[Wireless Japan] NTT DoCoMo Demos 'Tactile-kinesthetic Sense' Communications

Jul 28, 2009 16:23 Tetsuo Nozawa, Nikkei Electronics

NTT DoCoMo Inc demonstrated a technology that transmits the feel and hardness of an object in real time via a network at Wireless Japan 2009, which took place from July 22 to 24, 2009, at Tokyo Big Sight.

The company calls the technology "tactile-kinesthetic sense media." It is a kind of "haptic feedback" technology and can transmit various kinesthetic senses including impulsive force via a network with delay.

In the demonstration, a remote handle was controlled via a network by rotating another handle at hand. When a sponge ball, rugged metal plate, guitar string and glass bottle are touched by the remote handle, their hardness, rough feel, etc can be transmitted to the handle at hand. It is possible to feel the sensation of playing the guitar with a pick and the impact of hitting a glass bottle.

NTT DoCoMo expects the new technology to be used for checking the feel of clothes via the Internet before purchasing them at an online store, determining hardness of objects in various industries, manipulation tests for remote medical care and other applications.

Smaller delay required

Each of the two handles is equipped with a rotation angle sensor, motor and electric circuit for information processing. When the handle at hand is moved, the sensor determines the rotation angle, sends it to the remote handle via the network and moves the remote handle by using the motor.

The rotation angle can be converted to the velocity and acceleration of the handle by temporal differentiation. Therefore, when the remote handle receives force from an object, it can be calculated with the equation of motion, F = ma (F: force, m: mass, a: acceleration).

Based on this information, the motor of the handle at hand reproduces the force received by the remote handle, providing a kinesthetic sense to the hand.

According to NTT DoCoMo, the key to the development is a short and stable "delay," the time it takes to exchange data. Specifically, if it takes less than 30ms to transmit the positional information of the handle at hand to the remote handle via a network and transmit the acceleration information of the remote handle to the motor at hand and if the transmission speed is stable, tactile and kinesthetic senses can be communicated without creating discomfort.

This limit is much stricter than the limit for voice communications, such as phone calls, which normally require a round-trip transmission time of 200ms or less. When a person is touching an object with the hand while looking at it, his or her tactile sense becomes very acute. So, when the delay is larger, it creates, for example, a feeling of a handle sinking in a glass object (when a glass object is hit by a metal handle), NTT DoCoMo said.

This time, the company reduced the fluctuation (jitter) by information processing in terminal devices so that a minor fluctuation of delay does not cause any problem. The network used in the experiment is not a wireless network but Ethernet. For the demonstration of picking the guitar string, this jitter reduction technology was used after artificially adding delay and jitter, according to the company.

The jitter reduction technology is an information processing technology for terminal devices, so it can be used with any type of network, NTT DoCoMo said. However, the delay of less than 30ms cannot be easily achieved by the existing mobile phone networks. Commenting on this point, the company said that the round-trip transmission time of the LTE (long term evolution) is designed to be less than 30 to 50ms and, thus, may be appropriate for the new technology.

24 Hours | 7 Days