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Friedlander, Jeffrey B.Wireless Strain Measurement with Surface Acoustic Wave Sensors
Master of Science, The Ohio State University, 2011, Electrical and Computer Engineering

The instrumentation of rotating machinery with sensors typically requires wires and sliprings for electrical connection to measurement equipment. These wired connections are subject to noise and have a high failure rate. Conventional wireless sensors are bulky, require delicate electronics, and their batteries need to be replaced periodically. Passive wireless sensors based on surface acoustic wave (SAW) devices, which are miniature, rugged, and require no electronics have been developed.

These sensors have been shown to measure strain wirelessly in a multipath, time-variant environment. Sensors were fabricated on langasite using electron beam lithography. Detailed characterization of these SAW sensors is preformed. An RF interrogation system has been developed to record the strain measurements and convert the data into usable information. Measurements from SAW sensors have been correlated with conventional strain measurements at high frequencies. A rugged package has been designed to encapsulate the delicate sensor and protect it from harsh environments. A miniature patch antenna was integrated into this package. Finally, conclusions and future work are discussed.

Committee:

Roberto Rojas-Teran (Committee Chair); Eric Walton (Committee Member); Yakup Bayram (Advisor)

Subjects:

Electrical Engineering

Keywords:

SAW device; langasite; miniaturized antenna; wireless sensing; wireless sensor; strain gauge; electron beam lithography

Hosseininejad, JustinDesign and Implementation of a Custom Force Pole Assembly for the Measurement of Primate Locomotor Kinetics
Master of Science in Engineering, Youngstown State University, 2013, Department of Electrical and Computer Engineering
The purpose of this research is to design and implement a custom force transducer assembly for the measurement of primate locomotor kinetics. The measurement system incorporates various strain gauges, accelerometers, high-speed video cameras, and a data acquisition system to generate quantitative stability measurements during primate locomotion. The tasks for this research include: (1) designing and constructing Wheatstone bridge circuitry to read outputs from the constructed force transducers, (2) calibrating and verifying force transducer outputs, (3) constructing a compliant force pole base to simulate tree branch mobility, and (4) constructing, wiring, and testing of accelerometers to independently measure force pole movement during animal locomotion on the compliant substrate. This system is used to gather locomotor kinetics of squirrel monkeys (Saimiri boliviensis), common marmosets (Callithrix jacchus), long-tailed macaques (Macaca fascicularis), and pig-tailed macaques (Macaca nemestrina). The transducer assembly is applied in two experimental contexts: (1) animals moving over static force poles and (2) animals moving over force poles mounted on a compliant base to simulate tree branch mobility. The design surpasses other similar testing structures through the use of accelerometers to independently measure relative movement and acceleration on compliant substrates. Most importantly, the system allows for adaptation and scalability required for application in other species, such as reptiles and other mammals. Data gathered from this system can be applied to impaired mobility studies in disabled individuals and elderly people.

Committee:

Jalal Jalali, PhD (Advisor); Jesse Young, PhD (Committee Member); Faramarz Mossayebi, PhD (Committee Member)

Subjects:

Biomechanics; Electrical Engineering; Engineering

Keywords:

force transducer; Wheatstone bridge; accelerometer; strain gauge; high-speed video camera; data acquisition system; DAQ; primate locomotor kinetics; arboreal stability; biomechanics

Li, SihaoEffect of aeroelasticity in tow tank strain gauge measurements on a NACA 0015 airfoil
Master of Science (MS), Ohio University, 1993, Mechanical Engineering (Engineering)

Effect of aeroelasticity in tow tank strain gauge measurements on a NACA 0015 airfoil

Committee:

Gary Graham (Advisor)

Subjects:

Engineering, Mechanical

Keywords:

Effect of aeroelasticity; Tow tank strain gauge measurements; NACA 0015 airfoil

Tuncay, OrbayWireless Strain Gauge System in a Multipath Environment
Master of Science, The Ohio State University, 2008, Electrical and Computer Engineering

A wireless strain sensing system utilizing passive, wireless, physically small and light weight sensors is desirable for measuring strain in harsh environments such as jet engine compressor and turbine blades. A cluttered and time varying environment results in high loss, blockage, multipath and modulation of the electromagnetic wave. Also, temperature changes affect the sensitivity of the strain measurement. Isolating the information signal from the reverberations in the environment requires time delays in the order of 100s of ns for jet engine environment. Therefore, a wireless strain gauge system that utilizes surface acoustic wave (SAW) strain sensors was studied and tested.

SAW strain sensors are designed to operate at 2.45GHz. Electron beam lithography is used to achieve minimum required feature size at this frequency. The fabrication process is outlined and scanning electron microscope images of some results are given.

A transceiver circuit is designed and constructed. The circuit is tested in free space, in the presence of signal blockage and a time varying channel. Measurements are shown to be in good agreement with predicted data. Sources of errors in the setup are identified to be leakage from transceiver circuit switches and bounce waveforms from the transceiver antenna.

A General Electric J85 jet engine compressor section is analyzed for signal propagation characteristics. Minimum frequency that can propagate through the compressor section is determined to be 5.2GHz. Measurements are done to show that circumferential polarization propagates stronger than radial inside the compressor section. An analytical approximation for the compressor section is generated by modeling compressor section blades as rectangular waveguides. Good agreement on cutoff frequency is achieved for circumferential polarization with the analytical predictions and measurement.

SAW temperature and strain sensors are measured in comparison to traditional gauges. This concept can be generalized to measuring many different physical quantities wirelessly without disturbing the operation of the equipment.

Committee:

Roberto Rojas-Teran (Advisor); Eric Walton K. (Committee Member); Jonathan Young D. (Committee Member)

Subjects:

Electrical Engineering; Engineering; Experiments

Keywords:

wireless strain sensor; surface acoustic wave (SAW); jet engine; multipath; RFID; strain gauge; wireless strain measurement; SAW fabrication; Lithium Niobate