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I am a newbie to embedded systems design so this question might seem very fundamental in nature.

I have been working as part of an Avionics team to develop an on board computing device for a unmanned aerial vehicle which would need to interact with various subsystems like camera, ir sensors, actuators, etc. We will be using a customized board design for this purpose, the cost of which comes to approx. 200k INR. Someone at work proposed why not use the chip inside a general purpose computer for the purpose or even a smartphone. The computer would cost between 50-60k while a smartphone would cost 20k which is cheaper than a customized board design. The idea seems ridiculous because of obvious reasons.

Firstly, the power consumption for a laptop board would be far more than any electronic board. But the same can't be said for a smartphone.

Secondly, an onboard computing device will require much more interfaces than a general computer/smartphone would provide.

The electronic board can be interacted with using several development kits like Vivado which I don't believe is possible in PCs/phones without an OS. I am not sure about this point.

Lastly, any smartphone/pc will be prone to bugs by design. We generally see laptops crashing and phones not reacting to touch commands which we can't afford in a real time based system like an unmanned aerial vehicle.

I gave the above arguments but none seem to be compelling enough to make someone of a non technical background understand this point. Is there an obvious/compelling reason which would prove the validity of my points to someone who doesn't have technical knowledge and is only concerned about bringing down the costs?

Edit: The unmanned vehicle needs to be mil-grade precise in our application, so it will need to handle a good amount of data efficiently that too in real-time while interacting with various sensors like camera, ir sensors, etc.

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    \$\begingroup\$ This is essentially a raspberry pi. There are also a huge number of 'single board computer' manufacturers who make industrial grade raspberry pi style systems. If the 200k costs of rolling your own doesn't make sense for your project, then you should have a look at one of them. \$\endgroup\$ – Jon May 27 '17 at 10:23
  • \$\begingroup\$ Will the heat dissipation, at continual 100 frames/second, of the smartphone cause overheating? \$\endgroup\$ – analogsystemsrf May 27 '17 at 10:44
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    \$\begingroup\$ You won't get commercial grade equipment (0..70°C) through avionics equipment qualification (-40..85°C operating). \$\endgroup\$ – TonyM May 27 '17 at 11:02
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    \$\begingroup\$ You might use any of the things named above a hobby project or a university assigment or research. You almost certainly won't want or be able to use them in a commercial system - and military use is right out. \$\endgroup\$ – JRE May 27 '17 at 11:27
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    \$\begingroup\$ If a purpose built embedded system to mil-spec and aviational reliability and recovery only costs ten times as much as a common phone, you are either doing pretty decent volumes, or your management should stop griping about it and just start the development. Assuming the Architect of the project isn't grossly mis-estimating the total dev cost. Having something that is guaranteed to not crash (metaphorically, or literally) is no small feat, regardless whether you put that responsibility in firmware or hardware. Especially at higher elevations. \$\endgroup\$ – Asmyldof May 27 '17 at 11:27
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Yes, you can replace an embedded solution with standard parts. However, you might not be able to.

For example, you listed specs such as:

  • mil environment, temperature, vibration, reliability.
  • real time software
  • avionics (weight and size restrictions?)

You won't get a standard pc or smartphone outside 0 to 40 degree ambient. They are also not real time at all, you will have to start bare metal software. Or at least, get some custom kernel running. And that is hard, because you won't have documentation.

You might be able to get a small industrial pc without moving parts for $2000, carrying an ssd and some mobile intel chip with build-in IO. (CAN, rs-485, io)

You can use PLC controllers, they come in various forms and classifications. But they are large and expensive as well.

What you can do however, is call around for oems supplying processor and io boards. Various companies do, for example in the automotive sector there are only a few companies making the actual hardware.

There won't be a catalog and price on their website. You have to ask, its a niche and closed market.

With these boards you can save a lot of time, which is also expensive. You might still need to fabricate an enclosure or interfacing boards. But the most difficult part, the multilayer cpu board, will be ready.

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It seems you are looking for something called a single board computer. These things exist in many varieties and tradeoffs, and the industry is quite competitive. You can get something beefy enough to run Windows 10 IOT, for example, for $350, including the Windows license and 0-70°C operating temperature. There are also ruggedized fanless computers in small boxes for a bit more money.

In your case, you have to look carefully at the operating temperature rating, and get something designed for a high-vibration environment. That's basically the difference between something low end like a Raspberry Pi and a real industrial SBC.

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