Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
1999-02-22
2001-05-29
Chin, Gary (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S220000, C701S216000, C342S357490
Reexamination Certificate
active
06240367
ABSTRACT:
FIELD OF THE PRESENT INVENTION
Background of the Present Invention
Although vehicle positioning systems have become widely known only during the last few decades, their historical roots go much deeper. The world's first vehicle positioning system was the “south-point-chariot”, an automatic direction-keeping system developed by the Chinese around 200-300AD (possible earlier according to some legendary accounts), almost 1000 years before the magnetic compass was invented. Its operation was based on the phenomenon that as a vehicle changing heading, the outer wheels travel farther than the inner wheels by a distance that is a simple mathematical function of the change in heading. When changing heading, a gear driven by the outer wheel of the south-point chariot automatically engaged and rotated a horizontal turntable to exactly offset the change in heading. Thus, a figure mounted on the turntable continuously pointed an outstretched arm in the same direction, like a compass needle, regardless of which way the chariot turned. As technologies in positioning systems and in other fields are improved and expanded, Newsday, there are various types of the positioning system.
The new technology development in positioning system, which will lead to a low cost, small size, and high accurate positioning system, will have broad applications in the commercial community. The applications of vehicle positioning systems are spreading like wildfire, to car, taxi, busses, trains, robotics, to mining/construction, and to the paging and data portions of the personal communications services market as well as cellular emergency 911 service.
The ability to determinate vehicle location is the most fundamental requirement of advanced commercial vehicle tracking systems, automobile navigation and route guidance systems, and intelligent vehicle highway systems.
Developments of Intelligent vehicle highway systems are major worldwide movement to improve the efficiency, safety, and environmental aspects of road traffic through the application of information, communication, positioning, and control technologies.
Generally, some conventional methods for determining the position of a vehicle are to employ dead reckoning systems, radio positioning systems, and hybrid systems. The method of the present invention is a hybrid, fully fusion method for determining position and attitude of a vehicle.
A dead reckoning system based on inertial angular rate sensors and acceleration sensors can provide the position and attitude information of a vehicle. It consists of an inertial measurement unit (IMU) and a processor. The inertial measurement unit consists of three orthogonally or more than three skewed mounted accelerometers, which serve as acceleration sensors to measure the vehicle acceleration, and three orthogonally or more than three skewed mounted gyros, which serve as angular rate sensors to measure the vehicle angular rate, and associated hardware and electronics. These components provide the necessary information to stabilize the navigation reference frame for the purpose of providing isolation from vehicle rotation motions, either physically, in a gimbaled inertial system, or analytically, in a strapdown inertial system. The processor processes the platform's acceleration and angular rate from the inertial measurement unit. After initializing the starting position and initiating an alignment procedure, a continuous output of position, velocity, and attitude data from the processor is available, independent of any outside agency and environmental conditions.
The dead reckoning system based on inertial angular rate sensors and acceleration sensors, which is often referred to inertial navigation system, or inertial positioning system, or inertial reference system has the advantage, over all other positioning methods, that it is totally self-contained and that it outputs the full solution and that it offers wide bandwidth.
However, an inertial positioning system is expensive and subjects to drift over an extended period of time. This is primarily caused by its sensor error sources, such as gyro drift, accelerometer bias, and scale factor errors.
Generally, the ways of improving accuracy of inertial positioning systems include employing highly accurate inertial sensors and aiding an inertial positioning system using an external sensor.
The global positioning system (GPS) is a satellite-based, worldwide, all-weather radio positioning and timing system. The system is originally designed to provide precise position, velocity, and timing information on a global common grid system to an unlimited number of adequately equipped users.
A specific receiver is the key for a user to access the global positioning system. A conventional, single antenna receiver of the global positioning system supplies world-wide, highly accurate three dimensional position, velocity, and timing information, but not attitude, by processing so-called pseudo range and delta range measurements from the code tracking loops and the carrier tracking loops respectively. In a benign radio environment, the signal propagation errors and satellites errors, including selective availability, serve as the bounds for positioning errors the global positioning system. However, the signals of the global positioning system may be intentionally or unintentionally jammed or spoofed, and the receiver antenna may be obscured during vehicle attitude maneuvering, and the performance degrades when the signal-to-noise ratio of the global positioning system signal is low and the vehicle is undergoing highly dynamic maneuvers.
As both the cost and size of high performance receiver of the global position system are reduced in the past decade, a multiple-antenna receiver of the global positioning system can provide both position and attitude solution of a vehicle, using interferometric techniques. This technology utilizes measurements of carrier phase difference on the multiple-antenna to obtain highly accurate relative position measurements. Then, the relative position measurements are converted to the attitude solution. The advantages of this approach are long-term stability of the attitude solution and relative low cost. However, this system remains the characterization of low bandwidth and being susceptible to shading and jamming, and requires at least 3 antennas configurations for a three-axis attitude solution, and requires antenna separation enough for high attitude resolution.
Because of the inherent drawbacks of a stand-alone inertial positioning system and a stand-alone receiver of the global positioning system, a stand-alone inertial positioning system or a stand-alone receiver of the global positioning system can not meet mission requirements under some constraints such as low cost, long-term high accuracy, continuous output, etc.
Performance characteristics of the mutually compensating stand-alone global positioning system receiver and the stand-alone inertial positioning system suggest that, in many applications, an integrated global positioning/inertial system, combining the best properties of both systems, will provide superior accurate continuous navigation capability. This navigation capability is unattainable in either one of the two systems alone. Many public papers exist on the topic of an integrated global positioning/inertial positioning system. Numerous global positioning/inertial systems have been commonly used since the concept of the global positioning system was initiated in 1973.
The benefits offered by an integrated global positioning/inertial positioning system are outlined as follow:
(1) The aiding of the global positioning system receiver signal-tracking loop process with inertial data allows the effective bandwidth of the loops to be reduced, resulting in an improved tracking signal in a noisy and dynamic environment.
(2) An inertial positioning system not only provides navigation information when the signal of the global positioning system is lost temporarily, but also reduce the search time required to reacquire the signal of the
Chan Raymond Y.
Chin Gary
David and Raymond Patent Group
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