sdformat/sdf/1.10/inertial.sdf at 24b80308991e6c61dd14e93c6d280fc138e69548 · gazebosim/sdformat · GitHub

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<!-- Inertial -->
<element name="inertial" required="0">
  <description>
    The link's mass, position of its center of mass, its central inertia
    properties, and optionally its fluid added mass.
  </description>

  <element name="mass" type="double" default="1.0" required="0">
    <description>The mass of the link.</description>
  </element>

  <element name="pose" type="pose" default="0 0 0 0 0 0" required="0">
    <description>
      This pose (translation, rotation) describes the position and orientation
      of the link's center-of-mass-frame C relative to the link-frame L.
      The first three components (x y z) specify the position vector from Lo
      (the link-frame origin) to Co (the link's center of mass) as
      `x L̂x + y L̂y + z L̂ᴢ`, where L̂x, L̂y, L̂ᴢ are link-frame L's orthogonal unit
      vectors. The subsequent values characterize C's orientation relative to
      link-frame L as a sequence of Euler rotations
      (r p y) documented in http://sdformat.org/tutorials?tut=specify_pose,
      or as a quaternion (x y z w), where w is the scalar component.
    </description>

    <attribute name="rotation_format" type="string" default="euler_rpy" required="0">
      <description>'euler_rpy' by default. Supported rotation formats are
        'euler_rpy', Euler angles representation in roll, pitch, yaw. The pose is expected to have 6 values.
        'quat_xyzw', Quaternion representation in x, y, z, w. The pose is expected to have 7 values.
      </description>
    </attribute>

    <attribute name="degrees" type="bool" default="false" required="0">
      <description>
        Whether or not the euler angles are in degrees, otherwise they will be interpreted as radians by default.
      </description>
    </attribute>

  </element>

  <element name="inertia" required="0">
    <description>
      This link's moments of inertia ixx, iyy, izz and products of inertia
      ixy, ixz, iyz about Co (the link's center of mass) for the unit vectors
      Ĉx, Ĉy, Ĉᴢ fixed in the center-of-mass-frame C.
      Note: the orientation of Ĉx, Ĉy, Ĉᴢ relative to L̂x, L̂y, L̂ᴢ is specified
      by the `pose` tag.
      To avoid compatibility issues associated with the negative sign
      convention for product of inertia, align Ĉx, Ĉy, Ĉᴢ with principal
      inertia directions so that all the products of inertia are zero.
      For more information about this sign convention, see the following
      MathWorks documentation for working with CAD tools:
      https://www.mathworks.com/help/releases/R2021b/physmod/sm/ug/specify-custom-inertia.html#mw_b043ec69-835b-4ca9-8769-af2e6f1b190c
    </description>
    <element name="ixx" type="double" default="1.0" required="1">
      <description>
        The link's moment of inertia about Co (the link's center of mass) for Ĉx.
      </description>
    </element>
    <element name="ixy" type="double" default="0.0" required="1">
      <description>
        The link's product of inertia about Co (the link's center of mass) for
        Ĉx and Ĉy, where the product of inertia convention -m x y  (not +m x y)
        is used. If Ĉx or Ĉy is a principal inertia direction, ixy = 0.
      </description>
    </element>
    <element name="ixz" type="double" default="0.0" required="1">
      <description>
        The link's product of inertia about Co (the link's center of mass) for
        Ĉx and Ĉz, where the product of inertia convention -m x z  (not +m x z)
        is used. If Ĉx or Ĉz is a principal inertia direction, ixz = 0.
      </description>
    </element>
    <element name="iyy" type="double" default="1.0" required="1">
      <description>
        The link's moment of inertia about Co (the link's center of mass) for Ĉy.
      </description>
    </element>
    <element name="iyz" type="double" default="0.0" required="1">
      <description>
        The link's product of inertia about Co (the link's center of mass) for
        Ĉy and Ĉz, where the product of inertia convention -m y z  (not +m y z)
        is used. If Ĉy or Ĉz is a principal inertia direction, iyz = 0.
      </description>
    </element>
    <element name="izz" type="double" default="1.0" required="1">
      <description>
        The link's moment of inertia about Co (the link's center of mass) for Ĉz.
      </description>
    </element>
  </element> <!-- End Inertia -->

  <element name="fluid_added_mass" required="0">
    <description>
      This link's fluid added mass matrix about the link's origin.
      This matrix represents the inertia of the fluid that is dislocated when the
      body moves. Added mass should be zero if the density of the surrounding
      fluid is negligible with respect to the body's density.
      The 6x6 matrix is symmetric, therefore only 21 unique elements can be set.
      The elements of the matrix follow the [x, y, z, p, q, r] notation, where
      [x, y, z] correspond to translation and [p, q, r] to rotation
      (i.e. roll, pitch, yaw).
    </description>
    <element name="xx" type="double" default="0.0" required="0">
      <description>
        Added mass in the X axis due to linear acceleration in the X axis, in kg.
      </description>
    </element>
    <element name="xy" type="double" default="0.0" required="0">
      <description>
        Added mass in the X axis due to linear acceleration in the Y axis, and vice-versa, in kg.
      </description>
    </element>
    <element name="xz" type="double" default="0.0" required="0">
      <description>
        Added mass in the X axis due to linear acceleration in the Z axis, and vice-versa, in kg.
      </description>
    </element>
    <element name="xp" type="double" default="0.0" required="0">
      <description>
        Added mass in the X axis due to angular acceleration about the X axis, and vice-versa, in kg * m.
      </description>
    </element>
    <element name="xq" type="double" default="0.0" required="0">
      <description>
        Added mass in the X axis due to angular acceleration about the Y axis, and vice-versa, in kg * m.
      </description>
    </element>
    <element name="xr" type="double" default="0.0" required="0">
      <description>
        Added mass in the X axis due to angular acceleration about the Z axis, and vice-versa, in kg * m.
      </description>
    </element>
    <element name="yy" type="double" default="0.0" required="0">
      <description>
        Added mass in the Y axis due to linear acceleration in the Y axis, in kg.
      </description>
    </element>
    <element name="yz" type="double" default="0.0" required="0">
      <description>
        Added mass in the Y axis due to linear acceleration in the Z axis, and vice-versa, in kg.
      </description>
    </element>
    <element name="yp" type="double" default="0.0" required="0">
      <description>
        Added mass in the Y axis due to angular acceleration about the X axis, and vice-versa, in kg * m.
      </description>
    </element>
    <element name="yq" type="double" default="0.0" required="0">
      <description>
        Added mass in the Y axis due to angular acceleration about the Y axis, and vice-versa, in kg * m.
      </description>
    </element>
    <element name="yr" type="double" default="0.0" required="0">
      <description>
        Added mass in the Y axis due to angular acceleration about the Z axis, and vice-versa, in kg * m.
      </description>
    </element>
    <element name="zz" type="double" default="0.0" required="0">
      <description>
        Added mass in the Z axis due to linear acceleration in the Z axis, in kg.
      </description>
    </element>
    <element name="zp" type="double" default="0.0" required="0">
      <description>
        Added mass in the Z axis due to angular acceleration about the X axis, and vice-versa, in kg * m.
      </description>
    </element>
    <element name="zq" type="double" default="0.0" required="0">
      <description>
        Added mass in the Z axis due to angular acceleration about the Y axis, and vice-versa, in kg * m.
      </description>
    </element>
    <element name="zr" type="double" default="0.0" required="0">
      <description>
        Added mass in the Z axis due to angular acceleration about the Z axis, and vice-versa, in kg * m.
      </description>
    </element>
    <element name="pp" type="double" default="0.0" required="0">
      <description>
        Added mass moment about the X axis due to angular acceleration about the X axis, in kg * m^2.
      </description>
    </element>
    <element name="pq" type="double" default="0.0" required="0">
      <description>
        Added mass moment about the X axis due to angular acceleration about the Y axis, and vice-versa, in kg * m^2.
      </description>
    </element>
    <element name="pr" type="double" default="0.0" required="0">
      <description>
        Added mass moment about the X axis due to angular acceleration about the Z axis, and vice-versa, in kg * m^2.
      </description>
    </element>
    <element name="qq" type="double" default="0.0" required="0">
      <description>
        Added mass moment about the Y axis due to angular acceleration about the Y axis, in kg * m^2.
      </description>
    </element>
    <element name="qr" type="double" default="0.0" required="0">
      <description>
        Added mass moment about the Y axis due to angular acceleration about the Z axis, and vice-versa, in kg * m^2.
      </description>
    </element>
    <element name="rr" type="double" default="0.0" required="0">
      <description>
        Added mass moment about the Z axis due to angular acceleration about the Z axis, in kg * m^2.
      </description>
    </element>
  </element> <!-- End fluid added mass -->
</element> <!-- End Inertial -->