Examining the size-weight illusion with visuo-haptic conflict in immersive virtual reality.

This is the author accepted manuscript. The final version is available from SAGE Publications via the DOI in this record.When we experience our environment, we do so by combining sensory inputs with expectations derived from our prior knowledge, which can lead to surprising perceptual effects such as small objects feeling heavier than equally weighted large objects (the size-weight illusion (SWI)). Interestingly, there is evidence that the way in which the volume of an object is experienced can affect the strength of the illusion, with a SWI induced by exclusively haptic volume cues feeling stronger than a SWI induced with only visual volume cues. Furthermore, visual cues appear to add nothing over and above haptic size cues in terms of the strength of the induced weight illusion-findings which are difficult to reconcile with work using cue-conflict paradigms where visual cues usually dominate haptic cues. Here, virtual reality was used to place these senses in conflict with one another. Participants ( N = 22) judged the heaviness of identically weighted cylinders across three conditions: (1) objects appeared different sizes but were physically the same size, (2) objects were physically different sizes but appeared to be the same size, or (3) objects which looked and felt different sizes from one another. Consistent with prior work, haptic size cues induced a larger SWI than that induced by visual size differences. In contrast to prior work, however, congruent vision and haptic size cues yielded a larger still SWI. These findings not only add to our understanding of how different modalities combine to influence our hedonic perception but also showcase how virtual reality can develop novel cue-conflict paradigms

Soft volume simulation using a deformable surface model

The aim of the research is to contribute to the modelling of deformable objects, such as soft tissues in medical simulation. Interactive simulation for medical training is a concept undergoing rapid growth as the underlying technologies support the increasingly more realstic and functional training environments. The prominent issues in the deployment of such environments centre on a fine balance between the accuracy of the deformable model and real-time interactivity. Acknowledging the importance of interacting with non-rigid materials such as the palpation of a breast for breast assessment, this thesis has explored the physics-based modelling techniques for both volume and surface approach. This thesis identified that the surface approach based on the mass spring system (MSS) has the benefits of rapid prototyping, reduced mesh complexity, computational efficiency and the support for large material deformation compared to the continuum approach. However, accuracy relative to real material properties is often over looked in the configuration of the resulting model. This thesis has investigated the potential and the feasibility of surface modelling for simulating soft objects regardless of the design of the mesh topology and the non-existence of internal volume discretisation. The assumptions of the material parameters such as elasticity, homogeneity and incompressibility allow a reduced set of material values to be implemented in order to establish the association with the surface configuration. A framework for a deformable surface model was generated in accordance with the issues of the estimation of properties and volume behaviour corresponding to the material parameters. The novel extension to the surface MSS enables the tensile properties of the material to be integrated into an enhanced configuration despite its lack of volume information. The benefits of the reduced complexity of a surface model are now correlated with the improved accuracy in the estimation of properties and volume behaviour. Despite the irregularity of the underlying mesh topology and the absence of volume, the model reflected the original material values and preserved volume with minimal deviations. Global deformation effect which is essential to emulate the run time behaviour of a real soft material upon interaction, such as the palpation of a generic breast, was also demonstrated, thus indicating the potential of this novel technique in the application of soft tissue simulation

Human factors considerations for ultrasound induced mid-air haptic feedback

The engineering design process can be complex and often involves reiteration of design activities in order to improve outcomes. Traditionally, the design process consists of many physical elements, for example, clay/foam modelling and more recently Additive Manufacturing (AM), with an iterative cycle of user testing of these physical prototypes. The time associated with creating physical prototypes can lengthen the time it takes to develop one product, and thus, comes at a burdensome financial and labour cost. Due to the aforementioned constraints of the conventional design process, more research is being conducted into applications of Virtual Reality (VR) to complement stages of the design process that would otherwise take and cost a significant amount of time and money. VR enables users to create 3D virtual designs and prototypes for evaluation, thus facilitating the rapid correction of design and usability issues. However, VR is not without its pitfalls, for example, it often only facilitates an audio-visual simulation, thus hindering evaluation of the tactile element of design, which is critical to the success of many products. This issue already has a wide body of research associated with it, which explores applications of haptic (tactile) feedback to VR to create a more realistic and accurate virtual experience. However, current haptic technologies can be expensive, cumbersome, hard to integrate with existing design tools, and have limited sensorial output (for example, vibrotactile feedback). Ultrasound Haptic Feedback (UsHF) appears to be a promising technology that offers affordable, unencumbered, integrable and versatile use. The technology achieves this by using ultrasound to create mid-air haptic feedback which users can feel without being attached to a device. However, due to the novel nature of the technology, there is little to no literature dedicated to investigating how users perceive and interpret UsHF stimuli, and how their perception affects the user experience. The research presented in this thesis concerns the human factors of UsHF for engineering design applications. The PhD was borne out of interest from Ultraleap (previously Ultrahaptics), an SME technology developer, on how their mid-air haptic feedback device could be used within the field of engineering. Six studies (five experimental and one qualitative) were conducted in order to explore the human factors of UsHF, with a view of understanding its viability for use in engineering design. This was achieved by exploring the tactile ability of users in mid-air object size discrimination, absolute tactile thresholds, perception of intensity differences, and normalisation of UsHF intensity. These measures were also tested against individual differences in age, gender and fingertip/hand size during the early stages, with latter stages focussing on the same measures when UsHF was compared to 2D multimodal and physical environments. The findings demonstrated no evidence of individual differences in UsHF tactile acuity and perception of UsHF stimuli. However, the results did highlight clear limitations in object size discrimination and absolute tactile thresholds. Interestingly, the results also demonstrated psychophysical variation in the perception of UsHF intensity differences, with intensity differences having a significant effect on how object size is perceived. Comparisons between multimodal UsHF and physical size discrimination were also conducted and found size discrimination accuracy of physical objects to be better than visuo-haptic (UsHF) size discrimination. Qualitative studies revealed an optimistic attitude towards VR for engineering design applications, particularly within the design, review, and prototyping stages, with many suggesting the addition of haptic feedback could be beneficial to the process. This thesis offers a novel contribution to the field of human factors for mid-air haptics, and in particular for the use of this technology as part of the engineering design process. The results indicate that UsHF in its current state could not offer a replacement for all physical prototypes within the design process; however, UsHF may still have a place in the virtual design process where haptic feedback is required but is less reliant on the accurate portrayal of virtual objects, for example, during early stage evaluations supplemented by later physical prototypes, simply to indicate contact with virtual objects, or when sharing designs with stakeholders and multidisciplinary teams

Soft volume simulation using a deformable surface model

The aim of the research is to contribute to the modelling of deformable objects, such as soft tissues in medical simulation. Interactive simulation for medical training is a concept undergoing rapid growth as the underlying technologies support the increasingly more realstic and functional training environments. The prominent issues in the deployment of such environments centre on a fine balance between the accuracy of the deformable model and real-time interactivity. Acknowledging the importance of interacting with non-rigid materials such as the palpation of a breast for breast assessment, this thesis has explored the physics-based modelling techniques for both volume and surface approach. This thesis identified that the surface approach based on the mass spring system (MSS) has the benefits of rapid prototyping, reduced mesh complexity, computational efficiency and the support for large material deformation compared to the continuum approach. However, accuracy relative to real material properties is often over looked in the configuration of the resulting model. This thesis has investigated the potential and the feasibility of surface modelling for simulating soft objects regardless of the design of the mesh topology and the non-existence of internal volume discretisation. The assumptions of the material parameters such as elasticity, homogeneity and incompressibility allow a reduced set of material values to be implemented in order to establish the association with the surface configuration. A framework for a deformable surface model was generated in accordance with the issues of the estimation of properties and volume behaviour corresponding to the material parameters. The novel extension to the surface MSS enables the tensile properties of the material to be integrated into an enhanced configuration despite its lack of volume information. The benefits of the reduced complexity of a surface model are now correlated with the improved accuracy in the estimation of properties and volume behaviour. Despite the irregularity of the underlying mesh topology and the absence of volume, the model reflected the original material values and preserved volume with minimal deviations. Global deformation effect which is essential to emulate the run time behaviour of a real soft material upon interaction, such as the palpation of a generic breast, was also demonstrated, thus indicating the potential of this novel technique in the application of soft tissue simulation.EThOS - Electronic Theses Online ServiceUniversiti Malaysia Sarawak (UMS)Malaysia. Jabatan Perkhidmatan Awam (JPA)Malaysia. Kementerian Pengajian Tinggi (KPT)GBUnited Kingdo

Human factors considerations for ultrasound induced mid-air haptic feedback

The engineering design process can be complex and often involves reiteration of design activities in order to improve outcomes. Traditionally, the design process consists of many physical elements, for example, clay/foam modelling and more recently Additive Manufacturing (AM), with an iterative cycle of user testing of these physical prototypes. The time associated with creating physical prototypes can lengthen the time it takes to develop one product, and thus, comes at a burdensome financial and labour cost. Due to the aforementioned constraints of the conventional design process, more research is being conducted into applications of Virtual Reality (VR) to complement stages of the design process that would otherwise take and cost a significant amount of time and money. VR enables users to create 3D virtual designs and prototypes for evaluation, thus facilitating the rapid correction of design and usability issues. However, VR is not without its pitfalls, for example, it often only facilitates an audio-visual simulation, thus hindering evaluation of the tactile element of design, which is critical to the success of many products. This issue already has a wide body of research associated with it, which explores applications of haptic (tactile) feedback to VR to create a more realistic and accurate virtual experience. However, current haptic technologies can be expensive, cumbersome, hard to integrate with existing design tools, and have limited sensorial output (for example, vibrotactile feedback). Ultrasound Haptic Feedback (UsHF) appears to be a promising technology that offers affordable, unencumbered, integrable and versatile use. The technology achieves this by using ultrasound to create mid-air haptic feedback which users can feel without being attached to a device. However, due to the novel nature of the technology, there is little to no literature dedicated to investigating how users perceive and interpret UsHF stimuli, and how their perception affects the user experience. The research presented in this thesis concerns the human factors of UsHF for engineering design applications. The PhD was borne out of interest from Ultraleap (previously Ultrahaptics), an SME technology developer, on how their mid-air haptic feedback device could be used within the field of engineering. Six studies (five experimental and one qualitative) were conducted in order to explore the human factors of UsHF, with a view of understanding its viability for use in engineering design. This was achieved by exploring the tactile ability of users in mid-air object size discrimination, absolute tactile thresholds, perception of intensity differences, and normalisation of UsHF intensity. These measures were also tested against individual differences in age, gender and fingertip/hand size during the early stages, with latter stages focussing on the same measures when UsHF was compared to 2D multimodal and physical environments. The findings demonstrated no evidence of individual differences in UsHF tactile acuity and perception of UsHF stimuli. However, the results did highlight clear limitations in object size discrimination and absolute tactile thresholds. Interestingly, the results also demonstrated psychophysical variation in the perception of UsHF intensity differences, with intensity differences having a significant effect on how object size is perceived. Comparisons between multimodal UsHF and physical size discrimination were also conducted and found size discrimination accuracy of physical objects to be better than visuo-haptic (UsHF) size discrimination. Qualitative studies revealed an optimistic attitude towards VR for engineering design applications, particularly within the design, review, and prototyping stages, with many suggesting the addition of haptic feedback could be beneficial to the process. This thesis offers a novel contribution to the field of human factors for mid-air haptics, and in particular for the use of this technology as part of the engineering design process. The results indicate that UsHF in its current state could not offer a replacement for all physical prototypes within the design process; however, UsHF may still have a place in the virtual design process where haptic feedback is required but is less reliant on the accurate portrayal of virtual objects, for example, during early stage evaluations supplemented by later physical prototypes, simply to indicate contact with virtual objects, or when sharing designs with stakeholders and multidisciplinary teams

Gestaltung visuell-haptischer Telepräsenz- und Teleaktionssysteme mittels psychologischer Grundlagen

Vor dem Hintergrund multimodaler Displays zukünftiger TPTA-Systeme wurde in dieser Arbeit die unimodal haptische und bimodale visuell-haptische Wahrnehmungsfähigkeit des Menschen beim Explorieren unterschiedlicher Materialproben untersucht und das menschliche Auflösungsvermögen in Abhängigkeit der Variation physikalischer Parameter bestimmt. Hierzu waren als relevante Materialeigenschaften Textur, bzw. Körnigkeit, und Härte, bzw. Nachgiebigkeit, sowie als bestimmende geometrische Eigenschaft, die Objektkante, ausgewählt worden