MATLAB: Is it possible to allow switching between cartesian grid and plot type grids in the Control System Toolbox 8.3 (R2009a)

Control System Toolbox

I am unable to select switching between the cartesian and plot type grids in the Control System toolbox. Currently, both the GRID and SGRID functions place a zeta-wn grid on the root locus.

I would like to be able to have the functionality to allow the Cartesian grid, which establishes lines of constant settling time and peak overshoot. For example:

h = tf([2 5 1],[1 2 3]);
rlocus(h)
sgrid

Yields the same result as:

h = tf([2 5 1],[1 2 3]);
rlocus(h)
grid

Best Answer

The ability to do switch between cartesian and plot type grids using SGRID or GRID is not available in the Control System Toolbox 8.3 (R2009a).

To work around this issue, you can superimpose horizontal and vertical lines on the plot as given below. The following example is for vertical grid lines and can be extended to horizontal lines as well.

ax = gca;
rlocus(zpk([],[-2,-3,-5],1))
hold on
yminmax = get(ax,'ylim'); % min max of vertical grid lines
xdata = get(ax,'xtick'); % Location of x grid lines eg xdata = [1,2,3,4]
lxdata = [];
lydata = [];
for ct = 1:length(xdata)
lxdata = [lxdata; xdata(ct)*ones(2,1); NaN];
lydata = [lydata; yminmax(:); NaN];
end
vertgridline = line(lxdata,lydata,'color',[.8,.8,.8],'linestyle',':');
% to delete these gridlines 
%remove grid lines
delete(vertgridline)

Related Solutions

MATLAB: How to show the major grid lines as dotted and the minor grid lines as solid in MATLAB 7.8 (R2009a)

This issue has to do with the fact that major grid lines overlap with the minor grid lines at the points with the major ticks. When you specify the 'MinorGridLIneStyle' as solid '-', and the 'GridLineStyle' as dashed '--', the dashed major grid lines are plotted on top of the solid minor grid lines and thus cannot be seen.

The ability to change this behavior of the grid lines is currently not available in MATLAB. To work around this issue, you can manually draw the solid minor grid lines using the PLOT command as outlined in the example below:

% generate a plot with the dashed major grid lines
figure
plot(1:10)
grid on
set(gca,'GridLineStyle','--')
axis([0 10 0 10]) 
% specify the minor grid vector
xg = 0:0.25:10;
% specify the Y-position and the height of minor grids
yg = [0 10];
xx=repmat(xg,[2 1]);
yy=repmat(yg',size(xg)');
% get rid of the elements in the xx vector corresponding to the major grid
% lines
xx(:,1:4:length(xg))=[];
yy(:,1:4:length(xg))=[];
% plot the minor grid lines
hold on
h_minorgrid = plot(xx,yy,'k');

MATLAB: Is there a difference in functionality in the selection/editing of Line Properties in Bode and Transfer funtion plots in the Control System Toolbox 7.0 (R2006a)

This enhancement has been incorporated in Control System Toolbox 8.2 (R2008b). For previous product releases, read below for any possible workarounds:

The reason for the loss of functionality to edit the Bode and Transfer function Line properties using the Figure Toolbar is the new organization structure of the graphics objects. While in previous releases the Line Objects were direct children of the respective Axes, in the current release, the Line Objects are children of a HGGROUP object, which in turn is the child of the Axes.

To access the Line object properties from the command line, refer to the sample MATLAB code shown below:

clear all
close all
clc
g = tf([1 0.1 7.5],[1 0.12 9 0 0]);
bode(g)
h.axes = get(gcf, 'Children');
h.axes1_children = get(h.axes(1), 'Children');
h.axes1_grandchildren = get(h.axes1_children(1), 'Children');
set(h.axes1_grandchildren, 'LineWidth', 2)

Best Answer

Related Solutions

MATLAB: How to show the major grid lines as dotted and the minor grid lines as solid in MATLAB 7.8 (R2009a)

MATLAB: Is there a difference in functionality in the selection/editing of Line Properties in Bode and Transfer funtion plots in the Control System Toolbox 7.0 (R2006a)

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