外文翻译-液位控制系统

1、毕业设计论文英文翻译系 别专 业班 级学生姓名学 号指导教师报告日期International Railway JournalLevel Control System【Title】 International Railway Journal【Publication Date 】2021【No.】 period MarchIon Matei, Dumitru Popescu, Ciprian Lupu, llie LuicanPolitehnica University of Bucharest - Control and Computer Science FacultySplaiul Inde

2、pendentei nr.313,sector6,Bucurcsti,Romaniaemail: inion 3 home .ro1 Level control systemThe fluid flow is controlled by an electric pomp. The process input is a voltage with values between 0 and 10 V and the output is the fluid level measured by an ultrasounds transducer. The process is nonlinear but

3、 it is approximated with linear mathematical model around a representative point of functioning. The approximated mathematical model which was obtained using the sample period Te = 5s. It is important to mention that for designing a numerical regulator three steps must be followed:- computing the di

4、screte model;- performances specification;- computing the adequate control algorithmIn this case for the level control were used the next numerical control algorithms: RST and PID with its two variants, PIDl and PID2. These algorithms have different performances so that the students will have the op

5、portunity to compare them. First it will be presented the RST algorithm and than the paper will continue with PID algorithms which will be structured analyzed and compared to the first one.2 PID algorithmNumerical PID algorithm comes from sampling the continuous PID algorithm with all appropriate sa

6、mpling period.Numerical PID controllers are suitable only for processes modeled by a second order transfer function with or without pure delay.It is worth to mention that some numerical PID controllers do not have a continuous equivalent.2.1 PIDl numerical algorithmLet us consider the algorithm:The

7、transfer functions of a continuous PID controller，This algorithm is specified by four parameters:K - proportional action;Ti - integral action;Td - derivative action;Td - filtered derivative action.There are many methods that can be used to sample this algorithm resulting in a numerical controller of

8、 the same form.As it may be seen, PIDl numerical regulator has also four parameters (rth r1 r2, s1) as its continuous form. This algorithm can be International Railway Journalstructured in a RST form if T(q-1)=R(q-1 ).It is easy to notice that PIDl is one freedom degree algorithm. The transfer funct

9、ion in closed loop which join the reference r(t) with the output y(i) is, where P(q-1)defines the poles wanted in closed loop that determine the performances for perturbations rejection. PIDl algorithm introduces new zeros in closed loop by polynomial R(q-1) that alter the performances. This negativ

10、e effect will be partially eliminated by thePID2 algorithm. Having already determined the RST algorithms it is now easy to calculate the PIDl parameters (if the rejection performances define by P (q-1) are not changed) because the polynomials R(q-1) and S(q-1) will be the same 3.As it may be observe

11、d in the next graphics the perforinanccs of the PIDl algorithm are inferior to the RST algorithm.2.2 PID2 numerical algorithmAs it was noticed above the PIDl regulator introduces supplementary zeros in closed loop by polynomial T(q-1)=R(q-1). Those zeros affect specially the control performances as

12、it was observed in figure 7. This disadvantage can be partially eliminated if the polynomial T(q-1) is chosen. assuring in this manner a unitary transfer function in stationary regime 3.The block schematics of the PID2 numerical algorithm structured as RST is presented bellow.This algorithm assures

13、superior performances compare to PIDl as it may be seen in the next graphics.3 RST numerical algorithmFor any control system there are defined two important objectives:1 . Reference 's tracking;2 . Rejection of the perturbations;A classical control structure. with only one liberty degree (fig. 2

14、) has the great disadvantage that it can not fulfill the two objective defined above.As it may be noticed the command is not pondered differentially by reference and measure. This means that some performances defined for perturbations rejection could restrict the reference tracking. If the polynomia

15、l R(q-1), which filter the reference, is replaced by another polynomial T(q-1) i t will lead to a RST structure with two liberty degree that accepts different performances in tracking and rejection3 4.The block structure of the RST numerical algorithm is presented in the next figure:The closed loop

16、transfer function is:The performances for rejection are established by characteristic polynomial P(q-1) obtained by sampling a second order continuous system. The polynomials R(q-1) and S(q-1) results from solving the next polynomial equation:A(q-1)S(q-1)+ q-dB(q-1)R(q-1)= P(q-1) (4)The tracking per

17、formances are controlled by T(q-1) and reference filtering. The polynomial T(q-1) is chosen so that the close loop International Railway Journaltransfer is unitary (the output will follow the imposed reference y*).T(q-1)=P(q-1) (5)Tracking dynamics can be modify by polynomials Bm(q-1) and Am(q-1) wh

18、ich filter the reference:Polynomials Bm, and Am, result also from sampling a second order continuous system. Therefore choosing the parameters and will determine the tracking performances 4.The block diagram of the RST control structure with filtered reference is presented below:The system tracking

19、performances are chosen by a second order system with ,I = 0.25, = 0.99 which results in:The rejection performances are also given by a second order system with: n= 2.5, = 0.8.The characteristic polynomial for the poles allocation method, will become:P(q-1)=1 - -1 + -2 (8)Solving the system (4) and

20、applying (5) results in:R(q-1)=-1 -2 (9)S(q-1) = 1 - 1q-1 + 1q-2 (10)T(q-1)=6.3423 -1 +-2 (11)System response to step and perturbations rejection are presented in the figure below:4 Virtual experimentThe experiment presented in this paper is a part of the laboratory activity of “Identification and C

21、ontrol Systems, course dedicated to the forth year students from the UPB-Control and Computer Science Faculty. The laboratory purpose is to train students in practical activity of system identification and numerical process control. During this part of the practical activity the students have the po

22、ssibility to control the level fluid from a tank by testing different type of numerical algorithms. In the figure IO is presented an image of the level control didactical platform. The lab activity. in the virtual version proposed.is structures in two parts. In the first part students practice the o

23、pen loop identification of the studied process, the presence of the students in the laboratory being necessary. The second part of the lab consists in numeric control of the identified process by testing various algorithms. For this section of the lab the prescnce of the students in the laboratory i

24、s not compulsory because the activity could be undertaken from any place with an internet connection. The virtual experment is formed from two components: a hardware and o software structure.4.1 Hardware structureThe base of this experiment is a hardware structure composed from:- an acquisition boar

25、d with analog to digital and digital to analog converters which acquires and send data to the process;- a PC compatible IBM with a Pentium II 350 MHz processor and 64 Mbytes RAM, which contain the acquisition board;- a video camera for real-time images broadcasting;International Railway Journal- a H

26、P LH3 server for Internet connection4.2 Software structureThe software structure is formed by to subsystems which allow access to the didactical platform local as well as distant - using the Internet as it may be observe in figure 10: The first subsystem represents a program written in Lab Windows/C

27、VI. It runs on the computer connected to the process and allows direct local access to the platform. This application represents a gate for the data that leave and come to the process.The second subsystem is a client-server application which assures distant interaction with the process.4. Local acce

28、ssThe program for local access was created using Lab Windows/CVI and it is an independent application that allows local access to the platform independent towards the distant access.This program makes the connection with the process acquiring and sending data from respectively to the process. The da

29、ta is sent further on to thc clients applications via the Internet.The local application assures a fcw operations over the platform such as:- reference changing;- automat/manual regime changing;- manual command;- algorithms configuration.For an easy use, the local program has a graphical user interf

30、ace (GUI) presented bellow.4.2.2 Distance accessThe base of the distant communication is a clientserver application. There are some key words that define such an architecture which will be described as follows:Server - entity that accepts requests and offers services to the clients connected to him

31、5. For this experiment the server is a program written in Java which runs on HP LH3 server machine. The server connects itself to the local application and become a proxy for the clients that connect to him. The server is a multithreading program that runs in background and sends periodically data a

32、bout the state of the process to the clients. Theoretically it can accept an infinite number of client connections but the number is limited by software to maintain a certain level of performances.Client - software entity which sends requests to the server and process the data received as answer 5.

33、For this experiment the client is a Java applet incorporated in a web page. Next to the applet there arc presented live images with the process evolution.International Railway Journal5. ConclusionsIn this paper a level control system with distant access option that allows monitoring and updating of

34、important parameters of the system is presented. There are presented the base theory for level control and the hardware and software structures for distant access via the Internet.A comparative study for performance evolution of different control algorithms can be realized.The system has been create

35、d as an educational tool through the students can experiment distant access to a technological platform. 国际铁路杂志液位控制系统【标题】国际铁路杂志【出版日期】 2021【编号】三月期离子马太，杜米特鲁·波佩斯库，西普里安卢浦， llie Luican控制与计算机科学系 - 布加勒斯特Politehnica大学Splaiul Independentei nr.313 ， sector6 ， Bucurcsti ，罗马尼亚电子邮件： INION 3家RO1液位控制系统所述流体流是由

36、一个电控的盛况。该过程的输入是用介于0和10 V值的电压输出是由一个超声波换能器测量的流体的水平。该过程是非线性的，但它是近似与周围的代表点功能的线性数学模型。这是利用样本时间段Te = 5秒得到的近似数学模型。重要的是要提的是设计一个数字调节器必须遵循三个步骤是很重要的：- 计算离散模型;- 性能标准;- 计算适当的控制算法在这种情况下为电平控制被用来在未来的数字控制算法： RST和PID与它的两个变种， PIDL和PID2 。这些算法有不同的表演，让学生们将有时机对它们进行比拟。首先，将介绍在RST算法和比纸张将继续与将在结构化分析和比拟，以第一个PID运算。2 PID算法数字PID算法来

37、自与所有适当的采样周期采样的连续PID算法。数字PID控制器只适合用带或不带纯滞后二阶传递函数建模的流程。值得一提的是一些数字PID控制器不具有持续等效。2.1 PIDL数值算法让我们考虑的算法：连续PID控制器的传递函数，该算法被指定由四个参数：的K - 比例作用;TI - 积分作用;TD - 微分作用;TD - 过滤派生诉讼。有许多方法可以用来采样这个算法产生的以相同的形式的数字控制器。由于可以看出， PIDL数字调节器还具有四个参数 RTH R1 R2 ， S1作为它的连续形式。该算法可以是国际铁路杂志结构采用了第一种形式，如果T Q- 1 = R Q- 1 。这是很容易看到， PIDL

38、是自由度算法。在闭环其中参加参考RT 与输出y i该传递函数，其中，P Q- 1限定的极点在闭环需求确实定的性能对扰动抑制。 PIDL算法由多项式R Q-1 ，该改变的性能引入闭环新的零。这种负面影响将被局部地消除PID2算法。在已经确定的RST的算法现在是很容易计算的PIDL参数如果拒绝表演定义为P Q-1不改变，因为多项式R Q-1 和S Q-1将相同的3。因为它可能会在未来的图形应遵守的PIDL算法的perforinanccs处于劣势的RST算法。2.2 PID2数值算法因为它上面的PIDL调节注意到引入闭环补充零多项式T Q-1 = R Q -1。那些零影响专门的控制性能，因为它是观察

39、到的图7中。这个缺点可以被局部地消除，如果多项式T Q-1 被选择。以这种方式保证在固定的制度一整体的传递函数3。结构为RST的PID2数值算法的结构原理图呈现波纹管。该算法保证了优异的性能比拟PIDL ，因为它可能会在未来的图形可以看出。3 RST数值算法对于任何控制系统中定义了两个重要目标：1 。参考的跟踪;2 。扰动的抑制;一个经典的控制结构。只有一个自由程度图2具有很大的缺点，即它不能满足这两个目标定义如上。因为它可能会注意到命令不被参考和测量差分思考。这意味着，对于扰动抑制定义了一些演出可能限制基准的跟踪。如果多项式R Q- 1 ，其中过滤器的引用，被替换为另一个多项式T Q- 1

40、，它会导致一个RST结构与接受的跟踪和排斥不同场次2自由程度 3 4 。在RST数值算法的块结构呈现下列图：的闭环传递函数是：表演拒绝通过由采样二阶连续系统获得的特征多项式P Q-1成立。多项式R Q-1 和S Q-1从解决下一多项式方程的结果：A Q-1 S Q-1 + Q -dB的第q- 1R Q-1 = P Q-1 4的跟踪性能进行由T Q-1和参考滤波的控制。多项式T Q- 1 的选择，使闭环国际铁路杂志转移是酉输出将按照规定的参考Y * 。T Q-1 = P Q-1 5跟踪动力学可以通过多项式进行修改Bm的第q- 1和Am Q-1该过滤器的参考：多项式BM和AM，从采样二阶连续系统也造成。因此选择的参数和将确定的跟踪性能4。在RST控制结构与过滤引用的方框图列示如下：该系统的跟踪性能是由一个二阶系统选择， I = 0.25 ， = 0.99结果为：拒绝演出是由一个二阶系统还给出为：n = 2.5 ， = 0.8 。为两极分配方法的特征多项式，将成为：P Q-1 = 1 - 1.2807q -1 + 0.4493q - 28求解系统4和应用5的结果如下：R Q-1 = 5.1232 - 6.5q -1 + 2.0516q - 29S Q-1 = 1 - 11.432q -1 + 0.4321q - 210