Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2000-04-17
2001-08-28
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C707S793000, C707S793000, C707S793000, C707S793000, C342S175000, C116S001000
Reexamination Certificate
active
06282495
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relate generally to vehicle navigation systems and more particularly to a vehicle navigation system with improved startup performance.
Known vehicle navigation systems generally include a plurality of motion and position determining devices, such as a GPS receiver, accelerometers, gyros, wheel speed sensors, etc. The navigation system further includes a CPU receiving data from all of the sensors and having a hard drive containing a database of roads which may be traveled by the vehicle. As is generally known, the navigation system determines the position of the vehicle relative to the database of roads and displays the current position of the vehicle on a display. Further, the driver can select a destination relative to the database of roads. The navigation system then displays turn-by-turn instructions to the driver to guide the driver to the selected destination.
In order to conserve battery power, navigation systems generally enter a “low power” mode when the vehicle engine is not running. In low power mode, the hard drive is not spinning, the CPU is not booted, the sensors do not consume power and the GPS receiver does not receive GPS signals. To determine whether the engine is running, the current systems are connected to the “ON” position of the vehicle ignition switch. When the ignition switch is turned to the ON position, the navigation system switches from low power mode to full power mode. At that time, the hard drive in the navigation system starts spinning, the CPU is booted, the motion sensors begin to warmup and stabilize, and the GPS receiver receives GPS signals and begins calculating a GPS position solution. This “warmup” period by the navigation system components requires time during which the driver of the vehicle may be taking other actions that the navigation system needs to monitor in order to know the current position of the vehicle. It would be difficult and undesirable to force the vehicle to remain still while the navigation system is in the warmup period. In cold weather, this warmup period could be 30 seconds or more.
Additionally, startup performance of the navigation system is closely related to the GPS receiver's “time to first fix.” To minimize this time, it is important for the GPS receiver to have fresh satellite ephemeris data. This data, which is used to determine the precise location of the GPS satellites, typically needs to be refreshed at least every four hours. If the vehicle is parked for more than four hours, the GPS receiver must first obtain fresh ephemeris data before calculating an accurate position solution. This further delays the startup performance of the vehicle navigation system.
SUMMARY OF THE INVENTION
The present invention provides a vehicle navigation system having improved powerup performance. The vehicle navigation system includes a sensor for detecting the presence of the driver, such as a motion sensor. When the sensor determines that the driver is present, the navigation system enters the warmup period, switching from low power mode to full power mode. The hard drive starts spinning, the CPU is booted, the sensors begin warmup and the GPS receiver and CPU begin calculating a GPS position solution. By the time the driver enters the vehicle and starts the car, the navigation system is operational.
If the presence of the driver is detected, but the vehicle engine is not running within a predetermined time period, the navigation system returns to the low power mode. This reduces power consumption in the event of a false detection of the driver's presence, or if the driver did not start the vehicle.
The vehicle navigation system can monitor the ignition switch of the vehicle to determine if the engine is running within the time period; however, preferably the vehicle navigation system includes engine running detection circuitry which simply monitors the power supply from the vehicle to the vehicle navigation system. The engine running detection circuitry monitors the electrical power supply of the vehicle. When the engine is not running, the voltage of the vehicle power supply is a fairly constant DC voltage, typically 12 to 14 volts. When the engine is running, there is a measurable AC voltage superimposed on the DC power supply output. The AC voltage is a result of transients generated by the ignition system primary circuit and charge of pulses from the generator/altemator.
Generally, the engine running detection circuitry monitors the amplitude of the AC content. The engine running detection circuitry may use both time and frequency domain techniques to monitor the AC content in the vehicle power supply. When the AC content exceed a predetermined threshold, the engine running detection circuitry determines that the engine is running. When the AC content falls below the predetermined threshold, the engine running detection circuitry determines that the engine is not running. If the engine running detection circuitry determines that the engine is not running within a predetermined time period after the presence of the driver has been detected, the navigation system reenters the low power standby mode. While the engine is running, the navigation system continues to operate at full power. When the engine running detection circuitry determines that the engine is not running for a predetermined time period, the navigation system enters the low power standby mode.
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Kirkhart Michael O.
Spencer, II Larry E.
Carlson & Gaskey & Olds
Cuchlinski Jr. William A.
Hernandez Olga
Magellan Dis, Inc.
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