Regarding the instrument cascade control system

A cascade control system is a complex control system that consists of multiple loops and multiple controllers. The main circuit and the auxiliary circuit refer to their series connection with each other; during the control process, they interact with one another to achieve the desired control outcome. In a cascade control system, the main controller and the secondary controller do not necessarily refer to control valves; they can also refer to other control devices. The main controller is usually located at the front end of the system, where it processes input signals and outputs control signals ； The auxiliary controller is responsible for monitoring the output signal of the main circuit and making adjustments as needed. In a typical cascade control system, there are usually multiple control valves, which are connected to form primary and secondary loops. Among them, the main circuit controls the primary parameters, while the secondary circuit controls the compensation parameters. These two circuits are coordinated by different controllers, thereby enabling precise control of the entire system. In summary, a cascade control system is a highly complex control system that requires the support of various control devices and technologies. I hope my explanation can help you understand better. .

Find a textbook to read; it will explain things in more detail

A control valve, a cascade control system – in such a system, the output of one control system serves as the setpoint for another control system; when they are connected in this manner, it is called a cascade control system.

A cascade control system has two loops in terms of structure, namely the main loop and the secondary loop； The main circuit includes the main controlled object, the main measurement transmitter, and the main controller ； The secondary circuit includes a secondary controlled object, a secondary measuring transmitter, a secondary controller, and a control valve. There are two controlled variables, namely the primary controlled variable and the secondary controlled variable. The output from the main controller is sent to the secondary controller as a setpoint, while the output from the secondary controller is sent to the control valve.

I have also been researching this recently. From my understanding, cascade control involves using two single-loop systems in series: the output of the main loop serves as the setpoint for the secondary loop, while the output of the secondary loop directly acts on the control valve. The variable that is being regulated in the secondary loop is our target value SP. Cascade control consists of multiple variables and one control valve.