Application_of_Automatic_Manual_Transmission.pdf

IEEE Vehicle Power and Propulsion Conference VPPC September 3 5 2008 Harbin China 978 1 4244 1849 7 08 25 00 C2008 IEEE Application of Automatic Manual Transmission Technology in Pure Electric Bus Xi Jun qiang and Xiong Guang ming and Zhang Yan Beijing Institute of Technology School of Mechanical and Vehicular Engineering Beijing China Email xjq Beijing Institute of Technology School of Mechanical and Vehicular Engineering Beijing China Email xiongguangming Abstract Two speed transmission system is usually employed by an electric vehicle to improve efficiency of an electric driving system and drivability of vehicle powered solely by electric power i e pure electric vehicle or series hybrid electric vehicle The improvement of the drivability and efficiency due to the application of the multi speed transmission system is shown based on motor drive system characteristics traction characteristics and cost Moreover in addition to optimization of multi speed automatic manual transmission AMT system and motor drive system integrated control technology and multi speed AMT system without clutch is also introduced With the result of conducting field test and on road test it is obvious to see that the drivability and efficiency of vehicle provided with multi speed AMT system is significantly improved Keywords Pure Electric Bus Automatic Manual Transmission Power Transmission Integration Control I INTRODUCTION To improve efficiency of an electric driving system meanwhile to meet the requirements of vehicle drivability the driving motor of the pure electric vehicle or series hybrid electric vehicle is usually provided with a decelerator or a transmission device Conventionally a two speed planetary gear transmission device is employed by the pure Electric vehicle or series hybrid electric vehicle The structure of the two speed planetary gear transmission device is relatively simple However a shift operation can not be performed when the vehicle is running which makes it difficult to optimize the drivability and the efficiency Accordingly based on the motor drive system characteristics and the overall requirements of the vehicle the feasibility and optimization as well as control strategy of applying AMT without clutch to the pure Electric vehicle or series hybrid electric vehicle are presented An AMT system which is suitable for both the pure Electric vehicle and the series hybrid electric vehicle is presented as well Excellent testing results indicate that the drivability and efficiency is significantly improved Prototypes of said AMT system have been installed in the pure Electric bus for serving the coming Beijing Olympic Games II NECESSITY OF EMPLOYING MULTI SPEED AMT SYSTEM A Requirements of drivability Fig 1 illustrates a characteristic curve of a driving motor installed in an electric vehicle Referring to Fig 1 the maximum torque obtained in a low rotation speed cannot meet mass transit requirements for example acceleration and hill climbing Therefore the pure Electric vehicle or series hybrid electric vehicle needs to be provided with an AMT system according to the drivability requirements 1 Fig 2 illustrates a traction characteristic curve of a driving motor provided with a three speed AMT according to the overall requirements of an electric vehicle As shown in Fig 2 though a two speed transmission device may meet operation requirements high power loss cannot be avoided Compared to the two speed transmission device a multi speed transmission device can make a good use of the power output of the motor with reference to the traction characteristic curve shown in Fig 2 Torque Nm Rotary Speed revolution per minute Fig 1 Torque characteristics of driving motor Vehicle Speed kilometer per hour Fig 2 Traction characteristic curve of a driving motor Driving Force KN 0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000 0 10 20 30 40 50 60 70 80 90 Authorized licensed use limited to CHONGQING UNIVERSITY Downloaded on September 13 2009 at 06 17 from IEEE Xplore Restrictions apply IEEE Vehicle Power and Propulsion Conference VPPC September 3 5 2008 Harbin China 978 1 4244 1849 7 08 25 00 C2008 IEEE B Requirements of efficiency In addition to the drivability the optimization of driving cycles and motor drive system is also determined by a fixed shift level and a fixed speed ratio Fig 3 illustrates an efficiency map of a motor drive system As shown in Fig 3 the high efficiency range is limited Fig 4 illustrates an efficiency curve of a motor drive system provided with a three speed transmission system Referring to Fig 4 a high efficiency curve over a much wider range is offered which indicates an improvement of the output of the motor drive system provided with the three speed transmission device C Requirements of operability To improve the drivability and the efficiency in other words to improve the operability of the vehicles there is a need to apply an automatic transmission system to the electric vehicle A gear set of a conventional pure Electric vehicle provided with the two speed transmission device however can not be shift automatically when the vehicle is in drive The operator has to stop the engine and shift manually Consequently the drivability and efficiency is limited to some degree III INTEGRATION OF MOTOR DRIVE SYSTEM AND MULTI SPEED TRANSMISSION SYSTEM A Design of integration of power and transmission system Automatic transmission system such as AT AMT CVT and DCT are widely used in vehicles nowadays However CVT and DCT are not suitable to bus or commercial vehicles For energy security and strict environmental requirements AMT system is more suitable to be applied to electrical vehicles due to its high efficiency and low cost However a clutch apparatus is a must for a conventional electric vehicle equipped with an AMT system as illustrated in Fig 5 A new electric vehicle is thus presented as shown in Fig 6 In this new electric vehicle the AMT system is integrated with the motor drive system An integrated automatic control system configured to operate the integrated system is provided according to the analysis of motor drive system characteristics and the shift As a result the clutch apparatus is not required The transmission efficiency is thus optimized which results in an improvement of the efficiency of the transmission system B Integrated control of a power transmission system The integrated control is achieved by a high speed CAN bus and two electric control units ECU A work procedure of the power transmission system is divided into five phases and shown in Fig 7 entering a neutral gear position adjusting output of the engine selecting an engagement position synchronizing for a next shift position changing shift level to enter the next shift position The work procedure is controlled by a transmission control system 2 C Design of AMT shift schedule By optimizing battery power transmission system and the vehicle a specific transmission control strategy is designed for the pure electric bus The energy stored in the battery is effectively supplied meanwhile high efficiency of motor drive system and its control system is obtained The designed electric vehicle follows an deactivated shift schedule determined by dual parameter As illustrated in Fig 8 the engagement point varies with vehicle speed and throttle position Wide throttle opening may ensure the drivability and a reduced throttle Fig 4 Efficiency curve of a motor drive system Rotary Speed revolution per minute Fig 3 Efficiency map of a motor drive system low efficiency point high efficiency point Torque Nm Fig 6 Structure of an integrated automatic power transmission system Integrated Automatic Power Transmission Differ ential Motor Gear Box Differ ential Clutch Fig 5 Structure of a conventional electric vehicle according to prior art Authorized licensed use limited to CHONGQING UNIVERSITY Downloaded on September 13 2009 at 06 17 from IEEE Xplore Restrictions apply IEEE Vehicle Power and Propulsion Conference VPPC September 3 5 2008 Harbin China 978 1 4244 1849 7 08 25 00 C2008 IEEE opening may improve the efficiency Meanwhile dual parameter shifting regularity is optimized by inactivating shifting strategy If just use dual parameter to control shifting shifting disturbance which is not expected may happen because the shifting regularity is sensitive to the throttle opening signal which changes in large extent and frequently What is called inactive shifting strategy is that weaken shifting disturbance led by the control parameter of throttle opening and reduce the sensitivity of shifting control when the throttle opening changes sharply IV TEST RESULT Tests were performed with a BK6122EV2 pure electric bus As shown in Fig 9 the weight of this bus fully loaded is 18000kg and the rated passenger capacity is 50 persons with the maximum speed 80Km h The type of the driving motor is YDB160 6 F the rated power capability 100KW the maximum power 160KW the rated torque 514N m the maximum torque 800N m the rated rotate speed 200rpm the maximum rotate speed 4500rpm The type of the transmission is 4A110 three speed automatic manual transmission with the maximum output torque 1100N m The transmission ratio of first gear to third gear is 4 403 2 446 and 1 507 Lithium battery is used as power battery and its total voltage is 388V with the total capacitance 360Ah Both the drivability and efficiency are improved using the integrated multi speed power transmission system Fig 10 illustrates energy consumption curves of a vehicle provided with the multi speed power transmission system in AMT mode two speed mode and three speed respectively the energy consumption decreases 9 when using the AMT Table 1 shows the acceleration time of an electric vehicle the acceleration time is shortened 18 when using the AMT V CONCLUSIONS V CONCLUSION The pure Electric vehicle provided with multi speed AMT system solves the cons for using the two speed planetary gear transmission device i e the motor drive characteristics cannot be made good use of Hence the drivability and the efficiency as well as the operability are improved Prototypes of said AMT system have been installed in the 50 BK6122EV2 pure Electric buses for 0 50km h Acceleration time with fixed second gear s 28 3 Acceleration time with AMT s 23 2 Fig 7 Shift up sequence Selection Position Shift Position Operating Mode of Motor Position Gear Rotary Speed of Motor throttle Position 10 20 30 40 50 60 70 80 90 100 101520253035404550 Vehicle speed km h Throttle positon Fig 8 Shift schedule TABLE 1 ACCELERATION TIME OF A