Eui S. Jung

Generation of visual fields for ergonomic design and evaluation

Abstract Among numerous factors that have an effect on the visual field, the effects of background conditions on the size of the visual field were investigated to obtain more practical visual fields that can be readily applicable to industrial settings. An experiment was conducted, in which the subject was instructed to search for a target with distinct orientations. Size contrast, nontarget density, and meridian, as experimental variables, showed a significant effect on the size of the visual field at α =0.01. The size of the three types of visual fields; stationary, eye, and head and eye fields, was linearly proportional to size contrast, and inversely proportional to nontarget density. The size of the visual fields on the horizontal axis was larger than that on the vertical axis, and the size of the head and eye field on the right meridian was also larger than that on the left meridian. The shape was found to be horizontally oriented oval and statistically non-symmetric with respect to both horizontal and vertical axes. The regression equations to predict the visual fields on the given background condition were suggested. The visual fields suggested in the study would be valuable to the design of visual displays and the panel layout of various displays and controls. Relevance to industry Guidelines to the design of displays, controls, and panel layouts are of great importance to designers in order to provide an ergonomically sound working environment to operators. In addition to the operators anthropometry and task geometry, design factors that ensure proper interfaces would be a key element to successful design. Among the factors, operators visual field has rarely been suggested in a practically applicable format. This study provides the designer with useful guidelines to the interface design of visual displays and panel layouts.

Modeling of Wrist Discomfort with External Loads

The objectives of this study are to analyze representative wrist postures while using hand tools and parts at general assembly processes, to evaluate perceived discomfort on the wrist when external loads are present, and to suggest an evaluation and prediction model of perceived discomfort. Sixteen subjects participated in an experiment to appraise perceived discomfort. Three types of the wrist postures with five levels of non-neutralities were analyzed when five levels of external load were applied to each posture. The ANOVA results showed that the perceived discomfort of wrist postures was significantly affected by both the wrist posture and external load (p<0.001). It was also shown that some of the interactions between external loads and the wrist postures(Flexion/Extension*Load, Flexion/Extension*supination/pronation, ulnar/radial deviation*supination/pronation) were significant(p<0.001). The result implies that a new posture classification scheme for workload assessment methods may be needed to reflect such effects of external load and wrist posture. A regression model of perceived discomfort was developed with respect to wrist posture and external load from the experimental data. A subsequent experiment revealed that the correlation coefficient between the predicted values of perceived discomfort from the model and the actual values obtained from the experiment was about 0.98. It is expected that the results help to properly estimate the body stress resulting from workers postures and external loads and can be used as a valuable design guideline to analyze potential hazard of musculoskeletal diseases in industry.

A cross-cultural user evaluation of the prototype extremity MRI

The proposed ergonomic design guidelines for the new extremity MRI led to the development of a prototype MRI. A cross-cultural user evaluation was conducted to guarantee the adequacy of the prototype for both Korean and Caucasian populations from 5th percentile female to over 95th percentile male potential patients. First, a scenario of MRI usage was defined from the chair setting, patient seating, scanning, and the egress of a patient. The user evaluation was done to measure participants’ local and whole body discomfort for the combinations of scanning types and durations, specifically focusing on the ingress and egress of the participant and the whole duration of scanning. The statistical analyses revealed that no significant change in discomfort was observed up to 40 min of scanning duration. Since no electrical adjustments can be implemented due to magnetic interferences, it is noted that existing mechanical adjustments caused local discomfort to certain extreme population of patients in specific body postures. Thus, a set of modifications of the design was suggested in terms of supplementary supporters.

An ergonomic user interface design for a new extremity MRI focusing on the patient chair

Ergonomic design guidelines for the new development of an extremity MRI have been developed to minimize patient’s postural discomfort on different scanning types with a specific focus given to the patient chair and leg supporter. The research started with a known zero gravity position as an optimal body posture and did a market survey on various industrial chairs. Based on the anthropometric characteristics of the populations being considered, the comfortable ranges of the dimensions and angles were defined for four scanning types: knee, ankle, elbow and wrist scannings. In order to validate these guidelines, a simple mockup was made and tested for a group of participants. The test was to find out 3-dimensional comfortable postures of 14 participants with respect to the scanning type and scanning duration, which subsequently yielded design dimensions and adjustable ranges of angles for MRI bore and exterior, chair and leg supporter.

Effective quality factors of multimodal interaction in simple and complex tasks of using a smart television

Influencing quality factors, related to the user and system, need to be considered when building a well-designed multimodal interaction system. User groups, access to input modes and tasks were defined as the user and system factors to examine effective factors of multimodal interaction with a smart TV, and its input modes consisted of voice, arrow key, and motion-based pointer modes and their combinations. User group 1 had experience of multimodal interaction with another device, while user group 2 had only experience of unimodal interaction. In addition, the sequential/simultaneous input modes and simple/complex tasks were considered as the system factors. Depending on the task complexity, two experiments were conducted. Nine input modes (three unimodes and six multimodes), sequentially and simultaneously given to both user groups, were investigated for the simple task of menu traversal and the complex task of manipulating broadcasting content, menu traversal, and web content navigation. A subjective rating of the level of preference was recorded in the sequential input mode using a modified Likert-type rating scale, while each participant’s preferred mode was observed in the simultaneous scenario. Additionally, the completion time and error rate were measured in both experiments. When performing the simple task, user group 1 used multimodes more so than group 2. However, in the complex task, both user groups preferred multimodes when modes were simultaneously presented. Considering effective quality factors, input modes of a smart TV should be simultaneously provided with a voice and motion-based pointer multimode.

An Ergonomic Shape Design for Automotive Push-Return Switches

Objective: The objective of this study is to understand the effect of angle and curvature of push-return switches, which are external factors in the operation environment inside the cars, on the feel of operation and to propose optimum alternatives. Background: Customers needs for products are changing from functional and performance aspects to customer-led type where customers can reflect on their needs on the products. The operation inside cars is executed by HMI. The push-return switch is utilized as the most intuitive mode of HMI; therefore, this push-return switch, which is widely used, has to be developed by assessing the preference and satisfaction of the customer. Method: The angle and curvatures, which are external factors that affect the feel of operation, are drawn through surveying the preceding research literatures. The stages to construct alternatives in experiments are as follows: (1) the tactile switch is replaced after dismantling the switch assembly to evaluate the internal characteristics proposed by preceding researches, (2) a drawing is prepared by using a design software, is printed using 3D printer, and then it is attached on the switch assembly, and (3) evaluation for satisfaction of operation is carried out by using a driving simulator. Results: Both the angle and curvature that are external factors of switch significantly affect the feel of operation. However, interaction between the two factors is found insignificant. Therefore, an optimum alternative is proposed considering the experimental outcomes. Conclusion: This study evaluates the satisfaction in operation that affects the feel of operation environment inside the cars. Based on the study results, a guideline for switch design in the center fascia is proposed. Application: This study is expected to be used as basic data for designing automotive switches, as well as switches in the industries similar with the operation environments of cars.

Input Behavior When Using Two Fingers on a Multi-Touch Device

ABSTRACT The purpose of this study is to analyze device input patterns using fingers in multi-touch mode and to derive Fitts’ law for multi-touch methods. Three specific input behaviors—dragging, rotating, and pinching—are investigated. Test participants performed two Fitts’ law experiments, a single-touch experiment using the thumb only and a multi-touch experiment using both the thumb and index finger. Within-subject factorial design was implemented with two levels of touch behavior (single-touch) and three levels of touch behavior (multi-touch), six levels of the index of difficulty (ID), four levels of direction, and two levels of repetition. The results indicate that a revised model of Fitts’ law is more appropriate for the multi-touch mode, achieving R2 values above 0.895, and identifying the best nonlinear model among several regression models. The results of this study are used to determine the relationship between ID and movement time in terms of Fitts’ law and to investigate whether this relationship is sufficient to serve as a model to predict movement times. This study contributes to the prediction of movement times for products with multi-touch interfaces.