Glossary · Motion control and drives
Master axis
Also known as: Leading axis, Master
German: Leitachse
In motion control, a master axis is the axis whose position or velocity serves as the reference for one or more coupled slave axes. It can be a real axis, an encoder on a line shaft or a virtual axis in the controller.
- Motion control
In one sentence
A master axis provides the reference position or velocity that coupled slave axes follow; it can be real or virtual.
Example
On a packaging machine, a virtual master axis sets the machine cycle, and all servo axes follow it with cams or gears.
How it applies
- Engineering: A virtual master decouples machine speed from any one motor and makes speed changes simple. An external master (encoder) links the machine to a process it does not control.
- Commissioning: Master signals must be clean and correctly scaled; noise on an external master encoder disturbs all followers.
- Operation: Stopping or faulting the master affects all coupled axes, so stop behavior must be planned.
- Documentation: Describe the master–slave structure in the software documentation with a diagram. Newer documents increasingly use terms such as "leading axis" and "following axis"; choose one pair, record it in the terminology database and use it consistently.
Master axis vs. real axis
A master axis is defined by its role (reference for others), not by its hardware. It may be real or virtual.