Recently, i studied most of the “fast line follower robots”. 75% of these use Pololu’s micro metal gear motors, QTR-8A/8RC, any motor Driver and Li-Po+Boost Converter.
I made a line follower of mine based on the same hardware. The result is quite satisfying
the video attached shows the initial build. the robot is slow but accurate. The details of the bot in short are–
MCU : Atmega328P @ 16Mhz
Supply : 7.4v
Motor Driver Supply : 9v (via boost converter)
PWM Value : 60
Size of bot : the size of a credit card
Control Algorithm : PD Controller
the most impressive line follower is saw was Hirai San’s Cartis 04.
Now i want to modify my bot completely; speed, hardware and software. Regarding this i have few questions as well as some issues i encountered while attempting to speed up the bot.
****** ISSUES *******
- when i step up the motor driver supply voltage or the PWM value, the bot overshoots,particularly at the corners.
- small chassis and fast bot, don’t go hand in hand.
- i had to define two drive routines: one for corner turning and one for normal line following. This led to improper line following sometimes.
4.Motor takes time to change its direction/speed. This delay became significant when speed of the bot was high.
****** QUESTIONS / DOUBTS *******
1.How do i tackle the overshooting? (Especially at the corners)
2. when i make the chassis longer (increasing the distance between sensor and the motors), balancing the bot became an issue. the wheels were not able to maintain contact with the ground. ( i used LEDs instead of castor wheels ). So, how do i ensure stability while using a longer chassis?
3.Differential is a must for crisp corner turns. Technically, two drive routines should work , but in my case line following wasn’t quite smooth on some parts of track, when i had two drive routines. Where did i go wrong?
4.How to tackle the time delay of motors?
5.Will, changing to an MCU clocked at freq. > 16Mhz, help? In fact, does the MCU Clock speed affect the performance in my case?
6. choosing a motor with gear ratio between 10:1 - 30:1 will require me to make the chassis longer which resulted in instability for me. Any advice?
7.how important is wheel selection? I’m using Pololu slick wheels. Should i switch over to thin, bigger diameter wheels?
8. Is/are there any other control algorithm(s) for line followers? should i switch to some different algorithm? (the core of my code is similar to Pololu 3pi’s Line Following sample code)
9.Can someone shed some light on Cartis 04? any information on its hardware, software, build, algorithm will help
thanks in advance!