Showing papers on "Vehicle dynamics published in 1998"

Control of a nonholonomic mobile robot using neural networks

Abstract: A control structure that makes possible the integration of a kinematic controller and a neural network (NN) computed-torque controller for nonholonomic mobile robots is presented. A combined kinematic/torque control law is developed using backstepping and stability is guaranteed by Lyapunov theory. This control algorithm can be applied to the three basic nonholonomic navigation problems: tracking a reference trajectory, path following, and stabilization about a desired posture. Moreover, the NN controller proposed in this work can deal with unmodeled bounded disturbances and/or unstructured unmodeled dynamics in the vehicle. Online NN weight tuning algorithms do not require off-line learning yet guarantee small tracking errors and bounded control signals are utilized.

The Manchester Benchmarks for Rail Vehicle Simulation

Abstract: This volume contains the results of the Manchester Benchmarking exercise for railway vehicle dynamics simulation packages. Five of the main computer packages currently used for this purpose were examined in the exercise and the results are presented in the form of tables and graphs.

A Non-Linear Rubber Spring Model for Rail Vehicle Dynamics Analysis

Abstract: SUMMARY A non-linear, dynamic rubber spring model is proposed. It mainly aims at representing the mechanical behaviour of rubber suspension components in rail vehicle dynamics. The model is one-dimensional, has five parameters and is based on a superposition of elastic, friction and viscous forces. The model is implemented in the computer packages MATLAB and GENSYS. Comparisons between model and measurement results for harmonic excitations show good agreement. A procedure to determine the model parameters from only two measured force-displacement loops is described. The model represents a reasonable compromise between accuracy and computational effort and should be a suitable tool in rail vehicle dynamics analysis.

A comparative study of vision-based lateral control strategies for autonomous highway driving

Abstract: This paper will present the results of a comparative study of a set of vision-based control strategies that have been applied to the problem of steering an autonomous vehicle along a highway. The aim of this work has been to further our understanding of the characteristics of various control laws that could be applied to this problem with a view to making informed design decisions. The control strategies that we explored include a lead lag control law, a full-state linear controller and input-output linearizing control law. Each of these control strategies was implemented and tested on our experimental vehicle, a Honda Accord LX, both with and without a curvature feedforward component.

Path-tracking for articulated vehicles with off-axle hitching

Abstract: A technique that complements path-tracking controller design procedures based on exact linearization is proposed. The objective is to make these procedures applicable to vehicles whose kinematic model is not necessarily exactly linearizable (as a tractor-trailer with off-axle hitching or a load-haul-dump mining vehicle). A key element of our approach is to control a inexactly linearizable vehicle by associating to it an auxiliary (ghost) vehicle whose model can be exactly linearized and whose behavior satisfies certain compatibility conditions. Main features of this approach are illustrated by considering articulated vehicles with off-axle hitching (which are not exactly-linearizable), and by focusing attention to a geometric path-tracking design procedure recently developed by Sampei et al. (1993, 1995).

Vehicle Steering Intervention Through Differential Braking

Abstract: This paper examines the usefulness of a brake steer system (BSS) which uses differential brake forces for steering intervention in the context of Intelligent Transportation Systems. The resulting moment on the vehicle affects yaw rate and lateral position, thereby providing a limited steering function. The steering function achieved through BSS can then be used to control lateral position in an unintended road departure system. Control design models for the vehicle and the brake system are presented. A state feedback regulator and PID controller are developed to explore BSS feasibility and capability. Computer simulation results, using a nonlinear seven degree-of-freedom vehicle model are included, and show the feasibility and limitations of BSS.

Simplified Analysis of the Steady-State Turning of Complex Vehicles

Abstract: SUMMARY The classic analysis of the steady-state turning of the motor vehicle is based on a simple vehicle model in which lateral acceleration is the only motion variable that affects tire slip angles. This paper examines a more complex vehicle whose slip angles depend on lateral acceleration plus another motion variable. Trucks with multiple, nonsteering rear axles are one example of the complex vehicle. A general analysis of the complex vehicle together with analyses of linear and nonlinear trucks provide new insights into the understeer/oversteer quality of all vehicles. It is shown that a complex vehicle can be represented as a simple vehicle with an equivalent wheelbase. A physical interpretation of equivalent wheelbase for trucks and a method for its measurement are presented.

Fast local obstacle avoidance under kinematic and dynamic constraints for a mobile robot

Abstract: This paper presents an efficient approach for reactive collision avoidance taking into account both vehicle dynamics and nonholonomic constraints of a mobile robot. Motion commands are generated by searching the space of actuating variables. Vehicle dynamics are considered by restricting the search space to values which are reachable within the next time step. The final selection among admissible configurations is done by an objective function which trades off speed, goal-directedness and remaining distance until an obstacle is hit when moving along the chosen path. The presented approach differs from previous ones in the selective use of precalculated lookup tables. These are the key to efficiency, and they especially allow the use of any-shaped robot contours. Furthermore, obstacle information from different sources can easily be considered without preprocessing. Extensive experiments on different robots have shown robust operation in dynamic and unprepared indoor environments with speed up to 1 m/s.

Dynamical investigation of railway vehicles on a curved track

Abstract: The main objective of this article is an examination of railway vehicle dynamics during motion along a curved track. Two main aspects are presented in the paper. First, two different methods used while investigating multi-rigid body systems such as railway vehicles are discussed, i.e. the quasi-statical (or kineto-statical) and dynamical approaches. Second, two practical problems dealing with vehicle motion along a curved track are investigated. The problems under consideration refer to vibrations as well as stability, examined via finding obtained with the author's software as a result of numerical simulation. The work has both a practical and a cognitive character. The aim of the investigations is firstly to indicate the limitations of quasi-statical (and kineto-statical) methods and secondly to study the problems which cannot be treated by these methods. Two specific problems of the type investigated using a dynamical approach are the influence of track geometrical irregularities on the evaluation of vehicle ride properties and limit cycle occurrence during vehicle curve negotiation. Due to the renewed interest in the rapid passenger railway, the investigations take into consideration curves of large radii introduced along railway routes for increased velocities. Furthermore, it is shown under which conditions the obtained results may have an important practical application. This concerns the influence of vehicle suspension parameters as well as conditions of motion (speed, superelevation, curve radius, transition curve existence) on limit cycle occurrence. The limited value of conclusions dealing with vehicle ride properties obtained while using quasi-statical (kineto-statical) methods is proved through quantitative analysis. The problem of the influence of geometrical irregularities on wheel-rail pair wear is also pointed out.

A transportable neural-network approach to autonomous vehicle following

Abstract: This paper presents the development and testing of a neural-network module for autonomous vehicle following. Autonomous vehicle following is defined as a vehicle changing its own steering and speed while following a lead vehicle. The strength of the developed controller is that no characterization of the vehicle dynamics is needed to achieve autonomous operation. As a result, it can be transported to any vehicle regardless of the nonlinear and often unobservable dynamics. Data for the range and heading angle of the lead vehicle were collected for various paths while a human driver performed the vehicle following control function. The data was collected for different driving maneuvers including straight paths, lane changing, and right/left turns. Two time-delay backpropagation neural networks were then trained based on the data collected under manual control-one network for speed control and the other for steering control. After training, live vehicle following runs were done under the neural-network control. The results obtained indicate that it is feasible to employ neural networks to perform autonomous vehicle following.

A collision warning algorithm for rear-end collisions

Abstract: The purpose of this paper is to develop an experimentally-based rear end collision warning algorithm for the situation where two vehicles are initially traveling at the same speed in the same direction when the lead vehicle begins to brake. The full variety of initial conditions of vehicular motion are analyzed to determine the proper collision warning algorithm. The analysis shows that knowledge of traveling speed, headway, and lead-vehicle deceleration is sufficient to determine the type of relative motion. This can be coupled with warning logic and principles of vehicle dynamics to produce warning algorithms. An approach to warning implementation is suggested that avoids the difficult problem of estimating the lead-vehicle deceleration; using instead other measurable quantities such as range and range-rate. For the covering abstract see IRRD E102514.

Robust nonlinear control of an underwater vehicle/manipulator system with composite dynamics

Abstract: The paper is devoted to the problem of nonlinear robust control design for underwater vehicle/manipulator (UVM) systems composed of a freefloating platform equipped with a robot manipulator. The different bandwidth characteristics of the composite vehicle/arm dynamics are used as a basis for the control design via singular perturbation theory. The main contribution of this paper is that a robust nonlinear control is only required in the slow-subsystem (vehicle dynamics). Thus, this control is only used to compensate the coupling effects from the arm to the base. The paper also presents a comparative study between simple PD, a partial linearized control and the nonlinear robust feedback.

Steering control of high speed vehicles: dynamic look ahead and yaw rate feedback

Abstract: A popular automatic steering control approach for passenger cars is to decouple the yaw motion from lateral motion by using yaw rate feedback. It will be shown in this paper that by re-defining the control position at a frequency-dependent distance ahead of the vehicle, the yaw dynamics can also be decoupled. The resulting system dynamics with this dynamic look-ahead scheme can be simplified into a double-integrator vehicle dynamics with a constant, open-loop gain. It is further shown in this paper that even though the simplified system dynamics obtained from the dynamic look ahead scheme appears similar to that from the decoupling approach using yaw rate feedback, the hidden (unobservable) dynamics of the closed control loop is fundamentally different.

Vehicle trajectory approximation and classification

Abstract: We present a variational technique for finding low curvature smooth approximations to trajectories in the plane. The method is applied to short segments of a vehicle trajectory in a known ground plane. Estimates of the speed and steering angle are obtained for each segment and the motion during the segment is assigned to one of the four classes: ahead, left, right, stop. A hidden Markov model for the motion of the car is constructed and the Viterbi algorithm is used to find the sequence of internal states for which the observed behaviour of the vehicle has the highest probability.

Motion planning for a mobile manipulator considering stability and task constraints

Abstract: In order for a mobile manipulator to be used in areas such as offices and houses, the mobile platform must be small-sized. In the case of a small-sized platform, the mobile manipulator may fall down when moving at high speed, or executing tasks in the presence of disturbances. Therefore, it is necessary to consider both stabilization and manipulation simultaneously while coordinating vehicle motion and manipulator motion. In this paper, we propose a method for coordinating vehicle motion planning considering manipulator task constraints, and manipulator motion planning considering platform stability. Specifically, first, the optimal problem of vehicle motion is formulated, considering vehicle dynamics, manipulator workspace and system stability. Next, the manipulator motion is derived, considering stability compensation and manipulator configuration. Finally, the effectiveness of this method is demonstrated by simulation.

Motor vehicle occupant protection device operation control method e.g. for airbag

Abstract: A method of controlling the operation of motor vehicle occupant protection devices, in which a vehicle dynamics safety system (4,6) detects vehicle travel dynamics data, which are at least partly taken into account in an algorithm for controlling the occupant protection device (8,10). During activation of the vehicle dynamics safety system (4,6), the occupant protection device (8,10) is transferred into an active state. More specifically, the vehicle dynamics safety system (4,6) is an ABS-system. The release threshold values of the occupant protection device are varied depending on vehicle speed, yaw rate and transverse acceleration.

Automatic steering control of vehicle lateral motion with the effect of roll dynamics

Abstract: The two dominant motions of automatic vehicle steering control are yaw and lateral motion. A two degree-of-freedom (DOF) model commonly used to describe these motions is called the bicycle model. Experimental results for certain vehicles, however, show the lowered gain characteristics in the lateral acceleration response to the steering input. This is attributed to suspension dynamics. In this paper, a 3 DOF linear model, which incorporate the suspension roll mode, is developed and verified against the experimental data. The H/sub /spl infin// theory is applied to the bicycle model and the 3 DOF model for synthesis of robust steering controllers. The simulation results indicate the importance of the effect of roll dynamics to steering controller design.

A variable look-ahead controller for lateral guidance of four wheeled vehicles

Abstract: A variable look-ahead controller for the lateral guidance of vehicles for automated highway systems is proposed. The control objective is to make the lateral error at a certain point ahead of the vehicle zero. The distance of this point from the vehicle is called the look-ahead distance. An input-output linearization controller to achieve this objective is proposed. It is shown that the yaw internal dynamics can be damped at all longitudinal velocities if the look-ahead distance is a certain quadratic function of the longitudinal velocity.

Process for determining vehicle dynamics

Abstract: A process for determining at least one dynamic of a vehicle, particularly slip angle, during travel. The process involves optically monitoring, in real time and from the vehicle itself, the movement in one or more camera images of surface features as the vehicle passes over the surface. The direction in which the surface features are moving at any given time indicates the actual direction of vehicle movement with respect to the orientation of the optical monitoring equipment. From this actual direction of movement, in combination with the known orientation of the optical monitoring equipment and the direction in which the vehicle is being steered, it is possible to calculate the slip angle in real time.

Experimental results in robust lateral control of highway vehicles

Abstract: Vehicle lateral dynamics are affected by vehicle mass, longitudinal velocity, vehicle inertia, and the cornering stiffness of the tires. All of these parameters are subject to variation, even over the course of a single trip. Therefore, a practical lateral control system must guarantee stability, and hopefully ride comfort, over a wide range of parameter changes. This article describes a robust controller that theoretically guarantees stability over a wide range of parameter changes. The performance of the robust controller is then evaluated in simulation as well as on a test vehicle. Test results for experiments conducted on an instrumented track are presented, comparing the robust controller to a PID controller that was tuned on the vehicle.

Control of a car-like robot using a dynamic model

Abstract: A solution to the problem of controlling a car-like nonholonomic robot is proposed using a "virtual" vehicle approach, which is shown to be robust with respect to errors and disturbances. The proposed algorithms are model independent, and the stability analysis is done using a dynamical model in which, for instance, the side slip angles are taken into account.

A Measure of Stability for Mobile Manipulators With Application to Heavy-Duty Hydraulic Machines

Abstract: This paper describes the development ofa suitable algorithm to compute the potential of tipping-over for vehicles that carry manipulators. The energy method developed by Messuri and Klein (1985) is extended here to quantitatively reflect the effect of forces and moments arising from the manipulation of the implement. The amount of the impact energy that can be sustained by the vehicle without tipping-over, about each edge of potential overturning is computed. First, the instantaneous onset of instability configuration of the machine about the edge is determined by constructing an equilibrium plane. Next, the work done by all acting forces and moments when the machine is virtually brought to this unstable stance from the current state, is calculated. This work is the indication of the proximity of the machine to tipping-over around that edge. The application of this study is directed at industrial mobile machines that carry human-operated hydraulic manipulators. The algorithm is there-fore used to study the stability of an excavator based log-loader. Simulation studies clearly show the importance of inertial loads in determining the stability of such machines.

The Illinois Roadway Simulator-a hardware-in-the-loop testbed for vehicle dynamics and control

Abstract: The Illinois Roadway Simulator (IRS) is a novel, hardware-in-the-loop (HIL) scale vehicle testbed used to study vehicle dynamics and controls. An overview of this system is presented, and individual hardware issues are addressed. System modeling results on the vehicles and hardware are introduced, and comparisons of the resulting dynamics are made with full sized vehicles. To address the realism factor of using scaled vehicles, comparisons are made between vehicle responses of full and 1:10 scale vehicles. Finally, the IRS is used to examine the effect of actuator dynamics on a particular vehicle control application.

Hierarchical modeling in multibody dynamics

Abstract: In this paper a hierarchical approach using several mechanical models with different complexities and modeling depths to describe a single engineering system is presented. The mechanical models are derived from (but not limited to) multibody dynamics. The computer power available and improvements in theoretical understanding allow today not only to perform analyses but also to attack the problem of multimodel synthesis. Therefore, hierarchical modeling is used as a basis to analyze simultaneously models with different complexities and different excitations, and to optimize the performance with the most appropriate model for an investigated mechanical effect. Since only one single engineering system is investigated, its different models must be coupled by shared parameters, and the different criteria have to be combined with multicriteria optimization algorithms in order to obtain a single feasible design. An example taken from vehicle dynamics demonstrates the application of the approach.

Autonomous Intelligent Cruise Control with Actuator Delays

Abstract: In this paper, we consider the control design problem of vehicle following systems with actuator delays. An upper bound for the time delays is first constructed to guarantee the vehicle stability. Second, sufficient conditions are presented to avoid slinky-effects in the vehicle following. Next, zero steady state achieved by the proposed controller is proven. Finally, simulations are given to examine our claims.

Validation of dynamic simulations of rail vehicles with friction damped y25 bogies

Abstract: Theoretical modelling of a container wagon fitted with Y25 bogies was compared to actual track test data, using the VAMPIRETM Rail Vehicle dynamics modelling software. The Y25 bogie makes use of load sensitive friction damping, and has highly non-linear behaviour. Elements of the vehicle design which were important in predicting vertical and lateral ride were identified and are described in the paper. Wheel profile, accurate modelling of primary and secondary suspensions, and coefficients of friction of the wheel/rail interface and suspension friction faces, were found to be particularly important to ride prediction. The behaviour of the vehicle was very input dependent. It was possible to produce a good correspondence between track test and model results for both vertical and lateral behaviour.