Motor Field Weakening Control via Rotor Velocity

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Solution Overview

Problem

Existing motor control systems during field weakening operations face inefficiencies due to resource-intensive calculations and reduced accuracy from relying on indirectly calculated flux values, leading to current regulator saturation and over-current faults.

Innovation Solution

A motor control system that generates a field weakening command by adding a field weakening adjustment signal to the rotor angular velocity signal, allowing for direct calculation of achievable current commands and reducing unnecessary processing, thereby improving motor efficiency and preventing current regulator saturation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If field weakening control is implemented using feedback and feedforward flux values, then motor efficiency is improved, but processing time increases and accuracy decreases due to resource-intensive calculations

Engineering Contradiction:

Improvemotor efficiencyVSAvoidprocessing time

Core Design Contradiction:

Loss of energyVSLoss of time

Solution Approach 1:

The patent extracts only the essential information needed for field weakening control by directly using rotor angular velocity from sensors, eliminating unnecessary flux calculation components. This extraction approach removes resource-intensive calculations while retaining the core control function, thereby improving processing speed without sacrificing motor efficiency.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of calculating flux from other measured values (the conventional approach), the patent inverts the methodology by directly using rotor angular velocity as the basis for field weakening commands. This inversion eliminates the intermediate calculation step, reducing processing time while maintaining control accuracy.

Inventive Principle:

Principle #13The other way round (Inversion)

2Adaptability or versatility

If unachievable current commands are provided to the current regulator, then field weakening control is attempted, but current regulator saturation occurs and performance deteriorates

Engineering Contradiction:

Improvefield weakening control capabilityVSAvoidcurrent regulator performance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent implements feedback by using actual sensor measurements of rotor angular velocity to generate achievable current commands. This feedback mechanism ensures that the field weakening commands are based on real-time motor state, preventing unachievable commands that would cause current regulator saturation and maintaining reliable operation.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the approach from calculating theoretical flux values to directly using measured rotor angular velocity as the control parameter. This parameter change ensures that the field weakening commands are based on achievable physical conditions, preventing current regulator saturation while maintaining field weakening control capability.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If indirectly calculated flux values are used for field weakening commands, then control is achieved, but accuracy is reduced

Engineering Contradiction:

Improvecontrol implementationVSAvoidfield weakening command accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent enables the control system to use its own sensor measurements ( rotor angular velocity) directly for field weakening control without requiring external flux calculations. This self-service approach eliminates the need for indirect calculations, improving accuracy while maintaining ease of operation through straightforward sensor-based control.

Inventive Principle:

Principle #25Self-service

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

The system enhances motor efficiency by eliminating resource-intensive calculations and ensuring accurate current commands, preventing current regulator saturation and over-current faults during field weakening operations.

Implementation Method 1

a sensor configured to generate a rotor angular velocity signal indicative of an angular velocity of a rotor of the motor

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

currents within components (e.g. field windings) of the motor create an electromagnetic flux, and a rotating member of the motor is caused to rotate by interaction with the magnetic flux

Methodology Applied

Scientific EffectElectromagnetic interaction: Electromagnetic Induction

Implementation Method 3

the motor will generate a counter-electromotive force ('back EMF') that opposes the voltage applied to the motor

Methodology Applied

Scientific EffectBack EMF: Electromagnetic Induction

Data Source

PatentUS8779702B2Motor control system implementing field weakening

Publication Date: 2014.07.15 CATERPILLAR INC

AI summary

A control system for use with a motor is disclosed. The control system may have a controller that is configured to receive a torque command for the motor and receive a rotor angular velocity signal indicative of an angular velocity of a rotor of the motor. The controller may also be configured to generate a field weakening command by adding a field weakening adjustment signal to the rotor angular velocity signal, and generate a torque voltage command and a flux voltage command based on the torque command and the field weakening command. Further, the controller may be configured to convert the torque voltage command and the flux voltage command into phase voltage commands and output the phase voltage commands.