电大机电控制工程基础第3次作业(答案).doc

专业好文档第3次作业一、填空1、时间响应由 响应和 响应两部分组成。 瞬态、稳态2、为系统的 ，它描述系统对不同频率输入信号的稳态响应幅值衰减（或放大）的特性。为系统的 ，它描述系统对不同频率输入信号的稳态响应，相位迟后或超前的特性。 幅频特性， 相频特性3、频率响应是 响应。 正弦输入信号的稳态4、惯性环节的传递函数为 。 5、当输入信号的角频率在某一范围内改变时所得到的一系列频率的响应称为这个系统的频率特性。6、控制系统的时间响应，可以划分为瞬态和稳态两个过程。瞬态过程是指系统从 到接近最终状态的响应过程；稳态过程是指时间t趋于 时系统的输出状态。 初始状态 无穷7、若系统输入为，其稳态输出相应为，则该系统的频率特性可表示为 。 8、2型系统的对数幅频特性低频渐近线斜率为 。40dB/dec9、对于一阶系统，当由0时，矢量D(j)逆时针方向旋转，则系统是稳定的。否则系统不稳定。二、选择1、根据下列几个系统的特征方程，可以判断肯定不稳定的系统为（ 2 ）A ； B ；C ；其中均为不等于零的正数。2、下列开环传递函数所表示的系统，属于最小相位系统的是（ 3 ）。A ； B （T>0）； C ；D 3、已知系统频率特性为 ，则该系统可表示为（ 3 ）（1） ；（2）；（3） ；（4）4、下列开环传递函数所表示的系统，属于最小相位系统的有 。DA ； B （T>0）； C ； D；5、题图中RC电路的幅频特性为 。BA ； B ； C ； D 。6、已知系统频率特性为 ，则该系统可表示为（ 2 ）A ； B ； C ；D 7、已知系统频率特性为 ，当输入为时，系统的稳态输出为（ 4 ）A ； B ；C ； D 8、理想微分环节对数幅频特性曲线是一条斜率为（ 1 ）A ，通过=1点的直线； B -，通过=1点的直线；C -，通过=0点的直线； D ，通过=0点的直线9、开环对数幅频特性对数相频特性如图所示，当K增大时：A 图A L()向上平移，不变； B L()向上平移，向上平移；C L()向下平移，不变； D L()向下平移，向下平移。10 系统如图所示，为一个 装置，实现起来比较简单（ B ）A 串联校正； B 并联校正；C 混合校正； D 正反馈校正。三、已知某单位反馈系统开环传递函数为,校正环节为绘制其校正前和校正后的对数幅频特性曲线以及校正环节图形与校正后的相角裕量 解答： 校正后 校正前 校正后 校正前 校正环节 2） 四、已知系统的开环传递函数为：试：1绘出对数渐近幅频特性曲线以及相频特性曲线 2确定系统稳定裕度解答：（1） 该系统是由积分、放大和两个惯性环节串联构成的（2） K=10 20lgK=20分贝 （3） 低频为积分放大环节，在，K=20分贝处作 -20dB/10倍频 线在处作 -40dB/10倍频 线，在处作 60dB/10倍频线 2L（）>0的范围内，相频特性在处没有穿越，所以系统稳定 ，所以 =180= 五、设系统的传递函数，求输入信号频率为，振幅为时，系统的稳态输出。解： 由，可以看出是由放大环节与惯性环节串联组成，放大环节只影响输出值的幅值，而惯性环节对输出的幅值及相位都有影响。1) 输出与输入频率相同 f=1Hz，所以=2f=6.3（）2) 求输出与输入相位差惯性环节相位落后为 3) 求输出幅值 4) 稳态输出六、已知最小相位系统开环对数频率特性曲线如图所示。试写出开环传递函数 。解： 1) <1的低频段斜率为-20，故低频段为K/。 增至1，斜率由-20转为-40，增加-20，所以1应为惯性环节的转折频率，该环节为 。增至2，斜率由40转为20，增加+20，所以2应为一阶微分环节的转折频率，该环节为 。增到3，斜率由-20转为-40，该环节为,>3，斜率保持不变。故系统开环传递函数应由上述各典型环节串联组成，即 2) 确定开环增益K当=c时，A(c)=1 。 所以 故 所以，七、 单位反馈系统的开环传递函数为 试用频域和时域关系求系统的超调量及过渡过程时间ts 。解答略八、系统开环传递函数为， 试绘制系统的开环对数频率特性并计算值。解：A 首先将分成几个典型环节。 显见该系统由放大环节，积分环节，惯性环节，一阶微分环节组成。2) 分别做各典型环节的对数频率特性曲线。 K=7.5 20lgK=17.5dB ； 1=2, 2=3对数幅频特性： 相频特性： 其对数频率特性曲线如图所示。3) 计算 所以 由图可知 部份，对-线无穿越，故系统闭环稳定。 九、已知单位反馈控制系统，开环对数幅频特性如图所示。 试求： 1） 位斜坡输入时稳态误差的值。2） 渡过程时间3） 穿越频率4） 相角裕量 解答:1）； 2） 秒； 3） ； 4） Winger Tuivasa-Sheck, who scored two tries in the Kiwis' 20-18 semi-final win 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 Charnley's effort in their first pool match against England on the opening day.Aussie winger Jarryd Hayne is the competition's 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 interest 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."I'd give every award back in a heartbeat just to get across the line this weekend," said Williams.The (lack of) air up there Watch mCayman Islands-based Webb, the head of Fifa's anti-racism taskforce, is in London for the Football Association's 150th anniversary celebrations and will attend City's Premier League match at Chelsea on Sunday."I am going to be at the match tomorrow and I have asked to meet Yaya Toure," he told BBC Sport."For me it's about how he felt and I would like to speak to him first to find out what his experience was."Uefa has opened disciplinary proceedings against CSKA for the "racist behaviour of their fans" during City's 2-1 win.Michel Platini, president of European football's governing body, has also ordered an immediate investigation into the referee's actions.CSKA said they were "surprised and disappointed" by Toure's complaint. In a statement the Russian side added: "We found no racist insults from fans of CSKA." Baumgartner the disappointing news: Mission 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 move 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 stratosphere. 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 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 England's Josh Charnley in the opening game of the tournament.That could 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-chase. They've 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 less experienced but winning a dramatic match like their semi-final against England will do wonders for their confidence.They defeated Australia in the Four Nations final in 2010 and the last World Cup, and know they can rise to the big occasion.