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Overview

Requirements table

Requirement ID	Description	Specification
REQ-PWR-01	Input Voltage Support	3S–6S LiPo (11.1V–25.2V)
REQ-PWR-01	Integrated Logic Power	5V @ 5A Buck Converter (for Flight Computer)
REQ-DRV-01	Continuous Current	30A per channel minimum
REQ-DRV-02	Protocol Support	PWM frequency up to 600 kHz
REQ-MECH-01	Form Factor	30.5 mm x 30.5 mm M3 mounting holes

ESC Algorithms

How a BLDC Works

All motors used for a drone need an Electronic Speed Control (ESC) to control speed, direction, and orientation. When it comes to using Brushless DC motors (BLDC) instead of Brushed motors, an ESC becomes significantly more complex due to the fundamental working properties of a BLDC motor.

Mechanism: To put things simply, both BLDC and BDC motors rely on the generation of an induced magnetic field to drive a magnet that creates rotation. A BDC motor has stationary agnets with a brush that brushes against copper coils to induce a magnetic field and cause rotation. A DC motor does not contain brushes, but rather has typically 6 coils that alternate current which induce a magnetic field that attracts a central magnet, causing rotation.

The Analogy: Imagine a compass and you are holding a magnet at a specific location close to the compass. This attracts the needle of the compass because of its magnetic field. You can then move the magnet around the compass and the needle follows. Imagine now 6 magnets placed around the compass that can be ‘turned on’ and ‘turned off’. This is the central idea behind a BLDC motor. Coils are activated, attracting a central magnet to cause constant rotation.

ESC Implementation

Schematic

Because of the alternation of activation of certain coils within the BLDC motor, this requires demanding and precise timing of an ESC of activating those coils to ensure smooth operation.

A BLDC motor has three large wires that connect to 3 pads on an ESC. This diagram shows where those 3 wires connect on an ESC.

Phase Control

The ESC controls 3 phases. Each phase controls 2 of 6 coils within the motor. These two coils are positioned opposite of each other so they work together to rotate the magnet.

When running, one phase is in a HIGH state, one is in a LOW state, and one in FLOAT state (or not active).

HIGH is classified as directing current to 12V
LOW is directing current to ground

HIGH and LOW are active at the same time.