In large retail stores, items received from deliveries are often manually sorted (categorized) into totes before being put on shelves. Manual sorting can be time-consuming, so automating this process would be useful.
Our objective was to create an autonomous tabletop-sized gantry which can locate items positioned randomly within a predefined "pickup area", then sort them into totes based on color. For simplicity, the items used were red/yellow/blue cubes of uniform size.
We chose a vacuum pump as the pickup mechanism. The vacuum moves in the 2 "horizontal" (X/Y) axes using a stepper motor/belt-and-pulley/wheeled plate along a V-slot rail, and in the "vertical" (Z) axis with a stepper motor/lead screw (the latter which was bought as a pre-built part). Limit switches are used to zero the position of the vacuum when the system initially starts.
Arduino was chosen as the microcontroller; a relay controls the vacuum, and a CNC shield connects the stepper motors and their drivers/battery supply. A Pixy2 camera was chosen for position/color detection (this is a relatively inexpensive camera which interfaces with Arduino). The camera is fixed to a stationary mount, looking down on the pickup area. From the coordinates of the cubes and their respective bins, the Arduino calculates the necessary sequence of displacements to move the vacuum.
Calculations verified that the vacuum could lift the weight of the cubes, and the stepper motors provided enough torque to move the weight of the frame. Parts were ordered from Amazon and McMaster; the total cost was $537.
| Stepper Motor | Direction Pin | Step Pin |
|---|---|---|
| X | 5 | 2 |
| Y | 6 | 3 |
| Z | 7 | 4 |