INFLUENCE OF BRAKING FORCE DISTRIBUTION ON BRAKING STABILITY

Former researches have shown that braking force distribution is the factor with greatest influence on the driving stability of a vehicle while it is braking. Imbalances of braking force between front and rear axles can lead to dangerous situations. This paper presents the results of some simulation studies to analyse these phenomena more precisely, objectively, and reproducibly. A tyre test stand measures the force transmission characteristics of a tyre, an inertia dynamometer delivers instantaneous values of braking force distribution, and an axle kinematic test stand produces elastokinematic characteristics. These data are processed by simulation programs, which are based on mechanical substitution models that can reconstruct mathematically the dynamic behaviour of commercial vehicles. The two manoeuvres applied in the testing procedures are: (1) braking straight ahead; and (2) braking in a turn. For braking straight ahead, reducing the braking torque to 75% of design specifications simultaneously reduces the line pressure control range, and reducing the braking force by only 10% at the rear axle negates rear wheel lockup. The instantaneous braking force distribution is found to be the most important factor influencing the directional stability of commercial vehicles while braking in a turn. For the covering abstract see IRRD 881545.