Stefano Toxiri

A wearable device for reducing spinal loads during lifting tasks: Biomechanics and design concepts

Manual material handling is one of the most frequent operations in industrial manufacturing processes. To avoid undesirable spinal loads, workers are often required to use external aid devices. This paper presents the analysis and design concept of a wearable assistive device for reducing the spinal loads during lifting tasks. A simplified model is used to compare the effects of two possible configurations for the device: the application of a force (a) parallel and (b) perpendicular to the spine. The model suggests that the perpendicular configuration (b) is preferable to (a). A subsequent numerical analysis suggests that the assistive device reduces substantially the spinal compression. This paper also discusses the design of a hardware prototype, that allows the operator to move mostly unhindered while performing lifting tasks. In particular the leg and torso movements on the sagittal plane are covered by the 90% and 60% respectively, while the movements on the frontal plane are fully covered.

Rationale, implementation and evaluation of assistive strategies for an active back-support exoskeleton

Active exoskeletons are potentially more effective and versatile than passive ones, but designing them poses a number of additional challenges. An important open challenge in the field is associated to the assistive strategy, by which the actuation forces are modulated to the user’s needs during the physical activity. This paper addresses this challenge on an active exoskeleton prototype aimed at reducing compressive low-back loads, associated to risk of musculoskeletal injury during manual material handling (i.e., repeatedly lifting objects). An analysis of the biomechanics of the physical task reveals two key factors that determine low-back loads. For each factor, a suitable control strategy for the exoskeleton is implemented. The first strategy is based on user posture and modulates the assistance to support the wearer’s own upper body. The second one adapts to the mass of the lifted object and is a practical implementation of electromyographic control. A third strategy is devised as a generalized combination of the first two. With these strategies, the proposed exoskeleton can quickly adjust to different task conditions (which makes it versatile compared to using multiple, task-specific, devices) as well as to individual preference (which promotes user acceptance). Additionally, the presented implementation is potentially applicable to more powerful exoskeletons, capable of generating larger forces. The different strategies are implemented on the exoskeleton and tested on 11 participants in an experiment reproducing the lifting task. The resulting data highlights that the strategies modulate the assistance as intended by design, i.e., they effectively adjust the commanded assistive torque during operation based on user posture and external mass. The experiment also provides evidence of significant reduction in muscular activity at the lumbar spine (around 30%) associated to using the exoskeleton. The reduction is well in line with previous literature and may be associated to lower risk of injury.

Exoshoe: A sensory system to measure foot pressure in industrial exoskeleton

This paper presents a novel sensor fusion methodology to dynamically detect weight variations and the position of an exoskeleton system. The proposed methodology is intended for tasks of lifting and lowering heavy weights with an industrial exoskeleton to substantially reduce spinal loads during these activities.

A Parallel-Elastic Actuator for a Torque-Controlled Back-Support Exoskeleton

A torque-controlled back-support exoskeleton to assist manual handling is presented. Its objective is to provide a significant portion of the forces necessary to carry out the physical task, thereby reducing the compressive loads on the lumbar spine and the associated risk of injury. The design rationale for a parallel-elastic actuator (PEA) is proposed to match the asymmetrical torque requirements associated with the target task. The parallel spring relaxes the maximum motor torque requirements, with substantial effects on the resulting torque-control performance. A formal analysis and experimental evaluation is presented with the goal of documenting the improvement in performance. To this end, the proposed PEA is compared with a more traditional configuration without the parallel spring. The formal analysis and experimental results highlight the importance of the motor inertia reflected through the gearbox and illustrate the improvements in the proposed measures of torque-control performance.

A Powered Low-Back Exoskeleton for Industrial Handling: Considerations on Controls

A powered low-back exoskeleton is being developed to support manual material handling in industry. Controlling this device poses several challenges. At the low-level, the actuation units need to be capable of large torque outputs as well as transparent interaction. At the high-level, the exoskeleton needs to modulate its assistance based on information acquired from the environment and the wearer, so as to maximise its beneficial effect. These challenges have great relevance to industrial applications, where complexity, cost and invasiveness are key to successful deployment. In describing the current progress in the development of the exoskeleton, an attempt is made to highlight and discuss these challenges and possible technical solutions.

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.

NEXT-GENERATION COLLABORATIVE ROBOTIC SYSTEMS FOR INDUSTRIAL SAFETY AND HEALTH

Occupational Safety and Health (OSH) is defined through three objectives: (i) maintenance of workers’ health; (ii) improvement of working environment and safety; and (iii) promotion of a work culture that supports health and safety. In industry, the most frequent threat to workers’ health is musculoskeletal disorders. Furthermore, even routine tasks in certain work environments (nuclear, construction, disaster response, marine, chemical, etc.) expose workers to extreme risks like explosions, contaminations, fires, confined spaces, debris, toxic gases, etc. The goal of this research is to design and develop advanced collaborative robotic technologies towards: (i) reducing workers’ physical stress and improving their health through a novel modular full-body wearable exoskeleton with arm, lower-back, and leg modules, allowing full motion dexterity; and (ii) avoiding hazard-prone worker environments and improving safety through a new collaborative master-slave teleoperation system consisting of: (a) a hydraulicallydriven, quadruped field robot with a robotic manipulator arm for operation in hazardous environments; (b) a hand exoskeleton master device for teleoperation control. The article presents the current status of development of these technologies. Preliminary validation of the exoskeleton shows reductions in muscular efforts of up to 30% for the lower back. For the master-slave collaborative system, (a) the Hydraulic Quadruped robot prototypes can traverse rough environments through capabilities that include stair climbing, walking over obstacles, omni-directional trotting with step reflexes, running, jumping, and self-righting; (b) the 7 degrees-of-freedom (DOF) manipulator arm allows object manipulation in a large workspace with dexterous grasping of up to 160 N of payload; and (c) the novel HEXOTRAC 3-digit hand exoskeleton provides high-resolution tracking of fingers and provides force feedback for intuitive bilateral teleoperation of robotic manipulators. These next-generation industrial exoskeletons and collaborative teleoperation systems can address the emerging challenges in industrial workers’ health and safety.

Actuation Requirements for Assistive Exoskeletons: Exploiting Knowledge of Task Dynamics

When selecting actuators for assistive exoskeletons, designers face contrasting requirements. Overdimensioned actuators have drawbacks that compromise their effectiveness in the target application (e.g. performance, weight, comfort). In some cases, the requirements on the powered actuator can be relaxed exploiting the contribution of an elastic element acting in mechanical parallel. This contribution considers one such case and describes an approach to fit the actuation requirements closely to the task dynamics, thereby mitigating the drawbacks of overdimensioned actuators.

Beyond Robo-Mate: Towards the Next Generation of Industrial Exoskeletons in Europe

The Robo-Mate project developed industrial exoskeletons to reduce the risk of physical injury associated to manual material handling tasks. Prototypes targeting different body areas were evaluated for their effectiveness but also for their applicability and usability in the field. Encouraging evidence of their effectiveness and informative feedback from the field have driven further research and development. This has additionally led the initiation of a new collaborative project, which aims at continuing technical advancements as well as at promoting the translation to diverse areas of application.

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.