Lecture 1 Text Book: ELEC 483-001 Sensors And Actuators

Lecture 1IntroductionText Book:ELEC 483-001Sensors and ActuatorsSENSORS AND ACTUATORS: Control System Instrumentation, C. W. de Silva, CRC Press, ISBN: 1420044834, 2007References:MECHATRONICS - An integrated approach, C. W. de Silva, Taylor & Francis, CRC Press, Boca Raton, FL, 2005Kalyana C. Veluvolu#IT1-817Tel: 053-950-7232E-mail: veluvolu@ee.knu.ac.krWebsite: http://ncbs.knu.ac.krIntroduction to Mechatronics and Measurement Systems, Histand, M. B.& Alciatore, D. G., McGraw-Hill, 2003School of Electronics EngineeringKyungpook National UniversityLECTURE NOTES DOWNLOADhttp://ncbs.knu.ac.kr1Lecture 1IntroductionGrading Policy Assignments constitute 20% of the grading.Syllabus A total 3-4 Assignments will be given and students arerequired to submit it by the due date. Copying of the solutions from solution manuals and fromfriends will be penalized.LECTURE NOTES on2Performance specification and analysis3Sensors and transducers4Analog sensors for motion5Effort sensors6Torque sensors7Tactile sensing8Midterm exam9Digital transducers10Actuators11Continuous drive actuators12Continuous drive actuators13Hydraulic actuators14Component interconnection and signal conditioning15Final examLecture 1Introduction4

Reasons for Crash of AF 447How Important are Sensors in Today’s World?1. Faulty Speed Sensor (Due to Icing)2. Wrong Control Action from the PilotDamn it, we’re going to crash, this can’t be happening’: Last words from Pilot(10 Seconds before the actual crash)65Autonomous Cars (Driverless Cars)Control, Instrumentation, and DesignPowerReferencePowerController(Digital orAnalog)PowerLecture er(for active esponseSensor/TransducerMechanical system(Plant, Process)Feedback signal7SignalConditioningPower8

ActuatorsLecture 1IntroductionActuators are needed to perform the control actions as well as drive the plant directly.Two types: Direct type: Motors of a robot arm likeSensors and Actuators used in some common engineering applicationsProcessTypical sensorsDisplacement, speed, acceleration, DC motors, stepper motors, relays,elevation, heading, force, pressure, valve actuators, pumps, heat sourcetemperature, fluid flow, voltage, cur- jet enginesrent, global positioning system (GPS)AutomobileDisplacement, speed, force, pressure,temperature, fluid flow, fluid level,voltage, currentDC motors, stepper motors, valveactuators, pumps, heat sourcesHome heatingsystemTemperature, pressure, fluid flowMotors, pumps, heat sourcesSensorsOften the active element of a sensor is referred as a transducerTypical actuatorsAircraft Indirect: Opening a valve of a hydraulic system which does the actual workSensor is an element in mechatronic or measurement system that detects the magnitudeof a physical parameter and changes it into a signal that can be processed by the system.Lecture 1IntroductionMilling machine Displacement, speed, force, acoustics DC motors, AC motorstemperature, voltage, currentRobotOptical image, displacement, speed,force, torque, voltage, currentDC motors, stepper motors, ACmotors, hydraulic actuatorsWood dryingkilnTemperature, relative humidity,moisture content, air flowAC motors, DC motors, pumps,heat sources109Sensors and Actuators employed in AutomobilesDifferent kinds of SensorsLecture 1IntroductionSensors and Actuators employed in AircraftsLecture 1IntroductionEngine actuatorsAir control valveDigital linear actuatorBrushless DC drivesPumps – Electrical water and Transmission oil pumpsElectronic Throttle Control (ETC) actuator1112

Sensors and Actuators employed in RoboticsLecture 1IntroductionLecture 1IntroductionSensors/Actuators Trends Bioloid, the most advanced robot, which is upgraded with powerful humanoidfunctions and software Bioloid is equipped with servo actuator, gyro sensor, IR sensor, and DMS sensor Worldwide sales of sensors/actuators are forecast to grow 14% to a highof 9.9 billion in 2014, followed by a 16% increase in 2015 to 11.4billion Between 2013 and 2018, the sensors/actuators market is projected to riseby a compound annual growth rate (CAGR) of 11.7% to reach 15.1billion13Lecture 1IntroductionControl System ack signal ConditioningLecture 1IntroductionOpen-loop )ActuatorPlantAnalog sensor/transducer Plant is the system or process that we are interested in controlling Control means to make the system respond in a desired manner. Toaccomplish this, we must have access to the drive system or actuator ofthe plant In feedback control systems, the control loop has to be closed The output measurements are made primarily using analog devices,typically consisting of sensor-transducer units15 No measurement of the response of the system to make it behave inthe desirable manner Plant has to be stable and completely and accurately known Inputs to the plants has to be precisely generated16

Lecture 1IntroductionFeedback (Closed-loop Control)ReferenceControllerPlantExample: Control the speed of a rotating diskLecture 1IntroductionOpen-loop control A DC motor is selected as an actuator to provide the disk rotation DC amplifier provides required power to the motorOutputMeasurementFeedback signal From sensors Measure the response and compare it with a reference to minimize theerror On-off control (bang-bang) Proportional (P) control Proportional control with integral (I) and derivative (D) action – PIDcontrolOpen-loop (without feedback) control of the speed of a rotating diskBlock diagram model17Example: Control the speed of a rotating disk18Digital ControlLecture 1IntroductionLecture 1IntroductionReal-timeclockClosed-loop controlReference OutputsAddressAnalogmultiplexingClosed-loop (with feedback) control of the speed of a rotating ressDigitalmultiplexerBlock diagram model19Digitalsensors/transducers In digital control, digital computer serves as the controller Computers have to be fast and dedicated machines for real-time operations20

Major advantages of digital controlLecture 1Introduction Less susceptible to noise or parameter variation in instrumentation Very high accuracy and speed Handles repetitive tasks extremely well through programming Complex control laws and signal conditioning methods can beprogrammed Large amount of data can be stored using compact, high-density datastorage methods Data can be stored or maintained for very long periods of time Digital control has easy and fast data retrieval capabilities Digital control is cost-effective Digital processing uses low operational voltages(e.g., 0 to 12 V DC)21 For complex processes with a large number of input or output variables,centralized control is difficult to implementReferenceInternet(TCP/IP,UDP)PD1(with direct I/O)PlantControllerOutputMeasurementFeedback signal From sensors In addition to feedback control, feedforward control is used to reducethe effects of a disturbance input that enters the plant The disturbance input is measured and fed into the controller22Lecture 1IntroductionHierarchical ControlGeographic distributionSupervisorycontrolcomputerLevel 3 Form of distributed control is appropriate in large systems such asmanufacturing work cells, factories, multi-agent robotic applicationsFieldbus(Foundation fieldbus, industrial Ethernet, etc.UnknownInputMeasurementforfeedforwardLecture 1IntroductionDistributed ControlLecture 1IntroductionFeedforward ControlProcess plant 1 2Level 2 l control 1 2 lsystemSet points (reference inputs)PDr(with direct I/O)PLCDCSLevel 1PD Process devicePLC Programmable logic controllerDCE Distributed control system (Supervisory atorSensors/transducersPlantsubsystemOutputs24

Hierarchical ControlInstrumentation and DesignLecture 1IntroductionLecture 1Introduction Identification of hardware components w.r.t their functions, operation, interfacing,tuning of the components, etc., in short, instrumenting a control system Identification of design parameters, modelling of various components, andanalysis are often useful in the design process Modelling is important in analyzing, designing, and evaluation of a controlsystemUsercommandsDigital onseActuator25Signal conditioning/filtering26Lecture 1IntroductionComponents Controllers: P, PI, PD, PID, Digital Actuating devices: Stepper motors, AC motors, DC motors, solenoids,valves, and relays Sensors: Potentiometers, differential transformers, resolvers, synchros,gyros, strain gauges, tachometers, piezoelectric devices, fluid flowsensors, pressure gauges, thermocouples, thermistors, resistancetemperature detectors Signal conditioning devices: Charge amps, power amps, filters (lowpass., high-pass, band-pass, notch) Power supplies Protection devices2728

Lecture 1IntroductionDesign considerations PerformanceQualityCostSpeedEase of operationControlActionOn-OffPID controlControlLaw error signal (controller input) control/actuating signal (controller output or plant input) proportional gain derivative time constant integral time tional1Programmable logic controllers (PLC)Comparison of some common control actions1Lecture ous chatterMechanical problemsPoor accuracySimpleFast responseOffset error (Steady state error)Poor stabilityEliminates offsetFilters out noiseLow bandwidth (slow response)Instability problemsHigh bandwidthInsensitive to DC error(Fast response)Allows high-frequency noiseImproves stability Amplifies noiseDifficult analog implementation2930Lecture 1Introduction PLC is a digital-computer-like system- sequence a complex task: discrete operations, several devices PLCs are rugged computers typically used in factories and processplants Computation and control tasks- PID control: continuous-state control, process variables continuouslymonitored and made to stay close to desired values- Discrete-state control* sequence of states (Steps)* in steps there may be continuous-state control PLCs are particularly intended for accomplishing discrete-state control31Example: Operation of a turbine blade manufactureLecture 1IntroductionMove the cylindrical steel billets intofurnace Heat the billets When a billet is properly heated move itto the forging machine Forge the billet into shape Perform surface finishing operations toget the required aero foil shape When the surface finish is satisfactory,machine the blade root 32

Programmable Logic Controller HardwareLecture 1Introduction33SummaryLecture 1IntroductionActuators are needed to perform the control action s as well as to drive theplant directlySensors and transducers are necessary to measure output signals (processresponses) and to measure input signals for feedforward controlOpen-loop (OL) and Closed-loop (CL) systemsOL control system uses a controller and actuator to obtain desired responseInputProcessOutputCL control systems use an additional measure of the actual output forfeedbackDesiredOutputControllerProcessFeedback (measurement)ActualOutput35Performance characteristicsLecture 1Introduction Stability- A stable system will respond in a reasonable manner to an applied input- Asymptotic stability: Response decays back to initial steady state for initialcondition excitation- Bounded input bounded output (BIBO) stability: The response to boundedinput should be bounded Speed of response (bandwidth): System should react quickly to a control input Sensitivity and robustness- Low sensitivity to noise, external disturbances, modeling errors, andparameter variations- High sensitivity to control inputs Accuracy- Low error, tracking error and steady state error Cross sensitivity (dynamic coupling)- Reduced coupling among system variables34

Sensors and Actuators employed in Robotics 13 Sensors/Actuators Trends Worldwide sales of sensors/actuators are forecast to grow 14% to a high of 9.9 billion in 2014, followed by a 16% increase in 2015 to 11.4 billion Between 2013 and 2018, the sensors/actuators market is projected to rise