Cam-Based Steer-by-Wire Angle Sensor for Shock Resistance

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Solution Overview

Problem

Traditional angular measurement devices for steer-by-wire systems, such as disc-shaped optical encoders, are fragile and prone to failure under heavy shock and vibration loads, requiring additional sensors to determine direction of rotation and lacking robustness for off-road vehicles.

Innovation Solution

A device using a cam with two sensors positioned to detect distance changes over specific portions of its surface, allowing a processor to determine the angular position and direction of rotation without the need for additional sensors, and featuring a robust design to withstand heavy loads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If disc-shaped optical encoders are used to measure angular displacement, then the system can determine angular position, but the device becomes fragile and prone to failure under heavy shock and vibration loads

Engineering Contradiction:

Improveangular position measurementVSAvoidrobustness under shock and vibration

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the mechanical disc-shaped encoder with a cam-based system that uses a follower sensor to track the contour of a cam lobe. This mechanical substitution eliminates the fragile disc structure while maintaining angular measurement capability through the cam's rotational profile, which the follower detects to determine steering wheel position.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

Instead of having the sensor rotate with the steering wheel (as in traditional encoders), the patent inverts the approach by keeping the sensor stationary and having the cam rotate. The follower sensor remains fixed while the cam profile passes by, allowing angular measurement without subjecting the sensor to rotational stresses and vibrations.

Inventive Principle:

Principle #13The other way round (Inversion)

2Device complexity

If a single sensor is used to detect angular position, then the device complexity is reduced, but the direction of rotation cannot be determined

Engineering Contradiction:

Improvenumber of sensorsVSAvoiddirection of rotation information

Core Design Contradiction:

Device complexityVSLoss of information

Solution Approach 1:

The patent adds a temporal dimension to the measurement by using a single stationary sensor to detect changes in the cam profile over time. The follower measures the distance to the cam surface at different rotational positions, and by analyzing the sequence of measurements over time, the system can determine both angular position and direction of rotation from a single sensor's data.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Measurement precision

If the number of slots around the circumference of the disc is increased to improve angular resolution, then the measurement precision is improved, but the disc becomes even more delicate and fragile

Engineering Contradiction:

Improveangular resolutionVSAvoidstructural integrity of disc

Core Design Contradiction:

Measurement precisionVSStrength

Solution Approach 1:

The patent replaces the slot-based disc encoder with a continuous cam surface that has no slots or openings. The cam's outer surface forms a complete, solid structure that is inherently stronger and more resistant to shock and vibration. Angular resolution is achieved through the precise contouring of the cam profile rather than through discrete slots, eliminating the structural weakness of slotted designs.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution provides accurate and reliable angular displacement measurement and direction determination, enhancing the robustness and reliability of steer-by-wire systems in off-road vehicles by eliminating the need for additional sensors and reducing the risk of mechanical failure.

Implementation Method 1

optical encoders which detect angular displacement based upon a detection of light transmission and/or blockage through a rotating object

Methodology Applied

Scientific EffectLight transmission and blockage detection: Photoelectric Effect

Data Source

PatentUS8380397B2Off-road vehicle with redundant non-contact multi-revolution angle sensor

Publication Date: 2013.02.19 CNH INDUSTRIAL AMERICA LLC

AI summary

An off-road work vehicle has a steer-by-wire steering system having a device for determining the angular displacement of a steering wheel. The device has a cam configured to rotate about an axis at an identical angular speed as the steering wheel, a first sensor proximal to a facing outer surface of the cam and being configured to determine a distance between the first sensor and the facing outer surface of the cam, a second sensor proximal to a facing outer surface of the cam and being configured to determine a distance between the second sensor and the facing outer surface of the cam, and a processor operably connected with the first and second sensors and configured to determine an angular position of the steering wheel and a direction of rotation of the steering wheel based upon data generated by the first and/or the second sensor. The distance between each of the first and second sensors and the facing outer surface of the cam changes gradually over a first major portion of the facing outer surface and sharply over a second, minor portion of the facing outer surface. The two sensors are redundant to one another and help maintain the robustness of the system.