Control System

What is an event-based controller?

In this control system, certain actions will be performed during an event, an example of this will be closing a valve if the liquid level reaches a predetermined value. The major use of an event-based controller is in alarm indications like if the pressure or temperature level is too high. The event based controller would act and the alarm will be on. This control system is also known as asynchronous control system. So in this system the control signal is calculated according to the level crossing of different signals. The event based control system should respond within certain time to a particular event.

Why event based controller?

The event-based controller can reduce the consumption of energy, in the actuator and sensor network we don’t like to do the control task so that the energy loss due to the communication won’t happen. Even the energy is not a concern the less often control tasks are executed the more processor time will be available for less important tasks. This case of controller would only operate if there is an event that needs to be controlled.

So basically this controller would act as a human controller. So because of this, the controller can handle the important tasks and it can handle the process in a good manner. The requirement for an event-based controller is that it must act very quickly in case if there is an event. This control system different from a time-based control system, in this type of controller, it would have an event detection part that uses the time-triggered sampling with a sampling interval.

What is the difference between a time-triggered control and event-triggered control?

In the time-triggered control, the sensing control and the actuation are driven by a clock, while in the event-triggered controller the input is kept constant. The input does not help periodically, but while the performance is satisfactory. In the event-based control system, the system will respond to an event at the required time and this time will be predetermined.

How the event based controller work?

In this type of control system, the controller will be connected to the system through sensors and these sensors would continuously check the system output. If the output value or signal stays in the limit then the controller won’t do anything, if the output signal is not within the limit then the controller would act, If the sensor senses any fault then the sensor would send a signal to the controller and after that, it would get connected and behaves as a feedback loop to solve this problem. So in this, the sensor working is time-triggered and the controller operation is event triggered. This event-based controller has two parts, one is the event detection part which uses the time-triggered sampling. The output of the event detection would be transferred to the PID controller and it would work as an event-triggered system.

The signals which are used for the detection would be of different types, so sampling will be done if the measurement is beyond the required level. The sampling must be done if the setpoint is changed. During the event condition, the error signal can be used as the basis for the event condition. Event detection is a complex process, there is a chance to create a samplict, while using the error derivatives for error detection and smaplict will be created before the error change. So in order to get a proper response in an event-based controller then the complexity must be reduced.

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