Mechatronics & Software
Self-Driving Luggage Cart
The assignment was to create an autonomous vehicle that could be controlled by an Android application. We had to research a use case and went with luggage transport at airports. Our idea was to design a cart that could follow a dark line on the floor and that could be controlled via a mobile phone. The goal was to build a working prototype from scratch in a little less than 10 weeks. During this project I was mainly responsible for the mechatronics part of the cart. This meant that I designed, programmed and built the drivetrain, the line tracking system and the safety system of the cart.
LiDAR System
A LiDAR Lite V3 was implemented to make sure the vehicle wouldn't hit any objects it could encounter on its track. This sensor measures the distance of a target by measuring the time between the transmission and the reflection of a near-infrared laser signal. A LiDAR was chosen for its low price and high accuracy. As the LiDAR only measures the distance in a small area, a servo motor was attached to it, to be able to scan the full surroundings in front of the vehicle. If the LiDAR would detect an object within a specified range it would turn off the motors until the object would be removed.
Line Follower
A line follower, built up out of LEDs and LDRs, was designed to function as a steering system. The LEDs and LDRs were placed in the same box so that the LDR could measure how much light would be absorbed by the floor. When the box was on top of the black line, more light would be absorbed than when it would be on the light blue floor. That's how the system could detect the position of the line, as there were multiple boxes placed in a row.
The line follower was placed just above the floor, so that background lighting wouldn't influence the LDRs. Before starting, the system would calibrate its LDR values, to adapt to the flooring. Based on these values, which represented the location of the line, the system would output different values to the motors and so the vehicle would keep itself on the line.
Drivetrain
The two electric motors that were used to make the vehicle move, were both brushless DC motors (Turnigy G160 Brushless Outrunner 290kv (160 Glow)). Each motor was connected to a motor controller (Brushless Car ESC 30A w/ Reverse). These controllers could be programmed to lower or build up the torque and the rpms. Both motors were powered by one rechargeable 4 cell, 3700 mAh, 14.8 V Zippy compact battery.
The transmission between the scooter wheels and the motors was done through a belt pulley system and was calculated to result in the right speed and torque through Matlab simulations.
