椭圆轨迹成形方法与控制技术研究

发布时间：2018-04-20 13:56

本文选题：运动成形法 + 动压比　；参考：《山东大学》2014年博士论文

【摘要】：研究了基于运动合成的椭圆内曲面成形方法,重点开展静压主轴椭圆轴心轨迹控制技术研究。构建了基于新型静压轴承和新型伺服节流阀的液压控制系统；研究了新型轴承—转子系统及新型伺服阀节流系统的动力学特性和控制特性；研究了椭圆轴心轨迹的控制技术和方法。为椭圆内曲面加工新方法的实现奠定了理论基础。开展了椭圆内曲面运动成形基础理论研究,并详细阐述了其实现方案和成形原理。研究了多种轴心公转轨迹与刀尖自转轨迹进行合成时形成椭圆刀尖轨迹的必要与充分条件；研究了刀具初始相位角对形成椭圆刀尖轨迹的影响；给出了多种轴心公转轨迹和不同刀具初始相位角下形成椭圆刀尖轨迹的特征和控制方程。针对椭圆轴心轨迹的空间要求,开展了椭圆廓形静压轴承的理论研究,给出了其雷诺方程和流量连续性方程等基础性方程及计算方法。提出了动压比的概念来衡量封油面上动压效应的大小,并对主轴轴心在新型静压轴承内运动轨迹为小椭圆时的动压比进行了仿真计算。利用偏导数法研究了半径间隙和椭圆度对新型静压轴承静动态特性参数的影响。设计了一种基于压电陶瓷的新型伺服节流阀,可以弥补普通电液伺服阀频响较低的缺点。基于新型油腔嵌套式轴承及新型伺服节流阀的结构,构建了轴心运动轨迹的液压控制系统。对新型节流阀的流量公式进行了仿真拟合。利用基于贝叶斯正则算法的BP神经网络对压电陶瓷的位移输出进行了仿真预测。根据动压效应的研究结果对封油面上的油膜力分布进行线性化处理,利用流量平衡方程以及高斯—勒让德积分公式得到了承载油腔以及控制油腔的压力计算公式,这种简化计算方法既简单又可以大大节省计算时间。仿真计算了轴心期望运动轨迹与新型节流阀控制电压的定量关系。利用最优控制理论对主轴轴心公转轨迹为椭圆的问题进行了最优控制建模。建立了基于新型静压轴承的轴承—转子系统的动力学模型,并以轴心位置坐标为待优化的状态变量,控制外力(这里为油膜合力)为控制变量,以待优化的轴心坐标与期望轴心坐标的偏差作为性能指标,得到系统的最优控制模型。求解勒让德零点以及对状态变量和控制变量近似化,通过高斯伪谱法将最优控制问题又转化成了非线性规划问题,最后通过序列二次规划法仿真得到了轴心运动轨迹的最优控制参数。仿真结果表明轴心的优化位置坐标与期望位置坐标非常接近,高斯伪谱法精度较高且可以应用在轴心运动轨迹的最优控制上。对主轴轴心的运动轨迹进行了开环控制仿真研究。利用轴心期望轨迹与新型节流阀控制电压的定量关系,通过欧拉方法迭代得到轴心的开环控制仿真轨迹。仿真得到轴心轨迹为不同椭圆度的椭圆时开环控制轨迹图,并对有瞬态干扰力时开环控制的轴心运动轨迹也进行了仿真。仿真结果表明开环控制方法不但可以控制轴心运动轨迹为不同椭圆度的小椭圆,还可以在系统受到干扰时保持较好的鲁棒性。对新型压电伺服节流阀以及油腔嵌套式轴承系统分别进行了动力学建模,得到系统的传递函数,并进行了前馈解耦。基于轴心期望运动轨迹的周期性特点,采用重复控制算法对系统进行了闭环控制仿真。在MATLAB的simulink环境下对系统进行建模,利用设计的重复控制器对轴心运动轨迹进行了闭环控制的仿真研究。仿真结果表明重复控制算法控制轴心跟踪期望轨迹时具有较高的精度。
[Abstract]:The elliptical inner surface forming method based on motion synthesis is studied, and the trajectory control technology of the elliptical axis of the hydrostatic spindle is studied. The hydraulic control system based on the new type of static pressure bearing and the new servo throttle valve is constructed, and the dynamic characteristics and control characteristics of the new type bearing rotor system and the new servo valve throttle system are studied. The control technology and method of elliptical axis trajectory were studied, which laid a theoretical foundation for the realization of new machining method for elliptical inner surface.
The basic theory of elliptical inner surface movement forming is studied, and its realization scheme and forming principle are described in detail. The necessary and sufficient conditions for forming the trajectory of elliptical blade tip are studied, and the influence of the initial phase angle of the tool on the formation of the ellipse tip trajectory is studied. The characteristics and governing equations of elliptical tool tip trajectories under different axis orbit and different tool initial phase angle are obtained.
In view of the spatial requirements of the elliptical axis trajectory, the theoretical study of the elliptical profile hydrostatic bearing is carried out. The basic equations and calculation methods, such as the Reynolds equation and the flow continuity equation, are given. The concept of dynamic pressure ratio is proposed to measure the size of the dynamic pressure effect on the sealing surface, and the motion trajectory of the spindle axis in a new hydrostatic bearing is given. The dynamic pressure ratio of small ellipse is simulated. The influence of radius clearance and ellipticity on the static and dynamic parameters of the new hydrostatic bearing is studied by partial derivative method.
A new type of servo throttle valve based on piezoelectric ceramics is designed, which can make up for the low frequency response of the ordinary electro-hydraulic servo valve. Based on the new type of oil chamber nested bearing and the new servo throttle valve structure, the hydraulic control system of the axis motion trajectory is constructed. The flow formula of the new throttle valve is simulated and fitted. The BP neural network of the Juliu regular algorithm is used to simulate the displacement output of the piezoelectric ceramic. According to the research results of the dynamic pressure effect, the oil film force distribution on the oil sealing surface is linearized, and the pressure calculation formula of the bearing oil cavity and the control oil cavity is obtained by using the flow balance equation and the Gauss Legendre integral formula. The simplified calculation method is simple and saves time greatly. The quantitative relationship between the desired trajectory and the control voltage of the new throttle valve is simulated and calculated.
The optimal control theory is used to model the elliptical trajectory of spindle axis. A dynamic model of the bearing rotor system based on a new type of hydrostatic bearing is established, and the axis position coordinates are used as the state variables to be optimized. The control variable is controlled by the external force (the oil film joint force) is the control variable to be optimized. The optimal control model of the system is obtained by the deviation of the coordinate and the expected axis coordinate. The Legendre zero point is solved and the state variable and the control variable are approximated. The optimal control problem is transformed into the nonlinear programming problem by the Gauss pseudospectral method. Finally, the axis center motion rail is obtained by the simulation of the sequence two times programming method. The simulation results show that the optimal position coordinates of the axis are very close to the desired position coordinates, and the Gauss pseudospectral method has higher precision and can be applied to the optimal control of the axis motion trajectory.
The opening loop control simulation of the axis of the spindle is studied. Using the quantitative relationship between the desired trajectory of the axis and the control voltage of the new throttle valve, the simulation trajectory of the open loop control of the axis is obtained by the Euler method. The trajectory of the open loop control of the axis of the axis with the ellipse of different ellipticity is obtained, and the transient interference force is also obtained. The axis motion trajectory of the time open loop is also simulated. The simulation results show that the open loop control method can not only control the axis motion trajectory as a small ellipse with different ellipticity, but also keep good robustness when the system is disturbed.
The dynamic modeling of the new piezoelectric servo throttle valve and the oil chamber nested bearing system is carried out respectively. The transfer function of the system is obtained, and the feedforward decoupling is carried out. Based on the periodicity of the desired trajectory of the axis, the system is simulated by the repetitive control algorithm. The system is introduced to the system under the Simulink environment of MATLAB. The simulation study of the closed loop control of the axis motion trajectory is carried out by the design of a repetitive controller. The simulation results show that the repetitive control algorithm has a high accuracy in controlling the desired trajectory of the axis tracking the desired trajectory.

【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TH137;TH133.36;TH134

【参考文献】