Double clutch automatic transmission, the starting control technology refers to the clutch control technology during the starting process. According to the structural characteristics of DCT, both single clutch and double clutch can be used for starting. Currently, the research on DCT starting process mainly focuses on single clutch, and there is relatively little research on double clutch starting. Fuzzy control theory was applied to the control of single clutch starting, and fuzzy control rules for clutch engagement speed during vehicle starting were formulated. The simulation results showed that the control effect was good.
The input parameters include driver's starting intention recognition, monitoring of engine running status and detection of clutch engagement status, and the output parameter is clutch engagement speed.
Recognition of driver's intention
In the DCT vehicle starting process, the clutch pedal is eliminated, so the accelerator pedal becomes the only linkage between the driver and the car. The driver sends a starting signal to the control system through the accelerator pedal. The driver's manipulation process can fully reflect his requirements for the vehicle starting method and his understanding of the external environment. In the actual manipulation process, the driver first steps on the accelerator pedal to a certain value within a specific time, inputs his own starting intention, and then analyzes whether the current manipulation has completed his starting intention and whether the current starting intention is reasonable. By continuing to adjust the opening degree of the accelerator pedal, the driver further adjusts his starting intention. It can be seen that the accelerator pedal is in a dynamic adjustment process during the starting process and must be recognized by the opening degree of the accelerator pedal and the change rate of the opening degree of the accelerator pedal.
Detection of clutch engagement status
During the clutch engagement process, the difference between engine speed (ne) and clutch input shaft speed (nc) (Δnec) can be used to indicate the clutch engagement status. At the initial stage of clutch engagement, Δnec is large, indicating that it takes a long time for the clutch input and output plates to synchronize, so the clutch engagement speed should not be too fast; when nec decreases, increase the clutch engagement speed; if the clutch input and output plates are close to synchronization, engage at maximum speed. Therefore, Δnec can reflect the clutch engagement status in real time.
Monitoring of engine running status
Preventing engine stall or excessive speed during starting is one of the difficulties in the control of automatic transmission with a clutch. The current strategy is to use the engine throttle or clutch engagement speed intervention control, but these methods have the following disadvantages: because the engine throttle is in a dynamic adjustment process during the starting process, it is difficult to define when the engine speed is too high or too low; even with intervention control, it is difficult to achieve ideal control effect due to the limitation of the response quality of the executing mechanism. Therefore, in the control strategy of clutch engagement speed, real-time monitoring of the engine running status and timely correction of the clutch engagement speed should be achieved through the selection of reasonable control parameters.
Clutch target pressure fuzzy controller: The starting control determines the best torque change rate of the clutch automatic transmission according to the driver's intentions and the vehicle running status based on the vehicle's best impact degree and sliding friction power. Considering the non-linear relationship between clutch pressure and torque, a fuzzy controller is designed to establish a reasonable clutch starting fuzzy control strategy. The clutch engagement process during vehicle starting can be analyzed into two stages:
The first stage is the vehicle stationary stage. At this stage, although the clutch pressure rises quickly, the torque transmitted by the clutch is not enough to overcome the resistance of the whole vehicle, so there is no impact. The initial pressure is mainly determined by the accelerator opening degree and oil temperature.
The second stage is the vehicle starting stage. The torque transmitted between the clutch input and output plates is greater than the starting resistance torque, and the vehicle starts to move, and the pressure increment during the pressure increase mainly depends on the driver's operating intention and vehicle status. This stage is the key point of clutch control.
In the process of vehicle driving, the accelerator opening degree is the most accurate reflection of the driver's intention and has the greatest influence on the dynamic friction coefficient of the clutch automatic transmission. Therefore, the fuzzy pressure decision system takes the clutch input and output plate angular velocity difference, accelerator opening degree, and oil temperature as input parameters, and clutch pressure change rate as output parameter. The starting fuzzy pressure decision system has a three-input and single-output structure.