Page 108 - Human Inspired Dexterity in Robotic Manipulation

106 Human Inspired Dexterity in Robotic Manipulation

Fig. 6.15 The string-potentiometer-based data glove. Right: A disassembled string-
potentiometer unit. Middle: The palmar view of the data glove showing the four
flexors connected to the thumb, index, middle, and coupled ring and little fingers.
Right: The dorsal view of the data glove showing the control inputs from the index
finger’s PIP joint and the ad/b motion of the thumb.

actuators. Depending on the type of the transmission system, the translated
commands could contain information ranging from the gear-ratio values,
configurations of a linkage system, to an m n Jacobian matrix that corre-
lates m joint angles with n actuators. However, none of these data gloves can
realize the one-to-one mapping from the human hand to the robotic hand
for two reasons. First, very few robotic hands directly implement electric
motors at their joints because small motors are neither compact enough
to fit into the finger joint nor strong enough to generate enough torque
at the fingertip to perform any meaningful task. So, the actuation system
of the robotic hand always requires a certain type of transmission system.
Therefore, the readings of joint angles measured from a data glove could
not be directly used for the control of any robotic hand without taking into
consideration of the transmission system. Second, the kinematics of these
robotic hands are based on simplified mechanical joints whose configura-
tions and rotational axes could be very different from the specific human
hand that is used in the teleoperation, posing an inherent mismatch in the
calibration procedure.
In contrast, our proposed anthropomorphic robotic hand can be catego-
rized as a cable-driven system in which all the strings mimick the extensor/
flexortendonsofthehumanhand.Differentfromalltheexistinganthropomor-
phic robotic hands, the kinematics of our proposed robotic hand inherently
matches that of the human hand. This means if we could directly provide