Does every joint need an actuator and transmission?

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Hi all,

I'm writing my own URDF-controller code for my robot. I have the URDF working well in rviz and warehouse but I can't get the controller to work. I am looking into this tutorial for a differential drive robot and I was wondering will I need actuators/transmissions for all of my motors in the joints of my robot's manipulator arms?

Here is a copy of my urdf:

<?xml version="1.0" ?>
<robot name="H20_robot">


 <link name="stand_link">
    <visual>
      <geometry>
        <box size="0.20 0.10 1"/>
      </geometry>
    <origin rpy="0 0 0" xyz="0 0 -.5"/>
          <material name="orange">
            <color rgba="1 0.5 0 1"/>
        </material>
    </visual>

    <collision>
      <geometry>
       <box size="0.20 0.10 1"/>
      </geometry>
    <contact_coefficients mu="0" kp="1000.0" kd="1.0"/>
    <origin rpy="0 0 0" xyz="0 0 -.5"/>
    </collision>

    <inertial>
      <mass value="20.0"/>
      <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
    <origin/>
    </inertial>


  </link>

 <link name="base_link">
    <visual>
      <geometry>
        <cylinder length="0.38" radius="0.0325"/>
      </geometry>
    <origin rpy="0 1.57057 0" xyz="0 0 0"/>
          <material name="grey">
        <color rgba="0.5 0.5 0.5 1"/>
      </material>
    </visual>

    <collision>
      <geometry>
        <cylinder length="0.38" radius="0.0325"/>
      </geometry>
    <contact_coefficients mu="0" kp="1000.0" kd="1.0"/> 
    <origin rpy="0 1.57057 0" xyz="0 0 0"/>   
    </collision>

    <inertial>
      <mass value="10.0"/>
      <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
    <origin/>
    </inertial>

</link>

 <link name="camera_link">
         <inertial>
      <mass value="1.0"/>
      <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
    <origin/>
    </inertial>

     </link>

  <joint name="camera_to_base" type="fixed">
    <parent link="base_link"/>
    <child link="camera_link"/>
    <origin xyz="0.05 -.1 .3" rpy="0 0.5 -1.57" /> 
 </joint> 


  <joint name="base_to_stand" type="fixed">
    <parent link="stand_link"/>
    <child link="base_link"/>
    <origin xyz="0 0 0" rpy="0 0 0" /> 
 </joint> 

 <link name="head_link">
    <visual>
      <geometry>
         <sphere radius="0.15"/>
      </geometry>
    <origin rpy="0 0 0" xyz="0 0 0.1825"/>
          <material name="orange"/>
    </visual>

    <collision>
      <geometry>
         <sphere radius="0.15"/>
      </geometry>
    <contact_coefficients mu="0" kp="1000.0" kd="1.0"/>
    <origin rpy="0 0 0" xyz="0 0 0.1825"/>
    </collision>

    <inertial>
      <mass value="2.0"/>
      <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
    <origin/>
    </inertial>

  </link>

  <joint name="head_to_base" type="fixed">
    <parent link="base_link"/>
    <child link="head_link"/>
    <origin xyz="0 0 0" rpy="0 0 0" /> 
 </joint> 


  <link name="left_shoulder_link">
    <visual>
      <geometry>
        <cylinder length="0.06" radius="0.0175"/>
      </geometry>
          <material name="grey"/>
    <origin rpy="0 1.57057 0" xyz="0.03 0 0"/>
    </visual>

    <collision>
      <geometry>
        <cylinder length="0.06" radius="0.0175"/>
      </geometry>
    <contact_coefficients mu="0" kp="1000.0" kd="1.0"/>
    <origin rpy="0 1.57057 0" xyz="0.03 0 0"/>
    </collision>

    <inertial>
      <mass value="2 ...