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Topic Name: Artificial Tactile Feeling and Finite Element Model of a Finger from Tadokoro Laboratory

Category: Robotics

Research persons: Tadokoro Laboratory team

Location: Tadokoro Laboratory, Tohoku University, Japan

Details

Representation of Artificial Tactile Feeling

Representation of artificial tactile feeling has been placed emphasis as new technology to augment virtual reality technology, also as new communication media for remote robotic manipulation or Internet shopping.

We have been studying presentation methods for qualitative surface textures of objects, such as clothes. Our major strategy for tactile presentation is applying vibratory stimuli to fingers.

We also have been studying tactile information processing of humans in psycophysic, engineering and numerical computation methods.

Synthesizing Tactile Feelings by Selectively Stimulating Mechanoreceptor Classes

Multiple tactile feelings, such as pressure, roughness and friction feelings can be synthesized by ICPF tactile display, which we have developed and studied effective displyaing methods.

A device in figure 2 replicates surface textures of objects including qualitative information by mechanically stimulating three receptor classes selectively. Activation of each class can be controlled using the device. Because each class has different frequency response characteristics and ICPF tactile display can produce superposed vibrations, each vibration activates each class.

Tactile Displaying Method in Response to Rubbing Motion

We are studying the relationships between rubbing motions and tactile represence. Rubbing motion cannot be ignored, discussing humans' natural touch. Therefore we are proposing tactile display methods in syncronization with hand motions.

Figure 1 illustrates our experimental setup, in which subjects virtually touch clothes.

Touch a 3D Staffed Pig in a Computer

As a demonstration of integrated technology studied in our laboratory, we developed a "touch a virtual pig" system. You can feel differences of clothes and rub it along its spherical nose or ears.

The system presents roughness, softness and friction feelings to fingers just by mechanically vibratory stimuli, which are controlled according to rubbing motions. See figure 3

Finite Element Model of a Finger

We are studying the deformation of human fingers and activities of tactile mechanoreceptors, using finite element model. Human fingers are structurely complex that numerical analysis by finite element model is considered to be an appropriate approach.

The model represents human fingers' complex tissue, like layered structure, epidermal ridges and the allocation of receptors. Physical parameters of tissue are modeled to be similar to those of human fingers.

This technology can be a new analysis method for receptors' activities while microelectrodes used to be unique methods. See figure 4

Note for Haptic

Haptic means pertaining to the sense of touch (or possibly from the Greek word haptesthai meaning “contact” or “touch”).

Haptic technology refers to technology which interfaces the user via the sense of touch by applying forces, vibrations and/or motions to the user. This mechanical stimulation is used to create haptic virtual objects. This emerging technology promises to have wide reaching applications. In some fields, it already has. For example, haptic technology has made it possible to investigate in detail how the human sense of touch works, by allowing the creation of carefully-controlled haptic virtual objects. These objects are used to systematically probe human haptic capabilities. This is very difficult to achieve otherwise. These new research tools contribute to our understanding of how touch and its underlying brain functions work (See References below).

Although haptic devices are capable of measuring bulk or reactive forces that are applied by the user it should not to be confused with touch or tactile sensors that measure the pressure or force exerted by the user to the interface.

Note for Virtual reality

Virtual reality (VR) is a technology which allows a user to interact with a computer-simulated environment, be it a real or imagined one. Most current virtual reality environments are primarily visual experiences, displayed either on a computer screen or through special stereoscopic displays, but some simulations include additional sensory information, such as sound through speakers or headphones. Some advanced, haptic systems now include tactile information, generally known as force feedback, in medical and gaming applications. Users can interact with a virtual environment or a virtual artifact (VA) either through the use of standard input devices such as a keyboard and mouse, or through multimodal devices such as a wired glove, the Polhemus boom arm, and omnidirectional treadmill. The simulated environment can be similar to the real world, for example, simulations for pilot or combat training, or it can differ significantly from reality, as in VR games. In practice, it is currently very difficult to create a high-fidelity virtual reality experience, due largely to technical limitations on processing power, image resolution and communication bandwidth. However, those limitations are expected to eventually be overcome as processor, imaging and data communication technologies become more powerful and cost-effective over time.

Note for Finite Element Method 

The finite element method (FEM) is used for finding approximate solutions of partial differential equations (PDE) as well as of integral equations such as the heat transport equation. The solution approach is based either on eliminating the differential equation completely (steady state problems), or rendering the PDE into an equivalent ordinary differential equation, which is then solved using standard techniques such as finite differences, etc.

In solving partial differential equations, the primary challenge is to create an equation that approximates the equation to be studied, but is numerically stable, meaning that errors in the input data and intermediate calculations do not accumulate and cause the resulting output to be meaningless. There are many ways of doing this, all with advantages and disadvantages. The Finite Element Method is a good choice for solving partial differential equations over complex domains (like cars and oil pipelines), when the domain changes (as during a solid state reaction with a moving boundary), or when the desired precision varies over the entire domain. For instance, in simulating the weather pattern on Earth, it is more important to have accurate predictions over land than over the wide-open sea, a demand that is achievable using the finite element method.