基于传感器增强的测力仪实验平台扩展方法

针对现有测力平台无法满足大尺寸特征实验、微细切削实验以及缺乏多信号融合等问题,提出了基于传感器增强的测力仪实验平台扩展方法。以Kistler 9257B压电测力仪为基础,对测力平台进行扩展。通过增加大尺寸测力板满足大尺寸特征的切削实验要求。同时增加加速度传感器,通过测量加工过程中工件的加速度,对切削力进行惯性力补偿,提高切削力的测量精度,并可用于微细切削实验。此外通过将声发射传感器监测加工过程中的声发射信号同切削力和振动信号融合,为加工过程中刀具状态的辨识提供依据。验证表明,经过扩展的测力平台可以达到预期的效果。     

滚削测力系统动态特性的检定

本文利用正弦激振法检定了滚削测力系统的动态参数:固有频率、阻尼比、工作频带和相位误差,为动态滚齿切削力的测试与分析提供了依据。     

PVD涂层刀具铣削大理石切削力研究

利用正交设计进行PVD涂层刀具铣削大理石试验,研究切削参数对加工过程中切削力的影响。通过测力仪测得切削力信号,分析信号幅值波动原因。根据试验结果,讨论单一切削参数对切削力的影响趋势。采用最小二乘法原理建立了切削力预测模型,综合分析了切削速度、进给量及切削深度对切削力变化的贡献。探讨切削力出现尖点现象的原因,对预测模型修正并作F检验具有较高的显著性。结果表明,切削深度对切削力的影响最大,切削深度增加导致切削力呈升高趋势;切削速度是影响切削力的次要因素,随着切削速度的提高切削力呈减小趋势;进给量对切削力影响最小,其增大使切削力缓慢变大。     

高灵敏度测力仪及传感器布置形式研究

文中提出一种新型传感器布置形式的测力仪结构,适用铣削、钻削等过程中动态切削力的测量.基于石英晶片不同切型的特点,提出了一种新的测量方式,设计了2种传感器布置形式.对测力仪原理进行分析,建立输入与输出之间的理论输出模型.分别对2种测力仪进行静态性能标定实验,结果表明:2种布置形式的测力仪的线性度和重复性误差均小于1％,并...     

NiCr薄膜传感器的切削力无线监测系统设计

为了达到实时无线测量切削力的目的,设计了基于自主研制的NiCr合金薄膜测力传感器与ZigBee模块的切削力无线监测系统。传感器实时输出切削力电压信号,数据经ZigBee模块与RS-232线缆上传至上位机(LabVIEW),通过不同的LabVIEW显示面板获取准确的切削力应变与电压值并换算出切削力值,且在上位机中完成数据显示、存储与报表生成等任务。经由静态力学标定试验与实际切削力测量试验验证,切削力无线实时监测系统方案完成了基本的实时采集、无线传输与实时显示功能,具有较好的静态力学采集与实际切削力测量精度。     

切削测力平台结构递进式拓扑优化设计研究

微切削加工过程中,切削力是影响加工质量的重要参数。测力仪是动态测量切削力的主要装置,其测力平台部分工作稳定性和准确性对测力仪整体性能起到决定性作用。目前使用的大部分测力平台设计均可以满足宏观较大振幅应力测量要求,但较差的灵敏度和严重的信号衰弱无法满足微切削状态下切削力的微小变化测量。因此提出了一种在满足测力平台弹性体结构强度等要求下,首先以固有频率为目标函数进行单目标优化,将优化后的固有平率作为约束条件,再以应力集中为目标函数进行二次优化的递进式拓扑优化方法;并对优化后的结构进行模态试验,从而证明采用递进式拓扑优化的结构设计方法可以极大的提高测力平台工作时的稳定性、灵敏度和测量精度等性能,同时也拓展了测力平台微切削条件下的适用性。     

CVD涂层刀具高速铣削大理石切削力研究

选定切削参数(切削速度、进给速度、切削深度)设计正交试验,进行CVD氮化钛涂层刀具高速铣削大理石切削力试验,利用测力仪测出各组试验的切削力信号图,分析信号图特征得出切削力值,并记录各组切削力试验结果。分析单一切削参数(切削速度、进给速度,切削深度)对切削力变化的影响规律。采用最小二乘法原理对切削力经验公式回归系数进行参数估计,并对经验公式进行相关性检验,检验结果表明显著性很高。最终通过试验结果得出:切削力随着进给速度和切削深度的增加而增大,随着切削速度的增加而减小;并且切削深度对切削力影响最大,切削速度次之,进给速度对切削力的影响最小。     

面向切削力测量的圆环式测力仪耦合分析

切削力是描述机械加工时切屑去除过程的重要参数,其精确测量是判断加工状态和提高加工系统可靠性的重要基础。为了提高切削力的测量精度,对圆环式测力仪进行了耦合分析。通过分析圆环式测力仪的组成结构,并通过理论分析研究了多个圆环式复合传感结构之间的耦合关系,修正了切削力分力计算公式。此外,根据刚度的计算公式,利用激光位移传感器测得了圆环式测力仪中多个圆环式复合传感结构的刚度。最后,通过试验研究了经过耦合分析后的圆环式测力仪的基本性能,验证了圆环式测力仪的耦合分析有助于提高切削力的测量精度。     

NiCr合金薄膜测力传感器设计制作与力学标定

为了满足切削力信号精确测量的要求,制作了两种结构的切削力测量用镍铬合金薄膜传感器样品、可调式改良应变测试仪桥盒,进行了传感器静力学标定与实际切削力测量试验。使用DASP 36通道振动与噪声信号采集分析系统与YD-15型动态电阻应变仪进行采集与读取测量时的电压信号与应变信号,将采集的应变信号经MATLAB转换为压力应变曲线图,将传感器应变、输出电压值与其对应的理论仿真值进行对比,结果表明测量值与其误差较小,两种传感器的力学测量性能良好。     

铣削加工测力刀柄参数优化设计研究

为适应高精密加工对切削力的监测需求,文中面向铣削加工设计了一种无线测力刀柄,使用压电薄膜和弹性检测梁采集力信号。为提高检测信号的灵敏度,基于COMSOL Multiphysics软件使用Nelder-Mead算法对刀柄的结构参数进行优化设计,并通过有限元仿真对优化结构进行刀柄结构刚度校核和动态特性分析,最后进行铣削对比实验,验证设计方案的可行性。结果表明,文中设计和优化的测力刀柄具有良好的灵敏度,刀柄的动静态特性满足使用需求,是一种有效的切削力监测方案。     

曲轴非圆磨削运动中动态误差及补偿

动态误差是影响曲轴非圆磨削加工精度的主要因素,动态误差补偿可实时修正磨削过程的各种误差,保证补加工工件的加工精度.通过分析曲轴非圆磨削过程中动态误差产生的原因,对非圆磨削中数控系统的伺服滞后误差进行了定量分析,并对以恒线速度为基础的运动模型进行了仿真计算,计算结果表明,伺服滞后误差严重影响加工精度,且数控系统的调整只能减少伺服滞后误差,不能消除伺服滞后误差.提出了采用神经网络预测曲轴非圆磨削过程的误差,并对补偿数据进行必要的延迟处理后进行相应的补偿,以解决在线测量的角度偏差.通过离线测量加工试验表明,采用径向基函数网络较好地解决了曲轴非圆磨削过程中的误差补偿.     

Dynamic wireless passive strain measurement in CNC turning using surface acoustic wave sensors

Wireless, passive and dynamic surface acoustic wave (SAW) strain sensors are especially advantageous in applications with harsh environments where complex force measurements are required. High frequency multiple axis force measurement during machining processes typically requires state-of-the-art piezoelectric dynamometer technologies. Integrating dynamometers and their associated measurement chains into the machining environment typically requires significant modification to the machine structure. In this paper, SAW sensors were developed for process monitoring operations. Single-axis continuous and interrupted cutting investigations were carried out using the SAW technology installed on cutting tool holders demonstrating high dynamic bandwidth strain measurement. SAW dual-axis oblique cutting measurements were carried out where four SAW sensors were set up as two differential pairs each measuring a single axis of applied force. Improvements in sensitivity and cross-talk compensation has been realised. High-frequency wireless passive realtime process signals are presented from a passive wireless SAW force measurement system successfully integrated into an LT15 Okuma machining centre. The paper aims to present wireless passive SAW technology as a potentially platform changing approach for process and tool condition monitoring applications in the future.     

薄壁筒件内孔车削振动建模与分析

分析了车削薄壁筒件内孔表面时影响振动的主要因素,以切削加工中工件过渡表面的法线方向为建模方向,重点考虑车削加工中动态切削力的影响,依据振动基本理论建立了薄壁筒件动态车削过程的振动模型方程,通过对方程的数值分析探讨加工过程中的振动问题。分析结果表明:切削用量三要素对动态切削力的影响起主导作用,进而对切削振动产生较大影响。刀具主偏角对动态切削力也有一定影响,车削产生的振动与主偏角之间是非线性的关系。这些结论为薄壁筒件加工中的振动研究提供有益的参考。     

Cutting deflection control of the blade based on real-time feedrate scheduling in open modular architecture CNC system

Machining accuracy of thin-walled parts which have low-rigidity is greatly influenced by cutting deflection in flank milling. In this paper, cutting deflection of aero-engine blade during processing is controlled within a required dimensional accuracy based on the strategy of real-time feedrate scheduling which is integrated into an open modular architecture CNC system (OMACS) of five-axis milling machine. The maximum deflection position of blade is determined through combining analytical cutting force model in flank milling and finite element analysis (FEA)-based transient dynamic analysis. Then, the numerical model of blade deflection is established to obtain the numerical relationship among feedrate, cutting force, and blade deflection, which is usually used to get optimized cutting force and feedrate by setting allowable value of blade deflection. To implement blade deflection control during machining, a real-time control strategy of feedrate scheduling based on nonlinear root-finding algorithm of Brent-Dekker and principle of feedrate smooth transition is developed and integrated into OMACS which has functions of real-time cutting force signal processing and real-time feedrate adjustment. Experimental results show that blade deflection is effectively controlled by proposed strategies, machining accuracy, and efficiency are improved.     

基于自抗扰控制的变速非圆车削技术研究

为了抑制非圆截面工件加工时的颤振,将变速加工应用于非圆截面车削中,设计了变速车削系统结构,分析了变速车削抑制颤振、提高稳定性的机理,设计了适于变速非圆车削的直线伺服单元,单元控制采用自抗扰控制技术.车床控制系统采用PMAC(Programmable multi-axis controller)时基控制法,实现刀具驱动进给和工件变速旋转的协调控制,完成非圆截面的变速车削.结果表明,直线伺服单元能很好地跟踪刀具目标值,非圆截面车削加工精度和稳定性得到了提高.     

Auto-tracking single point diamond cutting on non-planar brittle material substrates by a high-rigidity force controlled fast tool servo

This paper presents auto-tracking single point diamond cutting, which can conduct precision cutting on non-planar brittle material substrates without prior knowledge of their surface forms, by utilizing a force controlled fast tool servo (FTS). Differing from traditional force feedback control machining based on a cantilever mechanism such as an atomic force microscope (AFM) that suffers from low-rigidity and limited machining area, the force controlled FTS utilizes a highly-rigid piezoelectric-type force sensor integrated with a tool holder of the FTS system to provide sufficient stiffness and robustness for force-controlled cutting of brittle materials. It is also possible for the system to be integrated with machine tools to deal with the difficulties in the cutting of large area non-planar brittle materials, which requires not only high machining efficiency but also a high stiffness. Experimental setup is developed by integrating the force controlled FTS to a four-axis ultra-precision diamond turning machine. For the verification of the feasibility and effectiveness of the proposed cutting strategy and system, auto-tracking diamond cutting of micro-grooves is conducted on an inclined silicon substrate and a convex BK7 glass lens, while realizing constant depths of cuts under controlled thrust forces.     

Self-sensing of cutting forces in diamond cutting by utilizing a voice coil motor-driven fast tool servo

Cutting force measurement is important for monitoring the diamond cutting process. In this paper, a new measurement method of thrust cutting force associated with a voice coil motor (VCM) driven fast tool servo (FTS) system has been developed. Instead of integrating additional force sensors to the FTS which would influence the dynamics of the FTS, the force measurement in the proposed system is achieved associated with in-process monitoring the variation of the driving current of the VCM and pre-process determining the system parameters. In this way, the cutting forces are accurately obtained by subtracting the influences of the driving force, the spring force, the damping force and the inertial force associated with the system as well as the cutting process. Based on the proposed method, a microstructure array was machined using the developed VCM-FTS and the cutting force during the machining process was monitored in real time. The measured force signal was in good agreement with the machining result. The surface profile error of the fabricated microstructure could be clearly distinguished by the variation of the measured cutting force signal. This provides a new approach for in-process cutting force measurement associated with FTS based diamond cutting process.     

Feed Cutting Force Estimation from the Current Measurement with Hybrid Learning

It is very important to use reliable and inexpensive sensors to obtain useful information about manufacturing processing, such as cutting force, for monitoring automated machining. In this paper, the feed cutting force is measured using an inexpensive current sensor installed on the a.c servo motor of a CNC turning centre. The factors that affect a feed drive system are analysed in detail, and a model of the feed drive system for estimating feed cuttinng force is presented. The feed cutting force is estimated using feed motor current measurement and neuro-fuzzy techniques. Experimental results demonstrate that this medthod can accurately estimate feed cutting force within an error of 5%.     

A novel chatter stability criterion for the modelling and simulation of the dynamic milling process in the time domain

The modelling of the dynamic processes in milling and the determination of chatter-free cutting conditions are becoming increasingly important in order to facilitate the effective planning of machining operations. In this study, a new chatter stability criterion is proposed, which can be used for a time domain milling process simulation and a model-based milling process control. A predictive time domain model is presented for the simulation and analysis of the dynamic cutting process and chatter in milling. The instantaneous undeformed chip thickness is modelled to include the dynamic modulations caused by the tool vibrations so that the dynamic regeneration effect is taken into account. The cutting force is determined by using a predictive machining theory. A numerical method is employed to solve the differential equations governing the dynamics of the milling system. The work proposes that the ratio of the predicted maximum dynamic cutting force to the predicted maximum static cutting force can be used as a criterion for the chatter stability. Comparisons between the simulation and experimental results are given to verify the new model.     

非圆齿轮齿面加工余量匀化工艺研究与实现

针对非圆齿轮加工中,由齿坯节曲线曲率变化所引起的分次进刀过程中齿面加工余量分布不均的问题,提出一种匀化非圆齿轮齿面加工余量的工艺方法。以非圆齿轮插削工艺为研究对象,基于插齿加工原理,对齿面加工余量分布不均的成因进行了分析;在此基础上建立了非圆齿轮匀化工艺插削联动模型,通过实时调整插刀与齿坯的几何位置关系,实现了非圆齿轮齿面加工余量的匀化;开发了非圆齿轮插齿CAM系统,利用CAM系统对齿面加工余量匀化工艺进行了仿真验证,仿真结果表明,所提工艺方法正确、可行;将匀化工艺集成到自主开发的齿轮加工数控系统中,进行了非圆齿轮插削加工试验,试验结果表明,所提工艺方法能够有效匀化齿面加工余量;对加工出的非圆齿轮齿面进行了三维形貌检测,检测结果表明,所提工艺方法能够显著提高非圆齿轮的加工精度与表面质量。