Adaptive Control of an Externally Controlled Engine Cooling Fan- Drive

In this paper an adaptive control strategy applied to an externally controlled fan drive (ECFD) is presented. A bimetal actuated viscous clutch operation is solely a function of the engine under hood temperature while the ECFD can be controlled to maintain any fan speed within its operating range by an external controller. As compared to traditional viscous clutches by using the ECFD a saving of nearly 30% in overall fan power consumption is observed in normal city driving while in highway driving a saving of 85% can be achieved. An adaptive control strategy was developed to control the ECFD. When applied to the ECFD, the adaptive control strategy should be able to provide several advantages such as (1) the ability to compensate for any performance degradation observed over the life of the ECFD, due to the wear and tear of the device. (2) If minor changes are to be made to the ECFD to incorporate future customer needs, the adaptive control strategy will not require any re-calibration of the controller gains, hence saving development time and cost. In this paper the functioning of ECFD is explained along with the adaptive control structure applied to the ECFD. Testing was done on a bench-stand in a temperature-controlled environment and also in-vehicle. Both the in-vehicle and bench-stand testing shows the ability of the adaptive controller in maintaining any requested fan speed within the operating range of the ECFD. This paper ends with a discussion on the limitations of applying the adaptive controller strategy to the ECFD.