Verification of model predictive control laws using weispfenning's quantifier elimination by virtual substitution algorithm

© 2016 IEEE. A method based on a quantifier elimination algorithm is suggested for obtaining explicit model predictive control (MPC) laws for linear time invariant systems with quadratic objective and polytopic constraints. The structure of the control problem considered allows Weispfenning's 'quantifier elimination by virtual substitution' algorithm to be used. This is applicable to first order formulas in which quantified variables appear at most quadratically. It has much better practical computational complexity than general quantifier elimination algorithms, such as cylindrical algebraic decomposition. We show how this explicit MPC solution, together with Weispfenning's algorithm, can be used to check recursive feasibility of the system, for both nominal and disturbed systems. Extension to cases beyond linear MPC using Weispfenning's algorithm is part of future work.Engineering and Physical Sciences Research Council, and European Union Seventh Framework Programme FP7/2007-2013 grant agreement number 314 544, project “RECONFIGURE”

A longitudinal flight control law to accommodate sensor loss in the RECONFIGURE benchmark

The feedback gains in state-of-the-art flight control laws for commercial aircraft are scheduled as a function of values such as airspeed, mass, and centre of gravity (CoG). If measurements or estimates of these are lost due to multiple simultaneous sensor failures, the pilot must revert to an alternative control law, or, in the ultimate case, directly command control surface positions. This work develops a robust backup load-factor tracking control law, that does not depend on these parameters, based on application of theory from robust MPC and $H_2$ optimal control. Firstly, the methods are applied with loss only of airdata, and subsequently also with loss of mass and CoG estimates. Local linear analysis indicates satisfactory performance over a wide range of operating points. To keep the aircraft within an acceptable operating region, an outer protection loop is implemented using an override approach, based on ground speed, a model of the trim angle of attack and variation of load factor with respect to angle of attack, and $\textit{a priori}$ bounds on the wind speed. Finally, the resulting control laws are demonstrated on the nonlinear RECONFIGURE benchmark, which is derived from an Airbus high fidelity, industrially-validated simulator.European Union Seventh Framework Programme FP7/2007- 2013 (Grant ID: 314 544, project “RECONFIGURE”

A research agenda to improve incidence and outcomes of assisted vaginal birth.

Access to emergency obstetric care, including assisted vaginal birth and caesarean birth, is crucial for improving maternal and childbirth outcomes. However, although the proportion of births by caesarean section has increased during the last few decades, the use of assisted vaginal birth has declined. This is particularly the case in low- and middle-income countries, despite an assisted vaginal birth often being less risky than caesarean birth. We therefore conducted a three-step process to identify a research agenda necessary to increase the use of, or reintroduce, assisted vaginal birth: after conducting an evidence synthesis, which informed a consultation with technical experts who proposed an initial research agenda, we sought and incorporated the views of women's representatives of this agenda. This process has allowed us to identify a comprehensive research agenda, with topics categorized as: (i) the need to understand women's perceptions of assisted vaginal birth, and provide appropriate and reliable information; (ii) the importance of training health-care providers in clinical skills but also in respectful care, effective communication, shared decision-making and informed consent; and (iii) the barriers to and facilitators of implementation and sustainability. From women's feedback, we learned of the urgent need to recognize labour, childbirth and postpartum experiences as inherently physiological and dignified human processes, in which interventions should only be implemented if necessary. The promotion and/or reintroduction of assisted vaginal birth in low-resource settings requires governments, policy-makers and hospital administrators to support skilled health-care providers who can, in turn, respectfully support women in labour and childbirth

Verification of model predictive control laws using weispfenning's quantifier elimination by virtual substitution algorithm

© 2016 IEEE. A method based on a quantifier elimination algorithm is suggested for obtaining explicit model predictive control (MPC) laws for linear time invariant systems with quadratic objective and polytopic constraints. The structure of the control problem considered allows Weispfenning's 'quantifier elimination by virtual substitution' algorithm to be used. This is applicable to first order formulas in which quantified variables appear at most quadratically. It has much better practical computational complexity than general quantifier elimination algorithms, such as cylindrical algebraic decomposition. We show how this explicit MPC solution, together with Weispfenning's algorithm, can be used to check recursive feasibility of the system, for both nominal and disturbed systems. Extension to cases beyond linear MPC using Weispfenning's algorithm is part of future work

A longitudinal flight control law to accommodate sensor loss in the RECONFIGURE benchmark

The feedback gains in state-of-the-art flight control laws for commercial aircraft are scheduled as a function of values such as airspeed, mass, and centre of gravity (CoG). If measurements or estimates of these are lost due to multiple simultaneous sensor failures, the pilot must revert to an alternative control law, or, in the ultimate case, directly command control surface positions. This work develops a robust backup load-factor tracking control law, that does not depend on these parameters, based on application of theory from robust MPC and $H_2$ optimal control. Firstly, the methods are applied with loss only of airdata, and subsequently also with loss of mass and CoG estimates. Local linear analysis indicates satisfactory performance over a wide range of operating points. To keep the aircraft within an acceptable operating region, an outer protection loop is implemented using an override approach, based on ground speed, a model of the trim angle of attack and variation of load factor with respect to angle of attack, and $\textit{a priori}$ bounds on the wind speed. Finally, the resulting control laws are demonstrated on the nonlinear RECONFIGURE benchmark, which is derived from an Airbus high fidelity, industrially-validated simulator

The killer shrimp Dikerogammarus villosus (Crustacea, Amphipoda) invades Lithuanian waters, South-Eastern Baltic Sea

The killer shrimp Dikerogammarus villosus was recorded for the first time in Lithuanian waters in 2015. The species was detected in three sites in the Curonian Lagoon (on two buoys in the lagoon strait and the harbour, and one littoral sampling site) and in the mouth of the Šventoji River. The species presence in the buoy fouling suggests the involvement of shipping in species introduction. Most likely D. villosus has arrived to the Curonian Lagoon with commercial ships, while the invasion into the mouth of the Šventoji River may be associated with leisure shipping as the port situated therein is not currently functioning. Further northward expansion of the killer shrimp in the Baltic Sea basin seems very probable. As the species is highly aggressive, alterations of local macroinvertebrate assemblages can also be predicted