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Controller
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The controllers in Hysopt take inputs, coming from constants, sensors or the output from other controllers/operators and use either the PI algorithm or a self-defined algorithm to make computations.
The PI-algorithm
the Proportional-Integral (PI) controller computes and transmits a controller output signal every timestep to the component (e.g., valve). The computed output from the PI algorithm is influenced by the controller tuning parameters and the controller error. For more info about the PI algorithm itself, please visit https://controlguru.com/integral-action-and-pi-control/
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The controller is defined through multiple parameters:
- Proportional band:
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- The value of the proportional band determines how fast the system responds, whereas the value of the integral gain determines how fast the steady-state error is eliminated. When the value of these gains is larger, the control performance is better. However, large gains may lead to an oscillatory response and result in an unstable system.
- Repeat time:
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- Provides a separate weight to the integral term of the PI algorithm, so the influence of integral action can be independently adjusted. It is in the denominator so smaller values provide a larger weight to (i.e. increase the influence of) the integral term. It
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- had units of time so it is always positive.
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- Warning
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A Modulating Room Controller allows to increase or reduce the heating power to the actual required output and therefore allows efficient heating control and high comfort at the same time. It uses a PI control algorithm.
Parameters
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The most common room controller is still the On/Off control via a relay. It allows a controller to request either none or full heating power.
Parameters
- Trigger offset : when the room temperature exceeds the setpoint minus the trigger offset, the output is high. When the input exceeds the setpoint plus the trigger offset the output is low, and when the input is between the two levels, the output retains its value. This dual threshold action is called hysteresis.
- Setpoint configuration : see below
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A thermostatic room controller for application on the Base Circuit "Radiator with Thermostatic Radiator Valve"
Parameters
- Setpoint configuration : see below
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Write your own algorithm using the programmable controller.
You can use C-like syntax including :
- assignment statements
- if and if-else statements
- switch statements
- operators :
- increment operators (++ and --)
- unary operators (- and !)
- binary operators : power (^), multiply (*), modulo (%), divide (/), sum (+), min (-)
- ternary operator (a = x ? b : x) see https://www.freecodecamp.org/news/c-ternary-operator/
- conditional operators (|| and &&)
- comparison (<=', >=, >, <, ==, '!=)
- mathematical functions : exp, ln, sin, cos, sqrt, min, max
- comments : single line (//) and multiline (/*...*/)
here is an example with code : example.txt
Setpoint configuration
You can define 4 types of setpoint profiles :
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The Exclude weekends option will set a permanent night during saturdays and sundays>
The optional Holiday period allows you to set a period for permanent night setpoint.
You can define a range for randomness on both the setpoints as on the start/end hours.
You can 'lock' the randomness so the same randomness is applied for each simulation, by setting the re-randomize paramer to 'NO' :
Control delay
With the control delay up and down it is possible to insert the delay time of the valve actuator.
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- ; the proportional band and repeat time interact with each other and their influence must be balanced by the designer.
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How to overrule/de-activate the output of a PI controller?
Suppose you have a PI controller, of which you want to use the output in certain operating conditions.
In other operating conditions, you want to disable or overrule this PI controller, and just close the valve.
Sometimes this is done like in the following example.
The output of the PI controller is multiplied with an overruling signal (see the yellow line).
If the value of the yellow line is zero, then the valve will close, regardless of the output of the PI controller.
This practice has a problem : Allthough the PI controller is succefully overruled, the PI controller itself will still continuously execute it’s “I action” and keep integrating the error over time. As soon as you re-use the output of the PI controller (by sending the signal ‘one’ on the yellow line), this might result in temporary unexpected and undesired behavior, like unstable or overshooting output values.
Therefor use the de-activation (and reset) control signal on the PI controller itself, that will de-activate the error integration.
This signal behaves like the activation on a pump : it is optional, and by default it is activated.
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- Control delay: Inserts a delay time on the valve actuation, which may prove useful to remove quick oscillation, but also may lead to larger overshoot.
Available controllers
- Positive/negative PI controllers
- Positive/negative modulating room controllers
- Positive/negative on/off room controllers
- Thermostatic room controller
- Programmable controller