Controllers

Image of the Controllers tab in Consibio Cloud

Background & Definitions


In Consibio Cloud a controller is a user-defined “rule”, which dictates how the output of an actuator is adjusted automatically.

An actuator is a physical control-element (physically connected to a Consibio Connector or Monesco device), that can affect the process / production which it is in contact with. An example of an actuator could be:

  • A heating element, that heats the air inside an oven
  • An air fan, which directs the air flow into a pipe or an incubator
  • A valve, which can turn on/off to enable the flow of water in pipe

In most cases, the controller receives feedback on how well it’s controlling the process via. a sensor. A sensor measures the current value / state of the process / production, which is often termed “Process Value” (PV).

The feedback from the sensor enables the controller to automatically correct the output given to the actuator such that a desired process value is maintained. This desired value is termed setpoint (SP).

An example of a controller with this feedback could be:

  • A temperature-sensor (feedback) measures the air temperature inside a baking oven and dictates when the heating element (actuator) should be turned on or off, in order to maintain a desired baking temperature of e.g. 200 °C (setpoint)
  • A flow-sensor (feedback) measures how many liters of air passes through an incubation chamber every minute and adjusts the power output of an air fan (actuator), in order to maintain a desired average flow of 50 liters / min. (setpoint)
  • Etc.

Industry terminology related to Consibio

In the industry, the controllers are often a part of a Supervisory Control And Data Acquisition (SCADA) system, which is in charge of handling the process control in a production.

In Danish, this system is often termed SRO-system for “Styring, Regulering og Overvågning”.

Controller Types / Control loops


In general, there are two types of controllers – An open loop controller or a closed-loop controller.

The type of controller depends on whether a sensor is used as feedback in the controller, or not. In other words:

Open loop

  • Definition: Without feedback.
  • Example: A timer-controlled illumination/lighting in a greenhouse, or a toaster with a timer-controlled heating of your favourite bread

Closed loop

  • Definition: With feedback.
  • Example: The temperature control in a baking oven

These two general controller types / control loops are each subdivided into many different subcategories of controller types, which do not always follow the same terminology in the industry.

However, in the Consibio platform we define the subcategories of controller types as the following:

Figure 1: Closed-loop controller
Figure 2: Open-loop controller

Controller CategoryController typeExplanationNecessary Input
Open-loopFixed OutputA ”fixed output”-controller sends a fixed signal to its corresponding actuator. In other words, it doesn’t adjust over time until the user / operator changes the fixed signal again. 

An example of such a controller could be a fan-controller that makes sure that a ventilation fan is always running at 50% output
– An actuator
– A desired output for the actuator (e.g., 50 %)
Open-loopIntervalAn ”interval”-controller is a timer-based rule, that either turns an actuator on or off within a defined time-period and in this time-period, the output of the actuator can also be set at a certain level for when the actuator is turned on.

An example could be a controller for a valve, that opens/closes for the flow of water to plants in a greenhouse, where the valve must be 50% open for 1 hour, closed for the next 10 hours and then the pattern repeats itself indefinitely.

– An actuator
– Time-interval the actuator is turned on
– A desired output for the actuator when it is turned on
– Time-interval the actuator is turned off
Closed-loopOn/offAn ”on/off”-controller (or “tænd/sluk regulering” in danish) adjusts the output of the actuator, depending on a sensor value (i.e. feedback), such that the actuator is turned on or off when the sensor value is above (or below) a user-defined setpoint.


A normal baking oven uses an on/off-controller, since it turns on the heating element until a temperature sensor inside the oven registers a temperature that is above the setpoint (e.g. 200 °C). When above the setpoint, the heating element is turned off until the temperature again is below the setpoint.
This will continue indefinitely when the actuator (i.e. heating element) will be turned on and off, back and forth, and hence the name “on/off”-controller.


In practice, you can also have an on/off-controller that activates an actuator when a sensor value is both below and/or above a setpoint. An example would be a heating element that activates below a certain temperature setpoint and a cooling element that activates above the temperature setpoint.
– A sensor, used for feedback
– The desired setpoint (i.e. value for the parameter which the sensor measures
– Which actuator, that is turned on, when the sensor value is below the setpoint
– Which actuator, that is turned on, when the sensor value is below the setpoint
– (If applicable, a deadzone interval. For more info, see “Deadzone” section further down)
Closed-loopPIDA ”PID”-controller is inherently very similar to an on/off-controller, since it adjusts the actuator output based on feedback from a sensor measurement. However, the PID-controller is much more advanced and better at minimizing fluctuations around the setpoint, compared to an on/off-controller.


This is because a PID-controller doesn’t just turn the actuator on or off, but varies the output sent to the actuator based on several factors. For instance, the PID-controller considers how far the current measured sensor value is from the setpoint, for how long time the sensor value has been over/under the setpoint and anticipates how quickly the sensor value changes with an output. 


A PID-controller is more difficult to operate/set, but in some cases, it is highly necessary. For instance, the autopilot in a car is controlled using a PID-controller. Let’s just imagine that it was an on/off-controller for a moment. Then the car would accelerate 100% until the car reaches the setpoint, i.e. 60 km/h, then turn off the acceleration completely – and the keep on repeating this “bumpy” control so that your car would be averaging 60 km/h.


Luckily, this isn’t the case in real life since the autopilot is PID-controlled.
– A sensor, used for feedback
– The desired setpoint (i.e. value for the parameter which the sensor measures)
– Which actuator, that is turned on, when the sensor value is below the setpoint
– Which actuator, that is turned on, when the sensor value is below the setpoint
– Settings for how aggressive / careful the PID-controller shall react on the feedback. It requires three terms (Kp, Ki and Kd), but it will not be elaborated furthermore in this documentation.
– (If applicable, a deadzone interval. For more info, see “Deadzone” section further down)

Controller Settings


In this section, each individual controller setting will be described in detail.

Controller type

The controller type setting lets the you choose between the different controller types currently available in Consibio Cloud. The four different controller types available are:

  • Fixed Output
  • On/Off
  • Interval
  • PID

For more information on each specific controller type, including different examples, see the Controller Types / Control Loops section in this documentation page.

Input Module

This setting will only show up if the controller type setting is either On/Off or PID.

This setting defines which sensor value / parameter the controller should use as input for its calculations. For example, if the controller should regulate / control the temperature in a room, the input module would likely be a temperature sensor located inside the room.
Thus, the term “input module” is often used interchangeably with the term “input”, “feedback”, “sensor input” or “sensor signal” when speaking in feedback control terms

Static or Dynamic Setpoint

In some cases, it is desirable to have a setpoint that changes over time, i.e. a dynamic setpoint.

For instance, a temperature setpoint of 20 °C the first 24h, followed by a 25 °C setpoint the next 24h and finally 32 °C for the rest of the time (or until the experiment / batch is finished).

This can be applied to all controller-types and is thus another setting to adjust within the controller settings of the Consibio Cloud.

If a dynamic setpoint is chosen, the user has to fill out the the multiple setpoints and for how long this dynamic setpoint should be maintained (i.e. the maintain period). This is done in the setpoint configuration

Example of a dynamic setpoint configuration with 3 setpoints and corresponding maintain periods

An important notice is that the last desired value will continue to be the setpoint, unless a new batch (see batch mode under Project Settings) is started or that the loop setpoint sequence is set to true.

Setpoint

This setting will show up if the controller type setting is either On/Off or PID.

The setpoint setting is used to set a desired value of the selected input module. In other words, the setpoint is the just the value you want the controller to steer towards. Whether it is a specific tempererature, flow of air or concentration of a certain gas component all depends on the input module for which the setpoint is linked too.

The unit of the setpoint is therefore dependent on which input module was chosen when setting up the controller

Output Module – Below Setpoint

This setting will show up if the controller type setting is either On/Off or PID.

The below setpoint, output module setting defines which actuator (i.e. output module) should be turned on or activated if the measured proces value is below the desired setpoint.

For instance, if you want to bake a lemon pie in a baking oven, the output module would be the heating element that increases the temperature inside the baking oven if the temperature is below the setpoint.

Output Module – Above Setpoint

This setting will show up if the controller type setting is either On/Off or PID.

The above setpoint, output module setting defines which actuator (i.e. output module) should be turned on or activated if the measured proces value is above the desired setpoint.

For instance, if you want to maintan a cool temperature inside a fridge, the output module would be the cooling element that decreases the temperature inside the fridge if the temperature is above the setpoint.

It could also be a valve that turns on the flow of nitrogen gas in an environment where oxygen is prohibited and an oxygen sensor is used as the input module.

Deadzone

This setting will show up if the controller type setting is either On/Off or PID.

The deadzone (or dead band) defines a region around the setpoint in which the actuator (i.e. output module) will not turn on, no matter what. The deadzone thus indicates a value both above and below, in which the output module will not activate.

So if we have a setpoint of 23 °C and the deadzone is set to 2 °C, the temperature is allowed to be between 21 °C and 25 °C before the controller start acting. The deadzone is “plus-minus” 2 °C around the setpoint.

This setting is mostly advantageous if there is an actuator that is both affecting the desired process value when it is both above and below the setpoint. So typically, the deadzone setting is not needed in a simple control setup.

Loop Setpoint Sequence (Dynamic Setpoint)

This setting will show up if the controller type setting is a Fixed Output with a Dynamic Setpoint.

The loop setpoint sequence setting can either be false or true. If it is set to true, the dynamic setpoints set by the user will continue to loop once the last setpoint and maintain period has run out.

This can be useful for controlling cycles such as daily, weekly or monthly dynamic setpoints for production without having to start a new batch (see batch mode under Project Settings) every day, week or month.

Output Module (Fixed Output or Interval)

This setting will show up if the controller type setting is either Fixed Output or Interval.

The output module is often referred to as the actuator of the control-loop. This is also true for Consibio Cloud, where only actuator modules connected to the hardware will show up in the dropdown menu.

Examples of actuator modules are given in the Background & Definitions section of this documentation page

Velocity Control Mode

This setting will show up if the controller type setting is set to PID.

In a classic PID controller, the final parameter calculated is what the value of the output should be in order to either maintain or reach the desired setpoint. So here the output value is calculated. However, if the velocity control mode is turned on the required change in output (opposed to the output itself) is calculated.