LEGO MINDSTORMS Robot Inventor
4-Motor Arm
This robot arm has 4 motors that allow it to rotate left and right, lift up and down, twist its wrist to rotate and invert what it is holding, and open and close its claw. Watch it grab, flip, and move the two multi-colored blocks between the three platforms.
Three different programs provide three different ways to control the arm:
In autonomous mode, the arm automatically grabs, flips, and moves blocks between platforms in an endless sequence.
In app remote control mode, you control the arm from a remote control with 7 smart action buttons.
In gyro-controlled mode, grab the wired hand controller and use it to control the arm by having it mimic your hand motions.
The mechanical design of the arm is similar to the Ring Stacker (with an additional motor for the wrist), which I borrowed a lot of the basic design from.
Building Instructions
Arm
Base
Hand Controller
4-Motor Arm
Blocks
Using the Arm
See the descriptions in the program images and the end of the 4-Motor Arm building instructions for setup instructions for the three different programs.
For the autonomous and app remote control programs especially, it is important that the arm is built straight and level when the motors are in their zero positions and the various gears are engaged. It is easy to get the gears off by a tooth or so, which will affect the accuracy of the preset motions. Adjusting the gears is the best solution, but you could also adjust the motor positions used in the programs if necessary.