Different values in /cmd_vel/angular/z and /odom/.../angular/z
Hello. I am new in the use of ROS. I'm using simulation with model p3dx in ROS Indigo and Gazebo 2.x in Ubuntu 14.04 64bits. I'm struggling with the difference between: a) the cmd_vel.angular.z values (value sent to the robot) and b) the odom.twist.twist.angular.z (value obtained from odometry), after stabilize the speed, exacly as link image: link text
In the model p3dx using the differential-drive library, for which the sending angular velocity values (cmd_vel / angle / z). I wonder if this can be solved with configuration or is a platform of error.
Below the library insertion section in "pioneer3dx.gazebo":
<!-- differential drive -->
<gazebo>
<plugin name="differential_drive_controller" filename="libgazebo_ros_diff_drive.so">
<alwaysOn>true</alwaysOn>
<updateRate>100</updateRate><!-- original = 100 -->
<leftJoint>base_right_wheel_joint</leftJoint>
<rightJoint>base_left_wheel_joint</rightJoint>
<wheelSeparation>0.39</wheelSeparation>
<wheelDiameter>0.15</wheelDiameter>
<torque>5</torque>
<commandTopic>cmd_vel</commandTopic>
<odometryTopic>odom</odometryTopic>
<odometryFrame>odom</odometryFrame>
<robotBaseFrame>base_link</robotBaseFrame>
</plugin>
</gazebo>
What kind of different data? You're dealing with real values here.
I did not talk about "different data", but different values (angular speed) - as shown in the picture of the reported link. In the first, the angular velocity sent by control to cmd_vel is 0.385, while odometry returns 0.550 even after stabilize for PID joints action.
This also happens in the other two commands sent to cmd_vel. These values are also displayed in "rostopic echo". I think it can be fixed by some hidden configuration or is the problem Gazebo or drive-differential library.
I'm doubling the discussion on gazebosim-12559
I found this issue https://github.com/ros-simulation/gaz... and this video https://youtu.be/6WTu-mJ8Ukc which maybe related.
By suggest of another user, I change Gazebo 2.x to 6.5.1. But the offset remains as links above: https://drive.google.com/open?id=0B_s...https://drive.google.com/open?id=0B_s...