Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Robust reconfigurable flight control

From the perspective control practitioners, control of dynamics systems subjected to varying parameters is not a new topic. However systematic methods to accommodate such problems are relatively few and recent. This thesis addresses a subset of such problems falling under the nomenclature of Reconfigurable Control Systems in relation to flight control applications. A survey in the initial phase of research indicated a wide range of ad-hoc solutions with relatively brittle or non-existent theoretical guarantees towards to the stability of the entire system. Often the reconfigurable architecture consists of multiple conceptual components performing task of identifying system parameter changes, monitoring degradation in system performance and eventually finding some corrective action to regain lost performance. The change in system parameters if attributed to faults and damages to system, then the task of the control system is to achieve fault tolerance. Such fault tolerance is of high interest for flight control community since such a control system adaptation may lead to accommodation of real life faults during aircraft operation such as control surface damages, hydraulic actuation failures etc.The thesis work aims towards developing online control redesign methods capable of taking into account realistic requirements. The goals are 1) To find control input values in presence of faults. 2) Accommodate changes in performance criterion in presence of faults and, 3) Incorporate actuator limitations such as rate and position bounds. The research work is divided in three subparts. The initial phase consists of a study of existing solutions and methods capable of providing reconfigurable flight control architectures. This phase also covers some flight control literature relevant in the context of faults. Though the conclusions of this initial phase seem theoretically simple and straight forward, it is interesting to understand the amount of time and efforts invested by real world flight control practitioners to deduce these results. Essentially the work flow of this research work stems from practical requirement eventually leading to theoretical developments that can approximate the requirements often demanded by the people in field.The second phase consists of study and application of existing Model Predictive Control methods to the field of reconfigurable flight control. MPC has been successful in major complex control problems due to its online constrained optimisation methodology. Along-with certain theoretical extensions it is well capable of providing a successful means to redesign control action online in presence of failures. Simulation studies of sufficient fidelity and complexity on a full envelop fighter aircraft nonlinear model prove such control reconfiguration capabilities of MPC. Some new extensions of MPC have been developed to show it performing in a superior manner to conventional nominal formulations.The third phase of the research work focuses on further theoretical developments in the field robust adaptive control in MPC frame of operation. A new MPC formulation is derived which can accommodate constraints, uncertainty and constant disturbances (due to failed inputs). The novelty lies in the theoretical properties of this MPC as under certain conditions it is guaranteed to be asymptotically stable. This setup implements an optimization problem more complex than that of the nominal case. Typically, when disturbances and uncertainties are incorporated into the performance measure within MPC formulations, mini-max (worst-case) NP-hard problems can arise. The thesis contributes to the theory of robust synthesis by proposing a convex relaxation of a mini-max based MPC controller by adopting a Linear Matrix Inequality (LMI) optimisation formulation.<br/

Robust and stabilized MPC formulations for fault tolerant and reconfigurable flight control

Model Predictive Control (MPC) solves an optimization at every sampling instance to achieve commanded set-points and control objectives subject to constraints on control inputs and system states. Reconfigurable flight control is an application where the capabilities and flexibility of such optimization based control methods can be fully utilized and exploited. The online control optimization can incorporate many important factors to enable the control of systems subject to faults, changing dynamics, changing control objectives, failed control inputs and large disturbances. This paper presents formulations and experimental evaluations of various MPC schemes applied to a realistic full envelope non-linear model of a fighter aircraft. Investigations are carried out by exploring a variety of scenarios of fault and disturbance combinations along with modified and robust formulations of online constrained optimizatio

Stabilized MPC formulations for robust reconfigurable flight control

Model predictive control (MPC) solves an optimization at every sampling instance to achieve commanded set points and control objectives subject to constraints on control inputs and system states. Such online optimization can incorporate many important factors to enable the control of systems subject to faults, changing dynamics, changing control objectives, failed control inputs and large disturbances. Reconfigurable flight control is one such application where the capabilities and flexibility of optimization-based control methods can be fully utilized and exploited. This paper presents formulations and experimental evaluations of various MPC schemes applied to a realistic full envelope non-linear model of a fighter aircraft. Investigations are carried out by exploring a variety of scenarios of fault and disturbance combinations along with modified and robust formulations of online constrained optimization