Aerial Surveillance Drone: Power Management

Transcription

1 Aerial Surveillance Drone: Power Management The Aerial Surveillance Drone is a quadrotor controlled by a mobile application and a microcontroller programmed to identify and follow suspicious targets while transmitting pictures and video taken by an onboard camera over the internet. Power and Weight Management Samantha Kenyon Colin Donahue Samantha Kenyon Jason Lowden Benjamin Wheeler January 9, 2013

2 Aerial Surveillance Drone: Power Management 2 Table of Contents I. Overview... 3 II. Requirements Specification... 3 A. Marketing Requirements... 3 B. Engineering Specifications... 3 C. Analysis of Engineering Specification... 3 III. Risk Investigation... 4 A. Existing Systems... 4 B. Concepts Selected and Rationale... 4 IV. Risk Mitigation Design... 6 A. Overview 6 B. Quadrotor... 6 C. Microcontroller... 6 D. Camera... 7 E. Total... 8 F. Flight Time 8 G. Weight H. Design Diagram 9 V. Parts List VI. Testing Strategy VII. Uncertainties VIII. Appendecies

3 Aerial Surveillance Drone: Power Management 3 I. Overview The system needs to be able to record and send video as well as be controlled by alternative devices. This requires extra components be added. The system needs to be able to power all of these components as well as maintain flight. These added components pose a risk to both the power management of the system, and the overall flight ability based on the overall weight of the system. In order for this project to be successful these problems must be solved. II. Requirements Specification A. Marketing Requirements 1. Easily Portable Must be able to transport easily to allow for flying in new areas. 2. Low Weight - Cannot be too heavy in order to allow for easy transport. 3. Low Cost - Since this system is for personal use and security it must be reasonable price for the average person. a. Enough Power to Sustain Flight - It must be able to remain in flight for a significant period of time. B. Engineering Specifications Number Specification Associated Marketing Requirements 1 The total weight of the system will not exceed 1 pound. 1, 2, 5 3 The cost of the system shall not exceed $ The system will operate on full charge for at least 8 minutes. 9, 11 C. Analysis of Engineering Specification Number Justification 1 The system needs to be easily portable. Anything heavier than this amount could make the system hard to transport. A system that is too heavy will require more powerful motors and will have reduced flight time. Keeping the weight of the system low will allow it to operate longer and be more maneuverable. 3 The cost must remain affordable for an average person and presently the cost of systems such as this exceeds $ The system must be able to remain in flight long enough to be controlled to get to a location or to identify potential threats. Many systems of this type remain in flight for 5 minutes.

4 Aerial Surveillance Drone: Power Management 4 III. Risk Investigation A. Existing Systems There are two different ways that surveillance on a quadrotor system. There are systems that hold external cameras. The Draganflyer X4 has a module in which one of three styles of camera can be placed so that video and photos can be captured during flight. These cameras are self powered and self sustained. In this system the camera is completely separate from the quadrotor, and this does not allow for streaming back to the controller. Another way that this is done is using a camera that is integrated with the system. The Parrot AR Drone 2.0 is a quadrotor with a built in 1280 x 720 front facing camera that interfaces back to the controller. This camera is integrated into the quadrotor using some form of power from within the device. B. Concepts Selected and Rationale The system should stream video back to the controller from a camera integrated with the device. This is similar to the second existing system. The first system is too limiting for our system. It allows for recording video and then reviewing if after flight, but there is no way to review the footage during the flight. Camera Originally the system was going to stream HD video. Through research this idea was disregarded early on. There are very few options for streaming HD video with small devices, and these devices are all expensive.

5 Aerial Surveillance Drone: Power Management 5 The Hack HD 1080p camera module is one of only a few options. It requires a 3.7V supply and has a video out pin that can send a live feed. It also records to an SD card. This component has limited availability and goes over the project budget. For this reason the system will not be streaming at HD quality. The HP web-cam deluxe will be proficient to stream video from the device to the controller. This is a chosen component because it has relatively high resolution, a max of 1280 X 1024, as well as a small current draw. It is also available to us from the remnants of a previous project. This can interface with other devices through USB which is very helpful. Microcontroller There are many available microcontroller options to choose from. WiFi is being used to transmit data; therefore a microcontroller with WiFi capabilities is needed. A microcontroller that is able to power the HP web-cam through a USB port is also needed. To narrow down the search I focused on what was available to us. The Gumstix Overo Fire COM can be used with this project.

6 Aerial Surveillance Drone: Power Management 6 This microcontroller is available to us, also from a previous project, and it has everything needed for the system. It has both Bluetooth and WiFi capabilities so it has flexibility in regards to communication. It also has a camera connector and USB. This Gumstix also comes with an I/O board that can be used to interface with other devices. The Pinto-TH expansion board has 6 analog-to-digital converts, along with 6 pulse width modulators, and 8 GPIO lines. These all provide flexibility to use the microcontroller to control the quadrotor if needed. Since this microcontroller has everything needed and is available free of charge there is no need to look any further. This is the best available option. IV. Risk Mitigation Design A. Overview Power consumption is extremely important part of the design. The following design calculations show that all of these components can be used together and use the battery supplied by the quadrotor. The consumption of each component must be analyzed to show this. B. Quadrotor The quadrotor itself has a stock battery with the following specifications. Amp Hours Discharge Rating 500 mah 12C This battery needs to power the four motors of the quadrotor as well as the other components within the quadrotor. The following table shows the current draw of the quadrotor with no load. Average Current Draw Max Current Draw 2.7 A 3.7 A The stock batter on the quad rotor has a voltage of 3.7V. This results in a power consumption shown below. Average Power Consumption Max Power Consumption 9.99 W W C. Microcontroller The Gumstix microcontroller can at its peak of performance use 700 ma of current. The microcontroller will definitely be used for WiFi transmission and the CPU will also be used. It is difficult to find precise measurements of the current draw for these values, however it can be approximated.

7 Aerial Surveillance Drone: Power Management 7 Component CPU WiFi (Max) Total (Max) Approximate Current Draw ma 275 ma 675 ma This microcontroller needs an input voltage of at least 2.7V, but a max of 4.5V. This results in the following overall power consumption. Minimum Power Consumption Maximum Power Consumption W W D. Camera The power consumption of the camera depends on the resolution of the camera at any given time. On average the camera draws somewhere between 100 and 120 ma while active. The relationship between current and resolution is shown below. Resolution Approximate Current Draw 320 x ma 640 x ma 1280 x ma The camera needs to be powered with 5V. Resolution Approximate Power Consumption 320 x W 640 x W 1280 x W Since the battery provided with the quadrotor is only 3.7V another battery will be needed. It is easiest to just add another battery of the same type to the quadrotor and connect it in series with the previous value. This will retain the capacity of the original battery but double the voltage to 7.4V which is enough to power the camera. The batteries should be connected as shown below.

8 Aerial Surveillance Drone: Power Management 8 E. Total All of the individual components need to be powered at their maximum current draw. Component Helicopter Gumstix Camera Total Approximate Max Current Draw 3.7 A 675 ma 120 ma A All of the individual components and their maximum power consumption Component Quadrotor Microcontroller Camera Total (max) Max Power Consumption W W 0.6 W W F. Flight Time The system should be able to maintain flight for 8 minutes. The battery used to power the quad rotor should be enough to power all of the components based on these power calculations. The challenge now is determining for how long this battery can provide them all power. Using the following equation this time can be determined. Current Draw (A) Flight Time (min)

9 Aerial Surveillance Drone: Power Management 9 This table shows that on average the quad rotor without any of these components can be powered for around 11 minutes. At the maximum current draw it can remain powered for 8 minutes. Finally with all of the components added to it, the system can remain powered with that battery for a minimum of 6 minutes. This is with the maximum current being drawn from the components. This allows for some variation in that number and the assumption that on average the flight time will be larger than 6 minutes but less than 8 minutes. This shows however that it is possible to do this with an acceptable flight time, although it may be necessary to adjust the engineering specifications to match this outcome. G. Weight Weight is an important factor when working with systems that fly. The system can only withstand a certain payload value before it is unable to maintain or even reach any altitude. When adding components onto the system this is something that must be considered. Each of the components chosen is very low in weight. Component Gumstix Camera Battery (Extra) Total (payload) Weight (g) 11 g 10 g 20 g 41 g Since the camera is already stripped down from its original form it is extremely low weight. The board portion itself weighs only 4 g, where as the USB cable weighs 6 grams. The Gumstix microcontroller also is very low in weight. The total of these two components is 21 grams. The extra battery adds another 20 grams to the payload. This means that the quadrotor needs to be able to fly with an extra 41 grams attached to it. Based on the testing done so far this is possible. The system has successfully carried a load of 59.8 grams; therefore 41 grams should be possible. H. Overall Design Diagram The extra battery now requires that there is a voltage regulator before both the microcontroller and the camera, to ensure that the correct amount of voltage is applied to both devices. The following diagram shows the components connected together for power. Voltage regulator 1 is a 3.3V voltage regulator that can take a voltage value below 15V and produce an output voltage of 3.3V, perfect for the microcontroller. Voltage regulator 2 would be a 5V voltage regulator that can take a voltage in the range of 7 35 V and produce a 5V output, which is perfect for the camera. These regulators are very small ad have no effect on weight.

10 Aerial Surveillance Drone: Power Management 10 The microcontroller will be placed underneath the quadrotor next to the batter and will then be connected to the battery. The camera will then be connected to the microcontroller and placed underneath that facing down, as shown below. There are no existing patents for this design. V. Parts List Component Description Cost Our Cost Availability Gumstix Overo Fire COM Microcontroller $ $0 Helicopter Project HP 8.0 MP Deluxe Webcam $24.95 $0 Helicopter Project

11 Aerial Surveillance Drone: Power Management mAh 1-Cell 3.7V 12C LiPo: 120SR Elite Battery $8.49 $8.49 Available delivery in 1 week 5V Voltage Regulator µa7805c $1.25 $1.25 Available - delivery in 1 week 3.3V Voltage Regulator LD1117#33 $1.25 $1.95 Available - delivery in 1 week Total Cost $ $11.69 VI. Testing Strategy To further test power consumption it is necessary to connect all of the components and actually measure current draw and total power. The numbers given here are just estimates based on data sheets and expertise from others who have used these components before. They are not measured values, with the exception of the current draw of the quadrotor with no load. These values need to be measured once they are connected together to ensure that they remain within these ranges. The current draw of each component while they are all running in their maximum stage needs to be measured. All of these components are available so this test should occur within the next 2 weeks, by 1/23/13. Also the quad rotor needs to be tested with different weights. As flying the quadrotor becomes easier the flight time can be tested. Currently only tested its ability to fly with a given payload has been tested, not the duration of that flight. It is necessary to add weight and fly the quadrotor for as long as possible, and record that time. This test should be done within 1 week, by 1/16/13. VII. Uncertainties The uncertainty that I have now is the flight time. I found that at maximum load the system can only power all of the components for 6 minutes. This is less than our desired 8 but something I believe is still acceptable for the project; however this was assuming the quadrotor draws the same amount of current with no load as it would with the load. This is an incorrect assumption. The load will affect the current draw of the quadrotor because it will need more power to carry more weight. Therefore it can be assumed that with the load the flight time will be less than 6 minutes. How much less it will be is something that needs to be tested and determined. If it cannot sustain flight for at least 5 minutes our implementation will need to be reconsidered. Another uncertainty is the addition of sensors. We have not yet discussed this much as a group; however additional sensors will be needed for other portions of the project. These sensors will need to be powered and will also require a higher payload for the system. I do believe that the numbers shown

12 Aerial Surveillance Drone: Power Management 12 here should allow for additional sensors to be powered with the battery but the flight time will be affected. VIII. Appendices Parrot AR Drone quadricopter?bkiid=subcategory_games Toys_Electronic_Toys_Remote_Control_Toys SubCat egorywidget p&catId= Draganflyer X4 Sparkfun Hack HD 1080p Camera Module Gumstix Overo Fire COM Microcontroller HP 8.0 MP Deluxe Webcam Overall Reference for Gumstix and Webcam mentation/documentation.html Sparkfun 5V Voltage Regulator µa7805c Sparkfun 3.3V Voltage Regulator LD1117#33 Newegg 500mAh 1-Cell 3.7V 12C LiPo: 120SR Battery