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Difficulties in visual tracking in Ros-by-example book

asked 2017-10-19 17:39:33 -0600

Abdu gravatar image

updated 2017-10-20 07:36:51 -0600

Hi Rossers

I am stack over the flow, I need help plz, I don't know where I am mistaken.

I have Phantomx pincher robotic arm (with 5 dynamixel 12ax servos) connected with arbotix-m board, I am using ros indigo.

I am following this ros-by-example tutorial and this repo. In order to control the first servo (id = 1) based on the motion of coloured object that should be detected by webcam. I want the servo's id 1 rotate when the object is not in the centre of x-axis. For now, I want to get one servo rotating first, then I will consider y-axis for another servo.

The tutorial explains how to control the motion of the pan and tilt head servos. I am trying to consider the pan servo with my first servo.

I did the following :-

1- To get the video stream and detect the object based on colour and send the topic /roi which contains object's position.

roslaunch rbx1_vision usb_cam.launch
roslaunch rbx1_vision camshift.launch

2- To fire up the arbotix-m,

roslaunch rbx1_dynamixels arbotix.launch

I can also see the arm in rviz, and I can move the servo (id 1) individually rostopic pub -1 /head_pan_joint/command std_msgs/Float64 -- 1.0, it moves in rviz as well, it means there's real connection with the actual arm.

3- To launch the head tracking node (which should be my first servo tracking node, since I consider the pan_head_joint is my servo id 1). This video shows the demo for the tutorial work.

roslaunch rbx1_dynamixels head_tracker.launch

I got this out put

[INFO] [WallTime: 1508448519.996313] Waiting for joint controllers services...

When I run rostopic info /head_pan_joint/command I can see head_pan_joint is already ok.

imr@IMR-PC:~$ rostopic info /head_pan_joint/command 
Type: std_msgs/Float64

Publishers: 
 * /head_tracker (http://localhost:38610/)

Subscribers: 
 * /arbotix (http://localhost:41637/)

And my first servo is not moving, I do not know where I am mistaken, what to check with the third step as I mentioned above, I guess there's some thing wrong there. Please tell me !!

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answered 2017-10-23 16:57:08 -0600

jorge gravatar image

Hi, cannot try by myself, as I have now a quite different configuration. But looking at head_tracker code, looks like it tries to subscribe to a service that doesn't exists: torque_enable. Arbotix provides a service for each servo named just "enable"... looks like a reasonable bet that they are the same. So you can try to remap from torque_enable to torque.

Or given that ros-by-example code is several years old, probably better fork it so you can update those parts that had become obsolete, something that the author will probably appreciate.

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Asked: 2017-10-19 17:39:33 -0600

Seen: 145 times

Last updated: Oct 23 '17