Calling Matlab from a Scipt

It is possible to call matlab from a script to perform some calculation needed in the script. The following is a little example demonstrating how this is done.

The example is a simple truss example where I am trying to determine the value of the parameter A needed to hit a target displacement. I start off with setting some variables, my target displacement, a tolerance, and two bounding values on my parameter of interest Amin and Amax. I then define a proc getA(). In this procedur I write the two bounding values to a file, I invoke a matlab script to determine a new A, and then I read the result from a file. Next I create my truss model and the analysis and perform a single analysis step Then I iterate until i have converged on a solution or hit a bounding value. Finally I print a message indicating succcess or failure

<source lang="tcl">

2. set some variables

set targetDisp 1.2; # target displacement set tol 0.01; # tolerance

set Amin 1.0 set Amax 10.0

2. define a procedure: getA() which calls matlab script b.m in which our new A is computed

proc getA {Amin Amax} {

   set fileID [open data1 w]
   puts $fileID "$Amin $Amax"
   close $fileID

   if {[catch {exec matlab -r "b; quit"}]} {

puts "Ignore this $msg"

   }

   set fileIN [open data2 r]
   set A [read $fileIN]
   set A [expr ($Amin + $Amax)/2.0]

}

set A [getA $Amin $Amax]

2. create the model & perform one analysis step

model BasicBuilder -ndm 2 -ndf 2

node 1 0.0 0.0 node 2 144.0 0.0 node 3 168.0 0.0 node 4 72.0 96.0

fix 1 1 1 fix 2 1 1 fix 3 1 1 uniaxialMaterial Elastic 1 3000

element truss 1 1 4 [expr 2.0*$A] 1 element truss 2 2 4 $A 1 element truss 3 3 4 $A 1

timeSeries Constant 1 pattern Plain 1 1 {

   load 4 100 -50

}

system BandSPD numberer RCM constraints Plain integrator LoadControl 1.0 algorithm Linear analysis Static

analyze 1

2. iterate until convergence is reached, or failure

set xDisp [nodeDisp 4 1] set done 0

while {$done == 0} {

   if {$xDisp > $targetDisp} {

set Amin $A

   } else {

set Amax $A

   }

       set diffA [expr $Amax-$Amin]
   if {$diffA  < $tol} {

set done 2

     break
   }

   set A [getA $Amin $Amax]
   setParameter -value $A -ele A
   
   analyze 1
   set xDisp [nodeDisp 4 1]

   set diff [expr abs($xDisp - $targetDisp)]
   if {$diff < $tol} {

set done 1

   }

   puts "$A $xDisp"

}

2. print success or failure

if {$done == 1} {

   puts "SUCCESS: A = $A gives Displacement of $xDisp versus target of $targetDisp"

} else {

   puts "FAILURE: Hit limit A = $A gives Displacement of $xDisp versus target of $targetDisp"

}