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The deposition behavior of brake wear particles on the surface of a wheel and the mechanisms on it have not been fully understood. In addition, the proportion of brake wear particles deposited on the wheel surface compared to the total emitted particles is almost unknown. This information is necessary to evaluate the number- and mass-related emission factors measured on the inertia dynamometer and to compare them with on-road and vehicle-related emission behaviour. The aim of this study is to clarify the deposition behavior of brake particles on the wheel surface. First, the real deposition behaviour is determined in on-road tests. For particle sampling, collection pads are adapted at different positions of a front and rear axle wheel. In addition to a Real Driving Emissions (RDE)-compliant test cycle, tests are performed in urban, rural and motorway sections to evaluate speed-dependent influences.

The particulate emissions of two brake systems were characterized in a dilution tunnel optimized for PM10 measurements. The larger of them employed a fixed caliper (FXC) and the smaller one a floating caliper (FLC). Both used ECE brake pads of the same lining formulation. Measured properties included gravimetric PM2.5 and PM10, Particle Number (PN) concentrations of both untreated and thermally treated (according to exhaust PN regulation) particles using Condensation Particle Counters (CPCs) having 23 and 10 nm cut-off sizes, and an Optical Particle Sizer (OPS). The brakes were tested over a section (trip-10) novel test cycle developed from the database of the Worldwide harmonized Light-Duty vehicles Test Procedure (WLTP). A series of trip-10 tests were performed starting from unconditioned pads, to characterize the evolution of emissions until their stabilization. Selected tests were also performed over a short version of the Los Angeles City Cycle.

The measurement of brake dust particles is a complex challenge owing to its open system configuration; indeed, the emitted particles are directly spread into the environment. Measurements on the inertia brake dyno feature controllable and reproducible environmental and operational parameters. Although Real Driving Emission (RDE) measurements enable the detection of brake dust particles emitted in real driving conditions (i.e. traffic condition, driving style, air humidity, vehicle components’ wear and ageing, etc.), they are complex and not reproducible due to external, continuously changing parameters (e.g., flow conditions, changing traffic conditions, particulate matter from other sources). The motivation lies in developing a real driving emission sampling system for brake particle emissions, which meets the quality requirements of the measurements, as well as the prevention of particle losses and contamination, thereby supplementing and reviewing laboratory-based procedures.

The growing awareness of health relevance of fine dust emissions beyond traditional combustion engines becomes more and more important for state of the art research activities. Already existing emission regulations, which are exclusively dedicated to combustion engines, can also be helpful to regulate brake particle emissions since they are nearly in the same range of size and distribution. Another driver is customer satisfaction like surveys such as J.D. Power are showing. It can be stated that a major reason for complaints is the elevated wheel soiling by braking-caused emissions. The major goals of research activities are the development, realization and evaluation of countermeasures dedicated to brake particle emissions. For the development of measures a possibility is shown, which allows the characterization of particle loaded flows as well as the realization of countermeasures. Therefore numerical flow simulation (CFD) is used.

Stability of motion, turnability, mobility and fuel consumption of all-wheel drive terrain vehicles strongly depends on engine power distribution among the front and rear driving axles and then between the left and right wheels of each axle. This paper considers kinematic discrepancy, which characterizes the difference of the theoretical velocities of the front and rear wheels, as the main factor that influences power distribution among the driving axles/wheels of vehicles with positively locked front and rear axles. The paper presents a new algorithm which enables minimization of the kinematic discrepancy factor for the improvement of AWD terrain vehicle dynamics while keeping up with minimal power losses for tire slip. Three control modes associated with gear ratio control of the front and rear driving axles are derived to provide the required change in kinematic discrepancy. Computer simulation results are presented for different scenarios of terrain and road conditions.