图像局部纹理特性的静电力触觉渲染

目的 触摸触觉设备感知物体时,需要实现视觉-力触觉同步反馈,其中图像-力触觉反馈难点在于再现更真实的纹理触感的触觉渲染过程。本文提出了一种基于图像局部纹理特征的静电力触觉渲染模型,实现了更加清晰、触感真实的图像纹理的静电力触觉反馈。方法 首先,采用局部傅里叶变换方法强化局部纹理特征,提取傅里叶变换系数分离出表征形状和局部纹理、边缘的频域分量。其次,对局部纹理特征进行力触觉渲染,建立局部纹理特征与驱动信号的映射模型,采用比例模型将局部纹理特征值转化为同等级的静电力表达。最后,根据静电力与驱动信号的心理学模型,由局部纹理特征控制不同驱动信号的输出产生静电力触觉。结果 进行纹理触觉对比感知实验验证算法有效性,62.5%的实验参与者偏爱基于图像局部纹理的触觉渲染算法反馈的纹理触感,本文算法可以模拟多种图像的纹理、边缘的触感。结论 算法在频域分离图像局部纹理、边缘和形状特征,建立纹理-力触觉渲染模型,针对大多数图片可以有效地增强纹理触感,提升触觉再现交互技术的沉浸感。     

Electrostatic tactile display with thin film slider and its application to tactile telepresentation systems

A new electrostatic tactile display is proposed to realize compact tactile display devices that can be incorporated with virtual reality systems. The tactile display of this study consists of a thin conductive film slider with stator electrodes that excite electrostatic forces. Users of the device experience tactile texture sensations by moving the slider with their fingers. The display operates by applying two-phase cyclic voltage patterns to the electrodes. The display is incorporated into a tactile telepresentation system to realize explorations of remote surface textures with real-time tactile feedback. In the system, a PVDF tactile sensor and a DSP controller automatically generate voltage patterns to present surface texture sensations through the tactile display. A sensor, in synchronization with finger motion on the tactile display, scans a texture sample and outputs information about the sample surface. The information is processed by a DSP and fed back to the tactile display in real time. The tactile telepresentation system was evaluated in texture discrimination tests and demonstrated a 79 percent correct answer ratio. A transparent electrostatic tactile display is also reported in which the tactile display is combined with an LCD to realize a visual-tactile integrated display system.     

Data-Driven Texture Rendering on an Electrostatic Tactile Display

In this article, we present a data-driven texture rendering method applied to a tactile display based on electrostatic attraction. The proposed method was examined in two steps. First, accelerations occurring due to sliding a tool on three different surfaces were measured, and then the collected data were replayed on an electrostatic tactile display. The proposed data-driven texture rendering method was evaluated against a conventional method in which a standard input such as a square wave was used for texture representation. Second, data from the Penn Haptic Texture Toolkit were used to generate virtual textures on the same tactile display. Psychophysical experiments were carried out for both steps, during which subjects rated similarities among the rendered virtual textures and the real samples. Confusion matrices were created, and multidimensional scaling (MDS) analysis was performed to create a perceptual space for further examination and to extract underlying dimensions of the textures. The results show that the virtual textures generated using the data-driven method were similar to the real textures. Roughness and stickiness were the primary dimensions of texture perception. Together with the supporting results from the MDS analysis, this study showed that the data-driven method is a viable solution for realistic texture rendering with electrostatic attraction.     

Toward quality texture display: vibrotactile stimuli to modify material roughness sensations

For industrial purposes such as product design, texture displays should deliver a quality sense of touch to users. We have developed a vibrotactile texture display that uses real materials such as fabric, wood, and leather to enable the presentation of quality textures to users. By applying two types of vibrotactile stimuli to users’ finger pads through the materials, their fine and macro roughness sensations can be selectively modified while maintaining their original perceptual characteristics. This approach is effective for different types of textures such as paper, wood, leather, and cloth unless they possess strong damping properties that may attenuate the vibratory stimuli applied through them.     

A curved surface display for three fingers based on human visual and tactile sensory fusion

In general, it is difficult to present tactile information because arbitrary curvatures of the curved surface and many degrees of freedom need to be realised. On the other hand, psychophysical studies have suggested that human visual and tactile sensations have an illusory fusion characteristic. This means that we can recognise curved surfaces of objects through visual and tactile sensations, even if exact tactile information is not presented. Hence, by utilising the human characteristic of sensory fusion, realisation of a curved surface display can be simplified. From such motivation, the human fusion characteristics of visual and tactile sensation are measured, and are quantitatively analysed. Based on the analysed results, a curved surface display for three fingers is developed. In the curved surface display, only four curved patterns are utilised instead of presenting many curved patterns. Performance of the developed tactile display is proved through evaluated experiments.     

Efficient and Handy Texture Mapping on 3D Surfaces

There has been a rapid technical progress in three-dimensional (3D) computer graphics. But gathering surface and texture data is yet a laborious task. This paper addresses the problem of mapping photographic images on the surface of a 3D object whose geometric data are already known. We propose an efficient and handy method for acquiring textures and mapping them precisely on the surface, employing a digital camera alone. We describe an algorithm for selecting a minimal number of camera positions that can cover the entire surface of a given object and also an algorithm to determine camera's position and direction for each photograph taken so as to paste it to the corresponding surfaces precisely. We obtained a matching accuracy within a pixel on a surface through three experimental examples, by which the practicability of our method is demonstrated.     

振动触觉纹理再现技术研究综述

纹理力触觉再现是通过特定的硬件装置模拟产生与物体纹理表面接触时的触感，使用户能感受到物体的粗糙度、软硬度等纹理特征信息。振动刺激作为再现物体触觉信息的一种刺激方式，在纹理触觉再现中被广泛运用，产生了不同的振动触觉表达装置和纹理触觉表达方法。从纹理触觉认知的角度，阐述了人对振动刺激的触觉感知生理学基础；介绍了纹理触觉再现的原理和方法；从振动与纹理特征的映射方法以及振动刺激方式两个方面分析了目前振动触觉纹理再现技术的发展现状；最后对相关研究的发展进行了总结展望。     

Haptic texture generation using stochastic models and teleoperation

In this paper, a method is suggested to generate haptic textures for isotropic surfaces using stochastic models. A Master-Slave tele-haptic system was realized by using two PHANToMs. Moving the stylus of the Master PHANToM by a user caused the Slave to scratch the surface of objects such as sandpaper or printing paper. Force data, generated by using the error between the Master and the Slave positions, were recorded and served as measures of the texture of the object in the remote environment. An estimate of haptic texture was obtained after a simple dynamic compensation of the force data. The haptic texture was modeled using a filter that was designed by analyzing the power-spectrum of estimated texture data. By passing White Gaussian Noise through the filter, virtual texture data could be generated. The forces corresponding to the virtual texture and the real texture by teleoperation were individually delivered through the Master PHANToM to users who were asked to identify or discriminate the corresponding textures. The users?? responses show that the virtual modeled textures were quite similar to the real ones.     

一种虚拟环境温度触觉再现仿真系统设计

分析了温度触觉感知特性,提出了手指和物体接触时各自表面的温度变化过程,结合单热源温度触觉再现装置设计了一种基于三维力反馈手控器的虚拟环境温度触觉再现仿真系统。手控器可控制虚拟手的动作,对虚拟物体进行温度和力的感知。仿真系统中能再现手指与不同热属性物体接触时的温度变化和力变化,且视觉效果逼真,体现了温度触觉再现的实时性和有效性。     

基于Wang Tiles的几何纹理合成

提出了一种基于Wang Tiles的几何纹理合成方法来在不同物体表面上即时地生成几何纹理.首先根据给定的几何纹理预计算出一组Wang Tiles,然后用这组Wang Tiles在不同的目标物体上即时生成新的几何纹理.尽管基于Wang Tiles的方法已经应用于图像纹理,但由于几何纹理采用了与图像纹理完全不同的表示方式,因此需要用完全不同的方法来处理.采用了基于约束的几何纹理合成技术自动生成几何纹理Wang Tiles,从而保证了生成的几何纹理Wang Tiles在所有排列下都能保持其几何连续性.与现有的方法相比,生成的几何纹理Wang Tiles可以重用到不同的目标物体上,同时占用的存储空间及计算量更小,速度更快.     

Selectively stimulating skin receptors for tactile display

Research in virtual reality has recognized the need for more realistic tactile display in addition to touch and non-touch display and force display. We propose a method of selectively stimulating only superficial mechanoreceptors. We show that it makes people feel a more realistic, finer virtual texture than possible by adjusting the stimulator spacing. The apparatus is simple and we expect this idea to develop into a device to display varieties of tactile feeling     

KAT II: Tactile Display Mouse for Providing Tactile and Thermal Feedback

This paper proposes a tactile display mouse providing both pin-array-type tactile feedback and thermal feedback. The pin-array-type tactile display is composed of a 6 × 5 pin-array that is actuated by 30 piezo-electric bimorphs. Micro shape and vibrotactile feedback can be generated by the device, and various planar distributed patterns can be displayed as can Braille cell patterns. The thermal feedback device is composed of a thin-film resistance temperature detector, a Peltier thermoelectric heat pump and a water cooling jacket. Users can discriminate among different materials by considering the temperature variation that can be sensed as they touch an object's surface. This paper also includes an experimental evaluation of the tactile display mouse to prove the effectiveness of displaying textures. Evaluation of the ability to identify material properties was conducted using the thermal feedback part that displays a simulated temperature profile. To investigate thermo–tactile interaction, an experiment determining perceived magnitude of vibrotactile stimulus according to different temperature conditions was conducted.     

Fast and accurate texture placement

Mapping from parameter space to texture space separates textures from objects, enabling control of textured images without modifying the object or texture. Although conceptually straightforward, γ-mapping turns out to be very useful in practical texture mapping implementation. It logically separates the texture from the object and makes the texture mapping process flexible and easier to use. By modifying the γ-mapping, texture placement on the object is efficiently controlled without modifying either the texture image or the underlying geometry. We concentrate on efficiency issues related to γ-mapping, as well as its practical applications to parametric surfaces     

Remote Tactile Transmission with Time Delay for Robotic Master–Slave Systems

This study develops a method to compensate for the communication time delay for tactile transmission systems. For transmitting tactile information from remote sites, the communication time delay degrades the validity of feedback. However, so far time delay compensation methods for tactile transmissions have yet to be proposed. For visual or force feedback systems, local models of remote environments were adopted for compensating the communication delay. The local models cancel the perceived time delay in sensory feedback signals by synchronizing them with the users' operating movements. The objectives of this study are to extend the idea of the local model to tactile feedback systems and develop a system that delivers tactile roughness of textures from remote environments to the users of the system. The local model for tactile roughness is designed to reproduce the characteristic cutaneous deformations, including vibratory frequencies and amplitudes, similar to those that occur when a human finger scans rough textures. Physical properties in the local model are updated in real-time by a tactile sensor installed on the slave-side robot. Experiments to deliver the perceived roughness of textures were performed using the developed system. The results showed that the developed system can deliver the perceived roughness of textures. When the communication time delay was simulated, it was confirmed that the developed system eliminated the time delay perceived by the operators. This study concludes that the developed local model is effective for remote tactile transmissions.     

Surface textures improve the robustness of stereoscopic depth cues

This research develops design recommendations for surface textures (patterns of color on object surfaces) rendered with stereoscopic displays. In 3 method-of-adjustment procedure experiments, 8 participants matched the disparity of a circular probe and a planar stimulus rendered using a single visible edge. The experiments varied stimulus orientation and surface texture. Participants more accurately matched the depth of vertical stimuli than that of horizontal stimuli, consistent with previous studies and existing theory. Participants matched the depth of surfaces with large pixel-to-pixel luminance variations more accurately than they did surfaces with a small pixel-to-pixel luminance variation. Finally, they matched the depth of surfaces with vertical line patterns more accurately than they did surfaces with horizontal-striped texture patterns. These results suggest that designers can enhance depth perception in stereoscopic displays, and also reduce undesirable sensitivity to orientation, by rendering objects with surface textures using large pixel-to-pixel luminance variations.     

Texturing fluids

We present a novel technique for synthesizing textures over dynamically changing fluid surfaces. We use both image textures as well as bump maps as example inputs. Image textures can enhance the rendering of the fluid by either imparting realistic appearance to it or by stylizing it, whereas bump maps enable the generation of complex micro-structures on the surface of the fluid that may be very difficult to synthesize using simulation. To generate temporally coherent textures over a fluid sequence, we transport texture information, i.e. color and local orientation, between free surfaces of the fluid from one time step to the next. This is accomplished by extending the texture information from the first fluid surface to the 3D fluid domain, advecting this information within the fluid domain along the fluid velocity field for one time step, and interpolating it back onto the second surface -- this operation, in part, uses a novel vector advection technique for transporting orientation vectors. We then refine the transported texture by performing texture synthesis over the second surface using our "surface texture optimization" algorithm, which keeps the synthesized texture visually similar to the input texture and temporally coherent with the transported one. We demonstrate our novel algorithm for texture synthesis on dynamically evolving fluid surfaces in several challenging scenarios.     

Multisensory texture exploration at the tip of the pen

A tool for the multisensory stylus-based exploration of virtual textures was used to investigate how different feedback modalities (static or dynamically deformed images, vibration, sound) affect exploratory gestures. To this end, we ran an experiment where participants had to steer a path with the stylus through a curved corridor on the surface of a graphic tablet/display, and we measured steering time, dispersion of trajectories, and applied force. Despite the variety of subjective impressions elicited by the different feedback conditions, we found that only nonvisual feedback induced significant variations in trajectories and an increase in movement time. In a post-experiment, using a paper-and-wood physical realization of the same texture, we recorded a variety of gestural behaviors markedly different from those found with the virtual texture. With the physical setup, movement time was shorter and texture-dependent lateral accelerations could be observed. This work highlights the limits of multisensory pseudo-haptic techniques in the exploration of surface textures.     

Surface exploration using laparoscopic surgical instruments: The perception of surface roughness

During laparoscopic surgery video images are used to guide the movements of the hand and instruments, and objects in the operating field often obscure these images. Thus, surgeons often rely heavily on tactile information (sense of touch) to help guide their movements. It is important to understand how tactile perception is affected when using laparoscopic instruments, since many surgical judgements are based on how a tissue ‘feels’ to the surgeon, particularly in situations where visual inputs are degraded. Twelve naïve participants used either their index finger or a laparoscopic instrument to explore sandpaper surfaces of various grits (60, 100, 150 and 220). These movements were generated with either vision or no vision. Participants were asked to estimate the roughness of the surfaces they explored. The normal and tangential forces of either the finger or instrument on the sandpaper surfaces were measured. Results showed that participants were able to judge the roughness of the sandpaper surfaces when using both the finger and the instrument. However, post hoc comparisons showed that perceptual judgements of surface texture were altered in the no vision condition compared to the vision condition. This was also the case when using the instrument, compared to the judgements provided when exploring with the finger. This highlights the importance of the completeness of the video images during laparoscopic surgery. More normal and tangential force was used when exploring the surfaces with the finger as opposed to the instrument. This was probably an attempt to increase the contact area of the fingertip to maximize tactile input. With the instrument, texture was probably sensed through vibrations of the instrument in the hand. Applications of the findings lie in the field of laparoscopic surgery simulation techniques and tactile perception.     

High-fidelity haptic synthesis of contact with deformable bodies

A method for synthesizing the haptic response of nonlinear deformable objects from data obtained by offline simulation helps create surgical simulators with high-fidelity haptic feedback. Haptic displays provide users with artificially created tactile sensations. One important use of these displays is to recreate the experience caused by contact between a tool and an object. This capability can be useful in several applications, such as surgical simulators, because users experience an enhanced sense of realism when a haptic simulation is combined with a graphic simulation. Haptic displays require two essential subsystems: a haptic device, which typically has a handle connected to sensors and actuators, and a computational system that interfaces with the device.     

Surface exploration using laparoscopic surgical instruments: the perception of surface roughness

During laparoscopic surgery video images are used to guide the movements of the hand and instruments, and objects in the operating field often obscure these images. Thus, surgeons often rely heavily on tactile information (sense of touch) to help guide their movements. It is important to understand how tactile perception is affected when using laparoscopic instruments, since many surgical judgements are based on how a tissue 'feels' to the surgeon, particularly in situations where visual inputs are degraded. Twelve na?ve participants used either their index finger or a laparoscopic instrument to explore sandpaper surfaces of various grits (60, 100, 150 and 220). These movements were generated with either vision or no vision. Participants were asked to estimate the roughness of the surfaces they explored. The normal and tangential forces of either the finger or instrument on the sandpaper surfaces were measured. Results showed that participants were able to judge the roughness of the sandpaper surfaces when using both the finger and the instrument. However, post hoc comparisons showed that perceptual judgements of surface texture were altered in the no vision condition compared to the vision condition. This was also the case when using the instrument, compared to the judgements provided when exploring with the finger. This highlights the importance of the completeness of the video images during laparoscopic surgery. More normal and tangential force was used when exploring the surfaces with the finger as opposed to the instrument. This was probably an attempt to increase the contact area of the fingertip to maximize tactile input. With the instrument, texture was probably sensed through vibrations of the instrument in the hand. Applications of the findings lie in the field of laparoscopic surgery simulation techniques and tactile perception.