377 research outputs found
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
Design and Control of a Knee Exoskeleton for Assistance and Power Augmentation
Thanks to the technological advancements, assistive lower limb exoskeletons are moving from laboratory settings to daily life scenarios. This dissertation makes a contribution toward the development of assistive/power augmentation knee exoskeletons with an improved wearability, ergonomics and intuitive use. In particular, the design and the control of a novel knee exoskeleton system, the iT-Knee Bipedal System, is presented. It is composed by: a novel mechanism to transmit the assistance generated by the exoskeleton to the knee joint in a more ergonomic manner; a novel method that requires limited information to estimate online the torques experienced by the ankles, knees and hips of a person wearing the exoskeleton; a novel sensor system for shoes able to track the feet orientation and monitor their full contact wrench with the ground.
In particular, the iT-Knee exoskeleton, the main component of the aforementioned system, is introduced. It is a novel six degree of freedom knee exoskeleton module with under-actuated kinematics, able to assist the flexion/extension motion of the knee while all the other joint\u2019s movements are accommodated. Thanks to its mechanism, the system: solves the problem of the alignment between the joint of the user and the exoskeleton; it automatically adjusts to different users\u2019 size; reduces the undesired forces and torques exchanged between the attachment points of its structure and the user\u2019s skin.
From a control point of view, a novel approach to address difficulties arising in real life scenarios (i.e. noncyclic locomotion activity, unexpected terrain or unpredicted interactions with the surroundings) is presented. It is based on a method that estimates online the torques experienced by a person at his ankles, knees and hips with the major advantage that does not rely on any information of the user\u2019s upper body (i.e. pose, weight and center of mass location) or on any interaction of the user\u2019s upper body with the environment (i.e. payload handling or pushing and pulling task). This is achieved
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by monitoring the full contact wrench of the subject with the ground and applying an inverse dynamic approach to the lower body segments.
To track the full contact wrench between the subject\u2019s feet and the ground, a novel add on system for shoes has been developed. The iT-Shoe is adjustable to different user\u2019s size and accommodates the plantar flexion of the foot. It tracks the interactions and the orientation of the foot thanks to two 6axis Force/Torque sensors, developed in-house, with dedicated embedded MEMS IMUs placed at the toe and heel area.
Different tasks and ground conditions were tested to validate and highlight the potentiality of the proposed knee exoskeleton system. The experimental results obtained and the feedback collected confirm the validity of the research conducted toward the design of more ergonomic and intuitive to use exoskeletons
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
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