Industrial Electronic Department Copyright of German Malaysian Institute. All rights reserved

Industrial Electronic Department Copyright of German Malaysian Institute. All rights reserved OBJECTIVES: By the end of this chapter, you should be able to:- Explain the meaning of closed loop control.Explain the meaning of closed loop control. Understand the basic concept of closed loop control.Understand the basic concept of closed loop control. Name the type of closed loop control.Name the type of closed loop control. Give an example of closed loop control system.Give an example of closed loop control system. Draw a signal flow diagram of the closed loop control system.Draw a signal flow diagram of the closed loop control system.

Industrial Electronic Department Copyright of German Malaysian Institute. All rights reserved DEFINITION PROCESS Input Output FEEDBACK A process in which the variable to be controlled is continuously measured, compared with the set value and corrected A signal path which includes a forward path, a feedback path, and a summing point, and form a closed circuit

Industrial Electronic Department Copyright of German Malaysian Institute. All rights reserved Fixed Set Point Time Pattern Control Follower Control TYPE OF CLOSED LOOP CONTROL

Industrial Electronic Department Copyright of German Malaysian Institute. All rights reserved TYPE OF CLOSED LOOP CONTROL Fixed set point All closed loop control systems in which the specified set value must be kept constant. In other words, the command variable remains adjusted at a fixed value(set value). Set value control is applied in industry for controlling speed, level, temperature, flow rate and pressure.

Industrial Electronic Department Copyright of German Malaysian Institute. All rights reserved TYPE OF CLOSED LOOP CONTROL Follower control-variable set point control The set points follows the value of the variable. Variation of the set point causes of the controller to change its output that the controlled variable pursues the set point. Application; radar apparatus following a moving object Automatic course control systems for aero planes and ships.

Industrial Electronic Department Copyright of German Malaysian Institute. All rights reserved TYPE OF CLOSED LOOP CONTROL Time pattern control this is a follower control system in which the value of the command value is controlled in a time dependent manner.

Industrial Electronic Department Copyright of German Malaysian Institute. All rights reserved MANUAL C/L CONTROL Setpoint is in the operator’s mind and operator makes all of the control decisions e.g; Set point = 50% of level So the set point achieved inlet outlet Level Range = 0 – 10 ltr Indicator

Industrial Electronic Department Copyright of German Malaysian Institute. All rights reserved SIGNAL BLOCK DIAGRAM CONTROLLER (Brain) FCE (Hand) PROCESS (Level) Output Disturbances Input SENSOR / TRANSMITTER (Eye) feedback INFORMATION BEING FED BACK FROM THE OUTPUT TO MODIFY THE INPUT TO THE SYSTEM MANUAL C/L CONTROL

Industrial Electronic Department Copyright of German Malaysian Institute. All rights reserved AUTOMATIC C/L CONTROL Level Range = 0 – 10 ltr Set point = 30% of level inlet outlet 4-20 mA Transmitter (LT) Controller (LC) Control Valve

Industrial Electronic Department Copyright of German Malaysian Institute. All rights reserved AUTOMATIC C/L CONTROL SIGNAL BLOCK DIAGRAM CONTROLLER (LC) FCE (Control Valve) PROCESS (Level) Output Disturbances Input SENSOR / TRANSMITTER (LT) feedback INFORMATION BEING FED BACK FROM THE OUTPUT TO MODIFY THE INPUT TO THE SYSTEM

Industrial Electronic Department Copyright of German Malaysian Institute. All rights reserved EXAMPLE: C/L CONTROL Level Control System on a 2-phase separator Objective: To keep liquid in the separator at a desired level called "set point". The liquid level inside the separator is sensed and measured by LT. LC receives a signal from the LT. LC compares this measurement with SP and adjust the outlet valve. Difference between the LC measurement & LC Setpoint is the error signal. When the error is not zero, the LC opens or closes the outlet valve to return the level to the setpoint.

Industrial Electronic Department 13 Turntable Speed Control -Closed Loop Control A tachometer (sensor) provides an output voltage proportional to the speed of its shaft. The error voltage is generated by the difference between the input voltage and the tachometer voltage.

Industrial Electronic Department Copyright of German Malaysian Institute. All rights reserved EXAMPLE – CLOSED LOOP 1. Iron 2. Air Conditioning 3. Water Dispenser 4. Boiler system 5. Automatic Ship Steering 6. Satellite Control

Industrial Electronic Department Copyright of German Malaysian Institute. All rights reserved CONCLUSION - C- C- C- Closed loop is a feedback monitoring system (controlled variable continuously monitored) - The controller compares the desired value with the measured value generating an error signal - The controller then adjust the system until the error is reduces closed to desired value - C- C- C- Closed loop is error activated system - C- C- C- Closed loop is much more accurate in long term control system