Design a Line Follower Maze Robot using TI Robotics System Learning Kit. The goal of the project was to integrate the line sensor and the bump sensor to solve a maze that searches for a treasure. The project was a combinational lab with six modules: Module 6 for GPIO interface the line sensor, Module 10 for SysTick interrupts, Module 12 and 13 for bump sensor, motors and PWM control, and Module 13 for line follower building. To achieve the goal of the project, the robot should begin from the starting point on the platform, self-drive via the line, know how to find the right path to the treasure and how to back up for lost, and stop at the treasure spot.
- C Programming
- Eclipse
- PWM
- SysTick interrupts
- Microcontroller - MSP432P401R MCU LaunchPad
- Line IR sensors - QTR-8RC
- Bumper switch - TI-RSLK
- DC Motors - Mini Plastic Gear Motor
- Robot chassis and wheels - Parts
- Rechargeable battery, pack of 6, metal hydride, 1300mAh, 1.2V, AA
- GPIO & signal LEDs
. Periodic Timer A1 interrupts to run the high-level strategy. Edge triggered interrupts for collisions. Main program for debugging and low priority tasks.
The following required functionality is complete:
- Interface with the IR reflectance module
- Periodic SysTick interrupts to measure the line sensor
- Read sampling data to local memory
- Separate into different sernarios to determine the line position
- Control DC motor
- Able to drive robot forward, backward, left, right
- Drive motor based on sernarios
- Control Bumper sensor
- Able to backup when hitting the wall
- Retrack and go back to the line if lost
- Periodic Timer A1 interrupts to run the high-level strategy
- Edge triggered interrupts for collisions.
- Main program for debugging and low priority tasks.
The following future improvement features are implemented:
- Reduce the average time to reach the treasure (
<60second)- Refine cornercases for better tracking and drive motor more quickly and efficiently.
- Speed up the robot through better algorithm and reduce delay time.
- Increase successfull rate to >95%:
- Add more IR sensor that perpendicular to the current sensor to distinguish the black and white line since the fail case is when the robot perpendicular to the line which make it though as treasure and halt.
The first task was to test the IR reflectance of the sensor. By obtaining the sampling values read from memory, we can categorize the reflectance into nine cases to determine the line positions as shown in Table 1 below.
| Sernarios | Position(x) |
|---|---|
The robot stayed at the center (C) |
-47 < x < 47 |
Slightly off to the left (SOL) |
-47 < x < 142 |
Slightly off to the right (SOR) |
47 < x < 142 |
Off to the left (OL) |
47 <= x <= 142 |
Off to the right (OR) |
142 < x <= 237 |
Way off to the left (WOR) |
-332 < x <= -237 |
Way off to the right (WOL) |
237 <= x < 332 |
Lost (L) |
Data == 0b11111111 && x == 0 |
| At the treasure’s position (*) | Data == 0x00000000 && x == 333 |
When the robot stayed at the center position, it should go forward until the next instruction came. If the robot was not at the center, it should fix its path back to the center. In addition, the robot should be able to handle corner cases such as when it hit the dead end of the line or being obstructed by surrounding object as shown in Figure 1 below.
To handle the wall obstruction, bumper sensor modules were needed with Systic interrupts approach to quickly backup and return to the path. Theoretically, when any of the bumps were activated, meaning there was a wall exist, the robot should back up and search for a new path.
Last but not the least component, two DC motors were used to control the robot wheel with PWM implementation to control the rotation speed as well as different delay time for different sernarios to refine the tracking movement.
When combining all the components, the finite state machine was used to easily control the robot as shown in Figure 2 below.
The robot when over 20 tests with 95% of successful rate and found the treasure within 60 seconds. The failed test encounters only for the sernario where the IR sensor was perpendicular to the line which made it thought that it hit the treasure and stop as shown in Figure 3 below.
MIT License
Copyright (c) 2021 Phat Le
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
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