Transporte de objectos por equipas de robôs móveis autónomos : implementação e validação de uma arquitectura de controlo distribuída, baseada em sistemas dinâmicos não lineares

Dissertação de Mestrado em Electrónica Industrial - Área de Especialização em Automação e RobóticaEsta dissertação tem como objectivo a implementação e validação de uma arquitectura de controlo, baseada em sistemas dinâmicos não lineares, para uma equipa de robôs móveis autónomos que em conjunto devem transportar um objecto de grandes dimensões desde uma posição inicial até uma posição de destino, e em simultâneo evitar colisões com obstáculos estáticos e/ou dinâmicos que possam encontrar no seu caminho. A arquitectura de controlo foi desenvolvida por um elemento do Grupo de Robótica Autónoma e Sistemas Dinâmicos, do departamento de Electrónica Industrial, da Universidade do Minho, no âmbito do seu doutoramento. Os robôs não têm qualquer conhecimento prévio do ambiente que os rodeia. A arquitectura de controlo é estruturada em termos de comportamentos elementares. Os comportamentos individuais e a sua integração são gerados por sistemas dinâmicos não lineares. Para a implementação da arquitectura de controlo foram utilizadas equipas de dois e de três robôs móveis autónomos, tendo sido os resultados documentados em vídeos. Estes resultados mostram o bom desempenho dos robôs em vários cenários, quer com obstáculos estáticos, quer com dinâmicos. O comportamento resultante é estável e as trajectórias são suaves, isto porque à medida que a informação sensorial e/ou comunicada varia, os sistemas dinâmicos adaptam-se, gerando soluções atractoras adequadas.The goal of this dissertation is the validation of a distributed control architecture, based on non-linear dynamical systems, for a team of autonomous mobile robots that jointly carry a large object from a starting position to a position of destination, and simultaneously avoid collisions with obstacles static and/or dynamic that can encounter in their path. The architecture was developed by an element from the Dynamical Systems and Autonomous Robotics Group of the Department of Industrial Electronics, from University of Minho, this work was carried out for his PhD. The robots have no prior knowledge whatsoever of the surrounding environment. The control architecture of each one of the robots is structured in terms of elemental behaviours. The individual behaviours and their integration are generated by non-linear dynamical systems. The implementation of the control architecture was performed on teams of two and three robots, the results were documented in video. These results show the good performance of robots in several environments, with static and/or dynamic ones. The resulting behaviour is stable and the trajectories are smooth, this is achieved because the dynamical systems adjust to changes in the information provided by the sensors and/or the information comunicated between the robots, generating adequate attractor solutions

CoopDynSim : a 3D robotics simulator

This paper presents CoopDynSim, a multi-robot 3D simulator. The main motivations for the development of a new simulation software lie in the need to emulate specific, custom made sensors, combined with the desire to smoothly transfer controller code from simulation to real implementation. The latter is achieved through the use of the same middleware layer already implemented in the real platforms. The high modularity of the solution allows the user to easily add new components or design new platforms. By having independent simulation threads for each robot, distributed control algorithms can easily be tested, abetted by a socket based connection, granting the possibility for an asynchronous, over the network, controller architecture. The ability to run simulations in real or simulated time, as well as a play back option, represent valuable features of the software. The simulator has been used in several projects, with different platforms and distinct control applications, proving it as a heterogeneous and flexible solution. Furthermore, its usage as a teaching tool in a robotics’ summer school as well as in an introductory robotics class in our university, upholds its simplicity and user-friendliness.Fundação para a Ciência e a Tecnologia (FCT) - ref. SFRH/BD/38885/200

Multi-robot cognitive formations

In this paper, we show how a team of autonomous mobile robots, which drive in formation, can be endowed with basic cognitive capabilities. The formation control relies on the leader-follower strategy, with three main pair-wise con-figurations: column, line and oblique. Furthermore, non-linear attractor dynamics are used to generate basic robotic behaviors (i.e. follow-the-leader and avoid obstacles). The control archi-tecture of each follower integrates a representation of the leader (target) direction, which supports leader detection, selection between multiple leaders (decision) and temporary estimation of leader direction (short-term memory during occlusion and prediction). Formalized as a dynamic neural field, this additional layer is smoothly integrated with the motor movement control system. Experiments conducted in our 3D simulation software, as well as results from the implementation in middle size robotic platforms, show the ability for the team to navigate, whilst keeping formation, through unknown and unstructured environments and is robust against ambiguous and temporarily absent sensory information.Fundação para a Ciência e a Tecnologia (FCT) - FCOMP-01-0124-FEDER-022674Fundos FEDER - Programa Operacional Fatores de Competitividade - COMPET

Object transportation by a human and a mobile manipulator : a dynamical systems approach

In this paper we address the problem of humanrobot joint transportation of large payloads. The human brings to the task knowledge on the goal destination and global path planning. The robot has no prior knowledge of the environment and must autonomously help the human, while simultaneously avoiding static and/or dynamic obstacles that it encounters. For this purpose a dynamic control architecture, formalized as a coupled system of non-linear differential equations, is designed to control the behavior of the mobile manipulator in close loop with the acquired sensorial information. Verbal communication is integrated that allows the robot to communicate its limitations. Results show the robot’s ability to generate stable, smooth and robust behavior in unstructured and dynamic environments. Furthermore, the robot is able to explain the difficulties it encounters and thus contribute to success of the task and to enhance the human-robot physical interaction.FP6-IST2-EU-project JAST (project no 003747)Portuguese Science and Technology Foundation (FCT) and FEDER project COOPDYN (POSI/SRI/38081/2001)

Motion control for autonomous tugger vehicles in dynamic factory floors shared with human operators

We present a motion controller that generates collision free trajectories for autonomous Tugger vehicles operating in dynamic factory environments, where human operators may coexist. The controller is formalized as a dynamic system of path velocity and heading direction, whose vector fields change as sensory information varies. By design the parameters are tuned so that the control variables are close to an attractor of the resultant dynamics most of the time. This contributes to the overall asymptotically stability of the system and makes it robust against perturbations. We present several experiments, in a real factory environment, that highlight different innovative features of the navigation system - flexible and safe solutions for human-aware autonomous navigation in dynamic and cluttered environments. This means, besides generating online collision free trajectories between via points, the system detects the presence of humans, interact with them showing awareness of their presence, and generate adequate motor behavior.This work has been supported by National Funds through FCT -Fundacao para a Ciencia e Tecnologia within the Project Scope: UID/CEC/00319/2019, and by European Structural and Investment Funds in the FEDER component, through the Operational Competitiveness and Internationalization Programme (COMPETE 2020) [Project n degrees 002814; Funding Reference: POCI-01-0247-FEDER-002814]

Dynamical systems to control teams of autonomous mobile robots for joint transportation tasks: theory, implementation and validation in shop floor

Tese de Doutoramento - Programa Doutoral em Engenharia Eletrónica e de ComputadoresEsta tese apresenta uma arquitetura de controlo distribuída, baseada na topologia leader–helper, para equipas de dois robôs móveis autónomos que em conjunto transportam cargas de grandes dimensões evitando colisões com obstáculos (estáticos e/ou dinâmicos). O movimento de cada robô é controlado por uma série temporal de estados assintoticamente estáveis, que é formalizada através da abordagem dinâmica de atratores para a robótica baseada em comportamento. As vantagens são: (i) o comportamento resultante é suave e estável; (ii) como o comportamento é gerado como uma sequência de estados atratores (para as variáveis de controlo), contribui para a estabilidade assintótica do sistema, tornando-o robusto contra perturbações. Esta tese apresenta resultados de experiências em ambientes simulados e com robôs reais em ambientes reais. O Leader navega para uma posição desejada ou segue um colaborador (alvo móvel) e o Helper é responsável por manter a distância (que é igual ao comprimento da carga) relativamente ao Leader. Ambos os robôs partilham a responsabilidade de assegurar que a carga a transportar não colida com obstáculos. Não há necessidade de fornecer a priori um caminho para os robôs nem para a carga. A equipa é capaz de realizar a sua tarefa de transporte em ambientes desconhecidos nos quais podem existir corredores, esquinas que obriguem a realização de curvaturas acentuadas e alteração no ambiente enquanto os robôs navegam. A carga pode ter dimensões distintas. A equipa é capaz de lidar com perturbações abruptas que desafiem o comportamento dos robôs durante a execução da tarefa. Estas características tornam a abordagem baseada em sistemas dinâmicos capaz de ser implementada em ambientes como armazéns ou chãos-de-fábrica.This thesis presents a distributed leader–helper control architecture for teams of two autonomous mobile robots that jointly transport large cargos while avoiding collisions with obstacles (either static or dynamic). The motion of each robot is controlled by a time series asymptotically stable states, which is formalized using the attractor dynamics approach to behavior based robotics. The advantages are: (i) the overt behavior is smooth and stable; (ii) because the behavior is generated as a time sequence of attractor states, for the control variables, it contributes to the overall asymptotically stability of the system that makes it robust against perturbations. This thesis presents results of experiments in simulated environments and with real robots in real environments. The Leader navigates to the goal destination or follows a co-worker (moving target) and the Helper is responsible for maintaining the distance (that is equal to the length of the object) to the Leader. Both robots share the responsibility of ensuring that the transported object does not collide with obstructions. No path needs to be given a priori to the robots nor to the cargo. The team is able to perform the transportation task in unknown environments that can have corridors, corners and may change the layout online. The cargo can be of different dimensions. The team is able to cope with abrupt/strong perturbations that challenge the robots’ behavior during the execution of the task. These characteristics make our dynamical systems approach suitable to be deployed in warehouses or factory plants

Multi-constrained joint transportation tasks by teams of autonomous mobile robots using a dynamical systems approach

We present a distributed leader-helper architecture for teams of two autonomous mobile robots that jointly transport large payloads while avoiding collisions with obstacles (either static or dynamic). The leader navigates to the goal destination and the helper is responsible for maintaining an appropriate distance (which is a function of the object's length) to the leader. Both robots share the responsibility of ensuring that the transported object does not collide with obstructions. No path needs to be given a priori to the robots nor to the payload. The team is able to perform its transportation task in unknown environments that can have corridors, corners and may change the layout online. The payload can be of different dimensions. The team is able to cope with abrupt/strong perturbations that challenge the team behavior during the execution of the task. These characteristics make this approach suitable to be deployed in warehouses or office-like environments. The motion of each robot is controlled by a time series asymptotically stable states, which is formalized using the attractor dynamics approach to behavior based robotics. The advantages are: (i) the overt behavior is smooth and stable; (ii) because the behavior is generated as a time sequence of attractor states, for the control variables, it contributes to the overall asymptotically stability of the system that makes it robust against perturbations. We present results of experiments in simulated environments and with real robots in real environments.This work has been supported by COMPETE: POCI-01-0145-FEDER007043 and FCT - Fundação para a Ciência e a Tecnologia within the Project ˆ Scope: UID/CEC/00319/2013. Toni Machado would also like to thank the FCT for providing his Ph.D. scholarship (ref. SFRH/BD/38885/2007).info:eu-repo/semantics/publishedVersio

Transportation of long objects in unknown cluttered environments by a team of robots: a dynamical systems approach

We present a distributed architecture for teams of two autonomous mobile robots that act in coordination in a joint transportation task of long objects. The team is able to perform its transportation task in unknown environments while avoiding static or moving obstacles. The working environment can be cluttered and with narrow passages such as corridors, corners and doors. These characteristics make our approach suitable to be deployed in warehouses or office-like environments. The control architecture of each robot is formalized as a non-linear dynamical system, where by design attractor states dominate. The overt behavior is smooth and stable, because it is generated as a time sequence of attractor states, for the control variables, which contributes to the overall asymptotically stability of the system that makes it robust against perturbations. We present results with real robots in a real indoor cluttered environment.This work is also supported by FEDER Funds through Competitivity Factors Operational Program - COMPETE and National Funds by FCT Portuguese Science and Technology Foundation under the Project FCOMP-01-0124-FEDER022674. We would like to thank all the people that work in our laboratory, MARL (Mobile and Anthropomorphic Robotics Laboratory) at University of Minho. All of them contributed in several ways for the success of this work. Toni Machado would also like to thank the Portuguese Science and Technology Foundation for providing his Ph.D. scholarship (ref. SFRH/BD/38885/2007)

Geoeconomic variations in epidemiology, ventilation management, and outcomes in invasively ventilated intensive care unit patients without acute respiratory distress syndrome: a pooled analysis of four observational studies

Background: Geoeconomic variations in epidemiology, the practice of ventilation, and outcome in invasively ventilated intensive care unit (ICU) patients without acute respiratory distress syndrome (ARDS) remain unexplored. In this analysis we aim to address these gaps using individual patient data of four large observational studies. Methods: In this pooled analysis we harmonised individual patient data from the ERICC, LUNG SAFE, PRoVENT, and PRoVENT-iMiC prospective observational studies, which were conducted from June, 2011, to December, 2018, in 534 ICUs in 54 countries. We used the 2016 World Bank classification to define two geoeconomic regions: middle-income countries (MICs) and high-income countries (HICs). ARDS was defined according to the Berlin criteria. Descriptive statistics were used to compare patients in MICs versus HICs. The primary outcome was the use of low tidal volume ventilation (LTVV) for the first 3 days of mechanical ventilation. Secondary outcomes were key ventilation parameters (tidal volume size, positive end-expiratory pressure, fraction of inspired oxygen, peak pressure, plateau pressure, driving pressure, and respiratory rate), patient characteristics, the risk for and actual development of acute respiratory distress syndrome after the first day of ventilation, duration of ventilation, ICU length of stay, and ICU mortality. Findings: Of the 7608 patients included in the original studies, this analysis included 3852 patients without ARDS, of whom 2345 were from MICs and 1507 were from HICs. Patients in MICs were younger, shorter and with a slightly lower body-mass index, more often had diabetes and active cancer, but less often chronic obstructive pulmonary disease and heart failure than patients from HICs. Sequential organ failure assessment scores were similar in MICs and HICs. Use of LTVV in MICs and HICs was comparable (42·4% vs 44·2%; absolute difference -1·69 [-9·58 to 6·11] p=0·67; data available in 3174 [82%] of 3852 patients). The median applied positive end expiratory pressure was lower in MICs than in HICs (5 [IQR 5-8] vs 6 [5-8] cm H2O; p=0·0011). ICU mortality was higher in MICs than in HICs (30·5% vs 19·9%; p=0·0004; adjusted effect 16·41% [95% CI 9·52-23·52]; p<0·0001) and was inversely associated with gross domestic product (adjusted odds ratio for a US$10 000 increase per capita 0·80 [95% CI 0·75-0·86]; p<0·0001). Interpretation: Despite similar disease severity and ventilation management, ICU mortality in patients without ARDS is higher in MICs than in HICs, with a strong association with country-level economic status

Association of Country Income Level With the Characteristics and Outcomes of Critically Ill Patients Hospitalized With Acute Kidney Injury and COVID-19

Introduction: Acute kidney injury (AKI) has been identified as one of the most common and significant problems in hospitalized patients with COVID-19. However, studies examining the relationship between COVID-19 and AKI in low- and low-middle income countries (LLMIC) are lacking. Given that AKI is known to carry a higher mortality rate in these countries, it is important to understand differences in this population. Methods: This prospective, observational study examines the AKI incidence and characteristics of 32,210 patients with COVID-19 from 49 countries across all income levels who were admitted to an intensive care unit during their hospital stay. Results: Among patients with COVID-19 admitted to the intensive care unit, AKI incidence was highest in patients in LLMIC, followed by patients in upper-middle income countries (UMIC) and high-income countries (HIC) (53%, 38%, and 30%, respectively), whereas dialysis rates were lowest among patients with AKI from LLMIC and highest among those from HIC (27% vs. 45%). Patients with AKI in LLMIC had the largest proportion of community-acquired AKI (CA-AKI) and highest rate of in-hospital death (79% vs. 54% in HIC and 66% in UMIC). The association between AKI, being from LLMIC and in-hospital death persisted even after adjusting for disease severity. Conclusions: AKI is a particularly devastating complication of COVID-19 among patients from poorer nations where the gaps in accessibility and quality of healthcare delivery have a major impact on patient outcomes