Review and Development of Electromechanical Actuators for Improved Transmission Control and Efficiency 2004-01-1322

With the drive toward more fuel efficient vehicles, the individual and combined efficiency of powertrain subsystems is increasingly important. Development of alternative transmission types (AMT, DCT, CVT) has brought significant benefits arising from an increase in the number of ratios, ratio span and unit efficiency. However, it is recognised that further potential lies in improving actuation technology in controlled transmissions, of all types. Since the economic benefit of further refinement of traditional hydraulic devices appears to be limited, it is suggested that alternative technology is required. This alternative would seek to further reduce parasitic energy consumption due to pumping and associated system losses and also improve poor duty cycle controllability, whilst enabling cooling of any slipping sub-elements.

The reported research has focused upon the development of electromechanical systems that offer efficient intermittent actuation and also system simplification over hydraulic, and more recently electrohydraulic, systems. These improvements include overall energy conversion efficiency and idle power consumption, which support the trend towards the ‘more electric vehicle’ and 42 Volt architecture. However, there are a number of significant issues that need to be addressed in order that these devices can operate successfully within the given environment. This paper presents a review of current electromechanical actuation technology, a design example of an electromechanical actuator and identifies system simplification and integration with current technologies.