1,721,003 research outputs found
On the Synthesis of Discrete-time Energy-based Regulators for Port-Hamiltonian Systems
No full textThis paper aims at describing a synthesis procedure of discrete-time, energy-based regulators for continuous-time port-Hamiltonian systems. The methodology consists of three steps. The first twos deal with the definition of a discrete-time approximation of the plant to be successively employed in the development of the control law. Here, the focus is mainly on the last step, i.e. on how to interconnect digital controller and plant. The coupling is implemented via a zero-order hold and relies on the solution of an optimisation problem that determines the “best” and “minimal” correction to be applied to the nominal action to achieve the same performances obtained when the regulator is in closed-loop with the discrete-time model of the plant. This is the reference scenario used by the designer to develop and tune the control law. The procedure (time-discretisation, control design and coupling implementation) is illustrated in an example
Brayton-Moser formulation of high-order distributed port-Hamiltonian systems with one-dimensional spatial domain
No full textFor a class of distributed port-Hamiltonian systems with dissipation characterised by high-order differential operators, one-dimensional domain, and boundary actuation and sensing, an equivalent Brayton-Moser formulation is obtained. The result is that the state evolution is described by a gradient equation with respect to a storage function, the "mixed-potential," that has the dimensions of power. This is the main difference with respect to the port-Hamiltonian form, where the dynamic depends on the derivatives up to a certain order and with respect to the spatial coordinate of the gradient of the Hamiltonian function, i.e. of the total energy. (C) 2019, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved
Distributed control for infinite dimensional port-Hamiltonian systems
No full textThe aim of the paper is twofold. At first, a class of autonomous port-Hamiltonian systems whose dynamic is described by coupled PDEs and (nonlinear) ODEs is presented, and some properties (i.e., well-posedness and asymptotic stability of the origin) investigated. Secondly, an energy-based control design methodology is discussed. The finite-dimensional subsystem is equipped with an input, and a procedure for designing a state-feedback control action that maps the open-loop dynamic to a target one still in port-Hamiltonian form is illustrated. The idea is that the corresponding error system meets the requirements regarding the asymptotic stability of the origin stated in the first part of the paper. In this way, asymptotic convergence of the trajectories to the desired equilibrium configuration can be proved
Distributed-Parameter Port-Hamiltonian Systems in Discrete-Time
No full textThis paper presents a design framework of discrete-time regulators for linear, port-Hamiltonian, boundary control systems. The contribution is twofold. At first, a discrete-time approximation of the plant dynamics originally described by a linear PDE with boundary actuation is introduced. The discretisation is performed in time only. Thus, the 'distributed nature' of the state is maintained. Such a system inherits the passivity of the original one and is well-posed, namely the 'next' state always exists. The second result is the characterisation of discrete-time, linear controllers in the port-Hamiltonian form that render the closed-loop dynamics asymptotically stable. A numerical example illustrates the effectiveness of the proposed framework
A stability analysis based on dissipativity of linear and nonlinear repetitive control
No full textThis paper deals with repetitive control (RC). More specifically, a parametrised version of the repetitive compensator, i.e. of the infinite-dimensional controller employed in RC schemes, modelled as a boundary control system (BCS) in port-Hamiltonian form is presented. Well-posedness and stability of such control scheme are rigorously addressed thanks to novel tools based on dissipativity theory and originally developed for the stabilisation of BCS. Here, the linear and the nonlinear cases are tackled, and in both the cases the classes of plants for which RC schemes are exponentially stable are determined. Moreover, and explicit motivation of perfect asymptotic tracking and disturbance rejection for exponentially stable RC systems without relying on the internal model theory is provided. To show the validity of the analysis, simulations are reported. (C) 2019, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved
Port-Hamiltonian Control Design for an IPMC Actuated Highly Flexible Endoscope
No full textThis paper deals with modelling and control of an endoscope actuated by Ionic Polymer Metal Composites (IPMC) patches. The endoscope is modelled by a nonlinear partial differential equation (PDE) capable to describe large deformations. The dynamics of the flexible structure and of the IPMC patches are in port-Hamiltonian form, with the actuators interconnected to the mechanical device in power-conserving way. Thus, the complete model is a port-Hamiltonian system in which a PDE with fixed boundary conditions is coupled with a set of ordinary differential equations. The control inputs are the voltages applied to the patches, and the feedback law is designed within the Interconnection and Damping Assignment Passivity-based Control (IDA-PBC) framework. The asymptotic stability of the closed-loop system is proved, and the effectiveness of the design procedure is illustrated by a numerical example
Detectability analysis of faults affecting actuators and sensors of flexible space structures
No full textThe design of reliable and fault tolerant space flexible structures is a key point to guarantee successful space missions. This paper presents a study of detectability of faults affecting sensors and actuators of a continuous flexible structure subject to unknown disturbances. Several sensors and actuators configurations, also including the so called co-located setup, are investigated. The structural properties of these class of systems is studied by means of the geometric approach-based system theory which provides, in a coordinate-free framework, necessary and sufficient conditions for the resolvability of the fault detection problem
Robust motion control of aerial manipulators
Full text linkAerial manipulators are composed of a robotic arm installed on an unmanned aerial vehicle and are used in several applications because of their inherent ability in performing complex tasks. In real-world applications, these systems are required to be robust against exogenous disturbances, such as wind, to guarantee the desired level of accuracy in the execution of the tasks. In this paper, the reference scenario consists of an aerial manipulator with a camera mounted on the end-effector of the robotic arm, and the goal is to track a fast-moving target. A control system architecture able to assure that the tracking error remains bounded even in the presence of external disturbances is illustrated. The proposed approach is based on the compensation of the dynamic coupling between the robotic arm and the unmanned aerial vehicle. Stability is analytically proved, and the effectiveness of the proposed control solution is shown with some simulations
Energy-based control of a wave equation with boundary anti-damping
Full text linkIn this paper, we consider the asymptotic boundary stabilisation of a one-dimensional wave equation subject to anti-damping at its free end and with control at the opposite one. The control action, implemented through a state feedback or a dynamic controller, is derived by using the port-Hamiltonian framework. More precisely, the standard energy-shaping approach plus damping assignment is adapted to cope with infinite dimensional systems with anti-damping boundary conditions. It is shown how to modify the equivalent dynamic controller to account for the instability propagation along the domain
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