TW201408997A - Method for determining altitude and altitude meter using the method - Google Patents

Abstract

A method for determining altitude includes: determining an initial altitude corresponding to an initial pressure; sensing pressure according to a sampling frequency to obtain at least one sensed pressure value; calculating an altitude difference according to a presently sensed pressure value and a previously sensed pressure value; and accumulating the altitude difference with the initial altitude to generate an altitude reading.

Description

Height sensing method and altimeter using this method

The present invention relates to a height sensing method, and more particularly to a method of height sensing by a sensing unit and having a reduced sensing noise effect, and an altimeter using the method.

The current common method for sensing the height is to calculate the height of the position to be tested by the sensing unit according to the sensed air pressure value. However, the effect of sensing is often limited by the influence of the environment. For example, the speed of the car may change due to different speeds, but the height of the car may not change; plus the noise generated by the sensor itself. . The high degree of interpretation of noise caused by such reasons, the traditional way is to use the average method to calculate the sensed height, that is, accumulate multiple sensing records and calculate the averaged number to determine the sensed reading. There are several disadvantages to this type of processing: the memory space required to store multiple sensing records is large, and this calculation method cannot eliminate the influence of error sensing signals or noise; in addition, a large number of sensing signals are used. The average operation requires a large computational space and a long calculation time, and the obtained reading may be slightly oscillated, so the accuracy of the height reading is low.

In this problem, another conventional technique proposes a solution by first determining a pressure reference value and a corresponding height, and then converting to a height based on a function of the currently sensed pressure and the reference value. Referring to Figures 1 and 2, FIG. 1 is an experiment performed on the prior art, and the pressure sensing signal curve (S1) and the estimated height curve (A1) obtained by sensing one of the sensing units are statically placed. And Fig. 2 is a partial enlarged view of the height curve in Fig. 1. In Fig. 1, the sensing signal curve S1 (solid line) is higher (indicating a higher pressure) corresponding to the lower part of the height curve A1 (dashed line) (indicating a lower height), and the sensing signal curve S1 The lower point (indicating less pressure) corresponds to the height of the height curve A1 (indicating a higher height). Although the sensing unit itself is stationary, the height due to the change in atmospheric pressure itself is also changed, resulting in a numerical oscillation. Although this method has less computation and less memory space, it can be seen from the figure that the oscillation of the height value will cause some troubles in practical applications.

Therefore, how to reduce the influence of changes in atmospheric pressure on the correct value, and save the computing time and memory space technology is one of the important topics in related fields.

The present invention provides a method of height sensing and an altimeter using the method.

Other objects and advantages of the present invention will become apparent from the technical features disclosed herein.

In order to achieve one or a part or all of the above or other purposes, an embodiment of the present invention provides a method of height sensing, which may include the steps of: determining an initial height reading corresponding to an initial pressure sensing value; Obtaining at least one sensing value according to detecting the pressure according to a sampling period; generating a height difference according to the current sensing value and the previous sensing value; and sequentially accumulating the value according to the initial height reading and the at least one height difference A height reading is produced.

In an embodiment of the present invention, the height sensing method may further include: determining whether the height difference is a noise, and if the noise is not included in the accumulation. The manner in which the height difference is determined to be noise may be compared to one or more threshold values, and wherein the threshold value may be dynamically set.

In one embodiment of the invention, the sampling period is a dynamically set variable value.

In an embodiment of the invention, the current sensed value (P _t ), the previous sensed value (P _t-1 ), and the height difference (ΔH _t ) have the following relationship: ΔH _t =α*( 1-(P _t /P _t-1 ) ^1/5.255 ), where t is a positive integer and P ₀ is a known initial value. Also, wherein the initial pressure sensing value (P ₁ ) and the initial height reading (H ₁ ) may have the following relationship: H ₁ =α*(1-(P ₁ /P ₀ ) ^1/5.255 ), wherein P ₀ is the sea Planar atmospheric pressure, or self-set reference pressure.

In an embodiment of the invention, the current sensed value (P _t ), the previous sensed value (P _t-1 ), and the height difference (ΔH _t ) have the following relationship: ΔH _t =α*( 1-(P _t /P ₀ ) ^1/5.255 )-α*(1-(P _t-1 /P ₀ ) ^1/5.255 ), where t is a positive integer and P ₀ is a known initial value.

In an embodiment of the invention, an altimeter is also provided, comprising a pressure sensing unit for sensing pressure and a height calculating unit for converting pressure into height, the altimeter performing the aforementioned height sensing method.

The above described features and advantages of the present invention will be more apparent from the following description.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments. The directional terms mentioned in the following embodiments, such as up, down, left, right, front or back, etc., are only directions referring to the additional drawings. Therefore, the directional terminology used is for the purpose of illustration and not limitation.

3 and 4 are explanatory views of the pressure sensing signal curve and the related height curve principle according to an embodiment of the present invention. Among them, an embodiment of the present invention proposes a method of height sensing, assuming that the change in atmospheric pressure is as shown by the curve S2, and the corresponding height to be known is as shown by the curve A2. The height sensing method of this embodiment may include the following steps: first determining an initial height reading H ₁ corresponding to the initial pressure sensing value P ₁ ; the initial height reading H ₁ may be a preset value, or may be The initial pressure sensing value P ₁ and a reference value are calculated according to a preset functional relationship (described in detail later); the atmospheric pressure is sequentially sampled according to a sampling period T, and each sensing sample obtains a sensing value (for example: P ₁ ~P _t+1 , t is a positive integer); according to the current sensed value (for example: P _t ) and the previous sensed value (hereinafter also referred to as reference sensed value, such as but not limited to: P _t-1 ) Calculating a height difference (eg, ΔH _t ); and generating a height reading based on the cumulative value of the initial height reading H ₁ and at least one height difference (eg, H _t+1 =H ₁ +...+ ΔH _t +ΔH _t+1 ). In the above method, the threshold value can be selectively added, that is, when the height difference is not higher than a threshold value, the height is regarded as not changing without being accumulated, so that the noise can be filtered. Moreover, the selection of the initial pressure sensing value P ₁ is defined according to the use condition, which is preferably a stable pressure sensing value to obtain a more accurate result.

The sampling period T in the foregoing method may be a preset fixed value or a dynamically set variable value. For example, the sampling period T can be defined according to the use condition and the characteristics of the sensor. For example, when applied to a slower speed change application such as mountaineering equipment, the sampling period T can be set to a longer time. When applied to applications with high speed changes, such as aircraft and lifts, the sampling period T can be set to a shorter time. When the sampling period T is short, the pressure sensing value may be changed too small to be determined as noise, so this point should be considered when setting the sampling period. When the air pressure changes faster, the sampling period T is shorter or longer. Moreover, the selection of the sampling period T should also consider the characteristics of the sensor, such as sensitivity and reaction speed.

The foregoing example illustrates that a height difference (eg, ΔH _t ) can be calculated based on the current sensed value (eg, P _t ) and the previous sensed value (eg, P _t-1 ). In fact, the previous sensed value is not limited to the sensed value P _t-1 obtained from the previous sample, and may be between the sensed value P _t-1 obtained from the previous sample and the sensed value P ₁ obtained from the first sample. The sensed value obtained by sampling at any time is selected as the reference sensed value. For example, when applied to a slower change in height and a smaller change in pressure sensing value, the reference sensed value may take one or more of the previous sensed samples. In short, the reference sensed value should be selected according to actual needs, and can be adjusted due to changes in conditions.

In addition, the initial height reading H ₁ may be a preset value, or may be calculated from the initial pressure sensing value P ₁ , for example, by the following formula: H ₁ = α * (1 - (P ₁ / P ₀ ) ^1/5.255 )

The ratio of α to the gas gradient can be regarded as a constant, and P ₀ is a reference value. If the initial height reading H _{1 is} set to a height value (unit: meter) from the sea level, the reference value P ₀ is 1 atm; in other cases, P ₀ can be set to a known initial value. The unit of P ₁ and P ₀ may be, for example, a hectopascal (hPa), and if it is another unit, the formula may be adjusted according to the ratio between units.

The foregoing compares the sensed value obtained by sampling and the previous reference sensed value to generate a height difference, and the calculation method may be, for example, the current sensed value (P _t ), and the corresponding reference sensed value (P _{t- 1} ) and the resulting height difference (ΔH _t ) may have the following relationship: ΔH _t = α * (1 - (P _t / P _t-1 ) ^1/5.255 )

Further, ΔH _t = H _{t -} H _t-1 , that is, the current height value H _t can be obtained from H _t-1 + ΔH _t , or obtained by H _t = H ₁ +... + ΔH _t-1 . In the above description, t is a positive integer.

The unit of the sensing value and the reference sensing value may be a hectopascal (hPa), and the unit of the height difference may be a meter (m). This formula is suitable for operating environments close to one atmosphere, because the general operation is in the atmosphere of one atmosphere or nearly one atmosphere, so this The embodiment is exemplified by this formula, and the implementation is not limited to this formula. For example, temperature or other factors may be added, and the pressure is not limited to atmospheric pressure. In addition, if other units are used, the formula can be adjusted according to the ratio between units.

In the same concept of the present invention, the following method can also be used: H ₀ = α * (1 - (P ₀ / P ₀ ) ^1/5.255 ) = 0

H ₁ =α*(1-(P ₁ /P ₀ ) ^1/5.255 )

△H _t =H _t -H _t-1 =α*(1-(P _t /P ₀ ) ^1/5.255 )-α*(1-(P _t-1 /P ₀ ) ^1/5.255 )

H _t =H _t-1 +△H _t =H ₁ +...+△H _t-1 =△H ₁ +...+△H _t-1

The initial height reading H ₁ can also be regarded as an accumulated value (H ₁ = ΔH ₁ ), or H ₀ can be regarded as the initial height reading and H _{1 is} regarded as the first accumulated value. Similarly, in the above description, t is a positive integer.

As described above, the height difference can be compared with the threshold value to determine whether the height difference is a noise, and an example is given when the height difference is not higher than a threshold value, and the noise can be determined. In fact, the threshold value can not only set the low threshold, but also set the high threshold, that is, if the height difference is higher than the high threshold, it is also regarded as noise, only when the height difference falls below the high and low thresholds. When it is between, it is regarded as a normal signal. Determining the threshold setting of the noise range is related to the characteristics of the sensor and the use condition. For example, when the sensitivity of the sensor is too high, the noise range needs to be loose, and when the pressure change is low under the sensed condition, for example, The range setting should be stricter. Therefore, the noise range should be determined after considering a number of factors. Therefore, the threshold should be dynamically set, but it can of course be a fixed value.

Referring to FIGS. 5 and 6, FIG. 5 is a height sensing result obtained by pressure sensing a static sensing unit according to the method of the foregoing embodiment, and FIG. 6 is the first Figure 5 is a partial enlarged view of the height sensing value. However, similar to FIG. 1, the variability of the sensing signal curve S3 (solid line) in FIG. 5 is obvious, but the height curve A3 (dashed line) derived from the sensing signal curve S3 is quite stable, and the display is The invention is superior to the prior art.

According to the above method, an altimeter such as FIG. 7 can be fabricated, which includes a pressure sensing unit for sensing pressure and a height calculating unit that converts pressure into height, wherein the height calculating unit can be calculated according to the aforementioned formula, for example, but not limited to.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All of them are still covered by the patent of the present invention. For example, the initial pressure sensing value can be set to self-monitor at a fixed time to maintain the elasticity of environmental sensing; for example, when the pressure sensing value is much less than 1 atmosphere. The influence of temperature can not be neglected. The principle of temperature sensing can refer to the pressure sensing analogy operation, so as to reduce the time required for calculation and related applications such as memory, which are covered by the patent of the present invention. In addition, any of the objects or advantages or features of the present invention are not required to be achieved by any embodiment or application of the invention. In addition, the abstract sections and headings are only used to assist in the search of patent documents and are not intended to limit the scope of the invention.

A1, A2, A3‧‧‧ height curve

H ₁ ‧‧‧Initial height reading

H _t-1 , H _t , H _t+1 ‧‧‧ Height readings corresponding to different sampling time points

△H _t ‧‧‧ height difference

S1, S2, S3‧‧‧ pressure curve

P ₁ ‧‧‧ initial pressure sensing value

P _t-1 , P _t , P _t+1 ‧‧‧ Sense values corresponding to different sampling time points

T‧‧‧ sampling period

1 is a sense signal curve and associated height profile for an example operation of the prior art.

Figure 2 is a partial enlarged view of the height curve of Figure 1.

3 and 4 are explanatory diagrams of the pressure sensing signal curve and the related height curve principle according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of a sensing signal curve and phase of an example operation according to an embodiment of the present invention; Off the height curve. .

Figure 6 is a partial enlarged view of the height curve of Figure 5.

Figure 7 is an embodiment of an altimeter of the present invention.

A2‧‧‧ height curve

H ₁ ‧‧‧Initial height reading

H _t-1 , H _t , H _t+1 ‧‧‧ Height reading corresponding to different sampling points

△H _t , △H _t+1 ‧‧‧ height difference

T‧‧‧ sampling period

Claims (9)

A method for height sensing, comprising: determining an initial height reading corresponding to an initial pressure sensing value; detecting at least one sensing value according to a sampling period; and determining a current sensing value according to a current sense The measured value produces a height difference; and a successively accumulated value based on the initial height reading and the at least one height difference to produce a height reading. For example, the method of claim 1 of the patent scope further includes: determining whether the height difference is a noise, and if it is a noise, it does not count as an accumulation. The method of claim 1, wherein the method of determining whether the height difference is noise is comparing the height difference with one or more threshold values, and wherein the threshold value is dynamically set. The method of claim 1, wherein the current sensed value (P _t ), the previous sensed value (P _t-1 ), and the height difference (ΔH _t ) have the following relationship: ΔH _t =α *(1-(P _t /P _t-1 ) ^1/5.255 ), where t is a positive integer and P ₀ is a known initial value. The method of claim 1, wherein the initial pressure sensing value (P ₁ ) and the initial height reading (H ₁ ) have the following relationship: H1=α*(1-(P ₁ /P ₀ ) ^1/5.255 ) Where P ₀ is 1 atmosphere. The method of claim 1, wherein the current sensed value (P _t ), the previous sensed value (P _t-1 ), and the height difference (ΔH _t ) have the following relationship: ΔH _t =α *(1-(P _t /P ₀ ) ^1/5.255 )-α*(1-(P _t-1 /P ₀ ) ^1/5.255 ), where t is a positive integer and P ₀ is a known initial value. The method of claim 6, wherein the initial pressure sensing value (P ₁ ) and the initial height reading (H ₁ ) have the following relationship: H ₁ = ΔH ₁ = α * (1 - (P ₁ / P ₀₎ ) ^1/5.255 ), where P ₀ is 1 atmosphere. The method of claim 1, wherein the sampling period is a dynamically set variable value. An altimeter using the method of any one of claims 1 to 8, comprising a pressure sensing unit for sensing pressure and a height calculating unit for converting pressure into height.