【作者】 黄长征；

【导师】 谭建平；

【作者基本信息】 中南大学 ， 机械电子工程， 2007， 博士

【摘要】 300MN模锻水压机是我国国防建设和基础建设的关键设备,其动梁驱动及速度控制技术是它的关键技术之一。动梁驱动系统流量大,工作框架系统所受载荷巨大、变形大,锻压力不断变化,以及各参数之间耦合关系非常复杂等特点,是一个复杂的机电液耦合系统;当前该水压机无锻压自动化和等温锻压功能,其驱动系统的动态响应特性不明;动梁速度控制系统载荷瞬变、惯性巨大,控制滞后、控制精度低、鲁棒性差。因此,以动梁驱动及速度控制系统为研究对象,围绕其控制机理、动态响应特性、控制策略进行了研究,以提高速度控制精度,为实现模锻自动化、等温锻压或模拟等温锻压提供技术基础。论文的主要研究内容和结论如下:(1)分析国内外巨型模锻水压机动梁速度控制技术及液压系统特性研究的现状和发展趋势,针对控制系统惯性巨大、载荷瞬变、水路长而导致控制滞后、鲁棒性差、控制精度低等特点,基于“油控水”控制方式,采用“液压缸+齿轮齿条机构+凸轮机构+转角位移检测装置”的分配阀芯开启度控制方式,提出了内环采用PID-H_∞控制凸轮轴转角、外环采用PFC控制动梁速度的双闭环串级控制策略。(2)考虑流体的可压缩性、粘性阻力、泄漏及工作框架系统变形等因素,分空程、锻压和提升三种工况,建立分配阀口、液压管道、液压缸的流量方程,建立动梁和上横梁的动力学方程,建立动梁驱动系统动态模型,进行仿真和试验研究。同时,对锻压行程的动梁速度、位移,工作缸压力,以及分配阀口压力差的动态响应特性进行仿真分析。仿真和试验研究表明,动梁速度等参数在阀芯开启瞬间瞬变载荷的作用下产生振荡,响应时间约0.7秒,控制精度受到影响。(3)分析300MN模锻水压机动梁速度控制系统液压操作控制原理和结构,通过计算和仿真可知,液压操作系统存在瞬变载荷,且是影响控制系统的鲁棒性和控制精度的主要因素。建立瞬变载荷作用下的液压操作控制模型,分别采用单一PID和PID—H_∞两种控制策略,仿真和试验研究表明,采用PID—H_∞串级控制能很好抑制瞬变载荷的影响。同时基于液压操作系统载荷巨大、瞬变的特征,提出凸轮升程与转角成线性关系的一种巨型水压机分配阀芯开启凸轮升程曲线,以曲线最大压力角为优化目标,建立优化模型,优化设计升程曲线。(4)针对300MN模锻水压机动梁速度控制滞后、鲁棒性差和控制精度低的特点,提出并设计基于PFC-(PID-H_∞)双闭环串级动梁速度控制系统,从模型失配、干扰、轨迹跟踪等方面进行仿真研究。研究表明,控制系统具有良好的稳态精度、动态品质、鲁棒性和跟踪性能。(5)根据主分配器双轴同步、通道多、流量大的特点,优化设计阀芯开启图和阀体。研制基于总线技术的多系统协同的多主站结构的复杂网络分布式三级计算机动梁速度控制系统,以及基于比例流量控制原理液压操作系统。采用WINCC组态软件研制基于拓扑结构、多视窗分级的人机界面的动梁速度监控系统。集成这些系统,实现了300MN模锻水压机动梁速度控制。(6)在不同速度、不同工艺条件下,对300MN模锻水压机PFC-(PID-H_∞)动梁速度控制系统进行试验研究。研究表明,试验与仿真结果相互吻合,证明了控制模型、策略的正确性、可靠性和实用性。测试表明,分配器凸轮轴转角控制动态精度和静态精度均为±1°,分配阀芯位置控制静态精度±0.2mm、动态精度±0.5mm,在不同负载下速度控制精度为(0.26～1.35)mm/s。更多还原

【Abstract】 The 300MN die forging hydraulic press is key equipment of national defence and foundation construction of our country.Its moving beam’s drive and control technology is one of its key technology.The flow of the beam’s driving system is giant.The load and deformation of working house’s system are giant.The forging force is continuously varing.A complex coupling relation exists in all kinds of its parameters.The drive and control system is a complex mechanical-electrical-hydraulic coupling system.There are’t automation forging system or isothermal forging system in the hydraulic presses presently.The dynamics response characteristic of the driving system is unknown.Transient load,giant inertance,hysteretic control,low control accurancy and low robustness exist in the moving beam’s speed control system.Therefore,this paper studied the speed drive and control system of the hydraulic press,based on its control mechanism,dynamic response characteristic and control strategies,to improve speed control accurancy and supply technical base for realization of die forging automation,isothermal forging or simulation isothermal forging.In this paper,these main research works and conclusions as following:(1)Based on analysis of present state and perspectives on the speed control technology of these domestic and foreign giant die forging hydraulic press,and such characteristics as control hysteresis,low robustness and low control accuracy because of giant inertia,transient load,long waterway,"oil control water" control mode was applied.A new control mode of the distributor’s spools open gap was applied based on the mode of "hydraulic cylinder+gear and rack machnism+cam machnism+rotary displacement testing device",to control the flow and direction of the waterway distribution system.A double-closed-loops cascade control strategy was put forward that inner loop was used to control cam shaft angle by PID-H_∞control and external loop to control moving beam speed by PFC-(PID-H_∞)control.(2)Based on coercibility,viscosity resistance,leakage of the fluid, and working house system’s deformation etc,flow equation of distribution spool,hydraulic tube and fluid cylinder were established, dynamics eqation of moving beam and upper beam were established, during back play stage,forging stage and hoisting stage.These hydraulic-mechanical coupling dynamics models of drive system for the moving beam were first established,and their simulations and tests were done.At the same time,during the forging stage,these dynamic response characteristics of speed and displacement for the moving beam,pressure of the working cylinder,and pressure difference of the distribution spool were simulated.These simulations and tests showed that these models are correct,speed is vibrating under the the transient load,control hysterisis time is 0.7 second,and the control accrancy is influenced.(3)The principle and structure were analysed on hydraulic operation control system of the 300MN die forging hydraulic press.The phenomenon that the transient load existed in the control system was discoverred,and the load was a main factor to influence the control robustness and accrancy.The hydraulic operation control model was established based on the giant transient load.These strategies based on the single PID control and PID-H_∞control were simulated and tested.The research result shows that PID-H_∞control can suppress the influence from the transient load.Based on giant and transient load,a new right cam-lifting curve was put forward which was a linear relation between open gap of spool and cam shaft rotary angle,and based on which target is maxmal pressure angle of the curve,its optimization model was established,simulated and designed.(4)Based on such characteristics as slow response speed,low accuracy and low robustness,a double-closed-loop PFC-(PID-H_∞) cascade speed control system was put forward and designed.Its simulations were done under the mismatched model and the disturbance. The result shows that there are good steady-state accuracy,dynamic characteristic,robustness and traceability in the control system.(5)Based on the main distributor’s double-shaft synchronism, multi-channel and large flow,the open diagram of distributor,the structure and volume of the valve body were optimized.A speed control computer control system based on bus technique,multisystem cooperation,many main stations,complex network was put forward. Based on the control principle of proportional flow,the hydraulic operation system was developped.With WINCC configuration software, an upper computer intelligent speed monitoring and controlling system based on topology network structure,multi-window,grading man-machine interface was developped.These systems were originaly integrated.For the first time,the speed control of the 300MN die forging hydraulic press was developped.(6)The test on the PFC-(PID-H_∞)speed control system in 300MN die forging hydraulic press was carried out under different speeds and technical conditions,in order to prove the correctness,reliability and practicability of the application of the control theory,the establishment of the control model and the proposition of control strategy.The result shows that the test results coincide with the theory stimulation results. The test shows that dynamic and static rotary control accuracy of the cam shaft in the distributor is±1°.The static position control accuracy of the distributor spool is±0.2 mm,its dynamic accuracy is±0.5 mm,speed control accuracy is(0.26～1.35)mm/s under different load.更多还原