Hokuyo CHOP

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Summary

The Hokuyo CHOP is used for serial communication with serial Hokuyo laser scanners (eg. URG-04LX-UG01): Hokuyo Products

All of a computer's available serial ports can be found in the Device Manager under the Windows operating system. Their names begin with 'COM'. Example: COM1, COM2, COM3, etc.

The Hokuyo CHOP outputs the measurement data from the laser scan in meters, either in Polar or Cartesian Coordinates. The laser scan is done counter clockwise over N degrees (defined by the device, eg. URG-04LX-UG01 is 240 degrees) and returns the distance to the first object hit by the laser at that point.

The Hokuyo laser scanners have an angular resolution that specifies the number of data points returned from a full scan. For the URG-04LX-UG01 there is a data point every ~0.3515 degrees, so over a 240 degree scan there is a total of 682 data points. The Hokuyo laser scanners also have a start and end step that define a total detection range. For a visualization of the scan and a table of device specific numbers, see the image below:

Scan info.jpg

See also Serial DAT, serialDAT_Class, Arduino

PythonIcon.pnghokuyoCHOP_Class

Hokuyo CHOP on Old Wiki



Parameters - Connect Page

Active active - This check box enables the connection.

Port port - Selects the COM port that the serial connection will use. Default port names 1 through 8 are available in the popup menu, though any name can be manually entered in this field.

High Sensitivity highsensitivity - This check box enables the high sensitivity mode on the sensor. High Sensitivity mode increases the detection ability of the laser scanner, but with a higher chance of measurement error.

Motor Speed motorspeed - Modifies the motor speed of the laser scanner. This should be used when running multiple laser scanners in the same environment. Different motor speeds across multiple laser scanners will avoid light interference between them.

Start Step startstep - Specifies the first data point of the laser scan. Start step must be a number between first and last measurement point, and must be less than or equal to the end step parameter. Refer to the above table to get device specific first/last measurement points.

End Step endstep - Specifies the last data point of the laser scan. End step must be a number between first and last measurement point, and must be greater than or equal to the start step parameter. Refer to the above table to get device specific first/last measurement points.

Output output - - Outputs the scan data in either Polar or Cartesian coordinates. Polar coordinates outputs the distance to the first object hit at each specific scan angle, in degrees. Cartesian coordinates outputs x, y coordinates of each detected object from the counter clockwise scan, with the center of the device as the origin.

  • Polar Coordinates polarcoords -
  • Cartesian Coordinates cartesiancoords -



Parameters - Common Page

Time Slice timeslice - Turning this on forces the channels to be "Time Sliced". A Time Slice is the time between the last cook frame and the current cook frame.

Scope scope - To determine which channels get affected, some CHOPs use a Scope string on the Common page.

Sample Rate Match srselect - - Handle cases where multiple input CHOPs' sample rates are different. When Resampling occurs, the curves are interpolated according to the Interpolation Method Option, or "Linear" if the Interpolate Options are not available.

  • Resample At First Input's Rate first - Use rate of first input to resample others.
  • Resample At Maximum Rate max - Resample to the highest sample rate.
  • Resample At Minimum Rate min - Resample to the lowest sample rate.
  • Error If Rates Differ err - Doesn't accept conflicting sample rates.

Export Method exportmethod - - This will determine how to connect the CHOP channel to the parameter. Refer to the Export article for more information.

  • DAT Table by Index datindex - Uses the docked DAT table and references the channel via the index of the channel in the CHOP.
  • DAT Table by Name datname - Uses the docked DAT table and references the channel via the name of the channel in the CHOP.
  • Channel Name is Path:Parameter autoname - The channel is the full destination of where to export to, such has geo1/transform1:tx.

Export Root autoexportroot - This path points to the root node where all of the paths that exporting by Channel Name is Path:Parameter are relative to.

Export Table exporttable - The DAT used to hold the export information when using the DAT Table Export Methods (See above).


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