Users are often frustrated when a touch screen monitor inaccurately records their touches. Enlarging touch sensitive regions improves touch accuracy, but few specific guidelines are available in the literature. A controlled field experiment determined the effect of target location and visual target size on user accuracy and empirically derived quantitative guidelines for determining touch target size based. on target location. The experiment was conducted in a grocery store using a piezo-electric monitor in a public access kiosk. Participants pressed the screen as target squares appeared one at a time. Visual target size, horizontal viewing location, and screen sector of target were varied. X and Y offset between the target center and the touch location were recorded. Results showed Significant differences caused by target sector in X offsets among columns and in Y offsets among rows, but no differences caused by target size. Results showed that persons tended to touch below the target, with touch distance increasing as the location of the target moved down the screen. To a lesser extent, persons tended to touch toward the sides of the screen. Using collected data for each of nine screen sectors, graphs were prepared showing the relationship between touch target size and expected accuracy under harsh conditions. These empirically derived, quantitative guidelines will help designers plan for the worst case and create screens that decrease user errors and frustration. / Master of Science

This research was part of a program sponsored by the Army Electronics Research and Development Command. The program goals are to develop a generic input/output device based on a 4- x 8-in electroluminescent flat panel display coupled with a touch sensitive input device. The primary purpose of this dissertation was to evaluate the six major manufacturers' implementation of the three most common technologies for touch screens. The evaluation was based on operator performance. The three technologies represented in the research were IR beam matrix switches, conductive membrane switches, and transparent capacitance switches. A secondary goal of the research was to establish a link between measurable hardware parameters of any touch sensitive device (TSO) and operator performance. These parameters were then used to build models of operator performance under a variety of conditions. The primary goal of technology evaluation was approached through two experiments based on two generic types of tasks typical of current and expected TSD applications. These experiments compared six different TSDs from different manufacturers across varying conditions of lighting, viewing angle, and touch target dimensions. The secondary goal of TSD performance modeling was accomplished through careful measurement of many image quality and touch sensing characteristics of the six TSDs and subsequent construction of stepwise linear regression models of user performance. These models were built using the performance data collected in the first part of the evaluation. Results from the performance comparison revealed that across tasks and conditions, one device of the IR beam technology was found to be the best performer. Another device of the same technology was equivalent in reading aspects of performance but inferior with respect to touch inputting performance. This performance difference was hypothesized to be due to differences between these two devices in touch sensor parallax. The linear regression modeling effort resulted in the identification of several hardware parameters which are important to TSD user performance. Additionally, models of performance under specific conditions were developed which accounted for most of the variation observed in the performance data. / Ph. D.

The touchscreen user interface is an inherently dynamic device that is becoming ubiquitous. The touchscreen’s ability to adapt to the user’s needs makes it superior to more traditional haptic devices in many ways. Most touchscreen devices come with a very large array of sensors already included in the package. This gives engineers the means to develop human-machine interfaces that are very intuitive to use. This thesis presents research that was done to develop a best touchscreen interface for driving an industrial crane for novice users. To generalize the research, testing also determined how touchscreen interfaces compare to the traditional joystick in highly dynamic tracking situations using a manual tracking experiment. Three separate operator studies were conducted to investigate touchscreen control of cranes. The data indicates that the touchscreen interfaces are superior to the traditional push-button control pendent and that the layout and function of the graphical user interface on the touchscreen plays a roll in the performance of the human operators. The touchscreen interface also adds great promise for allowing users to navigate through interactive textbooks. Therefore, this thesis also presents developments directed at creating the next generation of engineering textbooks. Nine widgets were developed for an interactive mechanical design textbook that is meant to be delivered via tablet computers. Those widgets help students improve their technical writing abilities, introduce them to tools they can use in product development, as well as give them knowledge in how some dynamical systems behave. In addition two touchscreen applications were developed to aid the judging of a mechanical design competition.