A novel strategy to design time invariant motion controllers for underactuated mobile systems is applied to the position and attitude control of an underactuated 3D vehicle. The idea consists in defining a velocity vector field such that an ideal, fully actuated system would exponentially achieve the control objective by simply following such field. Then a steering law for the given underactuated system is designed such that it is exponentially stabilized parallel to the above mentioned velocity vector field. For the particular problem here addressed, due to the use of polar like coordinates, this method yields a discontinuous control law. Both the design process and the resulting solution have a most clear physical interpretation. Important practical requirements as approaching the target on a null curvature path, avoiding cusps in the whole path and moving in only one given forward direction are easily satisfied within this framework.

An underwater planar vehicle, actuated by rear thrusters and equipped with longitudinal control surfaces which allow the drag coefficient modulation in the sway direction, is considered in a dynamic setting. The maneuvring controls for the vehicle, in order to reach the required final position and attitude are devised by exploiting both the rear thrusters actuation and the capability offered by the admitted presence of the longitudinal, modulable, control surfaces.

A two layered hierarchical architecture is considered as the fundamental scheme for the closed loop control of robots in operational space. By considering different kinds of information transfer from the outer to the inner controllers, it is shown that the architecture can take into account a wide class of control schemes, then the analysis of their stability and robustness properties can be performed in a unified framework. Then on this basis some general results concerning such properties are given.

In this work we propose a Lyapunov based design of velocity observers and the controller for stable trajectory tracking by a robotic manipulator. It is shown how the proposed design is exponentially stable over a finite domain, and, in the high gain approximation, exponentially stable in the large domain. Moreover, the design proposed leads naturally to a reduced order observer structure, with considerable implementation advantages.

The problem of grasping rigid objects using robot hands is addressed. In particular, a representation of the space of the internal forces is given. Within this framework, an algorithm is proposed for the determination of feasible grasp and manipulation forces. sufficient conditions for the solution of this problem of coordinated manipulation are given.>

The authors deal with optimal control problems of deterministic queuing networks. The class of networks considered is characterized by a single-class population of customers, each of which has to undergo the same sequence of operations. The network is composed of a number of identically structured islands, where a decisional node has to route incoming customers to one between two different servers. With reference to the minimization of the mean flow time in the overall network, the optimality of an informationally decentralized, threshold-type, and quasi-stationary policy is proved.>

A solution for the connection of personal computers or workstations to a central station (represented by a mainframe or a server attached to a local area network) by means of a shared radio channel is presented. Issues regarding the multiple-access protocol are discussed, and an access scheme that is based on the independent stations algorithm (ISA) is presented. The necessary modifications of the basic ISA are discussed, and the overall algorithm is analyzed and tested by simulation. An implementation that is currently being developed is briefly described, focusing on the choices made for the logical link control protocol, the transmission techniques, and the interface software.>

In the class of multiple-access schemes utilizing channel feedback information, one has generally to face a multistep control problem. In order to simplify the structure of the access strategies, a single-step horizon can be considered, so that the goal becomes the maximization of the probability of transmission at each slot. However, even in this case the optimal solution turns out to be intractable for a large number of stations. To avoid this intractability some simplifying assumptions can be made at the price of a certain degree of suboptimality. Our approach is based on an independence assumption and yields a scheme which can be termed an independent stations approach (ISA).