Development of Essential Components for Soft Wearable Technologies

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.

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

Modular soft pneumatic actuator system design for compliance matching

Matthew Aaron Robertson

The future of robotics is personal. Never before has technology been as pervasive as it is today, with advanced mobile electronics hardware and multi-level network connectivity pushing âsmartâ devices deeper into our daily lives through home automation systems, virtual assistants, and wearable activity monitoring. As the suite of personal technology around us continues to grow in this way, augmenting and offloading the burden of routine activities of daily living, the notion that this trend will extend to robotics seems inevitable. Transitioning robots from their current principal domain of industrial factory settings to domestic, workplace, or public environments is not simply a matter of relocation or reprogramming, however. The key differences between âtraditionalâ types of robots and those which would best serve personal, proximal, human interactive applications demand a new approach to their design. Chief among these are requirements for safety, adaptability, reliability, reconfigurability, and to a more practical extent, usability. These properties frame the context and objectives of my thesis work, which seeks to provide solutions and answers to not only how these features might be achieved in personal robotic systems, but as well what benefits they can afford. I approach the investigation of these questions from a perspective of compliance matching of hardware systems to their applications, by providing methods to achieve mechanical attributes complimentary to their environment and end-use. These features are fundamental to the burgeoning field of Soft Robotics, wherein flexible, compliant materials are used as the basis for the structure, actuation, sensing, and control of complete robotic systems. Combined with pressurized air as a power source, soft pneumatic actuator (SPA) based systems offers new and novel methods of exploiting the intrinsic compliance of soft material components in robotic systems. While this strategy seems to answer many of the needs for human-safe robotic applications, it also brings new questions and challenges: What are the needs and applications personal robots may best serve? Are soft pneumatic actuators capable of these tasks, or âusefulâ work output and performance? How can SPA based systems be applied to provide complex functionality needed for operation in diverse, real-world environments? What are the theoretical and practical challenges in implementing scalable, multiple degrees of freedom systems, and how can they be overcome? I present solutions to these problems in my thesis work, elucidated through scientific design, testing and evaluation of robotic prototypes which leverage and demonstrate three key features: 1) Intrinsic compliance: provided by passive elastic and flexible component material properties, 2) Extrinsic compliance: rendered through high number of independent, controllable degrees of freedom, and 3) Complementary design: exhibited by modular, plug and play architectures which combine both attributes to achieve compliant systems. Through these core projects and others listed below I have been engaged in soft robotic technology, its application, and solutions to the challenges which are critical to providing a path forward within the soft robotics field, as well as for the future of personal robotics as a whole toward creating a better society.

EPFL2019

Design and dynamic analysis of soft pneumatic systems for wearable robots

Sagar Dattatray Joshi

There are many challenges in the development of pneumatically powered soft robots due to the non-linearities of the materials used, non-linear pneumatic flow, complex non-standard designs, and high compliance that leads to loading-specific mechanical behaviour. As a result, there is still a significant gap towards understanding these robots, as compared to standard well-known actuators such as motors, rigid pneumatic actuators, or voice-coils. This thesis develops a comprehensive system-wide understanding of soft wearable robots through investigation and quantification of their soft actuator mechanical outputs, dynamic performance, and biomechanical effects. Towards this goal, we explore methods for accurate and consistent experimental characterization, modelling of SPA pressure and flow dynamics, and musculoskeletal modelling and analysis of soft wearable robots. First, we present a novel experimental protocol and setup for recreating application-specific loading conditions, in order to accurately capture the mechanical behaviour of soft robots. This concept is based on emulating the physical constraints acting on the soft robot at its contact points, and measuring the mechanical outputs. Then, we analyse the dynamic behaviour of SPAs and its dependency on the PSS and loading conditions. Via simulations and experimental testing, we map a direct relationship between properties of the PSS and SPA, and dynamic performance metrics. Using these relations, we present design optimization of PSSs for simultaneously meeting requirements of performance, portability and additional user-defined metrics such as mass or volume. By further investigating the effect of loading conditions on SPA dynamic behaviour, we introduce a previously unknown property of SPAs, self-sensing, that allows estimation of force and displacement without dedicated sensors. Finally, we investigate the biomechanical effect of soft wearable devices via the design and modelling of a soft exosuit for the human torso. The research in this thesis can be broadly categorized into three sections: quantifying mechanical behaviour of soft robots, modelling pressure dynamics of soft pneumatic actuators, and evaluating biomechanical effect of soft exosuits.

EPFL2021

Comprehensive Interactive Soft Interfaces for Wearable Tactile Feedback

Harshal Arun Sonar

EPFL2021

Design and dynamic analysis of soft pneumatic systems for wearable robots

Sagar Dattatray Joshi

EPFL2021

Modular soft pneumatic actuator system design for compliance matching

Matthew Aaron Robertson

EPFL2019