Discrimination of trackball-produced forces

The ability of subjects to discriminate forces counter to user movement generated from a trackball with force feedback was examined as an underlying factor in the interpretation of tactually displayed forms. Subjects were required to report, using an adaptive two-alternative forced-choice method (2AFC), which of two sequentially presented stimuli felt weaker. In the first experiment, three reference force levels of 0.88 N, 0.99 N and 1.10 N by three movement displacements of 20°, 40° and 60° were presented. A second experiment was conducted to examine discrimination from reference forces below 0.88 N and to consider the influence of movement orientation. Results from two experiments indicated that ‘just noticeable differences’ (JNDs) in a range from 0.4 to 1.1 N were relatively constant at a level of 15%. In the lower force range, 0.2-0.4 N, JNDs were observed to increase with decreasing force level. The movement amplitude and orientation, whether horizontal or vertical, appeared to have no effect on the observed JND. The experiments showed that the discrimination of forces correlated with the subject's movement speeds within the upper force range

Dynamic cursor gain and tactual feedback in the capture of cursor movements

Recent research involving a trackball with force feedback has demonstrated that tactile feedback can enhance the acquisition of targets in graphical user interfaces in terms of movement times and errors. The present study seeks to explore the degree to which tactual feedback over a target, in contrast to changes in the display/control gain over the target, influences target acquisition performance. Tactual feedback over a target is felt as a pulling force towards the centre of a target, with a counterforce applied when moving out of the centre. Changes in the cursor gain can be used to create a cursor-catching effect by requiring more movement effort of the control device to leave than to enter the target centre, without increasing the total amount of effort to enter and leave the target area. User movement in entering a target is thus braked by the change in cursor gain. Results of an experiment indicated that target acquisition performance was generally higher in the tactual feedback condition, followed by cursor gain feedback, in comparison with no-cursor gain feedback. User interface design issues as related to gain feedback in visual interfaces and tactual feedback over targets are considered

Dynamic control gain and tactile feedback in the capture of cursor movements

Recent research at IPO involving a trackball with force feedback has demonstrated that tactile feedback can enhance the acquisition of targets in graphical user interfaces in terms of movement times and errors. The present study seeks to explore the degree to which being able to feel a target in contrast with changes in the display/control gain, over the target, influences movement performance. Tactile feedback over a target is felt as a pulling force towards the centre of a target, with counterforces applied when moving out of the centre. Changes in the target gain can create a cursor-catching effect by requiring more movement of the control device to enter than to leave the centre of the target. Results of an experiment indicated that target acquisition performance was generally higher in the tactile feedback condition, followed by target gain feedback, in comparison with no-target gain feedback. User interface design issues are discussed in respect to gain and tactile feedback

Estimation of virtually perceived distance

Increasingly, information is presented to users in a spatial domain where distances and orientation between objects imply some meaning. One's perception of distances between objects may be influenced by actual movement through space. Distances may be represented by visual, tactual, or auditory means. The current paper considers the relationship between the judgment of linear path distances which were presented either tactually, visually, or visually and tactually to subjects. Tactual paths were virtually created using force feedback fields. Additionally, the influence was examined of a constant simulated-friction force in terms of distance judgments. Based on the method of direct estimation ofmagnitude, a high correlation between tactual and visual estimates for eight path lengths was found. The results of the tactual condition with simulated friction indicated that the perceived distance between tactual objects can be manipulated without requiring longer movements of an input device. In general, results indicated that the spatial relations between objects can be accurately communicated by virtual tactual paths, which allows for the creation of dynamic spatial relations between user-interface elements

Talking about implications for design in pattern language

In this paper we present our approach to capture and share knowledge from field studies using pattern language and hereby inform the design of ubiquitous computing. In our case, we studied frontline firefighting by observing the existing practice, by developing empathy through participation and by introducing new technology as triggering artifacts. Applying grounded theory, we distilled our findings into pattern language describing core aspects of this practice and their interaction. In a workshop, we introduced the pattern language to developers who had no previous knowledge of this practice and, in follow-up interviews, confronted them with new technology proposals for firefighters. Our study shows that pattern language, while not to be confused with an immutable description of the status quo or a direct path from contextual analysis to design, supports a reflective discussion of novel technology and the fit with and potential impact on existing practice

TacTool: a tactile rapid prototyping tool for visual interfaces

This paper describes the TacTool development tool and input device for designing and evaluating visual user interfaces with tactile feedback. TacTool is currently supported by the IPO trackball with force feedback in the x and y directions. The tool is designed to enable both the designer and the user to apply and create tactile fields in a user interface with no knowledge of computer programming. The user works with a set of tactile object fields called TouchCons™ and visual representations to build a graphical interface with tactile feedback. Direct manipulation of objects enables creation of new complex fields which can be used for informational and navigational purposes. For example, the user can use a “path” object to draw a road which can be subsequently felt as a tactile channel, or a “hole” object which contains forces towards the centre of the hole. Tactile fields can be placed while an application is running; for example, a “tactile marker” can be placed to mark a significant point. A pulling force back towards this point can be always active or produced upon request. In addition to tactile feedback, TouchCons™ can provide active movement cues. For example, a “hint” field is used to a create tactile directional cue which is a system-driven ball movement. Tactile information can thus be used to support a two-way communication channel between the system and user

Angle discrimination for a tactile point stimulus moving across the fingerpad

The ability of subjects to discriminate between directions of a point contact moving across the fingerpad was examined. Subjects were required to report, using an adaptive two-interval, two-alternative forced-choice procedure, whether in two sequential stimuli, the apparent direction of motion changed in a clockwise or counter-clockwise direction. The overall mean discrimination threshold across eight stimulus orientations was approximately 14°, with the lowest threshold for the point motion towards the wrist. The results indicate that the lower threshold in the distal-to-proximal direction was most likely due to increased skin tension at the tip of the nail, whereby the skin in front of a moving contact point is subjected to compression and the skin behind the point (including where it is anchored to the fingernail) is subjected to tension. Thresholds across orientations were in general more uniform and higher for horizontal and vertical orientations than those reported for vibro-tactile linear contactor arrays

Angle discrimination for a tactile point stimulus moving across the fingerpad

The ability of subjects to discriminate between directions of a point contact moving across the fingerpad was examined. Subjects were required to report, using an adaptive two-interval, two-alternative forced-choice procedure, whether in two sequential stimuli, the apparent direction of motion changed in a clockwise or counter-clockwise direction. The overall mean discrimination threshold across eight stimulus orientations was approximately 14°, with the lowest threshold for the point motion towards the wrist. The results indicate that the lower threshold in the distal-to-proximal direction was most likely due to increased skin tension at the tip of the nail, whereby the skin in front of a moving contact point is subjected to compression and the skin behind the point (including where it is anchored to the fingernail) is subjected to tension. Thresholds across orientations were in general more uniform and higher for horizontal and vertical orientations than those reported for vibro-tactile linear contactor arrays