Velocity Control

The RMC fully supports velocity control. Velocity control can be achieved on either a position axis or a velocity axis.

On a Position Axis:

On a position axis (an axis that has a position feedback, such as an encoder), the RMC can control velocity in several ways:

With Position Moves
The most basic velocity control on a position axis is with standard position moves inPosition PIDmode (the standard control mode). For example, when issuing a Move Absolute (20) command, the speed must be specified in the command. The axis will move at the specified speed until it reaches the requested position.
Continuous Position Control
Velocity can also be controlled on a position axis with the Move Velocity (37) command inPosition PIDmode. In this mode, the Move Velocity command does not actually generate a Target Velocity. Instead, it generates a moving Target Position. Therefore, if the axis falls behind, it will not try to catch up to the Target Velocity; it will actually attempt to catch up to the Target Position. This may cause the axis to move considerably faster than the Target Velocity while it catches up.
The Move Velocity command works well on axes where position is important.
True Velocity Control
True velocity control can be achieved on a position axis with the Move Velocity (37)command in Velocity PID mode. In this mode, the Move Velocity command generates a Target Velocity. A Target Position is not calculated; it is set to the same as the Actual Position. Velocity I-PD mode can also be used for true velocity control.

Velocity control on a position axis is often done with a rotary encoder. See the Using Rotary Motion topic for details on using rotary motion.

On a Velocity Axis:

On a velocity axis (an axis that has a velocity feedback, such as a tachometer), the RMC can control true velocity. Notice that in velocity control on a velocity axis, it is impossible to achieve exactly zero speed. This is because velocity transducers report the speed in voltage, which can never be exactly zero due to its analog nature and noise.

The standard command for velocity control is the Move Velocity (37) command. The Velocity PID mode is typically used for velocity control on a velocity axis. See the Velocity PID topic for more details, such as commands, etc.

For advanced applications, the Velocity I-PD control mode may be used.