NANZAN-TR-2004-04

A Quantitative Approach to the Design of the Center
Console of Automobiles
Mihiro Sasaki, Fumio Ishizaki, Atsuo Suzuki, Isao Takami,
Yutaka Tanaka, Eiichi Yamamoto and Kazuhiko Nakashima

October 2004

Technical Report of the Nanzan Academic Society
Mathematical Sciences and Information EngineeringA Quantitative Approach to the Design of the Center Console ofAutomobiles
Mihiro Sasaki

Department of Mathematical Sciences
Nanzan University
27 Seirei, Seto, Aichi, 489-0863, Japan
Tel: +81-561-89-2000 Fax: +81-561-89-2083
Email: mihiro@ms.nanzan-u.ac.jp,Fumio Ishizaki

Dept. of Information and Telecommunication Engineering, Nanzan University,
Atsuo Suzuki, Isao Takami, Yutaka Tanaka

Dept. of Mathematical Sciences, Nanzan University,
Eiichi Yamamoto and Kazuhiko Nakashima

Kojima Press Industry, Co., Ltd.

Abstract

We consider a statistical approach to design the center console of automobiles. The
design of the center console is an important part in the sense that it has a strong eect
on user satisfaction. From this standpoint, the center console should be adequatelydesigned. However, the design process usually relies on a trial and error approach,which consumes lots of time. If the relationships between usability and physical specications are revealed, we may design the center console with higher user satisfaction
in a shorter time. For this purpose, we carry out a questionnaire survey. The results
show several interesting relationships.

1 Introduction
Dials and switches are major components of center consoles of automobiles. Since the usability of such components has a strong eect on user satisfaction, it is very important topay attention how to design each dial and switch within a center console. So far, we don't
have any quantitative relationships between the usability and the physical specications ofdials and switches. If we have some information about the relationship in advance, it will bea useful tool to reduce the design time.
Our rst target is to obtain the relationships between the usability and the physicalspecications by statistical methods. We prepared 12 samples of center consoles for ouranalysis, which are all commercially oered. We made a survey questionnaire for a sensory
test and measured each component of the 12 samples to know the specications of each ofthem, such as dimensions, stroke, friction and so on. We also made a statistical analysis of
the survey data and the physical data.
We used two statistical methods, which are the principal component analysis and thecanonical correlation analysis 1, 2]. It turned out that there was no clear relationshipbetween the linear combination of the survey results and the linear combination of thephysical data. However, there was partially strong correlation between the survey data andthe physical data. For example, the sense of heaviness for temperature control dial has astrong correlation to the range of its rotation angle.
1(a) Rotational Dials(b) Testing WorkFigure 1:
This paper is organized as follows. In Section 2, we describe the survey questionnaire indetail. In Section 3, we briey mention the specications of each center console. In Section
4, we show the results of the statistical data analysis. Finally, we will conclude the paper inSection 5.

2 Survey questionnaire
We carried out a questionnaire survey using the 12 samples by 10 respondents. The survey
questionnaire consists of 30 questions. Each question has ve choices: very good, good,fair, bad and very bad. An example of the questions is "How do you feel when you turnon the switch? Have you recognized clearly the click?" It took about one hour to answer
all questions of the 12 samples for a respondent. Figure 1 shows some of the photos taken
during the survey. The age of the respondents is distributed from twenties to sixties. Six
out of ten respondents are female. Table 1 shows a part of the questions of the survey. We
have seven such questions for each switch of the 12 samples. The other questionnaire items
are as follows:
How do you feel about the heaviness when you turn on or turn o the switch?
How do you feel about the stroke of the switch?
How do you feel when you touch the switch?
How easily do you recognize what the switch is for?
Do you operate the switch very easily?
Do you feel satisfaction when you operate the switch? Why?
2How do you feel about the click when you turn on or turn o the following switches?
Table 1: Questions

1. Air Conditioner On-O:

2. Air Conditioner Auto-Manual:
3. Temperature Control:
4. Mode of Cabin Air Duct:
5. Air Circulation Internal-External:
6. Rear Defroster :7. Hazard Lamp On-O 8. Front Defroster :In addition to these questions, we asked the respondents about their personal data including
driving experience, driving distance per day, and the frequency of operating each switch inthe center console of their own cars.

3 Physical specications of the switches
In order to get the specications of the 12 samples, we measured each component of eachsample. There are 59 items to measure. Table 2 shows a part of the results. The measured
items are the dimension of center console, the types of switches, the dimensions of switch
and the other physical data like stroke and friction of the switch. We have three types ofswitches. They are rotational dial type, lid dial type (knob type) and rectangular push type.
We incorporate dummy 0-1 variables to distinguish the types of switches.
Table 2: Physical specications
No.
VerticalHorizontal
Depth
Rotational dial
Lid dialRect. pushTemp. Dimensions
Verticalcontrol(mm)Horizontalswitch
HeightStroke
PhysicalFriction
data
Rotation range
Dial pitch
Dimensions ofcenter console(mm)Switchtype12345695 84.5 120 95 66.6 195
230 205 330 240 187 264
809665 150 82.1 163
101
1000
1001
1000000
60.4 35 48.3 44.7 36.4 41.5
60.4 35 48.3 44.7 24.4 41.5
10.5 27
15 10.2 11.6 12.2
0.88 0.88 0.88 0.88 0.88 0.88
2.2 1.2 2.75 2
3.5 1.7
180 250 220 220 290 180
12.4 10 13.5 7.5 24.8 17.4

37137264143
10053.1
53.1
11.60.882.5210
108270
370
150
100
55.3
55.3
22.2
0.88
2.8
250
7.8

9135
310
75
00
1
33.5
24.6
15.1
0.72
3.2
223
13.6

10144
240
215
001
32.6
31
15.1
0.66
1.94
223
13.6

1160
188
46.6
00
1
41
22.1
15.1
0.95
3.6
223
13.6

1296
200
81.3
001
25.8
25.8
14.5
1.17
2.38
223
13.6

4 Data Analysis
We made a data analysis of the survey data and the physical data. First, we made aprincipal component analysis for both the survey data and the physical data. Figure 2shows a scatterplot of the rst and second principal components of the survey data. We cansee two groups. The cumulative proportion up to the third component is about 65 % and up
to the fourth component is about 75 %. The rst component can be interpreted as heavinessand click feelings, although the meanings of other components are not so clear. Figure 3
shows a scatterplot of the 1st and 2nd principal components of the physical data. We canalso see three groups. The cumulative proportion up to the third component is 69 % and up
to the fourth component is 78 % . Each component can be interpreted as follows:the rst component: the type of switch is rotational dial and the dimension is bigger thesecond component: the type of switch is rectangular push and the stroke and the friction islight the third component: the type of switch is lid dial or round push and the height of theswitch and the range of dial rotation angle are both big.
For the next step, we applied the canonical correlation analysis so as to nd the correlation
between the linear combinations of the survey data and the physical data. As a result of thisanalysis, we do not nd clear correlations between them. We consider that a lack of samples
caused this rather unsatisfactory results. Another possible reason may be nonlinearity of therelationships. We need to make a sensory test by many respondents to collect more precise
survey data, and also do more precise analysis to check the nonlinearity of the data.
Finally, we simply calculated correlation factors between each item of the survey data andeach item of the physical data. This simple analysis provided several interesting relationships
between the user preferences and the physical specications of the center console. The results
are as follows:
Dimension of the center console should be bigger.
Dimension of the switches should be bigger.
Rotational dial switch is the best.
Stroke of the switch should be short.
Range of the dial rotation angle should be small.
There is no relationships between the user satisfaction of the design of center consoleand feelings of operation.
Click feeling, friction and stroke of the switches have strong correlation to feelings ofoperation.

5 Concluding remarks
We made a simple experimental analysis to obtain the relationships between the survey(sensory test) results and the physical specications of the center console. We used two
multivariate analysis methods, which are the principal component analysis and the canonical4Figure 2: Scatterplot of the 1st and 2nd principal components of the survey data

Figure 3: Scatterplot of the 1st and 2nd principal components of the physical data5

correlation analysis. We found some interesting features by the principal component analysis.
We also got some useful results from the correlation factors between each item of the survey
questionnaire and the physical specications. However, we do not get clear relationships by
the canonical correlation analysis. We could have obtained better results if we had made thesurvey by more samples. Other possible matters to nd better results are that we check thelinearity of the data and examine the experiments in themselves whether they are suitably
designed for our purpose of extracting the relationships.
Although our strategy of the experiments and the analysis is still in a preliminary stage,
we got some useful results and made a prototype of the center console based on the results.
Further research for sophisticated strategy to design a center console will be a necessary
future topic. For this purpose, we need to reconsider how to design the experiments andenlarge the questionnaire survey. We also should check the lineality of the data. Theseeorts will enable us to establish a useful integrated strategy to design a center console withhigher user satisfaction in a shorter time.

References
1] Chatterjee, S., Price, B.,: Regression Analysis by Example Wiley Series in Probability
and Mathematical Statistics Applied Probability and Statistics Sections, John Wiley &Sons Inc, (1991).
2] Okuno, T. et al: Multivariate Analysis 2nd edition (in Japanese) Nikkagiren, Japan(1976).

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