A tool for the evaluation of human lower arm injury: approach, experimental validation and application to safe robotics

Abstract

SUMMARYThis paper treats the systematic injury analysis of lower arm robot-human impacts. For this purpose, a passive mechanical lower arm (PMLA) was developed that mimics the human impact response and is suitable for systematic impact testing and prediction of mild contusions and lacerations. A mathematical model of the passive human lower arm is adopted to the control of the PMLA. Its biofidelity is verified by a number of comparative impact experiments with the PMLA and a human volunteer. The respective dynamic impact responses show very good consistency and support the fact that the developed device may serve as a human substitute in safety analysis for the described conditions. The collision tests were performed with two different robots: the DLR Lightweight Robot III (LWR-III) and the EPSON PS3L industrial robot. The data acquired in the PMLA impact experiments were used to encapsulate the results in a robot independent safety curve, taking into account robot's reflected inertia, velocity and impact geometry. Safety curves define the velocity boundaries on robot motions based on the instantaneous manipulator dynamics and possible human injury due to unforeseen impacts.

Analyzing soft tissue stiffness of human upper arms during physical dynamic and quasi‐static impacts in human–machine interaction

“…Furthermore, the material properties and the geometry of impactors also play a significant role in the measurement of pain thresholds (Mylaeus et al, 2019). A larger contact area of an impactor is associated with a higher pain threshold (Defrin et al, 2003; Povse et al, 2016). In contrast, impactors with small contact areas have a lower pain threshold.…”

“…A flat-ended cylinder with a diameter of 25 mm FL25 Figure 2a A flat-ended cylinder with a diameter of 10 mm FL10 Figure 2b A hemisphere with a diameter of 25 mm HS25 Figure 2c A cuboid with a 14 mm square end SQ14 Figure 2d F properties and the geometry of impactors also play a significant role in the measurement of pain thresholds (Mylaeus et al, 2019). A larger contact area of an impactor is associated with a higher pain threshold (Defrin et al, 2003;Povse et al, 2016). In contrast, impactors with small contact areas have a lower pain threshold.…”

“…Moreover, an evaluation utilizing porcine skin demonstrated the relationship between the robot mass, velocity, and impact geometry on the resulting soft tissue injury (Haddadin et al, 2012). Further, using a passive mechanical lower arm (PMLA) that mimicked the human impact response during pHRI, Povse et al (2016) determined the possibility of soft-tissue injury by taking into account the robot's reflected inertia, velocity, and impact geometry.…”

Control of Force Impulse in Human-Machine Impact

“…Human-machine interaction is often related to the study and definition of safe contacts: many studies concern the evaluation of the effect of such contacts on the human body [11,16], while other work deals with the identification of safety requirements [10,13]; the problem of safe interactions is also related to the control of the robot itself [12,24].…”