Sensor-based Human Motion Tracking

Drew WaltonCS525 Project

Dr. ChowUCCS

Overview

Describe the reason for evaluating different types of monitoring technologies

Define requirements for consideration as a good choice for monitoring body movement

Introduce four technologies that are capable of performing the required functions

Compare the selected technologies

Reason for this project

Interesting problem Remote monitoring of rehabilitative exercises!

Curiosity What technologies are available? How are they being used for this application?

Is there a problem to solve? Or am I too late?

The Present Situation

Numerous technologies exist to monitor the movement of the human body Mechanical Sonic Magnetic Accelerometers and gyros Video Combinations

Requirements: minimum

Track all types of motion Bending, twisting, circular, jumping

Track through realistic velocities of motion Accomplished by adequate sample rates

Track through all ranges of motion No motions should be out-of-bounds

Tracking must be accurate Accuracy must be fine enough to capture subtle

movements

Requirements: Nice to have

Non-bulky Must not interfere with the exercise

Easy to wear Not all patients will ave same range of motion,

strength or dexterity Easy to use

Not all patients will be technical Reasonable price

Doctors will want to own many Don't want them to “disappear”

Rugged Software to display the movement

Technology #1: Crossbow “Mote”

Uses a combination of sonic and radio frequency transmissions Similar to counting the time between lightning and

thunder Somewhat large circuit boards act as transmitters or

receivers Currently best at tracking an entire person

Multiple transmitter, single receiver approach

Technology #1: Crossbow “Mote”

Limitations Not very accurate Suffers from multi-path issues Too large to wear comfortably

Can't use at all on small body parts Not able to make rapid samples

Too slow to track quicker movements No software available to display the body moving One hand-held, or serial port needed for each receiver

Technology #2: MIT Body Suit

Uses ultrasonic transmissions, accelerometers and gyros

Very accurate Uses 8 transmitters, 18 receivers all mounted on

a body suit Must carry all equipment in a backpack Display software is available from somewhere

Technology #2: MIT Body Suit

Limitations Heavy backpack Can't target single area to track Suit may be difficult for some to put on There is potential for accumulated errors to result in

inaccurate displays

Technology #3: Moven Body Suit

Very accurate Uses only inertial sensors, immune to noise Wireless transmission of data to base PC Body suit can be worn whole, or select upper or

lower body Comes with display software

Technology #3: Moven Body Suit

Limitations Still is a suit: some people may not be able to put on Cost is very high: $50,000

Technology #4: Vicon video

The most accurate Uses 8 special video cameras all around the

person being tracked No suit required! Patient wears small sensor dots

for camera to pick up Display software is very nice Even has a language equivalent to Labanotation

Technology #4: Vicon video

Limitations Price! As much as $194,000

A lot of equipment Cameras and mounting gear Receivers Computer

A lot for a patient to set up

Comparison

Accuracy: All have but crossbow, and MIT has cumulative error

Bulkiness: Vicon is best, but Moven suit is very good

Easy to wear: Vicon is dots placed using glue or velcro. Moven suit looks very good though

Easy to use: Moven seems easiest. Cost: Crossbow is cheapest, but it doesn't really

work. MIT is next, but isn't a product yet. Software: Vicon is best, Moven is good. MIT is

from unknown source

References

http://www.xbow.com (Crossbow Industries) http://www.thinkartificial.org/artificial-intelligenc

e/whole-body-computer-interfaces/ (MIT Motion capture suit)

http://www.moven.com (Moven motion capture suit)

http://www.vicon.com (Vicon video motion capture system)

http://www.motion-capture-system.com/resources/hardware.html (Listing of many companies and their motion capturing technologies)