Projects:2014s2-75 Formation Control of Two Autonomous Smart Cars

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Aim

The aim of this project is to build a model of two smart cars which can move independently. The smart cars will not be controlled by any human intervention for its movement. The two cars should have autonomous control and be able to recognize the destination and should move to the destination in a definite path. There are two major modes in which the cars should move. The control mode and the signal relay mode. In control mode, the cars will move in a chase dodge model. That is one car chases the other one in a definite speed. The other car recognizes the chase and tries to avoid the first car. At a particular distance between them, the cars change their behavior and the dodger turns back and pursues the chaser. The chaser from the first scenario, turns away in order to evade the other car. In signal relay mode, the movements of both the cars are integrated together to send a signal from a source to destination. Car 1 carries a signal or information to a particular location. Car 2 moves from its initial position to the same location. Car 1 supplies the data to Car 2 and Car 2 carries the information from the location of the first car to the final destination.

Background and Significance

Over the years, driving has become one of the biggest life threatening risks. The rapid increase in the number of vehicles has proportionally increased the number of accidents. Studies show that about 1.24 million deaths occur due to traffic accidents in a year across the globe. Carelessness, drink driving and speeding are the major reasons for the cause of traffic accidents. Despite the safety advancements such as abs, airbags, anti-collision systems cars prove to be more dangerous than any other modes of transport such as buses, flight or trains. Apart from creating accidents, driving has additional disadvantages such as increase in stress and fatigue. Cases have been reported even of mental illness caused due to long distances and congested traffic driving. Autonomous cars could prove to be a solution for this situation. If a sophisticated system can be built, the smart cars can decrease the accidents due to human errors. Also, passengers can relax without the agony of driving. There has been significant improvement in the studies of smart cars in the recent past. Google’s autonomous smart car project has gone on to test the smart cars in real environment. GPS is an important factor in this autonomous smart car implementation. The GPS should not only provide the location and coordinates the car is driving but should provide detailed information about the environment which the car is driven in, such as color of traffic lights, curb width, height of the bump etc. Google uses its maps and satellite images for finding the path and sensors to find the inertia and wheel encoders for calculating speed. Due to constraints in finding the color of the traffic lights due to glare or rain, difficulties in detailed mapping of the whole world and in decision making smart car technology is still in its development stages. Intelligent Car is a branch of intelligent robot; it is a system which include automatic control, artificial intelligent, mechanical engineering, and image processing and computer sciences. The main difficulty in intelligent car is image processing. The accuracy of the image processing directly impact intelligent car’s driving directions, driving speed and the ability to dodge obstacles. The technique of moving target’s detecting and tracking are the main parts of image processing The image processing techniques and software have improved due to the introduction of advanced software, improved processing capabilities, digital image processing techniques and the improvement in hardware. Several methods have been introduced for processing the images and finding moving targets. The images we view are in RGB. These images are converted to HSV for processing. The cam shift algorithm, pixel processing, background subtraction, Gaussian distribution and noise elimination are some of the modern techniques used in image processing.

Motivation

This project deals with some of the ways in which the design of autonomous movements of the car can be managed. The robotic technology and artificial intelligence systems proposed in this project can be used in robotics and traffic advancements. The project gives hands on experience in dealing with the Arduino robotic technology which is a starting step for intense robotic technologies. Traffic signalling and camera systems use significant amount of image processing in the near past. The image processing used in the project will be a guideline for detecting moving target and controlling them. The project gives a guideline for using image processing technology for finding the target. The technology can be used in machine vision and medical imaging. With the use of accurate systems such as gyroscope in the future, the project can be used in remotely controlling the robots to reach and investigate inaccessible and congested areas.

Requirements

The project requirements can be classified in to hardware design and implementation and software application. The major requirements of the project are: -

• Research and design a hardware system which can serve as the model of two smart cars and a control system which is to be used as the nerve center of the process

• The hardware design should consist of a model of two smart cars which must move independently

• Design and implementation of a core algorithm to perform the chase dodge model

• Implementation of tracking system in order to track the locations of the car in real time

• Implementation of a communication system for the cars to recognize the locations from the tracking system and implementation of a drive and power system for the cars so that the cars follow the algorithm for the movements.

Hardware

The hardware components required for the project are: -

• Arduino robots – Model no. A001078 – 2 nos.

• Camera – AXIS P3364-VE

• Wi-Fi module - HDG204 wireless LAN

• Computer

• Network router – TP-Link G54

Arduino Robot

Arduino robots serve as the model of the cars in the project. An Arduino robot is a robot on wheels. It comes from the Arduino family of microcontroller based products. The Arduino is open source which means documentation and software is freely available. Arduino family contains boards build on microcontrollers such as Arduino Uno, Arduino Leonardo, Arduino Esplora, Arduino Mega etc. shields such as GSM shield, Ethernet Shield, Wi-Fi shield, Motor shield etc. and Accessory kits such as Arduino ISP, Serial adapter, proto shield etc.

Components

The Arduino robot mainly consists of a control board and a motor board. Each board is controlled by Atmel micro controller ATmega32u4. Motor board and control board are connected through serial connections. The major components of the Arduino robot are: -

• On board Infra-red sensors

• Compass

• TFT-LCD module

• Potentiometer voltage dividers

• External SD card

• 5V brushed DC motors

• Speakers (8 ohm)

• LED indicators

• Input keypad

The infra-red sensors in the robot are used to find the surface regularities in which the Arduino robot moves. The compass is used to find out the direction in which the robot moves although electrical interferences from the power lines and machines might reduce the accuracy. The Thin Film Transistor Liquid Crystal Display is used for projecting images and interrupt outputs of the robot through serial SPI communication. Potentiometer dividers divide the voltage to the two wheels of the robot. The other potentiometer knob can be used for alternating the voltage such that different outputs can be controlled by programming it. The external memory card is used for saving images, sound and data and can be used to project these images and speaker can be used for playing the music. The 5V brushed DC motors are used to convert the electrical energy from the battery to mechanical energy to the tyres for movement. There are 3 LED indicators also, one each for indicating data transmission and reception. The keypad can be used to give inputs to the robot.

Memory

The Arduino robot can be programmed in either control board or motor board. Each of the microcontrollers ATmega32u4 has 32KB of flash memory in which 4KB is used for boot loader program. So a total of 28KB is available for programming.

Input and Output

There are a number of pins in Arduino for input and output. These can be used for adding external parts such as sensors, inputs, switches etc. The control board TK0 to TK7 pins are multiplex pins multiplexed to the TK pin in Arduino. These pins are used for connecting sensors and actuators. The control board TKD0 to TKD5 pins and motor board TK1 to TK4 pins are connected to ATmega32u4 and are used as digital input and output. The Arduino also has 10 pins for serial communication and four I2C connectors [17].

Camera

AXIS P3364-VE cameras are usable both indoors and outdoors. It uses SVGA technology and has a resolution up to 5 mega pixels and it supports SMPTE HDTV video of 720p and 1080p.The SVGA technology offers excellent image quality. The camera comes with light finder technology from AXIS and is highly sensitive to light which enables it to capture high quality images in low light. It is developed with P-iris control technology which controls the field position through its iris to optimize its depth. AXIS P33 series provides H.264 and JPEG motion stream *which can be individually configurable. The cameras support Ethernet technologies with 802.3a/f and can work in extreme weather conditions. The camera is ideal for image processing due to its high quality imaging. The image sensor technology used in AXIS P3364-VE is progressive scan CMOS RGB technology. It comes with lens length 6mm and 12mm. 6mm models provides an angle of view up to 105° and is used in the project. An infrared cut vision enables it for night vision the shutter time is 1/24500s when operated in 50 hertz power supply and a frame rate of 25fps. Video compression technology used is H.264 baseline and motion JPEG. It supports Http, Https, FTP, SMTP, TCP, NTP, UDP, DNS, RTCP, SOCKS and DHCP protocols.

Wi-Fi module

The Wi-Fi module HDG204 is also manufactured by the Arduino. This module helps in connecting the Arduino robot to internet and local area networks without wires. The Wi-Fi shield is connected to Arduino by using Serial Peripheral Interface (SPI) through ICSP headers. It uses 802.11 wireless specifications for the connection and supports WEP and WPA2 encryptions. The Wi-Fi shield contains the microcontroller AT32UC3 which provides the internet protocols (IP) which supports Transmission Control Protocol (TCP) and User datagram Protocol (UDP). The Wi-Fi library in Arduino IDE is essential for programming the Wi-Fi shield. It contains an SD card slot and a micro USB port for firmware updates. The four LED indicators are for showing the status of digital pin 9 of Arduino, link for indicating a successful connection, error for indicating the error in a connection and data for indication of receiving/sending of data.

Network router

The network router is used to connect the camera Wi-Fi network to the computer Wi-Fi network. This helps the camera to send images as packets of data to the computer. The router used for the project is TP-link wireless router model G54. It accepts a maximum data rate of 54Mbps. It provides long distance wireless connectivity and support WPA and WPA2 encryptions apart from WEP. Wireless standards supported by the route are 802.11b/g and works in a 2.4 GHz frequency.

Computer

The computer is needed for the project to process the images which are received from the camera. The image processing is a real time procedure. The frame rate of the camera is 25fps and with 1.3MP of pixel data in each frame the computer needs a very high processing capability. The recommended technology is the use of Intel i7 core processors with a clock speed of 3.20 GHz and 8GB RAM. The processor has 2 cores and 4 threads. An Intel HD graphics 6000 processor is also recommended for higher performance in image processing. The processor supports up to 2560 x 1600 resolutions at 60 hertz. The operating system can be either windows, Linux or MAC OS.

Hardware Design and Methodology

The Arduino robots will be used as the model of the smart cars. Colour plates of colours red (RGB value) and green (RGB value) are fixed above the two robots respectively. The camera captures the images of the two robots and the background image. This image is send to the computer. A network router is used for exchanging the data from the camera Wi-Fi to the Wi-Fi network of the computer. The computer receives the images in packets of data. This data is combined to reproduce the image. Using programming (OpenCV) the location of the colour boards are recognised. Using the centre of mass method the centre point of the colour boards -which are the centre points of the robots- are found out. The coordinates of these central points are sent to the robots though the local Wi-Fi of the computer. With the help of Arduino Wi-Fi shield, the Arduino robots receive the coordinates of its location and the coordinates of other robots location. The robots are programmed in Arduino IDE program in order to realise the algorithm of chaser dodger model and the relay race model. To find out the orientation and direction the Arduino robots use the lantern fish method which provides the angle of deviation from geographic north. In the relay race model, the Wi-Fi Shields of one robot receives the data from the computer and moves to a particular location. From that location it shares the data with the other robot. The receiver robot in turn moves from the initial position to the destination where it delivers the data.

Determining Camera Specifications

Requirements

Height of the camera from the ground = 2.5m

Length x breadth of the field = 5m x 5m

Area to be covered by the camera = 5m x 5m =25m^2

Resolution >= 1cm

Frame rate >= 20fps

Support Wi-Fi with 802.11b/g network LAN Network protocol TCP/IP

Calculations

Field of view

Height of the camera from field = 2.5m

Distance to the farthest view on X axis = 2.5m




Angle from camera to farthest side = arctan(2.5/2.5) = 45°

Field of view in x axis = 2×45° = 90°

Angle from camera to farthest side = arctan(2.5/5.6) = 71°

Field of view in y axis = 71°

So minimum camera field of view = 90°

Resolution

Area to be covered = 25m^2

Resolution required in cm = 1cm

So,minimum resolution required in pixels = 500pixels = 0.5MP

Experiments

Lighting LEDs

One requirement of the project is to find out the suitable solution for the camera to detect the robots. Plan was proposed to use light LEDs above the robot so that the camera can detect. Programming and hardwiring was done in order to light the LEDs above the robots. But the actual results show that camera finds it difficult to detect the LEDs especially in the daylight glare. So a colour plate is used instead.

Wheel Calibration

Wheel calibration program is used to help the robot as straight as possible. This is done by dividing the voltages to the wheel motors proportionately. The potentiometer trim on the motor board of the Arduino divides the voltage to the wheels of the robot by a voltage divider. By controlling the potentiometer trim, the robot can be moved reasonably straight. Output is transferred as voltages to the wheels, trim values and instructions to the screen. The program reads the value of the potentiometer trim and displays it to the screen. Also programmed instructions are displayed on the screen for the user to make the adjustments. The values of the compass are constantly read to find out whether the robot moves in a particular direction. A screw driver can be used to turn the trim clockwise and anti-clockwise in order to distribute the voltages to the motors.

Robot Orientation

The robot deviates from its straight path, especially when moving large distances even after the wheel calibration execution. This is due to the imperfections in the shape of the tyres and difference in size between the two tyres. In order to eliminate these deviations a constant feedback should be given to find the direction in which the robot is heading and to compare it with the previous direction. The feedback used in this experiment is from the compass. The compass is read in each loop of the program. Initially equal voltage is given to both the wheels of the robot. The program reads the compass and compares it with the previous compass value. If it returns a difference, the voltage to the right wheel is varied by keeping the voltage to the left wheel constant. A positive error voltage is given to the right wheel if the robot tends to move right and a negative error voltage which decreases the original voltage is given otherwise. If the deviation tends to be a large value, the error voltage will be higher. This helps the robot to come back to its original orientation. The experiment is done in a controlled environment without the interference from external magnetism.

Eliminating oscillations

The feedbacks given to the robot motors make it unstable and force it to go in an oscillatory path. This makes the robot to wobble around. This is due to the behaviour of wheels to the feedback. The inertia of the motor tends to overcompensate for the deviations from the straight path which causes it to move to the other direction. This can be eliminated by controlling the error voltage supplied to the wheels. When the error voltage is more than a particular value, the program limits the error to its maximum value which in turn limits the voltage to the tyre. This helps the robot to move in a smooth direction and eliminates oscillations. The maximum value of the error voltage is found out using the trial and error method and is found as 0.39V.

Orientation control

The images send by the camera is processed by the computer and locations of the robots are identified. These locations are sent to the robots through Wi-Fi in terms of their coordinates. The program finds the direction in which the robot is pointing and the direction in which the chaser robot should turn in order to chase the dodger robot. The tangent function is the trigonometry and mathematical calculations are used to return the orientation to which the robot should turn. The program helps the robot to turn and move to the location. Once the orientation to which the robot needs to turn is determined, the program sends positive voltage to one wheel and negative voltage to the other. This makes one wheel to move forward and the other to roll backward creating the rotating motion of the robot on its axis. Feedback is read from the compass to determine whether the robot reached the orientation required. Once the orientation is reached, the polarity of the voltages to both the wheels is made in the positive direction which makes the robot move in a straight line. The value of voltages given to the wheels during rotation is directly proportional to the amount of rotation required. That is, when the robot nears the determined orientation, the speed of rotation of motors is reduced so that the torque and inertia is reduced to eliminate overshoot rotation. Also decision whether the robot needs to rotate clockwise or anti-clockwise depends on the angle of deviation required. That is if the robot needs the rotate less if it is rotating in anti-clockwise direction than clockwise direction then anti-clockwise rotation is implemented and vice versa.

Conclusion

The aims of the project were completed successfully. The project was able to find a solution for designing the smart cars. The use of camera and image processing is proposed as the output from the project. The control mode in which the cars can move independently and the signal relay mode in which the cars share the tasks were successfully completed. The proposed Bluetooth triangulation method was replaced with the camera due the infeasibility in finding the range using Bluetooth triangulation. The failure of compass as a direction sensor during magnetic interferences affected the project. But the project realised that modern equipment like gyroscope can replace the compass technology. The communication part was proposed to be using Bluetooth but was replaced with Wi-Fi technology due to its increased bandwidth and also less interference.

Future Work

In future the compass module and image processing can be replaced with gyroscopes. The gyroscope is a machine which can find the direction even in the absence of earth’s magnetism and interference from other magnetic equipment. The project can be improved using multiple robots and tracking them. The features such as LIDAR technology which uses laser to find out the external environment, SONAR which sends sound waves to find out the distance and behaviour of the system, RADAR, and IR sensors can be added for increased accuracy and feedback. The image processing used in the project can be improved for high speed measurements when the vehicles move faster. A local vision system in which the camera is place above each car can track the environment.

Other applications

Apart from the system of smart cars, the project can be extended in the mode of robotic technology. The robot can be controlled remotely to access congested areas and track other targets. The image processing technology used in the project can be extended to create technologies for image processing in traffic signals and for facial recognition.

References

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[2] Almaula, Varun, and David Cheng. "Bluetooth triangulator." Final Project, Department of Computer Science and Engineering, University of California, San Diego (2006).

[3] Stauffer, Chris, and W. Eric L. Grimson. "Adaptive background mixture models for real-time tracking." Computer Vision and Pattern Recognition, 1999. IEEE Computer Society Conference on.. Vol. 2. IEEE, 1999.

[4] Evans, Brian. Beginning Arduino Programming. Apress, 2011.

[5] Zivkovic, Zoran. "Improved adaptive Gaussian mixture model for background subtraction." Pattern Recognition, 2004. ICPR 2004. Proceedings of the 17th International Conference on. Vol. 2. IEEE, 2004.

[6] Lipton, Alan J., Hironobu Fujiyoshi, and Raju S. Patil. "Moving target classification and tracking from real-time video." Applications of Computer Vision, 1998. WACV'98. Proceedings., Fourth IEEE Workshop on. IEEE, 1998.

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[9] “AXIS P3364-VE network camera” viewed on 19/05/2015 <http://www.axis.com/lk/-en/products/axis-p3364-ve>

[10] “AXIS P33 network camera series” viewed on 19/05/2015 <https://www.use-ip.co.uk/datasheets/1215/axis_p3364ve_fixed_dome_network_camera_12mm_0484001.pdf>

[11] “G54 Wireless High Power Desktop Access Point” viewed on 20/05/2015 < http://www.tp-link.us/products/details/?categoryid=245&model=TL-WA5110G#spec>

[12] Agam, Gady. "Introduction to programming with OpenCV." Online Document 27 (2006) viewed on 21/05/2015 < http://www.cs.iit.edu/~agam/cs512/lect-notes/opencv-intro/opencv-intro.html>.

[13] “OPenCV” viewed on 21/05/2015 < http://opencv.org/>

[14] “Image filtering” viewed on 23/05/2015 < http://docs.opencv.org/modules/imgproc/doc-/filtering.html>

[15] “Structural Analysis and Shape Descriptors” viewed on 23/05/2015 <http://docs.opencv.org/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html>

[16] “Distance between two points (given their coordinates)” viewed on 24/05/2015 < http://www.mathopenref.com/coorddist.html>

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[19] “How to connect Arduino WiFi Shield to Arduino Robot” viewed on 27/05/2015 < https://arduinorobothelp.wordpress.com/>

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[21] “Global Health Observatory (GHO) data” viewed on 17/05/2015 < http://www.who.int-/gho/road_safety/mortality/en/>

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