Optimal Strategy of Clamping Force for Continuously Variable Transmission Based on Slip Ratio Feedback Control

In order to decrease vehicles' fuel consumption rate to the lowest and stabilize the engine running in an optimal rotary speed range, an optimization was made for the traditional clamping force control strategy of the continuously variable transmission (CVT). According to the general structure of the slip ratio feedback control method, a slip ratio dynamic model with nonlinear equations was set up based on measurements from the existing sensor devices inside CVT. For design of the slip ratio feedback controllers, the tight coupling problem between clamping force and speed ratio are solved using a separate inner-and outer-loop control scheme. In addition, bed tests and real tests were conducted to verify the effectiveness of the optimized control strategy for clamping force. The results show that the power matching ability of the CVT vehicle equipped with slip ratio feedback control is superior to that with the traditional clamping force control in all of the 0-100 km/h acceleration test, emergency braking, and comprehensive conditions. Using the slip ratio feedback control, the clamping force can decrease about 10% with non-slip and other application requirements satisfied, and the total fuel efficiency of CVT vehicles can increase 1%.