Browsing by Subject "Piezoelectric"
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Item Development of a PC-Based Eight-Channel WIM System(Minnesota Department of Transportation, 2007-10) Kwon, Taek; Aryal, BibhuWeigh-in-Motion (WIM) data provides vital information for pavement design and maintenance. The purpose of this research project was to improve the present piezoelectric WIM technologies through a better system design and signal processing algorithms. Present WIM systems are only available as proprietary systems, i.e., the internal system design and algorithms are highly guarded making it difficult to compare and improve the underlying technology. Therefore, the second objective was to develop a WIM system based on an open architecture, utilizing a standard PC and off-the-shelf components, and to publish the details of the design to promote an open architecture for continuous future improvements by other developers. The research team was able to successfully develop a working eight-channel WIM system, and the details are described in this report. The main innovation introduced in this research is a hardware-in-the-loop (HIL) WIM simulator that can generate analog axle and loop signals through software control. The HIL simulator can create ideal axle signals, as well as erroneous signal conditions, that can be directly fed into WIM systems. The main advantage of using a WIM HIL simulator for developing a WIM system is that the developers may run an unlimited number of signal tests without actually driving a single vehicle through the WIM sensors, thereby significantly reducing the development time and cost. The erroneous signal conditions generated by the HIL simulator can also identify the error handling capabilities of a WIM system. The proposed HIL simulator for WIM system development is new and provides an elegant solution to the unavailability of an ideal axle signal.Item New sensors and estimation systems for the measurement of tire-road friction coefficient and tire slip variables.(2009-11) Erdogan, GurkanThis thesis introduces two new measurement systems developed for the estimation of tire-road friction coefficient and tire slip variables on highway vehicles. The first part of the thesis focuses on the development and experimental evaluation of a friction estimation system based on a novel adaptive feedforward vibration cancellation algorithm. The friction estimation utilizes a small instrumented wheel on the vehicle. Unlike other systems previously documented in literature, the developed system can provide a continuous measurement of the friction coefficient under all vehicle maneuvers, even when the longitudinal and lateral accelerations are both zero. A key challenge in the development of the estimation system is the need to remove the influence of vibrations and the influence of vehicle maneuvers from the measured signal of a force sensor. An adaptive feedforward algorithm based on the use of accelerometer signals as reference inputs is developed. The parameters of the feedforward model are estimated by the adaptive algorithm and serve to determine the value of the friction coefficient. The experimental performance of the adaptive feedforward algorithm is shown to be significantly superior to that of a simple cross-correlation based algorithm for friction estimation. The second part of the thesis introduces a simple approach for the analysis of tire deformations and proposes a new wireless piezoelectric tire sensor for the measurements of physically meaningful tire deformations. The tire deformation profile inside the contact patch can be used for the estimation of tire slip variables, tire forces and tire road friction coefficient. A wireless piezoelectric tire sensor for the specific case of slip angle and tire-road friction coefficient estimation is developed in this work. A sensor which decouples the lateral sidewall deformation from the radial and tangential sidewall deformations is designed. The slope of the lateral deflection profile at the leading edge of the contact patch is used to estimate the slip angle. A second order polynomial is used to model the lateral deflection profile of the sidewall. The parameters of this function are employed to estimate the lateral force and the conventional brush model is employed to estimate the tire road friction coefficient.Item Wind generated electricity using flexible piezoelectric materials.(2010-10) Morris, Dustin LeeWind generated electricity using thin, flexible sheets of piezoelectric materials attached to flag like membranes termed bimorphs is presented. Piezoelectric wind generated electricity presents a simple, yet effective means to extract energy from the environment. The harvested energy would most likely be used to power wireless sensor networks and other low power applications where batteries would normally be used. Replacing batteries is inconvenient for the users of wireless sensor networks and consumers of other low power electronics. Recharging batteries with power extracted directly from the ambient eliminates the need for frequent battery replacement. Bimorphs are constructed with piezoelectric materials such as poled Polyvinylidene Fluoride (PVDF) and Lead Zirconate Titanate (PZT). Various thin, flexible polymers such as overhead projector film or ink jet transparency film make up the substrate. Several adhesives are researched to determine which can withstand the high strain levels over long periods of time. Bluff bodies were used to create vortex shedding; to increase the undulation amplitude of the bimorph and overall efficiency of the piezoelectric energy harvesting system. Due to the low source capacitance of piezoelectric materials and the low oscillation frequency of the bimorph, the source impedance is very high. In order to reduce the source impedance of the bimorph (increase output current), an inductor must resonate out some or all of the reactance of the piezoelectric. However, thousands of henries of inductance would be necessary to have a vast impact on piezoelectric source impedance. Hence, a quasi-resonant rectifier switching circuit is employed to reduce the source impedance of the bimorph. An energy harvesting circuit termed ‘Series Synchronized Switch Harvesting on Inductor’ (SSSHI) is implemented in order to maximize AC to DC power flow from a piezoelement bimorph to a storage capacitor. The circuit comprises of a peak-triggering circuit, inductor, switch, and regulated micro-power step-down converter powered directly from the piezoelement.