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The electro-mechanical brake is a novel concept of friction brake based on a force’s generator that is driven by purely electro-mechanical components instead of pneumatic or hydraulic components. The “sustainability” topic is addressed, being the electro-mechanical brake, a sub-system designed to support the transition from traditional train architecture to the novel “air-less train” concept. The brake system, together with the suspension system, are the main consumers of compressed air. This air is not only compressed but also filtered and dried by a component’s family called AGTU (air generation and treatment unit). The AGTU components, typically compressors and air dryers, are well known to have intrinsic limitations in terms of energy efficiency, electrical consumption, for the heavy weight, the maintenance duty and to be one of the main sources of acoustic noise. On the other hand, however, the compressed air is the traditional way used by the train to store the braking energy and to actuate the friction brake, that is the ultimate safety brake methodology associated to the emergency brake. To support the transition from the air-based train to the air-less train, the braking system shall revolutionize its technological solutions without any compromise on the “safety assessment” associated to the “braking performances”. The high-level challenges addressed by this research are: • Design a brake system that does not require compressed air/oil being compatible with the air-less train concept with consequent improvements: - Energy efficiency (i.e. electrical consumption) - Acoustic noise - Suspended weight - Simplified brake architecture with the removal of pneumatic piping - Maintenance associated to compressor and air dryer • Design an electro-mechanical brake capable to respect the railway safety requirements, for all the market segments (mass transit, regional, high speed, etc…) in terms of: - Brake performances - Safety integrity levels associated to: - the way to store the braking energy - the way to permanently monitor the effective storage of braking energy The high-level needs of the railway community, addressed by this development, are confirmed by the European projects Shift2Rail and by the upcoming ERJU program, highlighting the demand of sustainable, silent and green solutions. The methodology starts from a novel interpretation of the “postulates” of the railway braking system: The traditional way to apply the friction-brake is filling a brake cylinder. The traditional way to store the braking energy is cumulating compressed air into a reservoir. The traditional way to make sure that the braking energy is still available is monitoring the pressure inside the reservoir. The migration of the postulate n°1, towards an air-less system, leads to the design of an electro-mechanical system based on electrical motor/s and mechanical solutions to convert the rotational motion into a linear motion. The migration of the second postulate, towards an air-less system, leads to the scouting of a technology to cumulate energy. The batteries, which may seem like the obvious solution, do not offer sufficient guarantees in terms of safety, if the target is to achieve a safety integrity level 4 for the emergency brake application even in degraded condition (e.g., no electricity by the pantograph). The postulate n°3 is the one making the difference, leading to the selection of alternative way to store the braking energy based on cumulating the kinetic energy in a rotating element. The inertia of the rotating element is comparable to the volume of the air reservoir The monitoring of its rotational speed is comparable to the monitoring of the pressure inside the air reservoir. The techniques to safely measure a rotational speed are far more consolidated than the technologies to ensure the effective availability of power from a battery. The first phase of the research aims to ensure the feasibility of the solution mentioned above, the capability of the electro-mechanical actuator to convert kinetic energy into mechanical energy for brake application and/or into electrical power for the brake control unit. This is main scientific challenge. After that, the research and development process will be carried out like a braking device integrating mechanic, electronic and software according to applicable standards. Results: The results achieved so far at demonstrator level, are highly promising and show the feasibility of the concept, in relation to the main scientific challenges: kinetic energy storage and electrical energy recovery.
Wabtec: Dr. Matteo Frea