Merge pull request #270 from xela-95/fix/delassus-example-nb

Fix bug in Delassus matrix computation in example notebook

Author: diegoferigo

examples/jaxsim_as_multibody_dynamics_library.ipynb

@@ -728,7 +728,7 @@
     "Key methodologies in this area may involve the Delassus matrix:\n",
     "\n",
     "$$\n",
-    "\\Psi(\\mathbf{q}) = J_{W,C}^T(\\mathbf{q}) \\, M(\\mathbf{q})^{-1} \\, J_{W,C}^T(\\mathbf{q})\n",
+    "\\Psi(\\mathbf{q}) = J_{W,C}(\\mathbf{q}) \\, M(\\mathbf{q})^{-1} \\, J_{W,C}^T(\\mathbf{q})\n",
     "$$\n",
     "\n",
     "or the linear acceleration of a contact point:\n",
@@ -780,7 +780,7 @@
     "    J̇l_WC = js.contact.jacobian_derivative(model=model, data=data)[:, 0:3, :]\n",
     "\n",
     "# Compute the Delassus matrix.\n",
-    "Ψ = jnp.vstack(Jl_WC) @ jnp.linalg.lstsq(BW_M, jnp.vstack(J̇l_WC).T)[0]\n",
+    "Ψ = jnp.vstack(Jl_WC) @ jnp.linalg.lstsq(BW_M, jnp.vstack(Jl_WC).T)[0]\n",
     "print(f\"Ψ:     shape={Ψ.shape}\")\n",
     "\n",
     "# Compute the transforms of the mixed frames implicitly associated\n",