  Grasping an unknown object is difficult for robot hands. When the
characteristics of the object are unknown, knowing how to plan the speed at and
width to which the fingers are narrowed is difficult. In this paper, we propose
a method to realize the three functions of simultaneous finger contact, impact
reduction, and contact force control, which enable effective grasping of an
unknown object. We accomplish this by using a control framework called multiple
impedance control, which was proposed in a previous study. The advantage of
this control is that multiple functions can be realized without switching
control laws. The previous study achieved two functions, impact reduction and
contact force control, with a two layers of impedance control which was applied
independently to individual fingers. In this paper, a new idea of virtual
dynamics that treats multiple fingers comprehensively is introduced, which
enables the function of simultaneous contact without compromising the other two
functions. This research provides a method to achieve delicate grasping by
using proximity sensors. For the effectiveness of the proposed method, please
refer to https://youtu.be/q0OrJBal4yA.
