JP3711538B2 - Inertial altitude measurement method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an altitude measurement method that corrects altitude by integration of vertical acceleration with barometric altitude, and in particular, suppresses stepwise fluctuations in measured values when the barometric altitude cannot be acquired, thereby continuously measuring altitude. The present invention relates to an inertial altitude measurement method that enables
[0002]
[Prior art]
As a means for measuring the inertial altitude of a flying object such as an aircraft or a conventional means for correcting the measured altitude, there is a vertical movement displacement measuring apparatus disclosed in, for example, Japanese Patent Application Laid-Open No. 11-21472. This vertical movement displacement measuring device includes vertical acceleration measuring means, vertical movement displacement calculating means, and altitude measuring means. In the vertical movement displacement calculating means, the vertical height measuring means uses the height measured by the height measuring means as a reference height. The acceleration output is integrated via a negative feedback loop, and the integrated output is used as vertical movement displacement measurement data.
[0003]
FIG. 2 is a block diagram showing the configuration of the vertical movement displacement calculating means in the vertical movement displacement measuring apparatus. 2 includes subtracting circuits 23, 25, and 31, integrating circuits 24, 26, and 29, multiplying circuits 27 and 28, and an adding circuit 30. A vertical acceleration 117 is an output of the vertical acceleration measuring means, and a barometric altitude 120 is an output of the altitude measuring means.
[0004]
The vertical acceleration 117 is input to the subtraction circuit 23, and the atmospheric pressure altitude 120 is input to the subtraction circuit 31. The output of the subtracting circuit 23 is integrated by the integrating circuit 24. The output of the integrating circuit 24 is input to the integrating circuit 26 via the subtracting circuit 25 as the vertical speed 118 and integrated. The integration output of the integration circuit 26 is output as the vertical movement displacement 119 and also input to the subtraction circuit 31. The subtraction circuit 31 generates a difference 121 between the vertical movement displacement 119 and the atmospheric pressure altitude 120. The difference 121 is negatively fed back as a feedback signal 124 to the subtraction circuit 23 via the multiplication circuit 28, the integration circuit 29 and the addition circuit 30, and is negatively fed to the subtraction circuit 25 as a feedback signal 125 via the multiplication circuit 27. Returned.
[0005]
The feedback circuit including the multiplier circuit 28, the integrator circuit 29, the adder circuit 30, and the multiplier circuit 27 operates to shift the vertical movement displacement 119 to the atmospheric pressure altitude 120. In this feedback circuit, a negative feedback loop is formed, and the feedback constant is set to a value that does not cause oscillation. When the negative feedback loop is stable, the difference 121 in the subtraction circuit 31 shifts to zero. By shifting the difference 121 to zero, the vertical movement displacement 119 eliminates the influence of the accelerometer bias error in the vertical acceleration 117. Thus, in the vertical movement displacement calculation means of FIG. 2, the vertical movement displacement 119 with the atmospheric pressure altitude 120 as the reference altitude is measured with high accuracy.
[0006]
[Problems to be solved by the invention]
In the vertical displacement measuring apparatus disclosed in Japanese Patent Application Laid-Open No. 11-211472, when the barometric altitude is used as the reference altitude, if the barometric altimeter becomes invalid, the negative feedback loop cannot be formed, and the vertical acceleration In the process of integral calculation 117, the bias error of the vertical accelerometer is accumulated over time, and the value of vertical displacement 119 diverges, making it impossible to accurately measure the vertical displacement. Become. In addition, when the GPS altitude is used as the reference altitude instead of the barometric altitude, the accuracy of the GPS altitude is large compared to the barometric altitude, with the disadvantage that stable and highly accurate altitude measurement cannot be performed. Similarly to the case where the barometric altitude is used as the reference altitude as described above, there is a drawback that when the GPS receiver becomes invalid, the measurement altitude diverges and measurement is impossible.
[0007]
The object of the present invention is to eliminate the above-mentioned drawbacks, compare and collate the effectiveness of the barometric altitude with the effectiveness of the GPS altitude, give priority to the barometric altitude as the reference altitude, and select the more effective altitude. In addition to making it possible to measure the inertial altitude stably at all times, even when the atmospheric altitude is selected as the reference altitude, the effectiveness of the atmospheric altitude decreases and the reference altitude is switched to the GPS altitude. Another object of the present invention is to provide an inertial altitude measurement method capable of performing altitude measurement stably and smoothly by suppressing a sudden change in reference altitude and gradually shifting to a GPS altitude.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides the following means.
[0009]
(1) Comprising arithmetic processing means for processing the vertical acceleration and reference altitude of the accelerometer output, and a barometric altimeter that outputs the barometric altitude as the reference altitude, and by damping the vertical acceleration to the reference altitude, In an inertial altitude measurement method that includes a feedback loop that generates a pressure altitude and that selects the barometric altitude as the reference altitude only when the barometric altitude is valid,
Receive the GPS altitude from the GPS receiver,
In a state where the atmospheric pressure altitude is valid, a bias error of the GPS altitude is estimated based on the inertial altitude obtained by supplying the atmospheric altitude to the arithmetic processing unit as the reference altitude,
When the barometric altitude becomes invalid, a GPS corrected altitude is generated by correcting the GPS altitude by the bias error immediately before the barometric altitude becomes invalid, and the GPS corrected altitude is selected as the reference altitude. An inertial altitude measurement system characterized by
[0010]
(2) first, second and third subtracting means, first and second integrating means for measuring the inertial height by processing the vertical acceleration output from the accelerometer and the reference height; and First and second negative feedback means are provided, the first negative feedback means generates a first feedback value based on the output of the third subtraction means, and the second negative feedback means is the third negative feedback means. A second feedback value is generated based on the output of the subtracting means, the first subtracting means subtracts the vertical acceleration and the first feedback value, and the first integrating means is the first integrating means. The second subtracting means subtracts the output of the first integrating means and the second feedback value, and the second integrating means A time integral value relating to the output of the subtracting means is output as the inertia height, and the third subtracting means subtracts the inertia height from the reference height. In the inertial altitude measurement method,
A barometric altimeter that outputs a barometric altitude; a GPS receiver that outputs a GPS altitude; a GPS altitude bias estimating means; and a reference altitude selecting means.
The GPS altitude bias estimation means inputs the inertial altitude and the GPS altitude, estimates a bias error of the GPS altitude relative to the inertial altitude, and generates a GPS corrected altitude in which the GPS altitude is corrected by the bias error. ,
The reference altitude selecting means selects the barometric altitude as the reference altitude when the barometric altitude is valid, and selects the GPS corrected altitude as the reference altitude when the barometric altitude is invalid. Inertial altitude measurement method.
[0011]
(3) The GPS altitude bias estimation means includes a fourth subtraction means, a second switching means, a third integration means, and a fifth subtraction means.
The fourth subtracting means subtracts the inertial altitude and the GPS corrected altitude,
The second switching means connects the output of the fourth subtracting means to the output terminal as it is when the reference altitude selecting means selects the barometric altitude, and the reference altitude selecting means selects the GPS corrected altitude. The output end is the open end,
The third integrating means performs time integration with respect to the signal at the output terminal of the second switching means, and outputs an integrated value as a bias error of the GPS altitude.
The inertial altitude measurement method according to (2), wherein the fifth subtracting unit subtracts the GPS altitude from the bias error and outputs a subtraction value as the GPS corrected altitude.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, the inertial altitude measurement method of the present invention will be described more specifically with reference to an embodiment. In the present embodiment, as the reference altitude, the effectiveness of the barometric altitude and the GPS altitude are compared and selected, the measurement altitude having the higher effectiveness is selected, and the vertical acceleration is integrated by the double integration mechanism including the negative feedback loop. Through the processing, the inertial altitude is measured in a state of following the value of the reference altitude, and the altitude measurement is stably performed by the mutual complementary action of the barometric altitude as the reference altitude and the GPS altitude. Further, when the reference altitude is switched from the barometric altitude to the GPS altitude, the altitude measurement is smoothly performed while avoiding a sudden change in the reference altitude.
[0013]
FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention. As shown in FIG. 1, the present embodiment includes, as main components, an inertial altitude correction unit 1, a GPS altitude bias estimation unit 2, a reference altitude selection unit 3, an inertial accelerometer 4, and a barometric altimeter 5. And a GPS receiver 6. The inertial altitude correction unit 1 includes subtracting circuits 8, 10 and 12, integrating circuits 9 and 11, multiplying circuits 13 and 14, a switching circuit 15, an integrating circuit 16 and an adding circuit 17. The integration circuits 9 and 11 form a double integration mechanism. The multiplication circuit 14, the switching circuit 15, the integration circuit 16 and the addition circuit 17 constitute a first feedback circuit, the multiplication circuit 13 constitutes a second feedback circuit, and the first feedback circuit and the second feedback circuit are negative. A feedback loop is formed.
[0014]
The GPS altitude bias estimation unit 2 includes subtraction circuits 18 and 21, a switching circuit 19, and an integration circuit 20. The GPS altitude bias estimation unit 2 is formed as a negative feedback loop, estimates a GPS altitude error while the atmospheric pressure altitude 104 is selected as the reference altitude 114, holds the GPS altitude error in the integrating circuit 20, and stores the GPS altitude error 111. Is output from the integrating circuit 20 as follows. The reference altitude selection unit 3 includes an altimeter determination circuit 7 that determines the effectiveness of each altitude measured by the barometric altimeter 5 and the GPS receiver 6, and a switching circuit 22 that selects and outputs the reference altitude.
[0015]
Next, the operation when the reference altitude 104 is switched from the atmospheric pressure altitude 104 to the GPS altitude 112 when the atmospheric altitude 104 is selected as the reference altitude 114 will be described.
[0016]
In FIG. 1, the barometric altitude 104 output from the barometric altimeter 5 and the GPS altitude 112 output from the GPS receiver 6 are input to the altimeter determination circuit 7. The altimeter determination circuit 7 generates a reference altitude selection signal 116 that specifies which one of the barometric altitude 104 and the GPS altitude 112 should be selected as the reference altitude 114. The reference altitude selection signal 116 is input to the switching circuits 15, 19 and 22. When the reference altitude selection signal 116 is a logical value “1”, each movable segment of the switching circuits 15, 19 and 22 is connected to the contact a, and when the reference altitude selection signal 116 is a logical value “0”, the switching circuits 15, 19 and Each movable piece 22 is connected to a contact b.
[0017]
At the beginning (at start-up) when the power is turned on in this embodiment, the altimeter determination circuit 7 assumes that the accuracy of the barometric altitude 104 is higher than the accuracy of the GPS altitude 112, and the effectiveness of the barometric altitude 104 Is higher than the effectiveness of the GPS altitude 112, and the barometric altitude 104 should be selected as the reference altitude 114. Therefore, at the time of activation, the altimeter determination circuit 7 sets the reference altitude selection signal 116 to a logical value “1” that causes the barometric altitude 104 to be selected as the reference altitude 114. In the switching circuits 15, 19, and 22 that have received the reference altitude selection signal 116 at the time of activation, as shown in FIG. 1, all the movable segments are connected to the contact a side. At this time, in the reference altitude selection unit 3, the switching circuit 22 selects the barometric altitude 104 as the reference altitude 114, and in the GPS altitude bias estimation unit 2, there is a negative feedback loop that estimates and holds the altitude error of the GPS altitude 112. It is formed. In the inertial altitude correction unit 1, the switching circuit 15 guides the difference 105 of the output of the subtraction circuit 12 to the integration circuit 16. At this time, the first feedback circuit includes a multiplication circuit 14, an integration circuit 16, and an addition circuit 17.
[0018]
The vertical acceleration 101 detected by the inertial accelerometer 4 is input to the subtraction circuit 8 of the inertial altitude correction unit 1. The inertial altitude correction unit 1 includes integration circuits 9 and 11 as integration means corresponding to the vertical acceleration 101. The inertia altitude 103 output from the final stage integration circuit 11 is input to the subtraction circuit 12 and also input to the subtraction circuit 18 of the GPS altitude bias estimation unit 2. The subtraction circuit 12 generates a difference output 105 between the inertial altitude 103 and the reference altitude 104. The differential output 105 is input to the negative feedback loop composed of the first and second feedback circuits. The feedback signal 108 from the first feedback circuit including the multiplication circuit 14, the integration circuit 16 and the addition circuit 17 is negatively fed back to the subtraction circuit 8. The feedback signal 109 from the second feedback circuit composed of the multiplication circuit 13 is input to the subtraction circuit 10 as negative feedback. In these first and second feedback circuits, the feedback gain is set so that the negative feedback loop does not oscillate. The inertia speed 102 is output from the subtraction circuit 10 in the negative feedback loop. In addition, from the integration circuit 11 in the negative feedback loop, the inertial altitude 103 which is the measurement target of the present embodiment is always stably output in a state of following the atmospheric altitude 104 of the reference altitude.
[0019]
In the GPS altitude bias estimation unit 2, the inertia altitude 103 is input to the subtraction circuit 18 and the GPS altitude 112 is input to the subtraction circuit 21. At this time, since the subtracting circuit 18, the switching circuit 19, the integrating circuit 20, and the subtracting circuit 21 form a negative feedback loop, the integrating circuit 20 outputs a GPS altitude error 111 as an estimated error of the GPS altitude 112 with respect to the inertial altitude 103. Is output, and the GPS correction altitude 113 estimated with respect to the inertial altitude 103 is output from the subtraction circuit 21. The GPS altitude error 111 is a bias error of the GPS altitude 112 estimated on the basis of the inertial altitude 103, and does not vary even if time passes or the latitude and longitude of the GPS receiver 6 vary. The GPS corrected altitude 113 is an altitude obtained by correcting the GPS altitude 112 with the GPS altitude error 111.
[0020]
In a state where a negative feedback loop is configured in the GPS altitude bias estimation unit 2 and the GPS altitude error 111 is stably generated, the reference altitude selection signal 116 changes from the logical value “1” to the logical value “0”. If the movable piece of the switching circuit 19 is switched from the contact point a to the contact point b, the input 110 of the integration circuit 20 is opened, so that the integration circuit 20 holds the data at that time (GPS altitude error 111).
[0021]
As described above, in a state in which the atmospheric pressure altitude 104 is selected as the reference altitude, the inertial altitude correcting unit 1 stably outputs the inertial altitude 103 in a state of following the atmospheric altitude 104, and GPS altitude bias estimation. In the unit 2, a GPS altitude error 111 as an estimation error and an estimated GPS correction altitude 113 are generated.
[0022]
So far, the operation in a state where the altimeter determination circuit 7 determines that the atmospheric pressure altitude 104 is more effective than the GPS altitude 112 has been described. In this state, for example, the atmospheric pressure altitude 104 fluctuates in a stepwise manner and the reliability of the atmospheric pressure altitude 104 is suspected, or the altitude rises to the atmospheric pressure altitude measurement limit. Assume that the altimeter determination circuit 7 determines that the altitude 112 is more effective. At this time, the logical value of the reference altitude selection signal 116 becomes “0”, and all the movable segments in the switching circuits 15, 19 and 22 are switched to the contact b side. By this switching, the GPS altitude bias estimation unit 2 eliminates the negative feedback loop, and the GPS altitude error 111 at the time of switching is retained. The subtraction circuit 21 continues to generate a GPS corrected altitude 113 obtained by correcting the GPS altitude 112 with the GPS altitude error 111.
[0023]
Since the GPS altitude error 111 at this time is a bias error of the GPS altitude 112 generated based on the inertial altitude 103 when the barometric altitude 104 is selected as the reference altitude 114, the GPS altitude error 111 is used to correct the GPS altitude 112. The GPS corrected altitude 113 obtained in this way is continuous with the atmospheric pressure altitude 104 at the time of switching, and the GPS corrected altitude 113 after the switching follows the GPS altitude 112. Therefore, the value of the reference altitude 114 is continuous and does not change stepwise when the barometric altitude 104 is switched to the GPS corrected altitude 113. Thereafter, the inertial altitude correction unit 1 outputs the inertial altitude 103 corrected using the GPS corrected altitude 113 as the reference altitude 104. Of course, since the reference altitude 104 continues in switching, the inertial altitude 103 also continues in switching and does not fluctuate discontinuously in a staircase pattern.
The GPS corrected altitude 113 is input to the subtraction circuit 12 of the inertial altitude correction unit 1 as the reference altitude 114 via the switching circuit 22. In the inertial altitude correction unit 1, since the movable piece of the switching circuit 15 is switched to the contact point b, the integrating circuit 16 is removed from the first feedback circuit. Therefore, the difference 105 between the output of the integrating circuit 11 and the GPS correction altitude 113 is multiplied by a predetermined gain in the multiplication circuit 14 in the first feedback circuit, and becomes a multiplication value 107. The multiplication value 107 is input as negative feedback to the subtraction circuit 8 as it is through the adder circuit 17 as a feedback signal 108. The feedback signal 109 of the multiplication circuit 13 is negatively fed back to the subtraction circuit 10 as before the reference altitude 114 is switched. The integrating circuit 11 outputs the inertial altitude 103 generated by a new negative feedback loop excluding the integrating circuit 16 with the GPS corrected altitude 113 as the reference altitude 114.
[0024]
【The invention's effect】
As described above in detail with reference to the embodiment, according to the present invention, either the atmospheric pressure altitude or the GPS corrected altitude can be selected as the reference altitude, and the atmospheric altitude is selected by selecting the atmospheric altitude as the reference altitude. While measuring, a GPS corrected altitude is obtained by continuously generating and maintaining a GPS altitude bias error (GPS altitude error 111) estimated for the inertial altitude and correcting the GPS altitude by the bias error. By constantly generating (113), even when the reference altitude is switched from the barometric altitude to the GPS corrected altitude, the value of the reference altitude is continuous, and the inertial altitude can be measured without abrupt changes in steps. An inertial altitude measurement method that can be performed stably and smoothly can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a block diagram showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Inertial altitude correction | amendment part 2 GPS altitude bias estimation part 3 Reference | standard altitude selection part 4 Inertial accelerometer 5 Barometric altimeter 6 GPS receiver 7 Altimeter determination circuit 8, 10, 12, 18, 21, 23, 25, 31 Subtraction circuit 9, 11, 16, 20, 24, 26, 29 Integration circuit 13, 14, 27, 28 Multiplication circuit 15, 19, 22 Switching circuit 17, 30 Addition circuit 101, 117 Vertical acceleration 102, 118 Inertial speed 103, 119 Inertial altitude 104 Barometric altitude 105 Difference output 106 between inertial altitude 103 and reference altitude 104 Integration circuit 16 output 107 Multiplication value 108 of multiplication circuit 14 Feedback signal (addition value of addition circuit 17)
109 Multiplying value 110 of multiplication circuit 13 Switching circuit 19 Output 111 GPS altitude error 112 GPS altitude 113 GPS correction altitude 114 Reference altitude 113 GPS correction altitude 116 Reference altitude selection signal 119 Vertical movement displacement 120 Reference altitude 121 Inertial altitude 119 and reference altitude 120 Difference output 124 between and feedback signal 125 feedback signal (multiplier circuit 27 output)

Claims (3)

Computational processing means for processing vertical acceleration and reference height of accelerometer output and a barometric altimeter that outputs barometric height as the reference height, and generating inertial height by damping the vertical acceleration to the reference height In an inertial altitude measurement method that includes a feedback loop in the processing means and selects the barometric altitude as the reference altitude only when the barometric altitude is valid,
Receive the GPS altitude from the GPS receiver,
In a state where the atmospheric pressure altitude is valid, a bias error of the GPS altitude is estimated based on the inertial altitude obtained by supplying the atmospheric altitude to the arithmetic processing unit as the reference altitude,
When the barometric altitude becomes invalid, a GPS corrected altitude is generated by correcting the GPS altitude by the bias error immediately before the barometric altitude becomes invalid, and the GPS corrected altitude is selected as the reference altitude. An inertial altitude measurement system characterized by In order to measure the inertial height by processing the vertical acceleration output from the accelerometer and the reference height, first, second and third subtracting means, first and second integrating means, and first and Second negative feedback means, wherein the first negative feedback means generates a first feedback value based on the output of the third subtraction means, and the second negative feedback means is the third subtraction means. Based on the output of the second feedback value, the first subtracting means subtracts the vertical acceleration and the first feedback value, and the first integrating means is the first subtracting means. The second subtracting means subtracts the output of the first integrating means and the second feedback value, and the second integrating means is the second subtracting means of the second subtracting means. The time integral value relating to the output is output as the inertia height, and the third subtracting means is an inertia for subtracting the inertia height from the reference height. In time measurement method,
A barometric altimeter that outputs a barometric altitude; a GPS receiver that outputs a GPS altitude; a GPS altitude bias estimating means; and a reference altitude selecting means.
The GPS altitude bias estimation means inputs the inertial altitude and the GPS altitude, estimates a bias error of the GPS altitude relative to the inertial altitude, and generates a GPS corrected altitude in which the GPS altitude is corrected by the bias error. ,
The reference altitude selecting means selects the barometric altitude as the reference altitude when the barometric altitude is valid, and selects the GPS corrected altitude as the reference altitude when the barometric altitude is invalid. Inertial altitude measurement method. The GPS altitude bias estimation means includes a fourth subtraction means, a second switching means, a third integration means, and a fifth subtraction means.
The fourth subtracting means subtracts the inertial altitude and the GPS corrected altitude,
The second switching means connects the output of the fourth subtracting means to the output terminal as it is when the reference altitude selecting means selects the barometric altitude, and the reference altitude selecting means selects the GPS corrected altitude. The output end is the open end,
The third integrating means performs time integration with respect to the signal at the output terminal of the second switching means, and outputs an integrated value as a bias error of the GPS altitude.
The inertial altitude measurement method according to claim 2, wherein the fifth subtracting unit subtracts the GPS altitude from the bias error and outputs a subtraction value as the GPS corrected altitude.

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