Contents I. Introduction
Classical approach of controlling is based on time trigger controlling mechanism. In time-triggered control systems various states are sampled and calculated and control action is taken at every sampling instant in a periodic manner, also in the cases when there is no error which means there is no change in states and calculated control does not require any change. Systems with time triggered control and has fixed sampling period lack’s on flexibility and has the restrictive design process. All processes and their time specifications must be known by advance knowledge and studies. This classical approach indicates the transmission of unnecessary and useless data even there is no error, where computational efforts ultimately take to the inefficiency of the system. For networked systems, production of such unessential updates of the sampled signals results into wastage of the bandwidth of communication network and eventually results in overloaded network channel.The disadvantages of the time triggered control mechanism led to development of new control technique ETM (Event Triggered Mechanism). The distinguished property of an event-triggered control mechanism is its pre-defining of the Event Triggering Condition (ETC). The time instants when sampling and controller actions are updated according to system states or outputs are defined by a defined threshold level designed according to defined ETC. Thus only if the predefined ETC is not followed, then the current output of the system exceeds a defined threshold then the current system measured outputs should be sampled and transmitted to controller for updating. Thus it is found out, an event-triggered control system has advantages over a time-triggered control system in reducing unnecessary utilization of communication and computation resources.
