Multidisciplinary Senior Design ConferenceKate Gleason College of Engineering

Rochester Institute of TechnologyRochester, New York 14623

Project Number: P19001

DEXT: A WEARABLE INTERFACE

Alice FischerComputer Engineering

Tim PreskenisBiomedical Engineering

Sarah KordiyakElectrical Engineering

Nick BreemanElectrical Engineering

Vincent YuIndustrial Engineering

Jonathan HoeyElectrical Engineering

Willow BakerMechanical Engineering

ABSTRACT The aim of Project 19001 was to provide the primary customer, smartphone users, and RIT, with a

convenient, reliable device that can achieve the approximate response time and functionality of a computer or smartphone. The device must be sleek, aesthetically pleasing, durable, accurate, lightweight, simple to use, affordable, non-distractive, and should not disrupt normal motion of the user. The team utilized lightweight buttons, an inertial measurement unit, a custom printed circuit board, and durable case to carry out the requirements of the project. In addition, the team conducted various tests to provide qualitative results to determine if the prototype satisfies the customer and engineering requirements.

INTRODUCTION Today computers and phones require very present and in-depth interaction where the user is unable to easily detach from the device. Though typing with one hand is possible, a PC's lack of portability makes that unfeasible, and phones are often dropped. A portable, easy to use device that mitigates distraction, is not easily dropped, and does not cause any restriction of movement or normal hand functions needs to be developed that will competently mimic regular PC or phone purposes. This is a Phase 3 project following Phase 2, P18001.

The wearable, glove controller interface the project produced aimed to replace typical phone interfaces by using buttons, and the gyros and accelerometers in an inertial measurement unit to track finger motion and hand positions to provide input to a device via Bluetooth. The goals were to make it portable, functional, fully enclosed within housing, easy to use, and not be a distraction to the user or bystanders. Though most devices currently require two hands to effectively operate, this interface should be operable with one hand using little focus once the user has learned to use it. Other prototypes researched have not gained much traction due to issues with weight, size, connectivity, reliability, durability, and lack of comfort. For example, the Keyglove is a full, fabric glove, with protruding wires and is relatively expensive in comparison to other prototypes. This method did not achieve wide success mainly due to lack of convenience, bulkiness, unreliability and overall cost for a product with several issues. A more widely known device, the Tapstrap, did gain traction in technology circles. It is small in size, relatively inexpensive, and was not incredibly uncomfortable. Though this device was more popular, it requires a hard surface such as a table to function properly, and does not respond quickly enough therefore, it would not be usable in every environment and is less satisfying for the user. P18001’s prototype was bulky, had unreliable sizing for various hand sizes, and is not accurate and repeatable with respect to its ability to properly ascribe finger motions to letters and

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text functions. P19001’s goal was to create a smaller, more efficient, more reliable, and easier to use device that redesigned the inputs for the user’s comfort.

METHODOLOGYCustomer Requirements:

The device was required to provide the user a comfortable, protected, lightweight, and non-distracting interface. It was to properly and accurately provide a typing scheme that replicated output from a smartphone. The device should be chargeable with a standard charging cable. The device should be fully adjustable in sizing. The device should be completely wireless and connect to the phone via Bluetooth. The customer Requirements can be seen in the following Table.

Table 1- List of Customer Requirements

Engineering Requirements:The Engineering Requirements were directly gathered and mapped from Customer Requirements. They

were broken up into five categories; Convenience (CV), Comfort (CF), Durability (D), Functionality (F), and Safety (F). They can be found in the following table:

Table 2- List of Engineering Requirements

Selection Criteria:In order to determine the most feasible path to a prototype, after morphological charts were created,

selection criteria were decided upon. These were then paired with possible research, experiments, and brainstorming ideas to determine possible answers. They were as follows:

1. Ease of learning curve2. Fits within budget3. Weight of the device4. Size of device5. Number of gestures available

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6. Ease of actuation7. Speed of message delivery8. Distraction Level9. Steps to power on10. Can be completed in MSD1 and MSD2

Typing Scheme:The typing scheme should be as simple as possible. It was decided that the finger movements should be

limited to comfortable positions of four fingers with mainly positions involving one finger and combinations of two to three fingers right next to each other. Also, the hand positions would be limited to a natural range of motion with 4 to 5 different positions. This removes the possibility of unnatural and uncomfortable finger combinations and hand positions. Game:

The application is built for both iOS devices and can be ported to both pc and android. Ultimately the goal of the application is to train the user to use the device. This is done through different games such as hangman or a text adventure, requiring input from the user. While the app is still in the prototype stage, hopefully someday a user will be able to learn and implement the Dext more effectively by using it.

Figure 1: Dext Informational Game

RESULTS AND DISCUSSION Testing: (Testing still in development these paragraphs are theoretical)Mechanical

Testing was performed on the mechanical system to ensure fulfillment of engineering requirements. The mass of the device and dimensions of the device were measured to be XXX grams and XXX mm, respectively. To test adjustability, the device was adjusted to be worn by a XXX hand and a XXX hand. Notes were taken on the level of comfort/discomfort experienced by the wearers. Test subjects also practiced putting the device on and taking it off and notes were taken regarding the ease and speed of these attempts. The test subjects also wore the device for an extended period of time, and took notes on tasks that were affected by wearing the device, as well as how long the device could be worn comfortably. It was noted that the device was overall comfortable, but if the straps were too tight there was pressure on the knuckles that was deemed as uncomfortable. A dummy prototype of the same mass as the working prototype underwent a drop test to ensure both the device case and PCB would be durable enough to undergo drops from up to 6 ft. The force on the device was calculated based on the acceleration of the device as it dropped, to ensure the PCB components would not be damaged.Electrical The device was tested for a multitude of different parameters to both ensure meeting the expectations laid out in our engineering requirements and to improve the electrical system at this stage of the project. An area of primary concern is the battery life of the device. For the battery component, the battery that came with the BlueFruit board was used. In order to test the battery life, two experiments were run. The first was an idle test, whereby the battery was fully charged and allowed to power the selected microcontroller and its peripherals without the controller entering sleep mode. An outboard timer was used to observe how long the system stayed powered in this

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state. The timer observed an estimated XXX hours and XXX minutes of battery life in idle operation. A second battery test involved a simulation of a more realistic use case, where the device was played with and clicked throughout a day. The same outboard timer was used and observed an estimated battery life of XXX hours. In addition to battery life testing, Bluetooth connectivity testing was vital to the overall usability of our device. In order to test the Bluetooth connection, speed an outboard timer was configured to capture the moment that a character appeared on the screen of a paired device, an average of 105.75ms was found for iOS, 102ms for Android, 98ms for Windows, and 98.25ms for Mac OSX.

Description of the Prototype:Mechanical system

The current prototype can be seen in Figure 1 below. The case was designed to fit most hands, and will be made smaller for comfort.

Figure 2: Current PrototypeThe system will have a Velcro strap, which will secure the device to the hand via the wrist and palm. Four

switches attach to the bottom part of the case to connect to the fingers via adjustable finger loops. The length of the straps can be adjusted by taking the top cover of the case off, loosening the clamps which hold the finger straps on, pulling back the excess of the straps, and retightening the metal clamps. The Top cover of the case will be secured with 4 10mm screws. The charging port is at the rear of the device, next to the wrist

The construction of the physical system consists of three main parts: The 3D printed base, The PCB Case, and the button case. The 3D Base has an adjustable Velcro strap to attach to the button case and hand, and is the main mechanism for attaching the device to the hand. The base was 3D printed using another student’s printer. For final product manufacturing, the base can be made using a silicone mold. The PCB Case consists of a top component (Figure 3) and protects the PCB and other internal components of the device. For final product manufacturing, a draft can be added to build the case using injection molding processes. The button case (Figure 4) secures the buttons and has leverage switches to allow for tactile feedback when clicking the buttons.

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Figure 3: PCB Case Design

Figure 4: Button Case DesignElectrical: The electrical system was designed for minimum current consumption and a physically small footprint to make it compatible with the mechanical subsystem. The overall system can be described as a series of momentary buttons, one for each finger excluding the thumb, that trigger interrupts on the microcontroller to wake it from sleep and execute an IMU reading. The microcontroller constructs the command byte from the IMU reading and any flags set by the button interrupts. This byte is then passed into a function that sends a Bluetooth HID character based on the command byte. Surface mount parts are used where available to reduce vertical profile of the device. The Adafruit Bluefruit is used in its original breakout form to maintain compatibility with BLE libraries to reduce development time and improve portability between earlier revisions. The IMU is added as a surface mount component along with a button connector and several LEDs to convey device status. There is room for further improvement by foregoing the Bluefruit module in favor of a surface mount NRF51822 and utilizing the on-board 32-bit ARM processor as opposed to the 8-bit ATMega32u4 on the Bluefruit. The finished electrical schematic can be seen in Figure 5 and the PCB layout of this schematic can be seen in Figure 6.

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Figure 5: Electrical Schematic of Dext

Figure 6: PCB Layout of Dext Software For the software design, the main priority was to optimize timing and memory efficiency. Each combination of hand location and fingers actuated corresponded with one character to be sent via bluetooth connection to the paired device. In order to be efficient, a command word structure was formed, whereby each command word corresponds to one character in the ASCII alphabet. Each command word is comprised of 8 bits. The following figure provides an overview of the command word structure:

Figure 7: Command Word Setup If the device is off or not in active mode, this bit will always be an active ‘1,’ meaning no transmission will be carried out. If the device is on, paired, and ready to send data, this enable bit will be driven low. The next three bits, bits 7-4, are the hand position bits. There are six possible hand positions, which are determined by the current state of the accelerometer. Positions 1-5 correspond to binary numbers 000 - 100. The combinations of 000 and 111 are never used for bits 6-4. The final 4 bits, 3-0, are the finger bits. If the first finger is actuated, and no other fingers are actuated, bits 3-0 will be “1000”. If the first and third fingers are actuated, and the second and fourth fingers are relaxed, bits 3-0 will be “1010” and so on and so forth. Each command word therefore contains all the data from the physical input structure. Using a hash table, whereby each ASCII character is indexed by its corresponding command word, once a command word is generated it takes only one look-up operation to move the desired ASCII character into the Bluetooth pipeline. This is a significant improvement over the search algorithm needed to look-up a desired ASCII character in the previous iteration of this project. The Keyboard setup for the Dext with corresponding Key inputs can be seen in Figure 8 below.

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Figure 8: Dext KeyboardBudget/BoM:

In order to keep our product competitive with similar products in its field the cost was a factor that was considered throughout the process. The final cost of fully producing one of the prototypes designed here is around $XXX. This compared to the $200 for the keyglove, and $180 for the gest. However much of this cost can be reduced with the purchasing of supplies in bulk including the silicone material used for the straps and many of the components used on the PCB. The breakdown of the cost for the prototype can be seen in Figure 9 below.

Figure 9: Prototype BoM CONCLUSIONS AND RECOMMENDATIONSConclusions:

The current prototype may not have been completed to the point where it could easily be manufactured, but large amounts of progress were made when compared to last year’s prototype. A few issues along the way lead to this resolution but the main issue that halted progress were issues with team member availability. Illnesses and constraints due to specialization lead to the overall delay of this project. Even with this major setback progress was still made to show that this product could not only function as expected but could fit in a much smaller housing than in previous projects. Recommendations:

1.Consider switching the board for one with security features

2.Consider making the PCB double sided to make the Dext smaller.

3.Look into more comfortable materials

4.Reduce size of bolts to reduce overall size (be careful to make sure they’re strong enough

5.Look into making the PCB flexible if that increases comfort or spacing of components.

ACKNOWLEDGMENTS

Team P19001 would like to thank the RIT MSD Department for their sponsorship, our guide Jerry Adamski, and Willow Baker, for her feedback and for proposing this project. We would also like to thank the Construct for the use of their 3D printer.

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