The goal of this research is to develop a new type of haptic interface termed "Active Polyhedron", which realizes a physical human-machine interaction with virtual continuum objects in PCs. Active polyhedrons are polyhedron-shaped linkage mechanisms. In this paper, we deal with an active icosahedron consisting of 30 intelligent cylinders, which were specially developed for this purpose. In previous reports, the mechanism and kinematics of an active icosahedron and a simple force-presentation method using on/off pneumatic valves were given. In this report, a new force-presentation pneumatic-control system using pressure-control valves, which allows a highly accurate force presentation capable of handling complex continuum objects, and a new force-presentation algorithm, which applies to an apex of the polyhedron are described. These were applied to the active icosahedron. The experimental results showed that the active icosahedron was successful in realizing physical human-machine interaction, with which operators could change the shape, feel and compliance of virtual objects in a PC as if they actually touched them.