Nicholas Miller

A Robust Approach to High-Speed Navigation for Unrehearsed Desert Terrain

This article presents a robust approach to navigating at high-speed across desert terrain. A central theme of this approach is the combination of simple ideas and components to build a capable and robust system. A pair of robots were developed which completed a 212 kilometer Grand Challenge desert race in approximately seven hours. A path-centric navigation system uses a combination of LIDAR and RADAR based perception sensors to traverse trails and avoid obstacles at speeds up to 15m/s. The onboard navigation system leverages a human based pre-planning system to improve reliability and robustness. The robots have been extensively tested, traversing over 3500 kilometers of desert trails prior to completing the challenge. This article describes the mechanisms, algorithms and testing methods used to achieve this performance.

Dynamics of microscale thin film AlN piezoelectric resonators enables low phase noise UHF frequency sources

Miniaturized, multi-band and high frequency oscillators that are compatible with CMOS processes are highly desirable for the synthesis of compact, stable, and low power frequency sources for reconfigurable radio frequency communication systems and cognitive radios. Aluminum nitride (AlN) contour mode MEMS resonators (CMR) are emerging devices capable of high Q, low impedance, and multi-frequency operation on a single chip. The frequency stability of these AlN MEMS devices is of primary importance in delivering oscillators that exhibit low phase noise, and low sensitivity to temperature and acceleration. In this article we describe how the resonator dynamics impacts oscillator performance and present some preliminary demonstrations of ultra-high-frequency (UHF) oscillators. An example of an oscillator prototype we synthesized with a 586 MHz AlN CMR exhibited phase noise <; - 91 dBc/Hz and - 160 dBc/Hz at 1 kHz and 10 MHz offsets, temperature stability of 2 ppm from - 20 to + 85°C, and acceleration sensitivity <; 30 ppb/G.

Measurements of frequency fluctuations in aluminum nitride contour-mode resonators

As part of the current drive to engineer miniaturized monolithic high-performance microelectromechanical-enabled oscillators, there is a need for further study of frequency fluctuations in microelectromechanical resonators. To this end, we present the measurement of frequency fluctuations for 128 aluminum nitride contour-mode resonators. The measurements show that fluctuations are sufficiently large to play an important role in oscillator performance. These results were obtained for the first time from vector network analyzer measurements and are accompanied by an analysis of the experimental setup.

Vector network analyzer measurements of frequency fluctuations in aluminum nitride contour-mode resonators

As part of the current drive to engineer minitureized monolithic high performance microelectromechanical enabled oscillators there is a need for further study of frequency fluctuations in microelectromechanical resonators. To facilitate this we consider the measurement of frequency fluctuations using a vector network analyzer and demonstrate the utility of this approach using an aluminum nitride contour-mode resonator. We examine a generalized quasi-static model as well as a more detailed dynamic model and compare one- and two-port measurement setups.

A Complete System for High-Speed Navigation of Prescribed Routes

This paper presents an approach that achieves robust high-speed navigation of prescribed routes. We present the mechatronic and software considerations that resulted in two robots that have completed over 4000 km of autonomous navigation of trails and off-road terrain at an average speed of approximately 30 km/h, with sustained top speeds of 55 km/h

Nonlinear dynamics in aluminum nitride contour-mode resonators

In this work we discuss the self-heating dynamics of aluminum nitride contour mode resonators. The self-heating introduces a quadratic coupling between the resonator motion and its temperature. This coupling produces a nonlinear frequency response identical to the Duffing resonator in steady-state. However, since the thermal relaxation rate is much smaller than the mechanical relaxation rate the dynamics of the resonator differ from the conventional Duffing resonator.