An Enhanced Model Using the Kano Model, QFDE, and TRIZ with a Component-Based Approach for Sustainable and Innovative Product Design

Abstract

In order to increase their competitiveness, companies need to have five important capabilities in the product development process, namely, the ability to identify important customer and environmental requirements, convert them into technical requirements, create innovative designs, and determine the best improvement alternatives. Based on a literature survey, previous studies are still inadequate in incorporating these five important capabilities simultaneously and effectively. This study proposes an enhanced model using the Kano model, Quality Function Deployment for Environment (QFDE), and the theory of inventive problem solving (TRIZ), with a component-based approach for systematically designing sustainable and innovative products. An example of a desk lamp design improvement is used to demonstrate the proposed model. After identifying customer and environmental requirements, they are specifically characterized and transformed into a detailed design target using a combination of the Kano model and the improved QFDE method. A thorough evaluation method is developed to determine the most prominent TRIZ solutions. This enhanced model is accomplished at the component level. The results show that the proposed model is capable of incorporating the five important capabilities while reducing process complexity, which greatly assists designers in generating sustainable and innovative designs with minimal dependence on designers’ subjectivity.

1. Introduction

To survive global competition, companies must enhance their capacity to precisely and continuously identify customer requirements and fulfil them. A previous study showed that the voice of the customer (VOC) is the most frequently used tool in market research [1]. The fulfilment of customer requirements is related to customer satisfaction, which is an undeniable factor for business success. Customers with a high satisfaction level will have a high loyalty level. The profit of a business can be increased by 100% with only a 5% increase in customer loyalty [2]. However, this is not easy to achieve, due to the different impacts of the fulfilment of customer requirements on customer satisfaction. Therefore, companies need tools to accurately identify customer requirements.

In recent years, environmental problems have also become a critical issue for companies. Customers are becoming more aware of environmental problems, which have led many countries to implement and enforce ‘green’ environmental laws and regulations, such as ‘green material’, to reduce the negative effects of the product life cycle on the environment [3]. This growing pressure from the stakeholders has left companies with no choice but to adjust their environmental policies [4]. Many studies have discussed and proposed tools and methods for merging environmental aspects into the product development area. This approach, widely known as eco-design, is intended to avoid the repercussions of product development across the product life cycle [5,6,7].

Having knowledge of customer and environmental requirements is critical, but failure to transform the known knowledge into product specifications can be as harmful as not having the knowledge. It is important for companies to precisely identify the requirements and to incorporate them into product specifications [8]. In addition to fulfilment of the right requirements, companies that can transform the requirements into innovative products and offer value-added qualities will excel in market competition [9,10]. Companies need good problem-solving and decision-making tools.

In brief, in order to gain a sustainable competitive advantage, companies need to possess five important capabilities (C1–C5): to identify important customer requirements (C1), to identify environmental requirements (C2), to transform the requirements into product specifications (C3), to support idea creation and create innovative solutions (C4), and to evaluate and choose the best solutions (C5).

Furthermore, the previous research was mostly performed on a macrosystem basis to arrive at solutions. Either in the idea generation process or in the solution analysis, they mostly started from an overall system overview before studying more detailed areas. The application of a system approach in product development—especially in generating solution idea processes—can produce groundbreaking results; however, it heavily relies on the designer’s skills or knowledge. By doing so, no matter what methodologies are used, it will rarely produce a robust result. Another potential drawback of this approach is the possibility that the initial conceptualizations in the overall system lead to an incorrect approach regarding the core details. In an era where competition is very tight, companies cannot rely on something so vague for their business. An improper product design can cause consumer dissatisfaction and loss of customers. Redesign is not always a practical option, because it costs a business time and money, which are always critical.

Therefore, this study proposes a new method that is able to incorporate C1–C5 and is applicable in today’s product design processes. To do so, this study combines the Kano model, QFDE, and TRIZ with a component-based approach to systematically produce a sustainable and innovative product design.

2. Literature Review

2.1. Kano Model

The Kano model is frequently used to distinguish between categories of customer requirements [11] that result in either satisfaction or dissatisfaction to customers. The Kano model divides product features into six types of product requirements [12]: Must-be (M), One-dimensional (O), Attractive (A), Indifferent (I), Reverse (R), and Questionable (Q). Originally, the Kano Model was intended to describe the relationship between the customer and the product. However, more recent studies have applied the Kano model for perceiving environmental quality and sustainability as well [13].

2.2. QFDE

Quality Function Deployment (QFD) is widely used to integrate customer needs into product concepts in each stage of the product planning and development process [14]. QFDE is the modification of QFD by adding environmental aspects such as environmental voice of customers (VOE) and environmental engineering metrics (EMs) [15]. By using QFDE, companies can handle product quality and environmental requirements together and integrate them into product specifications. QFDE consists of four phases: phases I and II identify the important EMs based on the VOC and the important components based on EMs, while phases III and IV use Equations (1) and (2), respectively, to determine the product’s design targets.

$$i{r}_k=\frac{{{\displaystyle \sum }}_{l=1}^{L}r{s_{k,l}}^{\prime }i{r}_{k,l}}{{{\displaystyle \sum }}_{l=1}^{L}r{s}_{k,l}}\left(l=1, \dots , L\right)$$

(1)

$$i{r}_j=\frac{{{\displaystyle \sum }}_{k=1}^{K}r{s}_{j,k}i{r}_k}{{{\displaystyle \sum }}_{k=1}^{K}r{s}_{j,k}}\left(k=1, \dots , K\right)$$

(2)

where ir_k is the improvement rate of EM item k; K is the number of EM items; rs_k,l is the relational strength of EM item k for component l; rs_k,l′ is the relational strength of EM item k for component l after omission; L is the number of components; ir_k,l is the improvement rate of EM k for component l, which can take a real number from 0 to 1; ir_j is the improvement rate of VOC/VOE item j; J is the number of VOC/VOE items; and rs_j,k is the relational strength of VOC/VOE item j for EM item k. For simplicity, this study allows the ir_k,l value to take a binary value of 0 (improvement impossible) or 1 (improvement possible).

2.3. TRIZ

TRIZ is widely used to support idea creation in the conceptual design process [16]. One of the main concepts, and a basic tool in TRIZ, is contradiction. This refers to the incompatibility of the desired features that arises because of the deterioration of other features. To solve this kind of conflict, TRIZ users can utilize TRIZ’s most popular tools: 40 inventive principles [17]. Formerly, TRIZ tools were not intended for supporting the development of ‘green products’; thus, their effectiveness in this area is unproven. However, some studies have demonstrated that the solutions provided by TRIZ tools are more sustainable when applied to real problems [18,19,20].

2.4. Research Gap

There are numerous studies associated with combinations of the Kano model, QFDE/QFD, and TRIZ. In this study, we conducted extensive literature analyses in these areas and grouped the previous combination research into four different groups, as shown in

Table 1. Literature analysis of the Kano model, QFDE/QFD, and TRIZ combination.

Groups	Reference	Tools Used	C1–C5					Description
			1	2	3	4	5
Group 1: Kano + QFDE/QFD	[21]	Kano model, QFD	√		√			Showed how Kano categorization can be used as a QFD input by using a case study from the ski industry.
	[11]	Kano model, QFD	√		√			Proposed a process model for designing and developing innovative products by integrating Kano into QFD.
	[22]	Kano model, QFD	√		√			Proposed a methodology for designing multiple products simultaneously by integrating the Kano model into QFD.
	[23]	Kano model, QFD	√		√			Proposed an importance weight adjustment for customer satisfaction by using a case study from beer mug design.
	[24]	Kano model, QFD	√		√			Proposed an integrative approach by adjusting the traditional improvement ratio.
	[25]	Kano model, QFD	√		√			Integrated Kano model–QFD based on an ergonomic approach.
	[26]	Kano model, QFD	√		√			Constructed a framework for a shared research equipment service system based on integrating the Kano model and QFD.
	[27]	Kano model, QFD	√		√			Integrated Kano and QFD for city hotel service quality enhancements.
	[28]	Kano model, QFD	√		√			Improved the workflow for jewelry design development using Kano and QFD.
	[29]	Kano model, QFD	√		√			Combined Kano and QFD tools to achieve a better understanding of customer perceptions.
Group 2: Kano + TRIZ	[30]	Kano model, TRIZ	√			√		Developed a TRIZ and Kano model framework to create attractive quality by using an online game as an example.
	[31]	Kano model, TRIZ	√			√		Proposed four innovative principles to solve a problem in home-life industry innovation.
	[32]	Kano model, TRIZ						Integrated TRIZ trends of evolution with the Kano model in the E-commerce service quality strategy area.
	[33]	Kano model, TRIZ	√			√		Proposed a new method that approaches TRIZand Kano as two important quality and innovation techniques.
	[34]	Kano model, TRIZ	√			√	√	Integrated Kano–QFD tools to design an intelligent search-and-rescue robot for disaster rescue.
Group 3: QFDE/QFD + TRIZ	[35]	QFD, TRIZ			√	√		Showed which TRIZ tools are suitable for which QFD stages.
	[36]	QFD, TRIZ			√	√		Developed a systematic product process from product planning to conceptual design.
	[37]	QFD, TRIZ			√	√		Integrated QFD–TRIZ by using vice tools as a case study.
	[38]	QFD, TRIZ			√	√		Developed an application system to settle the technical conflict between TRIZ and QFD.
	[39]	QFD, TRIZ			√	√		Applied a four-phase QFD–TRIZ combination to achieve a green design solution for notebook products.
	[40]	QFD, TRIZ			√	√		Combined QFD–TRIZ for solving EMC problems in electronic products.
	[41]	QFD, TRIZ						Integrated a TRIZ contradiction matrix with House of Quality (HOQ) side roof matrices.
	[42]	GQFD, TRIZ			√	√		Proposed a grey QFD for identifying important engineering characteristics by integrating interval grey numbers into QFD–TRIZ.
	[43]	QFD, TRIZ			√	√		A new method to enhance the fabrication of molds for direct open molding by using a combination of QFD and TRIZ.
	[44]	QFD, TRIZ	√		√	√		Integrated QFD–TRIZ to achieve innovative mechanical product design.
	[45]	QFD, TRIZ	√		√	√		Improved the success rate of radical innovations based on an integrated QFD and TRIZ framework.
Group 4: Other combinations with three or more tools	[46]	LCA, QFDE, TRIZ		√	√	√		Integrated three tools for environmentally conscious product design.
	[47]	Kano model, TRIZ, SCAMPER	√			√		Proposed a creativity-based Kano model that integrates TRIZ and SCAMPER for creating attractive quality.
	[48]	QFD, TRIZ, refined Kano model	√		√	√		Created a QT–Kano model to construct new product functions of RFID products.
	[49]	LCA, QFDE, TRIZ, BPN		√	√	√		Proposed an integrated and intelligent eco-friendly and innovative product design to support green product development.
	[50]	QFDE, TRIZ, FEM		√	√	√	√	Created a framework to formulate and respond to the functional design of a high-temperature machine (HTM).
	[51]	QFD, TRIZ, AHP			√	√	√	Designed a virtual reality forestry trailer using the integrated tools.
	[52]	ECQFD, TRIZ, AHP		√	√	√	√	Proposed an integrated model for innovative and sustainable product development of automotive components.
	[53]	CSNs, QFD, TRIZ, FGDM	√		√	√	√	Proposed a four-step integrated model to design an innovative ergonomic product and to evaluate it in the early design stages.
	[54]	QFD, TRIZ, AHP, CA			√	√	√	Provided a way to handle engineering conflicts in the design of smartphones by combining QFD and TRIZ.
	[55]	Kano, QFD, FAST	√		√		√	Proposed a function-combining design method by fusing the Kano, QFD, and FAST methodologies.
	[56]	Kano, QFD, AHP	√		√		√	Integrated the Kano model, AHP, and QFD with an intuitionistic fuzzy set to solve decision-making problems.
	[57]	Kano, QFD, TRIZ, AD, ISM, DSM	√		√	√	√	Solved complex engineering problems involving social issues by using integrated transdisciplinary tools.
	[58]	Kano, QFDE, AHP	√	√		√	√	Combined different tools to generate more conceptual designs for packaging products.
	[59]	ECQFD, TRIZ, FMEA, fuzzy TOPSIS		√	√	√	√	Developed a framework for sustainable product development by integrating FMEA, ECQFD, TRIZ, and fuzzy TOPSIS.

Abbreviation: GQFD (grey Quality Function Deployment), LCA (life-cycle assessment), BPN (backpropagation network), FEM (finite element method), AHP (analytic hierarchy process), CSN (customer satisfaction needs), FGDM (fuzzy group decision-making), CAD (computer-aided design), CA (correspondence analysis), FAST (function analysis system technique), ISM (interpretive structural modeling), DSM (design structure matrix).

.

The Kano model has the ability to distinguish between the effects created by customer requirements, while QFDE can translate customer and environmental requirements into technical requirements of the product. Hence, the combination of these two tools (the first group) provides a better and clearer understanding of customer requirements. The majority of the previous studies combined these two tools with the aim of better understanding customer requirements, so as to improve their satisfaction. This combination can help product designers to identify and suggest the types of improvements to be made; however, this combination does not offer a concrete method to achieve such improvements. This combination is insufficient to solve problems that may occur during the improvement process. The second and third groups were designed with TRIZ, which has the ability to create ideas that solve invention problems. However, these two groups lose the first group’s superiority in identifying customer requirements—either VOC or VOE is overlooked in the design process. The fourth group was established to answer all of the previously mentioned problems. The majority of the studies belonging to the fourth group have two similarities: Firstly, the main purpose of each tool used in the combination is to incorporate parts of the five important capabilities. Most of them combined tools to identify customer and/or environmental requirements (e.g., the Kano model, LCA, CSNs), tools to transform customer and environmental requirements into product specifications (e.g., QFDE/QFD/ECQFD, FAST, AD), tools to create ideas and solve inventive problems (e.g., TRIZ, SCAMPER), and tools to evaluate the solutions (e.g., AHP, FEM). However, no previous study was capable of incorporating C1–C5 simultaneously and effectively. Secondly, improvement ideas were generated from the overall system perspective before placing more focus on the component basis. This approach in product development is highly dependent on the designer’s experience; thus, the results can vary dramatically depending on the designer. Therefore, the existing research is inadequate to support companies in gaining a sustainable competitive advantage.

3. Methodology

Our methodology consisted of five steps, as shown in Figure 1.

Step 1: Identifying customer and environmental requirements

This methodology uses a Kano questionnaire with the addition of a standardized set VOE and EM based on the work of Masui et al. [15]. The purpose of combining VOC with VOE in the questionnaire is to perceive both customer and environmental requirements.

Due to the different nature of each market segment, it is difficult to know whether the fulfilment of a certain product feature can actually increase satisfaction or merely prevent dissatisfaction. This is why it is important to know the influence of a given product’s requirements on customer satisfaction. The customer satisfaction (S) and dissatisfaction (DS) coefficients [60] can indicate the strength of the effect of requirements’ fulfilment or non-fulfilment on customer satisfaction and dissatisfaction. The satisfaction coefficient ranges from 0 to 1, and the dissatisfaction coefficient ranges from −1 to 0—the closer the value to 0, the less the impact on customer satisfaction or dissatisfaction.

Step 2: Identifying product specifications and improvement targets

The second step is to deploy the VOC/VOE items obtained from the previous step into product specification requirements (i.e., the product’s EMs and components). QFDE phase I is improved in this study by utilizing the Kano model’s results to determine customer weight cw_j, as shown in Equation (3):

$$c{w}_j=\{\begin{array}{ll}\left|\mathrm{DS}\right|& \mathrm{if} \mathrm{Kano} \mathrm{requirement} \mathrm{is} \mathrm{M} \\ \max \left(\mathrm{S},\left|\mathrm{DS}\right|\right)& \mathrm{if} \mathrm{Kano} \mathrm{requirement} \mathrm{is} \mathrm{O}\\ \mathrm{S}& \mathrm{if} \mathrm{Kano} \mathrm{requirement} \mathrm{is} \mathrm{A} (j=1,\dots ,J)\\ \min \left(\mathrm{S},\left|\mathrm{DS}\right|\right)& \mathrm{if} \mathrm{Kano} \mathrm{requirement} \mathrm{is} \mathrm{R}\\ 0& \mathrm{else}.\end{array}$$

(3)

where J is the number of VOC/VOE items. This equation lets the degree of influence of a particular requirement on customer satisfaction be reflected in the customer weight value. ‘M’ uses a DS value because it affects the dissatisfaction level if it is not fulfilled and it has no effect on the satisfaction level if it is fulfilled. This methodology utilizes the S/DS value as a customer weight; thus, the negative sign is trivial and can be omitted. The customer weight for ‘O’ is determined by the highest value of S or DS, because customer satisfaction and dissatisfaction levels are proportionally affected by the level of fulfilment and non-fulfilment. ‘A’ always affects satisfaction levels and never causes dissatisfaction to the customer; therefore, the S value is chosen for its weight value. ‘R’ is the opposite of a one-dimensional profile. Therefore, this requirement uses the minimum value of S or DS. ‘I’ and ‘Q’ have no effect on customer satisfaction/dissatisfaction; thus, they can be omitted from further analysis. Figure 2 shows the customer weight (cw_j) values for each Kano requirement based on their fulfilment effects.

The correlation table for VOC/VOE items, EM items, and components is introduced in QFDE phase I and II. This correlation table’s elements are denoted as rs_j,k (j;k|1 ≤ j;k ≤ J;K) and rs_k,l (k;l|1 ≤ k;l ≤ K;L), where rs_j,k is the relational strength of VOC/VOE item j for EM item k, rs_k,l is the relational strength of EM item k for component l, J is the number of VOC/VOE items, K is the number of EM items, and L is the number of components. The values of rs_j,k and rs_k,l are given by the designers, and the 9-3-1-0 scoring system is used to represent the relational strength value, where ‘9’ indicates the strongest relation and ‘0’ indicates no relation. The results from QFDE phases I and II are relative weight values to determine the importance level of each EM item and component.

Product designers use important EM items and components to generate design targets to improve the product’s overall qualities. This study proposes an improved QFDE phase III with a component-based approach. This improvement aims to determine the right components and the right parameters to be included in the product’s design targets. This methodology has two alternatives to propose the design targets: The first alternative is based on the EM items (QFDE phase I). To start with, the designers eliminate EM items with relative weight values below the average value. Then, the rs_k,l value is used to determine the components chosen. Components with relational strength values of ‘1’ or ‘0’ are omitted. The second alternative is based on the components (QFDE phase II) and uses the same evaluation method used for the EM items. These two alternatives are subsequently analyzed in QFDE phase IV by multiplying the ir_j value and the cw_j value to obtain the improvement effect (IE) for each VOC/VOE item. The results from this improved QFDE methodology are the product’s design targets.

Step 3: Generating general solutions

Contradiction problems occur when an increase in a desirable parameter (DP) causes an increase in another undesirable parameter (UP). TRIZ contradiction matrices can solve these conflicting situations [16]. This methodology thoroughly analyzes each selected component’s targets and their contradiction problems. By introducing a table whose element is determined by Equations (4) and (5), the most prominent TRIZ inventive principles (TIPs) for each design target can be determined:

$$ip{w}_{l^{\prime },n}={\displaystyle \sum }_{k=1}^{K}p{v}_{l^{\prime },n,k}\left(l^{\prime } =1,\dots , L^{\prime }\right), \left(n=1,\dots , 40\right)$$

(4)

$$p{v}_{l^{\prime },n,k}=\{\begin{array}{ll}r{s}_{l^{\prime },k}& \mathrm{if} \mathrm{inventive} \mathrm{principle} \mathrm{is} \mathrm{recommended} \\ \phi & \mathrm{else}.\end{array}$$

(5)

where ipw_l′,n is the total weight of selected component l′ for TIP n, L′ is the number of selected components, rs_l′,k is the relational strength of selected component l′ for EM item k, and pv_l′,n,k is the point value of selected component l′ of TIP n and EM item k. The higher the ipw_l′n value, the more relevant the TIP to generate better solutions.

Step 4: Generating specific solutions

The TIPs obtained from the previous step serve as general solutions that need to be converted into specific solutions. These specific solutions are proposed to satisfy customer and environmental requirements; hence, they need to be evaluated based on their significance to the fulfilment of VOC/VOE. The solution significance rate sr_p can be calculated by using Equation (6):

$$s{r}_p={\displaystyle \sum }_{j=1}^{J}c{w}_{j}s{v}_{p,j}\left(p=1,\dots , P\right)$$

(6)

where P is the number of solutions, J is the number of VOC/VOE items, cw_j is the customer weight of VOC/VOE item j, and sv_p,j is the significance value of solution p for VOC/VOE item j. The sv_p,j value uses the 9-3-1-0 scoring system, where ‘9’ is very significant and ‘0′ is not significant. The results from step four are specific solutions with significance rate values.

Step 5: Developing final solution(s)

Each specific solution obtained from the previous step is designed to work only for the designated component. By combining solutions from each component, product designers can amplify the significance of these solutions to the product’s overall qualities. Not all combinations can work; thus, product designers need to filter out infeasible combinations. The remaining combinations are evaluated by using the combination significance rate value, which is obtained by summing each sr_p value from the combined solutions. The higher the combination’s sr_p value, the more capable it is of improving the product’s overall qualities.

4. Results and Discussion

To further explain the proposed methodology, we carried out a case study of a desk lamp product. The desk lamp was selected because this product’s structure is relatively simple to understand. Figure 3 shows the information of the product used in this case study.

A total sample set of 85 people was taken in step 1.

Table 2. Kano analysis results.

VOC/VOE Items	M	O	A	I	R	Q	Profile	S = (A + O)/(A + O + M + I)	DS = (M + O)/((−1)∗(A + O + M + I))
VO1	28	44	6	7	0	0	O	0.59	−0.85
VO2	22	27	7	25	2	2	O	0.42	−0.60
VO3	4	4	28	44	3	2	I	0.40	−0.10
VO4	16	22	29	18	0	0	A	0.60	−0.45
VO5	2	6	20	57	0	0	I	0.31	−0.09
VO6	10	42	21	10	0	2	O	0.76	−0.63
VO7	10	47	16	12	0	0	O	0.74	−0.67
VO8	16	12	15	42	0	0	I	0.32	−0.33
VO9	26	20	10	15	14	0	M	0.42	−0.65
VO10	34	10	13	24	4	0	M	0.28	−0.54

shows the results obtained from the Kano questionnaire analysis.

Based on these results, two alternatives of product design targets were obtained and evaluated in step 2. Figure 4 shows the improved QFDE process.

In step 3, each target from the previous step was further analyzed for possible contradiction problems. For the sake of simplicity, only components with ipw_l′n values above average were used, and only the calculation for CO7 is shown, as can be seen in

Table 3. General solution analysis for CO7.

EM Items	DP	UP	TIP
			1	16	19	21	27	29	30	32	35
EM1	18	17			9					9	9
EM2	17	18		9		9			9	9
EM4	2	18			3					3	3
EM6	16	18
EM8	26	32	3				3	3			3
ipwl′,n (average value: 9.33)			3	9	12	9	3	3	9	21	15
Rank			7	4	3	4	7	7	4	1	2

. The complete analysis in step 3 identified the following TIPs used, where # denotes the TIP number: Segmentation (#1), cheap short-life instead of costly long-life (#27), use of copies (#26), composite materials (#40), extraction (#2), change of physical and chemical parameters (#35), pneumatic and hydraulic structures (#29), nesting (#7), feedback (#23), prior action (#10), changing color (#32), and periodic action (#19). This methodology utilizes the suggestions from TRIZ’s 40 inventive principles to produce solutions needed for product improvement [16]. TRIZ tools have been proven to possess a wide range of strategies to create innovative solutions for product development and eco-design. However, some studies have utilized certain TRIZ-related strategies in specific areas, such as material substitution [61], and can serve as a reference for solving the specific problem.

Step 4 produced specific solutions for each component, as shown in

Table 4. Specific solutions for each component.

No.	Component	TIP	Solution Description	Benefit
1	CO1	#1	Use modular design for base, post, head/shade	Improve the degree of adjustability and the ease of disassembly and disposal.
2		#27	Replace solid base and post with less expensive plastic suction hook.	Reduce the weight significantly.
3	CO2	#1	Same as no. 1.	Same as no. 1.
4		#27	Same as no. 2.	Same as no. 2.
5		#26	This principle has a similar concept to principle #27; thus, can use the same solution as no. 2 and 4.	Same with no. 2 and 4.
6		#40	Use composite material instead of plastic/steel.	Lighter and easier to recycle.
7	CO3	#40	Same as no. 6.	Same as no. 6.
8	CO4	#2	Use wireless design with rechargeable battery.	Simpler design and more portable
9	CO5	#1	Same as no. 1.	Same as no. 1.
10		#27	An inexpensive black (or other color) film is used to replace the solid material. This layer of black film can be attached or detached easily.	Cheaper and easier to recycle and dispose of.
11		#35	Use light reflector to enhance the brightness.	Increase brightness.
12		#29	Use inflatable design to replace solid head/shade.	Lighter, improved degree of adjustability, and easy to dispose of.
13	CO6	#7	Lamp socket with telescopic design to incorporate different bulb cap types.	More compact design.
14		#23	Add motion sensor, heat sensor, and light sensor to automatically adjust the lamp’s brightness according to the specific condition.	Save more energy and more environmental friendly.
15		#10	Use better insulation material to withstand higher temperatures.	Improve the physical lifetime and the safety.
16		#35	Replace socket cover with rubber material.	Improved safety, lighter, easy to dispose of, and more environmentally friendly.
17	CO7	#32	Bulb with color palette selection that can be personalized depending on the environmental condition or the customer’s needs.	More adaptive to customer and environmental needs.
18		#35	Replace gas inside bulb with liquid nitrogen.	Reduce bulb’s temperature drastically.
19		#19	Bulb with a smart sensor that will adjust the brightness based on the surrounding brightness and the bulb’s current temperature.	Reduce energy usage and increase safety.

. These specific solutions were further evaluated based on their significance rate sr_p to the VOC/VOE, as can be seen in

Table 5. Specific solution analysis.

VOC/VOE Items	cwj	CO1		CO2				CO3	CO4	CO5				CO6				CO7
		1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19
VO1	0.85	0	0	0	0	0	0	0	3	0	1	1	1	3	9	9	9	0	1	9
VO2	0.6	0	1	0	1	1	0	0	0	0	0	9	0	0	0	0	0	9	0	0
VO4	0.6	9	3	9	3	3	1	3	0	9	0	0	9	0	0	0	0	0	0	0
VO6	0.76	1	1	1	1	1	0	0	1	1	0	3	1	0	1	1	0	0	3	3
VO7	0.74	0	0	0	0	0	3	3	0	0	0	1	0	0	3	3	1	0	9	3
VO9	0.65	3	3	3	3	3	9	9	0	3	3	3	3	3	3	3	3	0	3	3
VO10	0.54	9	9	9	9	9	9	9	3	9	9	0	9	9	0	0	3	0	0	0
srp		12.99	10.00	12.99	10.00	10.00	13.54	14.74	4.93	12.99	7.68	11.25	13.84	9.37	12.55	12.55	11.94	5.44	11.74	14.07

. Higher sr_p values indicate a more significant solution.

Step 5 transformed these 19 specific solutions at the component level to a total of 384 possible combinations at the product level. From a thorough analysis, 180 combinations were found to be infeasible, for several reasons. For example, solution no. 1 cannot be combined with no. 4 because the designs are incompatible with one another. The combination sr_p value for the remaining 204 combinations served to rank the combinations, as shown in

Table 6. Specific solution combination analysis (top five solutions).

Solution No.							Combination srp Value	Rank No.
CO1	CO2	CO3	CO4	CO5	CO6	CO7
1	6	7	8	12	14	19	86.66	1
1	6	7	8	12	15	19	86.66	1
1	3	7	8	12	14	19	86.11	3
1	3	7	8	12	15	19	86.11	3
1	6	7	8	12	16	19	86.05	5

.

The solution with the highest combination sr_p value (86.66) proposes a modular design base (1), composite material post and goose neck (6 and 7), wireless design (8), inflatable design head/shade (12), adding sensors or using better insulation lamp sockets (14 or 15), and a bulb with a smart sensor (19). Compared with the standard desk lamp design, this solution offers better qualities, such as the following:

• Safer operation: A rubber material provides a better insulator.
• Less energy usage: The smart sensor can automatically adjust the brightness to save electricity usage.
• Longer bulb lifetime: Heat is one of the main factors that affect bulb lifetime. This new design can monitor and control the heat; thus, it can extend the lifetime of the bulb, which also reduces the cost needed to replace the bulb. This can lead to an increase in customer satisfaction.
• Less weight: Modular, wireless, and inflatable designs can reduce the overall weight significantly.
• Environmentally friendly: Composite materials with a modular/inflatable design are easy to recycle and dispose of in the end-of-life phase of the product.

Furthermore, this study tested customer acceptance of the proposed solution. The same 85 respondents were asked to rank their satisfaction with the proposed solution based on their VOC/VOE using a scale from 1 to 5, in order of satisfaction. This study used a probability value (p-value) for hypothesis testing with a 95% confidence level to measure the respondents’ satisfaction with the proposed solutions. The null hypothesis (H₀) was ‘Respondent not satisfied with the proposed solutions’, and the alternative hypothesis (H₁) was ‘Respondent satisfied with the proposed solutions’. We would reject H₀ if the p-value from the hypothesis test was less than 5%. The statistical significance test results can be seen in Figure 5. The proposed solutions are statistically significant because they successfully reject H₀ in all of the VOC/VOE items. This means that the proposed solutions comply with the VOC/VOE.

This case study revealed that our methodology accurately incorporates VOC/VOE into product design and can help product designers to create a sustainable and innovative design concept. This methodology can effectively assist designers in accurately identifying VOC/VOE by utilizing the Kano model. Each VOC/VOE is well distinguished by its effect on customer satisfaction. These VOCs/VOEs were meticulously translated into product specifications with the improved QFDE method, thereby preventing harmful side effects from misdirected VOCs/VOEs. TRIZ can help designers to solve the innovation problems resulting from the product specifications. These three tools, combined with the component-based approach, can provide a good synergy between the inputs and the outputs.

Next, we should explain the superiority of the proposed methodology compared to previous research. Our literature survey showed that no existing research satisfies all of C1–C5 simultaneously. The absence of one or more of these capabilities will lead to several problems, such as the following:

• Lack of concrete methods to achieve the improvements.
• Inaccurate VOC/VOE identification.
• Inaccurate transformation of VOC/VOE to product specifications.
• Neglecting environmental issues.

The results from this case study demonstrate the proposed methodology’s capability of incorporating C1–C5 simultaneously, which solves all of the problems mentioned above, proving its superiority to existing research.

In addition to the capability of simultaneously incorporating C1–C5, Figure 5 also shows that the proposed methodology is superior in creating solutions. The sheer quantity difference shows that the proposed methodology has a clear superiority in term of solution quantity compared to other methodologies. This case study shows that the proposed methodology is able to provide product designers with many improvement options, either at the component level (19 solutions) or the product level (204 solutions). This can be achieved by using a component-based approach that focuses on each main component. Previous studies used a product-based approach, limiting their ability to produce solutions. Product-based approaches need to analyze a broad area and are heavily reliant on the designer’s skills or knowledge. Component-based approaches target more specific areas. This can help designers to focus on specific problem and simplify the analysis process. Therefore, designers can produce more solutions, giving them the flexibility to choose solutions that best suit their requirements.

A large number of solutions without a way to determine the effectiveness of each solution can overwhelm the designers. The component-based approach in this methodology provides a decent evaluation method to suggest the most prominent solution(s) in a more efficient way. The evidence can be seen from step three in the case study. By using the provided evaluation method, designers do not need thoroughly analyze all possible TIPs, though they are still able to identify the significance rank of each principle. Therefore, this methodology is able to provide designers with a lot of solutions, while at the same time also giving them a method to analyze the effectiveness of each solution.

This proposed methodology, with its superiority compared to previous research, has real potential to be applicable to product design processes and improve their overall quality. Aside from the limitations of the original Kano model, QFDE, and TRIZ, there are no limitations on the applicability of the proposed methodology. Rather, this methodology enhances the performance of each tool by combining it with other tools to overcome its limitations. The added capabilities can identify environmental requirements and incorporate them into product specification targets, helping companies to resolve the critical issue of environmental problems in the product development area. This methodology is consistent with the purpose of eco-design or the circular economy, but its main goal is to minimize negative environmental impacts.

5. Conclusions

To excel in business competition today, companies need to possess five important capabilities (C1–C5). Although there have been many related studies, no previous study was able to simultaneously incorporate these five important capabilities. This study proposes a new methodology that combines the Kano model, QFDE, and TRIZ with a component-based approach. This methodology addresses the challenge of incorporating these five important capabilities simultaneously. Step one identifies VOCs/VOEs with specific characteristics for each requirement. Step two transforms this essential information into a detailed design target for the selected component(s). Step three generates general solutions, and step four transforms these general solutions into specific solutions. Step five combines these specific solutions to improve the solutions’ significance to the product’s overall qualities.

The key aspects of this methodology can be summarized as follows:

• It has a more precise customer weight value in QFDE phase I, because the value reflects the degree of influence of that particular requirement on customer satisfaction.
• It uses the component-based approach to determine the right components to be included in the product’s design target, as well as which parameter (EM) needs to be improved for that particular component.
• It offers a way to thoroughly analyze the contradiction problems from the product design targets and determine the most prominent TIP to create general solutions.
• It allows the evaluation of the specific solution’s significance to the fulfilment of customer and environmental requirements.
• It can amplify the significance of the specific solutions to the product’s overall qualities by combining each component’s solutions and determining the most prominent combination.

In summary, this methodology has three advantages compared to the previous studies: it simultaneously incorporates the five important capabilities; it produces a great number of solutions to provide designers with the flexibility to pick the most suitable solution(s); and it helps designers generate specific solutions with minimal dependence on designers’ subjectivity by reducing the complexity of the process to a more specific component level.

Regardless of the proposed methodology’s superiority, this study still has limitations. This study demonstrates the methodology’s ability to fulfil the VOC/VOE. However, the proposed methodology still neglects other stakeholders’ requirements. The requirements of other stakeholders throughout the product’s life cycle are equally important to develop a well-balanced product. It is necessary to consider as many aspects and interests as possible during the early phase of the product development process. In addition, this study was also limited in terms of its data collection method. This study utilized a survey method for collecting initial VOCs/VOEs as well as for evaluating the proposed design. The scope of this survey method is limited to the subjectivity of the customer concerns only. In future studies, we could extend our concerns to other stakeholder requirements such as carbon emissions, circular economy, social issues, etc. It is also highly recommended to develop a software system for the implementation of this methodology.