MULTI AV SYSTEM: System Description

Multi AV system means that the following systems are integrated.

FUNCTION NAME
Navigation system function
Audio function
DVD play function
Hands-free phone function
USB connection function
Voice recognition function
Touch panel function
Rear view monitor function
Sonar system
Vehicle information function

COMMUNICATION SIGNAL 

• AV control unit function by transmitting/receiving data one by one with each unit (slave unit) that configures them completely as a master unit by connecting between units that configure MULTI AV system with two AV communication lines (H, L).
• Two AV communication lines (H, L) adopt a twisted pair line that is resistant to noise.
• AV control unit is connected by CAN communication, and it receives data signal from ECM, unified meter and A/C amp. It computes and displays fuel economy information value with the obtained information.
• AV control unit is connected with display and serial communication, and it transmits the required signal of display and display control and receives the response signal from display.

NAVIGATION SYSTEM FUNCTION 

Description 

• The AV control unit controls navigation function while GPS tuner has built-in map data, GYRO (angle speed sensor), on the HDD (Hard Disk Drive).
• The AV control unit inputs operation signal with communication signal, through display (touch panel) and multifunction switch and steering switch.
• Guide sound is output to front speaker through BOSE amp. from AV control unit when operating navigation system.
• A vehicle position is calculated with the GYRO (angle speed sensor), vehicle sensor, signal from GPS satellite and map data stored on HDD (Hard Disk Drive), and transmits the map image signal (RGB image, RGB area, RGB image synchronizing) to the display.

Position Detection Principle 

The navigation system periodically calculates the current vehicle position according to the following three types of signals.

• Travel distance of the vehicle as determined by the vehicle speed sensor
• Vehicle turning angle determined by the gyroscope (angular speed sensor)
• The travel direction of the vehicle determined by the GPS antenna (GPS information)

The current position of the vehicle is then identified by comparing the calculated vehicle position with map data, which is stored in the HDD (Hard Disk Drive) (map-matching), and indicated on the screen with a current location mark. More accurate data is used by comparing position detection results from GPS to the map-matching.

The current position is calculated by detecting the travel distance from the previous calculation point, and its direction change.

• Travel distance

  The travel distance is generated from the vehicle speed sensor input signal. The automatic distance correction function is adopted for preventing a miss-detection of the travel distance because of tire wear etc.

• Travel direction

The gyroscope (angular velocity sensor) and GPS antenna (GPS information) generate the change of the travel direction. Both have advantages and disadvantages as per the following descriptions.

Type	Advantage	Disadvantage
Gyroscope (angular velocity sensor)	The turning angle is precisely detected.	Errors are accumulated when driving a long distance without stopping.
GPS antenna (GPS information)	The travel direction (North/South/East/West) is detected.	The travel direction is not precisely detected when driving slowly.

Input signals are prioritized in each situation. However, this order of priority may change in accordance with more detailed travel conditions so that the travel direction is detected more accurately.

Map-matching 

Map-matching repositions the vehicle on the road map when a new location is judged to be more accurate. This is done by comparing the current vehicle position (calculated by the normal position detection method) from the map data stored in the HDD (Hard Disk Drive).

There is a possibility that the vehicle position may not be corrected in the following case, and when vehicle is driven over a certain distance or time in which GPS information is hard to receive. Correct manually the current location mark on the screen.

• In map-matching, several alternative routes are prepared and prioritized in addition to the road judged as currently driving on.

  Therefore, due to errors in the distance and/or direction, an incorrect road may be prioritized, and the current location mark may be repositioned to the incorrect road.

  If two roads are running in parallel, they are of the same priority. Therefore, the current location mark may appear on either of them alternately, depending on maneuvering of the steering wheel and configuration of the road, etc.

  Fig 4: Identifying Actual Vehicle Traced Route (Using Road Data)

  Courtesy of NISSAN NORTH AMERICA, INC.
• Map-matching does not function correctly when road on which the vehicle is driving is new, etc. and not recorded in the map data. Also, map-matching does not function correctly when road pattern stored in the map data and the actual road pattern are different due to repair, etc.

  Therefore, the map-matching function judges other road as a currently driving road if the road is not in the map, and displays the current location mark on it. Later, the current location mark may be repositioned to the road if the correct road is detected.

• Effective range for comparing the vehicle position and travel direction calculated by the distance and direction with the road data is limited. Therefore, correction by map-matching is not possible when there is an excessive gap between current vehicle position and the position on the map.
  Fig 5: Identifying Actual Vehicle Traced Route (Road Data Not Registered)

  Courtesy of NISSAN NORTH AMERICA, INC.

GPS (Global Positioning System) 

GPS (Global Positioning System) is developed for and is controlled by the US Department of Defense. The system utilizes GPS satellites (NAVSTAR), transmitting out radio waves while flying on an orbit around the earth at an altitude of approximately 21, 000 km (13, 049 mile).

The receiver calculates the travel position in three dimensions (latitude/longitude/altitude) according to the time lag of the radio waves that four or more GPS satellites transmit (three-dimensional positioning). The GPS receiver calculates the travel position in two dimensions (latitude/longitude) with the previous altitude data if the GPS receiver receives only three radio waves (two-dimensional positioning). GPS position correction is not performed while stopping the vehicle.

Accuracy of the GPS will deteriorate under the following conditions:

• In two-dimensional positioning, GPS accuracy will deteriorate when altitude of the vehicle position changes.
• The position of GPS satellite affects GPS detection precision. The position detection may not be precisely performed.
• The position detection is not performed if GPS receiver does not receive radio waves from GPS satellites. (Inside a tunnel, parking in a building, under an elevated highway etc.) GPS receiver may not receive radio waves from GPS satellites if any object is placed on the GPS antenna.

AUDIO FUNCTION 

The audio system is equipped with the following functions. Each function is operated with multifunction switch, preset switch, touch panel, steering switch or audio recognition. Operation status of audio is indicated at display.

FUNCTION
AM/FM radio
Satellite radio
CD
Bluetooth™ audio
Music Box (Hard Disk Drive)
AudioPilot™
Sound equalizer automatic switching

Operating Signal 

Audio system operation can be performed with multifunction switch, preset switch, steering switch, touch panel function or voice recognition function.

• Operating signal is transmitted to AV control unit with AV communication when it is operated by multifunction switch or preset switch. The disk ejection operating signal is performed by hardwire.
• Operating signal is transmitted to AV control unit with steering switch signal when it is operated by steering switch.

Screen Display 

Switching of display is performed with serial communication between display unit and AV control unit.

AM/FM Radio Mode 

• AM/FM radio tuner is built into AV control unit.
• Audio signal is received by rod antenna, next it is amplified by antenna amp., and finally it is input to AV control unit. Audio signal is input to BOSE amp., and BOSE amp. outputs to each speaker.

Satellite Radio Mode 

• Satellite radio tuner is built into AV control unit.
• Audio signal (satellite radio) is received by satellite antenna, and it is input to AV control unit. AV control unit outputs audio signal to BOSE amp. The signal is also outputted from BOSE amp. to both woofer and each speaker.

CD Mode 

• CD function is built into AV control unit.
• AV control unit outputs audio signal to BOSE amp., and BOSE amp. outputs to each speaker when CD is inserted to AV control unit.

Bluetooth™ Audio Mode 

• Bluetooth™ audio function is built into AV control unit.
• Bluetooth™ audio can play music data in the portable audio by means of Bluetooth™ communications between the portable audio and the AV control unit.
• AV control unit outputs audio signal to BOSE amp., and BOSE amp. outputs to each speaker.

Music Box Mode 

• Music CD data is stored on HDD that is built into AV control unit, and it can be played.
• AV control unit outputs music (sound signal) that is stored on HDD to BOSE amp., and BOSE amp. outputs to each speaker.

AudioPilot™ 

AudioPilot™ is a sound improving system that picks up by a microphone in a driver headrest any noises or the sound of music coming into the vehicle, and that uses the BOSE amp. to revise the frequency feature of music in real time in response to the frequency feature of the noise while driving and listening to music.

• If the low frequency area noise from the vehicle is loud, it adjusts the low frequency element of music to be larger than the vehicle noise.
• If the high frequency area noise from the vehicle is loud, it adjusts the high frequency element of music to be larger than the vehicle noise.
• If the vehicle noise is smaller than the setting volume, correction is not performed. This eliminates the vehicle noise when listening to music.

Sound Equalizer Automatic Switching Function 

Sound quality in a fully-open retractable hard top condition is improved by the correction for bringing the frequency characteristics in a fully-open retractable hard top condition closer to the characteristics in a fully-closed retractable hard top condition. When the retractable hard top is in a fully-open condition, sound pressure is reduced due to the absence of sound echo generated by sound reflection from the retractable hard top. BOSE amp. detects an open-close condition of the retractable hard top by receiving a roof status signal from the retractable hard top control unit and switches the equalizer to correct the frequency characteristics in a fully-open retractable hard top condition. During the switching of the equalizer, audio stops temporarily due to the temporary mute.

DVD PLAY FUNCTION 

• DVD is played by inserting DVD into the AV control unit.
• DVD image signals are transmitted to the display unit and DVD sound signals are transmitted to each speaker via BOSE amp.

HANDS-FREE PHONE FUNCTION 

• AV control unit includes hands-free phone function.
• Hands-free communication can be operated by connecting using Bluetooth™ communication with cellular phone.
• Operation is performed by steering switch, and operating condition is indicated on display.
• Guide sound that is heard during operation is input from AV control unit to BOSE amp., and is output from front speaker and center speaker.
• System operation is available only when the retractable hard top is closed.

When A Call Is Originated 

Spoken voice sound output from the microphone (microphone signal) is input to AV control unit. AV control unit outputs to cellular phone with Bluetooth™ communication as a TEL voice signal. Voice sound is then heard at the other party.

When Receiving A Call 

Voice sound is input to own cellular phone from the other party. TEL voice signal is output to door speaker, and the signal is input to BOSE amp. via AV control unit by establishing Bluetooth™ communication from cellular phone.

USB CONNECTION FUNCTION 

• Connecting iPod® or USB memory allows the driver to play iPod® music files or USB memory-stored music files, video data, and image viewer data.
• Sound signals of music files stored in iPod® or USB memory are transmitted from the USB connector to the AV control unit. The AV control unit transmits the sound signals to the woofer and each speaker via BOSE amp.
• Video signals and image viewer file signals are transmitted from the USB connector to the AV control unit. The data and files are displayed on the front display unit screen.
• iPod® is recharged when connected to USB connector.
• Only files that meet the following conditions will be played.

	Music file	Video file	Image viewer file
File format	"MP3", "WMA", "AAC", "M4A"	"DivX", "MPEG4 (ASF)"	"JPEG"
File extension	".mp3", ".wma", ".aac", ".m4a"	".divx", ".afs", ".avi"	".jpg", ".jpeg"
Maximum file size	2 GB	2 GB	2 MB

VOICE RECOGNITION FUNCTION 

• Each operation of multi AV system can be performed by inputting sound to microphone.
• Start of sound recognition system can be performed by steering switch.
• System operation is available only when the retractable hard top is closed.

TOUCH PANEL SYSTEM 

Each operation of multi AV system can be performed by directly touching a display.

REAR VIEW MONITOR FUNCTION 

• The AV control unit supplies power to the rear view camera when receiving a reverse signal.
• The rear view camera transmits camera images to the display unit when power is supplied from the AV control unit.
• The AV control unit transmits a warning message, fixed guide lines, and predictive course lines to the display unit by RGB digital image signal. Rear view monitor images are displayed by combining the RGB digital image signal and the camera image signals from the rear view camera.
• Predictive course lines are controlled by a steering angle sensor signal received the AV control unit via CAN communication.

SONAR SYSTEM 

For further information about the sonar system, refer to "SYSTEM DESCRIPTION ".

VEHICLE INFORMATION FUNCTION 

• Status of audio, climate control system, fuel economy, maintenance and navigation are displayed.
• AV control unit displays the fuel consumption status while receiving data signal through CAN communication from ECM, unified meter and A/C amp.
• AV control unit is connected to BCM via CAN communication transmitting/receiving for the vehicle settings function.