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Circular and Linear Interpolation w/ PLCopen Motion Engine

Introduction

This application example details sample code for a 3 axis system:

X, Y Axis - Horizontal Axes
Z axis - Vertical Axis
FFLD (Free Form Ladder Diagram) , SFC"Sequential function chart" It can be used to program processes that can be split into steps. The main components of SFC are: - Steps with associated actions - Transitions with associated logic conditions - Directed links between steps and transitions, and ST"Structured text" A high-level language that is block structured and syntactically resembles Pascal languages were used.
PLCopenA vendor -and product- independent worldwide association active in Industrial Control and aiming at standardizing PLC file formats based on XML Motion Engine was used.
Motions: Group motion setup and operation including homing, 2 axis linear interpolation, and circular interpolation, motion blending and transition between coordinated motion moves, and stop and restart coordinated motion along the path.
Hardware: An X, Y, and Z motion table was used to demonstrate 2 axis coordinated motion capabilities of the KAS motion system. Each axis is equipped with hardware limit switches for homing and position initialization. A traditional circle, diamond, square figures are made using a pen lowered to paper.

Code was developed for an PDMM but can also be used with a PAC"Programmable Automation Controller" PAC is a compact controller that combines the features and capabilities of a PC-based control system with that of a typical programmable logic controller (PLC). A PAC thus provides not only the reliability of a PLC, but also the task flexibility and computing power of a PC. Additionally, because they function and communicate over popular network interface protocols, PACs are able to transfer data from the machines they control to other machines and components in a networked control system based KAS system.

Control Panel: Created inside 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 for use during development and operation.

Project file: Sample KAS Coordinated Motion Application CDS.kas. For zip file with sample code visit: http://www.kollmorgen.com/en-us/products/machine-controls/automation-platform/kollmorgen-automation-suite/kollmorgen-automation-suite#tab8

PLC Program Code

The application code provided with this application module is contained in four programs (that can be exported then imported into a project):

Program Name	FunctionA function calculates a result according to the current value of its inputs. A function has no internal data and is not linked to declared instances.	Language
Main	Initialize the axis, the axis group, and motion	Sequential Function Chart(SFC) with Structured Text (ST)
Jogging	Jog the axes	Structured Text (ST)
CircleDiamondSquare	Perform homing and the circle, diamond, square motion	FFLD (Free Form Ladder Diagram)
Common	Common application functionality: Error ResetNew start of the microprocessor, Power Axis On/Off, EnableEnable signal for the drive, Hardware-Enable with 24V signal to X8, Software-Enable command by setup Software, fieldbus or permanently set. Both are required for enabling the drive. Group Motion, Read Axis Status, Read Axis Positions, Read Axis Group Positions	FFLD (Free Form Ladder Diagram)

The key function blocks and Kollmorgen UDFBs used in the application:

Name	Function	Program
MC_InitAxesGrp	Home the axis	Main
MC_AddAxisToGrp	Set a motor/load position after homing	Main
IMC_GrpEnable	Enable the group motion	Common
MC_GrpReadActPos	Read group position	Common
MC_ReadActPos	Read individual axis positions	Common
MC_ReadStatus	Read axis status	Common
MC_Power	Power an axis	Common
MC_MoveRelative	Make a relative move	CircleDiamonSquare
MC_SetPosition	Establish axis position after homing	CircleDiamonSquare
MC_SetHomePosition	Establish home position for the axis group	CircleDiamonSquare
MC_MoveLinAbs	Move 2 axis (x, y) linear interpolation move	CircleDiamonSquare
MC_MoveCircAbs	Move 2 axis (x, y) circular interpolation move	CircleDiamonSquare

Main Program

The main program consists of 2 steps: Setup and IDLE:

In the Setup step:

The motion objects are created
The Axis Group is created
The Axis Group is initialized
Axes are added to the group
Motion engine is started

Jogging Program

The Jogging Program allows motor jogging in either direction. The following is the code for the X axis. The Y and Z axis are similar:

CircleDiamonSquare Program

The CircleDiamondSquare program performs 2 axis coordinated motion. Key parts of the program are as follows:

Network 2: Define default CM (coordinated motion) absolute positions, CM transition and CM move parameters. This is a large section that defines the starting parameters in the application. This network is executed once on program startup. Values can be change using the control panel ( CP_CircleDiamondSquare).
2. Network 3: DisableRemoval of the ENABLE signal. Disables power stage. limit switches before homing:
Network 4: Reset both single axis and CM axes command and actual positions to zero before any homing sequence. This is necessary so the summed super imposed axis positions are 0 and will not affect single axis motion.
Network 5: Home axes to limit switches after operator input. If the axis is on the limit switch back off first. Move to the axis 0 and set the position to 0.
Network 6: End limits and home switches are common for each axis, therefore the re-enable of end limits after the axis home sequence is completed is performed:
Network 7: Move X and Y axis to starting point. Move Z to starting point
Network 8: Lower knife to contact point
Networks 10 to 13: Make Square CM move. The starting position is the center or half way distance point of the top segment. This is required so the final corner of the square will transition with a radius. If the starting point was at the corner then the last segment would not be a radius. This starting position is also the ending point for the square. Restart the segment move if it has been halted while in motion.
Network 15: Make circle move. The default circle center XY positions are based on the square center point.
Network 19: Make diamond move

Common Program

The Common Program performs standard functions used in many applications.

This code powers up the axis and the axis group:
The following outputs the present motion status of each axis (only X axis shown):
The following outputs actual positions of each axis and the group (only X axis shown):

Key Drive I/O

For each of the X, Y, and Z axes an input on the drive (on connector X7) was mapped for the axis homing functionality. The following shows the X axis mapping:

Control Panel

A Control Panel has been created to run the program:

Motion

These bottons determine what motion is run. To jog the motors, select Jog in the Jog/Run bottom. To make a circle, diamond, square shape select Run and then the switch for the appropaite figure type or select the run all button to run all 3 figures.

Setup Parameters

These parameters setup the circle, diamond, or square motions.

Axis Position

Axis and Group Positions are both shown.

There can be a different coordinate system for each

Jogging

These controls are for the jogging motion.

Top Buttons

To make a circle, diamond, and/or square motion:
- Enable the drives:
- Select run:
- Home axis:
- Move Axis to starting position:
- Lower the pen:
- Select motion type:
Code has been added to the program to stop and restart along the path during the square motion move:

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