IK Solver Configuration#

The following is an example to compute the ee_pose_convertor for Panda robot:

  1. First, configure the IK config except for ee_pose_convertor.

robot:
urdf: ${oc.env:MANISKILL_ASSETS}/robots/panda/panda_v2.urdf
fix_root_link: false
cut:
    root: panda_hand
    cuts: [panda_hand_tcp, panda_leftfinger, panda_rightfinger]


ik:
ee_pose_convertor: [q: [1, 0, 0, 0]] # a default pose, TODO: compute this
ee_name: ["panda_hand"] # end-effector name
fix_joint_indices: []
n_retry: 0
max_iterations: 100
threshold: 1e-3
use_projected_ik: false # true
mod_2pi: false # true

  1. View “PickCube-v1” environment with Panda robot:

python3 tools.py view configs/examples/maniskill_panda/pick_cube.yaml

This will launch a built-in SAPIEN GUI.

  1. In the GUI, click Scene → Entities → panda_hand (the end-effector name), then find Show Coordinate Frame under Selection. Click it to show the local frame for the end-effector link.

../../_images/GUI_screenshot.png

steps to show end-effector local frame in SAPIEN GUI#

  1. Compare the local frame for controller frame and the end-effector frame. Align the controller frame to the end-effector frame with desired controlling direction, and find the difference between the two local frames.

../../_images/align_local_pose.png

  1. Analyze the axis relationships between the two local frames. In this example:

  • end-effector X axis aligns with controller X axis.

  • end-effector Y axis align with controller -Y axis.

  • end-effector Z axis aligns with controller -Z axis.

  1. Compute the quaternion to convert the controller frame to the end-effector frame using:

python3 tools.py convert "x -y -z"

  1. Replace the ee_pose_convertor in the IK config with the computed quaternion. And the final IK config should look like this:

robot:
urdf: ${oc.env:MANISKILL_ASSETS}/robots/panda/panda_v2.urdf
fix_root_link: false
cut:
    root: panda_hand
    cuts: [panda_hand_tcp, panda_leftfinger, panda_rightfinger]


ik:
ee_pose_convertor: [q: [0, 1, 0, 0]]
ee_name: ["panda_hand"] # end-effector name
fix_joint_indices: []
n_retry: 0
max_iterations: 100
threshold: 1e-3
use_projected_ik: false # true
mod_2pi: false # true

Reference Coordinate Frames#

The following figures show the controller & hand local frames for reference.

../../_images/controller.jpg

Controller local frame#

../../_images/hand.jpg

Hand local frame#