[Question]: Interesting behavior of EE under roll-only commands using set_ee_pose_components

[abadithela]

Question

Hi,

I was hoping to get some clarification on the following. I am using the WidowX 250S arm, and I am sending end-effector state commands ([x,y,z,roll,pitch,yaw]) in the Space frame (robot base link frame). If I am correct, I believe that set_ee_pose_components in arm.py is the right function to send these commands.

I am initializing the end effector to the following initial condition first (the last element 1 is to command open gripper)

[0.3225704114029329, -0.03003952329421948, 0.11128154572494338, 0.0002682576217025125, 1.334934652682799, 0.000374208349124746, 1]

Then, I only send a sequence of roll commands (x,y,z,pitch, and yaw are set to constant for the entire trajectory) as shown by the green curve in the following plot:

ee_roll_sim_ee_traj.pdf

Interestingly, the video of the real end-effector seems to "yaw" in the space frame as opposed to roll (as seen in the animation below). Furthermore, the recorded "yaw" seems to be zero as shown in the plot below:

ee_yaw_sim_ee_traj.pdf

real_animation.mp4

Can you please clarify if this is the intended behavior of the robot in the real? I would have expected the behavior to look something like this under roll-only commands with respect to the space frame which I believe is what set_ee_pose_components is designed for:

recorded_ee_traj.mp4

Thank you very much.

Robot Model

WidowX 250S

Simulation in Simpler

Operating System

Ubuntu 22.04

ROS Version

ROS 1 Noetic

Additional Info

No response

[haastregt]

Hi, I had the exact same issue and confusion which I managed to figure out. I posted my solution in this issue: #249

If you still are dealing with this issue, I hope this helps!