Machine-Centric Robotics – Motion ST Programming

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Machine-Centric Robotics – Motion ST Programming

Introduction

Machine-Centric Robotics (MCR) with Motion ST Programming provides a structured and flexible approach to robot motion control within B&R Automation Studio. This article explains the differences between ST application and robot programs, demonstrates a minimalistic demo project, introduces robotic path planning concepts, and provides detailed examples of ST commands and diagnostic tools.

Agenda

  • ST Application Program vs. ST Robot Program
  • Demo Project
  • Robotic Path Planning Basics
  • Examples and Diagnosis

1. ST Application Program vs. ST Robot Program

ST Application Program

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  • Used to operate the robot.
  • Inserted via toolbox into Automation Studio logical view.
  • Assigned to a CPU task class → runs in cyclic context.
  • Structure:
    • Type file: variable definitions, function blocks, parameter types, user-defined structures.
    • Init program: executed at PLC startup for initialization.
    • Cyclic part: typically contains a state machine (e.g., powering, homing, waiting, moving).
    • Stored in Logical View and compiled into binary with the Automation Studio project.

ST Robot Program

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  • Contains motion instructions the robot shall perform.
  • Inserted via toolbox; executed by Interpreter module of Motion Chain.
  • Can include variable declarations (constants, PLC variables).
  • Main part executed by interpreter.
  • Stored on a file device (e.g., CNC_PrgDir) and can be updated during runtime.
  • Executed via:

    • Function blocks (e.g., MC_BR_MoveProgram)

    • mapp Cockpit.

Comparison Table

ST Application Program ST Robot Program
Contains the application logic e.g., used to operate a robot Contains the (motion) instructions the robot shall perform
Cyclic execution Function block or mapp Cockpit
Init/cyclic/exit parts Interpreter-based
Logical View storage File device storage(CNC_PrgDir)
Compiled with AS project Runtime updates possible

2. Demo Project

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A minimalistic Automation Studio project was created for demonstration:

  • Hardware: APC3100 PLC with Powerlink interface.
  • Robot: Codian D4 1100 inserted via MCR template.
  • Required ACOPOS hardware.
  • Auto-generated Scene Viewer visualization.
  • Two file devices:
    • Visualization
    • CNC_PrgDir for motion programs.

Scene Viewer

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  • Standalone Windows application shipped with Automation Studio.
  • Connects via OPC UA to ArSim or hardware.
  • Visualizes robot motion.
  • Added manually:
    • Path Tracker: shows TCP trajectory.
    • Positioner: displays TCP position (and optionally orientation).

Frames

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  • Object hierarchy and frame hierarchy define coordinate systems.
  • For this training: robot programmed in base frame coordinates.

Executing ST Robot Program

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  • Specialized function blocks:
    • MC_BR_MoveProgram
    • MC_BR_GroupPower
    • MC_BR_GroupHome
  • Program name is referenced from the file device.

3. Robotic Path Planning

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Motion Chain Basics

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The motion chain consists of:

  • Interpreter: Reads ST program, generates motion commands.

  • Geometric Path Planning: Calculates TCP path.

  • Dynamic Path Planning: Applies speed profiles and axis limits.

  • Set Value Sampler: Generates cyclic setpoints for axes.

Execution Context:

  • Set Value Sampler → cyclic task.

  • Other modules → background tasks.

Buffer Time

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  • Buffer compensates for CPU load variations.
  • Robot starts moving when buffer reaches minimum fill level.
  • Dynamic planning maintains lookahead.
  • If CPU load is high, buffer may drop → possible motion slowdown.

4. ST Commands – Overview and Examples

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Available ST commands are documented in Automation Studio Help under:
Motion Control → mapp Motion → mapp Robotics/CNC → Programming → G-code and ST overview.

Example 1: Absolute Positioning and Circular Interpolation

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Video1

Example 2: Relative Positioning

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Example 3: Joint Space Motion

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Example 4: Feedrate and Rapid Motion

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Example 5: Rounding Edges

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Timing and Synchronization Commands

  • Wait time

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  • wait end move

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  • wait until flash

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  • do path synch

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5. Diagnosis Tools

  • Scene Viewer: Visualize robot motion.
  • Logger: Check for errors or unexpected behavior.
  • Block Monitor: Shows which program part is currently sampled.
  • Interpreter Monitor: Indicates which part was processed.
  • Override: Execute program slowly for debugging.

Summary

Motion ST Programming provides a structured approach to robot control in Automation Studio:

  • ST Application Programs handle robot operation logic.
  • ST Robot Programs define motion sequences and can be updated at runtime.
  • Robotic path planning uses a motion chain with buffering for smooth execution.
  • A wide range of ST commands enables precise control of motion and timing.
  • Diagnostic tools simplify troubleshooting and commissioning.
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