The spherical motor with gear structure to realize two degrees of freedom with crossed revolute axes has been developed. This spherical motor is called “spherical omnidirectional driving gear” because its structure is based on the theory of the omnidirectional driving gear with two gear structures that are perpendicular to each other developed by the authors in previous research. The gear structure with involute curve is deployed on the outer surface of the inner core gear and the inner surface of the outer shell gear. These gear structures are perpendicular to each other to realize rotational motions around two axes. Spur gears with conical teeth transmits power to the inner core gear and the outer shell gear. In this paper, we introduce two possible mechanisms of the spherical omnidirectional driving gear and explain their principles. The experiments to compare the power transmission efficiencies of the spherical omnidirectional driving gear and the ordinary spur gear were conducted.

This paper proposes a method to determinate an optimum height of bicycle saddle's surface in the upper body forward tilting posture of the movement supporting device by human power. Firstly, in this paper, we developed a theoretical equation with the length of the tibial part as a variable for optimum height of bicycle saddle's surface, that maximizes the driving distance of the movement supporting device, for people whose dorsiflexion angle of ankle is less than about 25 degrees. Then experimentally the driving distance of 6 subjects were measured while changing the height of the saddle's surface step by step. As a result, it was confirmed that the theoretical equation is validity.

In this paper, we attempt to explicate a numerical solution of inverse kinematics from the concept of virtual spring-damper hypothesis and joint damping control. Based on the minimization of elastic energy of the virtual spring, the sufficient condition for the stable convergence in the discrete time system is derived. Furthermore, we proposed two methods and a termination condition based on the stability condition. Simulation experiments are carried out to verify that calculation results are stably converged even in singular postures, unsolvable problems, and the redundant manipulator. Additionally, it is also clear that the proposed methods complete the calculation with a small number of iterations.