Overshoot in the step response of fractional-order control systems

In this paper, a sufficient condition for existence of an overshoot in the step response of fractional-order systems is presented. Based on this condition, it can be shown that the existence of an overshoot in the step responses of some classes of fractional-order systems (for example, the class of fractional-order systems having commensurate orders between 1 and 2) is unavoidable. To show the usefulness of the obtained condition, this condition is applied to prove some results on the time response analysis of fractional-order control systems.     

解决纯滞后系统问题的一种简单方法

把特制的磁性研磨头安装到卧式铣床的主轴上， 就可以进行磁性研磨，介绍研磨机床的结构及加工 原理，计算磁路及电磁线圈的技术参数。     

基于位置伺服系统数字PID算法研究

基于某项目运动控制组合系统,研究利用PID控制算法实现精确定位,提出一种利用超调的数字PID控制算法。     

Fractional-order unstable pole-zero cancellation in linear feedback systems

As a very well-known classical fact, non-minimum phase zeros of the process put some limitations on the performance of the feedback system. The source of these limitations is that non-minimum phase zeros cannot be cancelled by unstable poles of the controller since such a cancellation leads to internal instability. The aim of this paper is to propose a method for fractional-order cancellation of non-minimum phase zeros of the process and studying its properties. It is specially shown that the proposed cancellation strategy increases the phase and gain margin without leading to internal instability. Since the systems with higher gain and phase margin are easier to control, the proposed method can be used to arrive at more effective controls, which is also verified by the simulation results.     

Transient and steady-state analysis of catalyst poisoning and mixed potential formation in direct methanol fuel cells

The present dynamic model is developed to investigate the coupled reaction mechanisms in a DMFC and therein associated voltage losses in the catalyst layers. The model describes a complete five-layer membrane electrode assembly (MEA), with gas diffusion layers, catalyst layers and membrane. The analysis of the performance losses are mainly focused on the electrochemical processes. The model accounts for the crossover of both, methanol from anode to cathode and oxygen from cathode to anode. The reactant crossover results in parasitic internal currents that are finally responsible for high overpotentials in both electrodes, so-called mixed potentials. A simplified and general reaction mechanism for the methanol oxidation reaction (MOR) was selected, that accounts for the coverage of active sites by intermediate species occurring during the MOR. The simulation of the anode potential relaxation after current interruption shows an undershoot behavior like it was measured in the experiment [1]. The model gives an explanation of this phenomenon by the transients of reactant crossover in combination with the change of CO and OH coverages on Pt and Ru, respectively.     

Minimizing a convex combination of the overshoot and undershoot

We study the problem of minimizing a parameterized convex combination of the overshoot and undershoot of SISO continuous time system in response to a known input. From a dual formulation, we develop a condition for solution existence and specify the structure of optimal solution. In addition, an interrelation between the overshoot and undershoot in controller synthesis is analytically explained in our framework.     

Transient characteristics of proton exchange membrane fuel cells with different flow field designs

This work establishes three-dimensional transient numerical models of proton exchange membrane fuel cells (PEMFCs) with different cathode flow field designs. Exactly how flow field design and voltage loading affect the transient characteristics of the PEMFCs are examined. When the operating voltage instantaneously drops from 0.7 V to 0.5 V, the electrochemical reactions increase. To ensure sufficient oxygen supply for the fuel cell, the oxygen mass fractions are high in the cathode gas diffusion and cathode catalyst layers, causing overshoot of the local current density distribution. When the operating voltage suddenly increases from 0.5 V to 0.7 V, the electrochemical reactions become mild, and furthermore the oxygen mass fraction distribution becomes low, leading to undershoot of the local current density distribution. The transient response time required to reach the steady state for the parallel flow field with baffle design is longest in the event of overshoot or undershoot among the different cathode flow field designs. The overshoot or undershoot phenomena become more obvious with larger voltage loading variations. Moreover, the transient response time for the Z-type flow field with baffle design is longer than for the Z-type flow field design.     

A heuristic approach to solving a class of bilinear matrix inequality problems

Many canonical and modern control problems can be recast into the problem of a group of matrix inequalities. Some of them are in the form of linear matrix inequalities (LMIs), which can be solved very efficiently by the powerful LMI toolbox in Matlab, but some others are in the form of bilinear matrix inequalities. The characteristic of this latter class of problems is that when the so called “communicating variables” are fixed, the overall problem will be reduced to the problem in LMIs. Thus, how to find the communicating variables is the key to solve the whole problem. In this paper, an optimal estimate for the communicating variables is presented. We will illustrate our method by completely solving the problems of overshoot bound control and reachable set analysis for uncertain systems. Numerical examples are provided to show the effectiveness of the proposed method.     

一种新型的快速无超调预测控制器及其应用

该文采用一种比例积分型结构，建立了一种无超调预测控制器，通过钻杆热处理的退火过程控制的仿真研究，验证了该控制器的有效性。     

再论线性系统的超调

给出了一个评判状态空间系统是否可能发生超调的规则，并举例说明其在控制工程中应用。