A mobile manipulator is a robotic system consisting of a robotic manipulator mounted onto a mobile base. This greatly extends the workspace of the robotic manipulator and allows it to perform more tasks. However, combining both systems increases the complexity of the control task as well as introducing additional controller tasks such as coordination of motion, where executing the task can involve using both the mobile base and manipulator, and cooperation of task, where many tasks can be executed at once. In this thesis a controller for a mobile manipulator is developed from smaller, simple controller blocks, allowing the controller to be flexible, easy to understand, and straightforward to implement using well-known embedded software implementation approaches. A behaviour-based approach was used to build the individual controllers, and a hierarchical structure was used to organise the individual controllers to provide cooperation between them and coordinated motion. The task assigned to the controller was to reach a series of waypoints in a large workspace, while satisfying performance metrics of manipulability and tip-over sta- bility. The operation of the controller was tested in simulation using 100 randomly generated scenarios consisting of five randomly generated waypoints in each. Using default thresholds for manipulability and tip-over stability, the controller was success- fully able to complete all scenarios. Further simulations were then performed testing the effects of varying the thresholds of the performance metrics to explore the tradeoffs involved in different parameter choices. The controller was successful in a majority of these scenarios, with only a few failing due to extreme threshold choices. The reasons for these failures, and the corresponding lessons for robot designers are discussed. Finally, to demonstrate the modularity of the controller, an obstacle avoidance con- troller was added and simulation results showed the controller was capable of avoiding obstacles while still performing the same tasks that were used in previous tests. Successful simulation results of the controller across a range of performance metrics shows that the combination of a behaviour based and hierarchical approach to mobile manipulator control is not only capable of producing a functional controller, but also one that is more modular and easier to understand than the monolithic controllers developed by other researchers.

A novel algorithm for the simplified tele-operation of mobile-manipulator systems is presented. The algorithm allows for unified, intuitive, and coordinated control of mobile manipulators, systems comprised of a robotic arm mounted on a mobile base. Unlike other approaches, the mobile-manipulator system is modeled and controlled as two separate entities rather than as a whole. The algorithm consists of thee states. In the rst state a 6-DOF (degree-of-freedom) joystick is used to freely control the manipulator's position and orientation. The second state occurs when the manipulator approaches a singular configuration, a con guration where the arm instantaneously loses a DOF of motion capability. This state causes the mobile base to proceed in such a way as to keep the end-effector moving in its last direction of motion. This is done through the use of a constrained optimization routine. The third state is triggered by the user: once the end-effector is in the desired position, the mobile base and manipulator both move with respect to one another keeping the end-effector stationary and placing the manipulator into an ideal configuration. The proposed algorithm avoids the problems of algorithmic singularities and simplifies the control approach. The algorithm has been implemented on the Jasper Mobile-Manipulator System. Test results show that the developed algorithm is effective at moving the system in an intuitive manner.

In order to make the task of controlling Mobile-Manipulator Systems (MMS) simpler, a novel command strategy that uses a single joystick is presented to replace the existing paradigm of using multiple joysticks. To improve efficiency and accuracy, virtual fixtures were implemented with the use of a haptic joystick. Instead of modeling the MMS as a single unit with three redundant degrees-of-freedom (DOF), the operator controls either the manipulator or the mobile base, with the command strategy choosing which one to move. The novel command strategy uses three modes of operation to automatically switch control between the manipulator and base. The three modes of operation are called near-target manipulation mode, off-target manipulation mode, and transportation mode. The system enters near-target manipulation mode only when close to a target of interest, and allows the operator to control the manipulator using velocity control. When the operator attempts to move the manipulator out of its workspace limits, the system temporarily enters transportation mode. When the operator moves the manipulator in a direction towards the manipulator’s workspace the system returns to near-target manipulation mode. In off-target manipulation mode, when the operator moves the manipulator to its workspace limits, the system retracts the arm near to the centre of its workspace to enter and remain in transportation mode. While in transportation mode the operator controls the base using velocity control. Two types of virtual fixtures are used, repulsive virtual fixtures and forbidden region virtual fixtures. Repulsive virtual fixtures are present in the form of six virtual walls forming a cube at the manipulator’s workspace limits. When the operator approaches a virtual wall, a repulsive force is felt pushing the operator’s hand away from the workspace limits. The forbidden region virtual fixtures prevent the operator from driving into obstacles by disregarding motion commands that would result in a collision. The command strategy was implemented on the Omnibot MMS and test results show that it was successful in improving simplicity, accuracy, and efficiency when teleoperating a MMS. / UOIT

The objective of this thesis is to solve the trajectory tracking control problems of the mobile manipulators in two stages. In the first stage, a desired velocity input function for a steering system is designed by using Lyapunov stability theorem so that the posture of the mobile manipulator can track the reference trajectory. Further analysis shows that the vehicle of the mobile manipulator will achieve better result of trajectory tracking than the existent methods if the reference trajectory of the vehicle is not assigned to be static condition. In the second stage, the torque controller of the dynamic equations of the mobile manipulator with perturbations and input uncertainty is designed by adaptive variable structure control (AVSC) methodology, so that the actual velocity can track the desired velocity input function designed in the first stage. In addition, this controller with an adaptive mechanism embedded is capable of suppressing the perturbations with unknown upper bound except that from the input channel, and achieve asymptotical stability under certain mild conditions. Finally, an example of a two-link wheeled mobile manipulator is presented to demonstrate the feasibility of the proposed control schemes.

Opening a door is still a hard problem in robotics. Many robotic manipulators use open-loop position control to open doors, which reduces reusability and reliability in the face of slight differences or sensor errors. Many others use force feedback or impedance control but skip past the problem of grabbing the handle, which could lead to failures due to sensor errors. This research assumes that perception is faulty, and uses joint-level force feedback to probe the location of the door and its handle before attempting to open it. The resulting control strategy is at least 33% faster than the open-loop control system it replaces, and had an 83% success rate during testing in place of the previous method's 60% success rate. / Master of Science

This thesis investigates the strengths and weaknesses of omnidirectional drive and differential drive systems on mobile manipulator robots. Based on a literature study, a hypothetical use case, and identified Key Performace Indicators the drive system’s effects on the performance of the mobile manipulator are evaluated. A qualitative approach was used for evaluation. The research methodology involved analyzing the wheel characteristics of each drive system, identifying parameters affecting the performance, and assessing the two drive system characteristics within the context of the hypothetical use case. Six Key Performance Indicators such as pose accuracy, space utilization, and manipulability were formulated and examined to determine the comparative strengths and weaknesses of the drive systems. The results confirmed that omnidirectional drive systems exhibit greater maneuverability and agility while differential drive systems are less complex and often more durable in rough conditions. However, the results also show that in many cases the answer on what drive system to use will depend on many factors and that these factors can affect the overall performance of the mobile manipulator. This study provides insights into performance-affecting parameters and relevant performance aspects by examining the strengths and weaknesses of omnidirectional and differential drive systems. While acknowledging the need for caution in generalizing the findings and assuming validity in real-world applications, the results obtained serve as a starting point for further investigations. / Detta examensarbete undersöker styrkor och svagheter hos omnidirektionella drivsystem och differentialdrivsystem på mobila manipulatorer. En kvalitativ metod, baserat på en litteraturstudie, ett hypotetiskt användningsscenario och identifierade prestationsindikatorer, användes för att utvärdera drivsystemets effekter på den mobila manipulatorns prestanda. Forskningsmetodiken innebar att analysera hjulegenskaperna för varje drivsystem, identifiera parametrar som påverkar prestandan och bedöma de två drivsystemens egenskaper inom ramen för det hypotetiska användningsfallet. Viktiga prestationsindikatorer som poserings noggrannhet, utrymmesutnyttjande och manipulerbarhet undersöktes för att fastställa och jämförande styrkorna och svagheterna hos drivsystemen. Resultaten bekräftade att omnidirektionella drivsystem uppvisar större manövrerbarhet och smidighet medan differentialdrivsystem ofta är mindre komplexa och mer hållbara under tuffa förhållanden. Dock visar resultaten även att svaret på vilket drivsystem som ska användas i många fall beror på flertalet faktorer och att dessa faktorer kan påverka den mobila manipulatorns totala prestanda. Denna studie ger insikter i prestandapåverkande parametrar och relevanta prestandaaspekter genom att undersöka styrkorna och svagheterna hos omnidirektionella och differentiella drivsystem. Samtidigt som man erkänner behovet av försiktighet med att generalisera resultaten och anta giltighet i verkliga tillämpningar, tjänar de erhållna resultaten som en utgångspunkt för ytterligare undersökningar.

Individuals with disabilities yearn for an increased level of independence, seeking to supplement their missing function(s) and to carry on with their lives with minimal or no assistance from another person. A review of the existing assistive-care products has revealed that many of the defects in these devices, particularly in wheelchair-mounted robots, can be alleviated. Surveys have also identified tasks that users would like to perform by themselves, but are constrained from doing so by using currently available devices. An attempt has been made here to try to resolve these issues by developing a prototype of a marsupial robot that can dock into the powered wheelchair that is used for manipulation purposes. The primary function of this system is to assist the user in his/her daily tasks such as pick-up small objects and place them as per the user's commands, push to open/close doors and remove obstacles from the wheelchair path. It is with the objective of providing an enhanced quality of life to a person with impairment(s) that a proposal for a simple, safe and inexpensive approach to assist him/her in performing an activity is made here.

This thesis presents an in-depth investigation to determine the most suitable mobile base design for a powerful and dynamic robotic manipulator. It details the design process of such a mobile platform for use in an indoor human environment that is to carry a two-arm upper-body humanoid manipulator system. Through systematic dynamics analysis, it was determined that a variable footprint holonomic wheeled mobile platform is the design of choice for such an application. Determining functional requirements and evaluating design options is performed for the platform’s general configuration, geometry, locomotion system, suspension, and propulsion, with a particularly in-depth evaluation of the problem of overcoming small steps. Other aspects such as processing, sensing and the power system are dealt with sufficiently to ensure the feasibility of the overall proposed design. The control of the platform is limited to that necessary to determine the appropriate mechanical components. Simulations are performed to investigate design problems and verify performance. A basic CAD model of the system is included for better design visualization. The research carried out in this thesis was performed in cooperation with the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt)’s Robotics and Mechatronics Institute (DLR RM). The DLR RM is currently utilizing the findings of this research to finish the development of the platform with a target completion date of May 2008.

This thesis presents an in-depth investigation to determine the most suitable mobile base design for a powerful and dynamic robotic manipulator. It details the design process of such a mobile platform for use in an indoor human environment that is to carry a two-arm upper-body humanoid manipulator system. Through systematic dynamics analysis, it was determined that a variable footprint holonomic wheeled mobile platform is the design of choice for such an application. Determining functional requirements and evaluating design options is performed for the platform’s general configuration, geometry, locomotion system, suspension, and propulsion, with a particularly in-depth evaluation of the problem of overcoming small steps. Other aspects such as processing, sensing and the power system are dealt with sufficiently to ensure the feasibility of the overall proposed design. The control of the platform is limited to that necessary to determine the appropriate mechanical components. Simulations are performed to investigate design problems and verify performance. A basic CAD model of the system is included for better design visualization. The research carried out in this thesis was performed in cooperation with the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt)’s Robotics and Mechatronics Institute (DLR RM). The DLR RM is currently utilizing the findings of this research to finish the development of the platform with a target completion date of May 2008.

Une approche avancée de la fabrication flexible consiste à déplacer des manipulateurs robotisés AGV ou robot mobile, appelé manipulateurs mobiles, entre les postes de travail. L'utilisation de manipulateurs mobiles peuvent être avantageux dans un certain nombre de situations. Cela peut entraîner des coûts économies lorsqu'un seul manipulateur mobile peut être utilisé pour remplacer plusieurs stationnaires manipulateurs. Cependant, les manipulateurs mobiles sont «une discipline relativement jeune robotique. "Une revue de la littérature approfondie de la recherche menant à la commercialisation mobile manipulateurs et robots mobiles a été réalisée. La mesure de la performance du mobile les manipulateurs, y compris une base mobile avec un bras de robot embarqué, sont pratiquement inexistants. Cependant, les manipulateurs mobiles commencent à apparaître dans la fabrication, la santé, et peut-être d'autres industries et, par conséquent, une méthode pour mesurer leur performance est essentielle pour les fabricants et les utilisateurs de ces systèmes relativement complexes. Mesures de mobile manipulateurs effectuant des tâches standard (poses et mouvements) sont également inexistants, sauf pour simplement s'assurer que la tâche a été plus ou moins complétée. La tâche choisie pour cela thèse est l'assemblage en raison de son exigence de pose de système.Les méthodes de test de performance ont pris du retard par rapport aux méthodes de test de sécurité pour les manipulateurs mobiles qui progresse vers le développement d'une nouvelle norme de sécurité aux États-Unis. Métriques pour la sécurité et la performance des manipulateurs mobiles comprennent de nombreux domaines, tels que: l'achèvement des tâches, le temps nécessaire pour accomplir la tâche, la qualité et la quantité (c.-à-d.répétabilité, respectivement) des tâches accomplies. Avant l'acceptation industrielle et les normes développement pour les manipulateurs mobiles, les utilisateurs de ces nouveaux systèmes attendront des fabricants fournir des données de performance réelles pour guider leur approvisionnement et assurer l'aptitude à tâches d'application. En raison du coût relativement élevé pour acquérir et installer des systèmes de suivi de mouvement Pour mesurer la performance des systèmes, une méthode alternative à utiliser par les fabricants et les utilisateurs est idéal. Un nouveau concept de méthode de test qui utilise un artefact, appelé mobile reconfigurable Manipulateur Artefact (RMMA), est décrit dans cette thèse et comparé à un suivi optique système qui a été utilisé comme vérité de terrain pour le RMMA et manipulateur mobile. Système de modélisation du système de manipulation mobile, des composants et des les mesures peuvent aider à améliorer la compréhension de ces systèmes relativement complexes.Systems Modelling Language (SysML) a été choisi et utilisé tout au long de cette thèse, car de SysML a des modules logiciels réutilisables pour la structure, le comportement, les exigences et parametrics sur le manipulateur mobile. Les modèles décrivent les nombreux aspects de mesurer la performance des manipulateurs mobiles également en tant que nouveau domaine de recherche.Les modèles étaient évalué à travers des expériences sur un exemple de composants manipulateurs mobiles et l'ensemble système. SysML a été utilisé pour décrire la base théorique de la performance à travers la propagation de l'incertitude lorsque les équations mathématiques sont également modélisées.Un cas d'utilisation est modélisé et décrit où les concepts recherchés pour mesurer les mobiles les performances du manipulateur sont appliquées à une implémentation de fabrication. Le simpliste la nature du processus de mesure utilisant le RMMA peut être directement appliquée à processus de fabrication, et étendu au-delà des contributions de cette recherche à d'autres des besoins de mesure encore plus complexes (...). / An advanced approach to flexible manufacturing is to move robotic manipulators, using anAGV or mobile robot, called mobile manipulators, between workstations. The use ofmobile manipulators can be advantageous in a number of situations. It can result in costsavings when a single mobile manipulator can be used to replace several stationarymanipulators. However, mobile manipulators are “a relatively young discipline withinrobotics.” An extensive literature review of the research leading to commercial mobilemanipulators and mobile robots was performed. The performance measurement of mobilemanipulators, including a mobile base with an onboard robot arm, is virtually non-existent.However, mobile manipulators are beginning to appear in manufacturing, healthcare, andpossibly other industries and therefore, a method to measure their performance is critical toboth manufacturers and users of these relatively complex systems. Measurements of mobilemanipulators performing standard tasks (poses and motions) are also non-existent except forsimply ensuring that the task has been more or less completed. The task chosen for thisthesis is assembly due to its requirement for relatively precise system posing.Performance test methods have lagged behind safety test methods for mobile manipulatorswhich is progressing towards development of a new safety standard in the US. Metrics forsafety and performance of mobile manipulators include many areas, such as: safe operation,task completion, time to complete the task, quality, and quantity (i.e., accuracy andrepeatability, respectively) of tasks completed. Prior to industrial acceptance and standardsdevelopment for mobile manipulators, users of these new systems will expect manufacturersto provide real performance data to guide their procurement and assure suitability for givenapplication tasks. Due to the relatively high cost to procure and setup motion tracking systemsto measure systems performance, an alternative method for use by manufacturers and users isideal. A new test method concept that uses an artifact, called the Reconfigurable MobileManipulator Artifact (RMMA), is described in this thesis and compared to an optical trackingsystem that was used as ground truth for the RMMA and mobile manipulator.System modeling the mobile manipulator system, components, and the associatedmeasurements can help to improve the understanding of these relatively complex systems.Systems Modeling Language (SysML) was chosen and used throughout this thesis becauseof SysML has reusable software modules for structure, behavior, requirements andparametrics off the mobile manipulator. The models describe the many aspects ofmeasuring mobile manipulator performance also as new research area. The models wereevaluated through experiments on an example mobile manipulator components and the entiresystem. SysML was used to describe the theoretical basis of the performance throughpropagation of uncertainty where mathematical equations are also modeled.A use case is modeled and described where the concepts researched to measure mobilemanipulator performance are applied to a manufacturing implementation. The simplisticnature of the measurement process using the RMMA can be directly applied to today’smanufacturing processes, and extended beyond the contributions of this research to othereven more complex measurement needs. The research is also discussed to even apply tocross-industry test methods for exoskeletons worn by humans.