📦 Sample — QuickstartMotion

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🧠 Remarks and limitations

• This is an AI-generated sample/template project intended purely as a learning and quickstart reference. Before using any part of this code in a real machine or installation, a qualified automation engineer must review and validate it against the applicable safety standards (e.g. IEC 62061, ISO 13849), site-specific requirements, drive and encoder configuration, and commissioning procedures. No warranty of any kind is expressed or implied.
• Minimum TwinCAT version: 3.1.4026
• Requires the Tc2_MC2 library (ships with TwinCAT, no manual install needed)
• The NC axis object (GVL.ncAxis) must be linked to an actual NC axis in the I/O tree before activating the project — this is the only hardware-specific step.
• The project uses a generic analog drive with incremental encoder — no vendor-specific drive configuration is required.

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🔧 Functionality Overview

FB_AxisControl

Wraps the three core Tc2_MC2 motion function blocks (MC_Power, MC_Reset, MC_MoveAbsolute) for a single NC axis behind a simple, cycle-called interface.

• Internally calls all three MC function blocks every PLC cycle; operator commands are triggered via rising-edge inputs.
• Aggregates error status from all three FBs into a single bError / nErrorId output.
• Exposes live axis position and velocity from the NcToPlc structure.

Inputs

I/O	Name	Type	Default	Description
VAR_IN_OUT	stAxis	AXIS_REF	—	NC axis reference (link to I/O tree)
VAR_INPUT	bEnable	BOOL	—	TRUE = servo on
VAR_INPUT	bEnablePositive	BOOL	—	Allow motion in positive direction
VAR_INPUT	bEnableNegative	BOOL	—	Allow motion in negative direction
VAR_INPUT	bReset	BOOL	—	Rising edge clears axis error
VAR_INPUT	bMoveAbsolute	BOOL	—	Rising edge starts absolute move
VAR_INPUT	fTargetPosition	LREAL	—	Target position [axis unit]
VAR_INPUT	fVelocity	LREAL	—	Move velocity [axis unit/s]
VAR_INPUT	fAcceleration	LREAL	—	Acceleration [axis unit/s²]
VAR_INPUT	fDeceleration	LREAL	—	Deceleration [axis unit/s²]
VAR_INPUT	fJerk	LREAL	—	Jerk limit [axis unit/s³], 0 = disabled

Outputs

I/O	Name	Type	Default	Description
VAR_OUTPUT	bPowered	BOOL	—	Axis servo is on
VAR_OUTPUT	bReady	BOOL	—	Powered and no error
VAR_OUTPUT	bBusy	BOOL	—	Any motion command is active
VAR_OUTPUT	bError	BOOL	—	Any FB has an active error
VAR_OUTPUT	nErrorId	UDINT	—	First non-zero error ID
VAR_OUTPUT	fActPosition	LREAL	—	Actual position [axis unit]
VAR_OUTPUT	fActVelocity	LREAL	—	Actual velocity [axis unit/s]

MAIN

Program that implements a continuous shuttle (back-and-forth) between two configurable positions using FB_AxisControl.

• Uses a state machine driven by E_AxisState (7 states: IDLE → POWERING_ON → MOVE_TO_A ↔ MOVE_TO_B, with ERROR handling).
• Operator commands: bStart (rising edge), bStop (immediate power-down), bReset (clear error).
• Shuttle parameters (fPosA, fPosB, fVelocity, fAcceleration, fDeceleration, fJerk) can be changed online.
• A global stop and error guard run after the state machine to catch errors and stop requests from any active state.

E_AxisState

Qualified-only enumeration naming each state machine step. Values are spaced by 10 for readability (0, 10, 20, 30, 40, 50, 99).

GVL

Single global variable ncAxis : AXIS_REF — must be linked to the NC axis in the TwinCAT I/O tree.

Task	Cycle	Priority	Runs
PlcTask	10 ms	20	MAIN

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🧪 Example

PROGRAM MAIN
VAR
    fbAxis          : FB_AxisControl;
    bStart          : BOOL;
    bStop           : BOOL;
    bReset          : BOOL;
    fPosA           : LREAL := 0.0;
    fPosB           : LREAL := 100.0;
    fVelocity       : LREAL := 50.0;
    fAcceleration   : LREAL := 500.0;
    fDeceleration   : LREAL := 500.0;
    fJerk           : LREAL := 0.0;
    eState          : E_AxisState := E_AxisState.eIDLE;
    bEnableAxis     : BOOL;
    bMoveCmd        : BOOL;
    fMoveTarget     : LREAL;
END_VAR

// Call FB_AxisControl at the end of every PLC cycle
fbAxis(
    stAxis          := GVL.ncAxis,
    bEnable         := bEnableAxis,
    bEnablePositive := bEnableAxis,
    bEnableNegative := bEnableAxis,
    bReset          := bReset,
    bMoveAbsolute   := bMoveCmd,
    fTargetPosition := fMoveTarget,
    fVelocity       := fVelocity,
    fAcceleration   := fAcceleration,
    fDeceleration   := fDeceleration,
    fJerk           := fJerk
);

To adapt this sample for your own device, link GVL.ncAxis to your NC axis in the I/O tree, adjust fPosA/fPosB to match your travel range, and set velocity/acceleration values appropriate for your drive and mechanics.

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🧠 Notes

• FB_AxisControl must be called every PLC cycle — place the call as the last statement in MAIN so that all state-machine decisions are reflected before forwarding to the MC function blocks.
• bMoveCmd is asserted for exactly one cycle to generate the rising edge that MC_MoveAbsolute requires; it is cleared in the following wait state.
• The axis is considered ready (bReady) only when MC_Power.Status is TRUE and no error is active across any of the three MC FBs.
• All shuttle parameters can be changed online while the PLC is running — new values take effect on the next move command.

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🔢 Additional information

Required libraries

Library	Vendor	Purpose
Tc2_MC2	Beckhoff Automation GmbH	Motion control function blocks (MC_Power, MC_Reset, MC_MoveAbsolute)
Tc2_Standard	Beckhoff Automation GmbH	Standard PLC library
Tc2_System	Beckhoff Automation GmbH	System library

Supported platforms: x64

Minimum TwinCAT version: 3.1.4026

License: LICENSE.md