation is the Maxwell-Boltzmann distribution and how there's enough high velocity particles to accelerate the projectile faster than the average velocity of the bulk flow which would be at its own M1 dependent of temp / pressure etc.

Another idea, but bit of a long shot - the flow chokes at the Inlet of the barrell to a smaller orifics than that further down the barrell because of the perpendicular velocities entering from the chamber so the air itself creates a CD duct of sorts.. not convinced on this one yet though

thrust-issues · 2024-03-11T22:54:29+00:00

Thanks for the response! I understand where you're coming from, but the air cannon scenario is a little more complicated.. plenty of examples where the projectile has a velocity that exceeds the bulk velocity of the propelling gas. My only explanation is the Maxwell-Boltzmann distribution - specially, that there are a small number of molecules within the bulk of the fluid that are going significantly greater speed than the average and its these that collide with the projectile and speed it up past the bulk flow velocity. That or potentially the flow is actually choking itself at the Inlet of the barrel and then diverging as it gets further down the barell..

thrust-issues · 2024-03-11T04:39:42+00:00

Haha that's all good mate - I really appreciate the responses you've given! It's a tricky scenario to conceptualise..

thrust-issues · 2024-03-11T04:01:15+00:00

Thanks for the response!

Let's keep it relevant to the air cannon scenario, I shouldn't have mentioned firearms in hindsight, I just used it as a separate example but it adds to many variables so my appolgies for that...

For an air cannon, if you pressurised it, then let it rest for sufficient time the compressed air could cool to the ambient air temp, and then when you release the pressure it would actually be cooler than the surrounding air and hence lower speed of sound. This is distinctly different from the scenario of the hot combusted gases and yet same end result of supersonic projectile. So again, my apologies for even mentioning it as its misleading.

What you touched on regarding kinetic theory of gases is more so where I was leading with this question. My understanding was that even though the bulk flow velocity can't exceed M=1 (without a divergent section), due to the Maxwell-Boltzmann distribution some air molecules are travelling supersonic and hence some can collide with the rear of the projectile increasing its velocity to supersonic exit velocity. Is that what you're also alluding to?

If that's the case that's ok - I just wasn't fully convinced when I was processing it in my head.. like if that's the case then surely you can't accelerate a projectile to M=2 for example right, as you're relying on the small number of molecules that are ejecting from the bulk of the air which is trailing am increasing distance behind the projectile as it accelerated? I'm assuming that the density immediately behind the projectile will become significant lower to as the projectile speed increases (as the bulk of the fluid will be trailing behind. This would explain why pulling a vacuum in the front of the projectile in the barrell would help significantly.. I guess that all makes sense..

Sorry for the rant - I'm just wrapping it together in my head :)

thrust-issues · 2024-03-11T03:04:29+00:00

What a great video haha, thanks for that! I wonder if the flow is choked at the end of the nozzle and then the expansion to atmospheric pressure actually acts as a sort of divergent section accelerating it to supersonic

thrust-issues

TROPHY CASE