Head Tracking Interface Using a WiiRemote

 

Megha Sunny - Megha_Sunny@student.uml.edu

Electrical engineering, University of Massachusetts Lowell

1 University Ave, Lowell, MA, 01854

Ayse Kalkan-Savoy - Ayse_KalkanSavoy@student.uml.edu

Biomedical engineering, University of Massachusetts Lowell

1 University Ave, Lowell, MA, 01854

Prof. Charles Thompson - Charles_Thompson@uml.edu

Electrical engineering, University of Massachusetts Lowell

1 University Ave, Lowell, MA, 01854

Popular Version of paper 4aEA4

Presenting Thursday morning, April 22, 2010

159th ASA Meeting Baltimore, Maryland

 

In the case of 3-D audio reproduction or virtual acoustics, the sound pressure generated at the listeners ear drum should be the same as it would have been produced by the actual sound source. In such a case, the listener would not be able to distinguish between virtual sound and real sound. This can be achieved by the use of multiple loudspeakers in a closed room. The sound reproduction by headphones (binaural technology) is a special spatial configuration of a two channel loudspeaker reproduction setup. Hence in headphone-based sound reproduction, the recorded signal is electrically modified to produce the same auditory stimuli that would be present in their absence [1].

When sound waves travel from their source, the incident ray that reaches the inner ear of the listener is modified by reflections from the head, torso, pinna, and within the ear canal itself. One could simulate these effects of the head by measuring the lateral displacement and spatial orientation of the head from the sound source [1]. We are using Nintendo Wiis videogame controller WiiRemote to track the position and orientation of the head. The spatial data can be simulated by using a computer equipped with sound card. Simulation will allow one to adjust the location of the sound source relative to the listener position so that we will get the same sound source effect while reproducing the recorded sound as in the real case.

WiiRemote has an acceleration sensor, infrared camera and a Bluetooth telecommunication function. The WiiRemote can be connected easily to an ordinary PC using a Bluetooth adapter [5]. In the WiiRemotes position determining system, we are using the built-in infrared sensors inside the WiiRemote and an infrared LED glasses. The LED glasses are installed on the object person who should be tracked so that the infrared camera of the WiiRemote can detect the infrared rays from the LEDs [3][2]. In optical sensor system, the light sources and the sensors must be in a clear line of sight. The infrared cameras can detect up to 4 infrared lights and for the stable position determination, at least two infrared lights should be detected by the sensor. The positions of the infrared camera of the WiiRemote are recorded continuously on a PC. To convert the camera coordinates returned by the WiiRemote into absolute coordinates, a camera calibration was performed by multiplying the data obtained with a scale factor. The scale factor was determined by plotting the actual displacement with the WiiRemotes output [4].

Unlike the general inertial sensing device which consists of 3 accelerometers and 3 gyroscopes, the WiiRemote originally has 3 linear accelerometers but did not have a gyroscope. Hence the accelerometers of the WiiRemote were able to sense the tilt only in the pitch and roll orientations. WiiRemote loses its resolution when it is inclined in parallel to the direction of gravity [6]. However, Wii introduced an extension device for WiiRemote that has a two-axis tuning fork gyroscope, which can measure the rotational motion. The information captured by the angular rate sensor can then be used to distinguish true linear motion from the accelerometer readings. The angular orientation of the head was thus measured using a WiiRemote with its extension Wii-motion plus. The angular orientations are recorded continuously and the actual orientation was mapped by comparing the calibration data in advance.

Head position is tracked by integrating the output of a set of sensors inside the WiiRemote to compute the lateral displacement and spatial orientation of the head. The sensors used are gyro accelerometers and infrared sensors. Gyros measure the angular rate with respect to the inertial space, accelerometers measure the linear acceleration with respect to the inertial frame and infrared sensors measured the lateral displacement of the head by measuring the displacement of the infrared cameras of the WiiRemote with respect to the sensor bar. A human-computer interface virtual acoustic display was developed which synthesizes the three-dimensional, spatial auditory information over headphones to produce virtual localization.

 

   [1]            Brown, C. P., and Duda, R. O. A structural model for binaural sound synthesis. Speech and Audio Processing, IEEE Transactions, 6(5), 476-488. 1988

   [2]            Chow,Y. Low-cost multiple degrees-of-freedom optical tracking for 3D interaction in head-mounted display virtual reality, International Journal of Recent Trends in Engineering, 1(1). 2009

   [3]            Nakano.Y., Tatsumi. T., Tajitsu. K., Wiimote positioning system(WPS) An epoch-making system of indoor position detection .

   [4]            Attygalle. S., Duff. M., Rikakis. T., and He. J., Low-cost,at-home Assessment System with Wii Remote Based Motion Capture. IEEE, 2008.

   [5]            Shirai. A., Geslin. E., Richir. S., WiiMedia: motion analysis methods and applications using a consumer video game controller Sandbox symposium, 2007.

   [6]            Chow. Y., The wii remote as an input device for 3D interaction in immensive head-mounted display virtual reality, IADS international conference gaming, 2008.