  Interests in exploration of new energy resources are increasing due to the
exhaustion of existing resources. To explore new energy sources, various
studies have been conducted to improve the drilling performance of drilling
equipment for deep and strong ground. However, with better performance, the
modern drilling equipment is bulky and, furthermore, has become inconvenient in
both installation and operation, for it takes complex procedures for complex
terrains. Moreover, environmental issues are also a concern because of the
excessive use of mud and slurry to remove excavated soil. To overcome these
limitations, a mechanism that combines an expandable drill bit and link
structure to simulate the function of the teeth and forelimbs of a mole is
proposed. In this paper, the proposed expandable drill bit simplifies the
complexity and high number of degrees of freedom of the animal head. In
addition, a debris removal mechanism mimicking a shoulder structure and
forefoot movement is proposed. For efficient debris removal, the proposed
mechanism enables the simultaneous rotation and expanding/folding motions of
the drill bit by using a single actuator. The performance of the proposed
system is evaluated by dynamic simulations and experiments.
