An Actuated Indenter for Characterization of Soft Tissue Towards Human-Centered Design

The viscoelastic properties of human soft tissue influence the nature of interaction at attachment points in wearable devices. Characterizing these properties is especially critical for understanding physical human-robot interaction (pHRI) for exoskeleton design, prosthetics, and similar fields. This paper presents the design and control of a novel actuated indenter for the measurement of human soft tissue properties. The accuracy of position (0.025 mm) and force (111 mN) measurements allows for repeatable and controlled tissue deformation and monitoring at 36 different angular locations (10° increments). Controlled indentation displacement with force feedback is used in three types of applications on a human subject’s forearm. The soft tissue stiffness profile, viscoelastic relaxation behavior, and frequency domain response are measured. The ability to perform multiple characterizations with one indenter device broadens the scope of a human-centered approach to design, modeling, and perception as they relate to pHRI interfaces.