SCSC2003 Abstract S61663

A brake disc's temperature estimation module

A brake disc's temperature estimation module

Submitting Author: Dr. Sad HAYAT

One of the current methods to increase vehicles safety is the prevention of dangers by warning the drivers of detectable hazards (anti-collision and regulation of distance; sensors and actuators failures). The means to detect these dangers are covered by a numerous different sensors. These are managed by ECUs (Electronic Control Units). Indeed, each on-board computers manage a subsystem of the vehicle (braking system, engine, ...).

Indeed, some problems are caused by sensors multiplication. Particularly on a truck, where about 800 measures per seconds (provided by sensors) are exchanged between these calculators (ECU) via a bus CAN. That implies the existence of real-time constraints in data acquisition and fusion. Furthermore, the cost that sensors represent (purchase and maintenance) strongly increases the vehicle's price. Finally, sensor's possibilities are often reached in terms of integration or accuracy. An approach to reduce sensors number and/or approximate measures consists in estimating mathematically a variable targeted than to measure it. This paper formulate an approach to evaluate brake disc temperature of heavy duty vehicle.

The first part of this job was initiated by Reanult Trucks (Saint-Priest). This study fits within the framework of the European project "SAFE TUNNEL". Its main goal is to reduce considerably the number of trucks accidents in tunnels. One of the research areas is to determine and predict risks of fires into tunnels; particularly for mountains tunnels. It seems that fires could be direct or indirect consequences of brake system failure. Indeed, it is shown that brake failure correspond to about 6% of the tunnels accidents. Some would have been able to avoided by a good brake disc temperature estimation. In a second part, the problem will be to develop a thermal general management of the truck.. This implies "hot spots" detection on them."Hot spots" defines the points whose overheating has got a high probability to give birth to fires.

In this paper, we only answer to the first part of the study. So, we present two approaches in order to estimate brake disc's temperature : a direct and an indirect method. The direct method use a bond-graph modelling of the brake disc. This method was limited by brake model parameters knowledge. On the contrary, an indirect method which doesn't require direct temperature measures (sensors) or brake disc models is developed. Only by using the relations of dynamic applied on the truck and the relations of thermal between the disc brake and its environment, we elaborate a theoretical heating model. Then, the brake disc temperature estimation will allow to detect when a "hot point" reach its security temperature limit. This detection will be use to warn the driver of a its brake overheating. Simulations under Simulink environment complete this study. Comparison between field tests and simulation are under development in Renault Trucks. They will permit us to characterize the re
liability of our model. Moreover, under certain hypotheses on parameters, we show the feasibility of temperature prediction. The second part of the study, which is also the longest one, gives place to a doctoral thesis.

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