Showing papers on "Vehicle dynamics published in 2002"

Aircraft trajectory planning with collision avoidance using mixed integer linear programming

Abstract: Describes a method for finding optimal trajectories for multiple aircraft avoiding collisions. Developments in spacecraft path-planning have shown that trajectory optimization including collision avoidance can be written as a linear program subject to mixed integer constraints, known as a mixed-integer linear program (MILP). This can be solved using commercial software written for the operations research community. In the paper, an approximate model of aircraft dynamics using only linear constraints is developed, enabling the MILP approach to be applied to aircraft collision avoidance. The formulation can also be extended to include multiple waypoint path-planning, in which each vehicle is required to visit a set of points in an order chosen within the optimization.

Semi-autonomous adaptive cruise control systems

Abstract: The concept of a semi-autonomous adaptive cruise control (SAACC) system is developed, which enjoys significant advantages over present day adaptive cruise control (ACC) systems in terms of highway safety and traffic flow capacity. The semi-autonomous systems combine the deployment advantages of autonomous vehicles with the performance advantages of fully automated highway systems (AHSs) in which vehicles operate cooperatively as a platoon. Unlike platoon systems, the semi-autonomous systems are immediately deployable on present day highways, where both manually driven and adaptive cruise controlled vehicles can coexist. Our theoretical results show that the proposed system is able to maintain smaller time gaps safely, is string stable, and is guaranteed to have smaller actuator inputs than a standard autonomous ACC system. The simulation results indicate that more accurate and smoother tracking, smaller time gaps, smaller control efforts, and increased robustness to vehicle dynamics are achieved by semi-autonomous control.

Vehicle Handling improvement by Active Steering

Abstract: Summary This paper first analyses some stability aspects of vehicle lateral motion, then a coprime factors and linear fractional transformations (LFT) based feedforward and feedback H 8 control for vehicle handling improvement is presented. The control synthesis procedure uses a linear vehicle model which includes the yaw motion and disturbance input with speed and road adhesion variations. The synthesis procedure allows the separate processing of the driver reference signal and robust stabilization problem or disturbance rejection. The control action is applied as an additional steering angle, by combination of the driver input and feedback of the yaw rate. The synthesized controller is tested for different speeds and road conditions on a nonlinear model in both disturbance rejection and driver imposed yaw reference tracking maneuvers.

Nonlinear model predictive tracking control for rotorcraft-based unmanned aerial vehicles

Abstract: We investigate the feasibility of a nonlinear model predictive tracking control (NMPTC) for autonomous helicopters. We formulate a NMPTC algorithm for planning paths under input and state constraints and tracking the generated position and heading trajectories, and implement an on-line optimization controller using a gradient-descent method. The proposed NMPTC algorithm demonstrates superior tracking performance over conventional multi-loop proportional-derivative (MLPD) controllers especially when nonlinearity and coupling dominate the vehicle dynamics. Furthermore, NMPTC shows outstanding robustness to parameter uncertainty, and input saturation and state constraints are easily incorporated. When the cost includes a potential function with a possibly moving obstacle or other agents' state information, the NMPTC can solve the trajectory planning and control problem in a single step. This constitutes a promising one-step solution for trajectory generation and regulation for RUAVs, which operate under various uncertainties and constraints arising from the vehicle dynamics and environmental contingencies.

GPS-based real-time identification of tire-road friction coefficient

Abstract: Vehicle control systems such as collision avoidance, adaptive cruise control, and automated lane-keeping systems as well as ABS and stability control systems can benefit significantly from being made "road-adaptive." The estimation of tire-road friction coefficient at the wheels allows the control algorithm in such systems to adapt to external driving conditions. This paper develops a new tire-road friction coefficient estimation algorithm based on measurements related to the lateral dynamics of the vehicle. A lateral tire force model parameterized as a function of slip angle, friction coefficient, normal force and cornering stiffness is used. A real-time parameter identification algorithm that utilizes measurements from a differential global positioning system (DGPS) system and a gyroscope is used to identify the tire-road friction coefficient and cornering stiffness parameters of the tire. The advantage of the developed algorithm is that it does not require large longitudinal slip in order to provide reliable friction estimates. Simulation studies indicate that a parameter convergence rate of 1 s can be obtained. Experiments conducted on both dry and slippery road indicate that the algorithm can work very effectively in identifying a slippery road.

Self-adaptive recurrent neuro-fuzzy control for an autonomous underwater vehicle

Abstract: This paper presents the utilization of a self-adaptive recurrent neuro-fuzzy control as a feedforward controller and a proportional-plus-derivative (PD) control as a feedback controller for controlling an autonomous underwater vehicle (AUV) in an unstructured environment. Without a priori knowledge, the recurrent neuro-fuzzy system is first trained to model the inverse dynamics of the AUV and then utilized as a feedforward controller to compute the nominal torque of the AUV along a desired trajectory. The PD feedback controller computes the error torque to minimize the system error along the desired trajectory. This error torque also provides an error signal for online updating the parameters in the recurrent neuro-fuzzy control to adapt in a changing environment. A systematic self-adaptive learning algorithm, consisting of a mapping-constrained agglomerative clustering algorithm for the structure learning and a recursive recurrent learning algorithm for the parameter learning, has been developed to construct the recurrent neuro-fuzzy system to model the inverse dynamics of an AUV with fast learning convergence. Computer simulations of the proposed recurrent neuro-fuzzy control scheme and its performance comparison with some existing controllers have been conducted to validate the effectiveness of the proposed approach.

Evolution of Electronic Control Systems for Improving the Vehicle Dynamic Behavior

Abstract: Starting with ABS (Antilock Brake System) the steps towards integrated active safety systems dealing with vehicle dynamics is shown. While ABS and TCS were initially designed as open loop controllers for the lateral vehicle motion a first approach towards closed loop control of the lateral vehicle motion for active safety systems was realized by ESP (Electronic Stability Program. Estimation algorithms and model following control are used with ESP to compensate for the lack of sensors. Since 2001 ESP is available for cars with an electro hydraulic brake system. The extension of ESP in combination with active front steering is expected to enter the market in 2003.

Optimal and Cooperative Control of Vehicle Formations

Abstract: Control of vehicle formations has emerged as a topic of significant interest to the controls community. In applications such as microsatellites and underwater vehicles, formations have the potential for greater functionality and versatility than individual vehicles. In this thesis, we investigate two topics relevant to control of vehicle formations: optimal vehicle control and cooperative control. The framework of optimal control is often employed to generate vehicle trajectories. We use tools from geometric mechanics to specialize the two classical approaches to optimal control, namely the calculus of variations and the Hamilton-Jacobi-Bellman (HJB) equation, to the case of vehicle dynamics. We employ the formalism of the covariant derivative, useful in geometric representations of vehicle dynamics, to relate variations of position to variations of velocity. When variations are computed in this setting, the evolution of the adjoint variables is shown to be governed by the covariant derivative, thus inheriting the geometric structure of the vehicle dynamics. To simplify the HJB equation, we develop the concept of time scalability enjoyed by many vehicle systems. We employ this property to eliminate time from the HJB equation, yielding a purely spatial PDE whose solution supplies both finite-time optimal trajectories and a time-invariant stabilizing control law. Cooperation among vehicles in formation depends on intervehicle communication. However, vehicle communication is often subject to disruption, especially in an adversarial setting. We apply tools from graph theory to relate the topology of the communication network to formation stability. We prove a Nyquist criterionthat uses the eigenvalues of the graph Laplacian matrix to determine the effect of the graph on formation stability. We also propose a method for decentralized information exchange between vehicles. This approach realizes a dynamical system that supplies each vehicle with a common reference to be used for cooperative motion. We prove a separation principle that states that formation stability is achieved if the information flow is stable for the given graph and if the local controller stabilizes the vehicle. The information flow can be rendered highly robust to changes in the graph, thus enabling tight formation control despite limitations in intervehicle communication capability.

Target cascading in vehicle redesign: a class VI truck study

Abstract: The analytical target cascading process is applied to the redesign of a U.S. class VI truck. Necessary simulation and analysis models for predicting vehicle dynamics, powertrain, and suspension behaviour are developed. Vehicle design targets that include improved fuel economy, ride quality, driveability, and performance metrics are translated into system design specifications, and a consistent final design is obtained. Trade-offs between conflicting targets are identified. The study illustrates how the analytical target cascading process can reduce vehicle design cycle time while ensuring physical prototype matching, and how costly design iterations late in the development process can be avoided.

Development of a Six-Degree of Freedom Simulation Model for the REMUS autonomous Underwater Vehicle

Abstract: Describes the development and verification of a six degree of freedom, non-linear simulation model for the REMUS AUV, the first such model for this platform. In this model, the external forces and moments resulting from hydrostatics, hydrodynamic lift and drag, added mass, and the control inputs of the vehicle propeller and fins are all defined in terms of vehicle coefficients. The paper briefly describes the derivation of these coefficients. The equations determining the coefficients, as well as those describing the vehicle rigid-body dynamics, are left in non-linear form to better simulate the inherently non-linear behavior of the vehicle. Simulation of the vehicle motion is achieved through numeric integration of the equations of motion. The simulator output is then verified against vehicle dynamics data collected in experiments performed at sea. The simulator is shown to accurately model the motion of the vehicle. The paper concludes with recommendations for future model validation experiments.

Controller parameterization for disturbance response decoupling: application to vehicle active suspension control

Abstract: This paper derives a parameterization of the set of all stabilizing controllers for a given plant which leaves some prespecified closed-loop transfer function fixed. This result is motivated by the need to independently shape several different disturbance transmission paths in vehicle active suspension control. The result is studied in the context of quarter-, half-, and full-car vehicle models, to derive appropriate controller structures. A controller design is carried out for the full-car case and simulated with a nonlinear vehicle dynamics model.

Road Slope and Vehicle Mass Estimation Using Kalman Filtering

Abstract: SUMMARYKalman filtering is used as a powerful method to obtain accurate estimation of vehicle mass and road slope. First the problem of estimating the slope when the vehicle mass is known is studied using two different sensor configurations. One where speed is measured and one where both speed and specific-force is measured. A filter design principle is derived guaranteeing the estimation error under a worst case situation (when assuming first order dynamics). The simultaneous estimation problem required an Extended Kalman Filter (EKF) design when measuring speed only whereas the additional specific force ease yielded a simple filter structure with a time-variant measurement equation. Additionally the filter needs present propulsion force which in our case is calculated form the engine speed and amount of fuel injected. When the vehicle uses the foundation brakes the estimates are frozen since varying friction properties makes the braking force unknown. Both sensor configurations are concluded to be robus...

Active wheel steering and yaw moment control combination to maximize stability as well as vehicle responsiveness during quick lane change for active vehicle handling safety

Abstract: The aim of this paper is not only to present various methods for combining lateral force and yaw moment control but also to find out how the mix between them should be applied to maximize the stability limit as well as vehicle responsiveness. Approximated two-degree-of-freedom (2DOF) vehicle model responses of side-slip angle and yaw rate are used to introduce the required total lateral force and yaw moment control. Three different cases of combining lateral force and direct yaw moment control have been investigated using computer simulations. A direct yaw moment control to follow the yaw rate response only is taken as a comparison case in order to show the effect of the combined control on vehicle stability and responsiveness. A computer simulation of a closedloop driver-vehicle system subjected to quick lane change with braking is used to prove the influence of the combined control. It is found that the influence of the combined control on vehicle stability and responsiveness is significant.

Motion dynamics of a rover with slip-based traction model

Abstract: This paper investigates kinetic behavior of a planetary rover with attention to tire-soil traction mechanics and articulated body dynamics, and thereby study the control when the rover travels over natural rough terrain. Experiments are carried out with a rover test bed to observe the physical phenomena of soils and to model the traction mechanics, using the tire slip ratio as a state variable. The relationship of load-traction factor versus the slip ratio is modeled theoretically then verified by experiments, as well as specific parameters to characterize the soil are identified. A dynamic simulation model is developed considering the characteristics of wheel actuators, the mechanics of tire-soil traction, and the articulated body dynamics of a suspension mechanism. Simulations are carried out to be compared with the corresponding experimental data and verified to represent the physical behavior of a rover.

The Development of a Numerical Model for Railway Vehicles Comfort Assessment Through Comparison With Experimental Measurements

Abstract: Summary Appropriate modelling of the dynamic behaviour of the vehicle components, particularly car body flexibility, is essential in the analysis of railway vehicle comfort performance, especially for high-speed vehicles. This paper deals with the description of the adopted approach to set up a complex numerical model of the railway vehicle, suitable for reproducing its dynamic behaviour in the 0–50 Hz frequency range, especially with respect to the ride comfort problem. The implemented model is used to simulate in time domain the dynamic behaviour of a vehicle running on irregular track. Numerical results are validated by means of comparison with experimental data of on-line tests. Finally, the analytical model is used to perform a sensitivity analysis, in order to point out the parameters that most significantly affect comfort.

Vehicle and object models for robust tracking in traffic scenes using laser range images

Abstract: Detection and modeling of dynamic traffic scenes around a, driving passenger car is the long-term aim of the research project ARGOS at the University of Ulm. Each object close to the own car should be modeled and tracked using a specific individual dynamic model. The object classification is based on the geometric outlines and the dynamic behavior. For any sensor combinations usable to detect the environment, the velocity of the objects can be measured relatively to the movement of own vehicle. To. get the absolute velocity of the objects, the motion of the own vehicle must be measured for which the well know bicycle model is used. This ego-model is fed by sensor signals provided anyway by ABS, ASR or ESP. To eliminate the own motion from the object measurements, several coordinate transformations are required in the different stages of data processing. A proposal is given on how to solve this problem when using a laser range finder as a sensing device. Moreover, a simple object model is introduced for this task in order to save processing power. The algorithms can extended towards a multihypothesis approach which will result a more robust classification and tracking algorithm.

Variable power vehicle dynamics model for estimating truck accelerations

Abstract: This paper introduces the concept of a linearly increasing variable power to the basic vehicle dynamics model that has been proposed in the literature. The paper also calibrates the model to typical truck classifications 8–10 that travel along interstate highways in the United States. The proposed enhancement is demonstrated to result in significant improvements in vehicle performance curves, especially at low speeds when vehicles are engaged in gearshifts.

Integrated collision prediction and safety systems control for improved vehicle safety

Abstract: A control system for an automotive vehicle ( 50 ) has a radar or lidar system ( 22 ) used to generate a remote object signal. A vision system ( 26 ) confirms the presence of the target object in the detection zone. A controller ( 12 ) is coupled to the remote object sensor and a vehicle dynamics sensor and the brake system. The controller predicts a host vehicle trajectory in response to the host vehicle dynamic signal, determines an azimuth angle for the target object, determines an actuation value in response to the target range signal, the target relative velocity signal, the host vehicle trajectory, host vehicle brake system status and the target azimuth angle. The controller ( 12 ) activates a countermeasure in response to the actuation value.

Moving mass control for underwater vehicles

Abstract: We present two reduced-dimensional, noncanonical Hamiltonian models for a neutrally buoyant underwater vehicle coupled to an internal moving mass. It is expected that these models will be useful in designing nonlinear control laws for underwater gliders as well as for spacecraft, atmospheric re-entry vehicles, and other vehicles which use internal moving mass actuators. To illustrate, we investigate stability of a steady underwater vehicle motion using potential shaping feedback with a moving mass actuator.

Anti-lock braking control using a sliding mode like approach

Abstract: The paper starts with a brief history of the design of anti-lock brakes (ABS). The advantages of ABS are explained. For the analysis and controller design a nonlinear longitudinal car model is derived. It is shown that the dynamics can be separated conveniently into two different linear dynamics dependent on the tyre slip. The analysis of the dynamics show the highest possible braking performance. It is further shown that a continuous feedback law cannot not achieve the maximum braking performance. To achieve the maximum braking performance a sliding mode like controller design approach is suggested. The merits of this controller are shown in an example.

LPV control of a 6-DOF vehicle

Abstract: A linear parameter varying (LPV) controller design example for the position and attitude control of a spacecraft is presented. The six degree-of freedom (DOF) model including the aerodynamics is described. Simulations with the nonlinear 6-DOF model show the usefulness of the design procedure. The practical problem of "fast dynamics" in the controller is solved by an ad hoc method based on the use of a single quadratic Lyapunov function with pole clustering constraints for each frozen linear time invariant (LTI) system in the parameter variation set. The results show that the method facilitates simulation and allows for addressing implementation aspects such as the sampling rate.

Multiobjective control of a vehicle with triple trailers

Abstract: We consider the backing-up control of a vehicle with triple trailers using a model-based fuzzy-control methodology. First, the vehicle model is represented by a Takagi-Sugeno fuzzy model. Then, we employ the so-called "parallel distributed compensation" design to arrive at a controller that guarantees the stability of the closed-loop system consisted of the fuzzy model and controller. The control-design problem is cast in terms of linear matrix inequalities (LMIs). In addition to stability, the control performance considerations such as decay rate, constraints on input and output, and disturbance rejection are incorporated in the LMI conditions. In application to the vehicle with triple trailers setup, we utilize these LMI conditions to explicitly avoid the saturation of the steering angle and the jackknife phenomenon in the control design. Both simulation and experimental results are presented. Our results demonstrate that the fuzzy controller effectively achieves the backing-up control of the vehicle with triple trailers while avoiding the saturation of the actuator and "jackknife" phenomenon.

Interaction of Vehicles and Flexible Tracks by Co-Simulation of Multibody Vehicle Systems and Finite Element Track Models

Abstract: SUMMARYCo-Simulation gives a suitable framework for coupling software-tools specialized for the application in different fields of mechanics and/or physics, particularly if based on different mathematical methods For the computational analysis of a vehicle's running behaviour usually a Multibody System approach is used while flexible tracks—representing for example a bridge—are best examined with the help of Finite Element software Now, for the simulation of a vehicle running on a flexible track without neglecting the inherent interaction, an obvious and promising strategy is to simulate each of the two subsystems (vehicle and flexible track) with the appropriate software concurrently and to exchange the interfacing data at discrete communication points To minimize the numerical effort, the track's finite element model can be reduced modally to a linear description in a pre-processing step additionally; the resulting linear equations of motion of the track can then be solved analytically with high effi

Linear parameter varying controller for automated lane guidance: experimental study on tractor-trailers

Abstract: Proposes a linear parameter-varying (LPV) controller design for automated lane keeping for vehicles. The lane keeping objective is to keep the vehicle centered with respect to the lane boundaries by applying appropriate steering action. Most current implementation of lane keeping controllers were based on linear synthesis techniques because linear techniques offer a direct tradeoff between steering action, passenger comfort, robustness, and tracking performance. However, linear methods assume constant longitudinal velocity of the vehicle for controller synthesis. It is known that the position response of the vehicle to the steering input varies significantly with the longitudinal velocity of the vehicle. The LPV design technique deals with this issue by synthesizing a velocity dependent controller. The controller minimizes the induced /spl Lscr//sub 2/ norm of the closed loop from the road curvature to the tracking error. The design has been successfully implemented on a tractor-trailer vehicle and experiments conducted up to longitudinal velocity of 60 mi/h are presented.

Autonomous terrain characterisation and modelling for dynamic control of unmanned vehicles

Abstract: We discuss techniques to predict the dynamic vehicle response to various natural obstacles. This method can then be used to adjust the vehicle dynamics to optimize performance (e.g. speed) while ensuring that the vehicle is not damaged. This capability opens up a new area of obstacle negotiation for UGVs, where the vehicle moves over certain obstacles, rather than avoiding them, thereby resulting in more effective achievement of objectives. Robust obstacle negotiation and vehicle dynamics prediction requires several key technologies that are discussed in this paper. We detect and segment (label) obstacles using a novel 3D obstacle algorithm. The material of each labelled obstacle (rock, vegetation, etc) is then determined using a texture or color classification scheme. Terrain load-bearing surface models are then constructed using vertical springs to model the compressibility and traversability of each obstacle in front of the vehicle. The terrain model is then combined with the vehicle suspension model to yield an estimate of the maximum safe velocity, and predict the vehicle dynamics as the vehicle follows a path. This end-to-end obstacle negotiation system is envisioned to be useful in optimized path planning and vehicle navigation in terrain conditions cluttered with vegetation, bushes, rocks, etc. Results on natural terrain with various natural materials are presented.

Improvements in vehicle handling through integrated control of chassis systems

Abstract: In this paper, methods of improving vehicle stability and emergency handling using electronically controlled chassis systems are discussed. By analysing a simple nonlinear vehicle model in the yaw plane, it is shown that vehicles can become unstable during portions of handling manoeuvres performed at or close to the limit of adhesion. It is further demonstrated how small changes in the balance of tyre forces between front and rear axles may affect vehicle yaw moment and stability. The methods of effecting vehicle yaw dynamics using controllable brakes, steering, and suspension are discussed. Control authority of each chassis system, in terms of its ability to generate a corrective yaw moment, is evaluated and is shown to depend on the operating point of vehicle and tyres. Consequently, regions of effectiveness of each subsystem are defined, which is a prerequisite for development of integrated chassis control systems. Preliminary test results for a vehicle with integrated closed loop control of brakes and suspension, performing typical handling manoeuvres, are presented. They demonstrate the benefits of integrated control in terms of improved handling response, stability, and reduced driver steering effort.

Adaptive control of a hybrid electric vehicle

Abstract: A decentralized adaptive control system (ACS) for a four motor-generator four-wheel drive hybrid electric vehicle (HEV) is designed and its ability to deal with unknown tire dynamics, changing road surfaces, and vehicle loading is evaluated. A system composed of four separate adaptive controllers is designed to control the vehicle's speed, steering, side slip, and energy management system. A nonlinear simulation model for the vehicle dynamics and its power train components is developed and used to evaluate the performance of the ACS, while the vehicle is simultaneously turning and accelerating or braking under varying loading and icing conditions.

B2, an alternative two wheeled vehicle for an automated urban transportation system

Abstract: This paper describes the preliminary control work on a two-wheeled vehicle called B2 whose wheels belong to the same geometric axes. Closed-loop control is necessary because the passengers stand above the wheels, so that B2 behaves like an inverted pendulum. Using a simple model, two different control laws are compared. The first uses standard linear control techniques to achieve dynamic stability. Its most notable characteristic is that it stabilizes the vehicle inclination about the dynamic equilibrium by minimizing motor effort. A second control law approach, named PDC (parallel distributed compensation), is then investigated. This control law uses a fuzzy model and is another way of stabilizing the cabin angle and controlling the vehicle's speed. Simulations presented show the effectiveness of each control method.

Advanced guidance algorithms for spacecraft formation-keeping

Abstract: This paper presents advanced formation-keeping guidance algorithms that use linear programming (LP) to determine fuel-optimal control inputs and state trajectories. The overall formation-keeping problem is analyzed in terms of two key issues: (i) what dynamics model should be used to specify the desired state to maintain a passive aperture; and (ii) what dynamics model should be used in the LP to represent the motion about this state. Several linearized models of the relative dynamics are considered in this analysis, including Hill's equations for circular orbits, modified linear dynamics that partially account for the J/sub 2/ effects, and Lawden's equations for eccentric orbits. A controller is developed for formation-keeping using each of these models. A modified LP formulation is presented to include robustness to sensor noise while ensuring a feasible solution. The guidance algorithms are implemented in numerous very detailed nonlinear simulations that demonstrate effective control in the presence of all expected disturbances and sensor noises. The average fuel cost for the formation-keeping maneuvers over a two week simulation is on the order of 4 mm/s per orbit.

Analysis on dynamics of underwater robot manipulators based on iterative learning control and time-scale transformation

Abstract: A new method to analyze the dynamics of underwater robot manipulators is proposed in this paper. In the proposed method, hydrodynamic terms such as added mass, drag and buoyancy in dynamics of underwater robots are obtained by iterative learning control and time-scale transformation. The advantage of the proposed method is not to use parameter estimation of the dynamics. In this paper, we explain that the proposed method can be applied to hardware design, motion control and motion planning of underwater robots. Moreover, the experimental results using a 1-DOF and a 3-DOF manipulator demonstrate the effectiveness of the proposed method.