Brushed DC Motor Braking Rotation Estimation via Induced Current

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Solution Overview

Problem

Conventional methods struggle to accurately estimate the rotation amount of a brushed DC motor during a braking operation due to difficulties in detecting motor terminal voltage and pulse period, which hinders precise integration of back electromotive force.

Innovation Solution

Estimate the rotation amount of a brushed DC motor during braking by integrating the induced current over time using an attenuation characteristic curve, based on the induced current flowing through the motor during braking, rather than relying on back electromotive force.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional methods are used to detect motor terminal voltage and integrate back electromotive force, then rotation amount can be estimated during normal operation, but accurate estimation becomes difficult during braking operation due to inability to detect terminal voltage and determine pulse period

Engineering Contradiction:

Improverotation amount estimation accuracyVSAvoidterminal voltage detection difficulty

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The patent uses induced current as an intermediary measurement parameter to indirectly obtain rotation amount information during braking. Instead of directly measuring terminal voltage (which becomes difficult during braking), the system measures the induced current flowing through the motor terminals, which can be easily detected even when terminal voltage is hard to measure. This intermediary approach allows continuous rotation amount estimation throughout all operating conditions including braking.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If conventional back electromotive force integration method is used, then rotation amount can be calculated during normal operation, but the method fails during braking operation when terminal voltage detection is unreliable

Engineering Contradiction:

Improverotation amount estimation accuracyVSAvoidmeasurement reliability during braking

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent changes the measurement parameter from terminal voltage to induced current during braking operation. By switching to measuring induced current instead of terminal voltage, and using the relationship between induced current and rotation speed, the system maintains reliable rotation amount estimation during braking when conventional voltage-based methods fail. The control device calculates rotation amount by integrating induced current over time during the braking period.

Inventive Principle:

Principle #35Parameter changes

3Loss of time

If the motor is stopped by applying same potential to both terminals (braking operation), then stopping time is reduced, but rotation amount estimation becomes inaccurate due to inability to measure terminal voltage and determine pulse period

Engineering Contradiction:

Improvemotor stopping timeVSAvoidrotation amount estimation accuracy

Core Design Contradiction:

Loss of timeVSMeasurement precision

Solution Approach 1:

The patent employs induced current as a mediator to maintain rotation amount measurement capability during rapid braking operations. When the motor is stopped by applying the same potential to both terminals, the induced current flowing through the motor terminals provides a measurable signal that correlates with rotation speed, enabling the control device to calculate and integrate rotation amount even during the accelerated stopping process.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Accurately estimates the rotation amount of the DC motor during braking operations, improving estimation accuracy and enabling precise control of the motor's supply current.

Implementation Method 1

an induced current flowing through the DC motor in a braking operation of the DC motor

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS20250350227A1Rotation amount estimation device, rotation amount estimation method, and motor control device

Publication Date: 2025.11.13 DENSO CORP

AI summary

A curve estimation unit estimates, when a DC motor stops rotation through a braking operation by stopping supply of a drive current to the DC motor and applying a same potential to both terminals of the DC motor, an attenuation characteristic curve of an induced current from start of the braking operation to stop of the rotation of the DC motor, based on the induced current flowing through the DC motor in the braking operation. A time estimation unit estimates a time required from the start of the braking operation to the stop of the rotation of the DC motor. A rotation amount estimation unit estimates the rotation amount of the DC motor in the braking operation based on an integral value obtained by integrating the induced current over the time as estimated according to the attenuation characteristic curve of the induced current as estimated.