Abstract
In recent years, with the sharp rise in the number of vehicles in China, traffic congestion is becoming increasingly serious, affecting the rapid passage of ambulances. In addition, it is common that vehicles are generally parked indiscriminately in some old communities, which also hinders ambulances into residential areas and reduces rescue efficiency. Apart from external factors, the root cause is that existing ambulances are too large to easily pass narrow roads. Besides, there are problems such as frequent empty runs and serious homogenization in traditional ambulances. Therefore, it is necessary to improve the design of traditional large ambulances. First, the user needs of different users for ambulances were determined through questionnaires and user interviews; then, the need judgment matrix of ambulances was constructed by using the analytic hierarchy process to rank user needs by weight, so as to determine the direction for new type ambulance design. Through quality function deployment, the user’s demands were transformed into the technical demands of ambulances, and the conflicts were found. Meanwhile, top-ranked needs were analyzed by using theory of inventive problem solving to seek the corresponding feasible solutions quickly, and innovative design of ambulances was conducted on this basis. However, many designers have not considered the product validation link when using these three methods for innovative design. On the contrary, in this improved ambulance design, the FCE is introduced to score the new design, find the deficiencies, and improve them, thus completing the missing link in the traditional design and forming a complete set of scientific design process. The traditional large ambulance with standard length, width, and height of 5,800 mm, 2,000 mm, and 2,600 mm is modified into a mini-ambulance with length, width, and height of 3,500 mm, 1,600 mm, and 2,250 mm. Simultaneously, various details are optimized to design a community micro-ambulance that truly meets the needs of users and enhances user satisfaction. Quantifying and ranking users’ various functional needs for ambulances by using the AHP/QFD/TRIZ theory and providing corresponding feasible solutions have identified the breakthrough direction for the research on innovative design of community ambulances and have also provided references for the design of other products.
1. Introduction
In 1865, the first medical ambulance system appeared in the United States, which could provide services to transport patients to hospitals for treatment. In modern society, ambulances in many developed countries are not satisfied with just providing transport and emergency functions, but gradually developed a new function of a mobile hospital. A large number of ambulances are converted from specialized trucks with sufficient internal space and complete equipment, including lighting systems, medical systems, and access equipment systems, so that they can accommodate multiple patients, provide various medical services at the same time, improve the efficiency of emergency care, and perform the function of a mobile hospital. The design of ambulances has been a focus of designers in recent years, and Rooman Ignatowski and Maja Bryniarska have designed a self-driving ambulance powered by clean energy that has 90-degree swivel wheels. It can rotate in tight spaces and is easy to park anywhere because of its small size. In addition, designers have also taken into account the situation where vehicles cannot give way to ambulances in the fast-moving road. To solve this problem, they installed a drone in the upper part of ambulances, so as to detect road conditions in front of ambulances and alert vehicles in the front, which has greatly saved the driving time of ambulances. India’s Neura ambulance is designed to address the shortage of ambulances in emergency disaster situations. The ambulance uses modular components for quick assembly. In addition, it is designed with minimal parts, with only a stretcher and seat for the paramedics inside, so it has a narrow profile and can quickly navigate narrow roads in remote areas. Two Chinese professors have designed a Life Knight mobile hospital emergency vehicle. It mainly responds to the situation that it wastes too much time for an ambulance to take patients to return to the hospital for treatment. This mobile hospital emergency vehicle can achieve the function that patients can be rescued as soon as an ambulance arrives at the scene because the Life Knight is a mobile operating room inside, and after expansion, it can be expanded into 26 wards, so as to meet the disaster relief needs in some remote areas.
Traditional ambulances mainly provide transportation and first aid functions, which have high requirements of the speed and the capacity of ambulances. However, most of the roads in old residential areas in China are narrow and vehicles often stop and leave in violation of regulations, greatly affecting the passage of ambulances. Therefore, it is necessary to develop a micro-ambulance for the specific environment of the old community, so as to better meet the medical demands of residents in the community. Also, ambulances in China are mainly modified vehicles. Due to the body frame, its internal space is limited and the layout is not reasonable enough. In addition, its appearance is dull and homogeneous. Therefore, it is necessary to redesign the existing ambulances by thinking about the appearance and internal space from the perspective of user needs instead of letting users adapt to the existing body. At the same time, the study of community ambulances can also alleviate the lack of emergency resources in China. In recent years, because of the improvement of national health and safety awareness, residents often choose to call 120 when they encounter some unexpected situations in their lives and prefer to go to local tertiary hospitals when they are sick. But in fact, more than 90% of residents’ diseases and unexpected problems can be solved in nearby community hospitals, without the need for fully equipped ambulances across half the city. Thus, the new mini-ambulance design allows community residents to reach to local treatment in the event of accidents, which not only helps people get aid quickly but also facilitates the maximized use of limited medical resources. This also provides a new way of thinking about the design of the entire medical system.
Through the study of relevant literature, it is found that at present, there is no systematic design theory to assist the design of ambulances in China, while users’ demands for various functions of new ambulances are increasing, so it is necessary to develop a complete set of design methods and processes for the design of ambulances. The users of ambulances include different groups such as emergency doctors, drivers, and patients. The user needs are complex, and a more scientific research method is required. Previously, product designers commonly used questionnaire research and user interviews to obtain user needs [1]. Although it can obtain a large number of user requirements in a short time, the importance between the obtained user requirements cannot be judged, so it is not applicable to some complex products with many user requirements. The analytic hierarchy process (AHP) is particularly suitable for complex decision-making problems. It can mathematize the thinking process of decision making with less quantitative information, thus providing a simple and clear decision-making method for complex problems that contain multiple factors. So firstly, the AHP is introduced to hierarchically and quantitatively rank the various subjective evaluations of ambulance users and determine the needs to be satisfied as a priority. However, the AHP obtains only a ranking of user requirements and cannot provide a clear reference for design practice. A new method needs to be introduced to translate user requirements. The quality function deployment (QFD) can quantify the correlation between user requirements and technical requirements of a product and then determine the key technical requirements that contribute most to satisfying user requirements through data analysis, which translates the indirect user requirement ranking into technical attributes that can directly guide design practice. Therefore, the next step is to introduce the QFD to translate user requirements into technical requirements and better assist design. Moreover, it is also found in the study that the needs of different users for ambulances often conflict with each other, so it is necessary to introduce the theory of inventive problem solving (TRIZ) to obtain the innovative principle of resolving conflicts and provide innovative ideas for the final design. The TRIZ can subdivide the contradictions encountered in product design into physical and technical contradictions and then provide a clear reference basis for innovative design by finding tables and determining corresponding invention principles. Finally, since the fuzzy comprehensive evaluation (FCE) has the advantage of quantitatively assessing the degree of satisfaction of each requirement of a new solution, the FCE is introduced for product validation to identify shortcomings and to enhance and improve them. The abbreviations of methods are shown in Table 1.
In recent years, many scholars have used various design theories to assist design research, among which the more prominent methods include hierarchical analysis, quality function unfolding theory, and SUS scale analysis. In order to obtain a clearer auxiliary effect, most designers choose several theories together at the same time to assist the design. In this study, according to the complexity of the research object and the interconnection of theories, the integrated application of AHP/QFD/TRIZ theory and fuzzy comprehensive evaluation method was finally selected. It seems cumbersome, but in fact several theories are interlinked to ensure the maximum scientific and rational overall design process. Moreover, the integration of various theories can make up for the shortcomings of a single theory, enabling all theories to cooperate with each other and use various advantages to maximize the reference for ambulance innovation design research.
This article is organized as follows. Taking ambulances as the research object, the first is a literature review of the ambulance design and several theoretical methodologies adopted. Chapter 1 firstly obtains user requirements for ambulances through questionnaire research and user interviews and then uses the AHP theory to rank the requirements. Chapter 2 transforms the ranking of user requirements into the ranking of technical requirements through the QFD theory and determines the technical requirements that need to be satisfied as a priority. Chapter 3 combines the HOQ model to obtain the contradiction and conflict between different technical requirements, discovers the physical and chemical contradictions in the ambulance design, applies the TRIZ theory to solve the contradictions, and provides ideas for the innovative design of ambulances. Chapter 4 carries out the solution design according to the innovative methods provided by the TRIZ theory. Chapter 5 uses the fuzzy comprehensive evaluation method to evaluate and score the design solution, find and improve the shortcomings, and thus design a community mini-ambulance that truly meets the needs of users. The design process is shown in Figure 1.
2. Literature Review
In recent years, numerous scholars have optimized the design of ambulances on the basis of previous shortcomings and produced a large number of literature results. Ghani et al. [2] tried to power the operation of ambulances with green energy to respond to the resource consumption of conventional ambulances. They designed a green ambulance with solar power supply system and validated and evaluated the overall design solution to identify deficiencies and continuously improve it. Traditional ambulances are not fully informed about road conditions and vehicle congestion, resulting in improper dispatch and affecting the timely arrival of ambulances. Wang and Liu [3] combined the IoT technology and designed a new unified dispatching system for ambulances, which recommends the best route to ambulances and greatly saves the rescue time. Considering the time required for many cars in front of ambulances to give way when the ambulance is traveling through the blocked lane, Karkar [4] developed a smart medical emergency application that notifies drivers on each road in advance of the location of the ambulance behind them, thus allowing vehicles ahead to give way early and ensuring the rapid passage of the ambulance. Abdeen et al. [5] proposed an intelligent system designed to minimize ambulance response time, travel time from the patient’s location to the hospital, and waiting time at the hospital. This system collects road information in real time, calculates it by algorithm, and then recommends the best route to the ambulance driver and the hospital. The team also analyzed the performance of the algorithm and conducted simulations to verify that the simulation results were in good agreement with the analysis results, which verified the correctness and accuracy of the analysis and also improved the credibility of the intelligent system. Xu et al. [6] found that many ambulances may be bumpy in the patient compartment at high speed when studying the product pain points of ambulances, which affects the ambulance treatment of emergency physicians, especially in some complex roads in the field. Therefore, the team designed an intelligent ambulance for this situation. This can detect whether the ambulance is in balance through a gyroscope and through a micro-controller convert it into a pulse signal to drive the motor. Then, the ambulance is controlled by the motor to adjust the angle to gain full balance.
It can be concluded that various designers at home and abroad have proposed different solutions to the problems encountered by ambulances. But for the problem of ambulances not being able to cross narrow urban roads quickly, most designers have thought of only conceptual designs, which are not practical enough and lack attention to the needs of some special patients. Therefore, this article will carry out the design study of urban ambulance from different user needs and finally design an urban mini-ambulance to meet various needs. This design study will improve and optimize various details of ambulances to meet the needs of medical personnel and patients, thus making the work of first aid personnel more convenient and easier while also meeting the needs of some special patients and reflecting humanized design. In addition, under the premise that the current urban emergency resources are relatively tight in all countries, this article simplifies and improves the ambulance process, which will greatly improve the efficiency of the ambulance and alleviate the lack of emergency resources. Moreover, the ambulance design in this article also provides a new set of methods and ideas for the design of similar special vehicles for reference. In terms of theoretical research, the AHP, QFD, and TRIZ theories have been widely applied to the innovative design of various products by different scholars, and numerous results have been achieved. The QFD theory can assist enterprises to transform various user requirements into technical requirements of products and then determine the importance ranking between different technical requirements and discover the direction of optimization and improvement, so as to achieve precise design, minimize production cost, and enhance product quality. Li et al. [7] applied the QFD theory to reorganize and study the user needs and technological requirements of energy investment products by constructing a house of quality model to identify the existing economic innovations that need to be prioritized to provide a clear reference for investment in the energy sector. Xue et al. [8] calculated the index importance ranking of EMC indication with the help of house of quality (HOQ) in the QFD model. After the calculation, a fuzzy function is introduced to find the best indicator solution to assist in the improved design of EMC indication. However, when many scholars apply the QFD theory alone to assist product design, they lack a set of scientific research methods to obtain the preliminary user requirements and often cannot give full play to the role of the QFD theory for the design of some complex products. Instead, the AHP theory can provide a set of scientific and systematic research methods for user requirements, so some scholars use the AHP theory in combination with QFD theory to ensure that the design process is reasonable and scientific to the maximum extent. Hanumaiah et al. [9] established an AHP-QFD model for the special needs of the particular field of mold process selection, stratified the user requirements of mold process, and then transformed the user requirements in the top of the ranking into the technical requirements of mold process to assist customers in industrial upgrading. This also formed a set of standardized selection methods for mold process and provided reference for other related fields. Dai et al. [10] proposed an optimal strategy selection method for vehicle ballistic parameter calculation by combining the QFD and AHP theories to decompose the decision problem of vehicle ballistic parameter calculation into multiple single criteria evaluation problems. Based on this, a comprehensive evaluation is carried out and finally an optimal strategy selection method for the calculation of vehicle ballistic parameters is proposed.
Although the AHP and QFD theories can provide the technical requirements that need to be satisfied in priority when used together, there are contradictions and conflicts between different technical requirements, and often several requirements cannot be satisfied at the same time. Therefore, the TRIZ theory needs to be introduced to provide several solutions for conflicts. Taking a laptop computer as an example, Chen et al. [11] identified the user requirements that need to be met as a priority and the corresponding invention principles to meet these requirements through the integrated application of the QFD and TRIZ theories, which provides a clear reference for the solution of EMC problems in electrical products and new ideas for the innovative design of other products. Kim et al. [12] used the QFD theory in combination with the TRIZ theory to design a concept robot by refining the deficiencies in the design solution obtained from the QFD theory by the TRIZ theory. Hu et al. [13] applied the QFD and TRIZ theories together to design a novel intelligent hospital bed in an improved design of a traditional hospital bed. Cheng et al. [14] conducted a systematic study for the design of unattended system control stations and classified user needs in the design of control stations into three levels: physiological needs, psychological needs, and ergonomic needs, and then used the QFD theory to determine the priority of technical needs in the design of control stations and then discovered the corresponding invention principles according to the TRIZ theory to assist in the design of control stations. In their study, Zhang et al. [15] found that meeting the changing specific needs of actual and potential customers is an important challenge for any company to win the competition. However, customer requirements are always ambiguous, vague, and conflicting. To eliminate conflicting requirements and transform customer needs into measurable technical requirements, the team proposed an innovative design model integrating the AHP/QFD/TRIZ theory to standardize customer requirements.
Smart product service system (PSS) is an emerging intelligent product service system based on digital technology. Lee et al. [16] combined the advantages of PSS engineering and service engineering, proposed a generic method for structured service innovation based on the TRIZ theory, and achieved optimal upgrading of smart beauty services with the PRR method of service blueprints. Combining mobile application technology and license plate recognition system, Lee et al. [17] used the smart parking service in a high-end shopping center as a case to conduct a study. They elaborated a TRIZ paradox analysis and a service blueprint for parking services from the principles of problem solving and proposed a new smart parking mobile application. Their study enriches the service design literature and extends the scope of TRIZ applications. Li et al. [18] combined the AHP and QFD theories to determine the main user requirements for earthquake rescue robots. Then, they analyzed conflicting needs in the design process by the TRIZ theory and achieved an improved design of the traditional earthquake rescue robot under the invention principles.
However, when many scholars use AHP, QFD, and TRIZ theories to design products, the descriptions of functional and technical characteristics in QFD models are generally textual and semantic, lacking specific technical parameters. At the same time, many scholars use these theories with a lack of articulation between them. For example, the mapping of user requirements in the AHP to the technical requirements of the QFD theory is not adequately expressed. Therefore, the specific parameters of functional and technical characteristics of ambulances were first added to the design process of the new ambulance, improving the scientific objectivity of the design process. Then, a more specific study and analysis of the interface between the AHP and the QFD theory was done to give full play to the advantages of several theories and provide a detailed reference for the subsequent design. Last, when numerous designers use these theories to improve the design, they generally lack the product verification link and cannot verify the solution of the new scheme to product problems and the satisfaction of users’ demands. However, fuzzy comprehensive evaluation can obtain more comprehensive and accurate evaluation results by establishing a comment set, inviting a large number of users and relevant experts to evaluate and score each element level of the new scheme, respectively, and improve the deficiencies according to the evaluation conclusion, so as to continuously improve the demand satisfaction of products. Therefore, the integrated application of AHP/QFD/TRIZ and fuzzy comprehensive evaluation can assist designers to design a product that truly meets the demands of users. At the same time, as there are no system theory and process of medical transportation product design in China, the integrated application of AHP/QFD/TRIZ can provide a new and complete design method and process for medical transportation product design field and also provide a new idea for other product designs for reference.
3. Analytic Hierarchy Process for Sequencing Ambulance Demands
Analytic hierarchy process (AHP) is a systematic analysis method proposed by American operations research scientists [19] which has the characteristics of strong practicability and clear results and is widely used in various fields. The main steps are as follows.
3.1. Building Demand Hierarchy for Target Users
Firstly, an offline survey was conducted in two community hospitals in Shushan District, Hefei. The survey objects included 20 patients who had ever taken medical ambulances, 4 ambulance drivers, 2 emergency doctors, and 2 first aiders. A total of 28 paper questionnaires were distributed to them, mainly to understand the shortcomings of existing ambulances in the process of daily transportation and first aid and the expectations and demands for the new ambulance design scheme. In combination with 77 questionnaires distributed online to the families of patients who have ever taken medical ambulances, 105 questionnaires were distributed, and 95 valid questionnaires were recovered. Then, according to the results of the questionnaire, 10 community residents who had taken an ambulance and 3 daily ambulance drivers were selected to conduct in-depth user interviews, so as to obtain a large number of ambulance demand points. Finally, 2 car design experts and members of the design team were invited to conduct group discussions. The sorted ambulance requirements are divided into three layers, that is, target layer, principle layer, and element layer. The product design goal—“ambulance design”—is set as the target layer, denoted by the letter A. Different demand categories—“transportation,” “medical aid,” and “body appearance”—are set as the principle layer, which are represented by B1, B2, and B3, respectively [20]. 14 kinds of user demands including “quick departure at any time,” “not affected by congestion,” “through the narrow roads of the community,” “timely arrival at the scene,” “stable and safe driving,” “emergency rescue function,” “medical transport function,” “intensive care function.” “health and epidemic prevention function,” “hospital remote command,” “harmonious color matching,” “giving people a sense of security,” “reasonable vehicle proportion,” and “convenient to get on the ambulance” are set as the element layer, which is represented by C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, and C14, respectively. Ambulance demand hierarchy is constructed according to the above steps, as shown in Figure 2.
3.2. Building Rating Matrix
First, 3 automotive design experts, 20 patients who had been in a medical ambulance, 4 ambulance drivers, 2 emergency physicians and 2 first aid personnel were invited to score each need in a total of 31 paper questionnaires distributed to them. When scoring, a pairwise comparison is used, that is, if the scorer thinks that the importance of the two demands is equal, then the quantized value of the two demands after comparison is 1, and if the scorer thinks that one requirement is slightly more important than the other, the quantized values of the two comparisons are 3 and 5, respectively; otherwise, the fraction is taken [21], and the specific values are shown in Table 2. The questionnaires were then collected and analyzed and scored in aggregate, and the average was calculated, which is the quantified value after comparing the two needs. For example, comparing the importance of C8 “intensive care function” and C9 “health and epidemic prevention function,” 7 people thought that C8 was strongly important compared to C9, scoring 7; 19 people thought C8 was more important, with a score of 5; 2 people thought C8 was slightly more important, with a score of 3; and 3 people thought C8 was as important as C9, with a score of 1. Then, the scoring results are aggregated to calculate the average: (7 × 7) + (19 × 5) + (2 × 3) + (3 × 1) = 153, and 153/31 = 4.93. The value is finally rounded to 5. Therefore, the importance value of C8 “intensive care function” and C9 “health and epidemic prevention function” is 5. The specific scoring results are shown in Tables 3–6.
Then, the weight of each requirement is calculated. The main steps are as follows.(1)Calculate the product of matrix rows :(2)Calculate the nth root value of the product of each line :(3)Obtain the weight vector after normalization :
3.3. Consistency Verification
Next, consistency verification is required to avoid decision errors. First, calculate the maximum eigenvalue of each matrix:where (AW) i is the ith component of the vector AW.
Then, the consistency ratio coefficient CR is obtained after calculation:where CI is the index to judge the consistency of the matrix; CR is the consistency ratio coefficient; and RI is an average random consistency index, which can be directly found in Table 7.
According to Table 6, it can be found that Principle layer: RI = 0.58, CR = 0.0193 ≤ 0.1, meeting the condition. Transportation: RI = 1.12, CR = 0.0703 ≤ 0.1, meeting the requirements. Medical aid: RI = 1.12, CR = 0.0703 ≤ 0.1, meeting the requirements. Appearance of vehicle body: RI = 0.90, CR = 0.0438 ≤ 0.1, meeting the requirements.
3.4. Hierarchical General Sequencing and Decision Analysis
By building the matrix, the separate sequencing of each requirement can be obtained, but the separate sequencing is not enough to provide a clear reference for product design. Therefore, the comprehensive sequencing F of each requirement is required to be calculated (see Table 8 for the results).where Bi is the weight of the ith element corresponding to the principle layer, i = 1–3, and Cj is the weight of the jth element corresponding to the element layer, j = 1–14.
According to the overall sequencing of demand hierarchy, the top 5 users’ core demands for ambulances are C2 “not affected by congestion,” C4 “timely arrival,” C5 “stable and safe driving,” C6 “emergency rescue function,” and C7 “medical transfer function,” which provide a design direction for the improvement design of new ambulances.
4. Demand Transformation of Ambulance Users Based on QFD Theory
Through the analytic hierarchy process, the sequence order of user demands for ambulances can be obtained, but the user demands are relatively broad, which cannot provide reference for specific design practices. Therefore, the user demands can be converted into technical demands through the quality deployment theory [22], and then the importance weight of technical demands can be resequenced through the construction of the house of quality model to determine the technical demands that demand to be satisfied first [23]. The main steps are as follows.
4.1. Deployment of Technical Requirements
Firstly, technical requirements need to be deployed, that is, determine the corresponding technical requirements for each user requirement, as shown in Table 9.
By summarizing user requirements and technical indicators, the technical requirements of community ambulance design are divided into four categories: medical cabin design, body structure design, body appearance design, and layout design. Medical cabin design mainly includes more accompanying instruments (D9), network shared location (D1), proper height of patient cabin (D10), spacious interior (D12), and interior isolation space (D13). Body structure design includes low body chassis (D16), wheelchair lift structure (D17), high vehicle driving force (D5), large weight of the chassis (D7), strong performance of shock absorber (D8), lightweight body structure (D6), and convenience to get on and off (D11). Body appearance design includes a rounded outer contour line (D15), a harmonious combination of warm and cold colors (D14), and a length and width that meet the standards for minivans (D3). Layout design includes large number of ambulances (D2) and ambulances stopping at the nearest community hospital (D4). A quality characteristic unfolding diagram [24] is then constructed as shown in Figure 3.
In terms of medical cabin design, the complete accompanying instruments (D9) refer to equipping different medical devices according to different functions of ambulances. New mini-ambulance can be equipped with only a defibrillator, breathing facilities, and other essential medical equipment, when performing a short transport function. But if the surgical treatment is performed in the ambulance, it must be equipped with cardiac monitors, traction devices, and lighting facilities. The proper height of patient cabin (D10) requires that the patient cabin can accommodate several emergency doctors to do surgery. So, the height must exceed the height of a general adult, which is greater than 1,800 mm. Network shared location (D1) requires a new ambulance design incorporating 5th generation mobile networks, loaded with 5G network sources in mobile environments, thus enabling data sharing. The first aid center can determine the location of each ambulance and recommend the nearest hospital and the best route through the real-time electronic map navigation function to achieve intelligent dispatching. Although it is a little bit hard to achieve spacious interior (D12) under the premise of miniaturized design, an expansion cabin can be prepared to satisfy this demand. For example, the width of a van can be expanded to 4,000 mm from the original width of 2,980 mm. Internal isolation space (D13) requires negative pressure isolation chamber with 20 air changes per hour inside ambulances.
In terms of body structure design, low body chassis (D16) means a small ground clearance. Taking into account that new mini-ambulances may go through a variety of complex roads, the chassis must not be too low. Therefore, the minimum ground clearance of 195 mm is adopted. For wheelchair lift structures (D17), a wheelchair lift may be installed at the rear of mini-ambulances. For high vehicle driving force (D5), the front drive method used by Datong ambulances may be adopted, in which the front wheels are drive wheels and there is no need to make room for rear drive equipment. Large weight of the chassis (D7) has high requirements for the type of ambulance chassis. In the market, there are car chassis, truck chassis, and special ambulance chassis. The mini-ambulances may give priority to the special ambulance chassis with a large weight, which can improve the balance of the vehicle when turning. But the chassis can be changed according to different needs. For strong performance of shock absorber, a hydraulic damping and stabilization system may be adopted, which can monitor the road surface more than 100 times per second and adjust the strength of the suspension damping in real time according to the driving status of the vehicle, thus effectively absorbing the vibration from the road surface and maintaining the stability of driving. For lightweight body structure (D6), some high-strength and lightweight materials such as high-strength steel, aluminum alloy, and carbon brazing composite materials can be applied. At the same time, the structure design can be optimized in modules to reduce useless materials. The convenience to get on and off (D12) mainly considers the case in which drivers can get on and off the ambulance quickly to assist rescue and improve the rescue efficiency. In traditional ambulance design, divers get on and off the ambulance by the swing doors at the left and right sides. Although it is convenient, it undoubtedly conflicts with small and narrow ambulances. It may also affect drivers to get on and off in alleys.
In terms of body appearance design, length and width that meet the standards for minivans (D3) require that mini-ambulances should be designed in a 3,500 mm length and a 1,600 mm width. For a harmonious combination of warm and cold colors (D14), traditional ambulance colors, i.e., the mood-stabilizing blue and eye-catching red, are adopted to enhance product recognition. For a rounded outer contour line (D15), the design of body shape should avoid angles, and the edges should use chamfer.
In terms of layout design, the large number of ambulances (D2) requires that the number of ambulances in the same area should be higher than the number of existing ambulances. For example, in the central area of Wuhan, the current number of ambulances operating on duty is 105, which is far from being able to meet the emergency needs of nearly 7 million people. In the case that ambulance personnel and medical equipment are not easily changed for the time being, the ambulance emergency process needs to be reorganized and studied, and the overall number of operating ambulances needs to be increased through redesign. For ambulances stopping at the nearest community hospital (D4), each community hospital should be equipped with one to two medical ambulances to meet the actual needs of community residents.
4.2. Building House of Quality
Firstly, the user demands obtained by the analytic hierarchy process are taken as the left wall of the house of quality [25], and the technical requirements developed by the quality characteristics are taken as the ceiling of the house of quality, and the house of quality model is built. Then ●, ○, and △ are used to represent the strong correlation, medium correlation, and weak correlation between user demand and technical demand in the house body matrix, and blank means irrelevant, where ● = 5, ○ = 3, and △ = 1. After being converted into corresponding values, the absolute and relative importance weights of technical requirements shall be calculated according to the following formula as the bottom of the house of quality [26].where Wj is the absolute importance weight of technical demands; Wi is the weight of user demand; Wk is the relative importance weight of technical demands; and Pij is the correlation coefficient.
At the same time, “+” and “−”symbols are used on the roof of the house of quality to indicate the positive and negative correlations between any two requirements to obtain the conflicts between technical requirements, as shown in Figure 4.
Through the construction of the house of quality model, we can find that among the many technical requirements for ambulance design, network-shared location (D1), large number of ambulances (D2), length and width in line with microambulance standards (D3), appropriate medical cabin height (D10), and convenience for the driver to get on and off (D11) are more important than others, so we should give priority to meet these needs in the next stage.
5. Analysis and Solution of Ambulance Design Conflict Based on TRIZ Theory
5.1. Contradiction Analysis
TRIZ theory is a set of systematic innovative methods to solve problems summarized by former Soviet scientists [27], which can be perfectly combined with the QFD theory’s house of quality model. Firstly, the roof of the house of quality model, that is, the correlation between technical demands, is studied: the negative sign represents that the optimal satisfaction of one kind of demand will lead to the deterioration of the other kind of technical demand, which means there are contradictions and conflicts between the two kinds of demands [28]. A total of 5 pairs of contradictions are counted, as shown in Table 10.①The contradiction between the number of accompanying people/equipment and the number of ambulances: under the condition that the existing ambulance personnel and medical facilities are limited, the large number of accompanying people/medical equipment in a unit vehicle will inevitably lead to a small number of ambulances in operation, which forms a group of contradictions with the large number of ambulances in local areas.②The contradiction between narrow appearance of ambulance and convenient parking and opening: Traditional ambulances have left and right doors. In narrow lanes and blocked lanes, left and right doors will expand the width of ambulances, forming a group of contradictions with narrow vehicle appearance.③The contradiction between strong driving stability and high driving speed: when the speed of the ambulance is too high, it will inevitably affect the stability of the ambulance, and there is a group of contradictions between the two demands.④The contradiction between narrow vehicle appearance and easy to pass through and spacious interior space: If the ambulance is required to meet the core demands of “not affected by congestion,” the appearance of the ambulance must be narrow. Many emergency patients require first aid treatment in the ambulance and need to be accompanied with family members in the ambulance, which requires a spacious interior space of the ambulance, and thus the ambulance needs a wider appearance, so the two sets of requirements constitute a pair of contradictions.⑤The contradiction between light total weight of vehicle body and heavy chassis weight: In order to meet the needs of rapid transportation of patients, the overall weight of ambulance must be light, so that the driving speed can be faster. However, for the safety of patients, the chassis of the ambulance must be heavy to maintain stability, forming a pair of contradictions between the two.
5.2. Conflict Resolution
When making statistics on the technical demands of ambulances, although a total of 5 groups of contradictions were found, the relative weight of the technical requirements involved in the contradictions and conflicts is relatively low, which cannot attract high attention from users. It is not a pain point of traditional ambulances, and there is no need to discuss it specifically [29]. The conflicts and solutions of the first four groups of contradictions should be focused on, as shown in Table 11.①The number of ambulances constitutes a pair of physical contradictions. Through analysis, it can be found that these two demands do not have to be met at the same time. When patients have serious illness and need to be rescued immediately, patients and their families hope that the ambulances can be equipped with enough medical equipment and emergency doctors. The number of ambulances that can meet this point is small, but in general, most people just call 120 in case of “minor accidents.” At this time, the ambulance only serves as a transportation function, and it does not need to be equipped with too many medical devices and emergency doctors. Therefore, Principle No. 15-Dynamic Principle in the time separation principle can be adopted here [31], that is, the ambulance does not always carry medical equipment statically but is divided into a variety of states and changes dynamically. One state is fully equipped, and the other state is “light,” as shown in Figure 5. In the following design practice, it is necessary to consider the changes of various states of the vehicle body.②The narrow appearance of an ambulance and the convenience of parking and alighting constitute a pair of physical contradictions. The increase in width caused by the convenience of getting on and off the ambulance is limited to the opening and closing positions of the left and right door, while the narrow appearance means the narrow body of the whole body. These two can be applied to Inventive Principle No. 4-Increasing Asymmetry in the spatial separation principle [32]. That is to say, the original left-right symmetrical door opening is changed to open the door from one side combined with front-to-back opening, so that getting on and off the vehicle in the roadway will not increase the width too much, as shown in Figure 6.③The pair of physical contradictions formed by the narrow shape of the ambulance and the large internal space is considered to be solved by using the Principle 1: Segmentation Principle corresponding to the “space separation” principle [31]. That is, the complete ambulance compartment is divided into different modules, one ambulance is transformed into a combination of multiple ambulances, and the separation time becomes narrower and the combination time becomes wider to solve this problem [33], as shown in Figure 7.④The pair of technical contradictions formed by the stability of the product structure and the driving speed, as the ambulance has a large volume and provides multiple functions, and through analysis, if the new ambulance design can solve the contradictions ① and ③, that is, to meet different functions at different times through modular design, either only meeting the transport function when the speed is fast, passing through narrow roads, or meeting the rescue function when the speed is slow while transporting patients, it means that we do not need to worry about the impact of speed on the rescue stability, and then the contradiction ④ will be solved naturally.
6. Scheme Design of Community Ambulance
6.1. Conceptual Derivation
First of all, according to the TRIZ theory, it is recommended to use the principle of dynamization to solve the contradiction in the number of ambulances. The new ambulance design should be able to achieve dynamic changes in the number, and it can be combined and separated at any time. However, after structural analysis, it was found that the combination of several vehicles traveling together would lead to problems such as the front wheels of the new large ambulance not being able to steer and the carriage seal not being resolved, as well as posing a threat to patient safety. Therefore, the combination principle of motion and quietness is considered to meet various changes of multiple states. When the new mini-ambulance is in motion, it is in a single state. Only when it is at rest or docked, it can be combined, so as to expand the internal space. This will be convenient for surgical treatment and also ensure patient safety.
According to the TRIZ theory, it is recommended to solve the physical contradiction between narrow ambulance shape and convenient parking and dismounting by increasing asymmetry. Firstly, sliding door or swinging door design can be used in consideration of smooth opening in narrow aisles. Next, the sketch form can be extrapolated to determine which door design to use.
Finally, according to the TRIZ theory, it is recommended to use the partitioning principle to solve the contradiction between the narrow shape and large internal space of ambulances. The original fully equipped large traditional ambulances are separated into two parts, and various medical devices should be placed separately inside and combined together when needed. This will be convenient and space-saving and will reduce the size of ambulances. But in terms of how to combine vehicles to expand space, after in-depth study, it was found that direct combination will bring many problems. Therefore, the current mature RV expansion cabin structure design is used to first expand the internal space of ambulances through the expansion cabin and then combine with other ambulances.
6.2. Community Ambulance Positioning
User Orientation. This ambulance is mainly parked in the community hospital and driven by the community emergency doctor.
Use Scenario Positioning. This product is mainly designed for some old residential areas in China. In these residential areas, as the roads are narrow, traditional ambulances cannot get in at all, while newly designed micro-ambulances can pass quickly. In addition, this scheme can also play a key role in case of traffic jam. If we assume the traveling track of traditional large ambulances in central cities as arteries and veins in human bodies, the traveling track of new mini-ambulances may be blood capillary because it is small and flexible due to miniaturized design and then widely distributed with less equipment and personnel, so that they can quickly reach all corners of a city where large ambulances cannot, covering the whole city.
Function Positioning: Patient Transportation + Temporary Operating Room. According to the contradiction analysis and solution based on the TRIZ theory, new mini-ambulances adopt modular design, whose body can be combined and separated to precisely match the needs of patients. For patients requiring general transportation functions, one mini-ambulance may be dispatched. For patients requiring emergency treatment, two mini-ambulances may be dispatched to the scene quickly and combine with each other to form a temporary operating room, realizing access to medical treatment in ambulances. Then, after the medical treatment is completed, the two bodies can be separated quickly and the patient can be sent to the hospital by one mini-ambulance quickly.
Shape Positioning. After a lot of research and sketching, the following three options were identified, including machine and hi-tech style, simple and stable style, and round and soft style. The second style was finally chosen, as shown in Figures 8 and 9.
According to the TRIZ theory, the physical contradiction between narrow ambulance shape and convenience for getting on and off may be solved by increasing the asymmetry. The first thing is to enable people to get on and off smoothly in narrow alleys. So, the rotary door design is used as shown in Figure 10.
6.3. Workflow
When the emergency center receives the alarm call, it determines the emergency condition from the patient first. If it is ordinary, the emergency center contacts the surrounding community hospital to send a mini-ambulance with a doctor to quickly arrive at the scene to rescue the patient. After the emergency treatment of the patient, if the condition is serious, the community doctor immediately contacts the emergency center to dispatch a nearby mini-ambulance with the necessary medical equipment to come to the community hospital. If the patient can adapt to a short transport, with the consent of his family members, the emergency doctor and the driver can immediately transport the patient to converge with the mini-ambulance coming to transport the equipment. If the condition is more complicated, the doctor can wait at the patient for other mini-ambulances to come to the scene.
The ambulance patient cabin is an expansion cabin design, which can quickly extend the original space and form a new closed space conveniently, turning the ambulance into a temporary operating room where the patient’s condition can be treated on the road. Especially in combination with today’s rapidly developing 5G network, ambulances can transmit patient information back to the hospital’s 5G consultation center in real time, and in-hospital experts can guide the surgery remotely, thus greatly alleviating the shortage of hospital emergency resources. Considering the poor stability of ambulances in the process of high-speed driving, it is easy for two spliced mini-vehicles to cause secondary injury to the patient, so the new ambulance design uses the combination of static and dynamic ways. Specifically, combined vehicles are generally parked in a safe area while the treatment is being performed. When the physical condition of the patient is stable, the doctor can transfer the patient to one mini-vehicle, shrink the whole vehicle body, and reduce the width of ambulances to allow several drivers to drive the separated mini-vehicles quickly across the lane. The details are shown in Figure 11.
(a)
(b)
(c)
(d)
(e)
(f)
As most users want new ambulances to be designed to meet two main functions of not affected by congestion and arriving at the scene in time and quickly and have less requirement for functions such as intensive care, the accompanying equipment of new community ambulances for patient transport should be in line with transfer ambulances, and the medical equipment placed on the vehicle includes only essential portable facilities such as folding stretchers and monitors. Mini-ambulances specializing in the transport of equipment can be equipped with internal storage cabinets for drugs, oxygen supply facilities, family seats, and other facilities that take up more space like large ambulances. After the combination of two ambulances, it can accommodate several doctors and patients’ families to facilitate ambulance treatment. The details are shown in Figure 12.
(a)
(b)
(c)
(d)
6.4. Structure and Detail Description
It was found in the user demand research that the ordinary ambulance chassis is so high that makes it difficult for elderly family members and some patients who need wheelchairs to get on and off the vehicle. For this problem, the new concept ambulance is designed with a low chassis, and the telescopic pedal is installed in the rear of the vehicle with handle in the rear door, so as to provide convenience for elderly patients. At the same time, in order to facilitate the boarding and alighting of patients in wheelchairs, the new ambulance is equipped with a wheelchair lift at the rear of the vehicle. This mechanical structure has now been widely used in various models, reflecting the care for special people, as shown in Figure 13.
(a)
(b)
(c)
(d)
In order to ensure the safety of the patient cabin expansion module, to make emergency doctors and patients feel at ease to carry out surgery, the expansion module legs are electrically retracted to form a triangular support with better parking stability. The details are shown in Figure 14.
The patient cabin expansion module uses a slide system with internal motor-driven gear operation. This structure has now been developed and is widely used in various RV expansion pods. The details are shown in Figure 15.
6.5. Three-View Drawing and Dimension Sign
At present, the standard width of motorway of multi-lane highway above grade 3 in China is 3,500 mm to 3,750 mm, and the width of urban lane is 2,000 mm to 2,500 mm. The length, width, and height of traditional ambulance shape are about 5,800 mm, 2,000 mm, and 2,600 mm, respectively. In case of lane blockage or alleyway crossings, it is basically difficult for traditional ambulances to pass quickly, so the new mini-ambulance should be less than 2,000 mm wide. Moreover, on the basis of the QFD theory, it is concluded that the width of the new ambulance should meet the standard of minivans, i.e., between 1,400 mm and 1,800 mm. In combination with the internal field measurements of the ambulance, the technical parameters of the necessary equipment on the ambulance are determined. For example, the length, width, and height of general stretchers are 1,900 mm, 530 mm, and 550 mm, respectively. So, the width of the mini-ambulance should be 1,600 mm, which can accommodate general stretchers and some medical equipment. In terms of length, the new mini-ambulance is set at 3,580 mm to accommodate a minimum of basic cab space and a stretcher in the patient compartment. Taking into account the doctor’s standing operation and that the cabin cannot be easily reduced, the height inside the patient cabin should be 1,820 mm and the overall height of the ambulance should be 2,550 mm. In addition, the new mini-ambulance is positioned to cover the whole city. The axle base is 2,500 mm, and the wheel base is 1,270 mm. The details are shown in Figure 16.
7. Scheme Verification
7.1. Suggestions and Evaluation
In order to verify the actual effect of the new ambulance scheme, the fuzzy comprehensive evaluation method is specially adopted to score and evaluate the scheme. First, the evaluation set V = (very satisfied, satisfied, general, dissatisfied, very dissatisfied) is established. The five-level evaluation corresponds to 90 points, 70 points, 50 points, 30 points, and 10 points, respectively. Taking the functional requirement C1 “fast dispatch at any time” as an example, the question is set as “how would you rate the performance of the new ambulance design in terms of fast dispatch at any time.” The options are set as “(A) very satisfied; (B) satisfied; (C) general; (D) dissatisfied; and (E) very dissatisfied.” Then, 3 previous automotive design experts, 20 patients who had been in medical ambulances, 4 ambulance drivers, 2 emergency physicians, and 2 first aid personnel were invited and distributed with a total of 31 paper questionnaires, with 29 valid questionnaires collected. At the same time, 75 online questionnaires were distributed to the family members of patients who had been in medical ambulances, and 71 valid questionnaires were returned, making a total of 100 valid questionnaires. The research sites included school classrooms and local community hospitals. In addition to the questionnaire questions, the team members also showed the respondents a physical model of the new ambulance and an ambulance video. The research process is shown in Figure 17, and the scoring results are shown in Table 12.
In order to verify the credibility of the questionnaire results, we calculated the means and standard deviations for the evaluation data of each element layer separately, as shown in Table 13. It can be found that the standard deviations of the evaluation data of each element layer mainly ranged from 10 to 20. The main reason is that options in this questionnaire survey were set to 5 levels of evaluation, corresponding to 90 points, 70 points, 50 points, 30 points, and 10 points, with huge differences between the options. Even between the two close options of “very satisfied” and “satisfied,” they have a difference of 20 points. So, some element layers had great standard deviations. However, from the data in the table, we can see that the average satisfaction of demands of C3, C4, and C6, which are of high concern to users, scored above 70 or even close to 80, with relatively low standard deviations. Given that 90 points correspond to “very satisfied” and 70 points correspond to “satisfied,” these figures indicated that the new ambulance design essentially meets the core needs of most users. C9 and C12 and other needs that are of little concern to users had mean satisfaction scores around 60, with relatively large standard deviations. It indicates that the new ambulance design should further be optimized and continuously improved in the areas such as C9 “health and epidemic prevention” and C12 “the exterior appearance for delivering a sense of security.”
7.2. Determining Indicator Weight
The weights of ambulance indicators determined according to Table 5 are as follows:
7.3. Calculating Evaluation Vector
In order to obtain the comprehensive score of the scheme, it is necessary to synthesize and calculate the index weight obtained by the analytic hierarchy process with the corresponding fuzzy evaluation matrix and obtain the evaluation weight vector of each index as follows:where R1, R2, and R3 are the matrices formed separately by each principle layer in the satisfaction evaluation results in Table 11.
The fuzzy comprehensive evaluation of the overall index is
Then, we calculated the mean and standard deviation of each evaluation index separately, as shown in Table 14. We found that the survey data generally had low standard deviations, with stable user evaluations for each index layer, and credible experimental data.
Then, the comprehensive evaluation vector of the ambulance design scheme is
Finally, the overall evaluation vector of the program was weighted by the scores corresponding to the set of comments, resulting in a total score of N = 72 for the ambulance design program. Similarly, the two more popular ambulances on the market at present, the Oriental Wind ambulance and Iveco ambulance, were selected for evaluation. Previous scorers were invited to score the ambulances separately, resulting in a score of N2 = 41 for the Oriental Wind ambulance and N3 = 45 for the Iveco ambulance. As shown in Figure 18, several ambulances did not score high due to the strict scoring of this evaluation, but the new mini-ambulance design still scored much higher than the two more popular ambulances currently on the market, indicating that the new design better meets the needs of most users. Of course, some user needs have not been fully considered in this program. From Table 11, the new ambulance design is still inadequate in the appearance of the vehicle body, with low scores for needs such as “appearance of vehicle body proportion” and “sense of security provided.” It indicates that the new ambulance design still needs to continue to be improved and optimized.
8. Discussion
In recent years, various designers have used different theoretical methods to support design research, including the SET factor analysis method, the Kano model questionnaire analysis method, and the hierarchical analysis method in the preliminary requirement research. SET factor analysis is an analytical method proposed by Craig Vogel and Jonathan Cagan for identifying breakthrough points in product design. By summarizing and analyzing the problems and needs of products in the three levels of society, economy, and technology, it can determine the key words of user needs and discover the shortcomings of existing products, so as to provide suggestions for product innovation and design. As the quality of life has improved dramatically, there are often multiple functional requirements for the same product. However, SET factor analysis can only identify design gaps and cannot rank the importance of multiple design gaps. For large equipment such as ambulances, the user needs are complex and cannot be easily classified and analyzed from social, economic, and technical levels, so the SET factor analysis method is not applicable to researching ambulance user needs. Instead, when analyzing user requirements, the hierarchical analysis method can first divide the user requirements into multiple criterion layers, and each criterion layer can be subdivided into multiple element layers, and the comparative evaluation can be done in layers, which is more accurate and scientific.
The Kano model questionnaire analysis method is a structured questionnaire analysis method that quantifies users’ needs for various functions of a product. It was proposed by Professor Noriaki Kano, a renowned Japanese expert in quality management. In recent years, this analysis method has been widely used in product design and quality management. Before designing a new product, designers can use the Kano model to classify user needs into five categories, namely, must-be quality, one-dimensional quality, attractive quality, indifferent quality, and reverse quality. They then determine the priority issues to be addressed in the new product design based on the division of different user needs and understanding the level of user satisfaction with different features of the old product. However, the Kano model relies too much on subjective judgment when analyzing user requirements. For example, when judging whether a requirement is a must-be quality or a one-dimensional quality, the conclusion that the number of people who judge the requirement to be a must-be quality is higher than the number of people who judge the requirement to be a one-dimensional quality in the questionnaire research is too arbitrary without a scientific and rigorous calculation.
The hierarchical analysis method can combine the subjective evaluation of users with scientific calculation and minimize the error of subjective evaluation by the consistency test. Compared with other methods of user requirements research, the hierarchical analysis method has obvious superiority, so the first step in the ambulance design study is to analyze the user requirements by the hierarchical analysis method. However, most designers only use the hierarchical analysis method alone to obtain user requirements and then start designing. As a result, the user requirements are usually vague and subjective, and the designers have to satisfy their subjective imagination to meet these user requirements, which is unscientific. Therefore, our team introduces QFD theory to realize the convergence between user requirements and product technical attributes. Through the combination of AHP theory and QFD theory, a house of quality model can be constructed to translate the weight ranking of user requirements into that of technical attributes of a product while showing which technical attributes constitute contradictory conflicts between their satisfaction and providing a reference for design.
After obtaining the technical attributes of a product, new theories should be introduced to provide design elements and resolve the conflicts between different technical requirements. Theories in translating technical attributes into design elements include FBS theory and TRIZ theory. FBS (function-behavior-structure) theory describes the design process of product concepts by analyzing three variables: function, behavior, and structure. Since its introduction, it has been widely applied to the field of design research. FBS theory starts from user needs to determine what kind of functions a product should provide, identifies the product behavior corresponding to each segmented function according to the function-behavior mapping, and then fully considers which structure of the product is needed for each user behavior according to the behavior-structure mapping, so that the complex structure of the product can be broken down and studied to provide a clear reference for completing the structural innovation and optimization of the product. The analysis process of FBS theory shows that it is more applicable to some products that are closely related to user behavior, such as bathing products for the elderly and patient beds, and is not suitable for some large equipment with a complex design. On the contrary, TRIZ theory is very suitable for the structural research of large appliances. It can divide the conflicting demands in the product system into physical and technical contradictions and then provide methods to resolve the contradictions through 4 separation methods and 39 invention principles, which can provide a clear reference for product design. Therefore, TRIZ theory is chosen to support the innovative design of ambulances.
Finally, the design solution needs to be evaluated and validated. Theories for evaluating the effectiveness of the design solution include the SUS scale analysis method and fuzzy integrated evaluation method. The SUS scale analysis method mainly uses the system usability scale (SUS) to count users’ evaluation on the effectiveness of the design solution. The SUS scale adopts the Likert 5-point scale method with 10 questions, of which the 1st, 3rd, 5th, 7th, and 9th are positive questions and the 2nd, 4th, 6th, 8th, and 10th are negative questions. The transformed score for positive questions is the scale raw score − 1 (X − 1), and the transformed score for negative questions is 5 − raw score (5 − X). Both types of questions have a score range of 0–4 points, and the transformed score of all question items multiplied by 2.5 is the total score of the design solution. For users, the degree of importance of each requirement for a certain product is completely different. However, the calculation process of the SUS scale analysis method is relatively simple and less rigorous. The SUS scale analysis method treats all requirements equally and cannot provide designers with a clear reference. In addition, the SUS scale analysis method only yields an overall score and does not provide scores for different segments’ requirement. As a result, designers cannot identify the shortcomings of the design solution and cannot continue to improve it. In contrast, the fuzzy comprehensive evaluation can be combined with the weight of each type of requirement for the evaluation calculation, and the evaluation results are more convincing. In particular, the fuzzy comprehensive evaluation of the original and optimized versions of a product can show most intuitively in which aspects the optimized version is better than the original version and which aspects are still deficient, thus providing a clear reference and aid for continuous optimization and improvement of the product. Therefore, the fuzzy comprehensive evaluation method is chosen to evaluate and score the new ambulance design scheme, identify deficiencies, and improve it.
9. Conclusion
Through the integrated application of AHP/QFD/TRIZ theory, this paper quantifies the various needs of users for ambulances, so as to obtain the importance sequencing of different design elements and then analyzes the conflicts between different design elements. It provides a way to solve conflicts by using the principle of problem solving and finally realizes the improved design of community ambulance scheme. The research shows that this design process can not only reduce the subjective preference influence of designers in the product design process and ensure the objectivity and scientificity of the design process to the maximum extent but also quickly obtain reasonable innovation schemes, improve the efficiency of product design, and provide reference for other product design and development. Although this design process provides a relatively clear idea for the design of community medical ambulances, there are still deficiencies in the verification of the scheme, which remains at the concept evaluation level. Therefore, the simulation analysis and physical model verification of the scheme will be considered in the future to further improve the internal space structure and detail design of the mini-ambulance, so as to effectively improve the feasibility, rationality, and user satisfaction of the scheme design.
At the same time, in terms of theoretical research, most of the traditional medical products and special vehicle design are mainly based on scientific and technological breakthroughs, while not enough attention is paid to user needs. In addition, they lack a set of sound design theory to assist the design. The design process is often subjective, mainly relying on the subjective evaluation of designers and the judgment of some users, lacking data support and scientific verification. Moreover, some designs are time-consuming and laborious, but the results cannot really meet the needs of users. By integrating the AHP/QFD/TRIZ theories, this study has innovated the design by quantifying and ranking various functional requirements of users for medical ambulances. It has identified conflicts and also provided solutions, which shows a breakthrough in the innovative design research of ambulances. Then, on the basis of the fuzzy comprehensive evaluation method, this study invites a large number of users to score each aspect of the design solution, so that a more scientific and comprehensive evaluation result can be obtained. Through the systematic research and application of integrated theories, a new set of complete design methods and processes has been provided for the medical transportation product design, and a new way of thinking has been provided for other product designs. In addition, other scholars generally lack holistic thinking when using these theories to assist design research and simply take two or three theories from numerous methods for user needs research and contradiction analysis. They do not realize that the coherence between methods is very important, and the use of theories that do not match each other together can greatly reduce the effectiveness of the theories’ assistance and affect the advantages of different theories. This article not only introduces the respective advantages of AHP, QFD, and TRIZ theories but also shows the compatibility of the three theories with each other by taking the design of an ambulance as an example. Then, it combines the fuzzy comprehensive evaluation method to verify the overall solution and realize the real scientific design. Other designers can apply this set of integrated theories to other areas of design assistance, thus making the design process more scientific and rational and the handling of user needs more standardized and detailed and finally designing a product that truly meets user needs and improves user satisfaction.
Finally, there are still shortcomings in this study, such as the lack of in-depth research on theories such as TRIZ, which can provide a variety of invention principles to solve conflicts. However, the principles of invention provided by the TRIZ theory are broad and universal methods, and it is still difficult to use these methods to solve the specific conflicts of specific product systems. This is mainly because the authors have not fully grasped the essence of the TRIZ theory. In the future, there is a need to systematically sort out cases of the TRIZ theory applications so as to become more proficient in translating the inventive principles of the TRIZ theory into concrete solutions.
Data Availability
The data used to support the findings of this study are available from the corresponding author upon request.
Conflicts of Interest
The authors declare that they have no conflicts of interest.
Acknowledgments
This study was supported by the Youth Project of Humanities and Social Sciences of Hubei Province Education Department (16Q109).