Скачать или смотреть Handling MC_MoveAbsolute in PLC Programming: Optimizing for Same Position Calls

Discover effective strategies for managing the `MC_MoveAbsolute` function in PLC programming, especially when called with the same axis position. Learn how to avoid unnecessary movements and improve control logic.
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Handling MC_MoveAbsolute in PLC Programming: Optimizing for Same Position Calls

When working with Programmable Logic Controllers (PLCs), one common issue developers encounter is how to manage the MC_MoveAbsolute function when it is called with the same position as the current axis position. You might wonder, "How do I handle situations where no movement is necessary?" This guide aims to clarify this dilemma and provide an efficient solution for managing the operation of MC_MoveAbsolute when the target position matches the current position.

The Problem: Understanding MC_MoveAbsolute Behavior

In basic terms, MC_MoveAbsolute is a command to move an axis to a specified position. However, if the position it is commanded to move to is already the current position, complications can arise:

Done and Busy States: Typically, programmers monitor the done and busy states to manage movements. However, if the starting and target positions are identical, the busy state never becomes high, leading to difficulty understanding when the command has completed or been processed.

Control Flow Issues: This can disrupt the control logic flow if not handled properly, leaving the programmer at a standstill.

Suggested Solution: Simplified Control Logic

After analyzing the situation, I've found that a straightforward approach can handle this scenario effectively without relying on the busy state. Below are the steps to implement the solution.

Step 1: Execute the Move Command

Instead of checking if the busy state is active, initiate the move command simply. Here is how you can structure your code:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Check for Completion

In the control flow, proceed to check if the command has completed by looking at the done state:

[[See Video to Reveal this Text or Code Snippet]]

How This Works

No Reliance on Busy: By not depending on the busy state, you simplify your state handling. The code will move on without issues regardless of whether the axis was moved or not.

Execution Flow Control: The nature of your control structure ensures that on each program scan, new code isn’t executed until the previous command completion is confirmed. This means:

If no movement is needed (i.e., the positions match), the done bit will still be set correctly before checking in the second step.

Your logic remains clean and avoids unnecessary complex state monitoring.

Conclusion

In summary, dealing with MC_MoveAbsolute when both the target and current positions are the same can cause confusion, particularly for those new to PLC programming. However, by simplifying your approach and avoiding reliance on the busy state, you can create more robust and understandable control logic. As always, ensure that your program flow respects the timing of scans and state checks to maintain efficient operation of your PLC automation tasks.

By implementing this solution, you can improve your control strategies and ultimately enhance the performance of your PLC applications.