Development of a Force Perturbation Handle for Physical Interaction Research in Humans

The vision of advancing robots capable of direct physical engagement with humans begins with an understanding of how humans interact with each other. Even rudimentary interactive tasks, such as shaking hands, provide tremendous challenges for modern robotics, and current research into the biomechanics of such interactions is limited. Thus, further analysis of physical human-human interaction (HHI) will bolster efforts to enhance collaborative robot capabilities. To this end, a custom force perturbation handle (FPH) was developed, including the requisite mechanical, electrical, and software systems, to investigate the unique role of arm stiffness modulation in haptic communication between humans. The novel device records force and torque values generated by an interacting dyad and administers controlled force perturbations for estimating arm impedance metrics while maintaining a compact configuration that facilitates natural manipulation during pHHI tasks. To evaluate the capabilities of the FPH, a pilot experiment was conducted where subjects were instructed to exhibit specified levels of arm stiffness to which the calculated values from the FPH were compared. The results from four unbalanced two-way analysis of variance (ANOVA) analyses indicated a strong correspondence between the subjects' stiffness instruction and the estimated values from the FPH. The data were further validated through a qualitative analysis of arm displacement and actuation length. Considerations were addressed for deploying the FPH in future dynamic pHHI tasks to acquire valuable insight into motor communication strategies between humans and its applications for future interactive robotics.