Tech Report - Kevin

Owned by Kevin Li
2022-01-14
2 min read

Analysis of Alternate Solutions

Power Distribution

To analyze our solutions for power distribution, we began by defining the underlining requirements for all systems requiring power on-board the drone and the associated constraints to the design of our PCB. Power distribution was defined by the following parameters:

  • Required load voltages

  • Battery voltage

  • Total consumed load current on average

  • PCB size/area

By checking each load on-board the drone, it was concluded that no loads required voltages greater than 5V. Thus, a power distribution PCB could be made to generate a 5V output. Any 3.3V loads, which all consumed low current, could then be obtained by converting 5V to 3.3V using linear regulators.

Through flight-time requirements and optimization, it was found that for this particular application, 6S Lithium Polymer batteries could be used to achieve optimal flight time while still being able to carry the required payload mass. This eliminated the potential flight solutions of using 4S or 12S batteries which are suitable battery configurations for some drone applications. This corresponds to an input voltage range between roughly 19.6V-25.2V. Thus, the required buck converter IC to step down the battery input voltage from 19.2V-25.2V to 5V needed to be rated for those input and output voltages.

Based on power consumption analysis, it was determined that on average, all loads would likely consume a total of roughly 5A. With the potential for servos to stall or computer vision hardware to suddenly fluctuate, it was declared that the absolute maximum load current consumption could be 10A. Thus, power distribution could be designed to support 10A load without overcurrent shutdown or failure.

Based on the layout of components on the frame of the drone, the power distribution was constrained to an 80mm by 60mm space. This determined whether or not power distribution could be designed with two buck converters for 24V-5V rated at 5A maximum current or a single buck converter for 24V-5V rated at 10A maximum current. After some preliminary PCB component placement, it was found that the former option could not be completed under the required PCB size. This was because the board needed area for large copper polygons to provide current to the ESCs directed to the motors. With the former option, the polygons would be too small, resulting in poor thermal characteristics.

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