Tutorials to .com

Tutorials to .com » Mechine » Eda-pld » Vehicle navigation and positioning system simulation test

Vehicle navigation and positioning system simulation test

Print View , by: iSee ,Total views: 27 ,Word Count: 2689 ,Date: Sat, 27 Jun 2009 Time: 5:23 AM

With the development of vehicle information-based, satellite global positioning system (GPS) applications to be rapidly increasing. The system not only provides real-time vehicle location, speed and time, also has anti-theft function, provided for the pilot workshop and the latest traffic information communication in order to guarantee the smooth flow of traffic and road safety. At present, the goal of positioning technology with an independent position, terrestrial radio positioning and GPS satellite positioning three. Independent positioning of the largest drawback is that the cumulative effect of errors, the positioning accuracy of positioning with the ongoing process of decline; terrestrial radiolocation interference by ground obstacles, resulting in signal attenuation and multi-path effects significantly, resulting in decline or failure positioning accuracy; GPS positioning system and the establishment of the United States to develop a new generation of sophisticated satellite-based radio navigation system, the ground for global coverage, multi-function, high accuracy, GPS technology is therefore widely used in the value and development potential. Simulation of GPS vehicle navigation and positioning test can simulate the real satellite positioning, the experiment needed to be off-line virtual positioning data, experimental teaching, driving a virtual vehicle research is of great significance.

l GPS navigation principle and its application

Principle 1.1 GPS navigation

GPS is based in California, Los Angeles Air Force Base (AFB) in the United States Air Force systems Command Space Division under the Joint Program Office (JPO) is responsible for development. 1973, JPO in the United States Department of Defense (DOD) under the direct leadership of the beginning of the development program, development, testing and deployment of a satellite global positioning system. Today, with the timing and location of the navigation system capacity (NAVSTAR) - Global Positioning System (GPS) system is the first program. GPS can be seen as a spatial location from the known location of the satellite to the unknown land, sea and air, and near-Earth space, the user's location system. In fact, the launch of the satellite signal itself time with a clear sign, so the work of the use of synchronous receiver can receive the signals to measure signal propagation time. In addition to point positioning, the carrier to determine the instantaneous position, velocity and precise time is the most basic function of GPS. GPS system was built in 1993 and put into use. GPS satellites from space and ground monitoring stations and subscriber equipment is composed of three parts. Mainly refers to the user GPS receiver equipment. Satellite navigation and positioning system is known in every moment of the satellite position and velocity on the basis of a reference point for the space satellite, the receiving device through the test station to measure the distance to the satellite or concept, such as Doppler shift measurements to determine the station location, speed.

1.2 GPS positioning in the vehicle navigation application

The field of transport has always been a satellite navigation and positioning system, one of the largest application market. As the car manufacturing technology, modern transportation system, such as the development of the moving target based on GPS monitoring technology innovation in the automotive sector has gradually become the one of technical studies. ITS Intelligent Transportation System is a concrete manifestation of this area.

Modernization of urban transport is one of the infrastructure, how the rational use of resources to enhance the logistics capabilities and the operation of the vehicle safety and reduce traffic congestion and accidents is to build a modern city an important sign, logistics vehicle scheduling system for completed the design of this goal. The system uses computer technology, communication technology cluster and signal processing technology, the logistics of the operation of the unified management of vehicles, to provide users with a variety of services, vehicles and logistics management and monitoring of science. In addition, vehicle logistics network encounter danger warning to the Center at any time. The construction of the system in the community have had a positive response to the modernization of urban traffic management to a new level. GPS positioning system monitoring and management to the public security police patrol vehicles 110 to provide a practical monitoring and management of the scheduling program has greatly enhanced the capacity of the public security alarm, the realization of the previously static to dynamic alarm alarm leap.

GPS-based vehicle location and monitoring system in buses, taxis, logistics, postal delivery, as well as monitoring and management of private cars have a certain degree of practical value, it is to strengthen the management of vehicles to effectively prevent and combat vehicle crime with a feasible solution.

2 GPS Simulation System Design

The simulation system design, including the main core of the calculation of satellite position, showing stars to determine the best positioning satellite selection, error calculation and position calculation of solutions.

2.1 Calculation of satellite position

Simulation of GPS navigation systems do not need to receive from the true satellite signal, replaced by satellite through the known equation of motion of any epoch calculated satellite coordinates of the satellite in order to determine the distribution of vehicles over, as a projection of vehicle location data source.

In the simulation, only the Earth's gravitational force to consider the role of the satellite, but also the quality of the assumption that the Earth is a sphere of uniformly distributed, and its focus on the quality of the center of the earth. The text in the data processing is not taken into account at all times the satellite perturbation change, it is not the track of high-precision simulation data. However, in order to reflect the movement of satellites, the use of message data in the almanac as the basis for calculating the initial value, the simulation accuracy is sufficient. Figure 1 is based on UTC (US-NO) 1993 on 1 day 7 years at the time of epoch O time for the benchmark, using planar projection of the satellite orbit said. Shown in Figure 1 at all times the use of the satellite parameters for the simulation starting point, use of matlab and simulation of data-processing functions can be achieved through the programming operation of the GPS constellation in real-time solver. Modeling process, a long elliptical orbit satellite α check axle 26 560 km, elliptical eccentricity e check 0.02. From the figure can be seen the image of the GPS satellite constellation and the movement of the spatial distribution.

Shown in Figure 1 according to the GPS satellite system, the initial data, available April 1, 2008 10:00:00 moment the satellite in the WGS in a coordinate system 84 of coordinates, see table 1.

Vehicle navigation and positioning system simulation test

Picture not clear? Click here to view the image (larger).

2.2 stars can be seen to determine

Run-time satellite in space, not all satellites are visible to the user have. Stars can be seen through the rapid judgments can effectively limit the number of visible satellites, thereby reducing the portfolio of satellite space traversal. In addition to the analysis of the process of considering the impact of the Earth, but also must take into account the ground, buildings or other objects blocking the signal generated. In addition, the satellite elevation angle is too low, the atmosphere generated by multi-path delay and the possibility of a larger problem, it must also be the introduction of shielding angle. Shielding angle generally take the most commonly used between 5 ° ~ 10 °. The formula for calculating the angle of elevation as follows:

Vehicle navigation and positioning system simulation test

Picture not clear? Click here to view the image (larger).

Where: R is the radius of the Earth; H satellite of the vertical height from the ground; φp, Lp, respectively, for receiving the latitude and longitude points; φs longitude for the satellite. Set E = 7 °, in longitude 117 ° 10'34 ", latitude 36 ° 42'47" and 10 m height, the visible stars and their coordinates as shown in table 2.

Vehicle navigation and positioning system simulation test

Picture not clear? Click here to view the image (larger).

2.3 The selection of the best positioning constellation

The use of GPS for navigation and positioning, the user and the relative position of the satellite is affected by the performance of one of the factors. How to choose positioning constellation, usually GDOP GDOP use to determine that the positioning constellation GDOP value by making the smallest of the GPS satellites.

The Earth by satellites and ground coverage of the target characteristics, we can see that the greater elevation top of Block Star, GDOP smaller. Therefore, the best constellation is bound to include the heart of the largest satellite elevation. From the above analysis we can see that in the selection of the best constellation, first select the maximum angle of elevation of a satellite, and then can be seen from other satellites and then choose 3, 4 stars common computing components of the satellite constellation value GDOP GDOP. So again, the final will be the GDOP GDOP order to achieve the minimum, the minimum GDOP value corresponding to four stars is the best combination of satellite constellations.

GDOP satellite constellation based on the calculation model of the constellation is based on the state of the matrix. Here the direction of the most commonly used cosine law. For α, β, γ, respectively, for the measurement points to the satellite slant range with the X, y, Z-axis angle. Order:

Vehicle navigation and positioning system simulation test

Picture not clear? Click here to view the image (larger).

The use of the constellation matrix, GDOP calculated as follows:

Vehicle navigation and positioning system simulation test

Picture not clear? Click here to view the image (larger).

Constellation, through the selection of the best positioning, positioning accuracy to be highest for the four satellite 2-9-16-17, the GDOP (geometric orientation factor) value of 5.112 8; PDOP (position accuracy of the geometric factor) value of 4. 986 4; HDoP (plane position accuracy of the geometric factor) value of 4.368 1; VDOP (vertical position accuracy of the geometric factor) value of 2.405 0; TDOP (time accuracy of the geometric factor) value of 1.129 8.

2.4 Error calculation

GPS positioning through the ground receiving equipment to receive satellite information to determine the location of ground points, so the error comes mainly from the GPS satellites, the satellite signal and ground spread of the process of receiving equipment. In addition, high-precision GPS positioning in the overall movement of the Earth Earth tides, tidal loading and the impact of relativistic effects, etc., but also lead to error of the reasons that can not be ignored.

In order to facilitate the understanding of a variety of errors usually affect the projection of the observation station to the satellite's distance to the distance corresponding to that error, called the equivalent pseudo-range error. Table 3 lists the type of GPS positioning error and the equivalent pseudo-range error.

Vehicle navigation and positioning system simulation test

Picture not clear? Click here to view the image (larger).

Described in a variety of positioning error sources in the simulation process, the vehicle for real driving simulation process, to be added in the calculation of specific error. A variety of errors on the positioning accuracy of the impact is different, the simulation can not be distinguished accurately, taking into account its integrated to the maximum to simulate the positioning error.

2.5 Positioning Solution

Position to solve the formula is as follows:

Vehicle navigation and positioning system simulation test

Picture not clear? Click here to view the image (larger).

Where: Vehicle navigation and positioning system simulation test

Picture not clear? Click here to view the image (larger). Determination of R, see references [4]; [Xs, Ys, Zs] for the satellite coordinates of the instantaneous center of the earth; [Xp, Yp, Zp] geocentric coordinates for the vehicle.

WGS positioning of vehicles in a 84 position coordinates for a 2 429.8 lim (X direction of the coordinates), 4 569.8 km (y direction of the coordinates), 3 760.7 km (Z direction of the coordinates).

3 Simulation of the data flow system

Simulation of GPS satellite constellation will be a wGS all 84 satellites in real-time three-dimensional coordinates input to determine the visible stars of the stars can be seen through the observation points have been over to determine the visibility of satellites, and three-dimensional coordinate data input to select the best positioning constellation simulation part of the Constellation, based in part on the best choice of positioning methods can be seen from the composition of four stars in the constellation of the best positioning and vehicle location coordinates into the simulation of the simulation of vehicle location, based in part on the best positioning of the three-dimensional coordinates of the constellation of information Solution of three-dimensional coordinates to calculate the vehicle, and ultimately the determination of latitude and longitude of vehicles for vehicle positioning and navigation data to provide simulation results.

Vehicle navigation and positioning system simulation test

Picture not clear? Click here to view the image (larger).

4 Simulation results

The simulation model in Matlab modeling environment, the vehicle positioning information, such as Table 4 shown in table 6.

Vehicle navigation and positioning system simulation test

Picture not clear? Click here to view the image (larger).

Vehicle navigation and positioning system simulation test

Picture not clear? Click here to view the image (larger).

From the simulation results, the satellite almanac based on the positioning error of the introduction and vehicles has been calculated the location of the vehicle navigation and positioning system in all the simulation data. Under normal circumstances, the provisions of the PDOP value can not be greater than 6. From Table 5, we can see that a reasonable GDOP value, thus ensuring a reasonable positioning data. The output of the system all the virtual positioning data will be able to meet the vehicle navigation and positioning data simulation needs.

5 Conclusion

GPS is an advanced Global Positioning methods, are widely used in vehicle positioning and navigation. In this paper, based on satellite ephemeris, analysis of the trajectories of the constellation GPs, and on this basis the location of the receiver solver, the simulation of the vehicle navigation system GPS location information, to achieve positioning and navigation simulation. The vehicle model can simulate the real position of the satellite positioning for simulation debugging, virtual driving facilitate research.


EDA/PLD Articles


Can't Find What You're Looking For?


Rating: Not yet rated

Comments

No comments posted.