1,721,032 research outputs found
An Optimization Approach for a Robust and Flexible Control in Collaborative Applications
No full textIn Human-Robot Collaboration, the robot operates in a highly dynamic environment. Thus, it is pivotal to guarantee the robust stability of the system during the interaction but also a high flexibility of the robot behavior in order to ensure safety and reactivity to the variable conditions of the collaborative scenario. In this paper we propose a control architecture capable of maximizing the flexibility of the robot while guaranteeing a stable behavior when physically interacting with the environment. This is achieved by combining an energy tank based variable admittance architecture with control barrier functions. The proposed architecture is experimentally validated on a collaborative robot
Unified Power and Admittance Adaptation for Safe and Effective Physical Interaction With Unmodelled Dynamic Environments
No full textWhen interacting with unmodelled dynamic systems, a robot controller should be capable of adapting online its behavior, in order to be robust to the changing environmental conditions. In the paradigm of passivity-based control, virtual energy tanks allow to perform such adaptations in a robustly stable way, by bounding the amount of energy allocated to the controller. Nevertheless, when the workspace is shared with human collaborators, additional limits have to be imposed to the power the system can exert, in order to guarantee the overall safety. These bounds are difficult to estimate a priori, might vary over time and can significantly affect task execution. In this letter, we tackle this problem by simultaneously adapting online the admittance and the power limits in the controller, ensuring both safety and task performance. Experimental results with a collaborative manipulator validate the presented framework
A Null-space based Approach for a Safe and Effective Human-Robot Collaboration
No full textDuring 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
Bidirectional Communication Control for Human-Robot Collaboration
Full text linkA fruitful collaboration is based on the mutual knowledge of each other skills and on the possibility of communicating their own limits and proposing alternatives to adapt the execution of a task to the capabilities of the collaborators. This paper aims at reproducing such a scenario in a human-robot collaboration setting by proposing a novel communication control architecture. Exploiting control barrier functions, the robot is made aware of its (dynamic) skills and limits and, thanks to a local predictor, it is able to assess if it is possible to execute a requested task and, if not, to propose alternative by relaxing some constraints. The controller is interfaced with a communication infrastructure that enables human and robot to set up a bidirectional communication about the task to execute and the human to take an informed decision on the behavior of the robot. A comparative experimental validation is proposed
Visionary: A viewpoint-based visual language for querying relational databases
No full textThe adoption of a visual interface can simplify the query formulation process in DBMSs by enabling naive users to interact with a friendly environment. In this work, we propose a visual query language based on a diagrammatic paradigm, used for both data and query representation. The external data model is called vision and is made up of the visual primitives of concept and association. The external query model is based on the definition of a viewpoint, which is a perspective for accessing data defined dynamically by selecting a concept of primary interest. Internally, the data model is relational and the query language is SQL. An intermediate graph-based model ensures consistent mapping between the visual and the relational worlds. Our language has been implemented within a tool which can be mounted on top of any relational DBMS supporting ODBC. The system has been tested with naive users; the results of the experiment are reported and compared with those obtained with other visual languages. © 1999 Academic Press
Whole-Body Control of a Mobile Manipulator for Passive Collaborative Transportation
No full textHuman-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. Copyright (c) 2022 The Authors. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/
A Reinforcement Learning-based Control Strategy for Robust Interaction of Robotic Systems with Uncertain Environments
No full textVIsTool: A visual tool for querying relational databases
No full textIn this paper we describe VisTool, a prototype tool for querying relational databases by means of the visual query language VISIONARY
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