Modular soft pneumatic actuator system design for compliance matching

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

Practical control methods for vacuum driven soft actuator modules

Vacuum-powered Soft Pneumatic Actuator (VSPA) Modules have been described to afford advantages for rapid development of reconfigurable, multi-DoF soft pneumatic robots powered by vacuum by reducing their logistical complexity, however they also present new challenges in the control of resulting systems. This framework features modules joined together over a simple embedded pneumatic and serial communication network and requires a unique approach to both low-level control implementation and high-level control strategy. We describe the structure and activation characteristics of a V-SPA Module and present practical methods for its control. These methods utilize software generated PWM activation through a unique serial protocol designed for LED networks and a heuristic mapping strategy for simplifying the spherical control of 3-DoF actuator modules

New soft robots really suck: Vacuum-powered systems empower diverse capabilities

We introduce a vacuum-powered soft pneumatic actuator (V-SPA) that leverages a single, shared vacuum power supply and enables complex soft robotic systems with multiple degrees of freedom (DoFs) and diverse functions. In addition to actuation, other utilities enabled by vacuum pressure include gripping and stiffening through granular media jamming, as well as direct suction adhesion to smooth surfaces, for manipulation or vertical fixation. We investigate the performance of the new actuator through direct characterization of a 3-DoF, plug-and-play V-SPA Module built from multiple V-SPAs and demonstrate the integration of different vacuum-enabled capabilities with a continuum-style robot platform outfitted with modular peripheral mechanisms. We show that these different vacuum-powered modules can be combined to achieve a variety of tasks—including multimodal locomotion, object manipulation, and stiffness tuning—to illustrate the utility and viability of vacuum as a singular alternative power source for soft pneumatic robots and not just a peripheral feature in itself. Our results highlight the effectiveness of V-SPAs in providing core soft robot capabilities and facilitating the consolidation of previously disparate subsystems for actuation and various specialized tasks, conducive to improving the compact design efficiency of larger, more complex multifunctional soft robotic systems

Trunk postural tracking of assistive soft pneumatic actuator belt

Fiber-reinforced Soft Pneumatic Actuators (SPAs) are found in mobile robots, assistive wearable devices, and rehabilitative technologies. Being intrinsically compliant and readily manufacturable they are attractive for use where safety and customizability are a priority. While different types of SPAs can be found to match the force performance requirements of a variety of applications, outlying system-level issues of robustness, controllability, and repeatability are not traditionally addressed at the actuator level. The SPA pack architecture presented here aims to satisfy these standards of reliability as well as extend the basic performance capabilities of SPAs by borrowing advantages leveraged ubiquitously in biology; namely the structured parallel arrangement of lower power actuators to form the basis of a larger, more powerful actuator module. An SPA pack module consisting of a number of smaller SPAs will be studied using an analytical model and a physical prototype. For a module consisting of four unit actuators an output force over 112 N is measured, while the model indicates the effect of parallel actuator grouping over a geometrically equivalent single SPA scales as an increasing function of the number of individual actuators in the group. A 23% increase in force production over a volumetrically equivalent single SPA is predicted and validated, while further gains appear possible up to 50%, reasonably bounded by practical limitations from material properties and manufacturability. These findings affirm the advantage of utilizing a fascicle structure for high-performance soft robotic applications over existing monolithic SPA designs. An active wearable belt will be presented to demonstrate the capability of SPA pack modules to affect human trunk posture while standing, while further work may enable active modulation of trunk angle during walking to provide corrective assistance or gait modifying perturbations

A low-cost, actuated passive dynamic walker kit for accessible research and education

A low-cost bipedal walking robot kit with limited actuation and sensing capabilities was designed and built to achieve actively powered, passive dynamic walking locomotion over level ground. The walking system is composed of readily available parts and materials totaling less than $50 and can be assembled either from plans or pre-fabricated parts in less than a day. Indeed, the very first (and only) prototype was conceived and built in one day, and capable of walking within two more. In place of components utilized for the prototype shown and demonstrated, alternative parts and materials can be substituted and accommodated by relatively simple design changes, allowing this robot construction to be adapted to different resource availability, in some cases key to the success of research or education

A Compact Modular Soft Surface With Reconfigurable Shape and Stiffness

A variety of reconfigurable surface devices, utilizing large numbers of actuated physical pixels to produce discretized 3D contours, have been developed for different purposes in research and industry. The difficulty of integrating many actuators in close configuration has limited the DoF and resolution and performance of existing devices. Utilizing vacuum power and soft material actuators, we have developed a soft reconfigurable surface (SRS) with multi-modal control and performance capabilities. The SRS is comprised of a square grid array of linear vacuum-powered soft pneumatic actuators (linear V-SPAs), built into plug-and-play modules which enable the arrangement, consolidation, and control of many DoF. In addition to the practical benefits of system integration, this architecture facilitates the construction of customized assemblies with an overall compact form factor. A series of experiments is performed to illustrate and validate the versatility of the SRS for achieving diverse tasks including force controlled modulation of interface pressure through integrated sensors, lateral manipulation of a variety of objects, static and dynamic shape and pattern generation for haptic interaction, and variable surface stiffness tuning. This SRS concept is scalable, space efficient and features diverse functional potential. This will extend the utility and accessibility of tangible robotic interfaces for future applications from industrial to home and personal use

Soft Pneumatic Actuator Fascicles for High Force and Reliability

Soft pneumatic actuators (SPAs) are found in mobile robots, assistive wearable devices, and rehabilitative technologies. While soft actuators have been one of the most crucial elements of technology leading the development of the soft robotics field, they fall short of force output and bandwidth requirements for many tasks. Additionally, other general problems remain open including robustness, controllability, and repeatability. The SPA-pack architecture presented here aims to satisfy these standards of reliability crucial to the field of soft robotics, while also improving the basic performance capabilities of SPAs by borrowing advantages leveraged ubiquitously in biology; namely the structured parallel arrangement of lower power actuators to form the basis of a larger, more powerful actuator module. An SPA-pack module consisting of a number of smaller SPAs will be studied using an analytical model and physical prototype. Experimental measurements show an SPA-pack to generate over 112 N linear force, while the model indicates the benefit of parallel actuator grouping over a geometrically equivalent single SPA scales as an increasing function of the number of individual actuators in the group. For a module of four actuators, a 23 % increase in force production over a volumetrically equivalent single SPA is predicted and validated, while further gains appear possible up to 50 %. These findings affirm the advantage of utilizing a fascicle structure for high-performance soft robotic applications over existing monolithic SPA designs. An example high-performance soft robotic platform will be presented to demonstrate the capability of SPA-pack modules in a complete and functional system

Bi-Modal Control of Vacuum-Powered Soft Pneumatic Actuators with Embedded Liquid Metal-Based Strain Sensitive Skin

Soft robotic systems are composed of active and passively deformable structures which are intrinsically compliant, flexible, and elastic. Although these features offer benefits of adaptability, robustness, and safety, controlling these types of robots is a significant challenge, in part from the difficulty of obtaining feedback from sensors which provide state information without hindering the advantageous material properties which grant these systems their unique mechanical behavior. We demonstrate here the first integration of a flexible, stretchable, liquid metal-based strain sensor with vacuum powered soft pneumatic actuators (V-SPAs) for simultaneous controlled feedback of the soft actuators as well as user input and soft robotic device interaction. The soft sensors which are encapsulated within a Polydimethylsiloxane (PDMS) membrane are directly embedded in the outer body skin of the soft actuators, and can be used to correlate the deformation of the body under vacuum actuation to overall actuator strain or to detect external disturbances. This information is used to compute and control the angle of a rotational 3-DoF actuator module, as well as detect implicit user input control signals by direct interaction without the need for an external control interface. The dual use of embedded sensing shown in this work provides a fundamental strategy for soft collaborative robot applications

Interactive soft pneumatic actuator skin

The interactive soft pneumatic actuator (SPA) skin is a soft wearable device with integrated actuation and sensing. The SPA skin is a flat flexible patch that can be worn on the body, consisting of a 2-D matrix with independent actuation and sensing elements at each node (a taxel). The SPA skin acts as a bidirectional communication interfacing device. Vibrotactile actuation is achieved using SPAs and the tactile sensing is done via piezo-electric sensors. It can take in input from the user, as well as actuate in various patterns, simulating various sensations such as touch, brush, move, etc. thus allowing a bidirectional communication