TrackingDeviation

General

Functional Description

TrackingDeviation shows the dead time compensated deviation (tracking deviation) between MechRefPosition and MechPosition in units. It is displayed at the drive shaft (gear box output side) (see Reference and Actual Values). Coordinate displacement with SetPos (FC_SetposDual(), FC_SetposGroup(), FC_SetposSingle()) does not affect this parameter. The parameter Direction must be taken into account when interpreting TrackingDeviation.

The value of TrackingDeviation is calculated one time per Sercos cycle (CycleTime)

Relative to the drive shaft, the TrackingDeviation is delayed by the time ShaftDelay. Thus, a tracking deviation is displayed which is delayed to the drive shaft by the time ShaftDelay. Usually, the tracking deviation calculated in accelerating phases is too high. An acceleration-proportional error is calculated in the displayed tracking deviation during the dead time compensation.

NOTE: The parameter is only available without any constraints for the cyclic type tasks.

Restrictions

On tasks of the External type, the consistency of the RefPosition and the position by the calculation of the TrackingDeviation cannot be provided in every case. An additional, not identifiable dead time of a Sercos cycle can occur. This leads to a detected velocity-dependent error. With the setting type External event-driven and External event MDT_WRITE_ACCESS, the system helps to have a consistent access and provides an accurate value for the TrackingDeviation.

NOTE: The parameter value is calculated in dependency of the parameters that are transferred from the slave to the master via the real-time channel of the Sercos. If the Sercos bus is not in phase 4, then a standard value is indicated here. If the Sercos bus is in phase 4 (operating phase), then the parameter value is calculated and indicated. This parameter has no meaning for asynchronous motors without encoder (in open-loop V / f control mode, ControlMode = open-loop control / 1).