Friction measurement for electromechanical liquid level gauges

{
  "publication_number": "US10564023B2",
  "country": "US",
  "kind": "B2",
  "title": "Friction measurement for electromechanical liquid level gauges",
  "abstract": "An electromechanical servo gauge includes a displacer on a wire from a drum for causing a torque on the drum, a servo motor coupled by a drive shaft for rotating the drum, wherein a change in a liquid level moves the ESG out of balance, and a force transducer is positioned for measuring the torque on the drum and converting the torque into a physical quantity. The processor implements an automatic friction determination algorithm. A first move moves the displacer in a first direction for ≥1 motor step(s) to a first position and first physical quantity data including a first physical quantity (Q1) is measured by the transducer. Second moving moves the displacer in an opposite direction ≥1 step(s) to reach a second displacer position and second physical quantity data including a second physical quantity (Q2) is measured. A hysteresis measure is determined from the first and second physical quantity.",
  "claims": [
    "1. A method of measuring friction, comprising: providing an electromechanical liquid level gauge that uses a servo principle (ESG) including a controller having a processor, a displacer suspended on a measuring wire from a measuring drum for causing a torque on said drum having a servo motor with a gear (motor) coupled by moving parts including a drive shaft, and ball bearings associated with said servo motor for rotating said drum arranged to balance a weight of said displacer in a tank, wherein a change in a level of a liquid in said tank (liquid level) causes a change in a counterforce to move said ESG out of balance, a force transducer positioned for measuring said torque on said drum and converting said torque into a physical quantity, wherein said processor includes an associated memory storing an automatic friction determination algorithm executed by said processor automatically implementing: first moving said displacer in a first direction from an initial displacer position for at least one full step of said servo motor to reach at least a first displacer position; obtaining first physical quantity data including at least a first physical quantity (Q1) measured by said force transducer while said displacer is at said first displacer position; second moving said displacer in an opposite direction relative to said first direction for at least one full step of said servo motor to reach at least a second displacer position; obtaining second physical quantity data including at least a second physical quantity (Q2) measured by said force transducer while said displacer is at said second displacer position; determining a hysteresis measure from said first physical quantity data and said second physical quantity data; further comprising generating a graph of a plurality of different positions of the servo motor versus torque for the servo motor, and determining a condition of said ball bearings from whether said graph has a sawtooth pattern.",
    "2. The method of claim 1, wherein said determining comprises calculating |said Q1−said Q2| to determine a hysteresis value.",
    "3. The method of claim 2, further comprising automatically comparing said hysteresis value to at least one predetermined physical quantity value to classify a state of said ball bearings for determining whether to service said ESG.",
    "4. The method of claim 1, wherein said at least one full step for said first moving and for said second moving both comprise a plurality of said full steps, and wherein said obtaining at least said Q1 and said obtaining at least said Q2 each comprise a physical quantity measurement at each of said plurality of said full steps.",
    "5. The method of claim 1, wherein said second displacer position is set to said initial displacer position.",
    "6. The method of claim 1, further comprising determining a friction measure from said hysteresis measure, and automatically correcting at least one measured liquid level value rendered by said ESG based on said friction measure.",
    "7. The method of claim 1, wherein said physical quantity comprises frequency.",
    "8. The method of claim 1, wherein said first displacer position and said second displacer position are both above said liquid level.",
    "9. The method of claim 1, wherein said friction determination algorithm further provides a step of self-diagnosing a need for maintenance of said ball bearings.",
    "10. An electromechanical liquid level gauge that uses a servo principle (ESG), comprising: a controller having a processor; a displacer having a negative buoyancy suspended on a measuring wire from a grooved measuring drum for causing a torque on said drum having a servo motor with a gear (motor) coupled by moving parts including a drive shaft and ball bearings associated with said servo motor for rotating said drum arranged to balance a weight of said displacer in a tank, wherein a change in a level of a liquid in said tank (liquid level) causes a change in a counterforce to move said ESG out of balance, a force transducer positioned for measuring said torque on said drum and converting said torque into a physical quantity, wherein said processor includes an associated memory storing an automatic friction determination algorithm (algorithm) when executed by said processor automatically implementing: first moving said displacer in a first direction from an initial displacer position for at least one full step of said servo motor to reach at least a first displacer position; obtaining first physical quantity data including at least a first physical quantity (Q1) measured by said force transducer while said displacer is at said first displacer position; second moving said displacer in an opposite direction relative to said first direction for at least one full step of said servo motor to reach at least a second displacer position; obtaining second physical quantity data including at least at least a second physical quantity (Q2) measured by said force transducer while said displacer is at said second displacer position, and determining a hysteresis measure from said first physical quantity data and said second physical quantity; further comprising generating a graph of a plurality of different positions of the servo motor versus torque for the servo motor, and determining a condition of said ball bearings from whether said graph has a sawtooth pattern.",
    "11. The ESG of claim 10, wherein said determining comprises calculating |said Q1−said Q2| to determine a hysteresis value.",
    "12. The ESG of claim 11, further comprising said algorithm automatically comparing said hysteresis value to at least one predetermined frequency value to classify a state of said ball bearings.",
    "13. The ESG of claim 10, wherein said at least one full step for said first moving and for said second moving both comprise a plurality of said full steps, and wherein said obtaining at least said Q1 and said obtaining at least said Q2 each comprise a physical quantity measurement at each of said plurality of said full steps.",
    "14. The ESG of claim 10, wherein said second displacer position is set to said initial displacer position.",
    "15. The ESG of claim 10, further comprising said algorithm determining a friction measure from said hysteresis measure and automatically correcting at least one measured liquid value rendered by said ESG based on said friction measure.",
    "16. The ESG of claim 10, wherein said physical quantity comprises frequency."
  ],
  "description_excerpt": "Disclosed embodiments relate to electromechanical liquid level gauges that use the servo principle.\n\nElectromechanical liquid level servo gauges (ESGs) are used for the accurate measurement of product level and the water interface level in bulk storage tanks used for typical hydrocarbons (often referred to as fuel and oil) as well as for a variety of other liquid chemicals. These products range from very light chemicals, including so-called LPG's (mixtures of propane and butane or even liquefied natural gas (LNG)) to all types of refined products such as naphtha, gasoline, diesel, jet fuels, lubricants and all types of chemicals, both pure and mixed.\n\nThe servo principle is based on the measurement of the apparent weight of a displacer that is within the liquid in the tank. The displacer is a mechanical body suspended on a strong thin measuring wire, where the displacer material has a higher density than the liquid to be measured. The measurement wire is wound on a high accuracy machined grooved drum with a calibrated circumference that is coupled to a detection shaft that is coupled to a worm wheel (or servo motor) by ball bearings. The apparent weight resulting from the weight of the displacer minus the weight of the displaced liquid product is measured and is then used by a computing device such as a microcontroller with the servo motor used to rotate drum in order to position the displacer at a different height in the tank.\n\nBy rotating the drum the wire is spooled up or paid out into the tank and the displacer is raised or lowered until the measured apparent weight equals the programmed set point.",
  "cpc": [
    "G01F 23/0076",
    "B65G 43/00",
    "G01F 23/0023",
    "G01F 23/804",
    "G01F 25/20",
    "G05B 2219/42271"
  ],
  "ipc": [
    "B65G 43/00",
    "G01F 23/00"
  ],
  "assignees": [
    "Honeywell International Inc"
  ],
  "inventors": [
    "Ronald Schrier",
    "Dirk Van Duijn",
    "Jan De Goffau",
    "Stephan Walraven"
  ],
  "filing_date": "2016-08-29",
  "publication_date": "2020-02-18",
  "grant_date": "2020-02-18",
  "priority_date": "2016-08-29",
  "application_number": "US-201615250277-A",
  "family_id": "61241915",
  "cited_by_count": 0,
  "citations": [
    "US4786846A",
    "US5012589A",
    "US5243860A",
    "US20090122885A1",
    "JP2010066167A",
    "US20120073354A1",
    "US20130269432A1",
    "US20160194158A1",
    "WO2016037815A1"
  ]
}