Browsing by Subject "Wireless"

Now showing 1 - 3 of 3
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    Minutes: Senate Committee on Information Technologies: October 3, 2000
    (2000-10-03) University of Minnesota: Senate Committee on Information Technologies
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    New sensors and estimation systems for the measurement of tire-road friction coefficient and tire slip variables.
    (2009-11) Erdogan, Gurkan
    This 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.
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    Towards improving security on the wireless medium
    (2012-08) Foo Kune, Denis
    This thesis investigates security issues in the wireless medium surrounding many of today’s modern devices. Such devices that have analog sensors measuring physical processes also have circuits to amplify the signal before it gets converted into a digital format for processing and communication. Those analog input circuits by their use of low voltage signals are sensitive to electromagnetic interferences (EMI). This work investigates the use of EMI as a method of signal injection into the device. The analog inputs are typically not checked for forged waveforms and can be manipulated wirelessly by an attacker. The fundamental vulnerability of those circuits is explored and bounds are derived for the attack. Solutions are proposed for classes of devices depending on their individual constraints. The next part of this work looks at a subset of wireless communication protocols used by devices, focusing on integrated clinical environments. A corresponding list of security requirements is proposed and used to evaluate currently available standards, revealing large gaps. This section concludes by proposing a direction on composing secure integrated clinical environments based on the requirement list. On a larger scale, this thesis analyzes wireless cellular GSM networks. It first reveals location information leaks on the air interface due to the broadcast methods used to notify phones in a given geographic area that there is an incoming call. This section also proposes solutions to mitigate the information leaks discovered. This work then looks at the difficulty of properly and fairly accounting for bytes transferred on behalf of the application layer. A tradeo↵ point used by current transport layers based on wired networks is guaranteed delivery with increased overhead. This section investigates methods that could exploit transport layer retransmission mechanisms to exhaust the financial resources of a cellular user. This thesis focuses heavily on understanding the attacker and methods to wirelessly exploit vulnerabilities in systems. This is a necessary step in building better future systems and evaluating current systems.