Master Driven Coordinated Control (MDCC)

The Master Driven Coordinated Control (MDCC) instruction defines a Master:Slave relationship between a Master Axis and a Slave Coordinate System.

Available Languages

Ladder Diagram

Function Block

This instruction is not available in function block.

Structured Text

MDCC (SlaveCoordinateSystem, MasterAxis, MotionControl, MasterReference, NominalMasterVelocity);

Operands

Ladder Diagram and Structured Text

Master Reference

The Master Reference for an MDCC instruction selects the Master Axis position source.

The enumerations for Master Reference Axis are:

Actual – Slave motion is generated from the actual (current) position of the Master Axis as measured by its encoder or other feedback device.

Command – Slave motion is generated from the command (desired) position of the Master Axis. Because there is no Command Position for a Feedback Only Axis, if you select either Actual or Command for Master Reference, the Actual Position of the Master Axis is used. The Actual and Command Position are always the same for this case. No error is generated. Because there is no Actual Position for a Virtual axis, if you select either Actual or Command for Master Reference, the Command Position is used. No error is generated.

An error is generated if a MDCC instruction is executed that changes the Master Reference of a Slave Coordinate System that is in motion. The new MDCC instruction errors and the original one remains active.

Nominal Master Velocity

If master driven coordinated move is programmed to run at a speed that equals 100% of maximum and master axis runs at its Nominal Master Velocity, then the coordinated move will run at the configured maximum speed of the coordinate system.

Calculate actual master axis velocity in percentage of the maximum as a percentage of actual master velocity with respect to nominal master velocity. For example, nominal master vel =50 ips therefore actual vel = 40 ips = (40/50) * 100 = 80%.

Calculate actual slave velocity in a percentage of the maximum as a product of programmed slave velocity in the percentage of the maximum and actual master axis velocity percentage of the maximum. For example, programmed slave velocity = 50% of the maximum, master velocity = 80% of the maximum, final slave velocity = 80 * 50 = 40% of the maximum.

Convert final slave velocity in a percentage of maximum to Units/sec as usual. For example, final velocity = 40%, coordinate system maximum is speed 200 Units/sec, final velocity limit is 200 * (40/100) = 80 Units/sec.

Structured Text

See Structured Text Syntax for more information on the syntax of expressions within structured text.

You have the option to browse for enumerations in the Structured Text Editor as shown.

Outputs

Description

MDCC is a transitional instruction:

In relay ladder, toggle the Rung-condition-in from false to true each time the instruction should execute.

In structured text, condition the instruction so that it only executes on a transition.

The Motion Master Driven Coordinate Control instruction (MDCC) is used by the Master Driven Speed Control (MDSC) to synchronize one or more motion axes or Coordinate System to a common Master Axis when the Slave System is a Coordinate System.

The MDCC instruction defines the relationship between the external Master Axis and the Slave Coordinate System for the MCLM and the MCCM Instructions. When an MDCC is executed (goes IP), the specified Slave Coordinate System in the MDCC instruction is logically geared with the designated Master Axis. After motion on the Master Axis is initiated, all the axes in the Coordinate System specified as the Slave Coordinate System follow the Master Axis motion at the programmed dynamics of the programmed instruction.

There are no changes in any active motion when a new MDCC instruction is activated. Activating an MDCC instruction just puts the parameters programmed in the MDCC instruction into a pending state. The parameters in the pending MDCC instruction are changed if you execute a succeeding MDCC instruction before a new MCLM or MCCM instruction is activated. The MDCC becomes active (AC bit is set) only when all queued motion is complete and the motion queue is empty.

All motion in the queue keeps using the same Master Axis even if there is a pending MDCC with a different master. The values in the pending MDCC instruction are only used when the next MCLM or MCCM instruction is activated on the Slave Coordinate System when the queue is empty, or a MCLM or MCCM is executed (goes IP) with a Merge type of All or Coordinate. (Note that this is because the merge empties the queue.)

Motion Direct Command and the MDCC Instruction

To obtain Motion Direct support for the MDCC instruction, you must first program an MDCC in one of the supporting program languages before you execute an MCLM or MCCM in Master driven Mode.

Affects Math Status Flags

No

Major/Minor Faults

None specific to this instruction. A major fault can occur if an uninitialized reference or a reference of the incorrect type is passed to the Coordinate System or Axis operands. See Index Through Arrays for array-indexing faults.

Execution

Ladder Diagram

Structured Text

Error Codes

See Motion Error Codes (ERR) for Motion Instructions.

Verification Errors

An invalid or No Master Axis will cause new errors to be generated when verified by the programming software. The following conditions may cause this error:

Example

Ladder Diagram

Structured Text

MDCC(myMdccSlaveSystem,myMdccMasterAxis,myMdccMotionControl,Command,myMdccNominalMasterVelocity);