P. Di Giamberardino

Digital control through finite feedback discretizability

State feedback and diffeomorphism on a given nonlinear plant to get finitely discretizable dynamics are used as a first step of a digital design procedure. Links with nilpotent and nilpotentizable Lie algebras are pointed out. The effectiveness of the control procedure is demonstrated on the basis of a case study.

Trajectory tracking for a PVTOL aircraft: a comparative analysis

The PVTOL aircraft model has a nonminimum phase characteristic so that conventional input-output linearization techniques will perform very poorly when it comes to output tracking as it will render the unstable internal dynamics unobservable. This paper is an investigation of approximate output tracking methods in the context of aircraft dynamics. The methods considered for comparison are: approximate linearization techniques which ignore the coupling between the rolling moment and the lateral acceleration of the aircraft, the use of flat outputs as state tracker and digital techniques. The simulation results shows the effectiveness of all the presented approaches.

Digital control of nonholonomic systems two case studies

It is shown, through two classical examples, that multirate control can be very effective for solving the motion planning problem. The theory is discussed for a car with one trailer and a hopping robot. Simulation results concerning exact steering and path following are presented.<<ETX>>

Evaluation of a proposed test of the weak equivalence principle using Earth-orbiting bodies in high-speed co-rotation: re-establishing the physical bases

Test masses coupled by weak mechanical suspensions are sensitive to differential forces such as the force due to a possible violation of the equivalence principle (EP). If in addition they are put in rapid rotation, the differential signal is modulated at high frequency, which is beneficial for noise reduction. Galileo Galilei (GG) is a proposed space experiment for testing the equivalence principle to 1 part in 10 17 based on these concepts. A recent paper by Jafry and Weinberger (1998 Class. Quantum Grav.15 481-500) claims that GG can only reach 10 14 . We show that the analysis of this paper is flawed (by several orders of magnitude) because of two misconceptions: one on the physical nature of mechanical damping and the other on active control methods for the stabilization of spinning bodies.

ON HALO ORBITS SPACECRAFT STABILIZATION

Abstract The paper deals with the application of recent non-linear control techniques to the problem of tracking and maintaining a given satellite on prescribed orbits around the so-called translunar libration point L2. Such orbits, known in literature as Halo Orbits, have the property of ensuring visibility both from the dark side of the Moon and from Earth at any time. Their importance is strictly related to the placement of a base situated on the dark side of the Moon for advanced space missions as deep space observation, solar system exploration and scientific researches in a low gravity enviroment. Because of the instability of the equilibrium L2, such orbits cannot be maintained without an active control. In this paper we investigate the application of nonlinear control techniques to solve the problem. A comparison between linear and nonlinear methods is developed and simulation results are discussed.

Exact steering and stabilization of a PVTOL aircraft

A piecewise continuous control law for maneuvering a PVTOL aircraft is proposed. The control scheme is composed of two loops: a continuous inner state feedback one together with an outer piecewise constant one. The design procedure, based on some previous results on exact sampling and multirate techniques is briefly introduced and applied to our case study. An additional digital feedback is used to improve the robustness of the control scheme. Some simulation results are reported in order to show the effectiveness of the proposed control strategy.

Digital control of a PVTOL aircraft

In this work a multirate digital control scheme for an /spl epsiv/-nonminimum-phase systems is proposed and the case study of a PVTOL aircraft model is developed. Considering the nominal plant, it is firstly shown, on the basis of an exact sampled dynamics obtained under preliminary feedback and diffeomorphism, that an exact dead beat control scheme can be designed. This method was proposed by Chelouah et al. (1993), and concerns digital control of nonholonomic systems. To reduce the effects of the perturbation parameter /spl epsiv/ a control scheme, which allows to take into account this effect up to a desired fixed order of approximation, is proposed. In this paper, for computational reasons, only the first order of approximation is considered. Simulation results comparing previous continuous time control schemes and the present digital one are given.<<ETX>>

Nonlinear regulation in halo orbits control design

The design and simulation of feedback control laws for tracking prescribed quasi-halo orbits around the translunar libration point L/sub 2/ in the Earth-Moon system are considered. The nonlinear regulation approach is used to design control laws for asymptotically tracking those trajectories. The eccentricity of the system is considered and modeled by a periodic disturbance. Simulation with saturations on the controls validates the proposed strategies, which also give good results for large orbital maneuvers.<<ETX>>

Mobile sensors networks: a distributed solution to the area coverage problem

The paper deals with mobile sensor networks and the related problem of area coverage. A distributed solution to the motion planning of the moving sensors for dynamic area coverage is given and compared to a global one. The distributed approach, despite its lower performances w.r.t. the global one, shows several advantages, from reduced computational costs to lighter communication traffic and then lower energetic costs. Simulation results show some of such advantages and put in evidence the effectiveness of the proposed solution.

A Scalable Fractional Order Model for IPMC Actuators

Abstract IPMCs are a novel class of composite materials capable of electromechanical reversible transduction. It has been suggested in literature that they can be modeled by using fractional transfer functions. In this paper a gray box approach is used to identify IPMC actuators. Moreover the proposed transfer functions are ruled by using the device geometrical parameters, in such a away to guarantee the control of the transducer behavior during the design phase. Experimental validation of the proposed approach is reported.