Moon Young Park

With the development of robot technology, robot utilization is expanding in industrial fields and everyday life. To employ robots in various fields wherein humans and robots share the same space, human safety must be guaranteed in the event of a human–robot collision. Therefore, criteria and limitations of safety need to be defined and well clarified. In this study, we induced mechanical pain in humans through quasi-static contact by an algometric device (at 29 parts of the human body). A manual apparatus was developed to induce and monitor a force and pressure. Forty healthy men participated voluntarily in the study. Physical quantities were classified based on pain onset and maximum bearable pain. The overall results derived from the trials pertained to the subjective concept of pain, which led to considerable inter-individual variation in the onset and threshold of pain. Based on the results, a quasi-static contact pain evaluation method was established, and biomechanical safety limitations on forces and pressures were formulated. The pain threshold attributed to quasi-static contact can serve as a safety standard for the robots employed.

Purpose An electric field (EF) can be used to change the mechanical properties of cells and skin tissues. We demonstrate EF‐induced elasticity changes in human dermal fibroblasts (HDFs) and a human skin equivalent and identify the underlying principles related to the changes. Methods HDFs and human skin equivalent were stimulated with electric fields of 1.0 V/cm. Change in cellular elasticity was determined by using atomic force microscopy. Effects of EF on the biomechanical and chemical properties of a human skin equivalent were analyzed. In cells and tissues, the effects of EF on biomarkers of cellular elasticity were investigated at the gene and protein levels. Results In HDFs, the cellular elasticity was increased and the expression of biomarkers of cellular elasticity was regulated by the EF. Expression of the collagen protein in the human skin equivalent was changed by EF stimulation; however, changes in density and microstructure of the collagen fibrils were not significant. The viscoelasticity of the human skin equivalent increased in response to EF stimulation, but molecular changes were not observed in collagen. Conclusions Elasticity of cells and human skin equivalent can be regulated by electrical stimulation. Especially, the change in cellular elasticity was dependent on cell age.

In recent years, safety issues surrounding robots have increased in importance, as more robots are in close contact with humans, both in industrial fields and elsewhere. Safety standards for industrial robots operating in specific spaces have been established, but no such standards have been specified for collaborative and service robots. To establish safety standards for such robots, we assessed pressure pain thresholds for collisions between humans and robots, under the assumption that the pain threshold is lower than the mild injury threshold. The pressure pain threshold for collision with a robot was measured in 90 male Korean adults using a homemade collision system. The pain thresholds were measured three times at 15 sites, including the forehead. The highest threshold was 196.1 ± 85.8 N/cm² at the back of the hand, and the lowest was 65.1 ± 22.6 N/cm² at an arm nerve. Moderate thresholds, i.e., 100–120 N/cm², were noted on the forehead, neck muscle, ball of the thumb, and shin. The thresholds of participants < 30 years of age were lower, by 3–33%, than those of participants aged > 30 years. Thresholds differed by body mass index only at certain sites, including the shoulder joint, neck, and back of the hand. The pressure pain threshold depended on individual characteristics, body site, and age. The threshold relevant to potential human-robot collisions was determined to be between 65.1 ± 22.6 and 196.1 ± 85.8 N/cm².

Purpose: Robotics has evolved rapidly in terms of mechanical design and control in the past few years. Collaborative robots that have direct contact with humans are being introduced in various fields, including industrial and medical services. Because collaborative robot systems are being introduced rapidly, the safety of the humans who work with them is becoming an important issue. In this study, we investigated skin injuries resulting from a collision between robots and humans using a freefall experiment system.Methods: We particularly focused on closed skin injuries caused by a collision. To induce a closed injury, we struck mini‐pigs with cubic‐edge square and semi‐sphere impactors at collision speeds of 1 and 3 m/s. We did not observe any open injuries with those conditions. Closed injuries were observed in the dermal layer of the skin after the collision test at both speeds and with both impactors.Results: The collagen fiber in the dermal layer was separated and fragmented, and the subcutaneous fat layer became dense as a result of the collision.Conclusions: We closely observed and analyzed the histopathologic changes in the dermal and subcutaneous layers with intact epidermis after mechanical trauma to the inner skin layers.

Over the last few years, the robotics technology has rapidly evolved in terms of the safety enhancement. With the improvement the collaborative operation between the industrial robot and the human is now an appealing viable option. As the collaboration between the human and robot becomes more frequent, the requirement for the safety of the human in the case of collision with the robot draws much more attention. From this point of view, lot of research about the collision safety of the human has been reported recently. Most of them, however, are focused on the severe collision cases of the fatal injury. Which is mainly due to the lack of the analysis data for the minor injury. In this paper, the skin injury that is defined as a minor injury is analyzed with experimental data. Based on the analysis result, the acceptable impact (collision) condition for the robot is estimated.