Wearable exoskeletons to reduce physical load at work
By Brian D. Lowe, PhD; Robert B. Dick, PhD, Captain USPHS (Ret.); Stephen Hudock, PhD, CSP; and Thomas Bobick, PhD
Robotic-like suits which provide powered assist and increase human strength may conjure thoughts of sci-fi and superhero film genres. But these wearable exoskeleton devices are now a reality and the market for their applications in the workplace is projected to increase significantly in the next five years. As with any technologic innovation some of the pros and cons and barriers to adoption are not completely understood. In this blog our objectives are to: (1) describe wearable exoskeletons in the context of workplace safety and health control strategies; (2) highlight current and projected trends related to industrial applications of these technologies; and (3) invite input from our stakeholders on workplace health and safety experiences, positive or negative, with these devices.
The wearable exoskeleton was defined by de Looze et al. (2015) as “…a wearable, external mechanical structure that enhances the power of a person. Exoskeletons can be classified as ‘active’ or ‘passive’. An active exoskeleton comprises one or more actuators that augments the human’s power and helps in actuating the human joints. …A strictly passive system does not use any type of actuator, but rather uses materials, springs or dampers with the ability to store energy harvested by human motion and to use this as required to support a posture or a motion.” Passive systems require no external power and use springs, elastic cords, or other resilient elements to provide either a restoring moment that unloads the low back muscles, or additional vertical lift force to augment arm and shoulder muscles when supporting tools or materials. More complex active exoskeleton systems use electric servo-motors and powered actuators on an external frame with joints matched to those of the worker. The actuators augment the joint torque of the wearer so he or she can handle external loads with less effort than in their unassisted capability. These devices are often portrayed as modern or futuristic technology; however, they have a long history as a rehabilitation/assistive technology. A U.S. patent (see sketch below) was awarded in 1890 for an “Apparatus for facilitating walking” (Yagn, 1890 US Patent).
From the standpoint of workplace health and safety, wearable exoskeleton devices may be beneficial in reducing musculoskeletal loads that are not otherwise abated by engineering process change. Lifting and handling of heavy materials and supporting heavy tools are contributors to fatigue and musculoskeletal disorders (MSDs) which are known to account for approximately 30% of lost time workplace injuries and illnesses. Liberty Mutual Insurance Company estimated the direct costs of injuries due to overexertion involving an outside source (from lifting, pushing, pulling, turning, throwing, or catching) to be $15.1 billion in 2012 – representing one quarter of the total workplace injury direct costs (Liberty Mutual, 2014).
The preferred approach to reducing exposure to musculoskeletal injury risk factors follows the hierarchy of controls in which the work would be redesigned to mitigate the risk through engineering controls or process change. Examples include reducing weights of tools or materials, or changing the layout of the work area to avoid body postures and manual forces that put workers at risk when handling heavy tools or materials. Recognizing that this is not always feasible, a less preferred approach is to provide equipment worn by the employee as personal protection. Wearable passive corsets, in the form of back belts or lifting belts, have been commercially available for years as a form of personal equipment purported to reduce back injury risk during lifting. A NIOSH review of back belt studies in the 1990s (“Workplace Use of Back Belts. Review and Recommendations ”) found insufficient evidence of their effectiveness in preventing injury to classify back belts as an effective form of PPE. In its 1994 summary NIOSH recommended that, in lieu of the back belt, “…The most effective way to prevent back injury is to redesign the work environment and work tasks to reduce the hazards of lifting.” That recommendation, addressing the effectiveness of a control strategy involving a wearable device, is similarly applicable to the wearable exoskeleton of today.
Regardless of their place on the control hierarchy, the market for industrial use of wearable exoskeletons is projected to increase. According to a recent market research report (WinterGreen, Research Inc., 2015) in 2016 the medical/rehabilitation applications will likely comprise 97% of the total market for wearable exoskeletons compared with only 3% for work-related/industrial applications. This report projects that within five years the industrial market share will equal that of the medical/rehabilitation. Market forecasts from this report suggest growth in the industrial market from $2.9 million in 2016 to $1.12 billion in 2021 – an average growth of 229% per year. Use in the Shipbuilding industry, now underway, represents a high market percentage initially, but greater increases in market share are projected in the Construction, Warehousing, and Manufacturing industries.
NIOSH has not reviewed evidence related to wearable exoskeletons in the prevention of workplace musculoskeletal injuries and illnesses. However, a recent literature review by de Looze et al. (2015) identified 40 scientific studies conducted in 1995-2014 that examined the effect of exoskeletons on reducing musculoskeletal loading. The majority of these studies evaluated these effects in a laboratory setting and several studies did report decreased back muscle activity and compressive forces in the lower spine. Because most of the studies have been in laboratory environments, more information on worker acceptance and adoption of the devices and long-term use in real work environments is needed.
A number of active Department of Defense research programs are exploring the extent to which exoskeleton technologies can augment physical capabilities in military applications. An example is the DARPA (Defense Advanced Research Projects Agency) Warrior Web program in which injury mitigation technologies are an objective in research and development. Systems are being evaluated by the Naval Surface Warfare Center and the Natick Soldier Research, Development and Engineering Center. These groups have identified safety-based criteria for exoskeleton systems and are beginning to study longer term effects of their use. Additionally, a European consortium, called the “Robo-Mate” project, comprising 12 partners from seven European countries, has been formally established to evaluate current regulations relating to exoskeletons and to outline potential risks to workers using exoskeletons in manual handling activities in industrial settings. The partners include end-users from automotive and dismantling industries, industrial robotics/technology developers, a robotics integrator, and ergonomics research groups.
Several exoskeleton developers have recently approached NIOSH program managers with demonstrations of exoskeleton technology transfer. These devices appear to have benefits in some specific industry applications for reducing injury risk factors. As their prices decrease we may anticipate more workplace interest in exoskeleton technologies. However, their occupational use should be evaluated for their potential benefits and potential competing risks before widespread workplace adoption. Some questions to address include, but are not limited to: