Practical stabilization for uncertain pseudo-linear and pseudo-quadratic MIMO systems

In this paper the problem of practical stabilization for a significant class of MIMO uncertain pseudo-linear and pseudo-quadratic systems, with additional bounded nonlinearities and/or bounded disturbances, is considered. By using the concept of majorant system, via Lyapunov approach, new fundamental theorems, from which derive explicit formulas to design state feedback control laws, with a possible imperfect compensation of nonlinearities and disturbances, are stated. These results guarantee a specified convergence velocity of the linearized system of the majorant system and a desired steady-state output for generic uncertainties and/or generic bounded nonlinearities and/or bounded disturbances

New Robust Tracking and Stabilization Methods for Significant Classes of Uncertain Linear and Nonlinear Systems

Introduction There exist many mechanical, electrical, electro-mechanical, thermic, chemical, biological and medical linear and nonlinear systems, subject to parametric uncertainties and non standard disturbances, which need to be efficiently controlled. Indeed, e.g. consider the numerous manufacturing systems (in particular the robotic and transport systems,…) and the more pressing requirements and control specifications in an ever more dynamic society. Despite numerous scientific papers available in literature (Porter and Power, 1970)-(Sastry, 1999), some of which also very recent (Paarmann, 2001)-(Siciliano and Khatib, 2009), the following practical limitations remain: 1. the considered classes of systems are often with little relevant interest to engineers; 2. the considered signals (references, disturbances,…) are almost always standard (polynomial and/or sinusoidal ones); 3. the controllers are not very robust and they do not allow satisfying more than a single specification; 4. the control signals are often excessive and/or unfeasible because of the chattering. By taking into account that a very important problem is to force a process or a plant to track generic references, provided that sufficiently regular, e.g. the generally continuous piecewise linear signals, easily produced by using digital technologies, new theoretical results are needful for the scientific and engineering community in order to design control systems with non standard references and/or disturbances and/or with ever harder specifications. In the first part of this chapter, new results are stated and presented; they allow to design a controller of a SISO process, without zeros, with measurable state and with parametric uncertainties, such that the controlled system is of type one and has, for all the possible uncertain parameters, assigned minimum constant gain and maximum time constant or such that the controlled system tracks with a prefixed maximum error a generic reference with limited derivative, also when there is a generic disturbance with limited derivative, has an assigned maximum time constant and guarantees a good quality of the transient. The proposed design techniques use a feedback control scheme with an integral action (Seraj and Tarokh, 1977), (Freeman and Kokotovic, 1995) and they are based on the choice of a suitable set of reference poles, on a proportionality parameter of these poles and on the theory of externally positive systems (Bru and Romero-Vivò, 2009). The utility and efficiency of the proposed methods are illustrated with an attractive and significant example of position control. In the second part of the chapter it is considered a significant class of uncertain pseudo-quadratic systems subject to additional nonlinearities and/or external signals. For this class of systems, including articulated mechanical systems, several theorems are stated which easily allow to determine robust control laws of the PD type, with a possible partial compensation, in order to force the output and its derivative to go to rectangular neighbourhoods (of the origin) with prefixed areas and with prefixed time constants characterizing the convergence of the error. Clearly these results allow also designing control laws to take and hold a generic articulated system in a generic posture less than prefixed errors also in the presence of parametric uncertainties and limited disturbances. Moreover the stated theorems can be used to determine simple and robust control laws in order to force the considered class of systems to track a generic preassigned limited in “acceleration” trajectory, with preassigned majorant values of the maximum “position and/or velocity” errors and preassigned increases of the time constants characterizing the convergence of the error

Preface of the “Symposium on New Methods for Modeling and Control of Flexible Structures and Robots”

The flexible structures and robots are necessary and/or indispensable in: 1. winding and/or very cramped workspaces (where less invasive robots, and therefore with slender links, are required); 2. very wide workspaces or anyway robots with end-effectors very far from their bases, because of the presence of obstacles (rivers, buildings, etc.), or when it is impossible or not convenient to use robots with mobile base or more cooperative robots (e.g. to build and/or to maintain mega-structures, electric lines, etc.); 3. dangerous and/or harmful areas of work both for the human operators and for the actuators with the electronic control (rescue and security robots). For these reasons the modeling and control of robots with flexible links and, more generally, of flexible structures with degrees of freedom, has been a historic topic of research and it remains very interesting and significant for the scientific and engineering community. Nowadays, in fact, in the above mentioned cases higher and higher specifications are required in terms of operating speeds and/or amplitude of areas of work and security; the only way to satisfy the previous specifications is to reduce the mass and to make the structures slender, i.e. to employ articulated structures having flexibility properties. Obviously, in order to reduce the disadvantages due to flexibility (oscillations and/or vibrations, breaking and the spillover phenomenon when the structure is controlled by a closed-loop controller), it is necessary to design advanced control systems based on reliable and efficient models. This Symposium collects several multidisciplinary contributions in the automatic, mechanical, civil, aeronautical and naval sectors giving some significant answers to the above complex matters which remain still open

An Innovative Method for Robots Modeling and Simulation

INTRODUCTION. The robot dynamics modeling and simulation problem has been studied for the last three decades intensively. In particular, the forward dynamics problem of a robot is a very relevant issue, which there is still to say about in terms of efficient computation algorithms, that can be also simple to understand, to develop and to implement, above all for practical robots, robots with many links and/or with flexible links (Featherstone, 1987), (Featherstone and Orin, 2000), (Sciavicco and Siciliano, 2000), (Khalil and Dombre, 2002). Indeed, in these cases the methods based on the classical Lagrange formulation give rise to an analytical model with numerous terms that may be difficult to use. The methods based on the Newton-Euler formulation are not very easy to apply and do not provide easily manageable analytical formulae, even if they are efficient from a computational point of view (Featherstone, 1987). An important contribution to solve the previous problems is given (Celentano, 2006), (Celentano and Iervolino, 2006), (Celentano and Iervolino, 2007) by a new, simple and efficient methodology of analysis, valid for all of robots, that makes use of a mathematical model containing a lower number of algebraic terms and that allows computing, with a prescribed maximum error, the gradient of the kinetic energy starting from the numerical knowledge of the only inertia matrix rather than using, as usually found in the literature, complex analytical calculations of the closed-form expression of this matrix. This result is very strong because it allows solving the forward dynamics problem of a robot in a simple and efficient manner, by analytically or numerically computing the inertia matrix and the potential energy gradient only. Moreover, this method allows students, researchers and professionals, with no particular knowledge of mechanics, to easily model planar and spatial robots with practical links. From this methodology follows also a simple and efficient algorithm for modeling flexible robots dividing the links into rigid sublinks interconnected by equivalent elastic joints and approximating and/or neglecting some terms related to the deformation variables. In this chapter some of the main results stated in (Celentano, 2006), (Celentano and Iervolino, 2006), (Celentano and Iervolino, 2007) are reported. In details, in Section II the new integration scheme for robots modeling, based on the knowledge of the inertia matrix and of the potential energy only, is reported (Celentano and Iervolino, 2006). In Section III, for planar robots with revolute joints, theorems can be introduced and demonstrated to provide a sufficiently simple and efficient method of expressing both the inertia matrix and the gradient of the kinetic energy in a closed and elegant analytical form. Moreover, the efficiency of the proposed method is compared to the efficiency of the Articulated-Body method, considered one of the most efficient Newtonian methods in the literature (Celentano and Iervolino, 2006). In Section IV, for spatial robots with generic shape links and connected, for the sake of brevity, with spherical joints, several theorems are formulated and demonstrated in a simple manner and some algorithms that allow efficiently computing, analytically the inertia matrix, analytically or numerically the gradient of the kinetic and of the gravitational energy are provided. Furthermore, also in this case a comparison of the proposed method in terms of efficiency with the Articulated-Body one is reported (Celentano and Iervolino, 2007). In Section V some elements of flexible robots modeling, that allow obtaining, quite simply, accurate and efficient, from a computational point of view, finite-dimensional models, are provided. Moreover, a significant example of implementation of the proposed results is presented (Celentano, 2007). Finally, in Section VI some conclusions and future developments are reported

RFID-Assisted wireless sensor networks for cardiac tele-healthcare

As the baby boomers head into old age, America will see a dramatic increase in the number of elderly patients admitted to healthcare facilities, such as nursing homes. Due to this rising elderly population, it will be difficult for nursing home personnel to monitor all patients at once. One way to cut down on the amount of supervision by the staff is for patients to administer their own medication. This leads to new problems though, as a patient incorrectly administering one of their many medications could lead to a disastrous end. Technology to wirelessly transmit a patient’s electrocardiogram (ECG) has also been implemented to reduce supervision. Wireless transmissions are infamous for their error rate, but the ECG is a sensitive signal where every second of data matters and cannot tolerate such losses. Additionally, such existing networks employ an expensive communication infrastructure. Due to this healthcare crisis, the ability for a device to remotely monitor a patient’s medication intake and transmit accurate ECG readings, while being cost efficient, is a major innovation. To combat this crisis, this thesis focuses on a multi-hop wireless sensor network (WSN) composed of many wearable sensors, one for each patient, that host a radio frequency identification (RFID) reader and are capable of RF communication. Each wearable device is also assumed to contain an ECG sensor, though this was not implemented in this work. The system is responsible for two distinct features. The first is remotely supervised patient medication intake via RFID and a central workstation/database. The second is the accurate remote transmission of a patient’s ECG using the extended Kalman filter (EKF) for wireless error recovery

Surveillance of paediatric exposures to liquid laundry detergent pods in Italy

Objective To analyse paediatric exposures to pod and traditional laundry detergents in Italy and changes in exposure trends. Methods Analyses of a series of patients aged <5 years and exposed to laundry detergents between September 2010 and June 2015, identified by the National Poison Control in Milan. Results In comparison with patients exposed to traditional laundry detergents (n=1150), a higher proportion of those exposed to pods (n=1649) were managed in hospital (68% vs 42%), had clinical effects (75% vs 22%) and moderate/high severity outcomes (13% vs <1%). Exposure rates were stable over time for traditional detergents (average 0.65 cases/day), but an abrupt decline in major company pods was seen in December 2012, 4 months after the introduction of opaque outer packaging (from 1.03 to 0.36 cases/day and from 1.88 to 0.86 cases/million units sold). The odds of clinical effects was higher for exposure to pods than for traditional detergents (OR=10.8; 95% CI 9.0 to 12.9). Among patients exposed to pods, the odds of moderate/high severity outcomes was four times higher for children aged <1 years than for the other age groups (OR=3.9; 95% CI 2.2 to 7.0). Ten children exposed to laundry detergent pods had high severity outcomes while no children exposed to traditional laundry detergents developed high severity effects. Conclusions The study confirms that exposure to laundry detergent pods is more dangerous than exposure to traditional detergents. In Italy, 4 months after the introduction of opaque outer packaging by a major company, product-specific exposure rates decreased sharply, suggesting that reducing visibility of laundry detergent pods may be an effective preventive measure. Further efforts are needed to improve safety

A Robust Tracking Method for MIMO Uncertain Discrete-Time Systems: Mechatronic Applications

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Majorant-Based Control Methodology for Mechatronic and Transportation Processes

This paper provides a unified approach via majorant systems, which allows one to easily design a family of robust, smooth and effective control laws of proportional - h order integral - k order derivative (PIhDk) -type for broad classes of uncertain nonlinear multi-input multi-output (MIMO) systems, including mechatronic and transportation processes with ideal or real actuators, subject to bounded disturbances and measurement errors. The proposed control laws are simple to design and implement and are used, acting on a single design parameter, to track a sufficiently smooth but generic reference signal, yielding a tracking error norm less than a prescribed value, with a good transient phase and feasible control signals, despite the presence of disturbances, parametric and structural uncertainties, measurement errors, and in case of real actuators and amplifiers. Moreover, some guidelines to easily design the proposed controllers are given. Finally, the stated unified methodology and various performance comparisons are illustrated and validated in two case studies