Remote Control Surveillance Vehicle (RCSV)

By

Sebastian Gola

Dan Lim

FernandoLinero

Mylon Ortega


 
 

Introduction

This Remote Control Surveillance Vehicle was designed and build by the group of four DeVry students for Bachelor's degree senior project. This unit can be used for civilian and military proposes. For instance, it can be used to determine situation in a disaster area or survey hostage situation.

The vehicle is controlled remotely by a computer through joystick, mouse, or keyboard. The control signal is send using RF modem. The audio/video reciever is connected to computer's video capture card.  The feed is displayed on computer screen.  You can see the vehicle, RF modem, and audio/video receiver bellow.



Surveillance Vehicle

RF Modem

Audio/Video Receiver
 
 

The interface program shown bellow is used to control camera movement, head light, speed and steering. The program also can be set up to run camera sweep in any direction.
 
 

    
 
 

Design

    -Hardware

In the picture bellow you can see all the components of the vehicle.





The hart of the system is Handy Board controller board based on Motorola 68HC11 microcontroller. It was designed by MIT professor and under free licensing anyone can use his design for their own purpose.  It has four motor outputs, six servo outpours, and several analog and digital inputs and outputs. The board can be programmed in C language significantly reducing code size and time required to complete as opposed to assembly.
 
 

Handy Board

         For more information on this controller board refer to this link http://el.www.media.mit.edu/projects/handyboard/

We are using two RF modems to send control signal. The modems are half duplex and are capable of two way communications. However for our purpose we are using just one way communication. The modem that connects to PC's serial port is configured by software as a transmitter and modem on the vehicle is configured through jumpers as a receiver. The carrier frequency is 433Mhz

          For more information on modems modules refer to http://www.radiometrix.co.uk/index.htm

Servos are used to control steering, camera elevation and rotation. For camera rotation we modified the servo so it has 360 degree range instead of just 180 degrees. We simply added two gears so that position potentiometer of servo rotates twice slower than the shaft.

          We are using H-Bridge for driving motor to give us more current than the controller board can provide (see components picture above).

          The headlight (20W halogen lamp)  is connected to driver transistor (power darlington). Again, we are using driver circuit to give us enough current for halogen lamp.  

Audio/Video system consists of the camera, 2 microphones, microphone amplifiers with gain of 40 to 80dB, and video sender operating at 2.4 GHz and  manufactured by Nutex Communications.

 

    -Software

The microcontroller's program is written in C. It continuously pools (scans) the serial port and checks if correct start bytes are received. There are two start bytes. When one is detected  program waits for another one. If the second byte is correct it procceds to read and store the rest of the frame. However if the second byte is incorrect program goes back and waits for the first one. Cascading start bytes like this increases system immunity to noise.

The frame format is shown bellow.
 

PREAMBLE

4 BYTES (55H)

FFH

 00H

F0H 

CCH

M1

!M1 M2 !M2

  

S1

 !S1

S2 

!S2

S3

!S3 54H 2BH

"!”means inverted byte. 

M stands for motor value

S stands for servo value

The preamble code is required by modem module's data slicer to stabilize. It is basically a string of ones and zeros (1010101...) and is required to last for 3 ms. Sending 4 bytes at 9600bps takes little more than 3ms. Another modem requirement is 50/50 ratio codes. Meaning that the same amount of ones and zeros has to be send in 4ms interval. 

Each motor and servo value is send twice as true and inverted byte to preserve 50/50 ratio. Sending byte twice allowed us also to do simple error checking. We compare odd and even bytes and if they are equal to invert of each other the value is loaded, else it is discarded. In case of driving motor, if value is in error all stop is loaded.
 

The visual basic interface provides camera control through joystick's HAT view, mouse, and keyboard. Movement of vehicle is controlled by joysticks axis or keyboard arrows. All movements and states are displayed on the interface, so the user knows exactly the position of camera, wheels, speed of driving motor, state of headlight and its intensity.