宏/微结合双驱动进给控制系统的建模与仿真研究

采用宏/微结合双驱动进给系统能使系统在大行程范围内具有较高的定位精度。本文设计的宏/微结合双驱动进给系统,由交流伺服电机驱动滚珠丝杠作为宏动机构,压电陶瓷驱动柔性铰链工作台作为微动机构。分别对宏动机构和微动机构进行了数学建模。采用双伺服环控制策略,由宏动机构跟踪输入信号,由精密光栅尺检测宏动机构的实际位移进行反馈构成内伺服环;微动机构将宏动机构的跟踪误差作为输入信号,实时进行补偿,构成外伺服环,实现了宏/微结合双驱动进给系统的连续跟踪控制。最后进行了仿真研究,仿真结果表明跟踪幅值为1mm频率为0.4Hz的正弦曲线,采用宏/微结合双驱动进给系统比只采用宏动机构跟踪误差由±1.6μm减小到了±6nm。     

滚珠丝杠进给系统结构模态特性对位置环增益的影响性分析

为充分考虑滚珠丝杠结构模态特性对伺服控制器及进给驱动系统整体统态性能的影响,建立了基于特征模态的滚珠丝杠进给系统状态空间缩聚模型,以实现在模态特性影响下求解进给系统动力学响应的同时与伺服控制系统集成;在此基础上,建立了基于滚珠丝杠进给系统状态空间缩聚模型的伺服系统位置调节回路模型,推导了系统模态频率、开环幅值响应激增值与位置环增益之间的约束关系式,进行了滚珠丝杠进给系统模态特性对位置环增益的影响性分析,实现了特征模态影响下位置环增益参数的最优值估计。通过实例验证了基于状态空间的滚珠丝杠进给系统模态特性提取、滚珠丝杠进给系统模态特性对位置环增益的影响性分析结果、结构特征模态影响下的位置环增益参数最优值估计的正确性。     

滚珠丝杠粗糙度和螺距误差影响因素的正交分析

针对表面粗糙度和螺距误差对滚珠丝杠性能的影响,通过正交试验对磨削过程中影响滚珠丝杠粗糙度和螺距误差的因素:砂轮转速、修整进给速度、丝杠转速、磨削深度进行试验探究,确定各因素对滚珠丝杠性能影响的主次顺序和最佳组合。研究发现,磨削过程中,粗糙度最小的工艺参数组合为砂轮转速1 144 r/min,修整进给速度208 mm/min,丝杠转速16 mm/min,切削深度2μm。以上参数影响滚珠丝杠表面平均粗糙度的主次顺序为:砂轮转速→修整进给速度→磨床丝杠转速→切削深度。螺距误差最小的工艺参数组合为砂轮转速1 144 r/min,修整进给速度208 mm/min,丝杠转速16 mm/min,切削深度1μm。以上参数影响滚珠丝杠螺距误差的主次顺序为丝杠转速→磨削深度→修整进给速度→砂轮转速。     

高增益PID控制器实现纳米定位

建立了高增益PID闭环控制系统,在"直流伺服电机＋滚珠丝杠"驱动机构上实现了大范围的纳米定位。对于"伺服电机＋滚珠丝杠"驱动系统来说,摩擦是实现纳米定位精度的主要障碍,它影响着系统微动特性并导致稳态误差。针对这种驱动系统,在根据标定参数计算得到的线性传递函数的基础上,设计高增益不完全微分、比例反馈PID控制器,配置闭环控制系统的极点为负实轴上的多重极点,避免了摩擦力建模和补偿。实验结果表明,该高增益闭环控制系统有效地抑制了摩擦等非线性因素的影响,在系统的宏动和微动特性阶段都可以实现单步的纳米定位并取得了一致的响应,10 nm~10 mm阶跃响应的稳态误差不超过±2 nm。     

基于ANSYS的滚珠丝杠进给系统静动态特性分析

对一台数控车床滚珠丝杠进给系统的静、动态特性进行有限元分析,讨论了ANSYS中滚珠丝杠副结合面的建模方法。通过进给系统的死区误差和定位误差分析,校核了机床X向的定位精度和重复定位精度。并通过模态分析和谐响应分析,得到了机床进给系统固有频率和振动特性,为进给系统的合理使用和静、动态性能的提高提供了可靠的依据。     

使用直线光栅尺实现精密加工

机床精度受温度影响最重要的部位是进给驱动。高的速度和大的加速度使滚珠丝杠发热,丝杠膨胀。如果没有相应位置测量技术,几分钟内定位误差就能达到100μm。因此,公差要求严格的工件只能在热特性好的机床上加工,即使加工工艺非常不同也必须这样。     

不同指令轨迹条件下滚珠丝杠进给系统运动精度特性研究

滚珠丝杠进给系统是高档数控机床重要部件,其运动精度决定了多轴联动加工机床的加工精度,在高速、高精度滚珠丝杠进给系统中,其指令轨迹参数是影响运动精度的重要因素。基于Simulink和Simscape搭建滚珠丝杠进给系统半物理机电耦合仿真模型,考虑不同指令轨迹参数,开展运动精度仿真及分析。结果显示,指令轨迹的位置、速度和加速度等参数对滚珠丝杠进给系统运动精度有重要影响,因此,在多轴联动加工机床中,合理规划进给系统轨迹参数对于提高其运动精度具有重要意义。     

高精度大口径光栅拼接装置的控制算法

采用宏/微结合双驱动的少自由度并联进给结构,给出了一种光栅拼接装置设计算法.宏动部分是5PTS-1PPS型并联机构,采用步进电机驱动滚珠丝杠形式的进给机构;微动部分是5TSP-1PPS型并联机构,采用压电陶瓷驱动柔性铰链形式的进给机构;二者串联构成光栅拼接机构.计算了宏动部分和微动部分的并联机构自由度,利用并联机构运动学的逆解推导出该装置的控制算法,并根据控制算法进行了宏动、微动机构点位控制的运动学仿真.为了提高机构的定位精度,分析了机构的系统误差并提出了误差修正方法.最后,将以上算法应用到光栅拼接装置中.实验结果表明:宏动部分最大移动定位误差为3.6 μm,最大转动定位误差为4.4 μrad;微动部分最大移动定位误差为0.06 μm,最大转动定位误差为1.2 μrad;基本满足光栅拼接系统的精度要求.     

滚珠丝杠传动的发热及其计算

在滚珠丝杠传动机构中和支承中均有较大的预加负荷,再加上外部热源的传导,使传动机构发热,导致进给传动机构的参数热误差,影响工件的定位精度。提高支承的载荷,如不考虑发热的影响,会使其在设计的有效期内失去工作能力。在采用滚珠丝杠的结构设计中,一般是根据具体工作条件和传动原理选择标准的结构的,而很少考虑在机床工作中所产生的热变形。特别是对于快速工作和刚度要求高的两端轴向固定的滚珠丝杠传动机构,就必须进行发热计算。 传动机构的热源是内部热源(滚珠丝杠的传动机构和支承产生的热源)和外部热源(进给传动机构的电机、运动部件…     

高速机床滚珠丝杠副及其热特性分析

根据高速机床滚珠丝杠副结构组成特点和工作原理,结合高速切削实验结果,分析了引起滚珠丝杠副温升变形的主要热源及其影响因素,获得了温升随丝杠转速和预紧力的变化规律.基于能量守恒定律和傅里叶热传导定律,推导了滚珠丝杠副热传导微分方程并确定了其定解条件,建立了丝杠副温度变化的数学模型,为滚珠丝杠系统温度场仿真分析提供理论依据,可用于进一步研究高速进给系统热变形误差和提高定位精度.     

Development of a linear electrostrictive servo motor

This paper presents a linear electrostrictive servo motor with high resolution and large stroke for ultra-precision motion control. High thrust force is obtained by making use of an electromagnetic clamping mechanism with force magnifying structure in the motor design. An operator alterable iterative learning control algorithm is proposed for the motion control of the motor. A prototype is designed, fabricated and tested. Experimental results show that the prototype has a mechanical resolution of 0.02 μm, yaw error less than 2 μm and maximum thrust force of 30N. Applications of the motor include producing the servo feed motions required in micro electrical discharge machining (micro-EDM) system or as a motion control device for other precision machining systems.     

压电式微位移机构设计与实验研究

微机电系统、超精密加工等众多领域飞速发展且都需要高灵敏度的微位移致动设备,微位移技术有着广阔的应用背景.而压电驱动由于结构紧凑、位移分辨率高、频响高、承载力大、无噪声、不发热等优点成为微位移致动的较佳方案.文中设计了一种结构小巧的压电式高灵敏度微位移致动机构,对称式平行四杆柔性铰链作导向,在千级超净实验室内进行的驱动性能测试实验显示,机构位移灵敏度4 nm,位移响应速度100 ms,可应用于精密加工等需要纳米级驱动的领域.通过实验研究和分析,给出了影响压电驱动高灵敏度的关键因素.     

压电驱动柔性铰链机构传动实现超精密定位

简单介绍压电元件和柔性铰链的概念与特点。列举压电元件与柔性铰链机构结构实现超精密定位的典型例子，包括超精密测量、超精密加工、光学自动聚焦和大行程超精密定位。为使超精密定位工作台的结构紧凑，提出单驱动多自由度运动机构。应用蠕动式的运动原理可合成机构上的多自由度运动，并实现大行程运动。设计了对称结构的柔性铰链机构实现导向功能。制造和装配了微小型平面工作台。     

Control of a high precision macro-micro robotic manipulator system

A controller for macro-micro robotic manipulator system in which kinematically independent two robotic sub-systems work together to improve the accuracy of the motion is proposed. A nonlinear feedback linearization scheme is employed as basic architecture for the controller and additional formulations about the controller structure are made to assure the robustness of the overall control action and to restrict the motion of micro sub-system close to its nominal position without causing saturation of joints associated with micro-robot.     

蠕动式X—Y—θ微动工作台的设计实现

提出了一种新颖的X-Y-θ微动工作台。利用单一压电元件驱动及柔性铰链机构传动获得平面上3个自由度的运动,并与电磁夹紧机构配合实现蠕动式进给,使平面工作台具有高的位移分辨率、大的工作行程和简洁的结构。工作台的核心部件柔性铰链传动机构采用对称设计,有利于运动的导向。通过力学分析,对柔性铰链机构进行了参数选择。测试了工作台的性能,柔性铰链机构刚度的实测值同理论值接近。运动速度大于10um/s,位移分辨率小于0.1um。     

微通道结构带状电极电火花加工方法研究

针对大厚度、高深宽比金属微通道结构加工的难题,提出一种带状电极电火花加工方法,利用厚度30～100 μm的带状电极,在金属基体上高效制造微通道结构。研究了带状电极电火花加工机理,建立了带状电极在加工间隙中的运动模型,分析了影响带状电极运动的主要因素,搭建了带状电极电火花加工装置,开展了微通道结构带状电极加工实验研究,获得了带状电极电火花加工基础工艺规律。利用带状电极电火花加工方法成功加工出的具有200条微通道的反应器结构和44×45微换热器阵列结构,表明带状电极电火花加工可以实现窄宽度(100 μm以下)、大厚度(35 mm以上)、高深宽比(10以上)和高精度(缝宽标准差3 μm以内)的大批量微通道结构的高效加工,相关方法和技术有望在微模具、微散热器、微反应器等领域获得推广和应用。     

Applications of integrated motion controllers for precise CNC machines

The error resources of precise motion control systems are basically categorized into linear and nonlinear effects. To realize the precise motion of industrial computer numerical control (CNC) machines, this paper presents an integrated motion control structure with modular algorithms, including both the linear control and the nonlinear compensation. In the linear control design, this study applies three algorithms: (1) feedforward control to address the tracking errors, (2) cross-coupled control to reduce the contouring errors, and (3) digital disturbance observer to lessen the effects of modeling errors and disturbances in real applications. The results indicate that the linear motion controller achieves greatly improved accuracy in both tracking and contouring by reducing the servo lags and mismatched dynamics of the different axes. However, the adverse effect due to friction still exists and cannot be eliminated by applying the linear motion controller only. This study further integrates the nonlinear compensator and develops friction estimation and compensation rules for CNC machines. The digital signal processors are suitable to implement all the developed linear and nonlinear algorithms, and the present controllers have been successfully applied to industrial CNC machines. Experimental results on a vertical machining center indicate that, under different feed rates, the CNC machine with the integrated motion controller significantly reduces the maximum contouring error by 135% on average.     

Piezo微步进工作台主框架研究

为了扩大微动工作台的有效行程,提出一种新型的基于Piezo驱动的微步进X-Y工作台,通过机构仿真确定了微步进工作台主框架中各柔性铰链的转角参数,并据此确定了主框架中各柔性铰链的结构参数,最后通过非线性有限元对整个微步进工作台主框架的变形情况进行了分析.     

Dynamics synthesis and control for a hopping robot with articulated leg

To investigate the design and the applications of elastic underactuated mechanisms for improving the energy efficiency of dynamic mechanical systems, the dynamics and control of a one-legged hopping robot with articulated leg is studied in this paper. To ensure the controllability of the elastic underactuated mechanism, a dynamics synthesis method is proposed for designing the underactuated mechanism so that the dynamics of the system can be transformed into the strict feedback normal form. To improve the energy efficiency of the one-legged locomotion system, an optimal motion planning method is presented to optimize the trajectories of the robot joints. A nonlinear controller is proposed to stabilize the hopping robot to its balance configuration in stance phase, and a switched linear controller is proposed to stabilize the continuous hopping movement. The stability of the presented controllers is analyzed in theory and verified by some numerical simulations.     

Precision machining of micro tool electrodes in micro EDM for drilling array micro holes

Micro electro discharge machining (micro EDM) is suitable for machining micro holes on metal alloy materials, and the micro holes can be machined even to several microns by use of wire electro discharge grinding (WEDG) of micro electrodes. However, considering practicability of micro holes <Φ100 μm in batch processing, the controllable accuracy of holes’ diameter, the consistency accuracy of repeated machining and the processing efficiency are required to be systematically improved. On the basis of conventional WEDG method, a tangential feed WEDG (TF-WEDG) method combined with on-line measurement using a charge coupled device (CCD) was proposed for improving on-line machining accuracy of micro electrodes. In TF-WEDG, removal resolution of micro-electrode diameter (the minimum thickness to be removed from micro electrode) is greatly improved by feeding the electrode along the tangential direction of wire-guide arc, and the resolution is further improved by employing negative polarity machining. Taking advantage of the high removal resolution, the precise diameter of micro-electrode can be achieved by the tangential feed of electrode to a certain position after diameter feedback of on-line measurement. Furthermore, a hybrid process was presented by combining the TF-WEDG method and a self-drilled holes method to improve the machining efficiency of micro electrodes. A cyclic alternating process of micro-electrode repeated machining and micro holes’ drilling was implemented for array micro holes with high consistency accuracy. Micro-EDM experiments were carried out for verifying the proposed methods and processes, and the experimental results show that the repeated machining accuracy of micro electrodes was less than 2 μm and the consistency accuracy of array micro holes was ±1.1 μm.