On-line Compensation Method of Transmitting Torque Control Parameters of Wet/Dry Clutch Considering the Changes of Physical Properties while Driving

Abstract

Most of automobile is equipped with one or more clutch in powertrain. There are several types of clutch device such as wet clutch, dry clutch, cone clutch, centrifugal clutch. Most of clutch operates with frictional force caused by contact and relative motion of two rotational shafts except dog clutch. Therefore it is important to understand friction characteristic and force transmitting mechanism of each clutch type. The most typical types of clutch devices are dry clutch and multi plate wet clutch. Even in the case of HEV, transmissions may be employed in various structures thus clutch devices also installed in powertrain. In this dissertation on-line compensation method of transmitting torque parameters of wet/dry clutch considering changes of physical properties while driving was introduced. Both of wet clutch and dry clutch system were taken into target system. In order to achieve the objective of this research the analysis and modeling were performed for the clutch friction characteristic at first. Coefficient of friction is influenced by several factors such as temperature, slip speed, pressure, amount of wear (in the case of dry clutch), oil property (in the case of wet clutch). And the pressure to be controlled is also affected by those factors. Since friction coefficient of wet clutch change dominantly with temperature this study proposes a thermal model that can estimate the temperature of wet clutches in slip operating conditions of the vehicle. Compressive force of the dry clutch is applied by diaphragm spring structure that is composed with a disk spring and levers attached to disk spring and housing giving reaction force and cushion spring inserted between clutch plates. Mathematical compressive force modeling was derived considering the stiffness property of each component. And influences of each property on compressive force were analyzed. An on-line compensation method of hydraulic pressure control command points for wet clutch was proposed and that satisfied the dynamic performance in Launch start condition. To do this research, the conventional clutch control technique which is installed in the target model is analyzed. Sync engaging and input/output elements for a slip control, a speed control using hydraulic control, an unknown parameter learning method, are analyzed. Further, in order to simulate various driving situations, the modeling of clutch input/output torque and the modeling and the simulation of a vehicle transmission including a hydraulic control circuit model which is able to carrying out launch control are implemented. Using the implemented simulator, the learning factor of factors that can be controlled by driving under various conditions is extracted, and sensitivity analysis of target performance is carried out. Thus, a logic that can learn control factors at compensation point is implemented using the error performance mode division. The validity of logic built through a simulation of driving various conditions is derived. Finally, parameter compensation method for dry clutch transmitting torque during slip control was proposed and dynamic simulations were performed to validate control logics. A dynamic model was constructed by MATLAB/Simulink® to apply the compensation method proposed. The methods included kiss-point learning method and torque feedback with learning internal engine loss function. The simulation results reported that behaviors of dynamic model proved the validity of propose compensation methods and robustness to unpredictable changes of physical properties such as friction coefficient error, stiffness of diaphragm springs changes, amount of wear. In order to complement clutch control strategy at launch start condition, abnormal vibration at low speed need to be considered as objective function for control.