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Standard

SAE 2008-01-1737

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Abstract

Over more than 20 years 50 million LuK dual mass flywheels (DMF) have been produced for use in passenger cars and light trucks. A typical DMF consists of two flywheels connected by long travel arc-springs. It is located between the combustion engine and the clutch or automatic transmission. The DMF reduces driveline oscillations by mechanically decoupling the transmission from the periodic combustion events that excite the engine crankshaft. Existing engine control systems are generally designed for conventional single mass flywheel (SMF) systems. In the future, to facilitate the best possible control of engines equipped with DMF systems, these conventional control systems may require modification or even replacement. With the integration of the highly non-linear DMF, the complexity, and thus the order of the powertrain system increase. Beside important effects like significantly reduced gear rattle and booming noises, the protection of transmission components, lower engine idle speeds and consequently better real world fuel consumption, the higher system complexity increases the probability of inconvenient side effects like jerking and / or sub-harmonic vibrations (SHV). Jerking is a surging type of oscillation at the driveline's first natural frequency. This effect is generally excited by rapid engine and / or load torque changes. SHV are limit cycles which can occur in systems subject to both open- and closed-loop control. The frequencies of SHV are lower than the ignition frequency of the combustion engine. Both jerking and SHV are subjectively disagreeable to the driver and should be compensated for as far as possible in the engine controller design. In this paper novel model based controllers are described, which minimise the incidence of and also compensate for both jerking and sub-harmonic types of vibrations. Permitting active damping of these unpleasant oscillations in idle, drive, tip-in / tip-out and coast. For cost effective controller design and real-time implementation a linear state space model with a low system order is preferred. Therefore, a reduced state space model of the driveline including the DMF is introduced. In order to achieve a high degree of modelling fidelity a state observer has also been developed and implemented. This allows the reconstruction of system state values that are not easily or economically measured e.g. driveline load. The controllers developed have been integrated within an overall engine management system model to simulate interaction with other commonly used control algorithms e.g. cylinder balancing. By implementing intelligent strategies for controller activation and deactivation, negative side effects (e.g. cross compensation interactions) are avoided. These newly developed engine control concepts provide a good basis for improving passenger comfort and vehicle driveability by reducing both jerking and sub-harmonic vibrations in the driveline.

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  • Standard from SAE International
  • Published:
  • Document type: IS
  • Pages
  • Publisher: SAE International
  • Distributor: SAE International