Cascaded Vernier Gearing for Steer-by-Wire Rod Positioning

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Solution Overview

Problem

Existing steer-by-wire systems face challenges in accurately determining the position of the steering actuator's lifting rod due to ambiguities in sensor information, requiring large and expensive sensors, and are prone to mechanical deformation and noise, especially when using single-stage gearings with high transmission ratios.

Innovation Solution

A steering actuator with a two-stage gearing system utilizing three axes of rotation and vernier functions to determine the position of the lifting rod, incorporating sensors integrated into the drive device, which calculates vernier functions to resolve ambiguities and achieve precise positioning without external sensors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a single-stage gearing with high transmission ratio is used, then the transmission ratio is achieved, but the measurement precision deteriorates due to ambiguity of sensor information

Engineering Contradiction:

Improvetransmission ratioVSAvoidposition measurement accuracy

Core Design Contradiction:

PowerVSMeasurement precision

Solution Approach 1:

The single-stage gearing is divided into two separate gearing stages, each with its own sensor. This segmentation allows the system to resolve position ambiguity by combining information from both stages, achieving accurate measurement even with high overall transmission ratio.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a temporal dimension by using two sensors that capture position information at different stages of the gearing. By comparing the phase relationships and counting revolutions across both stages over time, the system resolves the ambiguity that would exist in a single-stage system.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Power

If a large gear wheel is used to achieve high transmission ratio, then the transmission ratio is increased, but the device complexity and installation space increase

Engineering Contradiction:

Improvetransmission ratioVSAvoidgearing structure complexity

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

Instead of using one large gear wheel, the patent segments the transmission into two smaller gear stages. Each stage uses a gear wheel of manageable size, reducing individual component dimensions while achieving the same overall transmission ratio through cascaded gearing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The two gearing stages are nested within each other, with the second stage positioned within the space occupied by the first stage. This nested arrangement reduces the overall footprint and installation space required compared to a single-stage design.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Measurement precision

If measurement is carried out on the gear rack, then the position can be determined, but the measurement is falsified due to deformation under load

Engineering Contradiction:

Improveposition measurementVSAvoidmeasurement accuracy under load

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent extracts the measurement function from the gear rack itself and places sensors on the rotating gear wheels instead. This separates the measurement point from the load-bearing component, eliminating the deformation issue while maintaining position measurement capability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The gear wheels serve as intermediary measurement points between the motor and the gear rack. By measuring the position of the rotating gears rather than the linear rack directly, the system obtains accurate position information without being affected by rack deformation under load.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Reliability

If robust and structurally large sensors are used to handle mechanical loads, then the sensors can withstand load, but the installation space, weight, and noise increase

Engineering Contradiction:

Improvesensor durability under loadVSAvoidsensor weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent extracts the sensors from the load-bearing path by placing them on the rotating gear wheels rather than on the load-bearing gear rack. This allows the use of lighter, more compact sensors that are not subjected to the same mechanical loads, reducing weight and installation space while maintaining durability.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS20250304163A1Cascaded vernier algorithm in a metrologically used two-stage gearing

Publication Date: 2025.10.02 HELLA GMBH & CO KGAA

AI summary

The present invention relates to a steering actuator and to a method for a steer-by-wire system for determining a position of a lifting rod for steering purposes. The steering actuator includes a measuring gearing having a first axis of rotation, a second axis of rotation, and a third axis of rotation. The steering actuator also includes a first sensor for ascertaining a first position of the first axis of rotation, a second sensor for ascertaining a second position of the second axis of rotation, and a third sensor for ascertaining a third position of the third axis of rotation. The steering actuator further includes a control unit for receiving the first position, the second position and the third position. The control unit is configured to calculate a first, second, and third vernier function and to operate the steering actuator.