Vehicle Stability Research Articles

(Keynote) Polyoxometallate Functionalized Membranes for Next Generation Fuel Cells, Electrolyzers and Other Devices

Using polyoxometalate moieties we are developing proton conducting membranes for proton exchange membrane fuel cells, electrolyzers and other devices that can solve the durability and environmental challenges and temperature limitations facing the state of the state-of-the-art perfluorinated sulfonic acid-based membranes. During recent work with perfluorinated membranes we have shown how to achieve stability enhancement that easily exceeds the Fuel Cell DOE accelerated stress tests (AST) for chemical stability and mechanical durability requirements for light duty vehicles. This indicates the potential of these For this perfluorinated polymer-HPA combination we obtained higher performance than the current state-of-the-art PFSAs under high humidity conditionsHPA moieties to give oxidative stability to hydrocarbon membranes as well. New membrane technology we are working on will utilize covalently bound heteropoly acids (HPA), inorganic super acids, that have both some of the highest proton conductivities when wet and have been proven to catalytically decompose oxygenated radicals that destroy existing membranes. We have already demonstrated similar membranes in fuel cells with high performance and some of the most stable long term durability ever demonstrated. In fuel cells, the materials always performed beyond state-of the-art when in humid conditions but struggled when the cells became dry, as electrolysis applications feeds water to the cell we have very high confidence that we will be able to easily exceed electrolyzer performance targets. We are improving upon this polymer chemistry and are now tailoring it specifically to electrolysis. When configured correctly within a hydrocarbon polymer membrane these HPA-hydrocarbon polymers will outperform perfluorosulfonic acid (PFSA) polymers. The correct HPA chemistry must be chosen, and we have shown that silicotungstic acid derivatives act as strong proton conducting moieties and also catalytically decompose oxygenated radicals. This will then enable hydrocarbon membranes with practical lifetimes and performance using the silicotungstic functionality. We are aiming to control the HPA channel morphology and allow for maximum proton conductivity with minimum water uptake. The engineered structures will facilitate proton conduction from ambient conditions to temperatures in excess of 120°C (the polymeric materials chosen are stable to 200°C when dry and potentially much higher when wet and pressurized), as well as achieving cost and durability targets for PEM membranes in electrolyzer applications. Our approach will also allow for development of an ionomer for optimal interfacing with the electrodes.

Developing an Apparatus to Analyze Volume Changes in a Pouch Battery Cell

Recently, there has been a significant increase in demand for lithium-ion batteries due to the growing demand for eco-friendly mobility. However, to ensure the stability of electric vehicles during operation, research on the structural and material characteristics of batteries is essential. The Battery Management System (BMS), responsible for managing battery degradation and performance, is directly impacted not only by the electrochemical characteristics but also by the structural and material stability of the battery. As the demand for high-density battery modules increases, the volume change of batteries after degradation can generate significant internal stresses, making it crucial to develop the vehicle's BMS in relation to this issue. Therefore, this study aims to measure the characteristics of batteries volume changes during degradation under various pressure conditions from the cell level. Ultimately, we propose a homogenized model that can predict the degradation characteristics of a battery pack subjected to pressure during charging and discharging. An apparatus capable of measuring the volume changes of batteries is developed for the modelling.Keywords: Battery volume changes, pouch cell, modeling, mechanical properties, compression test, apparatus

Realizing asynchronous finite-time robust tracking control of switched flight vehicles by using nonfragile deep reinforcement learning.

In this study, a novel nonfragile deep reinforcement learning (DRL) method was proposed to realize the finite-time control of switched unmanned flight vehicles. Control accuracy, robustness, and intelligence were enhanced in the proposed control scheme by combining conventional robust control and DRL characteristics. In the proposed control strategy, the tracking controller consists of a dynamics-based controller and a learning-based controller. The conventional robust control approach for the nominal system was used for realizing a dynamics-based baseline tracking controller. The learning-based controller based on DRL was developed to compensate model uncertainties and enhance transient control accuracy. The multiple Lyapunov function approach and mode-dependent average dwell time approach were combined to analyze the finite-time stability of flight vehicles with asynchronous switching. The linear matrix inequalities technique was used to determine the solutions of dynamics-based controllers. Online optimization was formulated as a Markov decision process. The adaptive deep deterministic policy gradient algorithm was adopted to improve efficiency and convergence. In this algorithm, the actor-critic structure was used and adaptive hyperparameters were introduced. Unlike the conventional DRL algorithm, nonfragile control theory and adaptive reward function were used in the proposed algorithm to achieve excellent stability and training efficiency. We demonstrated the effectiveness of the presented algorithm through comparative simulations.

Vehicle Lateral Control Based on Dynamic Boundary of Phase Plane Based on Tire Characteristics

Lateral control is an essential safety control technology for autonomous vehicles, but the effectiveness of lateral control technology relies heavily on the precision of vehicle motion state judgements. In order to achieve accurate judgements of the vehicle motion state and to improve the control effectiveness of vehicle maneuverability and the stability controller, this paper starts with an analysis of phase plane stability. A simulation analysis is conducted to investigate the effect of the vehicle steering angle of the front wheels, the longitudinal velocity, and the tire–road adhesion coefficient on the boundary of the stability area. The stable area of the phase plane was partitioned using the proposed novel quadrilateral method, and we established a stability area regression model using machine learning methods. We analyzed the inherent connection between the lateral tire forces and the principles of vehicle maneuverability and stability control, indirectly combining the characteristics of tire forces with vehicle maneuverability and stability control. An allocation algorithm for maneuverability and stability control was designed. A co-simulation indicates that the vehicle stability controller not only accurately assesses the motion state of the vehicle but also demonstrates a considerably better performance in maneuverability and stability control compared to a controller using the traditional partitioning method of stable regions. The suggested allocation method enhances vehicle maneuverability and stability by enabling a seamless transition between the two and improving the effectiveness of stability control.

Integrated control of path tracking and handling stability for autonomous ground vehicles with four-wheel steering

Accurate modelling of an autonomous ground vehicle (AGV) is challenging due to strong nonlinearity, model perturbations and external disturbances. This necessitates the design of path tracking controllers with robustness. In this paper, an integrated control strategy for path tracking and handling stability of AGVs is proposed, leveraging a four-wheel steering (4WS) system. To address the path tracking problem, a fuzzy logic-based steering strategy is developed, which enables parameter self-adjustment based on displacement error. Additionally, a reference model is employed to transform the path tracking problem into a reference signal tracking problem, ensuring the handling stability of vehicles. A sliding mode controller is designed to track the reference signal, utilizing an extended state observer to estimate and compensate for unmodeled dynamics and unknown external disturbances in real-time. Simulation results demonstrate the effectiveness of the proposed strategy in accurately tracking the desired path while maintaining the lateral stability of the vehicle. Furthermore, the strategy exhibits strong robustness against uncertainties and disturbances.

Enhancing Autonomous Vehicle Stability through Pre-Emptive Braking Control for Emergency Collision Avoidance

A pre-emptive braking control method is proposed to improve the stability of autonomous vehicles during emergency collision avoidance, aiming to imitate the realistic human driving experience. A linear model predictive control is used to derive the front wheel steering angle to track a predefined fifth-degree polynomial trajectory. Based on a two-degrees-of-freedom (DOF) vehicle dynamics model, the maximum stable vehicle speed during collision avoidance can be determined. If the actual vehicle speed exceeds the maximum stable vehicle speed, braking action will be applied to the vehicle. Furthermore, four-wheel steering (4WS) control and direct yaw moment control (DYC) are employed to further improve the stability of the vehicle during collision avoidance. Simulation results under a double lane change scenario demonstrate that the control system incorporating pre-emptive braking, 4WS, and DYC can enhance the vehicle stability effectively during collision avoidance. Compared to the 2WS system without pre-emptive braking control, the maximum stable vehicle speed of the integrated control system can be increased by at least 56.9%. The proposed integrated control strategy has a positive impact on the safety of autonomous vehicles, and it can also provide reference for the research and development of autonomous driving systems.

A Case Study on the Effect of Geometric Design Consistency on Road Crashes on Narayanghat-Muglin Road Section

Design consistency is overlooked while designing roads, resulting in unsafe road facilities. The safety performance of a highway can be greatly enhanced by detecting and addressing any inconsistencies present on the road. Over time, the application of geometric standards shifted from new road construction to upgrading, which could result in limited design options. Due to the emerging importance of design consistency in geometric design, this research has been initiated to evaluate horizontal curve consistency based on an established operating speed prediction model.
 Horizontal curve data of the Narayanghat–Mugling Road section has been collected from the Division Road Office, Bharatpur, and accident data has been obtained from the District Traffic Police, Chitwan. Out of 242 horizontal curves in the Narayanghat-Muglin road section, the design consistency of 223 horizontal curves was evaluated, while 19 horizontal curves with posted speed limits were not considered because these curves are not within the range of design criteria set out in Asian Highways Design Standards (1993).
 The average, maximum, and minimum 85th percentile speed was found to be 78, 101, and 32 kmph respectively. Out of 223 horizontal curves evaluated for individual consistency based on operating speed, 75% of the curves were categorized as “poor”, 16% as “fair”, and 9% as “good”. It was found that under successive element consistency evaluation based on operating speed, 22% of horizontal curves were categorized as “poor”, 23% as “fair”, and 55% as “good”. When studied under vehicle stability consistency evaluation criteria, 88% of the curves were classified as “fair” and 12% as “good”. It was found that the predicted accidents caused by geometric design inconsistency and vehicle stability are 5.12% of total accidents per year.
 From the safety standpoint, if the condition |V85-Vd|>20 is met, critical discrepancies between the design speed and operating speed arise, resulting in unsafe operations. Therefore, it is generally advisable to consider redesigning those road sections.

Adaptive fault-tolerant control based on linear matrix inequalities for actuator failures in steer-by-wire system

Aiming at the vehicle stability and safety problems caused by the actuator failure of Steer-By-Wire (SBW) system, a two-layer control strategy combining the Performance-Preserving Robust Control (PPRC) and Adaptive Fault-Tolerant Control (AFTC) using the Linear Matrix Inequality (LMI) processing is proposed. The PPRC of the SBW system by tracking the ideal reference model is the first layer of control, the vehicle is robust to speed and low failure rate defects of the SBW system actuator within the performance range of the SBW system, and the side slip angle ([Formula: see text]) and yaw rate ([Formula: see text]) of the vehicle can approach optimal values; The second layer of control: AFTC is added to the above PPRC based on the online estimation of the final failure, when a high failure rate failure in the actuator of the SBW system occurs and the performance limit of the PPRC is exceeded, this allows the vehicle state in the high failure rate failure mode of the actuator to still track the specified ideal reference state. Compared with the traditional Fault-Tolerant Control (FTC) that requires Fault Detection and Isolation (FDI), the control method used in this paper does not require accurate fault information, but only uses the system state change generated by the fault as the information to automatically adjust the control input, which can still achieve the purpose of stabilizing the whole SBW system when the actuator fails.

Finding a generic fixed brake force distribution through optimizing hydraulic brake system parameters to prevent wheel lock

Purpose The paper aims to identify a suitable generic brake force distribution ratio (β) corresponding to optimal brake design attributes in a diminutive driving range, where road conditions do not exhibit excessive variations. This will intend for an appropriate allocation of brake force distribution (BFD) to provide dynamic stability to the vehicle during braking. Design/methodology/approach Two techniques are presented (with and without wheel slip) to satisfy both brake stability and performance while accommodating variations in load sharing and road friction coefficient. Based on parametric optimization of the design variables of hydraulic brake using evolutionary algorithm, taking into account both the laden and unladen circumstances simultaneously, this research develops an improved model for computing and simulating the BFD applied to commercial and passenger vehicles. Findings The optimal parameter values defining the braking system have been identified, resulting in effective β = 0.695 which enhances the brake forces at respective axles. Nominal slip of 3.42% is achieved with maximum deceleration of 5.72 m/s2 maintaining directional stability during braking. The results obtained from both the methodologies are juxtaposed and assessed governing the vehicle stability in straight line motion to prevent wheel lock. Originality/value Optimization results establish the practicality, efficacy and applicability of the proposed approaches. The findings provide valuable insights for the design and optimization of hydraulic drum brake systems in modern automobiles, which can lead to safer and more efficient braking systems.

The prospect of chassis structure design for new energy battery electric vehicles

More focus has been placed on creating new energy cars that are safer and more energy-efficient due to the development of new energy vehicle technologies and their strategic importance in addressing current energy and environmental issues. The chassis system's primary components, whether for a conventional fuel vehicle or a new energy vehicle, are the braking, suspension, and steering subsystems. The functioning, comfort, and safety of modern energy vehicles are strongly correlated to their structural design. At the moment, the design of new energy vehicle chassis is mostly based on refining and adapting the chassis of conventional fuel vehicles. However, new energy vehicles have distinct driving systems compared to conventional vehicles. Thus it is important to account for these variations in the layout and make it compatible with the whole system. The chassis structural design of new energy cars is more adaptable and affects vehicle performance compared to fuel-powered vehicles. The integrated battery and high amount of unsprung mass affect the center of gravity and stability of the new energy vehicle. The coordination and collaboration between the power battery module and the chassis construction must therefore be carefully considered, as well as their effects on the entire vehicle performance, including its safety and economic effectiveness. In conclusion, thoroughly examining the chassis structure design plan for new energy vehicles is crucial for advancing these vehicles.

Aerodynamic Drag Reduction Around Vehicles Using a Curved Deflector

A passive flow control on a generic car model was numerically studied. The Ahmed’smodel with rear slant angle of 25° was used to study the aerodynamic effects. The concave deflector was tested for the first time in this paper to minimize the drag coefficient. The deflector was fixed between the end of the roof and the top of the rear window. Simulations were firstly performed for different straight deflector’s length rates based on the length of the model, for Reynolds number Re=7.89×105 and inlet velocity Uo=40m/s. A significant drag reduction was observed for the high length rate studied. Secondly, the length rate was fixed, and the deflector was investigated for different curvature radius and inclination angles. It was concluded that the Ahmed model with concave deflector gives the best drag reduction, compared to the model with straight deflector and the model without deflector. It was observed that the installation of a concave deflector on the Ahmed model widen the wake zone and remove the vortices from the rear base. For this case, the lift coefficient was reduced, this improves the stability of vehicle on the road at high speed.

An Active Front Steering System Design Considering the CAN Network Delay

The x-by-wire technology promotes the rapid development of intelligent vehicles, but it comes with the network delays, which would deteriorate the control performance. Therefore, this paper proposes an active front steering (AFS) design scheme considering the network delays to ensure the vehicle path-tracking accuracy and stability performance. First, the vehicle system with delays induced by the Controller Area Network (CAN) is analyzed, based on which an augmented model is built to describe the vehicle motion combined with the random network delays. Considering the uncertainty of the delay, the model is reconstructed by the polytope method. Then, a robust H∞ state feedback controller is developed to ensure the system performance when handling the parametric uncertainties. Furthermore, the robust invariant set is introduced to depict the system constraints, which can guarantee the vehicle stability. Through transforming into the linear matrix inequalities, a feasible solution is calculated. Finally, the rapid control prototype (RCP) based on the CarSim/Simulink test platform is used to validate the proposed controller. The results compared with the model predictive control show the effectiveness to ensure the prescribed performance.

Artificial intelligence-enhanced DTC command methods used for a four-wheel-drive system

This paper presents an artificial intelligence direct torque control (DTC) method for an electric vehicle (EV) drive system. The architecture of the proposed electric vehicle is that of four wheels each with an induction motor (IM). A comparative study of the different torque and speed controllers proposed in this paper is made. An electronic differential is used to control the speed of each wheel as well as a variable master-slave control (VMSC) for the management of the magnetic quantities because the motors on the same side are fed by the same converter. This study allows highlights the performance of the propulsion system in terms of dynamics and safety of the vehicle and better stability. The different controllers are implemented by the MATLAB/Simulink software and the simulation results obtained show better flexibility in the control of the vehicle. It is worth noting that direct torque control with fuzzy logic (DTFC) performs better than DTC associated with neural networks in terms of a time reduction increase of 1.47%, an overshoot of less than 5.33, and a static steady-state error close to zero.

Fault-Tolerant Vehicle Stability Control Based on Active Steering and Direct Yaw Moment With Finite-Time Constraint Performance Recovery

Fault-Tolerant Vehicle Stability Control Based on Active Steering and Direct Yaw Moment With Finite-Time Constraint Performance Recovery

A Review on Controlling Methods for Active Suspension Systems

Abstract: Active suspensions have emerged as a transformative technology in the field of vehicle dynamics and ride comfort. This review paper presents a comprehensive overview of the performance of active suspensions, exploring their fundamental principles, control strategies, and real-world applications. Active suspensions, equipped with sensors, actuators, and control systems, offer the ability to adapt in real-time to varying road conditions, providing enhanced ride quality, vehicle stability, and handling precision. It reviews various control strategies, highlighting the trade-offs between complexity and overall system effectiveness. Moreover, the review provides deep insights into the Fuzzy control of active suspension technologies, offering an analysis of their benefits and drawbacks. It also explores the environmental implications, safety considerations, and future prospects of this evolving technology

The research on the influence of multi-physical effect on the dynamic stability of high speed vehicle

In this paper, a kind of high speed vehicle similar to HTV-2 configuration is taken as the research object, and the influence of chemical non-equilibrium effect and rarefied flow effect on the vehicle's three-channel dynamic derivative and yaw channel free motion stability is studied by using the dynamic numerical simulation method based on rigid dynamic grid. The sensitivity of three-channel dynamic stability to multi-physical effects is analyzed, and the influence of multi-physical effects on the dynamic stability of high speed vehicle is obtained. The research results show that the rarefied flow effect and chemical non-equilibrium effect have a small impact on the dynamic derivatives of pitch and roll channels, and a relatively significant impact on the dynamic derivatives of yaw. Compared with the dynamic derivatives of yaw under the condition of complete gas without slip, the deviation of slip results is - 45.2%, and that of chemical non-equilibrium gas with slip results is - 65.9%; The yaw channel has dynamic stability under the condition of complete gas with slip, and the yaw dynamic stability under the condition of chemical non-equilibrium gas with slip is further enhanced, which is consistent with the stability trend represented by the dynamic derivative results; Under the condition of complete gas without slip, the result of dynamic derivative is characterized by dynamic stability, while the result of free yaw oscillation is characterized by dynamic instability; The dynamic derivatives of yaw and the numerical simulation results of free yaw under different inflow conditions show that the dynamic stability of yaw channel is more sensitive to multi-physical effects than that of pitch and roll channels.

An original fuzzy control approach for active anti-roll bars to prevent rollover.

In this article, the author introduces a new fuzzy control solution to direct active anti-roll bars (hydraulic stabilizer bars) in order to enhance the vehicle's roll stabilization efficiency. The original fuzzy algorithm designed in this work can satisfy all the roll stability, comfort, and response speed requirements, while previous algorithms could only meet one of these criteria. In addition, a fully dynamic model is established to simulate the vehicle's roll oscillations instead of only using a simple half-dynamic model combined with the single-track dynamic model. The calculation and simulation processes take place in the Simulink environment. Two cases of steering are used as input to the simulation problem; the car's speed is gradually increased through three levels. According to results of research, the roll angle and roll index of the car increase as the speed and steering angle increase. The interaction between the road and wheel decreases sharply as the roll angle increases, which can lead to a rollover. In the first case, the rollover occurs only when the car travels at v3 without the stabilizer bar and has a maximum roll angle of 9.81°. In the second case, this occurs for the (None) situation when traveling at speed v1 with a maximum roll angle of 9.52° and for the (Passive) situation when traveling at speed v2 with a peak value of 11.93°. Meanwhile, the vehicle's stability is still well guaranteed when utilizing active anti-roll bars controlled by an original fuzzy algorithm.

Improved particle swarm optimisation tuned PID position control of voice coil semi-active electrohydraulic damper

Control on the variable damping coefficients in the semi-active damper enhances ride comfort and vehicle stability. The semi-active electrohydraulic damper (SEH) presented in this study incorporates voice coil-based robust valve control to modify the damping coefficients. However, the position tracking accuracy of the voice coil actuator (VCA) gets negatively influenced by the nonlinearities such as load variations due to external disturbances, back emf, and dynamic damper characteristics. Therefore, to achieve excellent position control, a restart particle swarm optimisation with the Gompertz function (PSO-RG) is presented to obtain optimal tuning control gain for the proportional integral derivative controller. The PSO-RG algorithm applies Gompertz function-based particle coefficients and restarting technique. These techniques allow the PSO-RG to overcome the limitations of standard PSO, such as premature convergence and particle entrapment in local minima. The algorithm is tested in five selected benchmark functions for 10, 30 and 50 dimensions. The test data conveys that PSO-RG outperforms the standard PSO in mean, standard deviation, the best solution, and convergence speed. The transient response on identified and validated model of VCA demonstrated a 75.21% reduction in integral absolute error value than conventional PSO. The obtained maximum sensitivity and total variation values proved the robustness and smoothness of PSO-RG tuned PID control. Furthermore, the experimental analysis on the quarter car model shows that PSO-RG tuned PID precisely tracked the reference position with a 21.66% decrease in root mean square error to conventional PSO tuned PID. The CarSim co-simulation test results in the large van model indicate the need for precise VCA position control in enhancing ride comfort and improving the roll stability of the vehicle.

Development and verification of a virtual prototype of a vehicle

BACKGROUND: Methods of mathematical modelling are widely used in vehicle development. In order to study vehicle dynamics, stability and handling, as well as to accelerate and to reduce the cost of on-board software development, it is necessary to build a digital twin which contains description of special motion of a vehicle with models of units and subsystems as parts of the vehicle. AIMS: Development and verification of a virtual prototype of a vehicle. METHODS: Development of the virtual prototype and vehicle modelling were done in the MATLAB/Simulink software package. Main derivation of the equations necessary to build the models of vehicle’s units and subsystems is given. Verification testing was conducted using special measuring equipment. RESULTS: The vehicle virtual prototype containing description of combined dynamics of bodyframe, transmission elements, suspension and wheels was developed. Comparison of results of field and virtual testing was made in order to confirm operability and adequacy of the virtual prototype. Main graphs showing dynamics of real and virtual vehicles are presented. CONCLUSIONS: Practical value of development and study lies in ability of using a virtual prototype in vehicle dynamic studies and development of on-board control systems.

Slope-climbing coordinated control strategy of trajectory tracking and stability regulation for tractor-trailer trucks

This paper proposes a coordinated control strategy according to the slope-climbing maneuver for autonomous tractor-trailer trucks, with considering tracking accuracy and underactuated trailer stability. First of all, a slope-deconstruction method is adopted to establish a coupled slope-climbing dynamics and trailer articulation model, to investigate motion characteristics and mechanical properties in the target operating condition. After that, a stability assessment is presented on the stable domain of articulation states to determine the underactuated stability. Furthermore, a hierarchical coordinated strategy can be consequently constructed to guarantee the vehicle stability during slope-climbing tracking. Specifically, feedforward model predictive control (MPC) is designed to compensate for system errors in coupled nonlinear dynamics for improved tracking performance. Besides, a robust H∞ is also introduced to govern articulation stability with coordinated braking regulation. At last, co-simulation analysis will be carried out to verify the feasibility and effectiveness of the control strategy, where the practical application adjustment has been discussed to satisfy the driving operation as well.