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URDF Transmissions

The transmission element is an extension to the URDF robot description model that is used to describe the relationship between an actuator and a joint. This allows one to model concepts such as gear ratios and parallel linkages. A transmission transforms efforts/flow variables such that their product - power - remains constant. Multiple actuators may be linked to multiple joints through complex transmission.

Here is an example of a transmission element:

   1 <transmission name="simple_trans">
   2   <type>transmission_interface/SimpleTransmission</type>
   3   <joint name="foo_joint">
   4     <hardwareInterface>EffortJointInterface</hardwareInterface>
   5   </joint>
   6   <actuator name="foo_motor">
   7     <mechanicalReduction>50</mechanicalReduction>
   8     <hardwareInterface>EffortJointInterface</hardwareInterface>
   9   </actuator>
  10 </transmission>

<transmission> Attributes

The transmission element has one attribute:

<transmission> Elements

The transmission has the following elements:

Development Notes

Currently, only the ros_control project uses this transmission elements. Developing an updated transmission format that is extensible to all use cases was complicated endeavor that can be reviewed here.

2019-06-08 13:24