Part 2
Navigation System Description
System Diagram
USA Models
Canada Models
Navigation Function
The navigation system is composed of the audio-navigation unit, the PCM (vehicle speed pulse), the AcuraLink control unit (XM receiver) (traffic and weather information), the HandsFreeLink control unit (to send a POI phone number or place a call), the GPS antenna, the microphone, the voice control switch, the navigation display unit, interface dial, and the rearview camera.
Function Diagram
GA-Net Bus Configuration
The GA-Net bus passes audio, navigation, and HFL commands throughout the audio, navigation, and HFL components. These commands include navigation audio/XM selections by voice, and XM station and music title names. Because the entire bus is interconnected between components, an open or short in the GA-Net bus harness may cause any or all of these functions to become inoperative.
Vehicle Speed Pulse
The vehicle speed pulse is sent by the PCM. The PCM receives a signal from the output shaft (countershaft) speed sensor, then processes the signal and transmits it to the speedometer and other systems.
Yaw Rate Sensor
The yaw rate sensor (located in the audio-navigation unit) detects the direction change (angular speed) of the vehicle. The sensor is an oscillation gyro built into the audio-navigation unit.
Sensor Element Structure
The sensor element is shaped like a tuning fork, and it consists of the piezoelectric parts, the metal block, and the support pin. There are four piezoelectric parts: one to drive the oscillators, one to monitor and maintain the oscillation at a regular frequency, and two to detect angular velocity. The two oscillators, which have a 90-degree twist in the center, are connected at the bottom by the metal block and supported by the support pin. A detection piezoelectric part is attached to the top of each oscillator. The driving piezoelectric part is attached to the bottom of one oscillator, and the monitoring piezoelectric part is attached to the bottom of the other oscillator.
Oscillation Gyro Principles
The piezoelectric parts have electric/mechanical transfer characteristics. They bend vertically when voltage is applied to both sides of the parts, and voltage is generated between both sides of the piezoelectric parts when they are bent by an external force. The oscillation gyro functions by utilizing this characteristic of the piezoelectric parts and Coriolis force. (Coriolis force deflects moving objects as a result of the earth's rotation.) In the oscillation gyro, this force moves the sensor element when angular velocity is applied.
Operation
- The driving piezoelectric part oscillates the oscillator by repeatedly bending and returning when an AC voltage of 6 kHz is applied to the part. The monitoring-side oscillator resonates because it is connected to the driving-side oscillator by the metal block.
- The monitoring piezoelectric part bends in proportion to the oscillation and outputs voltage (the monitor signal). The navigation unit control circuit controls the drive signal to stabilize the monitor signal.
- When the vehicle is stopped, the detecting piezoelectric parts oscillate right and left with the oscillators, but no signal is output because the parts are not bent (no angular force).
- When the vehicle turns to the right, the sensor element moves in a circular motion with the right oscillator bending forward and the left oscillator bending rearward. The amount of forward/rearward bend varies according to the angular velocity of the vehicle.
5. The detecting piezoelectric parts output voltage (the yaw rate signal) according to the amount of bend. The amount of vehicle direction change is determined by measuring this voltage.
Global Positioning System (GPS)
The global positioning system (GPS) enables the navigation system to determine the current position of the vehicle by using the signals transmitted from the satellites in orbit around the earth. The satellites transmit the satellite identification signal, orbit information, transmission time signal, and other information. When the GPS receiver receives a signal from four or more satellites simultaneously, it calculates the current position of the vehicle based on the distance to each satellite and the satellite's position in its respective orbit.
Position Detection Image with GPS Satellite
Precision of GPS
The precision of the GPS varies according to the number of satellites from which signals are received and the view of the sky. The accuracy is indicated by the color of the GPS icon shown on the display.
GPS Antenna
The GPS antenna amplifies and transmits the signals received from the satellites to the GPS receiver.
GPS Receiver and Clock
The GPS receiver is built into the audio-navigation unit. It calculates the vehicle position by receiving the signal from the GPS antenna. The current time, vehicle position and signal reception condition is transmitted from the GPS receiver to the audio-navigation unit to adjust vehicle position and the clock in the audio-navigation switch panel display.
Audio-Navigation Unit
The audio-navigation unit calculates the vehicle position and guides you to the destination. The unit performs map matching correction, GPS correction, and distance tuning. It also controls the menu functions and the HDD, and interprets voice commands. With control of all these items, the audio-navigation unit makes the navigation picture signal, then it transmits the signal to the navigation display unit.
Calculation of Vehicle Position
The audio-navigation unit calculates the vehicle position (the driving direction and the current position) by receiving the directional change signals from the yaw rate sensor and the travel distance signals from vehicle speed pulse (VSP) signal of the PCM.
Map Matching Tuning
The map matching tuning is accomplished by indicating the vehicle position on the roads on the map. The map data transmitted from the HDD is checked against the vehicle position data, and the vehicle position is indicated on the nearest road. Map matching tuning does not occur when the vehicle travels on a road not shown on the map, or when the vehicle position is far away from a road on the map.
GPS Tuning
The GPS tuning is accomplished by indicating the vehicle position as the GPS's vehicle position. The audio-navigation unit compares its calculated vehicle position data with the GPS vehicle position data. If there is large difference between the two, the indicated vehicle position is adjusted to the GPS vehicle position.
Distance Tuning
The distance tuning reduces the difference between the travel distance signal from the VSP and the distance data on the map. The audio-navigation unit compares its calculated vehicle position data with the GPS vehicle position data. The audio-navigation unit then decreases the tuning value when the vehicle position is always ahead of the GPS vehicle position, and it increases the tuning value when the vehicle position is always behind the GPS vehicle position.
Traffic Information
The Acura navigation system's real-time traffic feature helps you avoid traffic delays by providing up to the minute traffic information in many metropolitan areas across the contiguous USA. Color coded freeways appear on the navigation screen, displaying current traffic flow, and/or the locations of accidents and traffic conditions affected by construction and weather. Real-time traffic data services are offered on a subscription basis for a nominal fee following the 90-day free trial period.
Weather Information
The Acura navigation system's weather information option allows you to view the weather forecast, warning list, warning map, and weather radar. The weather information is available in a subscription basis for a fee following the 90-day free trial period.