Traiko Dinev

Add second order derivatives `fxx`, `fuu`, `fxu` using finite differences and check against cartpole's implementation and ordering convention.

As of the latest version, the example is broken. https://github.com/JuliaRobotics/RigidBodyDynamics.jl/blob/master/examples/6.%20Symbolics%20using%20SymPy/6.%20Symbolics%20using%20SymPy.jl Using version 2.2.0 works. The issue is that Quaternion does not support type Sym. I can update later with more...

Why is the last state from the trajectory removed?

1

In (`LQRStep.lqr_forward`) https://github.com/locuslab/mpc.pytorch/blob/master/mpc/lqr_step.py, we have the following: ```python if t < T-1: if isinstance(true_dynamics, mpc.LinDx): F, f = true_dynamics.F, true_dynamics.f new_xtp1 = util.bmv(F[t], new_xut) if f is not None and...