Project Name: SpyBot

Transcription

1 EEL 4924 Electrical Engineering Design (Senior Design) Final Report April 23, 2013 Project Name: SpyBot Team Members: Name: Josh Kurland Name: Parker Karaus

2 TABLE OF CONTENTS Project Abstract...3 Introduction...4 Technical Objectives...5 Cost Objectives...10 Parts List...11 Division of Labor...13 TABLE OF FIGURES Block Diagram. 9 Gantt Chart. 14 Schematics. 15 PCB Layouts. 17 Software Flowcharts 19 2

3 Abstract Our project consists of a remote controlled vehicle equipped with a servo turret and mounted wireless camera. The vehicle is controlled remotely by a portable device using Xbee Wireless transceivers. Utilizing two joysticks the user can control the movement of the vehicle as well the camera direction. A large push button operates a laser that can be used to mark specific targets. The remote control also houses a Beagleboard-XM computer with an ARM8 processor. The Beagleboard takes the live video feed from the camera and implements a color tracking algorithm, which is then sent to a monitor through HDMI. 3

4 Introduction The SpyBot is used as a search and destroy device capable of tracking a subject (colored ball) from a distance. The purpose of this project was to build a remote controlled vehicle with a camera attached to a pan/tilt servo turret. The device will provide the user with a video feed in order to drive the vehicle and move the camera. The vehicle can be driven in close range within eyesight or over longer range through use of the video feed. The video displayed to the user has the option to track a colored target. The rover vehicle and camera can be driven or turned independently of one another. 4

5 Technical Objectives This project consisted of two distinct spheres of focus: Driving the vehicle and following an object. The vehicle uses DC motors driven by a microprocessor with H bridges in between. The H bridge takes the PWM pulse from the microprocessor and uses it as a signal to open and close the transistor gates and allow the voltage to flow to the motor. The wider the PWM pulse (the more area under the curve) the longer the gates will be opened, and the faster the motor will run. This also allows the motors to be controlled both forward and reverse. By using four control signals we can precisely control left and right steering. Sending a pulse to A and C will move the motors forward. A pulse on B and D will put the motors in reverse. Turning is achieved by sending signals to opposite directions. For example, 5

6 to turn left at an angle, C can be set to full speed while B will drive back at a fraction of its maximum, thus turning at precise angle. The vehicle and the remote control are both powered by 9.6V NiMH rechargeable batteries. To recharge the cells, we built a recharging circuit that provides a current source (from a 12V 500mA power pack) of about 200 ma. This slowly charges the battery packs until they reach their peak charge. Upon reaching their peak, the voltage curve will start to dip. To sense this voltage drop, a TL081 op amp was used as a comparator, with one input being the battery voltage by itself (in the negative input of the op amp), the other being the battery voltage along with a charging capacitor (in the positive input of the op amp). The capacitor will discharge slowly and still be greater than the pure battery voltage after the drop. This will result in a large increase in voltage from the output pin (from about 1-2 V to above 9 V). The op amp output is applied to the gate pin of a power PMOS transistor. When it receives a high voltage, there is not enough of a differential between source and gate to close the transistor, as the source end is receiving the voltage from the regulator. When the output is low (meaning the two compared voltages are near equal), the gate will have little voltage applied, meaning the source is being biased enough to create a large gate source differential, closing the transistor and allowing the batteries to charge. As the circuit must be closed to begin charging initially and obtain the voltage comparison, a switch is used to bridge the PMOS temporarily, after which it can be open to allow the PMOS and op amp to start or stop charging on their own. A large capacitor was used to ensure that the difference in peak voltage and dropped voltage would not be missed. Target color identification is achieved by using a thresholding algorithm. First the image is converted from RGB into an HSV color scale. Then the specific color s minimum and maximum HSV range values are set. This converts the video into a binary image, where all the pixels that fall outside of the threshold range are removed, leaving just the pixels of interest. The threshold 6

7 values can be set using a calibration algorithm that takes the average and standard deviation of all of the H, S, and V values. The maximum will be the average plus one standard deviation up to account for slightly brighter or duller values. The minimum will be the average minus the standard deviation. This will work as long as the entire frame is filled by the object. Any background color will affect the calibration. Target tracking is done by finding the spatial moment of the already thresholded binary image. The spatial moment of the image is the weighted average of the centroid over the area. ( ) ( ) ( ) ( ) This algorithm returns the first order moment of the colored object as it changes position in pixel space. This method is limited to tracking just one object at a time. If multiple objects of the same color are in the frame, the algorithm will attempt to detect the change in both objects. This will result in the moment being in the middle of both objects, instead identifying the correct position. Lastly, the processed video needed to be displayed to a screen. In the original proposal, we had not yet settled on what type of device we were going to use to process the video, so the specifics of the display output were not given. The Beagleboard was chosen due to its supported DVI-D output as well as special LCD expansion headers. It wasn t until later that it was discovered that the operating system chosen for its OpenCV support did not also include support to those expansion headers. The next option was to acquire an analog composite screen and use a digital to analog converter to output the video. After spending far longer than necessary modifying the kernel to support different screen resolutions, we learned that the 7

8 signal converter was in fact not compatible with the DVI-D video output used by the Beagleboard, so that the board would never get the digital handshake that it was expecting. Therefore the third choice was taken to use a standard computer monitor to view the camera video feed. While this method is not very portable, it is able to support far higher resolutions than the previous LCD designs could, resulting in a much better overall image. 8

9 Block Diagram 9

10 Cost Objectives Our initial goal was to spend less than $300 on this project, not including the cost of the computer and xbees. We ended up using the BeagleBoard as the computer for the image processing software, which cost a significant amount. The project still cost less than $500 overall, which was our absolute limit in purchasing, so our estimate was not too far off. According to the parts list below, which also includes spare parts and some unused parts, we spend a total of $ on all parts of the project. This includes the remote, rover, motor drivers, and PCBs (all of our PCBs were milled for free by UF or Advanced Circuits). Our project is similar to a handful of RC cars on the market with live video feeds. For example, the Spy Gear Spy Video Car VX-6 ( VX-6/dp/B004QM91JE/ref=sr_1_3?ie=UTF8&qid= &sr=8-3&keywords=rc+car+with+camera) is a remote controller car with LCD mounted in the controller. It costs far less than our project, mostly due to the lack of image processing of any sort, which we performed with the BeagleBoard. Our Spybot project is also able to turn the camera without turning the rover, since it is mounted on the pan/tilt servos rather than directly on the car. 10

11 Parts List SPYBOT Item Quantity Cost Shipping Total Remote Joystick 2 $3.95 $2.00 $7.90 Xbee NiMH Battery Pack 1 $16.00 $10.00 $26.00 Switch 3 $0.00 $0.00 $0.00 9V to 5V Regulator 1 $0.00 $0.00 $0.00 5V to 3.3V Regulator 1 $0.00 $0.00 $0.00 Large Push Button 1 $0.00 $0.00 $0.00 Enclosure 1 $8.00 $0.00 $8.00 MicroController 1 $0.00 $0.00 $0.00 Computer BeagleBoard 1 $ $0.00 $ HDMI - DVI Connector 1 $2.00 $0.00 $2.00 Computer Monitor Rover Rover-5 Platform 1 $27.00 $25.13 $52.13 IP Camera 1 $49.99 $0.00 $49.99 Xbee NiMH Battery Pack 1 $16.00 $10.00 $26.00 Processor 1 $0.00 $0.00 $0.00 Pan/Tilt Bracket 1 $5.95 $0.00 $5.95 Pan/Tilt Servo 2 $8.95 $0.00 $17.90 Low Power Laser 1 $7.95 $0.00 $7.95 Proximity Sensor 1 $13.95 $4.43 $18.38 Voltage Regulator 3 $0.00 $0.00 $0.00 Barrel Jack 1 $3.88 $0.00 $3.88 Recharge Circuit Op Amp 1 $0.00 $0.00 $0.00 Resistor 1 $0.00 $0.00 $0.00 Capacitor 3 $0.00 $0.00 $0.00 Switch 1 $0.00 $0.00 $0.00 Potentiometer 1 $0.00 $0.00 $0.00 Transistor 1 $0.20 $0.00 $0.20 Voltage Regulator 1 $0.00 $0.00 $0.00 Diode 3 $0.00 $0.00 $

12 H Bridges NPN MOSFET 20 $0.77 $0.00 $15.40 *includes spares/extras PNP MOSFET 10 $0.91 $0.00 $9.10 *includes spares/extras Resistor 12 $0.00 $0.00 $0.00 Opto-Isolator 8 $0.00 $0.00 $0.00 TOTAL $

13 Division of Labor Parker Karaus was responsible for H Bridge design and construction Battery Recharging circuit design and construction Xbee transceiver communication Josh Kurland was responsible for Beagleboard kernel, Operating System and OpenCV installation Image processing and tracking Camera setup and interface Shared tasks consist of PCB design Motor/servo drive code Parts selection 13

14 Gantt Chart Project Selection P+J Joystick Testing Xbee Communication P+J MicroProcessor PWM J DC Motor Interfacing P IP Camera Interacing P+J LCD Driver J Testing P+J Time 14

15 Schematics Rover: Recharge/Regulator: 15

16 H-Bridge: Remote: 16

17 PCB Layouts Rover: Recharge/Regulator: 17

18 H-Bridge: Remote: 18

19 Software Flowcharts Rover: 19

20 Remote: 20