Ângelo Marcelo Tusset

An optimal linear control design for nonlinear systems

This paper studies the linear feedback control strategies for nonlinear systems. Asymptotic stability of the closed-loop nonlinear system is guaranteed by means of a Lyapunov function, which can clearly be seen to be the solution of the Hamilton-Jacobi-Bellman equation thus guaranteeing both stability and optimality. The formulated Theorem expresses explicitly the form of minimized functional and gives the sufficient conditions that allow using the linear feedback control for nonlinear system. The numerical simulations the Duffing oscillator and the nonlinear automotive active suspension system are provided to show the effectiveness of this method.

Thermal-hydraulic analysis under partial loss of flow accident hypothesis of a plate-type fuel surrounded by two water channels using RELAP5 code

Thermal-hydraulic analysis of plate-type fuel has great importance to the establishment of safety criteria, also to the licensing of the future nuclear reactor with the objective of propelling the Brazilian nuclear submarine. In this work, an analysis of a single plate-type fuel surrounding by two water channels was performed using the RELAP5 thermal-hydraulic code. To realize the simulations, a plate-type fuel with the meat of uranium dioxide sandwiched between two Zircaloy-4 plates was proposed. A partial loss of flow accident was simulated to show the behavior of the model under this type of accident. The results show that the critical heat flux was detected in the central region along the axial direction of the plate when the right water channel was blocked.

Control of Slewing Motions of Flexible Structures Using Shape Memory Alloy

This paper presents the position and vibration control of a single flexible slewing structure driven by a DC motor at the slewing axis. The position is controlled over the current applied to the DC motor armature. To control the vibration of the flexible structure Shape Memory Alloys (SMA) are applied to them. The control is made through the State Dependent Ricatti Equations (SDRE) technique which uses sub-optimal control and system local stability search. Numerical simulations and experimental results are presented which demonstrate the effectiveness of the proposed control strategy.Copyright

Influence of Smart Material on the Dynamical Response of Mechanical Oscillator

The dynamical response of systems with shape memory alloy (SMA) or magnetorheological damper (MRD) presents a different behavior due to their nonlinear characteristics. Both systems have a nonlinear behavior due to adaptive dissipation related to their hysteretic behavior. This property is very attractive in engineering field. This paper investigates the nonlinear dynamical behavior of an SMA or MRD oscillator system. The LuGre mathematical model is used to represent the MRD behavior. On the other hand, the SMA model is based on a thermomechanical consistent model with four state variables.

Rubbing Effect Analysis in a Continuous Rotor Model

One of the most important malfunction that can cause severe damage in rotating machines is the contact between fixed and rotating parts. The most common sources for rubbing is mass unbalance and instabilities due to fluid-rotor interaction. In this way, this paper presents a continuous rotor model for rubbing applications considering transverse shear, rotatory inertia, and gyroscopic moments. The contribution of it is to present a model to be applied in cases where these effects are not negligible. It is shown that for low slenderness ratio the model is equivalent to the commonly used Euler-Bernoulli continuous model. The normal and friction contact forces between the rotor and the stator are modeled using the Hertz contact theory, which is a nonlinear contact model, and the Coulomb friction model, respectively. In addition, the response of the rotor under impact was studied in the frequency domain using Wavelet Techniques for detection and characterization of rubbing phenomenon.

Proposal of a Nonlinear Piezoelectric Coupling Term to Energy Harvesting Interactions

Nowadays, new technologies have triggered the needs of new energy sources, smaller and more efficient, so the research about energy harvesting has increased substantially. Several researchers have developed the conversion of wasted mechanical energy to electrical energy using piezoelectric materials as a transducer. This chapter proposes a mathematical model for the constitutive equation of a piezoelectric transducer. Experimental results involving piezoelectric elements were considered. The proposed mathematical model allows a considerably better description. The results are closer to those obtained in a real system, reducing inaccuracy of predictive behaviour of the piezoelectric energy harvesting system. In this work, the numerical simulations show a significant difference between results obtained with the proposed model and other models available in literature.

On Optimal Control of a Nonlinear Robotic Mechanism Using the Saturation Phenomenon

In this paper a robotic arm is modelled by a double pendulum excited in its base by a DC motor of limited power via crank mechanism and elastic connector. In the mathematical model, a chaotic motion was identified for a wide range of parameters. Controlling of the chaotic behaviour of the system were implemented using two control techniques, the nonlinear saturation control (NSC) and the optimal linear feedback control (OLFC). The actuator and sensor of the device are allowed in the pivot and joints of the double pendulum. The NSC is based in the second order differential equations and its action in the pivot/joint of the robotic arm is through of quadratic nonlinearities feedback signals. The OLFC involves the application of two control signals, a nonlinear feedforward control to maintain the controlled system to a desired periodic orbit, and a feedback control to bring the trajectory of the system to the desired orbit. Simulation results, including of uncertainties show the feasibility of the both methods, for chaos control of the considered system.

Suppression of chaotic vibrations in a nonlinear half-car model

The present work investigates the nonlinear response of a half-car model. The disturbances of the road are assumed to be sinusoidal. After constructing the bifurcation diagram, we using the 0-1 test for identify the chaotic motion. The principal objective of this study is to eliminate the chaotic behaviour of the chassis and reduce its vibration, and for this reason a control system for semi-active vehicle suspension with magnetorheological damper is proposed. The control mechanism is designed based on SDRE technique, where the control parameter is the voltage applied to the coil of the damper. Numerical results show that the proposed control method is effective in significantly reducing of the chassis vibration, increasing therefore, passenger comfort.