Date of Award

12-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Automotive Engineering

Committee Member

Dr. Todd H. Hubing, Committee Chair

Committee Member

Dr. Pierluigi Pisu

Committee Member

Dr. Robert Prucka

Committee Member

Dr. Simona Onori

Abstract

This dissertation describes three independent studies related to electrical component failures affecting vehicle electronics. The topics covered are: comparison of the accelerator-pedal-to-engine-control module (AP-to-ECM), the effect of electrical fast transients on multi-layer ceramic (MLC) capacitors, and electrical behavior of MLC capacitors damaged by electrostatic discharge.

The first chapter examines the AP-to-ECM interfaces of five vehicles equipped with electronic throttle control systems. All five vehicles employ simple voltage level sensing from two or three sensors in the accelerator pedal assembly. The purpose of the study is to identify any differences in the AP-to-ECM interfaces of vehicles with high reported rates of unintended acceleration compared to vehicles with low reported rates of unintended acceleration. The study does not attempt to identify the root causes of unintended acceleration; however it points out important design issues that suggest a set of best practices for electronic throttle control design.

The second chapter investigates the susceptibility of MLC capacitors to high-voltage electrical fast transients (EFTs). X7R and NP0 MLC capacitors with a 50-V voltage rating and 0603 package size were tested. X7R capacitors often failed during a spike in the voltage, but exhibited no obvious degradation in the measured insulation resistance at low voltages immediately after the failure. NP0 capacitors usually failed by suddenly shorting and maintaining the short after the failure. With the application of additional voltage spikes, some X7R capacitors exhibited a full recovery in terms of the measured resistance, returning to their initial state. The resistance of an X7R capacitor damaged by an EFT event is a function of the applied voltage. The terminal impedance can be modeled as two diodes in parallel.

The third chapter investigates the electrical behavior of MLC capacitors subjected to electrostatic discharge (ESD). The degradation of MLC capacitors subjected to repeated discharges manifests itself as a non-linear resistance. The leakage current in degraded capacitors increases exponentially with an applied voltage. The I-V characteristics of these capacitors are symmetric with voltage and independent of the polarity of the ESD discharges responsible for the degradation. A model for a degraded capacitor consisting of two parallel diodes with opposite polarities is proposed.

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