Downhole Actuator Linear Position via Rotary Potentiometer Gearbox

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Solution Overview

Problem

In oil and gas exploration, the use of linear potentiometers to measure the extended length of a piston in a linear actuator consumes significant space, which is not feasible in environments with limited space.

Innovation Solution

Employing a gearbox coupled with a rotary potentiometer to indirectly measure the extension length of the actuator shaft, utilizing a gearbox to reduce multiple rotations of the motor to a measurable range for the rotary potentiometer, allowing for absolute angle measurement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a linear potentiometer is used to measure piston extension length, then measurement capability is achieved, but device volume increases significantly

Engineering Contradiction:

Improvepiston extension length measurementVSAvoidspace consumption in downhole environment

Core Design Contradiction:

Measurement precisionVSVolume of moving object

Solution Approach 1:

A rotary potentiometer is introduced as an intermediary measurement device that does not directly measure linear piston displacement. Instead, it measures the rotational position of a shaft connected to the piston, indirectly providing linear position information through a more compact rotational sensing mechanism.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The linear measurement system (linear potentiometer) is replaced with a rotational measurement system (rotary potentiometer). This substitution changes the measurement approach from direct linear sensing to indirect rotational sensing, achieving the same measurement function with reduced volume.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If a rotary potentiometer is used to measure motor shaft angle, then measurement capability is achieved, but the shaft may rotate more than the maximum rotation limit

Engineering Contradiction:

Improvemotor shaft angle measurementVSAvoidmeasurement validity when exceeding rotation limit

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

A gearbox is introduced as a mechanical intermediary between the motor shaft and rotary potentiometer. The gearbox reduces the rotational speed and range of the motor shaft to a smaller range that fits within the potentiometer's maximum rotation limit, while maintaining accurate angle measurement capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The rotational parameters (speed and angle range) of the motor shaft are transformed through the gearbox to match the operational limits of the rotary potentiometer. This parameter transformation ensures the measurement system operates within its valid range while still capturing the full motion spectrum.

Inventive Principle:

Principle #35Parameter changes

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

Enables accurate measurement of the actuator shaft extension length without occupying excessive space, facilitating efficient control of the piston's extension in confined downhole environments.

Implementation Method 1

The rotary potentiometer may then be used to indirectly measure the extension length of the actuator shaft from the actuator

Methodology Applied

Scientific EffectResistive measurement: Electrical Resistance

Implementation Method 2

utilizing a gearbox to reduce multiple rotations of the motor to a measurable range for the rotary potentiometer

Methodology Applied

Scientific EffectMechanical advantage: Mechanical Advantage

Data Source

PatentUS12460482B2Absolute linear position for downhole tool using rotary potentiometer

Publication Date: 2025.11.04 HALLIBURTON ENERGY SERVICES INC

AI summary

A method, that includes obtaining a calibration curve, reading a voltage from a rotary potentiometer, and calculating an extension length of an actuator shaft, using the voltage and the calibration curve, where a potentiometer shaft, of the rotary potentiometer, is coupled to a potentiometer gearbox, where the potentiometer gearbox is coupled to a motor, and where the motor is coupled to the actuator shaft.