Abstract: Industrial human-machine interface, or HMI for short, also known as touch screen monitor, is an intelligent operation control display device.
Industrial Human-Machine Interfaces (HMIs), also known as touchscreen monitors, are intelligent operation control and display devices. The main functions of an HMI include: data input and display; real-time display of system or equipment operating status; enabling the HMI to function as an operation panel by setting touch controls; alarm handling and printing; in addition, the new generation of industrial HMIs also features simple programming, data processing, data entry, and recipe management, among other intelligent control functions. The following points should be considered when designing an HMI.
1. Interface style design
The console's human-machine interface adopts a non-standard Windows style to meet users' personalized requirements. However, considering that most users are familiar with the standard Windows system, the interface design tries to be compatible with the features of the standard Windows interface as much as possible. Because bitmap buttons can achieve effects such as high brightness, protrusion, and recess during operation, the interface presentation is more flexible, and it is also easier for users to identify the controls.
However, the dialog boxes, edit boxes, combo boxes, etc., used in the interface all use standard Windows controls, and the buttons in the dialog boxes also use standard buttons. The size and spacing of the controls conform as closely as possible to the recommended values for Windows interfaces.
The default color of the form is light gray. Gray is easily distinguishable under different lighting conditions and avoids inconvenience for colorblind users. To differentiate between input and output, the input area uses white as the background color, making it easy for users to see that this is the active area of the form; the display area is set to gray (or the form's color) to indicate to the user that it is a non-editable area. All controls in the form are arranged left-aligned according to Windows interface design standards. For multiple groups of controls in different positions, each group is also left-aligned.
2. System Interface Layout Analysis
The layout design of a human-machine interface (HMI) should achieve simplicity, balance, and stylistic consistency according to ergonomic requirements. A typical industrial control interface consists of three parts: a title menu, a graphical display area, and buttons. Following the principle of consistency, all objects on the screen, such as windows, buttons, and menus, should maintain a consistent style. The size, embossing, and font of buttons at all levels should be consistent, and the button colors should match the background color of the interface.
3. Interface Structure
The concept of interface selection depends on the number of interfaces. Interfaces can be designed as loops; if a large number of interfaces are running, a reasonable structural system must be designed to open them. Choose a simple and permanent structure so that operators can quickly understand how to open the interface.
Users can only process a limited amount of information at a time, so piling up too much information on the screen can negatively impact the user experience. To provide sufficient information while maintaining a concise interface, a hierarchical and layered layout of controls was adopted in the design. Hierarchy refers to dividing controls into multiple groups based on their functions, and each group is further subdivided into multiple levels according to their logical relationships.
Using a primary button to control the pop-up and hiding of secondary buttons ensures a clean interface. Layering involves vertically expanding buttons of different levels into separate areas with clear boundaries between them. Using a specific button to pop up a lower-level button while hiding other buttons at the same level makes the logical relationships clearer.
Typically, it consists of three layers. Layer 1 is the overview interface. This layer contains information about the different system components displayed within the system, and how these system components work together. Layer 2 is the process interface. This layer contains detailed information about a specified process component and shows which device object belongs to that process component. This layer also displays the device object corresponding to an alarm. Layer 3 is the detail interface. This layer provides information about individual device objects, such as controllers, control valves, control motors, etc., and displays messages, status, and process values. If appropriate, it also includes information related to the operation of other device objects.
4. Application of text
Commonly used fonts in interface design include Chinese Song and Kai, and English Nitrogen, because these fonts are easy to recognize and have good readability. Considering consistency, all text in the console software interface uses Chinese Song font, and the font size is selected in two sizes according to the size of the control to make the displayed information clear and ensure a consistent style.
Ergonomics requires that interface text be concise, using affirmative sentences and active voice as much as possible, and avoiding abbreviations for English words. The text used in the console HMI falls into two categories: label text and interactive text. Label text is written on controls such as buttons, indicating the function of the control; therefore, it uses verbs describing operations, such as "set operation" and "system settings." Interactive text is the text required for interaction between humans and computers, as well as between computers and systems such as the main control console; it includes both input and output text.
To ensure conciseness and clarity, the interactive text uses familiar sentences and polite expressions, such as "Please check AC voltage" and "System warning: device locked." For large amounts of information, vertical scrolling is used instead of horizontal scrolling, as this is more in line with human operating habits.
5. Color selection
Color selection is also crucial in human-computer interface design. The human eye reacts to color faster than to text, so using color to distinguish different information is more effective than using text. Different colors evoke different physiological and psychological responses, so appropriate color selection can impact operator efficiency. Different colors have different effects in specific areas. For example, foreground colors should be brighter for easier user identification, while background colors should be darker to avoid eye strain.
Therefore, bright colors such as red, yellow, and grass green should not be used as background colors. Blue and gray are colors to which the human eye is less sensitive; the eye's sensitivity is the same whether the color is in the center or at the edge of the visual field, making them very suitable as background colors for human-computer interfaces. However, blue is not easily perceived in small areas, while red and yellow are very eye-catching. Therefore, signs for prompts and warnings should use red and yellow.
Several points should be noted when using colors:
(1) Limit the number of colors displayed at the same time. Generally, no more than 4 or 5 colors should be displayed on the same interface. Different layers and shapes can be used to match the changes in color.
(2) The colors of active objects in the interface should be bright, while those of inactive objects should be dark. The colors of objects should be different, with the foreground color being brighter and the background color being darker. Neutral colors (such as light gray) are often the best background colors. Light colors tend to jump to the foreground, while black makes people feel like they are receding into the background.
(3) Avoid putting incompatible colors together (such as yellow and blue, red and green, etc.) unless they are used for contrast.
6. Use of graphics and icons
Graphics and icons can convey information more vividly than text. The console's human-computer interface uses visualization technology to convert various data into graphics and images displayed in the graphic area. When selecting icons, simplicity and standardization are prioritized, with a focus on using standardized graphics and icons that have already been created and are widely accepted.
