1、1（1）The advantages and disadvantages between feedback control and forward control 反馈控制与前馈控制的优缺点 Feedback control： advantages Corrective action is taken regardless of the source of the disturbance Reduces sensitivity of the controlled variable to disturbances and changes in the process disadvantage a
2、. No corrective action occurs until after the disturbance has upset the process b. Very oscillatory responses or even instability Feedforward control： advantages Corrective for disturbance before it upsets the process disadvantage a. must be able to measure the disturbance b. no corrective action fo
3、r unmeasured disturbance 2（8）Advantages of on-off controller and its application situation Advantages: simple and cheap Application: used in residential heating and domestic refrigerators; limited use in process control due to continuous cycling of controlled variables. 3（12）Desirable controller fea
4、tures. Stable; adequate disturbance rejection; quick responding; good set-point tracking; steady-state errors are eliminated. 4（20）when should predictive control be used? Processes are difficult to control with standard PID controller, such as long time constants Among controls have dynamic interact
5、ion Limits on process and manipulated variables are important for normal control 5（12）List Guidance for Common Control Loop such as flow rate, liquid level, gas pressure, temperature and composition.【本题可不看】 For flow rate, PI control is generally used with intermediate values of the controller gain;
6、For liquid level, integral control action is often used, while derivative action is not normally used ; For gas pressure, PI controller are normally used with only a small amount of integral control action; For temperature, PID controllers are commonly employed to provide quicker than the PI control
7、lers; For composition, it is generally the same as temperature. 6（16）List the advantages and disadvantages of Smith Predictor. Advantages: a. Improve the performance of system containing time delays b. Be beneficial for handling disturbance. Disadvantages: a. It is model-based; that is, a dynamic mo
8、del of process is required 1（2）An isothermal, irreversible reaction A k B takes place in the liquid phase in a constant-volume reactor. The mixing is not perfect. Observations of flow patterns indicates that a two-tank system with back mixing as shown in the figure below, should approximate the impe
9、rfect mixing. CA0、CA1、CA2 is component of initial F, V1 and V2 respect. Assume F and FR are constant. Write the equation describing the system. According to the conservation of mass（物料守恒） 2212212011)()()()(AARARAARARAAFCCFCFFdtCVdCFFCFCFdtCVdAfter the simplification, we can get : )()()()()(212212101
10、1AARAAARAAACCFFdtCVdCCFCCFdtCVd2（8）If the input Ym to a PI controller changes stepwise( Ym(s)=2/s ) and the controller output changes initially as in the figure below, what are the values of the controller gain and integral time? )11()( )()(1)()( *0*sKsEspdtteteKptpIctIc Thus 2.1262IccKKThen the con
11、troller gain Kc is 3 and integral time I=5 3（12）A process has the transfer function 12)( 2.0 sesG s . Compare the PI controller settings for the following design approach. （1）direct synthesis method (c=0.2) （2）direct synthesis method (c=1) （3）ITAE performance index( disturbance ) （4）ITAE performance
12、 index( set point ) （1）（2）Solve For 1)( sKesG s , KcK= c, I Thus, =1、=0.2、K=2 Then, either c=0.2 or c=1, I=1; Kc= )(2 c, when c=0.2, Kc=1.25 and when c=1, Kc=0.417 （3）Solve According to )977.0,859.0()( BAKKAY cB , we can work out that:Kc=2.069；According to )680.0,674.0()( BAAYIB , we can work out th
13、at: I=0.497 （4）Solve According to )916.0,586.0()( BAKKAY cB , we can work out that:Kc= ；According to )/( BAI , we can work out that: I=。 4（16）The cascade control system is shown in the figure below. (1) Draw the block diagram of the system; (2) Explain why the cascade control system can correct the
14、disturbances in fuel gas supply pressure. （1）The diagram is below （2）The secondary control loop lies more near the disturbances than the primary loop, so it is respond faster than the primary loop. Therefore, when a disturbance in fuel gas supply pressure, the secondary control loop can correct the
15、disturbance as soon as possible rather than the situation that the disturbance upsets the process. 5（16）The cascade control system is shown in the figure below, where D1 and are variables. Develop the transfer function for Y1/D2, Y1/Ysp1,Y2/Ysp2 and Y1/D1. Solve： Suppose that D1=Ysp1=0 1212122221211
16、112211222222222111 mvppccmpvc dpmmcspcvpdpGGGGGGGGGGGGDYYGEYGEGYEEGGGDGYYGY121212221212111 1mppVccmpVcmppvccsp GGVGGGGVGGKGGGGGYY 2222221 1mpVcpvcsp GVGGGGGYY 11221222222111 1 )1(mppvccmpvcmpvcdGGGGGGGGGGGGGGGDY 6（作业2.1）建立模型。 7（作业8.2） (a) show how to obtain this transfer function with a parallel arr
17、angement of two much simpler function in the following figure. 1)(1)()(12112211 s KKsKKsKsE sP (b) Find expression for K1, K2 and I that can be used to obtain desired values of Kc, D and (c) Verify the relations for Kc =3, D =2, =0.1 8（例12.1） )15)(110( 2 ss eG s ，c=1、3、10 (a) The process model is perfect (b) The model gain is incorrect, 9.0 K , instead of K=2 【只需记住】 2121212121 ,)1)(1(）（ DIccs KKssKesG
