Adaptive vehicle posture and height synchronization control of active air suspension systems with multiple uncertainties

This paper addresses the tasks of height and posture motion control for an electronically controlled active air suspension (AAS) system. A mathematical model of a vehicle body with AAS system is established to describe the dynamic characteristics and then formulated into a multi-input multi-output nonlinear system by considering parametric uncertainties and unmodelled dynamics. Based on this mathematical model, a synchronization control strategy is proposed to adjust the heights of adjacent AASs simultaneously, driving the pitch and roll angles closely to an arbitrarily neighborhood of zero, achieving global uniform ultimate boundedness. The proposed controller is robust to parametric uncertainties and external disturbances. A projection operator is utilized to limit the estimated parameters to their corresponding prescribed bounds in finite time. A co-simulation is conducted by combining a virtual vehicle plant with ASS system in AMEsim with the proposed synchronization controller in MATLAB/Simulink. Simulation results demonstrate that the proposed synchronization controller is effective and robust.     

Design and experimental validation of a nonlinear controller for underactuated surface vessels

Nonlinear Dynamics - This paper addresses the problem of trajectory tracking control of an underactuated surface vessel moving in a two-dimensional space in the presence of unknown disturbances. In...     

Stokes equations under nonlinear slip boundary conditions coupled with the heat equation: A priori error analysis

In this work, we consider the heat equation coupled with Stokes equations under threshold type boundary condition. The conditions for existence and uniqueness of the weak solution are made clear. Next we formulate the finite element problem, recall the conditions of its solvability, and study its convergence by making use of Babuska–Brezzi's conditions for mixed problems. Third we formulate an Uzawa's type iterative algorithm that separates the fluid from heat conduction, study its feasibility, and convergence. Finally the theoretical findings are validated by numerical simulations.     

Photosensitized Thymine Dimerization via Delocalized Triplet Excited States

A new mechanism of photosensitized formation of thymine (Thy) dimers is proposed, which involves generation of a delocalized triplet excited state as the key step. This is supported by chemical evidence obtained by combining one benzophenone and two Thy units with different degrees of freedom, whereby the photoreactivity is switched from a clean Paternò–Büchi reaction to a fully chemo‐, regio‐, and stereoselective [2+2] cycloaddition.     

Laser Desorption Ionization of As<Subscript>2</Subscript>Ch<Subscript>3</Subscript> (Ch = S,Se, and Te) Chalcogenides Using Quadrupole Ion Trap Time-of-Flight Mass Spectrometry: A Comparative Study

Laser desorption ionization using time-of-flight mass spectrometer afforded with quadrupole ion trap was used to study As₂Ch₃ (Ch = S, Se, and Te) bulk chalcogenide materials. The main goal of the study is the identification of species present in the plasma originating from the interaction of laser pulses with solid state material. The generated clusters in both positive and negative ion mode are identified as 10 unary (S _p ^+/– and As _m ^+/– ) and 34 binary (As _m S _p ^+/– ) species for As₂S₃ glass, 2 unary (Se _q ^+/– ) and 26 binary (As _m Se _q ^+/– ) species for As₂Se₃ glass, 7 unary (Te _r ^+/– ) and 23 binary (As _m Te _r ^+/– ) species for As₂Te₃ material. The fragmentation of chalcogenide materials was diminished using some polymers and in this way 45 new, higher mass clusters have been detected. This novel approach opens a new possibility for laser desorption ionization mass spectrometry analysis of chalcogenides as well as other materials.

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Strong Solutions to the Navier-Stokes Equations Around a Rotating Obstacle

We study the existence of strong solutions to the three-dimensional Navier-Stokes initial-boundary value problem in the domain, , exterior to a rigid body that rotates with constant angular velocity, . We show that when the initial data, u₀, are prescribed in an appropriate functional class, a strong solution exists at least in some finite time interval. Moreover, the solution exists for all times, provided u₀, in suitable norm, and the magnitude of do not exceed a certain constant depending only on the kinematic viscosity and on the regularity of . In this latter case, we also show that the velocity field converges to the velocity field of the corresponding steady-state solution.     

On the Self-Propelled Motion of a Rigid Body in a Viscous Liquid and on the Attainability of Steady Symmetric Self-Propelled Motions

In this paper we study the motion of a self-propelled rigid body through a Navier-Stokes fluid that fills all the three-dimensional space exterior to it. We formulate the problem and prove the existence of a weak solution that is defined globally in time, provided that the net flux across the boundary, of the prescribed boundary values for the velocity, is zero. It is these prescribed boundary values that propel the body, and the body is free to rotate during its motion. In the special case of a body which is symmetric about an axis, and propelled by symmetric boundary values, we obtain strong solutions representing translational motions in the direction of the axis. Further, we prove that for small Reynolds numbers every steady solution with such axial symmetry is attainable as the limit, as time tends to infinity, of a strong nonsteady solution which starts from rest.