Calibrating a Tool Point

This procedure enables you to adjust the tool profile of a robot based on measurements of multiple points. Select a robot and a tag group representing uploaded mount plate positions; you are subsequently provided with tool calibration results. The positions and orientations of the tag points of the mount plate tag group are significant for this procedure. However, only the tool profile position [X, Y, Z] will be adjusted; the tool profile orientation is not changed.

Before you begin: You must have:
  • a robot with a predefined tool profile
  • a tag group generated at the robot's mounting plate while moving the tool tip to a fixed point in space at different orientations of the robot's wrist.
  • an initial guess for the tool point parameters. The guess should be within a few centimeters of the actual tool parameters.
Note: Clicking Undo while this command is active causes the command to cancel.
See Also
About Tool Point Calibration
  1. Click Tool Point Calibration .
  2. Select the robot whose tool point you wish to adjust.
  3. Select the tag group that represents the simulation points used to compute the true TCP. (Typically, this tag group is uploaded.)
    Two dialog boxes appear:
    • Default TCP Values
    • Calibration Parameters
  4. Alter the tool point parameters as desired.
    1. Select the desired tool profile (the default value is Default)
    2. Translate X, Y, Z (i.e., set as Free or Fixed). This step specifies which components of the tool frame are to be adjusted. Unless the resource is known to be aligned with an axis or on a plane, the [X, Y, Z] parameters should all be set Free during calibration.
    3. Set the estimated measurement noise, which is an estimate of the uncertainty of the positional measurements during the calibration experiment. The measurement noise need only be an order of magnitude estimate, for example 0.1 mm or 1.0 mm.
  5. Click OK.

    The tool point Calibration Results dialog box appears.

    The table below describes the values provided:

    Value Explanation
    Maximum uncertaintiesThis value represents the maximum of the uncertainties for the fit on the parameters to be identified. Large uncertainty values are an indication that the experimental observation strategy is flawed, even if the RMS fitting error is small.
    Number of iterations to convergenceThe number of iterations required by the numerical identification method.
    Number of fitting tag points The number of points used for the least squares fitting procedure.
    Root mean square fitting error The root mean square fitting error on the points after adjusting the tool profile to the best fit possible.
    Note: The robot's tool profile is adjusted in an attempt to get the tool tip to move to the same point in space from each of the different wrist orientations. The algorithm works by minimizing the mean square position error between the tool tip positions from each of the mounting plate tag points while maintaining the constraints of the Translate X, Y, Z selections.
  6. Click OK when completed.