60 lines
3.4 KiB
Typst
60 lines
3.4 KiB
Typst
#let post_slug = "building-a-drone"
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#let post_preview_image = "top.jpg"
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#let post_summary = "Using a raspberry pi and 3d printer to build a drone from scratch"
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= Building a Drone
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I chose to build a drone from scratch for my AP Physics final project.
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We were given an open ended assignment to _build something cool_
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and I wanted a drone. My choice was much more ambitious than the course required,
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and took quite a while to complete.
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For the drones frame I finally had an excuse to purchase a 3d printer. I
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modelled the frame and arms modularly to support future upgrades and
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replacements from damage, reducing the cost of operation. Initially I
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was using some 3d printed torodial propellers due to their higher
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efficiency and lower sounds usage. Due to safety concerns of the
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propellers not withstanding tension at higher RPMs and exploding I
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switched to some generic acrylic propellers I bought. A challenge in
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designing the frame was leaving enough room to contain the volume of the
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wires. I went with the Elegoo Neptune 3 as the printer was open-source
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and had a much better cost-to-utility than proprietary printers such as
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the Ender series. I am not sponsored I just really like the printer.
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The flight computer was the most difficult part to program. Using an
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ultrasonic distance sensor, gyroscope, and accelerometer the drone has
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enough information to probably never crash. The autopilot is implemented
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on an Arduino UNO using a
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#link("https://en.wikipedia.org/wiki/Proportional%E2%80%93integral%E2%80%93derivative_controller")[PID Controller]
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for stabolization. The autopilot quality is currently impacted every time
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the drones mass distribution changes, which can be fixed with a reinforcement
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machine learning algorithm. For the higher level programming such as flight
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automation, video transmission and WiFi communications I used a Raspberry
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Pi Pico. There is also a 2.4GHz line of sight receiver for manual control.
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A future upgrade may contain a SIM card for near-infinite remote control
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connection, but drone regulations would make this difficult.
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The power system is the most physically challenging portion of the
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drone. The motors took 14.6 Volts, while the UNO microcontroller took 5
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Volts, and the Pico and most sensors run at 3.3 Volts. All of the power
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to the motors ran through the power distribution board, which I modified
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to also output the lower voltages and used Bidirectional Logic Level
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Converters to shift between 3.3 and 5V signals where needed. A potential
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flaw with having all the power coming from the same source is spikes in
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energy consumption to the motors may cause the microcomputers to receive
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too little power, which could be fixed with a capacitor. Luckily, I
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haven't experienced this yet as the 2C discharge rate on the 2.5Ah
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capacity battery is more than enough. Having a battery this big does
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mean it takes up about half the internal electronics volume and is half
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of the drones mass, but it can also maintain full throttle for half an
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hour making for long flights.
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The motors I used were a bit overkill for a 1.1kg drone, as going past
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20% throttle sends it shooting through the sky, which is not a bad
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issue to have. Here's the technical numbers behind that: I have
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propellers with a 6cm radius on motors with a 2450KV rating (2450 rpm
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per volt) and peaking at 14.6 Volts. From this the tip speed is ~225m/s
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under no load at max throttle, quite a lot more than what
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is safe or necessary to get into the air.
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