Abstract
The main goal of the project reported here is to develop a laboratory track endurance test mode for ultra-high performance brake pads under severe vehicle driving conditions. The basis for the study is the measurement of brake behaviour on a dynamometer and on proving ground using as a reference the front axle of an AUDI R8 V10 with iron brakes.
The project activities are based on the correlation of the dyno and vehicle test results to define the main factors affecting the brake performance drop. The laboratory test mode will be focused on these parameters to develop the dynamometer test procedure.
The research has been divided into five activities:
1. To build a general methodology to measure and analyse brake pad testing data.
The first step in the project is to define the basis for the testing and the analysis. A robust method will simplify the analysis activities, as all tests are focused on generating the expected result, in this case, the brake performance drop.
2. Brake pad characterization on brake dynamometer and proving ground.
The aim of this pre-activity is the evaluation of the brake pad performance with no vehicle influence (dynamometer testing) in order to tune the test modes and to get robust results.
3. To find influencing parameters related with brake pad performance.
Based on dyno and vehicle testing test results, the scope of the work is to identify the main variables affecting the brake response. Statistical tools are used to identify which of the potential candidates are really significant parameters to explain the brake performance drop.
4. Brake pad testing on an Audi R8 in Castelloli circuit (Spain).
The brake pad performance drop is also characterized by driving the vehicle on Castelloli circuit, performing a subjective and objective evaluation of the brake performance, analysing the evolution of the relevant parameters under study. The results obtained in the circuit are correlated with dyno results.
5. Development of brake pad lab test mode.
Taking into account all the data and information gathered in the previous activities, a well correlated brake pad lab test mode is developed.
The analysis to find the main factors for the brake performance drop starts by considering all output variables from the dyno tests to narrow the study to the potential candidates (disc temperature and accumulated power). The statistical tool shows both the temperature and the brake application accumulated power as significant variables of the study, which confirms them as the main parameters affecting the brake performance drop in the defined area of
study. The test results of the Lab Test Mode generated by IDIADA based on the Brake Laboratory test mode calculator are robust evidence that the tools aim is achieved. Thus, the brake performance driving an AUDI R8 on Castelloli circuit can be emulated by generating an equivalent dyno procedure. Representative brake temperature measurement is difficult when using wheel torque transducers, which reduce brake cooling. Hence, when measuring brake torque on the real vehicle, brake temperatures are always higher than expected. Also brake dyno cooling is difficult to match with the real in-vehicle cooling conditions and needs to be correlated by doing extra tests.
This paper not only identifies the main parameters that affect brake pad performance drop, but also achieves a good correlation between the brake dynamometer and the real vehicle results under circuit driving conditions.
This work shows how the Brake Lab Test Mode has been developed, considering the dominating braking parameters, a brake dynamometer correlation and a final validation of the designed procedure. The Brake Lab Test Mode has been validated for an Audi R8 using iron brakes on Castelloli circuit, but can be adapted to other vehicles and circuits.
KEYWORDS Brake performance, Brake dyno, Brake dynamometer dorrelation, Brake dyno development tool, Endurance test.