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To improve the comprehensive performance of vehicles equipped with stepped automatic transmission (SAT), the optimization of gearshift schedule should take into account various performance such as power performance, fuel economy, etc. In addition, the SATs would become more acceptable if the optimized gearshift schedule could also be individualized to reflect the driver’s expectation on vehicle performance to a reasonable extent. For the purpose of ensuring the comprehensive performance and improving the individual-ability (i.e., the ability to adapt to different driver’s performance expectation) of vehicles equipped with SAT, a linear weighted method has been proposed to construct a performance evaluation function, which applies different weights to represent driver’s expectation on performance by using these weights to multiply the normalized value of each sub-performance index.

For the vehicle equipped with stepped automatic transmission (SAT) that has a fixed number of gears, gearshift schedule is crucial to improve the comprehensive performance that takes into account power performance, fuel economy, and driver’s performance expectation together. To optimize and individualize the gearshift schedule, an optimization method and an improved performance evaluation approach for multi-performance gearshift schedule were proposed, which are effective in terms of reflecting the driver's expectation on different performance. However, the proposed optimization method does not consider the influence of the road slope on the comprehensive performance. As the road slope changes the load of vehicle that is different from the load when a vehicle runs on a level road, the optimized gearshift schedule without considering road slope is obviously not the optimal solution for a vehicle equipped with SAT when it runs on ramp.

Precise control of the pressure of hydraulic oil acting on the dual clutches plays a crucial role during the gear-shift process of wet-type dual clutch transmission (DCT) to implement power shift (i.e., torque-interruption-free gear-shift) and to improve shift quality. Firstly, the hydraulic control system for the dual clutches of DCT were developed, based on that, the dynamic model of the hydraulic control system was built that was further integrated into a dynamic model of wet-type DCT. Secondly, the influence of oil pressure on evaluation indices for the gear-shift process such as shift jerk and friction work were discussed theoretically, and the determinant principle of the target oil pressure of dual clutches during both up- and downshift processes was discussed, a PID controller and a fuzzy controller were also designed respectively to trace the oil target pressure of dual clutches during the gear-shift process of DCT.

Shift schedule determines the gear-shift timing of stepped automatic transmissions that directly affects the power performance, fuel economy, and emission of vehicle. Under the circumstance with ever increasing concerns about the issues of energy saving and environment protection, an optimized shift schedule that could make the powertrain system provide sufficient power with minimum fuel consumption and less emission has been becoming a very critical factor to improve the overall performance of vehicles equipped with stepped automatic transmission. Traditional methods usually only consider a certain unique performance index, such as power or economical performance, in a certain shift schedule, i.e., using one unique performance as optimization objective for one shift schedule.

To reach the goal of optimal performance match between engine and transmission, the dynamic characteristics of engine should be taken into consideration. In the paper, the dynamic torque and fuel consumption models of engine, described by a multi-layers feed forward neural network, were established. Based on that, the methods used to calculate the optimal dynamic and economical shift schedules with dynamic 3-parameters were put forward. The shift schedule with dynamic 3-parameters based on neural network model is proven to be superior to the shift schedule with only 2-parameters in both dynamic performance and fuel economy by the test.

Gearshift schedule of stepped automatic transmission (SAT) determines the timing when the gearbox should be shifted from a certain gear position to an adjacent one, which directly affects the performance of complete vehicle. To optimize the comprehensive performance considering power performance, fuel economy, and driver’s performance expectation, the formulation of gearshift schedule needs to take into account a number of factors such as the expression of different performance indices, the identification of driver’s intention on each sub-performance, and the adaption to driving conditions especially the road slope and curve. Based on our previous work, this investigation is focused on the adaptability of the gearshift schedule to curves of the road that could ensure the safety of vehicle and meanwhile maintain an optimal comprehensive performance reflecting a specific driver’s performance expectation.

The clutch-to-clutch gear-shift process of dual clutch transmission (DCT), which consists of the overlapping of the engagement of the incoming clutch and the disengagement of the outgoing clutch, is a vital stage for the shift quality improvement. The paper investigated an integrated control strategy for the gear-shift process that takes into account the influences of oil pressure of dual clutches and engine speed on shift quality. Firstly, the evaluation indices for the shift quality of DCT were summarized, and the factors affecting the shift quality were analyzed. Secondly, an integrated control strategy for dual clutches pressure and engine speed was proposed. Through analyzing the states of clutch in the gear-shift process and the desired traction torque for different gears, the strategies of variable oil pressure and invariable oil pressure were determined for every gear-shift process.