Planning to Minimize the Human Muscular Effort during Forceful Human-Robot Collaboration

This work addresses the problem of planning a robot configuration and grasp to position a shared object during forceful human-robot collaboration, such as a puncturing or a cutting task. Particularly, our goal is to find a robot configuration that positions the jointly manipulated object such that the muscular effort of the human, operating on the same object, is minimized while also ensuring the stability of the interaction for the robot. This raises three challenges. First, we predict the human muscular effort given a human-robot combined kinematic configuration and the interaction forces of a task. To do this, we perform task-space to muscle-space mapping for two different musculoskeletal models of the human arm. Second, we predict the human body kinematic configuration given a robot configuration and the resulting object pose in the workspace. To do this, we assume that the human prefers the body configuration that minimizes the muscular effort. And third, we ensure that, under the forces applied by the human, the robot grasp on the object is stable and the robot joint torques are within limits. Addressing these three challenges, we build a planner that, given a forceful task description, can output the robot grasp on an object and the robot configuration to position the shared object in space. We quantitatively analyze the performance of the planner and the validity of our assumptions. We conduct experiments with human subjects to measure their kinematic configurations, muscular activity, and force output during collaborative puncturing and cutting tasks. The results illustrate the effectiveness of our planner in reducing the human muscular load. For instance, for the puncturing task, our planner is able to reduce muscular load by 69.5\% compared to a user-based selection of object poses.

Análisis biomecánico en la actividad de recolección café en Colombia

During this case study, the risks of posture, strength and repetition associated with the activity of manual coffee harvesting were evaluated. The sample studied was 26 volunteers who participated in the completion of a Nordic questionnaire, 10 of these were evaluated using observational,and postural tools and 8 people participated in the biomechanical evaluation of postural and muscular load using electromyography and inertial. Seven muscles and two body segments of the upper limbs were evaluated. The goal was to assessthe working conditions of coffee manual harvesting considering ergonomics.The results of the discomfortsweremanifested in the Nordic questionnaire where it was evident that throughout a workday harvesting coffee, the discomfort focuses on the back, lower back, hands,and feet. In the muscle load evaluation was identified that the muscles with the highest activity were the Extensor, Flexor Carpi Ulnar and the trapezius.On average,their muscular activity was20% of their maximum volunteer contraction when performing the statistical analysis. -Tics showed a greater correlation in muscle activationbetween the Carpi Radial Extender and the trapezius. In the postural evaluation of the body segments from the coffee harvesters evaluated, it was identified that they only maintain between 10% and 20% in neutral ranges, so they are always in risky conditions. In conclusion, it is necessary to carry out interventions in the Colombian coffee sector not only because of these evaluated conditions but also for theconditions in theirwork environment.

Neck Muscular Load When Using a Smartphone While Sitting, Standing, and Walking

Objective Myoelectric activity of neck extensor muscles and head kinematic variables, when using a smartphone for one-handed browsing and two-handed texting while sitting, standing, and walking, were evaluated to compare the neck muscular load during these tasks and across the posture conditions. Background There has been limited research on the relation between head-down postures and the muscular load on the neck of smartphone users. Methods Twenty-one asymptomatic young users were asked to perform one-handed browsing and two-handed texting tasks in each of the posture conditions, and the myoelectric activities of the neck extensor muscles, head kinematic variables, and upper back posture were quantified. Results The muscle activation level when using a phone during walking was 21.2% and 41.7% higher than that of sitting and standing on average ( p < .01). Head vertical and angular accelerations were also significantly greater ( p < .01) for walking than for sitting and standing conditions. Between the two conducted tasks, participants flexed their heads more significantly ( p < .01) with higher activation of the neck extensor muscles ( p < .01) when texting as compared to when browsing. Conclusion Results indicate that two-handed texting while walking would be the most physically demanding scenario for neck musculature, and it might be attributable to the dynamics of the head while walking with the head facing downwards. Application These findings can be used to better understand the potential relation between smartphone use and the occurrence of neck musculoskeletal problems and to inform the users of the ergonomic risks of using smartphones while walking.

Neck muscle activation and head kinematics when using a smartphone while walking

Using a smartphone while walking has been common in countries with high smartphone penetration rates. While pedestrian safety issues have been studied frequently, research regarding ergonomics issues such as neck discomfort of smartphone use while walking has been limited. An experimental study was conducted to evaluate the neck muscular load of smartphone use while walking. Twenty-one asymptomatic young smartphone owners conducted one-handed browsing and two-handed texting while walking on a treadmill. Their neck muscle activation level, head and upper back posture were quantified. Compared to when walking upright without using a smartphone, the two smartphone-use tasks demanded 33.3% to 101.8% more activation of the neck extensor muscles. Mean head tilt angles (relative to upright standing) were 28.9° and 36.9° for the one-handed browsing and two-handed texting, respectively. Between the two smartphone tasks, the head tilt angle and the muscle activation level were significantly greater for texting than for browsing. Results indicated that conducting two-handed texting while walking would pose larger muscular load to the neck extensor muscles compared to when conducting one-handed browsing while walking due to the larger head tilt angle.