Vehicle Positioning Device Clock Error Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current positioning devices for moving bodies, such as vehicles, face challenges in accurately calculating three-dimensional vehicle velocity due to differences between GPS-derived two-dimensional velocities and actual velocities, especially on sloped roads, and suffer from built-in clock errors that affect measurement accuracy.
Innovation Solution
A positioning device that calculates a time difference in pseudo distances and Doppler shifts from GPS signals to estimate built-in clock errors, modifying range rates to improve velocity calculations in an orthogonal coordinate system, thereby enhancing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS satellite positioning results are used to correct sensor measurements, then positioning accuracy is improved, but measurement error remains due to built-in clock drift
Solution Approach 1:
The system continuously monitors the difference between GPS-derived velocity and sensor-measured velocity, using this feedback to dynamically correct sensor scale factors and drift. This closed-loop approach compensates for built-in clock errors by constantly adjusting sensor parameters based on GPS reference measurements, thereby improving both positioning accuracy and measurement reliability
Solution Approach 2:
The system changes sensor parameters (scale factors, zero voltages) based on GPS reference measurements. By dynamically adjusting these parameters to match GPS-derived values, the system compensates for clock drift effects and maintains accurate measurements despite built-in clock errors
2Ease of operation
If three-dimensional vehicle velocity is calculated from GPS positioning results, then velocity measurement capability is improved, but accuracy deteriorates at low speeds due to small range rate differences
Solution Approach 1:
The system uses sensor measurements as an intermediary to bridge the gap between GPS positioning and velocity calculation. By combining sensor-derived velocity with GPS range rate corrections, the system maintains accurate velocity measurement capability across all speed ranges, including low speeds where direct GPS velocity calculation is inaccurate
3Adaptability or versatility
If map matching is performed to identify vehicle position on road links, then positioning utility is improved, but positioning accuracy deteriorates when measured distance exceeds road link length
Solution Approach 1:
The system dynamically adjusts the scale factor based on the relationship between measured distance and road link length. When the measured distance exceeds the road link length (indicating slope effects), the system modifies the scaling to account for the three-dimensional nature of GPS velocity versus two-dimensional map data, thereby maintaining positioning accuracy while preserving the utility of map matching
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces errors caused by built-in clock errors, increasing the accuracy of velocity measurements, especially at low speeds and on sloped roads, by modifying range rates based on clock error corrections.
Implementation Method 1
a first range rate is calculated based on a Doppler shift of a carrier frequency of a GPS satellite radio wave
Data Source
AI summary
An object is to provide in a positioning device of a moving body such as a vehicle, a technique which can modify a built-in clock error of a moving body to increase accuracy of a velocity. The positioning device includes a built-in clock error estimating unit which estimates a built-in clock error of the vehicle as a built-in clock error based on a difference between a delta range and a calculated range rate, and a range rate estimating unit which estimates a vehicle stop range rate based on position and velocity of GPS satellite based on transmission signal and a vehicle position, and modifies a calculated range rate, based on the built-in clock error. Further, the positioning device includes an own vehicle velocity calculating unit which calculates own vehicle velocities in three axial directions which form an orthogonal coordinate system, based on a navigation matrix, the vehicle stop range rate and the modified calculated range rate.