Concept Decision Matrices
- NOTE: Following the Detailed Design Review, the team re-scoped the needs for the modular motion tracking system. As a result, the potentiometer was no longer used and instead, the Razor 9DOF sensor was used for both systems.
The following decision matrices were used to help select the concept that best fit our needs and specifications for a device that measures knee flexion.
- Based on the matrix, we selected the Honeywell 785-380C3100K Potentiometer.
- *NOTE: Calculating Expected Potentiometer Lifetime
From the paper Expected Values for Steps per Day in Special Populations, the mean steps per day for a poststroke patient is approximately 4000 steps/day. Since the knee flexion device will only measure the motion of one knee, the number of rotations the device will experience will be 2000 steps/day. For a minimum cycle count of 100k cycles prior to failure, the device will last for at least 50 days of daily use. For a minimum cycle count of 1 million cycles, the device will last for at least 500 days or approx 1 year and 3 months of use on a daily basis.
If the device is being used in the clinic, it will be
used by approximately 15 patients per week for 20 weeks
out of the year. Dr. Mowder approximated that each
patient will take 100 steps per session (50 steps per
leg). At 50 steps/session, 15 patients per week, a 100k
minimum cycle device will function for 133.3 weeks or
6.67 clinic years. A 1 million cycle device will last for
1333.3 weeks or approximately 66.7 clinic years. A 25k
cycle device will last for 33.33 weeks, or approximately
1.67 clinic years.
The following decision matrix was used to help select the concept that best fit our needs and specifications for a device that measures head tilt and motion.
- Based on the matrix, we selected the Razor IMU.
- Based on the matrix, we selected the headlamp strap.
The following decision matrix was used to help select the concept that best fit the specifications for a device that would regulate the connection interface between the sensors and the base unit.
- Based on the matrix, we selected the Arduino Board.