PEDAGOGÍA DEL AFECTO:

Because of their dynamic interface, stable operation and reconfigurable controls, touchscreens are often used as control panels for industrial automation within environments where dirt, dust and fluids are prevalent. A touchscreen can provide an intuitive interface in which the options available can be clustered in a number of layers, and only the options relevant to the task in hand at the time are displayed. However, if there is a lack of multisensory feedback, especially tactile feedback, a touch-enabled control panel will have to rely heavily on visual feedback in an audio-

visually distracting industrial working environment. Acoustic feedback can often be drowned out by the background noise of the environment. Thus, tactile feedback offers a useful way of ex- ploiting a further sensory channel to help improve user confidence and working efficiency in a conventional touchscreen.

In harsh industrial environments, touchscreens needs to be resistant to scratches, breakage and accidental spillage, and have to withstand fluid splashes and aggressive cleaning; they must also be capable of being activated directly by a gloved hand, a stylus or a bare finger. Thus, resistive touch sensors and surface wave touch sensors are viable options for applications typical of indus- trial automation system. Such applications range from a low-priced entry-level solution with a 6- inch portable touchscreen display to cover basic requirements, to a powerful panel PC with a 19- inch touchscreen to meet high performance requirements. In these solutions, the touchscreen interface may constitute either part or all of the interactive display.

A sample scenario takes place in a beverages plant where Mr. Chambers works on an automated mineral juice bottling line. Bottles are collected from a stainless steel conveyor by a turret wheel, which carries them to a filling station for volumetric dosing and piston filling. The dosing vol- ume is electronically controlled using flow meters, which Mr. Chambers has preset on the touch- screen-based control panel. He uses the same touchscreen to select the bottom-down filling op- tion at the filling station. Once the bottles are filled, the turret wheel transports them to a capping station where each bottle has a cap placed on it ready to tighten. For the tightening station, Mr. Chambers selects screw-capping and multiple bottles from the options of screw-capping, press- capping, and single and multiple bottles. When tightening is complete, the turret wheel carries the capped bottles to an outlet conveyor for final packaging.

When operating a touch control panel in this kind of machine control applications, users have to make decisions and accomplish tasks depending on the information and notifications they re- ceived. This generally involves manipulating controls and operating functions on the user inter- face and entering characters into the system. A keyboard layout will need to be selected that is suitable with respect to input content (e.g. numerical or alphabetical input) and available screen space (e.g. a standard QWERTY layout is likely to occupy too much space on a small-size touchscreen). A full-size QWERTY keyboard may actually decrease character input efficiency on a touchscreen in a workshop, which is especially critical where mechanics who have to resort to single-tap input from among a large amount of characters suffer an increased cognitive load from using the control panel screen and lose concentration on what the machine is doing. In this case, a keyboard with less keys, such as twelve-key keypad, could be used to save screen space while still being intuitive to manipulate. As the means of entering characters on a touchscreen, a virtual screen keyboard (see Figure 55 (a)), a membrane key keyboard (see Figure 55 (b)) or physical buttons (see Figure 55 (c)) can be designed to be called up when required or to be per- manently available on the interface. Soft keys or virtual keys - simulated keys displayed on- screen – often employ on touchscreens to graphically render physical UI controls such as but- tons. These keys can easily be changed in size, style and appearance according to the type of interaction, the context of use and the available screen real estate. Physical keys can be also inte-

grated into touchscreen systems for very frequently used or emergency function such as power on/off and alert.

(a) 12-key keypad (b) Touchscreen with integrated

keypad (c) SIMATIC HMI PRO with exten-sion units

Figure 55: Varying keyboards for character input and for control functions7

Tactile effects added into touchscreens will not be degraded by a harsh industrial environment. On the contrary, they provide the instantaneous confirmation of communication with process and machine control systems while alleviating the visual and auditory burden, and offer a more me- chanical-like behavior to improve the usability of touch solutions for control panels. Tactile feedback on a touchscreen not only necessitates fewer repeated and less forceful taps in compari- son with pressing a touchscreen with a hard and unresponsive surface, but also allow smaller on- screen controls at the same time as reducing reliance on visual feedback cues. However, it is also necessary to consider adapting the design of tactile effects to deliver suitable performance under conditions of ambient vibration in a workshop.

Usage-based design helps in envisioning tactile touchscreen-based UIs pragmatically and sys- tematically. Based on use context and on available technology, tactile touchscreens used for pri- mary tasks in the two applications described above can be developed by defining set of on-screen widgets for direct manipulation. A series of tasks are then accomplished by touching (with the feel of pressing and releasing) an area of a screen that is usually implemented with graphical UI controls. Sometimes mechanical buttons can be integrated into a touchscreen for certain special tasks such as numeric input or alarm management. Feedback as to what is happening on the user interface can be displayed on a status bar or by a new content conveyed through tactile cues such as vibration or impulse emission to reduce glance time. Matched tactile feedback can make a touchscreen system easy to learn, efficient to work with and pleasant to use. The selection of a suitable solution for a tactile touchscreen will also depend on how the user employs the system to accomplish tasks, in what working environment the tasks are executed, whether gloves are used, and how expensive the touchscreen solution can be. A touchscreen-based design incorpo-

rating tactile feedback needs to consider realistic use context and users’ capabilities, as well as user behavior and experience as determined by analysis and modeling of well-specified tasks.

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Haptically enhanced touchscreen used for a secondary