Mitsubishi PLC FX5U Built In PID Control Function For Temperature Control

1) Open a New Project in Melsoft GX-Works 3:

Begin by launching the Melsoft GX-Works 3 programming software. Once Gx-Works 3 is open, click create a new project. This can typically be done by selecting the "New Project" option from the start menu or the file menu. Be sure to specify the appropriate settings for your project, such as selecting the correct PLC model, project name, and any other initial configuration that may be required for the specific application you are working on.

2) Click on the CPU Parameter:

After the project is set up, navigate to the "CPU Parameter" section within the software. This area is where you can configure various parameters related to the central processing unit (CPU) of the PLC, which is responsible for processing the control logic. You can find the CPU parameter by either using the project tree on the left side or by selecting the appropriate tab that lists all hardware configurations. Clicking on it will open the CPU configuration settings.

 3) In the CPU Parameter, Click on PID Control Setting:

Once you are in the CPU Parameter settings, locate and click on the "PID Control Setting" option. PID control stands for Proportional-Integral-Derivative control, a widely used feedback mechanism in industrial control systems that adjusts a process based on three key parameters: proportional, integral, and derivative actions.. This option allows you to configure PID-related settings for controlling processes such as temperature, pressure, or other variables in your system. 

 4) Click on Detailed Setting in Heating / Cooling PID Control Setting:

In the PID Control Settings menu, you will see an option for more detailed configuration, specifically for heating and cooling applications. Click on the “Detailed Setting” button. This option allows you to configure more advanced parameters tailored to specific control applications, such as adjusting the behavior of the PID control loop for heating or cooling systems. It ensures that you can fine-tune the control settings according to your process requirements.

 

 5) Set the PID Control Function as “Use”:

In the detailed settings for the heating and cooling PID control, you will find an option to enable or disable the PID control function. Set this option to “Use” to activate the PID control function. This step ensures that the system will use the PID algorithm to control the process, allowing the system to maintain a desired setpoint by continuously adjusting the output based on the error signal.

6) Set Device Registers as per the Requirements:

In this step, you will need to assign specific device registers that will be used by the PID control system. These registers hold values that correspond to different aspects of the control process. In this example, you will define the following:

• SV (Setpoint Value) is assigned to D0.
• PV (Process Variable) is assigned to D1.
• MV (Manipulated Variable) is assigned to D2.
• kP (Proportional Gain) is assigned to D3.

These device registers are essential for the PID control function to work correctly, as they store the necessary data for the controller to process and adjust accordingly.

 7) Set Ti (Integral Time), Td (Derivative Time), and Heater SSR Control Output:

Continuing with the configuration, assign the following device registers:

• Ti (Integral Time), which is assigned to D4. This register controls the Ti action of the PID controller.
• Td (Derivative Time), which is assigned to D5. This register controls the derivative action.

Set the control output for PID control output, which is used to control the solid-state relay (SSR) that powers the heater. In this case, Y4 is selected as the control output. This output will directly control the SSR, and thus, regulate the power to the heater based on the PID control logic. It is possible to choose another output for controlling the SSR, depending on your system’s requirements.

 8) Control and Monitoring Bits:

In this section, you will configure several control and monitoring bits that help manage and monitor the PID control system:

• M0 is used to enable the PID control function.
• M1 is used to enable the Autotuning feature, which automatically adjusts PID parameters to optimize performance.
• M10 is a monitoring bit that indicates the execution status of the PID control.
• M11 is used to show the execution status of the Autotuning process.
• M12 is used to display any errors related to the PID control function.

These bits provide essential feedback and control capabilities, allowing the user to monitor the performance of the PID loop and make adjustments as necessary.

 9) Data Register D6 for Error Code:

Finally, D6 is used as a data register to store any error codes related to the PID control function. If there are any faults or issues with the PID control system, this register will contain a specific error code that can help in diagnosing the problem. By monitoring this error code, you can identify whether the PID control loop is functioning correctly or if there is an issue that needs to be addressed.

                        

By following these detailed steps, you will successfully configure the PID control settings in Melsoft GX-Works 3 for your heating and cooling applications. This setup allows for precise control of your system and provides real-time feedback to ensure proper operation.