Showing papers in "Jsae Review in 1999"

Application of active yaw control to vehicle dynamics by utilizing driving/breaking force

Abstract: In line with improvements in vehicle performance and increasing diversification in vehicle applications, improvements in active safety are becoming increasingly important. For its part, Mitsubishi Motors has developed a variety of wheel control technologies that enhance both safety and performance by exploiting the inherent properties of wheels and tyres. This paper describes two of Mitsubishi Motors’ latest developments: the AYC (Active Yaw Control) system and the ASC (Active Stability Control) system. These systems control the driving and braking forces acting upon the right and left wheels in such a way that cornering force can be controlled directly by the driver. As a result, they enable significantly safer and more enjoyable driving.

Study on dynamic characteristic analysis of air spring with auxiliary chamber

Abstract: The characteristics of air springs, such as the effects of bellows and those of heat transfer on spring constant and damping factor, have been studied. However, auxiliary chambers and pipes are required in addition to air springs, to vary spring constant in the case of spring rate change by electronically controlled air suspension systems of a vehicle. Few reports have dealt with the effects of auxiliary chambers and pipes. In our study, the relation between vibration frequency and spring reaction has been investigated to clarify the effects of pipes on dynamic spring constant. Our proposed model has proved effective in understanding the phenomena.

Improvement of vehicle handling by nonlinear integrated control of four wheel steering and four wheel torque

Abstract: A nonlinear control system that integrates active four wheel steering and four wheel torque control is introduced in this paper. The theory for continuous time nonlinear predictive control is applied to the design of the control system. The advantages of coordination of four wheel steering and individual wheel torque control are demonstrated through computer simulations. Simulations in which the driver dynamics are taken into account are also carried out. The results of the simulation show that the vehicle maneuverability and stability can be remarkably improved even in a near limit cornering condition by the proposed nonlinear control system.

Drive force control of a parallel-series hybrid system

Abstract: Since each component of a hybrid system has its own limit of performance, the vehicle power depends on the weakest component. So it is necessary to design the balance of the components. The vehicle must be controlled to operate within the performance range of all the components. We designed the specifications of each component backward from the required drive force. In this paper we describe a control method for the motor torque to avoid damage to the battery, when the battery is at a low state of charge.

Development of the scanning laser radar for ACC system

Abstract: In recent years, the development of the adaptive cruise control (ACC) system with the aim to improve driving convenience and comfort, has been progressing. To put this ACC system to practical use, the elimination of unexpected acceleration or deceleration caused by incorrect judgment is highly demanded. From 1997, the Laser Radar ACC system has been produced for the domestic version of the Lexus LS400. It provides high recognition capability with a two-dimensional scanning technology at an affordable price. This paper introduces this Laser Radar with a high-performance two-dimensional scanning technology.

Application of sliding-mode theory to direct yaw-moment control

Abstract: It has become popular to control vehicle manoeuvering with independent brakes for the avoidance of spin and drift-out. To ensure effective control, we applied sliding-mode theory, which enabled a robust control system against various driving conditions including changes in velocity, road friction and vehicle weight. By estimating the tyre status with a simple tyre model, the side slip angle of vehicle and road friction, we made it possible to easily install the system on vehicles. Our system is also equipped with parameter identification for correcting model errors. We confirmed the effectiveness of our system through full vehicle simulation and field tests.

Analysis of lateral stability with integrated control of suspension and steering systems

Abstract: Stability of the integrated control system that consists of an active control of vehicle suspension and a steering system in cornering on curved and randomly uneven roads is analyzed by means of LQR control theory under a preview driver control It is confirmed that maneuverablity is much improved for safer cornering along a desired curve on uneven roads The simultaneous optimization of design parameters by the integrated control system is necessary and more effective to realize a desired vehicle motion than the summation of controls obtained by individually optimized systems

Self-powered active control applied to a truck cab suspension

Abstract: A method of active vibration control using regenerated vibration energy, i.e. self-powered active control, applied to the cab suspension of a heavy duty truck. In the proposed system, an electric generator that is installed in the suspension of the chassis regenerates vibration energy and stores it in the condenser. An actuator in the cab suspension achieves active vibration control using the energy stored in the condenser. Numerical simulations and basic experiments demonstrate better isolation performance of the self-powered active vibration control system than that of a passive and a semi-active control.

Driving characteristics of the elderly: risk compensation of the elderly driver from the viewpoint of reaction behavior

Abstract: Driving characteristics of elderly and younger drivers who were following another vehicle were examined. Vehicle and driver behavior data (vehicle speed, space headway, operation of brake/accelerator pedals and road traffic conditions) were recorded on videotape. Reaction time, time headway and braking time in the case that a driver reacted to braking of a lead vehicle were analyzed. The result shows; reaction time of the elderly driver is longer than that of the younger, however driving speed of the elderly is lower and their time headway is longer to compensate for their longer reaction time.

Life cycle assessment, evaluation method for sustainable development

Abstract: This report presents automotive applications of life cycle assessment (LCA) which has attracted public attention as an effective tool for evaluating environmental burdens quantitatively. It also reviews the background of how LCA has been introduced, and discusses future possibilities of LCA applications to automobiles as well as important aspects of LCA.

Approach to minimization of piston slap force for noise reduction-investigation of piston slap force by numerical simulation

Abstract: Impact force caused by piston slap is one of the major mechanical noise sources in a diesel engine The optimization of piston pin offset for impact force reduction has been reported by many researchers However, if a modification has large effect at idling, high-speed noise tends to increase and vice versa It was very difficult to reduce piston slap noise at all engine speeds In this paper, the mechanism of the piston slap was investigated precisely utilizing numerical simulation Simultaneous noise reduction in the conditions of both idling and high speed was achieved successfully by optimizing the piston's center of gravity as well as piston pin offset Furthermore, engine sound quality was also significantly improved

Using multiple regression analysis to estimate the contributions of engine-radiated noise components

Abstract: The respective contributions of combustion noise, mechanical noise, load-dependent noise and other engine noise components must be identified in order to devise effective measures for reducing diesel engine noise under full load operation. This paper describes a method for estimating the contributions of engine noise components using multiple regression analysis. With this method, the engine noise level is regarded as a criterion variable and the cylinder pressure level and engine torque as explanatory variables. The accuracy of this method has been confirmed by comparing the results with experimental data. Some examples of its application are also presented.

Analysis on fuel economy and advanced systems of hybrid vehicles.

Abstract: Basic ideas on operation of hybrid vehicles were discussed from a view point of energy saving. Almost double fuel economy of series–parallel–hybrid vehicles was estimated on condition of no engine idling during vehicle stop, energy saving in acceleration using brake energy recovery and high efficiency operation on low load condition using series–hybrid system. From the discussion of overall efficiency, involving fuel cycle, under both low and high load conditions, both series–parallel–hybrid vehicles with internal combustion engine and fuel cell are supposed to have a high potential for the future.

Closed-loop analysis of vehicle behavior during braking in a turn

Abstract: This paper discusses an analysis of “driver-vehicle” behavior during braking in a turn. In this study, a new braking model was developed in consideration of actual driver's operation, and experiments were conducted on mountain roads to identify one novice and one skilled driver's braking model parameters. The computer simulations have shown the following tendency. The novice driver needed more compensatory steering operation than the skilled driver to trace the course. A controlled braking force distribution was particularly effective for the novice driver.

Method for measuring force transmitted from road surface to tires and its applications

Abstract: The force transmission from road surface to a rolling tire has been successfully measured by force measurements on suspension parts and correction for interia forces of suspension parts. The results of the measurement have shown that the force from road to tire has a sharp directivity, which is inclined rearward in side view, within the frequency range between 5 and 15 Hz. And the inclination angle of the direction of action has been found to be dependent on the vehicle velocity. As the application of the finding, the optimal wheel center locus inclination in side view has been studied, to minimize the longitudinal force transmission. And the optimum angle has been confirmed to exist.

Research on automated lane tracking using linear quadratic control : control procedure for a curved path

Abstract: When an automated vehicle is travelling along a curved path, the yaw rate and yaw angle do not have values of zero. This means that it is impossible to apply a simple regulator that converges the values of all state variables to zero. This paper describes the use of a set point regulator, which applies linear quadratic control theory while shifting the equilibrium point in a situation where the road curvature is given as feed-forward information. It also proposes a control method that enables an automated vehicle to navigate curves without feed-forward information by estimating the road curvature as it proceeds.

Possibilities to improve the ride and handling performance of delivery trucks by modern mechatronic systems

Abstract: The ride and handling qualities of conventional delivery trucks are wores compared to modern passenger cars. However this vehicles have the power to drive as fast as passenger cars. Vehicle comfort and driving safety are mostly influenced by vertical accelerations and vehicle movements caused by pitch and roll motions. In the paper “Vehicle Dynamics with Adaptive or Semi-Active Suspension Systems – Demands on Software and Hardware” Wallentowitz and Ridlich have shown at AVEC'94 in which way tyre stiffness, shock absorber characteristics, spring stiffness and unsprung mass have an influence on vehicle comfort and active safety. They achieved these results by the theoretical analysis of a quarter-vehicle-model. Their examinations are extended in this paper on the model of a complete delivery truck. By the use of the multibody-simulation tool SIMPACK the road performance of a delivery truck will be analysed. Therefore a complex model of the vehicle has been built up in SIMPACK. Several computer simulations have been carried out to analyse the vehicle comfort and handling characteristics in different standard driving manoeuvres. Furthermore, the potential of improvements is shown by simulating different driving manoeuvres with the complete vehicle model by varying some vehicle characteristics such as tyre stiffness, shock absorber characteristics, spring stiffness and unsprung mass. In addition to that, simulations with models of unconventional spring- and damper-systems have been carried out to demonstrate the potential of improvements by the use of these systems. Two different controller algorithms for a semiactive and an active suspension system have been used an will be compared in this paper.

Gravity center height estimation for the rollover compensation system of commercial vehicles

Abstract: This paper concerns a technology to estimate the vehicle dynamics transfer function and to correct the control parameter of roll-over compensation system. ARX-model is applied to estimate the transfer function of an actual vehicle. The gravity center height, one of the control parameters of the control model, is corrected so that the transfer function could be in congruence with that of the actual vehicle. The control model forecasts the critical roll-over condition and the control system compensates the critical condition by controlling the braking force distribution.

Pseudo cylinder pressure excitation for analyzing the noise characteristics of the engine structure

Abstract: A new in-cylinder excitation system has been developed to analyze the engine structure attenuation experimentally. A hydraulic and a piezoelectric actuator are used to exactly reproduce the cylinder pressure in non-running engine conditions. The structure attenuation measured in this system has a good coincidence with that measured in actual engine operating conditions, however the conventional excitation method, which applied only high-frequency components as the excitation pressure, resulted in poor agreement. As a result, the proposed system has been proved to be very useful and effective to estimate the engine noise characteristics without engine running.

Nonlinear H∞ control for semi-active suspension

Abstract: This paper describes the development of a damping control system for semi-active suspension which is based on nonlinear H ∞ control theory instead of conventional linear control theory. A two degrees of freedom system is used as the structure for the vehicle suspension model. Since the structure is bilinear, it's not easy to design the controller. We designed the controller based on the Hamilton-Jacobi inequality by solving a linear Riccati equation. We were able to verify by simulation that nonlinear H ∞ control theory made it possible to control vehicle vibration optimally and smoothly.

Development of high-performance all-polyester sound-absorbing materials

Abstract: This paper describes two kinds of newly developed polyester sound-absorbing materials. One mainly consists of modified cross-section polyester fabric, and the other consists of recycled polyester fabric. They provide noticeably higher sound-absorbing performance than traditional materials like shoddy or urethane foam. This is because the new materials have greater surface area than that of traditional materials at an identical weight. Another feature of the new materials is their excellent recyclability since they are made of polyster. Application of the new materials to the dash silencer and floor carpeting resulted in a significant improvement in sound insulation performance while achieving weight savings.

Theoretical analysis of bearing considering elastic deformation – effects of the housing stiffness and bearing length on bearing performance

Abstract: In recent high power, compact and light weight automotive engines, the bearing load has been increasing and housing stiffness has been decreasing. As a result, the bearing performance is greatly influenced by elastic deformations of both the housing and the bearing. The effects of changing both the housing stiffness and the bearing length on bearing performance were studied by using the elastohydrodynamic lubrication theory on connecting rod bearings for diesel engines.

Development of platoon driving in ahs

Abstract: This paper describes a platoon driving control system on an automated highway system (AHS). The system implemented on a test vehicle is described first, followed by a description of a vehicle control method based on the use of throttle and brake actuators. Experimental and simulation results obtained with this method are presented. A control method is then described that uses inter-vehicle communication to maintain a constant headway. The results of simulations and driving tests conducted with three vehicles are presented to illustrate that the use of inter-vehicle communication is highly effective in improving headway control performance.

Analysis of odor in car cabin

Abstract: Odor in a new car cabin is caused by a complex mixture of various compounds evolved from parts and materials. To understand the odor and the compounds responsible for the odor, sensory evaluations and instrumental gas analysis were carried out. In sensory evaluations, odor intensity, pleasantness and odor characters were evaluated for 73 new cars. The odor compounds of 17 new cars were analyzed with GC and GC-MS using adsorbent tubes and canisters. From the principal components analysis of sensory evaluations, odor characters were classified into six types. The correlation between sensory evaluation results and concentrations of odor compounds identified the compounds that are responsible for the odor.

Technology for measuring and diagnosing the damping force of shock absorbers and the constant of coil springs when mounted on a vehicle

Abstract: Diagnosis of the individual function of shock absorbers and coil springs has been simplified by an off-the-car-type tester. We studied methods of analyzing coil springs and shock absorbers independently without removing them from the vehicle. The damping force of the shock absorber itself, excluding the spring effect, can be indicated according to the axle weight/road wheel at the point of displacement 0.

Study on a metal pushing V-belt type CVT: band tension and load distribution in steel rings

Abstract: The power transmitting mechanisms for laminated belts were numerically investigated to analyze belt tension in each band of the ring of metal V-belts. The numerical model consists of linear springs and frictional elements. It was shown that the innermost band must support significantly greater load than any other bands when the frictional coefficients between two bands are lower than that between the innermost band and the blocks. The frictional coefficients between bands should be slightly larger than that between the innermost band and the blocks in order to reduce the load distribution to the innermost band.