计算机数控(CNC)闭环系统

一九七九年十一月在昆明召开的中国机械工程学会机械工业自动化学会第一次学术讨论会暨成立大会上有四十八位同志在大、小会上宣读了论文,进行了交流。本刊上期已刊登了部份摘要,本期将其余部份登载如下。     

计算机数控机床(CNC)的坐标轴校准

本文主要描述闭环CNC系统坐标轴校准的原理与方法,这种思想的基本思想是采用计算机技术与精密测量技术相结合,测定机床直线坐标和旋转坐标的全程分布误差,在计算机内存中建立起反馈增量修正表,从而在CNC运行期间由软件实现对反馈增量的实时修正。采用这种技术不但可以提高加工精度,而且可以放宽对CNC机床本身制造精度的要求,降低成本。     

Material bead deposition with 2 + 2 ½ multi-axis machining process planning strategies with virtual verification for extruded geometry

Process planning for hybrid manufacturing, where additive operations can be interlaced with machining operations, is in its infancy. New plastic- and metal-based hybrid manufacturing systems are being developed that integrate both additive manufacturing (AM) and subtractive (machining) operations. This introduces new process planning challenges. The focus of this research is to explore process planning solution approaches when using a hybrid manufacturing approach. Concepts such as localized AM build ups, adding stock to a CAD model or section for subsequent removal, and machining an AM stock model are investigated and illustrated using virtual simulations. A case study using a hybrid laser cladding process is used to demonstrate the opportunities associated with a hybrid solution. However, unlike machining, the process characteristics from system to system vary greatly. These are portrayed via a high power, high material deposition feed rate laser cladding system. There are unique challenges associated with AM processes and hybrid manufacturing. New tools and design rules need to be developed for this manufacturing solution to reach its potential.     

基于IPC的计算机数控(CNC)系统

用工业个人计算机开发ＣＮＣ系统具有很多的优越性。本文主要介绍了一种基于ＩＰＣ的ＣＮＣ系统的硬件和软件以及对一些关键问题的解决措施。该系统已经与某型加工中心机床联调试切成功     

最新的计算机数控(CNC)及其功能

就NC装置而言,最近,采用微处理器的计算机数控(CNC)已很普遍了。下面拟就当前在市场上出售的CNC的特点及其功能,从机械加工自动化现状这一角度作一些介绍。在最新的CNC中,采用了高速微处理器和大容量磁泡存储器。此外,还有不少采用了集成度非常高的专用大规模集成电路(CustomLSI)。在这样出色的装置中,由于存储了能发挥高功能的新的NC软件(控制程序),使得     

基于数控机床(CNC)机群的工业移动机器人设计

根据中国企业现状,本文研究了适用于经济数控机床或改进数控机床的智能移动机器人,它可以自动完成以下三个数控加工步骤:装料、卸料及刀具更换,可以节约人力,降低产品成本。机器人的执行机构采用双四杆机构,无工作盲区。为实现远程控制,应用如zigbee无线通讯技术、GPRS和3G模块等的最新技术建立了数控机床组网络。除此之外,为完成在装料、卸料及刀具更换过程中的精确定位,还安装了视觉导航系统。机器人能综合利用模式识别技术、多传感器信息技术、嵌入式技术智能地估计工作条件,较大地大提高了工作效率及自动化水平。     

可编程控制器(PLC)在 CNC 机床中的应用

分析了可编程控制器在ＣＮＣ机床中的应用方式及其特点，ＰＬＣ在ＣＮＣ机床中的作用及数控装置Ｉ／Ｏ口和机床控制面板、强电信号的联接方法，研究了数控机床中Ｔ功能代码和Ｍ功能代码在ＰＬＣ上的实现方法。     

Regulation Method for Torque–Angle Characteristics of Rotary Electric–Mechanical Converter Based on Hybrid Air Gap

The torque–angle characteristics of electric–mechanical converters are important determinants of the quality of electrohydraulic proportional control systems. It is far more di cult for a rotary electric–mechanical converter(REMC) to obtain flat torque–angle characteristics than traditional proportional solenoid, greatly influencing the promotion and application of rotary valves for electrohydraulic proportional control systems. A simple and feasible regulation method for the torque–angle characteristics of REMCs based on a hybrid air gap is proposed. The regulation is performed by paralleling an additional axial air gap with the original radial air gap to obtain a flat torque–angle characteristic and increase output torque. For comparison, prototypes of REMCs based on hybrid and radial air gaps were manufactured, and a special test rig was built. The torque–angle characteristics under different excitation currents and step responses were studied by magnetic circuit analysis, finite element simulation, and experimental research. The experimental results were consistent with the theoretical analysis. It was shown that REMCs based on a hybrid air gap can obtain a flat torque–angle characteristic with further optimizing of key structural parameters and also increase output torque. This regulation method provides a new approach for the design of proportional rotary electromechanical converters.     

An adaptive inverse control method based on SVM–fuzzy rules acquisition system for pulsed GTAW process

This paper proposes a new method of adaptive inverse control based on support vector machine–fuzzy rules acquisition system (SVM-FRAS) for the gas tungsten arc welding (GTAW) process. In this control mechanism, an identifier is established based on SVM-FRAS, and an inverse controller based on SVM-FRAS is designed. The proposed adaptive inverse control method can automatically extract control rules from the process data. Comprehensibility is one of the required characteristics for a complex GTAW process control. We use the proposed SVM-FRAS-based adaptive inverse control method to obtain the rule-based process and the control model of the aluminum alloy pulse GTAW process. Based on the simulation experiments for GTAW process, the SVM-FRAS adaptive inverse control method is found to be effective.     

实现经济型CNC系统C刀补的算法研究(上)

提出一种基于直线插补思想的C刀补算法,将三角函数及开方运算转换为加、减运算,算法简单实用,解决了C刀补在单片机开发的经济型CNC系统中的实现问题。     

CNC加工中尖角过渡处理和切入切出程序设计(下)

二、切入切出程序的设计在数控机床上进行轮廓铣削时 ,为了保证工件的精度和加工表面的粗糙度 ,减少接刀的痕迹 ,对切入和切出程序要精心设计。　图 7　轮廓进、退　　　刀示意图在铣削平面工件时 ,一般采用立铣刀的端刃和侧刃铣削。这样在加工外形时 ,其切入和切出程序应考虑外延 ,一般取外延距离 1<Ｌ <5ｍｍ ,以保证工件轮廓的平滑。在进行如图 7所示的工件类加工时 ,应避免法向切入或切出工件 ,而应沿工件轮廓的延长线切入和切出工件轮廓 ,这样可避免切入和切出处在轮廓上留下刀痕。铣削平面时 ,要特别避免在垂直工件表面的方向上进刀或…     

CNC加工中尖角过渡处理和切入切出程序设计(上)

详细论述了CNC加工中对零件轮廓、型腔尖角过渡的处理方法 ,对尖角的形成及特性进行了全面的分析 ,将辅助圆弧应用于内角过渡 ,并给出了计算通式。同时对切入切出程序进行了定性定量分析 ,提出了预引切向进、退刀的方法 ,有效地消除了由于系统滞后在切入切出点产生的干涉问题     

Tribological performances of ZDDP and ashless triphenyl phosphorothionate (TPPT) as lubricant additives on Ti–N and Ti–Al–N coated steel surfaces

Abstract

In recent years, there has been much attention on the effects of lubricant additives on the friction and wear properties of surface coatings. However, little research has been conducted to investigate the influence of antiwear additives on the tribological performances of titanium nitride (Ti–N) and titanium aluminium nitride (Ti–Al–N) coatings. It has been reported that introducing aluminium into Ti–N coatings enhanced their oxidation resistance. In this study utilising a pin on cylinder tribometer, lubricants containing zinc dialkyl dithiophosphate (ZDDP) or a more environmentally friendly alternative, ashless triphenyl phosphorothionate (TPPT), were used. Experimental results revealed that ZDDP and TPPT helped to reduce wear on both coatings through the formation of a tribofilm, although it was also found that both additives increased the friction coefficient on both surfaces. Based on overall findings, this paper suggests the use of TPPT as a suitable ZDDP replacement for providing wear protection on Ti–N and Ti–Al–N coatings.     

实现经济型CNC系统C刀补的算法研究(下)

3圆弧接直线以顺圆接直线为例,其刀补转接过渡类型如图6中虚线(刀具中心轨迹)所示四种,即缩短型(见图6a)、伸长型(见图6b)、插入型(见图6c)和直接过渡型(见图6d)。图6顺圆接直线的刀补转接类型3.1确定转接角如图7所示,定义编程圆弧AB的半径BO1与直线BC之间的逆时针夹角α为转接     

从4520C(CNC型)看中小型无心磨床发展方向

本文通过对日本光洋机械工业株式会社的4520C型无心磨床进行解析,对我国今后中小型无心磨床的发展方向进行了探讨。     

Advances and applications on micro-defocusing digital particle image velocimetry (μ-DDPIV) techniques for microfluidics

Reliable measurements of the three-dimensional, three-component (3D3C) velocity field in microfluidics are becoming increasingly important for the design and optimization of lab-on-a-chip devices in biochemical applications. Among the many microscale 3D3C velocity field measurement methods, the μ-DDPIV technique is the most convenient and reliable, but the low seeding rates and low light intensity due to the small pinholes are the major limitations of this technique. The present review demonstrates the principle of the defocusing technique, calibration procedures and particle tracking algorithms to extract the 3D3C velocity vectors. As an example of μ-DDPIV applications, this paper presents measurements of a complex 3D3C velocity field in chaotic mixers. This technique can be extended to measure the refractive index of an unknown fluid and to a nano/micro hybrid PIV system for multi-scale measurements. Future perspectives on the development of μ-DDPIV are addressed.     

Multi response optimization of process parameters based on Taguchi��Fuzzy model for coal cutting by water jet technology

The process of material cutting and fracture by high velocity water jets is a complex series of phenomena which may involve compression, tension, shear, erosion, wears, cracking, wave propagation, and cavitations damage. This makes the exact analysis of the jet cutting process to be very complicated. The problem of water jet coal cutting is a multiresponse problem. There are two output variables, depth of cut and cutting width whose optimization will result in the increase in the productivity of coal cutting. In this paper, a Taguchi?CFuzzy decision method has been used to determine the effective process parameters for improving the productivity of coal mines. The Taguchi method of experimental design is a widely accepted technique used for producing high quality products at low cost. The optimization of multiple responses in complex processes is common; therefore, to reduce the degree of uncertainty during the decision making, fuzzy rule-based reasoning was integrated with the Taguchi loss function.     

Enhancement of Satellite Image Compression Using a Hybrid (DWT–DCT) Algorithm

Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT) image compression techniques have been utilized in most of the earth observation satellites launched during the last few decades. However, these techniques have some issues that should be addressed. The DWT method has proven to be more efficient than DCT for several reasons. Nevertheless, the DCT can be exploited to improve the high-resolution satellite image compression when combined with the DWT technique. Hence, a proposed hybrid (DWT–DCT) method was developed and implemented in the current work, simulating an image compression system on-board on a small remote sensing satellite, with the aim of achieving a higher compression ratio to decrease the onboard data storage and the downlink bandwidth, while avoiding further complex levels of DWT. This method also succeeded in maintaining the reconstructed satellite image quality through replacing the standard forward DWT thresholding and quantization processes with an alternative process that employed the zero-padding technique, which also helped to reduce the processing time of DWT compression. The DCT, DWT and the proposed hybrid methods were implemented individually, for comparison, on three LANDSAT 8 images, using the MATLAB software package. A comparison was also made between the proposed method and three other previously published hybrid methods. The evaluation of all the objective and subjective results indicated the feasibility of using the proposed hybrid (DWT–DCT) method to enhance the image compression process on-board satellites.