Ik problem of phantomX

[robotfan4]

Hi, thank you for your great work. The IK class works well with the 4 DOF legs, however, it can't get the correct joint angles for the phantomX robot. Could you give me some suggestions?

[r3n33]

Could you please try to describe the problem that you are having in more detail? I cloned the current source on my PhantomX, compiled and executed:

roslaunch hexapod_bringup hexapod_simple.launch config:=phantomX joy_mapping:=joystick_ds4

The IK is solving for 3dof without problems and the robot is able to walk around.

[KevinOchs]

R3n33 is correct, make sure you are using the proper config at launch and all should work well. Using the one that is called by default is Golem's and will not work properly on a phantomX.

[robotfan4]

thank you for your quick answer, i will use a clear workspace and check it further.

[robotfan4]

I don't have a joy stick, so i write a node to use a keyboard to simulate the joy_stick message, press key "1 " for standing up, "w" for moving forward. I modified the the hexapod_simple.launch and got the "/cmd_vel" topic like this:

linear: x: 0.0787199493647 y: -0.0 z: 0.0 angular: x: 0.0 y: 0.0 z: 0.0

It should work for the robot, however i got a mess movement for the PhantonX and a nice movement for the Golem, As the video in the attachment. if you have time please check it. Bests. Here is the video and the code: source code and video.zip

[KevinOchs]

Your command velocity looks high for a phantomx. Is the terminal giving you warnings of IK failing??

[robotfan4]

nope. it's growing from 0, the movement looks similar at start. To let the robot move forward, I just need let the robot stand up, pub the "/cmd_vel" , is that right?

[KevinOchs]

Are you using a picture of my Golem project as your profile picture?

[robotfan4]

while i am sorry about that, that's some work about the map based hexapod motion planning. I will change it, sorry again for that potential copyright conflicts.

[KevinOchs]

No worries... So your video does look odd for the phantomX. Did you change the yaml for at all? If not there might be an error in either the xacro file for the phantomX or the yaml config file.

[KevinOchs]

The screen top, outer legs look very wrong. R3n33 does the physical robot walk properly? If physical is walking properly that means the joint state is correct since the servos are controlled by that. If it is just wrong in rviz this might be an easy fix. robotfan can you compare my Golem xacro file to the phantomX xacro file? Ignoring the tarsus of course.

[KevinOchs]

R3n33 messaged me the robot physical is fine. So we must have a bug in the robot xacro file.

(BTW your robot in your avatar look fantastic!)

[robotfan4]

Thank you for your commends, I control my robot based on the ros crab hexapod robot project.

I compare the two xacros, Does the phantomX xacro need a foot link?

[KevinOchs]

It appears the coxa axis is backwards. Line 194 axis xyz="0.0 0.0 ${-axis}" should be axis xyz="0.0 0.0 1.0

Try that.

[KevinOchs]

And yes the phantomX could use a foot joint. Especially if you are going to use Gazebo

[robotfan4]

yes, that works! thank you a lot!

[KevinOchs]

Issue is now fixed and updated in both master and indigo branch