Moving Lego NXT's motor

NXT
Lego

asked 2011-08-10 09:46:32 -0500

Rafael Aroca
1 ●1 ●1 ●1

updated 2014-01-28 17:10:11 -0500

ngrennan
1 ●1 ●1

I've been playing with ROS+Lego NXT and after successfully playing with the sensors I got stuck trying to move one motor.

The only parameter I found on nxt_msgs related to that is JointCommand, but JointCommand only has "effort".

So I tried:

rostopic pub /joint_command nxt_msgs/JointCommand '{name: 'motor', effort: 10}'

And confirmed that this value changed with:

rostopic echo joint_command

name: motor effort: 10.0

But no movement. I also tried the nxt_teleop demo, but no matter the arrow key I press, none of the motor move.

I also tried the steps described in this post, but had no success ( http://answers.ros.org /question/486/trouble-following-lego-nxt-tutorials)

Any ideas? thanks

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Comments

were you able to run the test on the installation page (http://www.ros.org/wiki/nxt/Installation)? or run the first tutorial (http://www.ros.org/wiki/nxt_ros/Tutorials/Getting%20started)

mmwise ( 2011-08-10 10:03:21 -0500 )edit

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answered 2011-08-11 07:35:38 -0500

Jhatch
16

Try using the command rxgraph when your system is running to see what is subscribing and publishing in order to better diagnose the problem.

nxt_teleop should publish to cmd_vel which publishes to base_controller which publishes to joint_command

There are 2 tutorials online for Teleoperation, I found the nxt_teleop (http://www.ros.org/wiki/nxt_teleop) works, and I have not had success with nxt_assisted_teleop.

So I run roscore, a robot.launch file (which reads robot.yaml for parameters), and then I launch teleop_keyboard.launch from the directory .../stacks/nxt_apps/nxt_teleop and then use the arrow keys to drive the nxt.