Control of a Driveline with a Slipping Clutch
A clear trend is that automatic clutch systems will be introduced and used in a wider variety of applications. The introduction of a new actuator opens up new opportunities for controlling the engine and driveline, and new strategies that can improve the driveline performance are predictable. Several applications would benefit from advanced clutch control. For example start and stop strategies for heavy trucks can be employed and in addition the clutch control can be utilized in automated manual transmissions to reduce the time for gear changes, which is a crucial parameter for preventing stall in heavy trucks during hill climbing. Furthermore clutch control is also a factor in look ahead control.
It is also possible to use the clutch to damp oscillations in the driveline, but to handle this more research is necessary. An important first step was to gain the fundamental knowledge about the important characteristics of a driveline with a slipping clutch, and the starting point will focus on modeling for control.
In the project it has been identified that the thermal effects have an important impact on the torque transmitted in a clutch and a new model that captures these effects has been developed, validated and integrated in an observer. The observer estimates the thermal state of the clutch and also the estimated torque as well as it includes an additional state that tracks the aging and wear of the clutch. The observability of the system has also been investigated and it is shown that the system is globally observable. The observer and is used in a vehicle launch controller. As a final step in the project microslip clutch control is investigated for heavy duty applications, which is a new investigation where the impact of the powerlosses in the clutch and its thermal effects are clarified. The results from the subproject is reported in the PhD Thesis of Andreas Myklebust.