Sensor Mapping¶

Preliminaries¶

Earlier we discussed sensor mapping theory, we will now extend that discussion to creating, modifying and retrieving information about sensors

Sensor Mapping Process:

• Create sensor either manually or in the Optimizer

  • Sensor Properties: Name, Type, Size

• Map sensor to model surface

  • All sensors are initially unmapped

• Repeat as necessary
• Save sensors directly on the model or into a separate file

Strain Gage Basics¶

Sensors are initally placed in the center of the current view. To map the sensor to the model, select and drag it to the desired location.

Strain gages can be selected either using the Sensor Editor GUI or selecting them on the model. It is highly recommended to use the Sensor Editor to select strain gages. Selecting them on the model will result in a slight movement of the gage, and if the sensor is on the opposite surface, it will be pulled through.

Strain Gage Mapping Preferences¶

• Options -> Preferences or Tools -> Preferences within the sensor editor

• Mapping tolerances

  • Increase this tolerance to permit strain gages to be placed in regions of high curvature
  • Used by optimizer

• Logging

  • Enable logging to identify why gages will not map to certain regions of the model

• Reporting: normalization basis

Adjusting Sensor Positions¶

• Strain gages can either be adjusted by drag-n-drop or using user defined increments

  • Translation
  • Rotation

• Available in Sensor Editor

Distancing and Dimensioning (D&D)¶

• Distancing & dimensioning was originally developed in order to translate location information to sensor application technicians

  • Not recommended for precise location definitions
  • Use strain gage position information (in SGA file) and translate to CAD surface
  • D&D using CAD

• However, D&D should be used to adjust the gage positions as needed

  • Parallel to edges
  • Accommodate lead-out wiring and/or substrate size
  • Etc.

• 4 D&D methods are available

  • Gage center to node distance
  • Gage center to element edge
  • Center line to node
  • Center line to edge angle

• Tools -> Distances in the Sensor Editor

If Sensors Do Not Map¶

• Is there too much curvature between faces?

  • Increase the adjacent face normal tolerance under Options -> Preferences

• Do edges of the gage fall of the edge of the model?

• Make sure the gage size is in consistent model units.

• Options -> Preferences

  • Enable “Log Sensor Mappings”

  • Review log file:

    

  • GageMap cannot resolve the natural coordinates of the corner from the underlying element

  • What is the quality of the underlying element?

  • ANSYS models: Were 20 node bricks converted to 10 nodes tets via the TCHG command?

Reports¶

Two Reports are available:

Detailed sensor:

• Requires an active (selected) gage
• Detailed information about the active gage
• IS updated as the gage position is adjusted

Sensor summary:

• Does not require an active gage
• Information regarding the current sensor design
• IS NOT updates as gage positions are adjusted

Mode Identification¶

Cosine of the angle between modes

• Lower the value the higher the angle (cos 0 deg = 1, cos 90 deg = 0), i.e., low = goodness
• 90 deg -> orthogonal (best possible scenario to discern between modes)
• Table entry ~= 0

Misplacement Estimation¶

• Numerical model that estimates the change in strain ratio due to misplacement

  • Internally maps the gage at up to 125 different locations by varying the following:

    • Misplacement along length (X) direction
    • Misplacement along width (Y) direction
    • Rotation

  • Forms a linear least-squares (over determined) problem to estimate coefficients A, B, C, & D
  • Reports model, unperturbed strain ratio and model fit statistics

• Strain ratio range due to misplacement

  • Using the same 125 mappings as above reports just the extrema of the strain ratios