Calibration device and method for self-keeping time of positioning and orientation test system

Abstract

The invention discloses a calibration device and method for self-keeping time of a positioning and orientation test system, and the method comprises the steps: connecting a second pulse signal generated by a second pulse signal generation circuit of a Beidou / GPS receiver unit of the positioning and orientation test system to a signal input terminal Vi1 of an adapter; a signal output terminal Vo1 of the adapter is connected with an input end of a channel CH1 of the waveform recorder; a second pulse signal A2 generated by a second pulse signal generation circuit of the self-keeping time unit is connected to a signal input terminal Vi2 of the adapter and is respectively connected with a channel CH2 input terminal of the waveform recorder, a channel 1 input terminal of the general frequency counter / timer and an external trigger input terminal; a 2.5 ms time base signal A3 generated by the self-punctuality time unit is connected to a signal input wiring end Vi3 of the adapter and is connected with the input end of a channel CH3 of the waveform recorder; the problem that the self-keeping time starting point is difficult to capture and the self-keeping time cannot be measured in the prior art is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of measuring instrument calibration, and particularly relates to a calibration device and method for the autochronous time of a positioning and orientation test system. Background Art

[0002] The principle block diagram of the positioning and orientation test system is as Figure 1 shown, and it mainly consists of two parts: The first part is the Beidou / GPS navigation positioning and orientation test system composed of an antenna, a Beidou / GPS receiver unit, etc.; The second part is the inertial navigation positioning and orientation test system composed of an autochronous time unit and a fiber optic gyro navigation unit, etc.

[0003] The positioning and orientation test system has the advantages of small size, light weight, and high precision, and is usually installed on vehicles, such as vehicles, ships, aircraft, projectiles, satellites, etc. It is mainly used to test the time parameters, attitude parameters (heading angle, pitch angle, roll angle and their angular velocities), position parameters (longitude, latitude, altitude), speed parameters (eastward speed, northward speed, upward speed) at the location and at that moment, etc.

[0004] According to whether the Beidou / GPS signal received by the antenna is normal, the positioning and orientation test system has two working modes.

[0005] Working mode 1 means that the Beidou / GPS signal received by the antenna is normal, and the Beidou / GPS navigation positioning and orientation test system composed of the antenna, the Beidou / GPS receiver unit, etc. works to measure parameters such as the location, time, attitude, position, and speed at that moment, and its accuracy is determined by the accuracy of the Beidou / GPS navigation positioning and orientation test system.

[0006] Working mode 2 means that when the Beidou / GPS signal received by the antenna is abnormal (such as when there are situations of weak signal, interference, shutdown, etc.), the Beidou / GPS navigation positioning and orientation test system cannot work properly, and the inertial navigation positioning and orientation test system immediately starts to work to measure parameters such as the location, time, attitude, position, and speed at that moment, and its accuracy is determined by the accuracy of the inertial navigation positioning and orientation test system.

[0007] The working process of the positioning and orientation test system automatically switches between working mode 1 and working mode 2 according to whether the Beidou / GPS signals received by the antenna are normal. That is, when the Beidou / GPS signals received by the antenna are normal, it works in working mode 1. Once the Beidou / GPS signals received by the antenna are abnormal, it immediately and automatically switches to working mode 2. When the Beidou / GPS signals received by the antenna return to normal again, it immediately switches to working mode 1. Once the Beidou / GPS signals received by the antenna are abnormal again, it immediately switches to working mode 2, and such repeated automatic switching ensures that in the presence or absence of Beidou / GPS signals, parameters such as the location, time, attitude, position, and speed at that moment can be continuously measured without interruption, so that the direction and position will not be lost.

[0008] In addition, working mode 1 and working mode 2 can also be manually switched, and the antenna can also be turned off so that the positioning and orientation test system only operates in working mode 2.

[0009] The positioning and orientation test system is an integrated application of Beidou / GPS positioning and orientation technology and inertial navigation positioning and orientation technology, realizing dynamic timing, positioning, orientation, and speed measurement. The differences and similarities between the positioning and orientation test system and the Beidou / GPS receiver:

[0010] The similarities are that when the received Beidou / GPS signals are normal, both rely on receiving Beidou / GPS signals to measure parameters such as time, attitude, position, and speed, and the measurement accuracy is determined by the accuracy of the Beidou / GPS receiver.

[0011] The differences are that when the received Beidou / GPS signals are abnormal, the Beidou / GPS receiver cannot work properly and cannot measure parameters such as time, attitude, position, and speed, thus losing direction and position. While the positioning and orientation test system immediately activates the inertial navigation positioning and orientation test system to measure parameters such as time, attitude, position, and speed, so as to know the direction and position and will not lose direction and position.

[0012] The block diagram of the self - contained time unit is as Figure 2 shown: It is mainly composed of the four parts indicated by the four virtual boxes in the figure. The first part is the time - base oscillator; the second part is the second - pulse signal A2 generation circuit, and the signal it generates is represented by A2; the third part is the 2.5 - ms time - base signal A3 generation circuit, and the signal it generates is represented by A3; the fourth part is the control unit. The function of the self - contained time unit is that when the received Beidou / GPS signals are abnormal and the Beidou / GPS receiver cannot work properly, thus losing direction and position. At this time, it automatically switches to working mode 2, the time - base oscillator is in a free - oscillation state, providing a time - reference signal for the inertial navigation positioning and orientation test system, enabling the positioning and orientation test system to still work properly and provide information such as time, attitude, position, and speed.

[0013] The time-base signal generated by the time-base oscillator is processed by the second pulse signal A2 generation circuit to generate the second pulse signal A2 and by the 2.5 ms time-base signal A3 generation circuit to generate the 2.5 ms time-base signal A3. The control unit commands and controls the time-base oscillator, the second pulse signal A2 generation circuit, and the 2.5 ms time-base signal A3 generation circuit to realize their corresponding functions.

[0014] The block diagram of the working principle of the holdover time unit is as Figure 3 shown. The output waveforms of the second pulse signals A1, A2 and the 2.5 ms time-base signal A3 are as Figure 4 shown. The horizontal axis represents time, denoted by t, and in the vertical direction, A1, A2 and A3 are all pulse voltage signals. The low level of 0.0 V of A1, A2 and A3 is marked in the figure. Taking the typical unsynchronized segment T 11 , synchronization segment T 12 , unsynchronized segment T 13 and the Beidou / GPS signal interruption segment T 14 as an example of the four working processes for explanation.

[0015] After the positioning and orientation test system is powered on at time t 10 , it enters the unsynchronized segment T 11 . When the antenna receives the Beidou / GPS signal normally, the positioning and orientation test system works in working mode 1. The second pulse signal A1 generated by the second pulse signal A1 generation circuit of the Beidou / GPS receiver unit has an output waveform as Figure 4 shown by the A1 waveform in it. Its nominal period is 1 s, so it is called the second pulse, and its period is denoted by T A1 . In the segments of T 11 , T 12 and T 13 , since the Beidou / GPS signal is not interrupted, therefore, in these 3 segments, its period is T A1 , and its accuracy is determined by the accuracy of the Beidou / GPS receiver. In the segment of T 14 , since the Beidou / GPS signal is interrupted, the second pulse signal A1 is interrupted.

[0016] The time-base signal generated by the time-base oscillator is processed by the second pulse signal A2 generation circuit to generate the second pulse signal A2, and its output waveform is as Figure 4 shown by the A2 waveform in it. Its nominal period is 1 s, so it is called the second pulse. In the segment of T 11 , its period is denoted by T A2 . Since the time-base oscillator is not synchronized and is in a free oscillation state, its accuracy is determined by the accuracy of the time-base oscillator. In the segment of T 12 , since it is synchronized by A1, its period is the same as the period T A1 of A1, and is also denoted by T A1It is indicated that its accuracy is determined by the accuracy of the Beidou / GPS receiver. During the T 13 section, the time base oscillator is not synchronized. During the T 14 section, the Beidou / GPS signal is interrupted. Therefore, the time base oscillators in both sections are in a free oscillation state, and their periods are the same as those in the T 11 section, and are also represented by T A2 .

[0017] The time base signal generated by the time base oscillator generates a 2.5 ms time base signal A3 after passing through the 2.5 ms time base signal A3 generation circuit, and the output waveform is as shown by the A3 waveform in Figure 4 . Its nominal period is 2.5 ms, and its period in the T 11 section is represented by T A3 . Since the time base oscillator is not synchronized and is in a free oscillation state, its accuracy is determined by the accuracy of the time base oscillator. During the T 12 section, since the time base oscillator is synchronized by A1, its period is represented by T A4 , and its accuracy is determined by the accuracy of the Beidou / GPS receiver. During the T 13 section, the time base oscillator is not synchronized. During the T 14 section, the Beidou / GPS signal is interrupted. Therefore, the time base oscillator is in a free oscillation state, and its period is the same as that in the T 11 section, and is also represented by T A3 . Although the nominal periods of A1 and A2 are both 1 s, their accuracies in the T 11 , T 12 , T 13 and T 14 sections are not exactly the same. For the convenience of explanation, Figure 4 is drawn under the assumption that the actual value of the period T A2 is smaller than the actual value of T A1 . A2 and A3 are respectively generated by the time base signal generated by the time base oscillator passing through the second pulse signal A2 generation circuit and the 2.5 ms time base signal A3 generation circuit, and under the control of the control unit, A2 and A3 have the same accuracy and are synchronized. T A2 / T A3 = 1 s / 2.5 ms = 1000 ms / 2.5 ms = 400, that is, one period of the A2 waveform corresponds to 400 periods of the A3 waveform. If drawn strictly to scale, the 400 periods of the A3 waveform are too dense to be clearly seen, and only 4 periods of the A3 waveform corresponding to one period of the A2 waveform are drawn in the figure.

[0018] At the moment of t 10 , it enters the unsynchronized section T 11 . A2 and A3 are not synchronized by A1, but A2 and A3 are synchronized, and there is: T A2 = 400TA3 Its accuracy is determined by the accuracy of the time base oscillator.

[0019] At time t 11 moment, it enters the synchronization section T 12 , A2 and A3 are synchronized by A1. The periods of A2 and A1 are the same, denoted by T A1 , and there is: T A1 = 400T A4 , and its accuracy is determined by the accuracy of the Beidou / GPS receiver.

[0020] At time t 12 moment, when there are situations such as weak Beidou / GPS signals or interference, the synchronization is disrupted and it enters the unsynchronized section T 13 , A2 and A3 are not synchronized by A1, but A2 and A3 are synchronized, and there is: T A2 = 400T A3 , and the accuracy of A2 and A3 is determined by the accuracy of the time base oscillator.

[0021] At time t 13 moment, the Beidou / GPS signal is interrupted and it enters the Beidou / GPS signal interruption section. The A1 signal is interrupted, but A2 and A3 are synchronized, and there is: T A2 = 400T A3 , and its accuracy is determined by the accuracy of the time base oscillator.

[0022] For the calibration of the positioning and orientation test system, it is also to Figure 1 calibrate the two parts in it separately. For the calibration of the Beidou / GPS navigation positioning and orientation test system composed of the antenna, Beidou / GPS receiver unit, etc. in the first part, it can refer to the metrological technical specifications such as JJF 1403-2013 "Calibration Specification for Global Navigation Satellite System (GNSS) Receivers (Time Measurement Type)" and JJF 1118-2004 "Calibration Specification for Global Positioning System (GPS) Receivers (Geodetic Type and Navigation Type)".

[0023] The time parameter of the inertial navigation positioning and orientation test system composed of the holdover time unit and the fiber optic gyro navigation unit, etc. in Part 2 is an important indicator. Parameters such as attitude, position, and speed are all calculated using mathematical formulas corresponding to angles, electromagnetic wave propagation speed, distance, and time. Therefore, when the received Beidou / GPS signal is abnormal or even interrupted, the Beidou / GPS receiver cannot work properly and immediately switches to working mode 2. The time base oscillator is in a free oscillation state, providing a second pulse signal and a 2.5 ms time base signal for the inertial navigation positioning and orientation test system, enabling the positioning and orientation test system to still work normally and providing information such as time, attitude, position, and speed. Therefore, the time accuracy of the holdover time unit determines the accuracy of the inertial navigation positioning and orientation test system. Conducting precise measurement and calibration on it to ensure the unity of the quantity value of the time parameter is an important task.

[0024] The main technical indicators of the holdover time unit of a typical positioning and orientation test system are as follows:

[0025] Holdover time range: 0 - 7 d, maximum allowable error: ±20 ms;

[0026] Second pulse signal period range: 1 s, maximum allowable error: ±1 μs.

[0027] Currently, the positioning and orientation test system is a special test equipment developed for specific tasks. There is no corresponding verification regulation or calibration specification for the calibration of the holdover time unit parameters. The main difficulties in calibration are as follows:

[0028] First, it is difficult to capture the starting point of the holdover time

[0029] Under normal circumstances, the positioning and orientation test system operates by receiving Beidou / GPS signals. The second pulse signal generated by the second pulse signal A1 generation circuit of the Beidou / GPS receiver unit triggers and synchronizes the time base oscillator of the holdover time unit, enabling the time base signal generated by the time base oscillator to be synchronized with the second pulse signal A1 of the Beidou / GPS receiver unit. The time base signal generated by the time base oscillator generates a second pulse signal A2 after passing through the second pulse signal A2 generation circuit, and the time base signal generated by the time base oscillator generates a 2.5 ms time base signal A3 after passing through the 2.5 ms time base signal A3 generation circuit. At this time, the second pulse signal A2 and the 2.5 ms time base signal A3 have the same accuracy as the second pulse signal A1 of the Beidou / GPS receiver unit, and their accuracy is determined by the accuracy of the Beidou / GPS receiver. Since the second pulse signal of the Beidou / GPS receiver is synchronized with the national time and frequency standard, during the operation of the Beidou / GPS receiver in the positioning and orientation test system, the second pulse signal and the 2.5 ms time base signal generated by the holdover time unit are synchronized to the national high-precision time and frequency standard.

[0030] When the received Beidou / GPS signal is abnormal, the second pulse signal A1 generated by the Beidou / GPS receiver is interrupted. Due to the lack of triggering and synchronization of the second pulse signal A1, the time base oscillator of the self - contained time unit is in a free - oscillation state. The accuracy of the second pulse signal A2 and the 2.5 - ms time base signal A3 is determined by the technical specifications of the time base oscillator itself. Since the second pulse signal A1 generated by the Beidou / GPS receiver and the second pulse signal A2 generated by the self - contained time unit have the same waveform parameters such as frequency, amplitude, and pulse width, there is no difference between them when observed from the waveforms measured by an oscilloscope. Therefore, it is impossible to find the last second pulse signal generated by the Beidou / GPS receiver and the first second pulse signal generated by the self - contained time unit, that is, the starting point of the self - contained time.

[0031] Second, the self - contained time is long, with high precision and difficult to measure

[0032] When the received Beidou / GPS signal is abnormal, the second pulse signal generated by the Beidou / GPS receiver is interrupted, and the positioning and orientation test system immediately uses the second pulse signal generated by the self - contained time unit as the starting point of time. In the case where the received Beidou / GPS signal is abnormal, the inertial navigation positioning and orientation test system composed of the self - contained time unit and the fiber optic gyro navigation unit of the positioning and orientation test system still operates normally, and corresponding parameters are measured. The 2.5 - ms time base pulse signal A3 generated by the self - contained time unit is used as the timing reference for cumulative timing. The cumulative number of pulses in 7 days is: 7d×24h×3600s×400 = 241920000, the maximum allowable error is ±20ms, and its relative error is: ±20ms / 7d = ±3.31×10 -8 The time is long and the precision is high, exceeding the measurement range and precision of conventional instruments such as oscilloscopes and general - purpose counters.

[0033] Third, the second pulse signal has a narrow width, high precision and is difficult to measure

[0034] The second pulse signal output by the positioning and orientation test system has a very narrow pulse width compared to its period, that is, a very small duty cycle, and it is difficult to measure its second pulse with a general - purpose counter. Summary of the Invention

[0035] The technical problem to be solved by the present invention is to provide a calibration device and method for the self - contained time of a positioning and orientation test system to solve the technical problems such as the inability of the prior art to calibrate the time parameters of the self - contained time unit of the positioning and orientation test system.

[0036] The technical solution of the present invention is as follows:

[0037] A calibration device for the self-holding time of a positioning and orientation test system. The device includes an adapter. The second pulse signal A1 generated by the second pulse signal generation circuit of the Beidou / GPS receiver unit of the positioning and orientation test system is connected to the signal input terminal V of the adapter. i1 , the signal output terminal V of the adapter o1 is connected to the input terminal of channel CH1 of the waveform recorder; the second pulse signal A2 generated by the second pulse signal generation circuit of the self-holding time unit is connected to the signal input terminal V of the adapter i2 , the signal output terminal V of the adapter o2 is respectively connected to the input terminal of channel CH2 of the waveform recorder, the input terminal of channel 1 of the general frequency counter / timer, and the external trigger input terminal; the 2.5ms time base signal A3 generated by the 2.5ms time base signal generation circuit of the self-holding time unit is connected to the signal input terminal V of the adapter i3 , the signal output terminal V of the adapter 03 is connected to the input terminal of channel CH3 of the waveform recorder.

[0038] The 10MHz frequency signal output by the cesium clock is connected to the external reference input terminals of the waveform recorder and the general frequency counter / timer as its reference time base.

[0039] The adapter includes three independent common-emitter amplifiers; the base of the NPN-type transistor T 11 of the first common-emitter amplifier is connected to one ends of the resistors R 11 , R 12 , and R 13 . The other end of the resistor R 11 is led out to the signal input terminal V i1 . The other end of the resistor R 12 is connected to one end of the resistor R 14 and is led out to the power supply voltage input terminal V cc1 . The other end of the resistor R 13 is connected to the ground GND; the other end of the resistor R 14 is connected to the collector of T 11 and one fixed end of the potentiometer W 11 and is led out to the signal output terminal V o1 . The other fixed end of the potentiometer W 11 is connected to the ground GND; the emitter of T 11 is connected to one ends of the resistor R 15 and the capacitor C 11 . The other end of the resistor R 15 and the other end of the capacitor C 11 are connected to the ground GND; the second and third common-emitter amplifiers have the same principle and wiring as the first common-emitter amplifier.

[0040] A calibration method for a calibration device of the holdover time of a positioning and orientation test system, the method comprising:

[0041] Step 1: Preheat the adapter, waveform recorder, general frequency counter / timer, and cesium clock until the specified preheating time is reached;

[0042] Step 2: Select the 10 MHz frequency signal output by the cesium clock to provide an external reference frequency standard for the waveform recorder and the general frequency counter / timer;

[0043] Step 3: Set the time T to be calibrated for the holdover time unit x ;

[0044] Step 4: According to the holdover time to be calibrated and the calibration point, select the measurement channel of the waveform recorder, set it to the voltage measurement function, with an input impedance of 1 MΩ, DC coupling, and set the horizontal sweep coefficient t / div and the vertical deflection coefficient V / div;

[0045] Step 5: According to the period of the second pulse signal to be calibrated, set the function of the general frequency counter / timer to the period measurement function, select the gate time, with an input impedance of 1 MΩ, DC coupling, manually trigger and set the trigger level;

[0046] Step 6: Turn on the positioning and orientation test system to run normally in working mode 1, and turn on the voltage measurement function of the waveform recorder and the period measurement function of the general frequency counter / timer;

[0047] Step 7: Turn off the antenna output signal of the positioning and orientation test system, and automatically switch from working mode 1 to working mode 2 for operation;

[0048] Step 8: Use the waveform recorder to measure the waveform, measure the values at times t 21 and t 22 , calculate the holdover time measurement error, and determine whether it meets the technical index requirements;

[0049] Step 9: Use the general frequency counter / timer to measure the period T A2 of the pulse voltage waveform, calculate the period measurement error of the second pulse signal of the holdover time unit, and determine whether it meets the technical index requirements.

[0050] The method for calculating the holdover time measurement error includes: If the set holdover time is T x , at time t 21 , the antenna signal is turned off, the Beidou / GPS signal is disconnected, the positioning and orientation test system automatically switches to working mode 2, and the V o1 signal disappears, which is the starting point of the holdover time; the time base oscillation circuit is in a free oscillation state, and at time t 22When the set T is reached x Time, the time interval measured by the waveform recorder is: t 22 -t 21 , then the autoconservative time measurement error is calculated according to formula (1):

[0051] ΔT=T x -(t 22 -t 21 ) (1)

[0052] Where:

[0053] ΔT is the automorphic time measurement error, T x The time set for the automorphic time unit, t 22 The last 2.5ms time base signal V o3 The moment t 21 The last second pulse signal V o1 moment.

[0054] The method for calculating the autostatic time measurement error includes: the second pulse signal A2 output by the autostatic time unit of the positioning and orientation test system, the pulse voltage signal V amplified by the adapter o2 Add to the channel 1 input of the universal frequency counter / timer. At the same time, V o2 Add to the external trigger input of the universal frequency counter / timer, and use the external trigger synchronization method to realize the second pulse signal period T A2 Measurement: The measurement error of the second pulse signal output by the autostatic time unit is calculated according to formula (2):

[0055] ΔT=TT A2 (2)

[0056] Where:

[0057] ΔT is the measurement error of the automorphic time unit second pulse signal period;

[0058] T is the nominal value of the automorphic time unit second pulse signal period;

[0059] T A2 The actual value of the general frequency counter / timer period.

[0060] Beneficial effects of the present invention:

[0061] The present invention is simple, reliable and easy to use. An adapter, a waveform recorder, a universal frequency counter / timer and a cesium clock form a calibration device.

[0062] The pulse voltage signal V after the second pulse signal A1, second pulse signal A2 and 2.5ms time base signal A3 of the positioning and orientation test system are amplified by the adapter o1, V o2 , V o3 , are respectively added to the three channels CH1, CH2, and CH3 of the waveform recorder. CH1 is used to monitor the moment when the last second pulse signal of V o1 appears when the positioning and orientation test system automatically switches from working mode 1 to working mode 2, so as to capture the starting point of the holdover time. CH2 is used to monitor the waveform of V o2 . CH3 is used to monitor the last pulse signal of V o3 when the set holdover time ends, so as to find the end point of the holdover time, and thus measure the holdover time. It solves the problem in the prior art that it is difficult to capture the starting point of the holdover time, so that the holdover time cannot be measured. Description of the Drawings

[0063] Figure 1 is the principle block diagram of the positioning and orientation test system;

[0064] Figure 2 is the block diagram of the composition of the holdover time unit;

[0065] Figure 3 is the working principle block diagram of the holdover time unit;

[0066] Figure 4 is the output waveform diagram of the second pulse signals A1, A2 and the 2.5 ms time base signal A3;

[0067] Figure 5 is the circuit diagram of the adapter in the specific implementation;

[0068] Figure 6 is the structural schematic diagram of the calibration device in the specific implementation;

[0069] Figure 7 is the output waveform diagram of the second pulse signals Vo1, Vo2 and the 2.5 ms time base signal Vo3 in the specific implementation. Specific Implementation

[0070] A calibration device for the holdover time of a positioning and orientation test system includes an adapter, a waveform recorder, a general-purpose frequency counter / timer and a cesium clock. The circuit diagram of the adapter is as shown in Figure 5 , and it consists of three independent common-emitter amplifiers.

[0071] The base of the NPN-type crystal triode T 11 of the first common-emitter amplifier is connected to one ends of the resistors R 11 , R 12 and R 13 . The other end of the resistor R 11 is led out to the signal input terminal V i1 . The other end of the resistor R 12The other end is connected to resistor R 14 at one end and led out to the power supply voltage input terminal V cc1 , resistor R 13 The other end is connected to ground GND. Resistor R 14 The other end is connected to the collector of T 11 and one fixed end of potentiometer W 11 and led out to the signal output terminal V o1 , and its output signal is also denoted by V o1 , potentiometer W 11 The other fixed end is connected to ground GND. The emitter of T 11 is connected to resistor R 15 and one end of capacitor C 11 , resistor R 15 The other end and the other end of capacitor C 11 are connected to ground GND.

[0072] The principles and wiring of the second and third common-emitter amplifiers are the same as those of the first common-emitter amplifier. The second common-emitter amplifier consists of an NPN-type bipolar junction transistor T 21 , resistor R 21 , R 22 , R 23 , R 24 , R 25 , capacitor C 21 , potentiometer W 21 , signal input terminal V i2 , signal output terminal V o2 , power supply voltage input terminal V cc2 , ground GND, and the signal output terminal V o2 Its output signal is also denoted by V o2 .

[0073] The third common-emitter amplifier consists of an NPN-type bipolar junction transistor T 31 , resistor R 31 , R 32 , R 33 , R 34 , R 35 , capacitor C 31 , potentiometer W 31 , signal input terminal V i3 , signal output terminal V o3 , power supply voltage input terminal V cc3 , ground terminal GND, and the signal output terminal V o2 Its output signal is also denoted by V o3 .

[0074] Potentiometer W 11, W 21 , W 31 have the same function and are used to adjust the amplitude of the output signals of each common-emitter amplifier so that it is continuously adjustable between zero and its maximum output. The role of the three amplifiers in the adapter is to amplify the input signal to within the input sensitivity range of the waveform recorder and the general-purpose frequency counter / timer, so as to realize the measurement of it. The input waveform schematic diagrams of the three signal input terminals V i1 , V i2 , V i3 and the output waveform schematic diagrams of the three signal output terminals V o1 , V o2 , V o3 are also drawn in the figure. Since the output waveforms of V o1 , V o2 , V o3 are obtained by amplifying A1, A2, and A3 respectively through the three amplifiers, only the phases are opposite and their periods are not changed. Therefore, the relationship among V o1 , V o2 , V o3 is exactly the same as the relationship among A1, A2, and A3 shown in Figure 4 , and only A1, A2, and A3 in the figure need to be replaced with V o1 , V o2 , V o3 respectively.

[0075] The autochronous time unit calibration connection diagram is as shown in Figure 6 . The second pulse signal A1 generated by the second pulse signal A1 generation circuit of the Beidou / GPS receiver unit of the positioning and orientation test system is connected to the signal input terminal V i1 of the adapter, and the signal output terminal V o1 of the adapter is connected to the input terminal of channel CH1 of the waveform recorder. The second pulse signal A2 generated by the second pulse signal A2 generation circuit of the autochronous time unit is connected to the signal input terminal V i2 of the adapter, and the signal output terminals V o2 of the adapter are respectively connected to the input terminal of channel CH2 of the waveform recorder, the input terminal of channel 1 of the general-purpose frequency counter / timer, and the external trigger input terminal. The 2.5ms time base signal A3 generated by the 2.5ms time base signal A3 generation circuit of the autochronous time unit is connected to the signal input terminal V i3 of the adapter, and the signal output terminal V 03 of the adapter is connected to the input terminal of channel CH3 of the waveform recorder.

[0076] The high-precision 10 MHz frequency signal output by the cesium clock is connected to the external reference input terminals of the waveform recorder and the general-purpose frequency counter / timer as their reference time base, thereby improving the time measurement accuracy of the waveform recorder and the general-purpose frequency counter / timer.

[0077] Principle of operation

[0078] The measurement principle of the waveform recorder is continuous sampling. The entire measurement process is continuous without interruption and no information is lost. The waveforms measured by the waveform recorder at the three output terminals of the amplifier during calibration are as Figure 7 shown. The figure is divided into a synchronization segment T 21 and a Beidou / GPS signal disconnection segment T 22 . The horizontal axis is time, represented by t; the vertical directions V o1 , V o2 , V o3 are all pulse voltage signals. The low level of 0.0 V of the three waveforms is marked in the figure. From t 20 to t 21 , that is, between positions m1 and m2, the Beidou / GPS signal received by the antenna is normal and it works in operating mode 1, in a stable synchronous working state. V o2 and V o3 are synchronized by V o1 . Therefore, the periods of V o1 and V o2 are the same, the same as that in Figure 4 , both represented by T A1 . The period of V o3 is the same as that in Figure 4 , also represented by T A4 , and there is: T A1 = 400T A4 .

[0079] If the set holdover time is T x , at the position m2 at time t 21 , the antenna signal is turned off and the Beidou / GPS signal is disconnected. The positioning and orientation test system automatically switches to operating mode 2, and the V o1 signal disappears, which is the starting point of the holdover time. The time base oscillation circuit is in a free oscillation state. At the position m3 at time t 22 , when the set T x time is reached, the time interval measured by the waveform recorder is: t 22 -t 21 . Then the holdover time measurement error is calculated according to formula (1):

[0080] ΔT = T x -(t 22 -t 21 ) (1)

[0081] In the formula:

[0082] ΔT - Autonomous time measurement error, unit: s;

[0083] T x - Time set by the autonomous time unit, unit: s;

[0084] t 22 - Moment when the last 2.5 ms time base signal V o3 appears, unit: s;

[0085] t 21 - Moment when the last second pulse signal V o1 appears, unit: s.

[0086] The second pulse signal A2 output by the autonomous time unit of the positioning and orientation test system, after being amplified by the adapter, the pulse voltage signal V o2 is applied to the input end of channel 1 of the general frequency counter / timer. At the same time, V o2 is applied to the external trigger input end of the general frequency counter / timer. In the way of external trigger synchronization, the period T A2 of the second pulse signal is measured. The measurement error of the second pulse signal output by the autonomous time unit is calculated according to formula (2):

[0087] ΔT = T - T A2 (2)

[0088] In the formula:

[0089] ΔT - Measurement error of the second pulse signal period of the autonomous time unit, unit: s;

[0090] T - Nominal value of the second pulse signal period of the autonomous time unit, unit: s;

[0091] T A2 - Measured actual value of the period of the general frequency counter / timer, unit: s.

[0092] A method for calibrating the autonomous time of a positioning and orientation test system includes:

[0093] Step 1, preheat the adapter, waveform recorder, general frequency counter / timer and cesium clock until the specified preheating time is reached, and connect each instrument with cables according to Figure 6 the connection;

[0094] Step 2, select the 10 MHz frequency signal output by the cesium clock as the external reference frequency standard for the waveform recorder and the general frequency counter / timer;

[0095] Step 3, set the time T x to be calibrated by the autonomous time unit;

[0096] Step 4: According to the autochronous time to be calibrated and the calibration points, select the measurement channel of the waveform recorder, set it to the voltage measurement function, with an input impedance of 1 MΩ, DC coupling, set the horizontal sweep coefficient t / div and the vertical deflection coefficient V / div, and turn on the low-pass filter, etc.

[0097] Step 5: According to the period of the second pulse signal to be calibrated, set the general frequency counter / timer function to the period measurement function, select the gate time, with an input impedance of 1 MΩ, DC coupling, manually trigger and set the trigger level, and turn on the low-pass filter, etc.

[0098] Step 6: Turn on the positioning and orientation test system to run normally in working mode 1, and turn on the voltage measurement function of the waveform recorder and the period measurement function of the general frequency counter / timer.

[0099] Step 7: Turn off the antenna output signal of the positioning and orientation test system, and automatically switch from working mode 1 to working mode 2 to run.

[0100] Step 8: Use the waveform recorder to measure the Figure 7 shown waveform, measure the values at times t 21 and t 22 , calculate the autochronous time measurement error using formula (1), and determine whether it meets the technical index requirements.

[0101] Step 9: Use the general frequency counter / timer to measure the period T A2 of the pulse voltage waveform, calculate the period measurement error of the second pulse signal of the autochronous time unit using formula (2), and determine whether it meets the technical index requirements.

[0102] Step 10: After calibration, remove each cable and turn off the power of each instrument.

[0103] This embodiment takes the calibration of the autochronous time of a certain type of positioning and orientation test system set to T x = 7 d as an example for illustration. The main technical indicators of the autochronous time unit are:

[0104] Autochronous time range: 0 - 7 d, maximum allowable error: ±20 ms;

[0105] Second pulse signal period range: 1 s, maximum allowable error: ±1 μs.

[0106] The cesium clock used in this embodiment is the 5585B type cesium clock produced by OSCILLQQUARTZ Company of Switzerland, and its main technical indicators are:

[0107] Frequency range: 5 MHz, 10 MHz, relative frequency deviation: ±5×10 -12 .

[0108] The general frequency counter / timer used in this embodiment is the 53230A general frequency counter / timer produced by Agilent Corporation, USA. Its main technical specifications are as follows:

[0109] Internal crystal oscillator frequency: 10 MHz, relative frequency deviation: ±6×10 -8 , with an external reference frequency marker function. Frequency measurement range: DC~15 GHz, period measurement range: 67 ps~1000 s.

[0110] The waveform recorder used in this embodiment is the 8861-50 waveform recorder produced by HIOKI Corporation, Japan. Its main technical specifications are as follows:

[0111] Internal crystal oscillator frequency: 10 MHz, relative frequency deviation: ±1×10 -6 , with an external reference frequency marker function. Equipped with an 8957 high-resolution unit, frequency band width: DC~10 MHz, ±3 dB. Vertical deflection coefficient range: 50 μV / div~20 V / div, voltage measurement range: 50 μV~300 V, maximum allowable error ±0.3%. Input impedance: 1 MΩ, coupling mode: DC, AC, with a filter function. Horizontal sweep coefficient range: 0.5 μs / div~5 min / div. Time measurement range: 0.5 μs~347 d. Display screen display range: horizontal 25 div, vertical 20 div, resolution: 0.1 div.

[0112] Extract the second pulse signals A1, A2 and the 2.5 ms time base signal A3 from the positioning and orientation test system, and then connect each instrument with a cable according to Figure 6 the connection method.

[0113] Manual setting method for the cesium clock frequency:

[0114] After the cesium clock is powered on, without setting, it directly outputs frequency signals of 5 MHz and 10 MHz.

[0115] Manual setting method for measuring the period of the second pulse signal with the 53230A general frequency counter / timer:

[0116] 1. Select the period measurement function

[0117] Press the frequency / period button (Freq Period) on the front panel to select Period.

[0118] 2. Parameter setting

[0119] Press the Channel 1 button on the front panel (Note: The button refers to the button on the instrument panel), and press the corresponding soft key on the display screen (Note: The soft key refers to the button on the instrument panel corresponding to a certain parameter, function, item, etc. displayed on the display). Select Coupling as DC, Impedance as 1 MΩ, and BW Limit as 100 kHz (i.e., turn on the low-pass filter to filter out high-frequency interference signals above 100 kHz).

[0120] Press the soft key corresponding to Level Setup, and select Off (i.e., turn off the automatic level setting function and use manual setting of the trigger level). Press the soft key corresponding to Level, and turn the digital increment / decrement knob on the front panel to reach the desired trigger level setting; or press the Shift key on the front panel, according to the size of the trigger level to be set, press the corresponding digital key on the front panel, and then press the soft key corresponding to μV, mV, or V to select the level unit, and the desired trigger level setting is achieved.

[0121] Press the Gate button on the front panel, press the soft key corresponding to Gate Time, and turn the digital increment / decrement knob on the front panel to reach the desired gate time setting; or press the Shift key on the front panel, according to the size of the gate time to be set, press the corresponding digital key on the front panel, and then press the soft key corresponding to μSec, mSec, or Seconds to select the time unit, and the desired gate time setting is achieved. Here, select the gate time as: 1 s.

[0122] Manual setting method for the dwell time measurement of the 8861-50 waveform recorder:

[0123] Select channels CH1, CH2, and CH3 of the 8957 high-resolution unit respectively, and all are set to the voltage measurement function. The input impedance is set to 1 MΩ for all, and the coupling is set to DC coupling for all. Set the horizontal sweep coefficient to: 5 ms / div, then there are approximately 2 2.5 ms time-base signal waveforms per div in the horizontal direction on the display screen. If the peak-to-peak amplitudes of V o1 、V o2 、V o3 are all adjusted to 5 V, and the vertical deflection coefficient is set to: 1 V / div, then the three waveforms of V o1 、V o2 、V o3 each occupy 5 divs in the vertical direction.

[0124] The nominal period of the second pulse signals V o1 and V o2 is 1 s, that is, the frequency is 1 Hz, and the 2.5 ms time-base signal Vo3 The nominal period is 2.5 ms, i.e., the frequency is 400 Hz. The principle for selecting the channel filter bandwidth of the 8957 type high-resolution unit is that the filter bandwidth is more than 10 times the frequency of the measured signal. In this way, the waveform recorded by the waveform recorder will not be distorted. The filter bandwidths of the waveform recorder are: 0ff, 5 Hz, 50 Hz, 500 Hz, 5 kHz, 50 kHz, a total of 6 gears can be selected, and 0ff means turning off the filter. Here, 50 Hz is selected for both CH1 and CH2, so that interference signals above 50 Hz can be filtered out. 5 kHz is selected for CH3, so that interference signals above 5 kHz can be filtered out. In this way, the interference signals of each channel can be well filtered out, so as to achieve the purpose of accurate measurement.

[0125] The second pulse voltage signal V measured by the general frequency counter / timer o2 The period T A2 is:

[0126] T A2 = 0.999999971816 s

[0127] Then the measurement error ΔT of the second pulse signal period of the self-holding time unit:

[0128] ΔT = T - T A2 = 1 s - 0.999999971816 s = 0.000000028184 s = 0.028 μs

[0129] The self-holding time t measured by the waveform recorder 22 -t 21 is:

[0130] t 22 -t 21 = 604800.017 s

[0131] Then the self-holding time measurement error ΔT:

[0132] ΔT = T x -(t 22 -t 21 ) = 604800 s - 604800.017 s = 0.017 s = 17 ms

[0133] The actual measurement shows that both the measurement error of the second pulse signal period and the measurement error of the self-holding time are within the maximum allowable error range of the self-holding time unit of the positioning and orientation test system, meeting the technical requirements.

[0134] Main technical indicators of the calibration device:

[0135] A calibration device consists of 1 adapter, 1 waveform recorder, 1 general-purpose frequency counter / timer, and 1 cesium clock. The main technical specifications of the calibration device are as follows:

[0136] Frequency range of frequency standard: 5 MHz, 10 MHz, relative frequency deviation: ±5×10 -12 ;

[0137] Period measurement range: 67 ps to 1000 s, maximum allowable error: (±5×10 -12 + trigger error + display least significant bit / period of measured signal);

[0138] Time interval measurement range: 0.5 μs to 247 d, maximum allowable error: (±5×10 -12 × time interval + trigger error + display least significant bit).

Claims

1. A calibration device for the self-holding time of a positioning and orientation test system, the device comprising an adapter, characterized in that: The second pulse signal A1 generated by the second pulse signal generation circuit of the Beidou / GPS receiver unit of the positioning and orientation test system is connected to the signal input terminal V of the adapter. i1 , the signal output terminal V of the adapter o1 is connected to the input terminal of channel CH1 of the waveform recorder; the second pulse signal A2 generated by the second pulse signal generation circuit of the autonomous time unit is connected to the signal input terminal V of the adapter i2 , the signal output terminal V of the adapter o2 is respectively connected to the input terminal of channel CH2 of the waveform recorder, the input terminal of channel 1 of the general frequency counter / timer and the external trigger input terminal; the 2.5 ms time base signal A3 generated by the 2.5 ms time base signal generation circuit of the autonomous time unit is connected to the signal input terminal V of the adapter i3 , the signal output terminal V of the adapter 03 is connected to the input terminal of channel CH3 of the waveform recorder.

2. The calibration device for the self-holding time of a positioning and orientation test system according to claim 1, characterized in that: The 10 MHz frequency signal output by the cesium clock is connected to the external reference input terminals of the waveform recorder and the general-purpose frequency counter / timer as its reference time base.

3. The calibration device for the self-holding time of a positioning and orientation test system according to claim 1, characterized in that: The adapter includes three independent common-emitter amplifiers; the NPN bipolar junction transistor T of the first common-emitter amplifier 11 has its base connected to one ends of resistors R 11 , R 12 and R 13 . The other end of resistor R 11 is led out to the signal input terminal V i1 . The other end of resistor R 12 is connected to one end of resistor R 14 and is led out to the power supply voltage input terminal V cc1 . The other end of resistor R 13 is connected to the ground GND; the other end of resistor R 14 is connected to the collector of T 11 and one fixed end of the potentiometer W 11 and is led out to the signal output terminal V o1 . The other fixed end of the potentiometer W 11 is connected to the ground GND; the emitter of T 11 is connected to one ends of resistor R 15 and capacitor C 11 . The other end of resistor R 15 and the other end of capacitor C 11 are connected to the ground GND. The second and third common-emitter amplifiers have the same principle and wiring as the first common-emitter amplifier.

4. The calibration method of the calibration device for the self-holding time of a positioning and orientation test system according to claim 1, characterized in that: The method includes: Step 1: Preheat the adapter, waveform recorder, general-purpose frequency counter / timer, and cesium clock until the specified preheating time is reached. Step 2: Select the 10 MHz frequency signal output by the cesium clock to provide an external reference frequency standard for the waveform recorder and the general-purpose frequency counter / timer. Step 3: Set the time T to be calibrated for the automorphic time unit x ; Step 4: According to the autonomous time to be calibrated and the calibration point, select the measurement channel of the waveform recorder, set it to the voltage measurement function, with an input impedance of 1 MΩ, DC coupling, and set the horizontal sweep coefficient t / div and vertical deflection coefficient V / div. Step 5: According to the period of the second pulse signal to be calibrated, set the function of the general-purpose frequency counter / timer to the period measurement function, select the gate time, with an input impedance of 1 MΩ, DC coupling, manually trigger and set the trigger level. Step 6: Turn on the positioning and orientation test system to run normally in working mode 1, and turn on the voltage measurement function of the waveform recorder and the period measurement function of the general-purpose frequency counter / timer. Step 7: Turn off the antenna output signal of the positioning and orientation test system and automatically switch from working mode 1 to working mode 2 for operation. Step 8. Measure the waveform with a waveform recorder, and measure the values at time t 21 and t 22 . Calculate the self-holding time measurement error, and determine whether it meets the technical specification requirements; Step 9: Measure the period T of the pulse voltage waveform using a general-purpose frequency counter / timer A2 , calculate the measurement error of the period of the second pulse signal of the automorphic time unit, and determine whether it meets the technical specification requirements.

5. The calibration method of a calibration device for the self-holding time of a positioning and orientation test system according to claim 4, characterized in that: The method for calculating the autonomous time measurement error includes: If the set autonomous time is T x , at time t 21 , the antenna signal is turned off, the Beidou / GPS signal is disconnected, and the positioning and orientation test system automatically switches to working mode 2. The V o1 signal disappears, which is the starting point of the autonomous time. The time base oscillation circuit is in a free oscillation state and reaches the set T 22 at time t x . The time interval measured by the waveform recorder is: t 22 - t 21 . Then, the autonomous time measurement error is calculated according to formula (1): ΔT=T x -(t 22 -t 21 ) (1) Where: ΔT is the autochronous time measurement error, and T x is the time set for the autochronous time unit, and t 22 is the moment when the last 2.5 ms time base signal V o3 appears, and t 21 is the moment when the last second pulse signal V o1 appears.

6. The calibration method of a calibration device for the self-holding time of a positioning and orientation test system according to claim 4, characterized in that: The method for calculating the measurement error of the self-holding time includes: locating the second pulse signal A2 output by the self-holding time unit of the positioning and orientation test system, and the pulse voltage signal V after being amplified by the adapter o2 is added to the input end of channel 1 of the general-purpose frequency counter / timer. At the same time, V o2 is added to the external trigger input end of the general-purpose frequency counter / timer, and the cycle T of the second pulse signal is measured by the way of external trigger synchronization A2 measurement; the measurement error of the second pulse signal output by the self-holding time unit is calculated according to formula (2): ΔT = T - T A2 (2) Where: ΔT is the measurement error of the period of the second pulse signal of the autonomous time unit; T is the nominal value of the period of the second pulse signal of the autonomous time unit; T A2 Is the measured value of the period of the general frequency counter / timer.

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