1、專業好文檔機電控制與可編程序控制器技術課程作業（二）1.簡述機電設備電器控制線路的基本設計步驟。2.在選擇機電設備拖動用的電動機時，應主要考慮哪些內容？3 試問下列控制線路是否合理（注：圖中km1、km2為交流接觸器，ya為直流電磁鐵）？若不合理，應怎樣改正？4現有三臺電動機m1、m2、m3要求起動順序為：先起動m3，經10s后起動m2，再經20s后起動m1。而停車時要求：首先停m1，經20s后停m2，再經10s后停m3。試設計該三電動機的起、停控制線路。 5設計一條由兩臺電動機拖動的裝配車間的一輸送機控制線路，應滿足下列要求： （1）m1電動機與m2電動機均單向運轉； （2）m1電動機起動工

2、作后，m2電動機才能起動工作； （3）m2電動機先停機，而后m1電動機才能停機； （4）m1電動機過載時，兩臺電動機同時停機，m2電動機過載時，僅m2電動機停機； （5）要有必要的保護環節。試畫出控制電路。 6設計組合機床的兩臺動力頭的電氣控制線路。設計要求如下： （1）加工時兩臺動力頭電動機同時起動； （2）兩臺動力頭電動機單向運轉； （3）兩臺動力頭電動機，在加工完成后各自停機； （4）若其中一臺動力頭電動機過載，另一臺動力頭電動機也應停機。畫出其控制電路。 7. plc主要特點有哪些？plc的發展趨勢如何？ 8.比較plc控制和繼電接觸器控制、微機控制的優缺點。 9.繼電接觸器控制系統，

3、plc控制有哪些相同和不同之處？ 10plc基本硬件由哪幾部分組成？ 11什么叫掃描工作方式？什么叫掃描周期？它主要受哪些因數影響？ 12.為什么稱plc的內部繼電器為軟繼電器？和硬件繼電器相比，軟繼電器的觸點在使用上有何特點？ 13.plc的工作過程分為哪幾個工作階段，各完成什么任務？ 14.什么是plc的輸入輸出滯后現象？造成這種現象的原因是什么？可采取哪些措施縮短輸入輸出滯后時間？ 15.plc的性能指標主要有那些？plc是怎樣分類的？winger tuivasa-sheck, who scored two tries in the kiwis 20-18 semi-final win

4、over england, has been passed fit after a lower-leg injury, while slater has been named at full-back but is still recovering from a knee injury aggravated against usa.both sides boast 100% records heading into the encounter but australia have not conceded a try since josh charnleys effort in their f

5、irst pool match against england on the opening day.aussie winger jarryd hayne is the competitions top try scorer with nine, closely followed by tuivasa-sheck with eight.but it is recently named rugby league international federation player of the year sonny bill williams who has attracted the most in

6、terest in the tournament so far.the kiwi - with a tournament high 17 offloads - has the chance of becoming the first player to win the world cup in both rugby league and rugby union after triumphing with the all blacks in 2011.id give every award back in a heartbeat just to get across the line this

7、weekend, said williams.the (lack of) air up there watch mcayman islands-based webb, the head of fifas anti-racism taskforce, is in london for the football associations 150th anniversary celebrations and will attend citys premier league match at chelsea on sunday.i am going to be at the match tomorro

8、w and i have asked to meet yaya toure, he told bbc sport.for me its about how he felt and i would like to speak to him first to find out what his experience was.uefa hasopened disciplinary proceedings against cskafor the racist behaviour of their fans duringcitys 2-1 win.michel platini, president of

9、 european footballs governing body, has also ordered an immediate investigation into the referees actions.cska said they were surprised and disappointed by toures complaint. in a statement the russian side added: we found no racist insults from fans of cska. baumgartner the disappointing news: missi

10、on aborted.the supersonic descent could happen as early as sunda.the weather plays an important role in this mission. starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. the balloon, with capsule attached, will m

11、ove through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. it will climb higher than the tip of mount everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratos

12、phere. as he crosses the boundary layer (called the tropopause),e can expect a lot of turbulence.the balloon will slowly drift to the edge of space at 120,000 feet ( then, i would assume, he will slowly step out onto something resembling an olympic diving platform.they blew it in 2008 when they got

13、caught cold in the final and they will not make the same mistake against the kiwis in manchester.five years ago they cruised through to the final and so far history has repeated itself here - the last try they conceded was scored by englands josh charnley in the opening game of the tournament.that c

14、ould be classed as a weakness, a team under-cooked - but i have been impressed by the kangaroos focus in their games since then.they have been concentrating on the sort of stuff that wins you tough, even contests - strong defence, especially on their own goal-line, completing sets and a good kick-ch

15、ase. theyve been great at all the unglamorous stuff that often goes unnoticed in the stands but not by your team-mates.it is as though their entire tournament has been preparation for the final.in johnathan thurston, cooper cronk, cameron smith and either billy slater or greg inglis at full-back they have a spine that is unmatched in rugby league. they have played in so many high-pressure games - a priceless asset going into saturday.the kiwis are a lot l