Robotics2024 · Royal Holloway · Group project

Bob

A LEGO robot that sorts marbles by colour.

An autonomous LEGO EV3 robot programmed in Java with LeJOS. It reads a marble’s colour, finds the matching container and drops the marble in, with over 90% colour-detection accuracy. I worked on the sensor logic and navigation.

Skills it shows

Bob from four sides, from our presentation.

RoleSensor logic and navigation

TeamGroup project

When2024, Royal Holloway

Built withJava, LeJOS, LEGO EV3

Skills it shows

Java on hardware

Programmed in Java with LeJOS, running on the LEGO EV3 brick.

Sensor processing

Colour readings turned into reliable decisions, with over 90% detection accuracy after calibration.

Behaviour-based control

Seven behaviours under one arbitrator, from emergency stop to marble detection, plus explicit states.

Navigation

Finds containers with the distance sensor and drives to the one that matches the colour.

Problem, build, result

1Problem

Sort coloured marbles into matching containers with no human help.

2What I built

With the team: a conveyor, a ramp and two sensors. My part was reading colour reliably, finding containers and getting Bob between them.

3Result

An autonomous sorter with over 90% colour-detection accuracy. Adding explicit states stopped behaviours firing out of turn.

>90%colour-detection accuracy

7behaviours, one arbitrator

5states keeping them in order

In pictures

Select any image to see it larger.

Slide “What is Bob?”: the robot with arrows labelled detects colour of marbles, locates a container, travels to containers and drops marbles. — What Bob does, in four steps.

Slide “The Behaviours”: emergency stop, low voltage, scan container, detect container, travel, celebration and detect marble, in priority order. — The behaviours, highest priority first.

Slide “The conveyor”: a close-up photo of the conveyor that separates one marble from storage. — The conveyor separates one marble at a time.

Slide “The ramp”: a close-up photo of the ramp that drops the marble. — The ramp drops it into the container.

Tech stack

Tools and data

Java

LeJOSLEGO Mindstorms EV3Colour and distance sensors

Methods

Behaviour-based controlPriority arbitrationFinite-state machineSensor calibration

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