Universal Robot.

robots/ur_description/urdf/ur3_joint_limited_robot.urdf

@@ -228,6 +228,11 @@
       </geometry>
       <origin rpy="0 0 0" xyz="-0.01 0 0"/>
     </collision>
+    <inertial>
+      <mass value="0.0"/>
+      <origin rpy="0 0 0" xyz="0 0 0"/>
+      <inertia ixx="0.0" ixy="0.0" ixz="0.0" iyy="0.0" iyz="0.0" izz="0.0"/>
+    </inertial>            
   </link>
   <transmission name="shoulder_pan_trans">
     <type>transmission_interface/SimpleTransmission</type>
@@ -305,7 +310,13 @@
     <selfCollide>true</selfCollide>
   </gazebo>
   <!-- ROS base_link to UR 'Base' Coordinates transform -->
-  <link name="base"/>
+  <link name="base">
+    <inertial>
+      <mass value="0.0"/>
+      <origin rpy="0 0 0" xyz="0 0 0"/>
+      <inertia ixx="0.0" ixy="0.0" ixz="0.0" iyy="0.0" iyz="0.0" izz="0.0"/>
+    </inertial>        
+  </link>
   <joint name="base_link-base_fixed_joint" type="fixed">
     <!-- NOTE: this rotation is only needed as long as base_link itself is
                  not corrected wrt the real robot (ie: rotated over 180
@@ -316,7 +327,14 @@
     <child link="base"/>
   </joint>
   <!-- Frame coincident with all-zeros TCP on UR controller -->
-  <link name="tool0"/>
+  <link name="tool0">
+    <inertial>
+      <mass value="0.0"/>
+      <origin rpy="0 0 0" xyz="0 0 0"/>
+      <inertia ixx="0.0" ixy="0.0" ixz="0.0" iyy="0.0" iyz="0.0" izz="0.0"/>
+    </inertial>        
+  </link>
+
   <joint name="wrist_3_link-tool0_fixed_joint" type="fixed">
     <origin rpy="-1.57079632679 0 0" xyz="0 0.0819 0"/>
     <parent link="wrist_3_link"/>

robots/ur_description/urdf/ur3_robot.urdf

@@ -228,6 +228,11 @@
       </geometry>
       <origin rpy="0 0 0" xyz="-0.01 0 0"/>
     </collision>
+    <inertial>
+      <mass value="0.0"/>
+      <origin rpy="0 0 0" xyz="0 0 0"/>
+      <inertia ixx="0.0" ixy="0.0" ixz="0.0" iyy="0.0" iyz="0.0" izz="0.0"/>
+    </inertial>        
   </link>
   <transmission name="shoulder_pan_trans">
     <type>transmission_interface/SimpleTransmission</type>
@@ -305,7 +310,14 @@
     <selfCollide>true</selfCollide>
   </gazebo>
   <!-- ROS base_link to UR 'Base' Coordinates transform -->
-  <link name="base"/>
+  <link name="base">
+    <inertial>
+      <mass value="0.0"/>
+      <origin rpy="0 0 0" xyz="0 0 0"/>
+      <inertia ixx="0.0" ixy="0.0" ixz="0.0" iyy="0.0" iyz="0.0" izz="0.0"/>
+    </inertial>        
+  </link>
+  
   <joint name="base_link-base_fixed_joint" type="fixed">
     <!-- NOTE: this rotation is only needed as long as base_link itself is
                  not corrected wrt the real robot (ie: rotated over 180
@@ -316,7 +328,14 @@
     <child link="base"/>
   </joint>
   <!-- Frame coincident with all-zeros TCP on UR controller -->
-  <link name="tool0"/>
+  <link name="tool0">        
+    <inertial>
+      <mass value="0.0"/>
+      <origin rpy="0 0 0" xyz="0 0 0"/>
+      <inertia ixx="0.0" ixy="0.0" ixz="0.0" iyy="0.0" iyz="0.0" izz="0.0"/>
+    </inertial>        
+  </link>
+
   <joint name="wrist_3_link-tool0_fixed_joint" type="fixed">
     <origin rpy="-1.57079632679 0 0" xyz="0 0.0819 0"/>
     <parent link="wrist_3_link"/>

robots/ur_description/urdf/ur5_joint_limited_robot.urdf

@@ -238,6 +238,11 @@
       </geometry>
       <origin rpy="0 0 0" xyz="-0.01 0 0"/>
     </collision>
+    <inertial>
+      <mass value="0.0"/>
+      <origin rpy="0 0 0" xyz="0 0 0"/>
+      <inertia ixx="0.0" ixy="0.0" ixz="0.0" iyy="0.0" iyz="0.0" izz="0.0"/>
+    </inertial>    
   </link>
   <transmission name="shoulder_pan_trans">
     <type>transmission_interface/SimpleTransmission</type>
@@ -315,7 +320,13 @@
     <selfCollide>true</selfCollide>
   </gazebo>
   <!-- ROS base_link to UR 'Base' Coordinates transform -->
-  <link name="base"/>
+  <link name="base">
+    <inertial>
+      <mass value="0.0"/>
+      <origin rpy="0 0 0" xyz="0 0 0"/>
+      <inertia ixx="0.0" ixy="0.0" ixz="0.0" iyy="0.0" iyz="0.0" izz="0.0"/>
+    </inertial>
+  </link>
   <joint name="base_link-base_fixed_joint" type="fixed">
     <!-- NOTE: this rotation is only needed as long as base_link itself is
                  not corrected wrt the real robot (ie: rotated over 180
@@ -326,7 +337,13 @@
     <child link="base"/>
   </joint>
   <!-- Frame coincident with all-zeros TCP on UR controller -->
-  <link name="tool0"/>
+  <link name="tool0">
+    <inertial>
+      <mass value="0.0"/>
+      <origin rpy="0 0 0" xyz="0 0 0"/>
+      <inertia ixx="0.0" ixy="0.0" ixz="0.0" iyy="0.0" iyz="0.0" izz="0.0"/>
+    </inertial>        
+  </link>
   <joint name="wrist_3_link-tool0_fixed_joint" type="fixed">
     <origin rpy="-1.57079632679 0 0" xyz="0 0.0823 0"/>
     <parent link="wrist_3_link"/>