Ripple Count Circuit for DC Motor Speed and Position Sensing

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Solution Overview

Problem

Conventional DC motor position systems using Hall Effect Sensors and magnetic rings are expensive and complex, requiring additional computations to determine rotor speed, leading to longer processing times.

Innovation Solution

A motor control system with a ripple count circuit that extracts the AC signal from the armature current to generate a pulsed output indicative of the rotor speed and position, eliminating the need for expensive controllers and magnetic rings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If Hall Effect Sensors and magnetic rings are used to determine rotor speed, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improverotor speed measurementVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts the speed measurement information directly from the existing drive current signal by filtering out ripple components, eliminating the need for separate magnetic rings and Hall Effect sensors. The ripple count circuit processes the current already flowing through the motor windings to derive rotational speed data.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The drive current serves multiple functions: it both drives the motor and provides the signal source for speed measurement. The same current that powers the motor also contains ripple information that, when filtered, reveals rotational speed, making the system more efficient and less complex.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If Hall Effect Sensors and magnetic rings are used to determine rotor speed, then measurement precision is improved, but processing time increases

Engineering Contradiction:

Improverotor speed measurementVSAvoidprocessing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent extracts speed information directly from the drive current's ripple components through filtering, avoiding the need for separate sensor signal processing. This direct extraction method reduces computational overhead and processing time compared to conventional sensor-based systems.

Inventive Principle:

Principle #2Taking out (Extraction)

3Measurement precision

If Hall Effect Sensors and magnetic rings are used to determine rotor speed, then measurement precision is improved, but manufacturing cost increases

Engineering Contradiction:

Improverotor speed measurementVSAvoidmanufacturing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent eliminates expensive magnetic rings and Hall Effect sensors by extracting measurement information from the existing drive current. The ripple count circuit uses only the current already present in the motor system, significantly reducing component costs and simplifying manufacturing.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces expensive, delicate magnetic components with a simple electronic filtering circuit that processes existing electrical signals. This substitution with cheaper electronic components reduces manufacturing costs while maintaining measurement functionality.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 effectively determines rotor speed and position without expensive digital controllers or magnetic rings, reducing complexity and processing time while providing accurate rotational data.

Implementation Method 1

The amplifier is configured to amplify a drive current that drives rotation of a rotor included in a direct current (DC) motor

Methodology Applied

Scientific EffectElectrical amplification:

Implementation Method 2

The bandwidth filter is configured to filter the derivative current signal based on a rotational speed (ω) of the rotor

Methodology Applied

Scientific EffectFrequency filtering: Filter (electronic)

Implementation Method 3

The downstream low pass filter is configured to filter the first filtered signal based on the rotational speed (ω) of the rotor so as to output a second filtered signal that eliminates harmonics

Methodology Applied

Scientific EffectLow pass filtering: Filter (electronic)

Implementation Method 4

The comparator circuit is configured to compare the second filtered drive current to a reference voltage potential, and generate a pulsed output signal

Methodology Applied

Scientific EffectVoltage comparison:

Implementation Method 5

The DC motor includes a rotor induced to rotate in response to a drive current generated by a variable supply voltage

Methodology Applied

Scientific EffectElectromagnetic conversion: Electromagnetic Induction

Data Source

PatentUS11177809B2Ripple count circuit

Publication Date: 2021.11.16 INTEVA FRANCE

AI summary

A motor control system includes a variable voltage supply in signal communication with a direct current (DC) motor. The DC motor includes a rotor induced to rotate in response to a drive current generated by a variable supply voltage delivered by the voltage supply. The rotation of the rotor generates a mechanical force that drives a component. A ripple count circuit is configured to filter the drive current based on a rotational speed (ω) of the rotor, and to generate a pulsed output signal indicative of the rotational speed (ω) of the rotor and a rotational position (θ) of the rotor.