Collaborative robots have many advantages and have proven to be useful, although there are still currently very few actual implementations of collaborative robots on the industrial shop-floors. One major reason for this is the high safety requirements within the industry and the difficulties to fulfil current safety regulations when using collaborative robots. The purpose of this thesis is to identify the most important safety aspects in collaborative robot applications and to discuss how different solutions can aid in fulfilling current safety regulations. In order to fulfil the purpose, a physical demonstrator will be developed in collaboration with Volvo Cars Engine that can be used for evaluation and testing. To investigate what the general opinion of the automotive industries thoughts are on collaborative robots, a questionnaire based survey was conducted with 143 participants. The survey result show that the majority thinks that collaborative robots can benefit them in their own work, and that assembly- and material handling tasks is well suited applications for collaborative robots. The literature review of the thesis project is focused on collaborative robot safety peripherals for minimizing injury by collisions, but also to investigate other related work with collaborative robots. Input from the survey and the literature review clarifies the problem at hand and tentative idea of a physical demonstrator is suggested. The demonstrator which resembles an industrial assembly station with bolt tightening, has been created using a light weight structure UR10 robot from Universal Robots. Together with the operator, a work sequences was proposed for both the human and the robot, and once implemented, three optional scenarios where recorded for evaluation. By observing the recordings it is identified that a seamless workflow can be achieved even though the robot and human works in the same area and on the same work piece. Other benefits include improved ergonomics and reduction of operator physical fatigue. To evaluate the demonstrator further, experiments with test- and control groups were proposed as future work.

European manufacturing companies are facing challenges of increasing prices of raw material, more customized products and competitiveness from industries outside Europe. Those challenges make the manufacturing require flexible production processes. The remanufacturing industry has the advantages of produce products using less raw material and to a lower cost compared with manufacturing. This makes the remanufacturing industry a way for the European companies to stay competitive. Challenges of the remanufacturing process are the operator exposure of vibrations, monotony tasks and ergonomic issues when disassembling the incoming core. To meet the challenges and stay competitive the Swedish manufacturing industries is currently examine the advantages of collaborative robots and how implementation of collaborative robots can improve production. Implementation of a collaborative robot at a workstation requires risk assessment as human safety is an important aspect to consider. Simulation modelling can advantageously be used to examine future state scenario or investigate how a current system is affected by different variables. To meet the challenges described the aim of this thesis has been to examine how to facilitate the design of a collaborative disassembly workstation by means of simulation. The work with the thesis is based on a case study made at a Swedish remanufacturing company. Following research questions has been formulated to fulfil the purpose:    <li data-leveltext="-" data-font="Arial" data-listid="48" data-aria-posinset="0" data-aria-level="1">What are the challenges of verifying the operators´ safety by using simulation?  <li data-leveltext="-" data-font="Arial" data-listid="48" data-aria-posinset="0" data-aria-level="1">What are the advantages and disadvantages of implementing a cobot in a disassembly station?  <li data-leveltext="-" data-font="Arial" data-listid="48" data-aria-posinset="0" data-aria-level="1">How can simulation be used to facilitate decision making when developing a collaborative workstation?    Results show simulation challenges as human’s movements, robot characteristics and the ability to simulate it, core condition uncertainty, software knowledge and time consuming simulation modeling. Human-robot collaboration enables to combine the characteristics of human flexibility and robot precision and repeatability. The robot can advantageously perform tasks which are detected as monotonous or not ergonomic to a human. Simulation can advantageously be used in an early stage of designing layout of a collaborative workstation for reachability verification.

The need for automation is increasing at Sandvik Coromant. However, high equipment-, education-, and implementation costs connected to automation are usually obstacles when automating smaller and simpler tasks. During the recent years, a new type of robot has been introduced to the market. It is called a collaborative robot, or cobot. It is easy to use/program, has a lower cost and has built-in safety features. The user friendliness of the robot as well as the built-in safety features could lower the implementation costs of these robots to open new areas for automation. This thesis evaluates a cobot from Universal Robots, UR5, to determine if such technology could be useful at Sandvik Coromant’s Insert Plant in Gimo, Sweden. This would be done by performing a physical demonstration of a UR5 put into Sandvik Coromants production. The task includes identifying, conceptualizing and evaluating the possible applications where cobots could create the most value. The work showed that cobots are indeed easy to work with and could create more areas of automation. However, the way Sandvik Coromant looks at automation should change for the technology to make the biggest impact. A company guideline must be setup regarding the use of the built-in safety features to set a limit of what is acceptable when creating an open cell environment at the factory. The results and conclusion of this thesis will hopefully lead to the implementation of collaborative robots at Sandvik Coromant which will result to lower automation costs, better working environment and higher production. / Automationsbehovet på Sandvik Coromant har ökat under de senaste åren. Höga utrustnings-, utbildnings-, och utvecklingskostnader kopplade till automation sätter oftast stopp för automation av mindre och enklare uppgifter. Under de senaste åren har en ny typ av robot blivit introducerad på marknaden. Den kallas för samverkansrobot, eller cobot. Den är enkel att använda/programmera, har lägre kostnad och inbyggda säkerhetsfunktioner. Användarvänligheten av roboten samt de inbyggda säkerhetsfunktionerna kan leda till lägre implementationskostnader, som öppnar nya möjligheter för automation. Detta mastersarbete utvärderar en cobot från Universal Robots, UR5, för att fastställa om sådan teknologi kan vara användbar på Sandvik Coromants skärfabrik i Gimo, Sverige. Utvärderingen kan göras genom att fysisk demonstration av UR5 i Sandvik Coromants produktion genomförs. Uppgiften består av att identifiera, konceptualisera och utvärdera de applikationer i fabriken där samarbetsrobotar skulle kunna skapa mest värde. Arbetet visade att cobots är enkla att arbeta med och kan skapa mer möjligheter för automation. Dock så måste sättet Sandvik Coromant ser på automation att ändras för att teknologin ska ha störst inverkan. En intern riktlinje måste skapas angående användandet av de inbyggda säkerhetssystemen för att sätta en gräns på vad som är accepterat ur en arbetsmiljösynpunkt när det gäller öppna robotceller. Resultaten och slutsatsen av arbetet kommer förhoppningsvis leda till implementering av samverkansrobotar på Sandvik Coromant som i sin tur leder till lägre automationskostnader, bättre arbetsmiljö och högre produktion.

Parce qu’elle permet d’associer les capacités physiques d’un robot aux capacités perceptives et cognitives de l’Homme, la robotique collaborative peut être une solution pour répondre au problème des troubles musculo-squelettiques dans l’industrie. Cependant, le gain d’ergonomie qu’apporte l'utilisation de tels robots est rarement quantifié, à cause du manque d’outils adéquats.Ce travail vise à développer un outil générique permettant d’effectuer des évaluation ergonomiques d'activités de co-manipulation, à partir de très peu de données d’entrée. Cet outil s’appuie sur une évaluation en simulation, à l’aide d’un mannequin virtuel. Afin d'estimer les différentes sollicitations biomécaniques auxquelles sont exposés les ouvriers lorsqu’ils réalisent des tâches manuelles, de nombreux indicateurs d'ergonomie sont définis, et mesurés grâce à une simulation dynamique. Le mannequin virtuel est animé avec une technique d’optimisation LQP, et le robot est contrôlé par une commande en amplification d’effort. L'outil proposé est validé à l'aide d'expériences basées sur la capture de mouvement.Cependant, le choix d’un robot plutôt que d’un autre est rendu difficile par le nombre élevé d’indicateurs d'ergonomie à prendre en compte. Une méthode pour analyser la sensibilité des indicateurs aux différents paramètres du robot et de la tâche considérée est donc développée. Une telle analyse permet de réduire le nombre d’indicateurs à prendre en compte, tout en rendant suffisamment compte de l’ergonomie de chaque situation.Enfin, l’outil de simulation mis en place est couplé à un logiciel d’optimisation par algorithme génétique, afin d' optimiser la cinématique d’un robot collaboratif. / The growing number of musculoskeletal disorders in industry could be addressed by the use of collaborative robots, which allow the joint manipulation of objects by both a robot and a person. Designing such robots requires to assess the ergonomic benefit they offer. However there is a lack of adapted assessment tools. This work presents a generic tool for performing accurate ergonomic assessments of co-manipulation activities, with very little input data. This tool relies on an evaluation carried out within a digital world, using a virtual manikin to simulate the worker. A framework is developed to enable the estimation of the different biomechanical solicitations which occur during manual activities. Multiple ergonomic indicators are defined and measured through a dynamic simulation of the considered activity. The virtual manikin is animated through a LQP optimization technique, and the robot is controlled according to the manikin-robot interaction force. The proposed framework is validated with motion capture experiments. However, the high number of indicators that are measured makes any kind of conclusion difficult for the user. Hence, a methodology for analyzing the sensitivity of the various indicators to the robot and task parameters is proposed. The goal of such an analysis is to reduce the number of ergonomic indicators which are considered in an evaluation, while sufficiently accounting for the global ergonomic level of the considered activity. Finally, an application of the proposed methodology is presented. The evaluation framework is linked to a genetic algorithm software in order to optimize the morphology of a collaborative robot for a given task.

Until recently, few technologies have been applicable to increase flexibility in the manufacturers’ assembly applications, but the introduction of industrial robots in collaborative assembly applications provides such opportunities. Specifically, these collaborative assembly applications present an opportunity to, in a fenceless environment, combine the flexibility of the human with the accuracy, repeatability, and strengths of the robot while utilizing less floor space and allowing portable applications. However, despite the benefits of industrial robots in collaborative assembly applications, there are significant gaps in the literature preventing their implementation. Based on this background, the objective of this work is to support the implementation of industrial robots in collaborative assembly applications. To fulfill this objective, this work included two empirical studies; first, an interview study mapped the attributes of industrial robots in collaborative assembly applications. Second, a multiple-case study mapped the critical challenges and enabling activities when implementing these collaborative assembly applications. The studies were also combined with literature reviews aiming to fill the theoretical gaps.  The work provides an implementation process with enabling activities that can mitigate critical challenges when implementing industrial robots in collaborative assembly applications. The implementation process shows enabling activities in the three first phases: pre-study, collaborative assembly application design, and assembly installation. These enabling activities are mapped to the 7M dimensions as a way to clearly show how they can support the implementation of industrial robots in collaborative assembly applications. The implementation process contributes to filling the identified gaps in the literature and provides practitioners with activities that managers could consider when implementing collaborative robots in collaborative assembly applications. Finally, this work suggests that future research could aim to validate the implementation process in a case study or investigate further the last two phases of the process. / Hittills har få tekniker kunnat öka flexibiliteten i tillverkarnas monteringsapplikationer, men introduktion av industrirobotar i samarbetande monteringsapplikationer öppnar upp för sådana möjligheter. Specifikt så presenterar dessa samarbetande monteringsapplikationer en möjlighet att, i en staketlös miljö, kombinera människans flexibilitet med industrirobotens precision, repeterbarhet och styrka men samtidigt nyttja litet golvutrymme och tillåta bärbarhet. Emellertid, trots fördelarna med industrirobotar i samarbetande monteringsapplikationer, finns det signifikanta gap i litteraturen som förhindrar dess implementering.  Baserat på denna bakgrund är syftet med detta arbete att stödja implementeringen av industrirobotar i samarbetande monteringsapplikationer.  För att fullfölja detta syfte inkluderade detta arbete två empiriska studier. Först, en intervjustudie som kartlagde attributen för industrirobotar i samarbetande monteringsapplikationer. För det andra, en flerfallstudie som kartlagde de kritiska utmaningarna och möjliggörande aktiviteterna för implementeringen av dessa samarbetande monteringsapplikationer. Studierna kombinerades också med litteraturstudier med målet att fylla de teoretiska gapen.  Detta arbete ger en implementeringsprocess med möjliggörande aktiviteter som kan mildra de kritiska utmaningarna under implementeringen av industrirobotar i samarbetande monteringsapplikationer. Implementeringsprocessen visar möjliggörande aktiviteter i de tre första faserna; förstudie, design av samarbetande monteringsapplikationer och monteringsinstallation.  Dessa möjliggörande aktiviteter är kartlagda mot 7M dimensionerna som ett sätt att tydligt visa hur dessa kan stödja implementeringen av industrirobotar i samarbetande monteringsapplikationer. Implementeringsprocessen bidrar till att fylla de identifierade gapen i litteraturen och ger till praktiker aktiviteter som ledare kan beakta vid implementeringen av industrirobotar i samarbetande monteringsapplikationer. Slutligen, detta arbete föreslår att framtida forskning syftar att validera implementeringsprocessen genom en fallstudie eller vidare undersöka de två sista faserna av denna process.

<p>Robot grasping is emerging as an active area of research in robotics as the interest in human-robot interaction is gaining worldwide because of diverse industrial settings for sharing tasks and workplaces. It mainly focuses on the quality of generated grasps for object manipulation. However, despite advancements, these methods need to consider the human-robot collaboration settings where robots and humans will have to grasp the same objects concurrently. Therefore, generating robot grasps compatible with human preferences of simultaneously holding an object is necessary to ensure a safe and natural collaboration experience. In this work, we propose a novel, deep neural network-based method called CoGrasp that generates human-aware robot grasps by contextualizing human preference models of object grasping into the robot grasp selection process. We validate our approach against existing state-of-the-art robot grasping methods through simulated and real-robot experiments and user studies. In real robot experiments, our method achieves about 88% success rate in producing stable grasps that allow humans to interact and grasp objects simultaneously in a socially compliant manner. Furthermore, our user study with 10 independent participants indicated our approach enables a safe, natural, and socially aware human-robot objects' co-grasping experience compared to a standard robot grasping technique.</p> <p>To facilitate the grasping process, we also introduce a vision-language model that works as a pre-processing system before the grasping action takes place. In most settings, the robots are equipped with sensors that allow them to capture the scene, on which the vision model is used to do a detection task and objectify the visible contents in the environment. The language model is used to program the robot to make it possible for them to understand and execute the required sequence of tasks. Using the process of object detection, we build a set of object queries from the sensor image and allow the user to provide an input query for a task to be performed. We then perform a similarity score among these queries to localize the object that needs attention, and once identified, we can use a grasping process for the task at hand.</p>

Today, majority of the manufacturing industries are willing to implement automation in their plants depending on their specific benefits. Implementing automation into an existing production line requires a pre-study of all the operations to find out the optimal working area and working sequence that is possible to automate with the highest possible degree of efficiency. Thereby, this thesis work involves the study on the potential of implementation of collaborative robot in manual assembly lines of 13-Litre diesel engines thereby creating a human-robot collaboration scenario in the assembly line. This project was carried out at Volvo's powertrain production plant located in Skövde, Sweden. The initial study of assembly lines consisting of a predefined number of stations in the production of diesel engines was conducted. Concepts were developed and evaluated considering the results from pre-study using a suitable method. The finalized concept was simulated to visualize the practical benefits, obtain accurate timing data, and also to check for bottlenecks in the presented solution. A preliminary risk assessment process was carried out to identify and evaluate the possible risks that were involved in the finalized concept. The risk assessment process ensures the safety of the operator within the collaborative robot work cell. The study is concluded with an economic analysis which includes the figures for investment, payback period as well as the profit estimation for the simulated automation solution.

Ursprünglich wurden Industrieroboter hauptsächlich hinter Schutzzäunen betrieben, um den Sicherheitsanforderungen gerecht zu werden. Mit der Flexibilisierung der Produktion wurden diese scharfen Trennbereiche zunehmend aufgeweicht und externe Sicherheitstechnik, wie Abstandssensoren, genutzt, um Industrieroboter schutzzaunlos zu betreiben. Ausgehend vom Gedanken dieser Koexistenz bzw. Kooperation wurde die Sicherheitssensorik in den Roboter integriert, um eine wirkliche Kollaboration zu ermöglichen. Diese sogenannten kollaborierenden Roboter, oder Cobots, eröffnen neue Applikationsfelder und füllen somit die bestehenden Automatisierungslücken. Doch welche Automatisierungsvariante ist aus wirtschaftlichen Gesichtspunkten die geeignetste? Bisherige Forschung untersucht zum Großteil isoliert eine der beiden Technologien, ohne dabei einen Systemvergleich hinsichtlich technologischer Spezifika und Wirtschaftlichkeit anzustellen. Daher widmet sich diese Dissertation einer Methodik zum wirtschaftlichen Vergleich von kollaborierenden Robotern und Industrierobotern in schutzzaunlosen Maschinenbeladungssystemen. Besonderer Fokus liegt dabei auf dem Herausarbeiten der technischen Faktoren, die die Wirtschaftlichkeit maßgeblich beeinflussen, um ein Systemverständnis der wirtschaftlichen Struktur beider Robotertechnologievarianten zu erhalten. Zur Untersuchung werden die Inhalte eines solchen Planungsvorhabens beschrieben, kategorisiert, systematisiert und modularisiert. Auf wirtschaftlicher Seite wird ein geeignetes Optimierungsmodell vorgestellt, während auf technischer Seite vor allem die Machbarkeit hinsichtlich Greifbarkeit, Layoutplanung, Robotergeschwindigkeiten und Zykluszeitbestimmung untersucht wird. Mit deduktiven, simulativen, empirischen und statistischen Methoden wird das Systemverhalten für die einzelnen Planungsinhalte analysiert, um die Gesamtwirtschaftlichkeit mit einem Minimum an Investment,- Produktions,- und Zykluszeitinformationen a priori vorhersagen zu können. Es wird gezeigt, dass durch einen Reverse Engineering Ansatz die notwendigen Planungsdaten, im Sinne von Layoutkomposition, Robotergeschwindigkeiten und Taktzeiten, mithilfe von Frontloading zu Planungsbeginn zur Verfügung gestellt werden können. Dabei dient der Kapitalwert als wirtschaftliche Bewertungsgrundlage, dessen Abhängigkeit vom Mensch-Roboter-Interaktionsgrad in einem Vorteilhaftigkeitsdiagramm für die einzelnen Technologiealternativen dargestellt werden kann. Wirtschaftlich fundierte Entscheidungen können somit auf quantitiativer Basis getroffen werden.:1. Introduction 25 1.1 Research Domain 25 1.2 Research Niche 26 1.3 Research Structure 28 2. State of the Art and Research 31 2.1 Turning Machines and Machine Tending 31 2.1.1 Tooling Machine Market Trends and Machine Tending Systems 31 2.1.2 Workpiece System 34 2.1.3 Machine System 36 2.1.4 Logistics System 39 2.1.5 Handling System 41 2.2 Robotics 43 2.2.1 Robot Installation Development and Application Fields 43 2.2.2 Fenceless Industrial and Collaborative Robots 48 2.2.3 Robot Grippers 55 2.3 Planning and Evaluation Methods 56 2.3.1 Planning of General and Manual Workstations 56 2.3.2 Cell Planning for Fully Automated and Hybrid Robot Systems 59 2.3.3 Robot Safety Planning 61 2.3.4 Economic Evaluation Methods 70 2.4 Synthesis - State of the Art and Research 71 3. Solution Approach 77 3.1 Need for Research and General Solution Approach 77 3.2 Use Case Delineation and Planning Focus 80 3.3 Economic Module – Solution Approach 86 3.4 Gripper Feasibility Module – Solution Approach 89 3.5 Rough Layout Discretization Model – Solution Approach 94 3.6 Cycle Time Estimation Module – Solution Approach 97 3.7 Collaborative Speed Estimation Module – Solution Approach 103 3.7.1 General Approach 103 3.7.2 Case 1: Quasi-static Contact with Hand 107 3.7.3 Case 2: Transient Contact with Hand 109 3.7.4 Case 3: Transient Contact with Shoulder 111 3.8 Synthesis – Solution Approach 114 4. Module Development 117 4.1 Economic Module – Module Development 117 4.1.1 General Approach 117 4.1.2 Calculation Scheme for Manual Operation 117 4.1.3 Calculation Scheme for Collaborative Robots 118 4.1.4 Calculation Scheme for Industrial Robots 120 4.2 Gripper Feasibility Module – Module Development 121 4.3 Rough Layout Discretization Module – Module Development 122 4.3.1 General Approach 122 4.3.2 Two-Dimensional Layout Pattern 123 4.3.3 Three-Dimensional Layout Pattern 125 4.4 Cycle Time Estimation Module – Module Development 126 4.4.1 General Approach 126 4.4.2 Reachability Study 127 4.4.3 Simulation Results 128 4.5 Collaborative Speed Estimation Module – Module Development 135 4.5.1 General Approach 135 4.5.2 Case 1: Quasi-static Contact with Hand 135 4.5.3 Case 2: Transient Contact with Hand 143 4.5.4 Case 3: Transient Contact with Shoulder 145 4.6 Synthesis – Module Development 149 5. Practical Verification 155 5.1 Use Case Overview 155 5.2 Gripper Feasibility 155 5.3 Layout Discretization 156 5.4 Collaborative Speed Estimation 157 5.5 Cycle Time Estimation 158 5.6 Economic Evaluation 160 5.7 Synthesis – Practical Verification 161 6. Results and Conclusions 165 6.1 Scientific Findings and Results 165 6.2 Critical Appraisal and Outlook 173 / Initially, industrial robots were mainly operated behind safety fences to account for the safety requirements. With production flexibilization, these sharp separation areas have been increasingly softened by utilizing external safety devices, such as distance sensors, to operate industrial robots fenceless. Based on this idea of coexistence or cooperation, safety technology has been integrated into the robot to enable true collaboration. These collaborative robots, or cobots, open up new application fields and fill the existing automation gap. But which automation variant is most suitable from an economic perspective? Present research dealt primarily isolated with one technology without comparing these systems regarding technological and economic specifics. Therefore, this doctoral thesis pursues a methodology to economically compare collaborative and industrial robots in fenceless machine tending systems. A particular focus lies on distilling the technical factors that mainly influence the profitability to receive a system understanding of the economic structure of both robot technology variants. For examination, the contents of such a planning scheme are described, categorized, systematized, and modularized. A suitable optimization model is presented on the economic side, while the feasibility regarding gripping, layout planning, robot velocities, and cycle time determination is assessed on the technical side. With deductive, simulative, empirical, and statistical methods, the system behavior of the single planning entities is analyzed to predict the overall profitability a priori with a minimum of investment,- production,- and cycle time information. It is demonstrated that the necessary planning data, in terms of layout composition, robot velocities, and cycle times, can be frontloaded to the project’s beginning with a reverse engineering approach. The net present value serves as the target figure, whose dependency on the human-robot interaction grade can be illustrated in an advantageousness diagram for the individual technical alternatives. Consequently, sound economic decisions can be made on a quantitative basis.:1. Introduction 25 1.1 Research Domain 25 1.2 Research Niche 26 1.3 Research Structure 28 2. State of the Art and Research 31 2.1 Turning Machines and Machine Tending 31 2.1.1 Tooling Machine Market Trends and Machine Tending Systems 31 2.1.2 Workpiece System 34 2.1.3 Machine System 36 2.1.4 Logistics System 39 2.1.5 Handling System 41 2.2 Robotics 43 2.2.1 Robot Installation Development and Application Fields 43 2.2.2 Fenceless Industrial and Collaborative Robots 48 2.2.3 Robot Grippers 55 2.3 Planning and Evaluation Methods 56 2.3.1 Planning of General and Manual Workstations 56 2.3.2 Cell Planning for Fully Automated and Hybrid Robot Systems 59 2.3.3 Robot Safety Planning 61 2.3.4 Economic Evaluation Methods 70 2.4 Synthesis - State of the Art and Research 71 3. Solution Approach 77 3.1 Need for Research and General Solution Approach 77 3.2 Use Case Delineation and Planning Focus 80 3.3 Economic Module – Solution Approach 86 3.4 Gripper Feasibility Module – Solution Approach 89 3.5 Rough Layout Discretization Model – Solution Approach 94 3.6 Cycle Time Estimation Module – Solution Approach 97 3.7 Collaborative Speed Estimation Module – Solution Approach 103 3.7.1 General Approach 103 3.7.2 Case 1: Quasi-static Contact with Hand 107 3.7.3 Case 2: Transient Contact with Hand 109 3.7.4 Case 3: Transient Contact with Shoulder 111 3.8 Synthesis – Solution Approach 114 4. Module Development 117 4.1 Economic Module – Module Development 117 4.1.1 General Approach 117 4.1.2 Calculation Scheme for Manual Operation 117 4.1.3 Calculation Scheme for Collaborative Robots 118 4.1.4 Calculation Scheme for Industrial Robots 120 4.2 Gripper Feasibility Module – Module Development 121 4.3 Rough Layout Discretization Module – Module Development 122 4.3.1 General Approach 122 4.3.2 Two-Dimensional Layout Pattern 123 4.3.3 Three-Dimensional Layout Pattern 125 4.4 Cycle Time Estimation Module – Module Development 126 4.4.1 General Approach 126 4.4.2 Reachability Study 127 4.4.3 Simulation Results 128 4.5 Collaborative Speed Estimation Module – Module Development 135 4.5.1 General Approach 135 4.5.2 Case 1: Quasi-static Contact with Hand 135 4.5.3 Case 2: Transient Contact with Hand 143 4.5.4 Case 3: Transient Contact with Shoulder 145 4.6 Synthesis – Module Development 149 5. Practical Verification 155 5.1 Use Case Overview 155 5.2 Gripper Feasibility 155 5.3 Layout Discretization 156 5.4 Collaborative Speed Estimation 157 5.5 Cycle Time Estimation 158 5.6 Economic Evaluation 160 5.7 Synthesis – Practical Verification 161 6. Results and Conclusions 165 6.1 Scientific Findings and Results 165 6.2 Critical Appraisal and Outlook 173

Robot arms require actuators that are powerful, precise and safe. The safety concern is amplified when these robots work closely with people in collaborative applications. This thesis investigates the design and implementation of hybrid pneumatic-electric actuators (HPEA) for use in robot arms, particularly those intended for collaborative applications. The initial focus was on improving the control of an existing single HPEA-driven rotary joint. The torque is produced by four pneumatic cylinders connected in parallel with a small DC motor. The DC motor is directly connected to the output shaft. A cascaded control system is designed that consists of an outer position control loop and an inner pressure control loop. The pressure controller is based on a novel inverse valve model. High precision position tracking control is achieved due to the combination of the model-based pressure controller, model-based position controller, adaptive friction compensator and offline payload estimator. Experiments are performed with the actuator prototype rotating a link and payload with a rotational inertia equivalent to a linear actuator moving a 573 kg mass. Averaged over five tests, a root-mean-square error of 0.024° and a steady-state error (SSE) of 0.0045° are achieved for a fast multi-cycloidal trajectory. This SSE is almost ten times smaller than the best value reported for previous HPEAs. An offline payload estimation algorithm is used to improve the control system’s robustness. The superior safety of the HPEA is shown by modeling and simulating a constrained robot-head impact, and comparing the result with equivalent electric and pneumatic actuators. This research produced two journal papers. Since HPEAs are redundant actuators that combine the large force, low bandwidth characteristics of pneumatic actuators with the large bandwidth, small force characteristics of electric actuators, the effect of using optimization-based input allocation for HPEAs was studied. The goal was to improve the HPEA’s performance by distributing the required input (force or torque) between the redundant actuators in accordance with each actuator’s advantages and limitations. Three novel model-predictive control (MPC) approaches are designed to solve the position tracking and input allocation problems using convex optimization. The approaches are simulated on a HPEA-driven system and compared to a conventional linear controller without active input allocation. The first MPC approach uses a model that includes the dynamics of the payload and pneumatics; and performs the motion control using a single loop. The latter methods simplify the MPC law by separating the position and pressure controllers. Although the linear controller is the most computationally efficient, it is inferior to the MPC-based controllers in position tracking and force allocation performance. The third MPC-based controller design demonstrated the best position tracking with root mean square errors of 46%, 20%, and 55% smaller than the other three approaches. It also demonstrated sufficient speed for real-time operation. This research produced one journal paper. The research continued with the design and implementation of a two degree-of-freedom HPEA-driven arm. A HPEA-driven “elbow” joint is designed and added to the existing “shoulder” joint. The force from a single pneumatic cylinder is converted into torque using a 4-bar linkage. To eliminate backlash and keep the weight of the arm low, a 2nd smaller DC motor is directly connected to the joint. The kinematic and kinetic models of the new arm, as well as the geometry of the new elbow joint are studied. The resulting joint design is implemented, tested and controlled. This joint could achieve a SSE of 0.0045° in spite of its nonlinear joint geometry. The arm is experimentally tested for simultaneous tracking control of the two joints, and for end-effector position tracking in Cartesian space. The end-effector is able to follow a circular trajectory in pneumatic mode with position errors below 0.005 m. / Thesis / Doctor of Philosophy (PhD) / Robots that work with, or near, humans require greater safety considerations than other robots. A significant concern is collisions between the robot and humans that may happen when sensors or software fails. An actuator for robots that combines the inherent safety of pneumatic actuators with the accuracy of electric actuators, termed a “hybrid pneumatic electric actuator” (HPEA), is investigated. The design, instrumentation, modelling, and control of HPEAs are studied theoretically and experimentally. The proposed actuator could achieve high position control accuracy in a variety of experiments, with steady state error of less than 0.0045 degrees. Simulated impacts with a human head also showed that a HPEA-driven robot arm can achieve a 52% lower impact force, compared to an arm driven by conventional electric actuators. The HPEA design and control experiments are performed on a single HPEA-driven joint and extended to an arm consisting of two HPEA-driven revolute joints.

Collaborative robots, cobots, are seen as an alternative to traditional industrial robots since they are more flexible, less space-consuming, and can share the workspace with human operators. For small and medium-sized enterprises, SMEs, the adoption still is in an early stage. This study aims to examine the challenges for manufacturing SMEs when introducing collaborative robots in the business. A literature review is conducted as well as a case study, where managers and operators from five Swedish companies are interviewed about their experiences regarding the introduction of collaborative robots. Additional interviews with international researchers in the field are conducted as well. Since the aim is to understand the challenges in a rather new field, which human-robot collaboration still is for SMEs, this is a qualitative explorative study, with the purpose to gather rich insight about the field. The data has been analyzed in an inductive qualitative analysis. The results show that the biggest challenges for manufacturing SMEs when introducing collaborative robots are related to safety, performance, strategy, involvement, and training. Safety aspects are crucial since human operators work closely with collaborative robots and risk serious injuries even though the managers and operators in the case study do not seem to worry since they perceive the robots as quite slow and safe. Proper safety assessments are important as well, even though there is a concern about the lack of proper safety regulations. Other challenges are related to performance and strategy, e.g how to achieve cost-effectiveness with small production volumes and get the robotic investment to pay off in the long turn, but also to choose a proper cobot solution and a reliable supplier, find suitable work tasks, and obtain quality if the cobot fails to recognize a defective product or skewed inputs on the production line. The recommendation from the companies in the case study is to start with an easy task and to see it as a long-term investment. One important key to success is to find a flexible cobot solution that suits the company's individual needs. Employee involvement is another success factor since involving the operators from the beginning leads to better acceptance and understanding of the new technology and the changed work situation. There is a need for skilled, educated workers as well, although the case study shows that the SMEs highlight the importance of choosing a robot system that is easy to learn and easy to use for everyone. The researchers in the study highlight the need for smarter solutions equipped with enabling technologies and the SME managers call for flexible removable solutions with sensors and vision systems for quality control and the ability to handle surprises on the way.