混合動力汽車動力系統運行模式分析

伍慶龍 于長虹 王燕

（中國第一汽車股份有限公司研發總院，長春 130013）

Abbreviation

BMS Battery Management System

BSG Belt-Driven Starter Generator

CAN Controller Area Network

EMS Engine Management System

HCU Hybrid Control Unit

HEV Hybrid Electric Vehicle

HV High Voltage

MCU Motor Control Unit

SOC State Of Charge

TCU Transmission Control Unit

0 Introduction

The power sources of hybrid electric vehicle include en?gine and motor[1].HV battery is used to provide electric en?ergy for the motor,and the motor can not only drive the ve?hicle,but also adjust the operating point of the engine[2-3].Based on control strategy, it can effectively reduce fuel consumption and emissions,and further improve the pow?er performance and economy of the vehicle[4-5].At present,the configuration schemes of hybrid electric vehicle sys?tem include series, parallel and series-parallel system[6].Series hybrid vehicle has the advantages of simple struc?ture and easy control, but it has the disadvantages of low efficiency and high cost[7]. Parallel hybrid vehicle has good fuel economy, but it requires high performance of engine and transmission,and the control strategy of paral?lel hybrid vehicle is more complex than that of series hy?brid vehicle[8]. Series- parallel hybrid vehicle has the characteristics of both series and parallel, and it also has different operation modes and control methods[9-10].

This paper analyzes the hybrid dynamic system with dual motor configuration.The dual motor dynamic system can realize series function, parallel function and seriesparallel function, and it can be developed different dy?namic system operation modes.The dual motor hybrid dy?namic system can effectively improve fuel economy and reduce emissions while enhancing the vehicle′s power performance through effective and reasonable control methods. Based on the dual motor dynamic system, the structure and operation principles are described, and the control strategies are analyzed in this paper. These can be used to provide information references for relevant en?gineers.

1 Hybrid Electric Vehicle Dynamic System

1.1 Structural Scheme of Dynamic System

The dual motor dynamic system of hybrid electric vehicle in this paper is composed of engine,main motor,BSG mo?tor, gearbox, clutch, HV battery, drive axle, main reduc?er,etc.,as shown in Figure 1.The BSG motor is connect?ed with the engine through the gear train belt, the crank?shaft output shaft of the engine is connected with the clutch C2, and the clutch C2 is connected with the input shaft of the gearbox.The gearbox transmits dynamic pow?er to the front wheels through the reducer and differen?tial. The HV battery outputs electric energy to the main motor and BSG motor.The main motor transmits dynamic power to the rear wheels through the clutch C1 and trans?mission mechanism. The main motor can drive the vehi?cle alone, or jointly drive the vehicle with the engine,and can also recover energy from vehicle braking or coasting.

1.2 Dynamic System Operation Mode

HCU communicates with EMS, MCU1, MCU2, BMS and TCU through the CAN network. HCU receives the work?ing status of each assembly of the dynamic system, and determines the dynamic system power and torque output through the control strategies according to the driver’s accelerator pedal, brake pedal and gear shifter status.HCU receives the feedback information from the motor and HV battery, such as battery SOC, motor speed and torque, and then determines the dynamic system power and torque output through the control algorithm to realize the management and control of various operation modes.

Fig.1 The structure of hybrid dynamic system

During the hybrid vehicle driving,the switching con?trol between different operation modes of the dynamic system is realized through the cooperative control strate?gies of HCU. The operation modes include: pure electric start mode, 4WD start mode, engine start mode, idle charge mode, series drive mode, drive charge mode, par?allel drive mode and energy recovery mode.

2 Pure Electric Start Mode

When all of the following conditions are met, the hybrid dynamic system drives the vehicle with the pure electric start mode.

(1)The vehicle speed is 0 km/h.

(2)The shifter position is in D or R gear.

(3)The engine is stop.

(4) The brake master cylinder pressure is more than the threshold value(for example,pressure>0.3 MPa).

(5)The parking brake state is not activated.

(6) The HV battery SOC is more than the threshold value(for example,SOC value>30%).

If the adhesion of the rear wheels of the vehicle is sufficient, and the driver releases the brake pedal and presses the accelerator, the dynamic system will drive the vehicle independently with the main motor.

In this mode, the status of each assembly is con?trolled as follows: The engine is stop, the main motor is driving, the BSG motor is in shutdown state, the C1 clutch is engaged, the C2 clutch is disengaged and the HV battery is in discharge status. The energy flow dia?gram of pure electric start mode is shown in Figure 2.

Fig.2 Energy flow of pure electric start mode

3 4WD Start Mode

When all of the following conditions are met, the hybrid dynamic system drives the vehicle with the 4WD start mode.(1)The vehicle speed is 0 km/h.(2)The shifter po?sition is in D or R gear. (3) The brake master cylinder pressure is more than the threshold value (for example,pressure > 0.3 MPa). (4) The parking brake state is not activated. (5) The HV battery SOC is more than the threshold value (for example,SOCvalue > 30%). If the adhesion of the front and rear wheels is insufficient, and the driver releases the brake pedal and presses the accel?erator, the powertrain uses the 4WD starting mode to drive the vehicle.

In this mode, the status of each assembly is con?trolled as follows: The engine is running, the main motor is driving,the BSG motor is following the engine rotation,the C1 clutch is engaged, the C2 clutch is engaged and the HV battery is in discharge status.The energy flow di?agram of 4WD start mode is shown in Figure 3.

4 Engine Start Mode

When all of the following conditions are met, the hybrid dynamic system drives the vehicle with the engine start mode.

(1)The vehicle speed is 0 km/h.

(2)The shifter position is in P or N gear.

(3)The engine is stop.

(4) The BSG motor output power is more than en?gine starting power.

Fig.3 Energy flow of 4WD start mode

If the driver operates the shift lever to engage D or R, the HCU controls the BSG to drag the engine to the set speed, and then the EMS controls the engine injec?tion and ignition. Then the engine speed is controlled to increase. When the engine speed reaches the target speed,the engine start-up is completed.

In this mode, the status of each assembly is con?trolled as follows: The engine is starting, the main motor is in shutdown state, the BSG motor is driving, the C1 clutch is disengaged,the C2 clutch is disengaged and the HV battery is in discharge status. The energy flow dia?gram of engine start mode is shown in Figure 4.

Fig.4 Energy flow of engine start mode

5 Idle Charge Mode

When all of the following conditions are met, the hybrid dynamic system drives the vehicle with the idle charge mode.

(1)The vehicle speed is 0 km/h.

(2)The shifter position is in P or N gear.

(3)The engine is running.

(4) The BSG motor output power is more than en?gine starting power.

(5) The HV battery SOC is less than the threshold value(for example,SOCvalue<30%).

HCU controls the engine to maintain a target gener?ating speed by sending a signal to the EMS.The BSG mo?tor is in the generating state, and the generating power meets the HV battery charging demand and accessory power demand.

In this mode, the status of each assembly is con?trolled as follows: The engine is in generation state, the main motor is in shutdown state, the BSG motor is gener?ating,the C1 clutch is disengaged,the C2 clutch is disen?gaged and the HV battery is in charge status. The energy flow diagram of engine start mode is shown in Figure 5.

6 Series Drive Mode

When all of the following conditions are met, the hybrid dynamic system drives the vehicle with the series drive mode.

(1) The vehicle speed is less than the threshold val?ue(for example,speed value<120 km/h).

(2)The shifter position is in D or R gear.

(3)The accelerator pedal is pressed.

(4)The engine is running.

(5) The HV battery SOC is less than the threshold value (for example,SOCvalue <30%). If the HV battery power is insufficient, the front wheel adhesion coefficient of the vehicle is insufficient,and the rear wheel adhesion coefficient is sufficient,the dynamic system drives the ve?hicle in series mode.

In this mode, the status of each assembly is con?trolled as follows: The engine is in generation state, the main motor is driving, the BSG motor is generating, the C1 clutch is engaged, the C2 clutch is disengaged and the HV battery is in discharge status.The energy flow di?agram of series drive mode is shown in Figure 6.

Fig.6 Energy flow of series drive mode

7 Drive Charge Mode

When all of the following conditions are met, the hybrid dynamic system drives the vehicle with the drive charge mode.

(1)The vehicle speed is more than the threshold val?ue(for example,speed value>120 km/h).

(2)The accelerator pedal is pressed.

為驗證改進后的遺傳算法在排課問題中的應用效果，與文獻[10]及基本遺傳算法進行對比實驗。種群數量設為400，基本遺傳算法迭代數設為500，本文改進的遺傳算法最大允許停滯代數設為20，交叉概率為0.89，變異概率為0.02。分別在不同授課任務數時，三種算法得到的平均運行時間及適應度值如圖所示。

(3)The shifter position is in D or R gear.

(4)The HV battery SOC is in a certain range(for ex?ample,20%

(5) The HV battery power can not support the driv?ing demand but can meet the power demand of electric accessory equipment.

If the front wheel adhesion coefficient of the vehicle is sufficient,and the engine is in the efficient working ar?ea,HCU shall control the dynamic system to drive the ve?hicle with engine running.At the same time,according to the energy management strategy of hybrid vehicle dynam?ic system, when the HV battery SOC is low, HCU shall control the BSG motor to generate electricity.

In this mode, the status of each assembly is con?trolled as follows: The engine is running, the main motor is in shutdown state,the BSG motor is generating,the C1 clutch is disengaged, the C2 clutch is engaged and the HV battery is in charge status. The energy flow diagram of drive charge mode is shown in Figure 7.

Fig.7 Energy flow of drive charge mode

8 Parallel Drive Mode

The hybrid dynamic system drives the vehicle with paral?lel drive mode if all of the following conditions are met.

(1)The vehicle speed is more than the threshold val?ue(for example，speed value>100 km/h).

(2)The accelerator pedal is pressed.

(4) The HV battery SOC is more than the threshold value(for example，SOCvalue>30%).

When the single axle drive adhesion coefficient of the vehicle is insufficient or the total driving torque de?mand of the vehicle is more than the peak output torque of the main motor, the engine will drive the vehicle to?gether with the main motor. The dynamic system of the hybrid electric vehicle runs in parallel drive mode and drives the vehicle by triggering the 4WD function.

In this mode, the status of each assembly is con?trolled as follows: The engine is running, the main motor is driving, the BSG motor is driving, the C1 clutch is en?gaged, the C2 clutch is engaged and the HV battery is in discharge status. The energy flow diagram of parallel mode is shown in Figure 8.

Fig.8 Energy flow of parallel drive mode

9 Energy Recovery Mode

The hybrid dynamic system drives the vehicle with energy recovery mode if all of the following conditions are met.(1)The vehicle is the process of braking or coasting.(2) The vehicle speed is between 15 km/h and 120 km/h.

(3)The shifter position is in D or R gear.

(4)The brake pedal is pressed.

(5) The HV battery SOC is less than the threshold value(for example,SOCvalue<90%).

According to the braking energy recovery strategy,the recovered torque and mechanical braking torque are distributed. The braking energy of the main motor meets the braking energy recovery demand. HCU controls the hybrid electric vehicle dynamic system to operate in the energy recovery mode.

In this mode, the status of each assembly is con?trolled as follows: The engine is in shutdown state, the main motor is generating, the BSG motor is in shutdown state, the C1 clutch is engaged, the C2 clutch is disen?gaged and the HV battery is in charge status. The energy flow diagram of recovery mode is shown in Figure 9.

Fig.9 Energy flow of energy recovery mode

10 Summary

The dynamic system and the control strategies of the hy?brid electric vehicle are analyzed and researched in this paper,and the different operation modes are described in detail. The dual motor dynamic system is a hybrid ener?gy-saving technology that can effectively improve power performance and reduce energy consumption of the vehi?cle.

Based on the configuration characteristics of the hy?brid dynamic system, since there are multiple power sources of the hybrid dynamic system, it is necessary to control multiple power sources to play their respective roles under different driving demand conditions.By coor?dinating the control of the engine、the main motor, the BSG motor and the HV battery, the hybrid dynamic sys?tem can meet the driver′s needs and improve the power,economy and drivability of the vehicle. The technical analysis described in this paper can provide some refer?ences for correlative engineering research and develop?ment.