Mehmet Turan Söylemez

Fast Calculation of Stabilizing PID Controllers for Uncertain Parameter Systems

Abstract This paper introduces a new and very fast way of calculating the limiting values of the proportional, integral, and derivative action terms of the set of stabilizing PID controllers for a given SISO system. An extension of this method to systems with an interval uncertainty structure is presented that allows the characterization of stabilizing PID controllers for such systems, and offers several important advantages over the recent results of Ho et al (1998). Computational experiments have shown that the approach presented here is several orders of magnitude faster than previously published results that we are aware of, being almost instantaneous on a 266MHz PC, and could therefore be of interest to the robust control community. A summary of previous work in this area is given, and the new approach is presented and illustrated by examples.

Fail-Safe Signalization Design for a Railway Yard: A Level Crossing Case

Abstract Level crossings (grade crossings or railroad crossings) are one of the most crucial parts of the railway lines as two different types of transportation intersect at these points. Human failures including ignorance of warning signs, device troubles or carelessness can easily result in accidents especially at such cross-sections. In order to decrease the possibility of accidents on level crossings, several standards have been developed. In accordance with these standards, formal methods are required to be used specially in the development of interlocking systems that control safe operation of such crossings. In this study, a railway yard with a level crossing is modeled by Automation Petri Nets in order to design a failsafe signalization system. A SCADA testbed is also developed to test several possible failure situations. The methods proposed in the design are expected to be used as part of an interlocking system in a railway station in Turkey.

The Application of Automation Theory to Railway Signalization Systems: The Case of Turkish National Railway Signalization Project

Abstract The application of control and automation theory to practical areas can provide significant means for improvement in developing countries like Turkey, where human (brain) power is relatively inexpensive. A possible application area for the well established automation theory is railway signalization, where formal methods are required to be used in order to comply with the related safety standards. Turkish National Railway Signalization Project (TNRSP) is examined in this paper with this perspective as a case study. Development stages, architecture and design of the software produced in this project are briefly discussed.

A parametric solution to the pole assignment problem using dynamic output-feedback

A technique is presented for pole placement of linear time-invariant systems using dynamic feedback. A previously developed method for partial pole assignment using constant feedback is generalized to the dynamic output-feedback case. Subject to a mild assumption on the number of complex conjugate poles to be assigned, it is almost always possible to arbitrarily assign all the closed-loop system poles using a compensator of order [(n-/spl phi/)/max(m,l)] using this new method. Here, n, m, and l are the order of the system, and the number of inputs and outputs, respectively, and /spl phi/ /spl Delta//=max(m,l)+[max(m,l)/2]+...+[max(m,l)/min(m,l)] where [x] denotes the nearest integer lower than or equal to x (i.e., floor (x)), and [x] denotes the nearest integer greater than or equal to x (i.e., ceiling (x)). An equivalent result is that using a compensator of order q, it is almost always possible to arbitrarily assign min(n+q,(max(m,l)+1)q+/spl phi/) closed-loop system poles. Only the normal procedures of linear algebra are required to implement the technique. Note that /spl phi//spl ges/l+m-1 and, therefore, the result is stronger than previous exact pole assignment results. Since it does not involve iteration or any other numerical techniques, it is possible to implement the method symbolically and, therefore, to obtain general parametric solutions to the pole assignment problem. The freedom in this design approach can also often be used to guarantee the internal stability and/or robustness of the resulting closed-loop system.

Designing control systems using exact and symbolic manipulations of formulae

The potential of symbolic algebra for the design of control systems is illustrated through several examples. It has been shown in particular, that (a) the exact calculations provided by symbolic algebra can be used to utilize some of the direct (but numerically error prone) methods efficiently in control system design, and (b) symbolic manipulations by a computer can help control engineers at several stages of the design. The block diagram reduction, calculation of all stabilizing controllers, dominant pole assignment and robust pole assignment are taken as case studies.The potential of symbolic algebra for the design of control systems is illustrated through several examples. It has been shown in particular, that (a) the exact calculations provided by symbolic algebra can be used to utilize some of the direct (but numerically error prone) methods efficiently in control system design, and (b) symbolic manipulations by a computer can help control engineers at several stages of the design. The block diagram reduction, calculation of all stabilizing controllers, dominant pole assignment and robust pole assignment are taken as case studies.

Guaranteed Dominant Pole Placement with Discrete-PID Controllers: A Modified Nyquist Plot Approach

Abstract Guaranteed dominant pole placement problem has already been considered in the literature (Journal of Process Control 19(2009):349–352). For the systems that are higher-order or have dead-time, pole placement procedure with PID controllers via modified Nyquist plot and root-locus has been proposed. Based on this idea, the dominant pole placement problem with discrete-PID controllers in z-domain is studied since it is important to take advantage of discrete-time domain representation during the pole placement procedure for time-delay systems. It is shown that modified Nyquist plot method is still valid in discrete-time domain and it is possible to find relevant discrete-PID controller parameters. Controller zeros are also considered in the study, since in the closed-loop controller zeros can disrupt the dominance. Success of the method demonstrated on example transfer functions.

Design of a Hardware and Software based Test Bed for Railway Signalization Systems

Abstract It is vital that an interlocking system is thoroughly tested before its deployment. The conduction of the tests of an interlocking system on the real field is cumbersome and expensive. It is necessary that fast and efficient methods are utilized to test the hardware and the software of interlocking systems before its final installation. In this manuscript, the design of hardware and software based test beds for a railway signalization system is presented.

Satisfaction of gain and phase margin constraints using proportional controllers

Gain and phase margins (GM and PM) are frequently used as robustness indicators for linear time invariant systems. In many cases, the design problem is reduced to determination of a loop gain to satisfy several design criteria including gain and PM specifications. Therefore finding the set of fixed order compensators that satisfy given gain and PM specifications attracted the attention of a considerable part of the scientific community recently. It is possible to show that it may not be possible to satisfy the required gain and/or PM specifications using only a proportional controller. As a result, finding the limits of the proportional controllers for a given plant (i.e. finding the maximum achievable gain and PMs, MAGM and MAPM) is also important. After providing alternative methods (to those that already exist in the literature) for determining all stabilising proportional controllers that satisfy gain and PM constraints, a new method for calculating MAGM and MAPM using proportional controllers is given in this article. A formulation to calculate maximum gain that results in MAGM is also provided.

MULTI-TRAIN SIMULATION OF DC RAIL TRACTION POWER SYSTEMS WITH REGENERATIVE BRAKING

This paper describes how simulation is an important part of the design and optimization of DC rail traction power systems. With the help of simulation, it is possible to determine possible problems, reduce the design costs and optimize for several design criteria such as power consumption, passenger flow, and passenger comfort. This paper presents a new simulation tool that can be used for these purposes, while discussing several problems that must be tackled in writing a rail traction power simulator.

A new technique for partial pole placement using constant output-feedback

A technique is presented for partial pole placement of linear time-invariant systems. It is almost always possible to arbitrarily assign min(n, /spl phi/) poles using this method. Here n is the order of the system, and /spl phi/=/spl Delta/max(m,l)+[max(m,l)/2]+[max(m,l)/min(m,l)] where m and l are the number of inputs and outputs, respectively, and [.] denotes the nearest integer lower than or equal to (i.e. floor(.)). Only the normal procedures of linear algebra are required to implement the technique. We note that /spl phi//spl ges/m+l-1, which has been a long-standing barrier for linear algebra methods in the partial pole placement problem.