The configuration and control strategy of hybrid powertrain systems are significant for the development of hybrid electric vehicles (HEV) because they significantly affect their comprehensive performance. In this paper, the types, features, and applications of the mainstream hybrid powertrain configurations on the market in recent years are summarized and the effects of different configurations on the comprehensive performance of HEVs are compared. Moreover, the technical routes for each hybrid configuration are highlighted, as configuration optimization methods have become a technical difficulty. In addition, the technological advances in the steady-state energy management strategy and dynamic coordinated control strategy for hybrid powertrain systems are studied. The optimization of the steady-state energy management strategy mainly involves assigning the working point and working range of each power source reasonably. However, with the increase in the complexity of optimization algorithms, real-time control of HEVs still needs to be improved. The optimization of the dynamic coordinated control strategy mainly focuses on the stability and smoothness of the dynamic process involving switching and shifting the working mode. The optimization of the dynamic control process for the system remains to be further improved. It is pointed out that the configurations and strategies should be optimized jointly to obtain a comprehensive improvement in the system performance. This paper provides an informative basis and technical support for the design and optimization of a hybrid powertrain system.

In this study, the noise of the gear transmission system for two-speed automatic transmission (2EAT) of pure electric vehicles was analyzed and optimized. Firstly, through vehicle noise tests, poor working conditions and noise contribution of each gear pair were determined with the order analysis method. Secondly, a dynamics calculation model and a simulation model of the gear transmission system were established and the poor meshing state of the main reducer gear pair under specific conditions was determined as the main cause of noise. Finally, a genetic algorithm combined the weight method was used for gear modification. After gear modifications, the fluctuation range of transmission error was reduced and the contact condition of the tooth surface was significantly improved.

At present, the noise of pure electric vehicles is a research hotspot, especially the noise of automatic transmission. In order to reduce the noise problem in the test, this paper proposes a method to optimize the local structure of the gearbox housing. First, the noise is evaluated and analyzed by combining subjective and objective methods, and the subjective score and noise order information are obtained. Then the factors that have great influence on the transmission error are explored, and the gearbox housing is finally determined as the optimization objective. Through finite element analysis, the weak position of the gearbox housing can be located quickly and accurately, and then the static and dynamic stiffness of the housing can be improved by adding and changing stiffeners. The simulation results show that the performance of the optimized housing is significantly improved. After the noise test of the whole vehicle, the noise of the two-speed automatic transmission is significantly reduced, and the subjective evaluation results are good.

Suspension-type small rail personal rapid transit systems are widely concerned due to their high efficiency and reliability. The increasing demands for ride comfort have put forward higher requirements for vehicle stationarity. In the study, with a single-bogie vehicle as the research object, a dynamic equation and a simulation model are firstly established to calculate the attitude angle and lateral velocity of the vehicle. Then, with the small amplitude and fast attenuation of the attitude angle and lateral velocity in a straight line and a bend as optimization objectives, the simulation model is optimized in terms of a series of variables, including the bogie with or without the supporting wheel, the supporting wheel tread, the driving wheel tread, the guide wheel tread, and the changes of the center of mass of the vehicle. Then, the problem of severe vehicle pitch with the double-bogie structure is solved. Finally, the simulation results and the optimization scheme are experimentally verified. The above optimization measures can significantly improve the driving stationarity of suspension-type small rail vehicles and enhance ride comfort.

The two-speed electric drive automatic transmission (2EDAT) is an effective scheme to improve the economy and power performance of electric vehicles. It is significant to carry out forward design, valve body improvement, and oil circuit optimization of the hydraulic system for 2EDAT. In the study, the functional requirement of 2EDAT hydraulic system was firstly analyzed and key parameters were calculated to determine the principle design of the hydraulic system. Then, the simulation model of the hydraulic system was established in the multidisciplinary dynamic simulation platform ITI-SimulationX and the changes in the pressure of the main oil circuit, the clutch oil pressure, and the cooling and lubrication flow in the shift process of the hydraulic system were simulated and analyzed. Furthermore, according to the principle scheme and constraint conditions of the whole machine, the overall layout and the hydraulic valve plate of the hydraulic system were designed and the valve plate and hydraulic system were tested on the bench. The test results of clutch pressure were 5.73%–13.12% lower than the designed value and did not meet the design requirements. Finally, according to test results, the processing defects of the pressure reducing valve were mitigated and the main oil circuit was optimized for another test of the valve plate and the hydraulic system. The test results of clutch pressure were 0.35%–8.60% higher than the designed value and met the design requirements. The results showed that the optimized hydraulic system realized the better control effects on the main oil pressure and clutch oil pressure in the shift process, including the fast and accurate clutch shift response, the sufficient cooling and lubrication flow, and smooth working conditions.