Introduction to Control System CHAPTER 1 Introduction to Control System School of Computer and Communication Engineering KUKUM Prepared By: Amir Razif A. B Jamil Abdullah ENT 364 : Rev-1

Chapter Objective. Basic terminologies. Open-loop and closed-loop. Block diagrams. Control structure. Advantages and Disadvantages of closed-loop.

1.0 Introduction to Control System 1.2 Basic Terminologies. 1.3 Open Loop System. 1.4 Close-Loop System. 1.5 Design Process. 1.6 Servo Control. 1.7 Block Diagram. 1.8 Control Signal. 1.9 Model. 1.10 Design Analysis. 1.11 Design.

1.1 Introduction. Application of control systems; Rocket fire, space shuttle lifts off the earth orbit, self guided vehicle and ect. God created automatically controlled systems in human body; pancreas, which regulate the blood sugar, our adrenaline increases along the heart rate causing more oxygen to be deliver to our cells. Definition of a control system; The control system consists of subsystems and process (or plant) assembled for the purpose of controlling the output of the process.

Advantages of control systems; Cont’d… Advantages of control systems; Can move large objects with precision; for example (i) elevator, (ii) radar antenna to pickup strong radio signal and (iii) robot to operate in the dangerous environment. (i) Elevator Figure 1.1 Early elevators were controlled by hand ropes or an elevator operator. Modern Duo-lift elevators make their way up the Grande Arche in Paris, driven by one motor, with each car counterbalancing the other. Today, elevators are fully automatic, using control systems to regulate position and velocity.

Figure 1.2: Applications of Control. Cont’d… Figure 1.2: Applications of Control.

Cont’d… (ii) Antenna. Figure 1.3: Antenna azimuth position control system: (a) system concept; (b) detailed layout; © schematic; (d) functional block diagram

Cont’d… (iii) Robot Figure 1.4: Rover was built to work in contaminated areas at Three Mile Island in Middleton, PA, where a nuclear accident occurred in 1979. The remote controlled robot’s long arm can be seen at the front of the vehicle.

1.2 Basic Terminologies. (a) Sub-system and System subsystem subsystem subsystem System is a combination of physical and non-physical components that are configured to serve certain tasks to maintain the output Subsystem is part of the system that is grouped for a certain function (b) Plant subsystem input output Plant is a subsystem where an output signal is derived from the input signal blower room thermostat plant

Cont’d… (c) Input and Output Input = Stimulus Output = Response

Cont’d… (d) System Response Ability of system to achieve desired result is measured in terms of system response: comparison of output versus input. Transient response. Steady State Response. Steady State Error.

1.3 Open Loop System. Disturbance is the unwanted signal that may sway the output . Controller is a subsystem that is used to ensure the output signal follows the input signal. The Open-Loop System cannot compensate for any disturbance that add to the system. Example; bread toaster.

1.4 Close-Loop System. The Close-Loop (feedback control) System can overcome the problem of the Open Loop System in term of sensitivity to disturbance and inability to correct the disturbance.

1.5 The Design Process. The design of a control system follows these steps; Step 1: Transform Requirement into a Physical System. Step 2: Draw the Functional Block Diagram. Step 3: Create the Schematic. Step 4: Develop the Mathematical Model or Block Diagram. Step 5: Reduce the Block Diagram. Step 6: Analyze and Design.

Figure 1.5: Process Control System uses in the Laboratory. Cont’d… Figure 1.5: Process Control System uses in the Laboratory.

Figure 1.6: Servo Control Uses in the Laboratory.

1.7 Block Diagram. Transfer function is the ratio of the output over the input variables. The output signal can then be derived as; c = Gr (a) Multi-variables.

Figure 1.7: Block Diagram of Summing Point. Cont’d… (b) Block Diagram Summing point. Figure 1.7: Block Diagram of Summing Point.

© Linear Time Invariant System. Cont’d… © Linear Time Invariant System. Figure 1.8: Components of a Block Diagram for a Linear, Time-Invariant System.

(d) Cascade System. Cont’d… Figure 1.9: Cascade System and the Equivalent Transfer Function. Figure 1.10: Parallel System and the Equivalent Transfer Function.

(e) Summing Junction. (f) Pickoff Points. Cont’d… Figure 1.11: Block diagram algebra for summing junctions: equivalent forms for moving a block (a) to the left past a summing junction; (b) to the right past a summing junction. Figure 1.12: Block diagram algebra for pickoff points— equivalent forms for moving a block (a) to the left past a pickoff point; (b) to the right past a pickoff point.

Cont’d… Figure 1.13: Block diagram reduction Example 1. (a) collapse summing junctions; (b) form equivalent cascaded system in the forward path and equivalent parallel system in the feedback path; © form equivalent feedback system and multiply by cascaded G1(s)

1.8 Control Signal. E(s) error signal R(s) reference signal Y(s) output signal Feed forward transfer function, Feedback transfer function, Open-loop transfer function,

Close-Loop transfer function, Assume give Cont’d… Close-Loop transfer function, Assume give Variable difference, Characteristic equation, .

1.9 Model. Physical model. Graphical model. Mathematical model. (a) Current-voltage relationship v = ir. v – voltage in Volt (V). i – current in Ampere (A). r – resistance in Ohm. (b) Force-deflection realtionship f – force in Neuton (N). k – spring constant x – displacement in meter (m). © Mass-spring model fo - applied force x - displacement fs - reaction force

1.10 Design Analysis. Transient state A state whereby the system response after a perturbation before the response approach to a steady condition Steady state A state whereby the system response becomes steady after a transient state. Stability The condition of the steady state. If the response converges to a finite value then it is said to be in a stable condition and if the response diverges, it is known to be unstable. A system must be stable in order to produce the proper transient and steady state response. Transient response is important because it effects the speed of the system and influence human patience and comfort.

Figure 1.14: Controller in Computer Subsystem. 1.11 Design. Analogue controller A controller that used analogue subsystem. Digital Controller A controller that used computer as its subsystem. computer drive plant sensor _ + Referene input Actual output Figure 1.14: Controller in Computer Subsystem.