[TRNSYS-users] PID controller parameters setting

[Ben Heymer]

I recommend that you first consider using a different Type of cooling coil
that does internal flow control calculations (such as Type508c).

PID controllers are useful in real machines, where things may change every
millisecond. In simulations with reasonable timesteps of 1 minute or
longer, PI controllers, or even just proportional controllers should be
enough.

There is also an iterative controller (Type 22), which will slow the model
down, but is capable of controlling as you would expect a real PID to
behave.

I have also had some luck in TRNSYS using simple feed-forward type
controls, where you predict the output using a simple equation then adjust
that output with a proportional controller. For example:
control signal = predicted signal f(input 1, input 2) + adjustment f(actual
result - desired result)

Ben Heymer. PE

On Tue, Sep 23, 2014 at 10:01 PM, 何磊 <swjtuhl822 at 126.com> wrote:

> Hi everyone,
> I have encountered some problems when the PID controller(type23) was used
> for controling the outlet air temperature of cooling coil.
>
> The fluid flow rate of cooling coil is conected with a outlet of flow
> diverter(type11), the fluid flow rate of cooling coil is determined by the
> control signal of the flow diverter. It is in order to model a cooling
> cooling with a bypass in fluid side.
>
> Then, the PID control is used for keeping the outlet air temperature
> (Controlled variable) of cooling coil at a setpoint, the control signal is
> the fluid proportion of the flow diverter.
>
> But no matter how to adjust the parameters of PID, the outlet air
> temperature oscillation cann't be eliminated.
>
> so, I have two questions about this simulation.
>
> 1)How to determine the parameters of PID controller, sunch as Gain
> constant, Integral time and Derivative time, to avoid  Controlled variable
> oscillation ?
>
> 2)is there some regular between the simulation time step and the
> parameters ?
>
> If anyone has experience in this respect, could please tell me how to
> choose the simulation time step and the PID parameters ?
>
>
>
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>
>
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