Cruiser is my line following robot.
Cruiser can follow either a dark line in bright background or a bright line in a dark background.
Cruiser competed in Racerbots, the Autonomous Robot Competition in Techkriti 2003, organized by Indian Institute of Technology, Kanpur and secured 2nd position. The objective of the competition was to traverse a track in shape of an 8 with a black line painted in centre in minimum possible time.
A very remarkable fact about Cruiser is that it was made in 3 days only!
|SENSOR(s) ON/OFF||Relative Displacement|
|LEFT||2 to RIGHT|
|LEFT & CENTRE||1 to RIGHT|
|CENTRE & RIGHT||1 to LEFT|
|RIGHT||2 to LEFT|
At any given time, at most two
sensors can be ON/OFF. The relative displacement of the robot with
respect to its center can be calculated from the adjoining table. With
this information the software reduces the stepping frequency of the
corresponding opposite motor by a factor proportional to the relative
i.e. if displacement is towards LEFT reduce the speed of RIGHT motor and vice-versa.
The brain of Cruiser is the Atmel AVR 90S8515 microcontroller with the following features:
|Up to 8 MIPS throughput at 8 MHz|
|8K In-System Serial Programmable Flash Memory|
|512 Bytes SRAM + 512 Bytes EEPROM|
|16-bit Timer/Counter - Dual PWM|
|Master/Slave SPI Interface|
A big advantage of using this microcontroller is the In-System Serial
programming which means that there is no need to pull out the
microcontroller to program it, just plug in the 5-pin programmer socket of
the serial programmer (connected to a computer serial port) and you are
done! This is especially useful during development and testing.
Cruiser circuit is laid out on two boards. The power supply + motor driver board and the controller board. The controller board hosts the 90S8515 microcontroller, 4 comparators for sensor inputs, a potentiometer to set the sensor reference voltage, 4-way DIP Switch to set the speed, two press switches for start/stop/reset, 5-pin programmer connector, 4-pin connector for motor driver board, 2-pin power supply connector, three red LEDs to display sensor data, a green LED as power indicator.
As Cruiser was made on a very short notice, it was made with the components in hand at the moment and thus the design is not very optimum. Firstly its speed is severely limited because of the use of stepper motors. DC Motors controlled by PWM will allow it to go at higher speeds. Instead of using 12 batteries to provide sufficient voltage to driver the motors, less number of batteries with a step-up switching regulator can be used to reduce its weight and allow it to attain higher speeds. Lastly instead of using three sensors with digital outputs, two sensors with A/D converters will offer higher precision in measuring displacement with respect to the track and thus would result in a smoother run.
This site was last updated 04/28/07