Hello everyone, I am currently facing challenges in controlling an air-driven liquid piston pump when using various volume outlet test hoses. This pump, along with a plc controller and transducer, is utilized to regulate the pump and other devices. The issue arises when testing different hoses, such as a small hose holding 400psi (resulting in 28.5 psi air pressure at a 1:14 ratio) and a larger hose with 50 times the volume at the same pressure. Despite applying the same control method to both hoses, the larger hose tends to overshoot the target pressure due to its faster pumping rate. One solution I have implemented involves incrementing air pressure by intervals and waiting for the pump to stabilize before adding more pressure. However, this method can be slow and not always effective, especially with smaller hoses. I am considering adding separate buttons for small and large hoses, but this may not address all variations in hose size. I am seeking suggestions on improving this process, such as detecting when the pump has stalled or increasing the pumping speed without overshooting the target pressure. Any input on optimizing the control of different hose sizes would be greatly appreciated. Thank you.
What is the role of the control element in regulating air pressure without a transducer on the air side? How does it effectively increase air pressure by 1psi and adjust as it approaches the setpoint? This scenario suggests an I-only feedback control, but the system's response varies based on the hose volume, requiring specific tuning for each hose.
Is it possible to install a flow switch or flow meter at the outlet of the pump? This added component can help monitor flow rates and ensure efficient operation of the system.
In accordance with drbitboy's recommendation, it may be beneficial to adjust the loop constants to better suit the size of the hose being used. This can help optimize the efficiency and performance of the system.
Upon reexamination, it appears that the system under consideration may function similarly to a PID feedback controller, with the Proportional (P) and Derivative (D) parameters set to zero, essentially operating as an Integral-only controller. This means that as long as the water pressure in the hose is below the target level, the air pressure is increased in regular intervals based on the difference between the measured and target pressures, without overshooting the target value. In the context of varying hose volumes and pressures, adjustments in the increment rate of the air pressure may be needed to effectively reach the desired pressure levels. For larger hoses with slower pressure increases, a higher rate of air pressure increment is required to avoid overshooting the target pressure. On the other hand, smaller hoses with faster pressure rises may need a lower increment rate to reach the target pressure without overshooting. It is suggested to consider different control approaches, such as adjusting the increment rate based on the error (KI tuning) or using a Proportional-only control method initially before switching to an Integral-only approach. By observing the behavior of the system and making empirical adjustments, it may be possible to find a suitable control method without the need for complex mathematical calculations, making it easier to implement and debug in practical applications.
Aljubovic mentioned that it is difficult to calibrate the IP transducer to achieve 100% accuracy. This may result in uncertainty regarding the exact pressure values. Viewing the process curves would be beneficial instead of solely relying on luck. Drbitboy added that for a large hose volume, if the pressure rises slowly when the pump is running, the air pressure increases at a faster rate over time due to the lower pressure. This can lead to a higher margin of error. The reason for this increased error and potential overshoot may be attributed to the elastic deformation of hoses.
The issue you're facing seems complex, but it could be a matter of tuning your control loop more effectively for different hose sizes. It sounds like a classic problem of process control where the system overshoots or undershoots its target due to different process dynamics. You might want to look into PID Control (Proportional, Integral, Derivative). This controller takes into account past errors (Integral term) and predicts future ones (Derivative term), thus preventing this from happening. With this kind of control, you can have a more dynamic approach that adjusts according to the hose size instead of having to manually increment air pressure. As for detecting when the pump has stalled, perhaps embedding a sensor to monitor pump operation could be beneficial. These are just suggestions and may need some tweaking before it works seamlessly for your setup.
From your description, it sounds like the problem lies in the controlling method not being perfectly adaptable to the variations in hose size. One approach you might consider is implementing a feedback control system, something akin to a PID controller, which could autonomously adjust the air pressure based on the rate at which the target pressure is being approached. Adding pressure sensors near both the inlets and outlets of the pump would offer more accurate real-time pressure data, enabling the system to react more quickly and appropriately. This might help avoid overshoot and stabilize the pressure more efficiently across different hose sizes.
It sounds like you’re dealing with quite the balancing act! Have you considered implementing a feedback loop that continuously monitors the pressure and adjusts the air supply dynamically? This way, you could fine-tune the output based on real-time conditions for each hose. Additionally, incorporating a PID controller could help smooth out those overshooting issues by calculating the necessary adjustments based on current versus target pressure. It might take some time to tune it just right, but it could lead to a more consistent performance across varying hose sizes. 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: Answer: The main challenge is that different hoses, such as small and large ones, can lead to variations in pumping rates and pressures, causing issues with maintaining target pressure.
Answer: Answer: One solution involves incrementing air pressure by intervals and waiting for the pump to stabilize before adding more pressure, although this method can be slow and not always effective.
Answer: Answer: Suggestions include detecting when the pump has stalled, increasing pumping speed without overshooting the target pressure, and potentially adding separate control buttons for small and large hoses to address variations in size.
Join hundreds of satisfied customers who have transformed their maintenance processes.
Sign up today and start optimizing your workflow.