A Example for Calculating Robot Dynamics Using Pinocchio Library

Developed by: Xinyang Tian.

Platform: Linux + Pinocchio.

In this work, i use Pinocchio to verify the dynamics of kuka iiwa7. This library has a lot of functions, such as forward/inverse dynamics and their analytical derivatives, jocobian and its analytical derivatives, etc. The main functions of this script are as follows:

1. Calculating inverse dynamics of the 7-DOF manipulator (kuka iiwa7 as example), include:
   • Total torque of each joint;
   • Gravity contribution G(q);
   • Inertia Matrix M of each joint;
   • Coriolis Matrix C of each joint.
2. Verify the anti-symmetric property of dM/dt - 2* C

Implementation

First, you should install Pinocchio on your system，please follow the procedure described here. Then, put the dy.py file and iiwa7_description.urdf file in the same folder, run the script using Python, finally you can get the M, C, and G with your model.

Note: if you change the .urdf file with your model, you should also change the dimension of q, qdot, and qddot equal to your model' DOF at the same time.

References

[1] Carpentier, J., Saurel, G., Buondonno, G., Mirabel, J., Lamiraux, F., Stasse, O., and Mansard, N, "The Pinocchio C++ library: A fast and flexible implementation of rigid body dynamics algorithms and their analytical derivatives," in 2019 IEEE/SICE International Symposium on System Integration (SII), pp. 614-619.
[2] R. Featherstone, Rigid Body Dynamics Algorithms. Springer, 2008.