Marvin: an Innovative Omni-Directional Robotic Assistant for Domestic Environments

Population ageing and pandemics recently demonstrate to cause isolation of elderly people in their houses, generating the need for a reliable assistive figure. Robotic assistants are the new frontier of innovation for domestic welfare, and elderly monitoring is one of the services a robot can handle for collective well-being. Despite these emerging needs, in the actual landscape of robotic assistants there are no platform which successfully combines a reliable mobility in cluttered domestic spaces, with lightweight and offline Artificial Intelligence (AI) solutions for perception and interaction. In this work, we present Marvin, a novel assistive robotic platform we developed with a modular layer-based architecture, merging a flexible mechanical design with cutting-edge AI for perception and vocal control. We focus the design of Marvin on three target service functions: monitoring of elderly and reduced-mobility subjects, remote presence and connectivity, and night assistance. Compared to previous works, we propose a tiny omnidirectional platform, which enables agile mobility and effective obstacle avoidance. Moreover, we design a controllable positioning device, which easily allows the user to access the interface for connectivity and extends the visual range of the camera sensor. Nonetheless, we delicately consider the privacy issues arising from private data collection on cloud services, a critical aspect of commercial AI-based assistants. To this end, we demonstrate how lightweight deep learning solutions for visual perception and vocal command can be adopted, completely running offline on the embedded hardware of the robot.Comment: 20 pages, 9 figures, 3 tabl

Multi-robot cooperative platform : a task-oriented teleoperation paradigm

This thesis proposes the study and development of a teleoperation system based on multi-robot cooperation under the task oriented teleoperation paradigm: Multi-Robot Cooperative Paradigm, MRCP. In standard teleoperation, the operator uses the master devices to control the remote slave robot arms. These arms reproduce the desired movements and perform the task. With the developed work, the operator can virtually manipulate an object. MRCP automatically generates the arms orders to perform the task. The operator does not have to solve situations arising from possible restrictions that the slave arms may have. The research carried out is therefore aimed at improving the accuracy teleoperation tasks in complex environments, particularly in the field of robot assisted minimally invasive surgery. This field requires patient safety and the workspace entails many restrictions to teleoperation. MRCP can be defined as a platform composed of several robots that cooperate automatically to perform a teleoperated task, creating a robotic system with increased capacity (workspace volume, accessibility, dexterity ...). The cooperation is based on transferring the task between robots when necessary to enable a smooth task execution. The MRCP control evaluates the suitability of each robot to continue with the ongoing task and the optimal time to execute a task transfer between the current selected robot and the best candidate to continue with the task. From the operator¿s point of view, MRCP provides an interface that enables the teleoperation though the task-oriented paradigm: operator orders are translated into task actions instead of robot orders. This thesis is structured as follows: The first part is dedicated to review the current solutions in the teleoperation of complex tasks and compare them with those proposed in this research. The second part of the thesis presents and reviews in depth the different evaluation criteria to determine the suitability of each robot to continue with the execution of a task, considering the configuration of the robots and emphasizing the criterion of dexterity and manipulability. The study reviews the different required control algorithms to enable the task oriented telemanipulation. This proposed teleoperation paradigm is transparent to the operator. Then, the Thesis presents and analyses several experimental results using MRCP in the field of minimally invasive surgery. These experiments study the effectiveness of MRCP in various tasks requiring the cooperation of two hands. A type task is used: a suture using minimally invasive surgery technique. The analysis is done in terms of execution time, economy of movement, quality and patient safety (potential damage produced by undesired interaction between the tools and the vital tissues of the patient). The final part of the thesis proposes the implementation of different virtual aids and restrictions (guided teleoperation based on haptic visual and audio feedback, protection of restricted workspace regions, etc.) using the task oriented teleoperation paradigm. A framework is defined for implementing and applying a basic set of virtual aids and constraints within the framework of a virtual simulator for laparoscopic abdominal surgery. The set of experiments have allowed to validate the developed work. The study revealed the influence of virtual aids in the learning process of laparoscopic techniques. It has also demonstrated the improvement of learning curves, which paves the way for its implementation as a methodology for training new surgeons.Aquesta tesi doctoral proposa l'estudi i desenvolupament d'un sistema de teleoperació basat en la cooperació multi-robot sota el paradigma de la teleoperació orientada a tasca: Multi-Robot Cooperative Paradigm, MRCP. En la teleoperació clàssica, l'operador utilitza els telecomandaments perquè els braços robots reprodueixin els seus moviments i es realitzi la tasca desitjada. Amb el treball realitzat, l'operador pot manipular virtualment un objecte i és mitjançant el MRCP que s'adjudica a cada braç les ordres necessàries per realitzar la tasca, sense que l'operador hagi de resoldre les situacions derivades de possibles restriccions que puguin tenir els braços executors. La recerca desenvolupada està doncs orientada a millorar la teleoperació en tasques de precisió en entorns complexos i, en particular, en el camp de la cirurgia mínimament invasiva assistida per robots. Aquest camp imposa condicions de seguretat del pacient i l'espai de treball comporta moltes restriccions a la teleoperació. MRCP es pot definir com a una plataforma formada per diversos robots que cooperen de forma automàtica per dur a terme una tasca teleoperada, generant un sistema robòtic amb capacitats augmentades (volums de treball, accessibilitat, destresa,...). La cooperació es basa en transferir la tasca entre robots a partir de determinar quin és aquell que és més adequat per continuar amb la seva execució i el moment òptim per realitzar la transferència de la tasca entre el robot actiu i el millor candidat a continuar-la. Des del punt de vista de l'operari, MRCP ofereix una interfície de teleoperació que permet la realització de la teleoperació mitjançant el paradigma d'ordres orientades a la tasca: les ordres es tradueixen en accions sobre la tasca en comptes d'estar dirigides als robots. Aquesta tesi està estructurada de la següent manera: Primerament es fa una revisió de l'estat actual de les diverses solucions desenvolupades actualment en el camp de la teleoperació de tasques complexes, comparant-les amb les proposades en aquest treball de recerca. En el segon bloc de la tesi es presenten i s'analitzen a fons els diversos criteris per determinar la capacitat de cada robot per continuar l'execució d'una tasca, segons la configuració del conjunt de robots i fent especial èmfasi en el criteri de destresa i manipulabilitat. Seguint aquest estudi, es presenten els diferents processos de control emprats per tal d'assolir la telemanipulació orientada a tasca de forma transparent a l'operari. Seguidament es presenten diversos resultats experimentals aplicant MRCP al camp de la cirurgia mínimament invasiva. En aquests experiments s'estudia l'eficàcia de MRCP en diverses tasques que requereixen de la cooperació de dues mans. S'ha escollit una tasca tipus: sutura amb tècnica de cirurgia mínimament invasiva. L'anàlisi es fa en termes de temps d'execució, economia de moviment, qualitat i seguretat del pacient (potencials danys causats per la interacció no desitjada entre les eines i els teixits vitals del pacient). Finalment s'ha estudiat l'ús de diferents ajudes i restriccions virtuals (guiat de la teleoperació via retorn hàptic, visual o auditiu, protecció de regions de l'espai de treball, etc) dins el paradigma de teleoperació orientada a tasca. S'ha definint un marc d'aplicació base i implementant un conjunt de restriccions virtuals dins el marc d'un simulador de cirurgia laparoscòpia abdominal. El conjunt d'experiments realitzats han permès validar el treball realitzat. Aquest estudi ha permès determinar la influencia de les ajudes virtuals en el procés d'aprenentatge de les tècniques laparoscòpiques. S'ha evidenciat una millora en les corbes d'aprenentatge i obre el camí a la seva implantació com a metodologia d'entrenament de nous cirurgians.Postprint (published version

A model-based approach to robot kinematics and control using discrete factor graphs with belief propagation

Much of recent researches in robotics have shifted the focus from traditionally-specific industrial tasks to investigations of new types of robots with alternative ways of controlling them. In this paper, we describe the development of a generic method based on factor graphs to model robot kinematics. We focused on the kinematics aspect of robot control because it provides a fast and systematic solution for the robot agent to move in a dynamic environment. We developed neurally-inspired factor graph models that can be applied on two different robotic systems: a mobile platform and a robotic arm. We also demonstrated that we can extend the static model of the robotic arm into a dynamic model useful for imitating natural movements of a human hand. We tested our methods in a simulation environment as well as in scenarios involving real robots. The experimental results proved the flexibility of our proposed methods in terms of remodeling and learning, which enabled the modeled robot to perform reliably during the execution of given tasks

Vision-based Global Path Planning and Trajectory Generation for Robotic Applications in Hazardous Environments

The aim of this study is to find an efficient global path planning algorithm and trajectory generation method using a vision system. Path planning is part of the more generic navigation function of mobile robots that consists of establishing an obstacle-free path, starting from the initial pose to the target pose in the robot workspace.In this thesis, special emphasis is placed on robotic applications in industrial and scientific infrastructure environments that are hazardous and inaccessible to humans, such as nuclear power plants and ITER1 and CERN2 LHC3 tunnel. Nuclear radiation can cause deadly damage to the human body, but we have to depend on nuclear energy to meet our great demands for energy resources. Therefore, the research and development of automatic transfer robots and manipulations under nuclear environment are regarded as a key technology by many countries in the world. Robotic applications in radiation environments minimize the danger of radiation exposure to humans. However, the robots themselves are also vulnerable to radiation. Mobility and maneuverability in such environments are essential to task success. Therefore, an efficient obstacle-free path and trajectory generation method are necessary for finding a safe path with maximum bounded velocities in radiation environments. High degree of freedom manipulators and maneuverable mobile robots with steerable wheels, such as non-holonomic omni-directional mobile robots make them suitable for inspection and maintenance tasks where the camera is the only source of visual feedback.In this thesis, a novel vision-based path planning method is presented by utilizing the artificial potential field, the visual servoing concepts and the CAD-based recognition method to deal with the problem of path and trajectory planning. Unlike the majority of conventional trajectory planning methods that consider a robot as only one point, the entire shape of a mobile robot is considered by taking into account all of the robot’s desired points to avoid obstacles. The vision-based algorithm generates synchronized trajectories for all of the wheels on omni-directional mobile robot. It provides the robot’s kinematic variables to plan maximum allowable velocities so that at least one of the actuators is always working at maximum velocity. The advantage of generated synchronized trajectories is to avoid slippage and misalignment in translation and rotation movement. The proposed method is further developed to propose a new vision-based path coordination method for multiple mobile robots with independently steerable wheels to avoid mutual collisions as well as stationary obstacles. The results of this research have been published to propose a new solution for path and trajectory generation in hazardous and inaccessible to human environments where the one camera is the only source of visual feedback

Modelling, simulation and experimental verification of a wheeled-locomotion system based on omnidirectional wheels

The following work focuses on the kinematic and dynamic study of a four-wheeled robot, which is equipped with omnidirectional Mecanum wheels. The main objective of the thesis is to obtain a mathematical model from which both the kinematics and kinetics of the robot can be analyzed. Furthermore, the study presents a methodology to optimize the torques (and subsequent associated voltages) provided by each of the motors on the robot for a given trajectory. A system in which a non-powered trailer pulled by the robot is also analyzed at a kinematic level. In this stage, four different cases are considered. The construction of the trailer is also described on this work. In the first chapter, the global state of the art on analysis and control of omnidirectional robots (with focus on robots with Mecanum wheels) is presented. In the second chapter, the physical considerations for the general movement of the robot are analyzed, in order to derive the kinematic constrain equations of the locomotion system. The differential equation of motion is then derived using Lagrange-equations with multipliers. This chapter presents as well the kinematic analysis for a robot-trailer system. The third chapter describes the general process on the design of the trailer, including the rejected ideas for its construction. The fourth chapter focuses on verifying the final results of the design process, as well as tests to check the mobility of the system. Conclusions and future work are analyzed on the final part of the document, as well as the references and the acknowledgments to all the people involved in the project.Tesi

Design And Comparison Of Controller Performance On Four Mecanum Wheeled Mobile Robot

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2016Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2016Bu tez çalışmasında çok yönlü hareket edebilen dört tekerlekli mobil robotun tasarımı ve farklı tipteki denetleyicilerin dizayn edilmesi ve bunların sonuçlarının kıyaslanması hedeflenmiştir. Denetim algoritması oluşturmaktaki amaç, gerçek sistem üzerinde oluşabilecek üretim hataları, motorların stabil olmaması ve diğer dış etkenler dolayısıyla meydana gelen hataları kabul edilebilir düzeye indirmektir. Çünkü herhangi bir kontrol algoritması kullanmadan sistemin istenilen stabilitede hareket etmesi ve farklı yüklerin motorlara binmesi durumunda hızların istenilen düzeyde tutulması zor bir durumdur. Gerek dıştan gelen etkiler, gerekse içten kaynaklanan birtakım sebeplerden dolayı sisteme uygulanacak denetleyiciler seçilmiş olup, bunların sonuçları kıyaslanmıştır. Fakat denetleyici tasarlamadan önce sistemin matematik modelinin bilinmesi gerekmektedir. Bunun için sistemin ilk önce ileri ve ters kinematik denklemleri matris şeklinde çıkarılmıştır. Matematiksel modeli oluştururken sistemin hesaplamaları kolaylaştırmak amacıyla bazı kabuller yapılmıştır. Bunlara örnek olarak sistemin rijit olduğu varsayılmış, zemin ile tekerler arasında oluşan yuvarlanma direncinin tekerlerin kaymadan ilerlemesi varsayılmış, tekerlerin zemin ile sürekli temasta olduğu ve diğer sistem bileşenleri modellenirken lineer denklemler kullanılmıştır. Model de tekerlerde üretim hatalarının olmadığı göz önüne alınmıştır. Her tekerin açısı 45° olduğu ve sistem simetrik şekilde dizayn edildiği varsayılmıştır. Oluşturulan matematiksel model ile sistemin istenilen doğrultuda gitmesi için herbir tekerin birbirinden bağımsız olarak hangi hıza sahip olacağı bu model sayesinde hesaplanabilmektedir. İleri kinematik denklemleri sayesinde sistemin kartezyen kordinat üzerindeki hızları ve her bir motorun devir sayısı elde edilebilmektedir. Oluşturulmuş olan ters kinematik denklemleri sayesinde ise sistemin dışarıdan kaynaklanan bozucu etkenlere karşı sistemin istenilen doğrultuda hareket etmesini sağlamak için yeniden motor hızları hesaplanmasına imkan vermektedir. Matematiksel denklemleri elde edilen sistemin sonuçlarını almak için model simulasyon ortamına aktarılmıştır. Bu ortamda sistemin oluşturulan ters ve ileri kinematik denklemleri, dc motor modeli, denetleyici ve input output arasındaki sistemler arası dönüştürücü denklemler yer almaktadır. Oluşturulan model sayesinde simulasyonlar gerçekleştirilmiştir ve alınan sonuçlar neticesinde denetleyici için gerekli olan katsayılar belirlenmiştir. Kontrolcü performansını denetlemek amacıyla ise alınan bu veriler gerçek sistem üzerinde test edilmek amacıyla kullanılmıştır. Gerçek sistem ise dört adet dc motor, dört adet manyetik enkoder, iki adet dc motor sürücü kartı ve mikrodenetleyiciden oluşmaktadır. Sistemde kullanılmış olan dc motor 350 wattlık güce sahip ve bu motorlar 12v luk seri bağlanmış iki adet kuru tip akülerle beslenmektedir. Sistemin istenilen tork değerlerine ulaşması için redüktör kullanılmıştır. Kullanılan iki adet dc motor sürücü kartı kanal başına 30 amper çıkış verebilmektedir ve her kart iki adet motoru sürebilmektedir. Ayrıca kartı kullanmak için üretici firma C++ ve python2.x kütüphanelerini de vermektedir. İstenilen datalar bu kartlar üzerinden bilgisayara seri haberleşme ile aktarılabilmektedir. Kullanılan çokyönlü tekerler 12 adet dış dış tekere sahip olup bunların yanında tekerin hareketini kolaylaştırmak amacıyla da 24 adet küçük yarım tekerleklerde ilave edilmiştir. Amaç tekerlerin dönüşü esnasında süreklilik sağlamak. Montaj sonrası sistemin matematiksel modeli oluşturulması için gerekli ölçümler yapılmıştır. Bunlara örnek olarak dc motor modelinin belirlenmesi ve bu modelde kullanılacak olan parametrelerin saptanması gerekmektedir. Bunları belirlemek için sisteme giriş verilerek çıkışlar gözlenmiş ve Matlab/Simulink system identification toolbox sayesinde sistem belirlenmiş ve parametreler belirlenmiştir. Daha sonra elde edilen bu değerler ile sistem tekrardan doğrulanarak değelerin güvenilirliği ölçülmüştür. Daha sonra sistemin diğer bileşenlerine ait olan tekerleklerin birbirine olan uzaklıkları redüktör oranları, maksimum motor devirleri ve bunun gibi önemli diğer parametrelerin ölçümleri yapılarak matematiksel model oluşturulmuştur. Motor için elde edilen transfer fonksiyonları ve durum uzay modeli denetleyici tasarımında büyük rol oynamaktadır. Denetleyici olarak sisteme uygulanabilir denetleyicilerden lineer quadratic regulator ve model öngörülü kontrolcü kullanılmıştır. LQR denetleyici için sistemde durum geri besleme yapılmaktadır ve bu geri beslemeler için motorların transfer fonksiyonlarına ihtiyaç duyulmuştur. Bu tip denetleyicide optimal geri besleme katsayılarını bulmak için hali hazırda bulunan yöntemler kullanılmıştır ve ayrıca mükemmel sonuçlar için simülasyonlar gerçekleştirilmiştir. Geri besleme katsayıları belirlenirken Matlab’de bulunan fonksiyonlar yardımıyla bulunmuştur. Fakat Q matrisi ve R katsayısı denetleyiciyi tasarlayan kişi tarafından seçilmektedir. Bu katsayılar performansı etkileyen en önemli kriterlerdendir. Kullandığı yazılım ve donanım itibariyle MPC ileri düzey bir denetim yöntemi olarak sınıflanabilir. İleri denetim tekniği olması denetim sinyallerini oluştururken optimizasyon algoritması çalıştırarak ilgilenilen süreç çıkış sinyallerini tasarımcının arzu ettiği optimizasyon ölçütüne uygun olarak sağlayan yapıya sahip olmasındandır. MPC yönteminden daha önce analog kontrol yöntemleri ve nümerik optimizasyonlar kullanılarak kontrol sağlanmıştır. Bugünkü teknolojiye bakarak işlemci teknolojilerini göz önüne aldığımızda bu denetleyicinin başarılı olabilmesini mümkün kılmıştır. Lineer olmayan sistem modelleri için az sayıda MPC algoritması varlığına karşın, lineer sistem modelleri için geliştirilmiş olan hali hazırda çeşitli algoritmalar bulunmaktadır. Model öngörülü kontrolcü ideal çalışma için denetlenmek istenen sistemin kesin modeline gerek duyar; ancak sistem modelindeki belirsizlikler durumunda dahi uygun geri besleme konfigurasyonları kullanılarak MPC algoritması başarılı olarak çalıştırılabilir. Başlangıçtan itibaren T saniyelik süre boyunca arzu edilen süreç çıkış yörüngesini daha önceden kullanıcı tarafından hazırlanabilir. Diğer denetleyici olarak model öngörülü kontrol seçilmiştir bu denetleyicide ki amaç büyük sistemlerin sisteme giriş verilmeden önce kumanda sinyalinin tespit edilmesi amacıyla kullanılmaktadır. Sistemi bir kapalı kutu olarak algılayıp bu sistem ile arka planda çalışan algoritma yardımıyla kullanıcı istekleri doğrultusunda sistem davranışı belirlenmiş olur. Sistem denetleyicisi adım cevabı veya darbe cevabı modeliyle belirlenebilir. Ayrıca Matlab/Simulinkte yer alan toolbox sayesinde denetleyici parametreleri ayarlanabilir. Bunlar kontrol ufku, saniyedeki hesaplama sayısı, tahmin edilen adım sayısı, sistem cevap süreleri gibi parametrelerdir. Bu denetleyiciler belirlenirken amaç motorun farklı senaryolar altında kullanıcı tarafından belirlenen doğrultudaki hızını sabit tutmasıdır. Fakat LQR denetleyicide geri besleme katsayıları sabit olduğundan belli her senaryo için adaptif olarak çalışamamaktadır. Bunun yanında MPC denetleyicide ise sistemin o anki davranışına göre ileride gerçekleşecek olan davranışı tahmin ettiğinden anlık verilerden yeni bir kumanda sinyali hesaplanır. Temelde kullandığı kontrol ufku ve tahmin ufku iterasyon sayılarından dolayı o andaki sistemin durumunu ölçüp gelecekte olabilecek durum hakkında bir kumanda sinyali üretilmektedir. Tahmin ufkunun fazla olması bir kaç adım sonra karşılaşabilecek durum hakkında daha stabil bir kestirim yapılabilmektedir. Ayrıca kumanda sinyallerinde oluşturulan kısıtlamalar sayesinde simulasyonlardan istenilen kumanda çıkışları ve sistem cevapları alınmıştır.In this thesis the main aim is to design and compare controller performance on omnidirectional mobile robot based on mecanum wheels and it can be use for further researches for elemination system errors. On the purpose of to increase orientation capability the system is equipped with four mecanum wheels which have twelve rollers around it. In the scope of this thesis to control dc motor speeds according to user demans and to minimize heading errors in the band of accaptable area. Before start to develop controller for the large scale system experimental test rig has been equipped with system components which are mecanum wheels, dc motors, encoders and controller. Also before start design controller all system elements should have mathematical models to take best controller results. Such as Dc motor model, system forward and backward kinematics, which help to minimize heading errors in real nonlinear environment. For the developing linear quadratic regulator and model predictive controller transfer function of the system is needed. Especially for LQR controller owing to feedback constants. The dc motor model is implemented to the simulation enviroment to see system output according to user inputs. In order to validate designed model, different system scenarios are tested independetly. After validation of system outputs cross validation test is conducted to maximize dependability. Designed model simulated in Matlab/Simulink environment with real dc motor coefficients. To improve controller performance for LQR controller different Q matrixes and R constants are tested and simulated. In the end admissible feedback constants are chosen. For MPC system inputs and outputs are simulated with modelled system. The controller performance is adjusted according to time interval, control horizon, weights of inputs and prediction horizon constants. Based on simulated model the aim is to take smooth response from system without overshoot, minimal oscillation and minimize settling time. Simulated results will be compared to real system results in future.Yüksek LisansM.Sc

Planning and Control Strategies for Motion and Interaction of the Humanoid Robot COMAN+

Despite the majority of robotic platforms are still confined in controlled environments such as factories, thanks to the ever-increasing level of autonomy and the progress on human-robot interaction, robots are starting to be employed for different operations, expanding their focus from uniquely industrial to more diversified scenarios. Humanoid research seeks to obtain the versatility and dexterity of robots capable of mimicking human motion in any environment. With the aim of operating side-to-side with humans, they should be able to carry out complex tasks without posing a threat during operations. In this regard, locomotion, physical interaction with the environment and safety are three essential skills to develop for a biped. Concerning the higher behavioural level of a humanoid, this thesis addresses both ad-hoc movements generated for specific physical interaction tasks and cyclic movements for locomotion. While belonging to the same category and sharing some of the theoretical obstacles, these actions require different approaches: a general high-level task is composed of specific movements that depend on the environment and the nature of the task itself, while regular locomotion involves the generation of periodic trajectories of the limbs. Separate planning and control architectures targeting these aspects of biped motion are designed and developed both from a theoretical and a practical standpoint, demonstrating their efficacy on the new humanoid robot COMAN+, built at Istituto Italiano di Tecnologia. The problem of interaction has been tackled by mimicking the intrinsic elasticity of human muscles, integrating active compliant controllers. However, while state-of-the-art robots may be endowed with compliant architectures, not many can withstand potential system failures that could compromise the safety of a human interacting with the robot. This thesis proposes an implementation of such low-level controller that guarantees a fail-safe behaviour, removing the threat that a humanoid robot could pose if a system failure occurred

Model predictive control for a Mecanum-wheeled robot navigating among obstacles

Mecanum-wheeled robots have been thoroughly used to automate tasks in many different applications. However, they are usually controlled by neglecting their dynamics and relying only on their kinematic model. In this paper, we model the behaviour of such robots by taking into account both their equations of motion and the electrodynamic response of their actuators, including dry and viscous friction at their shafts. This allows us to design a model predictive controller aimed to minimise the energy consumed by the robot. The controller also satisfies a number of non-linear inequalities modelling motor voltage limits and obstacle avoidance constraints. The result is an agile controller that can quickly adapt to changes in the environment, while generating fast and energy-efficient manoeuvres towards the goal.Peer ReviewedPostprint (published version