초록 ▼

A method of GPS accuracy adjustment for an integrated INS/GPS navigation system which utilizes microelectro mechanical systems (MEMS) based inertial sensors to mitigate multipath problems arising when a vehicle is in an area with many high-rise buildings is disclosed. Even when GPS measurement outpu

A method of GPS accuracy adjustment for an integrated INS/GPS navigation system which utilizes microelectro mechanical systems (MEMS) based inertial sensors to mitigate multipath problems arising when a vehicle is in an area with many high-rise buildings is disclosed. Even when GPS measurement output values are deviated from that expected, the INS/GPS navigation system uses as many measurement outliers as possible without discarding, unless they are obvious error values, thereby maintaining a practical level of accuracy. The measurement outliers typically occur when the integrated INS/GPS navigation system receives GPS signals which have transmitted through multipaths such as reflection by buildings, since the signal path lengths vary.

대표청구항 ▼

What is claimed is: 1. A method of GPS measurement accuracy adjustment for microelectro mechanical system (MEMS) based integrated INS/GPS (inertial navigation system)/(global positioning system) navigation systems, comprising the following steps of: defining a situation when GPS multipath problems

What is claimed is: 1. A method of GPS measurement accuracy adjustment for microelectro mechanical system (MEMS) based integrated INS/GPS (inertial navigation system)/(global positioning system) navigation systems, comprising the following steps of: defining a situation when GPS multipath problems are prone to occur based on a number of visible GPS satellites; detecting measurement outliers in GPS measurement output based on a difference between a residual value and a reference residual value; and employing the measurement outliers for a position tracking operation while lowering GPS reporting accuracy; wherein the measurement outlier is a parameter in the GPS measurement output whose difference from the corresponding Kalman filter estimate overly exceeds the reference residual value predetermined by the Kalman filter. 2. The method of GPS measurement accuracy adjustment as defined in claim 1, wherein said step of defining the situation when the GPS multipath problems are prone to happen includes a process for determining the situation based on a number of visible GPS satellites or a time length after recovering the number of visible GPS satellites to a predetermined value. 3. The method of GPS measurement accuracy adjustment as defined in claim 1, further comprising a step of defining degrees of accuracy adjustments depending on degrees of difference between the residual and the predetermined reference residual value. 4. The method of GPS measurement accuracy adjustment as defined in claim 3, wherein said step of defining the accuracy adjustments includes a process for lowering the degree of accuracy adjustment of the measurement outlier with a small degree when the amount of difference is small, and lowering the degree of accuracy adjustment of the measurement outlier with a large degree when the amount of difference is large. 5. The method of GPS measurement accuracy adjustment as defined in claim 1, wherein said step of detecting the measurement outliers includes a process for discarding the measurement outlier when the difference from the predetermined reference residual value is too large. 6. The method of GPS measurement accuracy adjustment as defined in claim 4, wherein said step of employing the measurement outliers for the position tracking operation includes a process for attaching information showing the degree of accuracy adjustment to the measurement outlier when the measurement outlier is sent to an integration Kalman filter which integrates INS and GPS. 7. An integrated INS (inertial navigation system)/GPS (global positioning system) navigation system implementing microelectro mechanical system (MEMS) sensors for a grand vehicle, comprising: an inertial navigation system (INS) having an inertial measurement unit (IMU) which incorporates MEMS sensors; a GPS (global positioning system) receiver which receives GPS satellite signals from a plurality of GPS satellites to produce GPS measurement output indicating an absolute position and velocity of the ground vehicle; a Kalman filter which combines outputs of the INS and the GPS receiver and performs a Kalman filter processing; and an accuracy adjustment controller which controls an overall operation of the navigation system including accuracy adjustment operations with respect to measurement outliers contained in the GPS measurement output; wherein the measurement outlier is a parameter in the GPS measurement output whose difference from the corresponding Kalman filter estimate overly exceeds a predetermined reference residual value, and the measurement outlier is used for a position tracking operation while lowering its accuracy reported by the GPS receiver. 8. The integrated INS/GPS navigation system as defined in claim 7, wherein said MEMS sensors are configured by three-axis accelerometers and three-axis gyroscopes in which accelerations corresponding to coordinates of the vehicle are detected by the three accelerometers and angular rates corresponding to coordinate directions of the vehicle are detected by the three gyroscopes. 9. An integrated INS (inertial navigation system) /GPS (global positioning system) navigation system implementing microelectro mechanical system (MEMS) sensors for a ground vehicle, comprising: means for defining a situation when GPS multipath problems are prone to occur based on a number of visible GPS satellites; means for detecting measurement outliers in GPS measurement output based on a difference between a residual value in the measurement output and a reference residual value; means for employing the measurement outliers for a position tracking operation while lowering GPS reporting accuracy; wherein the measurement outlier is a parameter in the GPS measurement output whose difference from Kalman filter estimate overly exceeds the reference residual value. 10. The integrated INS/GPS navigation system as defined in claim 9, wherein said means for defining the situation when the GPS multipath problems are prone to happen includes means for determining the situation based on a number of visible GPS satellites or a time length after recovering a number of visible GPS satellites to a predetermined number. 11. The integrated INS/GPS navigation system as defined in claim 9, further comprising means for defining degrees of accuracy adjustments depending on degrees of difference between a residual value and the reference residual value. 12. The integrated INS/GPS navigation system as defined in claim 11, wherein said means for defining the degrees of accuracy adjustments includes means for lowering the degree of accuracy adjustment of the measurement outlier with a small degree when the amount of difference is small and for lowering the degree of accuracy adjustment of the measurement outlier with a large degree when the amount of difference is large. 13. The integrated INS/GPS navigation system as defined in claim 9, wherein said means for detecting the measurement outliers includes means for discarding the measurement outlier when its residual value is too large compared with the reference residual value. 14. The integrated INS/GPS navigation system as defined in claim 12, wherein said means for employing the measurement outliers for the position tracking operation includes means for attaching information showing the degree of accuracy adjustment to the measurement outlier when the measurement outlier is sent to an integration Kalman filter which integrates INS and GPS.