@article {nair2018robust, title = {Robust adaptive gain higher order sliding mode observer based control-constrained nonlinear model predictive control for spacecraft formation flying}, journal = {IEEE/CAA Journal of Automatica Sinica}, volume = {5}, number = {1}, year = {2018}, pages = {367{\textendash}381}, publisher = {IEEE}, author = {Nair, Ranjith Ravindranathan and Behera, Laxmidhar} }