Changeset 1130 for branches/maintenance/3.0_ImprovedFriction/Modelica/Mechanics/Translational.mo

Timestamp:

05/25/08 13:11:28 (6 months ago)

Author:

otter

Message:

maintenance/3.0_ImprovedFriction/Modelica:
New, much simplified method without state machine to describe friction in Rotational and Translational library. The efficiency will be usually enhanced because less event iterations. Since no state machine any longer, inconsistent friction states, due to initialization and/or impulses are no longer possible.
Release notes updated.

Files:

• branches/maintenance/3.0_ImprovedFriction/Modelica/Mechanics/Translational.mo (modified) (14 diffs)

branches/maintenance/3.0_ImprovedFriction/Modelica/Mechanics/Translational.mo

@@ -898 +898 @@
             Text(
               extent={{-98,-68},{102,-94}},
-              textString="positive force => spool moves in positive direction ",
+              textString="positive force => spool moves in positive direction ", 
+
               lineColor={0,0,255}),
             Text(
@@ -1990 +1991 @@
 
     // Friction force
-      f = if locked then sa*unitForce else 
-         (if startForward then          Modelica.Math.tempInterpol1( v, f_pos, 2) else 
-          if startBackward then        -Modelica.Math.tempInterpol1(-v, f_pos, 2) else 
-          if pre(mode) == Forward then  Modelica.Math.tempInterpol1( v, f_pos, 2) else 
-                                       -Modelica.Math.tempInterpol1(-v, f_pos, 2));
+       f = if mode == Locked then  sa*unitForce else 
+           if mode == Free then      0 else 
+           if mode == Forward then  Math.tempInterpol1( v, f_pos, 2) else 
+                                   -Math.tempInterpol1(-v, f_pos, 2);
+
     end SupportFriction;
 
@@ -2179 +2180 @@
       free = fn <= 0;
 
-      // friction force
-      f = if locked then sa*unitForce else 
-          if free then   0 else 
-          cgeo*fn*(if startForward then          Modelica.Math.tempInterpol1( v, mue_pos, 2) else 
-                   if startBackward then        -Modelica.Math.tempInterpol1(-v, mue_pos, 2) else 
-                   if pre(mode) == Forward then  Modelica.Math.tempInterpol1( v, mue_pos, 2) else 
-                                                -Modelica.Math.tempInterpol1(-v, mue_pos, 2));
+    // friction force
+      f = if mode == Locked then  sa*unitForce else 
+          if mode == Free then 0 else 
+          cgeo*fn*(if mode == Forward then  Math.tempInterpol1( v, mue_pos, 2) else 
+                                           -Math.tempInterpol1(-v, mue_pos, 2));
     end Brake;
 
@@ -2627 +2626 @@
               textString="Length L",
               lineColor={0,0,255})}));
+
     encapsulated partial model PartialFrictionWithStop
         "Base model of Coulomb friction elements with stop"
@@ -2658 +2658 @@
       Real sa(unit="1")
           "Path parameter of friction characteristic f = f(a_relfric)";
-      Boolean startForward(start=false, fixed=true)
-          "= true, if v_rel=0 and start of forward sliding or v_rel > v_small";
-      Boolean startBackward(start=false, fixed=true)
-          "= true, if v_rel=0 and start of backward sliding or v_rel < -v_small";
-      Boolean locked(start=false) "true, if v_rel=0 and not sliding";
+
       extends PartialRigid(s(start=0, stateSelect = StateSelect.always));
-      constant Integer Unknown=3 "Value of mode is not known";
-      constant Integer Free=2 "Element is not active";
-      constant Integer Forward=1 "v_rel > 0 (forward sliding)";
-      constant Integer Stuck=0
-          "v_rel = 0 (forward sliding, locked or backward sliding)";
-      constant Integer Backward=-1 "v_rel < 0 (backward sliding)";
-      Integer mode(
-        final min=Backward,
-        final max=Unknown,
-        start=Unknown, fixed=true);
+
+      constant Integer Free=2 "Element is not active" annotation(HideResult=true);
+      constant Integer Forward=1 "Forward sliding" annotation(HideResult=true);
+      constant Integer Locked=0 "Locked (no relative motion)" annotation(HideResult=true);
+      constant Integer Backward=-1 "Backward sliding" annotation(HideResult=true);
+      Integer mode(final max=2, final min=-1, start=Free)
+          "Mode of friction element: 2: free, 1: forward sliding, 0: Locked, -1: Backward sliding";
       protected
+      constant SI.Velocity v_eps = 1e-8
+          "If newFrictionDescription: defines region around zero, where the friction state is determined by acceleration, otherwise by v";
       constant SI.Acceleration unitAcceleration = 1 annotation(HideResult=true);
       constant SI.Force unitForce = 1 annotation(HideResult=true);
@@ -2680 +2675 @@
           "Value of sa when start of forward sliding at w=0";
     equation
-    /* Friction characteristic
-   (locked is introduced to help the Modelica translator determining
-   the different structural configurations, 
-   if for each configuration special code shall be generated)
-*/
-      startForward  = pre(mode) == Stuck and sa >  f0_max/unitForce and s < (smax - L/2) or 
-        pre(mode) == Backward and v_relfric >  v_small or initial() and v_relfric > 0;
-      startBackward = pre(mode) == Stuck and sa < -f0_max/unitForce and s > (smin + L/2) or 
-        pre(mode) == Forward  and v_relfric < -v_small or initial() and v_relfric < 0;
-      locked = not free and 
-        not (pre(mode) == Forward or startForward or pre(mode) == Backward or startBackward);
-      a_relfric/unitAcceleration = if locked then               0 else 
-                                   if free then                 sa else 
-                                   if startForward then         sa - sa0 else 
-                                   if startBackward then        sa + sa0 else 
-                                   if pre(mode) == Forward then sa - sa0 else 
-                                                                sa + sa0;
-    /* Friction torque has to be defined in a subclass. Example for a clutch:
-   f = if locked then sa else 
-       if free then   0 else 
-       cgeo*fn*(if startForward then          Math.tempInterpol1( v_relfric, mue_pos, 2) else 
-                if startBackward then        -Math.tempInterpol1(-v_relfric, mue_pos, 2) else 
-                if pre(mode) == Forward then  Math.tempInterpol1( v_relfric, mue_pos, 2) else 
-                                             -Math.tempInterpol1(-v_relfric, mue_pos, 2));
-*/
-    // finite state machine to determine configuration
-      mode = if free then Free else 
-        (if (pre(mode) == Forward  or pre(mode) == Free or startForward)  and v_relfric > 0 and s < (smax - L/2) then 
-           Forward else 
-         if (pre(mode) == Backward or pre(mode) == Free or startBackward) and v_relfric < 0 and s > (smin + L/2) then 
-           Backward else 
-           Stuck);
+    /* Friction characteristic */
+       mode = if free then Free else 
+              if v_relfric >  v_eps and s < (smax - L/2) then Forward else 
+              if v_relfric < -v_eps and s > (smin + L/2) then Backward else 
+              if sa >  f0_max/unitForce and s < (smax - L/2) then Forward else 
+              if sa < -f0_max/unitForce and s > (smin + L/2) then Backward else Locked;
+
+       a_relfric = unitAcceleration*(if mode == Locked then  0 else 
+                                     if mode == Free then    sa else 
+                                     if mode == Forward then sa - sa0 else sa + sa0);
     end PartialFrictionWithStop;
+
     equation
       // Constant auxiliary variables
@@ -2718 +2692 @@
       f0_max = f0*1.001;
       free = f0 <= 0 and F_prop <= 0 and s > smin + L/2 and s < smax - L/2;
+
       // Velocity and acceleration of flanges
       v = der(s);
@@ -2723 +2698 @@
       v_relfric = v;
       a_relfric = a;
+
     // Equilibrium of forces
       0 = flange_a.f + flange_b.f - f - m*der(v);
+
     // Friction force
-      f = if locked then sa*unitForce else 
-          if free then   0 else 
-                        (if startForward then         F_prop*v + F_Coulomb + F_Stribeck else 
-                         if startBackward then        F_prop*v - F_Coulomb - F_Stribeck else 
-                         if pre(mode) == Forward then F_prop*v + F_Coulomb + F_Stribeck*exp(-fexp*abs(v)) else 
-                                                      F_prop*v - F_Coulomb - F_Stribeck*exp(-fexp*abs(v)));
+       f = if mode == Locked then  sa*unitForce else 
+           if mode == Free then    0 else 
+           if mode == Forward then F_prop*v + F_Coulomb + F_Stribeck*exp(-fexp*abs(v)) else 
+                                   F_prop*v - F_Coulomb - F_Stribeck*exp(-fexp*abs(v));
+
     // Define events for hard stops and reinitiliaze the state variables velocity v and position s
     algorithm
@@ -3561 +3537 @@
             preserveAspectRatio=true,
             extent={{-100,-100},{100,100}},
-            grid={1,1}), graphics={Line(points={{-70,0},{-90,0}}, color={0,0,0}),
+            grid={1,1}), graphics={Line(points={{-70,0},{-90,0}}, color={0,0,0}), 
               Text(
               extent={{80,-28},{114,-62}},
@@ -3593 +3569 @@
             preserveAspectRatio=true,
             extent={{-100,-100},{100,100}},
-            grid={1,1}), graphics={Line(points={{-70,0},{-90,0}}, color={0,0,0}),
+            grid={1,1}), graphics={Line(points={{-70,0},{-90,0}}, color={0,0,0}), 
               Text(
               extent={{80,-28},{111,-61}},
@@ -3627 +3603 @@
             preserveAspectRatio=true,
             extent={{-100,-100},{100,100}},
-            grid={1,1}), graphics={Line(points={{-70,0},{-90,0}}, color={0,0,0}),
+            grid={1,1}), graphics={Line(points={{-70,0},{-90,0}}, color={0,0,0}), 
               Text(
               extent={{80,-28},{115,-60}},
@@ -4681 +4657 @@
 </html>
 "));
-    //extends Translational.Interfaces.PartialRigid;
-      parameter SI.Velocity v_small=1e-3
-        "Relative velocity near to zero (see model info text)" 
-         annotation(Dialog(tab="Advanced"));
+
     // Equations to define the following variables have to be defined in subclasses
       SI.Velocity v_relfric "Relative velocity between frictional surfaces";
@@ -4697 +4670 @@
       Real sa(unit="1")
         "Path parameter of friction characteristic f = f(a_relfric)";
-      Boolean startForward(start=false, fixed=true)
-        "true, if v_rel=0 and start of forward sliding";
-      Boolean startBackward(start=false, fixed=true)
-        "true, if v_rel=0 and start of backward sliding";
-      Boolean locked(start=false) "true, if v_rel=0 and not sliding";
-      constant Integer Unknown=3 "Value of mode is not known";
-      constant Integer Free=2 "Element is not active";
-      constant Integer Forward=1 "v_rel > 0 (forward sliding)";
-      constant Integer Stuck=0
-        "v_rel = 0 (forward sliding, locked or backward sliding)";
-      constant Integer Backward=-1 "v_rel < 0 (backward sliding)";
-      Integer mode(
-        final min=Backward,
-        final max=Unknown,
-        start=Unknown, fixed=true);
+
+      constant Integer Free=2 "Element is not active" annotation(HideResult=true);
+      constant Integer Forward=1 "Forward sliding" annotation(HideResult=true);
+      constant Integer Locked=0 "Locked (no relative motion)" annotation(HideResult=true);
+      constant Integer Backward=-1 "Backward sliding" annotation(HideResult=true);
+      Integer mode(final max=2, final min=-1, start=Free)
+        "Mode of friction element: 2: free, 1: forward sliding, 0: Locked, -1: Backward sliding";
+
     protected
+      constant SI.Velocity v_eps = 1e-8
+        "If newFrictionDescription: defines region around zero, where the friction state is determined by acceleration, otherwise by v";
       constant SI.Acceleration unitAcceleration = 1 annotation(HideResult=true);
       constant SI.Force unitForce = 1 annotation(HideResult=true);
@@ -4718 +4686 @@
         "Value of sa when start of forward sliding at w=0";
     equation
-    /* Friction characteristic
-   (locked is introduced to help the Modelica translator determining
-   the different structural configurations, 
-   if for each configuration special code shall be generated)
-*/
-      startForward  = pre(mode) == Stuck and sa >  f0_max/unitForce or 
-        pre(mode) == Backward and v_relfric >  v_small or initial() and v_relfric > 0;
-      startBackward = pre(mode) == Stuck and sa < -f0_max/unitForce or 
-        pre(mode) == Forward  and v_relfric < -v_small or initial() and v_relfric < 0;
-      locked = not free and 
-        not (pre(mode) == Forward or startForward or pre(mode) == Backward or startBackward);
-      a_relfric/unitAcceleration = if locked then               0 else 
-                                   if free then                 sa else 
-                                   if startForward then         sa - sa0 else 
-                                   if startBackward then        sa + sa0 else 
-                                   if pre(mode) == Forward then sa - sa0 else 
-                                                                sa + sa0;
-    /* Friction torque has to be defined in a subclass. Example for a clutch:
-   f = if locked then sa else 
-       if free then   0 else 
-       cgeo*fn*(if startForward then          Math.tempInterpol1( v_relfric, mue_pos, 2) else 
-                if startBackward then        -Math.tempInterpol1(-v_relfric, mue_pos, 2) else 
-                if pre(mode) == Forward then  Math.tempInterpol1( v_relfric, mue_pos, 2) else 
-                                             -Math.tempInterpol1(-v_relfric, mue_pos, 2));
-*/
-    // finite state machine to determine configuration
-      mode = if free then Free else 
-        (if (pre(mode) == Forward  or pre(mode) == Free or startForward)  and v_relfric > 0 then 
-           Forward else 
-         if (pre(mode) == Backward or pre(mode) == Free or startBackward) and v_relfric < 0 then 
-           Backward else 
-           Stuck);
+       mode = if free then Free else 
+              if v_relfric >  v_eps then Forward else 
+              if v_relfric < -v_eps then Backward else 
+              if sa >  f0_max/unitForce then Forward else 
+              if sa < -f0_max/unitForce then Backward else Locked;
+
+       a_relfric = unitAcceleration*(if mode == Locked then  0 else 
+                                     if mode == Free then    sa else 
+                                     if mode == Forward then sa - sa0 else sa + sa0);
+
+       /* Friction force has to be defined in a subclass. Example:
+      f = if mode == Locked then sa*unitForce else 
+          if mode == Free   then 0 else 
+            cgeo*fn*(if mode==Forward then  Math.tempInterpol1( v_relfric, mue_pos, 2)
+                                      else -Math.tempInterpol1(-v_relfric, mue_pos, 2));
+   */
     end PartialFriction;