A Hybrid Nonlinear Active Control Strategy Combining Dry Friction Control and Nonlinear Velocity Compensation Control

Friction dampers are widely used in structural vibration suppression in various fields, such as aeronautics, astronautics, robotics, precision manufacturing, etc. Traditional friction dampers are mainly used in a passive way to optimize vibration suppression with an immutable pressure around certain excitation. In this manuscript, a hybrid control strategy by considering both the friction force in the active control law and a nonlinear velocity compensation force is put forward: First, the normal force applied on the friction damper was adjusted to ensure its vibration reduction effect under different excitation for a first passive control; second, the active control law was established by combining the dry friction force and the velocity control force in the state space; lastly, the stability of the nonlinear control law was determined by Lyapunov criterion. Numerical simulations were conducted on a three degree-of-freedom system (3-DOF) based on the proposed hybrid control strategy, to show the control efficiency in vibration suppression and economic efficiency in energy input into the system. Simulation results showed that the proposed control law could reduce the amplitude of the active control force by about 5% without degrading the control efficiency.

Boundary Layer Flow Over a Vertical Cylinder Embedded in a Porous Medium Moving with non Linear Velocity

In this work, we consider a steady flow of an incompressible fluid over a cylinder which is semi-infinite. The cylinder is embedded in a porous medium and is considered to move vertically with nonlinear velocity. A system of ordinary differential equations is obtained from the partial differential equations governing the motion using a self-similarity transformation. Such system of ordinary differential equations is solved numerically after obtaining the missed initial conditions. The problem has been solved analytically for the linear velocity case. Numerical and analytical results for such case are given to validate the numerical method used.

Analysis of Carreau fluid flow by convectively heated disk with viscous dissipation effects

The primary motive of this study is to examine boundary layer flow of Carreau fluid over a convectively heated disk stretching with nonlinear velocity. The flow is assumed to be two dimensional. Moreover, viscous dissipation possessions are taken into description. The dominating nonlinear differential equations involving partial derivatives are changed into nonlinear differential equations involving ordinary derivatives by applying suitable transformations. Numerical outcomes for velocity and temperature are obtained from MATLAB’s built-in solver bvp4c and presented graphically and in tabular form.