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In recent years, concerns for environmental pollution and oil price stimulated the demand for vehicles based on technologies alternative to traditional IC engines. Nowadays several carmakers include hybrid vehicles among their offer and first full electric vehicles appear on the market. Among the different layout of the electric power-train, four in-wheel motors appear to be one of the most attractive. Besides increasing the inner room, this architecture offers the interesting opportunity of easily and efficiently distribute the driving/braking torque on the four wheels. This characteristic can be exploited to generate a yaw moment (torque vectoring) able to increase lateral stability and to improve the handling of a vehicle. The present paper presents and compares two different torque vectoring control strategies for an electric vehicle with four in-wheel motors. Performances of the control strategies are evaluated by means of numerical simulations of open and closed loop maneuvers.

This paper describes the development of a simulation technology for analyzing vehicle chassis transmissibility for the vibrations induced by tire-wheel imbalance and brake torque fluctuation. A multi-body simulation model is created for the coupled front chassis system consisting of steering, suspension, floating sub-frame, tire-wheel and a virtual excitation rig. Non-linear elements, such as frictions of joints, displacement-dependent bushings and detailed hydraulic power assist system, are considered. The simulation model is validated extensively by a unique laboratory excitation test in both frequency and time domain under different levels of excitation. Good agreement between simulation and measurement is achieved, and example results are presented.

In order to advance vehicle stability control strategies and provide enhanced customer benefits, a methodology for combining the capabilities of an active driveline system capable of direct yaw control with a vehicle stability assist controller (also referred to as ESC, electronic stability control) has been developed. As a basis, the traditional ESC operation of using only brake and throttle control is compared and contrasted against customer needs and expectations. Using the existing ESC stability control system as a representative yaw stability control algorithm, the actuation capabilities of a controllable AWD system are arranged through a simple CAN communication scheme to serve as an available extension to the ESC actuator set (i.e. brake, throttle and now AWD direct yaw moment control). The ESC unit is allowed to request a rear axle torque amount change to the controllable AWD unit ECU.

Tire-road interaction is one of the main concerns in the design of control strategies for active/semi-active differentials oriented to improve handling performances of a vehicle. In particular, the knowledge of the friction coefficient at the tire-road interface is crucial for achieving the best performance in any working condition. State observers and estimators have been developed at the purpose, based on the measurements traditionally carried out on board vehicle (steer angle, lateral acceleration, yaw rate, wheels speed). However, until today, the problem of tire-road friction coefficient estimation (and especially of its maximum value) has not completely been solved. Thus, active control systems developed so far rely on a driver manual selection of the road adherence condition (anyway characterized by a rough and imprecise quality) or on a conservative tuning of the control logic in order to ensure vehicle safety among different tire-road friction coefficients.

Electronic Stability Program (ESP) and Antilock Braking System (ABS) are nowadays a standard equipment for passenger cars. ESP increases vehicle safety by applying differential braking torque to the wheels while cornering, thus it extends the area of intervention of ABS which prevents the wheels from being locked up in emergency braking, especially on low friction road surfaces, allowing the driver to maintain steering control of the vehicle, to avoid obstacles and to reduce vehicle stopping distance on most road surfaces. This paper describes a flexible mechatronic test bench for ESP/ABS Electronic Control Unit (ECU) based on Hardware-In-the-Loop (HIL) simulation technique. It consists of a passenger car hydraulic braking system (from master cylinder to brake calipers), with the ESP/ABS ECU integrated and a flexible real-time platform, which simulates vehicle dynamics.

Fuel economy can be increased by reducing running resistance or mechanical drag. Since modern disk brake systems produce mechanical drag, a component-level test method was developed to measure and understand this effect. Measuring brake drag typically requires a vehicle test on a chassis dynamometer, and an engineer must distinguish brake drag from other sources of drag (e.g., tire, wheel bearing, transmission, and others). This method often generates brake drag data that lacks in resolution, accuracy, and repeatability. Alternatively, a new method of measuring drag on a traditional brake dynamometer has been developed that yields statistically relevant and repeatable results. To accurately measure brake drag on a brake dynamometer, pad temperature, wheel bearing temperature, and caliper experience pressure need to be controlled. Also, depending on the type of wheel bearing used, a correction factor for bearing drag may be needed.

The aim of this study was to assess the crash injury benefits of an Automatic Emergency Braking System (AEBS), for the passenger vehicle population in France. These benefits were examined in regards to the number/proportion of fatalities and serious injured crashes that could be saved per annum. The two crash types investigated included pedestrian crashes and rear-end collisions. AEBS was expected to intervene 0.6sec prior to the crash and at published levels of force according to whether braking previously occurred and the road condition/surface adherence. The analysis involved national crash data, BAAC, collected by the French Ministry of transport, in-depth crash data made available from the European EACS (European Accident Causation Survey) database by LAB, as well as findings from the U.S. NASS/CDS and NHTSA PCDS in-depth databases. A step-wise methodology was used to calculate the crash injury benefits of AEBS across the two crash types.

The durability performance of brake hoses is a crucial issue for such components. Accelerated fatigue testing of brake hoses is necessary for understanding achievable lifetime, actually computation of durability is quite cumbersome due to the many different materials the hoses are made from. Despite SAE standards are available, accelerated testing of brake hoses subject to actual torsional and bending stresses seem important to provide relevant feedback to designers. In this paper, an innovative methodology for assessing the fatigue behavior of brake hoses of road vehicles is proposed. A dynamic testbed is specifically designed and realized, able to reproduce the actual assembly conditions of the hoses fitted into a vehicle suspension. The designed testbed allows to replicate actual loading conditions on the brake hoses by simulating the vertical dynamics and steering of the suspension system together with brake pressure.

A multi-objective optimal design of a brushless DC electric motor for a brake system application is presented. Fifteen design variables are considered for the definition of the stator and rotor geometry, pole pieces and permanent magnets included. Target performance indices (peak torque, efficiency, rotor mass and inertia) are defined together with design constraints that refer to components stress levels and temperature thresholds, not to be surpassed after heavy duty cycles. The mathematical models used for optimization refer to electromagnetic field and related currents computation, to thermo-fluid dynamic simulation, to local stress and vibration assessment. An Artificial Neural Network model, trained with an iterative procedure, is employed for global approximation purposes. This allows to reduce the number of simulation runs needed to find the optimal configurations. Some of the Pareto-optimal solutions resulting from the optimal design process are analysed.

Brake calipers for high-end cars are typically realized using Aluminum alloys, with Silicon as the most common alloying element. Despite the excellent castability and machinability of Aluminum-Silicon alloys (AlSix), anodization is often required in order to increase its corrosion resistance. This is particularly true in Chlorides-rich environments where Aluminum can easily corrode. Even if anodization process is known for almost 100 years, anodization of AlSix -based materials is particularly challenging due to the presence of eutectic Silicon precipitates. These show a poor electric conductivity and a slow oxidation kinetics, leading to inhomogeneous anodic layers. Continuous research and process optimization are required in order to develop anodic layers with enhanced morphological and electrochemical properties, targeting a prolonged resistance of brake calipers under endurance corrosive tests (e.g. >1000 hours Neutral Salt Spray (NSS) tests).

The work investigates the use of cathodic protection -based strategies (e.g. sacrificial anodes) with the aim of extending the corrosion resistance of Aluminum components to be used in disc brake systems. Lab-scale electrochemical measurements, including voltammetry and zero resistance ammetry (ZRA), are used to: a) define the requirements of a cathodic protection system for a 42200 Aluminum alloy; b) evaluate the protection capability of a Zn-based sacrificial anode; and c) demonstrate an extended corrosion resistance of the protected part even in the presence of a galvanic coupling, with respect to the unprotected condition.