Design and Characterization of a Low-Cost and Efficient Torsional Spring for ES-RSEA

The design of torsional springs for series elastic actuators (SEAs) is challenging, especially when balancing good stiffness characteristics and efficient torque robustness. This study focuses on the design of a lightweight, low-cost, and compact torsional spring for use in the energy storage-rotary series elastic actuator (ES-RSEA) of a lumbar support exoskeleton. The exoskeleton is used as an assistive device to prevent lower back injuries. The torsion spring was designed following design for manufacturability (DFM) principles, focusing on minimal space and weight. The design process involved determining the potential topology and optimizing the selected topology parameters through the finite element method (FEM) to reduce equivalent stress. The prototype was made using a waterjet cutting process with a low-cost material (AISI-4140-alloy) and tested using a custom-made test rig. The results showed that the torsion spring had a linear torque-displacement relationship with 99% linearity, and the deviation between FEM simulation and experimental measurements was less than 2%. The torsion spring has a maximum torque capacity of 45.7 Nm and a 440 Nm/rad stiffness. The proposed torsion spring is a promising option for lumbar support exoskeletons and similar applications requiring low stiffness, low weight-to-torque ratio, and cost-effectiveness

An active back-support exoskeleton to reduce spinal loads: actuation and control strategies

Wearable exoskeletons promise to make an impact on many people by substituting or complementing human capabilities. There has been increasing interest in using these devices to reduce the physical loads and the risk of musculoskeletal disorders for industrial workers. The interest is reflected by a rapidly expanding landscape of research prototypes as well as commercially available solutions. The potential of active exoskeletons to reduce the physical loads is considered to be greater compared to passive ones, but their present use and diffusion is still limited. This thesis aims at exploring and addressing two key technological challenges to advance the development of active exoskeletons, namely actuators and control strategies, with focus on their adoption outside laboratory settings and in real-life applications. The research work is specifically applied to a back-support exoskeleton designed to assist repeated manual handling of heavy objects. However, an attempt is made to generalise the findings to a broader range of applications. Actuators are the defining component of active exoskeletons. The greater the required forces and performance, the heavier and more expensive actuators become. The design rationale for a parallel-elastic actuator (PEA) is proposed to make better use of the motor operating range in the target task, characterized by asymmetrical torque requirements (i.e. large static loads). This leads to improved dynamic performance as captured by the proposed simplified model and measures, which are associated to user comfort and are thus considered to promote user acceptance in the workplace. The superior versatility of active exoskeletons lies in their potential to adapt to varying task conditions and to implement different assistive strategies for different tasks. In this respect, an open challenge is represented by the compromise between minimally obtrusive, cost-effective hardware interfaces and extracting meaningful information on user intent resulting in intuitive use. This thesis attempts to exploit the versatility of the active back-support exoskeleton by exploring the implementation of different assistive strategies. The strategies use combinations of user posture and muscular activity to modulate the forces generated by the exoskeleton. The adoption of exoskeletons in the workplace is encouraged first of all by evidence of their physical effectiveness. The thesis thus complements the core contributions with a description of the methods for the biomechanical validation. The preliminary findings are in line with previous literature on comparable devices and encourage further work on the technical development as well as on more accurate and specific validation

A method to quantify the reduction of back and hip muscle fatigue of lift-support exoskeletons

Cumulative back muscle fatigue plays a role in the occurrence of low-back injuries in occupations that require repetitive lifting of heavy loads and working in forward leaning postures. Lift-support exoskeletons have the potential to reduce back and hip muscle activity, thereby delaying the onset of fatigue in these muscles. Therefore, exoskeletons are being considered a potentially important tool to further reduce workload-related injuries. However, today no standards have been established on how to benchmark the support level of lift-support exoskeletons. This work proposes an experimental protocol to quantify the support level of a lift-support exoskeletons on instant changes in muscle activity and fatigue development while maintaining a static forward leaning posture. It then applies the protocol to experimentally assess the effect of the support provided by a commercially available lift-support exoskeleton, the LiftSuit 2.0 (Auxivo AG, Schwerzenbach, Switzerland), on the user. In a sample of 14 participants, the amplitude of the muscle activity of the back muscles and hip muscles was significantly reduced. Wearing the exoskeleton significantly reduced the amount of fatigue developed during the task . Changes in muscle fatigue can be objectively recorded and correlated with relevant changes for exoskeleton users: the time a task can be performed and perceived low-back fatigue. Thus, including such measures of fatigue in standardized benchmarking procedures will help quantify the benefits of exoskeletons for occupational use

Rehabilitation Engineering

Population ageing has major consequences and implications in all areas of our daily life as well as other important aspects, such as economic growth, savings, investment and consumption, labour markets, pensions, property and care from one generation to another. Additionally, health and related care, family composition and life-style, housing and migration are also affected. Given the rapid increase in the aging of the population and the further increase that is expected in the coming years, an important problem that has to be faced is the corresponding increase in chronic illness, disabilities, and loss of functional independence endemic to the elderly (WHO 2008). For this reason, novel methods of rehabilitation and care management are urgently needed. This book covers many rehabilitation support systems and robots developed for upper limbs, lower limbs as well as visually impaired condition. Other than upper limbs, the lower limb research works are also discussed like motorized foot rest for electric powered wheelchair and standing assistance device

Design methodology of an active back-support exoskeleton with adaptable backbone-based kinematics

Abstract Manual labor is still strongly present in many industrial contexts (such as aerospace industry). Such operations commonly involve onerous tasks requiring to work in non-ergonomic conditions and to manipulate heavy parts. As a result, work-related musculoskeletal disorders are a major problem to tackle in workplace. In particular, back is one of the most affected regions. To solve such issue, many efforts have been made in the design and control of exoskeleton devices, relieving the human from the task load. Besides upper limbs and lower limbs exoskeletons, back-support exoskeletons have been also investigated, proposing both passive and active solutions. While passive solutions cannot empower the human's capabilities, common active devices are rigid, without the possibility to track the human's spine kinematics while executing the task. The here proposed paper describes a methodology to design an active back-support exoskeleton with backbone-based kinematics. On the basis of the (easily implementable) scissor hinge mechanism, a one-degree of freedom device has been designed. In particular, the resulting device allows tracking the motion of a reference vertebra, i.e., the vertebrae in the correspondence of the connection between the scissor hinge mechanism and the back of the operator. Therefore, the proposed device is capable to adapt to the human posture, guaranteeing the support while relieving the person from the task load. In addition, the proposed mechanism can be easily optimized and realized for different subjects, involving a subject-based design procedure, making possible to adapt its kinematics to track the spine motion of the specific user. A prototype of the proposed device has been 3D-printed to show the achieved kinematics. Preliminary tests for discomfort evaluation show the potential of the proposed methodology, foreseeing extensive subjects-based optimization, realization and testing of the device

Preventing and monitoring work-related diseases in firefighters: a literature review on sensor-based systems and future perspectives in robotic devices.

: In recent years, the necessity to prevent work-related diseases has led to the use of sensor based systems to measure important features during working activities. This topic achieved great popularity especially in hazardous and demanding activities such as those required of firefighters. Among feasible sensor systems, wearable sensors revealed their advantages in terms of possibility to conduct measures in real conditions and without influencing the movements of workers. In addition, the advent of robotics can be also exploited in order to reduce work-related disorders. The present literature review aims at providing an overview of sensor-based systems used to monitor physiological and physical parameters in firefighters during real activities, as well as to offer ideas for understanding the potentialities of exoskeletons and assistive devices