Showing papers on "Vehicle dynamics published in 2004"

Integrating Inertial Sensors With Global Positioning System (GPS) for Vehicle Dynamics Control

Abstract: This paper demonstrates a method of estimating several key vehicle states-sideslip angle, longitudinal velocity, roll and grade-by combining automotive grade inertial sensors with a Global Positioning System (GPS) receiver. Kinematic Kalman filters that are independent of uncertain vehicle parameters integrate the inertial sensors with GPS to provide high update estimates of the vehicle states and the sensor biases. Using a two-antenna GPS system, the effects of pitch and roll on the measurements can be quantified and are demonstrated to be quite significant in sideslip angle estimation. Employing the same GPS system as an input to the estimator, this paper develops a method that compensates for roll and pitch effects to improve the accuracy of the vehicle state and sensor bias estimates. In addition, calibration procedures for the sensitivity and cross-coupling of inertial sensors are provided to further reduce measurement error The resulting state estimates compare well to the results from calibrated models and Kalman filter predictions and are clean enough to use in vehicle dynamics control systems without additional filtering.

Virtual sensor: application to vehicle sideslip angle and transversal forces

Abstract: This paper compares four observers (virtual sensors) of vehicle sideslip angle and lateral forces. The first is linear and uses a linear vehicle model. The remaining observers use an extended nonlinear model. The three nonlinear observers are: extended Luenberger observer, extended Kalman filter and sliding-mode observer. Modeling, model simplification, and observers are described, and an observability analysis is performed for the entire vehicle trajectory. The paper also deals with three different sets of sensors to see the impact of observers results. Comparison is first done by simulation on a valid vehicle simulator, and then observers are used on experimental data. Our study shows that observers are more accurate than simple models as regards unmeasurable variables such as sideslip angle and transversal forces. It also shows that speed of center of gravity is not an indispensable variable here.

Estimation of vehicle roll and road bank angle

Abstract: This work presents a new method for identifying road bank and vehicle roll separately using a disturbance observer and a vehicle dynamic model. The authors have previously shown that vehicle states and parameters of a vehicle model can be precisely estimated using measurements from Global Positioning System (GPS) and Inertial Navigation System (INS) sensors. Based on these results, a dynamic model, which includes vehicle roll as a state and road bank as a disturbance, is first introduced. A disturbance observer is then implemented from the vehicle model using estimated vehicle states. Experimental results verify that the estimation scheme is giving appropriate estimates of the vehicle roll and road bank angles separately.

Fundamentals of Rail Vehicle Dynamics: Guidance and Stability

Abstract: Alan Wickens was Director of Research at British Rail, and already highly respected internationally in the field of railway vehicle dynamics, when this reviewer joined BR Research as a new graduate in 1980. At that time, much of the basic knowledge in railway engineering was being developed by the state railways and was generally passed on from one generation to the next. The world has changed since then and an understanding of the railway system is now required by many engineers within the wider railway industry and its diverse suppliers. Vehicle dynamics is now studied across many organizations, in particular through the use of several commercially available software packages. It is a relatively mature science, but the reliance on a software package can lead to the neglect of the basic insight that was the hallmark of earlier generations of engineers. As the preface to the book puts it, ‘computer output must be tempered with understanding and scepticism’. It is therefore timely that this book on the fundamentals of rail vehicle dynamics should be published. Professor Wickens, now Emeritus Professor at Loughborough University, was largely responsible for defining modern rail vehicle dynamics, beginning in the 1960s, and is thus well qualified to write the definitive text on this subject. As stated in its title, this book is about fundamentals. It therefore sets out to describe principles, not the specifics, of any particular vehicle design. However, as its opening sentence states, ‘the railway vehicle is one of the most complex dynamical systems in engineering’. Thus, although it is about fundamentals, it is not suitable on its own as an introductory text for the complete beginner. It requires, in fact, quite a wide prior subject knowledge of both dynamic analysis and the railway system. For example, concepts such as cant, cant deficiency, conicity or Hertzian stiffness are given little explanation. Chapter 1 forms a brief introduction to the basic concepts of the railway vehicle dynamic system. Chapter 2 sets out the equations of motion of the wheelset and ultimately the two-axle vehicle, including coverage of creep forces and creepage. Subsequent chapters deal with the issues of guidance, principally curving behaviour, and stability, which is the onset of unstable ‘hunting’ behaviour at a certain speed. Chapter 3 covers the single wheelset, Chapters 4 and 5 the two-axle vehicle or bogie and Chapter 6 the bogie vehicle; the last three chapters deal with three-axle vehicles, articulated vehicles and unsymmetrical vehicles. The compromises in vehicle design between the requirements for curving and stability lie at the heart of most vehicle dynamics calculations. As is clear from the title, no attention is given to vertical dynamics or ride, which would require another book on their own. A strong point is that the book is well grounded in literature. Around 250 references are given, although as they are given at the end of each chapter this number includes some overlap; a single reference list would have been preferable in many ways. The historical basis of the subject is also well covered, as well as aspects that bring the topic up to date quite well. Inevitably, the references include some BR Research reports, which are not generally available. Nevertheless, the comprehensive survey of literature included in the book is a very useful aspect. The text is well written, if difficult in places. Throughout, graphs are given of numerical examples that are mainly helpful in illustrating the text, although the interpretation of some of the less obvious figures could be explained more clearly in places. Mostly the data used in producing the examples are given, the main exception being the ‘typical’ wheel and rail transverse profiles used throughout, which are only given graphically. The inclusion of these data, and possibly example programs either in appendices or on an enclosed disc, would have enhanced the usefulness of the book, allowing readers to explore various aspects for themselves. From a production point of view, the quality of the figures is rather varied, with many graphs suffering from quantization effects, making the lines ‘wiggly’ when presumably this is not intended. Where multiple lines are present in a single graph, which is often, they are mostly of the same line style, which makes identification difficult at times. The system of section and equation numbering can be rather confusing, although it is explained clearly at the beginning, and it is not clear when looking at an average page in which section or chapter it is located. Despite these minor criticisms, as a thorough and definitive text on a difficult subject this book should be widely welcomed. D J Thompson Institute of Sound and Vibration University of Southampton 265

Three Dimensional Receding Horizon Control for UAVs

Abstract: This paper presents a receding horizon controller (RHC) that can be used to design trajectories for an aerial vehicle flying through a three dimensional terrain with obstacles and no-fly zones. To avoid exposure to threats, the paths are chosen to stay as close to the terrain as possible, but the vehicle can choose to pop-up over the obstacles if necessary. The approach is similar to our previous two-dimensional algorithms that construct a coarse cost map to provide approximate paths from a sparse set of nodes to the goal and then use Mixed-integer Linear Programming (MILP) optimization to design a detailed trajectory. The main contribution of this paper is to extend this approach to 3D, in particular providing a new algorithm for connecting the cost map and the detailed path in the MILP. This connection is done by introducing a new cost-to-go function that includes an altitude penalty and accounts for the vehicle dynamics. Initial guess for MILP RHC is constructed from the previous solution and is shown to reduce the solution time. Several simulation results are presented to show that the path planning algorithm yields good overall performance and is computationally tractable in a complex environment.

The use of GPS for vehicle stability control systems

Abstract: This paper presents a method for using global positioning system (GPS) velocity measurements to improve vehicle lateral stability control systems. GPS can be used to calculate the sideslip angle of a vehicle without knowing the vehicle model. This measurement is combined with other traditional measurements to control the lateral motion of the vehicle. Noise estimates are provided for all measurement systems to allow the sensors to be accurately represented. Additionally, a method to calculate the lateral forces at the tires is presented. It is shown that the tire estimation algorithm performs well outside the linear region of the tire. Results for the controller and force calculations are shown using a nonlinear model to simulate the vehicle and the force calculations are validated with experimental measurements on a test vehicle.

Integrated vehicle dynamics control using active brake, steering and suspension systems

Abstract: Active chassis systems like brake, steering, suspension and propulsion systems are increasingly entering the market. In addition to their basic functions, these systems may be used for functions of integrated vehicle dynamics control. A global architecture is required to prevent negative interference, for an optimised functionality and for managing system complexity. Several approaches are known under names like Integrated or Global Chassis Control and Integrated Vehicle Dynamics Control. Vehicle Dynamics Management (VDM) is the Bosch approach for co-ordinating vehicle dynamics functions by integrated control of active chassis systems. Its essential features are a clearly structured, extensible functional architecture with appropriate control structures and system interfaces with physical meaning.

Vehicle dynamics model for estimating maximum light-duty vehicle acceleration levels

Abstract: A vehicle dynamics model for predicting maximum light-duty vehicle accelerations for use within a microscopic traffic simulation environment is presented and validated. The research also constructs a database of unconstrained vehicle acceleration data for 13 light-duty vehicles and trucks. With the use of the field data, the proposed vehicle dynamics model is validated and compared with a number of state-of-the-art vehicle acceleration models, including the Searle model and the dual-regime, linear decay, and polynomial models. The advantages of the proposed model include its ability to predict vehicle behavior accurately with readily available input parameters and its flexibility in estimating acceleration rates of both large and small vehicles on varied types of terrain.

Vehicle dynamics control apparatus

Abstract: In a vehicle dynamics control apparatus capable of balancing a vehicle dynamics stability control system and a lane deviation prevention control system, a cooperative control section is provided to make a cooperative control between lane deviation prevention control (LDP) and vehicle dynamics stability control (VDC). When a direction of yawing motion created by LDP control is opposite to a direction of yawing motion created by VDC control, the cooperative control section puts a higher priority on VDC control rather than LDP control. Conversely when the direction of yawing motion created by LDP control is identical to the direction of yawing motion created by VDC control, a higher one of the LDP desired yaw moment and the VDC desired yaw moment is selected as a final desired yaw moment, to prevent over-control, while keeping the effects obtained by both of VDC control and LDP control.

Robust two degree-of-freedom vehicle steering controller design

Abstract: Robust steering control based on a specific two degree-of-freedom control structure is used here for improving the yaw dynamics of a passenger car. The usage of an auxiliary-steering actuation system for imparting the corrective action of the steering controller is assumed. The design study is based on six operating conditions for vehicle speed and the coefficient of friction between the tires and the road representing the boundary of the operating domain of the vehicle. The design is carried out by finding the region in controller parameter plane where Hurwitz stability and a mixed-sensitivity frequency-domain constraint are simultaneously satisfied. A velocity-based gain scheduling type implementation is used. Moreover, the steering controller has a fading effect that leaves the low-frequency driving task to the driver, intervening only when necessary. The effectiveness of the final design is demonstrated with linear simulations and nonlinear simulations using a highly realistic model of an actual car.

Self sustaining bicycle robot with steering controller

Abstract: Bicycle is a transportation device without any environmental burden. However, bicycle is unstable in itself and it is fall down without human assistance like steering handle or moving upper body. In these days, electric power assistance bicycles are used practically, but all of those bicycles merely assist human with pedal driving and there are no bicycles that help to stabilize its position. Hence, stabilizing the posture and realizing stable driving of a bicycle have been researched. Dynamic model of running bicycle is complicated and it's hard to recognize completely. However, assuming that the rider doesn't move upper body, dynamics of bicycle is represented in equilibrium of gravity and centrifugal force. Centrifugal force is risen out from the running velocity and turning radius determined by steering angle. Under these conditions, it is possible to stabilize bicycle posture by controlling its steering. In this paper, the dynamic model derived from equilibrium of gravity and centrifugal force is proposed. Then the control method for bicycle steering based on acceleration control is proposed. Finally, the validity of this method is proved by the simulations and experimental results.

A study on lateral speed estimation methods

Abstract: The estimation of vehicle lateral speed, a critical variable for vehicle stability control, four-wheel-steering and other advanced dynamic control systems, is studied in this paper. We presented three different approaches, one each from three categories: transfer function approach, state-space approach, and kinematics approach. The first two methods rely on a vehicle dynamic (bicycle) model, and the last approach is based on the kinematics relationship of measured signals. The basic formulation of all three methods assumed that the road bank angle is negligible, and thus needs to be enhanced by a road bank angle estimation algorithm to work satisfactorily when the road bank is significant. The performance of these three (enhanced) methods are investigated using simulation and experimental data. For the experimental verification, we present four cases: nominal (high friction, flat road), banked road, low-friction, and low-friction-near-spin. Weakness of the three estimation algorithms is discussed.

Rollover stability index including effects of suspension design. in: occupant and vehicle responses in rollovers

Abstract: With the growing popularity of vehicles with high centers of gravity, the evaluation of rollover propensity of these vehicles becomes an issue of increasing importance. This chapter on a rollover stability index is from a comprehensive textbook on occupant and vehicle responses in rollovers. The author proposes a simple model to predict vehicle propensity to rollover; the model includes the effects of suspension and tire compliance. The model uses only a few parameters, most of which are known at the design stage. The author compares the lateral accelerations at the rollover threshold that are predicted by the model to the results of simulations. In the simulations, vehicles with the same static stability factor, but with different suspension characteristics and payloads, are subjected to roll-inducing handling maneuvers. The results of simulations correlate well with the predictions based on the proposed model. An analytical expression for the optimal roll center height from the viewpoint of rollover resistance was developed.

A sensorless optimal control system for an automotive electric power assist steering system

Abstract: This paper considers the analysis and design of a double-pinion-type electric power assist steering (EPAS) control system. A simplified model of the augmented steering assembly-electric motor system is developed using Lagrangian dynamics, and an optimal controller structure for the model is proposed. Three main advances to the state of the art are presented in this paper. First, a state-space design model is used rather than an input-output model. A state-space formulation for a system model that incorporates motor electrical dynamics is obtained with the assist motor angular position as the output. Second, linear quadratic regulator (LQR) and Kalman filter techniques are employed to arrive at an optimal controller for the EPAS system. The selection of weighting coefficients for the LQR cost function is discussed. Finally, the authors present a control strategy that eliminates the steering column torque sensor, a critical component in existing EPAS controller designs. The proposed control strategy presents an opportunity to improve EPAS system performance and also reduce system cost and complexity.

A semi-empirical three-dimensional model of the pneumatic tyre rolling over arbitrarily uneven road surfaces

Abstract: Nowadays virtual prototyping tools play an important part in the development of vehicles. For studying the dynamics of a vehicle, complex vehicle models are required that are composed of several accurately modelled components. As the tyre constitutes the only contact between the vehicle and the road surface, it is one of the most important components of a vehicle model. For performing ride comfort and durability analyses, there is a need for accurate tyre models that can predict the loads that are transmitted from the tyre to the wheel axle when driving over road irregularities. In this study, such a tyre simulation model is developed that can represent the dynamic response of a tyre when rolling over uneven road surfaces. The approach followed is the combination of the well-known rigid ring dynamic tyre model and a suitable enveloping model that generates a three-dimensional effective road surface, which is used as input for the rigid ring model. The thesis deals with the development of the enveloping models and with the extension of the rigid ring tyre model so that this model is capable of handling the effective road surface. It is shown that the combination of the rigid ring model and the enveloping model can be used successfully to describe the tyre dynamic response to uneven road surfaces. In this research project, numerous experiments have been carried out for model development, parameter identification and model validation. The results of many of these experiments are presented in the thesis.

Motion stabilization control of electric vehicle under snowy conditions based on yaw-moment observer

Abstract: In this paper, novel direct yaw moment control and anti-skid control are proposed for electrical vehicles with two in-wheel motors. The proposed controllers are composed of double disturbance observers. The inner-loop observer controls the vehicle traction, and outer-loop observer stabilizes the yawing motion. The advantages of these approaches are 1) the stability robustness for road condition is guaranteed and 2) the proposed controllers require no immeasurable parameters. The experiments demonstrate the performance of these controllers under snowy conditions, and the stability is theoretically analyzed as inertia variation and dead-time system.

Simulation and control of an automotive dry clutch

Abstract: In this work the dynamic behavior and control of an automotive dry clutch is analyzed. Thereto, a straight-forward model of the clutch is embedded within a dynamic model of an automotive powertrain comprising an internal combustion engine, drivetrain and wheels moving a vehicle through tire-road adhesion. The engagement of the clutch is illustrated using the model best suited for simulation, based on work of Karnopp. These simulation results are used for conceiving a decoupling controller for the engine and clutch torque. Simulation results with the controller showing significant improvement over the un-controlled case in terms of vehicle launch comfort. A modified controller is proposed that results in even more appreciated drive comfort while not deteriorating other system behavior.

Observer Kalman filter identification of an autonomous underwater vehicle

Abstract: This paper deals with the identification of linear discrete-time multivariable models of an autonomous underwater vehicle (AUV). The observer Kalman filter identification (OKID) method is applied with the main objective of evaluating its effectiveness to the experimental identification of the dynamic behaviour of an AUV. After presenting the mathematical background of the OKID algorithm, the proposed method is first validated on the basis of simulated data of both the linearized and nonlinear yaw dynamics of an AUV. Subsequently, the identification algorithm is applied to a set of experimental data. Results suggest that the method can be an efficient tool for the experimental identification of AUV dynamics.

California Partners for Advanced Transit and Highways (PATH)

Abstract: In the first two chapters of this report, the development of discrete compression brake and transmission models is explained. In the vehicle model development, special efforts have been put in transmission shifting scheduling. Transmission up-shift and down-shift scheduling are separated in the modelling. Hysteresis during shifting is introduced to reduce chattering. A compression brake effect on transmission shifting is identified and considered in the modelling. The new transmission shifting model has been validated through experimental data. The transmission shifting model is combined with the compression brake model and the model of the longitudinal vehicle dynamics for a high-fidelity predictive simulation software tool. Power-width-modulation (PWM) actuation for brake coordination is proposed to further exploit the capacity of the compression brake and reduce the usage of service brake. Simulation results indicates that the PWM actuation strategy will have the same speed regulation performance as the direct torque split strategy, while the usage of the service brake is significantly reduced, and the compression brake can handle a down slope of -4 when tracking a speed of 56 mile per hour. Simulation results also indicated the importance of vehicle mass and road grade estimation in controller performance. The estimation problem is addressed in detail next. In the third chapter, a recursive least square scheme with multiple forgetting factors is proposed for on-line estimation of road grade and vehicle mass. The estimated mass and grade can be used to robustify many automatic controllers in conventional or automated heavy-duty vehicles. We demonstrate with measured test data from the July 26-27, 2002 test dates in San Diego, CA, that the proposed scheme estimates mass within 5% of its actual value and tracks grade with good accuracy. The experimental setup, signals, their source and their accuracy

Gain-scheduled controller design based on descriptor representation of LPV systems: application to flight vehicle control

Abstract: This paper is concerned with a synthesis method of gain-scheduled controllers based on descriptor representations of LPV systems and its application to design of flight vehicle control. By representing a linear parameter-varying system in the descriptor form, parameter-dependent LMI to seek a gain-scheduled controller are formulated so that they have simple structure with respect to the parameter. A gain-scheduled controller is computed directly via an explicit formula in terms of the variable of LMI for LPV descriptor systems. This synthesis procedure is applied to design of flight vehicle control to satisfy multiple control specifications under large variation of the airspeed. Dynamics of the vehicle is modeled as an LPV descriptor system and a gain-scheduled controller is obtained by solving the proposed LMI. Control performance is improved by employing parameter-dependent Lyapunov matrices.

The DARPA grand challenge - development of an autonomous vehicle

Abstract: The DARPA Grand Challenge (DGC) was an opportunity to test autonomous vehicles in a competitive situation. In addition to intelligent behaviour, the participating vehicles must also exhibit ruggedness and endurance in order to survive the fast ride over rough terrain ("win with the software- lose with the hardware"). The SciAutonics teams decided to use compact and agile vehicles that employ proven mechanical designs very suitable for the desert environment. 4-wheel drive ensures robust controllability even in slippery ground, and a roll cage protects the vehicle components from damage in case of a collision. The control system relies primarily on a differential GPS (Starfire) and a set of inertial sensors for navigating between the given set of waypoints. A sensor suite using infrared laser (LIDAR) and ultrasound sensing provides the capability of obstacle avoidance and path following. This paper shows the components of the vehicle and results from driving at the DGC.

A full-car model for active suspension - some practical aspects

Abstract: In this paper a full-car dynamic model with passengers has been designed. A four conventional quarter-car suspension models are connected to a get full-car model. In the next, braking, accelerating and steering influences are reflected, i.e. longitudinal and lateral acceleration are considered. Then impacts of steering to lateral motion are discussed. Finally passengers' models were added. The resulting car model has been implemented in Matlab software. Usage of a vehicle model for simulation in many automotive control applications has great significance in money savings for test-beds, test circuits and another devices, which in simulations are not required.

Design and experimental study of an ultrasonic sensor system for lateral collision avoidance at low speeds

Abstract: In this study, we-design and implement an ultrasonic sensor system for lateral collision avoidance of vehicles at low speeds The developed sensor system is useful for detecting vehicles, motorcycles, bicycles and pedestrians that pass by the lateral side of a vehicle The system can be adopted to enhance the rear-view mirrors of present vehicles, which have blind spots on the lateral sides Ultrasonic sensors, which have been widely used on cars for rear object detection during parking, are developed for lateral object detection at low speeds Detailed experimental studies are presented in this paper Experimental results show that the proposed system can detect a vehicle at speeds up to 40 km/hr with a maximum range of 6 meters Moreover, the influence of wind on the measurement is also investigated The developed sensor system gives satisfactory results for a wind speed up to 35 km/hr

Estimation of slip angles using a model based estimator and GPS

Abstract: This paper demonstrates a method for estimating key vehicle states and sensor biases using Global Positioning System (GPS) and an Internal Navigation System (INS). Two Kalman filters, a model based filter and a kinematic filter, are used to integrate the INS sensors with GPS heading and velocity to provide a high update rate of the vehicle states and sensor biases. Additional key vehicle parameters, such as tire-cornering stiffness, are identified and used to correct the model based estimator. The vehicle estimated states compare favorable with values predicted with a theoretical model.

Active steering systems based on model reference adaptive nonlinear control

Abstract: This paper presents a model reference adaptive nonlinear control strategy for active steering of a two wheel steering car which is realized by steer-by-wire technology. The ideal fixed property of a steering system, which is provided by a reference model, is attained by D * control. The proposed method can treat the nonlinear relationships between the slip angles and the lateral forces on tires, and the uncertainties on the friction of the road surface, whose compensations are very important under critical situations. Some results of realtime simulation with a steering equipment show the effectiveness of the proposed method.