System Description

1. It is essential that the navigation system correctly tracks the current vehicle position and displays it on the map. There are 2 methods to track the current vehicle position: autonomous (dead reckoning) and GPS* (satellite) navigation. Both navigation methods are used in conjunction with each other.

   HINT:

   *: GPS (Global Positioning System)

   Fig 1: Navigation System Description

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   NAVIGATION DESCRIPTION CHART
   
   

   Operation	Description
   Vehicle Position Calculation	Navigation ECU calculates current vehicle position (direction and current position) using direction deviation signal from gyro sensor and running distance signal from vehicle speed sensor, and creates driving route.
   Map Display Processing	Navigation ECU processing vehicle position data, vehicle running track, and map data from map disc.
   Map Matching	Map data from the map disc is compared to vehicle position and running track data. Then, vehicle position is matched with nearest road.
   GPS Correction	Vehicle position is matched to position measured by GPS. Then, measurement position data from GPS unit is compared with vehicle position and running track data. If the position is very different, GPS measurement position is used.
   Distance Correction	Running distance signal from vehicle speed sensor includes error caused by tire wear and slippage between tires and road surface. Distance correction is performed to account for this. Navigation ECU automatically offsets the running distance signal to make up for difference between it and distance data of map. Offset is automatically updated.

   HINT:

   The combination of autonomous and GPS navigation makes it possible to display the vehicle position even when the vehicle is in places where the GPS radio wave cannot receive a signal. When only autonomous navigation is used, however, the mapping accuracy may slightly decline.

   Fig 2: GPS Navigation System

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

This method determines the relative vehicle position based on the running track determined by the gyro and vehicle speed sensors located in the navigation ECU.

1. Gyro sensor

   Calculates the direction by detecting angular velocity. It is located in the navigation ECU.

2. Vehicle speed sensor

   Used to calculated the vehicle running distance.

This method detects the absolute vehicle position using radio waves from a GPS satellite*.

HINT:

*: GPS satellites were launched by the U.S.

Department of Defense for military purposes.

Fig 3: GPS Navigation (Satellite Navigation)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

The current driving route is calculated by autonomous navigation (according to the gyro sensor and vehicle speed sensor) and GPS navigation. This information is then compared with possible road shapes from the map data in the map disc and the vehicle position is set onto the most appropriate road.

Fig 4: Identifying Map Matching

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Touch switches are touch-sensitive (interactive) switches operated by touching the screen. When a switch is pressed, the outer glass bends in to contact the inner glass at the pressed position. By doing this, the voltage ratio is measured and the pressed position is detected.

Fig 5: Identifying Multi-Display Outline

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HINT:

*: The communication performance of Bluetooth may vary depending on the Bluetooth version, obstructions or radio wave conditions between communication devices, electromagnetic radiation, communication device sensitivity, or antenna capacity.

Fig 6: Identifying Bluetooth Outline

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

AVC-LAN, an abbreviation for "Audio Visual Communication Local Area Network", is a united standard developed by the manufacturers in affiliation with Toyota Motor Corporation. This standard pertains to audio and visual signals as well as switch and communication signals.

Fig 7: Audio System Communication Each Other Through AVC-LAN

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Recently, car audio systems have rapidly developed and the functions have vastly changed. The conventional car audio system is being integrated with multimedia interfaces similar to those in navigation systems. At the same time, customers are demanding higher quality from their audio systems. This is merely an overview of the standardization background. The specific purposes are as follows:

1. To solve sound problems, etc. caused by using components of different manufacturers thorough signal standardization.
2. To allow each manufacturer to concentrate on developing products they do best. From this, reasonably priced products can be produced.

   HINT:

   • If a short +B or short to ground is detected in the AVC-LAN circuit, communication is interrupted and the audio system will stop functioning.
   • If an audio system is equipped with a navigation system, the multi-display unit acts as the master unit.

     If the navigation system is not equipped, the audio head unit acts as the master unit instead. If the multi-display is equipped, it is the navigation ECU master unit.