What are the best ways to reduce settling time in a control loop?

2 Reduce the dead time

Another way to reduce settling time is to reduce the dead time, which is the delay between the controller output and the process response. Dead time can be caused by factors such as sensor lag, transport delay, valve stiction, and communication latency. Dead time can degrade the performance and stability of the control loop, as it limits the maximum achievable gain and introduces phase lag. To reduce the dead time, you can try to minimize the sources of delay, use faster sensors and actuators, or apply advanced control techniques, such as dead time compensation or predictive control.

4 Reduce the noise and disturbances

A fourth way to reduce settling time is to reduce the noise and disturbances that affect the control loop. Noise and disturbances are external or internal factors that cause variations in the process output or input. They can make the control loop oscillate, deviate, or saturate, which increases the settling time. To reduce the noise and disturbances, you can use filters, shields, or isolators to protect the sensors and actuators, or use feedforward or cascade control to compensate for the known or measurable disturbances.

5 Select the appropriate control mode

A fifth way to reduce settling time is to select the appropriate control mode for the control loop. Control mode refers to the combination of controller actions, such as proportional, integral, derivative, or on-off. Different control modes have different effects on the settling time, depending on the characteristics of the process and the setpoint. For example, proportional-only control can have a steady-state error, integral-only control can have a large overshoot, derivative-only control can amplify the noise, and on-off control can have a large oscillation. Therefore, you should choose the control mode that best suits your process and setpoint.

6 Test and monitor the control loop

A sixth way to reduce settling time is to test and monitor the control loop regularly. Testing and monitoring the control loop can help you identify and correct any issues that may affect the settling time, such as sensor drift, valve wear, process changes, or controller faults. You can use various tools and methods to test and monitor the control loop, such as step tests, trend charts, performance indicators, or online analyzers. By testing and monitoring the control loop, you can ensure that it is operating at its optimal condition and performance.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?