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

Systematic framework for performance evaluation of exoskeleton actuators

AbstractWearable devices, such as exoskeletons, are becoming increasingly common and are being used mainly for improving motility and daily life autonomy, rehabilitation purposes, and as industrial aids. There are many variables that must be optimized to create an efficient, smoothly operating device. The selection of a suitable actuator is one of these variables, and the actuators are usually sized after studying the kinematic and dynamic characteristics of the target task, combining information from motion tracking, inverse dynamics, and force plates. While this may be a good method for approximate sizing of actuators, a more detailed approach is necessary to fully understand actuator performance, control algorithms or sensing strategies, and their impact on weight, dynamic performance, energy consumption, complexity, and cost. This work describes a learning-based evaluation method to provide this more detailed analysis of an actuation system for ourXoTrunkexoskeleton. The study includes: (a) a real-world experimental setup to gather kinematics and dynamics data; (b) simulation of the actuation system focusing on motor performance and control strategy; (c) experimental validation of the simulation; and (d) testing in real scenarios. This study creates a systematic framework to analyze actuator performance and control algorithms to improve operation in the real scenario by replicating the kinematics and dynamics of the human–robot interaction. Implementation of this approach shows substantial improvement in the task-related performance when applied on a back-support exoskeleton during a walking task

Overview and challenges for controlling back-support exoskeletons

Exoskeletons were recently proposed to reduce the risk of musculoskeletal disorders for workers. To promote adoption of active exoskeletons in the workplace, control interfaces and strategies have to be designed that overcome practical problems. Open challenges regard sensors invasiveness and complexity, accurate user’s motion detection, and adaptability in adjusting the assistance to address different tasks and users. Focusing on back-support exoskeletons, different control interfaces and strategies are discussed that aim at automatically driving and modulating the assistance, according to the activity the user is performing

Back-Support Exoskeletons for Occupational Use: An Overview of Technological Advances and Trends

OCCUPATIONAL APPLICATIONSMany new occupational back-support exoskeletons have been developed in the past few years both as research prototypes and as commercial products. These devices are intended..

Towards standards for the evaluation of active back-support exoskeletons to assist lifting task

Back-support exoskeletons have been recently proposed to reduce the risk of injuries for workers performing repetitive lifting tasks. Appropriate standards for their evaluation do not exist, but their definition would promote large-scale adoption in workplaces. This paper presents relevant standards and evaluation metrics as applied to similar devices and discusses their applicability to back-support exoskeletons, with the final goal to propose a reference methodology

Towards design guidelines for physical interfaces on industrial exoskeletons: Overview on evaluation metrics

On exoskeletons, physical interfaces with the body are one of the key enabling component to promote user acceptance, comfort and force transmission efficiency. A structured design workflow is needed for any application-driven product, such as industrial exoskeletons. In this paper, we review objective and subjective evaluation metrics that can be applied to physical interfaces. These indexes can be evaluated to create an ordered list of requirements to guide their future design. Pressure magnitude, duration, distribution, direction and time to don and doff are relevant objective indexes related to interfaces. Pain, comfort and ease of operation are subjective indexes. We propose that collecting a suitable set of metrics will lay the foundation for effective design guideline for industrial exoskeletons