Why is nominal trajectory not used in iLQR control law?

[sklaw]

It seems the following line computes new action without any use of nominal trajectory: https://github.com/cbfinn/gps/blob/82fa6cc930c4392d55d2525f6b792089f1d2ccfe/python/gps/algorithm/traj_opt/traj_opt_lqr_python.py#L257

But in the following papers, nominal trajectory seems to be essential in the whole iLQR algorithm: equation (8b) in this paper equation (3) in this paper

[dujinyu]

@sklaw hello, I am confused by the linear-gaussian policy u = K x + k, if we use iLQR, why not the cotrol u = \bar{u} + k + K (x - \bar{x})

[sklaw]

@sklaw hello, I am confused by the linear-gaussian policy u = K x + k, if we use iLQR, why not the cotrol u = \bar{u} + k + K (x - \bar{x})

Hi. I'm also confused by this part, too. It seems the author of this code assumed the nominal trajectory is 0... But if so the whole trajectory optimization would be really weird