虚轴钻尖刃磨机的设计与控制

【作者】 李晓西；

【导师】 罗学科；

【作者基本信息】 北方工业大学 ， 机械电子工程， 2003， 硕士

【摘要】 目前，含有并联机构的机床得到越来越广泛的应用，以Stewart平台为基础的并联机床相对于传统的串连机床有其自身的优缺点。虚轴机床的运动是通过控制六根杆的长度实现的，由于杆只承受轴向力，所以切削时杆的变形小，机床零部件截面小。更重要的是虚轴机床六根杆没有误差累积，所以虚轴机床比传统机床刚度高、精度高、机床制造成本低，其缺点则是控制复杂。对这种机床机构进行研究，有利于开发新的机床品种，实现钻尖刃磨自动化、数控化。本论文主要研究虚轴钻尖刃磨机的设计以及控制方法。重点研究了相应虚轴钻尖刃磨机的机床活动空间计算方法和位姿控制方法；研究了钻头几何参数和刃磨参数之间的关系和求解方法。 要设计和控制虚轴钻尖刃磨机，首先要建立描述钻头的数学模型。普通麻花钻的后刀面可以描述成锥面的一部分。论文论述了普通麻花钻锥面刃磨的数学模型，根据这个模型，可以求解钻头的几何参数和刃磨参数之间的关系，钻头刃磨参数决定刃磨时钻头和砂轮间的安装角度。根据钻头锥面刃磨的数学方程，可以求解钻头的刃磨方程，钻头的刃磨方程描述钻头刃磨时钻头和砂轮的相对运动。当钻头围绕锥面轴转动，就形成了钻头的锥形后刀面。 为确定机床参数，首先根据机床活动空间的分析设定机床的一系列参数。根据机床的运动方程和机床参数，可以求解出钻头围绕锥轴转动时动平台的位置和姿态，从而可以计算出两平台每一个关节在固定坐标系中的坐标，就可以求解出每一根杆的杆长。然后验证设定的机床参数能否满足杆长和杆的干涉约束，如果不能，修改机床参数，重复以上步骤直到可以满足这些要求。确定了机床参数，根据钻头刃磨运动方程控制每根杆的长度，就可以控制动平台产生相应的运动，实现钻头的锥面刃磨。更多还原

【Abstract】 Recently, the application of machine tools with parallel mechanism becomes more and more popular. There are many advantages also disadvantages of the Stewart platform based machine compared with traditional serial mechanism machine. The motions of a virtual axis machine tool are provided by the legs which bear only axial load. Due to its parallel construction, the deflection of the load is thus reduced significantly and legs with small cross section can be used. Moreover, the parallel structure does not accumulate the moving errors of its legs. As a result, the virtual axis machine tools are more rigid, more accurate and can move much faster than that of the conventional machine tools. But the control system of the virtual axis machine tools is much more complicated than that of the conventional machine tools. It is very helpful to using this kind of mechanism to develop new style grinder to realize cutting tools grinding automatically and numerically. In this paper, the author mainly deal with how to design and control the virtual axis drill point grinding machine; a solution of calculating the workspace needed when grinding and the way of controlling the position and orientation of the platform where machine spindle is installed relative to the platform which is immovable and the relationship between the design parameters and grinding parameters of the drill point and the way of calculating the grinding parameters also was presented.To design and control the virtual axis drill point grinding machine, mathematical representation to describe the drill point configuration is badly needed. According to former research, the flank of the conventional twist drill can be modeled as the surface of a cone. The mathematical model can be applied to the design of drill point grinder by examining the relationship between the grinding parameters and the design parameters. The grinding parameters were used to determine the drill fix angle and grinding wheel angle when grinding. By the mathematical model of drill point geometry, the grinding motion equation of drill points can be established. The grinding motion equation specifies the relative motion of the drill and the grinding wheel surface during the drill point grinding process. When the drillpoint revolves about the axis of cone (here the cone is the surface which forms the flank of the drill point to be grinded), the flank is generated.To design the drill point grinding machine, the diameters of the two platforms and the maximum and minimum length of the legs should be decided firstly, secondly, whether the workspace decided by the parameters meet the strut length constraints and the interference restriction of legs must be verified. The position and orientation of the movable platform and the length of each strut of each step when grinding can be calculated and controlled according to the grinding motion equation and the parameters of the grinding machine.更多还原