Study On Powertrain Control Strategy For An Electric Bus

Due to the influence of the energy crisis and environmental pollution,the development of the electric vehicles has already become the concern all over the world.Since it possesses two big advantages,the pure electric vehicle is considered as one of the most ideal direction for development of cars.At present,because of the limitations of production cost and relevant technology,electric vehicles have not yet been universalized.However,the research and development of sample vehicles,in China and abroad,has been operated experimentally to some degree in a large number.With the promotive influence of the the Beijing Olympic Games and the concerns of China's government,the research on electric vehicle in recent years in China,has been proceeded.At present,the research on the relevant control strategy of pure electric vehicles is limited in the field of the respective control and the expension of function and seldom focuses on the part control and management of a whole vehicle.The manufacturer of battery and motor is mainly on focus on the research on the battery and motor themselves,but the assembly manufacturer emphasizes the whole harmonization and the integration control, which forms a research system that shares a clear division of production of the electric vehicle.According to the situation of its development at present,the research,based on the program of the Science and Technology Agency in Jilin province,"Research and Development for prototype vehicle and its control system of FAW Electric Bus",and from the point of the accumulation on theory and the actual need on driving,focuses on the field of the control strategy of the powertrain of electric bus,considering the safety and economy and relevant relationship within.The thesis first of all fixes its powertrain structure and the motor-and-battry design,and proceeds the electric vehicle powertrain system parameter matching according to the index of the project preserving parts of the traditional fuel bus.According to the result,the test bed is set up,and the chosen batteries and moters are tested.And so their funtions of controllers, batteries and the operating systems are testified.Based on the result of experiment,the control strategy of powertrain has been made mainly including three parts:Control Strategy of drive,of the brake and of the energy Management.The control system of the whole vehicle based on CAN net communication which has achieved the control of driving force,the overload of the motor,the control of regenerative brake,the distribution and management of the battery,is a proof of the safety and economy of the electric vehicle.The pure electric vehicle which makes a good use of permanent magnet synchronous motor(PMSM) formulates the control strategy of drive,determines the relationship between the input pedal parameters and the response characteristics of torque when runing forward and backward,according to the responsive characteristics of motor torque and the characteristics of the need of torque when driving.Then a description,given on the characteristics of the permanent magnet synchronous motor(PMSM) according to the chosen type of motor emphasizes the analysis of the temperature.The permanent magnet synchronous motor(PMSM) is very sensitive to the overload temprature.A higher temprature not only harms to some degree the inside of the insulator's components,but also creates the demagnetization to the permanent magnetic materials.As a result,the monitor and control of the process of the overload of motors is very important. According to the characteristics of overload temperatures,the thesis designs the control strategy of motor's overload,and the control process which limits the motor's overload in a short period of time according to the index of time,and fixes the main strategy index based on the data and the experiences.According the Charge-discharge characteristics of Lithium Battery,in order to avoid the battery over discharging when the electric vehicle running,the control strategy of energy monitors and controls the state of charge(soc),the electric current and voltage making the vehicle reture to the charging station when the power of the battery is not enough.The recycling of the braking energy which is a important part of the power control of the electric vehicle,is the most significant advange.It could increase the rate of energy utilization and so enlarge the Cruising range of the vehicle.Based an analysis of the characteristics of the recircling brake and the elements of the possible influences,the redistribution of the braking force between axles has been made according to the braking funtion of the permanent magnet synchronous motor(PMSM) and the traditional fuel vehicle. Under the condition of the braking stability,a strategy which is easily realized but also possesses a high recirling rate is designed.According to the control strategies put forward,the model control strategy and the model car is set up making use of MATLAB/Simulink and ADVISOR software.The control strategies are embed into the model cars and then an simulation analysis is made.With the limitation of the simulation model and the software precision,the result of simulation and of the road experimentation deviated a bit.Considering the definition of function and the results of simulation,the strategy of power control of the pure electric vehicle could better control the working range of every components from the point of the need of driving and coordinated control and at the same time realizes the braking recircling of power which increases the total driving range of electric vehicles.The control strategy mainly satisfies the research of electric vehicles on the function of fixing and control.The thesis gives an emphasis on the calculation of the data and the theory study making itself a basis of model cars.The control strategy is available,and the capability of the whole vehicle could basicly satisfy the requests of the project.