2002:36M
DEGREE WORK
Humidity sensor for car seat
Haris Dedic Sep 06, 2002
University of Trollhättan/Uddevalla Department of Technology
Box 957, S-461 29 Trollhättan, SWEDEN Phone: +46 520 47 50 00 Fax: +46 520 47 50 99
E-mail: teknik@htu.se
Humidity sensor for car seat
Summary
CONFIDENTIAL
Publisher: University of Trollhättan/Uddevalla, Department of Technology Box 957, S-461 29 Trollhättan, SWEDEN
Phone: + 46 520 47 50 00 Fax: + 46 520 47 50 99 E-mail: teknik@htu.se Author: Haris Dedic
Examiner: Mats Eriksson
EXAMENSARBETE Fuktsensor för bilstol
Sammanfattning
KONFIDENTIELL
Utgivare: Högskolan Trollhättan/Uddevalla, institutionen för teknik Box 957, 461 29 Trollhättan
Tel: 0520-47 50 00 Fax: 0520-47 50 99 E-post: teknik@htu.se Författare: Haris Dedic
Examinator: Mats Eriksson
Handledare: Christer Andersson, Lear Corporation
Poäng: 10 Nivå: C
Huvudämne: Maskin konstruktion Inriktning: Produkt utveckling
Språk: Engelska Nummer: 2002:36M Datum: 2002-09-06
Preface
This report is the result of a degree work prepared, conducted and written in the spring of 2002 at Lear Corporation AB in Trollhättan. The degree work is the final, compulsory moment in the education for Bachelor of Science in Mechanical Engineering, Product Development, in the University of Trollhättan/Uddevalla, Department of Technology, Sweden.
I will use the opportunity to thank all, who contributed to the conduct of this work. Great thanks to the Advanced Engineering group, advisor at Lear, Christer Andersson, Lear’s testing laboratory, and in HTU, Hans Dahlin and Gunne Andersson.
Trollhättan, Sep 06,2002
____________________
Haris Dedic
Humidity sensor for car seat
Contents
Summary...i
Sammanfattning ...ii
Preface...iii
Contents ...iv
1 Introduction ...1
1.1 Background ...1
1.2 Company presentation ...1
1.3 Problem background...1
1.4 Goal...1
1.5 Limitation of the work ...1
1.6 System requirements ...1
2 Theoretic background ...2
2.1 Thermal comfort ...2
2.1.1 Physical factor...2
2.1.2 Perspiration...3
2.2 Humidity...3
2.2.1 Humidity Measurement...3
2.2.2 Humidity transportation ...3
2.3 Sensors ...3
2.3.1 Humidity sensor ...3
3 Method ...4
3.1 Preliminary study ...4
3.2 Work with selected quality- and development tools...4
3.3 Evaluation and selection of ideas ...4
3.4 Verification...4
4 Implementation...5
4.1 Time plan...5
4.2 Preliminary study ...5
4.2.1 Conducting interviews with experts ...5
4.2.2 Literature ...5
4.2.3 Internet ...5
4.3 Work with the selected quality- and development tools...5
4.3.1 QFD –matrix ...5
4.3.2 Brainstorming...5
4.3.3 Pugh- and Kepner-Tregoe-matrix...6
4.4 Evaluation and selection of ideas ...6
5 Verification of selected concept ...6
6 Sensing system operation...6
7 Result...6
8 Conclusions ...6 9 Sources ...7
Humidity sensor for car seat
1 Introduction
1.1 Background
This report is the result of work conducted and a thesis written at Lear Corporation AB, Seat Systems Division, in Trollhättan. The degree work is the final, compulsory moment in the course of the education in Mechanical Engineering, Product Development, in the University of Trollhättan/Uddevalla, Department of Technology, Sweden. The report presents the work of 10 points at C-level. These pints correspond to 10 weeks of full-time work.
1.2 Company presentation
Lear Corporation AB was founded in 1917 in Detroit as American Metal Products, a manufacturer of tubular, welded and stamped assemblies for the automotive and aircraft industries. Today, the company exclusively serves the global automotive industry and develops all eight interior systems: seats, instrument panels/cockpits, doors and trims, overheads, floorings, acoustics, electronics, and electrical distribution systems.
The company's world-class products are designed, engineered, manufactured, validated and delivered by over 100,000 employees in more than 300 facilities located in 33 countries [1].
1.3 Problem background
CONFIDENTIAL
1.4 Goal
CONFIDENTIAL
1.5 Limitation of the work
• The scope of the thesis is at the conceptual level
• The production process of integral parts is not treated.
• The choice of materials and solutions for integration of the system is not elaborated.
1.6 System requirements
Lear Corporation has stated that the following requirements apply to the system:
• Product must not cost over 30 SEK.
• It has to fulfill American safety standard FMVSS 302
2 Theoretic background
2.1 Thermal comfort
Thermal comfort is defined as ”the condition of mind that expresses satisfaction with the thermal environment”. Human’s sense of thermal comfort depends on physical, physiological and psychological factors:
• Physical: parameters as air temperature, temperature of radiation and air velocity, clothing and relative air humidity.
• Physiological: parameters as age, sex and the ability to adapt.
• Psychological: understanding the thermal environment [2].
It is important to mention that the body does not reach thermal comfort once it feels humidity [3].
2.1.1 Physical factor
• Air temperature; the so called “neutral climate zone” has an approximate air temperature within an interval of 10-30°C [4]. For a man to feel comfortable it is necessary to keep air temperature in between 21-28°C [5]. At the same time the difference in temperature between the head and feet shall be less than 3°C [4].
• Air humidity; research has shown that a relative air humidity of around 40 – 70 % is a suitable level and comfortable human environment [6].
• Air velocity; in case of increased air velocity, also the temperature should be increased in order to maintain a comfortable temperature, see diagram 2.1.1.1[7].
Diagram 2.1.1.1. Variation of air velocity with temperature [7].
Air velocity (m/s)
Air temperature °C
Humidity sensor for car seat
2.1.2 Perspiration
The human body starts to perspire when the skin temperature reaches 34,5-35 °C. If the skin temperature is below 32 °C, the body will feel cold. Hence a person will feel a satis-factory thermal climate if the skin temperature, in the stage of tranquility, is 33-34 °C [8].
2.2 Humidity
2.2.1 Humidity Measurement
In practice, the air almost always contains a certain amount of water, and is called humid air.
Dry air is a mixture of a large number of gases: nitrogen 77%, oxygen 21%, argon 1% and around ten other gases [9].
The following concepts are mentioned in research of the air humidity:
Relative Humidity
Relative Humidity (RH) is a measure of the actual amount of water in the air compared with the maximum amount of water the air can hold at the measured temperature [10].
Absolute Humidity
Absolute Humidity is the mass of water vapor in a given volume of air, while Specific Humidity is Absolute Humidity divided by the total mass of the given volume of air.
2.2.2 Humidity transportation
Humidity transportation occurs in steam phase or water phase.
In the steam phase transportation is possible in different ways: diffusion or convection of humidity (steam is transported with the air used as the transportation medium).
In the water stage transportation happens through some operational power such as:
gravitation, water overpressure, through the wind or capillary attraction [9].
2.3 Sensors
2.3.1 Humidity sensor
There are several different humidity sensors for a variety of different applications. The majority of them function so that the humidity in a material serves as an electric conductor and is measured by the electric current going through the material. By using the output voltage and current it is possible to calculate the humidity. In modern humidity sensors it is possible to combine humidity sensors with temperature sensors, for automatic temperature compensation during the measuring [11].
3 Method
The degree work is executed using a systematic approach:
• preliminary study
• work with selected quality- and development tools for identification of customer needs, design requirements, and concept selection
• evaluation and selection of ideas
• verification
• compilation of results and analysis.
3.1 Preliminary study
The preliminary study includes, visits to and discussions with humidity sensor producers, taking decisions on working methods to be used and problem identification.
3.2 Work with selected quality- and development tools
Use of information and decisions made in preliminary studies.
• A QFD -matrix was prepared to determine design requirements and customer needs[12].
• Brainstorming was conducted to obtain a broad spectrum of ideas.
• Pugh- and Kepner-Tregoe matrixes were prepared to establish technical value of different concepts, but also to create a base for concepts to be compared [12].
3.3 Evaluation and selection of ideas
For concept selection has been based on the results of quality- and development instruments.
In the case of several good ideas being equal, necessary tests are conducted for the purpose of finding the best concept.
3.4 Verification
Verification of the concept selection has been made through comparison to requirements made by Lear Corporation and the QFD-matrix needs satisfaction.
Humidity sensor for car seat
4 Implementation
4.1 Time plan
Before starting the degree work, a time plan was established. The plan was prepared in Microsoft Project.
4.2 Preliminary study
To be able to conduct such a project it was necessary to be introduced to the problem, and to gain the knowledge needed for solving the problem. After being introduced to the problem, through discussions and internal documentation at Lear Corporation, information collection was started.
4.2.1 Conducting interviews with experts
Lear´s expert Harry Eriksson [13] pointed to the basic points. Theachers at HTU, working colleagues and humidity sensor producers were also interviewed.
4.2.2 Literature
Beside internal literature at Lear, the services of the University libraries in Göteborg and Trollhättan have been used. In addition records and results of research made at the Institute for Work and Life in Stockholm have been used.
4.2.3 Internet
Internet has been used to find articles related to project and persons competent in the field of relation between climate and humidity.
4.3 Work with the selected quality- and development tools
4.3.1 QFD –matrix
CONFIDENTIAL 4.3.2 Brainstorming
Brainstorming was used to obtain a wide range of ideas. To conduct this exercise the following activities were performed:
• Five independent persons were invited, and informed about the problem.
• The result was processed so the possibility of idea combination was checked first, seeking for new opportunities. After that all ideas were analysed in a sense of their possibility to be realised and if they were applicable.
4.3.3 Pugh- and Kepner-Tregoe-matrix
Pugh-matrix and Kepner-Tregoe-matrix were prepared with the aim to see which idea (or ideas) that best could fulfill the design requirements and the customer needs according to QFD -matrix. Ideas having negative sum of points after processing in Pugh-matrix were eliminated from further analyses in Kepner-Tregoe matrix.
Practical tests of the conceptual solutions were needed for the decision on the final solution that would be used.
4.4 Evaluation and selection of ideas
CONFIDENTIAL
5 Verification of selected concept
CONFIDENTIAL
6 Sensing system operation
As a part of this work it was required to develop the proposal for the functional description of a sensing system. The following description was prepared in collaboration with Christer Andersson, at Lear Corporation.
7 Result
CONFIDENTIAL
8 Conclusions
CONFIDENTIAL
Humidity sensor for car seat
9 Sources
[1] http://www.lear.se (2002-04-20).
[2] ASHRAE. 1997. HVAC systems and equipment. Atlanta: Ga. American Society of Heating, Refrigerating and Air-Conditions Engineers. ISBN 1-883413-45-1.
[3] Johansson, Peter and Neander, Gustav. 2002. Reglering av 3 Step Vent Seat. Luleå:
Thesis. Luleå Tekniska Universitet.
[4] Arbetarskyddstyrelsens författningssamling. 1995. Arbetslokaler. Stockholm. Göran Lindh. AFS 1995:3. ISBN 91-7930-294-7.
[5] Haug, Egil. 1998. Människans fysiologi. Stockholm: Liber. ISBN 91-47-04806-9.
[6] Arbetarskyddsfonden. 1980. Klimat i förarhytter. Conference: Klimat i förarhytter, Uppsala, Sweden, 30 August 1979. ASF. 86 S.
[7] Lindholm, Emy and Lindholm,Nore. 1982. Klimatkomfort i förarhytter. Stockholm.
Statens Miljömedicinska Laboratorium. Report No 4/1982.
[8] Andersson, Per. 2002. Climatic Seats – Thermal Comfort and Health and Safety Aspect., Mullsjö. Kongsberg Automotive. Technical Report
[9] Nevander, Lars Erik and Elmarson, Bengt. 1994. Fukt. 2:nd edition. Stockholm:
Handbok. ISBN 91-7332-716-6.
[10]http://www.globalspec.com/Frames?Url=http%3A//www.globalspec.com/ProductFinder
%3Fse%3Davka (2002-05.01).
[11] Alfredsson, Alf and Mårtensson, Lars. 1998. Elteknik. 3:th edition. Fallköping:
Studentlitteratur. ISBN 91-47-01381-8.
[12] Bergman, Bo and Klefsjö, Bengt. 2001. Kvalitet från behov till användning. Lund:
Studentliteratur. ISBN 91-44-46331-6.
[13] Harry Eriksson, Manager HVAC (Heating, Ventilation and Air Condition), Lear Corporation 0528-754 04.
