Compact Pneumatic Clutch With Integrated Stiffness Variation and Position Feedback

Stiffness variation and real-time position feedback are critical for any robotic system but most importantly for active and wearable devices to interact with the user and environment. Currently, for compact sizes, there is a lack of solutions bringing high-fidelity feedback and maintaining design and functional integrity. In this work, we propose a novel minimal clutch with integrated stiffness variation and real-time position feedback whose performance surpasses conventional jamming solutions. We introduce integrated design, modeling, and verification of the clutch in detail. Preliminary experimental results show the change in impedance force of the clutch is close to 24-fold at the maximum force density of 15.64 N/cm(2). We validated the clutch experimentally in (1) enhancing the bending stiffness of a soft actuator to increase a soft manipulator's gripping force by 73%; (2) enabling a soft cylindrical actuator to execute omnidirectional movement; (3) providing real-time position feedback for hand posture detection and impedance force for kinesthetic haptic feedback. This manuscript presents the functional components with a focus on the integrated design methodology, which will have an impact on the development of soft robots and wearable devices.

Design Methodology for Engineering Multifunctional Mesoscale Robots

Zhenishbek Zhakypov

In this thesis our research goal is to develop, study and demonstrate multifunctional multi-robot systems in mesoscale. Particularly, our goal is to study and demonstrate terrestrial multi-locomotion and collective behaviours with mesoscale robots, similar to small-scale natural systems, by feeling the gap in the field. Our research objective is to develop, evaluate and demonstrate minimal, compact, variable power and efficient actuation mechanisms for multi-locomotion and rapid fabrication methods for robot multiplicity employing functional materials and composite design. In doing so, we intend to establish a comprehensive and systematic design methodology for designing multifunctional, mass-producible mesoscale robots for various applications. This dissertation first attempts to explore and answer the following key research question: how to achieve variable power, efficient and compact actuation in mesoscale? The relation between performance and physicality is significant for especially mesoscale robot design and is poorly studied. Our goal is to achieve high power, variable speed and high efficiency actuation in mesoscale. We attempt to address this by exploring unconventional active material-based actuation methods using shape memory alloy and composite material. In doing so, we quest of the following: what are the compromises should be made between force, speed, efficiency and size of functional material-based actuators? We investigate and demonstrate new, compact multimaterial actuators and mechanisms that possess power density superior to conventional motors, produce high speed and high force actuation and achieve multifunctionality when distributed and actuated selectively, all with minimal and compact forms and integrity. While we study and develop design methods at the component level, like actuation, based on performance and physical features, we look for the same at the composite level or robotic system level. The next research question we attempt to address is what, if any, is the general design methodology for constructing composite robots?. To address this we formulate and analyze robogami design in terms of mechanisms, geometry, functional components, materials and fabrication to highlight their relation, potential and the challenges, as well as to structure the knowledge in the field. This leads to a systematic design approach that consolidates these critical design features and facilitates robot design and fabrication process. To ensure applicability of our methodology, we analyze the design process of composite robots reported in the literature and design a multi-locomotion mesoscale robot, called Tribot, as a case study. We further investigate the application of the proposed actuation and rapid composite robot design methods by questing of how to achieve multifunctional multi-robot behaviors in mesoscale? We address this by constructing a unique, untethered, multi-locomotion robotic collective to study locomotion and cooperative behaviors. We investigate minimal, compact and tunable mechanisms that generate high power jumping and low power crawling locomotion. We overcome the key trade-off between the actuation power and weight and construct a 10 g palm-sized prototype, the smallest and lightest self-contained, multi-locomotion robot to date, by folding a quasi-2-D mechamatronic composite with locomotion mechanisms, smart actuation and sensing layers, enabling robot multiplicity assembly-free mass-production.

EPFL2019

Comprehensive Interactive Soft Interfaces for Wearable Tactile Feedback

Harshal Arun Sonar

As the field of robotics continues to grow outside the manufacturing environment into our daily lives, the interactions between humans and robots are increasingly becoming close and dynamic. This type of environment requires robots to be less rigid, multi-functional, safer, and compliant with human bodies. Such robotics interfaces are ideally suited for medical rehabilitation, elderly assistance to at-home entertainment devices. However, the traditional rigid robotic devices fail to address some of the design criteria posed for safety, compliance, and physical limitations on the mechanical design. In the case of wearable technologies, the robotic device additionally requires a lightweight, compliant, and safe interface to provide smooth communication and interaction with humans. The traditional robotic systems are fast, accurate, and can handle large torques. However, they are also, application-specific and not suitable as it is for the wearable scenario due to the contradictory design requirements. In the past decade, soft robotics has emerged as a novel approach to solve the complex problems faced by rigid robots using inherent softness and compliant material properties. The design for the future interactive wearable interfaces thus may lie in the intersection of developments in the fields of wearable technology and soft robotics.Designing a wearable interactive interface with soft materials for wearability, portability, cost-effectiveness, and modularity would be one of the ideal solutions to tackle the wearability challenge. It can be a cost-effective solution for at-home assistive rehabilitation or entertainment. It also allows developing novel methods of soft sensing, actuation, control strategies, and human in loop protocols to maximize the utility of inherent material properties and environment around the robotic device.In my Ph.D. research, I develop and create hardware and software towards an immersive interactive soft virtual-tactile environment focusing on the wearability, portability, easy customization, and modularity aspects. I developed a low profile soft pneumatic actuator-skin (SPA-skin) with distributed sensing and actuation capabilities for testing various levels of complex vibrotactile feedback: the multilayer composite of high-sensitivity PZT pressure sensors and vibratory SPA can produce up to 3 N output force at 0-100 Hz. This demonstrated that SPA-skin produces distinctive and dynamic haptic force feedback under modulated varying time, force, and spatial resolution. Furthermore, a complete framework for designing a tactile feedback skin for specific wearable applications is developed, starting from the material selection and actuator design, and concluding with the validation of the subjectâs perceived feedback. As soon as, the SPA-skin is required to be worn by humans, the complexity of the problem multiplies due to lack of proper grounding to ensure the blocked forces. The platform is further optimized for application space in fMRI compliant environment and a user study protocol for somatosensory thresholds is designed. The modulable and controllable nature of SPA-skinâs tactile feedback provides much-needed validation using BOLD signals from brain imaging. SPA-skin and findings presented herein, provide a foundational platform to further investigate the sensitivity of human skin and decipher mechanoreceptor reactions for a diverse range of human-robot interactions and wearable technology.

EPFL2021

Development of Essential Components for Soft Wearable Technologies

Amir Firouzeh

The rising demand for safe human-robot interaction in daily tasks has motivated significant research effort in the robotics field towards compliant and conformable robots, capable of replicating complex human movements in applications such as wearable rehabilitative devices and haptic interfaces. Novel manufacturing, actuation, and sensing technologies contributed significantly to this field by providing design and manufacturing frameworks for inherently compliant robots. Although promising, these technologies are still in the early stages of development and base research for refining their design, improving their performance, and defining design criteria is still required for these technologies to reach their full potential. In this thesis, some of the main challenges hindering the effective application of robotics in wearable devices are tackled. We propose the robotic origami (robogami) framework with multiple but finite degrees of freedom (DoFs) for soft wearable devices. Robogamis are low profile robots that provide conformity and compliance with their multiple DoFs driven by soft actuation methods. The finite DoFs in these robots enable better prediction and planning of their motion while highly customizable joint designs, thanks to the layer-by-layer manufacturing and the precise quasi-2D fabrication processes, allows the multiple DoFs to be embedded to achieve the required level of conformity. The main contributions of this thesis are: -Study of the robogami framework as a design platform for soft robots with programmable reconfiguration and compliance. -Design and validation of actuation solutions based on smart materials for independent actuation of robogami joints. -Adoption of the smart materials' variable mechanical properties to adjust the stiffness of robogami joints and the overall compliance of the robot. -Development of customized sensing methods to measure robogami joint angles and stretchable sensors based on the same principles to measure body movements. We believe that these contributions facilitate some of the main challenges for the effective application of robogamis in wearable devices for safe and yet capable interaction with humans. The highly customizable components can also be used in design frameworks other than robogamis and other applications where compliance and conformity are required.

EPFL2017