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Journal of Geoscience and Environment Protection, 2019, 7, 115-124
http://www.scirp.org/journal/gep
ISSN Online: 2327-4344
ISSN Print: 2327-4336
DOI:
10.4236/gep.2019.76010 Jun. 27, 2019 115 Journal of Geoscience and Environment Protection
Human Comfort Instrument Design
Based on Embedded
Shucheng Chen, Jing Shi*, Xiaobo Li, Ming Cui, Lianwei Su
Tianjin Meteorological Observation Centre, Tianjin, China
Abstract
The traditional human comfort meter has the following defects: the interface
is not uniform; the operation is cumbersome and complicated;
the interface is
unfriendly, and the stability and adaptability are poor. This paper presents a
design scheme for human comfort instrument based on embedded system,
using S3C2440 embedded development board and
the sensors to collect the
real-time temperature, relative humidity and wind speed data and to process
the collecting data; then obtaining the human body comfort value according
to the basic algorithm of human body comfort instrument; giving the human
comfort conclusion according to the diastolic index range of human comfort
,
and showing the temperature and humidity, wind speed, comfort value and
conclusion through writing the Qt graphical user interface program. At the
same time, the human comfort instrume
nt has the data storage function. The
human comfort instrument is high in integration, strong in real time, high in
sensitivity, stable and reliable, and it meets the development goals of the in-
telligent meteorological service, and meets the demand of the
meteorological
service that is closer to life, and it has broad development prospect.
Keywords
Human Comfort Instrument, Embedded, S3C2440, Qt
1. Introduction
Human comfort is a comprehensive reflection of the human body’s meteorolog-
ical elements such as temperature, relative humidity and wind speed, and is a
requirement for higher quality meteorological services. The human comfort in-
dex is a meteorological indicator defined by the heat exchange between the hu-
man and the meteorological environment from the meteorological point of view
to evaluate the comfort of the human body in different meteorological environ-
How to cite this paper:
Chen, S. C., Shi, J.
,
Li
, X. B., Cui, M., & Su, L. W. (2019). Hu-
man Comfort Instrument Design Based on
Embedded
.
Journal of Geoscience and
Environment Protection
, 7,
115-124.
https:
//doi.org/10.4236/gep.2019.76010
Received:
November 26, 2018
Accepted:
June 24, 2019
Published:
June 27, 2019
Copyright © 201
9 by author(s) and
Scientific
Research Publishing Inc.
This work is licensed under the Creative
Commons Attribution
International
License (CC BY
4.0).
http://creativecommons.org/licenses/by/4.0/
Open Access
S. C. Chen et al.
DOI:
10.4236/gep.2019.76010 116 Journal of Geoscience and Environment Protection
ments (Moustris et al., 2018). Foreign experts and scholars have laid a good
foundation for the study of human comfort. Takaya et al. (2017) proposed rea-
listic temperature based on the cold and hot feelings of the human body under
different meteorological conditions; Wallace et al. (2017) studied and proposed
the concept of discomfort index, according to the study by the National Weather
Service. Regarding forecast summer comfort and working hours; Mostafavi Te-
hrani et al. (2017) proposed the sensible temperature theory, he considered the
heat exchange in the meteorological environment, and calculated the somato-
sensory temperature model. Domestic experts and scholars started late on the
study of human comfort. Slater et al. (2017) proposed the “Climate comfort
evaluation model”; Zhu et al. (2014) analyzed the spatial and temporal distribu-
tion trend of Hulunbeier human comfort index.
The physiological functions of the human body are affected by various me-
teorological factors (Li et al., 2016), such as temperature, relative humidity, air
pressure, duration of illumination, wind speed and wind direction. Relevant re-
search shows that the three meteorological elements of temperature, relative
humidity and wind speed have the greatest impact on human comfort. The hu-
man comfort index is a nonlinear equation composed of these three meteoro-
logical elements. The equation is derived from the Beijing Meteorological Bu-
reau since 1997. In 2013, the Meteorological Department of Guangdong Prov-
ince of China developed a “Bio Comfort Measuring Instrument” that reflects the
human comfort index (Kai et al., 2014). The comfort measuring instrument con-
sists of sensors, digital collectors, fully automatic water supply systems, and
power supply systems. Guangdong Province has begun pilot deployment, and
plans to cover 80 to 90 bio-comfort measuring instruments covering the whole
province. This “bio-comfort measuring instrument”, which reflects the human
comfort index, is the first in the country of the scientific research team of the
Guangdong Provincial Meteorological Bureau. It has been piloted in Guangzhou
and Shenzhen in 2013. As a highlight of Guangdong’s pilot project for the con-
struction of meteorological modernization pilots and people’s livelihood servic-
es, the provincial meteorological department plans to deploy such measuring in-
struments in the observation fields of cities and counties throughout the prov-
ince in 2014, initially forming 80 to 90 sites, covering the comfort of the prov-
ince. The monitoring network will further refine the layout to more hot spots of
public concern. Regarding the human comfort index prediction model used
(Peng et al., 2011), the human comfort meter designed in this paper is to use the
model as the basic algorithm.
The IEEE defines an embedded system as a device for controlling, monitoring,
or assisting in the operation of machines and equipment (Wang et al., 2015;
Chen et al., 2013). Embedded systems consist of embedded processors, operating
systems, application software, and peripherals. The embedded system features
real-time, tailorable, unified interface, simple operation, friendly graphical in-
terface, high stability and strong interactivity (Guo et al., 2016). Embedded
technology provides a good platform for the design of human comfort meters.
S. C. Chen et al.
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The traditional human comfort meter has the following defects: the interface
is not uniform, the operation is cumbersome and complicated, the interface is
unfriendly, and the stability and adaptability are poor. In order to effectively
make up for the above defects, this paper newly designs a human comfort meter
based on embedded technology. It uses the embedded development board to
connect the temperature and humidity and wind speed sensors. The data is col-
lected in real time through the LCD screen and gives the conclusion of comfort.
2. Overall Design of Human Comfort Meter
2.1. Functional Requirements Analysis
Preliminary design of a human comfort meter based on real-time operating sys-
tem, using embedded development board and sensor to collect the temperature,
relative humidity and wind speed data of the location in real time, and process
the acquired data, and obtain the human body according to the basic algorithm
model of human comfort. The comfort value is finally given according to the
range of human comfort indicators. The temperature, humidity, wind speed,
comfort value and conclusion result are displayed on the LCD screen. At the
same time, the human comfort meter has data storage function and can expand
the alarm function.
2.2. System Design
According to the functions that the human comfort meter needs to implement,
the overall structural block diagram of the system is shown in Figure 1. The sys-
tem is mainly composed of a core processor module, a sensor module, a signal
acquisition and processing module, an RTC clock circuit, a debugging module, a
data storage module and a display module, and can expand the alarm module.
The temperature and humidity sensor and the wind speed sensor collect tem-
perature, relative humidity and wind speed data, and after processing by the
signal processing circuit, finally enter the S3C2440 core processor module, and
the processor applies the basic algorithm of the human comfort meter to process
Figure 1. Overall structure of the system.
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the obtained data, and finally outputs the processing. After the temperature, rel-
ative humidity, wind speed, human comfort value and conclusion, the display
program of the system is called to display. The RTC clock circuit is designed to
provide accurate and reliable system time for the system to ensure the system
has good real-time performance; the data storage module is used to save the data
collected and processed by the system; the system debugging module is used for
downloading and debugging the system program; the alarm module as an ex-
tended function, it can expand the sound and light alarm or increase the GSM
module to send SMS alarms.
The main features of the human comfort meter designed in this paper are low
power consumption, miniaturization, high precision measurement and rich ex-
pandability. In order to achieve the above features, the system uses Samsung’s
32-bit RISC microprocessor S3C2440, which uses ARM920t core, has 0.13 mi-
cron COMS standard macro unit and memory unit and new bus architecture
(Xia & Niu, 2011); provides 1 channel LCD dedicated DMA, 4-channel PWM
timer and 1-channel internal timer/watchdog timer, 8-channel 10-bit ADC and
touch screen interface, 130 general purpose I/O ports and 24-channel external
interrupt source, powered by 1.2 V core and 3.3 V external I/O supply, ideal for
processing embedded applications that require high integration and low power
consumption.
Embedded software is an integral part of embedded systems, including em-
bedded operating systems and development tools. The embedded software sys-
tem design mainly includes the following parts:
1) Initialization of the human comfort meter, preparation of the system star-
tup code;
2) The migration of the embedded operating system, the kernel is tailored and
configured according to the design requirements of the system;
3) The realization of the basic functions of the system, processing the data
collected by the sensor and outputting;
4) Develop a graphical user interface using Qt Embedded and cross-compilation
to display real-time data and human comfort conclusions.
3. System Hardware Design
3.1. Human Comfort Meter Temperature and
Humidity Acquisition Circuit Design
The temperature and humidity measuring instruments commonly used in me-
teorological services include the HMP45D temperature and humidity sensor and
the HMP155A temperature and humidity sensor produced by Vaisala, Finland.
Although the performance is very good in terms of accuracy and stability, the
price is high and the volume is large. Not suitable for use in this design. In this
paper, the new digital temperature and humidity sensor SHT10 is used to obtain
temperature and relative humidity data. The human body comfort meter tem-
perature and humidity acquisition circuit are shown in Figure 2.
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Figure 2. Human comfort meter temperature and humidity acquisition circuit.
The SHT10 is a temperature and humidity composite sensor with a calibrated
digital signal output (Li & Shi, 2011). It uses industrial CMOS process micro-
machining technology to make the sensor highly reliable and stable. The sensor
consists of a bandgap temperature measuring element, a capacitive tempera-
ture measuring element, a 14-bit A/D converter and a serial interface circuit.
The SHT10 sensor is accurately calibrated at the factory, and the calibration
coefficient is stored in the OTP memory. In the process, the sensor needs to
call the calibration coefficient (Ma et al., 2013) during the signal detection
process. The sensor has excellent quality, ultra-fast response, strong an-
ti-interference ability and high cost performance, which is very suitable for
this design.
The SHT10 temperature and humidity sensor has a temperature resolution
of 0.01˚C, a repeatability of ±0.1˚C, a relative humidity resolution of 0.03%
RH
, and a repeatability of ±0.1%
RH
. As shown in Figure 2, the S3C2440 uses
the GPC10 pin to control the SHT10 to reduce power consumption. The GPC8
and GPC9 pins are connected to the SHT10 DATA and SCK pins respectively.
The SCK is used between the SHT10 and the S3C2440. Communication syn-
chronization, DATA is used for data interaction between SHT10 and S3C2440.
The S3C2440 first initializes the data transfer. It includes: When GPC9 outputs
a high level, GPC8 outputs a low level, then GPC9 outputs a low level, and then
GPC8 turns high when GPC9 outputs a high level. Thereafter, the S3C2440
sends a command to the SHT 10, the command byte is 8 bits, consisting of the
upper 3 bits of the address bits and the lower 5 bits of the command bits,
“00000011” for temperature measurement and “00000101” for relative humid-
ity measurement. The S3C2440 indicates that the GPC8 is pulled low after the
falling edge of the eighth SCK clock to indicate that the command was cor-
rectly received. After the falling edge of the ninth SCK clock, the S3C2440 re-
leases the GPC8.
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3.2. Human Comfort Meter Wind Speed Acquisition Circuit Design
At present, there are roughly three types of sensors for measuring wind speed,
namely a propeller type wind speed sensor, a three-cup type wind speed sensor,
and an ultrasonic wind speed sensor. The measurement accuracy and measure-
ment stability of the three-cup wind speed sensor are superior to the other two
wind speed sensors. The design uses the three-cup wind speed sensor WM30 of
Vaisala, Finland to measure the wind speed of the human comfort meter. The
Vaisala Wind Sensor WM30 is a compact and economical wind speed and direc-
tion sensor (only wind speed measurement is used in this design). The rotating
three-cup anemometer is located at the top of the entire sensor unit and pro-
vides a linear response to wind speed. The material of the cup the shape and size
guarantee the accurate measurement of the wind speed, while the cup is rigo-
rously tested to ensure a linear response between the wind speed and the angular
speed of the cup wheel. Features and benefits of the WM30 include: lower cost,
lighter and lighter design, the best choice for mobile applications, low power
consumption, fast and linear response to wind.
The wind speed is output as a relay. The number of pulses in a fixed time
can be recorded to calculate the wind speed. The wind speed can also be calcu-
lated by measuring the time interval between successive pulses. In this paper,
the number of pulses in a fixed time is recorded to calculate the wind speed.
The human body comfort meter wind speed acquisition circuit is shown in
Figure 3.
In Figure 3, P1 is a transfer port for connecting the wind speed sensor WM30,
wherein the pin 3 is a signal output port; the TLP521 is an optocoupler element
for isolating the wind speed sensor from the S3C2440 to reduce signal crosstalk,
the TLP521 pin 1 is the signal input terminal, connected to pin 3 of P1, pin 3 of
TLP521 is the signal output port, and two non-gate devices are connected in se-
ries and connected to the GPD0 port of S3C2440. The wind speed sensor signal
output calculation formula is shown in Formula (1).
0.24 0.699*VF=−+
(1)
where
V
is the wind speed (in m/s) and
F
is the pulse frequency (in Hz) of the
Figure 3. Human comfort meter wind speed acquisition circuit.
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wind speed sensor output.
4. System Software Design
4.1. Software Design Environment
In an embedded system, the source file code must be compiled to be converted
into an executable binary object file (Zhang et al., 2012). A complete embedded
system requires a lot of object files, which requires a link tool to link all the tar-
get files into a total binary object file. The tools involved include compilers,
linkers, relocatable programs, and locators.
In this design, the host environment needs to be built. The solution is to in-
stall the virtual machine on the PC, and then install the Linux operating system
in the virtual machine environment. The host and the target communicate with
each other through the network. The IP address of the Linux operating system of
the virtual machine needs to be in the same network segment as the IP of the
Windows operating system. In order to generate executable code on another
platform on one platform, you need to build a cross-compilation environment
and install cross-compilation tools.
The transplantation of embedded operating system is an important step in the
process of building software development environment. The operating system
ported in this design is Linux, which mainly includes the transplantation of sys-
tem bootloader, kernel porting, and root file system porting.
4.2. System Software Design
The system software design includes system driver design, Qt/Embedded graph-
ical user interface programming and human comfort instrument algorithm pro-
gram.
System drivers include device drivers, temperature and humidity sensor driv-
ers, and wind speed sensor drivers. The application communicates with the ker-
nel via a Linux system call. Both the temperature and humidity sensors and the
wind speed sensor are connected to the I/O port of the S3C2440, while the I/O
device is used through a fixed entry point defined by the device driver. The driv-
er of the temperature and humidity sensor SHT10 is calculated by changing the
output value of the GPC9 port of the S3C2440 and reading the input value of the
GPC8 port according to the working principle of the SHT10. The working prin-
ciple of the specific code has been described in detail above. Let me repeat. The
driver of the wind speed sensor is relatively simple, mainly to enable a timer to
record the number of pulses of the GPDO port in a fixed time, and calculate by
the Formula (1).
Qt is a cross-platform C++ graphical user program that provides signal and
slot object communication mechanisms with queryable and designable proper-
ties, as well as powerful event and event filters (Jin & Cui, 2014). Qt/Embedded
is a complete GUI and Linux-based embedded platform development tool. Using
Qt/Embedded to write a graphical user program is to apply its good cross-platform
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properties, that is, to write programs and debug on the Windows platform, and
finally Run on an embedded platform. In this design, Qt/Embedded interacts
with the S3C2440’s I/O facilities through the Qt API. The construction of the Qt
environment includes the installation of the Qt Creator software and the con-
struction of the cross-compilation environment under the Linux platform. Using
Qt to develop the application program of human comfort meter, the program
interface has temperature, relative humidity, wind speed, comfort value and
comfort conclusion display function. After the program is compiled, the execut-
able file is generated, and the executable file is downloaded to the S3C2440 de-
velopment board. The design of the Qt/Embedded graphical user interface pro-
gram is completed.
The human comfort tester algorithm uses the human comfort index predic-
tion model used by the Beijing Meteorological Administration since 1997. The
nonlinear equation of the model is shown in Equation (2).
( )
1.8 0.55 1 32 3.2DI T RH V= + − +−
(2)
In the formula,
DI
is the calculated comfort value,
T
is the temperature,
RH
is
the relative humidity, and
V
is the wind speed. The higher the
DI
value, the hot-
ter the human body feels, and the lower the
DI
value, the colder the human body
feels. The correspondence between the
DI
value and the conclusion of human
comfort is shown in Table 1. The rank of
DI
calculated values is determine by
the Beijing Meteorological Administration of China.
It can be seen from Table 1 that when the calculated value of
DI
is too large or
too small, the human body feels uncomfortable. Only when the
DI
value is
moderate, that is, the temperature, relative humidity, and wind speed are con-
trolled within a certain range. The feeling is more comfortable.
5. Conclusion
This paper designs a human comfort meter based on embedded processor and
Table 1. Correspondence between
DI
calculated values and human comfort conclusions.
Serial number
DI
calculated value
Comfort conclusion
1
DI
< 0 very cold and uncomfortable
2 0 ≤
DI
≤ 25 very cold, uncomfortable
3 26 ≤
DI
≤ 38 cold, uncomfortable
4 39 ≤
DI
≤ 50 a few people comfortable
5 51 ≤
DI
≤ 58 most people are comfortable
6 59 ≤
DI
≤ 70 comfortable
7 71 ≤
DI
≤ 75 warm, most people are comfortable
8 76 ≤
DI
≤ 79 hot, a few people are not comfortable
9 80 ≤
DI
≤ 84 hot, most people are not comfortable
10 85 ≤
DI
≤ 88 hot, uncomfortable
11
DI
> 88 very hot, very uncomfortable
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10.4236/gep.2019.76010 123 Journal of Geoscience and Environment Protection
operating system. By collecting the temperature, relative humidity and wind
speed data in the environment, combined with the human comfort algorithm
model, the conclusion of human comfort is obtained. The software development
environment, through Qt to write a graphical user interface to display the mea-
surement values, comfort values and comfort conclusions of each element. After
testing, the human comfort meter can accurately collect the values of various
elements in the environment, and the real-time performance is good. The system
software and hardware design are reasonable; the function is perfect; the reliabil-
ity is high, meets the expected design goals, and has a good application prospect.
The human comfort index is a bio-meteorological indicator based on the me-
teorological point of view to evaluate the comfort of people in different climatic
conditions and based on the heat exchange between the human body and the
atmospheric environment. In general, the three meteorological elements of
temperature, relative humidity and wind speed have the greatest impact on hu-
man body perception. The application of this product can help people under-
stand the atmospheric environment, take timely measures to prevent people
from happening, and reduce the mistakes in work and life decisions caused by
emotions.
Acknowledgements
None.
Conflicts of Interest
The authors declare no conflicts of interest regarding the publication of this pa-
per.
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