Entry Vehicle Research Articles

Real-Time Evaluation Method of Vehicle Conflict Risk on Urban Expressway Based on Smartphone GPS Data

To effectively evaluate the traffic safety risk of urban expressways in real time and ensure their traffic safety and smoothness, a real-time evaluation method of vehicle conflict risk of an urban expressway based on smartphone GPS data was proposed. We screened and processed smartphone GPS data to obtain vehicle behavior data, including acceleration and angular acceleration, and road state data, including average vehicle speed. Urban expressways were divided into four categories, closed straight section, closed curve section, vehicle entry section, and vehicle exit section; the evaluation indexes of abnormal vehicle behavior were established. Based on the improved entropy weight method, the vehicle conflict risk entropy was established to distribute the weight of different types of abnormal behaviors of vehicles. The evaluation system of vehicle conflict risk entropy was applied to the vehicle behavior data. Urban Expressways with more abnormal vehicle behavior were obtained to evaluate the risk of vehicle conflict in real time. The results showed that the easily obtained smartphone GPS data may be effectively used to analyze the abnormal behavior of vehicles, identify vehicle conflict risk points hidden in urban expressways in real time to provide effective methods for batch and dynamic real-time evaluations of vehicle conflict risks on urban expressways, and improve the traffic safety service level of urban expressways.

InSight Entry, Descent, and Landing Preflight Performance Predictions

On 26 November 2018, the Interior Exploration Using Seismic Investigations, Geodesy and Heat Transport (InSight) lander successfully touched down on the surface of Mars. Over its more than seven year development, NASA Langley Research Center’s Program to Optimize Simulated Trajectories II (POST2) was used to assess the mission’s entry, descent, and landing (EDL) vehicle system performance against related requirements across the full range of possible environmental and spacecraft conditions. Due to the high degree of entry body, lander platform, and EDL design heritage, much of the simulation code was derived from the 2007 Mars Phoenix Lander mission. The InSight POST2 six-degree-of-freedom simulation included models for Mars atmosphere, gravity, and digital elevation maps of the landing location. Additionally, vehicle-specific aerodynamic, parachute, engine, navigation sensor, flight software, and landing radar models were included. A set of dispersions for each model, as well as for additional simulation input parameters, was also included in order to provide a statistical, Monte Carlo prediction of the EDL system performance. An overview of the preflight performance assessments completed, including the various simulation campaigns used, will be provided. Ultimately, this work was critical in the assessment of readiness for the InSight launch. A brief description of the use of this simulation in support of flight operations is also discussed.

Hexcomb-Pattern Roughness Effects on Blunt-Body Transition and Heating

An experimental investigation of hexcomb-pattern surface roughness effects on boundary-layer transition and convective heating has been performed. Two representative entry vehicle geometries, a spherical-cap aeroshell and a sphere-cone aeroshell, were considered. Multiple cast ceramic models of each geometry were fabricated with various roughness pattern densities and depths that simulated an ablated hexcomb-structure thermal protection system. Wind-tunnel testing was performed at Mach 6 over a range of Reynolds numbers sufficient to produce laminar, transitional, and turbulent flow. Aeroheating and boundary-layer transition onset data were obtained using global phosphor thermography. The experimental heating data are presented herein, as are comparisons to laminar and turbulent smooth-wall heat transfer distributions from computational flowfield simulations. The experimental data were used to develop a unified boundary-layer transition correlation for both sand-grain distributed roughness and hexcomb-pattern roughness.

On-demand ride-hailing platforms in competition with the taxi industry: Pricing strategies and government supervision

We consider the case where a large-scale entry of ride-hailing vehicles have significant impacts on the taxi market, which may result in many taxi drivers being forced to withdraw from the transport industry or promote the development of the whole transport industry. Specifically, we examine how an on-demand ride-hailing platform in competition with the traditional taxi industry designs its pricing strategies under the unregulated and regulated pricing scenarios, and we focus on government supervision strategies in the transport industry in view of the development of on-demand ride-hailing platforms and their impacts on both society and the traditional taxi industry. We find that the monopolistic on-demand ride-hailing platform's price rate and profit under the unregulated pricing scenario are relatively higher than those under the regulated pricing scenario. We also find that the government should encourage competition between on-demand ride-hailing platforms and the traditional taxi industry. In addition, the government's regulatory measures should depend on its situation and its degrees of attention to various stakeholders because the adjustment effects of the regulatory measures are different. When the taxi supply is less than customer demand, increasing the total number of taxis is the best regulatory measure, but when the taxi supply exceeds customer demand, the best regulatory measure depends on the specific situation. This suggests that the government should adopt pertinent supervisory policies to maximize the overall social welfare and profit based on the actual situation it is in.

Assessing Impacts to National Park Visitation From COVID-19

Yosemite National Park is a popular tourist destination with high visitation levels that have increased throughout the summer season over the past several decades. Like with other protected areas, high visitation levels pose challenges for coordinating resources, infrastructural capacity, and visitor experiences. Use limits, including rationing vehicle entry at gates by reservation, are one possible strategy to manage visitation levels. After an initial full closure, the park chose to operationalize a multiphased permit system for day-use and overnight entry over the course of the pandemic in accordance with local and national guidelines for operational safety. While park closures and other entry restrictions have been common in recent years due to wildland fires and other natural hazards, the pandemic-related entry limits represent a nearly yearlong experiment. The prolonged entry ration along with restrictions to group activities has limited visitation and potentially reduced transmission of the novel coronavirus. We review the per capita COVID-19 case count in surrounding counties given the flow of tourism from outside the region, assess the changes in access to the park with the novel reservation system, compare monthly visitation during the 2020 use limits with prior decadal averages, detail how high visitation levels and crowding persist, and review the Park’s plans for an ongoing day-use permit system. We conclude with the ongoing challenges managers face in light of continued high visitation. Readers will be able to debate the efficacy of use limits and what may be a sustainable level of visitation for the park.

Numerical simulation of cavitation characteristics in high speed water entry of head-jetting underwater vehicle

Autonomous underwater vehicle will be subjected to a huge impact load during high speed water entry, which will damage the structure and the internal instruments of the vehicle. Therefore, it is of great significance to study the buffer mechanism of the vehicle during the process of water-entry. In this paper, a kind of head-jetting device with disk cavitation is used. The complex cavitation forms, under the three-phase coupling of gas, liquid and solid, in the water entry process of the vehicle on which the device is installed. In this paper, the numerical simulation of high-speed water entry of the vehicle equipped with head jet device is carried out. Through the analysis of water entry cavitation under typical working conditions, the following conclusions are obtained. After the installation of head jet device, the water entry cavity of the vehicle changes gradually from cone to spindle shape. The air jet, compared with that without jet, can promote the formation of water inlet supercavitation, decrease the interaction area between the vehicle and water, and reduce the impact load during water entry. At the same water entry depth, the diameter of cavitation increases with the amount of air jet. The water entry velocity has a great influence on the difference of cavitation shape. The water entry depth closure phenomenon, when the water entry velocity is less than 100 m/s, can be observed in the depth of 3.5 times of the projectile length. The water entry angle has a significant effect on the cavitation shape. The cavity shows obvious asymmetry when the vehicle slants into the water, and the diameter and length of the bubbles decrease with the increase of the water entry angle. The research content of this paper provides technical support for the engineering practice of high-speed water entry and load reduction, and the conclusions are of great significance in related fields.

Aerodynamic Performance of the InSight Mars Lander

The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission touched down in Elysium Planitia on 26 November 2018, becoming NASA’s eighth successful entry, descent, and landing (EDL) at Mars. InSight inherited the successful 2008 Phoenix (PHX) EDL system, flying a nonspinning, ballistic trajectory with a 70 deg sphere–cone aeroshell (2.65 m diameter), a disk–gap–band parachute, and pulsed terminal descent and landing engines. InSight and Phoenix exhibited similar behavior, primarily in terms of trim attitude and an uninitiated roll reversal correlated with dynamic pressure, although the behaviors observed for InSight were more severe. For InSight, the initial clockwise roll and nonzero trim angle of attack were significant contributors to a short timeline, larger-than-predicted deceleration loads, and cross-track and up-track errors in landing location. The InSight and Phoenix reconstructions together indicate behavior more characteristic of a single, continuous instability region, suggesting that errors in the trim behavior from hypersonic nonequilibrium aerodynamics predictions along the dynamic pressure pulse may have a more substantial impact on nonspinning, ballistic entry vehicle performance.

A hybrid robust-stochastic optimization framework for optimal energy management of electric vehicles parking lots

The integration of electric vehicles (EVs) into the energy industry has introduced an unprecedented complexity into the energy supply system due to the uncertain nature of such vehicles. The uncertainty of arrival and departure times, as well as the state of charge (SOC) in the arrival and departure of the EVs, is a big challenge in the entry of such vehicles and their facilities into energy networks. These days, a novel approach known as the EVs smart parking lot (SPL) is widely studied in the energy industry looking to manage the charging and discharging electricity of EVs as well as energy supply issues. This study proposes an SPL equipped with heat and power sources, including renewable and non-renewable technologies such as wind turbines, locally installed generating facilities consisting of combined heat and power (CHP) plants, micro-turbines, and heat and power storage systems. The operator of the SPL, in addition to supplying its electricity for sale to the power market, can sell the heat generated by the CHP units locally to maximize its profit. In addition, the proposed model for the SPL can handle the uncertain nature of EV arrivals and departures and the associated SOC level. It can also manage wind-power output and gauge optimal power prices based on hybrid robust-stochastic programming, which is implemented in a case study to confirm its practicality and effectiveness. The analysis shows the effectiveness of the proposed hybrid robust-stochastic operation model in maximizing the profit of the SPL driver and managing the uncertainty level of the system parameters.

InSight Entry, Descent, and Landing Postflight Performance Assessment

On 26 November 2018, the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander successfully touched down on the surface of Mars. Program to Optimize Simulated Trajectories II (POST2) of NASA Langley Research Center was used during both project development and flight operations to assess the entry, descent, and landing (EDL) vehicle performance against related requirements across the expected range of possible environmental and spacecraft conditions. During flight operations, these analyses were used to evaluate the need for updating flight software EDL parameters and the effects of executing a trajectory correction maneuver. Therefore, the NASA Langley Research Center POST2 simulation had a critical role during the cruise, approach, and ultimately EDL phases of the mission. This paper presents the results of the final pre- and post-EDL flight performance assessments. A summary of the reconstructed “as-flown” trajectory with a comparison of key EDL metrics to the nominal and three-sigma bound pre-EDL predictions is also provided. Emphasis on the trajectory between entry interface and parachute deploy is provided, as this is the period during which deviations from the pre-EDL prediction occurred. The postflight assessment provides important verification of the POST2 models and analysis techniques used for InSight, providing critical feedforward information to future lander missions.

Uncertainty Analysis of Inflow Parameters for Mid-Lift-to-Drag Vehicle Transition

The boundary-layer transition and aerothermal environment for mid-lift-to-drag-ratio entry vehicles are highly complex and influenced by several factors. The uncertainty and sensitivity of transition and aeroheating predictions on such vehicles with respect to the inflow parameters are investigated in this paper. Five inflow parameters (freestream Mach number, freestream pressure, freestream temperature, wall temperature, and angle of attack) are chosen as the uncertainty variables. The transition predictions are obtained using Reynolds-averaged Navier–Stokes simulations with the -- transition model. The point-collocation nonintrusive polynomial chaos method is employed to describe and propagate the uncertainty of the output quantities of interests. Moreover, the Sobol index is adopted to quantify the contribution of each variable to the total uncertainty. Our results reveal that small changes (less than 3.4%) in the inflow parameters could yield roughly 10% uncertainty in the transition lengths and more than 15% uncertainty in the transitional aeroheating and skin friction. The freestream temperature and angle of attack strongly influence the transitional aeroheating. The angle of attack, freestream pressure, and freestream temperature are the major uncertainty contributors to the skin friction. The freestream pressure and angle of attack significantly impact the transition onset and length.

About the implementation of the project Safe hatch

The article highlights the problematic moments associated with the fall of young children, adults, domestic and wild animals, as well as the entry of vehicles into communication collectors. Similar technical developments, their advantages and disadvantages are considered, a legal assessment of the technical purpose and the admissibility of introducing new structures into the structure of existing material objects is given. The key point of the article is the author's proposal for the implementation of the obtained utility model into the practice of servicing the system of urban underground structures.

Expansion Tube Experiments of Magnetohydrodynamic Aerobraking for Superorbital Earth Reentry

A set of magnetohydrodynamic (MHD) aerobraking experiments was conducted with the aim of simulating the Earth reentry environment for Mars return trajectories, and to study the effects of MHD flow control on the ionizing shock layer surrounding a planetary entry vehicle. The X2 expansion tube of the University of Queensland was used, which could provide realistic flowfield boundary conditions, where ionization is spontaneously generated within the shock layer as in true flight and the freestream is nonconducting. Suitable flow conditions providing strong MHD interaction at superorbital Earth reentry velocities were developed. Steel ball and neodymium permanent magnet models were tested, both uncoated and coated with electrically insulating high-temperature epoxy. Shock-layer high-speed imaging showed a significant increase in shock standoff distance for the magnetic models. The experimental shock standoff results generally agreed well with analytical and numerical shock standoff predictions. These experiments demonstrate that a strong MHD interaction can be generated for a Mars return trajectory with moderate magnetic field strengths. Furthermore, they provide a promising framework for future MHD aerobraking experiments to investigate MHD drag force and heat-flux mitigation.

Home Security

Thesecurity and privacy ofourhomes and residencesareveryimportantthesedays.Thiscanprotectourhomes and valuables, thereby keeping our family safefrom potential intrusion by thieves. The purpose of thisproject is to allow entry of people and vehicles to a homeonly on owner’s approval.By designing and installing asmart home security systemwe canachieve this. Thesecurity system will be equipped with camera modulesand sensors whichcan detect the faces of people andvehiclesenteringourhome.HaarCascadealgorithmwhichis anobjectdetectionalgorithmidentifiesrealtime faces in a video and Optical Character Recognitionrecognizesvehiclesbasedonthenumberplate.Anandroidapplicationwillbeusedtocontrolthingshappening around the home, using which the users of theapplication can view requests from people or vehiclesenteringourhome.Onlytherecognizedorentryaccepted people and vehicles will be allowed to enter ourhome. The processwillbe repeated inallcases. Thesystem has a good accuracy level too. Thus, security isguaranteed

Smart Parking Management System

The demand for parking and security has increased in public areas which led us to bring this system into existence. The presented system guides the user to find a free parking slot without any effort and keeps the vehicle secure. Arduino-based systems control the movement of the toll gate to permits entry and exit vehicles to and through parking spaces. A camera in front captures the image of a vehicle passing through the toll gate and automatically stores the number plate text of a vehicle and other essential information like time and the parking slot, which is preserved in the database for security purposes. The system consists of a display that guides a user to a free parking slot. The systems also have a feature to send alerts to registered users.

Bilevel optimal control of urban traffic-related air pollution by means of Stackelberg strategies

Air contamination and road congestion are two major problems in modern cities. Both are closely related and present the same source: traffic flow. To deal with these problems, governments impose traffic restrictions preventing the entry of vehicles into sensitive areas, with the final goal of decreasing pollution levels. Unfortunately, these restrictions force drivers to look for alternative routes that usually generate traffic congestions, resulting in longer travel times and higher levels of contamination. In this work, blending computational modelling and optimal control of partial differential equations, we formulate and analyse a bilevel optimal control problem with air pollution and drivers’ travel time as objectives and look for optimal solutions in the sense of Stackelberg. In this setting, the leader (local government) implements traffic restrictions meanwhile the follower (drivers set) acts choosing travel preferences against leader constraints. We discretize the problem and propose a numerical algorithm to solve it, combining genetic-elitist algorithms and interior-point methods. Finally, computational results for a realistic case posed in the Guadalajara Metropolitan Area (Mexico) are shown.

Automation and Control of Vehicle Flow using Raspberry Pi


 
 
 The number of vehicles in the world's cities increases exponentially, this is the case of Latin American cities, and particularly in the city of Portoviejo, province of Manabí in Ecuador, has been growing considerably in recent years, the city has been expanding towards its surroundings. Due to this big number of vehicles, which also adds little planning to improve the use of public transport, little planning to improve urban vehicular flow, the centralization of administrative area and main shops in the city, are the main reasons why in certain times of the day the traffic can become a little slow.
 Universidad Técnica de Manabí, has the objective of modernizing the improvement of vehicular flow in its surroundings and in addition to automating the vehicular entrance to its facilities through the automation of the respective permit for visiting drivers and staff.
 In this paper we show the methodology and tools necessary to create a system to control vehicles entry and exit using a Raspberry Pi, an analysis of the different technologies that can be used to improve vehicular flow is also included, approaching the Internet of Things.
 
 

Sensitivity of Hypersonic Dusty Flows to Physical Modeling of the Particle Phase

The presence of dust in the Mars atmosphere can adversely affect heat shields of entry vehicles by enhancing erosion and increasing surface heat fluxes. However, the accuracy of numerical simulations investigating these effects is limited due to a lack of well-validated physical models of the particle phase. To address this issue, the sensitivities of computational predictions of dust-induced heating augmentation to different parameters and components of the disperse-phase model are evaluated. In particular, the drag correlation, the Nusselt-number correlation, various contributions to momentum and energy transfer, and particle diameter are examined. Numerical simulations are performed using an Euler–Lagrange methodology, in which the carrier gas is solved with a discontinuous Galerkin method. Very strong sensitivity to the drag correlation, moderate sensitivity to the Nusselt-number correlation, and strong sensitivity to the particle diameter are found. In addition, the quasi-steady drag force and heating rate are the most significant contributors to interphase momentum and energy transfer, respectively. These results can contribute to improving models and identifying knowledge gaps and uncertainties in the appropriate dust conditions.

IHG-MA: Inductive heterogeneous graph multi-agent reinforcement learning for multi-intersection traffic signal control

Multi-agent deep reinforcement learning (MDRL) has been widely applied in multi-intersection traffic signal control. The MDRL algorithms produce the decentralized cooperative traffic-signal policies via specialized multi-agent settings in certain traffic networks. However, the state-of-the-art MDRL algorithms seem to have some drawbacks. (1) It is desirable that the traffic-signal policies can be smoothly transferred to diverse traffic networks, however, the adopted specialized multi-agent settings hinder the traffic-signal policies to transfer and generalize to new traffic networks. (2) Existing MDRL algorithms which are based on deep neural networks cannot flexibly tackle a time-varying number of vehicles traversing the traffic networks. (3) Existing MDRL algorithms which are based on homogeneous graph neural networks fail to capture the heterogeneous features of objects in traffic networks. Motivated by the above observations, in this paper, we propose an algorithm, referred to as Inductive Heterogeneous Graph Multi-agent Actor–critic (IHG-MA) algorithm, for multi-intersection traffic signal control. The proposed IHG-MA algorithm has two features: (1) It conducts representation learning using a proposed inductive heterogeneous graph neural network (IHG), which is an inductive algorithm. The proposed IHG algorithm can generate embeddings for previously unseen nodes (e.g., new entry vehicles) and new graphs (e.g., new traffic networks). But unlike the algorithms based on the homogeneous graph neural network, IHG algorithm not only encodes heterogeneous features of each node, but also encodes heterogeneous structural (graph) information. (2) It also conducts policy learning using a proposed multi-agent actor–critic(MA), which is a decentralized cooperative framework. The proposed MA framework employs the final embeddings to compute the Q-value and policy, and then optimizes the whole algorithm via the Q-value and policy loss. Experimental results on different traffic datasets illustrate that IHG-MA algorithm outperforms the state-of-the-art algorithms in terms of multiple traffic metrics, which seems to be a new promising algorithm for multi-intersection traffic signal control.

NASA Ames Thermophysics Ground Test Facilities Supporting Future Planetary Atmospheric Entry

A review of the current facility capabilities for testing Thermal Protection Systems and quantifying their entry environments at NASA Ames Research Center is presented based on the expected targets of interest to the Planetary Science and Astrobiology communities. While the operational capabilities of these facilities are generally considered sufficient for supporting future missions to targets of interest, expanded ground test capabilities such as larger sample sizes, flight-relevant gas mixtures, dusty environments, and flight-relevant shear/pressure combinations would reduce future entry vehicle design uncertainties and applied margins. These reduced uncertainties may translate into reduced entry vehicle masses, increased robustness, and decreased operational risks during entry phases for science missions. Expanded ground test capabilities would also offer the ability to study material failure modes in environments even more representative of flight than are currently achievable. A list of desired future test capabilities is presented along with suggestions of possible methods of achieving each. The main recommendation of this paper is the undertaking of a detailed study of the benefits and associated costs of each of these expanded capabilities to determine the best future path.

Deployable Entry Vehicles for Future Science and Exploration Missions

Deployable Entry Vehicle (DEV) technology has made significant advances over the last decade with ground test development campaigns and flight test demonstrations. DEVs offer benefits over traditional rigid entry vehicles including lower volume and mass, while enabling larger payload delivery and greater landing access. A crucial mission benefit is the DEV capability to transform from a compactly stowed configuration within the launch vehicle to a high drag area entry system for delivery of landers, rovers, aerial platforms, and orbiters (via aerocapture). These benefits span the range of mission classes from Small Satellite (smallsat) to human-class exploration systems. This paper will describe DEV technology development status, highlight mission concepts, and recommend future investments.