高压共轨柴油机的柔性控制策略研究

【作者】 徐劲松；

【导师】 申立中；

【作者基本信息】 昆明理工大学 ， 机械设计及理论， 2014， 博士

【摘要】 高压共轨电控技术是唯一能够满足欧Ⅳ以上排放法规的柴油机控制技术,其控制策略也逐渐变得既复杂又灵活。高压共轨柴油机的工作实质是把高压燃油喷射到气缸中,通过燃烧转化为对外的输出转矩,其最终是一种转矩需求的控制。此外,共轨管中的燃油压力对喷射到气缸中的燃油雾化和喷射速率有所影响,进而对燃烧过程产生影响。多次喷射的喷油起始点和喷油量是整个控制系统中最为重要的一个控制环节。因此,通过分析高压共轨柴油机的控制需求,提出了基于“转矩—轨压—喷油”的柔性控制策略的解决方案,开展了以下研究工作。(1)研究了转矩控制的综合柔性控制架构及各控制子模块的控制策略发动机的转矩需求决定了喷油量的多少,而进气量与喷油量之间的空燃比是燃烧控制的一个重要因素。在转矩控制架构的信息流中采用主控通道和前导通道相结合的方式,使得进气与喷油量的控制能够相互统一、协调。主控通道是发动机转矩控制流的主要通道,通道中的数据是控制的基准值。前导通道是在发动机工况突变的情况下,对主控通道的一种动态补偿。研究了各控制子模块的控制功能和边界条件,建立了各自具体的控制模型,具备了一定的柔性控制特征。在怠速控制的相关模块中,采用“客户机一服务器”的控制策略,构建了怠速控制子框架。在转矩控制的一些子模块中,根据发动机的不同工况设计了PI、PD或PID自动切换的控制算法,还提供了一种PID控制的多参数选择方案。(2)研究了轨压控制的复合柔性控制架构及各控制子模块的控制策略针对轨压控制的需求分析,提出了轨压复合控制架构的解决方案,即：发动机起动时采用开环控制,起动结束后自动切换到串级控制。该架构具有一定的柔性特征：开环控制响应快,能够快速建立轨压,属于粗调,而串级控制相对复杂,属于精调。为了改变常规PID控制中的积分作用和微分作用,在某些工况下会显得其控制作用过强或过弱,串级控制中的主、副控制器采用了可分离积分作用、一阶微分和变PID参数的控制算法,使得控制过程能够随发动机工况的变化而改变,其控制响应快。(3)研究了喷油控制的准确柔性控制架构及各控制子模块的控制策略通过多次喷射控制的需求分析,提出了一种多次喷射协调控制架构的解决方案。设计使用了一种带喷射状态字的多次喷射协调控制器来完成对预喷控制器、主喷控制器和后喷控制器的使能选择,解决预喷、后喷是否释放及多次喷射的组合模式等问题。主喷、预喷和后喷控制器对喷射释放审核、喷射起始点、喷油量以及喷射持续时间的精确计算,有助于对发动机燃烧过程的精确控制。这些计算过程都会涉及到当前某个具体的喷射组合与最小喷油量、最小喷射起始点、主喷油量之间的关系等内容。(4)高压共轨柴油机柔性控制策略的试验验证及相关硬件驱动的实现采用自制的驱动电路板、ES1000硬件设备等相关试验平台进行软件在环测试。在发动机的起动、怠速、加速和减速工况的试验中,分别对转矩控制、轨压控制和喷射控制的柔性控制策略进行了试验验证,其动态控制响应和稳定性较好。为了实现前面介绍的软件控制系统,重点进行了高压泵电磁阀和电磁式喷油嘴的驱动电路设计。通过高压泵电磁阀硬件驱动的研究与设计,把驱动电流反馈引入轨压的软件控制系统,从而完成串级控制中的副环控制。在喷嘴硬件驱动中,采用英飞凌的TLE6282作为驱动主芯片,研究了电磁式喷油嘴的“Peak-Hold"电流硬件驱动方案,并配合软件系统完成了发动机台架试验。更多还原

【Abstract】 Electronic control technology of high pressure common rail was the only control technology of diesel engine to meet above Euro Ⅳ emission regulation, and the control strategy has gradually become complicated and flexible. The working substance of high pressure common rail diesel engine is that the injection fuel in cylinder is transformed into the external output torque through the oil combustion, and is ultimately a torque demand control. In addition, the fuel atomization in cylinder and the injection rate Impact of the fuel pressure in the common rail pipe, which affect the combustion process. Multiple injection start point and injection quantity is a important control link for the whole control system. So, by analysis of the control demand for high pressure common rail diesel engine, the flexible control strategy based on "torque the rail pressure, injection" were put forward, and the researching work were investigated as follows.(1) Researching the control strategy of flexible control architecture for torque control and control sub-modulesFuel quantity of injection was determined by the torque demand of engine. And air-fuel ratio between the intake air and fuel injection quantity was an important factor in combustion control. The main control channel and leading contol channel of information flow in torque control architecture made the control of air and fuel to unity and coordination. The main control channel was the main channel of engine torque control flow, whose data was a base value. The leading control channel was a dynamic compensation for the main control channel in the mutation condition of the engine.Through the research of the control modules for control function and boundary condition, it was established that the respective control models with a certain characteristics of flexible control.In the relevant modules of idle-speed control, it was constructed that the control subframe at idle-speed by means of the control strategy of "client-server". According to the different operating conditions of the engine, control algorithms among the PI, PD or PID switch were designed in some sub-module of torque control, and a multi-parameters selection scheme of PID control were put forward.(2) Researching the compound flexible control architecture of rail pressure control and control strategy of the sub-moduleAccording to the analysis of the rail pressure control needs, the solution of rail pressure control architecture was proposed, which was open loop control at engine start and the automatic switch to the cascade control after starting end. This architecture had some flexible features that the open loop control with the fast response was able to quickly build rail pressure, which belonged to the coarse, and cascade control was relatively complex, which belonged to fine tune.In order to change too strong or too weak effects for the integral and derivative of the conventional PID control under certain conditions, the main controller and auxiliary controller in cascade control system adopted some control algorithms with separable integral, first-order differential and variable PID parameter.(3) Researching the control strategy of flexible control architecture for accurate injection control and sub-moduleAccording to the analysis of the multiple injection control needs, a coordinate solution of the control architecture for multi-injection was proposed.With the use of injection status word, the multiple injection coordinator can select the pre injection controller, main injection and post injection controller. This solution can also resovle the combination model of multiple injection, and whether pre injection and post injection is released.For release of audit injection and accurate calculation of starting point, fuel injection quantity and injection duration, the main injection, pre injection and post injection controller was helpful to the accurate control of the combustion process of the engine. These calculations were related to the specific injection combined with minimum fuel injection quantity, the minimum injection starting point, main injection quantity.(4) The experimental verification of the flexible control strategy and related hardware driver on high pressure common rail diesel engineThe software in the loop test was run at the test platform of circuit driving board, ES1000hardware equipment. It was to be run that the torque control, rail pressure control and flexible control strategy in the engine starting, idle speed, acceleration and deceleration experiments, whose the dynamic control response and stability was better.In order to realize the software control system, it was chiefly designed that the driving circuit for the electromagnetic valve of high pressure pump and the solenoid injector. By means of the hardware driving design for the electromagnetic valve of high pressure pump, the driving current feedback of the rail pressure control system software composed the inner loop of cascade control. In the nozzle of the hardware drivers, using Infineon TLE6282as the main driving chip, was researched of the hardware driving solution for electromagnetic nozzle of "Peak-Hold" current type, and completed the engine bench test with the previous software control system.更多还原