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1. Continuous feedback stabilization of nonlinear control systems by composition operators

   https://doi.org/10.1051/cocv/2022022  

   Christopherson, Bryce A.; Mordukhovich, Boris S.; Jafari, Farhad (January 2022, ESAIM: Control, Optimisation and Calculus of Variations)

   The ability to asymptotically stabilize control systems through the use of continuous feedbacks is an important topic of control theory and applications. In this paper, we provide a complete characterization of continuous feedback stabilizability using a new approach that does not involve control Lyapunov functions. To do so, we first develop a slight generalization of feedback stabilization using composition operators and characterize continuous stabilizability in this expanded setting. Employing the obtained characterizations in the more general context, we establish relationships between continuous stabiliza|bility in the conventional sense and in the generalized composition operator sense. This connection allows us to show that the continuousstabilizabilityof a control system is equivalent to thestabilityof an associated system formed from a local section of the vector field inducing the control system. That is, we reduce the question of continuous stabilizability to that ofstability. Moreover, we provide a universal formula describing all possible continuous stabilizing feedbacks for a given system. 

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2. Technoeconomic and Sustainability Analysis of Batch and Continuous Crystallization for Pharmaceutical Manufacturing

   https://doi.org/10.69997/sct.107722  

   Rhim, Jungsoo; Nagy, Zoltan K (July 2024, Syst. Control Trans.)

   Continuous manufacturing in pharmaceutical industries has shown great promise to achieve process intensification. To better understand and justify such changes to the current status quo, a technoeconomic analysis of a continuous production must be conducted to serve as a predictive decision-making tool for manufacturers. This paper uses PharmaPy, a custom-made Python-based library developed for pharmaceutical flowsheet analysis, to simulate an annual production cycle for a given active pharmaceutical ingredient (API) of varying production volumes for a batch crystallization system and a continuous mixed suspension, mixed product removal (MSMPR) crystallizer. After each system is optimized, the generalized cost drivers, categorized as capital expenses (CAPEX) or operational expenses (OPEX), are compared. Then, a technoeconomic and sustainability cost analysis is done with the process mass intensity (PMI) as a green metric. The results indicate that while the batch system does have an overall lower cost and better PMI metric at smaller manufacturing scales in comparison with the continuous system, the latter system showed more potential for scaling-up for larger production volumes. 

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3. Design of smooth hybrid controllers for a class of non‐linear systems

   https://doi.org/10.1049/iet-cta.2019.1112  

   Shamgah, Laya; Getahun_Tadewos, Tadewos; Karimoddini, Ali (February 2021, IET Control Theory & Applications)

   Symbolic planning techniques rely on abstract information about a continuous system to design a discrete planner to satisfy desired high‐level objectives. However, applying the generated discrete commands of the discrete planner to the original system may face several challenges, including real‐time implementation, preserving the properties of high‐level objectives in the continuous domain, and issues such as discontinuity in control signals that may physically harm the system. To address these issues and challenges, the authors proposed a novel hybrid control structure for systems with non‐linear multi‐affine dynamics over rectangular partitions. In the proposed framework, a discrete planner can be separately designed to achieve high‐level specifications. Then, the proposed hybrid controller generates jumpless continuous control signals to drive the system over the partitioned space executing the discrete commands of the planner. The hybrid controller generates continuous signals in real‐time while respecting the dynamics of the system and preserving the desired objectives of the high‐level plan. The design process is described in detail and the existence and uniqueness of the proposed solution are investigated. Finally, several case studies are provided to verify the effectiveness of the developed technique. 

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4. Approximate Controllability of Continuity Equation of Transformers

   https://doi.org/10.1109/LCSYS.2024.3406255  

   Adu, Daniel Owusu; Gharesifard, Bahman (January 2024, IEEE Control Systems Letters)

   NA (Ed.)

   Building on the recent work by Geshkovski et al. (2023) which provides an interacting particle system interpretation of Transformers with a continuous-time evolution, we study the controllability attributes of the corresponding continuity equation across the landscape of probability space curves. In particular, we consider the parameters of the Transformer’s continuous-time evolution as control inputs. We prove that given an absolutely continuous probability measure and a non-local Lipschitz velocity field that satisfy a continuity equation, there exist control inputs such that the measure and the non-local velocity field of the Transformer’s continuous-time evolution approximate them, respectively, in the p-Wasserstein and Lp-sense, where 1 ≤ p < ∞. 

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5. Mechanism and kinetics of enzymatic degradation of polyester microparticles using a shrinking particle–shrinking core model

   https://doi.org/10.1039/D3LC00581J  

   Torabi, Hooman; Javi, Farhad; Deisenroth, Ted W; Pho, Toan V; Barbright, Victoria; Abbaspourrad, Alireza (October 2023, Lab on a Chip)

   Generalized shrinking particle (SPM) and shrinking core (SCM) models were developed to describe the kinetics of heterogenous enzymatic degradation of polymer microparticles in a continuous microflow system. 

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