MechatronicsIntel Mach Engr
MechatronicsIntel Mach Engr ME 4370
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This 9 page Class Notes was uploaded by Rogers Gulgowski DVM on Wednesday October 21, 2015. The Class Notes belongs to ME 4370 at Tennessee Tech University taught by Stephen Canfield in Fall. Since its upload, it has received 59 views. For similar materials see /class/225733/me-4370-tennessee-tech-university in Mechanical Engineering at Tennessee Tech University.
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Date Created: 10/21/15
Overview of Sensors A sensorrs a dewce that converts a physwca onenornena We a 5wgna that can be measured ororoeesseo n eonsrsts of two parts Transducer InterfaceSignal conditioning unit Transducer Swgna Conomonrng Umt Arnow mter oondrtron 5wgna We a meamngfm and easHy rnterraeeo souree Note Research m deve opmg new sensors rs enorrnous Tne doHar amount spent on new sensors eaen yearrs very arge ans drwes many e ds suen as r e c ofHHerSheW Sensors Examples ofSensors A sensorr ch s stem Tne Mars rover 5 mt Lu am rm x n r r w u an l unmm um u um IJknrnh iu m um mmwms m marr A Minimum Sensog robot system Considerations for Sensor Performance 1 Range or span 2 Error Accuracy Resolution 3 Hysteresis 4 Nonlinearity 5 Repeatibility 6 Stabilitydrift 7 Bandwidth speed 8 Cost 9 Reliability 10 Ease of application Catagorizing Commercial Sensors We could categorize sensors in several fashions for eX based on theory of operation or on type of application Commercial Navigation and Control Sensors ype sensors array Catagorize Based on Theory of Application 1 Contact mechanical a b can be used as proximity limit switches etc 0 comes in many forms o gto o SPST O DO Ovo DPDT O o O SPDT NO Pushbutton SPST SPDT DPDT momentary toggle etc d cheap reliable versatile e switch bounce f Another problem is low switching frequency and relatively short life 2 Mechanical movement of an input a Vary voltage Potentiometer Available in many forms cheap absolute measurement low to medium accuracy b Vary inductance LVDT RVDT c Vary capacitance 3 Time of Flight Sensors sensors used to measure distance a Acousticbased Examples include Polaroid Devantech E DLJ LRCC D E F I I F J L39N 139 I NIT T39CCEITLE p n Emma r CE139 d t2vT M Ultrasonics for NDE b EM waves 1 Radar radio waves adds Doppler shift to measure velocity 2 Lidar IR waves 3 GPS Sends a signal encoded with time use multiple to triangulate Calculate time for an acoustic wave to travel 2 m in air EM wave Triangulation Process of determining absolute position based on multiple measurements from known locations 1 1D 22D 3 3D 6 Pose Why 56 typical in GPS Other means to navigate Active beacon Landmarks 4 Optical Sensors a light sensitive devices 1 photodiodes 2 phototransisters Phototransistor Tr anSiStor C C B I f B For Saturatlon W VBE 07V and IBmin IC E E Can be sensitive to various wavelengths Used to measure proximity beambreak optoisolators remote controllers encoders discussed later 3 Photoresistor varies resistance wrt light 4 PSD position sensitive device Example Sharpe GP12 The PSD returns the position on the cell the light is received SHARP GP 2D12 IR FLAI IGEE 5 coo 5 Current sensing Hall effect sensors A current owing through a magnetic eld is deflected examples fuel tanks proximity Transformer Resolver type of encoder see below 6 Pyroelectric sensors PIR One that senses IR radiation 7 Resistance change due to strain Strain gauges Aproportional to strain 8 Piezoelectric sensors materials Generate a voltage when strained 1 form used in tactile sensors eg a PVDF film piezoelectric polyvinylidene uoride Materials for piezo electrics Lead Zirconate PZT Lead titante Lead metaniobate Barium titanate these are all ferro electric ceramics 9 Thermisters Materials metal oxides semiconductors whose resistance changes with temperature typically nonlinear change Rugged small fast response large output 10 Thermocouples Two dissimilair metals combined to form a junction A temperature differential bn two junctions creates a voltage J type lroncontantan 11 Acceleraometers Use a mass for inertia and strain gauge or PZT for sensing element Gyroscope Uses angular momentum and Euler s equation Or with three linear mass accelerometers Or with a RLG A few common sensors Encoders Used to measure rotational rate very common basic component in servo motors 1 Optical incremental encoder Uses an emitterdetector phototransistor pair a banded disk Resolution is a function of the disk Typical disks are 100 ppr or 500 ppr This output tells you the degree of rotation but not direction That requires quadrature the use of 2 detectors one offset from the other These would give the following output W W A D ip op could be used to give direction The quadrature output can be used to increase resolution by a factor of four One combination HP 2020 IC will perform quadrature counting and output a 16bit count when queried 2 Absolute optical encoder Unique coding signal for each location