Tweeted twitter.com/StackMma/status/1048770024633241600 occurred Oct 7 '18 at 3:00 4 tag update | link edited Oct 5 '18 at 16:21 ercegovac 73766 silver badges1616 bronze badges 3 edited body edited Oct 4 '18 at 6:25 Henrik Schumacher 68.4k55 gold badges9898 silver badges191191 bronze badges Consider a linear system . bandPassOL[omega_, k_] := Module[{a, b, c, d}, a = {{0, -omega}, {omega, 0}}; b = {{omega*k}, {0}}; c = {{1, 0}, {0, 1}}; d = {{0}, {0}}; StateSpaceModel[{a, b, c, d}] ](*Module*) osg2SSOL = SystemsModelParallelConnect[bandPassOL[omega1, k1], bandPassOL[omega2, k2], All, None]; osg2SSCL = SystemsModelFeedbackConnect[osg2SSOL, {{1, 1}, {3, 1}}];  If I want to plot frequency characteristic of such a SIMO system using BodePlot BodePlot[osg2SSCL /. {k1 -> 0.5, k2 -> 0.5, omega1 -> 2 Pi 50, omega2 -> 2 Pi 500}, {10^2, 10^4}, GridLines -> Automatic, PlotLayout -> "Magnitude"]  I get the following, incorrect result. If, on the other hand, I wrap the system with TransferFunctionModel and send it to BodePlot BodePlot[TransferFunctionModel[osg2SSCL, s] /. {k1 -> 0.5, k2 -> 0.5, omega1 -> 2 Pi 50, omega2 -> 2 Pi 500}, {10^2, 10^4}, GridLines -> Automatic, PlotLayout -> "Magnitude"]  I get the correct result. If I vary coefficients k1 and k2 from 0.01 to 1, the difference between outputs varies. For small values of k1 and k2, the difference is large and easy to spot, but as k1 and k2 approach 1 the difference gets smaller and easy to miss. I've tried several other systems and seamsseems that the errors starts to appear only if the system has more than 3 outputs. Though this was far from extensive verification. Should this be considered a bug? The problem persist through the following versions of MMA "11.2.0 for Microsoft Windows (64-bit) (September 11, 2017)" "10.2.0 for Microsoft Windows (64-bit) (July 28, 2015)" "11.3.0 for Microsoft Windows (64-bit) (March 7, 2018)" Consider a linear system . bandPassOL[omega_, k_] := Module[{a, b, c, d}, a = {{0, -omega}, {omega, 0}}; b = {{omega*k}, {0}}; c = {{1, 0}, {0, 1}}; d = {{0}, {0}}; StateSpaceModel[{a, b, c, d}] ](*Module*) osg2SSOL = SystemsModelParallelConnect[bandPassOL[omega1, k1], bandPassOL[omega2, k2], All, None]; osg2SSCL = SystemsModelFeedbackConnect[osg2SSOL, {{1, 1}, {3, 1}}];  If I want to plot frequency characteristic of such a SIMO system using BodePlot BodePlot[osg2SSCL /. {k1 -> 0.5, k2 -> 0.5, omega1 -> 2 Pi 50, omega2 -> 2 Pi 500}, {10^2, 10^4}, GridLines -> Automatic, PlotLayout -> "Magnitude"]  I get the following, incorrect result. If, on the other hand, I wrap the system with TransferFunctionModel and send it to BodePlot BodePlot[TransferFunctionModel[osg2SSCL, s] /. {k1 -> 0.5, k2 -> 0.5, omega1 -> 2 Pi 50, omega2 -> 2 Pi 500}, {10^2, 10^4}, GridLines -> Automatic, PlotLayout -> "Magnitude"]  I get the correct result. If I vary coefficients k1 and k2 from 0.01 to 1, the difference between outputs varies. For small values of k1 and k2, the difference is large and easy to spot, but as k1 and k2 approach 1 the difference gets smaller and easy to miss. I've tried several other systems and seams that the errors starts to appear only if the system has more than 3 outputs. Though this was far from extensive verification. Should this be considered a bug? The problem persist through the following versions of MMA "11.2.0 for Microsoft Windows (64-bit) (September 11, 2017)" "10.2.0 for Microsoft Windows (64-bit) (July 28, 2015)" "11.3.0 for Microsoft Windows (64-bit) (March 7, 2018)" Consider a linear system . bandPassOL[omega_, k_] := Module[{a, b, c, d}, a = {{0, -omega}, {omega, 0}}; b = {{omega*k}, {0}}; c = {{1, 0}, {0, 1}}; d = {{0}, {0}}; StateSpaceModel[{a, b, c, d}] ](*Module*) osg2SSOL = SystemsModelParallelConnect[bandPassOL[omega1, k1], bandPassOL[omega2, k2], All, None]; osg2SSCL = SystemsModelFeedbackConnect[osg2SSOL, {{1, 1}, {3, 1}}];  If I want to plot frequency characteristic of such a SIMO system using BodePlot BodePlot[osg2SSCL /. {k1 -> 0.5, k2 -> 0.5, omega1 -> 2 Pi 50, omega2 -> 2 Pi 500}, {10^2, 10^4}, GridLines -> Automatic, PlotLayout -> "Magnitude"]  I get the following, incorrect result. If, on the other hand, I wrap the system with TransferFunctionModel and send it to BodePlot BodePlot[TransferFunctionModel[osg2SSCL, s] /. {k1 -> 0.5, k2 -> 0.5, omega1 -> 2 Pi 50, omega2 -> 2 Pi 500}, {10^2, 10^4}, GridLines -> Automatic, PlotLayout -> "Magnitude"]  I get the correct result. If I vary coefficients k1 and k2 from 0.01 to 1, the difference between outputs varies. For small values of k1 and k2, the difference is large and easy to spot, but as k1 and k2 approach 1 the difference gets smaller and easy to miss. I've tried several other systems and seems that the errors starts to appear only if the system has more than 3 outputs. Though this was far from extensive verification. Should this be considered a bug? The problem persist through the following versions of MMA "11.2.0 for Microsoft Windows (64-bit) (September 11, 2017)" "10.2.0 for Microsoft Windows (64-bit) (July 28, 2015)" "11.3.0 for Microsoft Windows (64-bit) (March 7, 2018)" 2 content update edited Oct 3 '18 at 23:53 ercegovac 73766 silver badges1616 bronze badges Consider a linear system . bandPassOL[omega_, k_] := Module[{a, b, c, d}, a = {{0, -omega}, {omega, 0}}; b = {{omega*k}, {0}}; c = {{1, 0}, {0, 1}}; d = {{0}, {0}}; StateSpaceModel[{a, b, c, d}] ](*Module*) osg2SSOL = SystemsModelParallelConnect[bandPassOL[omega1, k1], bandPassOL[omega2, k2], All, None]; osg2SSCL = SystemsModelFeedbackConnect[osg2SSOL, {{1, 1}, {3, 1}}];  If I want to plot frequency characteristic of such a SIMO system using BodePlot BodePlot[osg2SSCL /. {k1 -> 0.5, k2 -> 0.5, omega1 -> 2 Pi 50, omega2 -> 2 Pi 500}, {10^2, 10^4}, GridLines -> Automatic, PlotLayout -> "Magnitude"]  I get the following, incorrect result. If, on the other hand, I wrap the system with TransferFunctionModel and send it to BodePlot BodePlot[TransferFunctionModel[osg2SSCL, s] /. {k1 -> 0.5, k2 -> 0.5, omega1 -> 2 Pi 50, omega2 -> 2 Pi 500}, {10^2, 10^4}, GridLines -> Automatic, PlotLayout -> "Magnitude"]  I get the correct result. If I vary coefficients k1 and k2 from 0.01 to 1, the difference between outputs varies. For small values of k1 and k2, the difference is large and easy to spot, but as k1 and k2 approach 1 the difference gets smaller and easy to miss. I've tried several other systems and seams that the errors starts to appear only if the system has more than 3 outputs. Though this was far from extensive verification. Should this be considered a bug? I have two version of MMA installed and theThe problem exists on bothpersist through the following versions. of MMA "11.2.0 for Microsoft Windows (64-bit) (September 11, 2017)" "10.2.0 for Microsoft Windows (64-bit) (July 28, 2015)" "11.3.0 for Microsoft Windows (64-bit) (March 7, 2018)" Consider a linear system . bandPassOL[omega_, k_] := Module[{a, b, c, d}, a = {{0, -omega}, {omega, 0}}; b = {{omega*k}, {0}}; c = {{1, 0}, {0, 1}}; d = {{0}, {0}}; StateSpaceModel[{a, b, c, d}] ](*Module*) osg2SSOL = SystemsModelParallelConnect[bandPassOL[omega1, k1], bandPassOL[omega2, k2], All, None]; osg2SSCL = SystemsModelFeedbackConnect[osg2SSOL, {{1, 1}, {3, 1}}];  If I want to plot frequency characteristic of such a SIMO system using BodePlot BodePlot[osg2SSCL /. {k1 -> 0.5, k2 -> 0.5, omega1 -> 2 Pi 50, omega2 -> 2 Pi 500}, {10^2, 10^4}, GridLines -> Automatic, PlotLayout -> "Magnitude"]  I get the following, incorrect result. If, on the other hand, I wrap the system with TransferFunctionModel and send it to BodePlot BodePlot[TransferFunctionModel[osg2SSCL, s] /. {k1 -> 0.5, k2 -> 0.5, omega1 -> 2 Pi 50, omega2 -> 2 Pi 500}, {10^2, 10^4}, GridLines -> Automatic, PlotLayout -> "Magnitude"]  I get the correct result. If I vary coefficients k1 and k2 from 0.01 to 1, the difference between outputs varies. For small values of k1 and k2, the difference is large and easy to spot, but as k1 and k2 approach 1 the difference gets smaller and easy to miss. I've tried several other systems and seams that the errors starts to appear only if the system has more than 3 outputs. Though this was far from extensive verification. Should this be considered a bug? I have two version of MMA installed and the problem exists on both versions. "11.2.0 for Microsoft Windows (64-bit) (September 11, 2017)" "10.2.0 for Microsoft Windows (64-bit) (July 28, 2015)" Consider a linear system . bandPassOL[omega_, k_] := Module[{a, b, c, d}, a = {{0, -omega}, {omega, 0}}; b = {{omega*k}, {0}}; c = {{1, 0}, {0, 1}}; d = {{0}, {0}}; StateSpaceModel[{a, b, c, d}] ](*Module*) osg2SSOL = SystemsModelParallelConnect[bandPassOL[omega1, k1], bandPassOL[omega2, k2], All, None]; osg2SSCL = SystemsModelFeedbackConnect[osg2SSOL, {{1, 1}, {3, 1}}];  If I want to plot frequency characteristic of such a SIMO system using BodePlot BodePlot[osg2SSCL /. {k1 -> 0.5, k2 -> 0.5, omega1 -> 2 Pi 50, omega2 -> 2 Pi 500}, {10^2, 10^4}, GridLines -> Automatic, PlotLayout -> "Magnitude"]  I get the following, incorrect result. If, on the other hand, I wrap the system with TransferFunctionModel and send it to BodePlot BodePlot[TransferFunctionModel[osg2SSCL, s] /. {k1 -> 0.5, k2 -> 0.5, omega1 -> 2 Pi 50, omega2 -> 2 Pi 500}, {10^2, 10^4}, GridLines -> Automatic, PlotLayout -> "Magnitude"]  I get the correct result. If I vary coefficients k1 and k2 from 0.01 to 1, the difference between outputs varies. For small values of k1 and k2, the difference is large and easy to spot, but as k1 and k2 approach 1 the difference gets smaller and easy to miss. I've tried several other systems and seams that the errors starts to appear only if the system has more than 3 outputs. Though this was far from extensive verification. Should this be considered a bug? The problem persist through the following versions of MMA "11.2.0 for Microsoft Windows (64-bit) (September 11, 2017)" "10.2.0 for Microsoft Windows (64-bit) (July 28, 2015)" "11.3.0 for Microsoft Windows (64-bit) (March 7, 2018)" 1 asked Oct 3 '18 at 23:21 ercegovac 73766 silver badges1616 bronze badges