In 2020 approximately 12 million vehicles will be produced with either full electric propulsion or a hybrid drive-train requiring regenerative braking for enlarged autonomy. Already today the first vehicles with partly automated highway driving are introduced in the markets with an expected rollout of increased performance levels and new automated-driving and -safety functions. Further enhancements of road safety is targeted by EuroNCAP as well as initiatives e.g. in NA and Japan. Future EuroNCAP rating will require surround sensing technologies like radar and / or video to be installed in each vehicle as a precondition to achieve a 5 star safety ranking.

This will lead to a democratization of surround sensing based safety functions requesting enhanced performance levels of future brake systems in respect to brake dynamics and brake boost, NVH, load on the power supply and performance in case of failures. Since most of the vehicles with such new functions share the same platform with more or less standard vehicles, the aspect of scalability and modularity plays a major role in selecting the respective brake system architectures and product designs.

The paper will present in detail the changes on brake systems triggered by the evolution of requirements. The focus is on the upcoming modifications of technologies and product concepts for brake-actuation and -modulation systems. The paper will present new developments covering the upcoming years until 2020 and beyond.

The optimal brake control in the case of a full electric vehicle must not only guarantee high brake performance but also aim at maximum possible level of energy regenerated during the manoeuvre. Targeting integrated electric vehicle control, the driving comfort should be also considered as a component requiring optimization. These factors have motivated the presented study and allowed to formulate the main objective: Development of optimal brake control strategy based on three criteria – brake performance, energy efficiency, and ride comfort. The research is subjected to a full electric passenger vehicle equipped with four in-wheel motors and an electro-hydraulic brake system. On the first stage of the research, the optimization procedure is proposed for the brake torque distribution. Three domains are chosen for the shaping of the corresponding optimization cost function: the brake performance is being estimated by deceleration tracking during the manoeuvre; the energy consumption is quantified through regenerative energy and tyre dissipation energy; the indicator for the ride comfort (in the case of straight-line braking) is the pitch angle. The verification of the developed brake control functions is carried out using the vehicle simulator in IPG CarMaker and hardware-in-the-loop platform with installed electro-hydraulic brake system. The straight-line braking manoeuvre has been investigated as the case study. The proposed technique allowed to reach an optimal brake force distribution with high level of brake energy recuperation and simultaneous keeping of required safety level. The pitch oscillations caused by the vehicle behaviour at emergency braking have been also reduced as compared with the brake manoeuvre without brake distribution / blending control. The experiments were done on the basis of model- and hardware-in-the-loop simulations. The characteristics of electric motors are deduced from experimental data. The real hardware components of the brake system are used including the hydraulic control unit. The controller is emulated in real-time mode using dSPACE tools. The results of the presented study have showed that an optimal brake control in the case of the electric vehicle allows to achieve a multilateral effect in reduction of the brake distance, increase of brake energy regeneration and improvement of the ride comfort at braking.

On trains different incidents lead to the activation of an emergency brake despite the fact that the present safety target might be different. Due to the application of the emergency brake the reaction of the train, in this case the deceleration is ideally the same. For example, the automatic train protection system which is related to the infrastructure is initiating a penalty brake using the emergency brake channel to ensure a safe stop before the potential hazard point. In some applications also a penalty brake is initiated to prevent damage from the braking equipment in case of severe malfunction. An emergency brake initiated by the driver is targeting to prevent hazards. An emergency brake initiated by the passenger alarm system is targeting to protect the passengers. This brief overview is indicating that different safety targets are treated in a common way. For some of these incidents highly reliable deceleration rates are necessary to ensure brake distances within the infrastructure demands. Other incidents require the highest possible deceleration independent of a reproducibility to avoid crashes. Actual trains achieve their minimum brake distance based on preset parameters. To achieve the shortest brake distance that is physically possible, the emergency brake would need to be parameterized based on the actual operational parameters observed.