The handling characteristics of a vehicle play an important role regarding vehicle safety and the overall enjoyment of the driving experience. Presently applied procedures are based on international standards, which are usually legitimated on large proving grounds and their application is quite time consuming. Newer approaches focus on the on-board identification of vehicle parameters. This procedure differs substantially from currently used methods. New evaluation methods and criteria are developed, especially for heavy commercial vehicles. The paper describes two methods how to speed up and increase the information value of the currently used vehicle evaluation procedures. The focus of the paper is on the application of new procedures to evaluate the vehicle dynamics of heavy commercial vehicles, which are already applied to measurement data of passenger cars. These methods enable the use of simple test manoeuvers instead of the commonly used complex and time consuming driving procedures, which require steering machines and large dynamic platforms. In the first method, system identification algorithms are used to calculate different vehicle parameters and frequency responses from any transient driving manoeuvers. These parameters are system gain, system damping, natural frequency and delay constants. These calculated parameters are widely known and different investigations have shown that a short time delay and high system gain and high system damping are positively evaluated by the vehicle drivers. The application of the developed method to simple and freely driving manoeuvers (e.g. double lane change) shows a reduction of needed driving maneuvers and a sufficiently high accuracy. In a second evaluation method a nonlinear optimization algorithm enables the identification of side force characteristics from vehicle measurement data. These characteristics include tire and chassis attributes and affect the handling performance in an important manner. They can be also used to validate and parameterize simulation models. This method is applied to measured data of asteady state cornering manoeuvre. The needed measurement data are steering wheel angle, yaw velocity, lateral velocity and lateral acceleration. Figure 1 shows the identified side force characteristics from the measurements of a steady state cornering manoeuvre. The figure on the left shows a good correlation between the identified side force Fsr and the calculated tyre force Fsy TMeasy of th tyre model TMcasy for the rear axle of the vehicle. Also the identified characteristic of the front axle Fsf shows feasible results, because they also include the stiffness of the steering system additionally to the tyre characteristics, These characteristics state an important fingerprint of the vehicle's dynamics and can be used to compare and evaluate vehicles. Another advantage of this method is that the calculation of tire maps from vehicle measurements is less costly and easier available than expensive tire test bench measurements.
Objective handling evaluation of heavy commercial vehicles by means of model based parameter identification
2010
9 Seiten, 8 Bilder, 10 Quellen
Conference paper
English
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