284 research outputs found
Position Drift Compensation in Port-Hamiltonian Based Telemanipulation
Passivity based bilateral telemanipulation schemes are often subject to a position drift between master and slave if the communication channel is implemented using scattering variables. The magnitude of this position mismatch can be significant during interaction tasks. In this paper we propose a passivity preserving scheme for compensating the position drift arising during contact tasks in port-Hamiltonian based telemanipulation improving the kinematic perception of the remote environment felt by the human operato
Transparency in Port-Hamiltonian-Based Telemanipulation
After stability, transparency is the major issue in the design of a telemanipulation system. In this paper, we exploit the 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
Whole-Body Control of a Mobile Manipulator for Passive Collaborative Transportation
Human-robot collaborative tasks foresee interactions between humans and
robots with various degrees of complexity. Specifically, for tasks which
involve physical contact among the agents, challenges arise in the modelling
and control of such interaction. In this paper we propose a control
architecture capable of ensuring a flexible and robustly stable physical
human-robot interaction, focusing on a collaborative transportation task. The
architecture is deployed onto a mobile manipulator, modelled as a whole-body
structure, which aids the operator during the transportation of an unwieldy
load. Thanks to passivity techniques, the controller adapts its interaction
parameters online while preserving robust stability for the overall system,
thus experimentally validating the architecture
A Null-space based Approach for a Safe and Effective Human-Robot Collaboration
During physical human robot collaboration, it is important to be able to
implement a time-varying interactive behaviour while ensuring robust stability.
Admittance control and passivity theory can be exploited for achieving these
objectives. Nevertheless, when the admittance dynamics is time-varying, it can
happen that, for ensuring a passive and stable behaviour, some spurious
dissipative effects have to be introduced in the admittance dynamics. These
effects are perceived by the user and degrade the collaborative performance. In
this paper we exploit the task redundancy of the manipulator in order to
harvest energy in the null space and to avoid spurious dynamics on the
admittance. The proposed architecture is validated by simulations and by
experiments onto a collaborative robot
Sampled data systems passivity and discrete port-Hamiltonian systems
In this paper, we present a novel way to approach the interconnection of a continuous and a discrete time physical system first presented in [1][2] [3]. This is done in a way which preserves passivity of the coupled system independently of the sampling time T. This strategy can be used both in the field of telemanipulation, for the implementation of a passive master/slave system on a digital transmission line with varying time delays and possible loss of packets (e.g., the Internet), and in the field of haptics, where the virtual environment should `feel¿ like a physical equivalent system
A Comparison of Signal Analysis Techniques for the Diagnostics of the IMS Rolling Element Bearing Dataset
In this paper, a comparison of signal analysis techniques for the diagnostics of rolling element bearings is carried out. Specifically, the comparison is performed in terms of fault detection, diagnosis and prognosis techniques with regards to the first rolling element bearing dataset released by NASA IMS Center in 2014. As for fault detection, it is obtained that RMS value, Kurtosis and Detectivity, as statistical parameters, are able to properly detect the arising of the fault on the defective
bearings. Then, several signal processing techniques, such as deterministic/random signal separation, time-frequency and cyclostationary analyses are applied to perform fault diagnosis. Among these techniques, it is found that the combination of Cepstrum Pre-Whitening and Squared Envelope Spectrum, and Improved Envelope Spectrum, allow the faults to be correctly identified on specific bearing components. Finally, the Correlation, Monotonicity and Robustness of the previous statistical parameters are computed to identify the most accurate tools for bearing fault prognosis
collision avoidance for multiple lagrangian dynamical systems with gyroscopic forces
This article introduces a novel methodology for dealing with collision avoidance for groups of mobile robots. In particular, full dynamics are considered, since each robot is modeled as a Lagrangian dynamical system moving in a three-dimensional environment. Gyroscopic forces are utilized for defining the collision avoidance control strategy: This kind of forces leads to avoiding collisions, without interfering with the convergence properties of the multi-robot system's desired control law. Collision avoidance introduces, in fact, a perturbation on the nominal behavior of the system: We define a method for choosing the direction of the gyroscopic force in an optimal manner, in such a way that perturbation is minimized. Collision avoidance and convergence properties are analytically demonstrated, and simulation results are provided for validation purpose
Image Analysis and Automatic Composition of Ceramic Mosaics
The automatic composition of ceramic mosaics by computer vision techniques is studied. In the proposed system, images are reproduced onto a ceramic mosaic based on image resolution, ceramic tile's dimensions, available colours. A camera takes images of ceramic tiles to be used and guides a robot to pick the correct tile and place it at the right position in the mosaic. Colour-based segmentation and colour calibration are needed to select and extract the correct tile according to the colour to be reproduced. The input image is quantized and dithered to find the best representation given the available tiles. Issues related with the interface with robotic system are addressed.
[DOI: 10.1685 / CSC06103] About DO
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