【作者】 龚时华；

【导师】 段正澄；

【作者基本信息】 华中科技大学 ， 机械制造及其自动化， 2008， 博士

【摘要】 凸轮轴是许多重要装备如轿车发动机、高端纺织机械的关键零件,其加工精度直接影响这些装备的工作性能。传统的凸轮轴磨削加工一般采用普通砂轮、运用靠模的方法来实现,这种磨削加工方法难以满足凸轮轴高精度、高效率、高柔性和工序集中的加工要求。本文从凸轮轴零件高精度、高效率和高柔性磨削加工的综合目标出发,在分析和总结国内外磨削加工领域最新研究成果的基础上,面向CBN砂轮磨削的特定工艺要求,深入系统地研究了凸轮轴高速磨削加工控制系统所包含的理论、优化算法、关键技术等问题。本文的主要研究工作有以下几个方面:针对凸轮表面轮廓型线复杂的特点,采用三次样条曲线对凸轮表面轮廓进行拟合,然后基于磨削点搜索算法与解析算法推导了任意旋转角度工件与砂轮切点位置的表达式,并基于系统速度、加速度约束提出了一种凸轮表面轮廓曲线插补算法,使机床在磨削过程中具有良好的动力学特性,提高了磨削加工精度。深入研究了凸轮轴磨削加工的运动控制数学模型,推导了磨削点(即凸轮轮廓与砂轮的切点)线速度与工件旋转速度的数学关系、磨床机械传动系统和伺服系统的传递函数,为凸轮轴磨削加工控制优化提供了理论依据。凸轮轴磨削加工中,如何提高砂轮高频率往复运动的响应能力是一个主要的控制难点。本文设计了基于预见前馈的砂轮往复运动控制器,解决了砂轮运动的响应滞后问题,提高了砂轮进给单元对扰动及参数变化的适应能力。在提高单轴控制精度的前提下,建立了基于伺服模型的两轴误差补偿互耦模型。基于此模型,在加工过程中采用模型参考自适应控制技术在线调节进给量(即利用轮廓误差,实时估计误差信息来调节插补器的进给量),提高了轮廓加工精度。在上述研究基础上,以凸轮轴CBN磨削加工机床为控制对象,开发了基于PC+NC体系结构的开放式数字化平台,提出了控制系统中各种控制参数的整定方法。本文相关研究成果已应用在开发的CBN数控凸轮轴、曲轴磨床上,取得了良好的效果。更多还原

【Abstract】 Camshafts are very important for automobile engines and advanced textile equipments. Their machining quality directly influences the performance of these devices. The conventional method to make the camshafts is to utilize modular and ordinary grinding wheel. The products made by this way have not enough contour precision, efficiency and flexibility.To improve contour precision, efficiency and flexibility for camshafts grinding, this thesis is emphasized on the research on the key technologies and optimization algorithm for the grinding process control system according to the special grinding method with CBN grinding wheel .During this research,the latest research achievements in this field are followed.This thesis puts stress on the following aspects:According to the complexity of the camshaft surfaces contour, the three cubed splines are used to fit them, then the point of tangency between the grinding wheel and the camshaft part is calculated, which is based on the grinding point searching arithmetic and the analytical arithmetic.With that,the interpolation arithmetic for the camshaft surfaces contour is proposed according to the restrictions of the machine tool’s velocity and accelerated velocity.which ensures that the grinding process meets the machine tool dynamical characteristics.The mathematical model has been deeply studied for the motion in machining camshafts.The mathematical function between the surface linear velocity and the part rotational velocity is established, and the mathematical models of the transmission units and the servo units of the machine tool have also been studied.With the high speed rotation of camshaft workpiece,the response of the grinding wheel reciprocating motion unit is slow down due to inertia ,which is a difficult control problem .The controller of the grinding wheel reciprocating motion based on a look-ahead forward technique is designed to solve the problem,and in the grinding wheel motion unit, the adaptability against the system disturbance is enhanced.Based on the fact that the control precision for a single axis is improved, the cross-coupled biaxial error compensation model has been established.A model- referenced adaptive control is introduced to adjust feedrate on line, which process is that the online error information is estimated by terms of contour error in order that the interpolation controller calculates the biaxial commond value. Therefore, the grinding process precision is advanced highly.Above all, an open CNC system is developped aiming at the CBN grinding machine for camshafts, following that a series control parameters are made certain. The experiment shows that the control arithmetics and the key techniques in this thesis have capacity of grinding camshafts with high speed and high precision.更多还原