In this study, we consider cooperative control issues for a multi-unmanned aerial vehicle (UAV) system. Specifically, we present a cooperative formation control strategy for a multi-UAV system with unidirectional netw...
详细信息
ISBN:
(纸本)9781479964666
In this study, we consider cooperative control issues for a multi-unmanned aerial vehicle (UAV) system. Specifically, we present a cooperative formation control strategy for a multi-UAV system with unidirectional network links. Our strategy is to apply a consensus-based algorithm and leader-follower structure to the UAVs so that they can cooperatively fly in formation. The leader provides each UAV with commands to generate a geometric configuration of the formation. Convergence is guaranteed when the cooperative formation control algorithm is applied to the UAVs. Collisions among UAVs can occur when they are flying with the cooperative control UAVs. Our strategy for collision avoidance is to apply an artificial potential approach to the UAVs. Experiments are performed on multiple commercial small UAVs to validate the proposed formation control algorithm with collision-avoidance capability.
This study provides a new mode of transport in urban areas inhabited by many elderly people. In some of these areas, public transport systems are inadequate and parking spaces for private cars are in short supply. In ...
详细信息
ISBN:
(纸本)9781479918829
This study provides a new mode of transport in urban areas inhabited by many elderly people. In some of these areas, public transport systems are inadequate and parking spaces for private cars are in short supply. In addition, the decline of shopping malls around these areas makes life inconvenient for the inhabitants. Here we introduce a car-sharing service of vehicle-following personal vehicles along streets in residential areas inhabited by elderly people. This study achieves a vehicle control function with high reliability, high accuracy, and ease of handling by a measuring device that uses a draw wire encoder. First, we consider background issues pertaining to transports and residential streets in Japan. Next, we give an introduction on vehicle-following technologies we have developed. We then describe a measuring device that uses a draw wire encoder for the proposed vehicle-following service, as well as the underlying control algorithms implemented by the measuring device. Finally, we report the results of experiments conducted on small electric vehicles (EVs). The results verify that the proposed device and vehicle-following control algorithms enable vehicles to drive with vehicle-to-vehicle distance errors of approximately +/- 10 cm.
To enable further growth of wind turbine dimensions and rated power, it is essential to decrease structural loads that wind turbines experience. Therefore a great portion of research is focused on control algorithms f...
详细信息
ISBN:
(纸本)9783952426913
To enable further growth of wind turbine dimensions and rated power, it is essential to decrease structural loads that wind turbines experience. Therefore a great portion of research is focused on control algorithms for reduction of structural loads, but typically wind turbine rotor is considered to be perfectly symmetrical, and therefore such control algorithms cannot reduce structural loads caused by rotor asymmetries. In this paper, the reduction of wind turbine structural loads caused by rotor asymmetries is discussed. To this aim, suitable transformation of structural loads and control algorithm based on such transformation are proposed. Simulation results show that proposed control algorithm is capable of reducing structural loads caused by rotor asymmetries.
The focus of this dissertation is design and analysis of scheduling algorithms for distributed computer systems, i. e., data centers. Today's data centers can contain thousands of servers and typically use a multi...
详细信息
The focus of this dissertation is design and analysis of scheduling algorithms for distributed computer systems, i. e., data centers. Today's data centers can contain thousands of servers and typically use a multi-tier switch network to provide connectivity among the servers. Data centers are the host for execution of various data-parallel applications. As an abstraction, a job in a data center can be thought of as a group of interdependent tasks, each with various requirements which need to be scheduled for execution on the servers and the data flows between the tasks that need to be scheduled in the switch network. In this thesis, we study both flow and task scheduling problems under the features of modern parallel computing frameworks. For the flow scheduling problem, we study three models. The first model considers a general network topology where flows among the various source-destination pairs of servers are generated dynamically over time. The goal is to assign the end-to-end data flows among the available paths in order to efficiently balance the load in the network. We propose a myopic algorithm that is computationally efficient and prove that it asymptotically minimizes the total network cost using a convex optimization model, fluid limit and Lyapunov analysis. We further propose randomized versions of our myopic algorithm. The second model consider the case that there is dependence among flows. Specifically, a coflow is defined as a collection of parallel flows whose completion time is determined by the completion time of the last flow in the collection. Our main result is a 5-approximation deterministic algorithm that schedule coflows in polynomial time so as to minimize the total weighted completion times. The key ingredient of our approach is an improved linear program formulation for sorting the coflows followed by a simple list scheduling policy. Lastly, we study scheduling coflows of multi-stage jobs to minimize the jobs' total weighted completion t
The join operation combines information from multiple data sources. Efficient processing of join queries is a pivotal issue in most database systems. My PhD research focuses on joins in two categories of novel applica...
详细信息
The join operation combines information from multiple data sources. Efficient processing of join queries is a pivotal issue in most database systems. My PhD research focuses on joins in two categories of novel applications. The first is continuous joins in data streams. Specifically, we exploit two key properties of the streaming join. First, the initial plan of a long query may gradually become inefficient due to changes in data characteristics. This necessitates dynamic plan migration, an online transition from the old plan to a more efficient one generated based on current statistics. The only known solutions MS and PT have some serious shortcomings. Hence, we propose HybMig, which combines their merits, and outperforms them on every aspect. Another important property is that an output tuple from an upstream join (called the producer) may never generate any result in downstream operators (the consumers) during its entire lifespan. Motivated by this, we propose just-in-time (JIT) processing, a novel methodology that enables a producer to selectively generate outputs based on feedback returned from consumers that express their current demand. Extensive experiments show that JIT achieves significant savings in terms of both CPU time and memory consumption. The second class of joins studied in this thesis are authenticated ones in outsourced databases. In particular, database outsourcing requires that the query server constructs a proof of result correctness, which can be verified by the client using the data owner's signature. Addressing such queries, we propose a comprehensive set of new solutions that cover the entire spectrum of index availability. Furthermore, we extend them to authenticate complex queries, involving multi-way joins and other relational operators. Our experiments demonstrate that, the proposed methods outperform two existing benchmark solutions, often by orders of magnitude.
The method of studying the synchronization of relaxation self-oscillations, based on a modified axiomatic method and using the properties of uniform almost-periodic functions is used. A computational algorithm is used...
详细信息
ISBN:
(纸本)9783030391621;9783030391614
The method of studying the synchronization of relaxation self-oscillations, based on a modified axiomatic method and using the properties of uniform almost-periodic functions is used. A computational algorithm is used to study the synchronization of relaxation self-oscillations, using axiomatic algebraic models and properties of the theory of uniform almost periodic functions. It is shown that synchronization is a flexible and efficient process for shaping the attention of other cognitive processes to certain external informational influences. The five synchronization modes of neural ensembles of 100 peripheral neurons were investigated: asynchronous mode, full synchronization, partial synchronization, "incorrect" synchronization mode, transient phase-dynamic process. The complex synchronization regimes of relaxation self-oscillations are considered: "incorrect" synchronization, the presence of specific and "phase-dynamic" transient processes caused by the properties of uniform almost-periodic functions. Discussed the adequacy of the used mathematical computer model for the formation of attention.
In this paper, a predictive Direct Torque Control strategy with constant switching frequency of Brushless Doubly Fed Machine is presented. Firstly, the classical Direct Torque Control strategy for Brushless Doubly Fed...
详细信息
ISBN:
(纸本)9781424407545
In this paper, a predictive Direct Torque Control strategy with constant switching frequency of Brushless Doubly Fed Machine is presented. Firstly, the classical Direct Torque Control strategy for Brushless Doubly Fed Machine has been developed, obtaining the voltage vector table. The vector voltage table has been developed analyzing the flux and torque derivates for each voltage vector as a function of control winding flux angle. In order to employ constant switching frequency, predictive Direct Torque Control is applied. Reduced torque ripple strategy has been implemented to improve the behavior at constant switching frequency. Simulation results show effectiveness of the proposed control algorithm.
A cascade controller was proposed for mobile robot navigation because of the simplicity of control algorithm. For a robot that requires to only complete straight path navigation, the cascade controller is an attractiv...
详细信息
ISBN:
(纸本)9781457719677
A cascade controller was proposed for mobile robot navigation because of the simplicity of control algorithm. For a robot that requires to only complete straight path navigation, the cascade controller is an attractive solution. Compared to typical mobile robot navigation algorithms, this cascade control does not need any path tracking control and only uses simple PID for navigation. For each mobile robot wheels, a position PID controller is cascaded to a velocity PID controller. An additional PID controller is added in between both wheels to make sure the mobile robot moves in a straight path. An experiment was done on a differential drive robot and results were presented.
暂无评论