HRRE materiály ke zkoušce

HRRE EXAM 2018

Control: The control is every purposeful acting on a controlled object with the goal to reach some preselected state. If the actions are generated automatically then we are talking about automatic control.

Automatic control appears in real systems in two basic forms:

• sequential control

• control of dynamic systems

Sequential control is a process when controlled system sequentially passes from one state to another. The transient usually takes place when some condition is fulfilled. Typical example is starting or finishing of some technological process. Before you make a coffee in a coffee machine you have to wait for a given period of time from startup until the machine is heated and performs some initial tests and becomes ready to make coffee. Sequential automatic control of power plant is much more complex and number of the states which are passed during the normal operation counts to tens of thousands.

Control of dynamic systems. The aim is to reach the behaviour when the system output follows (tracks) set point as precisely as possible. All the disturbances and parametric uncertainties should influence this tracking as low as possible. The controller generates control action which act on a controlled system has two main tasks:

• Faithful control tracking - which is difficult according to time delays (generally due to dynamical properties) of the system;

• Disturbance compensation / attenuation - we are dealing with static and dynamic compensation

The control can be subdivided according to different viewpoints:

According to number of inputs and outputs:

• systems with single input and single output (Single Input Single Output (SISO) system)

• with multiple inputs and outputs (Multiple Input Multiple Output (MIMO) system)

• in the literature we can meet with TITO systems (Two Input Two Output)

According to a control system:

• control of linear systems - the main topic of this course, unfortunately all systems in practice are nonlinear, different kind of linearization exist

• control of nonlinear systems - this is a much harder task

Linear system obeys the superposition principle and the fact that the output is proportional to the input.

According to a realization of actuators:

• self-acting - simple controllers in fridges, irons, water level control, ...

• with additional power supplies The way of the control in time:

• discrete - changes in control action appear regularly in given time instants - most commonly used today using computers

• continuous - using operational amplifiers

According to a shape of set point:

• constant set point control - frequency control in mains, flush device in a toilet, temperature control in individual rooms – generally controllers

• servomechanism – set point changes according to some plan which is known in advance, disturbance compensation is just a secondary task

• program control – set point evolution in time is known in advance

According to a type of control:

• feed forward control - without feedback

• feedback control - control with feedback