Showing papers on "Vehicle dynamics published in 1990"

Longitudinal Control of a Platoon of Vehicles

Abstract: This paper presents a systematic analysis of a longitudinal control law for a platoon of non-identical vehicles using a non-linear model to represent the vehicle dynamics of each vehicle within the platoon. The basic idea is to take full advantage of recent advances in communication and measurement and using these advances in longitudinal control of a platoon of vehicles: in particular, we assume that for i = 1,2,... vehicle i knows at all times v l and al (the velocity and acceleration of the lead vehicle) in addition to the distance between vehicle i and the preceding vehicle, i - 1.

Adaptive sliding mode control of autonomous underwater vehicles in the dive plane

Abstract: The problem of controlling an autonomous underwater vehicle (AUV) in a diving maneuver is addressed. Having a simple controller which performs satisfactorily in the presence of dynamical uncertainties calls for a design using the sliding mode approach, based on a dominant linear model and bounds on the nonlinear perturbations of the dynamics. Nonadaptive and adaptive techniques are considered, leading to the design of robust controllers that can adjust to changing dynamics and operating conditions. The problem of using the observed state in the control design is addressed, leading to a sliding mode control system based on input-output signals in terms of drive-phase command and depth measurement. Numerical simulations using a full set of nonlinear equations of motion show the effectiveness of the proposed techniques. >

Vehicle Lateral Control for Highway Automation

Abstract: The objectives of lateral control for highway automation are to let vehicles track the center of a lane with small error and to maintain good ride quality under different vehicle speeds, loads, wind gust disturbances, and road conditions. In this paper, the lateral feedback and feedforward controllers are designed to satisfy these objectives by utilizing the frequency-shaped linear quadratic (FSLQ) control theory. This design method allows that the ride quality be included in the performance index explicitly, and the high-frequency robustness characteristic be improved by properly choosing the weighting factors. It is shown that a controller with fixed gains does not perform satisfactorily under all conditions. Therefore, an estimator for comering stiffness of the tires is proposed to enhance performance. Simulation results show that this adaptive control approach works satisfactorily under a variety of conditions including intermittent measurement of lateral tracking error.

Robust Control for Automatic Steering

Abstract: Robust control problems in automatic steering are due to the wide range of velocity, mass and road conditions under which such vehicles operate. In earlier design studies and road tests for a bus it has been shown that it is possible to design a fixed gain controller such that the automatic steering operates satisfactorily over the entire range of parameters. In the present paper it is shown that the performance of such a robust automatic steering system can be considerably improved by the addition of a gyro measuring the yaw rate and feeding it back into the controller.

Vehicle Modelling and Control for Automated Highway Systems

Abstract: This study evaluates the feasibility of longitudinal control of a platoon of automated vehicles. As a prerequisite to controller design, a nine state nonlinear model including an internal combustion engine, engine transmission dynamics, and tire friction characteristics has been developed. Parametric studies revealed that simple linear models cannot predict the vehicle transients. Due to this highly nonlinear nature of the vehicle, the use of a nonlinear controller was proposed. A nonlinear control strategy using throttle engine control for a platoon of two vehicles was studied using the technique of Sliding Control. In our analysis, the quantities of primary concern are position and velocity tracking errors. Simulation results demonstrate excellent tracking even in the presence of sizable modelling errors and disturbance inputs.

A review of low cost accelerometers for vehicle dynamics

Abstract: In the last few years, vehicle manufacturers have been recognising the advantages, in terms of passenger comfort and driveability, that can be achieved using electronically controlled vehicle suspension systems. A critical component in all of these, other than the manually adjusted ride control systems, is the accelerometer, a number of which are used for measuring vehicle motion in all directions. These accelerometers are required to have a high sensitivity and accuracy and yet be sufficiently robust to operate in the relatively harsh environment of a vehicle. Further to this, the unit cost of the accelerometers must be very low. This paper reviews the main technologies and sensor designs, which have the potential to meet the required suspension systems and other vehicle dynamics performance specifications within the cost constraints.

Model for human use of motion cues in vehicular control

Abstract: A feedback model for human use of motion cues in tracking and regulation tasks is offered. The motion cue model is developed as a simple extension of a structural model of the human pilot, although other equivalent dynamic representations of the pilot could be used in place of the structural model. In the structural model,it is hypothesized that proprioceptive cues and an internal representation of the vehicle dynamics allow the human to create compensation characteristics that are appropriate for the dynamics of the particular vehicle being controlled. It is shown that an additional loop closure involving motion feedback can improve the pilot/vehicle dynamics by decreasing high-frequency phase lags in the effective open-loop system transfer function. Data from a roll-attitude tracking/regulation task conducted on a moving base simulator are used to verify the modeling approach.

Keeping layered control simple (autonomous underwater vehicles)

Abstract: The status of research on adapting layered control to fully autonomous underwater vehicles (AUVs) is described. Handling vehicle dynamics, communication between layers, sensor processing, mission configuration, resolving conflict between layers, and avoiding states in which the vehicle becomes trapped are studied. The complex nonlinear dynamics and large sensor processing requirements inherent in AUV applications have led to the modification of the traditional layered control approach. Of particular importance is the need to move closed-loop control and sensor processing outside the layered control architecture to reduce the memory and throughput requirements imposed on the main computer. The major research issues involved with making layered control less complex, reconfigurable, and suitable for underwater operations are considered. >

Optimal motion planning of autonomous vehicles in three dimensional terrains

Abstract: A method is presented for optimally planning the motions of autonomous vehicles, considering vehicle dynamics, terrain topography, obstacles, and surface mobility. The terrain is represented by a smooth cubic B patch, and the geometric path consists of a two dimensional B spline curve mapped to the three-dimensional surface. The path is optimized with a parameter optimization procedure, using motion time as the cost function. The optimal motion time along the path is computed by transforming the constraints between the vehicle and ground to limits on vehicle speeds. The optimal speeds which minimize motion time are then obtained below the velocity limits, using the maximum acceleration of deceleration at all times. Examples are presented which demonstrate the method for a simple dynamic model of a vehicle moving on mountainous terrain. >

Roadway simulator restraint

Abstract: A roadway simulator restraint system supports a vehicle at each of its wheels on simulated roadways which comprise endless belts suitably driven to cause wheel rotation. A plurality of passive links are provided for restraining the vehicle in longitudinal, lateral, and yaw degrees of freedom, while permitting free motion in roll and pitch moments, and vertical directions. Additionally, the linkages can provide inputs in aerodynamic force directions to simulate responses to vehicle dynamics during actual operation. The individual roadways that support the wheels can be independently controlled as to speed, and can be turned. Suitable force measurements are made in desired axes to provide for a complete controlled simulation of vehicle operation on an actual roadway.

An Adaptive Sliding Mode Vehicle Traction Controller Design

Abstract: An adaptive sliding-mode vehicle traction control strategy, which includes anti-skid braking and anti-spin acceleration, has been proposed, implemented and tested It integrates a sliding-mode control algorithm with a tire/road surface identification process, and it results in good performance regardless of vehicle environments The effectiveness of this scheme is demonstrated by experiments on anti-skid braking

Longitudinal Control of a Platoon of Vehicles; Ill: Nonlinear Model

Abstract: This paper presents a systematic analysis of a longitudinal control law for a platoon of non-identical vehicles using a non-linear model for the vehicle dynamics.

Longitudinal Control Of A Platoon Of Vehicles. III, Nonlinear Model

Abstract: This paper presents a systematic analysis of a longitudinal control law for a platoon of non-identical vehicles using a non-linear model for the vehicle dynamics.

Rear wheel steering dynamics compared to front steering

Abstract: The lateral dynamics of rear wheel steering vehicles are examined using low order linear mathematical models. The response to rear steer angle inputs differs significantly from the front wheel steering response at low speeds. The free control instability unique to rear wheel steering vehicles is analyzed using a torque input model which treats steer angle as a degree of freedom

4WS Technology and the Prospects for Improvement of Vehicle Dynamics

Abstract: FOUR-WHEEL STEERING (4WS) is beginning to find widespread use as a new approach to improving vehicle dynamics, especially in the medium and high speed ranges. Steering the rear wheels in the same phase as the front wheels enhances vehicle stability. Four-wheel steering systems have an even greater potential to improve stability and steering response through suitable control over the transient characteristics of the rear wheel steer angle. This paper traces the course of Nissan research and development work on four-wheel steering and the evolution of Nissan's HICAS (4WS) technology. It also describes research activities under way on vehicle dynamics using a newly developed Simulator Vehicle, equipped with a front and rear angle transient control system which makes it possible to vary the dynamic characteristics of the vehicle instantaneously and at will while driving.

Design of stability augmentation systems for automotive vehicles

Abstract: The high-speed cruising stability of passenger vehicles may be enhanced with stability augmentation systems. These systems would modify the driver's steering command to the vehicle's front wheels, and steer the rear wheels according to measured vehicle conditions such as is yaw-rate. In this simulation study, an explicit driver model is used in the design of these stability augmentation systems

Connectionist learning control systems: submarine depth control

Abstract: Control system design for vehicles with highly nonlinear, time-varying, or poorly modeled dynamics is considered. The use of connectionist systems as learning controllers is proposed. The ability of connectionist systems to approximate arbitrary continuous functions (e.g., control laws) overcomes the usual memory-intensive nature of learning systems. The backpropagation algorithm is extended to allow the connectionist system to learn to function as a closed-loop controller and to force the dynamics of the closed-loop system to match the prespecified dynamics of a reference system. An example of the application of this algorithm to the depth control of an autonomous underwater vehicle is included. >

Application of nonlinear control strategies to aircraft at high angle of attack

Abstract: Nonlinear control strategies as applied to a high-alpha vehicle are discussed. The intent is to evaluate these methods for their benefit and advantage over conventional gain-scheduled linear controllers. Several techniques and their associated mechanisms are identified. The test aircraft used is the X-29, which is particularly suited for manoeuvering at a high-alpha regime. A classical linear controller designed by Grumman and NASA is used for comparison. >

Stability Analysis of Automatic Lateral Motion Controlled Vehicle with Four Wheel Steering System

Abstract: The inherent dynamics of a vehicle are important factors in automatic vehicle control systems. This paper discusses the stability of an automatic lateral motion controlled vehicle equipped with a four wheel steering system focusing in particular on the vehicle dynamics. The four wheel steering system is configured around a model following control theory. The results of a stability analysis and simulations are presented to show that the four wheel steering system is effective in increasing the stability and performance of an automatic lateral motion controlled vehicle.

Self-organizing Control System For Underwater Vehicles

Abstract: A self-organizing neural-net controller system is devel­ oped as an adaptive motion control system for underwa­ ter vehicles, especially for AUVs (Autonomous Underwater Vehicles). The system can generate automatically an appro­ priate controller according to a specific evaluation of motion of the vehicle. An organizing process of the controller is also proposed to construct the system in practical environ­ ment. The premature Fuzzy controller initiation process is introduced to enable the system to generate the controller with minimum pre-knowledge about the effect of control actions. The developed system is demonstrated with AUV "PTEROA" and succeeded in self-organization of the con­ troller through free-swimming tank tests.

An Approach to Optimal Guidance of an Advanced Lauch Vehicle Concept

Abstract: This paper presents an approximate solution for the maximum payload trajectory of a 2-stage launch vehicle using a regular perturbation technique A zero-order solution for a two stage vehicle based on a flat Earth approximation and negligible atmospheric effect is obtained in closed form High order correction terms are obtained from the solution of non-homogeneous, first-order linear differential equations by quadrature This promises a capability for an on-board optimal guidance law implementation

Stability enhancement and traction control of road vehicles

Abstract: An algorithm that enhances the stability and traction of a road vehicle (which may be steering) during ‘acceleration’ (meaning either braking or accelerating) is presented. This algorithm has two domains: partial-effort acceleration and maximum-effort acceleration. During partial-effort acceleration, stability enhancement requires only proper distribution of longitudinal traction forces. During maximum-effort acceleration, stability enhancement requires distribution and reduction of longitudinal traction forces. The algorithm attempts to provide the desired levels of acceleration while it simultaneously constrains trajectory disturbance of the vehicle. The algorithm uses total information about the road surface characteristics, the driver's actions, and the vehicle's design and dynamic states. It fully accommodates non-linear vehicle dynamics and tyre force characteristics. The algorithm has the form of a linear program and its operation is traced in a series of graphs where the geometry of linear program...

On-line optimal terrain-tracking system

Abstract: The problem of on-line optimal tracking control is considered for an aircraft terrain-following system. An on-line optimal control law which reflects the non-linear airborne vehicle dynamics with bounded control input is obtained by using a pointwise optimization technique called optimal decision strategy. The stability of the resulting system is also discussed. To demonstrate the feasibility and effectiveness of the proposed scheme, simulations have been performed for a realistic terrain-following system.

Adaptive guidance for an aero-assisted boost vehicle

Abstract: An adaptive guidance system incorporating dynamic pressure constraint is studied for a single stage to low earth orbit (LEO) aero-assist booster with thrust gimbal angle as the control variable. To derive an adaptive guidance law, cubic spline functions are used to represent the ascent profile. The booster flight to LEO is divided into initial and terminal phases. In the initial phase, the ascent profile is continuously updated to maximize the performance of the boost vehicle enroute. A linear feedback control is used in the terminal phase to guide the aero-assisted booster onto the desired LEO. The computer simulation of the vehicle dynamics considers a rotating spherical earth, inverse square (Newtonian) gravity field and an exponential model for the earth's atmospheric density. This adaptive guidance algorithm is capable of handling large deviations in both atmospheric conditions and modeling uncertainties, while ensuring maximum booster performance.