Showing papers on "Vehicle dynamics published in 1995"

Toward an improved understanding of thruster dynamics for underwater vehicles

Abstract: This paper proposes a novel approach to modeling the four quadrant dynamic response of thrusters as used for the motion control of ROV and AUV underwater vehicles. The significance is that these vehicles are small in size and respond quickly to commands. Precision in motion control will require further understanding of thruster performance than is currently available. The model includes a four quadrant mapping of the propeller blades lift and drag forces and is coupled with motor and fluid system dynamics. A series of experiments is described for both long and short period triangular, as well as square wave inputs. The model is compared favorably with experimental data for a variety of differing conditions and predicts that force overshoots are observed under conditions of rapid command changes. Use of the model will improve the control of dynamic thrust on these vehicles.

Effects of model complexity on the performance of automated vehicle steering controllers : model development, validation and comparison

Abstract: SUMMARY Recent research on autonomous highway vehicles has begun to focus on lateral control strategies. The initial work has focused on vehicle control during low-g maneuvers at constant vehicle speed, typical of lane merging and normal highway driving. In this paper, and its companion paper, to follow, the lateral control of vehicles during high-g emergency maneuvers is addressed. Models of the vehicle dynamics are developed, showing the accuracy of the different models under low and high-g conditions. Specifically, body roll, tire and drive-train dynamics, tire force saturation, and tire side force lag are shown to be important effects to include in models for emergency maneuvers. Current controllers, designed for low-g maneuvers only, neglect these effects. The follow on paper demonstrates the performance of lateral controllers during high-g lateral emergency maneuvers using these vehicle models.

Estimation of absolute vehicle speed using fuzzy logic rule-based Kalman filter

Abstract: Accurate knowledge on the absolute or true speed of a vehicle, if and when available, can be used to enhance advanced vehicle dynamics control systems such as anti-lock brake systems (ABS) and auto-traction systems (ATS) control schemes. Current conventional method uses wheel speed measurements to estimate the speed of the vehicle. As a result, indication of the vehicle speed becomes erroneous and, thus, unreliable when large slips occur between the wheels and terrain. This paper describes a fuzzy rule-based Kalman filtering technique which employs an additional accelerometer to complement the wheel-based speed sensor, and produce an accurate estimation of the true speed of a vehicle. We use the Kalman filters to deal with the noise and uncertainties in the speed and acceleration models, and fuzzy logic to tune the covariances and reset the initialization of the filter according to slip conditions detected and measurement-estimation condition. Experiments were conducted using an actual vehicle to verify the proposed strategy.

Control properties of underactuated vehicles

Abstract: This paper studies control properties of the dynamics of underactuated vehicles (e.g. underactuated surface vessels, underwater vehicles, aeroplanes or spacecraft). The unactuated dynamics implies constraints on the accelerations. Both the necessary and sufficient conditions for these constraints to be second-order nonholonomic, first-order nonholonomic or holonomic are developed. It is shown that underactuated vehicles with a gravitational field where the elements corresponding to the unactuated dynamics are zero, are not C/sup 1/ asymptotically stabilizable to a single equilibrium.

A Review of Modelling Methods for Railway Vehicle Suspension Components

Abstract: SUMMARY The dynamic behaviour of railway vehicles has been the subject of study for over a century but the advances in computing technology in the last few years have led to a very rapid development in the use of numerical techniques for solving railway vehicle dynamics problems. As these techniques have developed, and have been applied to ever more complex problems, the modelling of the vehicle components has increased in importance. Mathematical models of railway vehicles may now include components such as swing links, air-springs, trailing arm suspensions, load sensitive friction dampers, rubber bushes with hysteresis etc, all of which require sophisticated modelling techniques to produce accurate results. This paper looks at the developments that have taken place in this area, the background to the need for sophisticated models, the improvements in accuracy that can result and some of the difficulties in applying these techniques to the modelling of real situations.

Periodic forcing, dynamics and control of underactuated spacecraft and underwater vehicles

Abstract: In this paper we describe spacecraft and underwater vehicle dynamics with small-amplitude, periodically time-varying forcing. The dynamic descriptions are derived so that they can be used to prescribe forcing laws for controlling the motion of these systems when they are underactuated, i.e., when the number of force inputs is less than the dimension of the configuration space. The use of periodic force inputs is motivated by the demonstrated success of using periodic velocity inputs in the associated nonholonomic kinematic spacecraft and underwater vehicle motion control problems, e.g., controlling underactuated spacecraft driven with internal rotors and underwater vehicles at low Reynolds number. By now addressing dynamic as well as kinematic response, we provide results that are useful in many practical problems in which the system cannot be modelled as purely kinematic, e.g., controlling underactuated spacecraft driven with gas jets and underwater vehicles at high Reynolds number.

Fuzzy logic for depth control of Unmanned Undersea Vehicles

Abstract: Fuzzy logic is a viable control strategy for depth control of undersea vehicles. It has been applied to the low speed ballast control problem for ARPA's Unmanned Undersea Vehicle (UUV), designed and built by Draper Laboratory. A fuzzy logic controller has been designed and tested in simulation that issues pump commands to effect changes in the UUV depth, while also regulating the pitch angle of the vehicle. The fuzzy logic controller performs comparably to the current ballast control design. The controller is also less sensitive to variations in the vehicle configuration and dynamics. The benefits of the fuzzy logic approach for this problem are: 1) simplicity, by not requiring a dynamic model, thus allowing for rapid development of a working design and less sensitivity to plant variations; 2) better matching of the control strategy and complexity with performance objectives and limitations; 3) the insight provided and easy modification of the controller, through the use of linguistic rules. >

Nonlinear control of roll moment distribution to influence vehicle yaw characteristics

Abstract: The influence of specifying a roll moment distribution to effect the handling dynamics of automobiles has long been appreciated by conventional automotive designers. With the advent of active suspension systems, it is now possible to actively vary the roll moment distribution via feedback control. Nonlinear vehicle dynamics are developed to describe the effect of roll moment distribution. Controllers based on feedback linearization and intuition are developed and simulated. Based on favorable simulation results, the intuitive nonlinear controller was implemented on a passenger automobile and results of its performance are included. >

Dynamic modeling of articulated vehicles for automated highway systems

Abstract: This paper is concerned with dynamic modeling of articulated vehicles in automated highway systems (AHS). A modeling approach for roll, pitch and yaw motions of articulated vehicles is proposed and a complex model for a tractor-semitrailer vehicle is derived using this approach. A simplified linear model, which includes lateral and yaw motions, is obtained from this complex model based on the assumptions that the longitudinal velocity is constant and that the vehicle lateral and yaw motions are small. It is shown that the vehicle system damping is inversely proportional to the longitudinal speed, and the gyroscopic forces are proportional to the product of trailer mass and longitudinal speed.

Brake system requirements for platooning on an automated highway

Abstract: To date, brake actuation has presented an obstacle to experimental demonstration of constant-spacing laws for automated vehicle following. Such difficulties can be traced to the lack of a unique actuation strategy and the strict, though not well defined, demands of platooning. This paper presents the results of a simulation study to examine the effects of brake dynamics within the multiple surface sliding control strategy proposed for platoon control. From these results, critical interactions among brake dynamics, spacing and passenger comfort are identified. Such analysis indicates that a brake system for platooning should bypass the vacuum booster, incorporate torque feedback and minimize delays in the time response.

Brake steer vehicle dynamics control intervention

Abstract: An electronic controller applies a braking force to selected wheels when sudden tire rupture is detected. A tire rupture signal indicative of whether a tire on the vehicle has ruptured is generated. Signals corresponding to a desired trajectory of the and the actual trajectory of the vehicle are calculated. Corresponding brake actuator signals are generated and applied to appropriate brakes of the vehicle, controlling the actual trajectory of the vehicle.

Kinematic GPS for Closed-Loop Control of Farm and Construction Vehicles

Abstract: Operating heavy equipment can be a difficult and very tedious task; control of an agricultural tractor requires the continues attention of the driver, and farmers often work long hours during the critical times. of planting and harvesting. Loaders and other ground vehicles are frequently used in situations which are unpleasant or. even hazardous for the human operator. In the past, some efforts have been made to automate agricultural vehicles, but they have been largely unsuccessful due to sensor limitations. This paper explores the use of kinematic GPS as the primary sensor in closed loop control of farm and construction vehicles. A single, low-cost GPS receiver can measure position to within a few centimeters and attitude to within O.l”, and does not drift with time. The ability to provide accurate information about multiple vehicle states makes GPS ideal for system identification and control of dynamic systems. In this work, a ground vehicle control system was designed and simulated using realistic plant, sensor, and disturbance models. Optimal control methods were examined to deal with non-linear and time-varying vehicle dynamics. To validate this simulation, experimental data was taken at Stanford using a GPS- equipped electric golf cart. This research builds upon previous work in developing GPS-based aircraft autopilots. It is significant because it is the first step towards a safe, low-cost system for adaptive, highly accurate control of a ground vehicle. It is anticipated that the implementation of these ideas will take place in three steps: (1) driver-in-the-loop control using a graphical display; (2) driver assisted automatic control, with an on-board operator making only high-level decisions; and (3) vehicle autonomous guidance and control with on-line parameter identification and adaptive control that will operate for several hours without human intervention.

A hybrid electric vehicle powertrain dynamic model

Abstract: This paper presents a discussion of mathematical modeling, analysis, and simulation as key elements in the iterative process that includes the development of vehicle hardware system performance measures, computer control software, and ultimately, hybrid electric vehicle powertrain system synthesis. A hybrid powertrain system is synthesized via amalgamation of a conventional internal combustion engine powerplant-alternator combination with a lead acid battery-AC induction motion motor electric vehicle system. The inclusion of alternative power source components in the hybrid vehicle is discussed.

Tire Modeling Requirements for Vehicle Dynamics Simulation

Abstract: The physical forces applied to vehicle inertial dynamics derive primarily from the tires. These forces have a profound effect on handling. Tire force modeling therefore provides a critical foundation for overall vehicle dynamics simulation. This paper describes the role tire characteristics play in handling. The paper discusses modeling requirements for appropriately simulating these effects. Tire input and output variables are considered in terms of their relationship to vehicle handling. General computational requirements are discussed. An example tire model is described that: (1) allows for efficient computational procedures; and (2) that provides responses over the full range of vehicle manoeuvring conditions. (A) For the covering abstract of the conference see IRRD 875861.

An investigation of road damage due to measured dynamic tyre forces

Abstract: A portable mat for measuring the dynamic tyre forces of commercial vehicles is described. The mat is 56 m long, 13 mm thick, and has 141 capacitative strip sensors, spaced at 0.4 m intervals. The accuracy of the mat for measuring dynamic tyre forces generated by heavy commercial vehicles is assessed using an instrumented vehicle. The measured dynamic wheel loads generated by 14 articulated vehicle configurations (three tractors with five trailers) are assessed in terms of a variety of road damage criteria. The results are used to investigate the effects of vehicle configuration, vehicle dynamics, speed, road strength, and road damage criteria on the relative theoretical road damage caused by the vehicles. Conclusions are drawn about tests for measuring and assessing the road-damaging potential of heavy lorries.

An Overview of the HVE Vehicle Model

Abstract: Developers of vehicle dynamics simulation software inherently use a mathematical/physical model to represent the vehicle. This paper describes a pre-programmed, object oriented vehicle model for use in vehicle dynamics simulations. This vehicle model is included as part of an integrated simulation environment, called HVE (Human-Vehicle-Environment), described in previous research. The current paper first provides a general overview of the HVE user and development environments, and then provides detailed specifications for the HVE Vehicle Model. These specifications include definitions for model parameters (supported vehicle types; vehicle properties, such as dimensions, inertias, suspensions; tire properties, such as dimensions and inertias, mu vs slip, cornering and camber stiffnesses; driver control systems, such as engine, transmission/differential, brakes and steering; restraint systems, such as belts and airbags). The paper also provides detailed specification of the HVE time-dependent vehicle output group parameters (kinematics, kinetics, tire data, wheel data, inter-vehicle connections, drivetrain, driver controls, contact surface forces, and restraint system forces). (A)

Emergency Maneuvers for AHS Vehicles

Abstract: This paper addresses the issue of emergency maneuvers of intelligent vehicles, treated in the context of time-optimal control. Time optimal trajectories are computed along specified paths for a nonlinear vehicle model, which considers both lateral and longitudinal motions.

Modular vehicle dynamics control system

Abstract: The movement of a vehicle is controlled by actuating actuators which apply a braking force to the wheels For this purpose, the rotational speeds of the wheels, the steering angle and at least one of the lateral acceleration and the yawing movement of the vehicle are detected A first module is configured so that the actuators are actuated by means of the actuation signals with the effect of controlling a first variable The second module is configured so that signals for influencing the actuation signals are formed with the effect of controlling a second control variable In order to obtain this second control variable, at least the variable which represents the steering angle is processed The second controller component brings about a control of a variable which is determined at least as a function of the lateral movement or the yawing movement of the vehicle

Process models for the high-speed navigation of road vehicles

Abstract: A nonlinear process model for the navigation of a high-speed conventional road vehicle is described. In simulations it is shown to significantly reduce the errors in estimating of vehicle position and orientation. The model also performs limited online estimation of certain critical tyre parameters such as mean radius and stiffness.

Vehicle dynamics control system using control variable derived by means of vehicle model

Abstract: Detection means are provided which detect the rotational movements of the wheels, a variable which represents the steering angle, and at least one variable which represents the lateral movement and/or the yawing movement of the vehicle. Signals for influencing actuators for braking the wheels are formed by controller means as a function of the detected data in such a way that a control variable which is dependent on at least the detected lateral movement or yawing movement of the vehicle is adjusted to a desired range of control variables, that is to say the actuators are influenced in such a way that the control variable is kept within a desired range. This desired range is defined by two specific limit values.

Vehicle dynamics control system with varying sensor configurations

Abstract: A movement variable which represents the movement of a vehicle is controlled by actuating at least one actuator for applying a braking force to the wheels. Controller means use controller internal variables to form signals for influencing the actuators with the effect of adjusting a control variable. The controller means has a first area adapted to the respective selected sensor configuration in such a way that the controller-internal variables are formed on the basis of the sensor signals, and a second area for processing the controller-internal variables independently of the selection of the sensor configuration. As a result, simple adaptation with low development and application outlay to a wide variety of sensor configurations is possible.

Adaptive compensation of fuel dynamics in an SI engine using a switching EGO sensor

Abstract: Current engine controllers employ a feedforward compensator to eliminate the effects of fuel dynamics ("wall-wetting") on the air-fuel ratio trace. Uncompensated or improperly compensated fuel dynamics may cause significant A/F excursions during transient operations, accompanied by increased emissions levels. This paper describes the development of an adaptive algorithm for transient fuel compensation using only a switching exhaust gas oxygen (EGO) sensor, in order to ensure proper compensation of fuel dynamics in spite of initial miscalibrations, vehicle-to-vehicle variability, changing dynamics due to aging (intake valve deposits build up), or changing dynamics due to changing fuel properties. Experimental results demonstrate the effectiveness of the proposed algorithm.

Developments in Vehicle Center of Gravity and Inertial Parameter Estimation and Measurement

Abstract: For some vehicle dynamics applications, an estimate of a vehicles's center of gravity (cg) height and mass moments of inertia can suffice. For other applications, such as vehicle models and vehicle simulations used for vehicle development, these values should be as accurate as possible. This paper presents several topics related to inertial parameter estimation and measurement. The first is a simple but reliable method of estimating vehicle mass moment of inertia values from data such as the cg height, roof height, track width, and other easily measurable values of any light road vehicle. The second is an error analysis showing the effect, during a simple static cg height test, of vehicle motion on the vehicle's calculated cg height. The third topic is a method of measuring the ratio of the sprung mass to the unsprung mass of any light vehicle without disassembly. Knowledge of this ratio is also important for vehicle development. For the covering abstract of the conference see IRRD 882390.

Adaptive Traction Control

Abstract: This report presents two different control algorithms for adaptive vehicle traction control, which includes wheel slip control, optimal time control, anti-spin acceleration and anti-skid control, and longitudinal platoon control. The two control algorithms are respectively based on adaptive fuzzy logic control and sliding mode control with on-line road condition estimation. Simulations of the two control methods are conducted using a complex nonlinear vehicle model as well as a simple linear vehicle model.