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Robotics 2: Arms

posted Jun 2, 2014, 4:00 PM by Michael Dreyfus-Pai   [ updated Sep 11, 2016, 3:00 PM by kmcmillan@ctkschool.org ]
A competition robot usually has at least 3 critical systems:
  • Drivetrain - a way of moving around the field
  • Object manipulator - some way of collecting or grabbing objects
  • Lift system - a method of raising the grabbed objects up or dropping them down
We're going to use our knowledge of robotics parts and gear systems to design and build a lift system.  The goal is to lift the maximum amount of weight.  Here is an example:


This robot has a drive system, lift, and object manipulator. The arm actually has a "shoulder" and "elbow" joint. We only need a shoulder joint. 

Instead of hand cranks, we will use motors for this project! Here's a good, stable way to attach motors and help axles turn freely:

Here are some important things to think about:
  • What kind of gear system should you use to maximize power?
  • We've practiced turning gears, but not arms. You have to fix your arm to a gear to make it turn!
  • Notice how the example above shows gears sandwiched between two bars? This is a great way to make your design more stable. Stability is important because gears slip and bars bend when weighted.
  • Remember how torque works: the farther away a weight is from the axis of rotation, the more power is required to lift it. To make things fair, we will lift weights at 10 holes from the axle, no matter how long your rails are.
  • Don't worry about building a base for your arm or an object manipulator.
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