A bionic controllable strain membrane for cell stretching at air–liquid interface inspired by papercutting

Lung diseases associated with alveoli,such as acute respiratory distress syndrome,have posed a long-term threat to human health.However,an in vitro model capable of simulating different deformations of the alveoli and a suitable material for mimicking basement membrane are currently lacking.Here,we present an innovative biomimetic controllable strain membrane(BCSM)at an air–liquid interface(ALI)to reconstruct alveolar respiration.The BCSM consists of a high-precision three-dimensional printing melt-electrowritten polycaprolactone(PCL)mesh,coated with a hydrogel substrate—to simulate the important functions(such as stiffness,porosity,wettability,and ALI)of alveolar microenvironments,and seeded pulmonary epithelial cells and vascular endothelial cells on either side,respectively.Inspired by papercutting,the BCSM was fabricated in the plane while it operated in three dimensions.A series of the topological structure of the BCSM was designed to control various local-area strain,mimicking alveolar varied deformation.Lopinavir/ritonavir could reduce Lamin A expression under over-stretch condition,which might be effective in preventing ventilator-induced lung injury.The biomimetic lung-unit model with BCSM has broader application prospects in alveoli-related research in the future,such as in drug toxicology and metabolism.

Adaptive composite anti-disturbance control for heavy haul trains

In this paper,an adaptive composite anti-disturbance control of heavy haul trains(HHTs)is proposed.First,the mechanical principle and characteristics of couplers are analysed and the longitudinal multi-particles nonlinear dynamic model of HHTs is established,which can satisfy that the forces of vehicles in different positions are different.Subsequently,a radial basis function network(RBFNN)is employed to approximate the uncertainties of HHTs,and a nonlinear disturbance observer(NDO)is constructed to estimate the approximation error and external disturbances.To indicate and improve the approximation accuracy,a serial-parallel identification model of HHTs is constructed to generate a prediction error,and an adaptive composite anti-disturbance control scheme is developed,where the prediction error and tracking error are employed to update RBFNN weights and an auxiliary variable of NDO.Finally,the feasibility and effectiveness of the proposed control scheme are demonstrated through the Lyapunov theory and simulation experiments.

Design and control of chemical compositions for high-performance austempered ductile iron

This paper presents the effects of chemical compositions of austempered ductile iron(ADI)on casting quality,heat treatment process parameters and mechanical properties of final products.Through experiment and production practice,the impacts of carbon equivalent on ADI and its mechanical properties have been studied. Proper content ranges for carbon and silicon have been obtained to avoid ADI casting shrinkage and graphite floatation,as well as to achieve the optimal mechanical properties.According to the impact of silicon content on austenite phase transformation,the existing form of carbon in ADI has been analyzed,and also the formula and diagram showing the relationship between austenitizing temperature and carbon content in austenite have been deduced.The chemical composition range for high performance ADI and its control points have been recommended, to serve as a reference for production process.

Composite Anti-Disturbance Control of Hidden Semi-Markov Jump Systems via Disturbance Observer

This paper focuses on the disturbance suppression issue of hidden semi-Markov jump systems leveraging composite control.The system consists of a semi-Markov layer and an observed mode sequence layer,and it is subject to a matched disturbance generated by an exogenous system and a mismatched disturbance that is norm bounded.The proposal is to design a composite controller based on a disturbance observer to counteract and attenuate the disturbances effectively.By constructing a special Lyapunov function comparison point,the exponential stability is analyzed with the stability criterion in the form of linear matrix inequality is established.Two simulation examples are provided to demonstrate the practical merits of the composite controller relative to the single H_(∞)control.

Turning mechanism and composite control of stratospheric airships

The parametric model of stratospheric airships is established in the body axes coordinate system. In this paper we study the turning mechanism of stratospheric airships including the generated forces and the key parameters for steady turning. We compare and analyze the different driven-characteristics between aerodynamic control surfaces and vectored thrust in turning. We design a composite control combining aerodynamic control surfaces and vectored thrust according to different dynamic pressure conditions, to achieve coordinated turning under high or low airspeed situations.

A Composite Adaptive Fault-Tolerant Attitude Control for a Quadrotor UAV with Multiple Uncertainties

In this paper,a composite adaptive fault-tolerant control strategy is proposed for a quadrotor unmanned aerial vehicle(UAV)to simultaneously compensate actuator faults,model uncertainties and external disturbances.By assuming knowledge of the bounds on external disturbances,a baseline sliding mode control is first designed to achieve the desired system tracking performance and retain insensitive to disturbances.Then,regarding actuator faults and model uncertainties of the quadrotor UAV,neural adaptive control schemes are constructed and incorporated into the baseline sliding mode control to deal with them.Moreover,in terms of unknown external disturbances,a disturbance observer is designed and synthesized with the control law to further improve the robustness of the proposed control strategy.Finally,a series of comparative simulation tests are conducted to validate the effectiveness of the proposed control strategy where a quadrotor UAV is subject to inertial moment variations and different level of actuator faults.The capabilities and advantages of the proposed control strategy are confirmed and verified by simulation results.

Composite Control of Nonlinear Singularly Perturbed Systems via Approximate Feedback Linearization

This article is devoted to the problem of composite control design for continuous nonlinear singularly perturbed(SP)system using approximate feedback linearization(AFL)method.The essence of AFL method lies in the feedback linearization only of a certain part of the original nonlinear system.According to AFL approach,we suggest to solve feedback linearization problems for continuous nonlinear SP system by reducing it to two feedback linearization problems for slow and fast subsystems separately.The resulting AFL control is constructed in the form of asymptotic composition(composite control).Standard procedure for the composite control design consists of the following steps:1)system decomposition,2)solution of control problem for fast subsystem,3)solution of control problem for slow subsystem,4)construction of the resulting control in the form of the composition of slow and fast controls.The main difficulty during system decomposition is associated with dynamics separation condition for nonlinear SP system.To overcome this,we propose to change the sequence of the design procedure:1)solving the control problem for fast state variables part,2)system decomposition,3)solving the control problem for slow state variables part,4)construction of the resulting composite control.By this way,fast feedback linearizing control is chosen so that the dynamics separation condition would be met and the fast subsystem would be stabilizable.The application of the proposed approach is illustrated through several examples.

Composite anti-disturbance position and attitude control for spacecrafts with parametric uncertainty and flexible vibration

The rendezvous and proximity operations with respect to a tumbling non-cooperative target pose high requirement for the position and attitude control accuracy of servicing spacecraft.However,multiple disturbances including parametric uncertainties,flexible vibration,and unknown nonlinear dynamics degrade the control performance significantly.In order to enhance the system anti-disturbance ability,this paper proposes a composite anti-disturbance control law for the spacecraft position and attitude tracking.Firstly,the relative position and attitude dynamic models with multiple disturbances are established,where the refined descriptions of multiple disturbances are accomplished based on their characteristics.Then,by combining a dual Disturbance ObserverBased Control(DOBC)and a sliding mode control,a composite controller with hierarchical architecture is proposed,where the dual DOBC in the feedforward channel is used to reject the flexible vibration,environment disturbance,and complicated nonlinear dynamics,while the parametric uncertainties are attenuated by the sliding mode control in the feedback channel.Stability analysis is carried out for the closed-loop system by unifying the sliding mode dynamics and observer dynamics.Finally,the effectiveness of the proposed controller is verified via numerical simulation and hardware-in-the-loop test.