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MC_Reference

Description

This function block is used to execute a fast home to a switch. If the application selects to reference to the index mark of an encoder, or the null of a resolver (which is typical), the new position value is assigned to the position of the index of the encoder (or the null of the resolver) and not the position of the switch. The ECATWriteSDO function block is used to setup the trigger event and any desired preconditions. This function block utilizes the Position Capture Mode of the AKD.

At this time, position capture is not available for PLCopenA vendor -and product- independent worldwide association active in Industrial Control and aiming at standardizing PLC file formats based on XML axes assigned to the secondary feedback input (digitizing axes). Therefore, MC_Reference cannot be used to home digitizing axes at this time.

MC_Reference

Figure 11-151: MC_Reference

When using position-based capture, the proper Capture Mode and FB Source may need to be set up in the drive. One place to do that is in the Position Capture Screen in the KAS IDE"Integrated development environment" An integrated development environment is a type of computer software that assists computer programmers in developing software. IDEs normally consist of a source code editor, a compiler and/or interpreter, build-automation tools, and a debugger embedded WorkBench:

When setting up Position Capture, check the CoE-Init Command settings shown below. This is to verify they do not overwrite the corresponding drive parameters with unwanted values when the EtherCATEtherCAT is an open, high-performance Ethernet-based fieldbus system. The development goal of EtherCAT was to apply Ethernet to automation applications which require short data update times (also called cycle times) with low communication jitter (for synchronization purposes) and low hardware costs network initializes.

Arguments

For more detail on how inputs and outputs work, refer to PLCopen Function Blocks - General Rules

Input

Execute	Description	Requests to queue the MC_Reference move and arms reference trigger events
	Data type	BOOL
	Range	0, 1
	Unit	n/a
	Default	—
Axis	Description	Name of a declared instance of the AXIS_REF library function. For more details,About Axis Name and Number)
	Data type	AXIS_REF
	Range	[1,256]
	Unit	n/a
	Default	—
TriggerInput	Description	TRIGGER_REF structure defines the trigger InputID INT : 0 = Capture Engine 0 1 = Capture Engine 1 Range is [0,1] For information on configuring the capture engines, refer to AKD Capture Engine Configuration. Direction INT; 1 = rising edgeA rising edge is the transition of a digital signal from low to high. It is also called positive edge of trigger, 2 = falling edge of trigger Trigid INT; must be zero TrigMode INT (TriggerInput.TrigMode) is not presently supported by this function. The TriggerInput.Mode may be supported in a future software version.
	Data type	TRIGGER_REF
	Range	See Description above
	Unit	n/a
	Default	—
Velocity	Description	Commanded velocity for the reference move
	Data type	LREAL
	Range	—
	Unit	User unit/sec
	Default	—
Acceleration	Description	Commanded acceleration for the reference move
	Data type	LREAL
	Range	—
	Unit	User unit/sec²
	Default	—
Deceleration	Description	Commanded deceleration for the reference move
	Data type	LREAL
	Range	—
	Unit	User unit/sec²
	Default	—
JerkIn physics, jerk is the rate of change of acceleration; more precisely, the derivative of acceleration with respect to time	Description	Commanded jerkIn physics, jerk is the rate of change of acceleration; more precisely, the derivative of acceleration with respect to time for the reference move (if zero, then trapezoidal acc/dec is used)
	Data type	LREAL
	Range	—
	Unit	User unit/sec³
	Default	—
Direction	Description	Commanded Direction of the reference
	Data type	SINT
	Range	[0,1]
	Unit	n/a
	Default	—
Position	Description	The position the axis will be reset to when at the machine reference location
	Data type	LREAL
	Range	—
	Unit	User unit
	Default	—
Option	Description	Option identifier for Resolvers/Modulo reference. 0 = Use latched position for reference 1 = use resolver position of nearest null for reference 2 pole resolver 2 = use resolver position of nearest null for reference 4 pole resolver 3 = use resolver position of nearest null for reference 6 pole resolver 4 = use resolver position of nearest null for reference 8 pole resolver 5 = use resolver position of nearest null for reference 10 pole resolver … 15 = use resolver position of nearest null for reference 30 pole resolver
	Data type	SINT
	Range	[0,15]
	Unit	n/a
	Default	—

Output

Done	Description	Indicates the reference move and position adjustment is complete
	Data type	BOOL
Busy	Description	Indicates this function block is executing
	Data type	BOOL
Active	Description	Indicates this move is the Active move
	Data type	BOOL
CommandAborted	Description	Indicates the move was aborted
	Data type	BOOL
Error	Description	Indicates an invalid input, or the move was terminated due to an error
	Data type	BOOL
ErrorID	Description	Indicates the error if the Error output is high See table in PLCopen Function Block ErrorID Output
	Data type	INT

Usage

The following lists the steps for homing a PLCopen axis, using the MC_Reference function block. Not all of the steps are necessary depending on the configuration and the homing cycle design.

The sequence of events of a PLCopen homing cycle consists of the following steps:

Ensure Axis is not on Reference switch.
If a switch is used in the homing cycle for the event or precondition to the event, check to ensure the axis is not already tripping the switches that trigger the event and precondition. If it is, move the axis off the switches.
Configure AKD capture engine
Configuration of the AKD capture engine is performed by writing drive CAN"Controller area network" CAN is a broadcast, differential serial bus standard developed for connecting electronic control units. Each node is able to send and receive messages, but not simultaneously objects via SDO. It is accomplished with the ECATWriteSdo function. The AKD Capture mode must be set to POSITION CAPTURE.
The available configurations are discussed in AKD Capture Engine Configuration . Example AKD capture engine configurations and reference examples are discussed in PLCopen Homing Methods.
Call the MC_REFERENCE function to initiate optional homing motion and to arm the AKD capture engine
The MC_Reference function block selects the trigger edge (rising or falling edge) and arm the capture. Then, it optionally moves the axis to the reference location as directed by inputs to this function. When the AKD indicates that the capture event has occurred, the coordinate system is shifted so that the reference position input to this function block is set to the reference location. Then, the reference motion is stopped.
Wait for the completion of the MC_Reference function block
The application is notified by the completion, abort or error of the homing by the MC_Reference function block.
Upon completion of the MC_Reference function block, the axis can be moved to the home position with a MC_MoveAbsolute function block.

For more details, see "PLCopen Homing"

Once the MC_Reference block is queued, but before it is completed, the cycle can be aborted with a MC_Halt or MC_Stop function block or by queuing a new motion function block with the Abort selected for buffer mode.

Related Functions

ECATWriteSdo

MC_MoveAbsolute

Example

Structured Text

(* MC_Reference ST example *)

TriggerInput.InputID := 0; //configure the reference InputID

TriggerInput.DIRECTION := 1; //configure the reference direction

Inst_MC_Reference( RefReq, Axis1, TriggerInput, 20.0, 100.0, 100.0, 100.0, 0, 0.0, 0 );

Ladder Diagram

MC_Reference: LD example

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