Fine Position Sensor Cam System for Large Shaft Angle Measurement

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Solution Overview

Problem

Current systems fail to accurately measure large gimbal angles with the precision required for applications like high-precision telescope pointing, as they struggle with precise measurement of angles up to 360 degrees due to manufacturing imprecision and wobbling axes of rotation.

Innovation Solution

A system utilizing high-precision Fine Position Sensors (FPSs) with cams designed to have specific harmonics, where pairs of sensors measure differential radial displacement during rotation, and a processor analyzes these measurements to determine the large shaft rotation angle and angular displacement relative to an ideal axis of rotation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional angle measurement systems are used for large gimbal angles, then the measurement range covers up to 360 degrees, but the measurement precision deteriorates due to manufacturing imprecision and axis wobble

Engineering Contradiction:

Improvegimbal angle measurement precisionVSAvoidmeasurement accuracy under large angle rotation

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces traditional mechanical angle measurement systems with a signal-based measurement approach. Fine position sensors (FPS) detect the position of a cam mechanism, and through signal processing algorithms, the system determines large gimbal angles with high precision. This substitution eliminates the cumulative errors inherent in mechanical encoders while maintaining 360-degree measurement capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a cam mechanism as an intermediary between the rotating shaft and the fine position sensors. The cam converts rotational motion into radial displacement that the FPS can accurately measure. This intermediary allows the system to measure large rotation angles by detecting small, precise radial movements rather than directly measuring large angular displacements.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If high precision measurement is required for telescope pointing applications, then sub-microradian accuracy is needed, but traditional systems cannot achieve this due to axis wobble and manufacturing limitations

Engineering Contradiction:

Improveangle measurement accuracyVSAvoidaxis wobble and manufacturing imprecision

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent employs feedback through the cam mechanism and fine position sensors to continuously monitor and detect axis deviations. The system measures the actual position of the rotating component relative to the ideal axis, allowing for real-time detection of wobble and manufacturing errors. This feedback enables precise measurement despite the presence of harmful factors like axis wobble.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent converts the harmful effect of axis wobble into useful measurement information. By using the cam mechanism to translate axial deviations into radial displacements that the FPS can detect, the system transforms manufacturing imperfections and axis instability into measurable signals that can be processed to achieve sub-microradian accuracy.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Measurement precision

If flexure-based mechanisms are used for angular measurement, then high precision is achieved for small angles, but the measurement range is limited to a few degrees

Engineering Contradiction:

Improveangular measurement precisionVSAvoidangular travel range

Core Design Contradiction:

Measurement precisionVSLength of moving object

Solution Approach 1:

The patent segments the measurement function into two parts: the cam mechanism handles the large rotation range by converting rotational motion into radial displacement, while the fine position sensors provide high-precision measurement of these radial displacements. This segmentation allows the system to achieve both large angular travel and high measurement precision that neither component could achieve alone.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS10030963B2Multidimensional angle determination using fine position sensors

Publication Date: 2018.07.24 RAYTHEON CO

AI summary

A method for measuring a large shaft rotation angle utilizes one or more cams attached to the shaft. Each cam shape is designed to have one or more detectable harmonics when rotated. Multiple harmonics in a single cam or amongst multiple cams may have a particular order. Pairs of fine position sensors, positioned at opposing sense angle positions relative to the cam(s) measure displacement of the cam during rotation. The data from the position sensors is then analyzed, with a processor, to determine the large shaft rotation angle and angular displacement relative to an ideal axis of rotation.