DC Motor Rotation Angle Detection from Current-Voltage Oscillations

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Solution Overview

Problem

Existing methods for determining the rotation angle of DC machines in motor vehicles are prone to errors, complexity, and imprecision, especially in the generator operating range due to signal interference, requiring additional hardware and evaluation electronics.

Innovation Solution

A method that combines current and voltage signals from a DC machine to create a combined signal, conditions it to produce a conditioned signal, and analyzes signal oscillations to determine the rotation angle, allowing for precise and reliable determination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If sensors are used to determine the rotation angle, then measurement precision is improved, but device complexity increases due to additional hardware and evaluation electronics

Engineering Contradiction:

Improverotation angle determination precisionVSAvoidhardware and evaluation electronics complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical/sensor-based rotation angle measurement system with an electrical signal analysis system. By analyzing oscillations in the motor current signal, the system determines rotation angle without requiring physical sensors or additional measurement hardware, thus substituting a complex mechanical measurement system with a simpler electrical signal processing approach

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent utilizes the motor current signal that already exists for actuator operation to simultaneously determine the rotation angle. The same electrical signals used to drive the DC machine are also used to extract position information through oscillation analysis, eliminating the need for separate measurement systems and making the existing components serve dual purposes

Inventive Principle:

Principle #25Self-service

2Device complexity

If signal oscillations of motor current are counted to determine rotation angle, then device complexity is reduced, but measurement precision deteriorates in the generator operating range due to signal interference

Engineering Contradiction:

Improveevaluation electronics complexityVSAvoidrotation angle determination precision in generator range

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent changes the analysis parameter from simple oscillation counting to analyzing the frequency spectrum of the motor current signal. By transforming the signal analysis approach and examining frequency characteristics, the system can accurately determine rotation angle even in the generator operating range where signal interference occurs, as the frequency-based analysis is more robust to such interference

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces an intermediary signal processing step that conditions the motor current signal before analysis. This intermediary processing stage filters and prepares the signal to remove interference components, allowing accurate rotation angle determination in the generator range without requiring additional sensors or complex hardware

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12194971B2Method for determining a rotation angle signal of a DC machine, and braking system and program code

Publication Date: 2025.01.14 ZF ACTIVE SAFETY GMBH

AI summary

In order to determine a rotation angle signal of a DC machine precisely, reliably and in a simplified manner, a method is proposed, wherein combining of a current signal of the DC machine and a voltage signal of the DC machine is used to determine a combined signal; wherein conditioning of the combined signal is used to determine a conditioned signal; and wherein a rotation angle signal is determined by analysing signal oscillations of the conditioned signal.