WSC353 Interfacing for Mechatronic Systems Lecture Notes PDF

Dr Gianfranco Claudio & Dr Tim Harrison WSC353 INTERFACING FOR MECHATRONIC SYSTEMS Part B: Practical Considerations Tim Harrison Lecture B2: Sensors (2) Lecture plan Sensors (1) 31st Oct 13:00 Sensors (2) 7th Nov 13:00 Strain...

Dr Gianfranco Claudio & Dr Tim Harrison WSC353 INTERFACING FOR MECHATRONIC SYSTEMS Part B: Practical Considerations Tim Harrison Lecture B2: Sensors (2) Lecture plan Sensors (1) 31st Oct 13:00 Sensors (2) 7th Nov 13:00 Strain Gauges, Charge Amplifiers, 14th Nov 13:00 Sensor Networks & Relays Actuators (1) 21st Nov 13:00 Actuators (2) 28th Nov 13:00 Thermal and Noise considerations 5th Dec 13:00 Some practical examples 12th Dec 13:00 Progress so Far: Motion Displacement Speed Inertial (acceleration, rotation) Mechanical Pressure (& sound) Force Fluids Level Flow https://pixabay.com/get/e831b30a20f1073ed1584d05fb0938c9bd22ffd41cb01 Temperature 6459cf4c678a7/pressure-1425856_1280.jpg Light  Pressure sensors Measure a pressure difference – relative to: Vacuum (absolute pressure) Atmospheric pressure (gauge pressure) Reference pressure (differential pressure) Sealed reference Pressure sensors Pressure sensors Practical Aside – Pressure Sensors Sensor and analogue to digital (A/D) conversion location Flow Sampling tube A/D Sensor Analogue signal wiring A/D Sensor Digital signal wiring A/D Sensor Pressure Wireless A/D Sensor Sampling tube – pressure changes may induce resonance in the tube Analogue wiring may pick up electrical noise Digital wiring locates sensitive electronics in an adverse environment Wireless can introduce timing uncertainties and is susceptible to radio frequency interference Practical Aside – Pressure Sensors Sensor and A/D conversion location https://www.lambdatechs.com/wp-content/uploads/CFM56-Case-Study.pdf Practical Aside – Pressure Sensors Sensor and A/D conversion location Pressure taps in hot section Tubes to pressure sensors located On the fan case Close to the ECU Pressure measurement locations Hot (& vibrating) Engine Control Unit Cool(er) (& less vibration) https://www.3dhorse.com/products/cfm-cfm56-turbofan-jet-engine-3d-model  Pressure measurement (sound) Usually 20Hz-20kHz (human hearing) Practical issues: Frequency response (filtering) Directional response (directional filtering) Amplitude response (saturation) By Nicoguaro - Own work, CC BY 4.0, http://www.stageart.com.tr/image/data/M%C4%B0CROF CC BY-SA 3.0, https://commons.wikimedia.org/w/inde ONLAR/DMS_03_D%20%C3%87%C4%B0ZELGE.jpg https://commons.wikimedia.org/w/index.php?curid=193252 x.php?curid=50230608 Pressure measurement (sound) Omni-directional (Uni-)directional Often disc-like Often stick-like Diaphragm horizontal Diaphragm plane at right angles to the direction of greatest sensitivity Microphones Moving iron (older) Moving coil (newer) Capacitor / condenser type Electret type Piezoelectric Often used for hydrophones Fibre optic / laser microphone (doppler shift) Technically measuring surface vibration, not pressure Force measurement Half bridge circuit Load beam Load beam Full bridge circuit  Load cells Detailed mechanical design of load element with strain gauges Careful design to ensure … Good linearity Minimum cross-axis sensitivity Load stud Load washer Axial load cell Lifting load cell Weighbridge load cell Progress so Far: Motion Displacement Speed Inertial (acceleration, rotation) Mechanical Pressure (& sound) Force Fluids Level Flow https://pixabay.com/get/e831b30a20f1073ed1584d05fb0938c9bd22ffd41cb01 Temperature 6459cf4c678a7/pressure-1425856_1280.jpg Light  Level sensing FLOAT By Pricol Limited - Pricol Limited, CC BY-SA 4.0, CAPACITIVE https://commons.wikimedia.org/w/index.php?curid=41471360 To atmosphere PRESSURE P = ρgh Processing ULTRASONIC Sound pulse Level sensing – float devices Simple switch Fully variable https://www.deeterelectronics.com /product/float-switches-level- sensors/plastic-float-switches/40- series-horizontal-float-switch/ Potentiometer LVDT Capacitive https://uk.rs-online.com/web/p/float- switches/1919465 Level sensing – capacitive 2 concentric tubes Fluid is the dielectric material Change in level results in https://www.ameteksfms.com/products change in capacitance /fuel-management-systems No moving parts http://mahalaxmiinstruments.com/capa citance-rf-admittance-type-level- transmitter-switches.html Level sensing – pressure Mass of fluid results in higher pressure at greater depths Pressure at the bottom of the tank is proportional to depth Level sensing – ultrasonic Bouncing sound waves off the surface Not in contact with the fluid By Steves.uk - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.ph p?curid=48198586 food corrosive temperature flood https://www.ecubelabs.com/fill-level-sensors- 7-variables-to-help- https://www.hkywater.org you-understand-the- /river-and-creek-levels ideal-applications/ Level sensing – ultrasonic Bouncing sound waves off the surface Not in contact with the fluid By Steves.uk - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.ph p?curid=48198586 food corrosive temperature flood https://www.ecubelabs.com/fill-level-sensors- 7-variables-to-help- you-understand-the- https://redsensors.com/car-reverse-sensor-2023/ ideal-applications/ Practical Aside - Aircraft fuel quantity measurement Practical considerations: Fuel/air mix is flammable Tanks are oddly shaped Aircraft attitude changes Fuel mass is equally important Vented to relieve pressure https://aircraft.airbus.com/en/ser System redundancy vices/enhance/systems-and- airframe-upgrades/operations- extension/ Practical Aside - Aircraft fuel quantity measurement Primary system: Capacitive sensors in pairs at least 2, preferably 3 locations in each tank Densitometer Temperature sensor Practical Aside - Aircraft fuel quantity measurement Secondary system: Tertiary system: Level sensors mag-level indicators High and Low level Fuel use data from engines to estimate fuel remaining https://twitter.com/chainsawrock s/status/1580031600032555013  Flow sensing One of the measurands with the largest variety of types! Differential Pressure Positive Displacement Velocity Mass Open-Channel Orifice Plate Reciprocating Piston Turbine Coriolis Weir Venturi Tube Oval Gear Vortex Shedding Thermal Flume Flow Tube Nutating Disk Swirl Flow Nozzle Rotary Vane Conada Effect & Momentum Pitot Tube Exchange Elbow Tap Electromagnetic Target Ultrasonic, Doppler Variable-Area(Rotameter) Ultrasonic, Transit-Time Fluid flow sensors – differential pressure Creating a differential pressure proportional to flow velocity Little disturbance to or + blockage to the flow Venturis and pitot tubes can be used for “external” measurement e.g. vehicle airspeed  Fluid flow sensors – positive displacement Gear pump in reverse accurate internal only Greater impedance to the flow jammed elements will block the flow https://www.flomec.com.au/blogs/articles/what- are-positive-displacement-flowmeters  Fluid flow sensors – rotational less accurate internal or external impedance to the flow depends on blockage ratio and friction jammed elements will not block the flow Paddle wheel sensor Turbine sensor By Mailtosap - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid IP Codes: =10353374  Mass flow sensors Thermal mass flow sensor Heating effect depends upon mass not volumetric flow Non contact By Biezl - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4188008 Fluid must not be sensitive to heat! Coriolis mass flow sensor Vibration applied to curved tubes – Coriolis effect causes twisting effect Phase difference of the leading/following arms is proportional to mass flow rate Progress so Far: Motion Displacement Speed Inertial (acceleration, rotation) Mechanical Pressure (& sound) Force Fluids Level Flow https://pixabay.com/get/e831b30a20f1073ed1584d05fb0938c9bd22ffd41cb01 Temperature 6459cf4c678a7/pressure-1425856_1280.jpg Light Temperature sensors Thermocouples Thermistors Band gap temperature sensor (IC) IR temperature sensor Thermocouples Commonly used for spot temperature measurements Two different metals (Seebeck effect) Thermocouples (Part II) Many different types of thermocouples! Split into groups and find the properties of the different types of thermocouples: J, K, L, N, T Metals, wire colour, effective range, μV/°C, linearity Find a data sheet What would you use them for? Thermocouples (Part III) Main ways of interfacing with thermocouples: Directly using a voltage meter/ADC Through an IC converter USB (devices) Other serial bus Make sure to get the correct version for your thermocouple type Always use the correct connectors when interfacing – connector material matters - check the colours!  Thermistors/RTDs Temperature-sensitive resistor Be careful – response curves can be highly nonlinear! Susceptible to permanent de- calibration when used at high temps Small and therefore fast to react Fragile Thermistor: Doped semiconductor or ceramic By Tolopito - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=10398581 NTC/PTC: Negative/Positive Temperature Coefficient RTD: Resistive Temperature Device (usually metals e.g. Platinum) IC Temperature sensors ‘Silicon bandgap temperature sensors’ like the LM35 Can come handily packaged on an IC like the AD7314 A typical interface to a microcontroller would be: Notes: Uses Motorla’s SPI bus Ground pin has best thermal path Chip has to be on the object we want to measure the temperature of!  Infra-red Temperature sensors Infra-red sensors typically detect changes in energy in the 7-20μm range Sensor is typically lithium tantalate By Philip Ronan, Gringer - File:EM spectrum.svg and File:Linear visible spectrum.svg, CC BY-SA 3.0, (LiTaO3) https://commons.wikimedia.org/w/index.php?curid=24746679 Commonly used for human detection Example 1, Example 2 https://www.flickr.com/photos/nasablueshift/9685685433 Temperature measurement caveats Any electronic/electric system produces heat due to inefficiencies in the circuitry This can give rise to misleading results. For very small specimens, energy from other sources (radio, vibration etc.) can contribute to temperature rises The effect of temperature changes on the rest of the measurement kit (wires, ICs, etc.) needs to be taken into account  Light sensors (I) Only a small section of EM spectrum (see earlier slide on IR temperature sensors) Different types of sensor: Photoresistors Photodiodes Phototransistors Photovoltaics  Light sensors (II) Photoresistor Changes resistance when light falls on the material Can get devices with different response peaks Example Photodiodes Allows current through when light falls on it Again watch for response peaks Example Phototransistors Basically a transistor in a transparent case so that light can hit the base-emitter or base-collector junction Example Others Lidar Digital camera sensors CCD (capacitive) CMOS (photodiode) …  Sensors, conclusions There are many things we want to measure (measurands) There are usually several ways to measure each of the measurands It’s important to choose the right one for the application Very rarely will you have only one type of sensor! Normally we need to measure a few different measurands at once We are usually converting what we want to measure to something that can be read electronically, voltage, inductance, capacitance etc. This can take several steps, e.g. fluid level  displacement  resistance  voltage Additional References Alan S. Morris & Reza Langari, Measurement and Instrumentation: Theory and Application Figliola, R. S. & Beasley, D.E. Theory and design for mechanical measurements Precision: The Measure of All Things - Episode guide on BBC Lecture plan Sensors (1) 31st Oct 13:00 Sensors (2) 7th Nov 13:00 Strain Gauges, Charge Amplifiers, 14th Nov 13:00 Sensor Networks & Relays Actuators (1) 21st Nov 13:00 Actuators (2) 28th Nov 13:00 Thermal and Noise considerations 5th Dec 13:00 Some practical examples 12th Dec 13:00 This is the mid-module feedback link for 24WSC353 Interfacing for Mechatronic Systems Please take a few minutes to tell us how we are doing. Only accessible on campus or VPN! Or access with the link: https://tinyurl.com/26usoc4c. This redirects to: https://module-feedback.lboro.ac.uk/form.php?modcode=24WSC353&period=1.