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Research
       
3D Navigation
We wish for robots to navigate and manipulate objects flexibly and autonomously
in three-dimensional environments, regardless of the presence, absence or
direction of gravity. Such robots must have the ability to propel themselves
along any direction in three-space in a controlled way. Consider a task in which
a robot is to climb up a complicated structure such as the Eiffel Tower, for
inspection. The Eiffel tower is made of a web of metal bars. The bars are almost
flat, they have varying lengths and directions, and they are oriented
arbitrarily in three-space. A robot executing this task requires several skills:
the robot should be able to climb vertically, the robot should be able to move
inverted, it should be able to travel on arbitrarily oriented surfaces and avoid
obstacles, and it should be able to make transitions between adjacent surfaces
(bars). We wish to do this task with an autonomous robot. We can view this task
as a navigation problem in a three-dimensional space.
We have engineered an Inchworm robot
that is a light linear structure made of four links. The end links are the
robot's two feet. Electromagnets placed on the feet allow the robot to attach to
arbitrarily oriented surfaces, much like the loopers. Similarly, the robot
alternates current to the two electromagnetic feet to simulate the inchworm
propelling motion. The basic gait for straight-line motion is a step and
consists of four phases: attach the back foot, extend the front foot, attach the
front foot, contract the back foot. The length of the steps taken by our robots
is proportional to their total length.In our lab, the inchworm walked hundreds
of steps over filing cabinets, doors, and closets. The robot also walked up a
fire escape outdoors.
The Inchworm robot can also manipulate objects while navigating over three
dimensional surfaces. The basic manipulation skills we have developed are
pushing an object (moving on a flat surface or climbing on an incline) and
pulling an object on a flat surface. In our lab the robot performed these
operations with great reliability. The robot was also capable of transitioning
between a pure navigation mode to a navigation and manipulation mode.
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