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Upgrading Slick Interface to Control Logix L71: Optimization and Tuning Advice

Question:

I have six motors controlled by PID commands, originally programmed in a Slick interface. When the Control Logix with an L71 processor became popular, the program was updated. While timers were upgraded, the PIDs continued to run freely on the main task. The RPI for the feedback (a dancer) is updated every 97 milliseconds. The PID Loop Update Time is set to 100ms, while the L71 program runs at 3ms. If I move the PID to a scheduled task at 30ms (1/10 speed) and adjust the Update Time accordingly, should I simply multiply my proportional and integral times by 10, or is there a more intricate relationship involved? Would this be a good starting point for tuning the system? Of course, I will also adjust the sensor update time accordingly. Thank you for your help in advance.

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Proportional control operates without a time factor, while integral control should ideally reflect the ratio between the time intervals and real time. This process involves multiple steps, as it not only addresses the initial discrepancy but also adjusts the sampling time.

If I understand correctly, do I multiply the Integral by ten and keep the proportional value the same?

In order to achieve optimal system response, it is crucial to consider the sample rate when applying corrections such as P correction. By multiplying the integral by ten and keeping the proportional unchanged, you can ensure stability in your system. However, it is important to choose a sample rate that aligns with the responsiveness of your overall system to prevent any potential instability.

I appreciate your assistance. This is just the beginning, and it's exactly what I was looking for.

A few years ago, I encountered a similar situation and conducted thorough bench testing to fully address the question at hand. To delve deeper into this topic, be sure to visit the following thread, especially focusing on post #8.

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Frequently Asked Questions (FAQ)

FAQ: 1. Why was the program updated from a Slick interface to Control Logix with an L71 processor?

Answer: - The program was updated to adapt to the popularity and advancements of the Control Logix with an L71 processor.

FAQ: 2. What is the significance of moving the PID to a scheduled task at 30ms and adjusting the Update Time accordingly?

Answer: - Moving the PID to a scheduled task at 30ms can help optimize the performance of the system by better aligning the PID loop update time with the overall program execution time.

FAQ: 3. When adjusting the PID Loop Update Time to match the scheduled task at 30ms, should the proportional and integral times be simply multiplied by 10?

Answer: - Multiplying the proportional and integral times by 10 may be a good starting point for tuning the system after moving the PID to a scheduled task, but there may be a more intricate relationship involved that should be considered for optimal performance.

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