131 research outputs found
Effect of pressure on density, porosity and flexural strength during cold isostatic press of alumina-ysz chromia cutting too
This study presented the effect of pressure on the density, porosity and
flexural strength when cold isostatic press (CIP) was applied to compact the ceramic
powders in the form of insert cutting tools. Specific composition of alumina (Al2O3)
wt.90%,yittria stabilized zirconia (YSZ) wt.10%, chromium oxide(Cr2O3) wt.0.6% and
polyethylene glycol (PEG) wt.0.6% were ball milled and hand pressed to form green
body of ceramic inserts. These green body were undergone further compaction inside
CIP with pressures variation of 200 MPa, 300 MPa, 400 MPa with 30 seconds and 60
seconds pressuring time. The ceramic composts were then sintered at 1440°C for 9 hours
before being assessed with density, porosity, Rockwell hardness (HRC) and bending
test. The results show that CIP use with 300 MPa parameters with 60 seconds shows the
best mechanical properties with relative density 95.5%, porosity 4.5% and HRC 65.5
hardness. Further assessment of microstructure revealed that the particles size distributed
evenly along fracture surface with coarse grain and porosity dominant in the certain area
Channel estimation and tracking algorithms for vehicle to vehicle communications
The vehicle-to-vehicle (V2V) communications channels are highly time-varying, making reliable communication difficult. This problem is particularly challenging because the standard of the V2V communications (IEEE 802.11p standard) is based on the WLAN IEEE 802.11a standard, which was designed for indoor, relatively stationary channels; so the IEEE 802.11p standard is not customized for outdo or, highly mobile non-stationary channels. In this thesis,We propose Channel estimation and tracking algorithms that are suitable for highly-time varying channels. The proposed algorithms utilize the finite alphabet property of the transmitted symbol, time domain truncation, decision-directed as well as pilot information. The proposed algorithm s improve the overall system performance in terms of bit error rates, enabling the system to achieve higher data rates and larger packet lengths at high relative velocities. Simulation results show that the proposed algorithms achieve improved performance for all the V2V channel models with different velocities, and for different modulation schemes and packet sizes as compared to the conventional least squares and other previously proposed channel estimation techniques for V2V channels
Controller Design and Experimental Validation for Connected Vehicle Systems Subject to Digital Effects and Stochastic Packet Drops
Vehicle-to-everything (V2X) communication allows vehicles to monitor the nearby traffic environment, including participants that are beyond the line of sight. Equipping conventional vehicles with V2X devices results in connected vehicles (CVs) while incorporating the information provided by V2X devices into the controllers of automated vehicles (AVs) leads to connected automated vehicles (CAVs). CAVs have great potential for improving driving comfort, reducing fuel consumption and advancing active safety for individual vehicles, as well as enhancing traffic efficiency and mobility for human-dominated traffic systems. In this dissertation, we study a class of connected cruise control (CCC) algorithms for longitudinal control of CAVs, where they respond to the motion information of one or multiple connected vehicles ahead. For validation and demonstration purposes, we utilize a scaled connected vehicle testbed consisting of a group of ground robots, which can provide us with insights about the controller design of full-size vehicles.
On the one hand, intermittencies in V2X communication combined with the digital implementation of controllers introduce information delays. To ensure the performance of individual CAVs and the overall traffic, a set of methods is proposed for design and analysis of such communication-based controllers. We validate them with the scaled testbed by conducting a series of experiments on two-car predecessor-follower systems, cascaded predecessor-follower systems, and more complex connected vehicle systems. It is demonstrated that CAVs utilizing information about multiple preceding vehicles in the CCC algorithm can improve the system performance even for low penetration levels. This can be beneficial at the early stage of vehicle automation when human-driven vehicles still dominate the traffic system.
On the other hand, we study the delay variations caused by stochastic packet drops in V2X communication and derive the stochastic processes describing the dynamics for the predecessor-follower systems. The dynamics of the mean, second moment and covariance are utilized to obtain stability conditions. Then the results of the two-car predecessor-follower system with stochastic delay variations are extended to an open chain as well as to a closed ring of cascaded predecessor-followers where stochastic packet drops lead to heterogeneity among different V2X devices. It is shown that the proposed analytical methods allow CCC design for CAVs that can achieve stability and stochastic disturbance attenuation in the presence of stochastic packet drops in complex connected vehicle systems.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/145874/1/wubing_1.pd
Consensus Tracking for Multiagent Systems Under Bounded Unknown External Disturbances Using Sliding-PID Control
This paper is devoted to the study of consensus tracking for multiagent systems under unknown but bounded external disturbances. A consensus tracking protocol which is a combination between the conventional PID controller and sliding mode controller named sliding-PID protocol is proposed. The protocol is applied to the consensus tracking of multiagent system under bounded external disturbances where results showed high effectiveness and robustness
Open Platforms for Connected Vehicles
L'abstract è presente nell'allegato / the abstract is in the attachmen
6G Wireless Systems: Vision, Requirements, Challenges, Insights, and Opportunities
Mobile communications have been undergoing a generational change every ten
years or so. However, the time difference between the so-called "G's" is also
decreasing. While fifth-generation (5G) systems are becoming a commercial
reality, there is already significant interest in systems beyond 5G, which we
refer to as the sixth-generation (6G) of wireless systems. In contrast to the
already published papers on the topic, we take a top-down approach to 6G. We
present a holistic discussion of 6G systems beginning with lifestyle and
societal changes driving the need for next generation networks. This is
followed by a discussion into the technical requirements needed to enable 6G
applications, based on which we dissect key challenges, as well as
possibilities for practically realizable system solutions across all layers of
the Open Systems Interconnection stack. Since many of the 6G applications will
need access to an order-of-magnitude more spectrum, utilization of frequencies
between 100 GHz and 1 THz becomes of paramount importance. As such, the 6G
eco-system will feature a diverse range of frequency bands, ranging from below
6 GHz up to 1 THz. We comprehensively characterize the limitations that must be
overcome to realize working systems in these bands; and provide a unique
perspective on the physical, as well as higher layer challenges relating to the
design of next generation core networks, new modulation and coding methods,
novel multiple access techniques, antenna arrays, wave propagation,
radio-frequency transceiver design, as well as real-time signal processing. We
rigorously discuss the fundamental changes required in the core networks of the
future that serves as a major source of latency for time-sensitive
applications. While evaluating the strengths and weaknesses of key 6G
technologies, we differentiate what may be achievable over the next decade,
relative to what is possible.Comment: Accepted for Publication into the Proceedings of the IEEE; 32 pages,
10 figures, 5 table
An Overview of Cyber Security and Privacy on the Electric Vehicle Charging Infrastructure
Electric vehicles (EVs) are key to alleviate our dependency on fossil fuels.
The future smart grid is expected to be populated by millions of EVs equipped
with high-demand batteries. To avoid an overload of the (current) electricity
grid, expensive upgrades are required. Some of the upgrades can be averted if
users of EVs participate to energy balancing mechanisms, for example through
bidirectional EV charging. As the proliferation of consumer Internet-connected
devices increases, including EV smart charging stations, their security against
cyber-attacks and the protection of private data become a growing concern. We
need to properly adapt and develop our current technology that must tackle the
security challenges in the EV charging infrastructure, which go beyond the
traditional technical applications in the domain of energy and transport
networks. Security must balance with other desirable qualities such as
interoperability, crypto-agility and energy efficiency. Evidence suggests a gap
in the current awareness of cyber security in EV charging infrastructures. This
paper fills this gap by providing the most comprehensive to date overview of
privacy and security challenges To do so, we review communication protocols
used in its ecosystem and provide a suggestion of security tools that might be
used for future research.Comment: 12 pages, 5 tables, 3 figure
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