Exploiting Heterogeneity in Networks of Aerial and Ground Robotic Agents

By taking advantage of complementary communication technologies, distinct sensing functionalities and varied motion dynamics present in a heterogeneous multi-robotic network, it is possible to accomplish a main mission objective by assigning specialized sub-tasks to specific members of a robotic team. An adequate selection of the team members and an effective coordination are some of the challenges to fully exploit the unique capabilities that these types of systems can offer. Motivated by real world applications, we focus on a multi-robotic network consisting off aerial and ground agents which has the potential to provide critical support to humans in complex settings. For instance, aerial robotic relays are capable of transporting small ground mobile sensors to expand the communication range and the situational awareness of first responders in hazardous environments. In the first part of this dissertation, we extend work on manipulation of cable-suspended loads using aerial robots by solving the problem of lifting the cable-suspended load from the ground before proceeding to transport it. Since the suspended load-quadrotor system experiences switching conditions during this critical maneuver, we define a hybrid system and show that it is differentially-flat. This property facilitates the design of a nonlinear controller which tracks a waypoint-based trajectory associated with the discrete states of the hybrid system. In addition, we address the case of unknown payload mass by combining a least-squares estimation method with the designed controller. Second, we focus on the coordination of a heterogeneous team formed by a group of ground mobile sensors and a flying communication router which is deployed to sense areas of interest in a cluttered environment. Using potential field methods, we propose a controller for the coordinated mobility of the team to guarantee inter-robot and obstacle collision avoidance as well as connectivity maintenance among the ground agents while the main goal of sensing is carried out. For the case of the aerial communications relays, we combine antenna diversity with reinforcement learning to dynamically re-locate these relays so that the received signal strength is maintained above a desired threshold. Motivated by the recent interest of combining radio frequency and optical wireless communications, we envision the implementation of an optical link between micro-scale aerial and ground robots. This type of link requires maintaining a sufficient relative transmitter-receiver position for reliable communications. In the third part of this thesis, we tackle this problem. Based on the link model, we define a connectivity cone where a minimum transmission rate is guaranteed. For example, the aerial robot has to track the ground vehicle to stay inside this cone. The control must be robust to noisy measurements. Thus, we use particle filters to obtain a better estimation of the receiver position and we design a control algorithm for the flying robot to enhance the transmission rate. Also, we consider the problem of pairing a ground sensor with an aerial vehicle, both equipped with a hybrid radio-frequency/optical wireless communication system. A challenge is positioning the flying robot within optical range when the sensor location is unknown. Thus, we take advantage of the hybrid communication scheme by developing a control strategy that uses the radio signal to guide the aerial platform to the ground sensor. Once the optical-based signal strength has achieved a certain threshold, the robot hovers within optical range. Finally, we investigate the problem of building an alliance of agents with different skills in order to satisfy the requirements imposed by a given task. We find this alliance, known also as a coalition, by using a bipartite graph in which edges represent the relation between agent capabilities and required resources for task execution. Using this graph, we build a coalition whose total capability resources can satisfy the task resource requirements. Also, we study the heterogeneity of the formed coalition to analyze how it is affected for instance by the amount of capability resources present in the agents

A review of aerial manipulation of small-scale rotorcraft unmanned robotic systems

Small-scale rotorcraft unmanned robotic systems (SRURSs) are a kind of unmanned rotorcraft with manipulating devices. This review aims to provide an overview on aerial manipulation of SRURSs nowadays and promote relative research in the future. In the past decade, aerial manipulation of SRURSs has attracted the interest of researchers globally. This paper provides a literature review of the last 10 years (2008–2017) on SRURSs, and details achievements and challenges. Firstly, the definition, current state, development, classification, and challenges of SRURSs are introduced. Then, related papers are organized into two topical categories: mechanical structure design, and modeling and control. Following this, research groups involved in SRURS research and their major achievements are summarized and classified in the form of tables. The research groups are introduced in detail from seven parts. Finally, trends and challenges are compiled and presented to serve as a resource for researchers interested in aerial manipulation of SRURSs. The problem, trends, and challenges are described from three aspects. Conclusions of the paper are presented, and the future of SRURSs is discussed to enable further research interests

A Hybrid Control Approach for the Swing Free Transportation of a Double Pendulum with a Quadrotor

In this article, a control strategy approach is proposed for a system consisting of a quadrotor transporting a double pendulum. In our case, we attempt to achieve a swing free transportation of the pendulum, while the quadrotor closely follows a specific trajectory. This dynamic system is highly nonlinear, therefore, the fulfillment of this complex task represents a demanding challenge. Moreover, achieving dampening of the double pendulum oscillations while following a precise trajectory are conflicting goals. We apply a proportional derivative (PD) and a model predictive control (MPC) controllers for this task. Transportation of a multiple pendulum with an aerial robot is a step forward in the state of art towards the study of the transportation of loads with complex dynamics. We provide the modeling of the quadrotor and the double pendulum. For MPC we define the cost function that has to be minimized to achieve optimal control. We report encouraging positive results on a simulated environmentcomparing the performance of our MPC-PD control circuit against a PD-PD configuration, achieving a three fold reduction of the double pendulum maximum swinging angle.This work has been partially supported by FEDER funds through MINECO project TIN2017-85827-P, and project KK-202000044 of the Elkartek 2020 funding program of the Basque Government. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 777720

A study towards the potentials of robotic technologies to decrease risk to personnel’s safety in Statnett

Background of the project Health, safety and the environment (HSE) is Statnett´s nr.1 priority and Statnett has a zero vision towards accidents. Unfortunately, Statnett and their entrepreneurs experience accidents each year. With an increasing activity level towards 2020, it is natural to estimate that the number of accidents will increase in line with the activity. It can therefore be interesting to study new technologies with high potential to reduce risk, if it is rapidly implemented. Goals There were three goals with this thesis. The first was to identify robotic technologies, available now or within a five-year period with potential for use in Statnett. The second goal was to identify dangerous operations performed by Statnett or Statnett´s entrepreneurs. The third goal was to provide a recommendation of which robotic technologies that can both execute the identified operations and reduce the risks of the operations. General information about the thesis This report was made as a master thesis at the end of a five-year study towards a Master's Degree in science at Norwegian University of Life Science(NMBU). The study was performed between January and May 2016, and represent 30 ECTS. The thesis is written under collaboration between Statnett and NMBU. Method This thesis is based on literature study, interviews, observations and data analysis. Results The main outcome was the following: • There are many types of robotic technologies with different abilities and potential for implementation in Statnett and Statnett´s entrepreneurs, all with a high level of technology readiness(TRL) or already in use. There are however limitations with every type of robotic technologies, e.g. many of the line suspended robotic devices have problems crossing suspension towers and there is actually only one that is supposedly able to cross dead-end towers. • There is no doubt that Statnett and their entrepreneurs perform dangerous operations. Many high risk operations are identified, but there are still reasons to believe that even more could be found. All of the identified operations contain different factors of risk. Some of the risk factors have led to tragic accidents ending with death or severe illness. The biggest identified risk factors are working with helicopter and working at height. • There are several robotic technologies with the possibility to both perform and reduce the risk of some of the dangerous operations identified in this thesis. Recommendation for further work Based on the robotic technology with the highest potential to both execute operations and reduce the operations risks, eleven technologies are recommended for further research and development towards permanent implementation in specific operations.Bakgrunn for prosjektet Helse, miljø og sikkerhet (HMS) er Statnetts topp prioritet. Statnett har en visjon om null ulykker, men opplever ulykker hvert år sammen med sine entreprenører. Frem mot 2020 er det planlagt økt aktivitet og det er derfor naturlig å anta at antall ulykker vil øke i takt med aktiviteten. Det kan derfor være interessant å se på ny teknologis mulighet til å redusere risiko, hvis det kan implementeres raskt. Mål: Oppgaven har tre mål. Det første er å identifisere robotteknologi tilgjengelig i dag eller innen en femårs periode med potensial for bruk i Statnett. Mål nummer to er å identifisere farlige operasjoner utført av Statnett eller deres entreprenører. Det siste målet er å gi en anbefaling av hvilken robotteknologi som har størst mulighet til å både utføre operasjonene samtidig som den kan redusere operasjonens risiko. Generell informasjon om oppgaven Oppgaven er skrevet som en masteroppgave i siste semester av et femårig masterstudie på Norges miljø- og biovitenskapelige universitet (NMBU). Oppgaven representerer 30 studiepoeng og er skrevet som et samarbeid mellom Statnett og NMBU. Metode Oppgaven er basert på litteratur, intervjuer, observasjoner og analyse av innsamlet data. Resultat Hovedresultatene var som følger: • Det er identifisert mange typer robotteknologi med forskjellige anvendelser og potensial for implementering hos Statnett og Statnetts entreprenører. Alle teknologiene var langt i utviklingen, høy ”technology readiness level” (TRL), eller var allerede i bruk. Det var like vell utfordringer med alle teknologiene, som f.eks. at få ”line suspended robotic devices” kan krysse bæremaster og at det faktisk bare er en som skal klare å krysse ankermaster. • Det er ingen tvil om at Statnett og deres entreprenører utfører farlige operasjoner. Det er identifisert mange høy risiko operasjoner, men det er fortsatt grunn til å tro at enda flere kan identifiseres ved et grundigere studium. Alle operasjonene inneholder forskjellige risikofaktorer og noen av risikofaktorene har ført til tragiske ulykker som har endt med død eller alvorlige skader. De største risikofaktorene er identifisert som bruk av helikopter og arbeid i høyden. • Det er identifisert flere robotteknologier med potensial for å både kunne utføre og redusere risikoen til noen av de identifiserte operasjonene. Anbefaling for videre arbeid Basert på den robotteknologien med høyest potensial for å bade utføre og redusere risikoen til noen av de identifiserte operasjonene er elleve teknologier anbefalt for videre arbeid.M-M

Aerial Manipulation: A Literature Review

Aerial manipulation aims at combining the versatil- ity and the agility of some aerial platforms with the manipulation capabilities of robotic arms. This letter tries to collect the results reached by the research community so far within the field of aerial manipulation, especially from the technological and control point of view. A brief literature review of general aerial robotics and space manipulation is carried out as well

Force-based Pose Regulation of a Cable-Suspended Load Using UAVs with Force Bias

International audienceThis work studies how force measurement/estimation biases affect the force-based cooperative manipulation of a beam-like load suspended with cables by two aerial robots. Indeed, force biases are especially relevant in a force-based manipulation scenario in which direct communication is not relied upon. First, we compute the equilibrium configurations of the system. Then, we show that inducing an internal force in the load augments the robustness of the load attitude error and its sensitivity to force-bias variations. Eventually, we propose a method for zeroing the load position error. The results are validated through numerical simulations and experiments

Multi-rotor Aerial Vehicles in Physical Interactions: A Survey

Research on Multi-rotor Aerial Vehicles (MAVs) has experienced remarkable advancements over the past two decades, propelling the field forward at an accelerated pace. Through the implementation of motion control and the integration of specialized mechanisms, researchers have unlocked the potential of MAVs to perform a wide range of tasks in diverse scenarios. Notably, the literature has highlighted the distinctive attributes of MAVs that endow them with a competitive edge in physical interaction when compared to other robotic systems. In this survey, we present a categorization of the various types of physical interactions in which MAVs are involved, supported by comprehensive case studies. We examine the approaches employed by researchers to address different challenges using MAVs and their applications, including the development of different types of controllers to handle uncertainties inherent in these interactions. By conducting a thorough analysis of the strengths and limitations associated with different methodologies, as well as engaging in discussions about potential enhancements, this survey aims to illuminate the path for future research focusing on MAVs with high actuation capabilities

Continuum Deformation of a Multiple Quadcopter Payload Delivery Team without Inter-Agent Communication

This paper proposes continuum deformation as a strategy for controlling the collective motion of a multiple quadcopter system (MQS) carrying a common payload. Continuum deformation allows expansion and contraction of inter-agent distances in a 2D motion plane to follow desired motions of three team leaders. The remaining quadcopter followers establish the desired continuum deformation only by knowing leaders positions at desired sample time waypoints without the need for inter-agent communication over the intermediate intervals. Each quadcopter applies a linear-quadratic-Gaussian (LQG) controller to track the desired trajectory given by the continuum deformation in the presence of disturbance and measurement noise. Results of simulated cooperative aerial payload transport in the presence of uncertainty illustrate the application of continuum deformation for coordinated transport through a narrow channel

Equilibria, Stability, and Sensitivity for the Aerial Suspended Beam Robotic System subject to Parameter Uncertainty

This work studies how parametric uncertainties affect the cooperative manipulation of a cable-suspended beam-shaped load by means of two aerial robots not explicitly communicating with each other. In particular, the work sheds light on the impact of the uncertain knowledge of the model parameters available to an established communication-less force-based controller. First, we find the closed-loop equilibrium configurations in the presence of the aforementioned uncertainties, and then we study their stability. Hence, we show the fundamental role played in the robustness of the load attitude control by the internal force induced in the manipulated object by non-vertical cables. Furthermore, we formally study the sensitivity of the attitude error to such parametric variations, and we provide a method to act on the load position error in the presence of the uncertainties. Eventually, we validate the results through an extensive set of numerical tests in a realistic simulation environment including underactuated aerial vehicles and sagging-prone cables, and through hardware experiments