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1. Model reference adaptive anti-windup compensation

   https://doi.org/10.1109/CDC51059.2022.9992768  

   Sofrony, Jorge; Turner, Matthew; Richards, Christopher (December 2022, IEEE)

   This paper proposes an anti-windup mechanism for a model reference adaptive control scheme subject to actuator saturation constraints. The proposed compensator has the same architecture as well known non-adaptive schemes, which rely on the assumption that the system model is known fairly accurately. This is in contrast to the adaptive nature of the controller, which assumes that the system (or parts of it) is unknown. The approach proposed here uses of an “estimate” of the system matrices for the anti-windup compensator formulation and modifies the adaptation laws that update the controller gains. It will be observed that if the (unknown) ideal control gain is reached, a type of “model recovery anti-windup” formulation is obtained. In addition, it is shown that if the ideal control signal eventually lies within the control constraints, then, under certain conditions, the system states will converge to those of the reference model as desired. The paper highlights the main challenges involved in the design of anti-windup compensators for model-reference adaptive control systems and demonstrates its success via a flight control simulation. 

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2. Modeling and Observer-Based Monitoring of RAFT Homopolymerization Reactions

   https://doi.org/10.3390/pr7100768  

   Lathrop, Patrick M.; Duan, Zhaoyang; Ling, Chen; Elabd, Yossef A.; Kravaris, Costas (October 2019, Processes)

   Reversible addition–fragmentation chain–transfer (RAFT) polymerization of methyl methacrylate (MMA) is modeled and monitored using a multi-rate multi-delay observer in this work. First, to fit the RAFT reaction rate coefficients and the initiator efficiency in the model, in situ 1 H nuclear magnetic resonance (NMR) experimental data from small-scale (<2 mL) NMR tube reactions is obtained and a least squares optimization is performed. 1 H NMR and size exclusion chromatography (SEC) experimental data from large-scale (>400 mL) reflux reactions is then used to validate the fitted model. The fitted model accurately predicts the polymer properties of the large-scale reactions with slight discordance at late reaction times. Based on the fitted model, a multi-rate multi-delay observer coupled with an inter-sample predictor and dead time compensator is designed, to account for the asynchronous multi-rate measurements with non-constant delays. The multi-rate multi-delay observer shows perfect convergence after a few sampling times when tested against the fitted model, and is in fair agreement with the real data at late reaction times when implemented based on the experimental measurements. 

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3. Constrained Control of Input Delayed Systems With Partially Compensated Input Delays

   https://doi.org/10.1115/DSCC2020-3271  

   Abel, Imoleayo; Janković, Mrdjan; Krstić, Miroslav (October 2020, ASME 2020 Dynamic Systems and Control Conference)

   null (Ed.)

   Abstract Control Barrier Functions (CBFs) have become popular for enforcing — via barrier constraints — the safe operation of nonlinear systems within an admissible set. For systems with input delay(s) of the same length, constrained control has been achieved by combining a CBF for the delay free system with a state predictor that compensates the single input delay. Recently, this approach was extended to multi input systems with input delays of different lengths. One limitation of this extension is that barrier constraint adherence can only be guaranteed after the longest input delay has been compensated and all input channels become available for control. In this paper, we consider the problem of enforcing constraint adherence when only a subset of input delays have been compensated. In particular, we propose a new barrier constraint formulation that ensures that when possible, a subset of input channels with shorter delays will be utilized for keeping the system in the admissible set even before longer input delays have been compensated. We include a numerical example to demonstrate the effectiveness of the proposed approach. 

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4. Anti-Windup Compensation for Nonlinear Dynamic Inversion Rigid Body Attitude Control

   https://doi.org/10.1109/LCSYS.2025.3577574  

   Soltani, Ali; Turner, Matthew C; Richards, Christopher M (June 2025, IEEE Control Systems Letters)

   Manzie, C (Ed.)

   The rigid body attitude stabilization problem with constrained control inputs has been studied by many researchers. However, if perfect eigen-axis rotation in rest to-rest maneuvers is also desirable, the control design problem becomes more challenging and, to the best of the authors’ knowledge, has not yet been addressed. In this letter, an anti-windup compensation approach to this problem is developed. A nonlinear dynamic inversion control is used to obtain satisfactory unconstrained performance and this is supplemented by an anti-windup compensator when constraints are encountered. The compensator provides global L2 performance under reasonable conditions. A highlight of the approach is that the anti-windup compensator can have a nonlinear structure, giving flexibility in the choice of its parameters. Simulation results demonstrate the effectiveness of the proposed scheme as well as the performance improvement achieved using a compensator with state-dependent parameters. 

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5. A Secure Control Design for Networked Control Systems with Linear Dynamics under a Time-Delay Switch Attack

   https://doi.org/10.3390/electronics10030322  

   Victorio, Mauro; Sargolzaei, Arman; Khalghani, Mohammad Reza (February 2021, Electronics)

   Networked control systems (NCSs) are designed to control and monitor large-scale and complex systems remotely. The communication connectivity in an NCS allows agents to quickly communicate with each other to respond to abrupt changes in the system quickly, thus reducing complexity and increasing efficiency. Despite all these advantages, NCSs are vulnerable to cyberattacks. Injecting cyberattacks, such as a time-delay switch (TDS) attack, into communication channels has the potential to make NCSs inefficient or even unstable. This paper presents a Lyapunov-based approach to detecting and estimating TDS attacks in real time. A secure control strategy is designed to mitigate the effects of TDS attacks in real time. The stability of the secure control system is investigated using the Lyapunov theory. The proposed TDS attack estimator’s performance and secure control strategy are evaluated in simulations and a hardware-in-the-loop environment. 

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