How Electronic Speed Controllers (ESCs) Work in Drones

A BLDC motor consists of a permanent magnet rotor and three stator windings. When DC voltage is applied to one winding, it becomes an electromagnet attracting the rotor magnet, causing rotation. For torque enhancement, voltage is applied to two windings simultaneously with specific polarity sequences. BLDC motors operate on three phases, with voltage applied to two phases per commutation cycle while the third floats. Each commutation moves the motor 60 degrees, completing a full 360-degree rotation in six cycles. An electronic control board manages phase energization. The control board must know rotor position at all times, achieved through Hall effect sensors (providing high/low signals when poles pass) or by measuring back EMF generated by the motor windings.

A brushless DC motor (BLDC) uses a permanent magnet rotor and electromagnetic stator coils, where the electronic controller energizes coils in sequence based on rotor position detected by Hall effect sensors, creating continuous rotation through magnetic attraction and repulsion forces; unlike brushed motors that suffer from brush wear and sparking, BLDC motors achieve higher reliability, efficiency, and constant torque output by using an electronic controller instead of mechanical brushes.

BLDC motors operate based on magnetic force principles where opposite poles attract and like poles repel. Inside the motor, enamel wires are wound around electromagnets. When electricity flows through these electromagnets, they generate magnetic force. A typical commercial BLDC motor contains three electromagnets that change their poles in sequence. The outer case has neodymium magnets attached. As the electromagnet poles change, the outer magnets push and pull, causing the motor to rotate continuously.

A 3-phase brushless DC motor operates using three-phase AC power to create a rotating magnetic field that drives the rotor without physical brushes, offering efficient and reliable operation through electronic commutation instead of mechanical commutation.

A Brushless DC (BLDC) motor is created by modifying a Permanent Magnet DC (PMDC) motor to eliminate mechanical brushes. The working principle involves converting DC supply to AC through electronic commutation, which generates a rotating magnetic field that attracts and rotates the permanent magnet rotor. Electronic commutation must fulfill two critical requirements: convert DC to AC for rotating magnetic field generation, and maintain synchronization between the rotating magnetic field and rotor position to prevent self-starting problems caused by inertia. The stator armature winding is divided into three phases (Phase 1, Phase 2, and Phase 3), each with a main coil side and opposite coil side. A balanced three-phase AC supply has three phases separated by 120-degree phase angles. To analyze how the rotating magnetic field develops, the three-phase waveform is divided into 60-degree intervals. The peak point tracking method determines magnetic pole positions: positive peak indicates North pole, negative peak indicates South pole. This systematic approach reveals that as the three-phase AC supply advances by 60 degrees, the North pole of the rotating magnetic field also shifts by 60 degrees, creating continuous rotation through the stator windings.

Pulse Width Modulation (PWM) is a pulse modulation technique where pulse width changes according to the amplitude of the modulating signal. Unlike Amplitude Modulation (AM) where pulse amplitude changes, PWM maintains constant amplitude while varying pulse duration. The fundamental principle states that pulse width is directly proportional to the modulating signal amplitude. When amplitude increases, pulse width increases; when it decreases, pulse width decreases. The power required to transmit each pulse varies with pulse width, meaning longer pulses require more power. For proper PWM operation, the sampling rate must be greater than or equal to twice the maximum frequency of the modulating signal (Nyquist rate).

Pulse Width Modulation (PWM) is a technique for controlling power to electrical devices by rapidly turning the power on and off. The term can be broken down: 'pulse' refers to a signal that goes on and off, 'width' refers to how long the pulse stays on, and 'modulate' means to change. PWM converts analog signals (continuous values) into digital signals (on/off states) by representing the analog value as a percentage of time that the signal is on within a repeating cycle. This allows computers to control devices like solenoids and throttle positions by varying the duty cycle rather than using continuous voltage levels.

Pulse Width Modulation (PWM) is a fundamental technique for controlling output voltage by varying gate pulse widths. The method generates gate pulses by comparing triangular carrier waves with DC reference signals. PWM operates in two main configurations: single-pulse modulation (one pulse per half-cycle) and multi-pulse modulation (multiple pulses per half-cycle). Multi-pulse modulation reduces lower-order harmonics by increasing pulse count, though this may increase higher-order harmonics that can be filtered. The technique enables precise control of converter output voltage and performance parameters through systematic pulse timing and width adjustment.

Pulse Width Modulation (PWM) is the process of converting an analog control signal (Vc) into a discrete two-level signal (high/low states). The pulse width (Ton) during each switching period Ts is made proportional to the amplitude of the input analog signal. This conversion allows continuous analog information to be represented as time-varying pulse widths, which can then drive power semiconductor switches in switch-mode power converters.

Pulse modulation encompasses three primary techniques: PWM (Pulse Width Modulation), PPM (Pulse Position Modulation), and PCM (Pulse Code Modulation). These methods transmit information through controlled pulses. In PWM, frequency and amplitude remain constant while pulse width varies, encoding information in the duty cycle percentage. A 50% duty cycle means the signal is high for half the period. This technique enables efficient energy transfer by varying average power delivery without changing voltage levels.

A drone requires several core components working together: the flight controller (brain) with sensors like accelerometer, gyroscope, and barometer for altitude control; power distribution board for organized 12V/5V power delivery; ESCs and brushless motors (920KV rating) for propulsion; radio controller with PPM/PWM/SBUS signals for pilot input; LiPo battery (3S, 12.6V max) for power; and propellers (10-inch, 45-degree angle) for thrust. Motor KV rating indicates RPM per volt, with 920KV motors reaching ~11,000 RPM on 3S batteries. Motors must be installed in clockwise/counterclockwise pairs for safety. The control system flows from radio receiver to flight controller to ESCs to motors, with battery power distributed through the power board.

Drones are complex flying machines based on circuits, algorithms, and optimized structures, yet they are composed of remarkably simple components. A basic drone consists of: a frame (the structural backbone), motors with their respective propellers, electronic speed controllers (ESCs), a flight controller (receptor), and a battery. More advanced drones may include additional components such as optical positioning sensors, collision avoidance sensors, and GPS systems. All components are dimensioned together as a system, and removing any single component causes the drone to fail.

The electrical architecture connects all drone components through the flight controller: (1) ESCs (Electronic Speed Controllers), receiver, and GPS connect directly to the flight controller, (2) The flight controller monitors and controls all connected components, (3) ESCs control motor speed based on flight controller signals, (4) All four motors connect to their respective ESCs, (5) The battery delivers power to both the distribution board and flight controller board, (6) The power distribution board distributes power efficiently to all motors.

The drone control system consists of interconnected components: (1) The radio transmitter sends pilot inputs to the receiver, (2) The receiver forwards signals to the flight controller (placa controladora), (3) The flight controller processes inputs and calculates required motor outputs, (4) Electronic Speed Controllers (ESCs) receive commands from the controller and regulate power delivery to individual motors. This hierarchical architecture ensures precise motor control based on pilot input, enabling complex flight maneuvers through coordinated motor speed adjustments.

A drone consists of four brushless motors (without brushes, reducing energy loss), four electronic speed controllers (ESCs) that convert battery voltage to AC and control motor speed via PWM signals (1000-2000 microseconds), a frame that serves as the structural skeleton and distributes power, a flight controller board that integrates sensors (accelerometer, gyroscope, magnetometer) and manages all motor coordination, a radio control system with receiver for wireless operation, a LiPo battery (typically 11.1V or 14.8V) as the power source, and an XT60 cable for battery connection; the frame's internal traces connect all ESCs, eliminating the need for separate power distribution circuits.