CN107315185B - System and method for detecting phase center of GPS antenna by continuous rotation method - Google Patents
System and method for detecting phase center of GPS antenna by continuous rotation method Download PDFInfo
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- CN107315185B CN107315185B CN201710756109.1A CN201710756109A CN107315185B CN 107315185 B CN107315185 B CN 107315185B CN 201710756109 A CN201710756109 A CN 201710756109A CN 107315185 B CN107315185 B CN 107315185B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/23—Testing, monitoring, correcting or calibrating of receiver elements
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
- G05B19/042—Programme control other than numerical control, i.e. in sequence controllers or logic controllers using digital processors
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D3/00—Control of position or direction
- G05D3/12—Control of position or direction using feedback
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/20—Pc systems
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Abstract
The invention discloses a GPS antenna phase center detection system adopting a continuous rotation method, which comprises a base, a rotary table and a control unit, wherein the rotary table is arranged on the base; the rotary table comprises a supporting rod, a cantilever supporting plate, a rotary supporting bearing, a driven gear and a GPS antenna connecting rod; the cantilever end of the cantilever supporting plate is fixed with a stepping motor, a driving gear meshed with the driven gear is arranged on an output shaft of the stepping motor, the stepping motor is connected with an encoder, and the encoder is used for feeding back the rotation angle of the stepping motor; the control unit comprises a man-machine interaction module, a GPS time service module and a motor driver which are all connected with the singlechip controller. The singlechip controller is connected with the encoder and is used for receiving motor rotation angle information fed back by the encoder, so that closed-loop control of the GPS antenna connecting rod is realized. The invention can accurately change the pointing direction of the antenna and effectively reduce the influence of observation errors such as multipath effect and the like. The detection result is accurate, the data is real, and the applicability is strong.
Description
Technical Field
The invention belongs to the field of GPS antenna detection methods and devices, and particularly relates to a continuous rotation system composed of a rotation table and a control system and a GPS antenna phase center detection method realized by the device.
Background
GPS observation is used as a geodetic measure and plays an important role in earth dynamics research and high-precision crust deformation monitoring. The GPS observation equipment consists of a receiver and an antenna, wherein the antenna is used for receiving satellite electromagnetic signals, and the receiver is used for setting an observation mode and processing the observation signals. In field observation, a baseline vector between observation antennas can be calculated using differential observations formed from synchronized observation data acquired by two or more GPS devices.
Because of the mechanical and electrical properties of the antenna itself, there is a deviation between the geometrical center (reference point) and the electrical center (phase center) of the antenna, and therefore it is necessary to detect the antenna phase center to improve the accuracy of observation by phase center correction in high-accuracy geodetic measurements.
The phase center correction value of the GPS antenna may be described by the antenna phase center offset (Phase Center Offset, PCO) and the phase center change (Phase center Variation, PCV), respectively. Wherein PCO is the spacing of the antenna average phase center (MPC) from the antenna reference point (Antenna reference point, ARP); PCV is the deviation of the instantaneous phase center from the average phase center of a single observation, which varies with satellite signal altitude, azimuth.
At present, the phase center detection method mainly comprises a rotary antenna method, a microwave darkroom method and an automatic robot detection method.
The rotating antenna method is a method commonly used in China at present, an antenna to be measured is rotated by 2 to 4 directions in an outdoor ultra-short base line, each direction observes a period, and the phase center offset of the antenna is calculated through the base line solution vector difference of each period. The rotating antenna method has mechanical rotation errors, has long measurement period, can introduce multipath effect and other observation errors due to different observation periods in all directions, and can not obtain phase center change due to method limitation.
The microwave darkroom method detects the phase center shift and change of the antenna by transmitting analog GPS signals in the darkroom, which was proposed and developed by the university of born in germany in 1994. The method cannot reflect the real field GPS observation environment, so that the detection result is in great dispute.
The automatic robot detection method uses a multi-degree-of-freedom robot to rotate and tilt a calibrated antenna in a certain step length outdoors, and uses a large number of observation values to calculate coefficients of spherical harmonics for fitting an antenna phase center model. The method is proposed by the university of Hanou in Germany in 1997, is currently considered as the most accurate detection method, but the technology has extremely high research cost and difficulty, no mature product exists in China at present, and is not beneficial to the detection of autonomous antennas such as Beidou system and the like.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a continuous rotation method GPS antenna phase center detection system. The continuous rotation system is used for accurately changing the pointing direction of the antenna, so that the operation error introduced by a rotation antenna method is avoided; the device is utilized to rotate the antenna to be measured in a high-frequency period under GPS time to change the antenna pointing direction of each observation epoch, so that the observation data of each pointing direction of the antenna is uniformly distributed in the whole observation period, and the phase center offset and the change of the antenna are calculated by utilizing the observation data. As the observation environment conditions of the pointing directions of the antennas have extremely strong correlation, the influence of observation errors such as multipath effect and the like can be effectively reduced. The method has the characteristics of accurate result, high degree of automation, real data and strong applicability.
In order to solve the technical problems, the invention provides a continuous rotation method GPS antenna phase center detection system, which comprises a base, a rotary table and a control unit, wherein the base is a standard base of a surveying instrument; the rotary table comprises a supporting rod, a central hole is formed in the upper portion of the supporting rod, and a cantilever supporting plate, a rotary supporting bearing, a driven gear and a GPS antenna connecting rod are sequentially arranged at the top of the supporting rod from bottom to top; one end of the cantilever support plate is a circular ring with the same shape as the top of the support rod, and the outer ring of the slewing support bearing, the circular ring and the support rod are coaxially connected; the driven gear is sleeved on the GPS antenna connecting rod, the lower part of the GPS antenna connecting rod passes through the driven gear and the inner ring of the slewing bearing and then is inserted into the central hole at the upper part of the supporting rod, and the GPS antenna connecting rod, the driven gear and the inner ring of the slewing bearing are coaxially connected; the top of the GPS antenna connecting rod is a threaded column used for being connected with a tested GPS antenna; the cantilever end of the cantilever supporting plate is fixedly provided with a stepping motor, the output shaft of the stepping motor is provided with a driving gear meshed with the driven gear, the stepping motor is connected with an encoder, and the encoder is used for feeding back the rotation angle of the stepping motor; the control unit comprises a man-machine interaction module, a GPS time service module and a motor driver which are all connected with the singlechip controller; the GPS time service module realizes time synchronization of the system and GPS time; the motor driver is connected with the stepping motor and drives the stepping motor to rotate according to an instruction output signal of the singlechip controller; the singlechip controller is connected with the encoder and is used for receiving motor rotation angle information fed back by the encoder, so that closed-loop control of the GPS antenna connecting rod is realized.
In the continuous rotation method GPS antenna phase center detection system, the transmission ratio of the driving gear to the driven gear is 8:1, the driving gear is made of forged steel, and the driven gear is made of nylon.
The precision of the slewing bearing is P5 grade.
The maximum fit clearance between the GPS antenna connecting rod and the slewing bearing is 0.04mm, so that the maximum homing error of the rotation of the GPS antenna to be detected is 0.06mm, and the detection of the phase center of the GPS antenna is met.
The stepping motor adopts a 60-degree stepping motor, the static torque is 3.0Nm, and the stepping angle is 1.8 degrees.
The encoder adopts an incremental photoelectric rotary encoder, and the resolution is 1000 pulses/rotation.
The singlechip controller adopts a singlechip controller taking C8051F020 as a CPU;
transmitting signals to the motor driver through three IO ports of pulse, direction and enabling of the singlechip controller so as to drive the stepping motor to rotate; realizing man-machine interaction with a man-machine interaction module with a key set and a display function through an SPI communication interface of the singlechip controller, and setting operation parameters of the GPS antenna connecting rod and observing operation states through the man-machine interaction module by a user, wherein the operation parameters at least comprise a time sequence and an angle sequence of rotation of the GPS antenna connecting rod; the serial communication interface of the singlechip controller is communicated with the GPS time service module to receive GPS satellite data in real time, the required UTC time is extracted from the GPS satellite data and converted into GPS time, and the rotation of the GPS antenna in the detection process takes the time as a reference; and receiving pulse information sent by the encoder through a counter interface of the singlechip controller, feeding back rotation angle information of the GPS antenna connecting rod, and realizing closed-loop control of the rotating table.
The motor driver is set to be in a 2 subdivision mode, the step angle of the motor corresponding to each pulse sent out by the IO port of the singlechip controller is 0.9 degrees, and the step angle transmitted to the GPS antenna connecting rod through the driving gear and the driven gear is 0.1125 degrees, so that the rotation angle precision required by phase center detection is achieved.
The GPS time service module is GPS terminal equipment taking an MT3329 satellite positioning receiving chip as a core, automatically locks satellites and receives GPS signals after being electrified, and continuously and outwardly transmits data through a serial interface, wherein the baud rate is 200bps, and the data updating frequency is 10HZ; the data instructions follow the NMEA-0183 standard format, including global positioning data, satellite state information, geodetic coordinate information, UTC time and date information.
Firstly, installing a tested GPS antenna on a threaded column at the top end of a GPS antenna connecting rod of a rotary table, installing the rotary table on a base, leveling the rotary table through the base, and installing the tested GPS antenna, the rotary table and the base on an observation pier which accords with the GPS observation environment condition; erecting a reference GPS device on an observation pier at a position which is not more than 20m away from the GPS antenna to be detected, and forming an ultra-short base line with the GPS antenna to be detected; then, detection is carried out, and the steps are as follows:
step one, when detection starts, initializing a system, namely setting the rotation time and angle sequence of a detected GPS antenna into a register of a singlechip controller by a user through a man-machine interaction module;
step two, the singlechip controller updates the system time in real time through the GPS time service module, and reads the rotation time sequence from the register;
step three, the singlechip controller reads the current time from the GPS time service module, judges whether the current time reaches the rotation starting time, executes the step four to perform one-time antenna rotation operation when the time when the tested GPS antenna needs to rotate is reached, otherwise, repeats the step three, reads the current time from the GPS time service module until the rotation starting time is reached;
and step four, antenna rotation operation comprises the following steps:
4-1) the singlechip controller reads the rotation angle sequence from the register;
4-2) calculating a required rotation angle and direction, outputting a command signal to a motor driver, and reading the rotated angle from an encoder;
4-3) judging whether the requirement of the angle sequence is met, if so, outputting a stop instruction to the motor driver, and then returning to the step two, otherwise, returning to the step 4-2) until the requirement of the angle sequence is met.
Compared with the prior art, the invention has the beneficial effects that:
(1) The result is accurate. Compared with the traditional rotary antenna method, the detection precision is improved in multiple aspects:
in the aspect of mechanism design, the leveling of the antenna in the measuring process is realized by adopting a standard base of the surveying instrument, and the leveling precision of the antenna is ensured; the centering precision of the rotation of the antenna is improved by controlling the fit clearance between the rotating shaft sleeves; the encoder is used for closed-loop feedback, so that the rotation angle precision of the antenna is improved; the load of the rotary table is improved by adopting a speed reduction gear transmission mechanism with a large transmission ratio, so that the device can meet the detection requirements of more types of antennas; the driven gear is made of nylon, the driving gear is made of metal, and therefore phenomena of tooth surface abrasion, gear tooth meshing overtightening, gear thermal deformation and the like can be effectively reduced or prevented, and the service life and stability of the device are effectively improved.
In the aspect of the detection method, a continuous rotation method is used for periodically and repeatedly observing the pointing direction of each antenna in an observation period, so that GPS observation results of all antenna directions are in the same period, and the observation environment conditions among all directions have extremely strong correlation, thereby effectively eliminating the influence of most observation errors such as multipath effect and the like; the continuous rotation system is utilized to realize strict synchronization with GPS time, so that time separation of antenna rotation and GPS signal acquisition in the detection process is ensured, rotation frequency can be effectively increased, rotation angle interval is reduced, sampling points are more dense, and fitting precision of detection results is effectively improved.
(2) The degree of automation is high. Compared with the traditional rotary antenna method, the invention uses the singlechip controller to control the work of the whole system, thereby realizing the automation of the detection process.
(3) The data is true. Compared with a microwave darkroom method, the continuous rotation method provided by the invention has the advantages that the antenna phase center is obtained through calculation by collecting GPS satellite signals, the actual working condition of the GPS can be reflected better, and the detection result is more real and effective.
(4) The applicability is strong. Compared with a robot method, the continuous rotation system is easier to move, convenient to maintain and lower in cost, and has a stronger application prospect.
Drawings
FIG. 1 is a schematic diagram of a rotary table in a continuous rotation method GPS antenna phase center detection system according to the present invention;
FIG. 2 is a control block diagram of a GPS antenna phase center detection system according to the continuous rotation method of the present invention;
FIG. 3 is a main control flow of the detection process of the present invention;
FIG. 4 is a flow of rotation control in the detection process of the present invention.
In the figure:
10-base, 20-revolving stage, 21-bracing piece, 22-centre hole, 23-cantilever backup pad, 24-slewing bearing, 25-driven gear, 26-GPS antenna connecting rod, 27-screw thread post, 28-step motor, 29-driving gear, 30-encoder, 31-singlechip controller, 32-man-machine interaction module, 33-GPS time service module, 34-motor driver.
Detailed Description
The technical solution of the present invention will be described in further detail with reference to the accompanying drawings and the specific embodiments, which are only illustrative of the present invention and are not intended to limit the present invention.
As shown in fig. 1 and 2, the system for detecting the phase center of a GPS antenna according to the present invention includes a base 10, a rotary table 20, and a control unit.
In order to improve the detection precision and realize the leveling of the antenna in the measuring process, the base 10 adopts a standard base of a surveying instrument.
The rotary table 20 comprises a supporting rod 21, a central hole 22 is formed in the upper portion of the supporting rod 21, and a cantilever supporting plate 23, a rotary supporting bearing 24, a driven gear 25 and a GPS antenna connecting rod 26 are sequentially arranged on the top of the supporting rod 21 from bottom to top; one end of the cantilever support plate 23 is a ring with the same shape as the top of the support rod 21, and the outer ring of the slewing bearing 24, the ring and the support rod 21 are coaxially connected; the driven gear 25 is sleeved on the GPS antenna connecting rod 26, the lower part of the GPS antenna connecting rod 26 passes through the driven gear 25 and the inner ring of the slewing bearing 24 and then is inserted into the central hole 22 at the upper part of the supporting rod 21, and the GPS antenna connecting rod 26, the driven gear 25 and the inner ring of the slewing bearing 24 are coaxially connected; the top of the GPS antenna connecting rod 26 is a threaded column 27 for connecting with a tested GPS antenna; the cantilever end of cantilever backup pad 23 is fixed with step motor 28, be equipped with on the output shaft of step motor 28 with the driving gear 29 of driven gear 25 meshing, step motor 28's mounted position is to guarantee to make driving gear 29 and driven gear 25's normal meshing, step motor 28 adopts 60 type step motor, and the dead torque is 3.0Nm, and the step angle is 1.8. The stepper motor 28 is connected with an encoder 30, and the encoder 30 is used for feeding back the rotation angle of the stepper motor 28; the encoder 30 employs an incremental photoelectric rotary encoder with a resolution of 1000 pulses/revolution (i.e., 0.36 °).
In order to improve the load of the rotary table to meet the requirements of more types of antennas, the gear of the speed reduction gear transmission mechanism adopts a single-mode straight-tooth cylindrical gear, and 8:1, such as: the driving wheel is 15 teeth, the driven wheel is 120 teeth, the driving gear is made of forged steel, and the driven gear is made of nylon, so that phenomena such as tooth surface abrasion, gear tooth meshing overtightening, gear thermal deformation and the like are effectively reduced or prevented, and the service life and stability of the device are improved.
In order to improve the service life and facilitate maintenance, the slewing bearing 24 in the invention adopts a P5 precision grade, and the slewing precision is better than 0.02mm.
In the invention, the screw thread column at the top end of the GPS antenna connecting rod 26 adopts American 5/8-11 screw thread column for fixing the tested GPS antenna. In order to ensure the rotation precision of the GPS antenna, the fit clearance between the GPS antenna connecting rod 26 and the rotation support bearing 24 is 0.04mm at maximum, so that the centering error of the rotation of the detected GPS antenna is 0.06mm at maximum, thereby meeting the requirement of the phase center detection of the GPS antenna.
As shown in fig. 2, the control unit includes a man-machine interaction module 32, a GPS timing module 33 and a motor driver 34, which are all connected with the single-chip microcomputer controller 31; the GPS time service module 33 realizes time synchronization of the system and GPS time; the motor driver 34 is connected with the stepper motor 28, and the motor driver 34 drives the stepper motor 28 to rotate according to the instruction output signal of the singlechip controller 31; the singlechip controller 31 is connected with the encoder 30, and is configured to receive motor rotation angle information fed back by the encoder 30, thereby implementing closed-loop control on the GPS antenna connecting rod 21.
In the control unit of the present invention, the single-chip controller 31 is a core device for control, and is responsible for analyzing input signals, executing operation instructions, outputting control signals, and the like.
The singlechip controller 31 adopts a singlechip controller taking C8051F020 as a CPU.
The man-machine interaction module 32 has a key set and a display function.
The GPS time service module 33 adopts GPS terminal equipment taking an MT3329 satellite positioning receiving chip as a core, automatically locks satellites and receives GPS signals after being electrified, and continuously and outwardly transmits data through a serial interface, wherein the baud rate is 200bps, and the data updating frequency is 10HZ; the data instructions follow the NMEA-0183 standard format and include at least global positioning data, satellite state information, geodetic coordinate information, UTC time and date information, wherein UTC time accuracy is 0.1 μs.
The motor driver 34 is set to a 2 subdivision mode, and the step angle corresponding to each pulse signal sent to the motor driver 34 by the IO port of the single-chip microcomputer controller 31 is 0.9 °, and the step angle transmitted to the GPS antenna connecting rod 26 through the driving gear 29 and the driven gear 25 is 0.1125 °, so as to achieve the rotation angle precision required by the phase center detection.
In the control process of the invention, signals are sent to the motor driver 34 through the three IO ports of pulse, direction and enabling of the singlechip controller 31 to drive the stepping motor 28 to rotate; man-machine interaction is realized through the SPI communication interface of the singlechip controller 31 and the man-machine interaction module 32 with a key set and a display function, and a user sets the operation parameters of the GPS antenna connecting rod 26 and observes the operation state through the man-machine interaction module 32, wherein the operation parameters at least comprise a time sequence and an angle sequence of rotation of the GPS antenna connecting rod 26. The serial communication interface of the singlechip controller 31 is communicated with the GPS time service module 33 to receive GPS satellite data in real time, extract the required UTC time from the GPS satellite data, convert the UTC time into GPS time, and take the rotation of the GPS antenna in the detection process as a reference. Pulse information sent by the encoder 30 is received through a counter interface of the singlechip controller 31, and rotation angle information of the GPS antenna connecting rod 26 is fed back, so that closed-loop control of the rotating table is realized.
The specific detection process comprises the following steps:
the GPS antenna to be measured is arranged on a threaded column 27 at the top end of a GPS antenna connecting rod 26 of the rotary table 20, the rotary table 20 is arranged on the base 10 and leveled through the base 10, and the GPS antenna to be measured, the rotary table 20 and the base 10 are all arranged on an observation pier which accords with the GPS observation environment condition. And erecting a reference GPS device on an observation pier at a position which is not more than 20m away from the measured GPS antenna, and forming an ultra-short base line with the measured GPS antenna.
As shown in fig. 3, when the detection starts, a user sets the rotation time and angle sequence of the detected GPS antenna to a register of the single-chip microcomputer controller 31 through the man-machine interaction module 32, after initialization, reads the rotation time sequence from the register, updates the system time in real time through the GPS time service module 33, reads the current time from the GPS time service module 33, judges whether the current time reaches the rotation start time, starts to execute one-time antenna rotation operation when the time when the detected GPS antenna needs to rotate is reached, and otherwise, continues to read the current time from the GPS time service module 33 until the rotation start time is reached. As shown in fig. 4, the flow of the antenna rotation operation is: (1) Starting a rotation operation, and reading a rotation angle sequence from a register; (2) Calculating the required rotation angle and direction, outputting a command signal to the motor driver 34, reading the rotated angle from the encoder 30, (3) judging whether the requirement of the angle sequence is reached, if so, outputting a stop command to the motor driver 34, and returning to the main flow, otherwise, returning to the step (2). Namely: the singlechip controller 31 sends an instruction signal to the motor driver 34 through the IO port to drive the stepping motor 28, the output shaft of the stepping motor 28 drives the driving gear 29 to rotate and is transmitted to the GPS connecting rod 26 through the driven gear 25, and then the GPS connecting rod 26 drives the antenna to be tested to rotate; in the rotation process, the singlechip controller 31 receives the rotation angle information of the output shaft of the stepping motor 28 through the encoder 30 so as to feed back the rotation angle of the GPS antenna to be measured in real time; when the rotation angle of the measured GPS antenna reaches the corresponding rotation angle requirement of the angle sequence, the single chip microcomputer controller 31 sends an instruction signal to the motor driver 34, and stops driving the stepper motor 28, and the measured GPS antenna stops rotating. At this time, the singlechip controller 31 continues to update the system time through the GPS timing module 33, and waits for the next start of the rotation operation.
In the whole observation period, the tested GPS antenna continuously rotates at a certain angle and at a certain time interval under the drive of the continuous rotation system, and the GPS receiver is set to collect satellite signals at the static moment of the antenna by utilizing the time synchronization function of the continuous rotation system and the GPS time, so that the tested GPS antenna points to different directions at equal time intervals in each period. When the observation period is sufficient, the phase center offset and the change of the antenna can be respectively calculated by analyzing the ultrashort baseline measurement values of different antenna orientations and different satellite signal incidence directions in the observation period.
The data processing process is as follows:
(1) Checking and preprocessing the observed data by using teqc software, and extracting the required epoch reconstruction observed data file;
(2) Respectively resolving ultrashort baseline vectors of each reconstructed file by using GPS resolving software;
(3) Calculating a phase center offset vector of the GPS antenna to be measured through the change of a base line result under the pointing direction of each antenna in the observation period, wherein the vector is represented by three components of north, east and high;
(4) And (3) combining the satellite track, fitting the coefficient of spherical harmonic function of the antenna phase center model by using the observation residual error except the phase center offset, and calculating the antenna phase center change value which is represented by the offset of satellite signals under the incident conditions of different zenith angles and different azimuth angles.
Examples:
the detection site is built in a region with firm and stable geological structure, at least one group of forced centering observation piers with the distance not more than 20m are arranged, strong electromagnetic signal interference does not exist around the observation piers, and the point position looking around the high angle is not obstructed by more than 15 degrees.
The rotary table 20 of the present invention is mounted on a standard base of a surveying instrument, is fixed to a GPS observation pier through the base 10, and is leveled. The GPS antenna to be tested is arranged on a threaded column 27 of the rotary table 20 of the invention, and forms an ultra-short base line with the reference GPS equipment. The sampling period of the measured GPS device and the reference GPS device is set to 15s, and the satellite height cut-off angle is set to 0 °.
The detection process comprises the following steps: with reference to continuous observation of GPS equipment, the antenna always points to the north direction; the tested GPS equipment starts to record data from any moment, the rotating table 20 drives the antenna to respectively point to four directions in a rotating period, the rotating period is 1 minute, and continuous observation is carried out for 24 hours. The operation per cycle is as follows:
baseline solutions were performed using GPS solution software and data were processed:
(1) And extracting data in the four antenna directions to form four observation files, namely obtaining four sampling files with sampling intervals of 1min pointed by different antennas in the same observation period, calculating four groups of super-segment baseline observation values by using the four observation files and the observation files of a reference instrument, and calculating the phase center offset vector of the GPS antenna.
(2) The satellite signal angle of incidence and the satellite signal azimuth angle are used to fit the antenna phase center change values by using the observation residual errors except the phase center offset in all the epochs in combination with the GPS ephemeris and the satellite orbit.
The detection result is in standard atx format, which includes antenna phase center offset and variation at each GPS signal frequency. The phase center offset is represented by three components of north, east and high, and the phase center change is represented by offset (angle step length 5 degrees) of satellite signals under the incident conditions of different zenith angles and different azimuth angles, wherein the unit is mm. The result file examples are shown in table 1.
Table 1: example of detection results
The invention can be obtained by the embodiment with the following characteristics:
(1) The result is accurate. The continuous rotation system drives the GPS antenna to automatically rotate with high precision by taking the GPS time as a reference, so that the phase center offset and the change of the GPS antenna are accurately calculated by using a method of continuously rotating the antenna to be measured, the influence of most observation errors such as multipath effect and the like is effectively eliminated, more dense sampling points are obtained, and the detection result of the phase center of the GPS antenna is more accurate.
(2) The degree of automation is high. The rotation of the GPS antenna to be detected in the detection process is realized by the continuous rotation system, and the detection process does not need manual intervention.
(3) The data is true. The detection process is completed outdoors, the used data are GPS satellite signal data, the actual working condition of the GPS can be reflected, and the detection result is more real and effective.
(4) The applicability is strong. The continuous rotation system is used in the GPS ultra-short baseline field, the antenna phase center detection work can be completed by utilizing the method for continuously rotating the antenna to be detected, and the device is simple and convenient to operate and has a strong application prospect.
Although the invention has been described above with reference to the accompanying drawings, the invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many modifications may be made by those of ordinary skill in the art without departing from the spirit of the invention, which fall within the protection of the invention.
Claims (10)
1. A phase center detection system of a GPS antenna by a continuous rotation method comprises a base (10), a rotary table (20) and a control unit, and is characterized in that,
the base (10) is a standard base of a surveying instrument;
the rotary table (20) comprises a supporting rod (21), a central hole (22) is formed in the upper portion of the supporting rod (21), and a cantilever supporting plate (23), a rotary supporting bearing (24), a driven gear (25) and a GPS antenna connecting rod (26) are sequentially arranged at the top of the supporting rod (21) from bottom to top; one end of the cantilever supporting plate (23) is a circular ring with the same shape as the top of the supporting rod (21), and the outer ring of the rotary supporting bearing (24), the circular ring and the supporting rod (21) are coaxially connected; the driven gear (25) is sleeved on the GPS antenna connecting rod (26), the lower part of the GPS antenna connecting rod (26) penetrates through the driven gear (25) and the inner ring of the rotary support bearing (24) and then is inserted into the central hole (22) at the upper part of the support rod (21), and the GPS antenna connecting rod (26), the driven gear (25) and the inner ring of the rotary support bearing (24) are coaxially connected; the top of the GPS antenna connecting rod (26) is provided with a threaded column (27) for connecting with a tested GPS antenna; a stepping motor (28) is fixed at the cantilever end of the cantilever supporting plate (23), a driving gear (29) meshed with the driven gear (25) is arranged on an output shaft of the stepping motor (28), the stepping motor (28) is connected with an encoder (30), and the encoder (30) is used for feeding back the rotation angle of the stepping motor (28);
the control unit comprises a man-machine interaction module (32), a GPS time service module (33) and a motor driver (34), which are all connected with the singlechip controller (31); the GPS time service module (33) realizes time synchronization of the system and GPS time; the motor driver (34) is connected with the stepping motor (28), and the motor driver (34) drives the stepping motor (28) to rotate according to an instruction output signal of the singlechip controller (31); the singlechip controller (31) is connected with the encoder (30) and is used for receiving motor rotation angle information fed back by the encoder (30), so that closed-loop control of the GPS antenna connecting rod (21) is realized.
2. The system for detecting the phase center of the continuous rotation method GPS antenna according to claim 1, wherein the transmission ratio of the driving gear (29) to the driven gear (25) is 8:1, the driving gear (29) is made of forged steel, and the driven gear (25) is made of nylon.
3. The continuous rotation GPS antenna phase center detection system according to claim 1, wherein the accuracy of the slewing bearing (24) is of the P5 scale.
4. The system for detecting the phase center of the GPS antenna by the continuous rotation method according to claim 1, wherein the fit clearance between the GPS antenna connecting rod (26) and the slewing support bearing (24) is 0.04mm at maximum, so that the centering error of the rotation of the GPS antenna to be detected is 0.06mm at maximum, so as to meet the detection of the phase center of the GPS antenna.
5. The system for detecting the phase center of a GPS antenna according to claim 1, wherein the stepping motor (28) is a 60-type stepping motor, the static torque is 3.0Nm, and the stepping angle is 1.8 °.
6. The continuous rotation GPS antenna phase center detection system according to claim 1, wherein the encoder (30) employs an incremental photoelectric rotary encoder with a resolution of 1000 pulses/revolution.
7. The continuous rotation method GPS antenna phase center detection system according to claim 1, wherein the single-chip microcomputer controller (31) adopts a single-chip microcomputer controller taking C8051F020 as a CPU;
the three IO ports are transmitted to the motor driver (34) through the pulse, the direction and the enabling of the singlechip controller (31) to drive the stepping motor (28) to rotate;
realizing man-machine interaction with a man-machine interaction module (32) with a key set and a display function through an SPI communication interface of the singlechip controller (31), and setting operation parameters of the GPS antenna connecting rod (26) and observing operation states through the man-machine interaction module (32), wherein the operation parameters at least comprise a time sequence and an angle sequence of rotation of the GPS antenna connecting rod (26);
the serial communication interface of the singlechip controller (31) is communicated with the GPS time service module (33) to receive GPS satellite data in real time, the required UTC time is extracted from the GPS satellite data and converted into GPS time, and the rotation of a GPS antenna in the detection process takes the time as a reference;
pulse information sent by the encoder (30) is received through a counter interface of the singlechip controller (31), and rotation angle information of the GPS antenna connecting rod (26) is fed back, so that closed-loop control of the rotating table is realized.
8. The system according to claim 1, wherein the motor driver (34) is set to a 2-segment mode, and a motor step angle corresponding to each pulse sent from the IO port of the single chip controller (31) is 0.9 °, and a step angle transmitted to the GPS antenna connection rod (26) through the driving gear (29) and the driven gear (25) is 0.1125 °, so as to achieve a rotation angle precision required for phase center detection.
9. The system for detecting the phase center of a GPS antenna according to claim 1, wherein the GPS timing module (33) is a GPS terminal device with an MT3329 satellite positioning receiving chip as a core, and automatically locks satellites and receives GPS signals after being powered on, the GPS timing module (33) continuously transmits data outwards through a serial interface, the baud rate is 200bps, and the data update frequency is 10HZ; the data instructions follow the NMEA-0183 standard format, including global positioning data, satellite state information, geodetic coordinate information, UTC time and date information.
10. A detection method of a continuous rotation method GPS antenna phase center detection system, characterized in that a detected GPS antenna is installed on a threaded column (27) at the top end of a GPS antenna connecting rod (26) of a rotary table (20), the rotary table (20) is installed on a base (10) and leveled by the base (10), and the detected GPS antenna, the rotary table (20) and the base (10) are all installed on an observation pier which accords with the GPS observation environment condition by using the continuous rotation method GPS antenna phase center detection system as claimed in any one of claims 1 to 9; erecting a reference GPS device on an observation pier at a position which is not more than 20m away from the GPS antenna to be detected, and forming an ultra-short base line with the GPS antenna to be detected; the detection steps are as follows:
step one, when detection starts, system initialization is carried out, namely a user sets the rotation time and angle sequence of a detected GPS antenna to a register of a singlechip controller (31) through a man-machine interaction module (32);
step two, the singlechip controller (31) updates the system time in real time through the GPS time service module (33) and reads the rotation time sequence from the register;
step three, the singlechip controller (31) reads the current time from the GPS time service module (33), judges whether the current time reaches the rotation starting time, executes the step four to perform antenna rotation operation once when the current time reaches the time when the tested GPS antenna needs to rotate, otherwise, repeats the step three, reads the current time from the GPS time service module (33) until the rotation starting time is reached;
and step four, antenna rotation operation comprises the following steps:
4-1) the singlechip controller (31) reads the rotation angle sequence from the register;
4-2) calculating a desired rotation angle and direction, outputting a command signal to a motor driver (34), reading the rotated angle from an encoder (30);
4-3) judging whether the requirement of the angle sequence is met, if so, outputting a stop instruction to a motor driver (34), and then returning to the step two, otherwise, returning to the step 4-2) until the requirement of the angle sequence is met.
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| CN108304002B (en) * | 2018-02-27 | 2024-05-14 | 成都凯天电子股份有限公司 | Method for controlling target movement angle of proximity sensor |
| CN110231032B (en) * | 2019-06-28 | 2022-07-08 | 南京市计量监督检测院 | Antenna phase center test system with north-seeking function |
| CN112285747B (en) * | 2020-10-16 | 2022-04-22 | 中国地震局第一监测中心 | GNSS receiver antenna phase center on-line measuring device and measuring method |
| CN113568011A (en) * | 2021-07-16 | 2021-10-29 | 航天科工海鹰集团有限公司 | PPK multi-path eliminating technology |
| CN113267794B (en) * | 2021-07-20 | 2021-10-29 | 杭州中科微电子有限公司 | Antenna phase center correction method and device with base line length constraint |
| CN115308814B (en) * | 2022-10-09 | 2023-01-06 | 中国地震局第一监测中心 | Time service error measurement method and device of low sampling data acquisition equipment |
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