Browse Topic: Stability control

Items (262)
Abstract A valuable quantity for analyzing the lateral dynamics of road vehicles is the side-slip angle, that is, the angle between the vehicle’s longitudinal axis and its speed direction. A reliable real-time side-slip angle value enables several features, such as stability controls, identification of understeer and oversteer conditions, estimation of lateral forces during cornering, or tire grip and wear estimation. Since the direct measurement of this variable can only be done with complex and expensive devices, it is worth trying to estimate it through virtual sensors based on mathematical models. This article illustrates a methodology for real-time on-board estimation of the side-slip angle through a machine learning model (SSE—side-slip estimator). It exploits a recurrent neural network trained and tested via on-road experimental data acquisition. In particular, the machine learning model only uses input signals from a standard road car sensor configuration. The model adaptability to different road conditions and tire wear levels has been verified through a sensitivity analysis and model testing on real-world data proves the robustness and accuracy of the proposed solution achieving a root mean square error (RMSE) of 0.18 deg and a maximum absolute error of 1.52 deg on the test dataset. The proposed model can be considered as a reliable and cheap potential solution for the real-time on-board side-slip angle estimation in serial cars.
Giuliacci, Tiziano AlbertoBallesio, StefanoFainello, MarcoMair, UlrichKing, Julian
Applying Automotive EDR Data to Traffic Crash Reconstruction Virtual Pre-Conference CertificationC20168/7/2020
EDR\'s were first installed in 1994 and are now installed in 99% of new light vehicles sold in the US. In the US EDR’s are not required, but vehicles with EDR’s made after 9/1/2012 must meet minimum standardized content requirements of 49 CFR, Part 563 including speed, throttle, brake on/off and Delta V. Data must be retrievable with a publicly available tool. Only a few manufacturers install EDR’s worldwide currently, but the EU and China are adopting regulations to require them in the next few years. Some manufacturers provide stability control system data far beyond the US regulation that aid in understanding vehicle movement in the 5 seconds prior to the crash. This course will provide the participant with the skills necessary to analyze EDR data that has already been imaged, apply it to crash reconstruction, and reconcile it with calculations using other data sources. The course will enable the participant to analyze current and potential future EDR data set without regard to manufacturer. The class presents the generic analysis step by step, then groups EDRs into manufacturer-specific families and their data limitations, and works case studies that highlight targeted key learning objectives. The student will also learn key points to satisfy court Frye and Daubert requirements for EDR data to be admissible, and suggest methods to present EDR data that will communicate the data understandably to attorneys and lay juries. This course has been approved by the Accreditation Commission for Traffic Accident Reconstruction (ACTAR) for 20 Continuing Education Units (CEUs). Upon completion of this seminar, accredited reconstructionists should mail a copy of their course certificate and the $5 student CEU fee to ACTAR, PO Box 1493, North Platte, NE 69103. By attending this seminar, you will be able to: Describe EDR sensor operation, recording interval and duration, resolution, accuracy, and time latency and articulate the limitations of applying the data to crash analysis Calculate min and max speeds prior to loss of control or braking, and at impact based on the last accurate EDR pre-crash speed data point Evaluate EDR vs. actual ground speed for specific vehicle operational conditions and vehicle equipment modifications Calculate speed at impact and closing speeds by combining EDR Delta V data with normally collected scene and vehicle data such as post crash travel distance, departure angle, drag factor, and vehicle weights Apply data to inline rear end, head on, and angular collisions Reconcile EDR data with other physical evidence and combine to narrow speed ranges Use time-distance and overlay EDR data on scene maps/diagrams to show where critical driving inputs were made vs. inputs required to avoid collisions CEUs
In-phase rear-wheel steering, where rear wheels are steered in the same direction of front wheels, has been widely investigated in the literature for vehicle stability improvements along with stability control systems. Much faster response can be achieved by steering the rear wheels automatically during an obstacle avoidance maneuver without applying the brakes where safe stopping distance is not available. Sudden lane change movements still remain challenging for heavy articulated vehicles, such as tractor and semitrailer combinations, particularly on roads with low coefficient of adhesion. Different lateral accelerations acting on tractor and semi-trailer may cause loss of stability resulting in jackknifing, trailer-swing, rollover, or slip-off. Several attempts have been made in the literature to use active steering of semi-trailer’s rear wheels to prevent jackknifing and rollover. However, loss of stability in an articulated vehicle is usually caused by an oversteered tractor, and the semitrailer’s rear wheels have little effect on the tractor’s directional control. In this study, viability of active rear-wheel steering of tractor to maintain the stability of an articulated vehicle during a high-speed obstacle avoidance maneuver is investigated. Two different controllers, fuzzy logic and linear model-based predictive controllers, are proposed to minimize the off-tracking behavior of an articulated vehicle. The controllers were tested in IPG/TruckMaker environment with MATLAB/Simulink interface on roads with various coefficient of adhesions, performing single lane change maneuvers. The simulated results showed that jackknifing occurring right after sudden lane changes can be successfully prevented using the tractor’s active rear-wheel steering based on model predictive control algorithm when the feedback gains are tuned correctly.
Sahin, HasanAkalin, Ozgen
Effect of Stator Surface Area on Braking Torque and Wall Heat Dissipation of Magnetorheological Fluid Retarder2020-01-09374/14/2020
Magnetorheological fluid (MRF) is used as the transmission medium of the hydraulic retarder. The rheological properties are regulated by changing the magnetic field to achieve accurate control of the retarder's braking torque. Under the action of the external magnetic field, the flow structure and performance of the MRF retarder will be changed in a short time. The apparent viscosity coefficient increases by several orders of magnitude, the fluidity deteriorates and the heat generated by the brake cannot be transferred through the liquid circulation, which will affect the braking torque of the retarder. Changing the surface area of the stator also has an influence on the braking torque of the retarder and the wall heat dissipation. In this study, the relationship between the braking torque of the MRF retarder and the stator surface area of the retarder was analyzed. In addition, phase change materials were used to directly dissipate heat on the retarder surface to improve the heat dissipation rate of retarder and improve the stability of the retarder's braking torque. In order to study the effect of stator radius on braking torque of MRF retarder under an external magnetic field, a braking torque model was established based on MRF with Bingham model properties, and a heat transfer model of wall phase change material was established to analyze the relationship between heat transfer and braking torque of MRF retarder. The results show that the braking torque of the MRF retarder increases rapidly with the increase of the radius outside the effective working area of MRF, which increases faster at high speed and increases the stator wall surface heat dissipation, but the rate of heat dissipation increases relatively slowly. The wall surface with a heat pipe can take away the heat generated by the retarder and cool the retarder. Under the appropriate stator surface conditions, phase change materials are used on the wall surface of the retarder to dissipate heat, which improves the stability of the braking torque of the retarder and promotes the development of MRF retarder to high power.
Liu, ZhiQiangTan, GangfengTian, ZhongpengZhou, MiAgyeman, PhilipFrimpong, Justice
A Pre-Warning Method for Cornering Speed of Concrete Mixer Truck2020-01-10034/14/2020
The high gravity center of the concrete mixer truck reduces the truck’s stability while steering. The rolling stirring tank makes the stability even worse than the regular engineering vehicle due to the dynamic variation of the centroid position. Most of the researches on the rollover stability of concrete mixer trucks focus on the rollover model establishment and dynamic simulation module. The change of concrete centroid is ignored when the safety cornering speed is calculated. This paper proposes a pre-warning method for the cornering speed of concrete mixer trucks based on centroid dynamic simulation. In the method, the mixing tank stirring model and the vehicle driving dynamic model are established on the Fluent and TruckSim simulation platforms, respectively. The theoretical speed threshold obtained by simulation is used as the evaluation index of the warning speed in the curve. Firstly, the dynamic simulation of the stirring tank model is carried out by Fluent. According to Newton Leibniz numerical calculation method, Matlab is used to obtain the mathematical model of the centroid position and the main parameters of the stirring tank. Then the model is verified by the neural network algorithm. Finally, according to the dynamic position and lateral acceleration of the vehicle’s centroid, the dynamic simulation is carried out by TruckSim to obtain the theoretical speed threshold. The pre-warning system can warn the driver according to the comparison of real-time speed and calculated velocity threshold. In this paper, a 7.8 m3 concrete mixer truck is selected for simulation experiments. The results show that the lateral offset of the centroid is up to 206.4 mm and the maximum lateral force is 682N under normal working conditions, and the safe turning speed of the vehicle is reduced by at least 4.71% due to the centroid change. The pre-warning method proposed in this paper can improve the safety of cornering traffic effectively, and can be utilized in the further intelligent transportation system.
Jiang, YifengTan, GangfengWang, HaoyuWang, ZelongWang, ZhenyuLi, Ming
Real-time and Accurate Estimation of Road Slope for Intelligent Speed Planning System of Commercial Vehicle2020-01-01154/14/2020
In the intelligent speed planning system, real-time estimation of road slope is the key to calculate slope resistance and realize the vehicles’ active safety control. However, if the road slope is measured by the sensor while the commercial vehicle is driving, the vibration of the vehicle body will affect its measurement accuracy. Therefore, the relevant algorithm is used to estimate the real-time slope of the road when the commercial vehicle is driving. At present, many domestic and foreign scholars have analyzed and tested the estimation of road slope by the least square method or Kalman filter algorithm. Although the two methods both can achieve the estimation, the real-time performance and accuracy still need to be improved. In this paper, for traditional fuel commercial vehicle, the Kalman filter algorithm based on the kinematics and the extended Kalman filter algorithm based on the longitudinal dynamics are respectively used to estimate the road slope. In the process of estimation based on kinematics, considering the influence of road slope rate to estimate, the recursive least squares method with forgetting factor is used to estimate the road slope rate.Finally, the estimation results obtained by kinematics and dynamics are combined. It is expected that the error based on the algorithm-estimated slope value and the true slope value will be within 6% after the commercial vehicle is driving. The proposed algorithm has high accuracy, good real-time performance and strong stability. Using the commercial vehicle as a motion node and estimating the slope of a certain road, the intelligent planning of other vehicles’ speed in that region can be realized through the cloud platform. Then the fuel economy of the commercial vehicle can be improved.
Zhou, MiTan, GangfengSun, MengTian, ZhongpengZhou, FangyuLiu, ZhiQiang
An Efficient, High-Precision Vehicle Testing Procedure to Evaluate the Efficacy of Fuel-Borne Friction Modifier Additives2019-01-235312/19/2019
Improved fuel economy is increasingly a key measure of performance in the automotive industry driven by market demands and tighter emissions regulations. Within this environment, one way to improve fuel economy is via fuel additives that deliver friction- reducing components to the piston-cylinder wall interface. Whilst the use of friction modifiers (FMs) in fuel or lubricant additives to achieve fuel economy improvements is not new, demonstrating the efficacy of these FMs in vehicles is challenging and requires statistical design together with carefully controlled test conditions. This paper describes a bespoke, efficient, high-precision vehicle testing procedure designed to evaluate the fuel economy credentials of fuel-borne FMs. By their nature, FMs persist on engine surfaces and so their effects are not immediately reversible upon changing to a non FM-containing fuel (“carryover” effect), therefore requiring careful design of the test programme. The solution presented here comprises a one-day chassis dynamometer test, internally referencing the fuel economy of an FM- containing test fuel to an FM-free reference fuel. When incorporated into a statistically designed test programme, two or more fuels are compared using a chosen test cycle. Comprehensive instrumentation, control and monitoring, integrated vehicle conditioning stages and strict acceptance criteria are major factors in achieving the required precision. This test design is also specially tailored to eliminate the problem of FMs carry-over effects to subsequent tests. Three programmes based on this test procedure have measured statistically significant fuel economy differences between FM-containing fuels and FM-free fuels, thus demonstrating that the required precision has been achieved to evaluate the efficacy of fuel- borne FMs.
Yow, ShuhuiZiman, PaulineSmith, Sue J.Walter, Dr. MarcBacchi, Robert J.
Analysis of Active Collision Avoidance Performance Based on Cooperative Regenerative Auxiliary Braking System2019-01-502711/4/2019
Active collision avoidance can assist drivers to avoid longitudinal collision through active brake. Regenerative braking can improve the driving range and braking response speed. At this stage, conventional hydraulic braking system limits the implements of above technologies because of its poor performance of response speed and coordinated control. While the brake-by-wire system is a better actuator that can fulfill requirements of automotive electric and intelligent development due to its rapid response and flexible adjustment. However, the system control algorithm becomes more complicated with introduction of regenerative braking and active collision avoidance function, which is also the main problem solved in this paper. First, a new type of cooperative regenerative auxiliary braking system (CRABS) of intelligent electric vehicles, which integrates the functions of brake-by-wire, regenerative braking and active collision avoidance, is proposed, for purpose of analyzing the improvement of active collision avoidance performance after the introduction of regenerative braking. The design of the system focuses on the Electro Hydraulic Brake (EHB) unit, control strategy of active collision avoidance and brake force distribution. Then, modeling and simulation are done to validate the feasibility of the proposed system scheme. Based on the Autonomous Emergency Braking (AEB) test procedures of European New Car Assessment Programme(Euro-NCAP), the simulation analysis scheme is made including simulation process, simulation test conditions and evaluation indicators. Finally, the hardware-in-loop (HIL) test bench based on the real motor system is set up to validate the conclusion drawn in the simulation analysis. The results show that compared with the conventional hydraulic braking system, CRABS system proposed in this paper conducts faster in braking response and closer to the ideal braking distance, and the performance of active collision avoidance is improved.
Hou, XiaohuiZhang, JunzhiZhang, ZhongshiHe, Chengkun
Comparative Analysis between American and European Requirements for Electronic Stability Control (ESC) Focusing on Commercial Vehicles2019-01-21419/15/2019
Analysis of road accidents has shown that an important portion of fatal crashes involving Commercial Vehicles are caused by rollovers. ESC systems in Commercial Vehicles can reduce rollovers, severe understeer or oversteer conditions and minimize occurrences of jackknifing events. Several studies have estimated that this positive effect of ESC on road safety is substantial. In Europe, Electronic Stability Control (ESC) is expected to prevent by far the most fatalities and injuries: about 3,000 fatalities (-14%), and about 50,000 injuries (-6%) per year. In Europe, Electronic Stability Control Systems is mandatory for all vehicles (since Nov. 1st, 2011 for new types of vehicle and Nov. 1st, 2014 for all new vehicles), including Commercial Vehicles, Buses, Trucks and Trailers. On 2015, NHTSA published Federal Motor Vehicle Safety Standard (FMVSS) No. 136, Electronic Stability Control systems for heavy vehicles, requiring Electronic Stability Control (ESC) systems on truck tractors and buses with a gross vehicle weight rating greater than 11,793 kilograms (26,000 pounds) for implementation in 2017. In South America, CONTRAN Resolution 641/2016 establishes mandatory installation of Electronic Stability and Rollover Control in Commercial Vehicles, including Trailers (Jan. 1st, 2022 for new types of vehicle and Jan. 1st, 2024 for all new vehicles). However there isn’t a Brazilian standard to validate the system and its performance shall comply with ECE R13 (Annex 21) or FMVSS 136, as applicable. This paper shows a technical review regarding ESC function, its impact on Commercial Vehicles and clarifies the different systems available for trucks and trailers, considering the differences between stability control systems - full stability and roll-only stability. In addition it will show a comparative analysis between American and European requirements and procedures to validate these vehicles safely.
Iombriller, Silvia FariaBolognesi Prado, WesleySilva, Marco Andre
GPU Implementation for Automatic Lane Tracking in Self-Driving Cars2019-01-06804/2/2019
The development of efficient algorithms has been the focus of automobile engineers since self-driving cars become popular. This is due to the potential benefits we can get from self-driving cars and how they can improve safety on our roads. Despite the good promises that come with self-driving cars development, it is way behind being a perfect system because of the complexity of our environment. A self-driving car must understand its environment before it makes decisions on how to navigate, and this might be difficult because the changes in our environment is non-deterministic. With the development of computer vision, some key problems in intelligent driving have been active research areas. The advances made in the field of artificial intelligence made it possible for researchers to try solving these problems with artificial intelligence. Lane detection and tracking is one of the critical problems that need to be effectively implemented. The ability of a self-driving car to successfully drive from point A to point B without going off track is dependent on lane tracking. Lane tracking in self-driving cars is a computationally intensive task and a fast implementation is needed to help a self-driving car track lanes in real-time to make the right decision at the right time. Lane tracking in self-driving cars is also dependent on the visibility of lane markings on the road. It will be difficult for a self-driving car to track lanes if the lane marking has faded, blocked by an object, or there were no lane markings on the road. Most available lane tracking implementations in the literature do not give account to these two problems. Our implementation is to solve these two problems by using artificial intelligence techniques to track lanes in all conditions and using GPU computing on NVIDIA Jetson TX2 to speed-up the process.
Yusuf, AyomideAlawneh, Shadi
Pressure Estimation Algorithms in Decoupled Electro-Hydraulic Brake System Considering the Friction and Pressure-Position Relationship2019-01-04384/2/2019
This paper presents several pressure estimation algorithms (PEAs) for a decoupled electro-hydraulic brake system (EHB), which is driven by an electric motor + reduction gear. Most of the pressure control solutions are based on standard pressure-based feedback control, requiring a pressure signal. Although the pressure sensor can produce the pressure feedback signal, it will increase cost and enlarge installation space. The rotation angle of electric motor is available by the built-in sensor, so the pressure can be estimated by using the rotation angle. Considering the typical nonlinearities (i.e. friction, pressure-position relationship) and uncertainties (i.e. disturbance caused by friction model), the estimation-oriented model is established. The LuGre model is selected to describe the friction, and the pressure-position relationship is fitted by a quadratic polynomial. Based on the estimation-oriented model, the force-based PEA (FPEA) and the interconnected PEA (IPEA) are designed, respectively. What makes these two PEAs different is that the IPEA considers the pressure-position relationship. The comparison and analysis of the proposed PEAs have been conducted via some typical ordinary braking scenarios. The sensitivity analysis has also been done to obtain the influences on the performance of the IPEA, if the estimation deviation of the friction occurs. Most importantly, this study realized a pressure estimation without add-in sensors, which makes decoupled EHB realizable to become the actuator for automobile active safety systems, giving a promising way to achieve far better performance.
Han, WeiXiong, LuYu, Zhuoping
This SAE Document specifies DSRC interface requirements for V2V Safety Awareness applications, including detailed Systems Engineering documentation (needs and requirements mapped to appropriate message exchanges). These applications include: Emergency Vehicle Alert, Roadside Alert, and Safety Awareness Alerts for Objects and Adverse Road Conditions. This document extends the V2V Communications capabilities defined in J2945/1 to support these applications, and the National ITS Architecture. The purpose of this SAE Document is to enable interoperability for V2V Safety Awareness communications.
V2X Core Technical Committee
Trajectory-Tracking Control for Autonomous Driving Considering Its Stability with ESP2018-01-16398/7/2018
With rapid increase of vehicles on the road, safety concerns have become increasingly prominent. Since the leading cause of many traffic accidents is known to be by human drivers, developing autonomous vehicles is considered to be an effective approach to solve the problems above. Although trajectory tracking plays one of the most important roles on autonomous driving, handling the coupling between trajectory-tracking control and ESP under certain driving scenarios remains to be challenging. This paper focuses on trajectory-tracking control considering the role of ESP. A vehicle model is developed with two degrees of freedom, including vehicle lateral, and yaw motions. Based on the proposed model, the vehicle trajectory is separated into both longitudinal and lateral motion. The coupling effect of the vehicle and ESP is analyzed in the paper. The lateral trajectory-tracking algorithm is developed based on the preview follower theory. Spacing control strategy is used in longitudinal trajectory-tracking algorithm. Yaw angular velocity and lateral deflection are the control variables for ESP. When the vehicle is under certain driving scenarios remains to be challenging, the influence of ESP to trajectory-tracking control is considered. With the purpose to prove the trajectory-tracking accuracy, the couple between the trajectory-tracking and ESP control is solved. The coupled control system is compared against the decoupled control system through simulation. The simulation results have shown the proposed control perform well.
Pan, FeiDeng, WeiwenZhang, SuminWang, JinsongWang, Shanshan
Consideration of Effective Chassis Control in Electric Vehicle2018-01-50358/6/2018
In this study, we focus on “camber angle control” and “derivative steering assistance” using “steer-by-wire” as maneuverability and stability improvement techniques that are appropriate for the electric vehicle (EV) era. Movements that produce a negative camber angle generate camber thrust, and vehicle motion performance improvements extend from the fact that the tire side force is increased by the camber thrust effect. In our experimental vehicle, a proportional steering angle system was used to create negative camber angle control via an electromagnetic actuator that allowed us to confirm improvements to both the effectiveness and stability of steering control in restricted cornering areas. More specifically, we determined that it is possible to improve critical cornering performance by executing ground negative camber angle control in proportion to the steering angle. Steer-by-wire refers to an electrical steering technique that allows the steering angle of the entire vehicle to be controlled independently of the front wheel steering angle, thereby providing a high level of steering system control freedom. When derivative steering assistance control is applied, the phase of the front wheel steering angle advances faster in proportion to the steering angle velocity change than would normally occur based on the driver’s steering actions, which can improve ease of operation and maneuvering stability. In an experimental vehicle equipped with derivative steering assistance via a steer-by-wire system, the steer effectiveness was improved because the phase of the front wheel steering angle advanced due to the derivative steering assist, thereby improving the vehicle responsiveness.
Yamaguchi, RyoNozaki, Hiromichi
A Braking Force Distribution Strategy in Integrated Braking System Based on Wear Control and Hitch Force Control2018-01-08274/3/2018
A braking force distribution strategy in integrated braking system composed of the main braking system and the auxiliary braking system based on braking pad wear control and hitch force control under non-emergency braking condition is proposed based on the Electronically Controlled Braking System (EBS) to reduce the difference in braking pad wear between different axles and to decrease hitch force between tractors and trailers. The proposed strategy distributes the braking force based on the desired braking intensity, the degree of the braking pad wear and the limits of certain braking regulations to solve the coupling problems between braking safety, economical efficiency of braking and the comfort of drivers. Computer co-simulations of the proposed strategy are performed. The braking force distribution strategy is verified under condition of equal wear of braking pad, condition of greater wear on the front axle of tractor and condition of greater wear on the rear axle of the tractor. The simulation results show that the proposed strategy balanced the braking pad wear by regulating the braking cylinder pressure of each axle and ensured the same braking distance under different wear conditions of braking pad. Under unloaded or loaded conditions, each axle braked according to the desired braking intensity and reached the control objective that the same braking pedal opening rate is in accord with the same braking intensity. Under different load conditions, the strategy ensured the same braking distance and reduced the hitch force, which definitely enhanced the braking safety, economical efficiency of braking and the comfort of drivers.
Zheng, HongyuLiu, ChenWang, Linlin
Evaluation of Alternative Steering Devices with Adjustable Haptic Feedback for Semi-Autonomous and Autonomous Vehicles2018-01-05724/3/2018
Emerging autonomous driving technologies, with emergency navigating capabilities, necessitates innovative vehicle steering methods for operators during unanticipated scenarios. A reconfigurable “plug and play” steering system paradigm enables lateral control from any seating position in the vehicle’s interior. When required, drivers may access a stowed steering input device, establish communications with the vehicle steering subsystem, and provide direct wheel commands. Accordingly, the provision of haptic steering cues and lane keeping assistance to navigate roadways will be helpful. In this study, various steering devices have been investigated which offer reconfigurability and haptic feedback to create a flexible driving environment. A joystick and a robotic arm that offer multiple degrees of freedom were compared to a conventional steering wheel. To evaluate the concept, human test subjects interacted with the experimental system featuring a driving simulator with target hardware, and completed post-test questionnaires. Based on the data collected, drivers’ lane keeping performance was superior using a haptic robotic arm with haptic feedback to the joystick and steering wheel with an improvement of up to 70.18% during extreme maneuvers. Haptic feedback, with a lane keeping algorithm, can assist the operator in steering the vehicle given the likely deterioration of driving skills when autonomous vehicles become prevalent.
Wang, ChengshiWang, YueWagner, John R.
Vehicle Sideslip Angle Estimation Considering the Tire Pneumatic Trail Variation2018-01-05714/3/2018
Vehicle sideslip angle is significant for electronic stability control devices and hard to estimate due to the nonlinear and uncertain vehicle and tire dynamics. In this paper, based on the two track vehicle dynamic model considering the tire pneumatic trail variation, the vehicle sideslip angle estimation method was proposed. First, the extra steering angle of each wheel caused by kinematics and compliance characteristics of the steering system and suspension system was analyzed. The steering angle estimation method was designed. Since the pneumatic trail would vary with different tire slip angle, distances between the center of gravity (COG) and front&rear axle also change with the tire slip angle. Then, based on the dynamic pneumatic trail and estimated steering angle, we modified the traditional two track vehicle dynamic model using a brush tire model. This model matches the vehicle dynamics more accurately. In addition, we designed two extended Kalman filters (EKF) based on the traditional two track vehicle dynamic model and modified two track vehicle dynamic model to estimate the vehicle sideslip angle. In the end, the extended Kalman filters were validated under simulations under multi-maneuvers in high friction road. The estimation results were compared with the actual sideslip angle which shows the accuracy of extended Kalman filter with modified two track dynamics model is higher than the extended Kalman filter with traditional two track dynamic model.
Xia, XinXiong, LuLin, XuefengYu, Zhuoping
Integrated Chassis Control for Vehicle Stability under Various Road Friction Conditions2018-01-05524/3/2018
This paper presents an integrated chassis control method for vehicle stability under various road friction conditions without information on tire-road friction. For vehicle stability, vehicle with an integrated chassis control needs to cope with the various road friction conditions. One of the chassis control method under various road conditions is to determine and/or limit control inputs based on tire-road friction coefficient. The tire-road friction coefficient, however, is difficult to estimate and still a challenging task. The key idea for the proposed method without the estimation of the tire-road friction coefficient is to analyze and control vehicle states based on a tire slip angle - tire force phase plane, i.e. based on these vehicle responses: tire forces and tire slip angles of front/rear wheels. Based on the phase plane, vehicle instability is detected and the vehicle is controlled to regain the vehicle stability and maneuverability under various road conditions without tire-road friction information. The proposed algorithm consists of two sequential parts: Supervisor part and Chassis control part. The supervisor detects the vehicle instability based on the tire slip angle and tire force phase plane. Based on this information, the supervisor determines a desired slip angle to make the vehicle stable. The chassis control part decides control inputs. From tire slip angle dynamics, a desired yaw moment is calculated to minimize error between the desired slip angle and current vehicle states. For tracking the desired yaw moment, the optimal coordination of the chassis control part optimally allocate the desired yaw moment to each chassis module. The proposed algorithm has been investigated through computer simulations under various road setting. The simulation results show that the proposed control method well copes with maneuver on the various road conditions.
Joa, EunhyekYi, KyongsuBae, HyungjuneSohn, Kimo
Externally-connected Electronic Control Units (ECUs) contain millions of lines of code, which may contain security vulnerabilities. Hackers may exploit these vulnerabilities to gain code execution privileges, which affect public safety. Traditional Cybersecurity solutions fall short in meeting automotive ECU constraints such as zero false positives, intermittent connectivity, and low performance impact. A desirable solution would be deterministic, require minimum resources, and protect against known and unknown security threats. We integrated Autonomous Security on a BeagleBone Black (BBB) system to evaluate the feasibility of mitigating Cybersecurity risks against potential threats. We identified key metrics that should be measured, such as level of security, ease of integration and system performance impact. In this paper, we describe the integration and evaluation process and present its results. We show that Autonomous Security can provide this protection with zero false-positives while meeting automotive constraints.
Harel, AssafBen David, TalKashani, AmeerIyer, GopalakrishnanMotonori, AndoMasumi, Egawa
The Influence of Autonomous Driving on Passive Vehicle Dynamics2018-01-05514/3/2018
Traditional vehicles are designed to be inherently stable. This is typically obtained by imposing a large positive static margin (SM). The main drawbacks of this approach are the resulting understeering behavior of the vehicle and, often, a decrease in peak lateral grip due to oversized rear tire characteristics. On the other hand, a lower SM can cause a greater time delay in the vehicle’s response which hardens the control of a vehicle at limit handling for a human being. By introducing advanced autonomous driving features into future vehicles, the human factor can be excluded in limit handling manoeuvers (e.g., obstacle avoidance occurrences) and, consequently, the need for a high SM (i.e., high controllability for human drivers) can be avoided. Therefore, it could be possible to exploit the passive vehicle dynamics and enhance the performance, both in terms of peak grip and transient response. The goal of this article is to explore if a decrease in SM can lead to a performance advantage on an obstacle avoidance manoeuver when the vehicle is driven by a robotic controller. This is achieved by analyzing the behavior of various vehicle models with different SMs and peak lateral acceleration on a nonstandard double lane change manoeuver. After having characterized the dynamic response of the various models in both steady-state and unsteady-state, several tests are run on a Driver-in-Motion (DiM) dynamic driving simulator driven by human drivers. The same tests are run again in a Model-in-the-Loop (MiL) simulation where the vehicle is controlled by means of a nonlinear model predictive control (NMPC). The results show that the robotic controller outperforms a human driver and poses interesting design challenges for autonomous vehicles in terms of passive stability and active controllers to modify vehicle stability online.
Novi, TommasoLiniger, AlexCapitani, RenzoFainello, MarcoDanisi, GiacomoAnnicchiarico, Claudio
Local Path Planning for Intelligent Vehicle Obstacle Avoidance Based on Dubins Curve and Tentacle Algorithm2017-01-19519/23/2017
Local path planning for obstacle avoidance is one of the core topics of intelligent vehicle. A novel method based on dubins curve and tentacle algorithm is proposed in this article, with the consideration of obstacle avoidance and vehicle motion constraints. First, the preview distance of the vehicle is given according to the current speed, so that the preview point can be found with the information of global path. Then dubins curve is adopted to find a path with appropriate turning radius, between the current position and preview point, satisfying the constraints of current direction and target direction, considering handling and ride comfort of the vehicle. In order to avoid obstacle, tentacle algorithm is adopted. 20 tentacle points are given by moving the original preview point, and then 21 local paths can be given by using dubins curve. Cost function is used to find out the best option of the 21 paths. The distance to obstacle, the final distance to original preview point and the change of moving direction are taken into consideration in the cost function. By applying dubins curve and tentacle algorithm, a local path with obstacle avoidance and better vehicle handling can be obtained. Simulations have been carried out with the co-simulation of Matlab /Simulink and CarMaker. Results show that the vehicle can avoid the collision with static and moving obstacles. The vehicle trajectories were smooth, and the turning radius was kept in a suitable range to ensure the vehicle handling. Simulation results show that the proposed local path planning method can realize obstacle avoidance with good handling performance.
Wu, LingfeiZha, HongshanXiu, CaijingHe, Qiaojun
Development and Validation of the SAE J3052 High Pressure Differential Flow Rate Recommended Practice2017-01-24989/17/2017
This paper describes the development work that went into the creation of the SAE J3052 “Brake Hydraulic Component Flow Rate Measurement at High Delta Pressure”, and also shows some example applications. The SAE J3052 recommended practice is intended to measure flow characteristics through brake hydraulic components and subsystems driven by pressure differentials above 1 bar, and was anticipated by the task force to be invoked for components and subsystems for which pressure response characteristics are critical for the operation of the system (such as service brake pressure response and stopping distance, or pressure rise rate of a single hydraulic circuit in response to an Electronic Stability Control command). Data generated by this procedure may be used as a direct assessment of the flow performance of a brake hydraulic component, or they may be used to build subsystem or system-level models. Two significant variants of test methodology were studied, including use of a servo-actuator against a hydraulic cylinder to push fluid through the test specimens at a high rate, and the use of a high pressure pump to create a target pressure differential across the test specimen. In the course of test development, experiments were run with two different calibrated orifice sizes, with two different ESC modules (representing common test specimens), and two different calipers (relevant to the servo-actuator based method). Data derived from each method were fitted into brake system models for two different vehicle (a car and a light truck). Observing which method produced better correlation to physical vehicle test results was the final arbiter of the best methodology, and shaped the final form of the recommended practice.
Antanaitis, David B.Lloyd, E
Vehicle Lane Change Automation with Active Steering - Theoretical Studies and Numerical Investigations2017-01-15553/28/2017
Lane change automation appears to be a fundamental problem of vehicle automated control, especially when the vehicle is driven at high speed. Selected relevant parts of the recent research project are reported in this paper, including literature review, the developed models and control systems, as well as crucial simulation results. In the project, two original models describing the dynamics of the controlled motion of the vehicle were used, verified during the road tests and in the laboratory environment. The first model - fully developed (multi-body, 3D, nonlinear) - was used in simulations as a virtual plant to be controlled. The second model - a simplified reference model of the lateral dynamics of the vehicle (single-body, 2D, linearized) - formed the basis for theoretical analysis, including the synthesis of the algorithm for automatic control. That algorithm was based on the optimal control theory. The algorithm includes the determination of time optimal reference profiles defining control input and vehicle response (the reference steering wheel angle of the "bang-bang" type). Implementation of the prescribed motion trajectory in the control system is made using Kalman regulators ensuring optimal trajectory following in the terms of the linear-quadratic problem. Presented in the paper exemplary simulation results demonstrate the effects of variations of the road surface, vehicle speed, and vehicle loading condition. The results show the complexity of the dynamic properties of the vehicle under study and confirm the benefits of the adopted solutions for vehicle automated control.
Gidlewski, Mirosław JanJANKOWSKI, KrystofMUSZYŃSKI, AndrzejŻARDECKI, Dariusz
Optimal Tire Force Control & Allocation for Longitudinal and Yaw Moment Control of HEV with eAWD Capabilities2017-01-15583/28/2017
Hybrid Electric Vehicles (HEV) offer improved fuel efficiency compared to their conventional counterparts at the expense of adding complexity and at times, reduced total power. As a result, HEV generally lack the dynamic performance that customers enjoy. To address this issue, the paper presents a HEV with eAWD capabilities via the use of a torque vectoring electric rear axle drive (TVeRAD) unit to power the rear axle. The addition of TVeRAD to a front wheel drive HEV improves the total power output. To further improve the handling characteristics of the vehicle, the TVeRAD unit allows for wheel torque vectoring at the rear axle. A bond graph model of the proposed drivetrain model is developed and used in co-simulation with CarSim. The paper proposes a control system which utilizes tire force optimization to allocate control to each tire. The optimization algorithm is used to obtain optimal tire force targets to at each tire such that the targets avoid tire saturation. The Youla parameterization technique is used to develop robust tracking controllers for each axle. The proposed control system is ultimately tested on the drivetrain model with a high fidelity CarSim vehicle model for validation. Simulation results show that the control system is able to maximize vehicle longitudinal performance while avoiding tire saturation on a low mu surface. More importantly, the control system is able to track the desired yaw moment request on a high speed double lane change maneuver through the use of the TVeRAD to improve the handling characteristic of the vehicle.
Velazquez Alcantar, JoseAssadian, FrancisKuang, Ming
Research on Vehicle Stability Control Strategy Based on Integrated-Electro-Hydraulic Brake System2017-01-15653/28/2017
A vehicle dynamics stability control system based on integrated-electro-hydraulic brake (I-EHB) system with hierarchical control architecture and nonlinear control method is designed to improve the vehicle dynamics stability under extreme conditions in this paper. The I-EHB system is a novel brake-by-wire system, and is suitable to the development demands of intelligent vehicle technology and new energy vehicle technology. Four inlet valves and four outlet valves are added to the layout of a conventional four-channel hydraulic control unit. A permanent-magnet synchronous motor (PMSM) provides a stabilized high-pressure source in the master cylinder, and the four-channel hydraulic control unit ensures that the pressures in each wheel cylinder can be modulated separately at a high precision. Besides, the functions of Anti-lock Braking System, Traction Control System and Regenerative Braking System, Autonomous Emergency Braking can be integrated in this brake-by-wire system. A sliding mode variable structure vehicle dynamics stability controller based on hierarchical control framework is built in MATLAB/Simulink. The I-EHB actuator model and vehicle dynamic model with 15 degrees of freedom are built in simulation package AMESim through a parameterized and modularized method. Simulations are conducted via co-simulation platform using MATLAB/Simulink and AMESim under scenarios of the typical braking and NHTSA FMVSS 126 standard-Sine With Dwell. Simulation results show that hydraulic braking forces are coordinated well during typical braking process, verifying the feasibility and effectiveness of the models built and the control strategy proposed. Under Sine With Dwell maneuver, compared with the base systems equipped without/with the conventional ESP, the proposed stability control system has a good improvement on the vehicle dynamics.
He, XiangkunYang, KaimingJi, XuewuLiu, YahuiDeng, Weiwen
Reduction of Steering Effort in the Event of EPAS Failure using Differential Braking Assisted Steering2017-01-14893/28/2017
Electric Power Assisted Steering (EPAS) is widely adopted in modern vehicles to reduce steering effort. It is probable that some EPAS systems will experience a shutdown due to reliability issues stemming from electrical and/or electronic components. In the event of EPAS failure, power assist becomes unavailable and the steering system reverts to a fully manual state, leading to excessive steering torque demands from the driver to maneuver the vehicle at lower speeds, i.e., under 30 mph. This situation has resulted in dozens of reported crashes and several OEM safety recalls in the past few years. Inspired by recent work which utilizes independent driving torque of in-wheel-motor vehicles to reduce steering torque, this paper proposes the use of Differential Braking Assisted Steering (DBAS) to alleviate steep increases in steering torque upon EPAS failure. DBAS requires software upgrades with minimal hardware modification to EPAS, which is preferable for a backup system. A preliminary evaluation of DBAS is carried out using simulations in CarSim. Results show that DBAS reduces steering torque to similar levels as EPAS in all of the steady state, transient and urban driving scenarios investigated. The results also show that DBAS triggers vehicle speed reduction and oversteer, the latter of which is in conflict with Electronic Stability Control (ESC) which is designed to inherently prevent oversteer. Since ESC is typically crucial at higher speeds, this conflict can be avoided by employing DBAS only at lower speeds where steering assist is most needed. This paper motivates further study of DBAS for emergency safety in the event of EPAS failure.
Zhang, DuanxiangLin, BoKirli, AhmetOkwudire, Chinedum
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