Eight control systems common in automated plants

It is used in cases where the thermal process or the transmission device has a long response time and large external disturbance. Feedforward control is used in conjunction with the feedback control mentioned above to detect external disturbances (in this case, the flow of water changes) before the temperature changes, and to correct the control signal before feedback control, so it is also called advance action. The feedforward control is usually composed of a single loop regulator and an addition and subtraction math operator. Choosing the appropriate regulator, tuning the optimal PID parameters and the math operator coefficients are important for improving the control effect of the feedforward control system.

To obtain warm water in the water tank, turn off the hot water inlet valve for a period of time, then turn off the cold water inlet valve for a while, although the temperature is not so accurate. Warm water is also available. Automating a series of ON/OFF operations like this is called sequential control, that is, "control in a predetermined order." This control has neither a target value nor a corrective action and is immune to external interference.

When mixing multiple fluids in proportion, use Ratio Control. For an example of the ratio calculation, please refer to the flow ratio calculation example.

The main regulator and the slave regulator are used to combine the circuits with different process variables, and the output of the main regulator is connected to the setting of the slave regulator. This control system is called a cascade control system.
Cascade has a series of processes. As a basic condition, the system response of the slave regulation loop is faster than the master regulation loop. For external disturbances such as changes in fuel pressure, it can be corrected as soon as possible.

The Override Control is a way to automatically select the output signals of multiple regulators to control the process. As shown in the figure, while ensuring the lowest fuel pressure of the burner, the control valve is controlled by automatically selecting the larger one of the pressure regulator and the flow regulator in the flow control loop. This control loop is also known as automatic selection (AUTO-selector) control.

The Program Control system is a control system that changes the set value in accordance with a predetermined time schedule.
It is mainly used in equipment such as calciners by using a program setter or a program regulator with a setting change function.

The Batch Control system is mainly used for loading equipment, such as loading equipment that loads gasoline or kerosene into the tank truck. The main function is to stop automatically when the filling amount reaches the set value.
The high-performance batch regulator has functions such as initial speed setting and pre-quantitative setting. The batch control system is usually completed by a flow totalizer with batch control. The relevant information is explained in detail on the product page of the flow totalizer. 1 The initial speed setting refers to the contact at the tip of the nozzle to prevent the nozzle tip from generating sparks due to static electricity when starting the injection. Set the small flow injection function before the liquid.
2 Pre-quantitative setting refers to the setting of the function of reducing the filling flow rate when a certain amount of accumulated value is reached to prevent over-injection.