【作者】 徐峰；

【导师】 隋振；

【作者基本信息】 吉林大学 ， 控制理论与控制工程， 2018， 硕士

【摘要】 凸轮作为一种复杂机械零件,已经在包装机械、纺织机械、交通运输机械、动力机械等领域到广泛的应用。随着对凸轮机构控制要求的提高,传统的靠模加工早已无法满足当今社会对于高端装备制造业的需要。现阶段高精度凸轮加工多采用CNC数控磨床实现。由于伺服电机制造技术与CNC数控技术的相对落后,国内数控机磨很难实现高精度控制,而类似规格国外CNC数控磨床的价格是国产数控磨床的10多倍。为了提高我国凸轮磨床的精度和效率,改变国内装备制造业对于进口 CNC数控磨床的依赖,本文对凸轮磨削算法进行了一定的研究。通过相关论文查找与实验研究后发现,磨削精度与当量磨削厚度值密切相关,加工中保持当量磨削厚度近似相等时可保证工件具有较高的轮廓精度。由于磨削过程中各轴速度不匹配等问题,造成实际加工的当量磨削厚度与理论当量磨削厚度相差较大,所以本文通过动态优化C轴转速度来达到补偿当量磨削厚度的目的。主要内容分为以下四点:1、凸轮磨削前相关数据处理。实际加工过程中凸轮升程数据常通过测量的方式获得,获得的数据中可能存在噪声误差,本文利用傅里叶变换实现升程光顺处理。在获得升程表之后,通过三次样条曲线对升程数据进行插值密化。最后利用速度瞬心法推导出C轴与X轴之间的磨削关系,求得凸轮磨床输入序列值。2、利用当量磨削厚度提出了凸轮磨削速度优化方法。由于传统的磨削厚度并不能很好的描述加工过程,所以想到利用当量磨削厚度来描述凸轮磨削过程。当量磨削厚度中主要受到磨削厚度、砂轮速度与切削速度的影响。加工过程中切削速度对加工精度影响较大,分析后决定通过优化C轴旋转速度曲线间接优化切削速度。3、结合Cycle-To-Cylce反馈控制理论与遗传算法,实现C轴磨削速度曲线的动态速度优化。由于在磨削过程中存在轴匹配度不一致等问题,造成在加工过程中当量磨削厚度会发生变化。为了求得更好的优化速度,本文将每利用Cylce-To-Cylce反馈控制理论,将每次的磨削过程看成一个周期,结合遗传算法动态优化速度曲线,最终求得一组符合精度要求的加工速度曲线。4、采用实验仿真证明算法有效性。为了更好的证明算法的有效性,本文基于MK8312C型凸轮磨床相关实测数据搭建了 MATLAB数控磨削系统仿真平台。基于该仿真平台对比了恒速磨削,限制最大加速度的准恒线速度磨削和本文优化方法。仿真实验结果表明,本文方法使得进给轴速度变化平缓,凸轮轮廓精度也得到了进一步的提高。更多还原

【Abstract】 Cam.as a complex mechanical part,has been widely applied in packaging machinery,textile machinery.transportation machinery,power machinery and other fields.With the improvement of control requirements for cam mechanisms.the process of traditional mode can no longer meets the needs of high-end equipment manufacture in contemporary society.At this stage,high-precision cam machine is mostly implemented by CNC grinding machines.Due to the backwardness of the technology in servo motor manufacture and CNC,Domestic CNC machine grinding is difficult to achieve high-precision control.The similar foreign CNC grinding machine is 10 times more expensive than the domestic CNC grinding machine.In order to improve the precision and efficiency of the cam grinder in our country.and to change the dependence of domestic equipment manufacture on imported CNC grinding machines,my paper carries out a research on the cam grinding algorithm.Through related paper research and experimental research.it was found that grinding accuracy has a close relation with the grinding thickness.Maintaining equivalent grinding thickness during machining ensures Machined parts have high contour accuracy.Due to problems such as the mismatch of speeds in the axes during grinding.The difference between the equivalent grinding thickness and the theoretical equivalent grinding thickness which is caused by actual machining is large.This paper is to achieve the purpose of compensating the equivalent grinding thickness by dynamically optimizing the shaft rotation speed.The main content is divided into the following four points:1、Data processing before cam grinding.In the actual machining process.the cam lift data is often obtained by means of measurement.There may exist some noise errors in the obtained data.This paper uses Fourier transform to achieve lift fairing.After the lift table is obtained,then the lift data is interpolated by the cubic spline curve.Finally.the grinding center relationship between c-axis and x-axis is deduced by using the instantaneous center of gravity method to obtain the input value of the cam grinder.2、An optimization method of cam grinding speed by using equivalent grinding thickness.Due to the traditional grinding thickness cannot describe the machining process well,it is thought that the equivalent grinding thickness is used to describe the cam grinding process.The equivalent grinding thickness is mainly affected by the grinding thickness,grinding wheel speed and cutting speed.In the machining process,the cutting speed has a great influence on the machining accuracy.After analyzing,it was decided to optimize the cutting speed indirectly by optimizing the shaft rotation speed curve.3、Combining Cycle-To-Cycle feedback control theory with genetic algorithm to achieve dynamic speed optimization of shaft grinding speed curve.Due to the problems about inconsistent matching of axes in the grinding process.the equivalent grinding thickness will change during the machining process.In order to obtain a better optimizational speed,this paper will use Cylce-To-Cylce feedback control theory to treat each grinding process as a cycle.Using genetic algorithms to dynamically optimize the speed curve,a set of processing speed curves which meets the accurate requirements is finally obtained.4、Experimental simulation is used to prove the validity of the algorithm.In order to.prove the validity of the algorithm better,this paper builds the MATLAB CNC grinding systematic simulation platform based on the measured data of the MK8312C cam grinder.Based on the MK8312C simulation platform,constant-speed grinding,quasi-constant-line-speed grinding which has limited maximum acceleration and the optimal method in this paper are compared.The results of the cam simulation show that the proposed method makes the feed axis speed change smoothly and the cam contour accuracy has been improved further.更多还原