OPEN LOOP & CLOSE LOOP AND BASICS ELEMENT OF CONTROL SYSTEM

4) OPEN LOOP SYSTEM & SCHEMATIC DIAGRAM


Definition:An open-loop controller, also called a non-feedback controller, is a type of controller that computes its input into a system using only the current state and its model of the system. An open-loop controller is often used in simple processes because of its simplicity and low cost, especially in systems where feedback is not critical. A typical example would be a conventional washing machine, for which the length of machine wash time is entirely dependent on the judgment and estimation of the human operator

An open loop system

CLOSED LOOP SYSTEM & SCHEMATIC DIAGRAM

Definition:

A type of control system that automatically changes the output based on the difference the feedback signal to the input signal. 

A closed loop system

INTRODUCTION TO CONTROL SYSTEM

CONTROL SYSTEM ENGINEERING

INTRODUCTION
Control engineering is based on the foundations of feedback theory and linear system analysis, and it generates the concepts of network theory and communication theory. Accordingly, control engineering is not limited to any engineering discipline but is applicable to  aeronautical, chemical, mechanical, environmental, civil, and electrical engineering. A control system is an interconnection of components forming a system configuration that will provide a desired system response.

A control system is a device, or set of devices, that manages, commands, directs or regulates the behavior of other device(s) or system(s). Industrial control systems are used in industrial production.

There are two common classes of control systems, with many variations and combinations: logic or sequential controls, and feedback or linear controls. There is also fuzzy logic, which attempts to combine some of the design simplicity of logic with the utility of linear control. Some devices or systems are inherently not controllable.

A control system is a system by virtue of which any quantity or condition (called controlled variable) of interest of a machine, mechanicsm or equipment can be controlled as per desire. Usually, the system has a command signal applied at the input and the controlled variable exhibited at the output. For example, the force applied on to an accelerator pedal causes the speed of the engine vehicle to increase. Here, force is the command signal and the speed of the engine is the controlled variable.

The term "control system" may be applied to the essentially manual controls that allow an operator, for example, to close and open a hydraulic press, perhaps including logic so that it cannot be moved unless safety guards are in place.

CONTENT

• Electrical - Electrical Control Systems specializes in the design and manufacture of high quality industrial control systems and offer innovative and practical solutions to all your automation requirements ranging from simple MCC and dedicated controller applications, to networked PLC and SCADA systems.

• Pneumatics - Pneumatic systems are used extensively in industry, and factories are commonly plumbed with compressed air or compressed inert gases. This is because a centrally located and electrically powered compressor that powers cylinders and other pneumatic devices through solenoid valves can often provide motive power in a cheaper, safer, more flexible, and more reliable way than a large number of electric motors and actuators. Pneumatics also has applications in dentistry, construction, mining, and other areas.

          They have two main advantages and disadvantages of pneumatics :

1. Advantages	Disadvantages
   Reliable and economical actuators	Good maintenance is required.
   Flexible and modular control components	Building monitoring is limited

Pneumatic circuit.

• Hydraulics -  A hydraulic drive system is a drive or transmission system that uses pressurized hydraulic fluid to drive hydraulic machinery. The term hydrostatic refers to the transfer of energy from flow and pressure, not from the kinetic energy of the flow.
  A hydraulic drive system consists of three parts: The generator (e.g. a hydraulic pump), driven by an electric motor, a combustion engine or a windmill; valves, filters, piping etc. (to guide and control the system); the motor (e.g. a hydraulic motor or hydraulic cylinder) to drive the machinery.
  Many types of equipment rely on some form of hydraulic control system, including aircraftand aerospace vessels. Marine vessels and elevators also use these types of controls, as do hydraulic cranes. Cars and trucks typically contain hydraulic brake systems, and a variety of industrial and manufacturing machines also rely on these controls for safe and effective operation. 
  Hydraulic control systems can influence the motion or operation of a machine in several ways. The most basic involves manual control, where a human or robotic users flips a switch, pulls a lever or turns a steering wheel. This motion drives hydraulic fluid throughout the system to accomplish the desired action. Other systems rely on automatic controls rather than manual input. For example, a sensor on a crane may detect heavy loads and automatically send extra fluid towards the crane's lifting system. This fluid in turn creates excess lifting power to safely move the heavy load. Similar systems rely on pressure sensors, electronic eyes, and a variety of additional inputs.
  
  
  They have two main advantages and disadvantages of hydraulics :
  
  

  Advantages	Disadvantages
  It uses 'incompressible' fluid which results in a greater, more efficient & consistent work or power output. This is due to the fact that hydraulic fluid molecules are able to resist compression under heavy load hence minimal energy loss is experienced and work applied is directly transferred to the actuating surfaces.	Hydraulic fluid is highly corrosive to most of the aircraft materials.
  As opposed to pneumatic system which uses air, a leakage in a hydraulic system is easier to spot during ground maintenance operations.	Due to the heavy loads experienced in a typical hydraulic system, structural integrity is a must which also means higher structural weight for the aircraft in addition to the weight of its hydraulic lines, pumps, reservoirs, filters, & etc.
  Hydraulic fluid operates very well in a very hot working environment, it is able to sustain its airworthiness viscosity, density & fluid temperature even if it subjected under extreme heat. This is specially important on aircraft structures that is abundant of hot working conditions during flight operations	Hydraulic system is susceptible to contaminations & foreign object damage (FOD).
  	If disposed improperly, a hydraulic fluid is an environmental risk.

hydraulic system