van de Mmj Marc Wal

Control structure design: a survey

The paper focuses on the selection of measured and manipulated variables and decentralized control configurations as a sub-problem of control system design. It outlines the key ideas of various methods encountered in literature and recommends topics for future research.The paper focuses on the selection of measured and manipulated variables and decentralized control configurations as a sub-problem of control system design. It outlines the key ideas of various methods encountered in literature and recommends topics for future research.

Selection of sensors and actuators for an active suspension control problem

A new method to select sensors and actuators for linear control systems is presented. The key idea is to eliminate candidate sensor/actuator combinations for which a controller achieving a desired level of nominal performance and/or robust stability against unstructured uncertainties cannot be designed. All combinations are subjected to six viability tests, which are necessary conditions for the existence of stabilizing controllers meeting the required H/sub /spl infin// norm bound. The new selection method is used for the active suspension of a truck. This application illustrates the need for a method dealing with structured uncertainties.A new method to select sensors and actuators for linear control systems is presented. The key idea is to eliminate candidate sensor/actuator combinations for which a controller achieving a desired level of nominal performance and/or robust stability against unstructured uncertainties cannot be designed. All combinations are subjected to six viability tests, which are necessary conditions for the existence of stabilizing controllers meeting the required H/sub /spl infin// norm bound. The new selection method is used for the active suspension of a truck. This application illustrates the need for a method dealing with structured uncertainties.

Selection of actuators and sensors for active surge control

Active control is one way to cope with surge in compression systems. For this, a suitable combination of actuators and sensors must be selected. In this paper, the goal is to find a combination fulfilling the condition that a controller exists, which stabilizes the nominal model in the face of disturbances and actuator limitations. For a collection of linearizations of the nonlinear system, this condition is quantified as an /spl Hscr//sub /spl infin// norm bound on the closed-loops. Among the proposed actuators and sensors, the close-coupled valve and mass flow sensor are the most promising for the considered system, but a movable wall should be added to meet the specifications.

Large-scale rigorous actuator and sensor selection

Control system performance depends on the actuators and sensors used in the closed loop. Selection of these devices based on an exhaustive candidate-by-candidate test is a combinatorial problem. The selection considered is based on a per candidate test, but using an efficient feasibility test combined with a search strategy that, under certain conditions, is polynomial in some measures of the problem size, large-scale problems can be tackled in acceptable time. An application with 28 input/output devices to choose from, making /spl ap/266/spl middot/10/sup 6/ unique combinations possible, shows the approach to be feasible. Only 270 or 658 candidate combinations were tested for feasibility, to completely determine all combinations of sensors and actuators that were guaranteed to reach a specified level of robust performance. This is almost 10/sup 6/ times less than an exhaustive search would require.

Exploiting H~~ Sampled-Data Control Theory for High-Precision Electromechanical Servo Control Design

Optimal design of digital controllers for industrial electromechanical servo systems using an Hinfin-criterion is considered. Present industrial practice is to perform the control design in the continuous time domain and to discretize the controller a posteriori. This procedure involves unnecessary approximations. Alternatively, a direct sampled-data control design can be made, where an optimal discrete time controller is computed for a continuous time standard plant. Though theoretically and numerically solvable, a sampled-data approach is hardly feasible in an industrial environment. In this paper, a discrete time control design approach is taken. Tools that stem from sampled-data control and multirate systems theory are presented to evaluate the intersample behavior in the frequency domain, since intersample behavior is not explicitly addressed during discrete time control design. Experimental results are given to illustrate the effectiveness of the proposed discrete time control design approach and to illustrate the importance of intersample behavior in practical applications

Efficient selection of inputs and outputs for robust control

A method is proposed to efficiently select controller inputs and outputs that assure a desired level of robust performance. It is based on an efficiently computable and sufficient existence condition test and it uses an effective search strategy. The selection condition is based on D-scales used in /spl mu/-analysis, while the search strategy uses a method to generate all so-called minimal dependent sets. The D-scale test is followed up with a more accurate test employing expensive DK-iterations for smaller-sized subproblems. The tests together yield a good compromise between efficiency and effectiveness. This is demonstrated with an application for a large scale active suspension design problem with a ten DOF model of a tractor-semitrailer. In the application, seven actuators and twenty-one sensors are available to choose from.A method is proposed to efficiently select controller inputs and outputs that assure a desired level of robust performance. It is based on an efficiently computable and sufficient existence condition test and it uses an effective search strategy. The selection condition is based on D-scales used in /spl mu/-analysis, while the search strategy uses a method to generate all so-called minimal dependent sets. The D-scale test is followed up with a more accurate test employing expensive DK-iterations for smaller-sized subproblems. The tests together yield a good compromise between efficiency and effectiveness. This is demonstrated with an application for a large scale active suspension design problem with a ten DOF model of a tractor-semitrailer. In the application, seven actuators and twenty-one sensors are available to choose from.

Aliasing of Resonance Phenomena in Sampled-Data Feedback Control Design: Hazards, Modeling, and a Solution

High-performance control design for electromechanical sampled-data systems with aliased plant dynamics is investigated. Though from a theoretical viewpoint the aliasing phenomenon is automatically handled by direct sampled-data control, such an approach cannot be used in conjunction with models derived through system identification. From a practical viewpoint, aliasing is often considered as an undesirable phenomenon and a typical remedy is the increase of the sampling frequency. However, the sampling frequency is upper bounded due to physical and economical constraints and aliasing may be inevitable. Control design for plants with aliased dynamics has not received explicit attention in the literature and it is not clear how to handle this situation. In this paper, it is shown that aliased resonance phenomena can effectively be suppressed in sampled-data feedback control design without the need for increasing the sampling frequency. Furthermore, it is shown experimentally on an industrial wafer stage that ignoring aliasing during control design can have a disastrous effect on closed-loop performance. Additionally, a novel, practically feasible procedure for identification of (possibly aliased) resonance phenomena based on multirate system theory is proposed.