RF-Based surveillance Vehicle :

Robot Construction:

This robot has two computers communicating with each other via RF Frequency modulated signals. One was a 89C51 micro controller on board and the other was a central control which was a P-IV 1GHz PC.

At the PC end: It consists of a Visual Basic based program and serial interface. It has a built in map of the effective controllable region restricted by the RF signal strength achievable on board to have fault free communication between the PC and the MuC. This map contains the static obstacles contained in the room like a wall in the region. There is a Yagi-Uda antenna to transmit modulated data to the micro-controller on board. Also there is a audio/video receiver connected to a Television which can display the color images as seen by the CCD camera on- board.

The Robot consists of the following sub-systems: It has a RF transceiver-filter-demodulator-amplifier module, a Micro controller, a CCD camera and a TV RF modulator and transmitter module, a gripper attached to a vertical extension (as in a SCARA robot) and a basic obstacle detection system of IR led and a TSop. It also had a Battery level indicator connected to the micro controller's interrupt line. There are Stepper motors to move the robot.


Working: The main aim of our project was to study different Path planning algorithms on a mobile system. The one we implemented was a Visibility Graph technique to reach a goal. Following are the typical steps to be followed to execute a task of reaching a goal position and performing a gripper task:


We developed a protocol for communication between the PC and the vehicular robot.
Commands to the Robot: Start/Stop Code, Vehicle Move, Camera ON/ OFF, Send Sensory Data, Send Battery Level Data (alive/ dead), for forward/reverse/right/left motions, Gripper OPEN/CLOSE, Gripper UP/ DOWN.


Data from the Robot: It basically executes the commands written by the PC to achieve a certain task. But in case of an obstacle it detects unknown to the PC map(stray moving/temporary objects ), or if its battery level goes LOW, it interrupts the PC. It also sends the current X and Y co-ordinates of the robot which it calculates internally by measuring the steps each stepper motor moves.

Future Enhancements possible: Here we implemented the Visibility graph because of its simplicity. The path planning can be done using Voronoi diagrams, Potential Field method, etc.
The protocols we developed for intercommunication between PC and Robot can be easily extended to multiple robots. For example, one robot could provide instructions to the rest. This Robot would take the place of the PC in our implementation. This robot will have greater processing power than the other robots.


Also the processing can be split amongst robots. As in some have better image processing, some better on-board obstacle avoidance and some others with other sensory devices attached. This will mean specialized robots performing a group activity.