Abstract
When a ship sails in rough water, severe ship motions limited the crew’s ability to perform command, control, communication, and navigation tasks. Therefore, the crew’s task performance is affected as a result of motion sickness, fatigue, lost of balance or degraded human abilities (e.g., perception, cognition, and motor ability) caused by motions. These negative effects especially occur in military operations. In military situation, matters of life or death may be decided in milliseconds. Stress and time load are very high and any delay or failure of task (e.g. classification and identification) will thus affect the safety of the ship and its crew. Hence, designing interfaces which are robust to the motions is an effectiveness approach to reduce these negative effects on human-machine interaction aboard.This study conducted three experiments to investigate the effects of motions on visual and manual control performance. The first experiment investigated a multi-response problem in terms of searching time, number of missing characters/buttons (NMCB), and visual fatigue by integrating the Taguchi method and the weighting method (Analytical Hierarchy Process, AHP) to optimize the Chinese interface design parameters (control factors) such as display type, character size, font type, and text/background color combination in motion environments (noise factor). The results indicated that subjects’ visual performance was improved when using the optimum interface setting (LCD, 7.5 * 7.5 mm, Kai font and white/blue color combination) rather than the current interface setting (CRT, 6.5 * 6.5 mm, Kai font and black/gray color combination).The second experiment with twelve men compared their performance of using four input devices (three trackballs: currently used trackball, trackwheel and erectly held trackballs as well as a touch screen) under five motion conditions of static, heave, roll, pitch and random movements. The input device and motion direction significantly affected the movement speed and accuracy, and their interaction significantly affected the movement speed. The touch screen was the fastest but the least accurate input device. The erectly held trackball was the slowest, whereas the error rate of the currently used trackball was the lowest. The impairments of the random motion on movement time and error rate were larger than those of other motion directions. The subjective assessment of the effects of motion direction was similar to the objective evaluation which the effect of random direction was the biggest, roll and pitch motions were larger than the static and heave motions. Taking the objective and subjective evaluations into account, the trackman wheel and currently used trackball were more efficient for operation than the erectly held trackball and touch screen under the motion environments.The third experiment extended the result of the second experiment by using the selected trackball, trackman wheel trackball, as the input device with four platform motions (static, heave, roll and pitch) and different orientations of onscreen targets (0o, 45o, 90o, 135o, 180o, 225o, 270o and 315o) to investigate the performance of using trackball to execute the simple point-and-click task in a motion simulator. The results indicated that the direction of platform motion and target orientation both significantly affect the time required to point and click, but not the accuracy of target selection. The movement times were considerably longer under rolling and pitching motions, and for targets located along the diagonal axes of the interface. Subjective evaluations carried out by the participants agree with these objective results. These findings could be used to optimize console and graphical menu design for use on maritime vessels.The results of the present study not only help the designer to develop and modify the current Chinese interface and to select a better input device which is suitable for using in motion environments, but also provide a method for designer to integrated consideration of multiple responses and design parameters at a time, and the selection and arrangement of console location as well as the arrangement of on-screen target orientation. Furthermore, an expert duty officer can use this knowledge to adjust the speed and heading of the ship to mitigate the effects of ship motion on manual control tasks.In order to increase the performance and reduce the motion effects on point-and-click task on aboard and solve the capacity limit in heave of the Stewart motion platform, future research should investigate the optimal gain value of the trackball and the target size of the touch screen, and combine the virtual reality with platform motion.