Estimating Vehicle Suspension Characteristics for Digital Twin Creation with Genetic Algorithm

Usage of simulation techniques like Vehicle-in-the-Loop, Scenario-in-the-Loop, and other mixed-reality systems are becoming inevitable in autonomous vehicle development, particularly in testing and validation. These methods rely on using digital twins, realistic representations of real vehicles, and traffic in a carefully rebuilt virtual world. Recreating them precisely in a virtual ecosystem requires many parameters of real vehicles to follow their properties in a simulation. This is especially true for vehicle dynamics, where these parameters have high impact on the simulation results. The paper's objective is to provide a method that can help reverse engineering a real car's suspension characteristics with the help of a genetic algorithm. A detailed description of the method is presented, guiding the reader through the whole process, including the meta-heuristic function's settings and how it interfaces with IPG Carmaker. The paper also presents multiple measurements, which can be effortlessly recreated without expensive devices or the need to disassemble any vehicle parts. Measurements are reproduced in two separate simulation tools with special scenarios providing an efficient way to analyze and verify the results. The provided method creates vehicle suspension characteristics with adequate quality, opening up the possibility to use them in the creation of digital twins or creating virtual traffic with realistic vehicle dynamics for high-quality visualization. Results show satisfying accuracy when tested with OpenCRG

Tyre models for vehicle handling analysis under steady-state and transient manoeuvres

The work presented in this thesis is devoted to the study of mechanism of tyre force generation and its influence on handling dynamics of ground vehicles. The main part of the work involves the development of tyre models for use under steady-state and transient operating conditions. The general capability of these models is assessedin a full vehicle simulation environment. The interaction between tyre and vehicle dynamics is critically evaluated and the observed vehicle behaviour is related to the inherent characteristics of different tyre models. In the field of steady-state tyre modelling, two versions of a numerical tyre model are developed. The modelling procedure is carried out in accordance with the viscoelastic properties of rubber, which influence the mechanical properties of the tyre structure and play a significant role in the determination of friction in the tyre contact patch. Whilst the initial simple version of the tyre model assumes a parabolic pressure distribution along the contact, a later more elaborate model employs a numerical method for the calculation of the actual normal pressure distribution. The changes in the pressure distribution as a result of variations in the rolling velocity and normal load influence mainly the levels of self-aligning moment, whilst the force characteristics remain practically unaffected. The adoption of a velocity dependent friction law explains the force generating behaviour of tyres at high sliding velocities. The analysis is extended to the area of transient tyre behaviour with the development of a tyre model appropriate for the study of transient friction force generation within the contact patch. The model incorporates viscoelasticity and inertial contributions, and incorporates a numerical stick-slip law. These characteristics are combined together for the successful simulation of transient friction force generation. The methodologies developed for the modelling of transient friction and steady-state tyre force generation are combined and further extended in order to create a generic transient tyre model. This final model incorporates a discretised flexible viscoelastic belt with inertia and a separate fully-dynamic discretised tread, also with inertia and damping, for the simulation of actual prevailing conditions in the contact patch. The generic tyre model appears to be capable of performing under a variety of operating conditions, including periodic excitations and transient inputs which extend to the non-linear range of tyre behaviour. For the evaluation of the influence of the aforementioned tyre models on the handling responses of a vehicle, a comprehensive vehicle model is developed, appropriate for use in handling simulations. The two versions of the steady-state models and the generic transient model are interfaced with the vehicle model, and the response of the vehicle to a step-steer manoeuvre is compared with that obtained using the Magic Formula tyre model. The comparison between the responses is facilitated by the definition of a new measure, defined as the non-dimensional yaw impulse. It is found that the transience involved in tyre behaviour may largely affect the response of a vehicle to a prescribed input

Tyre models for vehicle handling analysis under steady-state and transient manoeuvres

The work presented in this thesis is devoted to the study of mechanism of tyre force generation and its influence on handling dynamics of ground vehicles. The main part of the work involves the development of tyre models for use under steady-state and transient operating conditions. The general capability of these models is assessedin a full vehicle simulation environment. The interaction between tyre and vehicle dynamics is critically evaluated and the observed vehicle behaviour is related to the inherent characteristics of different tyre models. In the field of steady-state tyre modelling, two versions of a numerical tyre model are developed. The modelling procedure is carried out in accordance with the viscoelastic properties of rubber, which influence the mechanical properties of the tyre structure and play a significant role in the determination of friction in the tyre contact patch. Whilst the initial simple version of the tyre model assumes a parabolic pressure distribution along the contact, a later more elaborate model employs a numerical method for the calculation of the actual normal pressure distribution. The changes in the pressure distribution as a result of variations in the rolling velocity and normal load influence mainly the levels of self-aligning moment, whilst the force characteristics remain practically unaffected. The adoption of a velocity dependent friction law explains the force generating behaviour of tyres at high sliding velocities. The analysis is extended to the area of transient tyre behaviour with the development of a tyre model appropriate for the study of transient friction force generation within the contact patch. The model incorporates viscoelasticity and inertial contributions, and incorporates a numerical stick-slip law. These characteristics are combined together for the successful simulation of transient friction force generation. The methodologies developed for the modelling of transient friction and steady-state tyre force generation are combined and further extended in order to create a generic transient tyre model. This final model incorporates a discretised flexible viscoelastic belt with inertia and a separate fully-dynamic discretised tread, also with inertia and damping, for the simulation of actual prevailing conditions in the contact patch. The generic tyre model appears to be capable of performing under a variety of operating conditions, including periodic excitations and transient inputs which extend to the non-linear range of tyre behaviour. For the evaluation of the influence of the aforementioned tyre models on the handling responses of a vehicle, a comprehensive vehicle model is developed, appropriate for use in handling simulations. The two versions of the steady-state models and the generic transient model are interfaced with the vehicle model, and the response of the vehicle to a step-steer manoeuvre is compared with that obtained using the Magic Formula tyre model. The comparison between the responses is facilitated by the definition of a new measure, defined as the non-dimensional yaw impulse. It is found that the transience involved in tyre behaviour may largely affect the response of a vehicle to a prescribed input.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Vibration and force analysis of lower arm of suspension system

This study describes the analysis of suspension system and its lower arm. These analyses were specifically applied on lower suspension arm to determine its vibration and stress behaviour during its operation. The suspension system is one of the most important components of vehicle, which directly affects the safety, performance, noise level and style of it. The main objectives are to have less stress on lower suspension arm system as well as to reduce imposed load by optimization. The optimization of imposed load on lower suspension arm system is directly related to imposed force on the vehicle created by the road. This load has a direct effect on the value of imposed force on lower arm, where the lower arm force will be minimized by reducing the applied load. Hence, genetic algorithms for optimization and MATLAB optimization toolbar are used, as well as, specific M-file codes have been developed into MATLAB for optimization. By determining optimized design values of suspension system for reducing road force, it is possible to survey vibration condition of lower arm according to frequency respond of suspension system and its natural frequency. Therefore, frequency response of its acceleration has been determined according to the whole mass of suspension system. Using FFT technique and making transfer function for frequency response of suspension system, will present responded frequency of suspension system which is using for vibration analysis. For stress analysis, load condition of lower suspension arm system must be determined in advance. Hence, a typical model of McPherson suspension system has been selected for analysis. According to the road profile considered for analysis and the velocity of vehicle, it is possible to obtain both velocity and acceleration equations for whole components of McPherson suspension system. These values are used to determine dynamic force condition of lower arm suspension system during its operation. By using dynamic forces which are governing on lower arm of suspension system, in ABAQUS, the stress condition of lower arm can be determined during its operation

Cooperative agreement to foster the deployment of a heavy vehicle intelligent dynamic stability enhancement system

National Highway Traffic Safety Administration, Washington, D.C.http://deepblue.lib.umich.edu/bitstream/2027.42/1226/2/92867.0001.001.pd

Constraint-based navigation for safe, shared control of ground vehicles

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 138-147).Human error in machine operation is common and costly. This thesis introduces, develops, and experimentally demonstrates a new paradigm for shared-adaptive control of human-machine systems that mitigates the effects of human error without removing humans from the control loop. Motivated by observed human proclivity toward navigation in fields of safe travel rather than along specific trajectories, the planning and control framework developed in this thesis is rooted in the design and enforcement of constraints rather than the more traditional use of reference paths. Two constraint-planning methods are introduced. The first uses a constrained Delaunay triangulation of the environment to identify, cumulatively evaluate, and succinctly circumscribe the paths belonging to a particular homotopy with a set of semi autonomously enforceable constraints on the vehicle's position. The second identifies a desired homotopy by planning - and then laterally expanding - the optimal path that traverses it. Simulated results show both of these constraint-planning methods capable of improving the performance of one or multiple agents traversing an environment with obstacles. A method for predicting the threat posed to the vehicle given the current driver action, present state of the environment, and modeled vehicle dynamics is also presented. This threat assessment method, and the shared control approach it facilitates, are shown in simulation to prevent constraint violation or vehicular loss of control with minimal control intervention. Visual and haptic driver feedback mechanisms facilitated by this constraint-based control and threat-based intervention are also introduced. Finally, a large-scale, repeated measures study is presented to evaluate this control framework's effect on the performance, confidence, and cognitive workload of 20 drivers teleoperating an unmanned ground vehicle through an outdoor obstacle course. In 1,200 trials, the constraint-based framework developed in this thesis is shown to increase vehicle velocity by 26% while reducing the occurrence of collisions by 78%, improving driver reaction time to a secondary task by 8.7%, and increasing overall user confidence and sense of control by 44% and 12%, respectively. These performance improvements were realized with the autonomous controller usurping less than 43% of available vehicle control authority, on average.by Sterling J. Anderson.Ph.D

Objective Tyre Development : Definition and Analysis of Tyre Characteristics and Quantification of their Conflicts

The present work focuses on tyres for passenger cars, especially on its influence on power loss, lateral dynamics, ride comfort and interior noise. The objective of the work is the quantification of conflicts between four selected requirements considering the physical constraints given by the tyre. The method proposed in the present book is based on a set of functional tyre characteristics, a physical tyre model and a procedure for identifying and quantifying the conflicts

Active suspension control of electric vehicle with in-wheel motors

In-wheel motor (IWM) technology has attracted increasing research interests in recent years due to the numerous advantages it offers. However, the direct attachment of IWMs to the wheels can result in an increase in the vehicle unsprung mass and a significant drop in the suspension ride comfort performance and road holding stability. Other issues such as motor bearing wear motor vibration, air-gap eccentricity and residual unbalanced radial force can adversely influence the motor vibration, passenger comfort and vehicle rollover stability. Active suspension and optimized passive suspension are possible methods deployed to improve the ride comfort and safety of electric vehicles equipped with inwheel motor. The trade-off between ride comfort and handling stability is a major challenge in active suspension design. This thesis investigates the development of novel active suspension systems for successful implementation of IWM technology in electric cars. Towards such aim, several active suspension methods based on robust H∞ control methods are developed to achieve enhanced suspension performance by overcoming the conflicting requirement between ride comfort, suspension deflection and road holding. A novel fault-tolerant H∞ controller based on friction compensation is in the presence of system parameter uncertainties, actuator faults, as well as actuator time delay and system friction is proposed. A friction observer-based Takagi-Sugeno (T-S) fuzzy H∞ controller is developed for active suspension with sprung mass variation and system friction. This method is validated experimentally on a quarter car test rig. The experimental results demonstrate the effectiveness of proposed control methods in improving vehicle ride performance and road holding capability under different road profiles. Quarter car suspension model with suspended shaft-less direct-drive motors has the potential to improve the road holding capability and ride performance. Based on the quarter car suspension with dynamic vibration absorber (DVA) model, a multi-objective parameter optimization for active suspension of IWM mounted electric vehicle based on genetic algorithm (GA) is proposed to suppress the sprung mass vibration, motor vibration, motor bearing wear as well as improving ride comfort, suspension deflection and road holding stability. Then a fault-tolerant fuzzy H∞ control design approach for active suspension of IWM driven electric vehicles in the presence of sprung mass variation, actuator faults and control input constraints is proposed. The T-S fuzzy suspension model is used to cope with the possible sprung mass variation. The output feedback control problem for active suspension system of IWM driven electric vehicles with actuator faults and time delay is further investigated. The suspended motor parameters and vehicle suspension parameters are optimized based on the particle swarm optimization. A robust output feedback H∞ controller is designed to guarantee the system’s asymptotic stability and simultaneously satisfying the performance constraints. The proposed output feedback controller reveals much better performance than previous work when different actuator thrust losses and time delay occurs. The road surface roughness is coupled with in-wheel switched reluctance motor air-gap eccentricity and the unbalanced residual vertical force. Coupling effects between road excitation and in wheel switched reluctance motor (SRM) on electric vehicle ride comfort are also analysed in this thesis. A hybrid control method including output feedback controller and SRM controller are designed to suppress SRM vibration and to prolong the SRM lifespan, while at the same time improving vehicle ride comfort. Then a state feedback H∞ controller combined with SRM controller is designed for in-wheel SRM driven electric vehicle with DVA structure to enhance vehicle and SRM performance. Simulation results demonstrate the effectiveness of DVA structure based active suspension system with proposed control method its ability to significantly improve the road holding capability and ride performance, as well as motor performance

Investigations on the Roll Stability of a Semitrailer Vehicle Subjected to Gusty Crosswind Aerodynamic Forces

Threats of high crosswind gusts on running safety of modern road and rail vehicles have been reported around the world. Under high transient crosswind conditions, sudden changes in vehicle aerodynamic forces can lead to adverse effects on vehicle dynamics and stability. Moreover, due to increase in maximum speed limits and body dimensions of commercial vehicles as well as reduction in their weights, large class vehicles, in particular, are more prone to rollover accidents in strong crosswind situations, especially at cruising speeds or at exposed sites. Such crosswind accidents have been observed even at low vehicle speed of 15 m/s in adverse windy weather. It is therefore essential to conduct detailed investigations on the aerodynamic performance of commercial vehicles under crosswind conditions in order to improve their crosswind stability. In this study, estimation of unsteady aerodynamic forces acting on a high-sided tractor-trailer vehicle have been carried out based on experiential and numerical simulations. Although natural crosswind gusts are high-turbulent phenomena, and have a large variability in types and origins, this study suggests employing two gust scenarios based on two different methods: 1. Transient wind gust scenario developed in wind-tunnel to represents a high-sided tractor semitrailer vehicle moving on a road in moderate wind condition and immediately being hit by wind gust. 2. Deterministic crosswind scenario with gusts in exponential shapes has been considered to predict crosswind aerodynamic forces of a high-sided tractor semitrailer vehicle moving through wind exposed area. This scenario is specified in the Technical Specification for Interoperability (TSI) standard, but it has been employed in this study in combination with Computational Fluid Dynamics (CFD). A series of time-dependent crosswind aerodynamic forces acting on the tractor-semitrailer vehicle have been predicted. Moreover, to illustrate the potential influence of crosswind gusts on a high-sided tractor semitrailer vehicle, instantaneous gust flow structures for proposed wind scenarios and wind pressure fields were presented. The results show that both wind gust scenarios have significant unsteady effects on the side aerodynamic force and the roll moment of the vehicle. Furthermore, there are significant variations in aerodynamic loads, and the flow field becomes more complicated, consistent with the gust’s strength. These conclusions strongly suggested the importance of considering the unsteady aerodynamic forces in the analysis of heavy vehicle roll dynamics. Lateral load transfer ratio (LTR) is a criterion that is often used for designing ground vehicle rollover warning technologies to indicate the vehicles rollover status. Generally, LTR index depends on road geometry and vehicle dynamic characteristics. However, as mentioned above, crosswind loads have the potential to influence the roll stability and therefore the safety of large commercial vehicles. Therefore, this thesis presents the research carried out to improve the traditional LTR for a high-sided tractor semitrailer vehicle to be more efficient in crosswind environment. For this purpose, since experimental investigations on vehicle rollover dynamics are difficult to carry out, a coupled simulation of crosswind aerodynamic forces and multi-body vehicle dynamics has been proposed. In this method, the predicted aerodynamic forces result due to the proposed wind scenarios were input into multi-body dynamic simulations of the tractor semi-trailer vehicle that were performed through Adams/Car software. Based on this coupled analysis, dynamic responses of the vehicle to fluctuating crosswind conditions have been predicted. Moreover, all parameters of the LTR index such as body roll angle and lateral acceleration were estimated through a critical turning manoeuvre with crosswind actions. The investigation results show that, in the same manoeuvre, in comparison with the traditional LTR index (i.e., in which crosswind aerodynamic forces are ignored), the improved LTR rollover (crosswind) indicator, has successfully detected wheel lift–up conditions when crosswind aerodynamic loads are considered. Also, average values of the LTR measured under crosswind effects are about 22% higher than those of corresponding traditional LTR index. Therefore, the rollover indicator that has been improved by the proposed methodology can provide more reliable information to the warning or control system in the presence of wind conditions

Tyre Pressure Monitoring using Sensors

This thesis presents an implementation of a positioning and navigation system for a mobile robot using ultrasonic pulses and passive sensors that are part of a sensor network. The system uses the Telos Tmote Sky sensor-boards running Contiki. In addition to the Tmote Sky the mobile robot consists of a number of processors and is equipped with position encoders for the wheels in order to be able to accurately estimate the position using dead-reckoning. It is also equipped with an ultrasound transmitter. The sensor nodes are equipped with ultrasound receivers