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Functional Safety Oriented Design of an Electro-Hydraulic Stationary Braking System
Technical Paper
2016-01-8114
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
Stationary (parking) brake is a very important and safety critical function in many classes of machines. The new transmissions and the “by wire” systems increase the criticality of the role of stationary brake, as it is also an emergency (secondary) brake, and it’s often used to hold the vehicle when the transmission is not locking the wheels.
As an example, dual clutch and power-shift transmission gear systems, as well as hydrostatic transmissions under certain circumstances, are often unable to hold the vehicle stopped and this function is provided by the stationary brake.
Due to the main need of having the brake actuated when vehicle is stopped, without any hydraulic and electric power, the brake configuration is normally a “negative” configuration, usually called “spring applied” because of the actuator configuration, but this configuration causes the brake actuation when de-energized, even in case of system failure.
A thorough hazard analysis on fault cases, performed over the automatic stationary braking system of a big Agricultural machine, evidenced some fault cases, that could result in a unwanted actuation of the stationary brake, potentially causing serious damages.
The paper deals with the electro-hydraulic braking system analysis and analyzes three different circuit architectures, that increase the Safety Performance Level of the solution, avoiding dangerous hazards and increasing the reliability of the entire system. The discussion will also be referred to Agricultural Tractors, due to the recent changes in homologation regulation within the European Union, introducing changes in brake and steer systems requirements.
Authors
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Citation
Ruggeri, M., Marani, P., and Selvatici, M., "Functional Safety Oriented Design of an Electro-Hydraulic Stationary Braking System," SAE Technical Paper 2016-01-8114, 2016, https://doi.org/10.4271/2016-01-8114.Also In
References
- Directive 2006/42/EC Of The European Parliament And Of The Council of 17 May 2006 on machinery, and amending Directive 95/16/EC (recast) Official Journal of the European Union 9 6 2006
- Directive EU No 167/2013 Of The European Parliament And Of The Council, of 5 February 2013,on the approval and market surveillance of agricultural and forestry vehicle
- IEC 61508 Functional Safety of Electrical / Electronic / Programmable Electronic Safety-related Systems International Electrotechnical Commission Geneva 2010
- ISO 13849 Safety of machinery - Safety-related parts of control systems ISO Geneva 2006
- ISO 15998 Earth-moving machinery -- Machine-control systems (MCS) using electronic components --Performance criteria and tests for functional safety ISO Geneva 2008
- ISO 25119 Tractors and machinery for agriculture and forestry - Safety-related parts of control systems
- ISO4254 - 2013 Agricultural machinery - Safety International Organization for Standardization ISO Geneva, Switzerland 2013
- Ruggeri , M. , Cervesato , A. , and Ferraresi , C. Rear Wheels Electro-Hydraulic Steering Control System with Reduced Performance Level Required SAE Technical Paper 2015-01-2872 2015 10.4271/2015-01-2872