P17001: Wearable Glove-Based Controller
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Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase

PDDR Plan:

At the conclusion of the systems design phase, the team settled on the “Tappin’ Five” method for typing, but we have yet to decide which sensors will we use to achieve this method of typing. The team vision for the preliminary detailed design review is to test the Tappin’ Five typing concept with each sensor type. The team plans on exploring flex sensors, accelerometers, hall effect sensors and mechanical switches to see which is the best option. In order to do this, we plan on building a one finger mock-up of each concept and performing tests on each to determine feasibility. The ultimate goal at the end of this phase is to make a final concept decision on the type of sensors to be used.

Accomplishments:

During this phase, we were able to acquire four different types of sensors to test. We tested flex sensors, accelerometers, hall effect sensors and mechanical switches. Through this testing, we determined the feasibility of each concept. The flex sensors proved to be difficult to get a clear binary reading from, and carry a large risk of durability. The accelerometers proved to be a feasbile, yet difficult option. It was difficult to set up only one, and the signal processing that it would require would be very difficult and unreliable. During this phase, we were able to demonstrate the use of mechanical switches for this application. They were simple to set up, require no signal processing, remove electrical components from the finger, and are comfortable for the user.

Sensor Feasibility: Prototyping, Analysis, Simulation

Flex Sensors

 Flex Sensor

Flex Sensor

Question:

Can a flex sensor be used to accurately detect distinct finger movements?

Key Observations:

 Flex Sensor Test Results

Flex Sensor Test Results

Pros:

Risks:

Conclusion:

A flex sensor can be used to record finger movements as long as the proper boundary values are assigned. This will require additional configuring and restraints to prevent it from moving past the second major knuckle.

Accelerometers

 Accelerometer

Accelerometer

Question:

Can an accelerometer be used to detect finger movement?

Key Observations:

Results:

The GIF and excel table shows the accelerometer (ADXL327) works as intended, but may require some additional signal conditioning.

 Accelerometer Test Results

Accelerometer Test Results

GIFs showing the accelerometer tests

 Motion in X & Y axes

Motion in X & Y axes

 Motion in Y & Z axes

Motion in Y & Z axes

 Mounted on Finger

Mounted on Finger

Pros:

Risks:

Conclusion:

An accelerometer can be used to measure finger movement, but it may require some additional signal processing.The final accelerometer would likely need to be more sensitive, and probably digital to simplify inputs to microcontroller.

Hall Effect Sensors

 Hall Effect Sensor

Hall Effect Sensor

Question:

Can a hall-effect sensor (and magnet) be used to detect finger movement?

Can individual finger movement be detected? (What kind of cross-coupling can be expected?)

Results:

Four hall-effect sensors (AD22151) were obtained and placed on a breadboard, such that the distance between each sensor was approximately the average length between knuckles. A sample sketch was made to read from each sensor every second. Weak and semi-strong magnets were used to interact with each sensor.

 Hall Effect Sensor Setup

Hall Effect Sensor Setup

Results:

Good readings were obtained from the individual magnetic hall sensors. However, neighboring sensors could still pick up the magnetic field, even when the weak sensor was used. More testing needs to be done with smaller magnets to see if this effect could be reduced.

Pros

Cons

Conclusion

Hall effect sensors need a lot of additional components, which take up much-needed space and make the glove more expensive. Additionally, the maximum distance that can be allotted between neighboring sensors is currently too small to distinguish between individual sensors, which would require additional software to filter out the cross-interference.

Mechanical Switches

 Push Button Switch

Push Button Switch

Spring to Show Tension

 Spring

Spring

Question:

  1. Does flexing a finger cause measurable physical movement/tension in the string when the string runs from the top of the second knuckle to the wrist?
  2. Does adding a pivot point increase the movement of the spring?

Key Observations:

Results:

  1. As shown in the GIF, there is a ring around the index finger with a string running from the ring to a watch on the wrist. The string was spliced in order to attach a spring in the middle as seen on the back of the hand. The purpose of the spring is to give a visual of the change in tension in the string when the finger is bent.
  2. When the pivot (Jackie’s pinky finger in the GIF) is added on top of the major knuckle, the spring shows larger movement than without a pivot.

Conclusion:

Mechanical Switch Mock-Up

 Switch

Switch

Question:

Key Observations:

Results:

Finger Moves Light Turns On

 Switch

Switch

Demonstrates Software Feasibility

 Arduino code with switches

Arduino code with switches

Pros:

Risks:

Conclusion:

Overall, our team believes that the Mechanical Switch design would be superior to all the other designs. All the electrical components would be confined to the hand instead of extending to the finger, which would allow for the components on the fingers to be easily replaced if necessary. There would also be less wiring, which would help with the construction process. Because the programming would be a lot simpler, it would allow us more time to focus on the construction of the actual device.

Summary of Sensor Feasibility Testing

In summary, we were able to demonstrate that each sensor would be a feasible option for the device. However, we wanted to select the best sensor to continue forward with. At the conclusion of sensor testing, we created the chart shown below. We chose the evaluation characteristics based on observations of the testing performed. This is a complete evaluation of the work we done during this phase.

Recap

Flex Sensors

Accelerometers

Hall Effect Sensors

Mechanical Switches

Sensor Selection

Evaluation Characteristics:

 Sensor Selection

Sensor Selection


Click here for the working document.

Shown by the outstanding score, we have selected the mechanical switches as the sensor that we will use in the final design.

Bluetooth and Construction Feasibility: Prototyping, Analysis, Simulation

Bluetooth Module Feasibility

 BlueSmirf Silver

BlueSmirf Silver

Construction: Device Mock-up

 Device Mock-up

Device Mock-up

The final device will resemble the model shown above. Complete fabrication details will be finalized in the next phase, but the preliminary plan for materials and fabrication is as follows:

At this phase, we have investigated our 3-D printing options on campus with both the Brinkman lab and the Construct. The Construct will be obtaining a 3-D printer that is capable of flexible materials, and this option will be considered. The final design of material and construction plan will be finalized during the next phase.

Two potential finger attachments:

 Rubber ring with clamp

Rubber ring with clamp

 Chain with clasp, Full hand (chain with rubber clasp), Rubber clasp

Chain with clasp, Full hand (chain with rubber clasp), Rubber clasp

 Track for chain/cord

Track for chain/cord

Bill of Material (BOM)

A Bill of Materials was made by filling out the template provided by the Senior Design Office. This template was modified to also provide better information about our budget and inventory. The document is broken up into different sections. On the left, information about a specific part is available, such as the subsystem, part number, name, and quantity needed for a single prototype. The next section lists the sourcing information, such as the vendor, link, and the purchase price. The right-most section displays information about inventory, such as the quantity to be ordered, the quantity that was ordered, the quantity that was received, and the quantity that is currently in shipping, as well as the datasheet links. On the bottom, budgetary information can be found, such as what has been budgeted so far, expected (future) expenses, and the current/real budget. The real purchasing power is the additional allowable expense, taking into account our current budget and expected expenses (essentially, the extra amount that we could purchase, assuming we are also going to purchase items taken into account in Future Expenses).


 Bill of Materials

Bill of Materials


Click here for the working document.

Test Plans

 Battery Life Test Plan

Battery Life Test Plan


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Risk Assessment

 Mitigated Risks

Mitigated Risks


Click here for the working document (2nd Sheet).


 Risks Added During PDDR Phase

Risks Added During PDDR Phase


Click here for the working document.

Risks to be Addressed During Next Phase:

Plans for next phase

Gantt Chart

 Plans for Remaining Weeks


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Individual Three Week Plans

Team Member
Nicole
Arshia
Nick
Emmanuel
Carolyn
Jaclyn

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