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.

The Electrical Activity of the Orbicularis Oris Muscle in Children with Down Syndrome—A Preliminary Study

The aim of this study was to assess the electrical activity of the superior (SOO) and inferior (IOO) orbicularis oris muscles in children with Down syndrome (DS) and in children without DS. After applying the inclusion and exclusion criteria, 30 subjects were eligible to participate in the later stages of the research—15 subjects with DS (mean age 10.1 ± 1.1) and 15 healthy controls (mean age 9.8 ± 1.0). The electrical potentials of the SOO and IOO muscles were recorded using a DAB-Bluetooth electromyography machine (Zebris Medical GmbH, Germany) during the following tasks: At clinical rest, saliva swallowing, lip protrusion, lip compression, and production of the syllable/pa/. The Mann–Whitney U test was conducted to compare the study results between the groups. An analysis of the electromyographical (EMG) recordings showed that the electrical activity of the orbicularis oris muscle in children with DS and lip incompetence was significantly higher compared to healthy children during saliva swallowing, lip compression, and when producing the syllable/pa/, and this may suggest greater muscular effort due to the need to seal the lips during these functional conditions.

Pattern Recognition: Effectiveness of Teaching Girls Aged 15 Acrobatic Exercises

The purpose of the study was to determine the impact of exercise modes on the effectiveness of teaching girls aged 15 a cartwheel. Materials and methods. The study participants were 20 girls aged 15. The children and their parents were fully informed about all the features of the study and gave their consent to participate in the experiment. To solve the tasks set, the following research methods were used: study and analysis of scientific and methodological literature; pedagogical observation, timing of training tasks; pedagogical experiment, methods of mathematical statistics, discriminant analysis. Results. The analysis of averages shows that statistically significant differences in the number of repetitions are observed in performing series of training tasks 1, 2, and 4 (p < 0.05). The girls aged 15 who use the first mode (6 sets 1 time each with a rest interval of 60 s) need fewer repetitions to master the movements of the first (exercises to develop motor abilities) and the second (exercises to master starting and ending positions) series of tasks. The girls who use the second mode (6 sets 2 times each with a rest interval of 60 s) need fewer repetitions to master the movements of the fourth series of tasks (ability to assess movements in space, by time and muscular effort) (p < 0.05). Conclusions. Discriminant analysis made it possible to determine the impact of the number of repetitions on the effectiveness of developing the cartwheel skill in girls aged 15. During motor skills development, both the first and the second variants of exercise modes and rest intervals can be used. For series of tasks 1 and 2, it is advisable to use 6 sets 1 time each with a rest interval of 60 s; for series of tasks 3, 5, and 6 – 6 sets 1 time each with a rest interval of 60 s or 6 sets 2 times each with a rest interval of 60 s; for series 4 – 6 sets 2 times each with a rest interval of 60 s.

A longer stance is more stable for a standing horse

What is the effect of posture on the stability of a standing horse? We address this with a 2D quasi-static model. The model horse has 3 rigid parts: a trunk, a massless fore-limb and a massless rear limb, and has hinges at the shoulder, hip, and hooves. The postural parameter lg is the distance between the hooves. For a given lg, statics finds an equilibrium configuration which, with no muscle stabilization, is unstable. To measure the neuro-muscular effort to maintain stability, we add springs at the shoulder and hip; the larger the springs needed to stabilize the model, the more the neuro-muscular effort needed for stabilization. We find that a canted-in posture (small lg), observed in some pathological domestic horses, requires about twice the spring stiffness (representing twice the neuromuscular effort) as is needed for postures with vertical or slightly splayed-out (large lg ) legs.

Transtibial limb loss does not increase metabolic cost in three-dimensional computer simulations of human walking

Loss of a lower limb below the knee, i.e., transtibial limb loss, and subsequently walking with a prosthesis, is generally thought to increase the metabolic cost of walking vs. able-bodied controls. However, high-functioning individuals with limb loss such as military service members often walk with the same metabolic cost as controls. Here we used a 3-D computer model and optimal control simulation approach to test the hypothesis that transtibial limb loss in and of itself causes an increase in metabolic cost of walking. We first generated N = 36 simulations of walking at 1.45 m/s using a “pre-limb loss” model, with two intact biological legs, that minimized deviations from able-bodied experimental walking mechanics with minimum muscular effort. We then repeated these simulations using a “post-limb loss” model, with the right leg’s ankle muscles and joints replaced with a simple model of a passive transtibial prosthesis. No other changes were made to the post-limb loss model’s remaining muscles or musculoskeletal parameters compared to the pre-limb loss case. Post-limb loss, the gait deviations on average increased by only 0.17 standard deviations from the experimental means, and metabolic cost did not increase (3.58 ± 0.10 J/m/kg pre-limb loss vs. 3.59 ± 0.12 J/m/kg post-limb loss, p = 0.65). The results suggest that transtibial limb loss does not directly lead to an increase in metabolic cost, even when deviations from able-bodied gait mechanics are minimized. High metabolic costs observed in individuals with transtibial limb loss may be due to secondary changes in strength or general fitness after limb loss, modifiable prosthesis issues, or to prioritization of factors that affect locomotor control other than gait deviations and muscular effort.

The quadrupedal walking gait of the olive baboon, Papio anubis: an exploratory study integrating kinematics and EMG

ABSTRACT Primates exhibit unusual quadrupedal features (e.g. diagonal gaits, compliant walk) compared with other quadrupedal mammals. Their origin and diversification in arboreal habitats have certainly shaped the mechanics of their walking pattern to meet the functional requirements necessary for balance control in unstable and discontinuous environments. In turn, the requirements for mechanical stability probably conflict with mechanical energy exchange. In order to investigate these aspects, we conducted an integrative study on quadrupedal walking in the olive baboon (Papio anubis) at the Primatology station of the CNRS in France. Based on kinematics, we describe the centre of mass mechanics of the normal quadrupedal gait performed on the ground, as well as in different gait and substrate contexts. In addition, we studied the muscular activity of six hindlimb muscles using non-invasive surface probes. Our results show that baboons can rely on an inverted pendulum-like exchange of energy (57% on average, with a maximal observed value of 84%) when walking slowly (&lt;0.9 m s−1) with a tight limb phase (∼55%) on the ground using diagonal sequence gaits. In this context, the muscular activity is similar to that of other quadrupedal mammals, thus reflecting the primary functions of the muscles for limb movement and support. In contrast, walking on a suspended branch generates kinematic and muscular adjustments to ensure better control and to maintain stability. Finally, walking using the lateral sequence gait increases muscular effort and reduces the potential for high recovery rates. The present exploratory study thus supports the assumption that primates are able to make use of an inverted pendulum mechanism on the ground using a diagonal walking gait, yet a different footfall pattern and substrate appear to influence muscular effort and efficiency.

Does the Effect of Stereotypes in Older People Depend Upon Task Intensity?

This study examined the effect of negative and positive stereotypes on the strength produced by older adults at different perceived effort intensities, reflecting different levels of task difficulty. Fifty older women were randomly assigned to a positive stereotype, a negative stereotype, or a control condition. Before (T1) and after (T2) the stereotype manipulation, they were asked to perform a voluntary isometric contraction at a level of muscular effort that corresponded to four perceived effort intensities (“easy,” “moderate,” hard” and “very hard”). Results showed that participants attained greater strength during the easy and hard tasks after exposure to both positive and negative stereotypes. At the moderate and very hard intensities, stereotype induction did not significantly change the strength from the baseline performance. While these results are not fully in line with the stereotype threat theory, they provide evidence that task difficulty could modulate the effect of aging stereotypes during physical tasks.

Realization of a device for the evaluation of the muscular effort through the Electromyogram signal EMG

In this work, a device for the evaluation of the muscular effort through the electromyogram signal is produced. This device consists essentially of three parts: the sensor part, the shaping portion, the acquisition part and the software part. The sensor part allows the EMG signal to be collected by means of surface electrode. The shaping port is realized based on an instrumentation amplifier. The acquisition part concerns the analogue digital conversion and the transfer of the digital data to the pc; this is done via an arduino card, which is equipped with a microcontroller for the visualization in real time and the storage of the EMG signal on the pc on which the processing logitiels will be implemented. The signal thus processed must be displayed with the data allowing the evaluation of the effort on the monitor of the pc through a graphical interface; these are the different steps that are carried out to finalize this work.

A System for Neuromotor Based Rehabilitation on a Passive Robotic Aid

In the aging world population, the occurrence of neuromotor deficits arising from stroke and other medical conditions is expected to grow, demanding the design of new and more effective approaches to rehabilitation. In this paper, we show how the combination of robotic technologies with progress in exergaming methodologies may lead to the creation of new rehabilitation protocols favoring motor re-learning. To this end, we introduce the Track-Hold system for neuromotor rehabilitation based on a passive robotic arm and integrated software. A special configuration of weights on the robotic arm fully balances the weight of the patients’ arm, allowing them to perform a purely neurological task, overcoming the muscular effort of similar free-hand exercises. A set of adaptive and configurable exercises are proposed to patients through a large display and a graphical user interface. Common everyday tasks are also proposed for patients to learn again the associated actions in a persistent way, thus improving life independence. A data analysis module was also designed to monitor progress and compute indices of post-stroke neurological damage and Parkinsonian-type disorders. The system was tested in the lab and in a pilot project involving five patients in the post-stroke chronic stage with partial paralysis of the right upper limb, showing encouraging preliminary results.