Featured in the latest Nature Scientific Reports; New Finite Element Method (FEM) models predict behaviour of wearable robots to improve their design and performance… Read more
During the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) which happened recently in Vancouver, Canada, Harshal Sonar, Doctoral Assistant for the Paik Lab, has won the Best Poster Award for his presentation on “Interactive SPA skin”. For more information, please visit the RRL website. For a short Youtube video on Interactive Soft Pneumatic Actuator Skin for Tactile …
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Soft pneumatic actuators (SPAs) are versatile robotic components enabling diverse and complex soft robot hardware design. However, due to inherent material characteristics exhibited by their primary constitutive material, silicone rubber, they often lack robustness and repeatability in performance. In this article, we present a novel SPA-based bending module design with shell reinforcement. The bidirectional soft actuator presented here is enveloped in a Yoshimura patterned origami shell, which acts as an additional protection layer covering the SPA while providing specific bending resilience throughout the actuator’s range of motion. Mechanical tests are performed to characterize several shell folding patterns and their effect on the actuator performance. Details on design decisions and experimental results using the SPA with origami shell modules and performance analysis are presented; the performance of the bending module is significantly enhanced when reinforcement is provided by the shell. With the aid of the shell, the bending module is capable of sustaining higher inflation pressures, delivering larger blocked torques, and generating the targeted motion trajectory.
Wearable soft robotic systems are enabling safer human-robot interaction and are proving to be instrumental for biomedical rehabilitation. In this manuscript, we propose a novel, modular, wearable robotic device for human (lumbar) spine assistance that is developed using vacuum driven, soft pneumatic actuators (V-SPA). The actuators can handle large, repetitive loads efficiently under compression. Computational models to capture the complex non-linear mechanical behavior of individual actuator modules and the integrated assistive device are developed using the finite element method (FEM). The models presented can predict system behavior at large values of mechanical deformations and allow for rapid design iterations. It is shown that a single actuator module can be used to obtain a variety of different motion and force profiles and yield multiple degrees of freedom (DOF) depending on the module loading conditions, resulting in high system versatility and adaptability, and efficient replication of the targeted motion range for the human spinal cord. The efficacy of the finite element model is first validated for a single module using experimental results that include free displacement and blocked-forces. These results are then extended to encompass an extensive investigation of bio-mechanical performance requirements from the module assembly for the human spine-assistive device proposed.
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.