Decoupling Of Systems Research Articles

Dynamic long axis for ultra-precision machining of optical linear structures

Currently, fly cutting is the most popular manufacturing technology for the machining of planar groove structures. The disadvantage of this technology is the long machining time. A promising alternative technology for the machining of planar grooves is planing. The main disadvantage of planing in comparison to fly cutting is the limitation of conventional precision axes concerning a high dynamic movement. Regarding to this aspect the Fraunhofer IPT has developed a precise linear axis. It allows high dynamic movements by using an impulse decoupling system (AiF-FV-Nr.: 13,270 N). The paper describes the mechanical setup and the development and optimization of the mechanical main component. The detailed simulation of the drive system (including motor control loop and impulse decoupling system), results of static and dynamic measurements and test machining results are presented.

Safe Oxidation Reactions. Development of an Explosion Protection System from Process Development Lab to Large Scale Production Plant

The systematic development of an explosion protection system for an oxidation reaction in pure oxygen following a thorough risk analysis is described. By evaluating both probability and consequences of all risks identified it could be shown that an explosion in the investigated system cannot be prevented completely. Therefore the emphasis of the system was to protect humans and the environment from the consequences of this residual risk. Several design alternatives were considered. Only an explosion decoupling system, consisting of a combination of a flame interrupter and a fast-acting valve can fulfill this task. The successful start-up and running production process up to now confirm the chosen path.

Seals for plastic components: Integrated seals contribute to greater functionality of plastic components

Reinz-Dichtungs GmbH has worked as a system partner to the automotive and mechanical engineering industries for many years, and has developed considerable knowledge of the special requirements of seals for plastic components. In automotive applications, plastic components with integrated seals are required to satisfy increasingly stringent requirements. These include stability during exposure to temperature and various media, as well as noise reduction. To achieve the required noise reduction, it may be necessary to use special plastics or complex decoupling systems. The company has a successful history of developing innovative plastic systems for the European automotive industry, and is presenting some of the current trends in the area of seal technology for plastic components. Currently Dana supplies more than 30 valve cover systems worldwide for private cars and commercial vehicles.

Improvement of Pulse Characteristics of Neutrons from a Decoupled Liquid-Hydrogen Moderator Using a Multi-Layer Decoupler System at a Pulsed Spallation Neutron Source

Neutron pulse shapes are important in pulsed neutron sources, especially for high-resolution neutron scattering instruments. Around the region of thermal equilibrium energy, the moderator is the main factor in deciding the neutron pulse shapes from a decoupled moderator. However, in the slowing-down energy region, the reflector also affects the pulse shapes, and the neutrons in this energy region will be increasingly important for precise neutron-scattering experiments in the future. Lead has many preferable characteristics as a reflector from a neutronic point of view, but it has a disadvantage in that it creates a long pulse tail, since it takes a very long time for a neutron in lead to slow down. To shorten this pulse tail, we propose a multi-layer decoupler system and compare its performance with that of a traditional decoupler system. The multi-layer decoupler was found to shorten the pulse tail effectively without causing a large decrease in the pulse peak intensity, whereas the traditional decoupler caused a greater decrease in this intensity. This result indicates that the multi-layer decoupler is useful for improving pulse characteristics of neutrons from a decoupled moderator at the pulsed neutron source using a lead reflector.

Improvement of Pulse Characteristics of Neutrons from a Decoupled Liquid-Hydrogen Moderator Using a Multi-Layer Decoupler System at a Pulsed Spallation Neutron Source

Neutron pulse shapes are important in pulsed neutron sources, especially for high-resolution neutron scattering instruments. Around the region of thermal equilibrium energy, the moderator is the main factor in deciding the neutron pulse shapes from a decoupled moderator. However, in the slowing-down energy region, the reflector also affects the pulse shapes, and the neutrons in this energy region will be increasingly important for precise neutron-scattering experiments in the future. Lead has many preferable characteristics as a reflector from a neutronic point of view, but it has a disadvantage in that it creates a long pulse tail, since it takes a very long time for a neutron in lead to slow down. To shorten this pulse tail, we propose a multi-layer decoupler system and compare its performance with that of a traditional decoupler system. The multi-layer decoupler was found to shorten the pulse tail effectively without causing a large decrease in the pulse peak intensity, whereas the traditional decoupler caused a greater decrease in this intensity. This result indicates that the multi-layer decoupler is useful for improving pulse characteristics of neutrons from a decoupled moderator at the pulsed neutron source using a lead reflector.

Analysis of the local truncation error in the pressure‐free projection method for incompressible flows: a new accurate expression of the intermediate boundary conditions

AbstractThe numerical integration of the Navier–Stokes equations for incompressible flows demands efficient and accurate solution algorithms for pressure–velocity splitting. Such decoupling was traditionally performed by adopting the Fractional Time‐Step Method that is based on a formal separation between convective–diffusive momentum terms from the pressure gradient term. This idea is strictly related to the fundamental theorem on the Helmholtz–Hodge orthogonal decomposition of a vector field in a finite domain, from which the name projection methods originates. The aim of this paper is to provide an original evaluation of the local truncation error (LTE) for analysing the actual accuracy achieved by solving the de‐coupled system. The LTE sources are formally subdivided in two categories: errors intrinsically due to the splitting of the original system and errors due to the assignment of the boundary conditions. The main goal of the present paper consists in both providing the LTE analysis and proposing a remedy for the inaccuracy of some types of intermediate boundary conditions associated with the prediction equation. Such evaluations will be directly performed in the physical space for both the time continuous formulation and the finite volume discretization along with the discrete Adams–Bashforth/Crank–Nicolson time integration. A new proposal for a boundary condition expression, congruent with the discrete prediction equation is herein derived, fulfilling the goal of accomplishing the closure of the problem with fully second order accuracy. In our knowledge, this procedure is new in the literature and can be easily implemented for confined flows. The LTE is clearly highlighted and many computations demonstrate that our proposal is efficient and accurate and the goal of adopting the pressure‐free method in a finite domain with fully second order accuracy is reached. Copyright © 2003 John Wiley & Sons, Ltd.

A novel approach to control of nonminimum-phase nonlinear systems

We present an approach to control of nonminimum-phase multiple-input-multiple-output (MIMO) nonlinear systems based on a singular perturbation-like technique. First, we show that a MIMO nonlinear system can be converted into a singularly perturbed system through magnitude and time-scaling transformation. In particular, the proposed transformation technique can make the hidden or internal dynamics behave like a fast subsystem. However, the fast subsystem takes a weakly controllable form, which implies that a small positive low-gain parameter multiplies the control input in the fast subsystem. For this reason, the well-known integral manifold approach is then utilized to decompose the resulting singularly perturbed system into two subsystems in separate timescales, each of which is of a lower dimension and, more importantly, controllable in the sense that the control input will explicitly appear in the boundary-layer system. The proposed method is particularly useful to make the input-output dynamic characteristics of a decouplable nonminimum-phase nonlinear system decoupled and linear.

Adaptive decoupling predictive temperature control for an extrusion barrel in a plastic injection molding process

This paper presents an adaptive decoupling temperature control for an extrusion barrel in a plastic injection molding process. After establishing a stochastic polynomial matrix model of the system, a corresponding decoupling system representation was then developed. The decoupling control design was derived based on the minimization of a generalized predictive performance criterion. The set-point tracking, disturbance rejection, and robustness capabilities of the proposed method can be improved by appropriate adjustments to the tuning parameters in the criterion function. A real-time control algorithm, including the recursive least-squares method, is proposed which was implemented using a digital signal processor TMS320C31 from Texas Instruments. Through the experimental results, the proposed method has been shown to be powerful under set-point changes, load disturbances, and significant plant uncertainties. The proposed control law is shown to be less computational and more effective than other well-known multivariable control strategies, and more powerful than single-loop temperature-zone control policies.

Signal separation using second- and high-order statistics

This paper presents two methods for signal separation. In either method, the fundamental criterion for separation relies on reducing to zero, or at least minimizing, the output cross-correlation or cross-cumulant functions of a decoupling multi-input–multi-output system that is fed with mixed signals. In one of the approaches used, the parameters of this system are determined through solving — in a least-squares sense — a linearized set of equations describing the deviations from zero of either the cross-correlation or cross-cumulant functions when evaluated for different lags. An alternative rapidly convergent adaptive algorithm is also described for minimizing the cross-correlation or cross-cumulant functions. The paper also considers both FIR and IIR representations of the decoupling system. It shows that using IIR functions in the decoupling system does not offer any merit over the FIR case. Illustrative examples are given to show the performance of the proposed algorithms. Copyright © 2000 John Wiley & Sons, Ltd.

The analysis of arbitrarily-damped linear mechanical systems

The analysis of arbitrarily-damped linear mechanical systems is the subject of this paper, the main issue being the analysis of nondecouplable systems. It is well known that decouplable systems occur when the damping matrix happens to be a linear combination of the mass and stiffness matrices. Systems with this type of damping are said to have proportional damping, which nevertheless seldom occurs in practice, but many a damped system is analyzed under the assumption that it is proportionally damped. In fact, this property allows the analyst to study these systems using the same approach as that applicable to their undamped counterparts. In this paper, we show that proportional damping need not be assumed in order to analyze the system at hand with the same approach as used to analyze undamped systems. Moreover, we propose an algorithm to determine the natural frequencies, the damped frequencies and the damping ratios of an n-degree-of-freedom damped system, that does not require the casting of the system into first-order form. In this way, the characteristic equation is derived naturally as a 2n-degree polynomial, computing its roots being then straightforward. Furthermore, we propose a semigraphical method to ease this calculation, which should be attractive to practicing engineers.

Limiting zeros of decouplable MIMO systems

For sufficiently rapid zero-order hold (ZOH) sampling, it is known that the zeros of single-input/single-output discrete-time systems expressed in the forward shift operator converge to values determined only by the degrees of the finite and infinite zeros of the underlying continuous-time system. In this paper, it is shown how this result can be generalized to multi-input/multi-output (MIMO) systems decouplable by static-state feedback (equivalently, having a diagonal interactor matrix). In the fast sampling limit, the authors show how invariant and infinite zero structure is mapped under ZOH sampling for discrete-time systems expressed in either the delta (forward difference) or forward shift operators.

ROBUST DECOUPLING CONTROL BASED ON EXTERNAL LOOPS

Decoupling control can substantially simplify the design of multivariable control systems. However, decouplers are usually sensitive to modeling errors, especially for the systems with relative gains being far away from unity. Hence, decoupling control is limited in practical application. In the present study, robust control of a decoupling system with external loops is developed. Design of the control system consists of two steps. The first step is to design the decoupler and the controller based on the nominal plant. The second step is to design the filters in the external loops by using a robust stability criterion. The robust control is implemented without changing the original design of the decoupler and the controller. The control system with external loops for decoupling control significantly improves the control performance. The proposed robust control enhances the applicability of decoupling control.

Decoupled asymmetrical three-phase load flow study by parallel processing

A decoupling-compensation technique used to break the three-phase coupled power system model into three sequence-decoupled models is proposed. With such a decoupling, positive-, negative- and zero-sequence system models can be solved simultaneously. By combining these models with the well-known Newton–Raphson or fast-decoupled algorithms, two novel methods used for asymmetrical three-phase load flow study are established. Based on these the synchronous parallel algorithm can then be employed and the corresponding software used for this purpose can be implemented onto a multiprocessor system. The validity of the proposed methods is verified and the computation results are analysed herein.

Active elastic mount

An active elastic mount for the insulated mounting of an assembly affected by vibration, in particular an internal combustion engine in a motor vehicle, includes an active decoupling system disposed on an insulated side of the mount. The active decoupling system has a permanent magnetic field. A coil vibrates in the permanent magnetic field. A decoupler mass is coupled to the coil for high-frequency vibration. A sensor detects predetermined operating parameters as a function of which the decoupler mass can be set into vibration electrodynamically. Two radially rigid, mutually parallel spring systems extend transversely to the coil and elastically suspend the coil for exact vertical guidance of the coil.

Nonlinear decoupling control of aircraft motion

In this paper, decoupling theory for nonlinear multivariable systems based on differential geometry control theory is introduced. The influence of position exchange in components of input and decoupling variable on the decoupling law of the nonlinear system is discussed. The calculation of equilibrium points for nonlinear decoupling systems is also studied. For the engineering application, linear approximation of the aircraft nonlinear decoupling law is studied. The error made by the approximation is acceptable. Three types of decoupling controls for aircraft nonlinear motion are studied. Three basic modes of nonlinear direct force control and two types of extraordinary maneuvers are realized through the nonlinear decoupling controls. The calculation results show that the nonlinear decoupling control law can realize the modes of nonlinear direct force control and the extraordinary maneuvers thoroughly.

Input-output linearization with state equivalence and decoupling

The authors attempt to characterize the whole class of nonlinear systems that can be linearized to controllable and decouplable linear systems. The authors present the necessary and sufficient conditions for their problem to be solvable. More importantly, they explicitly characterize the nonlinear system satisfying these conditions by a set of parameters which are invariant under the group action of state feedback and transformation. This set of parameters can be calculated without solving a set of partial differential equations. Using this set of parameters, one can directly determine which of the canonical forms of decouplable and controllable linear systems is feedback equivalent to the nonlinear system. For the design of decoupled systems with linear input-output dynamic characteristics, it is more convenient to deal with the canonical form which is the simplest representation of the original system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An optical decoupling system for double-sided silicon microstrip detectors

This paper describes an optical decoupling system built for the readout of double-sided silicon microstrip detectors. The application of the system to the L3 silicon microvertex detector is also described, together with the results of the tests conducted on the readout system with a radioactive source and a prototype microstrip silicon detector.

Canonical forms of decouplable and controllable linear systems

In this paper, we present the canonical forms of decouplable and controllable linear systems. Some of the non-zero elements in Gilbert's canonically decoupled structure, which remain undetermined, are explicitly determined by a complete set of invariances. Our result constitutes the key step to characterization of the whole class of nonlinear systems that are feedback—equivalent to decouplable and controllable linear systems.

On the Good Choice of a Reference Model

In this paper we consider the minimal delay decoupling problem of linear multivariable systems via model reference based quadratic control. We show that the choice of a good reference model is a key point. We prove that the well known decoupling invariants i.e. The essential orders can be obtained directly through a simple simulation. This structural knowledge allows to choose a good reference model. Perfect decoupling can be obtained even for non state feedback decouplable systems.

General Active Micromotion Attenuator

This paper presents the one axis test bench of the microdynamic and accuracy pointing laboratory of the CNES and the preliminary results of a decoupling system which uses an inertial control mass to assume the decoupling function of a proof mass. The objective of this test bench is to compare on the same realisation, different types of control law in term of robustness versus external disturbances or modelling errors. The ability of real time implementation and the tuning facility will also be evaluated during this study.