Micro-end-milling-II. Extending tool life with a Smart Workpiece Holder (SWH)

A new procedure is proposed to extend tool life. The new procedure uses a Smart Workpiece Holder (SWH), which monitors the cutting force and reduces the metal removal rate when it predicts tool breakage possibility. The response includes a quick move in the opposite of the feed direction by using a piezo-electric actuator and by reducing the feed rate. The proposed system was tested with mild steel and aluminum workpieces. Based on the experimental results, better than 50% of the tool breakage cases could be predicted and tool life can be increased more than 30%.     

一种基于VB的超声波线切割机导轨误差的测量与补偿系统设计

以机床导轨误差理论为基础,基于VB设计了一种机床导轨误差测量与补偿系统。该系统采用光栅传感器来确定导轨的水平位置,通过电涡流位移传感器把被测量(机床导轨误差)转化成电信号,用USB2828数据采集卡的AD功能把传感器输出的电信号转化成数字信号,按传感器及驱动电源的灵敏度计算出补偿误差所需的电压值,再用采集卡的DA功能输出电信号给驱动电源。驱动电源的输出电压控制微位移器的位移(即刀尖的位移)变化,实现了导轨误差的补偿。实验结果表明测试系统的设计较合理,基本达到了补偿的要求。     

A ballscrew drive mechanism with piezo-electric nut for preload and motion control

This work reports the development of a ballscrew drive mechanism equipped with a piezo-electric nut for active ballscrew preload and fine motion control. This mechanism is intended for a motion stage of long-stroke, high-speed and ultra-precision applications. Motion of the piezo-electric nut ballscrew drive system consists of a high-speed coarse positioning and an ultra-fine positioning. Coarse positioning is done by a conventional servo motor and ballscrew where the piezo-electric nut exerts a light ballscrew preload in order to reduce the friction torque and wear at high speed motion. After the coarse positioning, a fine position adjustment is actuated by three piezo-electric actuators to get very precise positioning. Test results show that the positioning error can be fine-adjusted to the nanometer level. The low speed stability of the ballscrew drive mechanism has also been improved using the piezo-electric actuators by applying a dither signal to the ballscrew preload. The dither action can smooth and reduce the ballscrew friction force and consequently reduce the stick–slip phenomenon at low speed motion.     

使用Kelvin探头参比电极技术进行薄液层下电化学测量

研究了Ｋｅｌｖｉｎ探头参比电极技术测定薄液层下金属电化学行为的方法。为改善Ｋｅｌｖｉｎ探头装置的测试性能，采取和若干提高信噪比的措施，如采用压陶瓷振动驱动器和测量交流信号的电压成分等。实验结果表明，改进的这套装置可用于测试极薄液层下的金属电极电位，电位随时间的变化，腐蚀电位分布及极化曲线等稳态电化学行为，是研究大气腐蚀过程的有效工具之一。     

基于SimoDrive 611U/Ue的液压精密控制系统设计与实现

钢管数控成型机是一种通用型高端设备,应用于钢管圆形、方形等内孔成型加工。为了提高成型机液压系统位置控制精度并降低系统能耗,根据成型机工作条件,提出由伺服驱动器、伺服电机、光栅及传感器等构成液压精密控制系统的设计方案。该方案利用伺服驱动器控制伺服电机旋转,带动定量泵控制液压缸位移,光栅反馈位移量给伺服驱动器,构成闭环控制来达到精密控制效果。该设计具有改造费用低、加工效率高和精度高等优点。     

The development of a high-speed spindle measurement system using a laser diode and a quadrants sensor

Reducing the manufacturing time is the trend of precision manufacturing, and the precision of a work-piece is very important for manufacturing industry. High-speed cutting is becoming more widely used and the high-speed spindle is a very important element, whose precision may affect the overall performance of high-speed cutting. Most of the studies on high-speed cutting are focused on the cutting force, the vibration of the spindle and the effects of the spindle's thermal expansion; however, the measurement of the high-speed spindle continues to use the conventional spindle measurement method.As with the measurement of the high-speed spindle, more strict demands are set on the dynamic balance of cutting tools and the bandwidth of the measurement systems when compared with common spindles. The capacitance displacement sensor has been employed for the spindle error test. The precision of the measurement system is limited by the reference (such as a master ball or a master cylinder). Also the capacitance sensor and the reference must be grounded together. This paper presents a simple spindle measurement system using a laser diode and a quadrants sensor, with accuracy up to 1 μm, within 300,000 rpm for various spindles. The system does not need any reference and it is easy to set up. This system can be applied to measure the spindle errors, the spindle speed and the spindle indexing.     

基于组合控制的电液执行机构气门阀运动误差控制仿真研究

当前,发动机气门阀回程着落时不稳定,导致其跳动幅度较大。针对此问题,设计电液执行机构控制系统,并对气门阀运动位移和速度进行仿真验证。建立电液气门阀驱动平面简图,分析液压执行机构驱动方式。给出3种不同状态下伺服阀阀芯位置变化过程,从而得到气门阀液压驱动变化表达式。分析神经网络PID控制系统和跟踪微分器过滤原理,设计组合控制系统。为了验证不同干扰条件下气门阀运动位移和速度产生的误差,通过MATLAB软件对其进行仿真验证。仿真结果表明：在受到相同外界干扰条件下,采取传统PID控制系统,气门阀运动位移和速度的最大误差偏大,误差跳动幅度偏大;采用组合控制系统,气门阀运动位移和速度的最大误差偏小,误差跳动幅度偏小。采取组合控制系统,系统能够抑制外界的干扰,气门阀回程着陆时相对稳定,从而降低气门阀位移和速度的输出误差。     

基于数字液压动力管理系统的混合执行器控制研究

传统泵控系统由于溢流和节流损失产生较大能耗,同时需要根据系统需求的峰值功率进行选型,系统成本高。因此,提出一种基于6个活塞和18个开/关控制阀的数字液压动力管理系统的混合执行器。采用基于模型的控制器实现对混合执行器的有效控制,并对控制效果进行仿真验证。构建新型混合执行器系统液压回路简化图,建立数字液压动力管理系统、液压回路以及电动伺服电机数学模型。设计基于模型的控制器,实现对活塞以及数字液压动力管理系统的最优控制。采用MATLAB对基于数字液压动力管理系统的混合执行器进行仿真,并与传统阀控执行器的计算结果进行对比和分析。结果表明：采用基于数字液压动力管理系统的混合执行器活塞位置和速度跟踪误差分别减少61%和47%;基于数字液压动力管理系统的混合执行器的液压蓄能器会处理局部功率峰值,系统输入功率无较大波动,同时能耗也大大降低;采用基于数字液压动力管理系统的混合执行器可以有效控制活塞位置和速度,同时具有较高的能源效率。     

Dynamic modeling of cutting acoustic emission via piezo-electric actuator wave control

The fundamental understanding of the dynamic behavior of acoustic emission signals in relation to machining process parameters plays an important role in the automation monitoring and control of metal cutting operations. This paper presents an analytical model for acoustic emission dynamics in orthogonal cutting with chip thickness variation. An analytical expression for acoustic emission generated in turning is established as an explicit function of the cutting parameters and tool/workpiece geometry. Based on the theoretical static cutting acoustic emission model, the generation of the RMS acoustic emission is formulated as the function of three process parameters, namely tool displacement, cutting speed, and rake angle. The incremental change of the RMS acoustic emission is related to the chip formation process in an elemental cutting area and it is characterized by the dynamic variation of these process parameters. The analysis of the RMS acoustic emission is then extended into the dynamic transfer function between tool displacement and RMS acoustic emission. Experimental results via simultaneous tool displacement control by piezo-electric actuator and measurement of RMS AE generated during cutting confirm the validity of the analytical acoustic emission model in orthogonal cutting process.     

多环迟滞补偿的控制方法研究

对微位移驱动器的迟滞非线性系统建模和控制研究的现状分析，得知目前的迟滞非线性补偿控制主要是针对单环情况进行，而对多环迟滞补偿控制仍然很困难。通过对多环形成的原理研究，微位移驱动器控制信号可以被分解，使迟滞主环与次环分离。然后对所有的单环信号分别进行逆模型补偿后叠加输入迟滞非线性系统，得到了满意的补偿结果。     

以PLC主控单元作为控制器的数字控制系统设计

提出一种以PLC主控单元作为控制器的数字控制系统,即把被控设备执行机构位移检测装置(如光栅)所检测到的位移脉冲信号作为PLC主控单元的反馈信号,用PLC的计数器对位移检测脉冲信号进行计数,实现执行机构动作顺序及动作位移的数字控制。     

超磁致伸缩执行器位移测试系统的误差分析

超磁致伸缩执行器位移测试系统是其性能研究的基础。为提高测试数据的准确性,以常用超磁致伸缩执行器位移测试系统为基础,给出了测试系统的误差来源,建立了温升、电源、测量、采集等因素的误差模型以及多因素影响下的误差合成模型。实验与计算结果表明:所设计超磁致伸缩执行器在输出位移为18μm时,位移采集、超磁致伸缩执行器驱动与温升造成的相对误差分别为0.56%、2.83%、3.28%,各因素合成后的相对误差为4.37%。     

一种高效直驱液压角度位置伺服控制系统的研究和实现

基于直驱式液压系统效率高和阀控伺服系统精度高的特点,提出一种位置二元控制方法。第一元是步进电机控制的数字阀和执行器通过机械负反馈形成的闭环伺服系统,实现系统的精准位置控制。第二元是伺服同步电机控制的柱塞泵系统,系统根据执行器能够达到的加/减速度、最高速度、作动器的排量、初始位置和目标位置的差等,计算所需流量和具体执行的步进电机控制的节奏,并以步进电机控制节奏为参考,控制同步伺服电机速度及相应泵的流量,实现大偏差时高效运行;在小偏差时,在蓄能器压力达到设定值时,关闭同步伺服电机和柱塞泵,避免泵在低速低效区运行,用蓄能器储存的能量实现位置伺服纠偏控制;系统一直运行在高效状态。二元控制方法具有两个简洁的机制实现精准和高效目标,实用可靠。     

基于GA-BP的机电作动系统传感器故障诊断研究

机电作动器已经用于民航客机飞控舵面的控制,机电作动系统中传感器输出的正确性对系统正常工作影响较大,因此对传感器进行快速有效的故障检测非常必要。分析机电作动系统的传感器故障模式,针对当前故障检测在处理液态与非液态故障时所需信息多、检测时间长等问题,设计二级GA-BP神经网络对传感器故障模式进行诊断,对比分析了不同训练方式的神经网络方法,确定使用莱温伯格-马夸特学习方法的神经网络的故障诊断分类结果更加准确,并通过遗传算法对神经网络进行了优化。最后通过机电作动系统仿真实验平台验证该方法的有效性。创新之处在于采用了二级网络架构,快速检测液态故障与非液态故障,有效减少了网络故障检测的所需信息量和故障检测时间。     

Performance and work capacity of a polypyrrole conducting polymer linear actuator

This paper reports a performance analysis of a conducting polymer film actuator made of polypyrrole (PPy). Electrochemomechanical characterizations of the active displacement and the developed force of a PPy free-standing film at different loading conditions are performed. Two driving signals are used: the former, a cyclic voltammetry at 1 mV/s between ± 1 V, is used to carry out an accurate on-line analysis of the film displacement; the latter, a current square wave between 0.02 and 0.1 Hz, is helpful for evaluating the effectiveness of the actuator in terms both of actuation strain and of developed force. The experimental results indicate that 1 % displacement, 3 MPa force and working density of 73 kJ/m³ are achievable goals for a conducting polymer linear actuator, which are interesting results if compared with the limiting specifications of skeletal muscle. Additionally, two different approaches to the electrochemomechanical modeling of the conducting polymerfluid electrolyte system are illustrated, together with a discussion about foreseen improvements in the implementation of actuating structures.     

激光位移传感器在圆柱度误差检测中的应用研究

为了提高圆柱度测量的效率和准确性,针对目前手工检测效率低等缺点,提出一种以三维激光位移传感器的测量原理为依据的光电非接触圆柱度测量方法。与传统方法相比,该方法首先搭建了以回转主轴和伺服执行机构为主的测量控制系统平台;其次,利用机械装置的相对运动,通过传感器采样测量物体各测量截面的信息,实现圆柱度误差测量。     

错架图书识拣机器人结构设计及运动学分析

设计了一个四自由度直角坐标错架图书分拣机器人,传动机构由一个R方向的转动机构和X、Y、Z 3个方向上的滑动机构组成,通过各个传动机构的运动实现末端执行器所要到达的位置。利用D-H参数法建立机器人的运动学方程,对机器人末端执行机构的运动进行理论推导,利用SolidWorks进行建模,将模型导入到ADAMS软件中进行运动学仿真。结果表明:机器人末端位移、速度曲线变化平稳,能到达空间中的指定位置,验证了结构设计的合理性,从而为控制系统的设计提供了依据。     

基于回流能量调节的液压执行机构运动位移控制仿真研究

为提高液压执行机构控制系统响应速度,从而降低执行机构运动位移输出误差,采用超螺旋滑模控制器,并进行仿真验证。建立回流能量调节的液压执行机构简图,定义差动阀液压流量数学模型,推导出液压执行机构动力学方程式。针对传统滑模控制器进行改进,提出超螺旋滑模控制器。给出液压执行机构超螺旋滑模控制的流程,并分析控制系统的稳定性。为进一步验证超螺旋滑模控制器输出精度,采用MATLAB软件对液压执行机构运动位移进行仿真,并且与传统滑模控制器进行对比。结果表明：采用传统滑模控制器,在空载状态下,液压执行机构运动位移与期望值偏差较小,但是在负载状态下,其偏差较大;采用超螺旋滑模控制器,在空载或者负载状态下,液压执行机构运动位移与期望值偏差都较小,执行机构反应速度较快。采用超螺旋滑模控制器,可以有效降低液压执行机构滑模控制器的抖动幅度,提高运动精度。     

A fast tool servo design for precision turning of shafts on conventional CNC lathes

A technique for precision turning of shafts on conventional CNC turning centers is presented. The shaft is semi-turned on a conventional CNC lathe. The precision finish turning operation is delivered by a piezoelectric based fast tool servo which is mounted on the same CNC lathe's turret. The precision tool tip motion is delivered by a proposed sliding mode controller which is robust to changes in the cutting process and hysteresis in the piezo actuator. Sliding mode controller is also quick to compensate the cutting force disturbances, and keeps the tool tip at the desired location within the displacement measurement sensor resolution (±0.1 μm). The fast tool servo system is packaged in a PC, and its effectiveness is demonstrated on a bearing location turning.     

A fine tool servo system for global position error compensation for a miniature ultra-precision lathe

There is an increasing demand for single-point diamond turning to manufacture micro components as well as micro features on a large workpiece surface. In order to obtain high accuracy and a fine surface finish of the large area workpiece, position control of machine tool has become the main concern to achieve the high precision position control. A coarse-fine servo system is able to provide a cost-effective solution. This system can provide information on the entire guidance errors profile data and simultaneously compensate the error in real-time by using the fine position control technique. In this study, a piezoelectric actuator based fine tool servo (FTS) system has been developed and it has been incorporated with a miniature ultra-precision lathe. A cost-effective position sensitivity detector (PSD) is integrated in the FTS design, which is able to measure the global straightness error of the translational slide accurately. The detected error signals are compensated by the FTS during the turning process. For better tracking performance, a proportional-integral (PI) feedback controller has been implemented and tested in this study. Experimental results show that the developed FTS can effectively and successfully compensate the micro waviness error which is caused by the x-axis translational slide of the miniature ultra-precision lathe.