Papers by Keyword: Nonlinear Model

Abstract: This paper presents a Backstepping controller for five degrees of freedom Spherical Inverted Pendulum. Since the system is nonlinear, unstable, underactuated and MIMO and has a nonsquare form, the classic control design cannot be applied to control it. In order to remedy this problem, we propose in this paper a new method based on hierarchical steps of the Backstepping controller taking into a count the nonlinearities that cannot be neglected. Furthermore, a Linear Quadratic Regulator controller and LQR + PID based on the linearized system model are also designed for performance comparison. Finally, a simulation study is carried out to prove the effectiveness of proposed control scheme and is validated using the virtual reality environment that proves the performance of the Backstepping controller over the linear ones where it brings the pendulum from any initial condition in the upper hemisphere while the base is brought to the origin of the coordinates.

Abstract: The Boumerdes earthquake of May 21, 2003 in Algeria, which widely felt within a radius of ~ 400 km, caused damage in five provinces. Numerous structures have been devastated, others suffered of damages. Keddara rockfill dam which is situated approximately at 20 km from the epicentre was strongly shaken during this seismic event and can undergo significant deformations. In this study, numerical analysis of Keddara rockfill dam under Boumerdes earthquake is performed. It is mainly focus on the seismic amplification at different level of the dam under the main shock with dominant frequency close to the natural frequency of the dam. The low coherence between the input and the structural output indicates the need of nonlinear analysis of the dam under the spatial variation in excitation. Furthermore, the effect of plasticity on the seismic response is investigated by using maximum acceleration which is one of the most important properties selected. The analysis of the dam under stochastic non-uniform excitation is conducted using a 2-D finite difference modeling by using the software Fast Lagrangian Analysis of Continua (FLAC). The final results obtained after successive analyses on the dam configuration incorporating the nonlinear soil properties are presented.

Abstract: This article addresses the problem of the joint policy of production and maintenance under constraint of outsourcing. The production system considered brings together two companies; the principal represented by a machine Md, while the subcontractor represented by a machine Ms. Our production system aims to satisfy a constant and continuous demand for a single product type. Indeed, outsourcing is justified by the lack of production capacity. However, the main objective is to determine simultaneously for each period, the age of preventive maintenance, the optimal stock threshold level, the maximum capacity of subcontractor and its unit cost of production, to better satisfy the customer's need. The last two parameters encourage an optimal choice of subcontractor, while minimizing the total cost generated by the contractor, including the costs of maintenance, production, storage and shortage. The results show that the proposed model performs quite well and opens new research direction for future improvements.

Abstract: This work is devoted to modeling of nonlinear dynamics of the rotating drill-string taking into account initial curvature and finiteness of deformations. The drill-string is compressed by variable axial force. The case of flat bending of the drill-string with an initial curvature is studied, where drill-string considered as a one-dimensional rotating rod of a symmetric cross-section. A nonlinear model is developed on the basis of the variational principle Ostrogradsky-Hamilton and the theory of finite deformations. The numerical analysis of the model is carried out. The influence of bending forms and initial curvature of the drill-string on the amplitude of transverse vibrations is established.

Abstract: This paper discusses three kinds of typical one-dimensional nonlinear equations coming from low permeability reservoir seepage models with different boundary conditions. The several finite difference methods including forward difference method and second central order difference quotient method are used for the respective discrete process of three models. With these difference methods, the discrete schemes of models are obtained. Then the corresponding nonlinear discrete equations are deduced. While dealing with the boundary condition, the mid-rectangle formula is used. Finally, integrated discrete equations of three nonlinear equations are formed. The results should be meaningful for the numerical simulation of non-Darcy flow model of the low-permeability oil wells.

Abstract: The dynamics of the horizontal drill string considering frictional forces between the column and the borehole is investigated. A model of longitudinal vibrations of columns proposed in T.G. Ritto et al. is considered. The investigated model has a nonlinear character, and is modelled by the lumped parameters method. The drill-string is discretized with 100 nodes of lumped masses. Displacement of the bit, bit speed and also the ratio between the output power (obtained from the bit-rock interaction) and the input power is defined by the authors. The frictional force between the column and the borehole is relevant and uncertain. The frictional coefficient is modelled as a random field with exponential autocorrelation function. The obtained results are qualitatively and quantitatively consistent with the results of Ritto, where the dynamic model calculations are carried out by the finite element method.

Abstract: A nonlinear controller is presented for a digital hydraulic cylinder against disturbance. We first establish the nonlinear model of digital hydraulic cylinder position control system. Then a Lyapunov function and a nonlinear controller are presented. The controller designing problem is translated into the problem of solving a linear matrix inequality. The experiment results show that the controller proposed by this paper has much better performance than traditional one.

Abstract: Digital product development is very rapid, this paper use engineering method to establish electronic product development model, and use Shift-share method to analysis decompose the economic capacity of the electronics industry, with the high level of industrial economic quantity Comparative analysis of the overall strength of the digital industry. Shift-share model with a comprehensive economic assessment, and put forward development proposals of corresponding electronic products.

Abstract: We prove the existence of an invariant measure for the continuous semigroup associate with a nonlinear model under the compact set Lyapunov condition. Further,adding the ergodicity of the semigroup operator, we prove the asymptotic stability in distribution for the semigroup. We give a criteria of the asymptotic stability in distribution for the type of evolution equation having a linear generator. Our method is based on continuous semigroup and its generator.We illustrate the result by the Lorenz chaotic model and prove the existence of the natural invariant measure for Lorenz chaotic model.

Abstract: . Considering of the highly nonlinear, time-variable and complex dynamics and the easy variance of hydrogenerator set systems structure and parameters, a nonlinear dynamical model is presented, which can be analyzed by the bifurcation theory of nonlinear differential equations and simulated in computer. By using the genetic algorithm, the PID parameters of hydrogenerator set intelligent system are optimized and the control performances are improved. The algebra criterion about the existence of bifurcation is employed to study the bifurcation behavior of the nonlinear model which takes the PID parameters as the bifurcation ones. The simulations show that a supercritical bifurcation is likely to exist in hydrogenerator set system and the bifurcation will occur for the higher values of PID parameters. Theory and simulation results of this paper can be considered as good suggest for intelligent PID control system of hydrogenerator set system.