Showing papers in "Vehicle System Dynamics in 1990"
TL;DR: Roberson and Schwartzke as discussed by the authors reviewed the Dynamics of Multibody Systems R. E. ROBERSON and R. SCHWERTASSEK Berlin, 1988.
Abstract: (1990). A Review of: Dynamics of Multibody Systems R. E. ROBERSON and R. SCHWERTASSEK Berlin/ …: Springer-Verlag 1988. Vehicle System Dynamics: Vol. 19, No. 2, pp. 111-112.
51 citations
TL;DR: In this paper, a quasi-dynamic roll plane model of a partially filled cleanbore tank of circular cross-section is integrated to a three-dimensional model of the articulated vehicle, assuming constant forward speed.
Abstract: SUMMARY The influence of the lateral load shift on the dynamic response characteristics of an articulated tank vehicle is investigated assuming inviscid fluid flow conditions. A quasi-dynamic roll plane model of a partially filled cleanbore tank of circular cross-section is developed and integrated to a three-dimensional model of the articulated vehicle, assuming constant forward speed. The destabilizing effects of liquid load shift are studied by comparing the directional dynamics of the partially filled tank vehicle to that of an equivalent rigid cargo vehicle subject to steady steer input. Dynamic response characteristics demonstrate that the stability of a partially filled tank vehicle is adversely affected by the Liquid load shift The distribution of cornering forces caused by the liquid load shift yield considerable deviation of the path followed by the liquid tank vehicle. The influence of the vehicle speed on the dynamics of the liquid tank vehicle is also investigated for variations in the fill l...
41 citations
TL;DR: In this article, a test procedure, which utilized wind-generating fans arranged in alternating directions to provide a cross-wind "gauntlet" was introduced and described, and a two-stage vehicle design process was then recommended for predicting and analyzing the crosswind sensitivity of a particular vehicle or new design.
Abstract: SUMMARY Results of vehicle crosswind research involving both full-scale driver-vehicle tests and associated analyses are presented. The paper focuses on experimental crosswind testing of several different vehicle configurations and a group of seven drivers. A test procedure, which utilized wind-generating fans arranged in alternating directions to provide a crosswind “gauntlet”, is introduced and described. Driver preferences for certain basic chassis and aerodynamic properties are demonstrated and linked to elementary system responses measured during the crosswind gauntlet tests. Based on these experimental findings and confirming analytical results, a two-stage vehicle design process is then recommended for predicting and analyzing the crosswind sensitivity of a particular vehicle or new design.
37 citations
TL;DR: In this article, an optimal suspension system for a quarter-car model using multivariable integral control is derived for a quadratic model using linear full-state feedback control laws with and without integral control together with the performance of passive suspensions.
Abstract: SUMMARY In this paper, an optimal suspension system is derived for a quarter-car model using multivariable integral control. The suspension system features two parts. The first part is an integral control acting on suspension deflection to ensure zero steady-sate offset due to body and maneuvering forces as well as road inputs. The second is a proportional control operating on the vehicle system states for vibration control and performance improvement. The optimal ride performance of the active suspensions based on linear full-state feedback control laws with and without integral control together with the performance of passive suspensions are compared.
27 citations
25 citations
TL;DR: In this paper, a numerical procedure for finding the optimum values of a number of parameters describing a model vehicle suspension has been studied, where the vehicle has been modelled by dynamic systems of linear springs and dampers, and the goal is to obtain lower acceleration peaks at an elected design point in the vehicle.
Abstract: SUMMARY A numerical procedure for finding the optimum values of a number of parameters describing a model vehicle suspension has been studied. The vehicle has been modelled by dynamic systems of linear springs and dampers, and the goal is to obtain lower acceleration peaks at an elected design point in the vehicle. The problem is stated as a mathematical programming problem which can be solved by means of the sequential linear programming technique. The procedure has been implemented for a four wheel independent suspension model capable of being subjected to road irregularities and to centrifugal and braking accelerations.
23 citations
TL;DR: In this article, a new derivation of the expression for the cost, accounting for time delays, is given for a half car planar vehicle model and an estimate of the loss of performance which results from the restriction of the control law form in this case is made.
Abstract: SUMMARY Input correlations involving time delays are common in active vehicle suspension system problems. One approach to control law derivation fur such systems is to restrict attention to slate feedback laws in the interests of practicality and it is then of interest to determine the law which is, in some sense, the best. Under assumptions which are common in this area. relating to input, system and cost Function forms, a new derivation of the expression for the cost, accounting for time delays, is given. The use of the expression in numerical procedures for determining effective control gains is discussed and an example for a half car planar vehicle model is described. By comparing results with existing ones which are truly optimal, an estimate is made of the loss of performance which results from the restriction of the control law form in this case. Some generalisation of the results is attempted and they are placed in a contemporary context at the conclusion.
22 citations
TL;DR: In this article, the damping characteristics of a sequential hydraulic damper are compared to those of a constant orifice and a semi-active sequential damper, and discussed in view of their vibration isolation performance.
Abstract: SUMMARY Vibration isolation characteristics of a sequential hydraulic damper, employing external pressure relief valves, are investigated via analytical means. The sequential hydraulic damper is modelled as a nonlinear dynamical system incorporating nonlinearities due to orifice flows, gas spring and pressure relief mechanisms. The damping characteristics of the sequential hydraulic damper, are compared to those of a constant orifice and a semi-active sequential damper, and discussed in view of their vibration isolation performance. It is established that the performance characteristics of the sequential hydraulic damper are similar to that of a semi-active sequential damper. A tuning methodology to achieve appropriate control of the resonant peak and effective vibration isolation is proposed. The shock and vibration isolation performance of the vehicle model employing a sequential damper are evaluated and compared to those of the vehicle model employing a constant orifice hydraulic damper. It is conclude...
22 citations
TL;DR: In this paper, an unconventional method for calculating the forces developing in the wheel and rail contact patches of a railway vehicle has been implemented at the New Technology Laboratory of INRETS, taking into account the elastic deformations of the materials in the Hertzian elliptical contact areas; the possibility of having simultaneously several contact patches on each wheel, is introduced in the simulation of dynamic phenomena.
Abstract: SUMMARY An unconventional method for calculating the forces developing in the wheel and rail contact patches of a railway vehicle has been implemented at the New Technology Laboratory of INRETS. It takes into account the elastic deformations of the materials in the Hertzian elliptical contact areas; the possibility of having simultaneously several contact patches on each wheel, is introduced in the simulation of the dynamic phenomena. The theory is applied for a high speed bogie running on a perfectly straight track.
22 citations
TL;DR: In this article, a nonlinear vehicle model, nonlinear characteristics of the elasto- damping elements, and modified Nelder-Mead method are used to optimize the characteristics of elastodamping elements in the vehicle.
Abstract: Negative effects of the oscillatory motions of vehicles upon the ride comfort and controllability are reduced by optimizing the characteristics of the elasto-damping elements in the vehicle. The optimization reported in this work has been carried out by using a nonlinear vehicle model, nonlinear characteristics of the elasto- damping elements, and modified Nelder-Mead method. The modifications were made in order to enable the problem of optimization of the characteristics of elasto-damping elements to be solved in the presence of constraints on the values of the optimizing parameters of the vehicle (within the appropriate defining ranges). The method adopted in this work allowed simultaneous minimization of vertical oscillations, of the roll and pitch motions of the suspended mass, of the vertical oscillations of the wheels, and of the normal dynamic road reactions. Possibilities for application of the developed optimization method are illustrated by means of a case study involving a middle class passenger car. (A)
18 citations
TL;DR: In this article, the potential performance benefits of active high gain load levelers with specified configurations are investigated analytically using a quarter-car model and an analysis of the vehicle suspension systems is formulated for determining vehicle stability and response to body force and road disturbances.
Abstract: SUIMMARY The potential performance benefits of active high gain load levelers with specified configurations are investigated analytically using a quarter-car model. An analysis of the vehicle suspension systems is formulated for determining vehicle stability and response to body force and road disturbances. Both random and deterministic disturbances are considered Optimally controlled active suspensions with and without a derivative constraint in the performance index are also investigated. Results pertaining to the two optimal systems are presented and evaluated. It is shown that the load leveler offers a viable mechanism for controlling vehicle attitude without the necessity of reducing the isolation qualities and road-holding ability of the suspension.
TL;DR: In this article, the activation mechanism of the wobble oscillation is made clear in the framework of the energy flow concept and a designing guide to stabilize the bike wobble mode is mentioned.
Abstract: SUMMARY A concept of the energy flow is introduced in order to study the motorcycle wobble mode. The activation mechanism of the wobble oscillation is made clear in the framework of the energy flow concept It is found that the wobble mode is activated mainly by the yaw rate and roll rate motion and is suppressed by the lateral acceleration and the force of the front time. A designing guide to stabilize the wobble mode is mentioned.
TL;DR: In this paper, a vehicle is modelled as a dynamic system made of masses interconnected by, linear, springs and dampers, and the optimization method used is the sequential linear programming by iteratively applying the Simplex algorithm.
Abstract: SUMMARY The objective of this study is optimizing the components design of a vehicle suspension system under excitation due to road roughness. The vehicle is modelled as a dynamic system made of masses interconnected by, linear, springs and dampers. The optimizing code provides values corresponding to the caracteristics of masses, dampers and springs which, within a range, minimize the objective function for a defined excitation. This objective function auantifies the vehicle comfort level. The optimization method used is the sequential linear programming by iteratively applying the Simplex algorithm. The model response is obtained in frequency domain and the vehicle excitation can be either random or deterministic. The exact nature of the optimization problem, objective function and restrictions, depend on the type of excitation considered. In succeeding paragraphs, the problem formulation together with a comparison with other authors is presented.
TL;DR: In this article, a two-mass linear model is employed for the pantograph and the design of the proposed control system is based on the input admittance at low frequencies, and a simple dynamic controller is employed to achieve optimality in an equivalent transformed system, while minimising the number of feedback quantities to be measured.
Abstract: SUMMARY In pantographs used for current collection on high speed electric trains it is desirable to minimise the fluctuations in the contact force between the collector head and the catenary. A simple two-mass linear model is employed for the pantograph and the design of the proposed control system is based on the input admittance at low frequencies. Frequency shaping is incorporated in the performance index, and a simple dynamic controller is employed to achieve optimality in an equivalent transformed system, while minimising the number of feedback quantities to be measured. A significant reduction in the average contact force appears possible.
TL;DR: In this article, a nonlinear inverse model of a road vehicle which simulates combined steering and braking/driving is presented. But this model is restricted to a single vehicle and the inputs to the model are the lateral and longitudinal acceleration of the vehicle's sprung mass center.
Abstract: SUMMARY This paper presents a nonlinear inverse model of a road vehicle which simulates combined steering and braking/driving. The inputs to the model are the lateral and longitudinal acceleration of the vehicle's sprung mass center. The simulation returns the steering wheel angle and brake/drive torques required to obtain the desired accelerations. An example is presented which demonstrates the utility of inverse models for optimization purposes.
TL;DR: In this article, the effect of the cambering of the front frame on the cornering response of a fixed and free control of the steering axis of a motorcycle is investigated.
Abstract: Through linear analysis, the handling characteristics of the motorcycle with fixed control of added cambering of front frame are investigated under the variation of fixed and free controls of steering axis. The cornering responses and stability characteristics of the motorcycle are presented with the aid of the handling diagram. From numerical results for a typical motorcycle, it is found that the influence of the cambering of front frame on the cornering response of fixed steering control is opposite to that of free steering control. Moreover, the design philosophy of a so-called semi-direct steering mechanism, which cambers the front frame for cornering, is studied. (Author/TRRL)
TL;DR: In this paper, the authors describe the modelling of a two-axle railway-bogie with variable design configurations and its application in the investigation of the behaviour in transitional and circular curves.
Abstract: SUMMARY This paper describes the modelling of a two axle railway-bogie with variable design configurations and its application in the investigation of the behaviour in transitional and circular curves. Several results indicate possibilities to improve the curving properties and recommend the usage of forced-steering bogies, which show better performance in narrow curves without unbearable sacrifices to high-speed-behaviour on straight track.
TL;DR: In this paper, the reciprocity relation is used to determine the response of a beam-like structure (a beam on mass-spring supports, a model of a railroad) subjected to a moving constant force.
Abstract: SUMMARY Reciprocity relations are valid also for dynamic problems (Fung, reference [1]). In this paper, the reciprocity relation is first used to determine the response of a simply supported beam subjected lo an arbitrarily time-varying force moving with constant speed. Then the reciprocity relation is used to determine the response of a beam-like structure (a beam on mass-spring supports, a model of a railroad) subjected to a moving constant force. Numerical solutions, including also a pair of moving forces, are given.
TL;DR: In this paper, the authors present the description and results analysis for the modelling of an agricultural vehicle with self governing guidance, as well as for the simulation of its automatic control, achieved by means of the bond graph technique.
Abstract: SUMMARY Automatic guidance of agricultural vehicles has been a major topic covered in a number of projects developed worlwide during the last years. The complex structure these systems show, where singularities and non-linearities are often present, renders analytical study difficult. Computer simulation techniques prove to be of great help in these cases. This paper presents the description and results analysis for the modelling of an agricultural vehicle with self governing guidance, as well as for the simulation of its automatic control. Vehicle modelling is achieved by means of the bond graph technique. The method's main contribution is a unified treatment for variables that simultaneously includes different physical domains, so that all variables are lumped together in a single simulation model.