RU2451904C1 - Range-finding method - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method involves generating a time-setting clock pulse sequence with period T, generating and transmitting a probing signal S₀ with duration t_s>T to a target, wherein the time for generating the probing signal is synchronised with one of the pulses in the pulse sequence, taking said time as the point of origin. The form of the probing signal corresponds to the given sequence of its sampled values S_0i taken with interval T, recorded in an array {S_0i}. W ≥ 2 arrays of sampled values {S_0i}_w of the probing signal are generated and recorded, where w = 1…W is the index number of the array, where in the w-th array, the first sampling instance is shifted by an interval δt_w = (w - 1)T/W relative the point of origin. The reflected signal S is received, digitised by determining and recording relative the clock sequence of the array of its sampled values {S_j}. A shift p = P_w of the array {S_j} relative each of the arrays {S_0j}_w, for which the degree of their coincidence best satisfies a predetermined criterion R_W(P_W), is found. The number w = Q of the array of sampled values of the probing signal is determined, for which the estimate R_w(p) best matches the predetermined criterion, and range D to the target is determined using the relationship D = c(P + (Q - 1)/W)T/2 + ΔD₀, where c is the speed of light, ΔD₀ is a value which is determined by calibrating on a reference path for bias error compensation.

EFFECT: high accuracy of range finding.

5 cl, 6 dwg

Description

The invention relates to laser technology, namely to laser ranging.

Known location methods for measuring the distance to distant objects. A known method of measuring the distance to the target, including sending a laser pulse S ₀ (t, t ₀ ) to the target, recording the sending moment t ₀ , receiving the radiation reflected by the target S (t, t _D ), recording the receiving moment t _D and determining the time interval τ = t _D -t ₀ , which is used to judge the distance D to the target [1] according to the formula D = cτ / 2, where c is the speed of light. According to this method, the moment of reception of the reflected signal (time reference) is recorded when the signal exceeds a predetermined threshold (signal edge alignment). With this method, the error of the timing is large - of the order of the duration of the front of the received signal [2]. Another disadvantage of the method described in [1] is the low accuracy of determining the time interval τ, since the first generation meters used analog methods for measuring time intervals.

The closest in technical essence to the proposed method is a method of measuring range, including the formation of a timing clock pulse sequence with a period T, the generation and sending to the target of a probe signal S ₀ (t, t ₀ ) of duration t _s > T, the shape of which corresponds to a given sequence sampled value S _0i, registered in the array {S _0i}, order receiving a reflected signal S (t, t _D), its digitization and recording by determining its array of sample values {S _j} with respect to the clock pos edovatelnosti, determining the temporal position of the received signal with respect to the sounding signal by comparing arrays of sample probe values and the received signal, and t - current time, t ₀ - the moment of emission of the probing signal, t _D - the moment of receiving the reflected purpose signal, i = 1 ... K - ref the sample number of the probe signal S _0i relative to the clock sequence, K = t _s / T is the number of samples of the probe signal, j = 1 ... J _max is the sample sequence number of the received signal S _j relative to the clock sequence, J _max = 2D _max / cT - the number of samples of the received signal; D _max - the maximum measured range, s - the speed of light [3].

. Значение Р, при котором корреляционная зависимость R(P) принимает максимальное значение, считают соответствующим временному положению принятого сигнала и определяют дальность до цели по формуле D=сРТ/2, где с - скорость света.In the indicated source, the comparison of the arrays {S _0i } and {S _j } is performed by sequentially shifting the array {S _j } by p = 1, 2 ... J _max steps corresponding to step T of the clock sequence, and determining at each step the correlation coefficient

. The value of P, at which the correlation dependence R (P) takes the maximum value, is considered to correspond to the temporary position of the received signal and the distance to the target is determined by the formula D = cPT / 2, where c is the speed of light.

With this method of fixing the temporary position of the received signal S (t, t _D ), represented by an array of its sample values {S _j }, the accuracy of the range measurement is determined by the discreteness of the range cells d = cT / 2.

The objective of the invention is to increase the accuracy of determining the range.

где р=1, 2, …P_max, Р_mах=2D_max/cT - максимальное число ячеек дальности, соответствующее максимальной измеряемой дальности D_max, затем определяют номер w=Q массива выборочных значений зондирующего сигнала, для которого оценка R_w(p) в наибольшей степени соответствует установленному критерию, и судят о дальности D до цели по соотношению D=с(Р+(Q-1)/W)T/2+ΔD₀, где с - скорость света, ΔD₀ - постоянная величина, которую определяют предварительно путем калибровки на эталонной трассе для компенсации систематической ошибки.This problem is solved due to the fact that in the known method for determining the range, including the formation of a time-setting clock sequence of pulses with a period T, generating and sending to the target a probing signal S ₀ (t, t ₀ ) of duration t _s > T, the shape of which corresponds to a given sequence its sample values S _0i registered in the array {S _0i }, receiving the signal S (t, t _D ) reflected by the target, its digitization by determining and registering its sample values {S _j } with respect to the clock sequence of the array, determining the temporary position of the received signal relative to the probing signal by comparing arrays of sample values of the probing and received signals, where t is the current time, t ₀ is the moment of emission of the probing signal, t _D is the moment of reception of the signal reflected by the target, i = 1 ... K is the sample sequence number probing signal S _0i relative clock sequence K = t _s / T - number of samples of the probe signal, j = 1 ... J _max - sample number ref of the received signal S _j with respect to the clock _{sequence, J max = 2D max / cT} - Included quantity GUT samples of the received signal, D _max - maximum measurable distance, c - velocity of light, the time of the probing signal generation is synchronized with a clock pulse sequence, taking it as the origin is formed and recorded W≥2 arrays of sample values {S _{0i} w} probing signal, where w = 1 ... W is the serial number of the array, by forming samples with the interval T, and in the wth array, the time of the first sampling is shifted relative to the origin by the interval δt _w = (w-1) T / W, find such a shift p = P _w array {S _j} with respect to zhdogo arrays of {S _{0j} w,} wherein the degree of overlap to the greatest extent satisfies a predetermined criterion R _w (P _w), such as a minimum sum of absolute deviation

where p = 1, 2, ... P _max , P _max = 2D _max / cT is the maximum number of range cells corresponding to the maximum measured range D _max , then determine the number w = Q of the array of sample values of the probe signal, for which the estimate R _w (p ) meets the established criterion to the greatest extent, and they judge the range D to the target by the ratio D = c (P + (Q-1) / W) T / 2 + ΔD ₀ , where c is the speed of light, ΔD ₀ is a constant value, which is determined previously by calibration on a reference path to compensate for systematic error.

Arrays {S _0i } _w can be formed by pre-digitizing the probe signal, which consists in the probe radiation of the probe signal, converting it into an electrical signal, determining and recording its sample values S _0iw with period T.

It is advisable to place the arrays {S _0i } _w so that the samples with the maximum value have the same serial number in all arrays.

To quickly determine the optimal array with number w = Q in the array {S _j }, determine the sample serial number with the maximum value and combine the arrays of sample values of the probing {S _0i } _w and the received {S _j } signals by combining the samples with the maximum values.

выборочных значений, получаемых при каждом зондировании, где m - порядковый номер зондирования, N - количество зондирований.The sounding of the target can be performed many times, and an array of sampled values of the received signal at each jth position can be formed as a sum

sample values obtained with each sounding, where m is the sounding sequence number, N is the number of soundings.

На Фиг.3 показаны зависимости вида

и

полученные при воздействии шума. Фиг.4 иллюстрирует принцип формирования массивов {S_0i}_w=1 и {S_0i}_w=2. На фиг.5 представлены результаты формирования функций

при моделировании реального процесса измерения дальности. Фиг.6 поясняет процесс накопления данных при многократном зондировании.Figure 1 presents a timing diagram of the sensing process, its binding to the clock frequency and the formation of arrays {S _0i } and {S _j }. Figure 2 illustrates the formation of functions

Figure 3 shows the dependence of the type

and

obtained when exposed to noise. Figure 4 illustrates the principle of the formation of arrays {S _0i } _{w = 1} and {S _0i } _{w = 2} . Figure 5 presents the results of the formation of functions

when modeling a real range measurement process. 6 illustrates the process of data accumulation during multiple sounding.

,

или иной функциональной зависимости, отражающей степень совпадения формы переданного и принятого сигналов, содержащейся в массивах {S_0i}_w и {S_j}, где р=1, 2, …, Р_mах - номер ячейки дальности; Р_mах=2D_max/cT - количество ячеек дальности, D_max - максимальная измеряемая дальность, с - скорость света. На фиг.3а) показана зависимость вида

(6), а на фиг.3б) - зависимость вида

(7). Затем для каждого массива {S_0i}_w определяют номер ячейки Р=p(R_min), соответствующей оптимальному значению критерия (минимальному для зависимости 6 и максимальному для зависимости 7), и номер w=Q массива выборочных значений зондирующего сигнала, для которого оценка R_w(p) в наибольшей степени соответствует установленному критерию. Если в массивах {S_0i}_w выборка с максимальным значением находится в одной и той же позиции, то значение Р одинаково для всех массивов, и поиск оптимального массива {S_0i}_w может быть ускорен путем совмещения максимальных выборок {S_j} с максимальными выборками каждого из массивов {S_0i}_w и вычисления R_w(p) при сдвиге p=Р, соответствующем такому совмещению без построения всей кривой R_w(p). После определения оптимальных значений Р и Q вычисляют дальность D до цели по формуле D=с(Р+(Q-1)/W)T/2+ΔD₀, где с - скорость света, W - количество массивов {S_0i}_w, Т - период тактовой частоты, ΔD₀ - поправка, определяемая предварительно при калибровке измерителя на эталонной дистанции.At time t ₀ , a probe pulse S ₀ (t, t ₀ ) 1, represented by arrays of their sample values {S _0i } _w , is sent in the direction of the target. One of these arrays 2 is shown in FIG. Then, the pulse S (t, t _D ) 3 reflected by the target is received. The radiation moment t ₀ of the probe pulse 1 is tied to the clock sequence 4 by assigning the pulse of the clock sequence coinciding with the moment t ₀ with serial number i = 0. Clock pulses are generated using a highly stable source with a frequency of F _T = 1 / T, where T is the repetition period of clock pulses. Arrays {S _0i } _w can be formed by preliminary digitization of the probe signal, which consists in the probe radiation of the probe signal, its conversion into an electrical signal, determination and registration of its sample values S _0iw with period T. Arrays 2 are stored in the system memory and updated in the process preparation for measurements every time it is required by the conditions of metrological calibration. The received signal 3 is digitized by determining its sample values S (j) at the moments of generation of each j-th clock pulse; the numbering of samples S (j) is carried out from the clock pulse with number j = 0, which coincides with the moment t ₀ . The received sample values are stored in the array {S _j } 5 stored in the system memory. The arrays {S _0i } _w and {S _j } are normalized so that their samples with maximum values are equal. This minimizes the harmful effects of noise and dynamic distortion on subsequent data processing. After normalization, an evaluation function R (p) 6 is formed for each of the arrays {S _0i } _w by successively generating numbers p = 1, 2, ... P _max and determining for each p the values

,

or other functional dependence, reflecting the degree of coincidence of the shape of the transmitted and received signals contained in the arrays {S _0i } _w and {S _j }, where p = 1, 2, ..., P _max is the number of the range cell; P _max = 2D _max / cT is the number of range cells, D _max is the maximum measured range, and s is the speed of light. On figa) shows the dependence of the form

(6), and in fig.3b) - the dependence of the form

(7). Then, for each array {S _0i } _w, determine the cell number P = p (R _min ) corresponding to the optimal value of the criterion (minimum for dependence 6 and maximum for dependence 7), and number w = Q of the array of sample values of the probe signal, for which the estimate R _w (p) most closely matches the established criterion. If the sample with the maximum value is in the same position in the arrays {S _0i } _w , then the value of P is the same for all arrays, and the search for the optimal array {S _0i } _w can be accelerated by combining the maximum samples {S _j } with the maximum samples of each of the arrays {S _0i } _w and the calculation of R _w (p) with a shift p = P corresponding to such a combination without constructing the entire curve R _w (p). After determining the optimal values of P and Q, the distance D to the target is calculated by the formula D = c (P + (Q-1) / W) T / 2 + ΔD ₀ , where c is the speed of light, W is the number of arrays {S _0i } _w , T is the period of the clock frequency, ΔD ₀ is the correction determined previously when calibrating the meter at a reference distance.

определения позиции Р ее максимума и определения номера массива w=Q с максимальным значением R_w(P). Кривые 10 и 11 построены соответственно с помощью массивов 8 и 9. Аналогично, массивам 8 и 9 соответствуют кривые 12 и 13. На фиг.5а) максимум критерия R_w(P) обеспечивается для функции 10, для которой Q=1, в позиции Р=8. Тогда оценка задержки t_D сигнала в этом случае составляет t_D=(Р+(Q-1)/W)T=(8+(1-1)/2)Т=8Т. На фиг.5б) максимум критерия R_w(P) обеспечивается для функции 13, для которой Q=2, в позиции Р=8. Тогда оценка задержки t_D сигнала в этом случае составляет t_D=(8+(2-1)/2)Т=8,5Т. Обе оценки соответствуют истинным значениям задержки.Figure 4 shows an example of the formation of arrays {S _0i } ₁ 8 and {S _0i } ₂ 9 at W = 2 and, respectively, when shifting the sample values of the second array relative to the first by δt _w = (w-1) T / W = δt ₂ = (2-1) T / 2 = T / 2. Each of these arrays contains eight samples of the probing signal, and the samples with the maximum value are in the second position in both cases (S ₂₁ and S ₂₂ ). On figa) and 5b) shows the results of data processing when the signal S (t, t _D ) 3 is shifted by time t _D = 8T (figa) and t _D = 8.5T (fig.5b). In both cases, the signal is distorted by additive normal noise with an average value of zero and a standard deviation of σ = 0.1 from the maximum value (amplitude) of the signal S (t). The signal position is estimated using arrays 8 and 9 by forming a function

determining the position P of its maximum and determining the array number w = Q with the maximum value of R _w (P). Curves 10 and 11 are constructed respectively using arrays 8 and 9. Similarly, arrays 8 and 9 correspond to curves 12 and 13. In Fig. 5a), the maximum criterion R _w (P) is provided for function 10, for which Q = 1, in position P = 8. Then the estimate of the signal delay t _D in this case is t _D = (P + (Q-1) / W) T = (8+ (1-1) / 2) T = 8T. On figb) the maximum criterion R _w (P) is provided for the function 13, for which Q = 2, in position P = 8. Then the estimate of the signal delay t _D in this case is t _D = (8+ (2-1) / 2) T = 8.5T. Both estimates correspond to true delay values.

Thus, when using two arrays {S _0i }, the discreteness of determining the signal delay is reduced to T / 2. Similarly, as the number of arrays {S _0i } increases, the discreteness of the delay estimate decreases to T / W.

There is practically no need to build the dependences R _w (p). It is enough to combine the maximum samples {S _j } and each of the arrays {S _0i } _w , determine the values of the criterion R _w with this combination and determine the number Q of the array with the best value R _{w = Q.}

выборочных значений, получаемых при каждом зондировании, где m - порядковый номер зондирования, N - количество зондирований.The accuracy of the range measurement can be significantly increased by the accumulation method [5] by increasing the effective signal-to-noise ratio by repeatedly probing the target and forming an array of 14 sampled values of the received signal in each jth position as a sum

sample values obtained with each sounding, where m is the sounding sequence number, N is the number of soundings.

минимальное значение которой соответствует наилучшему совпадению массивов {S_0i}_w и {S_j}. Из фиг.3 видно, что такая зависимость 6 имеет более острый экстремум по сравнению с корреляционной зависимостью 7. Это снижает вероятность ошибки при воздействии возмущающих воздействий.To increase the resistance to noise and interference, it is possible to form a criterion for the coincidence of arrays as a function

the minimum value of which corresponds to the best match of the arrays {S _0i } _w and {S _j }. From figure 3 it can be seen that this dependence 6 has a sharper extremum compared with the correlation dependence 7. This reduces the likelihood of error when exposed to disturbing influences.

вычисляется в одной точке - в ячейке дальности p=Р, соответствующей совпадению максимальных выборок массивов {S_0i} и {S_j}. Максимальные выборки всех массивов {S_0i}_w находятся во 2-й позиции, а общее количество выборок К=5. Дальномер работает в режиме накопления с частотой зондирований 8000 Гц. Объем накопления N устанавливается автоматически в зависимости от величины отраженного сигнала - от N=128 при сильном сигнале до N=8000 при слабом сигнале. Среднеквадратичная ошибка измерения дальности не превышает 0,06 м. У известных дальномеров ошибка измерения в десятки раз больше этой величины.The proposed method is implemented in an experimental sample of a laser rangefinder with the following characteristics. Clock frequency F _T = 25 MHz (clock period T = 40 ns, which corresponds to discreteness in range ΔD = 6 m). The number of arrays {S _0i } W = 100. Criterion

it is calculated at one point — in the range cell p = P, corresponding to the coincidence of the maximum samples of the arrays {S _0i } and {S _j }. The maximum samples of all arrays {S _0i } _w are in the 2nd position, and the total number of samples is K = 5. The range finder operates in the accumulation mode with a sounding frequency of 8000 Hz. The accumulation volume N is automatically set depending on the magnitude of the reflected signal — from N = 128 for a strong signal to N = 8000 for a weak signal. The standard error of the range measurement does not exceed 0.06 m. For known rangefinders, the measurement error is ten times greater than this value.

The proposed method of measuring range in comparison with known methods provides a significantly more accurate estimate of the position of the reflected signal from the array of its sample values under noise exposure, including multiple sounding and data accumulation. The result is a significant increase in the accuracy of determining the range to the target.

Information sources

1. V.A. Volokhatyuk, V.M. Kochetkov, P.P. Krasovsky. Optical location issues. M .: Soviet Radio, 1971, p.176.

2. E.A. Meleshko. Integrated circuits in nanosecond nuclear electronics. M .: Atomizdat, 1977, p.77.

3. United States Patent No. 5805468, September 8, 1998, Method and apparatus for determining the light transit time over a measurement path arranged between a measuring apparatus and a reflecting object. - The prototype.

4. B.E. Gmurman. Theory of Probability and Mathematical Statistics. M .: Higher school, 1977.

5. Ya. D. Shirman, V.N. Manzhos. The theory and technique of processing radar information against the background of interference. M .: Radio and communications, 1981.

Claims (5)

1. A method of measuring range, including the formation of a time-consuming clock sequence of pulses with a period T, generation and sending to the target a probing signal S ₀ (t, t ₀ ) of duration t _s > T, the shape of which corresponds to a given sequence of its sample values S _0i recorded in array {S _0i }, receiving the signal S (t, t _D ) reflected by the target, digitizing it by determining and registering its sample values {S _j } relative to the clock sequence of the array, determining the temporal position of the received signal from relative to the probing signal by comparing arrays of sample values of the probing and received signals, where t is the current time, t ₀ is the moment of emission of the probing signal, t _D is the moment of reception of the signal reflected by the target, i = 1 ... K is the serial number of the probe signal S _0i relative to clock sequence, K = t _s / T is the number of samples of the probing signal, j = 1 ... J _max is the serial number of the samples of the received signal S _j relative to the clock sequence, J _max = 2D _max / cT is the number of samples of the received signal, D _max is the maximum measurable distance, c - velocity of light, characterized in that the moment of generation of the probe signal is synchronized with a clock pulse sequence, taking it as the origin is formed and recorded W≥2 arrays of sample values {S _{0i} w} probing signal, where w = 1 ... W is the serial number of the array, by forming samples with the interval T, and in the wth array, the time of the first sampling is shifted relative to the origin by the interval δt _w = (w-1) T / W, find such a shift p = P _{w of the} array { S _j } with respect to each of the arrays {S _0j } _w , for which the degree of their coincidence to the greatest extent satisfies the predetermined criterion R _w (P _w ), for example, the minimum of the total absolute deviation

,
where p = 1, 2, ... P _max ; P _max = 2D _max / cT - the maximum number of range cells corresponding to the maximum measured range D _max , then determine the number w = Q of the array of sample values of the probe signal, for which the estimate R _w (p) most closely matches the established criterion, and judge range D to the target according to the relation D = c (P + (Q-1) / W) T / 2 + ΔD ₀ , where c is the speed of light, ΔD ₀ is a constant value that is previously determined by calibration on a reference path to compensate for systematic error . 2. The method according to claim 1, characterized in that the arrays {S _0i } _w are formed by pre-digitizing the probe signal, which consists in the probe radiation of the probe signal, converting it into an electrical signal, determining and recording its sample values S _0iw with period T. 3. The method according to claim 1, characterized in that the arrays {S _0i } _w are placed so that the samples with the maximum value have the same serial number in all arrays. 4. The method according to claim 1 or 3, characterized in that the array number {S _j } determines the serial number of the sample with the maximum value and combines arrays of sample values of the probing {S _0i } _w and received {S _j } signals by combining samples having maximum values. 5. The method according to claim 1, characterized in that the sounding of the target is performed repeatedly, and an array of sampled values of the received signal in each jth position is formed as a sum

sample values obtained with each sounding, where m is the sounding sequence number, N is the number of soundings.

Images