Robot Hands and Grippers

Look at your hand. Now wiggle your fingers. Now pick up a pencil. Now gently pinch a piece of paper. Now make a fist. Your hand just did five completely different things in five seconds! Hands are unbelievably complicated and useful. Scientists say the human hand is one of the most sophisticated tools on Earth — and trying to build a robot hand that works even half as well is one of the biggest challenges in all of robotics.

Grippers: Simple But Clever

Most robots do not have hands at all — they have grippers. A gripper is a simpler tool attached to the end of a robot arm. It is designed to grab, hold, and release things. The most common gripper looks like two fingers that close together, like big flat tweezers. When the computer tells the gripper to close, the two fingers squeeze together to grip an object. When the computer says open, the fingers spread apart and drop it. This is called a parallel jaw gripper, and you see it everywhere in factories. It is simple, reliable, and strong. But it has limits — it can grip boxes and bottles, but it cannot pick up soft things like a grape or a piece of bread without crushing them. Engineers have invented all kinds of grippers for different jobs: grippers that use suction cups to lift flat things like glass panes, grippers with three fingers like a bird claw, and even soft grippers made of bendy rubber that wrap gently around delicate objects.

Here is what makes a good gripper so hard to design. When you pick up a glass of juice, your hand automatically adjusts its grip. You hold the glass firmly enough that it will not slip, but gently enough that you do not shatter it. You do this without even thinking about it. A robot gripper has to be told exactly how tightly to squeeze. If the engineer programs it too tight, it crushes the glass. Too loose, and the glass slips and falls. Getting that just-right grip requires pressure sensors — little detectors that tell the robot how hard it is squeezing — and very clever programming. For simple factory jobs where all the objects are the same shape and material, this is not too hard. But for a robot that needs to handle hundreds of different objects — a toy, a banana, a coffee cup, a piece of paper — getting the grip exactly right is genuinely difficult!

Some engineers have built robot hands that look almost exactly like human hands — five fingers, knuckles, and all! These hands can do many things: shake hands, open jars, play the piano. But five-finger robot hands are extremely complicated and expensive. They have dozens of tiny motors and sensors packed into a small space. They are interesting for research, but for most factory and warehouse jobs, a simple two-finger gripper does the job better and cheaper. The choice of gripper always comes back to the job. Pick the simplest tool that can do what you need — that is smart engineering!