Mauro Cimino

Brief paper: Design of linear time-invariant controllers for multirate systems

In this paper we discuss a frequency domain approach to model multirate single-input single-output (SISO) systems which facilitates design of linear time-invariant (LTI) controllers operating at the fast rate. To illustrate the approach we consider a dual-rate system with slow output measurements and fast control actions. We obtain necessary and sufficient conditions for the existence of stabilizing linear time-invariant (LTI) controllers for which model matching is also achieved at the fast rate with a desired single-rate system. Moreover, a solution to the problem of parameterizing the set of such LTI controllers is also given.

Optimal location of mouse sensors on mobile robots for position sensing

Optical mouse sensors have been utilized recently to measure the position and orientation of a mobile robot. This work provides a systematic solution to the problem of locating N optical mouse sensors on a mobile robot with the aim of increasing the quality of the position measurements. The developed analysis gives insights on how the selection of a particular configuration influences the estimation of the robot position, and it allows to compare the effectiveness of different configurations. The results are derived from the analysis of the singular values of a particular matrix obtained by solving the sensor kinematics problem. Moreover, given any mobile robot platform, an end-user procedure is provided to select the best location for N optical mouse sensors on such a platform. The procedure consists of solving a feasible constrained optimization problem.

Location of optical mouse sensors on mobile robots for odometry

Optical mouse sensors have been utilized recently to measure position of mobile robots. This work provides a systematic solution to the problem of locating N optical mouse sensors on a mobile robot with the aim of increasing the quality of the measurement. The developed analysis gives insights on how the selection of a particular configuration reflects on the quality of the measurement signal, and it allows to compare the effectiveness of different configurations. The set of all the optimal configurations is parameterized into two constraints. The results are derived from the analysis of the singular values of a particular matrix obtained by solving the sensor kinematics problem. Moreover, given any mobile robot platform, an end-user procedure is provided to select the best location for N optical mouse sensors on such a platform. The procedure consists of solving a feasible constrained optimization problem.

A Design Technique for Multirate Linear Systems

In this paper, a design technique for multirate linear digital control systems is described. This technique takes into account all the sampling rates involved in the system and generates a multirate system that mimics the dynamics of a desired single-rate closed-loop system. The desired closed-loop system is referred to as an ideal linear time-invariant single-rate system (ISRS) since it operates at the fastest sampling rate present in the system. The multirate system is designed to achieve state matching, at the fastest rate, with the ISRS and to exhibit a ripple-free response with zero steady-state error in response to a step reference signal. Unlike prior work in the literature, which is applicable only to static-feedback ISRS, the proposed state-space design procedure is applicable for any dynamic-feedback ISRS. The proposed design is successfully implemented on a hard-disk-drive platform for the seek control of the read-write arm. A representative sample of the experimental results are shown and discussed to highlight the proposed multirate technique.

Conditions for the ripple-free response of multirate systems using linear time-invariant controllers

Abstract In this work, necessary and sufficient conditions are derived for multirate systems using linear time-invariant (LTI) controllers to guarantee a ripple-free response to step reference signals. These conditions correspond to constraints on the coefficients of a finite impulse response pre-filter. The analysis is facilitated by the use of the lifting technique, the modified Z -transform, and up-sampling and down-sampling operators. Several examples of feasible filters are provided to show the existence of multiple solutions to the considered problem.

Input-state model matching and ripple-free response for dual-rate systems☆

Abstract In this paper, we address the model matching problem for dual-rate systems where the controller output is generated at a faster rate than the measurement update rate. The model matching problem that has been studied in the literature requires the input–output properties of the closed-loop multirate system to match those of a desired single-rate linear time-invariant (LTI) system. In this paper, we consider the model matching problem from the input-state viewpoint: given a desired LTI system, find conditions and provide a controller design procedure to achieve matching between the closed-loop system and the desired system state variables at the measurement update rate. We provide a solution to this problem using a particular time-varying controller structure. In addition, we give conditions to avoid ripples in the steady-state output of the continuous-time plant; in particular, we show that some constraints on the input matrix of the desired system have to be posed. Numerical examples are given to illustrate the proposed method.

Modeling and design of LTI controllers for multirate systems

In this paper we provide a frequency domain approach to model multirate SISO systems which facilitates design of linear time-invariant (LTI) controllers. To illustrate the approach we consider a dual-rate system with slow output measurements and fast control actions. We obtain necessary and sufficient conditions for the existence of stabilizing LTI controllers for which model matching is also achieved with a desired single-rate system. Moreover, a solution is given to the problem of parametrizing the set of such LTI controllers.

Reactive Power Control for Multiple Synchronous Generators Connected in Parallel

This work addresses the common problem of distributing reactive power among multiple synchronous generators in power plants. Multiple synchronous generators within the same power generation facility are often utilized to feed a power transmission line. Individually controlling each generator may not be adequate for proper distribution of reactive load among multiple generators. Some possible issues of such a strategy include the generation of circulating currents, a low power factor, or generators running at the limit of their capabilities. The focus of this work is on the design of a supervisory control strategy for interconnected synchronous generators in power plants with the aim of avoiding those issues. The design is facilitated by constructing a new modified power factor that is smooth and monotonically decreasing as a function of reactive power and provides a clear indication of whether the reactive power is leading or lagging. The proposed strategy is implemented in cascade with the existing Automatic Voltage Regulators widely employed to provide voltage output stability. The effectiveness of the proposed strategy is discussed by providing experimental results comparing the reactive load distribution before and after the deployment of such a strategy in a large power plant.

Analysis and design of multiscale controllers for linear systems

Multiscale theory has been used in the signal processing area and modeling of some physical and chemical processes since the early 1990s. This theory provides systematic methods to project a signal onto orthogonal subspaces, each containing signal information at a different resolution, which could be useful for the design of control systems. However, there has not been much work done to determine the capabilities and properties of controllers obtained using multiscale theory. In this paper we describe a method to construct and we show some of the properties of linear multiscale controllers for linear time-invariant systems using finite-duration discrete wavelet functions.

Input-state model matching for multirate systems

In this paper we address the model matching problem for multirate systems where the controller output is generated at a faster rate than the measurement update rate. The model matching problem is considered from the input-state viewpoint: given a desired LTI system, find conditions and provide a controller design procedure to achieve matching between the closed-loop system and the desired system state variables at the measurement update rate. We provide a solution to this problem using a particular time-varying controller structure. In addition we give conditions to avoid ripples in the steady-state output of the continuous-time plant.