Page 383 - Robot Builder's Bonanza

Chapter 29

Experimenting with

Robotic Grippers

rms aren’t much good without hands. In the robotics world, hands are usually called
A grippers (also end effectors) because the word more closely describes their function.
Few robotic hands can manipulate objects with the fine motor control of a human hand; they
simply grasp or grip the object, hence the name gripper. Never sticklers for semantics, I’ll use
the terms hands and grippers interchangeably.
Gripper designs are numerous, and no single design is ideal for all applications. Each grip-
per technique has unique advantages over the others, and you must fit the gripper to the
application at, er, hand. This chapter outlines a number of useful gripper designs you can use
for your robots. Most are fairly easy to build; some even make use of inexpensive plastic toys.
The gripper designs encompass just the finger or grasping mechanisms.

Concept of the Basic Gripper

In the world of robotics there are hundreds of ways to make a gripper. The designs tend to be
application- specific: like Captain Hook in Peter Pan, a metal hook offers advantages a nor-
mal hand cannot. A perfectly useful gripper might be designed for a single task, like collecting
Ping- Pong balls or picking up chess pieces— whatever the robot is made to do.
Figure 29- 1 shows a typical robotic gripper, depicted in three different states: all the way
open, halfway open, and all the way closed. This style of gripper uses “fingers” that stay par-
allel as they open and close. The design allows the gripper to apply even pressure on either
side of an object and close in on the object without pushing it away. The mechanism is not
difficult, but you can see that it adds a bit of complexity to the construction of the gripper.
To be useful, most grippers are attached to the end of an arm. If the arm is on a wheelbase,
the bot can steer around the room looking for things to pick up and examine. By orienting the
gripper vertically or horizontally via a rotating wrist mechanism, the robot can grasp all man-
ner of objects.
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