In this paper, we present a bilevel, model predictive controller for coordination of automated vehicles at intersections. The bilevel controller consists of a coordination level, where intersection ...occupancy timeslots are allocated, and a vehicle level, where the control commands for the vehicles are computed. We establish persistent feasibility and stability of the bilevel controller under some mild assumptions and derive conditions under which closed-loop collision avoidance can be ensured with bounded position uncertainty. We thereafter detail an implementation of the coordination controller on a three-vehicle test bed, where the intersection-level optimization problem is solved using a distributed Sequential Quadratic Programing method. We present and discuss results from an extensive experimental campaign, where the proposed controller was validated. The experimental results indicate the practical applicability of the bilevel controller and show that safety can be ensured for large positioning uncertainties.
A concept called Combined Alternate-Direction Lane Assignment and Reservation-based Intersection Control (CADLARIC) was recently proposed for better management of directionally unrestricted traffic ...flows in a Connected and Autonomous Vehicles (CAVs) environment. In CADLARIC, vehicles must position themselves in a proper lane before they reach the downstream intersection, which enables the resolution of vehicular conflicts both between intersections and, as traditionally, within the intersection boxes. CADLARIC has shown very promising results, but it is quite infrastructurally demanding, requiring six lanes per intersection approach. To overcome this problem, we propose here Combined Flexible Lane Assignment and Reservation-based Intersection Control (CFLARIC), a more robust concept that offers a full spectrum of lane assignment possibilities in combination with the appropriate reservation-based intersection control. Three distinctive CFLARIC strategies are tested on a simulated three-intersection corridor from West Valley City, Utah. The efficiency and safety performance of the proposed CFLARIC scenarios are evaluated through a comparison with Fixed-Time Control (FTC) and Full Reservation-based Intersection Control (FRIC), both with conventional lane assignments. The results illustrate that CFLARIC scenarios: (i) outperform FTC and FRIC in terms of efficiency (delay and number of stops), and (ii) improve overall safety (by reducing a number of conflicting situations) when compared to FRIC. The findings of this study prove that flexible control concepts such as CFLARIC have a great potential to improve safety and efficiency in future CAV environment. Future research needs to define under which conditions and how the proposed concept could be partially implemented in field operations.
•Flow test and numerical simulation solving NS equations on crossed fractures are conducted.•An expression for predicting hydraulic aperture of each segment of an intersection is proposed.•Influences ...of hydraulic gradient, surface roughness, intersecting angle, and scale effect are systematically investigated.•A necessary condition to apply the cubic law to flow through fracture intersections is suggested.
Fluid flow tests were conducted on two crossed fracture models for which the geometries of fracture segments and intersections were measured by utilizing a visualization technique using a CCD (charged coupled device) camera. Numerical simulations by solving the Navier–Stokes equations were performed to characterize the fluid flow at fracture intersections. The roles of hydraulic gradient, surface roughness, intersecting angle, and scale effect in the nonlinear fluid flow behavior through single fracture intersections were investigated. The simulation results of flow rate agreed well with the experimental results for both models. The experimental and simulation results showed that with the increment of the hydraulic gradient, the ratio of the flow rate to the hydraulic gradient, Q/J, decreases and the relative difference of Q/J between the calculation results employing the Navier–Stokes equations and the cubic law, δ, increases. When taking into account the fracture surface roughness quantified by Z2 ranging 0–0.42 for J=1, the value of δ would increase by 0–10.3%. The influences of the intersecting angle on the normalized flow rate that represents the ratio of the flow rate in a segment to the total flow rate, Ra, and the ratio of the hydraulic aperture to the mechanical aperture, e/E, are negligible when J<10−3, whereas their values change significantly when J>10−2. Based on the regression analysis on simulation results, a mathematical expression was proposed to quantify e/E, involving variables of J and Rr, where Rr is the radius of truncating circles centered at an intersection. For E/Rr>10−2, e/E varies significantly and the scale of model has large impacts on the nonlinear flow behavior through intersections, while for E/Rr<10−3, the scale effect is negligibly small. Finally, a necessary condition to apply the cubic law to fluid flow through fracture intersections is suggested as J<10−3, E/Rr<10−3, and Z2=0.
Verifiable delegated set intersection over outsourced private datasets (VDPSI) enables two parties to outsource their private datasets and delegate the computation of set intersection to the cloud ...while being able to check the correctness of the result. In this process, the cloud learns nothing about the datasets and the intersection result. However, the existing VDPSI schemes suffer from three substantial shortcomings that limit their use: i) the whole dataset consists of only one subset, ii) they are designed for the static data, and iii) they cannot support other operations. To resolve these problems, we introduce a novel primitive called tag-based VDPSI (TVDPSI), which is designed for the multi-subset case where each subset is associated with one single tag for data classification. To protect privacy, the data is encrypted before being resided to the cloud. The tag is implicitly hidden in each encrypted element. As a result, the cloud cannot learn which data belongs to the same subset beyond the intersection set. Besides, the cloud cannot calculate the intersection except under the permissions of data owners. To the best of our knowledge, TVDPSI is the first VDPSI scheme supporting dynamic update and count operations. The detailed performance evaluation and simulation show that our protocol is more practical in cloud computing.
Eco-driving for connected Fuel Cell Hybrid Electric Vehicles (FCHEVs) is a coupled problem of speed planning and energy management. To reduce the computational burden, bi-level optimization decouples ...and hierarchically solves the upper-level and lower-level subproblems. This paper proposes a bi-level convex approach for eco-driving of a connected FCHEV proceeding through multiple signalized intersections. On the upper level, the non-linear traffic light constraints are transformed into time-varying linear state constraints and the cost function becomes quadratic after using the average speed. On the lower level, model convexification is carried out for the fuel cell system and battery. Then the upper-level speed planning and lower-level energy management are sequentially solved by the MOSEK solver and the Alternating Direction Method of Multipliers (ADMM) algorithm. The results show that the proposed bi-level convex approach greatly reduces the computational cost while maintaining high energy efficiency, with only 6.59% computational time and almost the same fuel economy compared to the bi-level Dynamic Programming (DP) method.
•Bi-level convex optimization of eco-driving is proposed.•Upper-level speed planning is constructed as a convex quadratic programming problem.•Lower-level energy management is solved by the ADMM algorithm.•A comparison of the proposed method and benchmarking methods is conducted.
•Development of bidirectional sending and receiving functions for pedestrian flow modeling.•Compatibility with a bi-directional cell-transmission model in arbitrary network topologies.•Comprehensive ...theoretical and experimental investigation.
Pedestrian flow models are useful for the design and operation of pedestrian spaces. This article describes a macroscopic model of pedestrian flows through networks composed of bidirectional corridors that are connected by multidirectional intersections. The proposed model builds on an existing pedestrian bidirectional fundamental diagram to define bidirectional sending and receiving flows, and it relies on the incremental transfer principle to model bidirectional flows across nodes with an arbitrary number of adjacent links. The model is solved in a cell-transmission formulation that is in all of its unidirectional properties consistent with the kinematic wave model.
Despite many studies on exploring the behaviors of pedestrians crossing the road, there is a need for comprehensive studies that identify the factors that may influence pedestrians crossing behavior ...at signalized and unsignalized intersections. This study aims to comprehensively examine the influence of gender, age group, group-crossing, technological devices and carrying items on pedestrians crossing behaviors at signalized and unsignalized crosswalks simultaneously. Observational data of 552 pedestrians at two signalized and two unsignalized crosswalks in Tehran were collected. Temporal and spatial violations, conflict experience and collision avoidance, situational awareness, and pedestrians crossing speed were used as pedestrians crossing behaviors indicators. To model crossing behaviors, linear mixed models (LMMs) and Generalized linear mixed models (GLMMs) with fixed-effect approach were applied for the continuous outcome (pedestrians' crossing speed) and binary outcomes, respectively. Phi and Cramer's V coefficients were used to avoid multicollinearity. Results showed that traffic checks before and while crossing showed a high positive correlation with crossing at "don't walk" and flashing "don't walk" signals and conflict experience at signalized crosswalks. As compared to females, males started their crossing more on flashing "don't walk" signal and crossed the crosswalk faster. Older pedestrians exhibited more cautious behaviors at signalized intersections but less in unsignalized intersections. Alone pedestrians behaved more cautiously than groups and crossed the crosswalk more quickly. Using technological devices, regardless of their types, caused pedestrians to not exhibit one or more safe crossing indicators considered in this study. Pedestrians talking on their phones had the least cautious behaviors. Pedestrians listening to music mostly looked at the ground or straight direction rather than looking left-right for traffic. The findings from this study are a valuable resource to road authorities and policy makers to develop appropriate targeted strategies to prevent pedestrians' injuries and fatalities and improve crosswalks safety.
In this article a higher order support theory, called the
cohomological jump loci
, is introduced and studied for dg modules over a Koszul extension of a local dg algebra. The generality of this ...setting applies to dg modules over local complete intersection rings, exterior algebras and certain group algebras in prime characteristic. This family of varieties generalizes the well-studied support varieties in each of these contexts. We show that cohomological jump loci satisfy several interesting properties, including being closed under (Grothendieck) duality. The main application of this support theory is that over a local ring the homological invariants of Betti degree and complexity are preserved under duality for finitely generated modules having finite complete intersection dimension.
PDF
