Introduction of Control System

Control system is an interconnection of components forming a system
configuration that will provide a desired system response.There is two type of control system namely logic gate and feedback control or linear. The basis for analysis
of a system is the foundation provided by linear system, which assumes a causeeffect
relationship for the components of a system. A component or process to be
controlled can be represented by a block as shown in Figure 1.
  

What is electrical, pneumatic and hydraulic control?

ELECTRICAL  

Electrical energy is energy newly derived from electrical potential energy. When loosely used to describe energy absorbed or delivered by an electrical circuit (for example, one provided by an electric power utility) "electrical energy" refers to energy which has been converted from electrical potential energy. This energy is supplied by the combination of electric current and electrical potential that is delivered by the circuit. At the point that this electrical potential energy has been converted to another type of energy, it ceases to be electrical potential energy. Thus, all electrical energy is potential energy before it is delivered to the end-use. Once converted from potential energy, electrical energy can always be described as another type of energy.

Example of electrical circuit

PNEUMATICS

Pneumatic control system is a system which uses air that in compress to generate force / energy to carry out work. Pnuematic term describing fluid systems that use air or gas. Basically liquid and gas can be known from their incompressibility and the fact that the fluid can have a surface load, while the gas expands to fill the flask. Pneumatic system many in find out in system industrial like food industry,petrochemical and industry which uses robotics. Generally pneumatic system need:

• Air supply is compressed
• Control valve
• Tube link
• Transducer induce

The pneumatic control system can be handled human and automatic. These systems may be represented by diagram basic block in figure 1.5a and figure 1.5b.

                    

HYDRAULIC CONTROL SYSTEM

Hydraulic control system is a system which uses fluid to generate force / energy to carry out work. Hydraulic fluid acts as a lubricant, in addition to the thermal carrier. Relatively small-sized hydraulic actuator can build a large force or torque. Hydraulic system many in use in automobile industry like power system, system brake, crane, jack car,satellite and so on. Fluid that commonly used is oil. Generally hydraulic system need :

• Supply fluid is Hydraulic

• Control valve

• Cylinder

The hydraulic control system can be handled human and automatic. These systems may be represented by diagram basic block in Rajah 1.6a and figure 1.6b.

WHAT IS open loop system AND close loop system?

Open -loop Control System


     Open-loop control system is controlled directly, and only, by an input signal. The basic units of this type consist only of an amplifier and a motor. The amplifier receives a low-level input signal and amplifies it enough to drive the motor to perform the desired job. 

   The open-loop control system is shown in basic block diagram form in figure 2-1. With this system, the input is a signal that is fed to the amplifier. The output of the amplifier is proportional to the amplitude of the input signal. The phase (ac system) and polarity (dc system) of the input signal determines the direction that the motor shaft will turn. After amplification, the input signal is fed to the motor, which moves the output shaft (load) in the direction that corresponds with the input signal.

  The motor will not stop driving the output shaft until the input signal is reduced to zero or removed. This system usually requires an operator who controls speed and direction of movement of the output by varying the input. The operator could be controlling 

                        

Closed-loop Control System

Closed-loop Control System, also known as a feedback control system is a control system which uses the concept of an open loop system as its forward path but has one or more feedback loops (hence its name) or paths between its output and its input. The reference to “feedback”, simply means that some portion of the output is returned “back” to the input to form part of the systems excitation.

Closed-loop systems are designed to automatically achieve and maintain the desired output condition by comparing it with the actual condition. It does this by generating an error signal which is the difference between the output and the reference input. In other words, a “closed-loop system” is a fully automatic control system in which its control action being dependent on the output in some way.

So for example, consider our electric clothes dryer from the previous open-loop tutorial. Suppose we used a sensor or transducer (input device) to monitor the temperature or dryness of the clothes and fed the signal back to the controller as shown below.

 Characteristics of Closed-loop Control : 

• To reduce errors by automatically adjusting the systems input.
• To improve stability of an unstable system.
• To increase or reduce the systems sensitivity.
• To enhance robustness against external disturbances to the process.
• To produce a reliable, repeatable performance.

Basic process control system

Temperature Controller

temperature control. is a system that involves the transfer of heat from one substance to another substance. Thermal systems can be analyzed in terms of resistance and capacitance, although the heat capacitance and thermal resistance can not be accurately represented as a lumped parameter because usually both of these quantities are distributed throughout the material. for accurate analysis, a distributed parameter model should dignakan. here, however, to simplify the analysis, we will anngap that thermal systems can be represented by the model parameters tegumpal, that material featured by the resistance to heat flow with heat capacitance is negligible and that the material is characterized by the heat capacitance resistance can neglected to heat flow. there are three different ways in which heat can flow from one material to another material.

Process Level Control

1. A level transmitter (LT), a level controller (LC), and a control valve (LV) are used to control the liquid level in a process tank.
2. The purpose is to maintain the liquid level at some prescribed height (H) above the bottom of the tank.It is assumed that the rate of flow into the tank is random.
3. the level transmitter is a device that measures the fluid level in the tank and converts it into a useful measurement signal, which is sent to a level controller.
4. The level controller evaluates the measurement, compares it wiyh a desired set point (SP), and produces a series of corrective action that are sent to the control valve.
5. The valve controls the flow of fluid in the outlet pipe to maintain a level in the tank.

process temperature control