Practice English Speaking&Listening with: Practical Motion Capture in Everyday Surroundings

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We present a wearable, motion capture system

that can acquire emotions of an individual

almost anywhere over extended periods of time.

Our system consists of an array of small, low-cost, low-power

sensors placed on the body of a person.

The system is completely autonomous.

It does not require any external devices or signal sources.

In this prototype, we use eight signal sources and 18 signal

detectors as our sensors, our sources

are small, ultrasonic transducers

that sequentially emit pulses about 16 times a second each.

We use small microphones as signal detectors

for the ultrasonic pulses.

The detectors also contain three-axis accelerometers

and three-axis gyroscopes that sample accelerations

and angular velocities about 140 times per second,

significantly improving the precision and the frame rate

of the ultrasonic measurements.

Using the onboard microprocessor,

the accelerometer and gyro values

are digitally encoded and combined

with the analog audio signal from the microphones.

All signal sources and detectors are wired to the driver box.

The driver box consists of the following components--

18 second-stage amplifiers that further amplify the signal

from each of the sensors, 3 six-channel, analog-to-digital

converters that sample the signal from 18 sensors

at 150 kilosamples per second, a microcontroller that

synchronizes all HD converters and generates pulse

signals for the ultrasonic transducers.

The signal from the microcontroller

to the transducers is then amplified

by the transducer drivers.

The driver box is powered by a small, rechargeable battery

pack that lasts for more than four hours.

The data from all A-to-D converters

is transmitted using a USB 2.0 connection

to a laptop which records this data directly

to its hard drive.

The driver box and laptop can be carried in a small backpack.

Our prototype system was built from off-the-shelf components

for less than $3,000.

Here is a comparison between our reconstruction

and that of the Vicon optical system.

In this sequence, distance measurements

prevent drift in the left shoulder.

The mobility of our system allows

us to capture motion virtually anywhere, for example,

while driving a car.

We were able to track all limbs as well as recover more

detailed and subtle motions.

Even motions that are traditionally hard to acquire

are captured with ease using our system.

The Description of Practical Motion Capture in Everyday Surroundings