Information Technology Reference
In-Depth Information
a
c
b
e
d
f
Fig. 6.2
Water pressure sensor output for each situation
to the respiration volume. The upper of Fig.
6.3
shows a graph of conversion values
for the bathtub volume (including breathing volume) after low-pass filter processing
of the water level values with the cutoff set at 0.35 Hz. From these values we can
extract a breathing curve using low-pass filter processing and couple the breathing
depth information with sound control. However, this processing only works when
a person is bathing. If the water surface undulates a lot, the sensor will extract
other information in addition to the breathing component. Consequently, breathing
processing is limited to relatively mild undulations on the surface of the water.
This system also measures heartbeats in real time while bathing. The bath-
tub is a conventional bathtub with small electrodes, which provide a contactless
method to measure heartbeats when a bather enters the bathtub, attached to its side-
walls. The heartbeat measurement circuit eliminates noise and samples an amplified
waveform at 8 bit/kHz using an RS-232 C connection. Figure
6.4
shows an actual
electrocardiogram (ECG) waveform from a bather bathing in a bathtub.
6.2.2.3
Extracting and Processing Control Information
From the movement information and vital signs, we extract the parameters and events
needed to perform sound control processing. To control the type of sound, volume,
and production conditions, the following states and parameters are used: entering
the bath, exiting the bath, amplitude of water surface ripple, instantaneous heartbeat
based on R waves, R wave height, and T wave height. To control sound production
timing, events to detect triggers for R waves and T waves are used, and trigger
signals for water surface ripples above a threshold value are also used. Pretreatment
functions for measurement data are primarily handled by the microprocessor of the
water heater unit. However, if the water heater is connected to the Internet through a
home LAN, the water heater can send the measurement data to external processors
for pre- and post-processing.
