Wave Body MBARI: add collision mesh and change default BEM file (#77)

* Wave Body MBARI: add collision mesh for buoy - Add simplified collision meshes for the buoy at different levels of refinement. - Use the mesh with 316 faces in the model. - Add BEM file generated using Capytaine and the 5548 face mesh. Signed-off-by: Rhys Mainwaring <[email protected]> * Wave Body MBARI: change default the BEM data file - The excitation data in the hdf5 file generated from WAMIT data has the wrong sign, use Capytaine / bemio generated file in the meanwhile. - Simplify ramp function. Signed-off-by: Rhys Mainwaring <[email protected]>
srmainwaring · Nov 30, 2022 · ff049d0 · ff049d0
1 parent b025023
commit ff049d0
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Showing 7 changed files with 65 additions and 16 deletions.
diff --git a/gz-waves-models/models/mbari_buoy/config/hydrodata/buoy_float_collision_wp_f5548.h5 b/gz-waves-models/models/mbari_buoy/config/hydrodata/buoy_float_collision_wp_f5548.h5
diff --git a/gz-waves-models/models/mbari_buoy/meshes/buoy_float_collision_wp_f1436.stl b/gz-waves-models/models/mbari_buoy/meshes/buoy_float_collision_wp_f1436.stl
diff --git a/gz-waves-models/models/mbari_buoy/meshes/buoy_float_collision_wp_f316.stl b/gz-waves-models/models/mbari_buoy/meshes/buoy_float_collision_wp_f316.stl
diff --git a/gz-waves-models/models/mbari_buoy/meshes/buoy_float_collision_wp_f5548.stl b/gz-waves-models/models/mbari_buoy/meshes/buoy_float_collision_wp_f5548.stl
diff --git a/gz-waves-models/models/mbari_buoy/model.sdf b/gz-waves-models/models/mbari_buoy/model.sdf
@@ -21,6 +21,17 @@
         The inertial data in the data sheet looks like it may be for a
         coordinate system with y-up as the smallest diagonal element is Iyy
         and we'd expect the inertia to be approx. symmetric about the z axis.
+
+      Collision mesh:
+
+      The collision mesh buoy_float_collision_wp_f316.stl was generated
+      in Blender from a simple bevelled cylinder created in FreeCAD.
+      - The bevel at the base of 45 deg does not quite align with the visual
+        which has a slightly different angle (shallower).
+      - The collision mesh has the origin set 0.41m above the base, which is
+        less than the 0.5m from the engineering diagram, but is set to align
+        with the visual buoy_float.stl which is offset -2.27m below the
+        waterplane (= base_link origin)
     -->
     <link name="base_link">
       <pose>0 0 0 0 0 0</pose>
@@ -59,11 +70,15 @@
         </material>
       </visual>
       <collision name="collision">
-        <pose>0 0 0.19 0 0 0 </pose>
+        <!-- <pose>0 0 0.19 0 0 0 </pose> -->
+        <pose>0 0 0 0 0 0 </pose>
         <geometry>
-          <box>
+          <mesh>
+            <uri>model://mbari_buoy/meshes/buoy_float_collision_wp_f316.stl</uri>
+          </mesh>
+          <!-- <box>
             <size>2.34 2.34 1</size>
-          </box>
+          </box> -->
         </geometry>
       </collision>
     </link>

diff --git a/gz-waves-models/worlds/mbari_buoy.sdf b/gz-waves-models/worlds/mbari_buoy.sdf
@@ -42,7 +42,7 @@
     </light>
 
     <include>
-      <uri>model://regular_waves_6s_2m</uri>
+      <uri>model://regular_waves_15s_2m</uri>
     </include>
 
     <include>
@@ -54,12 +54,22 @@
           name="gz::sim::systems::LinearWaveBody">
 
         <!-- BEM HDF5 data file -->
-        <hdf5_file>model://mbari_buoy/config/hydrodata/mbari_buoy.h5</hdf5_file>
+        <!--
+            TODO: check the generation of HDF5 from WAMIT data - there is a
+            sign difference in the excitation data. May be different conventions
+            used in Capytaine vs WAMIT. Testing in WEC-Sim suggests that
+            mbari_buoy.h5 excitation coefficients have the wrong sign.
+        -->
+        <!-- generated from WAMIT data: BuoyA5.1, BuoyA5.3 -->
+        <!-- <hdf5_file>model://mbari_buoy/config/hydrodata/mbari_buoy.h5</hdf5_file> -->
+
+        <!-- independently generated using Capytaine and WEC-Sim bemio -->
+        <hdf5_file>model://mbari_buoy/config/hydrodata/buoy_float_collision_wp_f5548.h5</hdf5_file>
 
         <!-- waves parameter overrides -->
         <waves>
           <regular>
-            <period>6</period>
+            <period>15</period>
             <height>2</height>
             <direction>0</direction>
             <phase>0</phase>
@@ -82,19 +92,40 @@
         <!-- 
           Dimensioned hydrodynamics coefficients for T=6.0s (w = 1.0472 rad/s)
         -->
-        <!-- <hydro_coeffs>
+        <hydro_coeffs>
           <scaled>0</scaled>
           <hydrostatic>
+            <!-- cleaned coefficients for testing
             <linear_restoring>
-              0.      0.      0.      0.      0.      0.
-              0.      0.      0.      0.      0.      0.
-              0.      0.  34690.6     0.      0.      0.
-              0.      0.      0.  14256.3     0.      0.
-              0.      0.      0.      0.  14256.3     0.
-              0.      0.      0.      0.      0.      0.
-            </linear_restoring>
+                0       0       0       0       0      0
+                0       0       0       0       0      0
+                0       0   34690       0       0      0
+                0       0       0   14256       0      0
+                0       0       0       0   14256      0
+                0       0       0       0       0      0
+            </linear_restoring> -->
           </hydrostatic>
-        </hydro_coeffs> -->
+          <radiation>
+            <!-- symmetrised data for T=6s, H=2m - for testing
+            <added_mass>
+              704       0       0       0     343       0
+                0     704       0    -343       0       0
+                0       0    4592       0       0       0
+                0    -343       0     510       0       0
+              343       0       0       0     510       0
+                0       0       0       0       0       0
+            </added_mass> -->
+            <!-- as above, diagonals only - for testing
+            <added_mass>
+              704       0       0       0       0       0
+                0     704       0       0       0       0
+                0       0    4592       0       0       0
+                0       0       0     510       0       0
+                0       0       0       0     510       0
+                0       0       0       0       0       0
+            </added_mass> -->
+          </radiation>
+        </hydro_coeffs>
 
         <!-- enable / disable forces -->
         <forces>

diff --git a/gz-waves/src/systems/linear_wave_body/LinearWaveBody.cc b/gz-waves/src/systems/linear_wave_body/LinearWaveBody.cc
@@ -179,6 +179,9 @@ class gz::sim::systems::LinearWaveBodyPrivate
   ///
   /// 11. Optimise interpolation to eliminate unnecessary copies.
   ///
+  /// 12. Use math::eigen3::convert for converting Matrix and Vector types.
+  ///
+  ///
   ///
 
   /// \brief WEC-Sim BEMIO hydro data structure (read from HDF5 file)
@@ -2336,7 +2339,7 @@ void LinearWaveBodyPrivate::UpdateExcitationForces(const UpdateInfo &_info,
     double tau = t/tr;
 
     if (tau < 1)
-      return 0.5*(1.0 + std::sin(3.0/2.0*GZ_PI + GZ_PI*tau));
+      return 0.5*(1.0 + std::cos(GZ_PI*(1.0 + tau));
     else
       return 1.0;
   };