Merge branch 'devel_nav' into melodic

diff --cc twil_description/xacro/twil.urdf.xacro
index e97e71a,7ee5cd3..08b88e9
--- 1/twil_description/xacro/twil.urdf.xacro
--- 2/twil_description/xacro/twil.urdf.xacro
+++ b/twil_description/xacro/twil.urdf.xacro
@@@ -12,10 -12,10 +12,13 @@@
    <xacro:include filename="$(find twil_description)/xacro/battery_bosch_12v.urdf.xacro" />
    <xacro:include filename="$(find twil_description)/xacro/cpu.urdf.xacro" />
    <xacro:include filename="$(find twil_description)/xacro/eurocard.urdf.xacro" />
 +  <xacro:include filename="$(find twil_description)/xacro/tower.urdf.xacro" />
 +  <xacro:include filename="$(find twil_description)/xacro/step_motor.urdf.xacro" />
 +  <xacro:include filename="$(find twil_description)/xacro/sonar.urdf.xacro" />
  
+   <!--> Added camera description <-->
+   <xacro:include filename="$(find realsense2_description)/urdf/_d435.urdf.xacro" />
+ 
    <link name="twil_origin" />
  
    <xacro:chassis name="chassis" parent="twil_origin">