Robot Design
Robot Arm Grabber
Guided by Oussama Khatib
Build a robot arm that can pick up a marble and a paper clip without crushing either one. The grip is the whole challenge.
Watch
See it happen in the real world.
A robot arm has joints, just like yours. Each joint is run by a small motor, usually a servo. The hand at the end is called an end effector — that's the official word for 'gripper.' The hard part isn't moving the arm. The hard part is deciding how hard to squeeze. Oussama Khatib's lab works on robots that share space with people, which means the arm has to know the difference between picking up a glass and shaking your hand.
Think
A question worth sitting with.
If your robot grips a paper cup with the same strength it grips a hammer, what happens?
Build
Make something with your hands.
Build a claw out of two craft sticks, a rubber band, and tape. The rubber band closes the claw. Test it on three objects of different weights.
Step-by-step
Tape two craft sticks together at one end so they hinge like chopsticks.
Wrap one rubber band around the hinge so the sticks naturally close. Squeeze them open with your fingers to grab.
Pick three test objects: a marble, a paper clip, and a crumpled paper ball. Each is a different weight and softness.
Try to pick up each one. Don't crush the soft one, don't drop the heavy one. Note which is hardest.
Swap the rubber band for a thicker one. Now grip strength is higher. Re-test all three. What changed?
Add tiny pieces of foam or felt on the inner tips of the claw. That's friction padding — every real robot gripper has some version of this.
Toolkit
- Household
- LEGO
Play
Test it. See what it does.
Run a relay: pick up five objects of different sizes with your claw and move them across the table. Time yourself. Each crushed or dropped object adds a 5-second penalty.
Challenge
Push it a little further.
Modify the claw so it can pick up a soap bubble without popping it. You'll need to think hard about grip force.
Reflect
Notice what your robot taught you.
What surprised you about which objects were hardest to grip?
Also ask yourself
What surprised you?
Reward
Mission outro
+0XP
“Can you make your robot even smarter? Even smaller?”
Skills advanced: manipulation, servos
Badge
Robot Arm Rookie