Development of comfort sensing system for human environment

\ PERGAMON

Mechatronics 7 "0887# 348Ð355

Development of comfort sensing system for human environment Jeongho Kang\ Sekwang Park School of Electrical Engineering\ Kyungpook National University\ 0269 Sankyuk!don`\ Buk!ku\ Tae`u 691!690\ Korea Received 29 December 0886^ accepted 3 February 0887

Abstract This research is about a comfort sensing system for human environment using humidity\ temperature and ~ow sensors[ The system appears to be highly sensitive to temperature and air ~ow[ We have designed and fabricated a one!bodied humidity:temperature sensor and a ~ow sensor[ Micro!controller calculates a PMV "predicted mean vote# and CSV "comfort sensing vote# with sensing signals and displays the PMV and CSV with LCD[ Experimental results with simulated environment clearly suggest that our sensing system can be used in many applications such as an air conditioning system\ feedback!controlling in automobile\ home\ o.ce and hospital etc[ Þ 0887 Elsevier Science Ltd[ All rights reserved[

0[ Introduction The thermal comfort that a human being feels in indoor environment has been known to be in~uenced mostly by six parameters\ i[e[ air temperature\ radiation\ air ~ow\ humidity\ activity level and clothing thermal resistance ð0Ł[ It was not until Fanger empirically established the well known PMV equation that the formation of the parameters was successfully made[ Fanger|s PMV index basically quanti_es the degree of discomfort and is expressed on such psychophysical scale as hot\ warm\ slightly warm\ neutral\ slightly cool\ cool and cold[ The most important requirement for an air conditioning system such as cooling and "or# heating apparatus is to create a comfortable human environment with high energy e.ciency[ With the rapid development of microprocessor technologies\ bulk silicon micromachining tech!

 Corresponding author[ E!mail] skparkÝbh[kyungpook[ac[kr[ 9846Ð3047:87 ,*see front matter Þ 0887 Elsevier Science Ltd[ All rights reserved[ PII] S 9 8 4 6 Ð 3 0 4 7 " 8 7 # 9 9 9 0 4 Ð 3

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nologies and control tools such as fuzzy and neural network\ there has been growing need for in situ monitoring of parameters necessary for the optimal control of air conditioning system[ The most important prerequisite for the commercial applications of the PMV scheme is to extract correct values of PMV index at low cost[ Considering a thermal comfort\ we have designed and fabricated a one!bodied humidity:temperature sensor and a ~ow sensor that detect air temperature\ relative humidity and air ~ow in human environment using bulk and surface silicon micromachining technologies[

1[ Design and fabrication The design of sensors is based on a thermal comfort[ The controlling mechanism as a kind of heat exchanger helps the body core to maintain relatively constant temperature in given thermal environment[ Heat is generated inside a human body and dissipates through various channels for the heat exchange between the body and thermal environment[ To get values of PMV index in human environment\ it is necessary to know air temperature\ relative humidity and air ~ow[ Therefore devices that each sensor for their values are designed and fabricated by bulk and surface silicon micromachining technologies[ In humidity sensor\ after piezoresistors are di}used on silicon wafer\ the diaphragm is formed by micromachining technology\ then hygroscopic layer is coated with polyimide ð1\ 2Ł[ Each resistors are positioned at high sensitive region and the metal is deposited by evaporation[ According to increase relative humidity in environment\ hygroscopic layer is expanded[ Because the layer is in contact with diaphragm\ pie! zoresistors on diaphragm have increased value and is detected its relative humidity by electrical circuits such as driving and ampli_er circuit[ Fabrication processes are followed by standard cleaning\ thermal oxidation\ patterning of resistors\ di}usion\ Al evaporation\ back side etching\ dicing\ wire bonding and packaging[ Also temperature sensor using temperature coe.cient of di}used resistors has been constructed for testing and performance evaluation[ Di}used resistors on silicon have temperature coe.cient of resistance "TCR# and it was used as temperature sensor ð3\ 4Ł[ Temperature sensor and relative humidity sensor are in one!bodied chip and have a driving circuit[ The schematic diagram of the fabricated one!bodied humidity! :temperature sensor is given in Fig[ 0[ Flow sensor is made of Pt on ceramic plate[ Pt is sputtered on ceramic plate[ We design Pt patterns of 099 V and 0 kV[ Pt of 099 V is used for heater and 0 kV is used for detecting temperature of air ~ow in human environment[ By constructing Wheatstone bridge with other resistors\ unbalanced output will be generated by air ~ow[ A closed!loop con_guration\ in which the temperature is kept constant by supply power and that power is measured[ And these loop control potentially o}ers higher response speeds ð5Ł[ The schematic diagram of the fabricated air ~ow sensor is given in Fig[ 1[ It is consisted of heater and temperature sensor\ which is made of Pt on ceramic[ These fabricated sensors are packaged in probe with driving and ampli_er circuit

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350

Fig[ 0[ The schematic diagram of the fabricated one!bodied humidity:temperature sensor[

Fig[ 1[ The schematic diagram of the fabricated air ~ow sensor[

to detect temperature\ relative humidity and air ~ow in human environment[ Mic! rocontroller is used for measuring of output voltage of each sensor and calculates PMV index and displays the result of calculation of PMV on LCD[ Figure 2 shows a block diagram of the PMV!indicator constructed using a one! bodied humidity:temperature sensor and a ~ow sensor[ The PMV!indicator consists of] "0# a sensing unit with signal processing^ "1# MPU "79C20 microcontroller# which calculates PMV index and controls the control unit^ "2# a display part using LCD^ and "3# keyboard[ A PMV!indicator has been fabricated using these sensors and MPU with PMV eqn "0# in ISO6629 ð6Ł\ and experimental results with environment clearly suggest that our system can be used in many applications such as an air conditioning system\ feedback!controlling in automobile\ home and hospital\ etc[ PMV  "9[292e−9[25M¦9[917#""M−W#−2[94×09−2ð4622−5[88"M−W#−PaŁ −9[31ð"M−W#−47[04Ł−0[6×09−4 = M = "4756−Pa#−9[9903 = M"23−ta# −2[85×09−7 = fcl = ð"tcl¦162#3−"t¹r¦162#3Ł−fcl = hc = "tcl−ta## "0#

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Fig[ 2[ A block diagram of the PMV!indicator[

where tcl  24[6−9[917"M−W#−Icl = "2[85×09−7 = fclð"tcl¦162#3 −"t¹r¦162#3Ł¦fcl = hc"tcl−ta## Hc 

fcl 

M W Icl fcl ta tr Var Pa hc tcl

1[27"tcl−ta#9[14 for 1[27"tcl−ta#9[14 − 01[0zVar

6 6

01[0zVar 0[99¦0[18 = Icl

for 1[27"tcl−ta#9[14 ¾ 01[0zVar for Icl ¾ 9[967 = m1 = >C:W

0[94¦9[534 = Icl for Icl ¾ 9[967 = m1 = >C:W

7

7

metabolic rate ðmetŁ  ð47[1 W:m1Ł external work ðmetŁ thermal resistance of clothing ðcloŁ  ð9[044 m1 >C:WŁ ratio of man|s surface area while clothed\ to man|s surface area while nude air temperature ð>CŁ mean radiant temperature ð>CŁ relative air velocity ðm:sŁ partial water vapour pressure ðPaŁ convective heat transfer coe.cient ðW:m1 >CŁ surface temperature of clothing ð>CŁ

PMV!indicator calculates PMV index using eqn "0# and displays the result of PMV index in human environment on LCD[ Figure 3 shows a ~ow chart of PMV!indicate that "0# detect of temperature\ humidity and air ~ow in human environment^ "1# input parameters of metabolic\ external work and clothing using keyboard^ "2# calculate of

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352

Fig[ 3[ Flow chart of PMV!indicator[

PMV^ and "3# display on LCD[ Initial step prepares internal user setting in special function register\ internal RAM and other devices[ According to key input\ branch to modify of initial variable using key input and set default mode "home\ o.ce\ hospital and plant#[ Values of default mode are based on mean values of each place[ After mode selection\ temperature\ relative humidity and air ~ow in human environment are detected from sensors[ Temperature com! pensation of detected values is completed in software and calculated to PMV and displayed on LCD device[ Execution is returned to key input routine and repeat those routine[

2[ Results and discussion In order to construct a PMV!indicator using fabricated sensors\ it was necessary to investigate the characteristics of these sensors in response to temperature\ humidity and air ~ow among other things[ Figure 4 is the bridge output voltage variation of humidity sensor[ As shown in Fig[ 4\ sensitivity is 47[00 mV:)R[H[\ hysteresis is 0[56)FS\ nonlinearity is 5[58) FS and response time is 049Ð119 s[ TCO "temperature coe.cient of o}set# of humidity sensor is 21)R[H[:>C in the temperature range of 4Ð34>C\ and long term stability

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Fig[ 4[ The bridge output voltage variation of the humidity sensor with relative humidity[

during 49 days is within 24[35)R[H[[ Output voltage variation of temperature sensor is given in Fig[ 5[ In temperature sensor\ sensitivity is 445 mV:>C in the temperature range of −10[7Ð34[7>C[ Figure 6 is the output voltage variation of the air ~ow sensor with air ~ow and temperature[ The output voltage of bridge is decreased according to temperature\ thus the compensation of temperature is executed in software with temperature coe.cient of voltage output[ We designed and made a PMV!indicator using fabricated sensors[ Figure 7 describes the PMV and CSV index changing aspects of physical factors such as temperature

Fig[ 5[ The output voltage variation of the temperature sensor[

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Fig[ 6[ The output voltage variation of air ~ow sensor with air ~ow and temperature[

range of 19Ð29>C\ humidity of about 54) R[H[ and ~ow of 9[0 m:s[ Above healthy hundred men exposed to moderate thermal environment\ and PMV and CSV of the fabricated PMV!indicator and PMV and CSV of a human being were recorded at the same time according to the variation of temperature[ It is clear from Fig[ 7 that the output values from PMV!indicator are in a good agreement with PMV and CSV of a human being in Korea[ Because PMV!indicator is constructed for human being\

Fig[ 7[ The PMV index changing aspects of physical factors[

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not Korean[ It is necessary that PMV!indicator is modi_ed for Korean|s comfort using Korean|s comfort database[

3[ Conclusion Our work has demonstrated that a microsensor!based PMV!indicator can provide an e}ective means of measuring the comfort sensing of a human being[ Experimental results in simulated environment clearly suggest that our sensing system can be utilized in air conditioning system as a practical means of monitoring PMV indices and feedback!controlling in automobile\ home\ o.ce\ hotel and hospital\ etc[ Also base on comfort database of special environment in local region\ modi_ed PMV!indicator can be utilized in air conditioning system[

Acknowledgment This work was supported by Human Sensibility Ergonomics of G!6 project in Korea[

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