Glossary · Motion control and drives
Axis (motion control)
Also known as: Motion axis, Drive axis
German: Achse
In motion control, an axis is a single controlled degree of freedom of a machine, consisting of a drive, a motor, a feedback device and the mechanics that move a load along or around one direction. The controller commands the axis by position, velocity or torque.
- Motion control
In one sentence
An axis is one controlled degree of freedom of a machine: drive, motor, feedback and mechanics moving a load in one direction.
Example
A gantry robot has an X, a Y and a Z axis; each is driven by its own servo motor and ball screw and is homed at startup.
How it applies
- Engineering: In the control program each axis is an object (for example an axis reference used by PLCopen motion control function blocks) with its own scaling, limits and state machine.
- Commissioning: Each axis is scaled to engineering units, tuned (current, velocity and position loop), given software limits and homed.
- Operation: Axes can move independently, in Interpolation (motion control) with other axes or coupled to a Master axis.
- Documentation: Name axes consistently in drawings, HMI texts, alarm messages and manuals ("axis Y2" everywhere, not "lift" in one place and "Y2" in another). List travel ranges, speeds and the direction convention, and describe the Linear motion or Rotary motion hazards each axis creates.
Physical axis vs. virtual axis
A physical axis moves real mechanics. A virtual axis exists only in the controller; it generates a position profile that real axes follow, for example as the master of an Electronic cam.