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Fixed joints for publishing transform frames using URDF

asked 2016-09-17 14:16:15 -0600

Kishore Kumar gravatar image

I have developed an URDF file and i am using the URDF file to publish the robot transforms. I have made all the joints fixed in the urdf. Is that fine if i have fixed joints in URDF to publish transforms of continuous joints(wheels & casters) or i should make the wheels and caster joints as continuous joints for perfect operation.

Note: I don't want to simulate the URDF model with Gazebo. I just want the file to publish transforms and aid the operation of real robot.

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answered 2016-09-18 18:26:00 -0600

Mark Rose gravatar image

Often you don't need to model the wheel and caster joints to use the URDF with the navigation stack. (They're useful for visualizing the robot, of course.) For example, for a differential-drive robot you need a single frame for the robot base, probably halfway between the two wheels, often called base_link. Then you need frames for each of your sensors, unless you are publishing distances relative to base_link instead. The wheel positions don't really matter – your odometry layer will usually publish the transform between the odom frame and the base_link frame.

The transforms from base_link to the sensor frames are usually published automatically by robot_state_publisher and joint_state_publisher. Movable joint transformations are handled the same way, but you have to publish the joint positions so that joint_state_publisher can determine the right transformations.

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Asked: 2016-09-17 14:16:15 -0600

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Last updated: Sep 18 '16