Photo: Erin Papacki
Creating a robot capable of grasping a variety of door nobs but is light enough to fit onto a wheelchair is quite an engineering challenge. But Erin Rapacki of the University of Massachusetts at Lowell was up to the task, and built one from only $2,000:
A door-opening robot must be able to grasp a variety of designs of door knobs and handles. It also needs to calculate "how much force is needed to open the door, the twisting angles to unlatch the door, and how much force is needed to unlatch it", says Erin Rapacki, now at Anybots in Mountain View, California [...]
To keep her device simple, Rapacki used a single motor and avoided the expense of cameras and elaborate sensors. Instead, a motor-driven set of gears extends the gripper towards the handle with its three fingers spread apart (see diagram).
Rapacki first tried flexible neoprene fingers, thinking that they could bend to grasp the knob, but these proved too thick and soft. Stiff plastic fingers with plates to constrain their sideways motion proved much more effective.
She also added a slip clutch to the drive system, to allow the device to hold and turn the knob at the same time as pushing or pulling.
Link via Popular Science