ADDED   mttroot/mtt/lib/comp/simple/PS_eqn.m
Index: mttroot/mtt/lib/comp/simple/PS_eqn.m
==================================================================
--- /dev/null
+++ mttroot/mtt/lib/comp/simple/PS_eqn.m
@@ -0,0 +1,56 @@
+function  structure = PS_eqn(name,bond_number,bonds,direction,cr,args, ...
+    structure,eqnfile);
+% PS_eqn - equations for a power sensor
+% 
+%     %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+%     %%%%% Model Transformation Tools %%%%%
+%     %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% 
+% Matlab function  PS_eqn
+% PS_eqn(name,bond_number,bonds,direction,cr,args, ...
+%    structure,eqnfile);
+
+
+% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% %% Version control history
+% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% %% $Id$
+% %% $Log$
+% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+
+
+% Copyright (c) P.J. Gawthrop, 1997.
+
+
+if nargin<6
+  eqnfile = 'stdout';
+end;
+
+% Check that there are exactly three bonds.
+ports = 3;
+if check_bonds(bonds,ports,'PS')==0
+  return
+end
+
+
+% There are 3 ports; extract the information
+inout_bonds = bonds(1:2,:);
+power_bonds = bonds(3,:);
+
+inout_direction = direction(1:2,:);
+power_direction = direction(3,:);
+
+% Do ports [in] and [out] - unit gain TF.
+structure = TF_eqn(name,bond_number(1:2),inout_bonds,inout_direction, ...
+'lin','effort,1', structure,eqnfile);
+
+% Do port [power] - the power bit.
+% This computes f_2 = e_1*f_1
+fprintf(eqnfile,'%s := %s*%s;\n' , ...
+    varname(name,bond_number(3), -power_bonds(1)), ...
+    varname(name,bond_number(1),  1), ...
+    varname(name,bond_number(1), -1) );
+
+
+