Robocar

Robo-Car is a self-navigating vehicle. The Robo-Car is the small scale model of an Intelligent Transport System having four ultrasonic range finders to detect the obstacles and to monitor its progressive movements.

I had demonstrated the design of Robo-Car in a Science Show of Bangladesh Television. It was even published in several newspapers. See the article Robo-Car on the Road, from the newspaper The Daily Star.

Components of Robo-Car

Robo-Car has the Following components:

  • Brain: Basic Stamp Microcontroller
  • Actuator: Motors, Wheels
  • Sensor : Ultrasonic Range Finder

Interfacing of Microcontroller with Sensor

Pin P15, P14, P13, and P12 of the microcontroller are used to trigger the four ultrasonic range finders. From the pin P15 and P14, a trigger pulse is sent to activate the sensor and to detect the front obstacle. If any of the sensors detects an obstacle then the two front sensors will cease to work. After that a trigger pulse is sent from the pin P13 to the right sensor to activate it and to detect the right obstacle. The left sensor is interfaced with pin P12 to detect any obstacles on the left side of the car.

For effectiveness and less power consumption it was decided not to use the four sensors at the same time. Beside that if any one of two front sensors detects any obstacle at a specific distance then the right sensor will get the priority. In this project 30 inch is considered as the minimum distance of the obstacle. If the distance is more than 30 inch then the microcontroller will provide the desired pulse to wheel according to the sensor information. And again priority goes to front sensor. If the both front and right sensors detect obstacles then the priority goes to left sensor. And the same measurement of the obstacle will go on.

Interfacing of Microcontroller with Wheels of the Robo-car

To drive away the wheels of the Robo-car according to sensor information we have used the P10, P9, P8, P7 pins of the Basic stamp homework board. We also have used a switching circuit to communicate between the microcontroller and the wheels. In this case we have used BD136 PNP transistor. The switching circuit is a active low circuit i.e. if it is possible to send low pulse to the base of the transistor it will complete a circuit path. According to the sensor information if the forward path is clear then the algorithm we used, send a low pulse to the P10 pin of the microcontroller and as the switching circuit is connected to the microcontroller the forward wheel will act accordingly and immediately send P9 and P8 a high pulse for not to move right or left direction. If the front sensors find any obstacles the priority goes to the right sensor and if the right path is free the algorithm sends low pulses to P10 and P9 to move towards right direction for a certain amount of time. If the both forward and right sensors find any obstacles then the algorithm sends low pulses to P10 and P8 to move for left direction. If the entire forward, right and left path is not free, i.e. the distance of the obstacles from the car is not greater than 30 inches then the algorithm will send low pulse to P7 and send all the other pins high pulses to move backward.

Flowchart

Working Principle

Robo-Car has four ultrasonic range finders. Two range finders are on the front and one is in the left and other is on the right.

From the starting position the two front sensors will detect whether there is obstacle or not. If the path is free then it will send the signal to Basic Stamp and Basic stamp will send the High Pulse to the front wheel.

But if the path is not free then it will check whether the right side is free or there is obstacle by its right range finder. If the right side is free then it will turn right and again the forward sensors will work.

But if right side is not free then the Robo-Car will check using its left sensor and if it finds left path free then it will turn left and it will give priority to the forward sensors.

If both sides are blocked then the Robo-Car will turn back for 0.9 sec and again recheck the right and left sensors for the free path.

Flowchart