【作者】 高辉松；

【导师】 朱思洪；

【作者基本信息】 南京农业大学 ， 农业机械化工程， 2008， 博士

【摘要】 研究表明,新型电动拖拉机是解决由农业机械所造成的能源和环保问题的有效途径之一。而在我国,关于电动拖拉机方面的研究几乎是一片空白.因此,深入研究电动拖拉机的电驱动系统设计理论以及电驱动特性,对电动拖拉机的研究与开发具有重要的意义。本文基于电动拖拉机实际作业工况对电驱动系统的要求,结合当前国内外在电驱动系统方面的研究现状,研制了一种基于串励直流电动机的电动拖拉机驱动系统。主要研究内容和取得的结论归纳如下:1、电动拖拉机电驱动系统设计理论及计算方法研究。根据电动拖拉机作业特点,提出了一种电动机和变速箱相结合的电动拖拉机传动系统结构方案,并给出了电动拖拉机动力性能和经济性能评价指标以及电驱动系统主要参数的设计计算方法,以基于串励直流电动机的某型号小四轮电动拖拉机电驱动系统为设计实例,计算分析了该电动拖拉机的驱动力-行驶阻力平衡图、不同挡位下的爬坡度以及连续作业时间.研究结果表明:基于串励直流电动机的电动拖拉机电驱动系统的驱动力特性场接近理想驱动力特性场,其各挡下的驱动力特性是一组下凹的曲线,低速恒转矩,高速恒功率;同一行驶速度下所对应高挡驱动力大于低挡驱动力,这是由电机的调速特性决定的;电动拖拉机各个挡位下具有较广的稳定作业速度范围,但是各个挡位之间速度重合的范围较多,说明所用变速箱变速比与电动机匹配不合理;电动拖拉机最大爬坡度达到30%以上,并且各挡爬坡度变化范围较广,作业过程中不需要频繁换挡;影响电动拖拉机连续作业时间的因素较多,其中作业行驶速度和作业负荷影响最为明显,作业负荷越大,连续作业时间就越短,作业速度越快,连续作业时间就越短。2、电动拖拉机驱动特性仿真研究。从电动拖拉机牵引作业受力分析入手,建立其行驶平衡方程式以及驱动系统的仿真模型和控制策略,基于ADVISOR开发了电动拖拉机仿真系统,分别以低速EUDC工况和一匀速工况作为循环测试工况的输入,对电动拖拉机驱动特性与驱动系统各部件动力学特性进行了仿真研究,研究结果表明:仿真速度能够很好地跟踪目标速度,说明电驱动系统正常工作;驱动轮输出转矩主要受作业负荷的影响,匀速作业时,输出转矩不变,而在加减速或负荷有变化时,输出转矩也跟着变化;蓄电池输出电流受作业负荷和行驶速度的影响较大,随着作业负荷或行驶速度的增加,蓄电池输出电流也跟着增大;蓄电池SOC的大小反映了剩余电量的多少,SOC越小,剩余电量越少;电动拖拉机具有较强的抗过载能力,能够承受的最大突加载荷可达到额定载荷的1.4倍,并且具有自适应负荷能力,随着作业负荷的增加,作业速度降低,但仍能继续作业。3、电动拖拉机电驱动系统试验台研究.建立了模块化的电驱动系统试验台,开发了基于LabVIEW的试验台测控系统,对试验台所用传感器进行了标定.所得结论如下:所开发的电驱动系统试验台不仅能够完成整车性能试验,还能对单个部件的性能进行测试,并且具有较好的可扩展性;通过数据采集卡输出电压直接控制磁粉制动器制动力矩,可以方便的模拟不同作业工况的负荷。4、电动拖拉机电驱动系统驱动特性试验研究。试验研究了驱动轮驱动特性、功率特性、蓄电池电压、电流特性、电驱动系统传动效率、电机控制效率以及最高行驶速度、最大爬坡度等。研究结果表明:驱动轮各挡驱动特性与理论分析一致,受电动机外特性影响,是一组近似双曲线,随着转速增加,驱动转矩下降;蓄电池剩余电量的多少不影响驱动特性,只影响一次充电连续作业时间;不同挡位下电动拖拉机的驱动转矩和传动效率差别较大,在Ⅴ、Ⅵ两挡作业时,它的动力性和经济性最好;不同挡位的驱动力特性曲线适合不同类型作业工况,应为某些常用作业工况设计与之匹配的作业挡;蓄电池电压、电流特性与仿真研究结果一致;电机控制器具有较高的工作效率,正常工作时的效率都在90%以上,对电动拖拉机的传动效率影响不大。5、电动拖拉机模拟作业试验研究。试验研究了电动拖拉机不同作业工况下传动系统各部件的输出特性以及抗突加载荷的能力.研究结果表明:电动拖拉机在不同作业工况时,蓄电池的输出电压、电流变化趋势基本相同,载荷越大,电压下降越多,而在行驶速度波动时,输出电压波动不大,作业结束后,蓄电池电压有所回升,电压下降的多少反映了蓄电池输出能量的多少,电压下降越多,蓄电池输出的能量就越多;蓄电池电流則随着速度、载荷的波动而上下波动,速度、载荷越大,输出的电流就越大;犁耕作业的平均传动效率大于运输作业时的传动效率,这说明传动系统所用变速箱的适合重载作业工况;电动拖拉机在波动载荷比为1.57的最大突变载荷下从事犁耕作业时,作业速度有微小的波动,但不影响正常作业。通过本课题的研究,以期为电动拖拉机电驱动系统的研究及开发提供理论基础和技术支持。更多还原

【Abstract】 Researches show that the new type of electric tractor is one of the effective ways to solve the problems of energy and environmental protection caused by agriculture machinery. But in our country, there are few researches about the electric tractor. Therefore, carrying on an in-depth study on the design theory and drive characteristics of electric drive system has great significance to the development of agriculture electric tractor.Based on the requirements of the agriculture electric tractors for the electric drive system, and the nowadays study actualities of electric drive system home and abroad, a new type of electric tractor drive system based on series DC motor was deveoped. The finished work and achieved results are generalized as follows:1. Researches of the design theory and calculation method of electric tractor drive system. Based on the working condition of the tractor, a new type of electric tractor drive system which combines a motor and a gear, and the evaluation index and the calculation method for dynamic performance of electric tractor are suggested; taking an electric tractor drive system as design object, the balance graph of drive-resistance force, climbable gradient under different shifts, and continuous working time are calculation analyzed. Researches show that the drive force characteristics of the electric tractor drive system based on series DC motor is close the ideal characteristics, the curves are concave, low speed with constant power, and high speed with constant torque; the electric tractor has large working speed under different shifts, but the extensive coincidence speed shows that the variable ratio of the gear is unreasonable; the maximum climbable gradient of this electric tractor is more than 30%, and does not need frequent shift when working for its extensive climbable gradient; there are many influence factors of continuous working time, which the more obvious factors are working speed and working load, the working time increases with the increase of the working speed and working load.2. Simulation researches on the drive characteristic of the electric tractor. Begin with the traction force analysis of the electric tractor, the drive equilibrium equation, simulation model and control strategy of the drive system were established, and the simulation system of the electric tractor was developed based on the ADVISOR; taking the low speed EUDC cycle and a uniform speed cycle as the drive cycle input, some simulation were carrying on about the traction force and the dynamic characteristics of the drive system. Researches show that the electric drive system work normally because the simulation speed tracking the target speed exactly; the torque is related to the working conditions, it is constant under uniform speed condition and change under accelerating or decelerating condition; the current of the battery is affected by the working load and running speed, and increases with the increase of the working load or running speed; the SOC of the battery indicates the residual capacity, the smaller the SOC, the fewer the residual capacity; the electric tractor based on series DC motor has a strong anti-overload ability, and the maximum sudden load is more than 1.4 times of the rated load under normal working condition; and the electric tractor also has an adaptive load ability, it can still work under lower speed when the working load increasing.3. Researches of the electric drive system test-bed. Analysis was made on the advantages and disadvantages of different test study methods, and the researches on electric tractor drive system was carried on using indoor simulation test-bed; the test-bed of the electric tractor drive system was established with modularization, and a measurement and control system of the test-bed was developed based on LabVIEW; in addition, the static calibration of sensors used in the test was carried on. Research results show that the test-bed with good expansibility can used to finish the performance test not only the whole vehicle but also some components; the test-bed can control the braking torque of the magnetic powder brake by the output voltage of the data acquisition card, and simulates the resistance load of different conditions conveniently.4. Experimental researches on the drive characteristics of the electric tractor drive system. A series of test researches were carried on about the drive characteristics and power characteristics of the drive wheel researches, the voltage and current characteristics of the battery research, the transmission efficiency of the electric drive system research, the motor controller efficiency characteristics research, the maximum speed and maximum climbable gradient researches, etc. Research results show that the drive characteristics are consistent with the theoretical analysis, it is approximate hyperbola and affected by the external characteristics of the DC motor, the torque will increase with the speed decreasing; the battery SOC has no effect on the drive characteristics unless its voltage below the minimum voltage of the motor, but it can affects the continuous working time; the drive torque and transmission efficiency under different shifts have great difference, and the electric tractor has better power performance and fuel economy when working underⅤ、Ⅵshifts; in order to obtain higher transmission efficiency, we should design different gear ratios for different working conditions because the drive characteristics under different shifts is suitable for different working conditions; the voltage and current of the battery are consistent with the theoretical analysis; the efficiency of the motor controller has little effect on the transmission efficiency, because it is more than 90% under normal condition.5. Simulation working researches of the electric tractor. The output characteristics of the drive system under different working conditions were experimentally studied. Research results show that change trends of the battery voltage and current under different working conditions are almost uniform, the voltage decreases more with the working load increasing, and it has small fluctuation with the changing of the working speed; the voltage will increase after finish the working, and the voltage difference between initial voltage and terminal voltage can indicate how much power used; the battery current will be upper and lower with the fluctuation of the speed and load, and increases with the speed and load increasing; the gear is suitable for heavy load condition because the average transmission efficiency under plowing condition is higher than that under transport working condition; the electric tractor can work stably under fluctuation loading 1.57 times of rated load besides the slight fluctuation of the speed.Research on this subject is expected to provide theoretical and technological support for the study and development of electric drive system.更多还原