“…The ability to constrain a system often has a number of advantages that can play an important role in state and parameter estimation: they can be used to enforce physicality of modeled systems (non-negativity of physical quantities, for example); relatedly they can be used to ensure that computational models are employed only within state and parameter regimes where the model is well-posed; and finally the application of constraints may provide robustness to outlier data. Resulting improvements in algorithmic efficiency and performance, by means of enforcing constraints, has been demonstrated in the recent literature in a diverse set of fields, including process control [1], biomechanics [2], cell energy metabolism [3], medical imaging [4], engine health estimation [5], weather forecasting [6], chemical engineering [7], and hydrology [8]. Within the Kalman filtering literature the need to incorporate constraints is widely recognized and has been addressed in a systematic fashion by viewing Kalman filtering from the perspective of optimization.…”