PYNOCCHIO

A simple python pip package implementing a wrapper for pinocchio library's robot model object. It implements in a simple manner several useful functions:

• direct kinematics forward
• inverse kinematics ik
• jacobian calculation jacobian
• jacobian time derivative calculation jacobian_dot
• jacobian pseudo-inverse jacobian_pseudo_inv
• gravity vector gravity_torque
• mass matrix calculaiton mass_matrix
• coriolis matrix calculaiton coriolis_matrix

see the docs

Installation

pip install git+https://gitlab.inria.fr/auctus-team/people/antunskuric/pynocchio.git

Usage

import os
import numpy as np

import pynocchio as pynoc

tip_name = "panda_link8"
pynoc_abs_path = os.path.dirname(os.path.abspath(pynoc.__file__))
urdf_path = "models/urdf/panda.urdf"
# there should be a folder meshes with 2 subfolders visual and collision containing the mesh files
mesh_path = pynoc_abs_path + "/models" 

q0 = np.array([np.pi/2,-0.2,0,-2.1,0,1.9,0])

robot = pynoc.RobotWrapper(tip_name, urdf_path, mesh_path=mesh_path, q=q0)

fv = np.array([0.07, 0.20, 0.04, 0.23, 0.10, -0.01, 0.06])
robot_fric = FrictionRobotWrapper(robot, fv)

Parameters:

• tip (str): Name of the robot's end-effector frame.
• urdf_path (str or None): Path to the robot's URDF file (optional, either urdf or xml).
• xml_path (str or None): Path to the robot's XML file (optional, either urdf or xml).
• mesh_path (str or None): Absolute path to the robot's meshes folder for visualization (optional).
• q (np.ndarray or None): Array containing the robot's initial joint positions (optional).

Testing the code

pytest tests/test.py

and coverage report

coverage run -m pytest tests/test.py
coverage report -m

and for html version

coverage html

Examples

Example 1: Creating a RobotWrapper object and calculating the forward kinematics for the end effector.

import numpy as np
from pynocchio import RobotWrapper

# Define the path to the URDF file
robot_path = '/path/to/robot.urdf'

# Create the RobotWrapper object
robot = RobotWrapper(urdf_path=robot_path)

# Define the current robot configuration
q = np.zeros(robot.n)

# Calculate the forward kinematics for the end effector
oMf = robot.forward(q)

# Print the resulting transformation matrix
print(oMf)

Example 2: Creating a RobotWrapper object and calculating the Jacobian matrix for the end effector.

import numpy as np
from pynocchio import RobotWrapper

# Define the path to the URDF file
robot_path = '/path/to/robot.urdf'

# Create the RobotWrapper object
robot = RobotWrapper(urdf_path=robot_path)

# Define the current robot configuration
q = np.zeros(robot.n)

# Calculate the Jacobian matrix for the end effector
J = robot.jacobian(q)

# Print the resulting Jacobian matrix
print(J)

In both examples, the RobotWrapper class is imported from the pynocchio module. The first example calculates the forward kinematics for the end effector of the robot given a certain configuration. The second example calculates the Jacobian matrix for the end effector of the robot given a certain configuration. In both cases, the RobotWrapper object is constructed with the path to the URDF file, and then the required function is called with the current robot configuration.

see the tutorials for more examples.