Using PID Block Values in Mitsubishi PLC

Hi

I have modelled a simple PID system in Simulink and have now tuned the controller, to get the values in the image below. I now need to use these values in a Mitsubishi controller, however I am unsure exactly what each of the P, I and D unit values are in Simulink. The Mitsubishi controller requires the unit values to be as the second image below.

My thoughts on this are:-

KP = 250 %

TI = unsure (0.0058)

KD = 10 %

TD = unsure (0.1)

N = value appears makes no difference to the output

Regarding Ti and Td I am also wondering if the x100 and x10 ms in the PLC may be an issue with these values?

Can anyone offer guidance regards this?

Answer 1

[Kartik Saxena]

Hi,

The exact context of 'P', 'I', 'D' values in Simulink is:

• 'P' : Proportional gain, provided from a source external to the block. External gain input is useful, for example, when you want to map a different PID parameterization to the PID gains of the block. You can also use external gain input to implement gain-scheduled PID control. In gain-scheduled control, you determine the PID coefficients by logic or other calculation in your model and feed them to the block.
• 'I' : Integral gain, provided from a source external to the block. External gain input is useful, for example, when you want to map a different PID parameterization to the PID gains of the block. You can also use external gain input to implement gain-scheduled PID control. In gain-scheduled control, you determine the PID coefficients by logic or other calculation in your model and feed them to the block. When you supply gains externally, time variations in the integral gain are also integrated. This result occurs because of the way the PID gains are implemented within the block.
• 'D' : Derivative gain, provided from a source external to the block. External gain input is useful, for example, when you want to map a different PID parameterization to the PID gains of the block. You can also use external gain input to implement gain-scheduled PID control. In gain-scheduled control, you determine the PID coefficients by logic or other calculation in your model and feed them to the block.When you supply gains externally, time variations in the derivative gain are also differentiated. This result occurs because of the way the PID gains are implemented within the block.

KP (Proportional band): The proportional band is usually the reciprocal of the proportional gain. However, it's expressed as a percentage.

TI (Integral time): The integral time is the reciprocal of the integral gain when the gain is expressed as Kp/Ti.

KD (Derivative action): The derivative action is often expressed as a percentage of the proportional gain, similar to KP.

TD (Derivative time): The derivative gain (D) in Simulink is represented as Kp*Td, then Td is the derivative time and can be used directly.

N (Filter coefficient): The filter coefficient N is often specific to the Simulink model.

Refer to the following MathWorks documentations for detailed information about use of PID controller:

• https://www.mathworks.com/help/simulink/slref/pidcontroller.html
• https://www.mathworks.com/help/slcontrol/gs/automated-tuning-of-simulink-pid-controller-block.html

I hope this resolves your issue.

[Sam Chak]

@Kartik Saxena, the PID values are specified as follows: P = 2.5, I = 0.0058, D = 0.1, N = 70.

Could you please update your response to provide the equivalent values for the parameters that need to be entered into the Mitsubishi PLC, as indicated in the second image shared by the OP? I'm not familiar with the Mitsubishi PLC hardware.