~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~UNIVERSITI MALAYSIA SABAHFACULTY OF ENGINEERING~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

MAKMAL KAWALANKE38101

LAB 1Open and Closed Loop System

Name: NURUL ANIS AHMADMatrix No.:BK12110284Date: 7/11/2014Nurul Anis Ahmad (BK12110284)

Control Lab#1: Open and Closed Loop System 1-2KE38101/1415(1)1.0 Introduction

Process control is an engineering discipline that deals with architectures, mechanisms and algorithms for maintaining the output of a specific process within a desired range. A Open loop process control system is said to be of the open loop type when the measured variable has no influence on the action taken on the control element. In open loop system, the control element is set so that the inflow of the system is maintained on a certain level. A closed-loop controller uses feedback to control states or outputs of a dynamical system. There are two types of feedback possible in closed-loop control: positive feedback and negative feedback. Positive feedback increases the effect of disturbances and leads to instability. This type of feedback is never used in closed-loop control. Conversely, negative feedback decreases the effect of disturbances and acts in a way to restore the equilibrium and stability between the setpoint and the measured variable.

2.0 Objectives

2.1 Objective of Open Loop Process Control

To understand what is the purpose of process control To understand the principles of open loop process control

2.2 Objective of Closed Loop Process Control

To understand what are positive feedback and negative feedback To understand closed-loop process control

3.0 Methodologies3.1 Open loop Temperature Control System

Figure 3.1: Open-loop temperature control system

1. The POWER switch of the Process Control Trainer is set to the O (OFF) position. The appropriate connection is made on the Process Control Trainer to obtain the circuit as shown in figure 1.2. The following setting is made on the Process Control Trainer.

a. DC SOURCE-1 LEVEL= MIN (fully counterclockwise)b. LEVEL COMPARATOR HYSTERESIS= MINc. DC VOLTMETER INPUT SELECTOR=Ad. HEATER POWER= HIGHe. FAN SPEED=LOW

3. The POWER switch of the Process Control Trainer is set to the I (ON) position.4. The initial temperature of the radiator (indicated by the TEMPERATURE TRANSMITTER display) is recorded.5. The DC SOURCE-1 LEVEL control is set so that the DC VOLTMETER indicates+2.5 V dc. This sets the temperature setpoint. The temperature of the radiator is recorded in the table every minute during 15 minutes or until the temperature stabilizes.6. After 15 minutes or when the temperature has stabilized, the FAN SPEED switch is set to the HIGH position to increase the heat loss from the radiator then the temperature of the radiator is recorded every minute during 10 minutes or until the temperature stabilizes.7. Turn the DC SOURCE-1 LEVEL control fully counterclockwise (MIN). The SOLID STATE RELAY LED indicator remains off, thus indicating that power is no longer supplied to the HEATER.

3.2 Closed Loop Temperature Control System

Figure 3.2: Open-loop temperature control system

1. The POWER switch of the Process Control Trainer is set to the O (OFF) position. The appropriate connections are made on the Process Control Trainer to obtain the circuit as shown in figure 3.2.2. The following setting is made on the Process Control Trainer.a. DC SOURCE-1 LEVEL=MIN(fully counterclockwise)b. LEVEL COMPARATOR HYSTERESIS=MINc. TEMPERATURE TRANSMITTER ZERO=MID (mid position)d. TEMPERATURE TRANSMITTER SPAN=MINe. DC VOLTMETER INPUT SELECTOR=Af. LEVEL COMPARATOR HYSTERESIS=MINg. HEATER POWER=HIGHh. FAN SPEED=LOWi. PROPORTIONAL AMPLIFIER GAIN=1/4 of max (25% of maximum)j. LIMITER LEVEL=MAX3. The POWER switch of the Process Control Trainer is set to the I (ON) position.

The DC SOURCE-1 LEVEL control is set so that the DC VOLTMETER INDICATES +3.5V DC. This sets the setpoint voltage (VSP). The voltages at the outputs of the TEMPERATURE TRANSMITTER is measured (feedback voltage VT), ERROR DETECTOR (error voltage, VE), and LIMITER (amplified error voltage V0) using the B INPUT of the DC VOLTMETER. These voltages are recorded.

4. The 5-v B INPUT of the DC VOLTMETER is connected to the OUTPUT of the ERROR DETECTOR in order to monitor the error voltage (VE). Let the system operate until the temperature indicated by the TEMPERATURE TRANSMITTER display is approximately 35C (95F). Observe the error voltage (VE) during this time interval.

The voltage at the outputs of the TEMPERATURE TRANSMITTER is measured (feedback voltage VT), ERROR DETECTOR (error voltage VE), and LIMITER (amplified error voltage VO) using the B INPUT of the DC VOLTMETER. These voltages are recorded.5. The voltages that obtained in step 3 and 4 is compared.6. The DC SOURCE-1 LEVEL control is set so that the DC VOLTMETER indicates+3.5 V dc. This sets the temperature setpoint. The temperature of the radiator is recorded in the table every minute during 15 minutes or until the temperature stabilizes.7. After 15 minutes or when the temperature has stabilized, the FAN SPEED switch is set to the HIGH position to increase the heat loss from the radiator then the temperature of the radiator is recorded every minute during 10 minutes or until the temperature stabilizes.8. Turn the DC SOURCE-1 LEVEL control fully counterclockwise (MIN). The SOLID STATE RELAY LED indicator remains off, thus indicating that power is no longer supplied to the HEATER.

4.0 Results

4.1 Open-loop Temperature Control System

TIMETEMPERATURETIMETEMPERATURE

min ()min ()

024.51348.5

127.41448.7

232.81548.9

337.81646.4

440.51744.7

542.71843.8

644.41943.1

745.62042.7

846.52142.5

947.22242.4

1047.62342.3

1148.02442.2

1248.52542.1

Table 4.1:Temperature of the Radiator versus Time

4.2 Closed loop temperature Control SystemTIMETEMPERATUREVoltage Error (VE) (V)TIMETEMPERATUREVoltage Error (VE) (V)

min ()min ()

025.61.21336.20.1

131.00.61435.70.2

239.4-0.21536.70.1

338.4-0.11635.10.2

435.10.21735.90.1

536.20.11835.60.2

636.40.11935.50.2

735.40.22035.80.1

836.50.12135.40.2

935.60.22235.70.2

1036.10.12335.70.2

1136.00.12435.50.2

1235.80.22535.60.2

Table 4.2:Temperature of the Radiator versus Time

5.0 Discussions

1. The temperature of the radiator varies and increases before the fan speed passes from low to high. In order to improve the open-loop control temperature control system, the fan speed needs to be increased so that the stability of the controller can be stabilizing quickly. 2. The primary objective of the Process Control is to maintain the controlled variable to a desired specific value. The control element of this system is the temperature, pressure, flow rate, level and so on. The controlled variable must be measured to determine it is maintained at the desired value and this leads to the a new parameter which is referred to as the measured variable. A method is used in measuring the controlled variable, so this is the distinction between the measured variable and the controlled variable. 4. The Voltages at the outputs of the Temperature Transmitter (feedback voltage, VT), Error Detector (VE), and Limiter (amplifier error voltage (V0) is measured using the B INPUT of the DC Voltmeter.a) VSP = +3.5V dcb) VT = 2.4 V dcc) VE = 1.2 V dcd) VO = 5.0 V dc5. When the Temperature Transmitter displayed approximately 35 (95), the error voltage is observed during this time interval. The Voltages at the outputs of the Temperature Transmitter (feedback voltage, VT), Error Detector (VE), and Limiter (amplifier error voltage (V0) is measured using the B INPUT of the DC Voltmeter.a) VSP = +3.5V dcb) VT = 3.4 V dcc) VE = 0.2 V dcd) VO = 0.1 V dc6. By comparing the voltages measured in 4 and 5, after Temperature Transmitter displayed approximately 35 (95) and the Vsp is 3.5V, the feedback voltage VT is increased. The feedback used in this controller is negative feedback as it decreases the error voltage and acts as in a way to restore stability of the system. 7. Before the fan speed passes from low to high, the temperature of the radiator varies but as the fan speed passes from low to high, the system is seen achieved it stability quickly and the temperature stays around 35. This is because the temperature controller is using negative feedback that allows the system to stabilize.8. The Voltages at the outputs of the Temperature Transmitter (feedback voltage, VT), Summing Amplifier (VE), and Limiter (amplifier error voltage (V0) is measured using the B INPUT of the DC Voltmeter.a) VSP = +3.5V dcb) VT = 2.4 V dcc) VE = 6 V dcd) VO = 5 V dc

9. Negative feedback is used in process control system because it decreases the effect of disturbances and restores the stability between the setpoint and the measured variable. A feedback is a common and powerful tool when designing a control system. Feedback loop is the tool which takes the system output into consideration and enables the system to adjust its performance to meet a desired result of system.

10. The main disadvantages of using feedback in process control system is that the disturbance enters into the process and upsets it. It is after the process output is different from the setpoint that the controller takes some corrective actions. Although most processes allow some fluctuation of controlled variable within a certain range, there are two process conditions which can make the overall effectiveness of feedback control quite unsatisfactory. One of these is the occurrence of disturbances of a large magnitude that is strong enough to seriously affect or even damage the process. The other is the occurrence of a large amount of lag (time delay) within the process.

6.0 Conclusions

This experiment, the primary objective of process control to maintain some controlled variable near a desired specific value (setpoint) Has been introduced. Many Key terms related to process control, such as controller, manipulated variable, control element, load, measured variable, etc have been studied. It Can be seen that the process control systems can be of the closed loop type or open loop type. The Block diagrams can be used to represent process control loops and that these diagrams facilitate system analysis. Basic Principles and operating procedures of the Process Control Trainer Have been carried out. An Open loop temperature control system has been used to observe the temperature fluctuates depending on the heat loss (load).A process control system has been studied where feedback consists in feeding the information on the controlled variable (measured variable) back to the controller in order to compensate fluctuations of the controlled variable. It has been noticed that the negative feedback effectively decreases the effect of disturbances and acts in a way to restore the equilibrium between the setpoint and the measured variable, whereas positive feedback increases the effect of disturbances and leads to instability. It can be concluded that a minimum error exists in a control system using negative feedback.

7.0 References

http://eweb.chemeng.ed.ac.uk/courses/control/restricted/course/second/course/lecture1.html

http://en.wikipedia.org/wiki/Radiator_(engine_cooling)