Servo Loop
The servo loop decreases the quantity of error that occurs between the feedback positions and velocities and the commanded positions and velocities.
The units of the servo loop output depend on the type of axis being controlled. Refer to the table that follows.
Table: Servo Loop Axis Type, Output, and Units
| Axis Type | Servo Loop Output and Units |
|---|---|
|
Piezo axis |
Amplifier command in Volts. |
|
Stepper axis |
Commutation angle in microsteps. |
|
All other axes |
Current command in Amps. When the servo loop output is a current command, the current loop is used to generate the amplifier command in Volts. For more information, refer to Digital Current Loop Block Diagram. |
Servo Loop Block Diagrams
- Servo Loop Block Diagram - Typical shows the typical use-case for controlling a mechanical device that contains a single feedback sensor.
- Servo Loop Block Diagram - Single Feedback PI is for spring-like systems such as flexure-based piezo stages and the Yaw (Theta) axis of a rigid H-bridge gantry.
- Servo Loop Block Diagram - Dual Feedback (Secondary I Only) shows the Secondary I method of dual feedback control. This method is more robust than the Secondary PI method and might supply better stability.
- Servo Loop Block Diagram - Dual Feedback (Secondary PI) shows secondary PI method of dual feedback control. This method is high-performing, but it requires a relatively high resolution Auxiliary feedback device with a tight structural loop.
- Servo Loop Block Diagram - Full shows the full servo loop for the Automation1 drives.
