Experimental Vehicle Research Articles

Combining extended Kalman filtering and rapidly-exploring random tree: An improved autonomous navigation strategy for four-wheel steering vehicle in narrow indoor environments

Autonomous navigation in narrow indoor environments such as indoor factory, warehouse and laboratory environments, and so on requires higher flexibility and navigation accuracy of the vehicle. This article presents an autonomous navigation method for four-wheel steering vehicle which combines extended Kalman filtering (EKF) and rapidly-exploring random tree (RRT) to improve the precision and flexibility of autonomous navigation of the vehicle in narrow indoor environments. The four-wheel steering model was established by the key parameters such as shape size and minimum angle of rotation of the experimental vehicle. Considering the problem that the uncertainty of pose estimation increases with time during autonomous navigation, an error model is schemed by adding noise to the output terminal of the analog odometer sensor. In order to suppress the accumulation of the uncertainty and keep it stable for a long time, the prediction and update steps of Kalman filter are introduced to filter the error. Then, the simultaneous positioning and mapping are established. Based on accurate positioning, a set of driving paths to reach the target is generated by RRT sampling algorithm. The simulation results show that positioning uncertainty remains stable over time, which verifies the effectiveness of the method. The overall positioning percentage error is 0.21%. Compared with traditional dead reckoning algorithm, the positioning accuracy is improved by 73.1% and the vehicle flexibility is increased by 68.6%. The four-wheel steering vehicle can find an ideal trajectory in narrow indoor environments, which assures the efficiency of the autonomous navigation and the traveling quality of the navigation route. Finally, the experimental results are consistent with the simulation results, which further verifies the effectiveness of the proposed algorithm.

Optimal Control Method of Path Tracking for Four-Wheel Steering Vehicles

Path tracking is a key technique for intelligent electric vehicles, while four-wheel steering (4WS) technology is of great significance to improve its accuracy and flexibility. However, the control methods commonly used in path tracking for a 4WS vehicle cannot take full advantage of the additional steering freedom of the 4WS vehicle, because of restricting the relationship between the front and rear wheels steering angle. To address this issue, we derive a kinematic model without the restriction based on the small-angle assumption. Then, the objective function and constraints of system control quantity optimization are designed based on the tracking error model. After the optimization problem is solved in the form of quadratic programming with constraints, the control sequence with the smallest performance index is obtained through rolling optimization. The proposed method is tested on a high-fidelity Carsim/Simulink co-simulation platform and an experimental vehicle. The results show that the standard deviation of the lateral error and the yaw angle error of the algorithm is less than 0.1 m and 3.0°, respectively. Compared with the other two algorithms, the control of the front and rear wheels angle of this method is more flexible and the tracking accuracy is higher.

Catalytic characterization in plasma wind tunnels under the influence of gaseous recombination

The catalytic properties of materials used in re-usable thermal protection systems (TPSs) of re-entry vehicles are mainly characterized in plasma wind tunnels. These facilities are adequate to reproduce the thermo-chemical environment found in hypersonic flights. Catalytic recombination coefficients (W) determined empirically for the TPS design process are used to validate catalytic models. Recent experiments in plasma wind tunnels present some contradictions with current catalytic models used in computational fluid dynamics simulations. This work explores the coupling between homogeneous and heterogeneous reactions and its influence on the heat flux measurements, in order to explain such contradictions. For that, three copper calorimeters (at 350 K) are inserted in probes of different sizes, and they are tested in the Plasmatron facility at the von Karman Institute under different chemical regimes, which are modified by the probe diameter. A dimensional analysis of the acquired data based on previous non-equilibrium boundary formulations shows that an empirical recombination coefficient can be falsified by the presence of homogeneous reactions. Then, in the framework for the post-flight analysis of the European Space Agency's intermediate experimental vehicle, the local heat transfer simulations methodology is applied under peak heating conditions. A new probe is designed, manufactured, and tested in the Plasmatron to measure the recombination coefficient on C/SiC under the closest flow conditions with respect to the flight.

An effective energy management strategy in hybrid electric vehicles using Taguchi based approach for improved performance

ABSTRACT The key challenge in the innovation of hybrid electric vehicles is the energy management control strategies to split the energy between the sources. The objective of adding an auxiliary source of power to vehicles is to minimize battery stress as well as energy consumption rate (ECR) of the main source and to increase the range of the vehicle. Based on Taguchi and grey relational analysis, the optimal control factors were determined for each of the desired performance factors. In this experimental design, control strategy, vehicle model, battery SOC, and UC SOC are considered as control factors, and ECR, range of the vehicle, and battery stress remain as vehicle performance factors. The confirmatory results show the minimal error between the initial set and the optimum factor to be 7.68 for ECR, 8.54 for range, and 5.49 for battery stress, respectively. The results also reveal the importance of fuzzy-based strategy on hybridization of energy storage systems in electric vehicles and also identified the most and the least influencing factors that affect the vehicle performance.

A Recognition Method of Aggressive Driving Behavior Based on Ensemble Learning.

Aggressive driving behavior (ADB) is one of the main causes of traffic accidents. The accurate recognition of ADB is the premise to timely and effectively conduct warning or intervention to the driver. There are some disadvantages, such as high miss rate and low accuracy, in the previous data-driven recognition methods of ADB, which are caused by the problems such as the improper processing of the dataset with imbalanced class distribution and one single classifier utilized. Aiming to deal with these disadvantages, an ensemble learning-based recognition method of ADB is proposed in this paper. First, the majority class in the dataset is grouped employing the self-organizing map (SOM) and then are combined with the minority class to construct multiple class balance datasets. Second, three deep learning methods, including convolutional neural networks (CNN), long short-term memory (LSTM), and gated recurrent unit (GRU), are employed to build the base classifiers for the class balance datasets. Finally, the ensemble classifiers are combined by the base classifiers according to 10 different rules, and then trained and verified using a multi-source naturalistic driving dataset acquired by the integrated experiment vehicle. The results suggest that in terms of the recognition of ADB, the ensemble learning method proposed in this research achieves better performance in accuracy, recall, and F1-score than the aforementioned typical deep learning methods. Among the ensemble classifiers, the one based on the LSTM and the Product Rule has the optimal performance, and the other one based on the LSTM and the Sum Rule has the suboptimal performance.

Realization of the Autonomous Driving System on the Experimental Vehicle

Running control software on limited computing resources is considered one of the toughest problems. In this study, an autonomous driving software has been developed that can safely complete the map by tracking the lanes and avoiding obstacles on a robot vehicle with limited hardware components. The data was simplified with the image processing technique and the neural network was trained. Overfitting was prevented by hyperparameter tuning and synthetic data augmentation. In order to avoid obstacles, optical flow was calculated by detecting corners every 4 seconds and was used to find the focus of expansion of the vehicle. Time-to-collision was found with the FOE and the distance between the previous position and the current position of the detected point. Optimization was made by averaging the values of close points. The balance mechanism was created according to the TTC difference calculated on the right and left parts of the vehicle.

Tip of the Iceberg: Optimal Drive Train Qualities for Experimental Electric Vehicles

The Electrathon is a competitive electric vehicle endurance race. Each team is given a 1000kWhr battery and one hour to travel the longest distance. Therefore, the vehicles design can have a very large impact on its performance. There is also be strategy involved, such as knowing when to overuse power or save power. There are a great number of design aspects that go into a vehicle, but one of most important components is the drive train. Optimizing the design of the single transmission drive train is vital to enhance the performance of the electric vehicle. Through various calculations, the end seems to show how a small sprocket ratio can allow for less power at faster speeds.

Engineering Design Improvements for Experimental Electric Vehicle

The FHSU electric vehicle design team was challenged to improve design and performance of two existing electric vehicles. The team chose to perform an analysis of the characteristics of the car and then developed design changes to meet parameters they set.

Lightweight Design and Test of Electric Experimental Car

A light-weight electric experimental vehicle is designed. According to the light-weight design requirements, the power battery, the battery manager and the driving Motor controller are designed and selected, the chassis frame, anti-rolling frame, steering system and driving system are designed and validated with CAD and CAE software respectively. On this basis, we have carried out the production, assembly and commissioning of the real vehicle. The test results show that the electric experimental vehicle has high practical value and can meet the requirements of experimental teaching. It is worthy of further study, performance optimization and application.

Study on Propellant Supply System for a Small-scale Supersonic Flight Experiment Vehicle (Study on a Propellant Management Device)

Study on Propellant Supply System for a Small-scale Supersonic Flight Experiment Vehicle (Study on a Propellant Management Device)

Curvature estimation of track using a front view camera

Active steering is one of the methods to improve the curve passing performance of railway vehicle. It improves steering performance by driving the actuator in accordance with the curvature. Curvature is a necessary parameter for active steering. This paper proposes a method for estimating curvature of track using a front view camera. The proposed system can be divided into three parts. First, semantic segmentation is performed to estimate the position of track from camera images. Second, the track position and radius are calculated by performing circular and straight-line fitting based on the estimated track position used semantic segmentation. Finally, the proposed system calculates the mean squared error of the track position estimated by semantic segmentation and the track position calculated by circular or straight-line fitting, and the proposed system is determined whether the track section is a straight or curved section. Furthermore, the proposed system is verified by using a 1/10 scale model experimental vehicle. Validation results show that the proposed system is capable of estimating curvature of track.

Hydrogen Leakage Detection of Reusable Rocket Experiment Vehicle with Hydrogen/Oxygen Concentration Ratio Sensor

In future space transportation system, concept of fault tolerant is important. Propellant leakage is one of fault modes that should be considered in the system. The space transportation vehicles could have flight environment with very little or without oxygen. Therefore, for the propellant leakage detection, gas sensors that can work without oxygen are needed. The authors have developed the gas sensor that can work without oxygen and of which output depends on the ratio of hydrogen to oxygen concentration. The present sensors were installed on a hydrogen-fueled reusable rocket experimental vehicle so that the characteristics of the sensor’s behavior was measured and evaluated though ground firing test operation of the rocket engines. Comparison of the present sensor’s behavior to that of reference sensors shows validity of the present sensor.

Validation of Vehicle Driving Simulator from Perspective of Velocity and Trajectory Based Driving Behavior under Curve Conditions

With their advantages of high experimental safety, convenient setting of scenes, and easy extraction of control parameters, driving simulators play an increasingly important role in scientific research, such as in road traffic environment safety evaluation and driving behavior characteristics research. Meanwhile, the demand for the validation of driving simulators is increasing as its applications are promoted. In order to validate a driving simulator in a complex environment, curve road conditions with different radii are considered as experimental evaluation scenarios. To attain this, this paper analyzes the reliability and accuracy of the experimental vehicle speed of a driving simulator. Then, qualitative and quantitative analysis of the lateral deviation of the vehicle trajectory is carried out, applying the cosine similarity method. Furthermore, a data-driven method was adopted which takes the longitudinal displacement, lateral displacement, vehicle speed and steering wheel angle of the vehicle as inputs and the lateral offset as the output. Thus, a curve trajectory planning model, a more comprehensive and human-like operation, is established. Based on directional long short-term memory (Bi–LSTM) and a recurrent neural network (RNN), a multiple Bi–LSTM (Mul–Bi–LSTM) is proposed. The prediction performance of LSTM, MLP model and Mul–Bi–LSTM are compared in detail on the validation set and testing set. The results show that the Mul–Bi–LSTM model can generate a trajectory which is very similar to the driver’s curve driving and have a preferable generalization performance. Therefore, this method can solve problems which cannot be realized in real complex scenes in the simulator validation. Selecting the trajectory as the validation parameter can more comprehensively and intuitively reflect the simulator’s curve driving state. Using a speed model and trajectory model instead of a real car experiment can improve the efficiency of simulator validation and lay a foundation for the standardization of simulator validation.

Subacute AMD3100 Treatment Is Not Efficient in Neonatal Hypoxic-Ischemic Rats.

Despite the advances in treating neonatal hypoxic-ischemic encephalopathy (HIE) with induced hypothermia, the rates of severe disability are still high among survivors. Preclinical studies have indicated that cell therapies with hematopoietic stem/progenitor cells could improve neurological outcomes in HIE. In this study, we investigated whether the administration of AMD3100, a CXCR4 antagonist that mobilizes hematopoietic stem/progenitor cells into the circulation, has therapeutic effects in HIE. P10 Wistar rats of both sexes were subjected to right common carotid artery occlusion or sham procedure, and then were exposed to hypoxia for 120 minutes. Two subcutaneous injections of AMD3100 or vehicle were given on the third and fourth day after HIE. We first assessed the interindividual variability in brain atrophy after experimental HIE and vehicle treatment in a small cohort of rats. Based on this exploratory analysis, we designed and conducted an experiment to test the efficacy of AMD3100. Brain atrophy on day 21 after HIE was defined as the primary end point. Secondary efficacy end points were cognitive (T-water maze) and motor function (rotarod) on days 17 and 18 after HIE, respectively. AMD3100 did not decrease the brain atrophy in animals of either sex. Cognitive impairments were not observed in the T-water maze, but male hypoxic-ischemic animals exhibited motor coordination deficits on the rotarod, which were not improved by AMD3100. A separate analysis combining data from animals of both sexes also revealed no evidence of the effectiveness of AMD3100 treatment. These results indicate that the subacute treatment with AMD3100 does not improve structural and functional outcomes in a rat HIE model.

Aerodynamic Comparison of Two Concept Capsules in Earth Reentry

Aerodynamics of two capsules of different conception both equipped with aerodynamic control surfaces has been compared at high-altitude Earth reentry path. The capsules are comparable in size but completely different in shape and, hence, in the aerodynamic behavior. The capsules are: 1) a circular cylinder provided with four flapped fins (finned cylinder), 2) a capsule, here tagged as Reentry Space Vehicle (RSV), very similar in shape and dimensions to the Intermediate eXperimental Vehicle. The study was carried out computationally in hypersonic, rarefied flow in terms of aerodynamic global coefficients (lift, drag, moments, etc.) computed by a three-dimensional direct simulation Monte Carlo code at the altitudes of 100 and 120 km, in the interval of angles of attack 0–50 deg and with flap angles of 0 and 20 deg. Computations verified that while RSV exerts a stronger aerodynamic force for the reduction of the capsule reentry velocity, the finned cylinder is better in terms of the attitude control capability. In fact, equilibrium of the finned cylinder is stable at zero angle of attack at the two altitudes, whereas the angle of attack of stable equilibrium of RSV changes with altitude. Hence, RSV needs to be provided with an active attitude control system.

The adhesion force change of an experimental road vehicle

The Article deals with the controlled influence of the adhesive force in contact of the road vehicle’s wheel with the road. The first section shows how the adhesive force is reduced. The next step is the familiarization with the experimental vehicle with the Alternative SkidCar, where experimental measurements were carried out, assessment of the advantages and disadvantages of the experimental vehicle with the Alternative SkidCar and the drive on the sliding surface following the experimental test methods. The objective of the article is to determine how great the difference in vehicle behav-iour is when the adhesive force changes by modifying the radial reaction and the change in the coeffi-cient of adhesion.

Easy-Riding Compact Electric Shopping Vehicle

We are developing a small compact electric vehicle for shopping purposes. In this study, we fabricated an experimental vehicle, that uses only six small rechargeable AA batteries (7.2 V, approximately 2 A·h) as an electric power source. The vehicle user can select between two driving positions: standing and sitting. A compact transmission with a 90-W DC motor and a speed controller that uses pulse width modulation control was designed as an actuating system. Running experiments were conducted to observe the performance of the fabricated vehicle on a flat floor in a gymnasium. The fabricated vehicle was able to operate for 52 min at a speed of 2.73 km/h. The getting-on and getting-off processes in the vehicle were repeated many times during shopping. The human leg strain while getting on and off the vehicle was investigated by electromyogram measurement. During the getting-on and getting-off processes in the vehicle, the myoelectric potential of the quadriceps increased in the sitting position but did not increase in the standing position. The experimental results show that a user suffers more strain in the sitting position than in the standing position.

Electric Drive for an Agricultural Vehicle

Abstract. The authors showed the relevance of creating agricultural machines using an electric drive. (Research purpose) The research objective is to develop an experimental prototype vehicle using an electrical schematic diagram of charge and electric drive control. (Materials and methods) The VAZ 111 Oka car was chosen as an experimental vehicle model with an electric drive, since it has a light weight of 645 kilograms, a simple design and a low cost. Mechanical characteristics of the electric motor were calculated and a frequency converter was chosen to control the electric drive. Laboratory bench tests were conducted. (Results and discussion)The authors installed storage batteries to power the electric drive, developed an electrical circuit schematics getting charged from a 220 volt alternating voltage network, and received graphs for the discharge of a 40-storage-battery power supply. (Conclusions) An electrical schematic diagram of charge and electric drive control was developed and implemented on an experimental vehicle model. It was determined that at the electric motor continuous operation with the load current of 1 ampere, the batteries get discharged within 104 minutes; with the current load of 2 amperes, they get discharged within 83 minutes; with 3 amperes – within 65 minutes, and with 5 amperes – within 50 minutes, which is enough to drive around the farm. The authors graphically depicted the dependence of the available capacity level on the voltage, as well as the batteries’ discharge on the time at various load currents. The authors carried out two experimental studies on storage batteries’ charging from alternating voltage with the current of 2 and 3 amperes: in the first case, the charging time was 350 minutes, in the second – 310 minutes. It was found out that when using the developed scheme, the batteries are charged evenly.

Atmospheric Model Effect on Flight Data Reconstruction: Application to the Early Phase of the IXV Reentry

Recent work on the Intermediate eXperimental Vehicle (IXV) re-entry simulation in hypersonic rarefied regime highlighted several numerical and experimental key aspects for a satisfactory reconstruction of its aerothermodynamic flight data. Indeed, among the investigated sources of discrepancies, the atmospheric model uncertainty on the density estimation appeared as one of the major sources of error for the heat flux calculation. The initial investigation was based on the NRLMSISE-00 model of 2000 which was recently updated in the NRLMSIS 2.0 version of 2020. This last version incorporates major formulation changes and new measurements yielding significantly smaller densities for altitudes below 100 km. The present work therefore focuses on the impact of improving our knowledge of the atmospheric environment to reduce the error related to the numerical reconstruction of the heat flux.

Validation and Optimization of Suspension Design for Testing Platform Vehicle

With the application and popularization of the advanced driving assistance system (ADAS), the reliability and stability of ADAS have become its research focus. This article presents a car testing framework for ADAS reliability and stability. Its special suspension has been designed, verified, and optimized in real vehicles according to its working conditions. First, the structure and working principle of the testing platform vehicle are introduced. Then a simulation model is built in MATLAB/Simulink based on the dynamic equation to verify the working characteristics of the suspension. Experimental vehicle tests are conducted for simulation verification purposes. During the analysis, the root-mean-square (RMS) values of vehicle body displacement and dynamic tire deflection are considered evaluation indices. The nondominated sorting genetic algorithm (NSGA-II) is used to optimize the damping, stiffness, and installation position of the suspension system. The findings demonstrate that the specially designed suspension in this article can fulfill the test criteria. Compared with the optimized suspension performance, both the vehicle body displacement and dynamic tire deflection have decreased roughly by 17 and 40%, respectively, which significantly improves the suspension performance and provides a reference for the future designs of testing platform vehicles.