A cable-driven continuum robot arm is an underactuated mechanism and may suffer residual vibration at the end of a rest-to-rest maneuver. In this work, a time-delay filter is applied as an input shaper to the system to eliminate the excitation of vibratory modes. A non-robust and a robust time-delay filter are designed based on a linear system model and demonstrate improved response compared to a velocity-driven pulse input. Experimental results using the continuum robot validate the application of the input shaper, with reduced overshoot and settling time exemplifying the reduction in oscillation at the end of the maneuver. It is also shown that utilizing the robust shaper further improves the response of the arm in comparison to applying the non-robust shaper. These results are significant towards the precise and robust implementation of continuum robots in applications involving arbitrary end-effector trajectories.

Cyclic actuation tends to cause self-heating in the material as the structure experiences fatigue, where the movement and coalescence of defects lead to crack formation, propagation, and eventual fracture. This study explores the modeling aspects of the self-heating phenomenon using a one-dimensional inverse heat problem to analyze heat generation and dissipation to quantify the plastic work rates needed for predicting fatigue life. The approach is based on analyzing the surface thermography obtained using an infrared camera and numerically solving an inverse Fourier heat conduction equation. Formulation of the inverse problem via constrained optimization and method of solution for analyzing the fatigue behavior of CS 1018 flat dog bone specimens subjected to fully reversed bending fatigue are presented. The proposed model demonstrates superior accuracy in predicting the location of maximum heat generation and identifying potential fracture zones compared to traditional methods.

Concentric Tube Robots have been explored extensively for a variety of medical and surgical applications such as minimally invasive surgeries, with a maximum length found in the literature of approximately 200 mm. The same basic technology can be applied for tasks in industrial inspection, but the applications require longer robot lengths on the order of 1 m. Because of the additional steerability and control offered by the concentric tube idea, they can outperform traditional borescopes and other commercially available devices for some structural integrity assessment tasks. Concentric tube robots may provide new capabilities to inspect in hard-to-reach places and to deliver parts such as sensors, conductors, and other components, or to perform tasks like spray coating and wire harnessing. In this paper, we introduce and describe the design and testing of a novel handheld, miniaturized, and motorized actuation unit for the concentrically nested tubes to navigate the robot to the desired destination and allow for convenient use in the field by human operators, even with tubes that are much longer than previously designed concentric tube robots. The design concept winds the concentrically nested tubes onto concentrically nested spools to accomplish the independent translation and rotation of each tube in a compact form factor. To prevent buckling of the tubes inside the actuation unit, a novel anti-buckling support mechanism is incorporated. The prototype was successfully operated in a field-inspired lined pipe testbed for validation, and learnings from the test and future work are discussed in this article.

This study presents a novel approach for reconstructing localized heat sources associated with fatigue degradation in metallic materials using 1D and 2D Inverse Heat Conduction Problem (IHCP) techniques, integrated with a Finite Element Method (FEM) framework. Traditional fatigue analysis methods are often constrained in their ability to analyze complex geometries. To address these limitations, an approach is introduced that leverages the self-heating observed during cyclic loading to estimate plastic work rates and predict fracture locations. The 2D IHCP demonstrates superior accuracy in capturing variations in heat fluxes and identifying critical regions prone to crack initiation. Experimental validation tests using stainless teel (SS) 321 specimens are presented with thermal and stress analysis data supporting the effectiveness of the proposed methodology. The results indicate that the 2D IHCP method is highly effective in predicting plastic work rate, crack initiation onset, Fracture Fatigue Entropy (FFE), and provides a robust framework for analyzing fatigue in components with complex geometries.

Cable-driven continuum robots that consist of a flexible backbone and are driven by applying tension and displacement on the cables are of interest for use in unstructured environments. Previous work has explored methods to alter the stiffness along the length of the robot via the introduction of additional cables beyond those used for actuation. The introduction of these tendons on the robot would allow the operator to adjust and increase the stiffness value at different locations by prescribing and removing a fixed pretension on the stiffening tendons. This paper presents a continuum mechanism for robotics applications with continuously variable output stiffness. The new method introduces a nonlinear compliance at one side of the tendons that can be adjusted using a lead screw. The nonlinear compliance is provided by a soft hemispherical contact surface that is inspired by the Hertzian contact theory. Through the provided adjustment mechanism, the mechanism output stiffness can be continuously varied without any active control loop. The stiffening cables and adjustable stiffness mechanism allow for the stiffness to be adjusted between a range of 6x to 11x of the stiffness in the case of only actuating cables. The stiffening of a higher-order mode showed a reduced effect, allowing for stiffnesses in the range of 1.5x to 2.2x of the stiffness in the case of only actuating cables.

Concentric tube robots (CTRs) are well-suited to address the unique challenges of minimally invasive surgical procedures due to their small size and ability to navigate highly constrained environments. However, uncertainties in the manufacturing process can lead to challenges in the transition from simulated designs to physical robots. In this work, we propose an end-to-end design workflow for CTRs that considers the oftenoverlooked impact of manufacturing uncertainty, focusing on two primary sources — tube curvature and diameter. This comprehensive approach incorporates a two-step design optimization and an uncertainty-based selection of manufacturing tolerances. Simulation results highlight the substantial influence of manufacturing uncertainties, particularly tube curvature, on the physical robot's performance. By integrating these uncertainties into the design process, we can effectively bridge the gap between simulation and real-world performance. Two hardware experiments validate the proposed CTR design workflow. The first experiment confirms that the performance of the physical robot lies within the simulated probability distribution from the optimization, while the second experiment demonstrates the feasibility of the overall system for use in micro-laryngeal surgical tasks. This work not only contributes to a more comprehensive understanding of CTR design by addressing manufacturing uncertainties, but also creates a new framework for robust design, as illustrated in the context of microlaryngeal surgery

This study proposes an automated real-time inspection methodology using 2D LiDAR for construction-scale additive manufacturing, aimed at prompt defect detection and preventing excessive layer deformations during the robotic fabrication process. Two new data processing algorithms are designed, implemented, and compared with benchmark data to conduct a comprehensive analysis. The proposed inspection module is integrated into the concrete printing machine, eliminating the need for an additional inspection robot—an important consideration for fabrication operations in outdoor and remote environments. Based on the quantitative data from a systematic experimental program, the proposed Variable Standard Deviation (VSD) algorithm continuously performs extrudate width and height measurements with an average error of less than 1.2 mm and maximum error values under 1.33 mm when data collection cycles longer than 1 s are adopted. The findings of this study also provide new insights into the influence of the data collection cycle, extrudate size and number of layers, and extruder traversal speed on the performance of the proposed scanning system.

Legged locomotion is a highly promising but under-researched subfield within the field of soft robotics. The compliant limbs of soft-limbed robots offer numerous benefits, including the ability to regulate impacts, tolerate falls, and navigate through tight spaces. These robots have the potential to be used for various applications, such as search and rescue, inspection, surveillance, and more. The state-of-the-art still faces many challenges, including limited degrees of freedom, a lack of diversity in gait trajectories, insufficient limb dexterity, and limited payload capabilities. To address these challenges, we develop a modular soft-limbed robot that can mimic the locomotion of pinnipeds. By using a modular design approach, we aim to create a robot that has improved degrees of freedom, gait trajectory diversity, limb dexterity, and payload capabilities. We derive a complete floating-base kinematic model of the proposed robot and use it to generate and experimentally validate a variety of locomotion gaits. Results show that the proposed robot is capable of replicating these gaits effectively. We compare the locomotion trajectories under different gait parameters against our modeling results to demonstrate the validity of our proposed gait models.

Tendon-driven continuum robots have drawn interest for a wide variety of applications. Prior work in this area has elucidated the coupled kinematics and statics models that describe the motion and coupling of the robot's elastic backbone with the driving tendons that are tensioned to change the shape of the robot. However, the full design freedom associated with the routing of the tendon through the supporting "eyelets" in the structure has not been explored. This article describes designs that have multiple tendon paths designed to influence the shape of only one continuously deformable section. It is known that this type of solution generally results in highly coupled tendon kinematics, but we show experimentally that there exist paths for which the tendons are so weakly coupled (kinematically) that they can be locked off to provide configuration-independent stiffening. They could also be displaced independently from one another to control independent deformation modes. The approach reveals a strategy for reducing the uncontrolled compliance of the robot's body, including the torsional compliance, while retaining simplicity in design and control. In particular, we show that tendons that are routed sinusoidally and helically do not strongly couple to constant-curvature actuating tendons as long as they meet an orthogonality constraint. The added tendons increase the stiffness at the cantilevered end by 4.85x over straight tendons alone without impacting the range of motion in the stiffened condition.

Soft robotic snakes made of compliant materials can continuously deform their bodies and, therefore, mimic the biological snakes' flexible and agile locomotion gaits better than their rigid-bodied counterparts. Without wheel support, to date, soft robotic snakes are limited to emulating planar locomotion gaits, which are derived via kinematic modeling and tested on robotic prototypes. Given that the snake locomotion results from the reaction forces due to the distributed contact between their skin and the ground, it is essential to investigate the locomotion gaits through efficient dynamic models capable of accommodating distributed contact forces. We present a complete spatial dynamic model that utilizes a floating-base kinematic model with distributed contact dynamics for a pneumatically powered soft robotic snake. We numerically evaluate the feasibility of the planar and spatial rolling gaits utilizing the proposed model and experimentally validate the corresponding locomotion gait trajectories on a soft robotic snake prototype. We qualitatively and quantitatively compare the numerical and experimental results which confirm the validity of the proposed dynamic model.

Continuum robots offer many advantages for use in miniature diagnostic and interventional surgical devices. However, the creation of snake-like devices with extremely high slenderness ratios, those with great length and small diameter, remains challenging from a device design perspective. To facilitate improved slenderness ratios, high total accumulated bending angles, and high stiffness and mechanical stability of the active section, we propose the use of a flexible screw-driven mechanism to generate large distal actuation forces while still locating motors and other bulky system components at the base of the device. In comparison to tendon-based designs and push-pull rods, the design avoids the capstan-like buildup of friction. In this work, we present design, fabrication, kinestatic modeling, and experimental validation for a two-degree-of freedom, screw-based, multi-backbone continuum robot. The model that compensates the friction in the system most accurately predicts the behavior of the robot and eliminates most of the hysteresis in the input-output behavior.

Abstract Catheters integrated with microcoils for electromagnetic steering under the high, uniform magnetic field within magnetic resonance (MR) scanners (3–7 Tesla) have enabled an alternative approach for active catheter operations. Achieving larger ranges of tip motion for Lorentz force‐based steering have previously been dependent on using high power coupled with active cooling, bulkier catheter designs, or introducing additional microcoil sets along the catheter. This work proposes an alternative approach using a heat‐mitigated design and actuation strategy for a magnetic resonance imaging (MRI)‐driven microcatheter. A quad‐configuration microcoil (QCM) design is introduced, allowing miniaturization of existing MRI‐driven, Lorentz force‐based catheters down to 1‐mm diameters with minimal power consumption (0.44 W). Heating concerns are experimentally validated using noninvasive MRI thermometry. The Cosserat model is implemented within an MR scanner and results demonstrate a desired tip range up to 110° with 4° error. The QCM is used to validate the proposed model and power‐optimized steering algorithm using an MRI‐compatible neurovascular phantom and ex vivo kidney tissue. The power‐optimized tip orientation controller conserves as much as 25% power regardless of the catheter's initial orientation. These results demonstrate the implementation of an MRI‐driven, electromagnetic catheter steering platform for minimally invasive surgical applications without the need for camera feedback or manual advancement via guidewires. The incorporation of such system in clinics using the proposed design and actuation strategy can further improve the safety and reliability of future MRI‐driven active catheter operations.

Cervical collars are medical devices commonly used to restrict motion of the cervical spine after trauma or surgical intervention. Improvements to the kinematic adjustability of collars and the rigidity of the contact surface between the patient's body and the collar would result in better restriction of motion while maintaining comfort and fit. This paper reports on the initial design and prototyping of a new design concept for cervical collars consisting of pouches of granular material along the inside of two rings which are of similar geometry to the neck. The rings are connected by six adjustable length struts, analogous to the classical Stewart-Gough platform. Granular jamming is a reversible process in which a bladder containing a granular material, such as coffee grounds, becomes stiff when a vacuum is drawn on it. Thus, the pouches allow for a moldable interface with the neck with adjustable rigidity. The 3D printed rings are designed to accommodate the geometry of individual wearers by flexure hinges approximating a continuously deformable structure. The geometry of the rings was selected by surface modeling of the body geometry followed by extraction of coordinate curves and flattening. The struts provide patient specific adjustments for neck height and variance in head shape.

We propose a new method for improving the stability of concentric tube robots. Prior work sought to improve stability through laser-cut patterns that reduced $EI/GJ$, the ratio of flexural rigidity to torsional rigidity, but this strategy has always entailed a steep trade-off in overall robot stiffness. Instead, we show that stability can be improved much more efficiently by allowing transverse anisotropy (direction-dependent flexural rigidity, $EI_x\ne EI_y$). We provide a generalized robot model with this property and give its associated stability criterion. In the two-tube case, this provides a new version of the well-known $EI/GJ$ criterion, now generalized to reveal the independent effects of $EI_x$ and $EI_y$. It shows that the most efficient strategy to improve stability while preserving stiffness is to reduce the flexural rigidity about the axis of precurvature while maintaining high off-axis flexural rigidity and torsional rigidity. We validate the approach with a balanced-stiffness pair of laser-machined Nitinol tubes, demonstrating model accuracy and significant stability improvement while requiring less stiffness reduction than prior methods.

TeleLayering: Teleoperated Construction 3D Printing Using Multimodal Feedback for Extraterrestrial and Terrestrial Construction Ali Kazemian, Hunter Gilbert, Yimin Zhu, Michael R. Fiske, and Natalia Alexandrov Pages 13-16 (ICRA 2022 Future of Construction Workshop Papers, ISBN -, ISSN 2413-5844) Abstract: In this paper, we propose a teleoperatedconstruction 3D printing technology, called TeleLayering, forplanetary and terrestrial applications. The TeleLayeringtechnology is enabled by effective multimodal control andmonitoring systems and enhanced construction 3D printingrobots to build or repair a variety of structures in extremeenvironments without the need for human presence on thejobsite. This paper presents a general description, maintechnical requirements, implementation challenges, andapplications of this technology. Keywords: No keywords DOI: https://doi.org/10.22260/ICRA2022/0006 Download fulltext Download BibTex Download Endnote (RIS) TeX Import to Mendeley

Artists and designers have been exploring how robotics can be used to interact with our environment in new ways. Robots connect computational design processes with the physical environment, making digital interaction with nature possible. We present a robotic process for planting that enables the computational design of landscapes. We demonstrate how robotic planting can be used for generative art and design by creating a living typeface grown from seed. The robot draws a message by 3-dimensionally (3D) printing a blend of planting media and seeds. When the seeds germinate, the glyphs emerge from their substrate in a flush of green. The letterforms become dynamic living organisms. Artistic agency shifts from the artist to nature.

A local measure based on the Shannon entropy establishes connections among information, structures, and interactions.

Cable-driven continuum robots, which are robots with a continuously flexible backbone and no identifiable joints that are actuated by cables, have shown great potential for many applications in unstructured, uncertain environments. However, the standard design for a cable-driven continuum robot segment, which bends a continuous backbone along a circular arc, has many compliant modes of deformation which are uncontrolled, and which may result in buckling or other undesirable behaviors if not ameliorated. In this paper, we detail an approach for using additional cables to selectively stiffen planar cable-driven robots without substantial coupling to the actuating cables. A mechanics-based model based on the planar Cosserat equations is used to find the design conditions under which additional cables can be routed without coupling of the cable lengths for small deformations. Simulations show that even for relatively large deformations, coupling remains small. A prototype is evaluated, and it is demonstrated that the compliance of the robot is substantially modified relative to the same robot without stiffening cables. Additional stiffening cables are shown to increase the end-effector output stiffness by a factor of approximately 10 over a typical design with actuating cables.

The passive, mechanical adaptation of slender, deformable robots to their environment, whether the robot be made of hard materials or soft ones, makes them desirable as tools for medical procedures. Their reduced physical compliance can provide a form of embodied intelligence that allows the natural dynamics of interaction between the robot and its environment to guide the evolution of the combined robot-environment system. To design these systems, the problems of analysis, design optimization, control, and motion planning remain of great importance because, in general, the advantages afforded by increased mechanical compliance must be balanced against penalties such as slower dynamics, increased difficulty in the design of control systems, and greater kinematic uncertainty. The models that form the basis of these problems should be reasonably accurate yet not prohibitively expensive to formulate and solve. In this article, the state-of-the-art modeling techniques for continuum robots are reviewed and cast in a common language. Classical theories of mechanics are used to outline formal guidelines for the selection of appropriate degrees of freedom in models of continuum robots, both in terms of number and of quality, for geometrically nonlinear models built from the general family of one-dimensional rod models of continuum mechanics. Consideration is also given to the variety of actuators found in existing designs, the types of interaction that occur between continuum robots and their biomedical environments, the imposition of constraints on degrees of freedom, and to the numerical solution of the family of models under study. Finally, some open problems of modeling are discussed and future challenges are identified.

Current capsule endoscopes and next-generation robotic capsules for diagnosis and treatment of gastrointestinal diseases are complex cyber-physical platforms that must orchestrate complex software and hardware functions. The desired tasks for these systems include visual localization, depth estimation, 3D mapping, disease detection and segmentation, automated navigation, active control, path realization and optional therapeutic modules such as targeted drug delivery and biopsy sampling. Data-driven algorithms promise to enable many advanced functionalities for capsule endoscopes, but real-world data is challenging to obtain. Physically-realistic simulations providing synthetic data have emerged as a solution to the development of data-driven algorithms. In this work, we present a comprehensive simulation platform for capsule endoscopy operations and introduce VR-Caps, a virtual active capsule environment that simulates a range of normal and abnormal tissue conditions (e.g., inflated, dry, wet etc.) and varied organ types, capsule endoscope designs (e.g., mono, stereo, dual and 360∘ camera), and the type, number, strength, and placement of internal and external magnetic sources that enable active locomotion. VR-Caps makes it possible to both independently or jointly develop, optimize, and test medical imaging and analysis software for the current and next-generation endoscopic capsule systems. To validate this approach, we train state-of-the-art deep neural networks to accomplish various medical image analysis tasks using simulated data from VR-Caps and evaluate the performance of these models on real medical data. Results demonstrate the usefulness and effectiveness of the proposed virtual platform in developing algorithms that quantify fractional coverage, camera trajectory, 3D map reconstruction, and disease classification. All of the code, pre-trained weights and created 3D organ models of the virtual environment with detailed instructions how to setup and use the environment are made publicly available at https://github.com/CapsuleEndoscope/VirtualCapsuleEndoscopy and a video demonstration can be seen in the supplementary videos (Video-I).