Biomechanical Analysis of Stoop and Free-Style Squat Lifting and Lowering with a Generic Back-Support Exoskeleton Model

Musculoskeletal disorders (MSDs) induced by industrial manual handling tasks are a major issue for workers and companies. As flexible ergonomic solutions, occupational exoskeletons can decrease critically high body stress in situations of awkward postures and motions. Biomechanical models with detailed anthropometrics and motions help us to acquire a comprehension of person- and application-specifics by considering the intended and unintended effects, which is crucial for effective implementation. In the present model-based analysis, a generic back-support exoskeleton model was introduced and applied to the motion data of one male subject performing symmetric and asymmetric dynamic manual handling tasks. Different support modes were implemented with this model, including support profiles typical of passive and active systems and an unconstrained optimal support mode used for reference to compare and quantify their biomechanical effects. The conducted simulations indicate that there is a high potential to decrease the peak compression forces in L4/L5 during the investigated heavy loaded tasks for all motion sequences and exoskeleton support modes (mean reduction of 13.3% without the optimal support mode). In particular, asymmetric motions (mean reduction of 14.7%) can be relieved more than symmetric ones (mean reduction of 11.9%) by the exoskeleton support modes without the optimal assistance. The analysis of metabolic energy consumption indicates a high dependency on lifting techniques for the effectiveness of the exoskeleton support. While the exoskeleton support substantially reduces the metabolic cost for the free-squat motions, a slightly higher energy consumption was found for the symmetric stoop motion technique with the active and optimal support mode

Rapid response to the M_w 4.9 earthquake of November 11, 2019 in Le Teil, Lower Rhône Valley, France

On November 11, 2019, a Mw 4.9 earthquake hit the region close to Montelimar (lower Rhône Valley, France), on the eastern margin of the Massif Central close to the external part of the Alps. Occuring in a moderate seismicity area, this earthquake is remarkable for its very shallow focal depth (between 1 and 3 km), its magnitude, and the moderate to large damages it produced in several villages. InSAR interferograms indicated a shallow rupture about 4 km long reaching the surface and the reactivation of the ancient NE-SW La Rouviere normal fault in reverse faulting in agreement with the present-day E-W compressional tectonics. The peculiarity of this earthquake together with a poor coverage of the epicentral region by permanent seismological and geodetic stations triggered the mobilisation of the French post-seismic unit and the broad French scientific community from various institutions, with the deployment of geophysical instruments (seismological and geodesic stations), geological field surveys, and field evaluation of the intensity of the earthquake. Within 7 days after the mainshock, 47 seismological stations were deployed in the epicentral area to improve the Le Teil aftershocks locations relative to the French permanent seismological network (RESIF), monitor the temporal and spatial evolution of microearthquakes close to the fault plane and temporal evolution of the seismic response of 3 damaged historical buildings, and to study suspected site effects and their influence in the distribution of seismic damage. This seismological dataset, completed by data owned by different institutions, was integrated in a homogeneous archive and distributed through FDSN web services by the RESIF data center. This dataset, together with observations of surface rupture evidences, geologic, geodetic and satellite data, will help to unravel the causes and rupture mechanism of this earthquake, and contribute to account in seismic hazard assessment for earthquakes along the major regional Cévenne fault system in a context of present-day compressional tectonics

脚負荷情報に基づく脚相調整を用いた四脚動歩行の生成と安定化

Regarding the issue of legged locomotion stabilization, it can be pointed out that, atlow speeds, since gravity is dominant, posture control using sensory information suchas ground reaction force or vestibular information is predominant. On the other hand,at high speeds, since the influence of the inertial forces is dominant, rhythmic motioncontrol to construct a limit cycle becomes primordial. Consequently, legged locomotioncontrollers should integrate both posture control and rhythmic motion control to be ableto cover the whole range of locomotion speeds.This thesis considers the use of sensory information related to leg loading (i.e. theload supported by the leg) in a CPG type controller to generate stable quadrupedaldynamic walk. Leg loading information is used at the individual leg level to regulate thetransitions between the stance and the swing phases. Accordingly, the CPG activity isadjusted of via phase modulations, i.e. modulations of the relative durations of the stanceand swing phases of the stepping motion in each leg. This study concentrates on therole of the regulation of stance-to-swing transition using leg loading information. Usingdynamics simulations, it investigates the contribution of this mechanism to rhythmicmotion control and posture control, in the range from low- to medium-speed walking.This issue is investigated in the case of two-dimensional stepping motions and threedimensionalquadrupedal dynamic walk. In both cases, a sensor-dependent CPG isused, where phase transitions in each leg controller is controlled using leg loading information.Swing-to-stance and stance-to-swing transitions are respectively triggeredwhen the touchdown event is detected and when leg loading becomes smaller than agiven threshold.Generation of two-dimensional stepping motions is achieved with musculoskeletal modelsfaithful to the cat anatomy. For the hind legs, a preexistent model is used, whilean original model of the forelegs is developed. A neural leg controller architecture, ableto induce stepping motions of a leg at various speeds, is proposed. Using a pair ofleg controllers, stepping patterns at constant speed are generated with the hind legsmodel and the forelegs model separately, by replacing the not-actuated pair of legs bya wheeled support. As a result of the phase modulations based on leg loading information,stable alternate stepping coordination of the legs emerges, even when the two legcontrollers are independent. Next, the issue of speed modulation is considered with thehind legs model. The leg coordination maintains in the whole range of speeds considered and adaptations of walking patterns according to the speed are characterized. Strikingsimilarities with the adaptations taking place during real cat locomotion are found, reinforcingthe hypothesis that, in animals, stance-to-swing transition is mainly regulatedusing sensory signals related to leg unloading.In order to facilitate the study of the action of the phase modulations in the threedimensionalcase, a traditional robotic approach, combining trajectory generation andlocal PD control, is used instead of a muscular model to generate the motor patterns.Using four independent controllers, stable quadrupedal dynamic walk is generated in abroad range of cyclic periods and speeds. Phase modulations using leg loading informationcontribute to the emergence of left-right alternate stepping coordination of the legs.The phase difference between ipsilateral legs is adjusted by setting appropriately twocategories of the leg controllers parameters: the vertical coordinate of nominal touchdownposition of the feet and the PD control gains of the ankle and knee joints. Thestability of the walking patterns is assessed by subjecting the model to lateral perturbations.In most of the application timings, the phase modulations adjust the rhythmicmotion of the legs to stabilize the body rolling motion against the disturbance. However,when the perturbation results in a sufficient decrease of the rolling motion amplitude onone side, the foreleg on the other side cannot swing and the leg coordination is severelydisturbed. Hence, a leg coordination mechanism, promoting stance-to-swing transitionin the foreleg when the ipsilateral hind leg is swinging, is added to the previous architectureto improve the performances. With the additional coordination mechanism,the control system realizes good performances against the lateral perturbations for allthe timings of applications. Moreover, it is able to tackle terrain irregularities (such assteps and slopes) while stabilizing the posture. Hence, basic integration of posture controland rhythmic motion control is demonstrated with a simple and distributed controlarchitecture grounded on phase modulations using leg loading information.電気通信大学200

Kreativer Baukasten für nachgiebige Robotersysteme

Nachgiebige kleine Robotersysteme lassen sich sicher und flexibel in verschiedensten Umgebungen einsetzen. Ein Baukastensystem, das im Rahmen des EU-Projekts Myorobotics unter Beteiligung des Fraunhofer-IPA entwickelt wurde, vereinfacht und beschleunigt Entwicklung, Aufbau und Erforschung dieserneu en Art von Robotersystemen

Musculoskeletal robots and wearable devices on the basis of cable-driven actuators

Cable-driven actuators are a promising alternative for future kinematic designs, particularly when the combination of lightweight, high strength, compact designs and dynamic motions are required. Powered exoskeletons or wearable robots are typical candidates of these novel actuators as has been demonstrated by previous research. This chapter focusses on current work in cable-driven actuators, introduces the Myorobotics toolkit for supporting the engineer to build up prototypes from cable-actuates modules and gives an outlook to using cable-driven actuation for advanced wearable robots

Recovery at sea of abandoned, lost or discarded drifting fish aggregating devices

Tropical tuna purse-seine fishing vessels contribute to abandoned, lost or discarded (ALD) fishing equipment by deploying large numbers of drifting Fish Aggregating Devices (dFADs). Here we analysed more than 80,000 dFAD trajectories (56,263 tracking buoys) in the Indian and Atlantic oceans from 2012 to 2018. We found that more than 40% of dFAD trajectories ultimately drifted away from fishing grounds, becoming ALD. About 20% of these lost dFADs passed within 50 km of major ports, indicating that port-based programmes could be effective in collecting ALD dFADs at sea. We also identified areas within the fishing grounds where most dFADs exit and where high-seas recovery could be valuable. For example, most dFADs leaving Indian Ocean fishing grounds along their eastern border at ~70° E, particularly in October–December, do not return to fishing grounds. Despite considerable logistical challenges, at-sea dFAD recovery offers promising options for reducing the ecological footprints of purse-seine fisheries.