Soft pneumatic actuators produce more energy output per unit mass than conventional rigid pneumatic actuators and are safer for applications involving physical contact with users or fragile objects. The design, modelling, fabrication, and optimization of origami-inspired soft pneumatic actuators (OSPA) are investigated in this thesis. A novel fabrication method employing heat shrinkable polymers conforming to reusable 3D printed molds is proposed. It is rapid, cost-effective, and more systematic than prior OSPA fabrication methods. A nonlinear finite-element analysis (FEA) model for an OSPA based on the accordion crease pattern is developed for predicting the actuator's folding behavior and blocked force. The model includes a nonlinear hyperelastic model of the heat shrink material’s behaviour (obtained empirically) and nonlinear frictional contacts. It is validated with experimental results and is shown to predict the blocked force with a 5.7% maximum error. Prototypes of two OSPA designs (accordion and Yoshimura patterns) are fabricated. Isometric, isobaric, isotonic, and cyclic fatigue tests are performed on the accordion pattern OSPA. The tests demonstrate that it can lift more than 124 times its own weight, and had no decrease in performance after 150,000 contraction/extension cycles with a payload of 2 kg. This durability is superior to existing OSPA. Lastly, a FEA model-based design optimization approach is proposed. A multi-objective genetic algorithm (MOGA) is used to find the origami design parameters that maximize the accordion pattern OSPA's work output. The optimized design is validated experimentally. Although this research focuses on the accordion pattern OSPA, the proposed fabrication, modelling and optimization approaches can be easily adapted to other OSPA designs. In addition to linear force and motion, these actuators can be combined to produce different motions, e.g., a pair of actuators can be connected by a cable to a pulley in an agonist-antagonist arrangement to produce a bidirectional rotary actuator. / Thesis / Doctor of Philosophy (PhD) / Soft pneumatic actuators are lighter than conventional rigid pneumatic actuators and are safer for applications involving physical contact with users or fragile objects. The design, modelling, fabrication, and optimization of origami-inspired soft pneumatic actuators (OSPA) are investigated. A novel fabrication method that is rapid, cost-effective, and more systematic than prior OSPA fabrication methods is proposed. A nonlinear model is developed and shown to predict the OSPA’s output force with a 5.7% maximum error. An extensive series of tests are performed on OSPA prototypes. The accordion pattern OSPA can lift more than 124 times its own weight, and had no decrease in performance after 150,000 contraction/extension cycles with a payload of 2 kg. This durability is superior to existing OSPA. Lastly, a model-based approach for optimizing the OSPA design is presented and validated experimentally. The proposed fabrication, modelling and optimization approaches can be easily adapted to other OSPA designs.

The medical community has expressed a need for flexible medical instruments. Hence, this work investigates the possibility to use "flexible fluidic actuators" to develop such flexible instruments. These actuators are driven by fluid, i.e. gas or liquid, and present a flexible structure, i.e. an elastically deformable and/or inflatable structure. Different aspects of the study of these actuators have been tackled in the present work: • A literature review of these actuators has been established. It has allowed to identify the different types of motion that these actuators can develop as well as the design principles underlying. This review can help to develop flexible instruments based on flexible fluidic actuators. • A test bench has been developed to characterize the flexible fluidic actuators. • A interesting measuring concept has been implemented and experimentally validated on a specific flexible fluidic actuator (the "Pneumatic Balloon Actuator", PBA). Ac- cording to this principle, the measurements of the pressure and of the volume of fluid supplied to the actuator allow to determine the displacement of the actuator and the force it develops. This means being able to determine the displacement of a flexible fluidic actuator and the force it develops without using a displacement sensor or a force sensor. This principle is interesting for medical applications inside the human body, for which measuring the force applied by the organs to the surgical tools remains a problem. The study of this principle paves the way for a lot of future works such as the implemen- tation and the testing of this principle on more complex structures or in a control loop in order to control the displacement of the actuator (or the force it develops) without using a displacement or a force sensor. • A 2D-model of the PBA has been established and has helped to better understand the physics underlying the behaviour of this actuator. • A miniaturization work has been performed on a particular kind of flexible fluidic actu- ator: the Pleated Pneumatic Artificial Muscle (PPAM). This miniaturization study has been made on this type of actuator because, according to theoretical models, minia- turized PPAMs, whose dimensions are small enough to be inserted into MIS medical instruments, could be able to develop the forces required to allow the instruments to perform most surgical actions. The achieved miniaturized muscles have a design similar to that of the third generation PPAMs developed at the VUB and present a total length of about 90 mm and an outer diameter at rest of about 15 mm. One of the developed miniaturized PPAMs has been pressurized at p = 1 bar and it was able to develop a pulling force F = 100 N while producing a contraction of 4 %. Propositions have been made regarding a further miniaturization of the muscles.

The soft robotics field is developing rapidly and is poised to have a wide impact in a variety of applications. Soft robots have intrinsic compliance, offering a number of benefits as compared to traditional rigid robots. Compliance can provide compatibility with biological systems such as the human body and can provide some benefits for human safety and control. Further research into soft robots can be advanced by further development of pneumatic actuators. Pneumatic actuators are a good fit for exoskeleton robots because of their light weight, small size, and flexible materials. This is because a wearable robot should be human friendly, therefore, it should be light weight, slim, powerful, and simple. In this paper, a novel pneumatic artificial muscle using soft materials including integrated electronics for wearable exoskeletons is proposed. We describe the design, fabrication, and evaluation of the actuator, as well as the manufacturing process used to create it. Compared to traditional pneumatic muscle actuators such as the McKibben actuator and new soft actuators that were recently proposed, the novel actuator overcomes shortcomings of prior work. This is due to the actuator's very high contraction ratio that can be controlled by the manufacturing process. In this paper, we describe the design, fabrication, and evaluation of a novel pneumatic actuator that can accommodate integrated electronics for displacement and pressure measurements used for data analysis and control. The desired performance characteristics for the actuator were 100 ~ 400N at between 35kPa and 105kPa, and upon testing we found almost 120 ~ 300N which confirms that these actuators may be suitable in soft exoskeleton applications with power requirements comparable to rigid exoskeletons. Furthermore, a novel soft pneumatic elbow exoskeleton based on the pneumatic actuator concept and manufacturing process is presented. Each structure is designed and manufactured with all fabric. The distally-worn structure is only 300g, which is light weight for an arm exoskeleton, and the design is simple, leading to a low materials cost. / Master of Science

This thesis describes the concept of programmable materials with tunable physical properties applicable to soft robots. We present these materials for three major applications in soft robotics: sensing, actuation, and robotic manipulation. The strain sensors recognize the internal stimuli in a soft robot, whereas the conductors collect the sensors’ signals to the control part. In the first part, we want to develop both stretchable strain sensors and conductors from a single material by programming a nanowire network’s electrical property, which we achieve through Electrical Welding (e-welding). We demonstrate the transformation of a Silver Nanowire (AgNW)-polymer sponge from a strain sensor to a stretchable conductor through e-welding. Using this method, we produced a soft hybrid e-skin having both a sensor and conductor from a single material. In the second part, we propose new active actuation solutions by obtaining quick, tunable pressure inside a soft material that we achieve through a liquid-gas phase transition of a stored liquid using an efficient electrode. We discuss the significant design variables to improve the performance and propose a new design for the electrodes, for enhancing actuation speed. We propose using low voltage equipment to trigger the phase transition to produce compact actuation technology for portable applications. Using this method, we produced a portable soft gripper. In the third and last part, we want to develop a simple robotic manipulation technology using a single-chambered soft body instead of a multi-chambered system. We propose using on-demand stiffness change in soft material to control the shape change of a single-chambered soft body. For this, we introduce a new concept of a stiffness tunable hybrid fiber: a fiber with stiff and soft parts connected in a series. We demonstrate a substantial change in membrane stiffness in the fiber through locking/unlocking of the soft part of the fiber. We integrated these fibers into a pneumatically operated single-chambered soft body to control its stiffness for on-demand shape change. If applied together, these three concepts could result in a fully printable, cheap, light, and easily controllable new generation soft robots with augmented functionalities.

Soft robotic systems have recently been considered as a new approach that is in principle better suited for tasks where safety and adaptability are important. That is because soft materials are inherently compliant and resilient in the event of collisions. They are also lightweight and can be low-cost; in general, soft robots have the potential to achieve many tasks that were not previously possible with traditional robotic systems. In this paper, we propose a new manufacturing process for creating multi-chambered pneumatic actuators and robots. We focus on using fabric as the primary structural material, but plastic films can be used instead of textiles as well. We introduce two different methods to create layered bellows actuators, which can be made with a heat press machine or in an oven. We also describe origami-like actuators with possible corner structures. Moreover, the fabrication process permits the creation of soft and soft/rigid hybrid robotic systems, and enables the easy integration of sensors into these robots. We analyze various textiles that are possibly used with this method, and model bellows actuators including operating force, restoring force, and estimated geometry with multiple bellows. We then demonstrate the process by showing a bellows actuator with an embedded sensor and other fabricated structures and robots. We next present a new design of a multi-DOF soft/rigid hybrid robotic manipulator. It contains a revolute actuator and several roll-pitch actuators which are arranged in series. To control the manipulator, we use a new variant of the piece-wise constant curvature (PCC) model. The robot can be controlled using forward and inverse kinematics with embedded inertial measurement units (IMUs). A bellows actuator, which is a subcomponent of the manipulator, is modeled with a variable-stiffness spring, and we use the model to predict the behavior of the actuator. With the model, the roll-pitch actuator stiffnesses are measured in all directions through applying forces and torques. The stiffness is used to predict the behavior of the end effector. The robotic system introduced achieved errors of less than 5% when compared to the models, and positioning accuracies of better than 1cm. / Doctor of Philosophy / Future robotic systems are expected to deal with many tasks in real-world environments. The natural environment is highly unpredictable and unstructured, making manipulation and locomotion challenging for robots. Robots need to rely on adaptability, reconfigurability, and safety. Soft robotic systems have recently been considered as a new approach that is in principle better suited for tasks where safety and adaptability are important. That is because soft materials are inherently compliant and resilient in the event of collisions. They are also lightweight and can be low-cost; in general, soft robots have the potential to achieve many tasks that were not previously possible with traditional robotic systems. In this paper, we propose a new manufacturing process for creating multi-chambered pneumatic actuators and robots. We focus on using fabric as the primary structural material, but plastic films can be used instead of textiles as well. We introduce two different methods to create layered bellows actuators, which can be made with a heat press machine or household iron, or in an oven. We also describe origami-like actuators with possible corner structures. Moreover, the fabrication process permits the creation of soft and soft/rigid hybrid robotic systems, and enables the easy integration of sensors into these robots. We analyze various textiles that can be used with this method, and make models of bellows actuators including their operating force, restoring force, and estimated geometry with multiple bellows. We then demonstrate the process by showing a bellows actuator with an embedded sensor and other fabricated structures and robots. We next present a new design of a multi-DOF soft/rigid hybrid robotic manipulator. It contains a revolute actuator and several roll-pitch actuators which are arranged in series. To control the manipulator, we use a new variant of the piece-wise constant curvature (PCC) model. The robot can be controlled using forward and inverse kinematics with embedded inertial measurement units (IMUs). A bellows actuator, which is a subcomponent of the manipulator, is modeled with a variable-stiffness spring, and we use the model to predict the behavior of the actuator. With the model, the roll-pitch actuator stiffnesses are measured in all directions through applying forces and torques. The stiffness is used to predict the behavior of the end effector.

The medical community has expressed a need for flexible medical instruments. Hence, this work investigates the possibility to use "flexible fluidic actuators" to develop such flexible instruments. These actuators are driven by fluid, i.e. gas or liquid, and present a flexible structure, i.e. an elastically deformable and/or inflatable structure. Different aspects of the study of these actuators have been tackled in the present work:<p>• A literature review of these actuators has been established. It has allowed to identify the different types of motion that these actuators can develop as well as the design principles underlying. This review can help to develop flexible instruments based on flexible fluidic actuators.<p>• A test bench has been developed to characterize the flexible fluidic actuators.<p>• A interesting measuring concept has been implemented and experimentally validated on a specific flexible fluidic actuator (the "Pneumatic Balloon Actuator", PBA). Ac- cording to this principle, the measurements of the pressure and of the volume of fluid supplied to the actuator allow to determine the displacement of the actuator and the force it develops. This means being able to determine the displacement of a flexible fluidic actuator and the force it develops without using a displacement sensor or a force sensor. This principle is interesting for medical applications inside the human body, for which measuring the force applied by the organs to the surgical tools remains a problem.<p>The study of this principle paves the way for a lot of future works such as the implemen- tation and the testing of this principle on more complex structures or in a control loop in order to control the displacement of the actuator (or the force it develops) without using a displacement or a force sensor.<p>• A 2D-model of the PBA has been established and has helped to better understand the physics underlying the behaviour of this actuator.<p>• A miniaturization work has been performed on a particular kind of flexible fluidic actu- ator: the Pleated Pneumatic Artificial Muscle (PPAM). This miniaturization study has been made on this type of actuator because, according to theoretical models, minia- turized PPAMs, whose dimensions are small enough to be inserted into MIS medical instruments, could be able to develop the forces required to allow the instruments to perform most surgical actions. The achieved miniaturized muscles have a design similar to that of the third generation PPAMs developed at the VUB and present a total length of about 90 mm and an outer diameter at rest of about 15 mm. One of the developed miniaturized PPAMs has been pressurized at p = 1 bar and it was able to develop a pulling force F = 100 N while producing a contraction of 4 %.<p>Propositions have been made regarding a further miniaturization of the muscles. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

No description available.

The ability to convert photons into mechanical motion is of significant importance for many energy conversion and reconfigurable technologies. Establishing an optical-mechanical interface has been attempted since 1881; nevertheless, only few materials exist that can convert photons of different wavelengths into mechanical motion that is large enough for practical import. Recently, various nanomaterials including nanoparticles, nanowires, carbon nanotubes, and graphene have been used as photo-thermal agents in different polymer systems and triggered using near infrared (NIR) light for photo-thermal actuation. In general, most photomechanical actuators based on sp bonded carbon namely nanotube and graphene are triggered mainly using near infra-red light and they do not exhibit wavelength selectivity. Layered transition metal dichalcogenides (TMDs) provide intriguing opportunities to develop low cost, light and wavelength tunable stimuli responsive systems that are not possible with their conventional macroscopic counterparts. Compared to graphene, which is just a layer of carbon atoms and has no bandgap, TMDs are stacks of triple layers with transition metal layer between two chalcogen layers and they also possess an intrinsic bandgap. While the atoms within the layers are chemically bonded using covalent bonds, the triple layers can be mechanically/chemically exfoliated due to weak van der Waals bonding between the layers. Due to the large optical absorption in these materials, they are already being exploited for photocatalytic, photoluminescence, photo-transistors, and solar cell applications. The large breaking strength together with large band gap and strong light- matter interaction in these materials have resulted in plethora of investigation on electronic, optical and magnetic properties of such layered ultra-thin semiconductors. This dissertation will go in depth in the synthesis, characterization, development, and application of two- dimensional (2D) nanomaterials, with an emphasis on TMDs and molybdenum disulfide (MoS2), when used as photo-thermal agents in photoactuation technologies. It will present a new class of photo-thermal actuators based on TMDs and hyperelastic elastomers with large opto-mechanical energy conversion, and investigate the layer-dependent optoelectronics and light-matter interaction in these nanomaterials and nanocomposites. Different attributes of semiconductive nanoparticles will be studied through different applications, and the possibility of globally/locally engineering the bandgap of such nanomaterials, along with its consequent effect on optomechanical properties of photo thermal actuators will be investigated. Using liquid phase exfoliation in deionized water, inks based on 2D- materials will be developed, and inkjet printing of 2D materials will be utilized as an efficient method for fast fabrication of functional devices based on nanomaterials, such as paper-graphene-based photo actuators. The scalability, simplicity, biocompatibility, and fast fabrication characteristics of the inkjet printing of 2D materials along with its applicability to a variety of substrates such as plastics and papers can potentially be implemented to fabricate high-performance devices with countless applications in soft robotics, wearable technologies, flexible electronics and optoelectronics, bio- sensing, photovoltaics, artificial skins/muscles, transparent displays and photo-detectors.

Although in many of the tasks in robotics, what is sought mainly includes accuracy, precision, flexibility, adaptivity, etc., yet in wearable robotics, there are some other aspects as well that could distinguish a reliable and promising approach. The three key elements that are addressed are as follows: control, actuation, and sensors. Where the goal for each of the previously mentioned objectives is to find a solution/design compatible with humans. A possible way to understand the human motor behaviours is to generate them on human-like robots. Biologically inspired action generation is promising in control of wearable robots as they provide more natural movements. Furthermore, wearable robotics shows exciting progress, also with its design. Soft exosuits use soft materials to build both sensors and actuators. This work investigates an adaptive representation model for actions in robotics. The concrete action model is composed of four modularities: pattern selection, spatial coordination, temporal coordination, and sensory-motor adaptation. Modularity in motor control might provide us with more insights about action learning and generalisation not only for humanoid robots but also for their biological counterparts. Successfully, we tested the model on a humanoid robot by learning to perform a variety of tasks (push recovery, walking, drawing, grasping, etc.). In the next part, we suggest several soft actuation mechanisms that overcome the problem of holding heavy loads and also the issue of on-line programming of the robot motion. The soft actuators use textile materials hosting thermoplastic polyurethane formed as inflatable tubes. Tubes were folded inside housing channels with one strain-limited side to create a flexor actuator. We proposed a new design to control the strained side of the actuator by adding four textile cords along its longitudinal axis. As a result, the actuator behaviour can be on-line programmed to bend and twist in several directions. In the last part of this thesis, we organised piezoresistive elements in a superimposition structure. The sensory structure is used on a sensory gripper to sense and distinguish between pressure and curvature stimuli. Next, we elaborated the sensing gripper by adding proximity sensing through conductive textile parts added to the gripper and work as capacitive sensors. We finally developed a versatile soft strain sensor that uses silicone tubes with an embedded solution that has an electrical resistance proportional to the strain applied on the tubes. Therefore, an entirely soft sensing glove exhibits hand gestures recognition. The proposed combinations of soft actuators, soft sensors, and biologically inspired action representation might open a new perspective to obtain smart wearable robots. / Obwohl bei vielen Aufgaben in der Robotik vor allem Genauigkeit, Präzision, Flexibilität, Anpassungsfähigkeit usw. gefragt sind, gibt es in der Wearable-Robotik auch einige andere Aspekte, die einen zuverlässigen und vielversprechenden Ansatz kennzeichnen. Die drei Schlüsselelemente, sind die folgenden: Steuerung, Aktuatoren und Sensoren. Dabei ist das Ziel für jedes der genannten Elemente, eine menschengerechte Lösung und ein menschengerechtes Design zu finden. Eine Möglichkeit, die menschliche Motorik zu verstehen, besteht darin, sie auf menschenähnlichen Robotern zu erzeugen. Biologisch inspirierte Bewegungsabläufe sind vielversprechend bei der Steuerung von tragbaren Robotern, da sie natürlichere Bewegungen ermöglichen. Darüber hinaus zeigt die tragbare Robotik spannende Fortschritte bei ihrem Design. Zum Beispiel verwenden softe Exoskelette weiche Materialien, um sowohl Sensoren als auch Aktuatoren zu erschaffen. Diese Arbeit erforscht ein adaptives Repräsentationsmodell für Bewegungen in der Robotik. Das konkrete Bewegungsmodell besteht aus vier Modularitäten: Musterauswahl, räumliche Koordination, zeitliche Koordination und sensorisch-motorische Anpassung. Diese Modularität in der Motorsteuerung könnte uns mehr Erkenntnisse über das Erlernen und Verallgemeinern von Handlungen nicht nur für humanoide Roboter, sondern auch für ihre biologischen Gegenstücke liefern. Erfolgreich testeten wir das Modell an einem humanoiden Roboter, indem dieser gelernt hat eine Vielzahl von Aufgaben auszuführen (Stoß-Ausgleichsbewegungen, Gehen, Zeichnen, Greifen, etc.). Im Folgenden schlagen wir mehrere weiche Aktuatoren vor, welche das Problem des Haltens schwerer Lasten und auch die Frage der Online- Programmierung der Roboterbewegung lösen. Diese weichen Aktuatoren verwenden textile Materialien mit thermoplastischem Polyurethan, die als aufblasbare Schläuche geformt sind. Die Schläuche wurden in Gehäusekanäle mit einer dehnungsbegrenzten Seite gefaltet, um Flexoren zu schaffen. Wir haben ein neues Design vorgeschlagen, um die angespannte Seite eines Flexors zu kontrollieren, indem wir vier textile Schnüre entlang seiner Längsachse hinzufügen. Dadurch kann das Verhalten des Flexors online programmiert werden, um ihn in mehrere Richtungen zu biegen und zu verdrehen. Im letzten Teil dieser Arbeit haben wir piezoresistive Elemente in einer Überlagerungsstruktur organisiert. Die sensorische Struktur wird auf einem sensorischen Greifer verwendet, um Druck- und Krümmungsreize zu erfassen und zu unterscheiden. Den sensorischen Greifer haben wir weiterentwickelt indem wir kapazitiv arbeitende Näherungssensoren mittels leitfähiger Textilteile hinzufügten. Schließlich entwickelten wir einen vielseitigen weichen Dehnungssensor, der Silikonschläuche mit einer eingebetteten resistiven Lösung verwendet, deren Wiederstand sich proportional zur Belastung der Schläuche verhält. Dies ermöglicht einem völlig weichen Handschuh die Erkennung von Handgesten. Die vorgeschlagenen Kombinationen aus weichen Aktuatoren, weichen Sensoren und biologisch inspirierter Bewegungsrepräsentation kann eine neue Perspektive eröffnen, um intelligente tragbare Roboter zu erschaffen.

This thesis performs closed-loop control of a 3D printed soft bending actuator with feedback from a 3D printed strain sensor. This process utilizes the Finite Element Method (FEM) to design a bellow type pneumatic bending actuator that can handle pressures up to 4 bar. The developed actuator is produced with a Fused Deposition Modeling (FDM) 3D printer method with the elastic filament NinjaFlex. Soft sensors are 3D printed with the conductive filament Eel and their strain-resistive performance in hysteresis, linearity, and repeatability are investigated by testing 3D printed sensors with different shapes. The optimal sensor design is then selected and applied onto the soft actuator and the resistance signal from the sensor is used as the shape feedback signal for the soft actuator. Two different controllers are applied for the shape control of the soft actuator using the feedback from the sensor and the controller performance is compared experimentally. A gripper composed of three closed-loop controlled soft actuators is developed to perform complex grasping tasks. / Denna avhandling konstruerar ett 3D-skrivet mjukt ställdon som återkopplas med en 3D-skriven böjsensor. Arbetet använder Finita Elementmetoden (FEM) för att skapa ett böjande bälgställdon som klarar av 4 bar av lufttryck. Det framtagna ställdonet är tillverkad av det elastiska filamentet NinjaFlex med 3D-skrivarmetoden Smält Deponeringsmodellering (FDM). Dem mjuka sensorerna är 3D-skrivna med det elektriskt ledande filamentet Eel. Sensorernas ansträgning-resistiva prestanda med avseende på hysteres, linjäritet, och repeterbarhet är undersökta genom att utföra experiment med olika former. Den optimala sensorformen är sedan applicerad på det mjuka ställdonet och dess resistiva signal från sensorn används för återkoppling av det mjuka ställdonets böjning. Med den applicerade sensorn utvärderas två olika kontrollmetoder för att kontrollera böjningen av det mjuka ställdonet, kontrollmetodernas prestanda jämförs sedan experimentellt. Ett gripdon som består av tre återkopplade, mjukaställdon är sedan konstruerad för att utföra komplexa grepp.