How to use wobj of the T_ROB_R in T_ROB_L

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Summary

The problem at hand involves setting up a coordinate system (wobj) on the right arm of a YUMI (Double arm) robot by ABB and then using the left arm to move to coordinates defined in this wobj. The goal is to have the right arm hold an object while the left arm moves around it as the right arm moves the object.

Root Cause

The root cause of the issue lies in the inability to access the wobj defined in T_ROB_R from T_ROB_L. This is due to the following reasons:

  • Scope of variables: The wobj defined in T_ROB_R is not accessible in T_ROB_L because it is not a global variable.
  • Communication between tasks: In RAPID, tasks (like T_ROB_R and T_ROB_L) do not share variables directly.

Why This Happens in Real Systems

This issue occurs in real systems because of the way RAPID programming and RobotStudio handle variable scope and task communication. Key points include:

  • Task isolation: Each task in RAPID runs independently, which means they do not share variables unless explicitly defined as global or passed through specific communication mechanisms.
  • Variable scope: Variables defined within a task are only accessible within that task unless declared as global.

Real-World Impact

The real-world impact of this issue includes:

  • Limited coordination between robot arms: Without the ability to access and use the wobj defined on one arm from the other, achieving coordinated movements that require a shared reference frame is challenging.
  • Increased programming complexity: Workarounds, such as using global variables or other communication methods, can add complexity to the program and potentially introduce errors.

Example or Code (if necessary and relevant)

// Example of defining a global wobj
GLOBAL wobj_right_arm;

// In T_ROB_R
PROC main()
  // Define the wobj
  wobj_right_arm := [/* wobj definition */];
ENDPROC

// In T_ROB_L
PROC main()
  // Access the global wobj
  MoveL pos, v100, fine, left_tool\WObj:=wobj_right_arm;
ENDPROC

How Senior Engineers Fix It

Senior engineers fix this issue by:

  • Declaring the wobj as a global variable: This allows it to be accessed from any task.
  • Using appropriate communication mechanisms: If the wobj needs to be updated dynamically based on the right arm’s movements, using signals or messages to communicate between tasks might be necessary.
  • Carefully planning variable scope and task communication: Understanding how variables are shared and tasks communicate is crucial for designing and implementing coordinated movements between robot arms.

Why Juniors Miss It

Juniors might miss this because:

  • Lack of experience with RAPID and RobotStudio: Understanding the specifics of variable scope and task communication in RAPID requires experience.
  • Insufficient knowledge of programming principles: Not grasping the concepts of variable scope, global variables, and inter-process communication can lead to difficulties in solving such problems.
  • Overlooking documentation and resources: Failing to consult the official documentation and resources for RAPID and RobotStudio can mean missing critical information about how to handle such scenarios.