4 research outputs found
Millimetre-wave radar development for high resolution detection
Automotive technology today is focusing on autonomous vehicle development. The
sensors for these systems include radars due to their robustness against adverse
weather conditions such as rain, fog, ash or snow. In this constant search for advancement, high resolution systems play a central role in target detection and avoidance. In this PhD project, these methods have been researched and engineered to
leverage the best radar resolution for collision avoidance systems.
The first part of this thesis will focus on the existing systems consisting of the
state-of-the-art at the time of writing and explain what makes a high resolution
radar and how it can cover the whole field of view. The second part will focus on
how a non-uniform sparse radar system was simulated, developed and benchmarked
for improved radar performance up to 40% better than conventional designs. The
third part will focus on signal processing techniques and how these methods have
achieved high resolution and detection: large virtual aperture array using Multiple
Input Multiple Output (MIMO) systems, beampattern multiplication to improve
side-lobe levels and compressive sensing. Also, the substrate-integrated waveguide
(SIW) antennas which have been fabricated provide a bandwidth of 1.5GHz for the
transmitter and 2GHz at the receiver. This has resulted in a range resolution of 10
cm. The four part of this thesis presents the measurements which have been carried
out at the facilities within Heriot-Watt University and also at Netherlands Organisation for Applied Scientific Research (TNO). The results were better than expected
since a two transmitter four receiver system was able to detect targets which have
been separated at 2.2◦
in angle in the horizontal plane. Also, compressive sensing was used as a high resolution method for obtaining fine target detection and
in combination with the multiplication method showed improved detection performance with a 20 dB side-lobe level suppression. The measurement results from the
6-months placements are presented and compared with the state-of the art, revealing that the developed radar is comparable in performance to high-grade automotive
radars developed in the industry
Automatically Adjusting Concurrency to the Level of Synchrony
International audienceThe state machine approach is a well-known technique for building distributed services requiring high performance and high availability, by replicating servers, and by coordinating client interactions with server replicas using consensus. Indulgent consensus algorithms exist for realistic eventually partially synchronous models, that never violate safety and guarantee liveness once the system becomes synchronous. Unavoidably, these algorithms may never terminate, even when no processor crashes, if the system never becomes synchronous. This paper proposes a mechanism similar to state machine replication, called RC-simulation, that can always make progress, even if the system is never synchronous. Using RC-simulation, the quality of the service will adjust to the current level of asynchrony of the network --- degrading when the system is very asynchronous, and improving when the system becomes more synchronous. RC-simulation generalizes the state machine approach in the following sense: when the system is asynchronous, the system behaves as if k+1 threads were running concurrently, where k is a function of the asynchrony. In order to illustrate how the RC-simulation can be used, we describe a long-lived renaming implementation. By reducing the concurrency down to the asynchrony of the system, RC-simulation enables to obtain a renaming quality that adapts linearly to the asynchrony