Brake Parameters Influence over Vehicle Dynamics Performance of an Entry-Level Compact Vehicle 2013-36-0017

Through the new Automotive Regulation recently deployed by ANFAVEA, vehicles selled in Brazil will have strong incentives to reduce fuel consumption. OEMs are being pushed to develop alternatives to achieve lower levels of fuel consumption either by new engines or reduce overall weight for the vehicles. Reducing the weight is being the logical and first choice by automakers, since it represents a cost reduction as well. The problem lies on the crash resistance (Latin NCAP) that forces the vehicle to have reinforcements, especially in the near future for the lateral crash standard, still to be deployed in the market. Thus, in the opposite direction, there is a natural tendency to increase sprung mass. In this way, the solution is to reduce non-sprung masses.

The non-sprung parts likely to be reduced are normally components that impact the customer feeling the least, for example: dampers, stabilizer bars, tires, wheels, etc. In this context, front stabilizer bars are the first natural choice, especially for the entry-level vehicles.

It is well known the loss of yaw stability that a vehicle with low front roll stiffness tends to show. During severe braking maneuvers, for example, it is more likely for this kind of vehicle to lift off the inner rear wheel and then shows a tendency to spin out. At this scenario, different brake distribution along with ABS plays an important role at the vehicle yaw stability.

The present work shows the influence of brake parameters over the vehicle yaw stability by means of simulation. A vehicle dynamics model was created using a functional model and validated against measured data. The model represents an entry-level vehicle, with reduced front roll stiffness.

Functional simulation mode does not solve the multi-body equations for each integration step as any regular MBS software and so, can run simulation in a faster way. In this way, the brake model can be added into the vehicle dynamics model and brakes parameters can be changed. Even an ABS model was added into the model and its respective influence could be addressed at simulations. The focus was given to evasive maneuvers with brakes on, where yaw stability can be mapped and the importance of ABS, for example, also be addressed. Different brakes parameters were modified as well as suspension characteristics in a DOE environment. The main parameters and especially the interactions between suspension and brakes were identified and can be arranged into a best compromise for this vehicle category.