Project Overview

I designed and built a semi-autonomous robotic arm to detect, pick up, and sort coloured blocks into user defined storage locations. We named this robot KEVIN: Kinetic Extraction and Visual Identification Navigator.

So how did it work? KEVIN was equiped with a colour sensor on its claw and a distance sensor at its base. Spinning in a circle, It uses its distance sensor to scan for objects and extends the claw to pick up those within reach. Then, using the colour sensor on the claw and the locations of storage bins, KEVIN either drops the object into its designated bin or into a "discard bin" for objects with colours without a designated storage location.Throughout this process, KEVIN will print its current action on its screen, ensuring the user knows what is happening at all times

Mechanical System

The robot’s physical design gives it three controlled degrees of freedom—horizontal rotation, horizontal extension, and vertical lift—along with a fully actuated claw for picking up objects. All components were fabricated from the remains of a broken-apart VEX IQ robot and custom 3D-printed components.

Horizontal Rotation - Planetary Gear Base:

KEVIN’s horizontal rotation is powered by a motorized planetary gear system at its base, allowing it to spin 360 degrees to scan for and pick up objects. A VEX motor drives a 12-tooth sun gear, turning three planet gears inside a fixed 60-tooth ring. This 5:1 reduction provides a high-torque output, ensuring smooth and precise rotation even when the arm is extended with a load. This design choice was crucial for KEVIN’s ability to effectively navigate its environment and sort objects accurately.

Horizontal Extension - Rack and Pinion Arm:

KEVIN’s horizontal extension is achieved through a rack and pinion mechanism mounted along the top of the arm, allowing the arm to extend and retract along a linear axis. A motorized pinion gear engages with a linear rack attached to the arm, allowing the simple rotation of a VEX motor to be converted into controlled linear motion. Additional free-spinning pinions distribute mechanical load so the rack never disengages—a crucial component of the arm to reduce skipping and slippage. The entire arm is reinforced using both VEX plates and custom 3D-printed connectors to minimize flex and maximize stability during extension and retraction, even when handling heavier objects. This design choice provided precise control over the arm's position and was key to KEVIN’s ability to sort objects at varying distances with precision and reliability.

Vertical Lift - Lead Screw Elevator:

A centrally mounted lead screw mechanism provided vertical lift to the arm and claw. A VEX motor, geared 2:1 for speed, drives a shaft coupler connected to an M8 threaded rod acting as a lead screw. The Central Hub sits on this rod, connecting to the arm and claw.Support poles, 3D-printed in interlocking segments, guide the Hub's vertical motion and ensures that it does not wobble during operation. This mechanism provided a compact and efficient solution to convert the rotational motion of a motor into the linear motion needed for vertical lift.

Claw - Worm Gear Claw:

KEVIN's claw has a parallel gripper machanism, where claw uses a worm-gear-to-rack mechanism to slide one claw plate inwards and outwards while the other stays stationary. This design allows the stationary jaw to line up to the target object while the other moves linearly, ensuring that the gripping plates remain parallel as they open and close, providing a stable and precise grip on objects of varying sizes. A chain-and-sprocket transmission links the claw motor (which is mounted on the "Hub", the connection point between the arm and lead screw, to optimize balance and stress on the system) to the worm gear. A colour sensor mounted between the jaws allows for the identification of the picked-up object only.

Central Hub:

At the core of KEVIN’s design is a central hub that connects the arm, claw, and vertical lift mechanism.

Control System

KEVIN's control system was built using a VEX V5 Brain and programmed in VEXcode.