G. Celentano

Stability robustness of interval matrices via Lyapunov quadratic forms

A sufficient condition for the robust stability of a class of interval matrices is derived using the Lyapunov approach. The matrices considered have elements which are nonlinear functions of a vector of independent and bounded parameters. The robust stability condition requires that a quadratic form be positive definite in a finite number of conspicuous points of an enlarged parameter space. >

New sufficient conditions for the stability of slowly varying linear systems

The frozen-time approach is used to state some new sufficient conditions for the stability of linear time-varying systems. An upper bound on the norm of the time derivative of system matrix which, under different assumptions on frozen-time system eigenvalues, guarantees asymptotic stability or exponential stability of the system is established. >

Design and realization of a STEP-NC compliant CNC embedded controller

STEP-NC is a new model for data transfer between CAD/CAM and CNC that allows specifying machining process rather that tool motion with respect to the machine axes. STEP-NC CNC controllers are a new breed of CNC controllers that allow using this high-level model for a seamless integration in the CAD-CAM-CNC chain. Various prototypes of STEP-NC CNC controllers have been developed so far, mainly based on industrial PCs. In this paper we instead show how it is possible to realize a STEP-NC CNC controller using a low cost microcontroller, embedded in the CNC machine; this goal has been obtained by accurately parallelizing the tasks involved in the machining process. More precisely, this paper presents the design and realization of an embedded system able to control a CNC machine with two degrees of freedom, to machine STEP-NC part programs and to perform also other high level activities.

Embedded Multivalued Control for Ceramic Manufacturing

This paper presents the realization of a prototypal embedded system which implements a new control law characterized by a fixed and quantized control set. This effort is motivated by the observation that many industrial plants with high parametric uncertainties, both for constructive simplicity and/or in order to minimize the operation cost, are usually commanded with signals that can only assume a finite number of values. This paper proposes a new multivalued control algorithm which is robust with respect to disturbances and plants uncertain parameters and consents the plants output to practically track a given reference trajectory, with preassigned maximum values of the tracking error and its first derivative. Moreover, this paper deals with the digital realization of this new multivalued control law and the key issues associated with its microprocessor implementation. The efficiencies of the methodology and of the design procedure utilized for the realization of the embedded system are shown through a very interesting application: a temperature control system for a ceramic kiln.

Multi-valued robust control technique for uncertain systems

A variety of plants with high parametric uncertainties are usually controlled with signals that may assume only a finite number of values, both to simplify actuators construction and minimize the operation cost. The design of multi-valued control laws which provide a control signal that is discontinuous in time and quantized in magnitude is then of particular interest in many practical applications. This paper presents a new technique for robust control design in order to force a SISO linear plant, subject to disturbances and parametric uncertainties, to track a given sufficiently regular reference trajectory. The proposed approach is based on Lyapunov method and allows designing a control law which guarantees to follow the reference trajectory with prefixed values of the tracking error and of its derivatives up to the n1-th, where n is the order of the plant. Moreover, the control law is quite robust and guarantees the convergence of the error in a prefixed time. The technique is applied to design controllers characterized by control signals that may assume only a finite number of values. In this case, the control law can be seen as a generalization of the traditional relay control laws and of the sliding mode ones, with a relatively low switching frequency. Finally, a simple example shows the advantages of the control law obtained with the proposed design methodology with respect to the classical approaches.

Optimal Design of Robust Control Systems with Large Band Reference Signals

In this paper, a new technique in controller design is presented. Its aim is to force a linear plant to track, with a prefixed error, a class of reference trajectories characterized by an assigned band. Furthermore, the designed control is robust with respect to parametric uncertainties, disturbances and it guarantees limitations of some internal signals. The design methodology is based on the introduction of an important project parameter, the time delay within which the command can be considered to have been carried out, by a controller structure with sufficient degrees of freedom and by a constrained optimization technique where the initial values of controller parameters are determined by means of the most appropriate techniques of modern control theory. The efficiency of the proposed procedure is illustrated through the design of a realistic control system for the planar laser scanner. In result consistent improvement in performance can be measured

Embedded controller implementation of a new multi-valued control law

Many industrial plants with high parametric uncertainties, both for constructive simplicity and/or in order to minimize the operation cost, usually are commanded with signals that may only assume a finite number of values. The paper presents the realization of a prototypal embedded system, realized through a microprocessor, which implements a new control law characterized by a fixed and quantized control set. The proposed control algorithm is robust with respect to disturbances and plant uncertain parameters and consents the plant output to practically track a given reference trajectory, with preassigned maximum values of the tracking error and its first derivative. This paper deals with the digital realization of this new multi-valued control law and the key issues associated with its microprocessor implementation. The efficiency of the design method and of the technology utilized for the realization are shown through a very interesting application: a temperature control system of a ceramic kiln.

MODELLING AND EXPERIMENTAL VALIDATION OF A CAR STARTING SYSTEM

Abstract In this paper a new approach to the dynamic modelling of a car starting system is proposed. The system m odel isthe co mposition of three interacting parts: the battery, the starter and the internal combustion engine. Each part is modelled b y a small number of parameters and b y a relatively simple mathematical structure, in order toattain a trade-off between adequate modelling accuracy and param eter identification vi a simple dynamical experiments proposed by the au thors. The obtained model is validated b y a real starting experiment conductedo n a FIAT car.

Tracking control of flexible manipulators via an LMI approach

We consider the tracking problem for a robotic manipulator. First, we propose an approach which allows one to place the problem of designing an optimal control law for a rigid manipulator in the context of linear matrix inequalities (LMIs) optimization; this permits one to include in the synthesis of the control law and constraints concerning the control amplitude. Then we consider flexible links manipulators, showing how the synthesis of the controller has to be modified in order to obtain good performances in presence of flexible elements.

A control oriented approach to the time-discretization of delay systems

There are many examples of systems with delays, mainly due to transport phenomena, to the information transmission, to the calculation time of the integration digital devices, and so on. These systems, being infinite dimensional, are very difficult to analyze and to control. If they are forced by piecewise constant signals in time ranges of appropriate constant amplitude, such systems can be modeled by finite dimensional discrete-time systems. In this paper, theorems are stated that allow discretizing an LTI system with state, input and output delays, with an appropriate sampling period. A method is also proposed for the design of reduced order discrete-time controllers that allow assigning a set of arbitrary poles to the overall system. The accuracy of the discrete-time models and the effectiveness of the proposed controllers are illustrated by two interesting examples.