TELEMETRY, SENSORS, CONTROLS AND RADIO REDESIGN FOR METEOR PLATFORM

Transcription

1 Proceedings of the 2004/2005 Spring Multi-Disciplinary Engineering Design Conference Kate Gleason College of Engineering Rochester Institute of Technology Rochester, New York May 13, 2005 Project Number: TELEMETRY, SENSORS, CONTROLS AND RADIO REDESIGN FOR PLATFORM Christopher Ayre / RIT Carlos Barrios / RIT ABSTRACT The project is a multi-disciplinary, multiyear research project whose ultimate goal is the application of micro-technology to space exploration. The project is the first step in an ambitious plan to get RIT involved in a student led space program. This design project represents the first stage of realizing this ambitious goal, the design of a high altitude platform capable of deploying and launching a rocket. The platform travels to an altitude of 80,000 ft utilizing helium filled high-altitude balloons and, after performing the necessary mission tasks, returns to Earth using a parachute. The electrical engineers were responsible for developing a flight computer to tie all of the systems together, and gather data as well as designing a communications system to enable the platform to communicate with the ground station. The communication system, combined with a global positioning system enabled the team to locate and recover the platform and the captured images of the upper atmosphere. INTRODUCTION The main task for this year s team was to re-design the components of the platform, to improve the power consumption and decrease the overall weight of the platform. The team was divided into two separate groups. The two main focus areas were the onboard computer and the communications system. These were important design issues because of the overall weight of the components that these are comprised of, and their power consumption properties. NOMENCLATURE APRS Automatic Position Reporting System ATV Amateur Television DFing Frequency Finding FAA Federal Aviation Administration FCC Federal Communications Commission GPS Global Positioning System OSD On Screen Display PIC Microchip Microprocessor Unit RX Receiver TX Transmitter XCVR Transceiver BACKGROUND RESEARCH High altitude balloons have been used for meteorological research since the 1890s. [1] The highest altitude reached was 170,000 ft (51,820 mi) from Chico, California in Many amateur groups and universities have conducted experiments by launching modules into the atmosphere to collect data. Some of these groups are the University of Kansas, University of Washington, and the Central Iowa Technical Society. Groups such as HABET (High Altitude Ballooning Experiments in Technology) have done extensive research and conducted multiple launches that established a communication link to their payload in near space. [2] All of these launches involve sending a small payload into the upper atmosphere to collect data. Many of these payloads are no more than 30 lbs. To our knowledge, the concept of rocket deployable platforms has not been 2005 Rochester Institute of Technology

2 Proceedings of KGCOE 2005 Multi-Disciplinary Engineering Design Conference Page 2 explored at the university level. Some of the lessons that the team took from previous research are to limit weight, create redundancy in critical systems where possible, and try to plan for the unexpected. The team also learned that the FAA is responsible for evaluating the safe operation of unmanned free balloons. CONCEPT DEVELOPMENT Once the design team had gained a better understanding of the scope of the project and defined the needs and requirements, time was spent reviewing the concepts that were designed by the previous year s team. A brainstorming technique was employed to generate new concepts whose effectiveness would later be compared to the existing concepts. The following section describes the various aspects of the project that the team gave the most attention to. Model The small scale design concept answered the need to transport a small-scale rocket, containing a Picosatellite weighing proximately 1 lb., to an altitude of 80,000 ft. This small-scale model was to adhere to a 6 lb weight limit, which was divided among the electrical components and the payload. This design consisted of a bursting balloon, a parachute, and a platform. The design can be seen in Figure 1. The parachute attaches between the platform and the balloon, which ensures that the parachute will open untangled upon balloon burst. The platform structure consists of a metallic plate inside a Styrofoam box covered in Mylar, which houses the electrical components. Figure 1 Design Model - Concept Drawing and First Prototype The box protects the components from the cycling of environmental conditions as well as shielding them from impact, and the Mylar reflects any radiation. The metallic plate serves the purpose of holing the components in place, as well as a reflective ground plane for the radio communications. The main metallic plate was designed our of a very light weight metallic mesh, that proved to have enough strength for the purposes of carrying all the components. The shape of the structure was square. The choice of using zero-pressure balloons with a cut-down mechanism was rejected, since a burst balloon that would automatically burst when it reached an altitude of around 80,000 feet proved to be much more suitable for the purposes of this project. This way, the cutdown mechanism could be eliminated, and the balloon was much easier to handle during launch, since it was a lot smaller and more robust. Final Design The proposed design by the 2005 team consists of a platform composed of a helium burstballoon, a parachute, an electrical platform composed of several electrical boards including communication devices, a central microcontroller unit and sensors, a digital still camera to serve as the payload that models the rocket (since the rocket design has not yet been implemented), and a ground station, which is used to control and track the system. Data Acquisition and Platform Control The boards on the payload are all mounted on a mesh ground plane allowing for shielding from antenna s RF energy. These electrical boards consist of the microcontroller layout with sensory components, 2-meter transceiver, 73-cm transmitter, on-screen display, beacon, power regulation and distribution, GPS and video multiplexer, as well as the visual/audio circuitry in order to locate the payload easily once back on the surface of the Earth. Other components on-board are four video cameras, batteries, duplexer, and antenna. The system is capable of many functions. The primary function is the idea of tracking the payload in order to make it recoverable. There is redundancy in this functionality. Since the system transmits both in the 73cm and the 2-meter band, it transmits the payloads position on both bands for redundancy, thus decreasing the chance of telemetry loss. The latitude, longitude, altitude, speed, course, and time, as well as internal and external temperature, atmospheric pressure, acceleration in 3 axes, and orientation are transmitted via on screen display for the 73cm band at a frequency of MHz. The same data is transmitted in an APRS formatted packet via the 2- meter band at a frequency of MHz, so as to be repeated in the APRS system. Paper Number 05005

3 Proceedings of KGCOE Multi-Disciplinary Engineering Design Conference Page 3 The secondary function is the idea that the system can be controlled by the ground station. Thus, a digital camera is used to take the place of the rocket to be controlled in the future. Signals are sent via the 2- meter band to the platform. The 2-meter radio onboard takes this signals, sends them to the microcontroller to be processed, and the appropriate actions are taken. The signals are predefined and consist of the following commands: $COSDS Creates a new OSD screen template $HRCPW Turns High Res Camera On/Off $HRCSN Snaps a Picture $VCAM1 Choose camera channel 1 $VCAM2 Choose camera channel 2 $VCAM3 Choose camera channel 3 $VCAM4 Choose camera channel 4 $VCAMR Automatic Roll of video cameras $CUTDN Activate a cut down device if present $APRSx Change APRS packet period to 10x seconds $TNCUx Change APRS packet refresh period to 10x seconds $CAMPx Change video camera channel roll period to 2x seconds $HRCPx Change High Res Camera auto picture to 20x seconds Recovery Stage The recovery stage consists mainly of the parachute and a non-system beacon. The parachute hangs freely with eight separate tether attachment points leading from the edge of the parachute to the platform. The parachute will automatically deploy after the balloon bursts, due to air resistance. Although the atmosphere at such an altitude lacks density, there is still enough of a force to react against the parachute. The non-system beacon is used for final DFing. This allows the tracking group to be able to find the payload when they are in close vicinity to the landing site. Ground Station The ground station consists of many stations. The two main stations are called the Mission Control and the Launch Control. Mission Control is the main station which will be developed here at Rochester Institute of Technology. The station will have the full capability to communicate with the platform at its maximum altitude. The antennas designed are to be a cross polarized yagi antenna for both the 73cm band and the 2-meter band, thus acquiring the necessary gain associated with the reception of the signal at the payloads high altitude. These antennas are to be mounted on a rotor controlled mast on the top of building 9, room The station itself will be located in the same room, and will have to ability to control the rotor via computer. Eventually, a computer program should be implemented in order to move the directional antennas to the correct position in order to correctly receive the maximum signal possible. The station will also have a terminal node controller to convert the received audio signal to data, since the signal is modulated in AFSK format, and the computer needs to acquire serial data. The computer should have the ability to record the video stream as well as save the data received via the 2-meter band. Data such as flight pattern, sensor data, speed, and altitude should be kept in a log in order to analyze the data at a later time. An overview of this system can be seen in figure 2. = RF Connectors 2-Meter Cross Polarized Yagi Antenna C3i - FO Gain = 12.6dBi 12 Line Rotor (50-60)ft (20-25)ft Manual Rotor Control Yaesu G-5500 Computer Interface for Rotor Control GS-232B Mission Control Grounding from rotor is necessary. System to be designed. 2-Meter Transceiver FT-1500M Terminal Node Controller Kantronics -KPC-3+ Rotor (Mechanical Control) Interface Yaesu G-5500 Shielded Cable DB-9 to PS2 Building Ground Computer Cable DB-25 to DB9 TV/VCR Combination 70cm Cross Polarized Yagi Antenna C3i - FO22-ATV Gain = 17.9dBi (20-25)ft Lighting Arrestors Tessco #47001(x2) and #84145 Ground Bar - Tessco #65118 (15-20)ft Coax 75ohm F-connector (15-20)ft ATV Downconverter P.C. Electronics TVC-4G Coax 75ohm F-connector Communications Computer Figure 2 (15-20)ft Dual Band(2m/70cm) Vertical Antenna Diamond - X50A Gain = 4.5dB ROOF - Wire Raceway Computer Interface WinTV Tuner Card USB Inferface Server (50-100)ft Duplexer (2m/70cm) Main Communication Radio for Communications with Launch Control. Mission Control Block Diagram Mission Control is a full control station, but it is built in such a way that allows the user to transport it to the launch site and quickly store it in a car to move to the recovery area. The control station is also built to allow the user to receive and transmit signals from the moving vehicle. On this station, there exists two antenna switches to choose which of two antennas the station utilizes at any given time. The two antennas are a magnetic mount vertical dual band Copyright 2005 by Rochester Institute of Technology

4 Proceedings of KGCOE 2005 Multi-Disciplinary Engineering Design Conference Page 4 antenna located on the roof of any vehicle all the time, and the second is a dual band yagi antenna with more gain for when the vehicle is not in motion. A simple flick of a switch allows the operator to utilize this functionality. The overall station consists of a wooden box built specifically for the following components; 73cm video down converter, 2-meter data radio, terminal node controller, dual band communications radio, two antenna switches, video to USB device, antenna duplexer, GPS as well as laptop with a docking station. The Mission Control Station with the use of the GPS in the Launch Control Station will be able to track the Launch Control Station in relation to the platform. The communications radio will allow for voice communications between the Mission Control Station and other Amateur radio operators in the area. The laptop will act as the centralized data storage. It will be designed to allow both the Mission Control Station as well as the Launch Control Station to log any data received from the payload. Since the payload utilizes the frequency spectrum allocated for Amateur radio use, many Amateur Radio Operators in the area are ready to lend their services and equipment to help gather data for the team. An overview of the Launch Control is shown in figure 3. = RF Connectors = 12V Power Input Launch Control BNC (Female) - 2m BNC (Male) - 2m 2m/70cm Beam Arrow PL-259 (Male) - 2m BNC (Female) - 70cm BNC (Male) - 70cm PL-259/UHF (Female) 70cm Mounting Type PL-259 (Male) - 70cm PL-259/UHF (Female) 2m/70cm Mounting Type Connections made outside of mobile rig Dual Band(2m/70cm) Vertical Antenna Comet - M-24M 2m/70cm 2m/70cm Whip Dual Band(2m/70cm) Vertical Antenna Comet - M-24M Flight Tracking and Prediction Both Balloon Track, a free program written by Rick von Glahn, and UI-View, written by Roger Barker, will track the balloon. Balloon Track will be used for predicting the flight path of the platform before the launch. Given wind direction and speed obtained by a weather forecast, Balloon Track will be able to plot a predicted flight path for the payload. This way, the team will get in idea as to where the payload will come down. UI-View is a program that takes the APRS formatted string that is sent down via the 2- meter band, and plots the position of the payload based on the latitude and longitude sent by the payload. UI-View will also calculation speed and heading information, allow a terminal window to be accessed to send up commands, and log the flight for each point received. It will also be able to receive the telemetry sent down with the APRS String. This way, the data is stored to be analyzed at a later time. The team established procedures and checklists for ground station preparation and duties. These checklists divide up the duties and responsibilities among team members and assistants at the launch site. This will give the team a communications system to maintain organization during the mission. This will also prove to be valuable to future teams who wish to conduct balloon launches. PROTOTYPE FABRICATION Every single component on board plays an important roll on the success of the mission. However, the two main components which will be discussed further are the computer board and the communications components. Electrical Boards GPS Etrex Legend PL-259/UHF (Female) 2m Mounting Type Duplexer (2m/70cm) Antenna A/B Antenna A/B Switch Switch MFJ-1702C MFJ-1702C 2-Meter Transceiver ATV Downconverter FT-1500M P.C. Electronics TVC-4G Terminal Node Controller Computer Kantronics -KPC-3+ Interface WinTV Tuner Card The electrical board design seen in Figure 4 is the main subsystem that provides all processing and communications to the platform. The board layout includes various battery packs, a transceiver, an independent beacon, the flight computer, environmental sensors, video processing and transmission components, and an antenna to communicate with the ground station. Mobile Communications Laptop Communications Radio Yaesu ft-7800 Figure 3 Launch Control Block Diagram Paper Number 05005

5 Proceedings of KGCOE Multi-Disciplinary Engineering Design Conference Page 5 Power Control Switching Circuit / 5 Digital Still Camera Camera 1 Camera 2 Camera 3 Camera 4 / 4 Final Assembly VIDEO MUX / 2 Select Lines DEMUX / 2 Select Lines / 3 Select Lines 70-cm Tx Overlay / 2 Analog 2 Thermo Sensors MAX232 ( Driver) Analog Pressure Sensor DUAL UART MUX PIC ADC Figure 4 Duplexer / 3 Analog 3 Accelero meters Layout of Electrical Components 2-m Tx/Rx GPS TNC Digital Compass RTS Signal Beacon The integration of the electrical boards and motor package creates the final flight vehicle. The final assembly can be seen in Figure 5. Figure 5 Final Assembly This assembly provides an efficient and practical method for the interconnection of the flight computer with environmental sensors, GPS, payload control device, transceiver, video overlay and power supply, while complying with the 6 lb weight limitation. The flight computer gathers the data from the environment sensors and the GPS, and sends the information to the transceiver for transmission in an APRS data packet, and to the video overlay for transmission via the video downlink. The flight computer also controls the video multiplexer, which cycles through 4 video cameras on-board. The flight computer also triggers an interrupt to receive the commands that are sent from the ground station to the transceiver, and responds accordingly. PROTOTYPE TESTING Preliminary tests were conducted on various components of the assembly before connecting them together. After testing and verifying proper operation of all components, they were assembled and tested one-by-one. No two components were added and tested at the same time unless it was imperative to do so, so as to avoid multiple variables. This testing process made it easier to debug the system as we put it together. The system was tested by first testing and debugging the 3 main systems on the platform, and then putting them all together. These three systems were the video downlink system, the sensory and processing system, and the main communications system. Once all the systems were working, the platform was finally tested to respond to the commands that were being sent from the ground station. Before launch, some more issues had to be taken care of. In order to estimate the balloon path, the balloon trajectory software Balloon Track was used. Data was entered to test the ability of the software to estimate the trajectory of the platform. Results The results of the conducted tests proved the designed prototype to be worthy of flight. Therefore, the ultimate test of the platform was the first launch since true near space environment cannot be simulated. Once the first launch was conducted, a number of questions were answered and the planned launch process scheme was perfected. The environmental data that was retrieved showed that the temperatures that are encountered at high elevations were not detrimental to the system. All system components are rated for temperatures around negative 30 degrees Celsius, and the lowest temperature that was encountered inside the platform was about negative 5. All the components proved to have worked properly, and efficiently. The batteries provided enough power for the platform to be fully operational for over 4 hours of flight. After landing, the signal was lost from the transceiver possibly due to the landscape, so the system could have still been powered up. The estimated time of operation with the Copyright 2005 by Rochester Institute of Technology

6 Proceedings of KGCOE 2005 Multi-Disciplinary Engineering Design Conference Page 6 amount of batteries that were used was 12 hours. The first flight was much longer than predicted due to a miscalculation in the amount of helium that was used. Also, unexpected high winds made the balloon drift a longer distance. The maximum drift velocity encountered during the entire flight was about 158 miles per hour (253 km/hr). The video output from the 70-cm transmitter was verified to reach long distances with no distortion in video quality. The signal from the 2-m transceiver was also determined to be powerful enough to be reliable at very high altitudes. CONCLUSIONS From the results of the design and testing procedures, the team has been able to determine which facets of the design will be carried onto successive launches and which aspects need improvement. Design Successes The working payload of the team is its overall greatest success. The design was under the specified weight (6lbs), and could be controlled from a wireless station, and had the ability to gather sensor data and transmit this data to the ground station. The polystyrene insulation and survivability enclosure protects the electrical board and all of its components from damage upon landing impact. The polystyrene will cushion the impact and also provides insulation from the harsh near space environment. The Mylar covering is also good because it inhibits electromagnetic radiation from penetrating the package causing unwanted system behavior. The platform uses the Amateur radio bands for several reasons. The first and foremost is the availability of programs and knowledge into communications. Secondly, the program utilizes many Amateur Radio Operators in the area for tracking. There are many stations with the capability of tracking a system using APRS. During our first launch, we had many volunteers within the community. This also helps promote the project and RIT within the community. The frequencies used will be MHz for the ATV, MHz for the non-system beacon, for the downlink APRS system. This utilizes the vast repeater network of the state and country to help further track the platform. The 2-meter uplink frequency will be arbitrary defined at each launch depend on the amount of activity on the frequency. The frequency used will be a data frequency allocated by the FCC for Amateur Radio use. Design Improvements One major improvement suggestion is under the category of weight. Currently the payload uses 9-volt high capacity batteries for on-board power storage. Although other power sources were considered in this years project, the issue still remains that we need to reduce weight, thus reducing the amount of stored energy weight. Suggestions include solar panels and lithium polymer battery cells. These cells are lightweight as well as relatively high capacity. The other great feature of these batteries is the idea that they can be charged and used again, thus decreasing the cost per launch. The difficulty with this idea is that these cells require a specific charger circuitry, and may add more weight than the original high capacity 9-volt batteries used. Overall, project was a great success. The goals set forth were accomplished as well as many other goals set by this year s team. Project will and does create an atmosphere that fosters the advancement of science, through engineering. ACKNOWLEDGMENTS RIT Faculty Dr. Patru Project Sponsor, EE Advisor Dr. Phillips Project Coordinator Mr. Jim Stefano HAM Radio Industry Supporters Tyco Electronics Toshiba Ultralife REFERENCES [1] Mracek, Anna. History of Balloon Flight. 12 Feb < Ballooning/history.htm>. [2] High Altitude Balloon Experiments in Technology. 13 Dec < HABET/Home.html>. [3] Balanis, C., 1989, Advanced Engineering Electromagnetics Wiley, John. [9] Balanis, C., 1997, Antenna Theory, Analysis and Design Wiley, John. [4] 2003/04 Meteor Team Documents. Paper Number 05005