In the documentation ClosedLoopResponsesWithAPIDController, There is a very nice block diagram. I want to create my own block diagrams similar to this. I clicked on the diagram and pressed "command-shift-E" to show the underlying expression. I found the expression below. While this is explicit and reasonably easy to modify and extend, For really big graphs (which I have) it will rapidly become too difficult to manage by hand. I wonder if there is an easier way to produce such graphics? Is there a tool I just don't know about for drawing and / or automatically laying out such things?
Graph[{1, 2, 3, 4, 5, 6, 7, 8,
9}, {{{1, 2}, {2, 3}, {3, 4}, {4, 5}, {5, 6}, {6, 7}, {6,
2}, {8, 4}, {9, 6}}, Null}, {
EdgeLabels -> {DirectedEdge[8, 4] -> Placed[
Style["+", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], {1, {-0.8, 0.2}}],
DirectedEdge[3, 4] -> Placed[
Style["+", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], 0.9],
DirectedEdge[9, 6] -> Placed[
Style["+", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], {1, {-0.8, 0.2}}],
DirectedEdge[5, 6] -> Placed[
Style["+", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], 0.9],
DirectedEdge[6, 2] -> Placed[
Style["-", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], {0.965, {-0.7, 0}}],
DirectedEdge[1, 2] -> Placed[
Style["+", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], 0.9]},
EdgeShapeFunction -> {},
EdgeStyle -> {
GrayLevel[0, 1]}, Epilog -> {
Text[
Style["u", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], {2.5, 0.1}]},
ImageSize -> 500,
VertexCoordinates -> {{0., 0.}, {0.7, 0.}, {1.8, 0.}, {2.9,
0.}, {3.9, 0.}, {5., 0.}, {5.6, 0.}, {
2.9, 0.66}, {5., 0.66}}, VertexLabels -> {1 -> Placed[
Style["r", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], Center], 6 -> Placed[
Style["", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], Center], 9 -> Placed[
Style["m", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], Center], 2 -> Placed[
Style["", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], Center], 8 -> Placed[
Style["d", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], Center], 7 -> Placed[
Style["y", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], Center], 3 -> Placed[
Style["PID controller", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], Center], 4 -> Placed[
Style["", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], Center], 5 -> Placed[
Style["linear system", {FontFamily -> "Helvetica",
GrayLevel[0, 1], 12}], Center]},
VertexShapeFunction -> {
3 -> "Square", 4 -> "Circle", 7 -> "Square",
5 -> "Square", 9 -> "Square", 1 -> "Square", 6 ->
"Circle", 8 -> "Square", 2 -> "Circle"},
VertexSize -> {8 -> {0.1, 0.1}, 3 -> {0.6, 0.2},
2 -> {0.125, 0.125}, 1 -> {0.1, 0.1}, 9 -> {0.1, 0.1},
4 -> {0.125, 0.125}, 6 -> {0.125, 0.125},
5 -> {0.6, 0.2}, 7 -> {0.1, 0.1}},
VertexStyle ->
{2 -> Directive[GrayLevel[1],
EdgeForm[{GrayLevel[0], AbsoluteThickness[1]}]],
1 -> Directive[Opacity[0], EdgeForm[{}]],
8 -> Directive[Opacity[0], EdgeForm[{}]],
7 -> Directive[Opacity[0], EdgeForm[{}]],
5 -> Directive[GrayLevel[1],
EdgeForm[{GrayLevel[0], AbsoluteThickness[1]}]],
6 -> Directive[GrayLevel[1],
EdgeForm[{GrayLevel[0], AbsoluteThickness[1]}]],
4 -> Directive[GrayLevel[1],
EdgeForm[{GrayLevel[0], AbsoluteThickness[1]}]],
9 -> Directive[Opacity[0], EdgeForm[{}]],
3 -> Directive[GrayLevel[1],
EdgeForm[{GrayLevel[0], AbsoluteThickness[1]}]]
}}]
