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ROBOT HANDS
by Tom Carroll
Over the years, I’ve discussed all sorts of robot manipulators and arms, but most of
these have been related to industrial applications. The ‘end effectors’ of most factory
robots are quite varied in form and function but are usually specific to a particular task.
There are many types of welding robots including spot welders and cutting heads, but
these end effectors are not applicable to any other sort of task. Pick and place robots
may have several types of ‘hands’ or ‘claws’ such as the popular parallel-jaw claw, but
these devices might have a difficult time manipulating a piece of glass. SCARA robots
are great for precision x-y tasks such as populating circuit boards but their end effectors
might be designed for a narrow range of objects to be inserted such as resistors, caps,
or diodes. Human hands may tire and get injured in factory jobs but they are — without
a doubt — the most universal hand that has ever worked in a factory. Fingered robot
hands and similar manipulators are becoming the top priority for robot researchers
world-wide. The DARPA sponsored Autonomous Robot Manipulation (ARM) program is
a good example as they want to move robotic manipulation “from an art to a science.”
76 SERVO 01.2011
Last month, I featured the European space robot, Justin, and compared it with NASA’s Robonaut. These robots
use human-like hands to assist or replace astronauts in
difficult space-borne operations. In down-to-earth
applications, dexterous manipulators have been designed
by many university laboratories through the years to
provide amputees with the ability
to grasp and manipulate objects
in their daily lives. All robots do
not require complex five-fingered
hands in order to grasp and
handle objects. Willow
Garage’s PR- 2 shown in Figure 1
does a fine job with a two-fingered ‘pincer-type’ claw, bu
a humanoid style five-fingered
hand is the most universal
end-effector. It is also the most
complex and difficult to build.
Figure 2 is a patent drawing
of a hand designed in Germany
in 1916 for amputees. Designed
by William Carnes, the hand is very sophisticated for its
time. Notice that the Carnes hand’s fingers are driven by a
single worm gear though the thumb appears to be
stationary.
Anthropomorphic Robot Hands
‘Anthropomorphic’ is a
mouthful of letters that literally
means ‘man-formed’ or ‘in the
form of man.’ For those who
strive for the most realistic
humanoid robot, hands in the
form of human hands are the
way to go. Think about it for a
moment. If it weren’t for our
opposable thumb, much of our
hand’s uniqueness would be
lost. Without those thumbs,
much of our manipulation
FIGURE 1. Willow Garage’s PR- 2
with pincer claw hand.
