Sensing & Actuation.pptx

IoT Sensing and Actuation: Introduction, Sensors, Sensor Characteristics, Sensorial Deviations, Sensing Types, Sensing Considerations, Actuators, Actuator Types, Actuator Characteristics.

1. Introduction to Internet of Things (IoT) Department of Robotics & Automation JSS Academy of Technical Education, Bangalore-560060 (Course Code: 22ETC15H)

2. Books Sudip Misra , Anandarup Mukherjee, Arijit Roy, “Introduction to IoT”, Cambridge University Press 2021. Reference S. Misra , C. Roy, and A. Mukherjee, 2020. Introduction to Industrial Internet of Things and Industry 4.0. CRC Press. Vijay Madisetti and Arshdeep Bahga , “Internet of Things (A Hands-on-Approach)”,1st Edition, VPT, 2014. Francis daCosta , “Rethinking the Internet of Things: A Scalable Approach to Connecting Everything”, 1st Edition, Apress Publications, 2013. https://onlinecourses.nptel.ac.in/noc22_cs53/preview Further Learning National Programme on Technology Enhanced Learning ( NPTEL )

3. Course Learning Objectives List the salient features of sensors & transducers Differentiate between sensors and actuators Characterize sensors & Actuators

4. Course outcome (Course Skill Set) CO2: Classify various sensors actuators. At the end of the course, students will be able to,

5. Semester End Examination(SEE) The question paper shall be set for 100 marks. The duration of SEE is 03 hours. The question paper will have 10 questions . 2 questions per module . Each question is set for 20 marks . The students have to answer 5 full questions , selecting one full question from each module. The student has to answer for 100 marks and marks scored out of 100 shall be proportionally reduced to 50 marks .

6. Internet of Things Module 2: IoT sensing & Actuation

7. IoT Sensing and Actuation: Introduction, Sensors, Sensor Characteristics, Sensorial Deviations, Sensing Types, Sensing Considerations, Actuators, Actuator Types, Actuator Characteristics. Reference Textbook1: Chapter 5: 5.1 to 5.9 Module 2

8. IoT applications involves sensing in one or the other form . All the applications in IoT, consumer IoT, an industrial IoT , or hobby-based deployments of IoT solutions - sensing forms the first step . Actuation forms the final step The sensing and actuation is based on the process of transduction . Transduction is the process of energy conversion . Transducers take energy in any form - electrical, mechanical, chemical, light, sound etc. & convert it into other forms like electrical, mechanical, chemical, light, sound etc. Sensors and actuators are deemed as transducers. E.g., in a public announcement (PA) system, a microphone (input device) converts sound waves into electrical signals, amplified by an amplifier system (a process). A loudspeaker (output device) outputs this into audible sounds by converting the amplified electrical signals back into sound waves IoT Sensing & Actuation

9. Differences between Transducers, Sensors, and Actuators Parameter Transducer Sensor Actuator Definition Converts energy from one form to another. Converts various forms of energy into electrical signals Converts electrical signals into various forms of energy. Domain Represent a sensor as well as an actuator. It is an input transducer. It is an output transducer Function Work as a sensor or an actuator but not simultaneously. Used for quantifying environmental stimuli into signals. Used for converting signals into proportional mechanical or electrical outputs Examples Any sensor or actuator Humidity sensors, Temperature sensors, Manometers, Gas sensors etc. Motors, Pumps etc.

10. Sensors Sensors are devices that can measure, or quantify, or respond to the ambient changes in their environment. They generate responses to external or physical phenomenon and their conversion into electrical signals. E.g., Heat is converted to electrical signals in a temperature sensor Atmospheric pressure is converted to electrical signals in a barometer.

11. Sensors A sensor is defined as a device , helps to detect any changes in physical quantity like pressure, force or electrical quantity etc.

12. Industrial IoT Sensor Systems Industrial IoT Sensor Systems

13. Outline of a Sensing Operation Temperature sensor keeps on checking an environment for changes . In the event of a fire, the temperature of the environment goes up . Temperature sensor senses this change in the temperature of the room and communicates this information to a remote monitor via the processor A sensor node is made up of a combination of sensor/sensors, a processor unit, a radio unit, and a power unit.

14. Classification of Sensors 3. Property to be measured Active Sensor P assive Sensor Analog Sensor Digital Sensor The sensors are classified based on; Power requirements 2. Sensor output Scalar Vector

15. Classification of Sensors Active Sensor P assive Sensor Power requirements 1. Active Sensor: Do not require an external power source for their functioning. E.g.: LiDAR (Light detection and ranging), Photoconductive cell, piezoelectric crystal etc. 2. Passive Sensor: Requires an external power source for their functioning. E.g.: RTDs: Thermocouple

16. Classification of Sensors Active Sensor P assive Sensor Power requirements

17. Classification of Sensors Active Sensor P assive Sensor Power requirements Thermocouple, Piezoelectric sensor etc. RTDs: Strain Gauge

18. Classification of Sensors Analog Sensor Digital Sensor 2. Sensor output Analogue sensors : Produce an analog output (continuous function of time). Digital Sensors : Work with discrete or digital data . Typically, binary output signals in the form of a logic 1 or logic 0 for ON or OFF.

19. Classification of Sensors 3. Property to be measured Scalar Vector Scalar: These sensors produce an output proportional to the magnitude of the quantity being measured. The output is in the form of a signal or voltage. E.g. colour, pressure, temperature, strain, gas, smoke, strain etc. Vector : Sensors are affected by both magnitude & direction and/or orientation of the property being measured. Velocity require additional information besides magnitude for completely describe the information. E.g. Sound sensor, image sensor, velocity sensor, acceleration sensor etc.

20. The functional blocks of a typical sensor node in IoT

21. Sensor Characteristics 1. Sensor Resolution The slightest/smallest change in the input (measurable quantity) that the sensor can detect. For digital sensors, the smallest change in the digital output More the resolution of a sensor , the more accurate. A sensor’s accuracy does not depend upon its resolution . E.g. Temperature Sensor A can detect change in temperature up to 0:5°C ; Temperature Sensor B can detect change in temperature up to 0:25°C Therefore, the resolution of sensor B is higher than the resolution of sensor A .

22. Sensor Characteristics 2. Sensor Accuracy Accuracy is the ability of a sensor to measure the changes in the environment of a system close to its true value (Standard). E. g Weight sensor detects the weight of a 100 kg mass as 99.98 kg. We can say, this sensor is 99:98% accurate, with an error rate of 0:02%. Precision refers to the degree of reproducibility of a measurement. Exactly the same value were measured a no. of times (trials). An ideal sensor will provide am output exactly the same value every time . E.g . If a pressure of exactly 150 mm Hg is applied to a sensor. Even if the applied pressure never changes , the output values from the sensor will vary considerably . 3. Sensor Precision

23. Sensor Characteristics 4. Range Gives the highest and the lowest value of the physical quantity within which the sensor can actually sense. Beyond these values, there is no sense or no kind of response . e.g. RTD for measurement of temperature has a range of -200`c to 800`c The ratio of incremental change in the response of the system wrt incremental change in input. It is the smallest amount of difference in quantity ( i /p) that will change the instrument’s reading . 5. Sensitivity

24. Sensorial Deviations / Errors Sensor deviations are referred to as errors in sensors. Sensing in IoT is non-critical , where minor deviations in sensor outputs rarely changes the nature of the undertaken tasks (applications). The critical applications of IoT, such as healthcare, industrial process monitoring , etc., require sensors with high-quality measurement capabilities.

25. Full Scale Range (Sensor limits): When sensor’s output is beyond its maximum and minimum design capacity, the sensor output is truncated to its maximum or minimum value. The measurement range between minimum and maximum values is referred to as the full-scale range of the sensor. 2. Offset / Bias: If the output signal is not zero when the measured property( i /p) is zero , the sensor has an offset or bias error. 3. Non Linearity: If the sensitivity is not constant over the range of the sensor, this is called nonlinearity. Defined by the amount the output differs from ideal behaviour over the full range of the sensor Expressed as percentage of the full range. Sensorial Deviations / Errors

26. 4. Dynamic Error: If the deviation is caused by a rapid change of the measured property over time. 5. Drift: If the output signal of a sensor changes slowly and independently of the measured property. 6 . Hysteresis Error: if a sensor’s output varies/deviates due to deviations in the sensor’s previous input values, it is referred to as hysteresis error. Generally denoted as a positive and negative percentage variation of the full-range of that sensor. 1. Quantization Error: I f the digital output of a sensor is an approximation of the measured property. Defined as the difference between the actual analog signal and its closest digital approximation during the sampling stage of the ADC. Sensorial Deviations: Digital Sensors Sensorial Deviations / Errors

27. Dynamic Error caused due to mishandling of sampling frequencies can give rise to aliasing errors . Aliasing error leads to different signals of varying frequencies to be represented as a single signal in case the sampling frequency is not correctly chosen , resulting in the input signal becomes a multiple of the sampling rate. Sensorial Deviations: Digital Sensors Environment Some sensors may be prone to external influences. This sensitivity of the sensor may lead to deviations in its output values. E.g., Most sensors are semiconductor based , they are influenced by the temperature of their environment.

28. Sensing Types Sensing can be divided into four different categories based on the nature of the environment being sensed and the sensors being used; Scalar sensing Multimedia sensing Hybrid sensing Virtual sensing

29. Sensing Types Scalar sensing Encompasses the sensing of features that can be quantified by measuring changes in the amplitude (magnitude) of the measured values with respect to time. Measuring the changes in their values with time provides enough information about these quantities E.g., Ambient temperature, current, atmospheric pressure, rainfall, light, humidity, flux. A scalar temperature sensing of a fire detection event is shown in Fig.

30. Sensing Types 2. Multimedia sensing Encompasses the sensing of features that have a spatial variance property associated with the property of temporal variance . Multimedia sensors are used for capturing the changes in amplitude of a quantifiable property concerning space (spatial) as well as time (temporal). E.g. Images, direction, flow, speed, acceleration, sound, force, mass, energy, and momentum A camera-based multimedia sensing using surveillance as an example is shown in Fig.

31. Sensing Types 3. Hybrid sensing The act of using scalar & multimedia sensing at the same time is referred to as hybrid sensing. Various sensors are employed (scalar & multimedia sensors) to measure the various properties of the environment at any instant of time , and temporally map the collected information to generate new information. E.g : Smart parking systems, traffic management systems etc. Fig. shows an example of hybrid sensing, where a camera and a temperature sensor are collectively used to detect and confirm forest fires during wildlife monitoring.

32. Sensing Types 3. Hybrid sensing Example: Agricultural field. It is required to measure the soil conditions at regular intervals of time to determine plant health. Soil moisture & temperature sensors are deployed underground to estimate the soil’s water retention capacity and the moisture being held by the soil at any instant of time. This setup only determines whether the plant is getting enough water or not . There are other factors besides water availability , which may affect a plant’s health. The inclusion of a camera sensor with the plant, will determine the actual condition of a plant by determining the colour of leaves. This information from soil moisture, temperature , and the camera sensor will be able to collectively determine a plant’s health at any instant of time. .

33. Sensing Types 4. Virtual sensing There is a need for very dense and large-scale deployment of sensor nodes spread over a large area for monitoring of parameters . E.g. Agriculture The parameters being measured, are soil moisture , soil temperature , and water level, do not show significant spatial variations. Sensors are deployed in the fields of farmer A , the measurements from the sensors will provide almost concise measurements of his neighbour B’s fields ; (fields which are surrounding A’s fields). If the data from A’s field is digitized using an IoT infrastructure and this system advises him regarding the appropriate watering, fertilizer, and pesticide regimen for his crops, this advisory can also be used by B for maintaining his crops. In short, A ’s sensors are being used for actual measurement of parameters ; whereas virtual data is being used for advising B.

34. Sensing Types 4. Virtual sensing Figure shows an example of virtual sensing. Two temperature sensors S1 and S3 monitor three nearby events E1, E2, and E3 (fire). The event E2 does not have a dedicated sensor for monitoring it ; however, through the superposition of readings from sensors S1 and S3 , the presence of fire in E2 is inferred.

35. Sensing Considerations The choice of sensors in an IoT sensor node is cri tical and can either make or break the feasibility of an IoT deployment . The major factors influence the choice of sensors in IoT-based sensing solutions: Sensing range Accuracy & precision Energy Device size

36. Sensing Considerations 1. Sensing Range The sensing range of a sensor may be used to signify the upper and lower bounds of a sensor’s measurement range. Example: A proximity sensor has a typical sensing range of a couple of meters . A camera has a sensing range varying between 10 meters to 100 meters . As the complexity of the senso r and its sensing range goes up , its cost significantly increases.

37. Sensing Considerations 2 . Accuracy & Precision Accuracy and precision of measurements provided by a sensor are critical in deciding the operations of specific functional processes. Consumer sensors are low on requirements & their performance is limited to regular application domains. Example : A standard temperature sensor is not suitable for industrial processes. Regular temperature sensors have a very low-temperature sensing range & relatively low accuracy and precision. The industrial applications requires precision of up to 3 - 4 decimal places Industrial sensors are very sophisticated , and are very costly . Industrial sensors have very high accuracy and precision, even under harsh operating conditions.

38. Sensing Considerations 3. Energy The energy consumed by a sensor / sensor node is crucial to determine the lifetime of that solution and the estimated cost of its deployment . If the sensor / sensor node is energy inefficient, it requires replenishment of its energy sources frequently, the effort in maintaining the solution and its cost goes up & its deployment feasibility goes down.

39. Sensing Considerations 4. Device Size Modern-day IoT applications have a wide penetration in all domains of life . Most of the applications of IoT require sensing solutions which are so small that they do not hinder any of the regular activities. Larger the size of a sensor node , larger is the obstruction caused by it, higher is the cost and energy requirements, and lesser is its demand for the bulk of the IoT applications. Example: Human activity detector . If the detection unit is large / bulky to be carried, cause hindrance to regular movements , the demand for this solution would be low. The wearable sensors are highly energy-efficient & small in size.

40. Actuators

41. ACTUATORS An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system. E.g.: opening a valve. An actuator requires a control device (controlled by control signal) and a source of energy . The control signal may be electric voltage or current , pneumatic , or hydraulic fluid pressure, or human power . The control device is usually a valve . When it receives a control signal , an actuator responds by converting the source's energy into mechanical motion . Outline of a simple actuation mechanism

42. Actuator Types Broadly, actuators can be divided into seven classes : Hydraulic Pneumatic Electrical Thermal / Magnetic Mechanical Soft Shape memory polymers

43. Actuator Types Fig. shows some of the commonly used actuators in IoT applications

44. Actuator Types A works on the principle of compression and decompression of fluids . These actuators facilitate mechanical tasks such as lifting loads through the use of hydraulic power derived from fluids. The mechanical motion applied to a hydraulic actuator is converted to either linear, rotary , or oscillatory motion. used when exerting significant force. The actuator’s limited acceleration restricts its usage. Hydraulic Actuator

45. Actuator Types Pneumatic Actuator Pneumatic actuators use the energy of compressed air to generate rotary and linear movements to operate valves and dampers Characteristics: Quick response to starting and stopping signals. Small pressure changes can be used for generating large forces. E.g. Pneumatic brakes. Pneumatic actuators are responsible for converting pressure into force.

46. Actuator Types Electrical Actuator Electric actuators convert electrical energy into mechanical energy. Applications: Valve operation, cutting equipment , food and beverage manufacturing, and material handling. Easy to maintain and offer a high level of precision. Not suited for all environments and need supervision for overheating tendencies.

47. Actuator Types Thermal / Magnetic Actuator Thermal or magnetic energy is used. Have a very high power density and are compact, lightweight , and economical. Example: Shape memory alloys (SMAs). These actuators do not require electricity for actuation. They are not affected by vibration and can work with liquid or gases. Magnetic shape memory alloys (MSMAs) are a type of magnetic actuators. Magnetic technology for the Motor

48. Actuator Types Mechanical Actuator In mechanical actuation, the rotary motion of the actuator is converted into linear motion. The use of gears, rails, pulleys, chains , etc. are necessary for these actuators to operate. These actuators can be easily used in conjunction with pneumatic, hydraulic , or electrical actuators. They can also work in a standalone mode . Driving a pump actuator device (Linear) Rotary Actuator

49. Actuator Types Soft Actuator Polymer-based consists of elastomeric polymers, used as embedded fixtures in flexible materials such as cloth, paper, fiber, particles, etc. The conversion of molecular level microscopic changes into macroscopic deformations is the primary working principle. These actuators have a high stake in modern-day robotics . They are designed to handle fragile objects such as agricultural fruit harvesting , or performing precise operations like manipulating the internal organs during robot-assisted surgeries.

50. Actuator Types Shape Memory Polymers Shape memory polymers (SMP) are smart materials that respond to some external stimulus by changing their shape , and then revert to their original shape once the affecting stimulus is removed. Characteristics: high strain recovery, biocompatibility, low density, and biodegradability. Modern-day SMPs, designed to respond to a wide range of stimuli such as pH changes , heat differentials, light intensity, and frequency changes , magnetic changes , etc. Example: Photopolymer/light-activated polymers (LAP) , which require light as a stimulus to operate.

51. Actuator Characteristics The selection of actuators is crucial in an IoT deployment, where a control mechanism is required after sensing and processing of the information obtained from the sensed environment. Actuators perform the physically heavier tasks in an IoT deployment; tasks which require moving or changing the orientation of physical objects, changing the state of objects , etc. The correct choice of actuators is necessary for the long-term sustenance and continuity of operations, as well as for increasing the lifetime of the actuators themselves.

52. Actuator Characteristics A set of four characteristics can define all the actuators : Weight P ower Rating Torque to Weight Ratio Stiffness and Compliance

53. Actuator Characteristics 1. Weight: The physical weight of actuators limits its application scope. Example Use of heavier actuators is generally preferred for industrial applications and applications requiring no mobility of the IoT deployment. Lightweight actuators typically find common usage in portable systems in vehicles, drones , and home IoT applications . Heavier actuators also have selective usage in mobile systems , for e.g., landing gears and engine motors in aircraft.

54. Actuator Characteristics 2. Power Rating Helps in deciding the nature of the application . Power rating defines the minimum and maximum operating power an actuator can safely withstand without damage to itself. Generally, it is indicated as the power-to-weight ratio for actuators. Example Smaller servo motors used in hobby projects, have a maximum rating of 5 VDC, 500 mA , suitable for an operations-driven battery-based power source . Exceeding this limit might be detrimental to the performance of the actuator and may cause burnout of the motor. Servo motors in larger applications have a rating of 460 VAC, 2.5 A , requires standalone power supply systems for operations.

55. Actuator Characteristics 3. Torque to Weight Ratio The ratio of torque to the weight of the moving part of an instrument/device is referred to as its torque/weight ratio. This indicates the sensitivity of the actuator . Higher is the weight of the moving part; lower will be its torque to weight ratio for a given power.

56. Actuator Characteristics 4. Stiffness and Compliance : The resistance of a material against deformation is known as its stiffness. Compliance of a material is the opposite of stiffness. Stiffness can be directly related to the modulus of elasticity of that material. Stiff systems are considered more accurate than compliant systems as they have a faster response to the change in load applied to it. Example Hydraulic systems are considered as stiff and non-compliant , whereas pneumatic systems are considered as compliant .

57. End of Module