Transcript Managerial Design Review Presentation (SD II)x

Alexander Moulton
Marie Hammer
Xingwang Gao
Andrew Robertson
Team Lead
Mechanical Engineer
Electrical Engineer
Electrical Engineer
Project Goals
 The purpose of this project is to capture key-strike
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dynamics for integration into a full keyboard
Enhance text based communication by providing an
analog signal in parallel with binary keystroke data
Accurate differentiation of typing forces applied
Encapsulate typing forces with keystroke data and
communicate with a PC
Characterize human typing forces for future projects
Revised Project Goals
 Original project goal:
 capture emotion while typing
 Complications:
 Keyboards are binary devices
 Users are not trained to pay attention to how they type
 Revisions:
 No association between emotion and typing patterns
 Conscious user input expected
Customer Needs and Specifications
Need
Specification
Metric
Enhance text based Establish a voltage output linearly Linear relationship between force and voltage
communication
proportional to force applied while typing output
Couple analog data with keystroke
character
System is able to measure a large range of
input force
Differentiate
user Users are able to establish up to 8 distinct
input accurately
outputs while typing
Use sensors with static output
Ideal Value
d 2V
0
dF 2
Character data transmitted with analog data
(Boolean)
Range of force (N)
True
Number of output partitions
8
0 to 10N
Variation in output voltage under static load dV/dt = 0
(dV/dt)
Output is independent of simultaneous Variation in output voltage with and without
V  0
keystrokes
concurrent loads on multiple keys (V)
Compatible
with USB protocol used for communication
USB communication (Boolean)
True
modern PC/Laptop
Output is readable Applications able to monitor USB port Pass/fail of
True
by PC software
can be programmed to interpret and Communication (Boolean)
display the data received
Design Concept - Electrical
 Analog data acquisition is independent of the original keyboard design
 Four stages:
 Thin film pressure sensitive device acts as a variable resistor in a
voltage divider
 Conditioning circuitry
 Analog to digital conversion
 Communication
Conditioning Circuitry
Micro Controller
Design Concept - Mechanical
Keys: scissor switch,
buckling, dome spring
Materials: ABS plastic,
silicone, foam
Methods of
Manufacturing: refabrication of current
keyboard, rapid
prototyping with ABS
plastic, injection molding,
machining raw material
Test Plan
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Sensors have a static output (i.e. no capacitive loads)
 Load a sensor with a static weight and measure any variation in the output over time
Establish a voltage output linearly proportional to force applied while typing
 Calibrate device output (Voltage vs. Force) using weights ranging from 100g (~1N) to 2kg (~20N)
 A linear best-fit line should be possible
Force transmitted through the key to the sensor matches the force applied at the top of the key within
±10%.
 Calibrate the device output with and without the key and spring
Output of key strikes must be independent of simultaneous key strikes
 A test key is loaded with a static force while a second key is fully depressed
 The variation in output voltage with and without the second key being pressed is measured
Characterize human typing force
 Objective is to establish a baseline of normal typing force for future reference
 Result are compared with results from previous studies in typing force (1N to 2N) to ensure
device accuracy
determine the resolution of human typing force
 Objective is to determine the minimum amount of force a user can consistently increment
 Tap key with successively increasing force average difference between keystrokes is measured
Test Data
Modified: y = 0.002701 - 0.046
Unmodified: y = 0.002477 + 0.148
%errorm = (0.002701 – 0.002477)/0.002477 * 100% =
9.04%
ΔV << Vmax/(# of output partitions)
31mV << 3.7V/8 = 462mV
Force (N)
ΔV (mV)
1
0
5
0
10
31
Variation in output voltage for 1, 5, and 10N
test forces with a second key fully depressed
Test Data (cont.)
User
Alex (N)
Marie (N)
Xingwang (N)
Andrew (N)
Trial 1
1.73
1.70
1.81
1.69
Average typing force among users
Trial 2
Trial 3
Trial 4
1.79
1.68
1.68
1.74
1.76
1.80
1.69
1.84
1.75
1.78
1.75
1.72
Trial 5
1.74
1.69
1.72
1.80
User
Alex
Marie
Xingwang
Andrew
Number of distinct partitions without feedback
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
6
6
7
5
7
7
5
7
6
6
6
7
6
6
6
6
6
7
7
6
User
Alex
Marie
Xingwang
Andrew
Trial 1
8
6
8
8
Number of distinct partitions with feedback
Trial 2
Trial 3
Trial 4
Trial 5
7
8
7
6
8
7
5
7
7
6
8
7
8
7
8
8
Meeting Specifications
 Establish a voltage output linearly proportional to force
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applied while typing - PASS
Couple analog data with keystroke character - PASS
System is able to measure a large range of input force PASS (0 to 13N)
Users are able to establish up to 8 distinct outputs while
typing – Not met, only 6 levels were achieved
Use sensors with static output - PASS
Output is independent of simultaneous keystrokes – PASS
USB protocol used for communication - PASS
Applications able to monitor USB port can be programmed
to interpret and display the data received - PASS
Future Project Recommendations
 Printing Force Sensitive Resistors in a matrix
underneath the keys for future keyboards
 Designing modified keyboard to hold more circuitry as
an alternative to modifying the keyboard.