Acura TSX / Honda Accord CL. Manual — part 161

Fig. 21: Navigation System Schematic

NAVIGATION FUNCTION

The navigation system is composed of the navigation unit, the ECM/PCM (vehicle speed signal), the GPS
antenna, microphone, voice control switch, audio unit, climate control unit, and the display unit.

2004 Acura TSX

2004 ACCESSORIES & EQUIPMENT Navigation System - TSX

Fig. 22: Navigation Function Diagram

VEHICLE SPEED PULSE

The vehicle speed pulse is sent by the ECM/PCM. The ECM/PCM receives a signal from the countershaft
speed sensor, then the processes the signal and transmits it to the speedometer and other systems.

Fig. 23: Vehicle Speed Pulse Input

YAW RATE-LATERAL ACCELERATION SENSOR

The yaw rate-lateral acceleration sensor (located in the navigation unit) detects the direction change (angular
speed) of the vehicle. The sensor is an oscillation gyro built into the navigation unit.

SENSOR ELEMENT STRUCTURE

2004 Acura TSX

2004 ACCESSORIES & EQUIPMENT Navigation System - TSX

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

1. 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.

2. 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.

3. 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)

4. 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.

Fig. 24: Piezoelectric Operation

2004 Acura TSX

2004 ACCESSORIES & EQUIPMENT Navigation System - TSX

GLOBAL POSITIONING SYSTEM (GPS)

The global positioning system (GPS) enables the navigation system to determine the current position of the
vehicle by utilizing 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 three or more satellites simultaneously, it calculates the current position of
the vehicle based on the distance to each satellite and the satellite positions on their respective orbits.

Fig. 25: Position Detection Image With GPS Satellite

2004 Acura TSX

2004 ACCESSORIES & EQUIPMENT Navigation System - TSX