【正文】 l System of the Thermal Power Unit From the system point of view, we analyze and study the principle of two basic feedback control method early that “boiler follows steam turbine” and “steam turbine follows boiler” in order to find out the existent problem ad be able to design more reasonable control method. Boiler follows steam turbine mode This kind of control mode is first to let steam turbine trail the needs of power work load ,then let boiler trail steam turbine .Its advantage is to be able to fully use the heat accumulation of boiler ,make the unit meet the change of power work load paratively quickly.. But because the inertia and delay of boiler are greater ,the regulation of former turbine pressure pt cannot follow the speed of load regulation, thus pt has greater fluctuation, which is disadvantageous to the steady operation of boiler .The range and speed change of the unit’s output must be restricted . . Steam turbine follows boiler mode This kind of control mode is first to let boiler train the needs of power work load, then let steam turbine train boiler .It can be better to maintain steam pressure stabilize and beneficial to boiler steady operation .But it do not fully utilize the heat accumulation f boiler to regulate the unit’s output ,it is more slowly that the unit meets the load’s demand ,so this control mode is only to be applied to the unit undertaking basic load . Coordinate control mod According to the analysis above, it must use the heat accumulation of boiler fully and reasonably when the unit has better adaptability to power work load in safe operation. That is to let former turbine pressure changes, then to coordinate the interaction between two loops of power regulation and pressure regulation reasonably, so that unit39。s output meets the needs of the power work load promptly, and guarantee the control demand of unit steady operation. The practical method is to lead into properly feedforward control systems mentioned above and make boiler and steam turbine coordinate each other so that the schemes of various coordinate controls suitable to practical project can be attained, such as: coordinate control system based on“ boiler follows steam turbine” or“ steam turbine follows boiler”。 關(guān)鍵詞： 補(bǔ)償誤差 探針 找正 校準(zhǔn) 三維特性 觸發(fā) 坐標(biāo)測量機(jī)及其特點(diǎn) 坐標(biāo)測量機(jī)是一種具有很強(qiáng)柔性的尺寸測量設(shè)備， CMM在工業(yè)界的應(yīng)用開始于對(duì)棱柱零件的快速、精確測量。 CMM 在自動(dòng)化程度方面有很大的差別。 除了再質(zhì)量檢測方面使用 CMM 外， CMM 還可以用于對(duì)實(shí)物的仿物的信制加工中，即所謂逆向工程。接觸類的測頭主要包括觸發(fā)式、模擬式兩種。但是由于它具有了三坐標(biāo)的雛形，在使用測頭鉆孔的位置時(shí)也相當(dāng)有效。 6 個(gè) 觸點(diǎn)圖中的方式依次連接，并接一個(gè)恒定電流電源。這種測頭的特點(diǎn)是具有三維特性，即 X,Y,Z 三個(gè)方向的移動(dòng)接觸均能引起觸發(fā)。因此測量速度比硬探頭掃描測量速度低。在 CAD 指導(dǎo)的檢測系統(tǒng)中可以根據(jù)被測工件的 CAD 模型直接計(jì)算出被測點(diǎn)法向，讓測頭從法向接觸被測點(diǎn)，這樣就比較容易判斷觸點(diǎn)的位置。如圖所示，根據(jù)不同的需要可以選擇不同的類型的探針。選用直徑大的紅寶石探針，一方面可以減小加工表面缺陷時(shí)測量精度的影響，另一方面可以增大探針的有效工作長度。坐標(biāo)測量機(jī)的發(fā)展促進(jìn)了新型測頭的研制，新型測頭的開發(fā)又進(jìn)一步擴(kuò)大了測量機(jī)的應(yīng)用范圍。 (1)機(jī)械接觸式測頭 接觸式測頭又稱為“剛性測頭”、“硬測頭”，一般用于“靜態(tài)”測量，大多作為接觸元件使用。由于其明顯的缺點(diǎn)，目前這種測頭已很少使用。因此按其功能，電氣接觸式測頭又可分為作瞄準(zhǔn)用的開關(guān)測頭和具有測微功能的三向測頭。如何選用合適的測針類型和規(guī)格取決于被測工件的特征，但是在任何情況下，測針的剛性和測球的球度都是不可或缺的。球頭尺寸和測針有效工作長度的選取取決于被測工件。因?yàn)樵谠S多尺寸的測量當(dāng)中需要沿不同的方向進(jìn)行探測，系統(tǒng)記錄的是探針中心的坐標(biāo)而不是接觸點(diǎn)的坐標(biāo)。校準(zhǔn)球是一個(gè)已知直徑的校準(zhǔn)球，校準(zhǔn)探針的過程實(shí)際上就是對(duì)這個(gè)已知直徑的標(biāo)準(zhǔn)進(jìn)行測量直徑的過程，如圖 71 所示。 測量過程中所有要用到的探針都要進(jìn)行校準(zhǔn)，而且一旦探針改變位置，或者取下后下次再用時(shí)要重新進(jìn)行校準(zhǔn)，這樣一來在探針的校準(zhǔn)方面要用去大量的時(shí)間。因此在進(jìn)行實(shí)際檢測之前首先要確定工件坐標(biāo)系在 CMM機(jī)器坐標(biāo)系中的位置關(guān)系。在以上三步操作中檢測點(diǎn)位置的確定都是依據(jù)工件坐標(biāo)系來選擇的。 (2)測球半徑補(bǔ)償誤差 當(dāng)測針接觸到工件時(shí)，三坐標(biāo)測量機(jī)接收的的坐 標(biāo)值應(yīng)是紅寶石球頭中心