  To detach a permanent magnet with a controlled force much smaller than its
original attractive force, the Internally-Balanced Magnetic Unit (IB Magnet)
was invented and has been applied to magnetic devices such as wall-climbing
robots, ceil-dangling drones, and modular swarm robots. In contrast to its
drastic reduction rate on the control force, the IB Magnet has two major
problems on its nonlinear spring which cancels out the internal force on the
magnet: complicated design procedure and trade-off relationship between
balancing precision and mechanism volume. This paper proposes a principle of a
new balancing method for the IB Magnet which uses a like-pole pair of magnets
as a magnetic spring, whose repulsive force ideally equals the attractive force
of an unlike-pole pair exactly. To verify the proposed principle, the authors
realized a prototype model of the IB Magnet using magnetic spring and verified
through experiments its reduction rate is comparable to those of conventional
IB Magnets. Moreover, the authors discussed and realized a robotic clamp as an
application example containing proposed IB Magnets as its internal mechanism.
