Introduction to Control Systems: Regulation and Control System

 Basic Concepts  Control System Examples  Control System Design

January 11,  Tornado  Boeing 777 Highly nonlinear, complicated dynamics! Both are capable of transporting goods and people over long distances BUT One is controlled, and the other is not. Control is “the hidden technology that you meet every day” It heavily relies on the notion of “feedback”

 Control systems are an integral component of any industrial society and are necessary to provide useful economic products for society.  Control engineering is based on the foundation of feedback theory and linear system analysis, and integrates the concepts of network theory and communication theory. Therefore, control engineering is not limited to any engineering discipline but is equally applicable for aeronautical, chemical, mechanical, environmental, civil, and electrical engineering. For example, quite often a control system includes electrical, mechanical, and chemical components.

 System  A collection of components which are coordinated together to perform a function.  Dynamic System  A system with a memory.  For example, the input value at time t will influence the output at future instant.  A system interact with their environment through a controlled boundary.

 The interaction is defined in terms of variables. i. System input ii. System output iii. Environmental disturbances

 The system’s boundary depends upon the defined objective function of the system.  The system’s function is expressed in terms of measured output variables.  The system’s operation is manipulated through control input variables.  The system’s operation is also affected in an uncontrolled manner through disturbance input variables.

 Control is the process of causing a system variable to conform to some desired value.  Manual control Automatic control (involving machines only).  A control system is an interconnection of components forming a system configuration that will provide a desired system response. Control System Output Signal Input Signal Energy Source

 Control is a process of causing a system variable such as temperature or position to conform to some desired value or trajectory, called reference value or trajectory.  For example, driving a car implies controlling the vehicle to follow the desired path to arrive safely at a planned destination. i. If you are driving the car yourself, you are performing manual control of the car. ii. If you use design a machine, or use a computer to do it, then you have built an automatic control system.

 Transient response:  Gradual change of output from initial to the desired condition  Steady-state response:  Approximation to the desired response  For example, consider an elevator rising from ground to the 4 th floor.

 Component or process to be controlled can be represented by a block diagram.  The input-output relationship represents the cause and effect of the process.  Control systems can be classified into two categories: i. Open-loop control system ii. Closed-loop feedback control system Process OutputInput

 An open-loop control system utilizes an actuating device to control the process directly without using feedback.  A closed-loop feedback control system uses a measurement of the output and feedback of the output signal to compare it with the desired output or reference. Actuating Device Process Output Desired Output Response Measurement Output ControllerProcessComparison Single Input Single Output (SISO) System

Open-Loop Control System Missile Launcher System

Closed-Loop Feedback Control System Missile Launcher System

Desired Output Response Measurement Output Variables ControllerProcess Multi Input Multi Output (MIMO) System

 Static or Dynamic Systems: Static systems are composed of simple linear gains or nonlinear devices and described by algebraic equations, and dynamic systems are described by differential or difference equations.  Continuous-time or Discrete-time Systems: Continuous-time dynamic systems are described by differential equations and discrete-time dynamic systems by difference equations.

i. Power Amplification (Gain)  Positioning of a large radar antenna by low-power rotation of a knob ii. Remote Control  Robotic arm used to pick up radioactive materials iii. Convenience of Input Form  Changing room temperature by thermostat position iv. Compensation for Disturbances  Controlling antenna position in the presence of large wind disturbance torque

i. Ancient Greece (1 to 300 BC)  Water float regulation, water clock, automatic oil lamp ii. Cornellis Drebbel (17 th century)  Temperature control iii. James Watt (18 th century)  Flyball governor iv. Late 19 th to mid 20 th century  Modern control theory

i. Pancreas  Regulates blood glucose level ii. Adrenaline  Automatically generated to increase the heart rate and oxygen in times of flight iii. Eye  Follow moving object iv. Hand  Pick up an object and place it at a predetermined location v. Temperature  Regulated temperature of 36°C to 37°C

 Figure shows a schematic diagram of temperature control of an electric furnace. The temperature in the electric furnace is measured by a thermometer, which is analog device. The analog temperature is converted to a digital temperature by an A/D converter. The digital temperature is fed to a controller through an interface. This digital temperature is compared with the programmed input temperature, and if there is any error, the controller sends out a signal to the heater, through an interface, amplifier and relay to bring the furnace temperature to a desired value.

Car and Driver  Objective: To control direction and speed of car  Outputs: Actual direction and speed of car  Control inputs: Road markings and speed signs  Disturbances: Road surface and grade, wind, obstacles  Possible subsystems: The car alone, power steering system, breaking system

 Functional block diagram:  Time response: Measurement, visual and tactile Steering Mechanism Automobile Driver Desired course of travel Actual course of travel Error + -

 Consider using a radar to measure distance and velocity to autonomously maintain distance between vehicles.  Automotive: Engine regulation, active suspension, anti-lock breaking system (ABS)  Steering of missiles, planes, aircraft and ships at sear.

 Control used to regulate level, pressure and pressure of refinery vessel.  For steel rolling mills, the position of rolls is controlled by the thickness of the steel coming off the finishing line. Coordinated control system for a boiler- generator.

 Consider a three-axis control system for inspecting individual semiconducting wafers with a highly sensitive camera

i. CD Players  The position of the laser spot in relation to the microscopic pits in a CD is controlled. ii. Air-Conditioning System  Uses thermostat and controls room temperature.

i. System, plant or process  To be controlled ii. Actuators  Converts the control signal to a power signal iii. Sensors  Provides measurement of the system output iv. Reference input  Represents the desired output

Sensor Actuator Process Controller + + Set-point or Reference input Actual Output Error Controlled Signal Disturbance Manipulated Variable Feedback Signal

January 11,  Flight Control Systems  Modern commercial and military aircraft are “fly by wire”  Autoland systems, unmanned aerial vehicles (UAVs) are already in place  Robotics  High accuracy positioning for flexible manufacturing  Remote environments: space, sea, non-invasive surgery, etc.  Chemical Process Control  Regulation of flow rates, temperature, concentrations, etc.  Long time scales, but only crude models of process  Communications and Networks  Amplifiers and repeaters  Congestion control of the Internet  Power management for wireless communications  Automotive  Engine control, transmission control, cruise control, climate control, etc  Luxury sedans: 12 control devices in 1976, 42 in 1988, 67 in 1991  AND MANY MORE...

“The right half of the brain controls the left half of the body. This means that only left handed people are in their right mind…”