Abstract: The design of the IETM (Engineering, Technology, and Manufacturing) human-machine interface (HMI) for equipment maintenance is a crucial part of human factors engineering in equipment maintenance. Its core is how to display a vast amount of stored technical information on a limited screen, ultimately achieving "human-machine integration." Therefore, when designing the IETM, it is necessary to base it on the theory of "human factors," constrain human cognitive characteristics, and use the elements displayed on the interface as variables to organize the interface, striving to ensure that the IETM meets the user's requirements to the greatest extent possible.
Keywords: Equipment maintenance; IETM; Interface design
Interactive Electronic Technical Manuals (IETMs) are information data packages used for the diagnosis and maintenance of weapon systems or military and commercial equipment. Essentially, they are digital technical manuals providing technical information to equipment maintenance or operation personnel. For a long time, influenced by the traditional "function-oriented" concept, the sole criterion for evaluating the quality of application software was whether it possessed powerful functions and could meet user needs, while the design of the human-machine interface was often neglected by software developers. IETMs for equipment maintenance faced the same problem. It is well known that humans become familiar with and operate equipment only through learning and understanding its technical information. In this sense, technical manuals have become the link for achieving an organic integration between humans and equipment. Technical manuals were initially stored on paper. The advent of the information age has not only led to a massive increase in various technical data related to equipment but also demanded that the technical information meet the requirements of rapid retrieval and remote technical support. Therefore, paper-based technical manuals were no longer adequate for the demands of the times. With the development of computer technology, interactive electronic technical manuals gradually emerged, and their digital storage method brought many conveniences, making their replacement of paper-based technical manuals an inevitable historical trend.
However, while computers can store vast amounts of technical information, the space displayed on their screens is limited. With the rapid development of information technology, the requirements for equipment maintenance IETM (Internet Interface for Machines) have evolved towards higher technology, greater naturalness, and more human-centered design. Simultaneously, when using computers to store large amounts of technical information, the limited screen size cannot display the overall picture, and even when key technical information is highlighted, the screen often falls short. This issue necessitates optimizing the interface display to mitigate these limitations.
1. Basic Principles of IETM Human-Machine Interface Design for Equipment Maintenance
Ergonomics is a discipline that studies how humans and machines interact to achieve optimal efficiency. From an ergonomic perspective, both humans and machines have their advantages and disadvantages; machines are tools for humans to complete tasks. When human intervention is required for a machine to perform a task, the machine's design must be suitable for the user's requirements to allow both humans and machines to leverage their respective strengths. The IETM (Industrial Interface for Aircraft Maintenance) human-machine interface design is a part of ergonomics, focusing on how technological development revolves around human needs. It takes humans as the starting point for product and environmental design, ensuring that performance, operation methods, appearance, and color better adapt to and satisfy human physiological and psychological needs, thereby making maintenance personnel's work safer, more convenient, more comfortable, and more efficient. In typical human-machine interface design, developers often focus more on the usability and efficiency of the interface, neglecting user needs. For a human-machine interface, functionality and features are manifested by the user; without considering human factors, the system's functionality is difficult to truly realize. As shown in Figure 1, the research methods and evaluation means of the equipment maintenance IETM human-machine interface involve multiple fields such as psychology, physiology, medicine, anthropometry, aesthetics and engineering technology. This paper mainly studies the design of the equipment maintenance IETM human-machine interface from the perspective of human-machine harmony.
2. Understanding of users in Equipment Maintenance IETM
The most important principle in equipment maintenance IETM (Internet Interface for Equipment Maintenance) human-machine interface design is understanding the product's users. Only in this way can a usable product be provided to the users. The most basic idea of user-oriented equipment maintenance IETM human-machine interface design is to put the user first in every process. In the initial stage of the product life cycle, the product strategy should be based on meeting user needs as the fundamental motivation and ultimate goal. In the subsequent product design and development process, user research and understanding should serve as the basis for various decisions, and the evaluation information of the product at each stage should also come from user feedback. Therefore, the concept of the user is the center of the entire design. Simply put, a user refers to the person who uses the product. From this simple definition, it is not difficult to see that the concept of user includes two layers of meaning:
① Users are part of humanity. Users possess common human characteristics, which are reflected in various aspects when using any product. Human behavior is not only influenced by basic human abilities such as visual and auditory perception, analytical and problem-solving skills, memory, and responsiveness to stimuli, but is also constantly constrained by psychological and personality orientations, physical and cultural environments, educational environments, and past experiences.
② Users are those who engage with the product. User-centered design and evaluation research involves a specific group of people whose lives are directly related to product use. They may be current users, future users, or even potential users. Their behavior during product use is closely linked to several product-related characteristics. These include knowledge of the target product, expectations of utilizing its functions, the basic skills required to use it, and the future frequency and duration of its use.
Therefore, user research should begin with both general human attributes and product-specific attributes. It's evident that user-centered interface design utilizes methods from natural sciences such as biology and statistics, as well as humanities fields like psychology and sociology. These theories constitute an interdisciplinary field concerning human factors, known as "human factors." The general theories and methods of human factors can be applied to systems involving both humans and machines.
3. Human Factors-Based Equipment Maintenance IETM Interface Design
As an electronic display system, people need to interact with it through the Equipment Maintenance IETM human-machine interface to meet the requirements of finding and searching for relevant technologies or obtaining help. This interaction process can be summarized by Figure 2.
Based on this model, it can be seen that humans are coupled with computer processing systems through interactive interfaces. A higher degree of coupling results in a higher level of human-machine integration, leading to better efficiency and effectiveness of the equipment maintenance IETM (Internet Interface for Machines). Therefore, when designing an IETM for equipment maintenance, the interface must not only meet the precise and rapid requirements of computers but also conform to human physiological characteristics and cognitive patterns. Researching relevant materials and examining actual IETM interfaces reveals that they influence human perception, cognition, and reaction.
(1) Human sensory search
In human perception, people actively search for targets by scanning specific features of their environment. When encountering distractions (non-target stimuli that divert attention from the target stimulus) during the search, false alarms often occur. Not only does the number of distractions affect the difficulty of the target-finding task, but when distractions lack distinguishing features from the target (such as color, size, similarity to similar items, differences from different items, or orientation like vertical or horizontal), we can only perform a combined search, or the search speed slows down.
Human factors are inherently difficult or impossible to change in the short term. When designing the IETM (Internet Interface for Equipment Maintenance) human-machine interface, efforts should be made to ensure that the way the various contents of the IETM are presented on the computer screen aligns with human sensory characteristics. When paper manuals are transformed into IETMs, the storage and display methods of the technical information they contain undergo fundamental changes. The interface display method must be compatible with human cognition and operational behaviors, making the interface highly user-friendly so that equipment maintenance or operation personnel are willing and able to use the interactive electronic technical manual efficiently. Based on human cognitive characteristics, the following principles should be followed.
The interface can display text, vector graphics, images, audio, and video. For a single display format, based on human sensory search characteristics and referencing ergonomics research findings, the following principles are established.
The principle of placement selection: On a plane, the upper half evokes a sense of ease and comfort, while the lower half evokes a sense of stability and oppression. Similarly, the left half of a plane evokes ease and comfort, while the right half evokes stability and oppression. Therefore, the visual influence of a plane is stronger at the top than at the bottom, and stronger on the left than on the right. Thus, the upper and upper-middle parts of a plane are considered the "optimal viewing area," and are the most suitable locations. Therefore, the most important technical information should be placed in the upper left corner, and then arranged according to human reading habits, from left to right and from top to bottom.
Size selection principle: Generally, the size of text appearing on the interface can be determined by the formula suggested by Peter and Adams:
H=0.0022D+25.4×(K 1 +K 2 )In the formula, H is the height of the target (mm); D is the distance between the human eye and the target (mm); K1 is a coefficient related to the importance of the content, generally taken as 0, and 0.075 for important cases; K2 is a coefficient related to lighting conditions, taken as 0.06, 0.16, and 0.26 for very good, good, and average lighting conditions, respectively. The width of the text is proportional to its height, and its width can be calculated according to Table 1.
The principles of color selection are as follows: First, the choice of color itself. The IETM interface is primarily practical. Moreover, its use is often time-constrained, requiring operators to quickly locate relevant information. Therefore, its colors need to be natural. Generally, the color scheme uses light backgrounds paired with dark text or icons. For content that needs to be emphasized, a small amount of bright color should be used. These bright highlights will create a strong visual impact, but too much should be avoided. Excessive use will create a uniform noise, failing to achieve the desired emphasis. Secondly, the choice of color tone is crucial. Wartime conditions increase psychological stress. Using a dark color tone in the IETM could cause greater psychological barriers and lead to errors. Therefore, the color tone of the IETM interface should be consistent with the user's mood, conveying a sense of refinement and solemnity. The artistic element of color selection is significant.
The principle of comprehensive expression: Sometimes, a single display format is insufficient to fully express its meaning. Often, several formats need to be used simultaneously. For example, an icon can fully express what text cannot; however, icons also have limitations, such as their difficulty in conveying action-related knowledge. Audio can convey different meanings and easily lead to misunderstandings; video has a long response time, is difficult to describe, and is challenging to capture. To enhance learning effectiveness and improve interface usability, multiple formats can be used simultaneously to express the same content. For example, adding text hotkeys and sound to icons, and using video demonstrations to illustrate operation steps. This allows users to more accurately understand the meaning of the content provided by IETM.
(2) The human brain's representation of knowledge
Regarding human cognition, cognitive psychologists Allan Collins and Ross Quillian argue that knowledge is represented according to a hierarchical semantic network, a web of interconnected elements. According to this view, organized knowledge exists in the form of a hierarchical tree diagram. That is, knowledge storage in the human brain has two characteristics: first, concepts are stored using a multi-layered tree structure; second, any piece of knowledge can be linked to many other pieces of knowledge, like a network.
As mentioned earlier, the information displayed on the Equipment Maintenance IETM human-machine interface is limited; a large amount of knowledge is "hidden" within the computer. When a user searches for information on the interface, they will use their existing logical understanding to find the next step. The computer's expression of knowledge is similar to that of the human brain; it uses layered text, and the logical relationships between layers are expressed through links. The user interface design must ensure that the logical relationships in the human brain are consistent with the links in the computer. When the operator searches for the next layer of information on the display interface, if it matches their declarative memory expectations, it is easily understood. If it does not match, learning and memorization are required, thus increasing the time spent using the IETM.
When creating links, adhere to the following principles:
① The standards for establishing links within the same system must be consistent. This ensures that operators can clearly understand the link paths based on the standards, preventing them from getting "lost" when searching for information via links.
② Every link in the IETM human-machine interface for equipment maintenance must be meaningful. The basis for establishing accurate links is to unify the definitions and procedures of the information to be expressed, preventing semantic inconsistencies between link nodes and ultimately failing to meet user expectations.
③ The links in the equipment maintenance IETM human-machine interface should be complete. Similarly, the definitions and procedures of information should be analyzed to identify links between semantically similar content. At the same time, the number of links should be appropriately controlled to reduce the cognitive load on the user.
(3) Human operational behavior
Behavioral psychologist B.F. Skinner believed that human behavioral responses are learned. They rely on subsequent reinforcement stimuli, making operant conditions particularly important. The stronger the operant response, the more consistent the reinforcement stimuli. The purpose of Equipment Maintenance Instruments (IETMs) is to improve the technical skills of equipment maintenance personnel. To quickly acquire technical information, one must operate the IETM quickly. Improving usage speed involves reinforcing various operational actions. Through prolonged or intensive training, users may transition from conscious to unconscious operation of the IETM. This enables rapid operation and use of the equipment maintenance IETM, requiring continuous exposure to the same stimuli. This is mainly manifested in the following two aspects.
① Consistency of Interface Operations. A consistent interface allows users to transfer their previous operational experience to new tasks, improving task completion while reducing the user's memory burden. Interface consistency is typically reflected in the following aspects: First, stylistic consistency, such as color schemes, system terminology, icons, and symbols; second, control consistency, categorizing and grouping controls according to operating habits and interaction needs; and third, operational consistency, maintaining consistency in the operation methods for frequently used or important functions while also conforming to user habits. This consistency enables users to transfer existing knowledge to new tasks, allowing them to learn new knowledge more quickly.
② Design to prevent failure issues. First, provide clear prompts before each action, especially in situations prone to accidents or loss of control. Based on the different consequences, prompts can be divided into three levels: explanation, caution, and warning, indicating the potential consequences to the user. Second, when users operate according to the information provided by IETM, they may need to temporarily leave the screen to perform physical operations. When they return, they may easily forget the breakpoint location. The main method to solve this problem is to provide breakpoint memory assistance.
4. Example Demonstration of the IETM Human-Machine Interface for Equipment Maintenance
As shown in Figure 3, the page's overall framework can be divided into a functional area, a working area, and a status area. The functional area includes the title bar, menu bar, and navigation bar; the working area includes the navigation tree and status bar; and the status area includes the status bar. This overall framework is modeled after Microsoft Windows' window structure. Based on the human operating behavior described above, anyone who has used a computer will generally be familiar with its overall structure and will be able to quickly get started using IETM.
Based on sensory characteristics, the current payment item will be displayed in a dark color to highlight the current project. Furthermore, the font used within the workspace will differ from that within the various frames; the frames will use a bold, sans-serif font, while the workspace will use a serif font to differentiate them. The primary font color should be black text on a white background; any special fonts will be used according to relevant standards.
A tree structure and addresses are used to indicate the location of the main interface content, providing users with clear location guidance. Different colors are used to display deeper links, and the location reached by each link is recorded.
5. Conclusion
This paper explores the design of the human-machine interface (HMI) for equipment maintenance using the theory of "human factors." The research aims to make the design of the HMI for equipment maintenance more fully consider the "human factor," enabling better cooperation and collaboration between humans and machines in the HMI system. It seeks to allow machines to perform more tasks that would otherwise be done by humans, minimizing the user's memory and operational burden. Users can operate and use the system safely, comfortably, and efficiently, providing a framework for achieving "human-machine integration" in the equipment maintenance HMI. This paper has made valuable explorations in these areas and also provides ideas for the design of HMIs for other equipment.
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Research on IETM Human-Machine Interface Design for Equipment Maintenance Based on Human Factors
