Form Of Coordinate Transformations Research Articles

Design of decentralized adaptive control approach for large-scale nonlinear systems subjected to input delays under prescribed performance

For the first time, the issue of input delay and prescribed performance control is investigated in the same framework for large-scale nonlinear systems in this study, and an original adaptive decentralized control method is proposed by taking advantage of multi-dimensional Taylor network (MTN) method. Firstly, the problem of input delays is solved by introducing new variables, and a new form of coordinate transformation is introduced before controller design, which simplified the control system. Secondly, the problem of prescribed performance control is coped with by integrating the idea of prescribed performance into the Lyapunov functions of first step of backstepping of each subsystem. Thirdly, MTNs are employed to evaluate the combination of unknown functions, and then, a decentralized MTN-based adaptive control scheme is developed by way of backstepping technology. The theoretical analysis indicates that the proposed control scheme can implement the expected tracking goals under the condition of meeting the prescribed performance control. Finally, two examples are given to show the validity and rationality of the proposed control method.

Unification of Gravitational and Electromagnetic Fields in Curved Space-Time Using Gauge Symmetry of Bianchi Identities

This paper deals with the generalization of the linear theory of the unification of gravitational and electromagnetic fields using 4-dimensional gauge symmetry in order to solve the contradictions from the Kaluza-Klein theory’s unification of the gravitational and electromagnetic fields. The unification of gravitational and electromagnetic fields in curved space-time starts from the Bianchi identity, which is well known as a mathematical generalization of the gravitational equation, and by using the existing gauge symmetry condition, equations for the gravitational and electromagnetic fields can be obtained. In particular, the homogeneous Maxwell’s equation can be obtained from the first Bianchi identity, and the inhomogeneous Maxwell’s equation can be obtained from the second Bianchi identity by using Killing’s equation condition of the curved space-time. This paper demonstrates that gravitational and electromagnetic fields can be derived from one equation without contradiction even in curved space-time, thus proving that the 4-dimensional metric tensor using the gauge used for this unification is more complete. In addition, geodesic equations can also be derived in the form of coordinate transformation, showing that they are consistent with the existing equations, and as a result, they are consistent with the existing physical equations.

Unification of Gravitational and Electromagnetic Fields Using Gauge Symmetry

A new method for the unification of gravitational and electromagnetic forces is proposed. Previously, Kaluza-Klein theory dealt with the unification, but it has not yet been established as a complete theory. The main reason for this is that Kaluza-Klein theory has various contradictions due to the use of a 5-dimensional metric tensor. In this paper, unlike the conventional method, various equations related to gravitational and electromagnetic force are derived without any contradiction by processing equations having gauge symmetry within a 4-dimensional range. In this process, we propose that Maxwell’s equations for the electromagnetic force are expressed more simply and implicitly than the existing tensor form. Using the gauge symmetry, it shows that electromagnetic force can exist in single metric tensor along with gravity. In addition, since geodesic equations can be derived in the form of coordinate transformation, it has been shown that they are consistent with the existing equations. As a result, it has shown that they are consistent with the existing physical equations without contradiction.

Two-dimensional cylindrical thermal cloak designed by implicit transformation method

As a new-type technology of heat management, thermal metamaterials have attracted more and more attentions recently and thermal cloak is a typical case. Thermal conductivity of thermal cloak designed by coordinate transformation method is usually featured by inhomogeneity, anisotropy and local singularity. Explicit transformation method, which is commonly used to design thermal cloak with the coordinate transformation known in advance, has insufficient flexibility, making it hard to proactively reduce the difficulty of device fabrication. In this work, we designed the thermal conductivity of two-dimensional (2D) cylindrical thermal cloak using the implicit transformation method without knowledge of the coordinate transformation in advance. With two classes of generation functions taken into consideration, this study adopted full-wave simulations to analyze the thermal cloaking performances of designed thermal cloaks. Material distributions and simulation results showed that the implicit transformation method has high flexibility. The form of coordinate transformation not only influences the homogeneity and anisotropy but also directly influences the thermal cloaking performance. An improved layered structure for 2D cylindrical thermal cloak was put forward based on the generation function g ( r ) = r 15 , which reduces the number of the kinds of constituent materials while guaranteeing good thermal cloaking performance. This work provides a beneficial guidance for reducing the fabrication difficulty of thermal cloak.

Least Squares Collocation Alternative to Helmert’s Transformation with Hausbrandt’s Post – Transformation Correction

Abstract The paper presents a least squares collocation - based alternative to Helmert’s transformation with Hausbrandt’s post – transformation correction. The least squares collocation is used as an exact predictor i.e. it honors the data, thus the problem of zero residuals on transformation control points is overcome and zero residuals are assured by the method applied. Despite the fact that the procedure is presented for Helmert’s transformation it may easily be copied to any other form of coordinate transformation. A numerical example is provided within the content of the paper.

Geodesic equations for a charged particle in the unified theory of gravitational and electromagnetic interactions

A new model of gravitational and electromagnetic interactions is constructed as a version of the classical Kaluza-Klein theory based on a five-dimensional manifold as the physical space-time. The velocity space of moving particles in the model remains four-dimensional as in the standard relativity theory. The spaces of particle velocities constitute a four-dimensional distribution over a smooth five-dimensional manifold. This distribution depends only on the electromagnetic field and is independent of the metric tensor field. We prove that the equations for the geodesics whose velocity vectors always belong to this distribution are the same as the charged particle equations of motion in the general relativity theory. The gauge transformations are interpreted in geometric terms as a particular form of coordinate transformations on the five-dimensional manifold.

Control-Oriented Order Reduction of Finite Element Model

In the dynamics modeling of a structure, finite element analysis employs reduction techniques, such as Guyan’s reduction, that remove some of the “insignificant” physical coordinates, that is, degrees of freedom at a node point. Despite such reduction, the resultant model is still too large for control design. This warrants further reduction as is frequently done in control design by approximating a large dynamical system with a fewer number of state variables. A problem, however, arises because a model usually undergoes, before being reduced, some form of coordinate transformations that destroy the physical meanings of the states. To correct such a problem, we developed a method that expresses a reduced model in terms of a subset of the original states. The proposed method starts with a dynamic model that is originated and reduced in finite element analysis. The model is then converted to a state-space form, and reduced further by the internal balancing method. At this stage, being in the balanced coordinate system, the states in the reduced model have no apparent resemblance to those of the original model. Through another coordinate transformation that is developed in this paper, however, this reduced model is expressed by a subset of the original states, so that the states in the reduced model can be related to the degrees of freedom of the nodes in the original finite element model.

Generalized Lorentz transformations in the general theory of relativity and the behavior of certain physical quantities at the boundary of the R and T regions

The transition between diagonal metrics is considered. The transformations are written in generalized Lorentzian form. This form of coordinate transformations is used to obtain transformations for the velocity, acceleration, force, momentum, energy, and the components of the energy-momentum tensor. The relations obtained are used to estimate the physical quantities at the boundary of the R and T regions.