Project 1: Gripper Robot

The Crab mechanism with Raspberry Pi Controller

Highlights

The Crab was able to grab the Poke Ball and hold on to the ball while being moved 2 feet.
A 1:3 gear ratio was used to ensure the stepper motor had enough torque to pick up the ball.
A base was made using excess parts to allow for The Crab to easily reach the ball at the correct height.

IMG_9732.MOV

Core Mechanism of Project

Overview

The goal of this project was to build a gripper to hold onto a ball while being moved 2 feet. For our gripper, my group built a mechanism with linkages outside the gears to clamp down on the ball. To support the ball, we attached rubber bands to add friction to the holder. Finally, we used a 1:3 gear ratio with the gears, as we wanted to supply the mechanism with enough torque and slow down the overall movement.

Challenges

Several iterations of the gears were required for them to mesh properly while maintaining the correct gear ratio
The linkage system was prototyped using tape to test the angle to make the claws so they would be parallel when reaching for the ball
Numerous spacers had to be cut in varying sizes so they would friction fit to the dowel so the gears would not fall off.

IMG_9734.MOV

Video of The Crab moving 2 feet while holding onto the ball

Final Design of The Crab

Next Steps

Although the project is completed, future iterations could be made to improve the design of the robot. Firstly, the extra challenge of getting the Crab to move on its own was attempted. However, due to timing constraints, my group decided to prioritize the mechanism of the robot and forgo the extra challenge. A future iteration would be to finalize the base of a car for the Crab to fit on, thus allowing it to easily attach and detach from the car.

Secondly, the Crab experienced a wiring issue right before the presentation, thus hindering its ability to grab the ball. After the presentation, my group identified the issue coming from the wires of the stepper motor being frayed and disconnected from the motor drive despite appearing to be connected through the screw terminals. One improvement would be to check all the wiring 1 hour before the presentation to ensure success before the presentation.

One potential improvement would be to attempt to get the Crab legs to propel the robot. Due to the legs being a final addition to the design, they are fixed to the main frame of the robot. However, a future iteration could use the legs to mimic the movement patterns of a crab to push the robot forward. A ball caster wheel could be used to stabilize the underside of the robot to prevent it from falling over when using the gripper.

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