TwinCAT NC Axis components
Each axis consists of various elements, depending on the axis type. These elements include the encoder, the drive, the controller and the set value generator, along with the PLC interface. There are also more complex axes consisting of several encoders, switchable controllers or changing set-value generators.
Encoders
Depending on their operating modes, encoders determine the actual position, actual velocity or the actual acceleration. Actual values often fluctuate heavily, so a parameterizable filter is available for each mode to ensure a reasonable resolution. A wide variety of encoders versions is supported. Both absolute and incremental encoders are available. On top of this, there are simulation encoders and special encoders for the determination of force. The encoder parameters include the scaling, zero offset shift and the modulo factor. In addition, the encoder data includes the parameters for the software end locations and for the reference travel.
Drive
The drive transfers the output voltage to the motor's power section. A wide variety of drive versions is supported. Servo drives, a high/low speed drives, and stepper motor drives are available. The drive parameters include the motor polarity and the reference speed.
Controllers
The purpose of the controller is to operate based on the set velocity differences (following error) or other set magnitudes (acceleration) in such a way that the following error is kept as small as possible and that the axis does not undergo any overshoots in position or velocity. A wide variety of controller versions is supported. Servo position controllers and special controllers for particular types of axis are available.
Set value generators
Every axis is assigned to a set value generator, and this in turn consists of three components:
- Block preparation generator (in the block preparation task): checking the start parameters and, in the case of master axes, calculation of the dynamic profile.
- Block execution generator (in the block execution task): calculation of the local set values.
- Asynchronous generator for reaction to asynchronous requirements (override, new end position, position compensation etc.).