Measurement Systems PDF

EEP 311 Measurement Systems Dr. Mai Ismail Diab Faculty of Engineering, Alexandria University 1. What is Engineering? 2. Why do we learn Measurements? Introduction to We see measurement every day all the time Measurements Applications of measurements 1. Monitoring of pr...

EEP 311 Measurement Systems Dr. Mai Ismail Diab Faculty of Engineering, Alexandria University 1. What is Engineering? 2. Why do we learn Measurements? Introduction to We see measurement every day all the time Measurements Applications of measurements 1. Monitoring of process and operations 2. Control of process and operations 3. Experimental analysis  Signal Sensors conditioning System Actuator Controller Important definitions Transducer: A transducer is a device that converts one form of energy into another. Sensor Actuator Important definitions Sensor Sensor detects physical parameters (like temperature, pressure, motion, or light) and converts them into a signal that can be measured or interpreted by another system, typically into an electrical signal. Example: A thermocouple that measures temperature and converts it into a voltage. Important definitions Actuator Actuator takes electrical signals or energy and converts them into physical motion or mechanical output. It often works as the output part of a system, such as in robotics or automation. Example: A motor that receives an electrical signal and produces rotational movement. Components of Measurement system Active and Passive transducer Active: doesn’t need extra power supply/self generating Piezo Electric Transducer Photo Electric Transducer Active and Passive transducer Passive: require power mostly from external sources >> it produces the variation in one of passive elements like resistor (R), inductor (L) and capacitor (C). Analog vs digital measurements Analog vs digital measurements  Characteristics of Measurement Instrument Readability Accuracy and and least Sensitivity Resolution precision count Mean and Response Hysteresis standard time deviation Readability/least count Readability The ease in which the reading can be taken. Sensitivity Sensitivity refers to the ability of a measuring instrument to detect small changes in the quantity being measured. change in 𝑜𝑢𝑡𝑝𝑢𝑡 𝑆𝑒𝑛𝑠𝑖𝑡𝑖𝑣𝑖𝑡𝑦 = ch𝑎𝑛𝑔𝑒 𝑖𝑛 𝑖𝑛𝑝𝑢𝑡 Accuracy and precision Measurement error: refers to the difference between the actual value (true value/expected) of a quantity being measured and the value obtained from a measurement. Accuracy: The degree to which a measurement represents the true value. Accuracy and precision You have an air conditioner that is supposed to maintain the temperature of a room at 24°C. You want to check the accuracy of the air conditioner's temperature control by measuring the room temperature with a thermometer. After several measurements, you obtain the following results: 1.True Value (Expected Temperature): 24°C 2.Measured Value: 25°C 3.Absolute Error=∣25−24∣=1°C Accuracy=1−1/24=1−0.0417=0.9583 or 95.83%  Accuracy and precision Precision: The consistency of repeated measurements.  Hysteresis depending on whether the load is being increased or decreased. This happens because the system doesn't immediately return to its original state after the load is removed. Resolution Resolution is the smallest increment a tool can detect and display. Mean and standard deviation 100 200 400 200 100 98cm 99cm 100cm 101cm 102cm Response time The time a sensor takes to react to a change in its environment and produce a measurable output Next time Thank you! EEP 311 Measurement Systems Dr. Mai Ismail Diab Faculty of Engineering, Alexandria University Types of sensors that will be discussed 1. Limit switches 2. Proximity sensors Inductive Capacitive Optical Ultrasonic 3. Temperature sensors 4. Level sensors 5. Flow sensors 6. Position and velocity sensors 7. Chemical sensors ……………..and more Limit switches A limit switch is an Limit switches are electromechanical used to detect the device operated by a presence or absence physical force applied of an object. to it by an object. Next time Next time Usually used for: Presence/absence indication Door closed/open indication Types of Limit switches Types of Limit switches When an object contacts the mechanical part, the switch will operate causing an electrical connection to make or break. Configurations of limit switches SPDT Microswitch Proximity sensors Limit switches are slowly starting to disappear from some industrial applications. They are being replaced by proximity sensors. However, Limit switches are still used in different applications where operation-critical or safety-critical situations and where environment conditions preclude the use of other sensors. Unlike a limit switch, a proximity sensor has no mechanical moving parts. A proximity sensor performs the switching action with electronic switches. Types of Proximity sensors Inductive Proximity sensor Capacitive Proximity sensor Optical Proximity sensor Ultrasonic Proximity sensor Inductive Proximity sensor An inductive sensor is an electronic device that can detect ferrous metal targets without physical contact. The sensing range of an inductive sensor is the distance from the sensor’s face to the maximum distance the sensor can detect a metal target. Inductive Proximity sensor How does it work? The sensor creates an electromagnetic field that emits from the sensor’s face. Putting a metal target near the sensor’s face will disrupt the electromagnetic field, causing the sensor’s output and indicator light to turn on. Inductive Proximity sensor Normally open Vs Normally closed Inductive Proximity sensor PNP = Switched Positive (Sourcing) NPN = Switched Negative (Sinking) Inductive Proximity sensor PNP = Switched Positive (Sourcing) NPN = Switched Negative (Sinking) Inductive Proximity sensor Inductive sensors can get dirty and still work. Things like dirt, and dust do not affect how inductive sensors detect targets. Hall effect sensor A Hall effect sensor is a magnetic sensor. It specifically detects magnetic fields and operates based on the Hall effect, which involves the interaction between a magnetic field and the flow of electric current in a conductor. Reed switch Reed Switches are magnetic sensors that consist of two flat ferromagnetic reeds sealed in an inert atmosphere within a glass capsule. In the presence of a magnetic field the reeds are attracted to each other and close to complete the magnetic and electric circuit Capacitive Proximity sensor Capacitive sensors can detect both metal and non-conductive materials. A capacitive sensor is an electronic device that can detect solid or liquid targets without physical contact. To detect these targets, capacitive sensors emit an electrical field from the sensing end of the sensor. Any target that can disrupt this electrical field can be detected by a capacitive sensor.  Capacitive Proximity sensor Capacitive sensors can detect both metal and non-conductive materials. A capacitive sensor is an electronic device that can detect solid or liquid targets without physical contact. To detect these targets, capacitive sensors emit an electrical field from the sensing end of the sensor. Any target that can disrupt this electrical field can be detected by a capacitive sensor. Capacitive Proximity sensor Capacitive Proximity sensor Optical Proximity Sensors It consist of a light source (LED) and light detector (phototransistor). Optical Sensor is a device that uses light to detect the presence or absence of an object. The basic operation of a Photoelectric Sensor is, the sensor sends out a light beam from the part of the sensor called the emitter, and this light beam travels to the part of the sensor that collects the light called the receiver. Optical Proximity Sensors Optical Proximity Sensors Main Types: 1. Through-beam photoelectric sensor 2. Retroreflective photoelectric sensor 3. Diffused photoelectric sensor Optical Proximity Sensors Optical Proximity Sensors Through-beam photoelectric sensor: Through-Beam sensors have the emitter and the receiver in their own separate component. For the Through-Beam sensor to work, the emitter and receiver have to be pointed at each other and be aligned. When they are aligned and nothing is blocking the light, the output of the sensor will be on. If you put something between the emitter and receiver to block the light, the output of the sensor will turn off (but first check Light-on / dark-on mode if existing in the sensor). Optical Proximity Sensors Through-beam photoelectric sensor: Optical Proximity Sensors Through-beam photoelectric sensor: Through-Beam Photoelectric sensors have a longer detection range than Retroreflective and Diffused Photoelectric Sensors. This is because the light only has to travel in one direction to get from the emitter to the receiver. However, Through-Beam sensors cost more because they have two components that require two cables and two mounts, this is also why they take up more space. Optical Proximity Sensors Retroreflective photoelectric sensor Retroreflective Photoelectric Sensors have the emitter and receiver together in the same component. For the Retroreflective Sensor to work, the sensor’s emitter needs to be pointed at a reflector and aligned, so the light travels from the sensor’s emitter to the reflector and then bounces back to the sensor’s receiver. The Retroreflective sensor output works the same as the Through-Beam sensor output. The output is on if the light is not blocked and the output is off if the light is blocked. Retroreflective photoelectric sensor Retroreflective photoelectric sensor Retroreflective Sensors can also have a light-on, dark-on mode selector switch to change when the sensor’s output turns on. Retroreflective photoelectric sensor Retroreflective sensors have a shorter detection range compared to Through-Beam sensors. This is because the light has to travel to a reflector and then back to the sensor instead of just traveling straight to the receiver. Some disadvantages of using a Retroreflective sensor are you have to install the sensor with a reflector, if the object is shiny it might turn on the sensor’s output instead of the reflector, and the light beam is not as focused as a Through-Beam sensor’s light beam. Diffused photoelectric sensor Diffused Photoelectric Sensors have the emitter and receiver together in the same component. For the Diffused sensor to work, the sensor’s emitter needs to be pointed at an object so the light travels from the sensor’s emitter to the object and then bounces back to the sensor’s receiver. The Diffused sensor output works the same as the Through-Beam and Retroreflective sensor outputs. Diffused Sensors can also have a light-on, dark-on mode selector switch to change when the sensor’s output turns on. Diffused photoelectric sensor Diffused photoelectric sensor The main disadvantage of using a Diffused Sensor is it has the shortest detection range of the three sensors. Because depending on the object’s shape, size, and color it might not reflect light very well back to the receiver. Notes on Optical sensors Fast switching Insensitive to vibration and shock Alignment always required Can be blinded by ambient light conditions Requires clean, dust and water free, environment Light sensors Ultrasonic proximity sensor An ultrasonic sensor is a device which utilizes ultrasonic waves to measure distance or detect objects. Ultrasonic sensing is one of the best ways to sense proximity and detect levels with high reliability. Ultrasonic proximity sensor Ultrasonic proximity sensor Crosstalk and mounting Thank you! EEP 311 Measurement Systems Dr. Mai Ismail Diab Faculty of Engineering, Alexandria University Types of sensors that will be discussed 1. Limit switches 2. Proximity sensors Inductive Capacitive Optical Ultrasonic 3. Temperature sensors 4. Level sensors 5. Flow sensors 6. Chemical sensors 7. Biomedical sensors 8. Position sensors ………………….. Temperature sensors Thermocouple Resistance temperature detectors (RTD) Thermistor Integrated circuit IC temperature sensors Bimetal Temperature sensors Infrared temperature sensors Thermocouple A thermocouple is made of a couple of specific dissimilar wires joined together, forming the “sensing point” or “junction”. Based on physical characteristics called “Thermoelectric Effect”, when this junction is placed at different temperatures, different millivolt signals are generated which can be interpreted as an indication of the temperature. Therefore, when the junction of the two metals is heated or cooled, a small voltage is produced from the heating or cooling effects and can be correlated directly back to the temperature. How does a thermocouple work? When two wires composed of dissimilar metals are joined at both ends and one of the ends is heated, there is a continuous current which flows in the thermoelectric circuit. Which means that when the junction of the two metals is heated or cooled a voltage is produced that can be correlated back to the temperature. Seebeck Effect Temperature sensors  Thermocouple Voltage depends on the composition of metals used in the wires ==> Different Types of Thermocouple Based on “range” of temperature measurement, “sensitivity” and some other factors in each application, different types of Thermocouples are available, for example E, J, K, M, N, T. For instance, Type “J” is made up of “Iron-Constantan” combination with a range of −40°F to +1380°F and sensitivity of about 27.8 µV/°F. Type “K” (Chromel-Alumel) is one of the most common general-purpose thermocouples with a sensitivity of approximately 22.8 µV/°F. Type K is inexpensive and a wide variety of probes are available in its −330°F to +2460°F operating range. Thermocouple Resistance temperature detectors The RTDs use the phenomenon that the resistance of a metal changes with temperature. Since it is a “passive” device, an external electrical current should be applied to it and then the voltage drop across it can be measured. This voltage is an indication of the temperature. RTDs  Materials used for RTD Nickel has a high resistance to corrosion, making it ideal for use in harsh environments. It also has a relatively low cost compared to other materials, making it a popular choice. Platinum, on the other hand, has a high- temperature coefficient, making it highly accurate for temperature measurement. It is also corrosion-resistant, making it ideal for use in harsh environments. Finally, copper has a high electrical conductivity, making it ideal for use in applications where a fast response time is required. It is also relatively low in cost compared to platinum. RTD vs thermocouple Always refer to the data sheets for each temperature sensor before selecting it. Thermistors Thermistors are temperature-dependent resistors and are widely used in industrial purposes, such as: Over-current protection Inrush current limiters Thermistors Thermistors can be NTC or PTC. In NTC (Negative Temperature Coefficient) thermistors, resistance decreases as temperature rises. NTC’s are commonly used as inrush current limiters. With PTC (Positive Temperature Coefficient) thermistors, resistance increases as temperature increases. PTC thermistors are commonly used as overcurrent protection and in resettable fuses. Silicon IC temperature sensor Semiconductor Temperature Sensor is based on the fact that the junction voltage across a p-n combination of semiconductors, like a diode junction or “base-emitter” junction of regular transistors, is a function of temperature. This technology is vastly used in electronic devices and IC technologies. Linear characteristic, small size, and low cost are advantages of this technology, but it should be noted that the limited range of around - 40°F to 248°F makes it suitable for specific applications. Integrated Circuits IC temperature sensor Semiconductor Temperature Sensor is based on the fact that the junction voltage across a p-n combination of semiconductors, like a diode junction or “base- emitter” junction of regular transistors, is a function of temperature. This technology is vastly used in electronic devices and IC technologies. Linear characteristic, small size, and low cost are advantages of this technology, but it should be noted that the limited range of around -40°F to 248°F makes it suitable for specific applications. Temperature transmitter Bimetal temperature sensor Bimetal is a combination of two metals with different degrees of thermal expansion, and when the temperature of the bimetal increases, it bends toward the smaller degree of thermal expansion. A thermostat is a contact-type temperature sensor consisting of a bi-metallic strip made up of two dissimilar metals such as aluminum, copper, nickel, or tungsten. The difference in the coefficient of linear expansion of both metals causes them to produce a mechanical bending movement when it’s subjected to heat. Bimetal temperature sensor Bimetal is a combination of two metals with different degrees of thermal expansion, and when the temperature of the bimetal increases, it bends toward the smaller degree of thermal expansion. Such bimetals keep the temperature constant by disconnecting or connecting the power in electric irons. Infrared temperature sensor Infrared temperature sensor Fiber optic temperature sensor Fiber optic strain sensor Types of sensors that will be discussed 1. Limit switches 2. Proximity sensors Inductive Capacitive Optical Ultrasonic 3. Temperature sensors 4. Level sensors 5. Flow sensors 6. Chemical sensors 7. Biomedical sensors 8. Position sensors ………………….. Level sensors Level sensors Level sensors Level Measurement Sensors Level Measurement Sensors Capacitance level sensor Optical Level Sensor Vibrating (Tuning Fork) Level Sensor Float Switch Ultrasonic Level Sensor Radar Level Sensor Types of sensors that will be discussed 1. Limit switches 2. Proximity sensors Inductive Capacitive Optical Ultrasonic 3. Temperature sensors 4. Level sensors 5. Flow sensors 6. Chemical sensors 7. Biomedical sensors 8. Position sensors………………….. Flow sensors Venturi Flow sensor  Turbine Flow sensor Turbine Flow Meter is inserted in a pipe directly in the flow path. The mechanical part of the Turbine Flow Meter has a turbine rotor placed in the path of a flowing stream. The only moving part of the Turbine Meter is the mechanical rotor. The rotational speed of the rotor depends upon the flow velocity. The rotor blades are usually made of stainless steel. Magnetic Flow sensors The induced voltage between the electrodes calculated by simple equation Which illustrate the operation of an electromagnetic flow meter based on the Faraday's law Ultrasonic Flow sensors Types of sensors that will be discussed 1. Limit switches 2. Proximity sensors Inductive Capacitive Optical Ultrasonic 3. Temperature sensors 4. Level sensors 5. Flow sensors 6. Chemical sensors 7. Biomedical sensors 8. Position sensors………………….. Thank you! EEP 311 Measurement Systems Dr. Mai Ismail Diab Faculty of Engineering, Alexandria University Types of sensors that will be discussed 1. Limit switches 2. Proximity sensors Inductive Capacitive Optical Ultrasonic 3. Temperature sensors 4. Level sensors 5. Flow sensors 6. Chemical sensors 7. Biomedical sensors 8. Position sensors ………………….. Chemical sensors For example: Gas sensors MQ2 Gas Sensor The MQ2 sensor is one of the most widely used in the MQ sensor series. It is a MOS (Metal Oxide Semiconductor) sensor. The MQ2 gas sensor operates on 5V DC and consumes approximately 800mW. It can detect , Smoke, LPG, Hydrogen, and Methane. The module includes a potentiometer for adjusting the sensitivity of the digital output (D0). You can use it to set a threshold so that when the gas concentration exceeds the threshold value, the module outputs LOW otherwise HIGH. MQ2 Gas Sensor When a SnO2 semiconductor layer is heated to a high temperature, oxygen is adsorbed on the surface. When the air is clean, electrons from the conduction band of tin dioxide are attracted to oxygen molecules. This creates an electron depletion layer just beneath the surface of the SnO2 particles, forming a potential barrier. As a result, the SnO2 film becomes highly resistive and prevents electric current flow. In the presence of reducing gasses, however, the surface density of adsorbed oxygen decreases as it reacts with the reducing gasses, lowering the potential barrier. As a result, electrons are released into the tin dioxide, allowing current to MQ2 Gas Sensor The sensor’s analog output voltage (at the A0 pin) varies in proportion to the concentration of smoke/gas. The higher the concentration, the higher the output voltage; the lower the concentration, the lower the output voltage. The animation below shows the relationship between gas concentration and output voltage. The module includes a potentiometer for adjusting the sensitivity of the digital output (D0). You can use it to set a threshold so that when the gas concentration exceeds the threshold value, the module outputs LOW otherwise HIGH. Gas sensors Used in industries to monitor the concentration of toxic gases. Used in households to detect emergency incidents. Used at hotels to prevent customers from smoking. Used in air quality checks at offices. Used in air conditioners to monitor the CO2 levels. Used in detecting fire. Used to check the concentration of gases in mines. Breath analyzer.  Biomedical sensors Biosensors are a combination of both physical and chemical sensing together Biochemical Sensors: uses biological elements (like enzymes or antibodies) to detect specific substances (e.g., glucose biosensors). Biopotentials Biopotentials Measurement process Electrodes: Special sensors are placed on the skin or inserted into tissues to capture the electrical signals. Amplification: The signals are usually very small, so they need to be amplified for accurate measurement. Signal Processing: The recorded signals are processed and analyzed to get meaningful data. ECG Pulse oximeter Blood Pressure Position sensors Position sensors Position sensors are devices used to measure the position of an object in a given space. Position sensors fitted to actuators, whether hydraulic or electrical, measure the distance of travel and play a very important role in the accurate operation of these actuators, ensuring that they stop at a pre-defined place and only move as far as they are supposed to. In processing industries especially, the accuracy and reliable operation of actuators is imperative for monitoring the operation of the machinery and identifying quickly when things are not working as they should, thereby reducing downtime and wastage. Position sensors Potentiometers LVDT (Linear Variable Differential Transformer) Resolver Magnetostrictive Sensors Eddy Current Probes Capacitance Sensors Encoders  Potentiometers The most commonly used of all the “Position Sensors”, is the potentiometer because it is an inexpensive and easy to use position sensor. It has a wiper contact linked to a mechanical shaft that can be either angular (rotational) or linear (slider type) in its movement, and which causes the resistance value between the wiper/slider and the two end connections to change giving an electrical signal output that has a proportional relationship between the actual wiper position on the resistive track and its resistance value. Resistance is proportional to position. Potentiomete rs Potentiomete rs Low cost one main disadvantage of using the potentiometer as a positional sensor is the range of movement of its wiper or slider (and hence the output signal obtained) is limited to the physical size of the potentiometer being used. Multi-turn pots of up to 3600o (10 x 360o) of mechanical rotation are also available. LVDT (Linear Variable Differential Transformer) LVDT is linear position sensor. LVDT is an electronic device that has both electrical and mechanical processes, it requires an external power source to be able to operate, it stores electromagnetic energy and converts form of energy into a readable signal to describe the movement of a body along a linear displacement. LVDT Structure of an LVDT LVDT LVDT High Accuracy Linear operation Harsh Environment Analogue Position Control Embedding (in a cylinder for example) Resolver Magnetostrictive linear position Eddy Current Probes Please watch these videos to get clear idea of it https://www.youtube.com/watch?v=oriFJByl6Hs https://www.youtube.com/watch?v=3KsRjnn83T0&t=277s Capacitance Sensors Encoders Encoders are digital Sensors commonly used to provide position feedback for actuators Consist of a glass or plastic disc that rotates between a light source (LED) and a pair of photodetectors Disk is encoded with alternate light dark sectors so pulses are produced as disk rotate  Optical Linear Encoder As the encoder moves along the scale, the light source illuminates the patterned surface. The detector senses the light patterns (which can be encoded as binary or gray codes) to determine position. The processor translates these signals into a position reading. Optical Rotary Encoder Optical Rotary Encoder Optical Rotary Encoder Optical Rotary Encoder Magnetic encoder Speed Tachometer More ideas Force sensor Time of flight sensors examples Ultrasonic sensor (discussed earlier) Laser LiDAR time of flight (Tof) camera LiDAR LiDAR (Light Detection and Rangin g) is an active remote sensing system. LiDAR systems emit their own laser pulses, which are then reflected off objects and returned to the sensor. The system measures the time it takes for the pulses to return, allowing it to create a detailed 3D map of the environment,  A 3D time-of-flight (TOF) camera works by illuminating the scene with a modulated light source, and observing the reflected light. Tof camera The phase shift between the illumination and the reflection is measured and translated to distance. Actuators Actuators An actuator is a component of a machine that is responsible for moving or controlling a mechanism or system. Main types of Actuators are: ❑Electrical ❑ Hydraulic (uses hydraulic fluid) ❑Pneumatic (uses compressed air) Types of Motors and Actuators DC Motors Stepper Motors Servo Motors DC motor DC motor produces a continuous angular rotation that can be used to rotate pumps, fans, compressors, Brushed DC motor Brushless DC motor Stepper motor Moves one step at a time for each input. Appropriate excitation in winding/s, makes the rotor attract towards the stator. Precise positioning and repeatability of movement The rotation angle of the motor is proportional to the input pulse. It is possible to achieve very low speed synchronous rotation with a load that is directly coupled to the shaft. Servomotor The output shaft of servomotor motor can be moved to a particular angle, position and velocity Positional servos move the motor to a specific position. continuous servos rotate continuously in either direction. The pulse in this case controls the speed and direction instead of position.  Solenoid actuator Electromagnetic actuator Consist of a movable ferrite core that is activated by current flow When the coil is energized, a magnetic field is established that provides the force to push or pull the core. Hydraulic actuator Pneumatic actuator Pneumatic actuator Continuous servo EEP 311 Measurement Systems Dr. Mai Ismail Diab Faculty of Engineering, Alexandria University  Autonomous systems Meaning of Sensor fusion In this lecture, Sensors in Autonomous vehicles we will discuss: Sensor uncertainty Calibration Correlation Autonomy vs. automation There is a big difference between two concepts of automatic and autonomous operations. In automatic systems, the machine exactly follows the programmed commands, and it has no choice for making decisions. In contrast, the autonomous systems have the capability of recognizing different situations and making a decision accordingly without human interaction. Hence, developing more intelligent autonomous systems with the ability to run autonomously, reconfiguring based on varying situations, and efficient mission planning according to new circumstances, is one of the significant fields of interest for many system designers Autonomous systems Examples Autonomous Vehicle  Autonomous Vehicle Sensors − These are the devices used to capture data about surrounding conditions in real-time. They include cameras, radar, LiDAR, GPS, Ultrasonic, IMU, etc. These components act as the eyes and ears of the autonomous vehicles. Perception System − This system is responsible for processing raw data collected by sensors to identify and track the objects in the surrounding areas. This system can recognize other vehicles, lane markings, and road signs. Planning System − This system is employed for deciding vehicle’s actions depending on the data from the perception system. This system is crucial for ensure correct and safe movement of the vehicle. Control System − This system includes the control of components like steering, breaks, engine, speed, acceleration, etc. The primary function of control system is to execute actions decided by the planning system. Perception levels Solving this errors include: Sensor Fusion Machine Learning Algorithms Calibration Environmental Adaptability Testing in Diverse Conditions What is Sensor fusion? What is Sensor fusion? Sensor Fusion is the process of bringing together data from multiple sensors, such as radar sensors, lidar sensors, and cameras. The fused data enables greater accuracy because it leverages the strengths of each sensor to overcome the limitations of the others. What is Sensor fusion? Sensor fusion is the process of merging data from multiple sensors such that to reduce the amount of uncertainty that may be involved in a robot navigation motion or task performing. Sensor fusion helps in building a more accurate world model in order for the robot to navigate and behave more successfully. What is Sensor fusion? Sensor fusion involves three components: 1. Sensor: Measures a variable of interest, directly or indirectly 2. Model: A mathematical formulation that relates the variables of interest to the measurements 3. Estimation Algorithm: Combines the measurements and models to estimate the variables of interest Multiple measurements and multidimensional Applications of sensor fusion Autonomous vehicles Robots Healthcare applications Smart home systems Industry Let’s remember! Sensors in Autonomous vehicles  Sensors can be classified to Proprioceptive Exteroceptive sensors sensors Accelerometer Gyroscopes LiDAR RADAR Ultrasonic Camera  Sensors can be classified to Proprioceptive Exteroceptive sensors sensors Proprioceptive sensors provide information about the system’s internal state. (For example: speed) Exteroceptive sensors provide information about the surrounding environment (For example: object detection). Basics of Position estimation Dead reckoning  Basics of Position estimation Dead reckoning :Wheel odometry Magnetometer (digital compass) In robotics, a magnetometer is used to measure the magnetic field in the environment and helps the robot determine its orientation (heading) relative to the Earth's magnetic field. It's commonly integrated into robots, drones, and autonomous vehicles to improve navigation, positioning, and localization in combination with other sensors Magnetometers can be influenced by local magnetic fields caused by nearby electronics, metal structures, or electromagnetic interference. This can cause inaccuracies in heading data. Magnetometer Inertial Measurement Unit (IMU) Inertial Measurement Unit (IMU) is a device that combines multiple sensors(Accelerometers and Gyroscopes) to measure and report an object's specific force, angular velocity. IMUs use algorithms to combine the data from the accelerometers and gyroscopes (and to provide a comprehensive understanding of the object's motion and orientation.  Accelerometer An accelerometer sensor is a tool that measures the acceleration (the rate of change of velocity) of any object. When an accelerometer is subjected to acceleration, the internal sensing element (typically a small mass) experiences a force that can be measured to determine the level of acceleration. MEMS stands for Micro-Electro-Mechanical Systems. These are tiny integrated devices or systems that combine mechanical components, sensors, actuators, and electronics on a single chip MEMS accelerometer Gyroscopes A gyroscope measures angular velocity or the rate of rotation around a particular axis (pitch, roll, and yaw). IMU gyroscopes and accelerometers are combined to provide a full picture of motion.  Global Positioning System sensor (GPS) A GPS sensor is an electronic device that receives signals from a network of satellites and uses this data to calculate the sensor's geographic location. Using Trilateration and time correlation By knowing the distance to at least three satellites, the receiver can determine its position by finding the point where the three spheres (each centered on one of the satellites) intersect. Time correlation to make sure that all received at same time Ultrasonic An ultrasonic sensor uses sound waves to measure distance by emitting high-frequency sound pulses and timing how long it takes for the echoes to return. LiDAR LiDAR (Light Detection and Ranging) is an active remote sensing system. LiDAR systems emit their own laser pulses, which are then reflected off objects and returned to the sensor. Fast High cost RADAR A radar sensor emits radio waves in the form of pulses or continuous waves. These waves travel outward and reflect off surrounding objects (e.g., other vehicles, pedestrians, walls, road signs). The frequency shift (known as the Doppler effect) of the returned waves helps determine the speed of the object (whether it is moving toward or away from the vehicle). Radar excels in long-range detection and works well in adverse weather (fog, rain, snow). It is mainly used for measuring distance and relative speed. Camera Camera sensors in cars use visual data from cameras to capture high-resolution images 2D of the vehicle's surroundings. They play a key role in features like lane departure warning, traffic sign recognition, pedestrian detection, and parking assist. Cameras provide detailed information for object classification (e.g., recognizing pedestrians or road signs), but can struggle in low-light or adverse weather conditions. Combined with other sensors like radar and lidar, cameras help improve overall vehicle safety and autonomous driving capabilities. April tags Stereo vision Radar excels in long-range detection and works well in adverse weather (fog, rain, snow). It is mainly used for measuring distance and relative speed. Cameras provide high-resolution images for object classification (e.g., recognizing pedestrians, road signs, etc.) but struggle in poor visibility conditions. Lidar offers precise 3D mapping of the environment, making it great for object detection and braking, but it is more sensitive to environmental factors and weather conditions. Lidar-camera calibration establishes correspondences between 3-D lidar points and 2-D camera data to fuse the lidar and camera outputs together. Lidar sensors and cameras are widely used together for 3-D scene reconstruction in applications such as autonomous driving, robotics, and navigation. While a lidar sensor captures the 3-D structural information of an environment, a camera captures the color, texture, and appearance information. ROI region-of-interest Sensor uncertainty Sensor uncertainty Sensor uncertainty refers to the potential errors or inaccuracies in sensor measurements due to factors like noise, calibration errors, and environmental conditions. It can affect the reliability of data used for decision-making in systems like autonomous vehicles or industrial applications. Minimizing sensor uncertainty is crucial for improving system accuracy and performance. Sensor uncertainty can be reduced by: Calibration Sensor Fusion Environmental Compensation Noise Reduction Improved Sensor Quality Before we start! We will discuss some important points Calibration Collect data and fit model parameter Calibrate using hardware or software setting. Normal distribution curve Normal distribution curve Normal distribution curve Probability density function (PDF) Correlation Correlation Coefficient +1 indicates a perfect positive correlation (both variables move in the same direction). -1 indicates a perfect negative correlation (one variable increases while the other decreases). 0 indicates no correlation (the variables do not have a relationship).  Template matching Beat detection  Template matching Beat detection Template matching Template matching Frequency domain Frequency domain Noisy signal A noisy signal is a clean signal (e.g., a sine wave, speech signal) that has been contaminated by noise. The noise can be random or deterministic and can have a variety of sources, such as: Electronic interference Environmental factors (e.g., temperature, humidity) inherent limitations in the sensor's design Noise Filtering