Configuration design and correction ability evaluation of a novel external fixator for foot and ankle deformity treated by U osteotomy As a basic osteotomy technique, U osteotomy can be applied for certain complex foot and ankle deformities. Gradual correction cases using Ilizarov apparatus and Taylor Spatial Frame have been reported. This paper proposes a novel parallel distraction apparatus for U osteotomy (PDAUos) to supplement the correction equipment for surgeon. Designed with an adjustable structure, the PDAUos can adopt different assembly shapes (joint connection points). However, the influence of the change in assembly shape on interferencefree workspace and selfstructural performance of the external fixator have received little attention. To address this issue and enhance the selection of the most suitable assembly shape for patient, an algorithm to obtain the interferencefree workspace of different assembly shapes is proposed based on the inverse position solution of the PDAUos. Additionally, correction ability indices are defined according to the requirements of accurately controlled motion and high structural stiffness of the external fixator along the correction path. The results of simulation cases indicate that the interferencefree workspace and the correction ability vary according to the assembly shape and thus the proposed method can be used to select an assembly shape with sufficient workspace and the best correction ability before performing correction for a given patient.

Assistive method that controls joint stiffness and antagonized angle based on human joint stiffness characteristics and its application to an exoskeleton In this paper, we propose an assistance method that controls joint stiffness and the antagonized angle using variable elastic elements. The proposed system changes the stiffness and angle so that they correspond to the phase of movement and performs movement assistance in cooperation with the wearer. To achieve structural variability in the configuration of stiffness and the antagonized angle, we propose a joint structure in which the artificial muscle and tension spring are antagonistically arranged. While performing a movement, motion analysis was conducted to investigate the change in joint stiffness and antagonized angle. We confirmed that the proposed joint and human joint have the same tendency while in motion.