Jrl

Jrl ('Jeremy's robotics library') is a robotics library containing robot models for popular robots as well as efficient, pytorch based parallelized implementations of forward kinematics, inverse kinematics, end effector jacobian, and robot-robot + robot-environment collision checking. This library is used as the backbone for the IKFlow and CppFlow codebases.

Robots

Robot models include the following:

Robot	Class name	Alias
Franka Panda	Panda	panda
Fetch	Fetch	fetch
Fetch - Arm (no lift joint)	FetchArm	fetch_arm
Kuka LBR IIWA7	Iiwa7	iiwa7
Flexiv Rizon 4	Rizon4	rizon4
Ur5	Ur5	ur5

Robots can easily be visualized with python scripts/visualize_robot.py --robot_name=<alias>, where <alias> is one from the table above.

panda	iiwa7	iiwa14
fetch	rizon4	ur5

Functionality

Available operations include (all part of the Robot class):

function	description
forward_kinematics()	(batched) forward kinematics
jacobian()	(batched) Jacobian of the manipulators forward kinematics map (w.r.t. joint angles)
inverse_kinematics_step_levenburg_marquardt()	(batched) Inverse kinematics step using Levenburg-Marquardt
inverse_kinematics_step_jacobian_pinv()	(batched) Inverse kinematics step using the jacobian pseudo-inverse method
self_collision_distances()	(batched) Pairwise distance between each link of the robot
self_collision_distances_jacobian()	(batched) Jacobian of self_collision_distances() w.r.t. joint angles
env_collision_distances()	(batched) Pairwise distance between each link of the robot and each cuboid in the environment
env_collision_distances_jacobian()	(batched) Jacobian of env_collision_distances() w.r.t. joint angles

Quickstart code

This code will load a Panda robot model and then run forward and inverse kinematics on randomly sampled configs. See demo.py for the complete script, which includes robot-robot and robot-environment collision checking.

from jrl.robots import Panda
from jrl.evaluation import pose_errors_cm_deg
import torch

def assert_poses_almost_equal(poses_1, poses_2):
    pos_errors_cm, rot_errors_deg = pose_errors_cm_deg(poses_1, poses_2)
    assert (pos_errors_cm.max().item() < 0.01) and (rot_errors_deg.max().item() < 0.1)

robot = Panda()
joint_angles, poses = robot.sample_joint_angles_and_poses(n=5, return_torch=True) # sample 5 random joint angles and matching poses

# Run forward-kinematics
poses_fk = robot.forward_kinematics(joint_angles) 
assert_poses_almost_equal(poses, poses_fk)

# Run inverse-kinematics
ik_sols = joint_angles + 0.1 * torch.randn_like(joint_angles) 
for i in range(5):
    ik_sols = robot.inverse_kinematics_step_levenburg_marquardt(poses, ik_sols)
assert_poses_almost_equal(poses, robot.forward_kinematics(ik_sols))

Note: This project uses the w,x,y,z format for quaternions.

Installation

Clone the repo and install with poetry. Don't use the version on pypi - it will remain out of date until this project hardens

git clone https://github.com/jstmn/jrl.git && cd jrl/
poetry install --without dev
# or:
poetry install # includes dev dependencies, like the linter

Acknowledgements

• klampt is used as a visualizer, for testing the Jrl FK / jacobian calculations, and for single configuration collision checking
• David Millard developed the collision checking functionality, improved the efficiency of the FK code, and wrote the jacobian function.