MCT 102 - Introduction to Mechatronics Engineering - Lecture Notes - Sensors and Actuators PDF

MCT 102 – Introduction to Mechatronics Engineering CLO 4: identify, select, and integrate mechatronics components to meet product requirements Prof Christian Bolu Agenda - Week No 5 & 6: November 4, 2024 2 Week No 5 & 6: November 4 and 11, 2024...

MCT 102 – Introduction to Mechatronics Engineering CLO 4: identify, select, and integrate mechatronics components to meet product requirements Prof Christian Bolu Agenda - Week No 5 & 6: November 4, 2024 2 Week No 5 & 6: November 4 and 11, 2024 11:00 Sensors 11:30 Actuators 11:50 Break [10 mins] 12:00 Directional Control Valves 12:30 Quiz Preparation Sensors and Transducers  Sensors & Transducers Overview-Electronics ❑ Electronics is the science and technology of passage of charged particles in gases, vacuum, or in semiconductors - IEEE ❑ Electronics is the branch of physics, engineering and technology dealing with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies. ❑ Electronics is distinct from electrical and electro-mechanical science and technology, which deals with the generation, distribution, switching, storage and conversion of electrical energy to and from other energy forms using wires, motors, generators, batteries, switches, relays, transformers, resistors and other passive components.  Overview: Active Electrical Components Active element Has an auxiliary source of power that supplies a major part of the output power. There may or may not be a conversion of energy from one form to another Components ❑Semiconductor devices - Diodes ❑Transistors ❑ Integrated Circuits  Video to Watch on Semiconductors, Diodes, MOSFET https://www.youtube.com/watch?app=desktop&v=q NnTQTUyS1E https://www.youtube.com/watch?app=deskto p&v=DDalmLJr2_c https://www.youtube.com/watch?v=qY4lV4x TI_k https://www.youtube.com/watch?v=AwRJsze_9m4 Conductors, Insulators, Semiconductors Conductors  Conductors, Insulators, Semiconductors Semiconductors Semiconductor devices are made primarily of silicon (silicon's element symbol is "Si"). Pure silicon forms rigid crystals because of its four valence (outermost) electron structure -- one Si atom bonds to four other Si atoms forming a very regularly shaped diamond pattern  Conductors, Insulators, Semiconductors Semiconductors (N-Type) Pure silicon is not a conductor because there are no free electrons; all the electrons are tightly bound to neighboring atoms. To make silicon conducting, producers combine or "dope" pure silicon with very small amounts of other elements like boron or phosphorus. Phosphorus has five outer valence electrons. When three silicon atoms and one phosphorus atom bind together in the basic silicon crystal cell of four atoms, there is an extra electron and a net negative charge.  Conductors, Insulators, Semiconductors Semiconductors (P-Type) Boron has only three valance electrons. When three silicon atoms and one boron atom bind with each other there is a "hole" where another electron would be if the boron atom were silicon. This gives the crystal cell a positive net charge (referred to as p-type silicon), and the ability to pick up an electron easily from a neighboring cell.  Sensors & Transducers Analog Circuits-Overview ❑ Electric Circuit: Closed path through a series of electronic components in which current flow through. It can be analog or digital ❑ Analog Circuit: Voltage is continuous with value over a specified range. Sensitive to noise ❑ Digital Circuit: Voltage signal represented by only 2 values. Used to perform logic operations using hardware instead of software. ❑ Measurement Quantities: Voltage, Current (DC or AC), Electric Charge (Time integral of current) Analog Circuit Elements-Passive Elements Analog Circuit Elements-Passive Elements Analog Circuit Elements - Resistors  Analog Circuit Elements - Resistors Resistor Colour Codes. Analog Circuit Elements - Resistors Resistors ❑ Individual resistors are small cylindrical devices with color- coded bands indicating their value ❑ Resistor Color Code Table below yellow, violet, orange: First band: yellow-4 Second band: violet-7 Third band: orange-( x 1000) So have 47 x 1000 = 47,000 ohms, or 47k ohm. Analog Circuit Elements-Passive Elements Analog Circuit Elements-Passive Elements  Mechanical Switches [Mechanical Switches are devices that make or break contact in electric circuits] ❑ Toggle (‘break before make’) ❑ Push-button ❑ Rocker ❑ Slide, etc ❑ Toggle Specified by Poles and Throws Poles – possible no. of circuits to be completed by same switching action. Throw - No of individual contacts for each pole  Mechanical Switches [Mechanical Switches are devices that make or break contact in electric circuits] ❑ Toggle (‘break before make’) ❑ Push-button ❑ Rocker ❑ Slide, etc ❑ Push-Button Normally Open [NO] Normally Closed [NC] Widely used as reset switches and doorbells  Mechanical Switches [Mechanical Switches are devices that make or break contact in electric circuits] ❑ Toggle (‘break before make’) ❑ Push-button ❑ Rocker ❑ Slide, etc ❑ Rocker  Mechanical Switches [Mechanical Switches are devices that make or break contact in electric circuits] ❑ Toggle (‘break before make’) ❑ Push-button ❑ Rocker ❑ Slide, etc ❑ Slide  Mechanical Switches [Mechanical Switches are devices that make or break contact in electric circuits] ❑ Toggle (‘break before make’) ❑ Push-button ❑ Rocker ❑ Slide, etc ❑ Problems Bouncing when closing switch Normally solved by providing de-bouncing circuit using flip- flop elements  Operational Amplifiers[Op-Amp] [Analog circuit components that require power to operate. Widely used in amplification and signal conditioning] ❑ Comparator Op-Amp ❑ Inverter Op-Amp ❑ Non-Inverter Op-Amp ❑ Differential Op-Amp ❑ Integrating Op-Amp Ideal Op-Amp ❑ Power Amplifier Symbol Pin Layout 8-pin Op-Amp  Operational Amplifiers[Op-Amp] Power Amplifier Higher current output rating (>>25mA) Used to interface with digital- to-analog (D/A) converter that need to drive DC motors (actuators) Power Op-Amp OPA547 Texas Instruments  Grounding IEC 60417 Ground Symbols (International Electrotechnical Commission) No. 5017 Earth (ground): To identify an earth (ground) terminal in cases where neither the symbol 5018 nor 5019 is explicitly stated. No. 5018 Noiseless (clean) earth (ground): To identify a noiseless (clean) earth (ground) terminal, e.g. of a specially designed earthing (grounding) system to avoid causing malfunction of the equipment. No. 5019 Protective earth (ground): To identify any terminal which is intended for connection to an external conductor for protection against electrical shock in case of a fault, or the terminal of a protective earth (ground) electrode. No. 5020 Frame or chassis: To identify a frame or chassis terminal.  Solenoids and Relays Solenoids Inductive element widely used for on-off applications such as locking or triggering. Switching of electromechanical relays, door locks, ratcheting devices and gate diverters Electrically actuated with two states – Retracted and Extended Solenoid There are Linear (pull- type or push-type) and Rotary types  Solenoids and Relays Relays Electrically actuated switches that use solenoid to make or break the mechanical contact between electrical leads Advantage of Relays is that the input current is electrically insulated from the output current. Also Relays use small coil current to switch a much larger load current.  Analog Circuits and Components Mechatronics Systems Review Questions Review Questions 1 Define what is meant by an analog circuit. 2. List the different types of toogle switches. 3. List the different types of op-amp circuits. 4. Name one way to avoid a ground loop 5. List several applications of solenoids. 6. What is a relay? Digital Components  Analog Circuit Elements - Active Elements Active Elements - Has an auxiliary source of power that supplies a major part of the output power. There may or may not be a conversion of energy from one form to another ❑Semiconductor devices - Diodes ❑Transistors ❑ Integrated Circuits  Digital Components Diode Both p-type and n-type silicon will conduct electricity just like any conductor; however, if a piece of silicon is doped p-type in one section and n-type in an adjacent section, current will flow in only one direction across the junction between the two regions. This device is called a diode and is one of the most basic semiconductor devices.  Digital Components Diode Forward Biased Diode ❑ A diode is called forward biased if it has a positive voltage across it from the p- to n-type material. In this condition, the diode acts rather like a good conductor, and current can flow  Digital Components Diode Reverse Biased Diode ❑ If the polarity of the applied voltage is reversed, then the diode will be reverse biased and will appear non-conducting. Almost no current will flow and there will be a large voltage across the device.  Digital Components ❑ Diodes and Transistors are solid-state switches, in which switching action is caused by non-mechanical motion due to change in the electrical characteristics of the device. ❑ Diodes are direction element that allows current to flow in one direction. Usually current is low when forward-biased but becomes large when the forward- bias approaches the forward voltage, VF. ❑ Current-voltage relationship is non-linear Digital Components ❑ Rectification – change AC voltages to DC ❑ Diode Clamp – To limit the range of a signal in a circuit ❑ Flyback Diode – limit voltage spike generated when switching off inductive loads such as DC motors or relay coils  Digital Components Zener Diodes ❑ A special type of diode. ❑ Similar to ordinary diode when it is forward-biased but does not destroy itself when the reverse-biased voltage exceed the breakdown voltage, VR (called Zener voltage) ❑ Used for regulation of the output voltage in a circuit when the supply voltage is variable or unstable. Symbol Zener Diode  Digital Components Diodes: LED ❑ Light Emitting Diodes. ❑ Emit light when forward-biased ❑ Amount of light emitted is proportional Symbol to the current passing through the LED ❑ Usually encased in coloured plastic casing. ❑ Advantage of LED over light sources is that it takes only a few milliamps to light the diode ❑ LED can be powered by digital power supply (5VDC) ❑ The anode of LED or the positive terminal is longer that the cathode.  Digital Components Diodes: Photodiodes ❑ behaves like an LED but in opposite fashion ❑ amount of current that the photodiode passes is proportional Symbol to the amount of light it receives ❑The current flows from the cathode to the anode (reverse- biased ❑ Photodiodes commonly used as light sensors  Digital Components Thyristors ❑ Silicon-Controlled Rectifier (SCR) ❑ Three-terminal semiconductor. The additional terminal is called the GATE. ❑ When a small current flows into the gate, it allows a much larger current to flow from the anode to the cathode (provided that the voltage between the anode and the cathode is forward-based) Symbol ❑ Latching – ability of the thyristor to remain on even when the gate current is switched off. ❑ Note that if the current to the gate is cut off, the thyristor continues to conduct as long as the voltage applied to it causes it to be forward-based, The thyristor is turned off only when the current between the anode and the cathode drops below a certain value called the holding current Digital Components Thyristors-Uses ❑ Used in Power Control applications to control heaters, dimming switches and motors. It is used to control current from an AC-driven motors. ❑ Over-Voltage Protection Circuits or Crowbar Circuits. It protects from power surges or power- supply malfunction problems. Uses Zener diodes in combination with thyristors  Digital Components Transistor ❑ A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. ❑ There are two types of standard transistors, NPN and PNP, with different circuit symbols. The letters refer to the layers of semiconductor material used to make the transistor. Most transistors used today are NPN because this is the easiest type to make from silicon. Digital Components Types of Transistors ❑ Bipolar Junction Transistor (BJT). ❑ Field Effect Transistor (FET) ❑ Metal Oxide Semiconductor Field Effect Transistor (MOSFET)  Digital Components Bipolar Junction Transistor (BJT) - Characteristics ❑ Active device that requires power to operate ❑ Current-controlled device depending on the current supplied to the base ❑ Small base current allows much larger current to flow between the collector and the emitter ❑ Three states of operation – Off (non-conducting), Linear and saturation states. Depends on the Voltages magnitudes. ❑ Voltage at Emitter VE is always lower than voltage at the Base VB by about 0.6V ❑ Collector voltage VC has to be more positive than Emitter voltage VE ❑ If AC voltages are applied to the base input, then a DC offset voltage (bias voltage) needs to be added in series to the AC voltage to enable the transistor to be controlled by both the positive and negative parts of the AC signal. ❑ Types of BJT circuits: Transistor Switch and Emitter Follower Symbols BJT  Digital Components Phototransistor, Photo Interrupter, Opto-Isolator Phototransistor ❑ Uses light that is received by a photodiode instead of using a voltage to saturate the transistor. Photo Interrupter ❑ A phototransistor and an LED are packaged together to make optical sensors that can be used to detect objects ❑ The LED provides light that is received by the phototransistor. An interruption of the light received by the phototransistor causes the phototransistor to change state, thus indicating the presence of an object in the path between the LED and the phototransistor. Opto-Isolator ❑ Opto-coupler combines two elements (light emitting device such as a diode and a light sensitive device) similar to a photo interrupter but in an enclosed package ❑ It provides coupling between the input and the output sides and used to prevent voltage spikes on one side of the device to damage or effect components on the other side. Metal-Oxide Semiconductor Field Effect Transistor (MOSFET) - Characteristics ❑ Based on the original FET introduced in the 1960s ❑ Three terminal devices as BJT but different names ❑ Voltage applied to the gate is the signal that controls the transistor ❑ Gate insulated from Drain-Source circuit. ❑ Gate has very high internal resistance (input impedance0 and gives advantage in interfacing with other logic circuits. ❑ Act as voltage-controlled resistors. When OFF, D-S resistance is very high, When ON D-S resistance is very low ❑ N-type enhancement MOSFET operate with a positive voltage applied to the gate. ❑ MOSFET has higher power rating and generate less heat Symbol MOSFET  Metal-Oxide Semiconductor Field Effect Transistor (MOSFET) - Comparison Area BJT MOSFET No of Terminals 3 (Three) 3 (Three) Terminal Base (Gate), Collector (Drain), Emitter Gate (Base), Drain (Collector), names (Source) Source (Emitter) Types NPN, PNP n-type, P-Type Control Signal Current applied at Base Voltage applied at Gate States 3: cutoff, active, & saturation 3: cutoff, active, & saturation Rating Lower power rating & higher heat Higher power rating & lower heat generation generation MOSFET BJT  Digital Components Types of Logic Circuits Types of Logic Circuits ❑ Combinational – output is not dependent on the behaviour of the input ❑ Logic Gates ❑ Multiplexer ❑ Sequential – signal history is important and determines the output of the system ❑ Flip-flops ❑ Shift Registers ❑ Counters Truth Table: gives the output logic for all combination of the input logic.  Digital Components Combinational Logic Circuits The AND Device AND symbol Distinctive Shape AND symbol Rectangular Shape Boolean algebra between A & B A.B TRUTH TABLE INPUT OUTPUT A B A AND B 0 0 0 0 1 0 1 0 0 1 1 1  Digital Components Combinational Logic Circuits The OR Device OR symbol Distinctive Shape OR symbol Rectangular Shape Boolean algebra between A & B A+B TRUTH TABLE INPUT OUTPUT A B A OR B 0 0 0 0 1 1 1 0 1 1 1 1  Digital Components Combinational Logic Circuits The NOT Device (Inverter) NOT symbol Distinctive Shape NOT symbol Rectangular Shape Boolean algebra between A & B TRUTH TABLE INPUT OUTPUT A NOT A 0 1 1 0  Digital Components Combinational Logic Circuits The NAND Device NAND symbol Distinctive Shape NAND symbol Rectangular Shape Boolean algebra between A & B TRUTH TABLE INPUT OUTPUT A B A NAND B 0 0 1 0 1 1 1 0 1 1 1 0  Digital Components Combinational Logic Circuits The NOR Device NOR symbol Distinctive Shape NOR symbol Rectangular Shape Boolean algebra between A & B TRUTH TABLE INPUT OUTPUT A B A NOR B 0 0 1 0 1 0 1 0 0 1 1 0  Digital Components Combinational Logic Circuits The XOR Device XOR symbol Distinctive Shape XOR symbol Rectangular Shape Boolean algebra between A & B TRUTH TABLE INPUT OUTPUT A B A XOR B 0 0 0 0 1 1 1 0 1 1 1 0  Digital Components Combinational Logic Circuits The XNOR Device XNOR symbol Distinctive Shape XNOR symbol Rectangular Shape Boolean algebra between A & B Or TRUTH TABLE INPUT OUTPUT A B A XNOR B 0 0 1 0 1 0 1 0 0 1 1 1  Digital Components Combinational Logic Circuits Boolean Algebra A+B=B+A Commutative law A.B=B.A (A + B) + C = A + (B +C) Associative Law (A.B). C = A. (B. C) A. (B + C) = (A. B) + (A. C) Distributive Law A + (B. C) = (A + B). (A + C)  Digital Components Boolean Algebra De Morgan Rules Others Digital Components  Digital Components Combinational Logic Circuits Karnaugh Map (k-map) Using Karnaugh Map Solver ( 2 Variables)  Digital Components Karnaugh Map (k-map) Using Karnaugh Map Solver ( 3 Variables)  Digital Components Exercise Write the Boolean equation for each of the logic gate circuits. A is ON, but all B, C, D are OFF A is OFF but either B, or C or D is ON Solution: Step 1: Construct Truth Table that has all the input combination and follows the above rules Step 2: Construct a Karnaugh Map to map all the non-zero outputs. Step 3: Use the Solver  Combinational Logic Circuits Examples No 1: Two limit switches connected in series and used to control a solenoid valve Relay Schematic Ladder Logic Program Gate Logic Boolean Equation AB=Y  Combinational Logic Circuits Examples No 2: Two limit switches connected in parallel and used to control a solenoid valve Relay Schematic Ladder Logic Program Gate Logic Boolean Equation A+B=Y  Combinational Logic Circuits Examples No 3: Two limit switches connected in parallel with each other and in series with a relay contact, and used to control a pilot light Relay Schematic Ladder Logic Program Gate Logic Boolean Equation (A+B)C=Y  Sequential Logic Circuits Sequential Logic Circuits ❑Dependent on the history of the input ❑A Combinational logic with memory ❑A Basic Sequential Logic Circuit is the FLIP-FLOP. ❑Flip-flop is a sequential logic device that can store an switch between two binary states. Examples are: Counters, Shift Registers and Microprocessors ❑Types of Flip-flops ❑SR Flip-Flop (set-reset flip-flop) ❑Clocked SR Flip-Flop ❑JK Flip-Flop ❑D Flip-Flop ❑T Flip-Flop Digital Devices (555 Timer) 555 Timer Chip (e.g. NE555 8-pin chip from Texas Instruments) ❑This is a integrated circuit (IC) that uses transistor, resistor, flip-flop, comparators and capacitors to produce a variety of clock signals, including a fixed pulse, a periodic signal, and a frequency dividing signal  H-Bridge Drives H-Bridge Drives ❑A common application of transistors to construct drivers to drive motors. The circuit looks like the H-alphabet ❑An H bridge is an electronic circuit that enables a voltage to be applied across a load in either direction  Semiconductor Electronic Mechatronics Devices & Systems Digital Circuits Review Questions Review Questions 1 What is the functional difference between a normal diode and Zener diode? 2. What is a thyristor? 3. What is the difference between a relay and a transistor? 4. Name one major difference between a BJT and a MOSFET? 5. What is the difference between combinational and sequential logic circuit? 6. What is a Karnaugh map? 7. For what purpose is an H-bridge driver circuit used?  Introduction to Sensors & Sensitivity Analysis 1. Sensor Classification 2. Parameter Measurement in Sensors and Transducers 3. Quality Parameters 4. Errors and Uncertainty in Mechatronic Modeling 5. Sensitivity Analysis – Influence of Component Variation Sensor & Transducer Definitions  Introduction to Sensors & Sensitivity Analysis ❑ Sensor provide a mechanism for collecting different types of information about a particular process ❑ A Sensor is a device that produces an output signal for the purpose of sensing of a physical phenomenon. ❑ A transducer is a device that converts a signal from one physical form to a corresponding signal, which has a different physical form  Introduction to Sensors & Sensitivity Analysis Sensor Sensitivity Analysis ❑ A Sensor is an element that produces an output in response to changes in physical quantities (such as temperature, force, or displacement). ❑ The active element of some sensors is called a transducer, which is part of the sensor that converts the physical quantity (such as the force or displacement into an equivalent electrical signal in the form of voltage or current) ❑ The physical quantity changes a property of the transducer (such as its resistance, inductance or magnetic coupling). Through electronic circuits, these property changes of the transducer are converted into a low-level voltage or current electrical signals.  Introduction to Sensors & Sensitivity Analysis Sensor Sensitivity Analysis ❑The terms sensor and transducer are sometimes treated as synonymous, but not all sensors produce an electrical signal as an output. E.g. mercury bulb thermometer and spring scale force sensor ❑ Normally the output from the transducer is not suitable to be read by a display device or meter, and signal conditioning operations (such as filtering and amplification) are needed to process the output. ❑ Variety of Sensors: ❑ measure motion-related information (such as strain, speed, displacement and acceleration) ❑ measure process parameters ( such as temperature, level, and pressure)  Introduction to Sensors & Sensitivity Analysis Sensor Sensitivity Analysis ❑ A transducer is that part of the measurement system that converts information about a measurand from one domain to another, ideally without information loss. The domains are optical, electrical, magnetic, thermal and mechanical. ❑ A transducer has at least one input and one output. ❑ A input transducer – with non-electrical input (called Sensor) ❑ An output transducer - with non-electrical output (called Actuator) ❑ Smart Sensors – include signal conditioning  Digital Components Sensor Sensitivity Analysis ❑ Sensor Development ❑ There are over 100,000 types of sensors. This large number is due the following: a. Reduced Prices as a result of technology and volume b. Miniaturisation of IC technology and micro-machining. MEMS – micro-Electromechanical Systems are taking over from traditional mechanical sensors c. Smart Sensing - technology allows for integration of signal conditioning and sensing function in a single chip. ❑ MEMS sensors examples are accelerometers and gyroscopes developed by micro-machining technology. Sensor Nomenclature and Classification  Digital Components Sensor Classification Schemes  Digital Components Sensor Nomenclature Nomenclature Sensor Type Position & Distance Sensors – measures two defined points Movement Position Sensor – measures coordinates Displacement Sensors – measures change in position Range Sensor – measures 3D space distance Proximity Sensor – determines sign of linear distance Level Sensor – measures top level distance Angular Sensor – measures angle of rotation Encoder – binary displacement sensor Tilt Sensor - angle relative to Earth normal Tachometer – measures rotational speed Vibration Sensor – motion of vibrating object Accelerometer – measures acceleration  Digital Components Sensor Nomenclature Nomenclature Sensor Type Pressure Sensor – measures pressure differnece Measurement Force Sensor - measures exerted force of Force Torque Sensor – Measures torque (moment) Force-Torque Sensor – measure force & Torque Load Cell – measures weight Strain Gauge – measures linear elongation (+ve / –ve) Touch Sensor – Detects mechanical contact Tactile Sensor – measures 3D shape by touch  Digital Components Sensor Nomenclature Nomenclature Sensor Type Hall Sensor – measures magnetic field Operating Coriolis Mass Flow Sensor – mass flow measurement Principle Gyroscope – measures angle or angular velocity Eddy Current Sensor – short range distance LVDT – voltage transformer (Linear Variable Displacement Transformer) NTC – temperature sensor (Negative Temperature Coefficient) Sensors in Measurement & Instrumentation Systems  Digital Components Sensors & Information Image Sensors ❑ Used to acquire information related to structures and shapes ❑ Can be 1D, 2D or 3D images ❑ Imaging can be optical, acoustic or tactile ❑ Most imaging system use a Charge Couple Device (CCD) Camera ❑ Tactile Imaging Sensors are attractive for control purposes in assembly processes and robotics.  Digital Components Sensor Selection Steps 1. Analyse task to be supported and future requirement 2. List potential sensors with environmental conditions, mechanical and electrical constraints. Note interface electronics 3. If commercial sensor is available – BUY 4. Consider measurand principle and select optimal sensor component and type 5. Find suitable sensing method for each of the sensing principle 6. Final selection of components of the system 7. Decide what to make or buy with respect to cost and time.  Digital Components Physical Quantities in Sensors Classification of Criteria Quantities Direction Vector or Scalar Time behaviour Static (state variable) or Dynamic (rate variable) Energy Variable or Material (Constant) property Dependence on mass Intensive Quantity (independent of mass) or Extensive or size Quantity (dependent on mass) Resistivity & Resistance End-Points of lumped Across Variable – (difference in value between ends) element Through Variable same value at the ends. Cause and Effect Independent and Dependent variables Power Conjugate Product of Effort Variable and Flow Variables Energy Conjugate Product of Effort Variable and Flow Variables  Digital Components Power Conjugate Variables for Various Domains Domain Effort Variable Flow Variable Mechanical (Translational) Force Velocity Mechanical (Rotational) Torque Angular Velocity Pneumatic, Hydraulic Pressure Volume Flow Electrical Voltage Current Magnetic Current Voltage Thermal Temperature Energy Flow  Digital Components Sensor Classification Classification Based On: 1. Measurand – Physical quantities 2. Application Area – mobile robotics, industrial inspection 3. Port Models – need for auxiliary energy. Direct Sensors (Self-generating) need NO auxiliary energy. Modulating (Interogating) Sensors use additional energy for their operation Example of Direct Sensors – Piezoelectric acceleration sensor Examples of Modulating Sensors – All resistive, capacity and Inductive Sensors 4. Energy Domain - (9) Electomagnetic, Gravitational, Mechanical, Electrostatic, Molecular, Atomic, Nuclear, Mass Domains Sensor Performance  Digital Components Sensor Performance Terminology ❑ Static Characteristics: the sensor output after it has settled due to changes in the physical quantity being measured. ❑ Dynamic Characteristics: sensor characteristics from the time the physical quantity has changed to the time before the output has settled.  Digital Components Sensor Performance Terminology Static Characteristics Dynamic Characteristics ❑ Range ❑ Rise Time ❑ Accuracy ❑ Time Constant ❑ Sensitivity ❑ Settling Time ❑ Resolution ❑ Bandwidth ❑ Hysteresis ❑ Repeatability ❑ Non-linear Error/Linearity ❑ Stability ❑ Backlash  Sensor Performance Terminology Static Characteristics Description ❑ Range ❑ Minimum to maximum value that can be measured. ❑ Defines the allowable range of the physical quantity that can be detected by the sensor. ❑ Accuracy ❑ Difference between true and actual measured value ❑ Expressed as percentage of full-scale value ❑ Can be improved by calibration ❑ Sensitivity ❑ Relationship between the measured input and the output ❑ For linear input-output, the sensitivity is the slope of the curve ❑ Resolution ❑ The smallest change in input value that will produce an observable change in the output ❑ Hysteresis ❑ The maximum difference in sensor output for the same input quantity, with one measured while input was increasing from zero and the other decreasing the input from the maximum input. ❑ Repeatability ❑ Error in output value for repeated application of the same input value or Precision ❑ Smaller repeatable error the higher the measurement precision. ❑ Non-linear ❑ Measure of the maximum difference between the sensor actual output and a Error straight-line fit to the sensor input-output data. ❑ Stability or ❑ Variation of the output when the input quantity is not changing. When no input is Drift applied to the sensor, the output variation is called zero drift. ❑Stability affects repeatability. ❑ Backlash  Digital Components Sensor Performance Terminology Dynamic Description Characteristics ❑ Rise Time ❑ Time it takes the output to change a certain percentage ❑ Common measure is 10-90% of the final steady-state value. ❑ Time ❑ Time it takes the output to reach 63.2% of the final output. Constant Sluggish if time constant is large. ❑ First order response characteristics takes 4 time constant when subjected to a step input ❑ Settling Time ❑ Time it takes the output to reach within certain percentage of the final steady-state value, such as 2% settling time. ❑ Bandwidth ❑ Defines the frequency range for which the sensor is designed to operate. ❑ At the bandwidth frequency, the sensor output will be 70.7% of the DC level. Above that the output will be significantly diminished.  Digital Components Sensitivity In an electrical measuring instrument, if the movement of 0.001 mm causes an output voltage change of 0.02 V, the sensitivity of the measuring instrument is given as: V/mm  Digital Components Resolution, Accuracy Resolution: If a micrometer with a minimum graduation of 1mm is used to measure to the nearest 0.5mm, then by interpolation, the resolution is estimated as 0.5mm Accuracy: An accuracy of ±0.001 means that the measured value is within 0.001 units of actual value. It defined as: If a precision balance reads 1g with error of 0.001 g, then the accuracy of the instrument is specified as 0.1%. The difference between the measured value and true value is called bias (error)  Digital Components Sensor Performance Terminology - Precision Directional Control Valves  CLO 4: Directional Control Valves Directional Control Valves ❑ Directional control valves (DCVs) come in various types, each designed to control fluid flow paths within pneumatic or hydraulic systems. ❑ Their main function is to direct the flow of air or hydraulic fluid, enabling controlled movement of actuators such as cylinders or motors. ❑ DCVs are classified based on factors such as the number of positions, flow paths (or “ways”), actuation methods, and construction.  CLO 4: Directional Control Valves Types of Valves ❑ Directional control valves (DCVs): They determine the path through which a fluid transverses a given circuit. ❑ Pressure control valves: They protect the system against overpressure, which may occur due to a sudden surge as valves open or close or due to an increase in fluid demand. ❑ Flow control valves: Shock absorbers are hydraulic devices designed to smooth out pressure surges and to dampen hydraulic shock  CLO 4: Directional Control Valves Directional Control Valves A DCV is mainly required for the following purposes: ❑ To start, stop, accelerate, decelerate and change the direction of motion of a hydraulic actuator. ❑ To permit the free flow from the pump to the reservoir at low pressure when the pump’s delivery is not needed into the system. ❑ To vent the relief valve by either electrical or mechanical control. ❑ To isolate certain branch of a circuit.  CLO 4: Directional Control Valves Classification of DCVs based Fluid Path ❑ Check valves. ❑ Shuttle valves. ❑ Two-way valves. ❑ Three-way valves. ❑ Four-way valves.  CLO 4: Directional Control Valves Reviews What is the primary function of a directional control valve in a hydraulic or pneumatic system? A) To increase fluid pressure B) To control the direction of fluid flow C) To reduce system temperature D) To filter impurities Answer: B) To control the direction of fluid flow CLO 4: Directional Control Valves Classification of DCVs based on Design Characteristics CLO 4: Directional Control Valves Classification of DCVs based on Design Characteristics  CLO 4: Directional Control Valves Classification by Number of Positions and Ways ❑ 2-Way Valves: These have two ports—an inlet and an outlet—and allow for simple on-off control. They are often used in applications where flow needs to be turned on or off completely, such as controlling single-action cylinders. ❑ 3-Way Valves: These have three ports—typically an inlet, outlet, and exhaust port. They are used for controlling single-acting actuators or to release pressure from the system. Common applications include controlling single- acting pneumatic cylinders.  CLO 4: Directional Control Valves Classification by Number of Positions and Ways ❑ 4-Way Valves: These have four ports, with two outlets directing flow to double-acting actuators, one inlet, and one exhaust. They allow for reversing the direction of actuator movement, making them ideal for double-acting cylinders or motors. ❑ 5-Way Valves: These are similar to 4-way valves but with an additional exhaust port, allowing better control of exhaust flow from both outlets. They are mainly used in pneumatic applications to manage the exhaust on both sides of the actuator.  CLO 3: Directional Control Valves Reviews Which directional control valve configuration is typically used for double-acting cylinders? A) 2/2 valve B) 3/2 valve C) 4/2 valve D) 4/3 valve Answer: D) 4/3 valve CLO 4: Directional Control Valves Discuss  CLO 4: Directional Control Valves Classification of DCVs based on Design Characteristics 3/2 way valve : 3ports and 2 position DCV CLO 4: Directional Control Valves Classification of DCVs based on Design Characteristics CLO 3: Directional Control Valves Classification of DCVs based on Design Characteristics  CLO 4: Directional Control Valves Videos to Watch https://www.youtube.com/watch?v=bXXL-0sf8gs https://www.youtube.com/watch?v=CQPwvWXbV3w https://www.youtube.com/watch?v=_Ae77QL46_4 Q&A https://www.youtube.com/watch?v=FkgBjfWMA9U Pilot operated DCV  CLO 4: Directional Control Valves Reviews In hydraulic circuits, a 2-way directional control valve typically has: A) 2 positions and 2 ports B) 3 positions and 2 ports C) 2 positions and 3 ports D) 3 positions and 3 ports Answer: A) 2 positions and 2 ports  CLO 4: Directional Control Valves Reviews Which of the following directional control valves is most suitable for controlling bidirectional hydraulic motors? A) 2/2 valve B) 3/2 valve C) 4/2 valve D) 5/2 valve Answer: C) 4/2 valve  CLO 4: Directional Control Valves Reviews A 4/3 directional control valve indicates: A) 4 ports and 3 flow positions B) 3 ports and 4 flow positions C) 4 ports and 4 flow positions D) 3 ports and 3 flow positions Answer: A) 4 ports and 3 flow positions  CLO 4: Directional Control Valves Reviews In a schematic of a directional control valve, a T-shaped line represents: A) An open port B) An exhaust port C) A closed port D) A fluid reservoir Answer: C) A closed port  CLO 4: Directional Control Valves Reviews In a directional control valve symbol, what does a square represent? A) Fluid port B) Flow path C) Actuator D) Position Answer: D) Position  CLO 4: Directional Control Valves Classification by Actuation Methods ❑ Manual Actuation: Actuated by levers, pedals, or push- buttons, manual DCVs are used when the operator needs to control the valve directly. These are common in applications where manual control is desired or automation is unnecessary, such as in small machinery or industrial control panels. ❑ Mechanical Actuation: These valves are operated by mechanical means, such as cams, rollers, or springs. They are used in situations where the valve needs to respond automatically to physical contact with a part of the machine or workpiece.  CLO 4: Directional Control Valves Classification by Actuation Methods ❑ Solenoid (Electrically Actuated): Solenoid-actuated valves use an electrical current to actuate the valve via a magnetic coil. They are widely used in automated systems due to their ability to be remotely controlled by electrical signals, making them ideal for programmable logic- controlled (PLC) systems in automation. ❑ Pneumatic Actuation: Pneumatically actuated DCVs use compressed air to shift the valve. These valves are suitable for hazardous environments where electrical actuation might be risky.  CLO 4: Directional Control Valves Classification by Actuation Methods ❑ Hydraulic Actuation: Used in hydraulic systems where high forces are needed, these valves are actuated by pressurized hydraulic fluid, allowing them to control large hydraulic actuators.  CLO 4: Directional Control Valves Reviews Which type of actuator is commonly used to operate a directional control valve? A) Electric motor B) Pneumatic cylinder C) Solenoid D) Hydraulic pump Answer: C) Solenoid  CLO 4: Directional Control Valves Classification by Internal Design ❑ Spool Valves: Spool valves are among the most common types, with a cylindrical spool that moves within the valve body to open or close different ports. Spool valves can have multiple positions and are often used in high-pressure applications due to their durability and versatility. ❑ Poppet Valves: Poppet valves use a disc or ball that moves within a seat to open or close ports, creating a seal that controls fluid flow. They are known for fast response times and are often used in applications requiring high sealing ability, such as high-speed pneumatic circuits.  CLO 4: Directional Control Valves Classification by Internal Design ❑ Rotary Valves: These valves use a rotating element to connect or block different ports. They are less common but useful in applications where a compact design and low torque are required. Rotary valves are often found in simple pneumatic systems. ❑ Check Valves (One-Way Valves): While not always classified as directional control valves, check valves allow flow in only one direction, preventing reverse flow. They are typically used to protect equipment from backflow and can be combined with other DCVs for safety purposes.  CLO 4: Directional Control Valves Specialized Directional Control Valves ❑ Proportional Valves: These valves allow for variable control of flow direction and rate, rather than simply being open or closed. Proportional control is beneficial in applications requiring smooth, precise adjustments, such as in robotics or motion control. ❑ Servo Valves: These highly precise, electrically actuated valves provide closed-loop control and are used in applications where exact positioning and speed are critical, such as in aerospace or advanced manufacturing.  CLO 4: Directional Control Valves Reviews A double-acting cylinder is typically controlled by which type of directional control valve? A) 2/2 valve B) 3/2 valve C) 5/2 valve D) 5/3 valve Answer: C) 5/2 valve  CLO 4: Directional Control Valves Reviews Which of the following components in a directional control valve prevents the valve from moving freely when flow is stopped? A) Actuator B) Spool C) Check valve D) End cap Answer: B) Spool  CLO 4: Directional Control Valves Reviews In a 5/3 directional control valve, what does the "3" indicate? A) The number of input ports B) The number of output ports C) The number of flow paths D) The number of positions Answer: D) The number of positions  CLO 4: Directional Control Valves Reviews When designing a directional control valve circuit for safety, the valve should be in which position when the system is off? A) Neutral B) Fully open C) Closed D) Pressurized Answer: A) Neutral  CLO 4: Directional Control Valves Reviews The term "monostable" in directional control valves means: A) The valve has only one port B) The valve has one stable position C) The valve has a single spool D) The valve operates in multiple flow directions Answer: B) The valve has one stable position  CLO 4: Directional Control Valves Reviews In a hydraulic circuit, which device commonly assists a spring- return directional control valve to return to its original position? A) Solenoid B) Actuator C) Detent D) Spring Answer: D) Spring  CLO 4: Directional Control Valves Reviews Which directional control valve feature allows it to switch between positions without continuous external force? A) Detent mechanism B) Spool design C) Flow restrictor D) Pilot port Answer: A) Detent mechanism  CLO 4: Directional Control Valves Specialized Directional Control Valves Pilot-Operated Valves: Pilot valves use an auxiliary pressure source (air or hydraulic fluid) to assist in actuating the main valve. They are typically used in high-pressure systems where large valves require more force to actuate and offer enhanced control over large actuators.  CLO 4: Directional Control Valves Reviews The main advantage of a pilot-operated directional control valve over a direct-acting valve is: A) Greater flow capacity B) Faster switching time C) Higher pressure resistance D) Reduced operational cost Answer: A) Greater flow capacity  CLO 4: Directional Control Valves Reviews What is the function of a detent in a directional control valve? A) To create a pressure lock B) To hold the valve in a specific position C) To reduce flow rate D) To filter the fluid Answer: B) To hold the valve in a specific position  CLO 4: Directional Control Valves Reviews What type of directional control valve allows flow in one direction and blocks it in the opposite direction? A) Pressure relief valve B) Check valve C) Spool valve D) Flow control valve Answer: B) Check valve  CLO 4: Directional Control Valves Reviews Which type of directional control valve uses a spool that shifts to control fluid flow? A) Check valve B) Globe valve C) Spool valve D) Gate valve Answer: C) Spool valve  CLO 4: Directional Control Valves Applications Based on Valve Type ❑ Single-Acting Cylinders: Often controlled by 2- or 3-way valves. ❑ Double-Acting Cylinders: Controlled by 4- or 5-way valves. ❑ Automated Systems: Solenoid-operated 4- or 5-way valves are common. ❑ High-Precision Machinery: Proportional and servo valves are used due to their ability to control speed and position accurately.