Modeling, Sensing, and Interpretation of Viscoelastic Contact Interface

Abstract

Abstract Soft robotics is important in the next generation of robots because of the rapidly increasing need for robotics in biomedical applications and the advantages of providing a soft interface for interaction with the physical environment in service robots and other applications. It is indispensable to understand the fundamental behavior of such contact interface, typically viscoelastic, in order to accurately predict the actual elastic and temporal responses of the contact and to successfully control it. Viscoelasticity is a phenomenon of time-dependent strain and/or stress in soft materials. It is therefore important to model such behavior and to study the effects of such time-dependent strain and stress on stability and behavior at the contact interface. The contribution of this paper is the introduction of a novel latency model, which is a nonlinear model with differential equations that govern viscoelastic materials. Latency model describes various features of viscoelastic materials, such as stress relaxation and strain creep. The theoretical modeling was supported by experimental results in which we found two types of relaxation. Type I relaxation is well documented in existing literature but Type II relaxation has not been elaborated previously with the physical insights provided in this paper. The proposed theory can unify both types of time-dependent relaxation responses for modeling, sensing, and interpretation of viscoelastic contact interface. Keywords: viscoelasticitycontact interfacesoft contacthuman–robot interactionstress relaxation Acknowledgment This research has been supported by the NSF (National Science Foundation) Grants CMS0428403 and CMMI0800241, as well as a collaborative joint grant from JST H19/299–1 (Japan Science and Technology Agency). Notes 1. The “contact interface” used here is a more general term because the contact in robotics involves kinematics and other considerations, including the modeling of viscoelastic soft contact Citation[3]. 2. The equilibrium strain can also be obtained from Equations (4) and (3) by setting . The same result for the equilibrium strain, , can be obtained. 3. Although not the focus of this paper, the strain creep also displays similar patterns of two types of temporal response under force control.