What is a cascade control loop?
Cascade control is a control algorithm in which the output of one control loop provides the target for another loop, as shown in the diagram below. The ultimate goal of the cascaded loops is to control the end process. A standard PID control loop can be applied to this system, as shown in the figure.
What is the typical controller tuning procedure for a cascade control system?
Cascade control systems are also more complex than single-measurement controllers, requiring twice as much tuning. Then again, the tuning procedure is fairly straightforward: tune the secondary controller first, then the primary controller using the same tuning tools applicable to single-measurement controllers.
What is control loop tuning?
Loop tuning is the art of selecting values for the tuning parameters P, TI, and TD so that the controller will be able to eliminate an error quickly without causing the process variable to fluctuate excessively. That’s easier said than done. Consider a car’s cruise controller, for example.
When tuning a cascade control system which of the following actions should be done first?
When tuning such controller, the inner most loop should be tuned first. The loop that manipulates the set point of the inner-most loop should be tuned next and so for. The figure below shows an example of using two secondary loops, independent of each other, in a fuel combustion plant.
What is the purpose of loop tuning?
Loop tuning Tuning a control loop is the adjustment of its control parameters (proportional band/gain, integral gain/reset, derivative gain/rate) to the optimum values for the desired control response.
What are the disadvantages of cascade control?
Cascade control has three disadvantages. One, it requires an additional measurement (usually flow rate) to work. Two, there is an additional controller that has to be tuned. And three, the control strategy is more complex – for engineers and operators alike.
Why do we use cascade control?
The goal of Cascade Control is to improve process performance by reducing – or even eliminating – the effects of a known disturbance through control of an early warning variable.
What are key tuning parameters of control loop?
Tuning is the art of selecting values for the tuning parameters P , T I , and T D so that the controller will be able to eliminate an error quickly without causing the process variable to fluctuate excessively. That’s easier said than done.
What is loop rate?
The rateControl object enables you to run a loop at a fixed frequency. It also collects statistics about the timing of the loop iterations. Use waitfor in the loop to pause code execution until the next time step. The loop operates every DesiredPeriod seconds, unless the enclosed code takes longer to operate.