Modeling and parametric optimization of 3D tendon-sheath actuator system for upper limb soft exosuit

This paper presents an analysis of parametric characterization of a motor driven tendon-sheath actuator system for use in upper limb augmentation for applications such as rehabilitation, therapy, and industrial automation. The double tendon sheath system, which uses two sets of cables (agonist and antagonist side) guided through a sheath, is considered to produce smooth and natural-looking movements of the arm. The exoskeleton is equipped with a single motor capable of controlling both the flexion and extension motions. One of the key challenges in the implementation of a double tendon sheath system is the possibility of slack in the tendon, which can impact the overall performance of the system. To address this issue, a robust mathematical model is developed and a comprehensive parametric study is carried out to determine the most effective strategies for overcoming the problem of slack and improving the transmission. The study suggests that incorporating a series spring into the system's tendon leads to a universally applicable design, eliminating the need for individual customization. The results also show that the slack in the tendon can be effectively controlled by changing the pretension, spring constant, and size and geometry of spool mounted on the axle of motor

3D printed pneumatic soft actuators and sensors: their modeling, performance quantification, control and applications in soft robotic systems

Continued technological progress in robotic systems has led to more applications where robots and humans operate in close proximity and even physical contact in some cases. Soft robots, which are primarily made of highly compliant and deformable materials, provide inherently safe features, unlike conventional robots that are made of stiff and rigid components. These robots are ideal for interacting safely with humans and operating in highly dynamic environments. Soft robotics is a rapidly developing field exploiting biomimetic design principles, novel sensor and actuation concepts, and advanced manufacturing techniques. This work presents novel soft pneumatic actuators and sensors that are directly 3D printed in one manufacturing step without requiring postprocessing and support materials using low-cost and open-source fused deposition modeling (FDM) 3D printers that employ an off-the-shelf commercially available soft thermoplastic poly(urethane) (TPU). The performance of the soft actuators and sensors developed is optimized and predicted using finite element modeling (FEM) analytical models in some cases. A hyperelastic material model is developed for the TPU based on its experimental stress-strain data for use in FEM analysis. The novel soft vacuum bending (SOVA) and linear (LSOVA) actuators reported can be used in diverse robotic applications including locomotion robots, adaptive grippers, parallel manipulators, artificial muscles, modular robots, prosthetic hands, and prosthetic fingers. Also, the novel soft pneumatic sensing chambers (SPSC) developed can be used in diverse interactive human-machine interfaces including wearable gloves for virtual reality applications and controllers for soft adaptive grippers, soft push buttons for science, technology, engineering, and mathematics (STEM) education platforms, haptic feedback devices for rehabilitation, game controllers and throttle controllers for gaming and bending sensors for soft prosthetic hands. These SPSCs are directly 3D printed and embedded in a monolithic soft robotic finger as position and touch sensors for real-time position and force control. One of the aims of soft robotics is to design and fabricate robotic systems with a monolithic topology embedded with its actuators and sensors such that they can safely interact with their immediate physical environment. The results and conclusions of this thesis have significantly contributed to the realization of this aim

The role of morphology of the thumb in anthropomorphic grasping : a review

The unique musculoskeletal structure of the human hand brings in wider dexterous capabilities to grasp and manipulate a repertoire of objects than the non-human primates. It has been widely accepted that the orientation and the position of the thumb plays an important role in this characteristic behavior. There have been numerous attempts to develop anthropomorphic robotic hands with varying levels of success. Nevertheless, manipulation ability in those hands is to be ameliorated even though they can grasp objects successfully. An appropriate model of the thumb is important to manipulate the objects against the fingers and to maintain the stability. Modeling these complex interactions about the mechanical axes of the joints and how to incorporate these joints in robotic thumbs is a challenging task. This article presents a review of the biomechanics of the human thumb and the robotic thumb designs to identify opportunities for future anthropomorphic robotic hands

Design, Modeling and Control of a 3D Printed Monolithic Soft Robotic Finger with Embedded Pneumatic Sensing Chambers

IEEE This paper presents a directly 3D printed soft monolithic robotic finger with embedded soft pneumatic sensing chambers (PSC) as position and touch sensors. The monolithic finger was fabricated using a low-cost and open-source fused deposition modeling (FDM) 3D printer that employs an off-the-shelf soft and flexible commercially available thermoplastic polyurethane (TPU). A single soft hinge with an embedded PSC was optimized using finite element modeling (FEM) and a hyperelastic material model to obtain a linear relationship between the internal change in the volume of its PSC and the corresponding input mechanical modality, to minimize its bending stiffness and to maximize its internal volume. The soft hinges with embedded PSCs have several advantages, such as fast response to very small changes in their internal volume (~0.0026ml/°), linearity, negligible hysteresis, repeatability, reliability, long lifetime and low power consumption. Also, the flexion of the soft robotic finger was predicted using a geometric model for use in real-time control. The real-time position and pressure/force control of the soft robotic finger were achieved using feedback signals from the soft hinges and the touch PSC embedded in the tip of the finger. This study contributes to the development of seamlessly embedding optimized sensing elements in the monolithic topology of a soft robotic system and controlling the robotic system using the feedback data provided by the sensing elements to validate their performance

Soft Gloves: A Review on Recent Developments in Actuation, Sensing, Control and Applications

Interest in soft gloves, both robotic and haptic, has enormously grown over the past decade, due to their inherent compliance, which makes them particularly suitable for direct interaction with the human hand. Robotic soft gloves have been developed for hand rehabilitation, for ADLs assistance, or sometimes for both. Haptic soft gloves may be applied in virtual reality (VR) applications or to give sensory feedback in combination with prostheses or to control robots. This paper presents an updated review of the state of the art of soft gloves, with a particular focus on actuation, sensing, and control, combined with a detailed analysis of the devices according to their application field. The review is organized on two levels: a prospective review allows the highlighting of the main trends in soft gloves development and applications, and an analytical review performs an in-depth analysis of the technical solutions developed and implemented in the revised scientific research. Additional minor evaluations integrate the analysis, such as a synthetic investigation of the main results in the clinical studies and trials referred in literature which involve soft gloves

Design Criteria of Soft Exogloves for Hand Rehabilitation- Assistance Tasks

This paper establishes design criteria for soft exogloves (SEG) to be used as rehabilitation or assistance devices. This research consists in identifying, selecting, and grouping SEG features based on the analysis of 91 systems that have been proposed during the last decade. Thus, function, mobility, and usability criteria are defined and explicitly discussed to highlight SEG design guidelines. Additionally, this study provides a detailed description of each system that was analysed including application, functional task, palm design, actuation type, assistance mode, degrees of freedom (DOF), target fingers, motions, material, weight, force, pressure (only for fluids), control strategy, and assessment. Such characteristics have been reported according to specific design methodologies and operating principles. Technological trends are contemplated in this contribution with emphasis on SEG design opportunity areas. In this review, suggestions, limitations, and implications are also discussed in order to enhance future SEG developments aimed at stroke survivors or people with hand disabilities

텐던 드리븐 메커니즘을 이용한 유연한 입는형 손가락 로봇의 모델링

학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부, 2013. 2. 조규진.본 논문은 텐던 드리븐 메커니즘을 이용한 유연한 입는형 손가락 로봇의 제어능력을 향상시키기 위해 두 가지 방법을 제안한다. 텐던 엥커링 서포트는 모터의 힘을 와이어를 통해 원하는 구동 지점까지 전달하기 위한 파트로서 손에 고정이 잘 되어야 하는 특성을 가지도록 개발되었다. 텐던 엥커링 서포트는 손에 고정이 잘 되기 위하여 환자마다 손의 모양이 다른 것을 감안해 맞춤형으로 제작이 되었다. 이 파트를 간편하게 맞춤형으로 제작하기 위하여 공정과정이 개발이 되었다. 또한 본 논문에서 손가락의 각도를 추정하기 위한 장갑 변형 모델과 힘 추정 모델을 소개한다. 유연한 입는형 손가락 로봇의 손가락 끝 단의 힘을 제어하기 위한 모델을 만드는 첫 번째 과정으로 중수지절관절 장갑 변형 모델이 만들어졌다. 이 모델은 실험을 통하여 완성이 되었고, 이 모델을 바탕으로 중수지절관절 힘 추정 모델을 만들었다. 이 두 모델의 정당성은 실험을 통해 입증되었다. 텐던 드리븐 메커니즘을 이용한 유연한 입는형 로봇을 만드는 공학자라면 누구나 로봇의 제어에 관한 문제에 당면하게 된다. 이 논문에서 소개한 모델들은 이러한 문제를 해결하는데 좋은 방향성을 제시할 것이다.This paper presents two ways to increase controllability of tendon driven soft wearable robot for the finger. Tendon Anchoring Support (TA Support) was developed to be fixed to the hand to transmit force from motor to the target actuation point of the robot. TA Support was developed with several design considerations, especially customization to maximize fixation to individual patients hand. For that, fabrication process for customization to patients hand has been established and introduced in this paper. This paper introduces deformation model for posture estimation and force estimation model. After development of TA Support, to increase the controllability of the robot, deformation model for the MCP joint flexion has been built to consider deformation of glove and wire elongation. Experiments have been conducted to complete deformation model. Based on MCP joint flexion deformation model, force estimation for MCP joint flexion has been built. To verify these two models, MCP joint posture estimation experiment and force estimation experiment have been conducted. Engineers developing the soft wearable robot with tendon driven mechanism will always encounter problems to control the robot, and as stated in this paper, this paper will show prospective view to model and control soft exoskeletonAbstract i Chapter 1 Introduction 1 Chapter 2 Force Transmission Analysis 4 2.1 Comparison of Conventional Mechanisms 4 2.2 Development of Tendon Anchoring Support 7 Chapter 3 Tendon Anchoring Support 13 3.1 Design Considerations 13 3.1.1 Small and Compact 13 3.1.2 Position of TA Support 13 3.1.3 Fixation 14 3.1.4 Customization 14 3.2 Manufacturing Process 15 Chapter 4 Deformation of the Glove 20 4.1 Direct Attachment to Link Case 20 4.1.1 TA Support Movement 20 4.1.2 Palm Velcro Strap Movement 21 4.1.3 Finger Attachment Point Movement 21 4.1.4 Wire Elongation 22 4.2 Wire Passing Velcro Strap Case 22 Chapter 5 Modeling 29 5.1 Model for Wire Attachment at MCP Joint 29 5.2 Model for Force Estimation of MCP Joint 31 Chapter 6 Experiment 35 6.1 Experimental Setup 35 6.2 Spring Constant Estimation 35 Chapter 7 Posture and Force Estimation 47 7.1 Posture Estimation 47 7.1.1 Constant Force Applied 47 7.1.2 Random Force Applied 48 7.2 Force Estimation 49 Chapter 8 Conclusion 54 Bibliography 56 국문초록 60Maste

A Bioinspired Bidirectional Stiffening Soft Actuator for Multimodal, Compliant, and Robust Grasping

The stiffness modulation mechanism for soft robotics has gained considerable attention to improve deformability, controllability, and stability. However, for the existing stiffness soft actuator, high lateral stiffness and a wide range of bending stiffness are hard to be provided at the same time. This paper presents a bioinspired bidirectional stiffening soft actuator (BISA) combining the air-tendon hybrid actuation (ATA) and a bone-like structure (BLS). The ATA is the main actuation of the BISA, and the bending stiffness can be modulated with a maximum stiffness of about 0.7 N/mm and a maximum magnification of 3 times when the bending angle is 45 deg. Inspired by the morphological structure of the phalanx, the lateral stiffness can be modulated by changing the pulling force of the BLS. The lateral stiffness can be modulated by changing the pulling force to it. The actuator with BLSs can improve the lateral stiffness about 3.9 times compared to the one without BLSs. The maximum lateral stiffness can reach 0.46 N/mm. And the lateral stiffness can be modulated decoupling about 1.3 times (e.g., from 0.35 N/mm to 0.46 when the bending angle is 45 deg). The test results show the influence of the rigid structures on bending is small with about 1.5 mm maximum position errors of the distal point of actuator bending in different pulling forces. The advantages brought by the proposed method enable a soft four-finger gripper to operate in three modes: normal grasping, inverse grasping, and horizontal lifting. The performance of this gripper is further characterized and versatile grasping on various objects is conducted, proving the robust performance and potential application of the proposed design method