(精品)chapter2-2 (2).ppt

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1、Three basic formsG1G2G2G1G1G2G1G2G1G2G1G1G21+cascadeparallelfeedback2.6 block diagram models(dynamic)2.6.2.2 block diagram transformations behind a block x1yGx2x1x2yGGAhead a blockx1x2yGx1yGx21/G1.Moving a summing point to be:2.6 block diagram models(dynamic)2.Moving a pickoff point to be:behind a b

2、lockGx1x2yGx1x2y1/Gahead a blockGx1x2yGGx1x2y2.6 block diagram models(dynamic)3.Interchanging the neighboringSumming pointsx3x1x2yx1x3yx2Pickoff pointsyx1x2yx1x22.6 block diagram models(dynamic)4.Combining the blocks according to three basic forms.Notes:1.Neighboring summing point and pickoff point

3、can not be interchanged！2.The summing point or pickoff point should be moved to the same kind！3.Reduce the blocks according to three basic forms！Examples:Moving pickoff pointG1G2G3G4H3H2H1abG41G1G2G3G4H3H2H1Example 2.17G2H1G1G3Moving summing pointMove to the same kind G1G2G3H1G1Example 2.18G1G4H3G2G

4、3H1Disassembling the actionsH1H3G1G4G2G3H3H1Example 2.19Chapter 2 mathematical models of systems2.7 Signal-Flow Graph Models Block diagram reduction is not convenient to a complicated system.Signal-Flow graph is a very available approach to determine the relationship between the input and output var

5、iables of a sys-tem,only needing a Masons formula without the complex reduc-tion procedures.2.7.1 Signal-Flow Graph only utilize two graphical symbols for describing the relation-ship between system variables。Nodes,representing the signals or variables.Branches,representing the relationship and gain

6、Between two variables.Gb2.7 Signal-Flow Graph ModelsExample 2.20:x4x3x2x1x0hfgedca2.7.2 some terms of Signal-Flow GraphPath a branch or a continuous sequence of branches traversing from one node to another node.Path gain the product of all branch gains along the path.2.7 Signal-Flow Graph Models Loo

7、p a closed path that originates and terminates on the same node,and along the path no node is met twice.2.7.3 Masons gain formulaLoop gain the product of all branch gains along the loop.Touching loops more than one loops sharing one or more common nodes.Non-touching loops more than one loops they do

8、 not have a common node.2.7 Signal-Flow Graph Models 2.7 Signal-Flow Graph Models Example 2.21x4x3x2x1x0hfgedcba2.7 Signal-Flow Graph Models2.7.4 Portray Signal-Flow Graph based on Block Diagram Graphical symbol comparison between the signal-flow graph and block diagram:andBlock diagramSignal-flow g

9、raphG(s)G(s)G1G4G32.7 Signal-Flow Graph ModelsExample 2.22C(s)R(s)G1G2H2H1G4G3H3E(s)X1X2X3R(s)C(s)H2H1H3X1X2X3E(s)1G22.7 Signal-Flow Graph Models R(s)H21G4G3G2G11C(s)H1H3X1X2X3E(s)2.7 Signal-Flow Graph ModelsG1G2+C(s)R(s)E(s)Y2Y1X1X21-1 1-1-1-1-1 11G1G21R(s)E(s)C(s)X1X2Y2Y1Example 2.232.7 Signal-Flow Graph Models 1-1 1-1-1-1-1 11G1G21R(s)E(s)C(s)X1X2Y2Y17 loops:3 2 non-touching loops:2.7 Signal-Flow Graph Models 1-1 1-1-1-1-1 11G1G21R(s)E(s)C(s)X1X2Y2Y1Then:4 forward paths:2.7 Signal-Flow Graph ModelsWe have