Vehicle compass using telematics unit and vehicle sensor information
A software compass used during a GPS outage calculates vehicle heading and presents it upon request. The software compass gathers information from a yaw rate sensor, wheel steering angle sensor, wheel speed sensor, and PRNDL gear position sensor to calculate vehicle heading using a weighting algorithm. Because the yaw rate sensor data is a central factor in calculating vehicle heading, the quality of calibration of the yaw rate sensor is of importance. The disclosed calibration algorithm calculates the yaw rate bias and scale factors to calibrate the yaw rate sensor.
1. A vehicle position detection system for using a telematics unit and vehicle sensor information to estimate a current vehicle position, the system comprising:
a yaw rate sensor that measures an angle of turn of the vehicle;
a wheel steering angle sensor that measures the angle at which one or more vehicle wheels are turned;
a wheel speed sensor that measures a speed of rotation of one or more wheels of the vehicle;
a gear position sensor that senses a current gear condition of a transmission of the vehicle;
a global positioning system that provides vehicle location and heading; and
a software compass application that calibrates the yaw rate sensor using at least yaw rate parameter values provided by: the yaw rate sensor, the wheel steering angle sensor, and wheel speed sensor, and
wherein the compass application calibrates the yaw rate sensor by applying a minimization algorithm to a function of a scale factor and a yaw rate bias, and
wherein the yaw rate sensor is used to estimate vehicle heading information in the absence of GPS location information.
2. The vehicle position detection system according to claim 1 , further including a display unit to present a parameter related to the vehicle heading information.
3. The vehicle position detection system according to claim 1 , wherein the gear position sensor is adapted to sense at least a Forward gear position, a Reverse gear position and Park gear position of the vehicle transmission.
4. The vehicle position detection system according to claim 1 , wherein the telematics unit includes a vehicle positioning system for calculating a current vehicle position in the absence of GPS data based at least in part on the estimated vehicle heading.
5. The vehicle position detection system according to claim 1 , wherein the telematics unit comprises:
a central processing unit implementing the software compass application;
a memory module that stores the software compass application; and
a vehicle bus across which the software compass application gathers sensor and gear position information.
6. A method, carried out by a computer, for detecting a vehicle location parameter using internally-referenced vehicle sensor information, the internally-referenced vehicle sensor information comprising at least yaw rate information from a yaw rate sensor, the method comprising the steps of:
recording a GPS-based vehicle location at a first time moment;
gathering first yaw rate parameters including yaw rate sensor data, wheel steering angle sensor data, wheel speed sensor data, and gear position data;
calibrating the yaw rate sensor with a software compass application by reference to the GPS-based vehicle location and the first yaw rate parameters, wherein the compass application calibrates the yaw rate sensor by applying a minimization algorithm to a function of a scale factor and a yaw rate bias, and;
at a second time moment after calibration of the yaw rate sensor, detecting a GPS outage such that GPS position data is unavailable;
after the second moment, gathering second yaw rate parameters including yaw rate sensor data, wheel steering angle sensor data, wheel speed sensor data, and gear position data; and
calculating estimated vehicle heading information at substantially the second moment from the second yaw rate parameters.
7. The method according to claim 6 , further comprising calculating a first estimated vehicle position at substantially the second moment based on at least the estimated heading information.
8. The method according to claim 6 , further comprising receiving and servicing a request for vehicle heading information during the GPS outage.
9. The method according to claim 6 , wherein calculating vehicle heading information at substantially the second moment from the second yaw rate parameters further comprises applying a weighting algorithm.
10. The method according to claim 6 , wherein gathering first yaw rate parameters and gathering second yaw rate parameters comprise accessing sensor data via a vehicle bus.
11. The method according to claim 7 , further comprising calculating a second estimated vehicle position at substantially a third moment, later in time than the second moment, based on at least the estimated heading information.
12. A non-transitory computer-readable medium including computer-executable instructions or detecting a vehicle location parameter using internally-referenced vehicle sensor information, the internally-referenced vehicle sensor information comprising at least yaw rate information from a yaw rate sensor, the method comprising computer executable instructions, when executed, facilitating performing the steps of:
recording a GPS-based vehicle location at a first time moment;
gathering first yaw rate parameters including yaw rate sensor data, wheel steering angle sensor data, wheel speed sensor data, and gear position data;
calibrating the yaw rate sensor with a software compass application by reference to the GPS-based vehicle location and the first yaw rate parameters, wherein the compass application calibrates the yaw rate sensor by applying a minimization algorithm to a function of a scale factor and a yaw rate bias, and;
at a second time moment after calibration of the yaw rate sensor, detecting a GPS outage such that GPS position data is unavailable;
after the second moment, gathering second yaw rate parameters including yaw rate sensor data, wheel steering angle sensor data, wheel speed sensor data, and gear position data; and
calculating estimated vehicle heading information at substantially the second moment from the second yaw rate parameters.
13. The non-transitory computer-readable medium including computer-executable instructions according to claim 12 , further comprising calculating a first estimated vehicle position at substantially the second moment based on at least the estimated heading information.
14. The non-transitory computer-readable medium including computer-executable instructions according to claim 12 , wherein calculating vehicle heading information at substantially the second moment from the second yaw rate parameters further comprises applying a weighting algorithm.
15. The non-transitory computer-readable medium including computer-executable instructions according to claim 13 , further comprising calculating a second estimated vehicle position at substantially a third moment, later in time than the second moment, based on at least the estimated heading information.