Process Control Actuator Friction Analysis From Stem Force Response

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Solution Overview

Problem

Process control devices in industrial systems face challenges in detecting and managing friction changes, which affect the movement characteristics of actuators and can lead to impaired device operation due to wear, blockages, or inadequate supply pressure, resulting in sluggish or variable responses to applied forces.

Innovation Solution

A method to analyze friction effects by determining the differential force required to move a stem or shaft at different positions, comparing it to a predetermined value using a ratio, and sending alerts when the friction level reaches a predetermined threshold, thereby assessing the impact on movement characteristics such as sensitivity, preciseness, and responsiveness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If friction monitoring is implemented to detect deterioration, then reliability is improved, but device complexity increases

Engineering Contradiction:
Improvedetection of friction-related issuesVSAvoidmonitoring system complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The system uses the existing actuator's force application and position feedback to calculate friction effects, rather than adding separate sensing devices. The controller leverages data already generated during normal operation to assess friction conditions, making the monitoring system self-sufficient without external additions.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent replaces physical friction sensors with a computational approach that calculates friction effects from force and position data. Instead of mechanical measurement devices, the system uses mathematical relationships between actuator forces, stem positions, and friction models to detect deterioration.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If continuous monitoring of movement characteristics is performed, then reliability is improved, but use of energy increases

Engineering Contradiction:
Improvemonitoring of movement characteristicsVSAvoidenergy for monitoring operations
Core Design Contradiction:
ReliabilityVSUse of energy by moving object

Solution Approach 1:

The system continuously monitors friction effects using data already being collected during normal actuator operation. By leveraging the continuous position and force data already generated during useful work, the monitoring function runs without requiring separate energy-intensive measurement systems.

Inventive Principle:
Principle #20Continuity of useful action

Solution Approach 2:

The monitoring system uses the actuator's own operational data (force application and position feedback) to assess friction conditions. This self-service approach eliminates the need for additional sensors and processing systems that would consume extra energy.

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP3418824B1Methods and apparatus for analyzing effects of friction on process control devices
Publication Date: 2023.01.25 FISHER CONTROLS INT LLC
  • EP3418824B1 patent drawingFigure 1
  • EP3418824B1 patent drawingFigure 2
  • EP3418824B1 patent drawingFigure 3

AI summary

An apparatus, comprising a housing; a processor disposed in the housing, the processor to determine a first force or torque corresponding to friction of a process control device and an actuator operatively coupled to the process control device via a stem or shaft; in response to the first force or torque, determine a first command to operate the process control device via the stem or shaft to obtain a first response of the actuator; determine a second force or torque corresponding to friction of the process control device and the actuator; and in response to the second force or torque, determine a second command to operate the process control device via the stem or shaft to obtain a second response of the actuator.