【作者】 林添良；

【导师】 王庆丰；

【作者基本信息】 浙江大学 ， 机械电子工程， 2011， 博士

【摘要】 液压挖掘机是一种用量大、能耗高、排放差的工程机械,因此研究液压挖掘机的节能在当前社会能源紧缺和环境恶化问题日趋严重的情况下具有重要的现实意义。液压挖掘机各执行机构及负载惯性较大,各机械臂的上下摆动比较频繁,在机械臂下降制动时,具有很大的势能,若能将这部分能量进行回收并加以再利用,可进一步提高液压挖掘机的节能效果。在传统液压挖掘机中,这部分能量难以进行回收、存储和再利用。在液压挖掘机中引入混合动力系统后,由于动力系统中具备电池或电容等储能装置,易于实现能量的回收和存储,为能量回收提供了一条新的途径。论文针对液压挖掘机的节能需求,对液压挖掘机装备混合动力系统后进行能量回收的方法进行研究,包括能量回收系统结构,高效能量回收系统的参数优化,以及既可高效回收能量又可保证液压挖掘机执行机构采用能量回收系统后仍然具有良好操纵性的控制方法及策略,从而为混合动力液压挖掘机提供一种性能优异的、工程应用性强的能量回收方法,并且作为一种典型的工程机械,混合动力液压挖掘机的能量回收方法研究将为同类型的其它工程机械相关问题的解决提供借鉴。各章内容分述如下：第一章论述了在当前能源紧缺、环境恶化的情况下研究液压挖掘机能量回收系统的重要意义,介绍了各种类型的能量回收系统的特点及应用场合,对比分析了能量回收技术在汽车领域和液压挖掘机上应用的不同点,介绍了能量回收系统在工程机械领域和液压挖掘机的研究现状,概述了本论文的研究内容及论文的研究工作。第二章以某7吨级液压挖掘机为对象建立了液压挖掘机的负载测试系统,基于液压挖掘机工作中的实测数据,研究液压挖掘机各执行机构能量回收再利用的可行性以及各执行机构可回收能量所占比重,分析了液压挖掘机动臂势能回收的工况特点。针对液压挖掘机引入混合动力系统后具备电量储存装置的特点,分析了能量回收系统的基本结构和工作原理,建立动臂速度控制的数学模型并对控制特性进行了分析,同时建立了AMESim和MATLAB的联合仿真模型,从管道长度、等效转动惯量以及发电机控制参数等研究了其对系统操作性能的影响。第三章以斜轴式轴向柱塞液压马达为研究对象,建立了其效率数学模型,通过借助试验方法和MATLAB中辨识函数等辨识得到各损耗参数,从液压马达排量、液压马达压力等方面研究了液压马达的效率特性。基于考虑永磁同步发电机的铁损后的按转子磁场定向的d-q轴等效电路图以及id=O的控制策略,建立了发电机的效率数学模型,研究了发电机效率和转速、转矩等的关系。建立了超级电容的效率数学模型,通过试验平台测试了超级电容的容量特性、内阻特性以及超级电容效率与充放电状态的关系。最后,提出了能量转换单元在变转速控制模式和变转速和变排量复合控制两种模式时的效率优化策略。第四章提出了一种基于节流辅助调速的势能能量回收系统,分析了其系统结构及工作原理,建立了数学模型并完成了控制性能分析。提出了液压挖掘机采用能量回收系统后动臂新型工作模式的判断规则。以高效回收能量为目标,考虑到低速控制精度差、系统损耗以及防止液压马达吸空现象,提出了发电机动态修正工作点的控制规则。考虑到实际液压挖掘机难以安装速度传感器等特点,提出了一种基于发电机转速波动的比例节流阀分流以及比例方向阀限流的节流调速和容积调速的复合控制规则。从操作性能和能量回收效率两方面展开了试验研究,试验表明该方案可以解决基本能量回收系统中低目标速度时震荡较大和高目标速度时动态响应较低的问题,同时能量回收效率在无变量马达优化时维持在35%,而有变量马达优化时维持在39%。第五章提出了一种基于蓄能器的液压马达-发电机能量回收系统,分析了其系统结构及工作原理,建立了数学模型并完成了性能分析。基于蓄能器最大能量密度、动臂下放驱动性能等约束条件,完成了蓄能器、液压马达、发电机的参数优化设计。为了保证最小能量回收时间以及防止电磁换向阀的频繁切换造成压力和流量冲击,提出了两级压力判断的液压马达-发电机工作模式决策准则。分析了液压马达-发电机的最小能量回收时间、额定能量回收时间以及极限大能量回收时间的确定。针对采用能量回收系统后,动臂下放过程和液压马达-发电机能量回收过程实现相互独立的特点,研究了动臂下放和非下放两种模式的比例方向阀和发电机不同的控制规则。基于所研制的试验平台展开了试验研究,试验表明,该方案可以大幅度降低液压马达-发电机的功率等级,提高能量回收时间,在稳定发电机工作点方面、极限工况回收能量等方面具有明显的优势,同时不影响其操作性能。第六章概括了论文的主要研究工作和成果,并展望了今后的研究工作和方向。更多还原

【Abstract】 Following the "energy crisis", the demand for more environmental and fuel efficient construction machinery, especially for hydraulic excavator (HE), has been increased in response to growing concerns on the clean environment and saving energy. Most of the time, in a typical working cycle, the weight of the boom itself is much heavier than the load. When the load goes down it does not need energy, but energy losses rise up in breaking the load motion. The gravitational potential energy is dissipated into heat in the control valves of the hydraulic system. So it is required for us to make maximum use of regenerative energy for further improvement of fuel consumption and also to ensure higher system control performance equivalent to that of conventional control system. The successful application of hybrid system in construction machinery provides a new way for hydraulic excavator to achieve energy saving.The chapters of this dissertation are organized as follows.In Chapter 1, the the significance of the research on energy regeneration system (ERS) based on HEs is discussed, and some characteristics and shortcomings of kinds of ERS are analyzed. Then, the difference between the ERS based on the hybrid automobile vehicle and the ERS based on the hybrid hydraulic excavator (HHE) are reviewed. The development of ERS in construction machineries and HEs are introduced. Finally, the primary research contents of this dissertation are provided.In Chapter 2, Applying the ERS in HHE, the system has to be considered to fit its special working style, a 7-ton HE was tested and the data of the pressure of the cylinder raw chamber, the pressure of the cylinder rod chamber and so on. Then, we caculated the regenerated energy of the boom, the arm, the bucket and the swing. The typical working condition of Boom ERS based on HEs is analyzed based on the the measured working data. Then, we have proposed a Motor-generator ERS(MGERS), the mathematical model of MGERS is constructed. The effects and improvements of system dynamic response are analyzed. Secondly, united simulation of the MGERS with AMESim and MATLAB/simulink for the MGERS is carried out and the influence on the control performance of the the pipe length, the time constant of the generator and the rotary inertia of the motor and the generator is brought forward.In Chapter 3, when the boom goes down, the gravitational potential energy is converted into electric energy to be stored in the capacitor. And the motor, the generator, the capacitor is the key components. Hence, the efficiency mathematical model of the motor, the generator and the capacitor are constructed. As some parameter of the motor are unknown, we test a rig and propose a measure method to identify the unknown parameters. At last, the characteristics of efficiency of the key components in ERS are analyzed. The analyses provide rules for the control strategy applied in the two proposed ERSs which are shown in Chapter 4 and Chapter 5.In Chapter 4, In order to control the boom in quick and precise responses when the boom velocity is controlled by the motor and the generator in the ERS, a new ERS that used a proportional throttle valve to help the hydraulic motor contol the boom is proposed. here we call is JMGERS. The mathematical model of JMGERS is constructed. The effects of system dynamic response are analyzed.When the conventional boom control circuit is enabled, it works with two modes: ’Boom Up’, and’Boom Down’including digging. On the contrary, the operation of the boom system with an ERS is divided into four modes:’Boom Up’with holding function, ’Boom Stop Down’,’Boom ER Down’, and’Digging’. The working principle of the boom system is characterized by the status of the joystick and the pressure of the boom cylinder. Considering the bad control performance in the low rotational speed, the total-power loss, the efficiency of the motor and the generator, a dynamic-working-points of the generator and the motor is discussed. Then, as the displacement and the velocity sensors can not be assembled in HE, a compound control that consist of orifice control and volume control is presented. At last, a test rig is constructed, an estimated 35%-39%of the total potential energy could be regenerated at the lowering of the boom in the JMGERS and it is also shown that the JMGERS features better speed control of the boom and response characteristics than the MGERS. In Chapter 5, As the hydraulic accumulator systems have an order of magnitude advantage in terms of the power density over electric system and the energy storage density is severely limited relative to other competing technologies, an energy recovery system that combines the advantages of an electric and hydraulic accumulator is proposed, here we call is AMGERS. Then, the mathematical model of AMGERS is constructed. The effects of system dynamic response are analyzed.As the hydraulic accumulator plays a very important role in the AMGERS, it must be properly designed to offset the gap between the load power and the generator power input. The parameter matching for the AMGERS are discussed by considering economics, weight saving, installation and controllability. Then, the control strategy incuclude the working mode of the motor-generator, how to control the generator and the control valves at the lowering of the boom, how to improving the recovery effieciency when the boom stops to go down are presented.The main conclusions and achievements are summarized in Chapter 6, and the further research work is put forward.更多还原