Kinematic and kinetic functional requirements for industrial exoskeletons for lifting tasks and overhead lifting.

The aim of this study was to sample human kinematics and kinetics during simulated tasks to aid the design of industrial exoskeletons. Twelve participants performed two dynamic tasks; a simulated lifting task and an overhead lifting task. Based on the current data, to completely assist a worker with lifting loads up to 15 kg, hip actuators would need to supply up to 111 Nm of extensor torque at speeds up to 139°/s of extension velocity and 26°/s of flexion velocity. The actuators should allow the hip to extend to 11° and flex to 95°, and supply a power of 212 W. To completely assist workers lifting a 3 kg load overhead, actuators assisting shoulder flexion would need to supply up to 20 Nm of flexor torque at speeds up to 21°/s of extension velocity and 116°/s of flexion velocity. The actuators should also allow 67° of shoulder flexion and supply a power of 27 W. Practitioner summary: There is increasing interest in developing exoskeletons for industrial applications. This study details relevant kinetic and kinematic exposures for common production tasks, which can be used to inform functional requirements of industrial exoskeletons.AbbreviationsWMSD(s)work-related musculoskeletal disordersMMHmanual materials handlingDOFdegrees of freedomBLEEXBerkeley lower extremity exoskeletonLED(s)light emitting diodeRelrelativeHighlightsThis study sampled joint kinematic and kinetic activity to inform design of industrial exoskeletons.The study presents sample values to two types of common industrial tasks across the major joints as are often assisted.We also indicate considerations on which joints should be considered to be actively assisted.

Elongation of the surface of the spine during lifting and lowering, and implications for design of an upper body industrial exoskeleton.

The aim of this study was to assess the elongation of the skin surface of the spine for simulated industrial lifting and lowering tasks to aid the design of industrial exoskeletons worn on the back. Eighteen male participants lifted and lowered a box of varying loads (5 kg, 10 kg, 15 kg) using three techniques (squat, semi-squat, stooped) from the ground to a table. Motion capture sensors attached to the spine from C7 to S1 measured movement. Stoop lifting involved significantly more elongation (mean 71.1 mm; margin of error ±6.9) than squat lifting (mean 36.8 mm; margin of error ±6.9). Load and Task (lift vs. lower) did not have a significant effect on elongation. Elongation of the skin surface of the lumbar spine was greater than for the thoracic spine. These data detail example levels of elongation of the skin surface of the spine, which should be considered in upper body wearable industrial exoskeleton design. Further, exoskeleton design should take into account that the skin surface of the lumbar spine involves greater elongation than the skin surface of the thoracic spine during deep lifting.

Assessment of an active industrial exoskeleton to aid dynamic lifting and lowering manual handling tasks.

The aim of this study was to evaluate the effect of an industrial exoskeleton on muscle activity, perceived musculoskeletal effort, measured and perceived contact pressure at the trunk, thighs and shoulders, and subjective usability for simple sagittal plane lifting and lowering conditions. Twelve male participants lifted and lowered a box of 7.5 kg and 15 kg, respectively, from mid-shin height to waist height, five times, both with and without the exoskeleton. The device significantly reduced muscle activity of the Erector Spinae (12%-15%) and Biceps Femoris (5%). Ratings of perceived musculoskeletal effort in the trunk region were significantly less with the device (9.5%-11.4%). The measured contact pressure was highest on the trunk (91.7 kPa-93.8 kPa) and least on shoulders (47.6 kPa-51.7 kPa), whereas pressure was perceived highest on the thighs (35-44% of Max LPP). Six of the users rated the device usability as acceptable. The exoskeleton reduced musculoskeletal loading on the lower back and assisted with hip extensor torque during lifting and lowering. Contact pressures fell below the Pain Pressure Threshold. Perceived pressure was not exceptionally high, but sufficiently high to cause discomfort if used for long durations.

Evaluation of a passive exoskeleton for static upper limb activities.

The aim of this study was to evaluate the effect of a passive upper body exoskeleton on muscle activity, perceived musculoskeletal effort, local perceived pressure and subjective usability for a static overhead task. Eight participants (4 male, 4 female) held a load (0 kg and 2 kg) three times overhead for a duration of 30 s each, both with and without the exoskeleton. Muscle activity was significantly reduced for the Biceps Brachii (49%) and Medial Deltoid (62%) by the device for the 2 kg load. Perceived effort of the arms was significantly lower with the device for the 2 kg load (41%). The device did not have a significant effect on trunk or leg muscle activity (for the 2 kg load) or perceived effort. Local perceived pressure was rated below 2 (low pressure levels) for all contact areas assessed. Half of the participants rated the device usability as acceptable. The exoskeleton reduced muscle activity and perceived effort by the arms, and had no significant negative effect on the trunk and lower body with regards to muscle activity, perceived effort and localised discomfort.