ADDED   mttroot/mtt/lib/comp/simple/PS_cause.m
Index: mttroot/mtt/lib/comp/simple/PS_cause.m
==================================================================
--- /dev/null
+++ mttroot/mtt/lib/comp/simple/PS_cause.m
@@ -0,0 +1,62 @@
+function [bonds,status] = PS_cause(bonds);
+% Causality for PS component
+
+%SUMMARY PS: Power sensor
+%DESCRIPTION Port[in]: Inflowing bond
+%DESCRIPTION Port[out]: Outflowing bond e_2=e_1; f_2=f_1.
+%DESCRIPTION Port[power]: f = power = e_1*f_1 = e_2*f_2
+
+
+% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% %% Version control history
+% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% %% $Id$
+% %% $Log$
+% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+
+% Copyright (c) P.J. Gawthrop, 1997.
+
+status = -1;
+
+% Check that there are exactly three bonds.
+if check_bonds(bonds,3,'PS')==0
+  return
+end
+
+% Do the [in] and [out] ports -- like a TF
+inout_bonds = bonds(1:2,:);
+[inout_bonds,inout_status] = TF_cause(inout_bonds);
+
+% Do the power port -- must have flow out and effort in
+power_bonds = bonds(3,:);
+for i = 1:2
+  if (power_bonds(i)==1)
+    power_status = 0;
+  elseif (power_bonds(i)==0)
+    power_bonds(i)==1;
+    power_status = 0;
+  else
+    power_status = 1;
+  end;
+end;
+
+
+  
+  
+  
+  
+% Reconstruct the bonds
+bonds = [inout_bonds; power_bonds];
+
+% Generate an overall status
+if (inout_status==1)|(power_status==1)
+  status = 1;
+elseif
+  (inout_status==-1)|(power_status==-1)
+  status=-1;
+else
+  status = 0;
+end;
+
+