We have developed four generations of sonar scanning systems to automatically interpret surrounding environment. The first two are stationary 3D air-coupled ultrasound scanning systems and the last two are packaged as sensor heads for mobile robots. Template matching analysis is applied to distinguish simple indoor objects. It is conducted by comparing the tested echo with the reference echoes. Important features are then extracted and drawn in the phase plane. The computer then analyzes them and gives the best choices of the tested echoes automatically. For cylindrical objects outside, an algorithm has been presented to distinguish trees from smooth circular poles based on analysis of backscattered sonar echoes. The echo data is acquired by a mobile robot which has a 3D air-coupled ultrasound scanning system packaged as the sensor head. Four major steps are conducted. The final Average Asymmetry-Average Squared Euclidean Distance phase plane is segmented to tell a tree from a pole by the location of the data points for the objects interested. For extended objects outside, we successfully distinguished seven objects in the campus by taking a sequence scans along each object, obtaining the corresponding backscatter vs. scan angle plots, forming deformable template matching, extracting interesting feature vectors and then categorizing them in a hyper-plane. We have also successfully taught the robot to distinguish three pairs of objects outside. Multiple scans are conducted at different distances. A two-step feature extraction is conducted based on the amplitude vs. scan angle plots. The final Slope1 vs. Slope2 phase plane not only separates the rectangular objects from the corresponding cylindrical.

This thesis describes the design, assembly, and test of the FTDS-K, a new device in the Boundary Layer Data System (BLDS) family of flight data acquisition systems. The FTDS-K provides high-frequency, high-gain data acquisition capability for up to two pressure sensors and an additional three low-frequency pressure sensors. Development of the FTDS-K was separated into a core module, specialized analog subsystem, and practical testing of the FTDS-K in a flow measurement mission. The core module combines an nRF52840-based microcontroller module, switching regulator, microSD card, real-time clock, temperature sensor, and trio of pressure sensors to provide the same capabilities as previous-generation BLDS-P devices. An expansion header is included in the core module to allow additional functionality to be added via daughter boards. An analog signal chain comprised of two-stage amplification and fourth-order active antialiasing filters was implemented as a daughter board to provide an AC-coupled end-to-end gain of 7,500 and a DC-coupled end-to-end gain of 50. This arrangement was tested in a wind tunnel to demonstrate that sensors with a full-scale range of 103 kPa can be used to reliably discriminate between laminar and turbulent flows based on pressure fluctuation differences on the order of tens of Pa. A combination of wind-off correction and band-filtering was used to reduce the effect of inherent and induced electrical noise, while two-sensor correlation was tested and shown to be effective at removing certain types of noise. Total power consumption for the FTDS-K in a representative mission is 208 mW, which translates to an operational endurance of 9 hours with 2 AAA LiFeS2 cells at -40°C.

With the advent of thin film technology and more recently its applications in microelectronics and control of surface properties, the interest in mechanical properties of thin films has grown tremendously. Mechanical defects such as creep, fracture and adhesion loss, play a very important role in physical instabilities of thin film materials. An acoustic microscope has been built to study mechanical properties of thin-films. The microscope operates at a nominal frequency of 50 MHz. Rayleigh surface waves velocities on the surface of film-substrate systems were measured from V(z) curves generated by the acoustic microscope. V(z) curves are produced from interference between the Rayleigh surface wave and the specularly reflected waves. Technologically important materials, non-stoichiometric titanium nitride (TiN{dollar}\sb{lcub}\rm x{rcub}{dollar}) films and diamond films, were fabricated by using magnetron plasma deposition and hot filament chemical vapor deposition (HFCVD) on Si (100) and Si (111) substrates. Spectra from XPS (X-ray Photoelectron Spectroscopy) were used to determine the chemical composition of the films and SEM (Scanning Electron Microscope) micrographs were taken to study the morphology of the films. Rayleigh surface wave velocity measurements on TiN{dollar}\sb{lcub}\rm x{rcub}{dollar} films show a sharp increase in velocity at x = 0.7. A comparison with the phase diagram of TiN {dollar}\sb{lcub}\rm x{rcub}{dollar} suggests that the sharp increase in velocity might be due to a crystal structural transition from tetragonal {dollar}\varepsilon{dollar}-Ti{dollar}\sb2{dollar}N to fcc {dollar}\delta{dollar}-TiN.

This research identifies the resonant frequencies emitted by 2 types of stringed instruments, violins and guitars, in a definitive way that provides measured data for results. A resonance testing apparatus designed to support the instruments for testing, produce forced vibrations of precise period and amplitude to excite an instrument, and acquire measured data was used to perform the testing for this research. The output of this research presents a tabulation of the resonant frequencies and their amplitude that correlates the resonant frequencies below 1000 Hz pictorially to a location on the top plate of the instrument that represents the most significant displacement. The outcome of this research supports the viability of this method with opportunities for further research to focus on improved construction techniques, areas of a completed system that can be manipulated to improve tonal quality, or methods of manipulation that have previously not been explored.

This thesis contains the design, implementation, and testing of an original, small-scaled two degree-of-freedom telescope mount and a medium-scaled three degree-of-freedom telescope mount inspired by the six degree-of-freedom Stewart-Gough platform telescope mount. The end product is intended to achieve research-standard resolution of targeted sky coverage for binary star research. The scaled prototype was carried through concept design, manufacturing, software development, and testing. The mount software development and electronic design is applicable to a full-scale mount as the drivers have been designed to be easily adapted to different actuator configurations. It is recommended that this design be implemented into a telescope in the one to two meter range for economic practicality.

Data acquisition systems for rotordynamic analysis and machine vibration were explored for the purpose of replacing the obsolete Bently Nevada ADRE 208 and ADRE for Windows system. These included the development of Matlab based custom data acquisition systems and a user interface. A model of an anisotropic rotor response undergoing transient speed was developed for the rapid prototyping and testing of data acquisition systems. Several methods for the measurement of amplitudes and phase in both the time domain and frequency domain were developed and compared. An alternate data acquisition method which is more inline with industry practices was created for the purpose of spectral analysis. Additionally, an optimized data acquisition strategy was developed for implementation within the Matlab app which included batch processing, state-based acquisition, and differentiated vector and waveform acquisition rates. A Bently Nevada 2300/20 vibration monitor was configured for use in the lab but found unsuitable for replacing the ADRE 208. Ultimately a Bently Nevada ADAPT 3701/44 Vibration Monitor was configured and found to be an adequate replacement for the ADRE 208 system for use in the Cal Poly Vibrations Lab.

In this thesis, a discussion on the effectiveness of acoustic design in public spaces is made. The auditory properties of a location have noteworthy implications on the success of a building's design and how a room is perceived. Depending on the requirements of each location, either a reverberant or sound-absorbing approach is best suited for the environment. Moreover, public health is negatively affected by long-term involuntary noise exposure. Because of this, there is an obvious demand for continued and expanded study in acoustic design. This thesis aims to challenge interior design choices made in four testing locations: a classroom, a musical practice room, an ambient performance space, and an office. Reverberation time is tested at each site using both a Digital Sound Level Meter application (Decibel X) and a 732A Digital Sound Level Meter paired with a series of external source sounds at set testing frequencies. Depending on the results of each trial, an evaluation of possible improvements to each location's aural properties is made.

No description available.

Requirements exist for a unique type of underwater acoustic source. The transducer is in the form of a linear array of discrete elements and is required to have a constants transmitting voltage response and carefully controlled directivity characteristics over a two octave bandwidth. A generalized model of a linear array of cylindrical piezoelectric ceramic acoustic radiators is developed and applied to the design of a prototype which operates over approximately one half of the required bandwidth. The prototype transducer was built and the measured results are compared with those predicted by the model. Recommendations are made for improving the performance of both the prototype and the array required to meet the full bandwidth specified.

Piezoelectric actuators frequently exhibit a time-dependent behavioral phenomenon known as hysteresis, resulting in a lag in the deformation of the actuator compared to linear models. The presence of hysteresis complicates control systems involving piezoelectric actuators. However, traditional modeling methods for piezoelectric actuated smart structures often treat the piezoelectric patches as linear actuators without considering hysteresis, leading to suboptimal controller performance. This thesis aims to establish a comprehensive model by integrating the Euler-Bernoulli beam bending model with the hysteresis dynamics induced by two opposing piezoelectric patches attached to a beam. A model expansion method is employed to transform the partial differential equations describing beam vibration into a set of ordinary differential equations in the modal coordinate frame. These equations are then coupled with the Bouc-Wen model describing the hysteresis of piezoelectric materials. Model parameters are identified using a genetic algorithm tested against experimental data across varied excitation frequencies. The experimental dataset is divided into two sets: a training set for the genetic algorithm and a validation set to verify the identified model. Results demonstrate that the inclusion of hysteresis in a nonlinear model provides better agreement with experimental results than the linear model, thereby enhancing the predictive capability of piezoelectric actuator behavior. This thesis has laid the foundation for future work on advanced control methods to mitigate beam vibration under external excitation, thus optimizing smart structure performance.