ECE 480 DESIGN TEAM 11

Electronic Parachute Deployment System

Design Issues Paper

April 11, 2014

Michikazu Aono

Max Cooper

Zane Crawford

Qiaosen Huang

Pedro Rodriguez

Jessica Shelby

Texas Instruments (TI) assigned Michigan State University (MSU) the opportunity to build and design and electronic parachute deployment (EPD) system for a large scale model rocket. The EPD system will include a boosterpack for the MSP430 launchpad that will use the MSP430G2553 to determine the apogee, or highest point, of the rocket to deploy multiple parachutes to allow for a smooth landing of the rocket. The MSU team is required to consider how the design that could be released to market can be maintained throughout the product's entire lifecycle. Other considerations include the standards required to maintain when mass manufacturing the product. The final design criteria the group has focused on includes the safety of our project. Taking these criteria throughout the entire product lifecycle allows for the final EPD system to maintain reduced risks.

Managing the product lifecycle is a very important aspect to be considered for a product¡¯s success in the market. The EPD system that is currently in place can follow a specific product management lifecycle (PML). It was created to be inserted into the payload bay of model rockets and act as a dual deployment method for rocket recovery. In order to accomplish this task, the system has the capability to detect the peak altitude of the rocket¡¯s trajectory and launch the first parachute, followed by the second parachute shortly after. An analog altimeter, more specifically Freescale Semiconductor¡¯s MPXHZ6116, is included in the design to measure the apogee. Other major components that are used around the altimeter include a power section, an instrumentation amplifier (INA), a microcontroller, which is attached to TI¡¯s Launch Pad, and an igniter section used for the parachutes. The power section is used to power every other section mentioned. It has a buck-converter controller, TI¡¯s LM2574 which also uses Fairchild Semiconductor¡¯s 1N5817 Schottkey diode, which is used to convert 9V to 5V and also has TI¡¯s LM3940 voltage regulator to further convert the 5V to 3.3V. The INA used is TI¡¯s INA326 and it amplifies the altimeter output for a larger change in voltage per change in altitude. The output of the INA then feeds into the ADC included in the microcontroller. The microcontroller, namely TI¡¯s MSP430G2553, is used to read in the analog data and turn the relays on within the igniter section at the desired times which will ultimately enable the parachutes¡¯ departure. The igniter section is broken down into two independent and identical segments. Each segment consists of Omron¡¯s G6L-1F-DC3 relay, Fairchild Semiconductor¡¯s 1N5817 Schottkey diode and a fuse. The design undergoes a series of simulations to find desirable passive components to be added. Such passive components used include lead free RoHS compliant epoxy coated power and molded axial inductors, both lead free and lead contained RoHS compliant resistors, and lead free RoHS compliant ceramic and tantalum capacitors. Once the design is finalized, all parts are ordered. Upon arrival, the individual parts are breadboarded to confirm their functions, and finally the printed circuit board (PCB) can be designed. The PCB not only routes all the connections of each section, but also acts as a BoosterPack to the Launch Pad. The finalized PCB is sent for fabrication and returned for all the components to be soldered on. After the whole PCB is complete, more tests are run in lab to debug, if necessary, and again confirm functionality. The product is then ready to be released to the market.

Another important criteria for product management includes the ability to deliver updates to the current product line. The EPD system can incorporate both internal and external updates throughout the lifecycle of the system. The internal updates to the system can be incorporated for customers through USB provided with the MSP430 Launch Pad. The microcontroller which is attached to the Launch Pad will be released with the current version attached to the microcontroller. As the product becomes available to the public, more universal applications may be deemed necessary and TI can provide patches online for the user to easily update the code.

Technology is constantly advancing and this could lead to a change in the MSP430 microcontroller for a more efficient EPD system. As long as the manufacturer stays with less than a 16 pin microcontroller the company can modify the microcontroller shipped with the EPD system or if the user decided to upgrade the system could easily pry off the msp430G2553 microcontroller from the Launch Pad and replace it with the new microcontroller. This is also another opportunity for the user to obtain a patch that could be available on TI¡¯s website.

There are certain ways the EPD system can be disposed after its final use. Before disposing, many of the components can be salvaged and reused. Many companies are willing to take in old PCBs and recycle them for reuse. Also, the components can be desoldered and reused or donated. Because the capacitors used do not contain polychlorinated biphenyl, they do not need to be disposed with special care, and thus the EPD system can be disposed normally.

In order to improve upon the PML, the design process may be altered. Currently, the design process finds specific components to be used in each section of the system. This could pose a problem if companies discontinue their parts that are currently needed in the final design. This can be solved by finding more diverse components when designing the system. For example, the microcontroller communicates to other sections through the Launch Pad. The microcontroller is thus limited to the amount of pins it can have and still be compatible with the system. Future designs should take this into consideration and either opt to not use the Launch Pad or research for other replacement microcontrollers. Along with adding diverse components, the design could switch to all lead free components instead of using a mix of lead free and lead contained parts. Also as stated before, future software releases and microcontroller updates could be obtained by the customer to enhance the product. All of these changes in the future would help ensure the survival of the EPD system.

Standards are a part of ensuring the safe and proper use of the EPD system. The EPD system is designed to work in model rockets by sending a signal out from a microcontroller at appropriate heights using a analog altimeter. There are currently no standards regulating the use or operation of EPD systems in model rockets. There are standards for model rockets which influence design considerations for EPD systems to make them useful for model rocket users.

Model rockets have a need to return to the ground safely. If the model rocket user chooses to use an EPD system for recovery of the rocket, it must fit inside the rocket, not affect the trajectory of the rocket, and provide enough current to activate whatever charge is used to separate the stages of the model rocket. Most model rockets that would require a dual stage EPD system such as the one designed for this project are classified as class 2 or 3 rocket by the FAA. This standard is imposed by the FAA mostly based on the impulse the motor of the rocket uses. Model rockets with payloads can use the EPD as a recovery system, provided it can fit in the diameter of the rocket¡¯s payload bay. It is suggested that the EPD be small so it can be used in many devices, opting for length instead of height or width. The average diameter of EPD capable model rocket is around 3in, although some model rockets are 2in in diameter. Therefore, a company standard would look to downsize the device to fit in as many payloads as possible and choose to increase the length of the EPD system if increasing the size is necessary.

Model rockets can be dangerous devices if their trajectory is modified. It is assumed that the device that the EPD is launched in is safely positioned; however, the EPD system must not affect the integrity of the launch. In order to keep the integrity of the launch, the EPD system should not weigh too much nor should it malfunction when it detects deployment altitude. The EPD system will be in the payload bay of the rocket, which is generally in the upper half of the rocket. If the weight of the EPD system is not regulated, then the rocket could tip to the side and have an unstable flight. There is no standard for payloads for model rockets, except for the sake of competitions. However, to make the system usable for less-powerful rocket motors, the EPD should weigh no more than 5 ounces. To improve the current design, using a smaller, lighter battery will make the EPD system usable in more model rockets.

In addition to not altering the flight with its weight, the EPD system needs to have few faults. A fault with the EPD system can cause catastrophic damage to the model rocket and the user, depending on the charge system that is used in conjunction with the system. If the EPD triggers early, the charge can expand and launch part of the rocket, potentially knock down the stand, and damage users if it triggers before the user can evacuate the area around the rocket. Also, if it triggers in the air on the ascent, it can damage the rocket. To prevent these damages, it would be advised that the EPD have very good resolution, with a large range to detect launch height. By making sure a large change in voltage is needed to trigger the EPD system, there should be no chance for error on the ground and low error in the air.

The EPD system needs to be able to trigger what ever charges will separate the rocket. The average for the all-fire current for igniters varies by company. However, it is more reasonable to try to output as much current over a brief period of time that will not damage the device. When redesigning the EPD system to improve the design and meet new design considerations, the system should be able to provide 2A of current to igniters, as this is the highest all-fire current the team has encountered. This will give future iterations the job to find a way to maximize current safely, while minimizing the weight of the EPD system.

While there are no specific standards for the EPD system, there are standards for the electronics that make up the system. As mentioned before, it would be environmentally sound to comply with RoHS electronics standards. This would also allow the device to be sold in the European Union more easily. There are other electronics standards that our EPD system could attempt to achieve like Underwriters Laboratories(UL) approval. For future of customer relations about our product we could look into follow ISO9001 quality management standards. These are a few standards that our electronics could conform to, for the improvement of our design.

Safety, one of many design issues, is a primary feature when designing consumer products. The EPD system will need to consider the safety of the end user due to the nature of model rocketry, the system will be exposed to a wide range of age groups of varying skill sets and require the handling of highly combustible and explosive devices. The device is to be enclosed in a plastic housing to protect the users, especially younger children, from potential electrical shocks and lacerations from sharp edges found on the soldered components. In addition to protecting the user, the housing will provide protection to internal components from external environmental factors, such as moisture (specifically the altimeter is highly sensitive to moisture and is recommended not to get it wet), and physical shock experienced on impact. The housing would include a mounting point for the battery and house the MSP430 Launch Pad and BoosterPack in a tight secure package. The housing will ensure the system components remain connected during launch and the flight of the rocket. Heavy vibrations during the launch phase may potentially damage the soldering point and loosen up the connections, a properly designed case will significantly reduce such defects from occurring.

In addition to the main housing cell, the plastic case will be required to provide areas to contain black powder (or black powder substitutes such as pyrodex) used in the deployment of the parachutes. These compartments should be isolated from the main system, preventing untinted discharge via accidental short circuiting of the main system, and protect the charges from moisture which could render them useless. With these safety considerations put in place on the physical system, a great majority of disasters can be eliminated if not significantly mitigated.

As mentioned earlier premature and delayed detonation of parachute ejection charges are of major concern. To ensure the parachutes will eject at the intended moment, software coding will be of particular importance. An important issue in automation design is that input readings are not always expected values. The altimeter can generate readings with a 5% tolerance. This means there can be a situation were recorded values may indicate a drop in altitude even though the rocket is still ascending. To avoid such situations, an algorithm was incorporated such that the rocket was not considered to enter a state of dissension till the change in values were consistently negative or above a certain tolerance. Allowing for parachute deployment to occur once the intended condition has been met.

Overall there are many design issues that are taken into account when designing the EPD system. The product management lifecycle issue is highly considered to ensure the success of the product before and after it is released into the market. It also aims to keep the product competitive in the market by allowing software and hardware updates to address customer needs and changes in technology. In order to have the product sold in the market it must follow standards and also remain safe for the customers which contribute to the goals set by the lifecycle management.