<!-- Joint -->
<element name="joint" required="*">
  <description>A joint connections two links with kinematic and dynamic properties.</description>

  <attribute name="name" type="string" default="__default__" required="1">
    <description>A unique name for the joint within the scope of the model.</description>
  </attribute>

  <attribute name="type" type="string" default="__default__" required="1">
    <description>The type of joint, which must be one of the following: (revolute) a hinge joint that rotates on a single axis with either a fixed or continuous range of motion, (gearbox) geared revolute joints, (revolute2) same as two revolute joints connected in series, (prismatic) a sliding joint that slides along an axis with a limited range specified by upper and lower limits, (ball) a ball and socket joint, (universal), like a ball joint, but constrains one degree of freedom, (piston) similar to a Slider joint except that rotation around the translation axis is possible.</description>
  </attribute>

  <element name="parent" type="string" default="__default__" required="1">
    <description>Name of the parent link</description>
  </element> <!-- End Parent -->

  <element name="child" type="string" default="__default__" required="1">
    <description>Name of the child link</description>
  </element> <!-- End Child -->

  <element name="pose"  type="pose" default="0 0 0 0 0 0" required="0">
    <description>offset from child link origin in child link frame.</description>
  </element>

  <element name="gearbox_ratio" type="double" default="1.0" required="0">
    <description>Parameter for gearbox joints.  Given theta_1 and theta_2 defined in description for gearbox_reference_body, theta_2 = -gearbox_ratio * theta_1.</description>
  </element>

  <element name="gearbox_reference_body" type="string" default="__default__" required="0">
    <description>Parameter for gearbox joints.  Gearbox ratio is enforced over two joint angles.  First joint angle (theta_1) is the angle from the gearbox_reference_body to the parent link in the direction of the axis element and the second joint angle (theta_2) is the angle from the gearbox_reference_body to the child link in the direction of the axis2 element.</description>
  </element>

  <element name="thread_pitch" type="double" default="1.0" required="0">
    <description>Parameter for screw joints.</description>
  </element>

  <element name="axis" required="1">
    <description>The joint axis specified in the parent model frame. This is the axis of rotation for revolute joints, the axis of translation for prismatic joints. The axis is currently specified in the parent model frame of reference, but this will be changed to the joint frame in future version of sdf (see gazebo issue #494).</description>
    <element name="xyz" type="vector3" default="0 0 1" required="1">
      <description>Represents the x,y,z components of a vector. The vector should be normalized.</description>
    </element>
    <element name="dynamics" required="0">
      <description>An element specifying physical properties of the joint. These values are used to specify modeling properties of the joint, particularly useful for simulation.</description>
      <element name="damping" type="double" default="0" required="0">
        <description>The physical velocity dependent viscous damping coefficient of the joint.</description>
      </element>
      <element name="friction" type="double" default="0" required="0">
        <description>The physical static friction value of the joint.</description>
      </element>
    </element> <!-- End Dynamics -->
    <element name="limit" required="1">
      <description>specifies the limits of this joint</description>
      <element name="lower" type="double" default="-1e16" required="1">
        <description>An attribute specifying the lower joint limit (radians for revolute joints, meters for prismatic joints). Omit if joint is continuous.</description>
      </element>
      <element name="upper" type="double" default="1e16" required="1">
        <description>An attribute specifying the upper joint limit (radians for revolute joints, meters for prismatic joints). Omit if joint is continuous.</description>
      </element>
      <element name="effort" type="double" default="-1" required="0">
        <description>An attribute for enforcing the maximum joint effort applied by Joint::SetForce.  Limit is not enforced if value is negative.</description>
      </element>
      <element name="velocity" type="double" default="-1" required="0">
        <description>(not implemented) An attribute for enforcing the maximum joint velocity.</description>
      </element>

      <element name="stiffness" type="double" default="1e8" required="0">
        <description>Joint stop stiffness. Support physics engines: SimBody.</description>
      </element>

      <element name="dissipation" type="double" default="1.0" required="0">
        <description>Joint stop dissipation.</description>
      </element>

    </element> <!-- End Limit -->
  </element> <!-- End Axis -->

  <element name="axis2" required="0">
    <description>The second joint axis specified in the parent model frame. This is the second axis of rotation for revolute2 joints and universal joints. The axis is currently specified in the parent model frame of reference, but this will be changed to the joint frame in future version of sdf (see gazebo issue #494).</description>
    <element name="xyz" type="vector3" default="0 0 1" required="1">
      <description>Represents the x,y,z components of a vector. The vector should be normalized.</description>
    </element>
    <element name="dynamics" required="0">
      <description>An element specifying physical properties of the joint. These values are used to specify modeling properties of the joint, particularly useful for simulation.</description>
      <element name="damping" type="double" default="0" required="0">
        <description>The physical velocity dependent viscous damping coefficient of the joint.  EXPERIMENTAL: if damping coefficient is negative and implicit_spring_damper is true, adaptive damping is used.</description>
      </element>
      <element name="friction" type="double" default="0" required="0">
        <description>The physical static friction value of the joint.</description>
      </element>
    </element> <!-- End Dynamics -->

    <element name="limit" required="0">
      <description></description>
      <element name="lower" type="double" default="-1e16" required="0">
        <description>An attribute specifying the lower joint limit (radians for revolute joints, meters for prismatic joints). Omit if joint is continuous.</description>
      </element>
      <element name="upper" type="double" default="1e16" required="0">
        <description>An attribute specifying the upper joint limit (radians for revolute joints, meters for prismatic joints). Omit if joint is continuous.</description>
      </element>
      <element name="effort" type="double" default="-1" required="0">
        <description>An attribute for enforcing the maximum joint effort applied by Joint::SetForce.  Limit is not enforced if value is negative.</description>
      </element>
      <element name="velocity" type="double" default="-1" required="0">
        <description>(not implemented) An attribute for enforcing the maximum joint velocity.</description>
      </element>

      <element name="stiffness" type="double" default="1e8" required="0">
        <description>Joint stop stiffness. Supported physics engines: SimBody.</description>
      </element>

      <element name="dissipation" type="double" default="1.0" required="0">
        <description>Joint stop dissipation. Supported physics engines: SimBody.</description>
      </element>

    </element> <!-- End Limit -->
  </element> <!-- End Axis2 -->

  <element name="physics" required="0">
    <description>Parameters that are specific to a certain physics engine.</description>
    <element name="simbody" required="0">
      <description>Simbody specific parameters</description>
      <element name="must_be_loop_joint" type="bool" default="0" required="0">
        <description>Force cut in the multibody graph at this joint.</description>
      </element>
    </element>
    <element name="ode" required="0">
      <description>ODE specific parameters</description>
      <element name="provide_feedback" type="bool" default="false" required="0">
        <description>(DEPRECATION WARNING:  In SDF 1.5 this tag will be replaced by the same tag directly under the physics-block.  For now, this tag overrides the one outside of ode-block, but in SDF 1.5 this tag will be removed completely.)  If provide feedback is set to true, ODE will compute the constraint forces at this joint.</description>
      </element>

      <element name="cfm_damping" type="bool" default="false" required="0">
        <description>If cfm damping is set to true, ODE will use CFM to simulate damping, allows for infinite damping, and one additional constraint row (previously used for joint limit) is always active.</description>
      </element>

      <element name="implicit_spring_damper" type="bool" default="false" required="0">
        <description>If implicit_spring_damper is set to true, ODE will use CFM, ERP to simulate stiffness and damping, allows for infinite damping, and one additional constraint row (previously used for joint limit) is always active.  This replaces cfm_damping parameter in sdf 1.4.</description>
      </element>

      <element name="fudge_factor" type="double" default="0" required="0">
        <description>Scale the excess for in a joint motor at joint limits. Should be between zero and one.</description>
      </element>
      <element name="cfm" type="double" default="0" required="0">
        <description>Constraint force mixing for constrained directions</description>
      </element>
      <element name="erp" type="double" default="0.2" required="0">
        <description>Error reduction parameter for constrained directions</description>
      </element>
      <element name="bounce" type="double" default="0" required="0">
        <description>Bounciness of the limits</description>
      </element>
      <element name="max_force" type="double" default="0" required="0">
        <description>Maximum force or torque used to reach the desired velocity.</description>
      </element>
      <element name="velocity" type="double" default="0" required="0">
        <description>The desired velocity of the joint. Should only be set if you want the joint to move on load.</description>
      </element>

      <element name="limit" required="0">
        <description></description>
        <element name="cfm" type="double" default="0.0" required="1">
          <description>Constraint force mixing parameter used by the joint stop</description>
        </element>
        <element name="erp" type="double" default="0.2" required="1">
          <description>Error reduction parameter used by the joint stop</description>
        </element>
      </element>

      <element name="suspension" required="0">
        <description></description>
        <element name="cfm" type="double" default="0.0" required="1">
          <description>Suspension constraint force mixing parameter</description>
        </element>
        <element name="erp" type="double" default="0.2" required="1">
          <description>Suspension error reduction parameter</description>
        </element>
      </element>
    </element>

    <element name="provide_feedback" type="bool" default="false" required="0">
      <description>If provide feedback is set to true, physics engine will compute the constraint forces at this joint.  For now, provide_feedback under ode block will override this tag and given user warning about the migration.  provide_feedback under ode is scheduled to be removed in SDF 1.5.</description>
    </element>
  </element> <!-- End Physics -->

  <include filename="sensor.sdf" required="*"/>
</element> <!-- End Joint -->
