Vertical Trajectory System (with some 3D printed parts)

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SpaceManMat
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Re: Vertical Trajectory System (with some 3D printed parts)

Postby SpaceManMat » Thu May 19, 2016 9:18 am

Looks good, although you seem to be doing a lot of work just use an existing controller. Will you reuses all the parts when you build your own control device?
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 10,849 feet
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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OverTheTop
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Re: Vertical Trajectory System (with some 3D printed parts)

Postby OverTheTop » Sat Oct 07, 2017 8:06 pm

SYSTEM INTEGRATION – ELECTRONICS
Been a while since I have done any significant work on this. Life gets in the way sometimes.
So with a bit more thinking, a bit more designing, and a bit more building, here is where I am at :)

Electronics have been integrated, but there are three loose-ends to go still. I need to find my final part (G-switch) which I have somewhere, but is currently doing a good job of eluding me :( .

Construction is basically discs of 1.6mm G10 F/G, separated by spacers. Before flight I will change the spacers to custom titanium bike spokes with plain cylindrical spacers.

During deployment this module will stay attached to the NC.

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From Top to Bottom
The black cable connector plugs into the NC to interface to the TeleMega. It will provide logging of the servo signals for post-flight analysis.
Next is the flight controller and servo connectors.
Servo block (contains four servos and a few connectors)
Logging interface (converts the PWM signals to the servos into voltages the TeleMega can log)
Reference pulse generator and Control Interface PCA.
G-switch and external control/testing interface.
Two SBECs to provide power for the avionics and the servos on separate regulators.
Microswitches, with a pull-pin actuation, for turning everything on.
LiPo batteries (2S and 3S) for running everything.
Connectors for charging the batteries and connecting to the deployment altimeters that will control when the control system is operational.
Finally, an eyebolt to string it to the rest of the rocket.

You will notice that there is no PCB for interconnecting the wiring between the modules. I went with plain wires only for this breadboard.

I still have a 3D printed part to be made, and installed on the autopilot. More info on that later.

Next major step will be airframe integration, again, as I need a longer length of airframe than initially thought. I didn’t go particularly hard on miniaturising the assembly as it is really breadboard and will likely have lots of changes applied.

Following that will be some ground testing.

Now, if I can just find that G-switch...
TRA #13430
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Re: Vertical Trajectory System (with some 3D printed parts)

Postby SpaceManMat » Sun Oct 08, 2017 8:57 am

Looks really good.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 10,849 feet
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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OverTheTop
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Re: Vertical Trajectory System (with some 3D printed parts)

Postby OverTheTop » Mon Oct 09, 2017 4:44 pm

Looks really good.

Thanks Mat.

Answering your earlier question I missed:
Looks good, although you seem to be doing a lot of work just use an existing controller. Will you reuses all the parts when you build your own control device?

This is my own controller :) Built using COTS parts. Assuming it works I will happily keep developing it. If more time becomes available I might venture into a new flight controller and custom firmware. I would just need to convince the firmware people at work to volunteer to help me out so I can keep doing the fun stuff. I can write software, firmware and VHDL, but it isn't something that I find amusing in my spare time. Would probably only go down that route if I needed a high-performance VTS and had to include things like gain scheduling. Otherwise KISS is good.
TRA #13430
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"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

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Re: Vertical Trajectory System (with some 3D printed parts)

Postby OverTheTop » Sun Oct 15, 2017 9:16 pm

SOME MORE 3D PARTS

We had a new 3D printer delivered at work recently. This has a smaller build volume than our other printer (145x145x175mm) but uses stereolithography as the printing system. Basically liquid resins are spatially cured by LASERs. Many different resins are available: Tough, flexible, clear, rubber etc. Print resolution can be set from 100um down to 25um. The other advantage of SLA over the more common FDM process is that there is no z-axis weakness in the part. It is an inverted SLA print process.
https://formlabs.com/blog/ultimate-guid ... -printing/

I needed a “cage” to limit travel of the autopilot unit during severe accelerations. The AP usually sits on four foam adhesive pads for vibration isolation. The usual outcome in a fixed-wing flight with a bad landing is that the AP tears the foam and travel is limited by the length of the attached wires. I designed an enclosure that would sit over the AP, with room to move around on its mount, but limit its excursions when jolted while still allowing for vibration isolation.
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DSC07040resize.JPG

Left image shows the support structure added during the printing process.
Note that the small extension on one end is to hold the plugs captive on the AP, since they are not positively locked on.

Having the VTS on the bench proved a bit cumbersome, especially with the eyebolt stopping me from standing it up. I designed a stand that would take the VTS and support it while I worked on it. I also built in a voltage monitor so I can check battery voltage without getting the multimeter out, and added a switch to be able to have the VTS in active or fixed mode for testing purposes.
DSC07042resize.JPG

Note that the base has two diameters so it can stand the bare assembly or the airframe integrated unit (either way up).

I need to drill the airframe for the mounting points and fin hubs. Since the servos are fitted now I can’t use the same method I used before. I printed up a drill jig on the FDM printer for this one. It just slips directly over the airframe.
DSC07036resize.JPG


Continuing...
Work is progressing nicely. Electronics integration is complete. Testing individual components has commenced.

I'll drop another update shortly :)
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Bench Stand

Postby OverTheTop » Mon Oct 16, 2017 8:39 am

Bench Stand
Some very basic wiring was added to the base, for connection to the VTS.
A momentary pushbutton switch takes care of switching the system between fixed and active modes during bench testing. Having a 3D printed hole to mount it in makes things so easy!
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DSC07044resize.JPG

OnStand.JPG


A voltmeter module and switch was added to read the two battery voltages. The voltmeter module was glued in place using CA glue. These modules are great for having in place for voltage sanity checks when working on stuff. They can be purchased for $2-$5 on eBay, in whatever color you want. There are a couple of different types. Two-wire and three-wire. The three wire ones I have are good for indicating 0-100V on the input line, and require 5-30V to power them. The two-wire versions just measure their supply voltage and are typically only 5-30V or thereabouts.
Just search for “LED voltmeter module” on eBay
voltmeter.jpg
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TRA #13430
L3
"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

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OverTheTop
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Re: Vertical Trajectory System (with some 3D printed parts)

Postby OverTheTop » Fri Oct 20, 2017 7:50 am

TestPlanDone.png


Looking good so far. Now to dial in the required gains...
TRA #13430
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"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

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Re: Vertical Trajectory System (with some 3D printed parts)

Postby SpaceManMat » Fri Oct 20, 2017 8:56 am

Coming along nicely. You see of TRF that Jim busted a servo?
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 10,849 feet
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

User avatar
OverTheTop
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It's only money...
Posts: 2421
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Location: Melbourne, Australia

Re: Vertical Trajectory System (with some 3D printed parts)

Postby OverTheTop » Fri Oct 20, 2017 9:34 am

Coming along nicely. You see of TRF that Jim busted a servo?


I did see that. Interesting it gave up the ghost during the flight. Would be nice to know the failure mode.

Something like that is always a possibility. Hopefully it won't bite me!
TRA #13430
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"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

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SpaceManMat
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Re: Vertical Trajectory System (with some 3D printed parts)

Postby SpaceManMat » Fri Oct 20, 2017 5:24 pm

OverTheTop wrote:
Coming along nicely. You see of TRF that Jim busted a servo?


I did see that. Interesting it gave up the ghost during the flight. Would be nice to know the failure mode.

Something like that is always a possibility. Hopefully it won't bite me!


I imagine it broke a tooth. You should ask him what failed.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 10,849 feet
Largest Motor: CTI 1115J530 IM
Current Project: X Wing


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