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外文資料翻譯
護(hù)理床動力學(xué)優(yōu)化
5.1引言
動力學(xué)是理論力學(xué)的一個(gè)分支學(xué)科，它主要研究作用于物體的力與物體運(yùn)動的關(guān)系。動力學(xué)的研究對象是運(yùn)動速度遠(yuǎn)小于光速的宏觀物體。動力學(xué)是物理學(xué)和天文學(xué)的基礎(chǔ)，也是許多工程學(xué)科的基礎(chǔ)。
動力學(xué)以牛頓第二定律為核心，這個(gè)定律指出了力、加速度、質(zhì)量三者間的關(guān)系。牛頓首先引入了質(zhì)量的概念，而把它和物體的重力區(qū)分開來，說明物體的重力只是地球?qū)ξ矬w的引力。
多功能醫(yī)用護(hù)理床的運(yùn)動學(xué)分析是基于ADAMS建立于在運(yùn)動學(xué)分析的基礎(chǔ)之上的，根據(jù)先前的運(yùn)動學(xué)分析，以運(yùn)動學(xué)分析結(jié)果作為動力學(xué)分析的初始值，綜合考慮線性推桿的推、拉力的限制以及機(jī)架各支點(diǎn)的受力狀況，主要對線性推桿的受力狀況及各床架支點(diǎn)的受力狀況進(jìn)行動力學(xué)分析。
5.2側(cè)翻機(jī)構(gòu)動力學(xué)分析
5.2.1為機(jī)構(gòu)添加外力
側(cè)翻機(jī)構(gòu)在運(yùn)行的過程中，會有以下幾個(gè)方面對機(jī)構(gòu)運(yùn)動產(chǎn)生影響。它們是機(jī)構(gòu)自身質(zhì)量，患者體重以及各個(gè)運(yùn)動副之間的摩擦力。由于摩擦力很小，在此忽略不計(jì)，只考慮機(jī)構(gòu)的重量及患者的體重。
通過solidworks軟件對虛擬樣機(jī)進(jìn)行質(zhì)量測量，測得背板質(zhì)量為20kg，通過設(shè)計(jì)手冊查得我國身高1.85m的成年人平均體重為83kg左右。為了真實(shí)的模擬虛擬樣機(jī)的性能，本文采用背板質(zhì)量為20kg，人體背部重量為50kg。對機(jī)構(gòu)添加力之后，運(yùn)行一次動力學(xué)仿真。測量各個(gè)點(diǎn)的受力以及電機(jī)的受力。仿真時(shí)間為25s，步數(shù)為500步。
添加力測量，測得的各點(diǎn)受力曲線如圖5-1所示。
圖5-1 各點(diǎn)受力曲線
5.2.2側(cè)翻機(jī)構(gòu)動力學(xué)優(yōu)化仿真
從圖5-1中，得知MAKER_5點(diǎn)的受力最大，機(jī)構(gòu)的受力優(yōu)化就從MARKER_5著入。首先，測試各個(gè)設(shè)計(jì)變量對MARKER_5的受力變化的敏感度。運(yùn)行一次動力學(xué)仿真，時(shí)間為25s，步數(shù)為500步，線性推桿移動速度為5.5mm/s，背板質(zhì)心處加力500N，背板自重20kg。運(yùn)行優(yōu)化設(shè)計(jì)，優(yōu)化的目標(biāo)為將MARLKER_5點(diǎn)的受力的最大值進(jìn)行最小化，仿真后優(yōu)化數(shù)據(jù)如下：
Model Name : model_1
Date Run : 2009-04-14 17:13:51
Objectives
O1) Maximum of MARKER_5_MEA_1
Units : newton
Initial Value: 1444.34
Final Value : 1130.2 (-21.7%)
Iter. O1 DV_1 DV_2 DV_8
0 1444.3 150.00 295.00 136.30
1 1133.7 165.00 265.50 135.83
2 1130.2 165.00 265.50 134.94
3 1130.2 165.00 265.50 134.94
5-4 MARKER_21點(diǎn)優(yōu)化前后受力曲線 5-5各參數(shù)下的翻轉(zhuǎn)角度值
5-2 MARKER_5點(diǎn)優(yōu)化前后受力曲線 5-3 MARKER_1點(diǎn)優(yōu)化前后受力曲線
從圖5-2至5-4中，可以發(fā)現(xiàn)經(jīng)過動力學(xué)優(yōu)化之后，各支點(diǎn)受力均有明顯的改善，其中圖5-2中MARKER_5點(diǎn)受力從1443N減至1133N，從圖5-5中，背板的轉(zhuǎn)動角度在角度約束的范圍之內(nèi)。
5.2.3樣機(jī)的實(shí)際結(jié)構(gòu)
通過以上的分析，在實(shí)際設(shè)計(jì)中，各關(guān)鍵點(diǎn)的坐標(biāo)取值為如表5-1所示
表5-1各關(guān)鍵點(diǎn)實(shí)際取值
DV_L1/mm
DV_L2/mm
DV_L4/mm
DV_L7/mm
DV_L8/mm
初始值
250
245
330
400
370
優(yōu)化值
265
215
346.1
390.28
359.94
此時(shí)，樣機(jī)的背板轉(zhuǎn)動角加速度最小且各支點(diǎn)的受力也達(dá)到了最小化、滿足了機(jī)構(gòu)的設(shè)計(jì)要求。動力學(xué)優(yōu)化前后機(jī)構(gòu)構(gòu)件尺寸表如表5-2所示：
表5-2 優(yōu)化前后桿件尺寸對比
A、B水平距離/mm
A、B豎直距離/mm
BD/mm
初始值
50
65
98.4
優(yōu)化值
35
19
118
5.3抬背機(jī)構(gòu)動力學(xué)分析
5.3.1為機(jī)構(gòu)添加力
為了較為真實(shí)的模擬人體的質(zhì)量，以及考慮背板的推、拉力的限制，在抬背機(jī)構(gòu)的背部添加豎直向下的均布力，大小為400N，在臀部床板添加400N的力，運(yùn)行一次動力學(xué)優(yōu)化仿真。
5.3.2抬背機(jī)構(gòu)動力學(xué)優(yōu)化仿真
為了進(jìn)一步研究線性推桿的受力狀況，以及機(jī)架上各支點(diǎn)的受力狀況，使得機(jī)構(gòu)工作得更安全及更可靠，以抬背機(jī)構(gòu)運(yùn)動學(xué)優(yōu)化數(shù)據(jù)為動力學(xué)優(yōu)化的初始數(shù)據(jù)，優(yōu)化目標(biāo)函數(shù)為抬背過程中線性推桿受力的最大值最小化，進(jìn)行動力學(xué)優(yōu)化仿真，已得到滿足機(jī)構(gòu)設(shè)計(jì)要求的最優(yōu)化參數(shù)。通過設(shè)計(jì)研究對各個(gè)設(shè)計(jì)變量進(jìn)行敏感度測試。根據(jù)設(shè)計(jì)研究對各設(shè)計(jì)變量的測試，得到的數(shù)據(jù)報(bào)表如下：
Trial O1 DV_1 Sensitivity
1 1914.3 369.00 10.740
2 2134.5 389.50 -0.021580
3 1913.4 410.00 -2.5693
4 2029.1 430.50 -0.019588
5 1912.6 451.00 -5.6838
Trial O1 DV_2 Sensitivity
1 1913.3 -18.000 0.0037970
2 1913.3 -27.000 -0.0031447
3 1913.4 -36.000 -11.532
4 2120.9 -45.000 -0.0029932
5 1913.5 -54.000 23.048
Trial O1 DV_3 Sensitivity
1 1925.6 90.000 22.755
2 2039.4 95.000 -1.2229
3 1913.4 100.00 -12.825
4 1911.2 105.00 -0.42287
5 1909.2 110.00 -0.39627
Trial O1 DV_4 Sensitivity
1 1912.8 -50.800 -0.079290
2 1913.3 -57.150 -0.044021
3 1913.4 -63.500 -0.042952
4 1913.9 -69.850 -0.069998
5 1914.3 -76.200 -0.062845
Trial O1 DV_5 Sensitivity
1 1913.5 3.9200 0.011536
2 1913.4 0.00000 0.0081747
3 1913.4 -3.9200 -0.012181
4 1913.5 -7.8400 -3.5109
5 1940.9 -11.760 -6.9926
Trial O1 DV_6 Sensitivity
1 2163.3 -111.15 40.476
2 1913.4 -117.32 20.238
3 1913.4 -123.50 -15.895
4 2109.7 -129.68 -0.0067767
5 1913.5 -135.85 31.777
Trial O1 DV_7 Sensitivity
1 1985.6 306.74 -4.2359
2 1913.4 323.78 -2.1180
3 1913.4 340.82 6.3905
4 2131.2 357.86 0.0011642
5 1913.4 374.90 -12.779
Trial O1 DV_8 Sensitivity
1 2163.3 -111.15 40.476
2 1913.4 -117.32 20.238
3 1913.4 -123.50 -15.895
4 2109.7 -129.68 -0.0067767
5 1913.5 -135.85 31.777
通過設(shè)計(jì)研究，觀察計(jì)算結(jié)果，可以發(fā)現(xiàn)實(shí)際變量DV_3、DV_4、DV_6、DV_8的敏感度最大，所以在優(yōu)化設(shè)計(jì)的時(shí)候著重考慮上述幾個(gè)設(shè)計(jì)變量，對它們進(jìn)行優(yōu)化設(shè)計(jì)，以期望得到滿足設(shè)計(jì)要求的機(jī)構(gòu)最優(yōu)化參數(shù)。
5.3.3樣機(jī)的實(shí)際結(jié)構(gòu)
通過以上的分析，在實(shí)際設(shè)計(jì)中，各關(guān)鍵點(diǎn)的坐標(biāo)取值為如表5-3所示
表5-3各關(guān)鍵點(diǎn)實(shí)際取值
DV_2/mm
DV_5/mm
DV_6/mm
DV_8/mm
初始值
390
458
330
275
優(yōu)化值
381
452.603
32317
278.8
優(yōu)化前后桿件尺寸變化如表5-4所示。
表5-4 優(yōu)化前后桿件尺寸變化表
A、C豎直距離/mm
BC /mm
CD /mm
DE/mm
初始值
60
236
256
667
優(yōu)化值
62
228
248
659
圖5-6 抬背機(jī)構(gòu)動力學(xué)優(yōu)化前后電機(jī)受力曲線
觀察圖5-6可以得知在機(jī)構(gòu)動力學(xué)仿真之后，機(jī)構(gòu)表現(xiàn)出了良好的動力學(xué)性能，機(jī)構(gòu)的受力狀況得到了有效的改善，達(dá)到了預(yù)期的效果，即電機(jī)受力的最大值最小化。
5.4曲腿機(jī)構(gòu)動力學(xué)分析
為了真實(shí)的模擬曲腿機(jī)構(gòu)在運(yùn)行過程中的受力性能，以及線性推桿的受力狀況，所以對曲腿機(jī)構(gòu)在運(yùn)動學(xué)仿真的基礎(chǔ)之上進(jìn)行一次動力學(xué)仿真，為了得到較為真實(shí)的機(jī)構(gòu)運(yùn)行狀況，并進(jìn)行優(yōu)化仿真，得到理想機(jī)構(gòu)設(shè)計(jì)參數(shù)。
5.4.1為機(jī)構(gòu)添加外力
綜合考慮人體的自身重量以及床板的重量，在小腿板的質(zhì)心處及腳板的質(zhì)心處各添加豎直向下的力，大小為500N。
5.4.2曲腿機(jī)構(gòu)動力學(xué)仿真
以運(yùn)動學(xué)優(yōu)化的數(shù)據(jù)作為動力學(xué)優(yōu)化的初始數(shù)據(jù)，進(jìn)行動力學(xué)優(yōu)化，優(yōu)化的目標(biāo)函數(shù)為電機(jī)受力最大值的最小化。首先，對各個(gè)設(shè)計(jì)變量進(jìn)行設(shè)計(jì)研究，設(shè)計(jì)研究的報(bào)表如下：
Trial O1 DV_1 Sensitivity
1 4229.0 270.00 10.633
2 4548.0 300.00 10.659
3 4868.5 330.00 10.686
Trial O1 DV_2 Sensitivity
1 4435.8 -56.700 -17.645
2 4519.2 -61.425 -18.141
3 4607.2 -66.150 -18.637
Trial O1 DV_3 Sensitivity
1 4833.0 156.75 -32.756
2 4427.7 169.12 -28.017
3 4139.6 181.50 -23.278
Trial O1 DV_4 Sensitivity
1 3850.1 -243.00 -25.573
2 4367.9 -263.25 -26.353
3 4917.4 -283.50 -27.134
Trial O1 DV_5 Sensitivity
1 4792.4 -81.498 55.604
2 4434.7 -87.932 51.809
3 4125.8 -94.366 48.013
Trial O1 DV_6 Sensitivity
1 4541.0 -597.60 -0.10561
2 4548.0 -664.00 -0.098506
3 4554.0 -730.40 -0.091406
根據(jù)上述的設(shè)計(jì)研究的結(jié)果對DV_1、DV_2、DV_3、DV_4、DV_5、DV_7、DV_9七變量，作為優(yōu)化設(shè)計(jì)時(shí)的設(shè)計(jì)變量，進(jìn)行動力學(xué)優(yōu)化仿真。
圖5-7 曲腿機(jī)構(gòu)動力學(xué)優(yōu)化前后電機(jī)受力曲線圖
觀察圖5-7可以得知，經(jīng)過動力學(xué)優(yōu)化后的電機(jī)受力的最大值由原來的4550N減小為優(yōu)化后的2850N，電機(jī)的受力大大的減小，從而保證了機(jī)構(gòu)運(yùn)行的安全性及運(yùn)行的穩(wěn)定性。
5.4.3 樣機(jī)的實(shí)際結(jié)構(gòu)
通過以上的分析，在優(yōu)化設(shè)計(jì)時(shí)選取上述設(shè)計(jì)變量作為優(yōu)化設(shè)計(jì)時(shí)的設(shè)計(jì)變量，進(jìn)行動力學(xué)優(yōu)化，經(jīng)過動力學(xué)優(yōu)化之后，各關(guān)鍵點(diǎn)的坐標(biāo)取值為如表5.5所示
表5-5各關(guān)鍵點(diǎn)實(shí)際取值
DV_1/mm
DV_2/mm
DV_3/mm
DV_4/mm
DV_5/mm
初始值
300
-63
165
-270
-85.788
優(yōu)化值
270
-56.7
181.5
-243
-94.36
此時(shí)，樣機(jī)的線性推桿的受力最小且各支點(diǎn)的受力也達(dá)到了最小化、滿足了機(jī)構(gòu)的設(shè)計(jì)要求。優(yōu)化前后機(jī)構(gòu)桿件尺寸變化見表5-6。
表5-6 優(yōu)化前后構(gòu)件尺寸變化表
AB/mm
BC/mm
CD/mm
DE/mm
BE/mm
初始值
380
144.6
85
207.5
185.6
優(yōu)化值
350
136.7
83.6
209.35
192.8
5.5本章小結(jié)
本章在運(yùn)動學(xué)分析的基礎(chǔ)之上的，利用運(yùn)動學(xué)分析的數(shù)據(jù)作為動力學(xué)分析的初始數(shù)據(jù)，對機(jī)構(gòu)進(jìn)行動力學(xué)分析；在滿足機(jī)構(gòu)運(yùn)動學(xué)要求的基礎(chǔ)上改善機(jī)構(gòu)的動力學(xué)性能及機(jī)架的受力性能。使得樣機(jī)的運(yùn)動性能及受力性能達(dá)到最好，滿足人體工學(xué)以及機(jī)構(gòu)在工作過程中的穩(wěn)定性及安全性。本章是進(jìn)行樣機(jī)物理設(shè)計(jì)的依據(jù)。
6 護(hù)理床的力學(xué)分析
6.1 引言
多功能醫(yī)用護(hù)理床在滿足運(yùn)動學(xué)及動力學(xué)性能要求的基礎(chǔ)上，需要對其中的一些主要零件進(jìn)行強(qiáng)度校核，以便在設(shè)計(jì)的時(shí)候合理的選材，在保證多功能醫(yī)用護(hù)理床安全性和穩(wěn)定型以及盡可能的降低生產(chǎn)成本。
6.2 力學(xué)計(jì)算
護(hù)理床各主要部件及連桿材料均選用Q235A鋼
6.2.1床底架桿校核
考慮到由于多功能醫(yī)用護(hù)理床內(nèi)的機(jī)構(gòu)角度，不可避免的會使床的質(zhì)量增加。由于整床的重量將全部壓在床底架長桿上，所以底架長桿將會是受力最大的桿件，根據(jù)設(shè)計(jì)尺寸，底架長桿的長度為1440mm，床底架長桿上有兩個(gè)支撐點(diǎn)，假設(shè)床身的質(zhì)量為400kg，人體的質(zhì)量為150kg，總重為550kg。具體計(jì)算如下所示：
圖6-1 床底架受力示意圖
根據(jù)solidworks的稱重功能，測得床的質(zhì)量為365kg，假設(shè)床身的質(zhì)量為400kg，人體的質(zhì)量為150kg，總重為550kg。所以
F2=F3=2750N，=1440mm，=1020mm, =70mm。
根據(jù)力矩平衡公式：
F1×=F2×+F3×
得：F1==2215.3N
=F1+F4=F2+F3
得F4=3284.7N
通過上述已知條件，計(jì)算桿各段所受的剪力及彎矩：
以A為原點(diǎn)，在AB端內(nèi)：
剪力 F=F1=2215.3N，方向向下
彎矩 M=F1×x 得：M=0~775.355N·M，方向?yàn)槟鏁r(shí)針方向
在BC段內(nèi)：
剪力F=F2-F1=534.7N，方向向上
彎矩 M=F1×x-F2×（x-0.35） 得：M=229.9~775.355N·M，方向?yàn)槟鏁r(shí)針方向
在CD段內(nèi)：
剪力F=F4=3284.7N，方向向上
彎矩 M=F4×x 得：M=0~229.9N·M，方向?yàn)槟鏁r(shí)針方向
所以，根據(jù)計(jì)算分析，得出的結(jié)果為B點(diǎn)的受力最大且彎矩也最大，所以B點(diǎn)所在在截面為危險(xiǎn)截面。計(jì)算后的剪力圖及彎矩圖如圖6-2所示。
圖6-2 床底架剪力及彎矩圖
根據(jù)剪力及彎矩圖說明了床底架桿在整體上的受力并沒有發(fā)生突變，同時(shí)也不存在在某段的力值特別大的現(xiàn)象，所以從整體上而言，床框架的力學(xué)性能良好，受力情況滿足了機(jī)構(gòu)的設(shè)計(jì)要求。
6.2.2 抬背桿校核
多功能醫(yī)用護(hù)理床在抬背的時(shí)候，其抬背擺桿將是受力較大的桿件，由于人的背部質(zhì)量較大，所以其將會時(shí)比較危險(xiǎn)的桿件，對其的力學(xué)計(jì)算如下。
圖6-3抬背桿受力示意圖
按照人體的質(zhì)量及床板的質(zhì)量均分，則圓整后的數(shù)據(jù)為F1=500N，方向向上。
F3x=950N，F(xiàn)3y=2039N，=830mm，=680mm, =54mm。
F2x=F3x=950N，F(xiàn)2y=F1+F3y=500+2039=2539N
在AB段
剪力 F=F1=500N，方向向上
彎矩 M=F×x，得：M=0~340N·M，方向?yàn)轫槙r(shí)針方向
在BC段
剪力 F= F3y=2039N，方向向下
彎矩 M=F2y×（x-0.68）-F1×x (0.68≤x≤0.734)
得：M=229.9~340N·M，方向逆時(shí)針方向
M= F2y×（x-0.68）+F2x×-F1×x （0.734≤x≤0.83）
得：M=-18.5~229.9 N·M，方向逆時(shí)針方向
所以，根據(jù)上述計(jì)算結(jié)果，得知B點(diǎn)的剪力最大且所受的彎矩也是最大，綜上所述，B點(diǎn)所在的截面為危險(xiǎn)截面。根據(jù)計(jì)算結(jié)果畫出的剪力圖及彎矩圖如圖6-4所示。
10
外文資料翻譯
NC and CNC
數(shù)控技術(shù)
The History of NC and CNC Development
數(shù)字控制與計(jì)算機(jī)數(shù)字控制的發(fā)展歷史
Numerical Control (NC) is any machining process in which the operations are executed automatically in sequences as specified by the program that contains the information for the tool movements. The NC concept was proposed in the late 1940s by John Parsons of Traverse City, Michigan. Parsons recommended a method of automatic machine control that would guide a milling cutter to produce a "thru-axis curve" in order to generate smooth profiles on work pieces.
數(shù)字控制是按照含有機(jī)床(刀具)運(yùn)動信息程序所指定的順序自動執(zhí)行操作的加工過程。數(shù)控這一概念是由密歇根洲特拉華城的約翰·帕森于20世紀(jì)四十年代后期提出的。為了在工件上加工光滑的輪廓，帕森提出了一種自動的機(jī)床控制方式，它能夠引導(dǎo)銑床刀具加工出一種“過軸曲線”。
In 1949, The U.S. Air Force awarded Parsons a contract to develop a new type of machine tool that would be able to speed up production methods. Parsons commissioned the Massachusetts Institute of Technology (M.I.T.) to develop a practical implementation of his concept. Scientists and engineers at M.I.T. built a control system for a two-axis milling machine that used a perforated paper tape as the input media. In a short period of time, all major machine tool manufacturers were producing some machines with NC, but it was not until the late 1970s that computer-based NC became widely used. NC matured as an automation technology when inexpensive and powerful microprocessors replaced hard-wire logic-making computer-based NC systems.
1949年，美國空軍與帕森簽署了合同，要求開發(fā)一種能夠提高生產(chǎn)率的新型機(jī)床。帕森委托麻省理工學(xué)院(MIT)來開發(fā)一種新概念機(jī)床，麻省理工學(xué)院的科學(xué)家和工程師研制出了一種用穿孔紙帶作為輸入媒介的二軸聯(lián)動銑床控制系統(tǒng)。在較短時(shí)間內(nèi)，當(dāng)時(shí)所有主要的機(jī)床生產(chǎn)商都生產(chǎn)了一些數(shù)控機(jī)床，但直到20世紀(jì)七十年代后期，基于計(jì)算機(jī)的數(shù)字控制才被得到廣泛的使用。只有價(jià)格低廉且功能強(qiáng)大的微處理芯片代替了計(jì)算機(jī)數(shù)控系統(tǒng)中的硬連線邏輯發(fā)生器后，NC才真正成為一門自動化技術(shù)。
When Numerical Control is performed under computer supervision, it is called Computer Numerical Control (CNC). Computers are the control units of CNC machines, they are built in or linked to the machines via communications channels. When a programmer input some information in the program by tape and so on, the computer calculates all necessary data to get the job done.
當(dāng)數(shù)控機(jī)床在計(jì)算機(jī)監(jiān)控下工作時(shí)，它就被稱為計(jì)算機(jī)數(shù)控機(jī)床(CNC)。計(jì)算機(jī)是CNC機(jī)床的控制單元，它們內(nèi)嵌于數(shù)控機(jī)床或者通過通訊渠道與數(shù)控機(jī)床聯(lián)接，當(dāng)程序員編程時(shí)，通過紙帶或磁盤將一些信息輸入，計(jì)算機(jī)將對一些必要的數(shù)據(jù)進(jìn)行計(jì)算的完成工作。
On the first Numerically Controlled (NC) machines were controlled by tape, and
because of that, the NC systems were known as tape-controlled machines. They were able to control a single operation entered into the machine by punched or magnetic tape. There was no possibility of editing the program on the machine. To change the program, a new tape had to be made.
由于第一臺數(shù)控機(jī)床的數(shù)據(jù)是由紙帶控制的，因此數(shù)控系統(tǒng)被稱為紙帶控制機(jī)床。它們只能控制由輸入到機(jī)床內(nèi)的紙帶或磁帶所規(guī)定的單一操作，輸入到機(jī)床內(nèi)的程序是不能被編輯的，要改變程序必須重做新紙帶。
Today's systems have computers to control data; they are called Computer Numerically Controlled (CNC) machines. For both NC and CNC systems, work principles are the same. Only the way in which the execution is controlled is different. Normally, new systems are faster, more powerful, and more versatile
當(dāng)今的系統(tǒng)都由計(jì)算機(jī)來控制數(shù)據(jù)，因而稱之為計(jì)算機(jī)數(shù)控機(jī)床(簡稱CNC機(jī)床)。NC和CNC系統(tǒng)兩者的工作原理一樣，僅僅控制執(zhí)行的方式不同。新型的數(shù)控系統(tǒng)通常速度更快、功率更大、功能更齊全。
The Applications of NC/CNC
數(shù)字控制與計(jì)算機(jī)數(shù)字控制的應(yīng)用
Since its introduction, NC technology has found many applications, including lathes and turning Centers, milling machines and machining centers , punches , electrical discharg machines(EDM) Flame cutters,grinders,and inspection equipment. the most complex CNC machine tools are the turning center,shown in Fig.4-1(Amodern turning center with a ten-station turret that accepts quick-chang tools.Each tool can be positioned in Seconds with the press of a button).And the machine center shown in Fig.4-2(Vertical machining center,the tool magazine is on the machine.the control panel on the right can be swiveled by the operator)and Fig.4-3(horizontal machining center,equipped with an automatic tool changer .tool magazines can store 200 ctting tools.
數(shù)控技術(shù)自創(chuàng)立以來就得到了廣泛的應(yīng)用，包括車床和車削中心、銑床和加工中心、沖床、電火花(EDM)加工機(jī)床、線切割機(jī)床、磨床以及測試檢測裝置等。最復(fù)雜的計(jì)算機(jī)數(shù)控機(jī)床是車削中心，圖4—1所示一個(gè)具有十轉(zhuǎn)位的刀架能進(jìn)行快速換刀的現(xiàn)代車削中心，立式加工中心如圖4—2所示(刀具庫在機(jī)床的左邊。右邊的控制面板可由操作者通過轉(zhuǎn)臂轉(zhuǎn)動)，以及臥式加工中心，通過按下按鈕每把刀可在數(shù)秒鐘內(nèi)定位。如圖4—3所示(配有自動換刀系統(tǒng)。刀具庫儲備有200把切削工具)。
When preparing a progam for a particular operation ,the prommer must select all cutting data using recommendations for conventional machining .this includes proper
Selection of cutting speeds,feedrate,tools and tool geometry,and so on.when the programmer has chosen all of the necessary information properly,the operator loads the programme into the machine and presses a button to start the cutting crycle .the CNC machine moves automatically from one maching operation to another , changing the cutting tols and applying the coolent.in a surprisingly short time ,the workpiece is
Machined according to the highest quality stangards. But that is not all.no matter how big the work series is,all of the parts will be almost identical in size and surface finishing. At this time of advanced technology,with its high demands for surface finishing and tolerances of components in,for example ,aerospace,nuclear,and medical equipment manufacturing,only CNC machines provide successful results.
當(dāng)為某項(xiàng)操作編程時(shí)，程序員必須選擇傳統(tǒng)的加工切削數(shù)據(jù)推薦值。這些切削數(shù)據(jù)包括切削速度、進(jìn)給率、刀具和刀具幾何形狀等。當(dāng)程序員正確選擇所有必要信息后，操作人員將程序載入機(jī)床并按下按鈕，切削循環(huán)就開始。
Numerical control (NC) is a form of programmable automation in which the processing equipment is controlled by means of numbers, letters, and other symbols. The numbers, letters, and symbols are coded in an appropriate format to define a program of instructions for a particular workpart or job. The instructions are provided by either of the two binary coded decimal systems: the Electronic Industries Association (EIA) code, or the American Standard Code for Information Interchange (ASCII). ASCII-coded machine control units will not accept . EIA coded instructions and vice versa. Increasingly, however, control units are being made to accept instructions in either code. 121Automation operation by NC is readily adaptable to the
operation of all metalworking machines. Lathes, milling machines, drill presses, boring machines, grinding machines, turret punches, flame or wire-cutting and welding machines, and even pipe benders are available with numerical controls.
數(shù)控技術(shù)是一種利用程序?qū)崿F(xiàn)自動控制的技術(shù)，加工制造設(shè)備采用數(shù)控技術(shù)后能由數(shù)字、字符和符號等進(jìn)行控制。這些數(shù)字、字符和符號等被編碼成按一定格式定義的指令程序用于一個(gè)特定的加工或工件，這些指令可以采用兩種二進(jìn)制編碼的數(shù)字系統(tǒng)中的任意一種進(jìn)行定義，這兩種二進(jìn)制編碼數(shù)字系統(tǒng)分別為電工協(xié)會代碼(EIA)和美國標(biāo)準(zhǔn)信息交換代碼(ASCII)。一般來說，ASCII編碼的機(jī)床控制系統(tǒng)不能接受EIA編碼的指令，反之亦然。當(dāng)然，這樣的問題已經(jīng)逐漸得到解決。數(shù)控加工制造目前已經(jīng)廣泛地應(yīng)用于幾乎所有的金屬加工機(jī)床：車床，銑床，鉆床，鏜床，磨床，回轉(zhuǎn)沖床，電火化，線切割和焊接機(jī)床，甚至彎管機(jī)也采用數(shù)控加工技術(shù)。
Basic Components of NC
數(shù)控技術(shù)的基本組成
A numerical control system consists of the following three basic components:
一個(gè)數(shù)控系統(tǒng)主要由以下3個(gè)部分組成：
(1) Program instructions
(1)程序指令
(2) Machine control unit
(2)加工控制單元
(3) Processing equipment
(3)制造裝備
The program instructions are the detailed step by step commands that direct the processing equipment. [31In its most common form, the commands refer to positions of a machine tool spindle with respect to the worktable on which the part is fixtured. More advanced instructions include selection of spindle speeds, cutting tools, and other functions.
程序指令是由一條一條的詳細(xì)指令所組成，制造裝備按要求執(zhí)行這些指令。最常用的指令有：可以按要求使機(jī)床刀具主軸位于工作臺上的具體位置，工作臺是用于固定加工零件的，許多更高級的指令還包括用于主軸速度的選擇、刀具速度的選擇及其他一些功能。
The machine control unit (MCU) consists of the electronics and control hardware that reads and interprets the program of instructions and convert it into mechanical actions of the machine tool or other processing equipment.
加工控制單元(MCU)包括一些用于閱讀和解釋程序指令并將其轉(zhuǎn)換為機(jī)床刀具或其他制造裝備的機(jī)械動作的電子和控制硬件。
The processing equipment is the component that performs metal process. In the most common example of numerical control, it is used to perform machining operations. The process-ing equipment consists of the worktable and spindle as well as the motors and controls needed to drive them.
制造裝備是一種進(jìn)行金屬加工的數(shù)控技術(shù)裝備，在常用的數(shù)控技術(shù)領(lǐng)域中，制造裝備用于進(jìn)行機(jī)械制造。制造裝備包括工作臺、主軸、電機(jī)及控制驅(qū)動單元。
Types of NC
數(shù)控技術(shù)的類型
There are two basic types of numerical control systems: point to point and contouring.
數(shù)控技術(shù)系統(tǒng)主要有兩種類型：點(diǎn)對點(diǎn)數(shù)控系統(tǒng)和輪廓線數(shù)控系統(tǒng)。
Point to point control system, also called positioning, is simpler than contouring control system. Its primary purpose is to move a tool or workpiece from one programmed point to another. Usually the machine function, such as a drilling operation, is also activated at each point by command from the NC program. Point to point systems are suitable for hole machining operations such as drilling, countersinking, couterbofing, reaming, boring and tapping. Hole punching machines, spotwelding machines, and assembly machines also use point to point NC systems.
點(diǎn)對點(diǎn)數(shù)控系統(tǒng)也稱為位置數(shù)控系統(tǒng)，比輪廓線數(shù)控系統(tǒng)簡單，其主要的原理是移動刀具或工件從一個(gè)程序控制點(diǎn)到另一一個(gè)控制點(diǎn)，通常像鉆床這樣的加工功能，每個(gè)點(diǎn)幫司以通過NC程序中的指令進(jìn)行控制。點(diǎn)對點(diǎn)數(shù)控系統(tǒng)適用于像鉆孔、沉孔加工、沉孔鏜孔、鉸孔和攻絲等。其他沖孔機(jī)床、點(diǎn)焊機(jī)和裝配機(jī)床等也都采用點(diǎn)對點(diǎn)數(shù)控系統(tǒng)。
Contouring system, also known as the continuous path system, positioning and cutting operations are both along controlled paths but at different velocities. Because the tool cuts as it travels along a prescribed path, accurate control and synchronization of velocities and movements are important. The contouring system is used on lathes, milling machines, grinders,incrementally, by one of several basic methods. There are a number of interpolation schemes that have been developed to deal with the various problems that are encountered in generating a smooth continuous path with a contouring type NC system. They include linear interpolation,circular interpolation, helical interpolation, parabolic interpolation and cubic interpolation. In all interpolations, the path controlled is that of the center of rotation of the tool. Compensation for different tools, different diameter tools, or tools wear during machining, can be made in the NC .
輪廓線數(shù)控系統(tǒng)也稱為輪廓線路徑數(shù)控系統(tǒng)，定位和切割操作都是以不同的速度沿著控制的路徑進(jìn)行的。由于刀具沿路徑進(jìn)行切削，因此刀具的運(yùn)動和速度的精確控制和同步性能是非常重要的。輪廓線數(shù)控系統(tǒng)經(jīng)常應(yīng)用于車床、銑床、磨床、焊接機(jī)床和加工中心中。刀具沿著路徑的運(yùn)動，或稱為插補(bǔ)逐漸出現(xiàn)了幾個(gè)不同的方法。有許多類型的插補(bǔ)方法用于處理輪廓線數(shù)控系統(tǒng)中生成光滑的輪廓線時(shí)遇到的各種問題。幾種比較常用的方法有線性插補(bǔ)，圓形插補(bǔ)，螺旋形插補(bǔ)、拋物線插補(bǔ)和立方插補(bǔ)等，在所有的插補(bǔ)方法中，路徑控制是以刀具的旋轉(zhuǎn)中心為標(biāo)準(zhǔn)，對于不同類型、不同直徑的刀具，加工過程中的不同刀具磨削量在數(shù)控程序中獲得不同的補(bǔ)償。
Programming for NC
數(shù)控系統(tǒng)的編程
A program for numerical control consists of a sequence of directions that causes an NC machine to carry out a certain operation, machining being the most commonly used process. Programming for NC may be done by an internal programming department, on the shop floor, or purchased from an outside source. Also, programming may be done manually or with computer assistance.
一個(gè)數(shù)控系統(tǒng)(NC)的程序包括使數(shù)控(NC)機(jī)床進(jìn)行操作和加工的一系列指令。數(shù)控程序可以由數(shù)控機(jī)床內(nèi)部的程序庫開發(fā)生成，也可以從外面采購獲得。另外，程序可以通過手工編寫，也可以進(jìn)行計(jì)算機(jī)輔助編程。
The program contains instructions and commands. Geometric instructions pertain to relative movements between the tool and the workpiece. Processing instructions pertain to spindle speeds, feeds, tools, and so on. Travel instructions pertain to the type of interpolation and slow or rapid movements of the tool or worktable. Switching commands pertain to on/off position for coolant supplies, spindle rotation, direction of spindle rotation, tool changes, workpiece feeding, clamping, and so on. The first NC programming language was developed by MIT developmental work on NC programming systems in the late 1950s and called APT(Automatically Programmed Tools).
數(shù)控程序包括一系列指令系統(tǒng)和命令系統(tǒng)。幾何類指令用于定義刀具和工件之間的相對位置和運(yùn)動：加工類指令用于定義主軸轉(zhuǎn)速、進(jìn)給、刀具轉(zhuǎn)速等：傳送類指令用于定義刀具或工作臺的運(yùn)動速度和插補(bǔ)的類型等；開關(guān)類指令用于冷卻液供給、主軸旋轉(zhuǎn)、主軸旋轉(zhuǎn)方向選擇、換刀、工件進(jìn)給、夾具等的開關(guān)。第一個(gè)用于數(shù)控編程的數(shù)控編程語言是20世紀(jì)50年代由麻省理工學(xué)院數(shù)控編程系統(tǒng)開發(fā)小組專家開發(fā)的，并被命名為自動編程工具(APT)。
DNC and CNC
直接數(shù)字控制(DNC)和計(jì)算機(jī)數(shù)字控制(CNC)
The development of numerical control was a significant achievement in batch and job shop manufacturing, from both a technological and a commercial viewpoint. There have been two enhancements and extensions of NC technology, including:
數(shù)控技術(shù)的發(fā)展在批量生產(chǎn)和車間生產(chǎn)加工中，不管是在技術(shù)上還是在商業(yè)上都獲得了巨大的成功。目前，已經(jīng)有兩種數(shù)控技術(shù)系統(tǒng)得到了發(fā)展，分別是：
(1) Direct numerical control
(1)直接數(shù)字控制(DNC)。
(2) Computer numerical control
(2)計(jì)算機(jī)數(shù)字控制(CNC)。
Direct numerical control can be defined as a manufacturing system in which a number of machines are controlled by a computer through direct connection and in real time. The tape reader is omitted in DNC, thus relieving the system of its least reliable component. Instead of using the tape reader, the part program is transmitted to the machine tool directly from the computer memory. In principle, one computer can be used to control more than 100 separate machines. (One commercial DNC system during the 1970s boasted a control capability of up to 256 machine tools.) The DNC computer is designed to provide instructions to each machine tool on demand. When the machine needs control commands, they are communicated to it immediately.
直接數(shù)字控制(DNC)可以被定義為這樣一個(gè)生產(chǎn)制造系統(tǒng)，該制造系統(tǒng)有許多臺加工機(jī)床，而相互之間由一臺計(jì)算機(jī)采用直接連接，進(jìn)行實(shí)時(shí)控制。這樣，在傳統(tǒng)的數(shù)字控制技術(shù)中采用的磁帶閱讀器在直接數(shù)字控制中被取消，從而保證了系統(tǒng)的可靠性。不使用磁帶閱讀器，被加工的零件程序就從計(jì)算機(jī)的存儲器中直接傳送到進(jìn)行加工的刀具上。從原理上講，一臺計(jì)算機(jī)可以控制多達(dá)100臺加工機(jī)床，(在20世紀(jì)70年代一個(gè)商業(yè)使用的DNC系統(tǒng)宣稱可以控制多達(dá)256個(gè)機(jī)床刀具)。直接數(shù)字控制計(jì)算機(jī)用于按要求提供加工指令給每個(gè)進(jìn)行加工的刀具上，當(dāng)機(jī)床需要控制指令時(shí)，計(jì)算機(jī)就可以馬上將指令傳送到機(jī)床上。
Since the introduction of DNC, there have been dramatic advances in computer
technology. The physical size and cost of a digital computer has been significantly reduced at the same time that its computational capabilities have been substantially increased. In numerical control, the result of these advances has been that the large hard-wired MCUs of conventionalNC have been replaced by control units based on the digital computer. Initially, minicomputers were utilized in the early 1970s. As further miniaturization occurred in computers, minicomputers were replaced by today's microcomputers.
隨著直接數(shù)字控制(DNC)技術(shù)和計(jì)算機(jī)技術(shù)的飛速發(fā)展，數(shù)字式計(jì)算機(jī)的尺寸和價(jià)格的大幅度的降低，數(shù)字式計(jì)算機(jī)的計(jì)算能力的大大提高，大量傳統(tǒng)的以硬件線路為基礎(chǔ)的加工控制單元被以數(shù)字計(jì)算機(jī)為基礎(chǔ)的數(shù)字控制單元所替代。最初在20世紀(jì)70年代使用了小型計(jì)算機(jī)。后來，隨著計(jì)算機(jī)的進(jìn)一步小型化，早期的小型計(jì)算機(jī)逐漸被現(xiàn)在的微型計(jì)算機(jī)所取代。
Computer numerical control is an NC system using dedicated microcomputer as the machine control unit. Because a digital computer is used in both CNC and DNC, it is appropriate to distinguish between the two types of system. There are three principal differences:
計(jì)算機(jī)數(shù)控(CNC)使用專用的微型計(jì)算機(jī)作為加工控制單元。因?yàn)閿?shù)字計(jì)算機(jī)都用于計(jì)算機(jī)數(shù)控(CNC)和直接數(shù)控(DNC)，所以應(yīng)該注意兩者之間的區(qū)別，可以從3個(gè)方面來加以區(qū)分。
1) DNC computers distribute instructional data to, and collect data from, a large number of machines. CNC computers control only one machine, or a small number of machines.
(1) DNC計(jì)算機(jī)是將指令數(shù)據(jù)發(fā)送到許多機(jī)床去或從許多機(jī)床中收集數(shù)據(jù)，而CNC計(jì)算機(jī)每次只控制一臺或幾臺機(jī)床。
(2) DNC computers occupy a location that is typically remote from the machines
under their control. CNC computer are located very near their machine tools.
(2) DNC計(jì)算機(jī)一般位于距機(jī)床一定距離的位置，而CNC計(jì)算機(jī)一般都位于距機(jī)床較近的位置。
(3) DNC software is developed not only to control individual pieces of production equipment, but also to serve as part of a management information system in the manufacturing sector of the firm. CNC software is developed to augment the capabilities of a particular machine Tool.
(3) DNC計(jì)算機(jī)開發(fā)的軟件不僅可以用于控制單件生產(chǎn)，而且可以用于一個(gè)企業(yè)制造部門的管理信息系統(tǒng)，而CNC計(jì)算機(jī)開發(fā)的軟件一般只用于某個(gè)特殊加工的工具。
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