The vehicle mass, which was estimated from longitudinal dynamics formula based on longitudinal acceleration, vehicle speed, motor torque, was used as input parameter to calculate energy recovery feedback torque, to make the vehicle has the same target deceleration under different loads. Test results indicate that the accuracy of vehicle mass falls in the range of ±10% in the real road test, and when vehicle mass is used to calculate energy recovery, the energy consumption is optimized by 5.5% in CRUISE simulation based on China-World Transient Vehicle Cycle (C-WTVC).

A diagnosis device is designed, which can diagnose vehicle state through standard port of the On-Board Diagnostics Ⅱ (OBD Ⅱ). Its software is designed based on STM32 single chip microcomputer, the physics layer communicates with vehicle gateway via CAN, the communication standard abides by the Unified Diagnostic Services (UDS) protocol and operates in three modes, i.e. communication with cell phone via Bluetooth, communication with computer via serial port connection, and operate offline via command memory. The embedded software is developed by hierarchical architecture based on C programming language.

New power module driver chip has no simulation model, unable to simulate and verify the principle of drive unit circuit. To solve this problem, the paper, taking Infineon 1ED020I12FA2 chip as an example, studied the modeling of core devices and peripheral circuits of drive unit, and proposed a modeling and simulation method suitable for driver chip, and verified the correctness of the model through comparison with the chip data manual. And based on this model, software Saber was used to model the circuit principle for power conversion function, insulation and power amplification function and model protection function of Insulated-Gate Bipolar Transistor (IGBT), some of the important function logics were tested and verified. The results show that the corresponding function logics meet design expectation.

To accurately predict the lifetime of Insulated Gate Bipolar Transistor (IGBT), this paper proposed a model-based method for IGBT lifetime prediction. Based on simulated vehicle road spectrum, phase voltage, phase current and power factor were obtained. The switching frequency of the motor inverter was determined through table lookup, and IGBT losses were calculated accordingly. Combining the thermal network model, the junction temperature of the IGBT was calculated, allowing for the generation of the IGBT temperature variation curve. Using the rainflow counting method, characteristic parameters were extracted, and the corresponding IGBT damage rate was evaluated based on the IGBT lifetime model, this enables the assessment of whether the IGBT lifetime meets the design requirements.

For the design of power unit electro thermal performance of EV inverter, a simulation modeling and analysis method of power unit electro thermal performance based on software Saber was proposed. Power module voltage stress, current capability, junction temperature and inverter efficiency were simulated and analyzed, the power loss of the power module was evaluated, the inverter efficiency map was plotted, and the overall efficiency of the inverter under special working conditions was obtained to evaluate the inverter performance. The simulation results show that the performance of the power module meets the system requirements, and the maximum efficiency of the inverter reaches 98.44%.

In order to suppress the narrow pulse during the running process of Insulated Gate Bipolar Transistor (IGBT) module of Permanent Magnet Synchronous Motor (PMSM) inverter, this paper proposed a narrow pulse suppression method based on Pulse Width Modulation (PWM), analyzed the cause of the narrow pulse theoretically. Based on the premise of full consideration of PWM dead zone and narrow pulse, the paper proposed the segmented full-duty ratio PWM output scheme, and analyzed the PWM duty ratio segment that may generate narrow pulse, and the solution was given. Test results show that the above scheme can effectively suppress the generation of narrow pulse, achieve the effect of protecting the motor inverter, and improve the safety and stability of the control system.

A multi-unit modular direct-drive hub motor was designed for high torque density and high reliability requirements. The effects of different pole-slot ratios, stator structures, permanent magnet magnetization types, magnet fixing methods and etc. on the electromagnetic performance of the motor were investigated through theoretical analysis and finite element simulation, and an electromagnetic structure scheme suitable for achieving high torque density was explored. The effectiveness of the design scheme and related technology was verified by finite element simulation and bench test.

In this paper, a permanent magnet synchronous motor for vehicles was used as the research object. According to the specific structural size parameters and performance parameters of the stator and rotor blades of the motor, a two-dimensional simulation model was established in the electromagnetic field finite element analysis software to solve the electromagnetic field and loss distribution of the motor under special operating conditions. The loss density obtained by electromagnetic field simulation was imported into the temperature field simulation software to calculate the temperature distribution reaching the steady state under the operating conditions. Through the comparison of coupled simulation and single-physics simulation, it is concluded that the hot spots distribution of the coupled simulation is more concentrated, and the thermal risk of the motor can be discovered and improved in time. The working condition temperature rise test of this motor indicates that the coupled simulation temperature rise data is basically consistent with the test data, proving correctness of the motor coupled simulation results.

To improve the correlation between reliability test condition and user actual driving behavior, this paper proposed a method of user condition classification and test condition construction based on user big data. In this method, the principal component analysis method was used to reduce the dimensionality of a large amount of data, and the K-means clustering method was used to classify the data and select representative segments, sort the data through the Markov method, and finally construct a reliability test condition conforming to the actual driving situation of the user. Driving data from twenty users under a big data platform was calculated according to this calculation process. Compared with the condition commonly used at present, the method from perspective of data source can describe user actual driving state more accurately.

In order to solve the defects of hybrid-specific transmission including high power consumption of shift clutch pressure control system, complex pressure compensation algorithm and poor control accuracy, a wet clutch pressure control system and control method with characteristic of quick oil filling and substantial power consumption reduction was designed based on vehicle control strategy and one-dimension fluid flow equation, using pressure limited relief valve to replace fix orifice, using AMEsim to construct simulation model to obtain theoretical working characteristic of the system, and then electric pump control mode was studied and optimized with the oil filling speed of wet clutch as the optimization objective.