Development of intelligent McKibben actuator

The aim of this study is to develop an intelligent McKibben actuator with an integrated soft displacement sensor inside, so that displacement of this actuator can be controlled without having any extra devices attached. In addition, the high compliance which is a positive feature of the McKibben actuator is still conserved. This paper consists of four main parts. First of all, different types of soft displacement sensors made out of rubber were composed, and tested for their functional characteristics. Secondly, the intelligent McKibben actuator was developed with the soft displacement sensor incorporated within. Then, experiments of the position servo control with a single intelligent McKibben actuator were carried out. At last a robot arm mechanism was designed with two intelligent McKibben actuators, and those experimental results showed a great potential for its future applications.</p

HISSbot: Sidewinding with a Soft Snake Robot

Snake robots are characterized by their ability to navigate through small spaces and loose terrain by utilizing efficient cyclic forms of locomotion. Soft snake robots are a subset of these robots which utilize soft, compliant actuators to produce movement. Prior work on soft snake robots has primarily focused on planar gaits, such as undulation. More efficient spatial gaits, such as sidewinding, are unexplored gaits for soft snake robots. We propose a novel means of constructing a soft snake robot capable of sidewinding, and introduce the Helical Inflating Soft Snake Robot (HISSbot). We validate this actuation through the physical HISSbot, and demonstrate its ability to sidewind across various surfaces. Our tests show robustness in locomotion through low-friction and granular media.Comment: 7 pages, 9 figures, to be published in RoboSoft 202

Development of intelligent McKibben actuator with built-in soft conductive rubber sensor

This study aims at the development of an intelligent McKibben actuator, in which a soft rubber displacement sensor is integrated. Recently, the McKibben actuator has attracted engineers because of light weight, high output power and high compliance. But in the case of using it for servo control at present, the systems need encoders or potentiometers, therefore the systems tend to grow in size and take away from compliance which is an important advantage for a safe and secure mechanism. We have developed a soft displacement sensor and incorporated it in a McKibben actuator, named it the intelligent McKibben actuator, and proved its potential.</p

A New Approach to Dynamic Modeling of Continuum Robots

ABSTRACT In this thesis, a new approach for developing practically realizable dynamic models for continuum robots is proposed. Based on the new dynamic models developed, a novel technique for analyzing the capabilities of continuum manipulators to be employed in various real world applications has also been proposed and developed. A section of a continuum arm is modeled using lumped model elements (masses, springs and dampers). It is shown that this model, although an approximation to a continuum structure, can be used to conveniently analyze the dynamics of the arm with suitable tradeoff in accuracy of modeling. This relatively simple model is more plausible to implement in an actual real-time controller when compared to other techniques of modeling continuum arms. Principles of Lagrangian dynamics are used to derive the expressions for the generalized forces in the system. The force exerted by McKibben actuators at different pressure level - length pairs is characterized and is incorporated into this dynamic model. The constraints introduced in the analytical model conform to the physical and operational limitations of the Octarm VI continuum robot manipulator. The model is validated by comparing the results of numerical simulation with the physical measurements of a continuum arm prototype built using McKibben actuators. Based on the new lumped parameter dynamic model developed for continuum robots, a technique for deducing measures of manipulability, forces and impacts that can be sustained or imparted by the tip of a continuum robot has been developed. These measures are represented in the form of ellipsoids whose volume and orientation gives information about the various functional capabilities (end effector velocities, forces and impacts) of the arm at a particular configuration. The above mentioned ellipsoids are exemplified for different configurations of the continuum section arm and their physical significances are analyzed. The new techniques proposed and methodologies adopted in this thesis supported by experimental results represent a significant contribution to the field of continuum robots

Analysis of Nonlinear Behavior in Novel Pneumatic Artificial Muscles

Motivated by the excellent actuator characteristics of pneumatic artificial muscles (PAMs), two novel actuators based on this technology were developed for applications where traditional PAMs are not suitable. The first of these actuators is a miniature PAM that possesses the same operating principle as a full-scale contractile PAM, but with a diameter an order of magnitude smaller. The second actuator, a push-PAM, harnesses the operational characteristics of a contractile PAM, but changes the direction of motion and force with a simple conversion package. Testing on these actuators revealed each PAM's evolution of force with displacement for a range of operating pressures. To address the analysis of the nonlinear response of these PAMs, a nonlinear stress vs. strain model, a hysteresis model, and a pressure deadband were introduced into a previously developed force balance analysis. The refined nonlinear model was shown to reconstruct PAM response with higher accuracy than previously possible

The effect of diameter and length on blocked force and free contraction of various pneumatic artificial muscles

Abstract: The Pneumatic Artificial Muscle (PAM) is a long-standing actuator technology class in the field of soft robotics. These muscles typically use an input pressure to produce an expansion, contraction, or rotational motion. PAMs are renowned for their extremely high force output to weight ratio and comparatively low cost to traditional robotic actuators. Advancements in materials and manufacturing methods offer more opportunities for PAMs to improve their functional performance and expand their applications. Theoretical models for the force output of a pneumatic muscle would be essential for the design and optimization of PAMs to meet the application needs. Unfortunately, existing models are limited and are often backed by experiments conducted on a small sample of actuators. This study aims to evaluate the robustness of existing models for real-world applications by applying them to the design and optimization of PAMs made with multiple manufacturing methods and materials. Both fiber reinforced elastomer actuators and traditional McKibben actuators will be tested with varying geometric parameters. Traditional McKibben actuators consist of an inflatable inner bladder surrounded by an expandable woven sheath. Fiber reinforced elastomer actuators operate in the same way. However, the woven sheath is imbedded in the inflatable elastomeric bladder. Both types of actuators are a subcategory of Fiber reinforced elastomer enclosures (FREEs) and traditionally hold a cylindrical form factor. The effect of the actuator length was often neglected as radius appears to play a larger role in theoretical analysis, which will be considered in this test. The experimental data of the relationship between the blocked force output and the input pressure will be used to evaluate the theoretical models. The results will likely show that the theoretical models deviate from the experimental results because of the numerous assumptions required to generate a reasonably simple theoretical model including the assumptions of perfect cylindricity throughout inflation and neglecting friction. A comprehensive comparison between the tested PAMs will be provided considering the performance, material cost, end of life disposal, and ease of manufacturing. In summary, this study will provide insight into the accuracy of theoretical models used to predict the force output and contraction of a PAM in real world applications in addition to helping guide the future research and development of soft robotics.Résumé de la communication présentée lors du congrès international tenu conjointement par Canadian Society for Mechanical Engineering (CSME) et Computational Fluid Dynamics Society of Canada (CFD Canada), à l’Université de Sherbrooke (Québec), du 28 au 31 mai 2023

The Design, Construction, and Experimental Characterization of Spatial Parallel Architectures of Elastofluidic Systems

Creating organic, life like motion has historically been extremely difficult and costly for general applications. Traditional structures and robots use rigid components with discrete joints to produce desired motions but are limited in freedom by the range of motion each additional component allows. In a traditionally rigid robot complex motion is obtained through the addition of joints and links. These additions add complexity to a rigid robot but improve its ability to create motion. Soft robotics aims to overcome the limitations of traditional robotics by creating integrated actuation and structure which more closely imitates organic movement. Often the most effective examples to learn from are natural phenomenon or organisms such as underwater and land based invertebrates. In pursuit of the goal of effective soft robotics researchers have explored the idea of a pneumatic elastofluidic actuator, one which expands and deforms in response to applied pressure. While these systems have demonstrated some limited success, they are often used either as a single entity or in series with one another to produce novel motions. In this thesis parallel structures made of these actuators are shown to have the potential to be extremely powerful and useful for soft robotic applications. These spatial arrangements of connected and dependent actuators exhibit behaviors impossible for a single actuator. This research concerns the effective design and construction of these complex parallel structures in an attempt to define a method of characterization which produces useful and desirable spatial architectures and motions

Design and Testing of a Biomimetic Pneumatic Actuated Seahorse Tail Inspired Robot

The purpose of this study is to build and test a pneumatically actuated robot based on the biomimetic design of a seahorse tail. McKibben muscles, a form of pneumatic actuator, have been previously used to create highly flexible robots. It has also been discovered that the seahorse tail serves as a highly flexible and prehensile, yet armored appendage. Combining these topics, this research aims to create a robot with the mechanical flexibility of a pneumatic actuator and the protection of a seahorse tail. First, the performance of a miniature McKibben muscle design is examined. Then, the artificial muscles are implemented into a 3D-printed seahorse tail-inspired skeleton. The robot\u27s actuation was observed to determine its maximum bending capacities. The results of the experiments revealed that the miniature McKibben muscles performed comparably to larger sized McKibben muscles previously reported in literature. The pneumatically actuated robot achieved a maximum bend angle of ~22°. Further research is recommended to determine the behaviors of similar robots with additional plates or McKibben muscles spanning shorter plate sequences

SLUGBOT, an Aplysia-inspired Robotic Grasper for Studying Control

Living systems can use a single periphery to perform a variety of tasks and adapt to a dynamic environment. This multifunctionality is achieved through the use of neural circuitry that adaptively controls the reconfigurable musculature. Current robotic systems struggle to flexibly adapt to unstructured environments. Through mimicry of the neuromechanical coupling seen in living organisms, robotic systems could potentially achieve greater autonomy. The tractable neuromechanics of the sea slug $\textit{Aplysia californica's}$ feeding apparatus, or buccal mass, make it an ideal candidate for applying neuromechanical principles to the control of a soft robot. In this work, a robotic grasper was designed to mimic specific morphology of the $\textit{Aplysia}$ feeding apparatus. These include the use of soft actuators akin to biological muscle, a deformable grasping surface, and a similar muscular architecture. A previously developed Boolean neural controller was then adapted for the control of this soft robotic system. The robot was capable of qualitatively replicating swallowing behavior by cyclically ingesting a plastic tube. The robot's normalized translational and rotational kinematics of the odontophore followed profiles observed $\textit{in vivo}$ despite morphological differences. This brings $\textit{Aplysia}$-inspired control $\textit{in roboto}$ one step closer to multifunctional neural control schema $\textit{in vivo}$ and $\textit{in silico}$. Future additions may improve SLUGBOT's viability as a neuromechanical research platform.Comment: Submitted and accepted to Living Machines 2022 conferenc

Rotation, inversion, and perversion in anisotropic elastic cylindrical tubes and membranes

Cylindrical tubes and membranes are universal structural elements found in biology and engineering over a wide range of scales. Working in the framework of nonlinear elasticity we consider the possible deformations of elastic cylindrical shells reinforced by one or two families of anisotropic fibers. We consider both small and large deformations and the reduction from thick cylindrical shells (tubes) to thin shells (cylindrical membranes). In particular, a number of universal regimes can be identified including the possibility of inversion and perversion of rotation