ECE 480 Design Team 6Speed and Distance Sensor for Skiers and SnowboardersDesign IssuesMichael BekkalaECE 480 Design Team 6Speed and Distance Sensor for Skiers and SnowboardersDesign IssuesMichael BekkalaMichael BlairMichael CarpenterMatthew GuibordAbhinav ParvatananiDr. Shanker BalasubramaniamWednesday, November 25th, 2009IntroductionECE 480 Design Team 6 has been tasked with developing a speed and distance sensors for skiers and snowboarders. During development of this sensor, many design issues have been taken into consideration. The most significant design issues were accuracy, connectivity, and product lifecycle management. AccuracyIn measuring the speed and distance of skiers and snowboarders, accurate results are critical for performance tracking and improvement. The speed and distance sensor uses a Global Positioning System integrated with an Inertial Navigation System in order to acquire accurate measurements. Without accuracy, this product’s market valueis significantly decreased.Since this design criterion has been taken into account since the beginning of development, the final product will boast improved accuracy over competing projects. This improved accuracy is possible due to a GPS receiver and active antenna, accelerometers and gyroscopes. These devices are used effectively and fit appropriately within our budget and resource constraints. Accuracy is lower than high end devices with the same application due to project constraints such as time and budget. High end devices take advantage of multiple INS and GPS receivers. Integrating more systems improves accuracy as well as redundancy, but raises the cost considerably. Also, these devices take advantage of tightly coupled Kalman filtering which eliminates almost any system error. This relies on a complex processor such as those found in personal computers. In the future, a better solution would be to use a more powerful microprocessor to handle the heavy computational requirements of our design. It was not apparent during research how computational the integration and filtering of the INS and GPS receiver would be. Another improvement would be using a GPS receiver with a quicker hot start for recovery when signal is lost. This will improve the overall accuracy of the system as well as improve reliability.ConnectivityOriginally, it was planned to allow the user to connect the device to their personal computer and review the data via USB. Due to design issues using the initially chosen microprocessor, a PIC32, USB is unable to be implemented. The new dsPic30f4014 microprocessor does not support USB like the PIC32, and would require UART to USB hardware which adds to the cost. Because of this, a serial interface will be used to review data on the computer. This is unfortunate, as serial is an aging technology and is not included on all modern PCs and laptops. In the future and given more time for initial component research, a more capable microprocessor with USB support can be chosen.Another problem with using USB is that it is not a trivial technology to implement. Unlike serial communication that is always implemented in the same way, USB is set up to be a very universal technology and as such there are no set guidelines on how to set up a USB interface. Thus, this would require one to write a driver file in order to communicate with some device. Since implementing USB requires either past knowledge or time to learn about the technology, it is not feasible to try to implement with a deadline fast approaching.Product Lifecycle Management The product’s lifecycle, especially design and consumption, was taken into consideration in the development of the speed and distance sensor. Through the sensor’s design, we looked to keep energy usage and cost to a minimum as well as keep the form factor as small as possible. Each component, including our rechargeable Lithium-Ion battery, was carefully selected so we can run the entire system at 3.3V. To ensure maximum power efficiency abuck converter is being used instead of a voltage regulator when stepping down the battery voltage from 3.7V to 3.3V.The form factor was kept to a minimum by keeping the application in mind. Micro-Electrical-Mechanical Systems (MEMS) were selected for use in the INS and a miniature GPS receiver was purchased for GPS capability. The goal is to stack printed circuit boards (PCB), thus keeping the factor small enough to hold in your hand and be ofpractical use. Improvements in the future would be to use a smaller LCD screen, possibly an OLED for even better power efficiency and size. Also, a RadioShack case will be used for the final sensor; a manufactured case specifically for the product would be able to yield a smaller form factor.Consumption of the product has been taken into consideration through ease of use, lifetime of the product, and repair and maintenance. The sensor contains few controls and is designed to be placed on the snowboard or ski. This keeps things simple for the user and provides quick accessibility to data. The lifetime of the product is extended through the use of minimal components and can be extended through the packaging. Ideally the enclosure will be one piece, shock resistant, and water proof. Unfortunately, it was not possible to order a water proof LCD within our budget and time constraints. This is something to be improved upon due to the application of the sensor.Repair and maintenance is accounted for through use of off the shelf parts. The sensor is made with parts readably available and may be purchased by anyone. Due to the small form factor of the device, it might be more difficult than anticipated to take apart the sensor. This could be improved upon by designing the case so that it could be easily opened and the components could then be replaced. ConclusionThe issues of accuracy, connectivity, and product lifecycle management were key factors in the products development. These considerations were taken into account throughout the design process to produce an accurate and easy to use device. Further improvements, including accuracy improvement, USB connectivity, and a waterproof LCD, have been suggested and could be implemented into the design in the
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