Design and Modeling of a Novel Compliant Ankle Mechanism with Flexible Slider-Crank Limbs

This paper presents the conceptual design and modeling of a novel compliant ankle mechanism, which has flexible slider-crank limbs. Two elastic beams are utilized as the springy elements to connect the sliders and crank, which provides the ankle joint with passive rotational stiffness when two sliders are driven independently. Both the forward and inverse kinetostatic model are derived to determine the equilibrium configuration and the corresponding actuation variables. Besides, the rotational stiffness of the studied ankle mechanism is modeled based on results from the kinetostatic model. Results of stiffness analysis reveal that the proposed ankle joint is capable of varying its rotational stiffness if the sliders are controlled properly. The kinetostatic and stiffness models developed in this paper lay a foundation for stiffness design and prototype development in the future work.