More Like this

1. A Computationally Governed Log-domain Interior-point Method for Model Predictive Control

   https://doi.org/10.23919/ACC53348.2022.9867484  

   Leung, Jordan; Permenter, Frank; Kolmanovsky, Ilya V. (June 2022, Proceedings of 2022 American Control Conference (ACC))

   This paper introduces a computationally efficient approach for solving Model Predictive Control (MPC) reference tracking problems with state and control constraints. The approach consists of three key components: First, a log-domain interior-point quadratic programming method that forms the basis of the overall approach; second, a method of warm-starting this optimizer by using the MPC solution from the previous timestep; and third, a computational governor that bounds the suboptimality of the warm-start by altering the reference command provided to the MPC problem. As a result, the closed-loop system is altered in a manner so that MPC solutions can be computed using fewer optimizer iterations per timestep. In a numerical experiment, the computational governor reduces the worst-case computation time of a standard MPC implementation by 90%, while maintaining good closed-loop performance. 

   more » « less
2. Feasibility Governor for Linear Model Predictive Control

   https://doi.org/10.23919/ACC50511.2021.9483054  

   Skibik, Terrence; Liao-McPherson, Dominic; Cunis, Torbjorn; Kolmanovsky, Ilya; Nicotra, Marco M. (May 2021, Proceedings of 2021 American Control Conference, New Orleans, USA)

   This paper introduces the Feasibility Governor (FG): an add-on unit that enlarges the region of attraction of Model Predictive Control by manipulating the reference to ensure that the underlying optimal control problem remains feasible. The FG is developed for linear systems subject to polyhedral state and input constraints. Offline computations using polyhedral projection algorithms are used to construct the feasibility set. Online implementation relies on the solution of a convex quadratic program that guarantees recursive feasibility. The closed-loop system is shown to satisfy constraints, achieve asymptotic stability, and exhibit zero-offset tracking. 

   more » « less
3. A stability governor for constrained linear–quadratic MPC without terminal constraints

   https://doi.org/10.1016/j.automatica.2024.111650  

   Leung, Jordan; Permenter, Frank; Kolmanovsky, Ilya V (June 2024, Automatica)

   This paper introduces a supervisory unit, called the stability governor (SG), that provides improved guarantees of stability for constrained linear systems under Model Predictive Control (MPC) without terminal constraints. At each time step, the SG alters the setpoint command supplied to the MPC problem so that the current state is guaranteed to be inside of the region of attraction for an auxiliary equilibrium point. The proposed strategy is shown to be recursively feasible and asymptotically stabilizing for all initial states sufficiently close to any equilibrium of the system. Thus, asymptotic stability of the target equilibrium can be guaranteed for a large set of initial states even when a short prediction horizon is used. A numerical example demonstrates that the stability governed MPC strategy can recover closed-loop stability in a scenario where a standard MPC implementation without terminal constraints leads to divergent trajectories. 

   more » « less
4. Periodic Model Predictive Control for Tracking Halo Orbits in the Elliptic Restricted Three-Body Problem

   https://doi.org/10.1109/TCST.2023.3291548  

   Quartullo, Renato; Garulli, Andrea; Kolmanovsky, Ilya (September 2023, IEEE Transactions on Control Systems Technology)

   A periodic model predictive control (MPC) scheme is proposed for tracking halo orbits. The problem is formulated and solved in the elliptic restricted three-body problem (ER3BP) setting. The reference trajectory to be tracked is designed by using eccentricity continuation techniques. The MPC design exploits the periodicity of the tracking model and guarantees exponential stability of the linearized closed-loop system, through a suitable choice of the terminal set and weight matrices. A sum-of-norms cost function is adopted to promote fuel saving. The proposed control scheme is validated on two simulated missions in the Earth–Moon system, which, respectively, involve station keeping on a halo orbit near the L1 Lagrange point and rendezvous to a halo orbit near the L2 Lagrange point. Results illustrate the advantage of designing the reference trajectory and the periodic control directly in the ER3BP setting versus approximate solutions based on the circular restricted three-body problem (CR3BP). 

   more » « less
5. Time Shift Governor for Spacecraft Proximity Operation in Elliptic Orbits

   https://doi.org/10.2514/6.2024-2452  

   Kim, Taehyeun; Kolmanovsky, Ilya; Girard, Anouck (January 2024, American Institute of Aeronautics and Astronautics)

   This paper presents a parameter governor-based control approach to constrained spacecraft rendezvous and docking (RVD) in the setting of the Two-Body problem with gravitational perturbations. An add-on to the nominal closed-loop system, the Time Shift Governor (TSG) is developed, which provides a time-shifted Chief spacecraft trajectory as a target reference for the Deputy spacecraft, and enforces various constraints during RVD missions, such as Line of Sight cone constraints, total magnitude of thrust limit, relative velocity constraint, and exponential convergence to the target during RVD missions. As the time shift diminishes to zero, the virtual target incrementally aligns with the Chief spacecraft over time. The RVD mission is completed when the Deputy spacecraft achieves the virtual target with zero time shift, which corresponds to the Chief spacecraft. Simulation results for the RVD mission in an elliptic orbit around the Earth are presented to validate the proposed control strategy. 

   more » « less