Set-up of the drive controller

The drive controller consists of a cascade structure of three control loops:

• Inside are two PI current controllers (one controller each for the d- and q-directions)
• A superimposed PI speed controller
• An external P-loop position controller

The Modes of operation parameter can be used to make a choice about which parts of this controller structure are active: current (i.e., torque), speed, or position. In addition to the selected part of the control structure, all subordinate control loops are always active as well.

In addition, each active and subordinate control loop has one internal and one external feedforward control available. Internal feedforward control is calculated as a derivative of the setpoint values; external feedforward control can be specified using process data and, in some cases, statically via CoE parameters.

With the position control mode as the set-up, there is also the Drive motion control (DMC) drive motion control. The DMC is a cycle-synchronous setpoint/trajectory generator integrated into the drive controller. It allows acceleration and deceleration ramps for a motion to be calculated directly in the drive controller rather than in a higher level control system. In DMC mode, all three controllers are therefore active: current, speed, and position. The setpoints (target positions) normally used for these controllers are irrelevant. However, the external feedforward control can still be used if necessary.

The drive controller also incorporates several functions that have a close connection to the actual drive function:

• Holding brake control: An existing motor brake is automatically released as soon as the drive controller is completely in control. It is closed just as automatically before the control loops are shut down.
• The touch probe unit makes it possible to respond with very high temporal precision to external events (reference marks). When signal edges are detected at the corresponding inputs, the current position from the feedback system and the current DC timestamp are recorded.