Changeset 904

Timestamp:

12/09/2007 10:44:19 AM (13 months ago)

Author:

otter

Message:

Bug in MultiBody.Parts.Rotor1D corrected
(The 3D reaction torque was not completely correct and gave in

some situations a wrong result. This bug should not influence the
movement of a multi-body system, but only the constraint torques
are sometimes not correct).

4 Examples added as MultiBody.Examples.Rotational3DEffects to test and
demonstrate usage of Rotor1D and GearConstraint

Location:

Modelica/trunk/Modelica/Mechanics/MultiBody

Files:

• Examples/Rotational3DEffects.mo (added)
• package.mo (modified) (1 diff)
• parts.mo (modified) (5 diffs)

Modelica/trunk/Modelica/Mechanics/MultiBody/package.mo

@@ -1425 +1425 @@
     "Gravity field constant (default = field constant of earth)" 
     annotation (Dialog(enable=gravityType == Types.GravityTypes.PointGravity));
-  parameter Boolean driveTrainMechanics3D=false
+  parameter Boolean driveTrainMechanics3D=true
     "= true, if 3-dim. mechanical effects of Parts.Mounting1D/Rotor1D/BevelGear1D shall be taken into account";
 

Modelica/trunk/Modelica/Mechanics/MultiBody/parts.mo

@@ -2112 +2112 @@
 inertia (so called <i>rotor</i>) on its 3-dim. carrier body. Gyroscopic torques
 appear, if the vector of the carrier body's angular velocity is not parallel
-to the vector of the rotor's. The axis of rotation of the rotor is defined by
+to the vector of the rotor's axis. The axis of rotation of the rotor is defined by
 the parameter <tt>n</tt>, which has to be given in the local coordinate system
 of <tt>frame_a</tt>. The default animation of this component is
@@ -2122 +2122 @@
 carrier body.</p>
 <p>The Boolean parameter <tt>exact</tt> was introduced due to performance
-reasons. If <tt>exact</tt> is set to true, the influence of the carrier body
+reasons. If <tt>exact</tt> is set to <b>false</b>, the influence of the carrier body
 motion on the angular velocity of the rotor is neglected. This influence is usually
 negligible if the 1-dim.-rotational mechanical system accelerates much faster as the base body (this is,
@@ -2241 +2241 @@
 inertia (so called <i>rotor</i>) on its 3-dim. carrier body. Gyroscopic torques
 appear, if the vector of the carrier body's angular velocity is not parallel
-to the vector of the rotor's. The axis of rotation of the rotor is defined by
+to the vector of the rotor's axis. The axis of rotation of the rotor is defined by
 the parameter <tt>n</tt>, which has to be given in the local coordinate system
 of <tt>frame_a</tt>. The default animation of this component is
@@ -2251 +2251 @@
 carrier body.</p>
 <p>The Boolean parameter <tt>exact</tt> was introduced due to performance
-reasons. If <tt>exact</tt> is set to true, the influence of the carrier body
+reasons. If <tt>exact</tt> is set to <b>false</b>, the influence of the carrier body
 motion on the angular velocity of the rotor is neglected. This influence is usually
 negligible if the 1-dim.-rotational mechanical system accelerates much faster as the base body (this is,
@@ -2334 +2334 @@
     end if;
 
+   /* Reaction torque:
+        t = n*(J*a - flange_a.tau - flange_b.tau) + cross(w_a, nJ*w)
+ 
+     Since
+        J*a = flange_a.tau + flange_b.tau - nJ*der(w_a);
+ 
+     the reaction torque can be simplified to
+        t = n*(- nJ*der(w_a)) + cross(w_a, nJ*w)
+ 
+  */
     frame_a.f = zeros(3);
-    frame_a.t = nJ*a + cross(w_a, nJ*w);
+    frame_a.t = cross(w_a, nJ*w)-e*(nJ*der(w_a));
   end RotorWith3DEffects;