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In this paper, the port Hamiltonian model of a manipulator is presented as the result of the power-conserving interconnection of a set of main components (rigid bodies, flexible links and kinematic pairs). Since rigid bodies and flexible links are described within the port Hamiltonian formalism, their interconnection is possible once a proper relation between the power conjugated port variables is deduced. These relations are the analogous of the Kirchoff laws of circuit theory. The final model is a mixed port Hamiltonian system because of the presence of a finite dimensional subsystem modelling the rigid bodies and of an infinite dimensional one describing the flexible links. The intrinsic modularity of the approach simplifies the model deduction and simulation, while the Hamiltonian description suggests the development of energy-based controllers.

In several applications involving bilateral telemanipulation, master and slave robots act at different power scales (e.g. telesurgery, micromanipulation). Scaling forces and velocities means scaling the power that is exchanged between master and slave sides through the communication channel. In this paper we show how it is possible to embed power scaling in the scattering based communication channel used in port-Hamiltonian based telemanipulation. Furthermore, a strategy for passively dealing with variable communication delay is proposed in order to allow scaled teleoperation over packet switched networks as Internet.

In several applications involving bilateral telemanipulation, master and slave act at different power scales. In this paper a strategy for passively dealing with variable communication delay in scaled port-Hamiltonian based telemanipulation over packet switched networks is proposed.

This paper is about modelling and simulation of the µWalker, an electrostatic micro actuator based on stepper motion. Design optimization can be done fast and at low-cost, provided a competent model is available. The main accent lies on the modelling part of the electro-elastic plate, and on the stick-slip and beam stiffening effects. Simulations are compared to measurement results.

In several applications involving bilateral telemanipulation, master and slave act at different power scales. In this paper a strategy for passively dealing with variable communication delay in scaled port-Hamiltonian based telemanipulation over packet switched networks is proposed.

This paper is about modelling and simulation of the µWalker, an electrostatic micro actuator based on stepper motion. Design optimization can be done fast and at low-cost, provided a competent model is available. The main accent lies on the modelling part of the electro-elastic plate, and on the stick-slip and beam stiffening effects. Simulations are compared to measurement results.

In several applications involving haptic interfaces it can be desirable to scale the interaction force perceived by the user. The most intuitive approach is to change the stiffness of the virtual environment but, unfortunately, changing the physical parameters that characterize a virtual environment is a potentially destabilizing action. In this paper we embed in the intrinsically passive haptic scheme recently proposed in S. Stramigioli et al. (2005) a power scaling interconnection that allows to scale the force perceived by the user while preserving the passivity, and consequently the stable behavior, of the overall system

In several applications involving bilateral telemanipulation, master and slave robots act at different power scales (e.g. telesurgery). The aim of this paper is to embed power scaling into port-Hamiltonian based bilateral telemanipulation schemes, In order to deal with nonnegligible transmission delays we propose a novel scattering based communication strategy to properly scale the power exchanged by master and slave while preserving a stable behavior of the overall scheme.

In several applications involving bilateral telemanipulation, master and slave robots act at different power scales (e.g. telesurgery). The aim of this paper is to embed power scaling into port-Hamiltonian based bilateral telemanipulation schemes, In order to deal with nonnegligible transmission delays we propose a novel scattering based communication strategy to properly scale the power exchanged by master and slave while preserving a stable behavior of the overall scheme.

After stability, transparency is the major issue in the design of a telemanipulation system. In this paper we exploit a behavioral approach in order to provide an index for the evaluation of transparency in port-Hamiltonian based teleoperators. Furthermore we provide a transparency analysis of packet switching scattering based communication channels.

Energy-efficient control of bipedal walking robots requires both minimization of mechanical energy losses (often mainly due to impacts) and the use of natural oscillations in a mechanism to minimize actuator torques (as shown by research on passive dynamic walking). In this paper, we discuss how these aspects can be analyzed and optimized using mathematical models of the dynamics, as opposed to using only engineering intuition and experimental results. We use a simple planar three-link robot as an example to illustrate the ideas.

The paper presents a survey of the concepts which are handled in the the FP5 IST-2001-34166 project called GEOPLEX which was launched in March 2002 by the European Commission. The paper is purely intented as an introduction to the special session of which it makes part of and as such does not mean to be a scientific contribution.

This paper is about the /spl mu/Walker, an electrostatic stepper motor mainly intended for positioning the data probes with respect to the storage medium in a data storage device. It can deliver forces up to 1.7 mN for ranges as large as 140 /spl mu/m. Controlling the stick-slip effects at the sliding surfaces is of central importance for reliable operation. A model is introduced to estimate the operating voltage of the actuator plate, which is an essential part of the /spl mu/Walker. Several methods to obtain displacements smaller than one nominal step (/spl ap/ 50 nm) are discussed, as well as how to increase the step repeatability and accuracy.

Energy-efficient control of bipedal walking robots requires both minimization of mechanical energy losses (often mainly due to impacts) and the use of natural oscillations in a mechanism to minimize actuator torques (as shown by research on passive dynamic walking). In this paper, we discuss how these aspects can be analyzed and optimized using mathematical models of the dynamics, as opposed to using only engineering intuition and experimental results. We use a simple planar three-link robot as an example to illustrate the ideas.

The goal of this paper is to embed power scaling into port-Hamiltonian based telemanipulation schemes over packet switched networks. We propose a discrete scattering based communication strategy and a way to handle lost packets that allow power scaling while preserving a stable behavior of the system independently of any communication delay and of any possible loss of packets

This paper is about the /spl mu/Walker, an electrostatic stepper motor mainly intended for positioning the data probes with respect to the storage medium in a data storage device. It can deliver forces up to 1.7 mN for ranges as large as 140 /spl mu/m. Controlling the stick-slip effects at the sliding surfaces is of central importance for reliable operation. A model is introduced to estimate the operating voltage of the actuator plate, which is an essential part of the /spl mu/Walker. Several methods to obtain displacements smaller than one nominal step (/spl ap/ 50 nm) are discussed, as well as how to increase the step repeatability and accuracy.

We examine the control problem of curve-tracking for fully-actuated mechanical systems, applied to walking robots. First, we discuss earlier results on curve-tracking using a change of coordinates to split the kinetic energy in a desired and an undesired part. Then, we apply and extend these results to the case of a compass-gait biped, and show in a simulation how its robustness against surface height variations can be increased.

In this paper, the problem of online estimation of the mechanical impedance during the contact of a robotic system with an unknown environment is considered. This problem is of great interest when controlling a robot in an unstructured and unknown environment, such as in telemanipulation tasks, since it can be easily shown that the exploitation of the knowledge of the mechanical properties of the environment can greatly improve the performance of the robotic system. In particular, a single-point contact is considered, and the (nonlinear) Hunt-Crossley model is taken into account, instead of the classical (linear) Kelvin-Voigt model. Indeed, the former achieves a better physical consistency and also allows describing the behavior of soft materials. Finally, the online estimation algorithm is described and experimental results are presented and discussed.

In space application, it is of great interest the development of autonomous or semi-autonomous robotic devices that can substitute the astronauts in routine operations in order to free them from repetitive tasks and reduce mission costs. In this work, an experimental setup based on a 6 degrees of freedom (dof) manipulator with a 3 dof gripper designed for a possible application within PaT, the Payload Tutor proposed by ASI (Italian Space Agency), is presented. This system consists of a robotic arm, a vision system, and a gripper. Since the gripper has to interact with free-floating and irregular objects, the vision subsystem provides all the information needed for grasping unknown objects in an optimal way.

In space application, it is of great interest the development of autonomous or semi-autonomous robotic devices that can substitute the astronauts in routine operations in order to free them from repetitive tasks and reduce mission costs. In this work, an experimental setup based on a 6 degrees of freedom (dof) manipulator with a 3 dof gripper designed for a possible application within PaT, the Payload Tutor proposed by ASI (Italian Space Agency), is presented. This system consists of a robotic arm, a vision system, and a gripper. Since the gripper has to interact with free-floating and irregular objects, the vision subsystem provides all the information needed for grasping unknown objects in an optimal way.

The visual tracking of grasp points is an essential operation for the execution of an approaching movement of a robot arm to an object: the grasp points are used as features for the definition of the control law. This work describes a strategy for tracking grasps on planar objects based on the use of a homography. In particular, the homography is used for transferring (translating) a grasp from a view of an object to a second one, providing in this way a correspondence in the second view. The grasp tracking procedure combines the search of a new grasp with the translation and the evaluation of that grasp between object views. Results of the proposed grasp tracking strategy are shown in case of grasps computed for a two-finger and a three-finger gripper.

A discrete second order trajectory generator for motion control systems is presented. The considered generator is a nonlinear system which receives as input a raw reference signal and provides as output a smooth reference signal satisfying nonlinear constraints on the output derivatives as UM-(x) ≤ x ≤ UM+(x) and VM- ≤ x ≤ VM+. The trajectory is generated on-line and the imposed constraints can also be changed during system operation without modifying the system stability. Moreoever, almost minimum time response is ensured with guaranteed no overshoot. The performances of the nonlinear generator are tested through experiments on a linear motor.

In this work, we present the design and the realization of the motion control algorithm implemented in the Twente hu- manoid head, a seven degrees of freedom (dof) robotic sys- tem. The aim of the project is to have a humanoid head that can serve as a research platform for human-machine interac- tion purposes. The head should not only be able to percieve its environment and track objects, but also be able to move in a human-like way, i.e. to reproduce the motions of human beings and to mime the human expressions.