Posts Tagged Finite Element Analysis

[Abstract] A soft robotic glove for hand motion assistance


Soft robotic devices have the potential to be widely used in daily lives for their inherent compliance and adaptability, which result in high safety under unexpected situations. System complexity and requirements are much lower, comparing with conventional rigid-bodied robotic devices, which also result in significantly lower costs. This paper presents a robotic glove by utilizing soft artificial muscles providing redundant degrees of freedom (DOFs) to generate both flexion and extension hand motions for daily grasping and manipulation tasks. Different with the existing devices, to minimize the weight applied to the user’s hands, pneumatic soft actuators were located on the fore arm and drive each finger via cable-transmission mechanisms. This actuation mechanism brings extra adaptability, motion smoothness, and user safety to the system. This design makes wearable robotic gloves more light-weight and user-friendly. Both theoretical and experimental analyses were conducted to explore the mechanical properties of pneumatic soft actuators. In addition, the fingertip trajectories were analyzed using Finite Element Methods, and a series of experiments were conducted evaluating both the technical and practical performances of the proposed glove.


I. Introduction

Glove-type wearable robotic devices are developed to assist people with impaired hand functions both in their activities of daily living (ADLs) and in rehabilitation [1]–[12]. Most of such wearable robotic devices generate hand movements with linkage systems actuated by electrical motors which usually are heavy and inconvenient for using. Moreover, because of the human hand variation, most wearable robotic devices require customization in order to fulfill the geometrical fitting requirements between the exoskeleton device and the human hand joints. Approximating the high dexterity of human hands usually requires high complexity in both the mechanical and controller structures of the robotic systems, and hence also results in high costs for most users.

via A soft robotic glove for hand motion assistance – IEEE Conference Publication

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[Abstract+References] Finite element analysis of the wrist in stroke patients: the effects of hand grip.


The provision of the most suitable rehabilitation treatment for stroke patient remains an ongoing challenge for clinicians. Fully understanding the pathomechanics of the upper limb will allow doctors to assist patients with physiotherapy treatment that will aid in full arm recovery. A biomechanical study was therefore conducted using the finite element (FE) method. A three-dimensional (3D) model of the human wrist was reconstructed using computed tomography (CT)-scanned images. A stroke model was constructed based on pathological problems, i.e. bone density reductions, cartilage wane, and spasticity. The cartilages were reconstructed as per the articulation shapes in the joint, while the ligaments were modelled using linear links. The hand grip condition was mimicked, and the resulting biomechanical characteristics of the stroke and healthy models were compared. Due to the lower thickness of the cartilages, the stroke model reported a higher contact pressure (305 MPa), specifically at the MC1-trapezium. Contrarily, a healthy model reported a contact pressure of 228 MPa. In the context of wrist extension and displacement, the stroke model (0.68° and 5.54 mm, respectively) reported a lower magnitude than the healthy model (0.98° and 9.43 mm, respectively), which agrees with previously reported works. It was therefore concluded that clinicians should take extra care in rehabilitation treatment of wrist movement in order to prevent the occurrence of other complications.

Graphical abstract


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[THESIS] Design of Customized Rehabilitation Devices and Bench Testing System – Full Text PDF


Off-the-shelf rehabilitation devices are currently prescribed to assist patients with stroke. Current fabrication processes of custom-made rehabilitation devices are time consuming and laborious. The process could be only performed by skilled therapists. In addition, quantitative assessment of mechanical properties is crucial in the design of customized rehabilitation devices. By the design and the real time implementation of a 3D printed hand exoskeleton and a biomimetic testbed for AnkleFoot Orthoses (AFOs), the improved digitalized methodologies of design and bench testing systems for customized rehabilitation devices were presented in this study.

A customized 3D printed hand exoskeleton (the EXCELSIOR) was developed and prototyped to assist stroke patients for finger extension exercises. 3D printing was combined with 3D scanning to create a custom-fit clamp. Compliant finger elements were designed and optimized utilizing Finite Element Analysis. Embedded strain gauges were applied to measure angular positions of the finger joints. In addition, a novel biomimetic testbed was designed to perform stiffness measurement and functional analysis for AFOs.

A biomimetic footplate was designed to adjust pivot centers for the metatarsophalangeal (MTP) joint and the ankle joint according to the patient specific anatomy. Feedback control systems were developed and real time implemented to perform AFO stiffness measurement. An impedance control system was developed and real time implemented to simulate the kinematics of the human ankle for further functional analysis in gait. Real time implementation of the hand exoskeleton and AFO testbed proved the concepts of the design and the testing for customized rehabilitation devices.

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