BLDC Motor Resynchronization via Digital BEMF Sampling

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Solution Overview

Problem

Brushless DC motors experience delays in responding to control signals due to the need to determine initial position and speed, leading to increased resynchronization time, especially at lower speeds.

Innovation Solution

A system comprising an analog-to-digital converter (ADC), a computing device, and a driver that rapidly samples and processes back electromotive force (BEMF) waveforms to estimate rotor position and speed, enabling quick resynchronization by generating a drive signal based on these estimates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the controller waits to determine initial position and speed before responding to control signals, then measurement accuracy is improved, but resynchronization time increases

Engineering Contradiction:

Improveposition and speed determination accuracyVSAvoidresynchronization time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system performs preliminary sampling and processing of back-EMF waveforms to estimate rotor position and speed before control signals are received. By continuously monitoring and pre-processing the analog BEMF waveform through the ADC and computing device, the controller has position and speed data ready when control signals arrive, eliminating the delay of determining these parameters after signal receipt.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces traditional mechanical or analog measurement methods with digital signal processing. The analog BEMF waveform is converted to digital form through an ADC, then processed by a computing device to extract position and speed information. This digital substitution enables faster, more accurate measurements without the physical delays of traditional methods.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Speed

If the controller rapidly samples and processes BEMF waveforms to reduce resynchronization time, then response speed is improved, but device complexity increases

Engineering Contradiction:

Improveresynchronization speedVSAvoidcontroller complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The controller integrates multiple functions into a single unified system. The computing device performs both the sampling coordination and the BEMF waveform processing, while the ADC serves both conversion and timing reference functions. This multi-functionality achieves rapid resynchronization without proportionally increasing overall system complexity, as components serve multiple purposes within the control loop.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If the system uses analog BEMF waveform sampling to determine position and speed, then measurement accuracy is improved, but signal processing time increases

Engineering Contradiction:

Improveposition and speed estimation accuracyVSAvoidsignal processing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent substitutes digital signal processing for extended analog analysis. By converting the analog BEMF waveform to digital form through an ADC, the system can rapidly process the signal using digital algorithms in the computing device. This digital substitution maintains the accuracy benefits of analog waveform analysis while dramatically reducing the processing time required to extract position and speed information.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach reduces startup time and resynchronization time for brushless DC motors by providing accurate position and speed estimates in a shorter time frame, improving motor response to control signals.

Implementation Method 1

The ADC is configured to receive an analog BEMF waveform from the brushless DC motor and sample the analog BEMF waveform to produce a digital BEMF waveform

Methodology Applied

Scientific EffectAnalog-to-digital conversion:

Implementation Method 2

A brushless direct current (DC) motor includes a rotor and a stator and converts electrical energy into mechanical energy

Methodology Applied

Scientific EffectElectromagnetic conversion: Electromagnetic Induction

Implementation Method 3

analog back electromotive force (BEMF) waveform from the brushless DC motor

Methodology Applied

Scientific EffectBack electromotive force generation: Electromagnetic Induction

Data Source

PatentUS11728751B2Resynchronization of brushless DC motors

Publication Date: 2023.08.15 TEXAS INSTRUMENTS INC

AI summary

A controller is adapted to be coupled to a brushless direct current (DC) motor and includes an analog-to-digital converter (ADC), a computing device, and a driver. The ADC is configured to receive an analog back electromotive force (BEMF) waveform from the brushless DC motor and sample the analog BEMF waveform to produce a digital BEMF waveform. The computing device is coupled to the ADC and is configured to receive the digital BEMF waveform and determine a position and a speed of the rotor based on the digital BEMF waveform. The driver is coupled to the ADC and the computing device and is configured to receive the position and the speed of the rotor and provide a drive signal based on the position and the speed of the rotor of the brushless DC motor.