Open position loop mode for spindles
Functionality
For simple applications it might be appropriate to operate a spindle not in a closed position control loop but simply by outputting velocity commands.
Drive types
Configuration of a sensor less spindle is possible for drive types Terminal, Lightbus, and EtherCAT/Canopen.
Mode of operation
For a spindle in open position loop mode the velocity command value of the path interpolator is output to the axis and not the set value of the position controller.
The acknowledgement of velocity commands to the spindle is derived from the actual values telegram in the following order:
- If an actual position value is configured the actual velocity of the axis is calculated from the actual values. The encoder resolution must be set up in this case.
- If an actual velocity and no actual position is configured the actual velocity is used to acknowledge velocity commands.
- If there is neither a position actual value nor a velocity actual value configured (sensor less spindle) the acknowledgement of velocity commands is derived from the internal command velocity value. The command velocity is considered reached when the internal cycle by cycle calculated velocity command value is within the tolerance set up in the axis parameter list.
By nature, a sensor less spindle cannot be used for positioning tasks. If it is tried to use a spindle that way an error message is output.
To get the actual velocity of the spindle equal to the programmed spindle velocity the velocity scaling factor must be set up correctly.
 | For terminal drives offset voltages can lead to a slow spindle movement although a spindle velocity of zero is programmed. |