ECE 480 DESIGN TEAM 11

 

 

Electronic Parachute Deployment System

Proposal

February 21, 2014

 

Sponsor: Pete Semig (Texas Instruments)

 

 

Facilitator: Joydeep Mitra

 

Design Team Members:

Michikazu Aono

Max Cooper

Zane Crawford

Qiaosen Huang

Pedro Rodriguez

Jessica Shelby

 

 

 

 

 

EXECUTIVE SUMMARY

The Electronic Parachute Deployment System is to replace the traditional parachute deployment method on a large model rocket that employs the use of a multistage parachute, allowing improved consistency and reliability over the traditional fuse system. The system will be controlled by the Texas Instruments MSP430F5310 microcontroller in conjunction with a sensor, power supply unit, and parachute deployment system. The team pursued low cost innovative solutions in developing the EPD system.

 

 

 

 

Table of Contents

Introduction                                                                       2

Background                                                                       2

Objectives and Design Specification                                3

List of Objectives                                                        3

Specifications and Design criteria                              4

FAST Diagram                                                             4

Conceptual Design                                                            4

Sensors                                                                      5

MSP430 Microcontroller                                              6

Parachute Deployment/ Rocket                                   6

Power                                                                         7

Risk Analysis                                                                    8

Project Management Plan                                                  8

Budget                                                                               10

References                                                                       12

 

 

 

Introduction

            Texas Instruments (TI) has tasked a team of Michigan State University (MSU) students with the evaluation and development of a multistage Electronic Parachute Deployment (EPD) system for a large scale model rocket. The primary function of the EPD system is to initiate the rocket recovery process via parachute. Once the rocket reaches the desired altitude, the system will initiate the return of the rocket to ground by deploying the drogue chute. At a secondary point the EPD system will deploy the main parachute to minimize the impact force the rocket experiences during landing. To achieve the task, a sensor unit, power supply unit, and parachute deployment system will be built around the TI MSP430 microcontroller (MCU). The team will design, simulate, and fabricate each subsystem while applying lessons learned from the previous semester. The final design will be demonstrated to the sponsor with the unit integrated in a model rocket equipped with a multi-stage parachute system.

Background

            Rockets have been around for thousands of years, the Chinese being the first to start experimenting with them. Later on, in 1954, a man named Orville Carlisle first introduced model rockets. After some time, a man named Vernon Estes started his own company named Estes Industries. Estes Industries was the first major company to launch the model rocket industry, allowing cheap and reliable model rocket kits and engines to families and schools [4]. Today, model rockets are much more safe and technically advanced.

            Model rockets are fairly simple in design. They use black powder motors. For the motor to propel the rocket into the sky, first the igniter needs to be heated until the pyrogen lights on fire, causing the propellant to light. The propellant burns and thrusts the rocket upwards. The delay composition will then burn, slowing down the rocket [5]. The rocket then comes to a complete stop at its apogee, or highest point, and the first parachute, called the drogue chute, is ejected just above the motor. This parachute is smaller in size compared to the second parachute and does not slow the rocket much. It is intended to produce more aim and stability for the landing. The second parachute, ejecting behind the nose cone, is deployed once the rocket is closer to the ground. The rocket then slowly drifts toward ground for a safe landing.    

            The model rocket for this project will include the capability of deploying two parachutes at specific heights. To perform this task, an altimeter will be incorporated into a Printed Circuit Board (PCB) to measure the altitude of the rocket and send the data to a MCU. The MCU will then decide when the altitude starts to decrease and will then send the signal to the parachute to eject. Meanwhile, the power supply sub-system will be powering the sensor and MCU.

            This project was also given to a team last semester. Many of the same high-level design ideas will be used in this project. For example, last semester's team incorporated both an altimeter and an accelerometer. They chose to use an MPXM2102 pressure sensor for measuring their height and enabling the deployment system and the ADXL330 accelerometer to detect when the rocket started its descent. The revised design will not be incorporating an accelerometer. A digital (MS5607) and analog (MPXHZ6116) altimeter will be tested during the designing of the project to determine which will be best suitable for the final design. The previous team used voltage regulators in their design to power the system. They had a 10V battery supplying an LM2940CT dropout voltage regulator to convert the 10V to 5V. The 5V then powered an LM3940IT dropout regulator to output 3.3V. These voltage regulators provided the voltages needed, however, they may not have been the most efficient design. This project will utilize a switching mode power supply to increase the efficiency of the circuit. The previous team chose the MSP430G2553 MCU, however this project utilizes the MSP430F5310. Finally, the team used a level 3 Madcow Torrent kit for their rocket model. The build time for the team took about a month and with difficulties reported along the way. During the final demonstration, the rocket caught on fire and did not launch. The reported problem came from the unpredictability of black powder. This project will start off with a smaller prototype rocket for testing purposes and work its way up to the rocket model used previously. This project will also allow more time on rocket construction and will use a smaller version as its prototype. Overall, a lot can be learned from last semester's project. Knowing last semester's design allows the team to research the components used along with alternatives, such as the power sources. That allows this project to utilize the most efficient components and minimize the cost.           

Objective and Design Specifications

 

The EPD system is a complex design that consists of using a MCU, altimeter, power unit and all other necessary components. The MCU is functioning like the ÒbrainÓ of the system. It reads the data from the altimeter sensor and records it. When a certain altitude is met, the MCU will produce the signal to deploying the parachute.

 

The primary goal is to design a system such that the MCU will read data from the altimeter at a steady rapid frequency. The MCU will then compare the data to previous stored values. A signal will be sent out twice to deploy the drogue and main parachute at the correct times.

 

List of Objectives:

 

❏      PCB design

❏      MCU software design

❏      Assemble and prepare for first test launch

❏      Revise and Final test

           

A PCB is needed due to size constraints of the model rocket. It will be designed such that it will contain all the components (including MCU, sensors and PSU,etc) and fit within the specified dimensions of the rocket. The MCU will be programed to quickly process data received from the altimeter and make a decision on if the parachute needs to be deployed. To ensure the system function to our expectations, an experimental launch with prototype designs will be performed on a smaller platform. The data from the test launch will be analyzed so correct revisions can be made for the final design.

Specifications and Design Criteria:

           

1.     Number of sensors and Number of Analog-to-Digital Converter (ADC) on MCU.

2.     Precision of ADC.

3.     Rocket size/payload specification

4.     Power supply voltage/capacity

 

To meet price and packaging constraints, the number of sensors included in the EPD system should be kept to essentials. The MCU should have enough ADC pins to accommodate any sensors that are used, as well as have a fast timer to poll the sensors. This will give better accuracy of sampling where the rocket is in its flight path. The proposed EPD system should be robust enough to be applied to a large assortment of model rockets. This places a restriction on the system size, as rocket diameter varies. The power supply must be able to supply steady voltages for all the components, despite the size restrictions. It is power consuming and expensive in terms of spacing to regulate power into different voltages.

FAST Diagram

 

Figure 1: Fast diagram

 

Conceptual Design

The overall design of the parachute deployment system was constructed from the top-down. By breaking the overall system down into subsystems, the design process becomes easier. In Figure 2 below, the basic interactions between the different subsystems can be seen.

 

Figure 2: Subsystem Design Flow

 

Sensors

            The sensors are the only inputs into our system and must be selected carefully to achieve desired results. There are two altimeter sensors in our current design. This will allow a detailed comparison of the two sensors. The final design will have a single sensor. 

 

These altimeters are pressure sensors that sense the atmospheric pressure and create an output. The atmospheric pressure changes depending on the distance from the earthÕs surface. It is this concept that allows absolute altitude to be determined from atmospheric pressure. There is an approximate change of 1.2kPa for every 100m of altitude above sea level. One issue the sensors avoid is varying temperature. Depending on the air temperature the atmospheric pressure will change at a fixed height. Both of the sensors have built-in temperature compensation that will negate this potential issue.

 

The two sensors chosen convey the altitude output in different ways. The first sensor is an analog altimeter (MPXHZ6116). This sensor will output a varying DC level depending on the atmospheric pressure that is observed.  This analog altimeter is always outputting a DC level, which allows this sensor to be very fast. This sensorÕs speed is only limited by the rate, which the sensor is sampled. This analog sensor will only change its output by 46.2mV per kilopascals. This signal change is fairly small and the signal will have to be conditioned through analog circuitry before being sent to the microcontroller. The accuracy of this sensor is rated at 1.5% that should be adequate for its application, but will be tested thoroughly.

 

 The second sensor is a digital sensor (MS5607), which will output a binary string depending on the current atmospheric pressure sensed. The digital altimeter is highly accurate giving an output that is accurate to 20cm. The downside to this digital sensor is it can only produce an output every 9.5ms. This may not give the fast traveling rocket enough resolution to accurately determine the current height.

 

Employing both of these sensors in the current design will allow for direct comparison of the two altimeters.

 

 

 

 

MSP430 Microcontroller

 

            The MSP430 MCU from Texas Instruments is at the center of this project. This MCU takes in the various sensor inputs, filters them and ultimately outputs a signal to deploy a parachute.

 

           Using the analog to digital converter (ADC) built into the MSP430 will allow interfacing of the analog altimeter. This ADC will need to be properly set up and adjusted within the software. The data collected from the sensor can be stored on the MCU for later retrieval. The sensor data can later be extracted from the MCU and analyzed to reveal the rocketÕs flight characteristic during testing of the design. If time permits, there could be additional functions added to provide a USB connection to output flight data to the user.

 

            The overall software on the MCU during flight will be constructed like a simple linear state machine. Once a certain parameter is met in a particular state, the MCU will move to the next state. This process will continue until the parachute is untimely deployed. After the parachute is deployed, data about the rocketÕs descent will still be collected and stored.

 

The basic state machine functions triggers would be:

0) Idle state on power up.

1) Detect Launch of the rocket.

2) Start polling and recording

    altimeter data.

3) The altimeter starts detecting a drop

     in altitude.

4) Deploy the drogue parachute.

5) The altimeter reads a certain

     threshold height.

6) Deploy the main parachute.

7) Detect a landing and stop recording

    data.

 

 

 

 

Figure 3: Software State Flow

 

 

Parachute Deployment/ Rocket

 

            A successful parachute deployment all starts from a properly assembled rocket. The choice of rocket does impact all the other sub-system. The choice of rocket will determine the physical dimensions of the electronics we can put inside. The rocket will also have certain payload capacities, which may put a constraint on other sub-system. 

           

There will be two pre-designed rocket kits built by the team. The first rocket will be a small prototype and will give good rocket construction experience as well as launch experience. This smaller rocket will deploy its own single parachute automatically, but provides a payload bay. These features provide an opportunity to test the electronic components within the rocket, without having them actually operate the parachute. Once proper testing has been done on the smaller model, the larger and final model rocket will be built and used.

 

            The larger model (Madcow Torrent) will contain two parachutes and will be controlled by the tested electronic design. The parachutes will be deployed during flight using small explosive charges. This is the typical method of parachute deployment for large-scale model rockets. The figure below shows the different rocket sections within this larger rocket.

 

Figure 4: Sections of Model Rocket

 

 

Power

 

The Power sub-system is responsible for supplying properly regulated power to the other sub-systems. This sub-system will likely need to provide various voltages and currents to the other sub-systems. Limiting the number of needed voltages between the different sub-systems would simplify the design of the power system.

 

            Since the electronics are going up several hundred feet in the air, the simplest and most practical power source option available is batteries. A 9V battery will likely be our final choice as it provides a fair amount of stored energy. This battery is in a compact package and would provide enough voltage to power the other systems.

 

            To accommodate devices within the overall system that will use less than 9V, a switch mode power supply will be constructed. Using the common buck topology, shown below, the 9V could be regulated down to 5V or 3.3V needed. The analog altimeter runs at 5V and the digital altimeter runs at 3.3V. The microcontroller can run at either 5V or 3.3V. The last thing we would need to power is the electronic match (e-match), which will deploy the parachute. It would be best to run this e-match at the full 9V provided by the battery.

 

The major benefit to the buck converter topology is that the voltage step down will occur with at least 85% efficiency. Other common approaches of voltage step-down, such as using transistor regulator or a zener diode, are far less efficient. The buck converter would likely cost more to implement, but the power saving advantages could outweigh the cost. This power design will be thoroughly tested and analyzed before the finalized design is created.

Figure 5:  Simplified Buck Converter

 

Risk Analysis

The proposed project has two main aspects of the project that warrant analysis of their risk to the safety of humans, especially the project team, and the environment in which the project will be built. The components namely are the power source of the booster pack and the rocket itself. This section will briefly examine the risks of each component and some precautionary measure that will be taken to ensure the safety of all who might be affected by the project.

A power supply is a necessary component of this project. The booster pack and MSP430 Launchpad will both need a small power supply. This will supply the voltage and current needed to operate the chip and any other devices that are a part of that circuit. In addition to the booster pack and Launchpad, there will be a small electric match that will detonate the charge that will separate the rocket. This electric match will need a large spike in current, which can be dangerous to test and to implement.

Team members working on the project will need to be diligent when designing and installing the power supply. Strict adherence to the safety guidelines outlined by ÒElectric Safety,Ó provided by the Michigan State University ECE shop, will be mandatory. Failure to do so may result in damage to the circuit, as well as damage to the team member working on the project. Improper handling can cause current to flow across the body, which only needs 6 µA to cross the threshold of pain [3].

In addition, according to a report done by the ECE shop, any batteries that are used for the power supply should be properly stored to avoid problems such as accidental discharge as well as explosions from a material breakdown.

The rocket presents numerous risks to the safety of not only team members, but the members of the surrounding community in which the project will be tested. The team members will need to be careful when assembling the rocket to avoid injury. However, the larger risks come from the launch of the rocket. The assembly of the housing for the rocket motor, as well as the installation of the rocket motor, is very important. Failure to secure the housing will cause the rocket motor to do internal damage to the rocket. This damage can extend from destruction of the booster pack and Launchpad to the combustion of the rocket as a whole, which may result in fire and shrapnel. In addition to the proper assembly and installation of the rocket motor, the fins and wings of the rock must also properly install to ensure a smooth and predictable flight. Failure to do so puts anyone and anything in the vicinity of the launch site at risk of damage from a flying projectile.

Protocols will be in place to ensure the rocket launch is safe and has a minimum risk to those near the launch site and the land surrounding the launch site. The National Association of Rocketry has a list of guidelines that keeps those involved with model rocketry in accordance with national regulations set by the Federal Aviation Administration (FAA) and laws set by the state of Michigan. Several of these restrictions can be met by carefully choosing the rocket. There are other regulations that are pertinent to safety and will be adhered to when designating a launch site. The most important points to follow to minimize risk are to launch from an outdoor location that is clear of any obstacles and is prepared to minimize fires. The state of Michigan requires a launch site that is a minimum of 4180m2[7]. Team members should be at least 60m away from the rocket at launch[6]. To preserve the launch grounds, there needs to be some platform that the rocket will launch from that will protect the area from burning. The launch conditions, in accordance with FAA regulations, must be clear. The wind speed must be below 32km/h and have visibility up to 600m[1].

Project Management Plan

           The parachute deployment system contains several subsections that will allow each team member to contribute to an influential portion of the project.  The major sections for this project include determining the rockets, digital and analog sensors, MCU, power, ignition system, deployment system, and analog circuitry.  By dividing each of these critical functions to the rocket into a different set of group members, the team will be able to work both individually and collaborate with each other to ensure continuity with the project.  Under each section, the student will be expected to adequately research their portion, report their expected budget and proposal to the team, assemble the parts, test the individual components, and ensure it operates properly in the full scale system.  Below lists each team members individual project roles.

           

●      Zane CrawfordÕs critical assignment is to put together simulations in Tina-TI to determine proper operation between the analog and digital sensors output to the MCU.    ZaneÕs non-technical role is as the presentation coordinator, functioning to ensure the presentation is formatted properly. 

●      Pedro Rodriguez will also assist Zane in working on simulations and will build prototypes for testing that each of the sensors are appropriately outputting the correct signals.  PedroÕs non-technical role is the lab coordinator, ordering parts for the project and assisting with soldering components onto the projects PCB. 

●      Jessica ShelbyÕs technical role to the team is to debug any problems the team is currently encountering and continue to look over solutions to determine if there is any way to improve the current solution. JessicaÕs non-technical role includes the document preparation, which includes ensuring the documents are properly formatted for submission.

●      Michikazu AonoÕs primary technical role includes programming between the digital sensor and MCU to interpret the data over I2C.  MichÕs non-technical role is also the document preparation and works alongside Jessica in ensuring the professional documents are formatted properly for submission.

●      Qiaosen HuangÕs technical role also includes programming between the digital sensor and MCU.  On top of assisting Mich in writing the code for the digital sensor, Qiaosen will also write the program on the MCU to function the analog sensor.  QiaosenÕs non-technical role is the webmaster which includes creating and updating a website for the teamÕs document.

●      Max CooperÕs technical role includes designing a PCB to incorporate the sensors, MCU, and power system.  Designing the PCB will include creating multiple schematic files and layouts to incorporate both sensors and the individual sensor that is the cheapest cost with the most functionality.  MaxÕs non-technical role is the project manager.  This includes setting up meetings, distributing workload, updating the gantt chart, and managing the budget.

 

            The parachute deployment system will require finding a proper launch site. This will take time to research proper launch site due to the various regulation concerning large-scale rocket launches (as previously described). Resources to build the design have been found. The electronic components for this design can easily be found online through larger electronic distributors. Texas Instruments will supply specific components for the team. Most of the rocket supplies can be found online at Òwww.apogeerockets.comÓ.  PCBÕs will need to be fabricated throughout the design process. These PCBÕs can be manufactured through Advance Circuits or for slightly cheaper through www.oshpark.com. These listed resources will provide everything needed for the project to be completed on schedule.

           

The team has set goals to have different deliverables prepared for each deadline.  The first deadline to have a demonstration completed is March 17th.  The team plans to complete an initial prototype for testing the individual sensors along with a completed phase one rocket.  The second deliverable date is April 18th. At this date, the team should have launched the phase one and two rockets, completed the final testing and have results to present.  For the final deliverable, April 25th, the team will complete any last necessary revisions and create a deliverable to simulate how our product works without launching a rocket.

 

Budget

            The team is provided with a $500 budget for the project. Of this, nearly 85% of the budget will be spent on the model rockets to test the system on. Additionally the sponsor is requesting the team to conduct a mini project ensuring members are competent in the simulation of circuits and PCB design. This project is currently estimated to use $25 of the team budget.

 

Table 1. Estimated  Budget Allocation

 

 

 

Figure 6. Proposed Budget Distribution

 

 

 

 

 

 

 

 

 

 References

 

[1]        ÒChapter 31. Rocket and Launch-Vehicle Operations.Ó U.S. Department of Transportation Federal Aviation Administration. Web. 30 Jan 2014

<http://www.faa.gov/air_traffic/publications/atpubs/AIR/air3101.html#air3101.html.1>.

 

[2]        Sections of Model Rocket. 2014. Diagram. The Albuquerque Rocket Society Web. 14 Feb 2014. <http://www.arsabq.org/new_participants.htm>.

 

[3]        ÒElectrical SafetyÓ Electrical and Computer Engineering MSU. Web. 30 Jan 2014

<http://www.egr.msu.edu/classes/ece480/capstone/f13/safety.pdf>.

 

[4]        "History of Model Rockets." 321Rockets. Web. 30 Jan 2014. <http://www.321rockets.com/model-rocket-history.html>.

 

[5]        "How Rocket Engines Work." Apogee Components. Web. 30 Jan 2014. <http://www.apogeerockets.com/Tech/How_Rocket_Engines_Work>.

 

[6]        ÒModel Rocket Safety CodeÓ National Association of Rocketry. Web. 30 Jan 2014

<http://www.nar.org/NARmrsc.html>.

 

[7]        State of Michigan. MODEL ROCKETS Act 333 of 1965. State of Michigan, n.d. Web. 15 Feb. 2014. <http://www.legislature.mi.gov/(S(m54wca455nn1bkvqvgv5sg55))/documents/mcl/pdf/mcl-Act-333-of-1965.pdf>.