Incorporating General Contact Surfaces in the Kinematics of Tendon-Driven Rolling-Contact Joint Mechanisms

Abstract

This paper presents the first kinematic modeling of tendon-driven rolling-contact joint mechanisms with general contact surfaces subject to external loads. We derived the kinematics as a set of recursive equations and developed efficient iterative algorithms to solve for both tendon force actuation and tendon displacement actuation. The configuration predictions of the kinematics were experimentally validated using a prototype mechanism. Our MATLAB implementation of the proposed kinematic is available at https://github.com/hjhdog1/RollingJoint.

Figures (13)

• Figure 1: Tendon-driven rolling-contact joint mechanism with general contact surfaces considered in this paper. Two tendons are routed through the links, and control inputs are the tensions (i.e., pulling forces) or the displacements of the tendons.
• Figure 2: Variables and loads on link $i$.
• Figure 3: Configuration predictions of a $5$-link mechanism without external loads. The tensions applied in (a) were $(\tau_\text{l}, \tau_\text{r}) \in \{ (3,1), (1,1), (1,3) \}$. In (b), tensions were doubled from (a), while the configurations remained identical. The force unit is arbitrary but identical between $\tau_\text{l}$ and $\tau_\text{r}$.
• Figure 4: Configuration predictions of a $5$-link mechanism subject to an external pulling force. The tendon tensions were given as $(\tau_\text{l}, \tau_\text{r}) = (6,3)$, and the pulling force varied from $0$ to $1.5$. The forces are indicated by arrows with their lengths proportional to the force magnitudes. The force unit is arbitrary but identical to that of the tendon tensions.
• Figure 5: Prototype mechanism used in experiments: (a) manufactured mechanism, (b) vertical view of link $5$, and (c) front view of link $1$.