Search Results

The demands imposed on a braking system of passenger cars, under wide range of operating conditions, are high and manifold. Improvement of automotive braking systems' performance, under different operating conditions, is complicated by the fact that braking process has stochastic nature. The automotive brake's performance primarily affected the braking system's performance because their performance results from the complex interrelated phenomena occurring in the contact of the friction pair. These complex braking phenomena are mostly affected by the physicochemical properties of friction materials ingredients, its manufacturing conditions, and brake's operation regimes. Analytical models of brakes performance are difficult, even impossible to obtain due to complex and highly nonlinear phenomena involved during braking. That is why, in this paper all relevant influences on the disc brake operation of a passenger car have been integrated by means of artificial neural networks.

The neural computation ability to model complex non-linear relationships directly from experimental data, without any prior assumptions about nature of the input/output relationships, has been used in this paper. An artificial neural network technique was used to develop a neural model for predicting the friction materials behavior under prescribed testing conditions. By means of neural modeling of the friction materials behavior, the relationship between 26 input parameters and one output parameter (brake factor C) has been established. The input parameters are defined by the friction material formulation (18 parameters), manufacturing conditions (5 parameters), and testing conditions (3 parameters). Prediction abilities of the neural model have been evaluated by comparison the real cold performance obtained during friction material testing on the single end full-scale inertia dynamometer and predicted ones.

Active safety of vehicle combinations during braking highly depends on braking compatibility behavior. There are different influencing factors disabling partial deceleration of individual elements of a vehicle combination to be “compatible”, or balanced. The paper deals with an advanced Friction Monitoring and Control System (FMCS), which may be used in braking systems of vehicle combinations. This system is intended to improve vehicle combination braking compatibility behavior, but also braking force distribution performance of combination components by means of monitoring and controlling of braking force variations. Digital brake models are developed for this purpose. They relate analytically and/or numerically braking forces developed in individual brakes of a vehicle combination with the most dominant influencing factors, and in particular with the control pressure.

The development of a "Virtual Brake Testing" concept is presented in the paper, showing how a "virtual disc brake prototype" may be subject to "virtual testing" for performance and reliability evaluation. For this purpose, a large experience accumulated throughout many years of testing of various vehicle brakes by means of a couple of full-scale inertia dynamometers was collected in an appropriate Knowledge Database. It is used in this project to enable (i) to create the test schedule, (ii) to model the braking cycle influencing factors, and (iii) to model factors expressing brake performance and reliability for application within an advanced computer simulation. The development of the virtual disc brake model that was then subject to virtual testing was based on integrating Pro/Engineer & Pro/Mechanica parametric design capabilities, while subsequent virtual testing was performed by means of Pro/Motion.

A high quality providing customer satisfaction is first condition of success in contemporary automotive market, particularly for the subsystems having strong impact on road safety and riding comfort. Customer expectations with regard to the braking system performance are usually expressed in form of “voice statements”, i.e. not expressed explicitly, either quantitatively or statistically. The evaluation of the braking system quality that satisfies a customer makes problem. The newly developed fuzzy-set concept, dealing with fuzzy quantities and uncertainties, makes a convenient tool for those analysis. An application of fuzzy concepts to evaluate customer satisfaction of braking systems is elaborated in the paper in general terms.

It is assumed that braking system of a modern concept motor vehicle should be optimised with respect to a number of different parameters. There are cases where the brake performance under test conditions are significantly below designed (“nominal”) values. Such deviations are often attributed to the friction material characteristics, but there are also other possible causes such as mechanical losses in the brake itself. Contribution to the allocation of mechanical losses in drum brakes and quantification of their influence on the brake performance and braking force distribution is presented in this article. It was shown that there is a significant influence of mechanical losses on the drum brake performance, especially in unladen vehicles, vehicles equipped with highly sensitive brakes (high brake factor values) and in cases where vehicle is braked on low friction roads.

The prediction method for brake linings life named “Linear Wear Hypothesis” (LWH) was developed few years ago, based an short and quick lining life tests. In line with this method, a procedure for modelling the friction properties of friction material based on the theory of the design of experiments was elaborated. This investigation made possible the derivation of mathematical models describing wear of the lining and work done by the brake as a function of braking or application conditions. The models evaluated for a typical disc brake pad and a typical drum brake lining are explained in this article, and application of such models for prediction of the friction material life with help of the LWH, as well. Experiments realized demonstrate that combining the LWH procedure with modelling technique offers real possibilities for the prediction of lining life based on the rather short and quick tests using inertia dynamometer.

Brake lining/pad life can be predicted using the so called “Linear Wear Hypothesis - LWH”, which is based on two assumptions explained in details in this paper. The brake lining/pad life prediction method has been developed to be used against the brake dynamometer test results, in comparison to the previously determined brake loading under real service conditions(distribution of the work done by brakes and the corresponding disc/drum temperature levels in particular). The basic concept of L W H is verified experimentally during the first phase of investigation. In this paper a review of comprehensive dynamometer test results is presented. A number of samples of four different friction material disc brake pads for a light car of 1,2t have been tested. The prediction method, based on the LWH, is used to determine the predicted pad life, and the calculation of the pad life is explained. However, the obtained results are related only to the tested brake.