Introduction to Engineering Process

1. Introduction to Engineering Process

2. Module Objectives • define the concept of ‘Control System’ • identify the main elements of a control system and explain the role of each element • differentiate between the control system types • draw the system block diagram for a given system description and prototypes • build simple control systems and test their functionalities • use Tina software to build a simple control system and test its functioning.

3. Module Contents

4. Introduction to Systems & Control Control Systems are used • to regulate the temperature and humidity of homes and buildings for comfortable living • in the transportation sector, there is a need to control the movement of vehicles and • airplanes from one point to another accurately and safely.

5. Introduction to Systems & Control • Control systems are found in abundance in all sectors of industry, such as • automatic assembly lines, • power systems, • robotics, and • space technology. Systems and Control Technology is about making products or systems that combine parts or components.

6. More examples of control system applications include: • Steering control of automobile • Temperature control of electric furnace • Sun-tracking control of solar collectors. • Industrial operations such as controlling pressure, humidity, temperature in the process industries.

7. Control System Elements • A system is a collection of parts that work together to perform a function or task. • . A control system is a system that can command, direct or regulate itself or another system.

8. Main elements of a control system • Any control system consists of an input, process and output block. The blocks are linked by a signal.

9. Main elements of a control system • Input: The input starts the system, and is also called the actuating signal. • Process: The process is the brain that controls the system. It decides what should happen when the system is activated. • Output: The output is the system result and determines how the system must respond, and is also called the controlled variable.

10. Control System Classification • Control systems are classified into the following two basic types: • Open-loop control systems • Closed-loop control systems

11. Open-loop control system • Open-loop control system is one in which the control action is independent of the desired output.

12. Closed-loop control system • Closed-loop control system is one in which the control action is dependent on the desired output.

13. Comparison Open loop & Closed Loop

14. A closed-loop control system •  Accepting an order that defines the desired result • Determining the present conditions by some method of feedback • Comparing the desired result with the present conditions and obtaining a difference or an error signal • Issuing a correcting order (the error signal) that will properly change the existing conditions to the desired result • Obeying the correcting order

15. Systems Diagram/Block Diagram • A Systems Diagram or a Block Diagram is a schematic representation of a system. • Example 1: if the objective is to control the speed of the car, then the amount of force exerted on the pedal accelerator is the input, and the car speed is the output.

16. Speed control system Block Diagram • The block diagram for the system is shows the input, process and output.

17. Ice- alarm system • Example 2: An engineer wants to design an ice alarm system for his Ice cream machine that will sound an audible alarm when the ice cream reaches the desired temperature. The block diagram for this control system would be as follows:

18. Ice- alarm system block diagram

19. Curtain control system • Example 3: In this application, the requirement is to design a control system that automatically opens and closes curtains when it gets dark or bright.

21. Skill 1: Drawing block diagrams • A student wants to design a control system that switches ON the lights in his room when it turns dark. Help the student by drawing the block diagram for the system.

22. In a certain application, it is required to maintain the temperature of the room at 230C. Draw the block diagram for this temperature control system.

23. Lab Activity 1 • Objective: To explore the function of the given ‘Plant Waterer’ prototype, identify the system elements and draw the block diagram.

24. Background Information: • The Lego NXT sensor-controlled robot will sense the moisture level of the soil and automatically water the plant when it is too dry and stop when the soil is wet. • The soil will be considered “too dry” when the moisture level is between 0%–20%. If the Soil Moisture Sensor indicates the soil is too dry, the pump will force air into the reservoir and push water out through the tubing onto the plant. When the soil is sufficiently wet, the pump will shut down.

25. Procedure: • Identify the input, process and output of the given prototype, and draw System block diagram for each one of them. Clearly label the signals, input, process and output.

27. Sensors/Transducers • The primary task of a sensor is to detect a nonelectric physical quantity; the transducer transforms this signal into a measurable electrical signal. • Light Dependent Resistor (LDR):LDRs are special purpose resistors whose resistance varies as the intensity of light falling on it changes. • A typical example is to turn ON the street lights when it gets dark.

28. Sensors/Transducers • Proximity Sensor: Proximity sensors are used to detect the proximity (closeness) of an object. • An example of an application is detecting and counting the number of Pepsi cans passing through an assembly line.

32. Transistor • The transistor is mainly used to function as a switch and as an amplifier. • Electronic switch: To detect the sensor output and control the switching of an output device such as a light emitting diode (LED).

33. Transistor Automatic night lamp when the LDR is exposed to darkness, it has maximum resistance. Therefore, the voltage drop across the LDR increases (>0.6V) and the transistor turns on which lights the LED. When it is bright, the LDR has least resistance and therefore the voltage across it is low (<0.6V). Therefore, the transistor is off which turns the LED off.

34. Lab Activity-2