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With more and more countries proposing timetables for stopping selling of fuel vehicles, China has also issued a “dual-slope” policy. As electric vehicles are the most promising new energy vehicle, which is worth researching. The integration and control of the motor and gearbox have gradually become a hot research topic due to low cost with better performance. This paper takes an electric vehicle equipped with permanent magnet synchronous motor and two-gear automatic transmission without synchronizer and clutch as the research object.

Selection of gearshift point plays an important role in the field of automatic transmission technology, which directly affects the vehicle dynamic and economic performance, etc. In order to designing optimal gearshift strategies for conventional passenger vehicles equipped with stepped automatic transmission, in this paper, the vehicle power demand was defined under different environment, different driving intention and different vehicle operating conditions. Dynamic programming (DP) method is used to solve the optimal static gearshift decision sequence based on the simplified model of powertrain system. The drivability is respected by imposing an inequality constraint on the power reserve limit and the fuel economy is the objective function. Considering the change of vehicle additional load and road slope, the gearshift strategy based on power reserve is proposed.

Improvement of shift quality evaluation has become more prevalent over the past few years in the development of automatic transmission electronic control system. For the problems of the subjective shift quality evaluation that subjectivity is too strong, the standard cannot be unified and the definition of the objective evaluation index is not clear at present, this paper studies on the methods of objective evaluation of shift quality based on the multi-hierarchical grey relational analysis. Firstly, objective evaluation index system is constructed based on physical quantities, such as the engine speed, the longitudinal acceleration of the vehicle and so on, which broadens the scope of the traditional objective evaluation index further.

In a traditional shift control strategy, the gear range is selected based on the throttle opening and the vehicle speed. The disadvantage of two-parameter based system is that the shift map is lack of adaptability in certain special conditions. The driving environment and the true intentions of the drivers are not fully taken into account by the shift control system. Therefore, improving the feasibility of the shift control strategy for the true intentions of the driver and driving environment is of great significance. Under braking conditions, Automatic transmission shift map with two parameters is unable to use engine braking effectively, which affects the drivability and safety of vehicles greatly. This paper presents a newly developed shift control strategy under braking conditions. First of all, the necessity of engine braking was analyzed.

After the analysis of shift quality evaluation methods of stepped automatic transmission, the evaluation indexes of shift quality have been established based on power-on up-shift of DCT (dual clutch transmission). Shift quality objective evaluation method of DCT based on TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) model is proposed. Taking the ideal shift process as reference, the shift quality evaluation model based on absolute ideal solution is developed. A comparison with the subjective evaluations shows that the proposed method is in good agreement with the traditional subjective evaluation method. The TOPSIS model provides a new shift quality evaluation approach and thinking for stepped automatic transmission.