Sensorless FOC Motor Controller Eliminates Current Sampling

Solution Overview

Problem

Existing sensorless field-oriented control (FOC) techniques for motors require current sampling, which necessitates the use of analog-to-digital converters and operational amplifiers, increasing the size and cost of motor controllers.

Innovation Solution

A sensorless FOC motor controller that generates PWM signals using a pulse width modulation (PWM) controller, an angle sampler, and combiners to combine feed-forward voltage and amplitude signals, eliminating the need for current sampling by inferring motor characteristics from voltage and current timing information.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If current sampling is used in sensorless FOC techniques, then motor control accuracy is improved, but device complexity and cost increase due to requiring analog-to-digital converters and operational amplifiers

Engineering Contradiction:

Improvemotor control accuracyVSAvoidcontroller complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the current sampling function from the control system. Instead of measuring current to determine motor characteristics, the system uses only voltage measurements and timing information from voltage transitions to infer rotor position and speed, thereby removing the need for current sensors, analog-to-digital converters, and operational amplifiers

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent substitutes the electrical measurement approach (current sampling with analog-to-digital converters) with a voltage-based timing approach. By measuring the timing of voltage transitions and using feed-forward voltage angle signals, the system replaces complex analog measurement circuitry with simpler digital timing measurements

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If current sampling is used in sensorless FOC techniques, then motor control accuracy is improved, but manufacturing cost increases due to additional components

Engineering Contradiction:

Improvemotor control accuracyVSAvoidmanufacturing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent extracts and eliminates the current sampling function from the control system. Instead of measuring current to determine motor characteristics, the system uses only voltage measurements and timing information from voltage transitions to infer rotor position and speed, thereby removing the need for current sensors, analog-to-digital converters, and operational amplifiers

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces expensive, complex analog measurement components (current sensors, ADCs, operational amplifiers) with simpler, cheaper digital timing measurements and voltage-based inference algorithms, reducing the bill of materials cost while maintaining control functionality

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Measurement precision

If current sampling is used in sensorless FOC techniques, then motor characteristics can be accurately derived, but the controller size increases

Engineering Contradiction:

Improvemotor characteristic measurement accuracyVSAvoidcontroller size

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent extracts and eliminates the current sampling function from the control system. Instead of measuring current to determine motor characteristics, the system uses only voltage measurements and timing information from voltage transitions to infer rotor position and speed, thereby removing the need for current sensors, analog-to-digital converters, and operational amplifiers

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent merges the functions of current measurement, rotor position detection, and speed estimation into a unified voltage-based timing measurement approach. By combining feed-forward voltage angle signals with timing information from voltage transitions, the system achieves multiple measurement objectives using a single simplified methodology

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS8928265B2Sensorless field-oriented control (FOC) without current sampling for motors

Publication Date: 2015.01.06 TEXAS INSTRUMENTS INC

AI summary

An apparatus includes a sensorless field-oriented control (FOC) motor controller. The motor controller includes a pulse width modulation (PWM) controller configured to generate PWM signals and to provide the PWM signals to an inverter. The motor controller also includes an angle sampler configured to receive a commanded voltage angle signal and to provide the commanded voltage angle signal as an output signal in response to a triggering event. The triggering event is based on a voltage or a current associated with an input or an output of the inverter. The motor controller further includes a first combiner configured to combine (i) a feed-forward voltage angle signal and (ii) a second signal based on the output signal. The first combiner is configured to generate the commanded voltage angle signal. In addition, the motor controller includes a second combiner configured to combine a feed-forward voltage amplitude signal and the second signal.