ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: Piezoelectric AccelerometerOutlineReference listTo explore further (survival pointers of web references etc)Major ApplicationsBasic working principleSlide 7A Typical ApplicationSlide 9Major SpecificationsSlide 11Slide 12LimitationsOther Relevant IssuesSlide 15Slide 16ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Assignment#01: Literature Survey on Sensors and Actuators Topic: Piezoelectric AccelerometerPrepared by:Austin JensenDept. of Electrical and Computer Engineering Utah State University3/7/200601/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-2Outline –Reference list–To probe further–Sensor – Piezoelectric Accelerometer•Major applications•Basic working principle illustrated•A typical sample configuration in application (application notes)•Major specifications•Limitations•And many more relevant issues in applications (such as, how to choose, cost information, where to buy etc.)01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-3Reference list1. Bishop, Robert H.; The Mechatronics Handbook, CRC Press 20022. Guy Kulwanoski and Jeff Schnellinger; Sensor Magazine, “Piezoelectric Accelerometers”, Feb 2004 3. http://www.memx.com/01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-4To explore further (survival pointers of web references etc)01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-5Major Applications •General-Purpose Acceleration–Transportation systems, rockets, machine tools, engines, flexible structures–Ballistics - Combustion, explosion, and detonation •Shock & Vibration–Engine Testing - Combustion and dynamic stressing–Shock and vibration isolation01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-6Basic working principle•A mass is placed between two PZT crystals•When accelerated, the mass provides a force against one of the crystals•When excited by a force, the crystal will output a chargeDirection of motion (Ref#1)01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-7Basic working principle•Relationship between the force and the charge–When the crystal feels a force, it is excited and creates a proportional charge across it–dij represents the mechanical properties of the crystal•Transfer Function –Third order system–tau represents the time constant of the electric circuit connected to the sensor–Kq is the constant related to charge (C cm)01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-8A Typical Application•SumoBot–Description •A sumobot is a 20x20cm mobile robot used in a competition•The purpose of the bot is to autonomously find an opponents bot and push it out of a ring01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-9A Typical Application–Possible Implementation•Heading control to find opponent–IR sensors»Feeds back the heading of the opponent•Velocity control to make system more dynamic –Piezoelectric Accelerometer»Feeds back the actual velocity of the robot (through integrator)01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-10Major Specifications•Two basic design configurations–Compression type•Crystal is held in by compression•Vibration varies the stress–Shear-stress type•Vibration deforms the crystal•Transducer–Outside power source is not needed, provides all the power it needs01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-11Major Specifications•Output types–High impedance – Requires external charge to voltage converter–Low impedance – Output signal already converted via internal charge to voltage converter•Requires external voltage supply•Input Range – 0 - 20,000psi•Temperature Max - 930deg•Linear response–The relasionship between the output and the input is linear except for a deadband01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-12Major Specifications•High frequency operation•Other Specifications can be change depending on the sensorFrequency Response (Ref #1)01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-13Limitations•Cannot perform true static measurements–DC response is undefined•Only capable of sensing one degree of freedom–For more degrees of freedom, multiple sensors are needed •Transient Response–Shocks with a high amplitude may cause zero shift and ringing•Zero shift is the phase non-linearity not coming back to steady-state•Ringing is caused by excitation at the resonant frequency preventing the sensor from returning to steady-state01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-14Other Relevant Issues•Calibration–Must use a dynamic way of calibration–Electrodynamic Shaker•A machine designed to oscillate in a sinusoidal motion•Shows the frequency response of a dynamic system01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-15Other Relevant Issues•Cross-axis sensitivity –How sensitive the sensor is to acceleration perpendicular to the main-axis•Expressed as a percentage of the main-axis sensitivity•Check in calibration–Needs to be < 3-4%•Piezoelectric accelerometers tend to be 2-3% sensitive01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-16Other Relevant Issues•Selection Considerations–Mass•The Accelerometer should not be greater than one-tenth the mass of the object that the sensor is being mounted on–Frequency•To avoid zero-shift and ringing, select a sensor with a linear range in the frequency range you are working in•As a rule, set the upper frequency limit at one-third the resonance frequency•The Lower bound is set by the cutoff associated with the
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