Cascade control problem
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Series control of hydrogen concentration and hydrogen flow rate in a polypropylene loop reactor – how should it be implemented when using series control? Should it be the secondary circuit that activates automatically first, followed by the automatic activation of the main circuit and then the connection of the series link, or should the secondary circuit activate automatically first, the series link be connected, and then the main circuit activate automatically? What would happen if the order were reversed?
It is best to first set the PID values for both the primary and secondary control loops. First, use manual control to bring the primary parameters close to or equal to the desired values, while ensuring that the secondary parameters remain stable. Once the secondary control loop is operating in automatic mode, adjust the primary controller so that its parameters are also brought close to or equal to the desired values. After the secondary loop becomes stable, the primary controller can be switched to automatic mode as well. During operation, it is advisable to activate the secondary loop first and then the primary loop, ensuring a smooth transition with no disruptions.
It is best to first set the PID values for both the primary and secondary control loops. First, use manual control to bring the primary parameters close to or equal to the desired values, while ensuring that the secondary parameters remain stable. Once the secondary control loop is operating in automatic mode, adjust the primary controller so that its parameters are also brought close to or equal to the desired values. After the secondary loop becomes stable, the primary controller can be switched to automatic mode as well. During operation, it is advisable to activate the secondary loop first and then the primary loop, ensuring a smooth transition with no disruptions.
In cascade control, the setpoint for the primary controller is determined by the setpoint of the secondary controller; the output of the secondary controller controls the control valve. Therefore, it is necessary to tune the secondary loop first and then the primary loop. If this order is reversed, it will be difficult to achieve proper tuning, and fluctuations are likely to occur.