Showing papers on "Vehicle dynamics published in 1986"

Integrated path planning and dynamic steering control for autonomous vehicles

Abstract: A method is presented for combining two previously proposed algorithms for path-planning and dynamic steering control into a computationally feasible scheme for real-time feedback control of autonomous vehicles in uncertain environments. In the proposed approach to vehicle guidance and control, Path Relaxation is used to compute critical points along a globally desirable path using a priori information and sensor data. Generalized potential fields are then used for local feedback control to drive the vehicle along a collision-free path using the critical points as subgoals. Simulation results are presented to demonstrate the control scheme.

A real-time reflexive pilot for an autonomous land vehicle

Abstract: An automatic pilot has been built that can drive an autonomous land vehicle in real time. The purpose of the pilot is to generate vehicle control commands that will direct the vehicle from the starting point to the final destination without hitting unforeseen obstacles or leaving the vicinity of the planned path. The pilot uses a single microprocessor and sensor range measurement to generate vehicle control commands in less than 60 ms, Because the pilot guides a relatively large vehicle, it must compensate for the vehicle dynamics. The role of the pilot is discussed within the framework of real-time planning and control. Laboratory tests are done with a computer simulation. Field tests have demonstrated that the pilot is able to guide a 10-ton M113A2 armored personnel carrier on a 1-mi course around randomly placed obstacles without crossing the outer borders of the mission plan.

A perspective on superaugmented flight control - Advantages and problems

Abstract: Superaugmented aircraft are an important subclass of actively controlled, highly augmented aircraft. The aircraft without augmentation is unstable; the control system not only redresses the stability and control imbalance, but also provides effective vehicle dynamics that differ in kind from those associated with conventional aircraft. In this paper, the longitudinal properties of highly unstable aircraft and typical superaugmented control systems used to remedy their dynamic deficiencies are explored generically. The topics considered include: (1) Basic flight control system architectures suitable to reduce or completely alleviate the unstable aircraft characteristics. (2) The primary dynamic characteristics and regulatory properties of typical superaugmented aircraft control systems, including governing factors in the linear system, dominant mode characteristics, and fundamental stability margin properties. The total available gain range factor is presented as a basic measure that relates degree of instability, control system limitations, and key control system adjustments. (3) Some flying qualities features for superaugmented aircraft with rate command/attitude hold, extended bandwidth, and attitude command configurations.

Dynamic computer simulation of multiple closed-chain robotic mechanisms

Abstract: The direct problem of dynamics for robotic systems with multiple simple closed chains has been formulated and solved. These systems include multiple robot manipulators performing assembly or cooperative tasks as well as multilegged walking machines. The basic problem in direct dynamics is to determine joint accelerations given the applied torques or forces and the system state. As such its solution will allow control designers to test and evaluate the performances of various control algorithms through computer simulation without having to build several costly prototypes. A unified approach is taken so that a single set of equations may describe dynamics of both multiple manipulators and legged vehicles.

Non-linearities in Road Vehicle Dynamics

Abstract: SUMMARY In the study of lateral vehicle dynamics with the objective to enhance stability and handling qualities, non-linear aspects may have to be included to cover also larger lateral accelerations and amplitudes. The paper treats whole vehicle motions and relative motions of vehicle subsystems. In particular, single car stability, also in the large, is discussed as well as the shimmy phenomenon and the car-trailer instability.

Effects of suspension variations on the dynamic wheel loads of a heavy articulated highway vehicle

Abstract: The work reported here was supported jointly by Canroad and the National Research Council Division of Mechanical Engineering, Vehicle Dynamics Laboratory, as part of the RTAC/ccmta vehicle weights and dimensions study. The study investigated the dynamic wheel load behaviour of various heavy highway vehicle suspension systems under a controlled experimental program. A 45 tonne tractor-trailer was modified to measure the dynamic axle loads of all major load carrying axles simultaneously. Suspension parameters such as suspension type, axle spread and axle load were investigated as functions of road roughness and vehicle speed. The effects of brake torque and suspension pitch attitude on the load equalization of the suspension were also investigated. Road tests were conducted at various speeds over a variety of road roughness conditions. Findings relevant to the subject of dynamic road loading are highlighted. (Author/TRRL)

On modeling and adaptation in robot control

Abstract: Performance enhancement through modeling of high-frequency dynamics (such as structural resonant modes or actuator time-delays) and on-line parameter estimation (of large loads with unknown mass properties, or of characteristics of the environment in compliant motion control) is discussed in the context of sliding control. It is shown that such additions can be easily incorporated in existing controllers and yield predictable performance improvements.

A theoretical analysis on vehicle cornering behaviors in acceleration and in braking

Abstract: SUMMARY Disregarding the effects of the vehicle dynamics and the change of vehicle speed in a short period of time, a method to predict the turning behaviors of the vehicle in acceleration and in braking is developed, and US/OS concepts having the same implication as in a steady state turning are introduced. The effects of the drive arrangements and the locked differential(s) on the turning behaviors are investigated. Some results predicted by the method show well agreements with the simulation results, which suggests that the prediction method can give some insight into the turning behaviors of a real vehicle in acceleration and in braking.

Railway vehicle dynamics

Abstract: Various aspects of the dynamic behaviour of modern high-speed rail vehicles are discussed together with an explanation of some of the physical phendmena which occur.

A Pilot for a Robotic Vehicle System

Abstract: The role of an automatic pilot in an autonomous land vehicle system is to guide the vehicle along its mission path, while at the same time avoiding unexpected obstacles. We demonstrate an algorithm that accomplishes this task in real-time with the capability to generate vehicle guidance commands every 60 milliseconds. Many aspects of obstacle avoidance and path following can be shown to depend only on the current snapshots of the local work space with only a few global parameters needed. The algorithm works by finding conical-shaped usable subsets of the local work space and is motivated by the heuristic requirement of staying in sensor view of the subgoal. Our approach allows for vehicle dynamics which is often neglected in other approaches and yields smooth paths. The problem of traps inherent in potential field approaches is avoided by introducing a winding angle principle. Before field testing, the performance of the pilot was evaluated by the computer simulation of a 10-ton tracked vehicle. During recent field tests, the pilot was successful in guiding an M113 armored personnel carrier around obstacles while staying inside the path corridor.

Multibody Formalism Applied to Non-Conventional Railway Systems

Abstract: The paper presents the main features of the AUTODYN programme developed in Louvain-La-Neuve. This multi-purpose programme, based on the virtual work principle, can be used for vehicle dynamics as well as in robotics and for other mechanical systems. The generalized coordinates describe the relative motion in the joints between bodies. A library of joints, including rail-wheel connections, with their corresponding interaction models is available. Moreover the joints can be restricted by means of user-defined constraints and some of their coordinates can have a prescribed motion. Constraints resulting from closed loops are automatically generated and the final form of the equations is obtained by using the Lagrange multipliers technique and a coordinate partioning method.

A Methodology for Modeling the Dynamics of the Mechanical Paths of Automotive Drivetrains with Automatic Step-Transmissions

Abstract: A generic methodology is presented for modeling the dynamics of the mechanical paths of automotive drivetrains with automatic step-transmissions. The analysis of these dynamics was based on the lever analogy method and resulted in a set of equations which represents drivetrain shift dynamics for a wide range of kinematic arrangements. Various GM transmissions are shown to be compatible with the proposed methodology.

Body structure and vehicle dynamics

Abstract: SUMMARY This paper is a presentation of aspects on car body design for mass transit vehicles and methods which has been evolved for the analysis of non-linear flexible railway vehicles by use of normal modes. In the end of the paper results from an experimental modal analysis are shown.

Design of Underwater Vehicles for High Performance Control

Abstract: Design considerations for high performance control of remotely operated underwater vehicles are presented, focussing on the performance limits imposed by navigation, actuators, dynamic uncertainty, control strategies, and the dynamics of the vehicle. As coupling between translation and attitude present a major impediment to high bandwidth control, techniques for reducing this coupling are presented. In-water test data is presented for the new JASON Junior vehicle currently being designed and built at the Deep Submergence Laboratory.