Search and Rescue Copter
05/09/11
Group Members:
Karim Gilani
Jaydeep Patel
Patrick Fakhir
“I pledge my honor that I have abided by the Stevens Honor System”
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Contents
1 Introduction: 3
2 Technical Information: 4
2.1 Functional Description 4
2.1.1 Search and Rescue Copter Functional Description: 4
2.1.2 Functional Block Diagram: 5
2.1.3 Software Functional Description: 6
2.1.4 Software Functional Block Diagram: 7
2.2 Technical Description 8
2.2.1 Design #1 Hardware Realization Block Diagram: 8
2.2.2 The Gyroscope: 9
2.2.3 The GPS receiver: 9
2.2.4 The Infrared Camera: 9
2.2.5 The Camera/Video device: 10
2.2.6 The Ultrasonic Range Finder: 10
2.2.7 The Data Storage Device: 11
2.2.8 The Search and Rescue Copter Data Viewer Application: 11
2.2.9 The Microcontroller: 11
2.2.10 The Motors: 12
2.2.11 The Propellers: 13
2.2.12 The Battery: 13
2.2.13 Design #2 Hardware Realization Block Diagram: 14
2.2.14 The Laser Scanner: 15
2.2.15 Economic analysis: 15
2.3 Mathematical Principles Embedded in the Copter 16
2.3.1 Calculating Motor Requirements 16
2.3.2 Calculation of operating time 18
2.4 Performance Expectations/Objectives 19
3 Design Constraints: 20
3.1 Economic: 20
3.2 Environmental: 20
3.3 Health and Safety 20
3.4 Sustainability 20
3.5 Ethical Responsibility 21
4 Critical Evaluation of Project 21
4.1 The Good 21
4.2 The Scary 21
4.3 The Fun 21
4.4 Funding of Project 22
5 Summary 22
6 References: 23
7 Appendix A: Datasheets 24
1 Introduction:
The purpose of our design project is to create an aerial copter to help human search and rescue team. Earthquakes, tsunamis, and cyclones: disasters like these make a normal environment dangerous and hard to navigate. Built with off-the-shelf parts the robots are designed to provide easy access. Since the robots can be deployed quickly, a network can be established far more quickly than a technician on the ground might be able to. Manpower is costly. Copters, on the other hand have a much smaller onetime cost on top of the annual maintenance cost. These copters can be deployed to an area of interest where they can collect infrared and normal imaging data. Upon return to the base from their patrol, the data from the copter can be transferred to a centralized location where anyone interested in the data can access it.
Because the copters are autonomous, many considerations must be made in the design. We also have to take into consideration the many options we have for each individual component. The battery must be able to withstand the power requirements incurred by the components on the copter – mainly the motor, which will be responsible for providing thrust to keep the copter afloat. The frame must be light and made of the right materials such that the yield of power to weight is high enough to sustain a decent flight through the air.
When the safety of human beings is concerned, it is of utmost importance that trust in this technology is rightfully placed. Failure is not an option. Detailed research must be performed to ensure the success of this project.
2 Technical Information:
2.1 Functional Description
2.1.1 Search and Rescue Copter Functional Description:
The Search and Rescue Copter is essentially a patroller. It generally follows a preprogrammed path taking surveillance infrared/normal image data at user-specified spots. As the copter is autonomous, it is on its own upon departure from the base. It must be capable of navigating through a complex environment if it is to survive.
The Search and Rescue Copter must know what it is capable of doing energy-wise. The copter can calculate the distances it must travel. It can be provided with estimates of the amount of power consumed per unit distance from educated calculations made from previous runs. This information should be enough for the copter to determine whether or not it has enough energy to proceed forward while having reserve energy to return to the base with its valuable data for recharging and data upload.
The group would like the copter to not only be power level alert, but also alert to obstacles in its harsh environment. It needs a way to know where it is, where nearby obstacles lie, and the best path around the obstacles to its destination. GPS is an easy solution to the positioning. It is important to note, however, that GPS data may not be available in all locations, especially in enclosed areas.
As for the environment navigation, it is a tricky process with many options. One ingenious solution developed at MIT used laser scanning to map indoor environments. Another similar sound based nature inspired solution would be the bat preferred echolocation. Animal echolocation works using sound signals emitted and reflected back from surroundings. Objects in the environment reflect these sound waves, which take time to reach the left and right ears. From the arrival delay of the signal to the right and left ear, distances to nearby objects can provide a means for safe navigation.
The data collection in this diagram is represented by infrared and normal cameras. The type of data can of course be expanded to whatever is desired by user. The copter will collect this data from user input locations of interest. One feature that the group desires of the robot is the collection of data at an unspecified location if the data has been justified important. Specifically, the group wants data collected when infrared imaging detects heat signatures from human beings.
2.1.2 Functional Block Diagram:
2.1.3 Software Functional Description:
The client of this product will mainly be in contact with the Search and Rescue Copter application for controlling the entire surveillance copter fleet. There are two major parts/threads to the application: the user dedicated portion and the copter status focused portion.
The user input handling portion allows the user to access collected surveillance data as well as edit each of the copter’s patrolling parameters. In our case, the collected data will be of infrared/normal imaging. The user should be able to toggle between these two different views. If the copter is docked at the base, its parameters will be modified then and there. Otherwise, the copter is out on patrol, the modified parameters will be uploaded onto the copter upon its arrival.
The copter event thread is responsible for the all of the arrival/departure events of the copters. When a copter arrives, this thread is responsible for querying the copter for its data and uploading the data to a centralized storage location – preferably on a server accessible to all who may be interested in the data. The thread should also update the copter’s parameters upon arrival if they were modified by the user. Lastly, the thread will continuously check to see which copters are ready to be sent on patrol.
Lastly, the application has flexibility in which copter will perform which patrols. If all of the copters are equally capable of collecting the same data and travelling the same distance, it would make no difference to the user which particular copter performs which runs. The application can thus keep track of run priorities and assign runs to copters based on their availability, thus improving efficiency of the search/surveillance.
2.1.4 Software Functional Block Diagram:
2.2 Technical Description
2.2.1 Design #1 Hardware Realization Block Diagram:
Design 1 focuses on using the echolocation approach to the obstacle evasion problem to the autonomous copter. This approach uses the ultrasonic range finder mounted top, bottom, front left, and front right.
2.2.2 The Gyroscope:
The gyroscope provides data about the current x, y, and z axis orientation of the copter. This data is essential to the movement of the copter. If the copter is tilted forward, thrust from the motors will drive the copter forward. If the copter is tilted sideways, the copter will move sideways. The copter relies on its angular orientation to achieve movement in various directions.
The particular gyroscope the group chose for the copter is a dual axis gyroscope. The copter is concerned with only with angular orientation with respect to the x and y axis for movement. The gyroscope model consumes approximately 7 milliamperes of current at 3 volts. The weight of the gyroscope is very negligible – and unfortunately not even provided under the physical description in the datasheet.
2.2.3 The GPS receiver:
While the gyroscope provides angular orientation, the GPS provides coordinate location of the copter. The user will determine where the copter needs to go. GPS is how the copter will know that it has reached its goal.
This Parallax GPS receiver module can be queried via serial i/o commands for latitude, longitude, altitude, speed, and direction/heading. This satisfies the position and power alertness functionality previously discussed. In addition, the PMB-648 based module also supports querying for altitude as well as tracking of up to 20 satellites. An additional specification important to note is the acquisition time. On cold and warm starts, the chip requires 42 and 38 seconds respectively. The module consumes approximately 65 milliamperes of current at 5 volts. The weight of the gyroscope is also negligible and surprisingly not provided under the physical description in the datasheet.
2.2.4 The Infrared Camera:
The infrared image data is vital to the clients of this product. When tracking people, infrared heat emitted from people is better contrasted against environmental surroundings. Operators of the search and rescue copter can thus spend more time rescuing than searching for a person in a regular photo.
The ICI 7320 Pro infrared camera is the most expensive part of design 1. Though the exact price must be quoted from the supplier, similar products are prices at one thousand dollars. Though the price is high, this camera comes equipped with 320/240 resolution alongside an auto-tracking feature. Though software is provided alongside the camera, it would be sufficient to make use of the C++ software development kit provided with the product for interfacing with the Arduino Mega microcontroller. The infrared camera consumes 1 watt of power via USB connection. This is equivalent to 200 milliamperes of current at 5 volts operation. The camera weighs 148 grams total including the lens.
2.2.5 The Camera/Video device:
Though the infrared sensor provides an excellent means for which to search for someone, a more accurate visual on the status of the victim would be appreciable. Depending on the economic concerns of the project, a video device may not be worth the extra capital and power costs incurred to the search and rescue copter. A camera taking pictures at interval time increments would suffice.
The group chose a small camera with minimal weight: the CM-26N/P CMOS Camera Module. The camera has a 640 by 480 resolution and operating range of 5 to 15 volts with 50 milliampere current consumption at 12 volts.
2.2.6 The Ultrasonic Range Finder:
The ultrasonic range finder is capable of detecting objects within a 6.45 meter range. It consumes 2 milliamperes of current with a variable operating range of 2.5 volts to 5.5 volts, with improved performance at 5.5 volt operation. Readings can be taken at a rate of 20 Hz; every 50 milliseconds. With 4 range finders mounted on the copter weighing 4.3 grams a piece, the total weight contribution to the copter comes out to 17.2 grams.
2.2.7 The Data Storage Device:
The microcontroller has a limited amount of memory; much of it will be used in computing motor power from gyroscope data and in buffering image results from the infrared sensors and audio/video devices. If the data from these sensors is stored into volatile memory, a failure of the search and rescue copter would mean loss of this important information. Thus a high capacity data storage device such as an SD card with SD card reader/writer is essential to success of the copter. This data can be stored into the card in a format that would be recognized by the corresponding application on the operator’s laptop.
2.2.8 The Search and Rescue Copter Data Viewer Application:
The data written to the SD card by the copter could easily be viewed as images but an application would allow for possible future expansion of the project to include other features. These features may require additional processing of the data before meaningful results can be properly displayed to the user. The application would act as an organized base from which behavior of the copter can be programmed and the data retrieved from the copter viewed.
2.2.9 The Microcontroller:
The microcontroller is the main component of the project and is responsible for a number of functions. It has to interpret data retrieved from the dual-axis gyroscope to achieve the desired orientation. In determining the desired orientation, the controller must take into consideration obstacles sensed by the ultrasonic sensors. The final changes in power delivered to the motors will produce thrust in the desired direction. The controller will also save the data obtained from the infrared sensors and image device.
Given the number of components involved with the project, it is necessary that the microcontroller have sufficient input/output pins with sufficient power supply to each. The microcontroller does not have enough memory to buffer the image data but is able to buffer some data; which can be written to the SD card allowing the next packet of data to be written.
2.2.10 The Motors:
The TP2410-09 brushless motor provides a max power of 104 watts. Given that these motors become inefficient when operated at the limit of their maximum ratings, four of these motors should efficiently be able to counter the weight of the copter. Calculations regarding the motor power requirements will be discussed in detail in section 2.3.1 Calculating Motor Requirements.