MLMstAbs

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• This information applies to both MLMstAbs and MLAxisAbs.
  For simplicity, the term Axis Block also refers to Master Block.

When the Modulo is turned on, the Axis Block moves to the targeted position during the corresponding period and is calculated as:

• If the Position input is between 0 (zero) and the Modulo position, the Axis Block moves within the current period (no position rollover).
• If the Position input is greater than the Modulo position, the Axis Block moves during one of the next period (positive position rollover).

The Axis Block works similarly for negative positions.

If the Position input is less than 0 (zero), the Axis Block moves during one of the previous period (negative position rollover).

Forcing the Direction of Rotation

In some applications, the direction of rotation for the axis is forced in one direction only.

As a consequence, the motor movement goes to the next or previous modulo in these situations:

End Position is Less Than Start Position

If the End Position is less than the Start Position and the direction of rotation for the axis is forced to be clockwise, the red point shows when the Modulo position is reached.

See Row 2 of the MLMstAbs.

End Position is Greater Than Start Position

If the End Position is greater than the Start Position and the direction of rotation for the axis is forced to be counter clockwise.

See Row 4 of the MLMstAbs.

Example Table

Start Position	End Position	Direction of Rotation	Cross Modulo	Position Input to MLAxisAbs (1)	RelativeDistance Moved (2)
60	200	Clockwise	No	200	140	(i.e., 200 - 60 + 0)
60	30	Clockwise	Yes	390	330	(i.e., 30 - 60 + 360)
60	30	Counter clockwise	No	30	-30	(i.e., 30 - 60 - 0)
60	200	Counter clockwise	Yes	-160	-220	(i.e., 200 - 60 - 360)

With:

(1) Position Input = End Position ( + Modulo * Direction of rotation)

(2) Relative Distance Moved = End Position - Start Position ( + Modulo * Direction of rotation)

Where:

Direction of rotation = 1 when clockwise and -1 when anti-clockwise.

Travel Speed Update with MLAxisAbs

The travel speed of the generator can be updated using the function block MLAxisGenWriteSpd.

Depending on the state of the generator, this speed is directly reflected on the current move or a future move.

• If MLAxisAbs is not currently being executed, the new travel speed is applied for the trajectory calculation for a future MLAxisAbs command.
• If MLAxisAbs is currently being executed, and a new MLAxisAbs with the same target position is called, the new travel speed is taken into account only if the current state of the TMP "Trapezoidal Motion Profile" This pipe block is a source block that frequently serves as a virtual master for a system composed of several pipes. Generally, a trapezoidal motion profile generator is used to generate a flow of values with a first derivative which produces a trapezoidal trajectory profile is the constant velocity or acceleration.
  • If the axis was decelerating to stop at the goal position the new travel speed is not taken into account.
• If a MLAxisAbs is currently being executed, and a new MLAxisAbs with a different target position is called, the new travel speed is taken into account.

Example 1

First MLAxisAbs Second MLAxisAbs Initial Speed New Speed

Figure 6-183: Initial speed is smaller than the new speed.

Example 2

First MLAxisAbs Second MLAxisAbs Initial Speed New Speed

Figure 6-184: Initial speed is bigger than the new speed.

Example 3

Acceleration Constant Velocity Deceleration

Figure 6-185: The speed update is taken into account only if the second MLAxisAbs is triggered during acceleration or constant velocity.