Gabjong Han

Haptic simulation of refrigerator door

Recently, haptics has begun to impact consumer products, e.g., mobile phones and automobiles. In this paper, we introduce one such new application, that is, haptic simulation of refrigerator operation, and present an initial prototype for the front door. A one degree-of-freedom haptic interface is designed and built to provide torque feedback of the front door. Simulation software consisting of system control, graphic renderer, and haptic renderer are also developed. For haptic rendering, the motion dynamics of a refrigerator door is modeled, and the haptic renderer is implemented based on the dynamics model. Lastly, we report a user experiment carried out to assess the perceived similarity between simulated and real door operations, i.e., the realism, which shows promising results.

Haptic Pottery Modeling Using Circular Sector Element Method

This paper presents an efficient modeling system of virtual pottery in which the user can deform a body of virtual clay with a haptic tool. The clay body is represented with a set of circular sector elements based on the cylindrical symmetry of pottery. The circular sector element method allows much finer spatial resolution for modeling than previous techniques. Also described are efficient algorithms for collision detection and response where the viscosity of virtual clay is simulated along with the friction due to the rotating potters wheel. Empirical evaluation showed that the modeling system is computationally efficient, is intuitive to use, and provides convincing model deformation and force feedback.

Extended rate-hardness: a measure for perceived hardness

This paper presents a measure for assessing the perceived hardness of a haptic surface based on associated physical variables. This metric, named extended rate-hardness (ERH), is extended from rate-hardness originally proposed by Lawrence et al. in order to cover a larger class of rendering algorithms and applications. We also performed a psychophysical evaluation using absolute magnitude estimation to quantify the extent to which the ERH can account for perceived hardness. The findings have implications to developing haptic interfaces and rendering algorithms with improved perceptual hardness.

AR pottery: experiencing pottery making in the augmented space

In this paper, we apply augmented reality to provide pottery design experiences to the user. Augmented reality offers natural 3D interaction, a tangible interface, and integration into the real environment. In addition, certain modeling techniques impossible in the real world can be realized as well. Using our AR system, the user can create a pottery model by deforming a virtual pottery displayed on a marker with another marked held by the users hand. This interaction style allows the user to experience the traditional way of pottery making. Also provided are six interaction modes to facilitate the design process and an intuitive switching technique using occlusion-based interface. The AR pottery system can be used for virtual pottery prototyping and education.

Improving perceived hardness of haptic rendering via stiffness shifting: an initial study

Rendering a stiff virtual surface using a force-feedback haptic interface has been one of the most classic and important research issues in haptics. In this paper, we present an initial study for a novel haptic rendering technique, named stiffness shifting, which greatly increases the perceived hardness of a virtual surface. The key idea of stiffness shifting is to use a stiffness profile that includes an instantaneous increment shortly after a contact. The algorithm is very simple, and can be easily integrated into existing haptic rendering algorithms for 3D objects. Furthermore, the perceptual performance of the algorithm is impressive; a virtual wall rendered using stiffness shifting is perceived as hard as one rendered using the common linear spring model with 2.5 times higher stiffness. This result demonstrates a great potential of stiffness shifting to be a general means for improving the perceptual quality of haptic rendering.

Haptic Assistance for Memorization of 2-D Selection Sequences

This paper investigates the effect of haptic feedback on the learning of a 2-D sequential selection task, used as an abstraction of complex industrial manual assembly tasks. This mnemonic-motor task requires memorization of the selection order of points scattered on a 2-D plane and reproduction of this order using entire arm movements. Four information presentation methods, visual information only, visual information + enactment, visual information + haptic guidance, and visual information + haptic disturbance, are considered. The latter three methods provide different levels of haptic kinesthetic feedback to the trainee. We carried out a user study to assess the quantitative performance differences of the four training methods using a custom-built visuo-haptic training system. Experimental results showed the relative advantages and disadvantages of each information presentation method for both short-term and long-term memorization. In particular, training with only visual information was the best option for short-term memory, while training also with haptic disturbance was the most effective for long-term memory. Our findings have implications to designing a training method that is suitable for given training requirements.

Effects of kinesthetic information on working memory for 2D sequential selection task

In this paper, we study the effect of haptic information for memorizing an order of selecting positions scattered on a two-dimensional plane. The task was motivated by the need of an effective training system for a cell production line in manufacturing plants. We constructed a collocated visuo-haptic training system that covers the workspace of an adult arm, and implemented three training methods that varied in the degree of kinesthetic information provided to the trainee. The methods were visual display only, visual display with enactment, and visual display with haptic guidance. We experimentally assessed the training performances of the three methods in terms of the number of repeated trials necessary to memorize the order of 2D sequential selections, along with subjective evaluations. Overall, the method of visual display with enactment exhibited the best performance, whereas the method of visual display with haptic guidance the worst performance. These results indicate that enactment can improve the memory performance by presenting the information through the haptic sensory channel (in addition to the visual channel), but active guidance may prohibit such positive effects by making the trainee less focus on the training.

Haptizing Surface Topography with Varying Stiffness Based on Force Constancy: Extended Algorithm

This article introduces a novel haptization method for rendering surface topography with varying stiffness via a force-feedback haptic interface. Previously, we showed that when surface topography with varying stiffness is rendered with the conventional penalty- based method, topography information perceived by the user can be distorted from its model. This phenomenon was explained by the theory of force constancy which states that the user maintains an invariant contact force level when s/he strokes a surface to perceive its topography. To resolve the problem, we then developed a basic topography compensation algorithm (TCA) based on the force constancy, for a single height-change region with nonuniform stiffness perceived via lateral stroking. The basic TCA was mainly to test the applicability of force constancy to haptic rendering. In this article, we present an extended TCA that adequately delivers surface topography that may contain a number of height-changing regions with varying stiffness for any user exploratory patterns. We also measured the human detection thresholds of surface slope mediated with a force-feedback device and used these data for designing the extended TCA. The performance of the extended TCA was extensively examined in terms of proximal stimuli it creates and actual percepts induced from the stimuli. The extended TCA brings a one-step advance from the current practice of haptic rendering which requires constant surface stiffness for an adequate delivery of surface shape.

Effect of Active and Passive Haptic Sensory Information on Memory for 2D Sequential Selection Task

This paper introduces an education system for typical assembly procedures that provides various haptic sensory information including active and passive haptic feedbacks. Using the system, we implemented four kinds of training methods and experimentally evaluated their performances in terms of short-term and long-term memory over the task. In results, active haptic guidance showed beneficial effects on the short-term memory. In contrast, passive guidance showed the worst performance and even degraded the efficiency of short-term memory. No training methods resulted in noticeable improvements for the long-term memory performance.

Breast cancer palpation system using haptic augmented reality

In haptic augmented reality (AR), a stimulus from a real object is augmented by a synthetic haptic signal. We previously developed a haptic AR system wherein the stiffness of a real object can be augmented with the aid of a haptic interface. This demonstration presents a case study of this technology for medical training of breast cancer palpation. A real breast model made of soft silicone is augmented with a virtual tumor rendered inside. Haptic stimuli for the virtual tumor are generated based on a contact dynamics model identified via real measurements. With our palpation system, a user can experience excellent realism comparable to that of a real breast mock-up containing a real tumor.