Hello everyone, we need assistance with implementing flow control in our system. Specifically, we are looking to convert a PID loop in Productivity 2000 with an analog output to a relay. This relay will be used to open or close to regulate the flow of product. Our setup does not include a feedback loop, and we are currently utilizing a pneumatic air cylinder and inching valves. Any insights on how to achieve this conversion and improve flow control would be greatly appreciated. Thank you.
Adjust the PID output to a scale of 0 to 100 before performing calculations to synchronize it with a looping timer set for 100 units (such as 100 seconds, 1.00 seconds, or 10.0 seconds). Ensure that the timer does not run if the PID output is at 0. Utilize a limit instruction (LIM) to control the timer accumulator and adjust the valve output accordingly. The output will be determined based on the percentage of time indicated by the PID. Feel free to customize the timer preset to suit your needs, whether it's 1, 10, or 100 seconds, or even a 5.00-second loop. Simply adjust the multiplier to obtain the PID-adjusted value.
Using a PID controller without considering the Process Variable can lead to inefficiencies. One alternative approach is to create a table with two columns - Flow and Position - as the relationship between the two is likely non-linear. By referencing this table, the valve position can be determined based on the desired flow rate through interpolation. However, using a pneumatic cylinder may not be optimal due to inaccuracies related to movement, compressibility of air, and potential calibration issues with frequent position corrections. It would be advantageous to incorporate position feedback or consider using an electric linear positioner for improved precision and control in such applications.
MickW inquired about expertise in flow control and using a PID loop in the Productivity 2000 with an analog output to convert it to a relay for controlling product flow. Without a feedback loop, the setup utilizes a pneumatic air cylinder and inching valves. As noted by @lfe, a PID requires feedback to function properly. Therefore, if there is feedback on the flow of product but not on the position of the pneumatic cylinder or the device controlling product flow, the control scheme involves comparing the flow rate feedback to a setpoint and using any difference to activate a relay that controls the inching valve. This, in turn, regulates the speed of the final control element affecting product flow. Is this interpretation accurate, or could a more detailed explanation of the process be provided?
The topic of "timed proportional control" has been extensively analyzed and debated, so I recommend conducting a search for more information on this subject.
Thank you once more for your valuable input! The control scheme involves the PID system comparing the flow rate feedback to a setpoint. Any deviation (error) is utilized to either activate or deactivate a relay, which in turn regulates the inching valve.
It seems you're aiming for an open-loop control system where the PID settings from your Productivity 2000 would directly influence the relay state, thus controlling the pneumatic air cylinder. To implement this, you might want to determine the threshold for your analog output that would trigger the relay to open or close. Use these thresholds to create logic in your PLC program to trigger the relay accordingly. However, without a feedback loop, the system doesn't have any actual measure of the flow rate, which could lead to inaccuracies. So, while this approach might work, I'd highly recommend adding a sensor to measure the actual flow and feed that data back into your system. This would evolve your set up into a closed-loop system, which tends to be both more reliable and efficient.
Hey there! To convert your PID loop for controlling a relay instead of an analog output, you can start by adjusting your control logic to trigger the relay based on setpoint error thresholds. Since you don’t have a feedback loop, consider implementing a simple time-based control strategy where the relay is activated for a defined duration based on the desired flow rate. You can tune the timing based on the system’s response, which may require some trial and error. Additionally, think about using sensors that provide indirect feedback on the flow rate—instead of a full closed-loop system—this might give you valuable insights to adjust your relay timings better for more consistent flow control. Good luck!
Hey there! For your PID loop conversion, consider using a relay with a pulse-width modulation (PWM) signal to control the air cylinder. Since you're not implementing a feedback loop, focus on tuning your PID parameters to get the best response time for your application. You might also want to experiment with different duty cycles to see how that affects the flow when opening and closing the valves. Just remember to monitor the system closely, as the lack of feedback can lead to overshooting or undershooting in your flow regulation. Good luck!
✅ Work Order Management
✅ Asset Tracking
✅ Preventive Maintenance
✅ Inspection Report
We have received your information. We will share Schedule Demo details on your Mail Id.
Answer: - To convert a PID loop with an analog output to a relay for flow control without a feedback loop, you can implement a time-based control strategy. You can use a timer in the PLC program to control the opening and closing of the relay based on specific time intervals.
Answer: - When converting a PID loop to a relay for flow control in Productivity 2000, consider the response time of the relay, the hysteresis of the system, and the desired flow control accuracy. Additionally, ensure that the relay can handle the switching frequency required for the flow control application.
Answer: - To improve flow control using a relay in a system without a feedback loop, you can implement a feedforward control strategy. By measuring and compensating for disturbances or changes in the system input variables, you can enhance the accuracy and stability of the flow control process. Additionally, fine-tuning the relay switching parameters and the control algorithm can help improve flow control performance.
Join hundreds of satisfied customers who have transformed their maintenance processes.
Sign up today and start optimizing your workflow.