Luca Gentili

Modelling and control of a flying robot interacting with the environment

This work focuses on the problem of modelling and controlling a Ducted-Fan Miniature unmanned Aerial Vehicle (DFMAV) considering explicitly the interaction with the environment and the resulting constraints that affect the system dynamics. The goal is to address a scenario in which DFMAVs accomplish tasks requiring contact between the aerial vehicle and the environment such as remote manipulation, docking and flight in cluttered environments. Since the systems dynamics may be dramatically different when contacts happen and when they do not, an overall description of the system is obtained by collection of the different behaviours into a hybrid automaton. For this particular class of hybrid dynamical systems, a framework for robust control of the system based on a path following strategy is developed and tested on a scenario in which the DFMAV is required to dock with and undock from a vertical surface. Simulation results are also presented to show the effectiveness of the proposed framework.

Brief Robust nonlinear disturbance suppression of a magnetic levitation system

In this paper the problem of noise suppression for a magnetic levitation system is addressed. The problem is cast as a nonlinear regulation problem and an internal model-based regulator able to offset the noise in spite of the presence of unknown parameters affecting the model of the system is designed. The controller is designed using nested saturation functions and is able to provide a global region of attraction. Simulation results confirm the effectiveness of the design.

Modeling and control of VTOL UAVs interacting with the environment

In this paper we focus on the problem of modeling and controlling a certain configuration of UAV (Unmanned Aerial Vehicle) considering explicitly the interaction with the environment. This innovative problem is particularly interesting in order to employ unmanned aircrafts in tasks and operations which may require explicitly or implicitly contacts between the UAV itself and the environment such as manipulation of remote objects or indoor flight. For a class of VTOL (Vertical Take-Off and Landing) aircrafts we start studying the problem of safe take-off from hostile terrains and the control of the vehicle when in contact with vertical fixed surfaces.

Balanced robust regulation of a magnetic levitation system

In this brief, we consider the problem of disturbance suppression for a magnetic levitation system in presence of physical uncertainties. The problem is cast as a nonlinear regulation problem in presence of input constraint and an internal model-based regulator is designed. A control law which does not rely upon complementarity or relaxed complementarity conditions is proposed and compared, from an energetic viewpoint, with complementary control strategies usually presented in literature. Simulation results are presented to confirm the effectiveness of the design.

Regulation and input disturbance suppression for port-controlled Hamiltonian systems

In this paper the output feedback regulation problem for port-controlled Hamiltonian systems (PCHS) is addressed. Following the nonlinear output regulation theory, the regulator which solves the problem is given by a parallel connection of two subcontrollers: an internal model unit and a regulator to stabilize the extended system composed by the plant and the internal model unit. The main idea is to use the PCHS theory in order to design that stabilizer controller: as inmany cases the plant to be addressed is indeed a mechanical/electric system, and it is very easy to think about it as a PCHS, the paper shows the conditions to fulfill in order to design the internal model unit as a PCHS, allowing to use the powerful energy-shaping theory in order to stabilize the extended system. Moreover the same techniques are used to design an internal model based controller able to globally solve a problem of input disturbance suppression.

Robust takeoff and landing for a class of aerial robots

This paper focuses on the problem of robust takeoff and landing for a class of VTOL (Vertical Take-Off and Landing) aerial robots. One of the main challenge to be addressed derives from the fact that system dynamics may be remarkably different in case contacts with the landing surface happen or not. To this purpose an overall description of the system is obtained by considering the different behaviors and by defining a hybrid automaton. By taking explicitly into account the presence of possible model uncertainties and tracking errors in the definition of the reference trajectories, a control law is proposed which is shown to be able to achieve robustly the desired transitions between the hybrid states of the automaton. The solution described in the paper relies upon the general framework, for robust control of hybrid automata, described in the accompanying paper [15] which, for readers convenience, is also briefly recalled here.

A control framework for robust practical tracking of hybrid automata

This work proposes a robust control framework to address the problem of practical tracking for a class of nonlinear systems described as hybrid automata. The framework reposes both on a suitable definition of the references to be tracked and on Input-to-State Stability properties of the feedback laws in order to guarantee a desired behavior of the hybrid automata in terms of robust transition between operative modes or robust permanence in a specific operative mode. The robustness features of the proposed approach regard possible uncertainties both on the controlled dynamics and on the underlying hybrid automaton. The theory presented in this paper is applied in the accompanying work [14] where the case of takeoff and landing for a miniature ducted-fan Unmanned Aerial Vehicle (UAV) is explicitly addressed.

Modeling and control of the interaction between flying robots and the environment

Abstract This work considers the problem of modeling and controlling a class of underactuated aerial robots considering explicitly the interaction deriving from contacts with the environment and the resulting constraints which affect the system dynamics. The goal is to address a scenario in which unmanned aerial vehicles are allowed to accomplish tasks which may require contacts between the aerial vehicle and the environment, such as inspection of infrastructures or even remote manipulation. To this aim a novel control framework, based on a path following approach, is shown to succeed in achieving tasks such as docking / undocking to a certain working area by governing directly the contact dynamics of the system with the only help of vehicles own internal forces.

Robust regulation for a magnetic levitation system

In this paper we consider the problem of disturbance suppression for a magnetic levitation system in presence of uncertainties on the physical parameters of the system. It is shown how a saturated feedback can be successfully used in order to solve the problem. The problem is cast as a nonlinear regulation problem in presence of input constraint and an internal model-based regulator is designed.

Input Disturbance Suppression for Port-Hamiltonian Systems: An Internal Model Approach

In this paper an internal model based approach to periodic input disturbance suppression for port-Hamiltonian systems is presented; more specifically, an adaptive solution able to deal with unknown periodic signal belonging to a given class is introduced.