1,720,993 research outputs found
A graph-based algorithm for optimal control of switched systems: An application to car parking
Full text linkWe consider a finite element approximation of the Bellman equation for the optimal control of switched systems. We show that the problem belongs to a special class that we studied in a previous work, for which we developed an efficient solution algorithm. As an application, we present the problem of generating parking maneuvers for self-driving vehicles on two typical urban parking scenarios. The vehicle is described by four different switched systems in which every switching is associated to a penalization term. In this way, we obtain parking paths that have a small number of direction changes and have a simple structure
Generalized Bang-Bang Control for Multivariable Feedforward Regulation
No full textIn control engineering, effective implementations
require to take into account the constraints for both the
inputs and the outputs of the controlled system. A feedforward
regulation problem is then set out to achieve a minimum-time
rest-to-rest output transition for square MIMO (multi-input
multi-output) linear time-invariant systems. The found
time-optimal solution extends the well-known bang-bang control
to a generalized bang-bang control in which some amplitude
constraints on the outputs are active. A straightforward
sufficient condition to have a solution is provided. The structure
of the time-optimal input-output pair is also investigated.
A feasibility linear programming approach to compute an
approximate solution is proposed. An example highlights the
found results
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A solution of the minimum-time speed planning problem based on lattice theory
No full textFor a vehicle on an assigned path, we find the minimum-time speed law that satisfies kinematic and dynamic constraints, related to maximum speed and maximum tangential and transversal acceleration. We present a necessary and sufficient condition for the feasibility of the problem and a simple operator, based on the solution of two ordinary differential equations, which computes the optimal solution. Theoretically, we show that the problem feasible set, if not empty, is a lattice, whose supremum element corresponds to the optimal solution
Identification of Cyclists' Route Choice Criteria
No full textThe behavior of cyclists when choosing the path to follow along a road network is not uniform. Some of them are mostly interested in minimizing the travelled distance, but some others may also take into account other features such as safety of the roads or level of pollution, including carbon dioxide emission by the cars or even the noise pollution. Identifying the different groups of users, estimating the numerical consistency of each of these groups, and reporting the weights assigned by each group to different characteristics of the road network, is quite relevant. Indeed, when decision makers need to assign some budget for infrastructural interventions, they need to know the impact of their decisions, and this is strictly related to the way users perceive different features of the road network. In this paper, we propose an optimization approach to detect the weights assigned to different road features by various user groups, leveraging knowledge of the true paths followed by them, accessible, for example, through data collected by bike-sharing services
Efficient solution algorithms for the Bounded Acceleration Shortest Path problem
No full textThe purpose of this work is to introduce and characterize the Bounded Acceleration Shortest Path (BASP) problem, a generalization of the Shortest Path (SP) problem. This problem is associated to a graph: nodes represent positions of a mobile vehicle and arcs are associated to pre-assigned geometric paths that connect these positions. BASP consists in finding the minimum-time path between two nodes. Differently from SP, we require that the vehicle satisfy bounds on maximum and minimum acceleration and speed, that depend on the vehicle position on the currently traveled arc. We propose solution algorithms that achieves polynomial time-complexity under some additional hypotheses on problem data
Shortest path with acceleration constraints: complexity and approximation algorithms
Full text linkWe introduce a variant of the Shortest Path Problem (SPP), in which we impose additional constraints on the acceleration over the arcs, and call it Bounded Acceleration SPP (BASP). This variant is inspired by an industrial application: a vehicle needs to travel from its current position to a target one in minimum-time, following pre-defined geometric paths connecting positions within a facility, while satisfying some speed and acceleration constraints depending on the vehicle position along the currently traveled path. We characterize the complexity of BASP, proving its NP-hardness. We also show that, under additional hypotheses on problem data, the problem admits a pseudo-polynomial time-complexity algorithm. Moreover, we present an approximation algorithm with polynomial time-complexity with respect to the data of the original problem and the inverse of the approximation factor ε. Finally, we present some computational experiments to evaluate the performance of the proposed approximation algorithm
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