13-07-2012, 04:42 PM
VIDEO SURVEILLANCE USING MOBILE OPERATED LAND ROVER
Cell_Phone_Operated_LandRover_(1).doc (Size: 303 KB / Downloads: 55)
Abstract:
Conventionally, wireless-controlled robots use RF circuits, which have the drawbacks of limited working range, limited frequency range and limited control. Use of a mobile phone for robotic control can overcome these limitations. It provides the advantages of robust control, working range as large as the coverage area of the service provider no interference with other controllers and up to twelve controls. Although the appearance and capabilities of robots vary vastly, all robots share the features of a mechanical, movable structure under some form of control. The control of robot involves three distinct phases: preception, processing and action. Generally, the preceptors are sensors mounted on the robot, processing is done by the on-board microcontroller or processor, and the task (action) is performed using motors or with some other actuators.
I. Introduction
In this project, the robot is controlled by a mobile phone that makes a call to the mobile phone attached to the robot. In the course of a call, if any button is pressed, a tone corresponding to the button pressed is heard at the other end of the call. This tone is called ‘dual-tone multiple-frequency’ (DTMF) tone.
The robot perceives this DTMF tone with the help of the phone stacked in the robot.
Fig. 1: Block diagram of the cell phone operated land rover
The received tone is processed by the ATmega16 microcontroller with the help of DTMF decoder MT8870. The decoder decodes the DTMF tone into its equivalent binary digit and this binary number is sent to the microcontroller. The microcontroller is preprogrammed to take a decision for any given input and outputs its decision to motor drivers in order to drive the motors for forward or backward motion or a turn.
The mobile that makes a call to the mobile phone stacked in the robot acts as a remote. So this simple robotic project does not require the construction of receiver and transmitter units.
DTMF signaling is used for telephone signaling over the line in the voice-frequency band to the call switching centre. The version of DTMF used for telephone tone dialing is known as ‘Touch-Tone.’
Table I
Tones and Assignments in a DTMF System
Frequencies 1209 Hz 1336 Hz 1477 Hz
697 Hz 1 2 3
770 Hz 4 5 6
852 Hz 7 8 9
941 Hz * 0 #
DTMF assigns a specific frequency (consisting of two separate tones) to each key so that it can easily be identified by the electronic circuit. The signal generated by the DTMF encoder is a direct algebraic summation, in real time, of the amplitudes of two sine (cosine) waves of different frequencies, i.e., pressing ‘5’ will send a tone made by adding 1336 Hz and 770 Hz to the other end of the line. The tones and assignments in a DTMF system are shown in Table I.
II. Circuit Description
Fig. 1 shows the block diagram of the microcontroller-based mobile phone operated land rover.
The important components of this rover are a DTMF decoder, microcontroller and motor driver.
An MT8870 series DTMF decoder is used here. All types of the MT8870 series use digital counting techniques to detect and decode all the 16 DTMF tone pairs into a 4-bit code output. The built-in dial tone rejection circuit eliminates the need for pre-filtering. When the input signal given at pin 2 (IN-) in single-ended input configuration is recognized to be effective, the correct 4-bit decode signal of the DTMF tone is transferred to Q1 (pin 11) through Q4 (pin 14) outputs.
Table II
DTMF Data Output
Low
group (Hz) High
group (Hz) Digit
697 1209 1
697 1336 2
697 1447 3
770 1209 4
770 1336 5
770 1477 6
852 1209 7
852 1336 8
852 1477 9
941 1336 0
941 1209 *
941 1477 #
Table II shows the DTMF data output table of MT8870. Q1 through Q4 outputs of the DTMF decoder (IC1) are connected to port pins PA0 through PA3 of ATmega16 microcontroller (IC2) after inversion by N1 through N4, respectively. The ATmega16 is a low-power, 8-bit, CMOS microcontroller based on the AVR enhanced RISC architecture. It provides the following features: 16 kB of in-system programmable Flash program memory with read-while-write capabilities, 512 bytes of EEPROM, 1kB SRAM, 32 general-purpose input/output (I/O) lines and 32 general-purpose working registers. All the 32 registers are directly connected to the arithmetic logic unit, allowing two independent registers to be accessed in one single instruction executed in one clock cycle. The resulting architecture is more code-efficient. Outputs from port pins PD0 through PD3 and PD7 of the microcontroller are fed to inputs IN1 through IN4 and enable pins (EN1 and EN2) of motor driver L293D, respectively, to drive two geared DC motors. Switch S1 is used for manual reset. The microcontroller output is not sufficient to drive the DC motors, so current drivers are required for motor rotation.
The L293D is a quad, high-current, half-H driver designed to provide bidirectional drive currents of up to 600 mA at voltages from 4.5V to 36V. It makes it easier to drive the DC motors. The L293D consists of four rivers. Pins IN1 through IN4 and OUT1 through OUT4 are input and output pins, respectively, of driver 1 through driver 4. Drivers 1 and 2, and drivers 3 and 4 are enabled by enable pin 1 (EN1) and pin 9 (EN2), respectively. When enable input EN1 (pin 1) is high, drivers 1 and 2 are enabled and the outputs corresponding to their inputs are active. Similarly, enable input EN2 (pin 9) enables drivers 3 and 4.An actual-size, single-side PCB for cell phone-operated land rover is shown in Fig. 3.
III. Software description
The software is written in ‘C’ language and compiled using CodeVision AVR ‘C’ compiler. The source program is converted into hex code by the compiler. Burn this hex code into ATmega16 AVR microcontroller.
The source program is well commented and easy to understand. First include the register name defined specifically for ATmega16 and also declare the variable. Set port A as the input and port D as the output. The program will run forever by using ‘while’ loop.
Under ‘while’ loop, read port A and test the received input using ‘switch’ statement. The corresponding data will output at port D after testing of the received data.
IV. Working
In order to control the robot, you need to make a call to the cell phone attached to the robot (through head phone) from any phone, which sends DTMF tunes on pressing the numeric buttons.
The cell phone in the robot is kept in ‘auto answer’ mode. (If the mobile does not have the auto answering facility, receive the call by ‘OK’ key on the rover-connected mobile and then made it in hands-free mode.) So after a ring, the cell phone accepts the call.
Now you may press any button on your mobile to perform actions as listed in Table III.
The DTMF tones thus produced are received by the cell phone in the robot. These tones are fed to the circuit by the headset of the cell phone. The MT8870 decodes the received tone and sends the equivalent binary number to the microcontroller. According to the program in the microcontroller, the robot starts moving.
When you press key ‘2’ (binary equivalent 00000010) on your mobile phone, the microcontroller outputs ‘10001001’ binary equivalent.
Table III
Actions Performed Corresponding to the Keys Pressed
Number pressed by user Output of HT9170 DTMF Decoder Input to the micro
controller Output from micro
controller Actions performed
2
0×02
00000010
0×FD
11111101
0×89
10001001
Forward motion
4
0×04
00000100
0XFB
11111011
0×85
10000101
Left turn
Right motor forwarded
Left motor back warded
6
0×06
00000110
0XF9
11111001
0×8A
10001010
Right turn
Right motor back warded
Left motor forwarded
8
0×08
00001000
0XF7
11110111
0×86
10000110
Backward motion
5
0×05
00000101
0XFA
11111010
0×00
00000000
Stop
Port pins PD0, PD3 and PD7 are high. The high output at PD7 of the microcontroller drives the motor driver (L293D). Port pins PD0 and PD3 drive motors M1 and M2 in forward direction (as per Table III). Similarly, motors M1 and M2 move for left turn, right turn, backward motion and stop condition as per Table III.
V. Construction
When constructing any robot, one major mechanical constraint is the number of motors being used. You can have either a two-wheel drive or a four-wheel drive. Though four-wheel drive is more complex than two-wheel drive, it provides more torque and good control. Two-wheel drive, on the other hand, is very easy to construct.
Fig. 2: Top view of the land rover
Top view of a four-wheel-driven land rover is shown in Fig. 3.The chassis used in this model is a 10×18cm2 sheet made up of parax.
Motors are fixed to the bottom of this sheet and the circuit is affixed firmly on top of the sheet. A cell phone is also mounted on the sheet as shown in the picture.
So a single L293D driver IC can drive the rover. For this robot, beads affixed with glue act as support wheels. In the four wheel drive system, the two motors on a side are controlled in parallel.
MOBILE AIDED SURVEILLANCE SYSTEM (MASS)
MASS is a mobile phone controlled mini robot based on 3G technology. The robot has an integrated 3G mobile phone with video camera which enables it to be used as an advanced video surveillance system. Surveillance is the monitoring of the behaviour, activities, or other changing information, usually of people. It most usually refers to observation of individuals or groups by government organizations.
The word surveillance may be applied to observation from a distance by means of electronic equipment, or interception of electronically transmitted information. The MASS can be manually controlled from any location in the world by making a call to the mobile phone attached to the robot. Real-time surveillance is possible with the help of high speed 3G technology. Instructions to the robot are given using DTMF signal.
The DTMF signal received is decoded using DTMF decoder in the robot and the output of the decoder is fed to the microcontroller. The microcontroller controls the left and right motors based on this input.
The robot can detect obstacles in the path and stops on detecting the obstacle. When the robot detects an obstacle the obstacle sensor gives a positive input to the microcontroller. The microcontroller then stops both motors of the robot. Forward motion is automatically inhibited on detecting an obstacle MOBILE PHONE AIDED SURVEILLANCE SYSTEM by the program running inside the microcontroller. Video surveillance can be done by making a video call with the robot.
Features of MASS:
Automatic mode can be used to control the robot remotely. The main advantage of this mode is that the robot can be controlled from anywhere across the globe.
This is useful in operating the robot from very large distances or when the robot has to operate in areas unreachable for the user.
A highly secured system can be developed from the MASS by including an encrypt data transmission network.
The robot can be easily charged with the help of a charging port provided in the robot. Due to its low power consumption and high efficient batteries, the robot can be operated continuously for long hours.
MASS can also be used as an auto navigation device. For surveillance with the help of auto navigation the robot should be placed in a predetermined closed track. The robot will continue in the auto navigation mode until the user intervenes.
The robot is very useful to governments and law enforcement to maintain social control, recognize and monitor threats, and prevent or investigate criminal activity. We have made the system such that it is easily modifiable to suite various requirements. Being cost effective and user friendly, its application will be wide.