Systematic Synthesis Procedure Research Articles

Synthesis of partially decoupled multi-level manipulators with lower mobility

The nonlinearity of the position equations of most parallel manipulators is one of the main disadvantages for the industrial application of this kind of mechanisms. In this paper, a systematic procedure for the type synthesis of lower mobility platforms, characterized by partially decoupled equation sets in their position problem, is presented. The approach proposed consists in obtaining them using a multi-level serial morphology, in which each level is attached to the base in parallel by some limbs. The aim is to design manipulators with simpler limbs by distributing in different levels the contributions to obtain a motion pattern with translational and rotational degrees of freedom (DOF). Out of many possibilities to obtain 4 and 5 DOF parallel manipulators, three cases with a partially decoupled position problem are analyzed. Finally, a case study and a prototype of a double-platform 4 DOF manipulator with Schönflies’ motion is presented.

Nonlinear Controller Synthesis for Single-Input Multiple-Output Systems with Application to Cruise Missile

The purpose of this paper is to present a new systematic procedure for synthesis of nonlinear controllers for single-input multiple-output systems. The procedure is based on several describing function models of the plant, and the nonlinear gains are obtained via an inverse describing function technique. The procedure and associated software are applied to control the bank angle of a cruise missile. The results are compared with a linear controller and another nonlinear controller that was previously reported in the open literature; it is shown that the developed procedure has resulted in a less conservative design (i.e., performance is not sacrificed to assure absolute stability).

DSC-backstepping Based Robust Adaptive NN Control for Nonlinear Systems

摘要: 针对一类具有不确定系统函数和方向未知的不确定增益函数的非线性系统, 提出了一种鲁棒自适应神经网络控制算法. 本算法采用RBF神经网络(Radial based function neural network, RBF NN)逼近模型不确定性, 外界干扰和建模误差采用非线性阻尼项进行补偿, 将动态面控制(Dynamic surface control, DSC)与后推方法结合, 消除了反推法的计算膨胀问题, 降低了控制器的复杂性; 尤其是采用Nussbaum函数处理系统中方向未知的不确定虚拟控制增益函数, 不仅可以避免可能存在的控制器奇异值问题, 而且还能使得整个系统的在线学习参数显著减少, 与DSC方法优点结合, 使得控制算法的计算量大为减少, 便于计算机实现. 稳定性分析证明了所得闭环系统是半全局一致最终有界(Semi-global uniformly ultimately bounded, SGUUB)的, 并且跟踪误差可以收敛到原点的一个较小邻域. 最后, 计算机仿真结果表明了本文所提出控制器的有效性. 关键词: 不确定非线性系统 / 神经网络 / 动态面控制 / 自适应控制 / Nussbaum增益

E and H-plane wide-band ridge waveguide couplers

A systematic synthesis procedure for ridge waveguide branch line couplers in both E-plane and H-plane configurations is presented. Ridge waveguides are chosen to benefit from their wide mono-mode band and compact size compared to rectangular waveguides. Equivalent circuit parameters are used to synthesize the coupler sections. Rigorous mode matching method is used for full-wave analysis and optimization of the couplers. Ridge couplers both in empty waveguide and Low Temperature Co-fired Ceramic “LTCC” technology are designed using the proposed method and the design is verified with another numerical method. A prototype is built and its response is measured to verify the approach. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.

PID Stabilization of MIMO Plants

Closed-loop stabilization using proportional-integral-derivative (PID) controllers is investigated for linear multiple-input-multiple-output (MIMO) plants. General necessary conditions for existence of PID-controllers are derived. Several plant classes that admit PID-con- trollers are explicitly described. Plants with only one or two unstable zeros at or "close" to the origin (alternatively, at or close to infinity) as well as plants with only one or two unstable poles which are at or close to origin are among these classes. Systematic PID-controller synthesis procedures are developed for these classes of plants.

A systematic single-range controller synthesis procedure for nonlinear and multivariable liquid propellant engines

A new systematic single-range controller synthesis procedure for use with nonlinear, multivariable, and time-varying liquid propellant engines is developed. The developed procedure is based on one describing function model of the nonlinear plant coupled with two different linear algebraic controller design procedures; one of the algebraic procedures is to achieve decoupling, and the second one is to achieve command following. The developed procedure is demonstrated by solving an example problem comparing the results using a H ∞ controller design procedure.

Entrainer Selection and Systematic Design of Heterogeneous Azeotropic Distillation Flowsheets

We present a systematic procedure for entrainer selection and synthesis of heterogeneous azeotropic distillation flowsheets. First, we partition the flowsheet into tasks (mixing, decantation, and distillation) and identify the main distillation task. Then, we investigate the location of this task in the residue curve maps (RCMs) reported by Kiva et al. (Kiva, V. N.; Hilmen, E. K.; Skogestad, S. Chem. Eng. Sci. 2003, 58 (10), 1903−1953). Third, we analyze feasibility constraints on the main distillation task and the effect of pressure on these constraints. Furthermore, we demonstrate the case that performing this task requires a combination of the concepts of heterogeneous and extractive distillations in a hybrid scheme. The developed procedure is illustrated for 11 representative ternary mixtures. For these mixtures, the sensitivity of reflux and stage requirements of the column carrying out the main distillation task to continuous degrees of freedom (e.g., composition) and discrete degrees of freedom (e.g., use of multiple feeds) is discussed, besides other mixture-specific problems.

Multi-objective H2/H∞/Impulse-to-Peak Control of a Space Launch Vehicle

A multi-objective synthesis problem involving H 2 , H ∞ and impulse-to-peak performances is investigated. In general, multi-objective control problems are hard problems to solve and do not have exact solutions. Here, an LMI formulation is proposed for the mixed H 2 /impulse-to-peak optimization under an H ∞ constraint for LTI discrete-time systems. This framework is then used to control the attitude of a space launcher. A particular control structure is defined and a multiobjective H 2 / H ∞ /impulse-to-peak synthesis problem is solved to tackle specific specifications. A systematic synthesis procedure including the tuning of design parameters is defined and results from simulations are presented.

Simultaneous synthesis of waste interception and material reuse networks: Problem reformulation for global optimization

AbstractRecycling and reuse of materials are among the most important pollution prevention strategies. In many cases, direct recycling/reuse of process and waste streams may not be feasible because of the intolerable levels of contaminants that can be detrimental to the process performance or can build up to unacceptable levels. Therefore, interception may be used to selectively remove pollutants from the process streams using separation devices or interceptors. In this work, we develop a systematic procedure for the simultaneous synthesis of material reuse and interception networks. A structural representation of the solution alternatives is first presented using a source–interception–sink framework. Then, a generally applicable mathematical formulation is developed. Because of the nonconvexities associated with the general mathematical program, we invoke a number of simplifying assumptions to facilitate reformulation of the problem into a linear program. The concepts of source substreams and interceptor decomposition were used to facilitate the problem reformulation. Additionally, the tasks of assessing interceptor performance and cost were transformed into presynthesis calculations that can be conducted a priori without compromising the accuracy of the models. The problem reformulation yields a linear program that can be solved globally. A case study is solved to illustrate the developed procedure. © 2005 American Institute of Chemical Engineers Environ Prog, 2005

Gain Scheduling Control using Descriptor Equation (Application to Flexible Spacecrafts with Parameter Variable)

This paper describes the attitude control problem of a flexible parameter varying spacecraft. Considered herein is the spacecraft consisting of the main rigid body and some flexible solar paddles which rotate at the orbital rate in order to generate more electricity. In this case, the interference characteristics of the elastic vibration of the paddles and the attitude motion of the body changes depends on the paddle angle. Therefore, the attitude control system of such spacecraft becomes parameter varying. This paper is intended to establish the systematic robust control synthesis procedure for this problem by applying gain scheduling control using descriptor equation. Capability of the method is investigated by the numerical study using the model of the ETS-VI spacecraft.

Fault-tree structures of override control systems

Abstract The development of a systematic fault-tree synthesis procedure for the override control systems is presented in this paper. The unique configuration of the digraph model under study is first described and then analyzed in detail. On the basis of qualitative simulation of the fault propagation patterns, the corresponding generalized fault-tree structures are then established. It can be observed clearly from the simulation results that none of the existing techniques are capable of producing the correct fault-trees. To demonstrate the correctness of our analysis, successful application of the proposed structure to furnace operation is also presented.

Trajectory generation and modulation using dynamic neural networks

Generation of desired trajectory behavior using neural networks involves a particularly challenging spatio-temporal learning problem. This paper introduces a novel solution, i.e., designing a dynamic system whose terminal behavior emulates a prespecified spatio-temporal pattern independently of its initial conditions. The proposed solution uses a dynamic neural network (DNN), a hybrid architecture that employs a recurrent neural network (RNN) in cascade with a nonrecurrent neural network (NRNN). The RNN generates a simple limit cycle, which the NRNN reshapes into the desired trajectory. This architecture is simple to train. A systematic synthesis procedure based on the design of relay control systems is developed for configuring an RNN that can produce a limit cycle of elementary complexity. It is further shown that a cascade arrangement of this RNN and an appropriately trained NRNN can emulate any desired trajectory behavior irrespective of its complexity. An interesting solution to the trajectory modulation problem, i.e., online modulation of the generated trajectories using external inputs, is also presented. Results of several experiments are included to demonstrate the capabilities and performance of the DNN in handling trajectory generation and modulation problems.

Rotational motion control of a spacecraft

This note describes a systematic procedure for the control synthesis of a rigid spacecraft using the energy shaping method. The geometric concept of a mechanical system in a coordinate-independent form is used to derive a control algorithm for the Euler-Poincare equations. The main result of this note is a specialization of the method on the unit quaternion group. This note is concluded with the examples of the potential functions and implementation for the three-axis attitude control problem.

Circuit theory of power factor correction in switching converters

AbstractThis paper discusses the circuit theory aspects of power factor correction in switching converter circuits. The discussion begins with an examination of the requirement of power factor correction in dc/dc converters. Using the concept of zero‐order converter circuits, sufficient conditions for a dc/dc converter circuit to provide power factor correction are derived. The duality principle is applied to generate new converter circuits that can achieve power factor correction. The practical application of power factor correction is considered in conjunction with the requirement of tight output voltage regulation. Detailed study of the circuit configuration that can simultaneously provide power factor correction and output regulation is given. Based on a general three‐port model, the voltage regulator with power factor correction capability is studied in terms of the power flow between the input port, output port and energy storage port. A detailed consideration of the power flow among the three ports leads to the derivation of all possible minimal configurations that can achieve power factor correction and voltage regulation. The efficiencies of these minimal configurations are studied theoretically, leading to the concept of ‘reduced redundant power processing’ which provides important clue to efficiency improvement. Another issue addressed in this paper is the synthesis of practical circuits that can provide power factor correction and output regulation. In particular, four practical minimal configurations that achieve reduced redundant power processing are considered. A systematic synthesis procedure is derived for creating converter circuits that achieve power factor correction and output voltage regulation. The control issue is also investigated in depth, pinpointing the basic requirement on the number of control parameters needed and its relationship with the operating mode. Copyright © 2003 John Wiley & Sons, Ltd.

Synthesis of coupled-resonators group-delay equalizers

A systematic synthesis and design procedure for coupled-resonators cavity group-delay equalizers is presented. The procedure consists of solving the approximation problem by optimization and performing cascade synthesis. The error function for the optimization is computed from the given filter's group delay and the zeros and poles of the input impedance of the equalizer. Convergence of the optimization is fast and insensitive to the initial guess even when the number of resonators is large. Two examples, together with experimental results, are presented; comparisons between the externally equalized and self-equalized filters are made. The effect of the isolation of the cascading devices (circulator or 3-dB hybrid) on the ripple of the final group-delay response is also extensively investigated. The good agreement between the theoretical simulation and the experimental results demonstrates the powerful nature and effectiveness of the proposed design procedure.

A family of PFC voltage regulator configurations with reduced redundant power processing

This paper discusses a systematic method for deriving basic converter configurations that achieve power factor correction (PFC) and voltage regulation. The discussion begins with a general three-port representation of power supplies that provide PFC and voltage regulation. Based on this representation and a power flow consideration, a systematic procedure is derived to generate all possible minimal configurations. Among these configurations, only a few have been known previously and used in practice. It is found that the efficiency of PFC voltage regulators can be improved by reducing the amount of redundant power to be processed by the constituent converters. A systematic circuit synthesis procedure is proposed for creating PFC voltage regulators with reduced redundant power processing. Experimental measurements verify the improved efficiency.

Estimation-based synthesis of H∞-optimal adaptive FIR filters for filtered-LMS problems

This paper presents a systematic synthesis procedure for H/spl infin/-optimal adaptive FIR filters in the context of an active noise cancellation (ANC) problem. An estimation interpretation of the adaptive control problem is introduced first. Based on this interpretation, an H/spl infin/ estimation problem is formulated, and its finite horizon prediction (filtering) solution is discussed. The solution minimizes the maximum energy gain from the disturbances to the predicted (filtered) estimation error and serves as the adaptation criterion for the weight vector in the adaptive FIR filter. We refer to this adaptation scheme as estimation-based adaptive filtering (EBAF). We show that the steady-state gain vector in the EBAF algorithm approaches that of the classical (normalized) filtered-X LMS algorithm. The error terms, however, are shown to be different. Thus, these classical algorithms can be considered to be approximations of our algorithm. We examine the performance of the proposed EBAF algorithm (both experimentally and in simulation) in an active noise cancellation problem of a one-dimensional (1-D) acoustic duct for both narrowband and broadband cases. Comparisons to the results from a conventional filtered-LMS (FxLMS) algorithm show faster convergence without compromising steady-state performance and/or robustness of the algorithm to feedback contamination of the reference signal.

Robust fuzzy control of a magnetic bearing system subject to harmonic disturbances

Proposes a robust fuzzy logic-based control scheme for a rotating active magnetic bearing (AMB) system. We represent the nonlinear magnetic bearing by means of a Takagi-Sugeno-Kang fuzzy model. Subsequently a systematic synthesis procedure is used to derive a nonlinear fuzzy logic control strategy that overcomes the inherent characteristics of displacement sensitivity and position-dependent nonlinearity of the AMB. Experimentation and simulation results demonstrate that the proposed fuzzy controller yields robustness against harmonic disturbances and parameter uncertainties.

Control of Parameter Varying LSS. Gain Scheduled H.INF. Synthesis Via LMI.

This paper describes the attitude control problem of a flexible parameter varying spacecraft. Considered herein is the spacecraft consists of the main rigid body and some flexible solar panels which rotate at the orbital rate in order to generate more electricity. In this case, the interference characteristics of the elastic vibration of the panels and the attitude motion of the body changes depending on the panel angle. Therefore, the attitude control system of such spacecraft becomes parameter varying. This paper is intended to establish the systematic robust controller synthesis procedure for this problem by applying Gain Scheduling framework. This controller is designed by H∞ sysnthesis via LMI. Capability of the method is investigated by the numerical study using the model of the ETS-VI spacecraft.

Static Shape Control of Smart Structures Using Compliant Mechanisms

A novel approach to static shape control of smart structures is introduced. This approach uses a special class of mechanisms called compliant mechanisms powered by a single input actuator. The key design Issue in this approach is the synthesis of a suitable compliant mechanism for the task. A systematic procedure for synthesis of such compliant mechanisms is presented by combining the first principles of mechanics and kinematics through a structural optimization scheme. The procedure is illustrated by an example wherein a prescribed smooth shape change in the camber of an idealized airfoil structure is accomplished by a specially synthesized compliant mechanism actuated by a single torque input. The scope and benefits of the proposed approach in providing viable simple solutions for real-scale static shape control applications are also discussed.