# Control by CNC

With spindles, the limit at which the measuring system no longer supplies a valid signal may be exceeded at a higher speed. The parameter P-AXIS-00220 (vb_regelgrenze) specifies the speed at which the position control loop is opened and transits to speed-controlled mode. The actual values which are defined by the position lag depending on the specified speed are simulated automatically.

Control is automatically resumed starting from endless rotation when the control limit is undershot. However, the reference point is then lost. This is why referencing must be repeated before a positioning motion.

## Notice

With digital drive systems (e.g. SERCOS), the drive executes the control and monitoring of the control limit.