RU2359227C1 - Method of optical location range finding - Google Patents

Abstract

FIELD: instrument engineering.

SUBSTANCE: invention deals with laser pulse location range finding. Method of optical location distance measuring up to the target by way of incoherent concentration includes series of cycles. Each cycle consists of sending of laser sounding pulse to the target. Time is sampled by displacement units. Pulse reflected by the target is received. In each time sample there developed is hypothesis about signal presence or absence by way of threshold conversion of received mixture of noise and signal. The number that corresponds to hypothesis is formed and these numbers are accumulated in a form of summaries for each time sample. After series of cycles time samples the accumulated summary of which exceeds specified number are marked. These accumulated summaries help to form ranging evaluation up to the target. Note that calibration is performed beforehand.

EFFECT: increase of range finding accuracy in wide range of received signals swing.

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Description

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

A known method of radar determination of the range to the target [1]. The specified method consists in sending a laser probe pulse to the target, receiving the signal reflected by the target, and determining the time interval between the probe and reflected pulses by which the distance to the target is judged. This method cannot be implemented using semiconductor lasers, preferred for portable equipment, due to their insufficient power.

Closest to the technical nature of the proposed method is a method of radar determination of the distance to the target by the method of incoherent accumulation, including a series of cycles, in each of which a laser probe pulse is sent to the target, quantized time per sample, received reflected by the target pulse, generated in each of the time samples the hypothesis of the absence or presence of a signal by threshold conversion of the received mixture of signal and noise, the formation of the corresponding number and accumulation numbers in the form of sums for each time discrete, at the end of a series of cycles, those time discrete are selected in which the accumulated sum exceeds the specified number, and an estimate of the distance to the target is formed from these accumulated sums [2].

In this method, the procedure of digital incoherent accumulation [3], which implements the method of statistical testing of hypotheses [4]. The disadvantage of this method is the dependence of the estimate of the distance to the target from the amplitude of the signal reflected by the target. With a large signal / threshold ratio, the hypothesis of the presence of a signal is confirmed in each cycle, and the accumulated sums take the maximum possible value equal to the number of cycles in a series. As a result, when the duration of the probing signal exceeds a few discrete times, the configuration of the accumulated data arrays nonlinearly depends on the amplitude of the received signals, which leads to a change in the range estimate.

The objective of the invention is to increase the accuracy of determining the range in a wide range of amplitudes of the received signals.

The problem is solved due to the fact that in the known method of radar determination of the distance to the target by the method of incoherent accumulation, which includes a series of cycles, in each of which a laser probe pulse is sent to the target, the time is quantized to discrete, the reflected pulse is received, the pulse is generated in each of the discrete time hypothesis about the absence or presence of a signal by threshold conversion of the received mixture of signal and noise, the formation of a number corresponding to the hypothesis and the accumulation of generated numbers in the form of mm for each time discrete, at the end of a series of cycles, those time discrete are selected in which the accumulated amount exceeds a predetermined number, an estimate of the distance to the target is formed from these accumulated sums, a calibration is preliminarily performed, during which the true value of the distance to the target is determined, and the amplitude of the reflected the purpose of the pulses within the working dynamic range, for each amplitude value, an estimate of the range, its displacement relative to the true value and the sum of the accumulated amounts in the discrete are determined of time in the vicinity of the time discrete with the maximum accumulated sum, and in the working range determination after the formation of the range, the sum of the accumulated sums in the time discrete in the vicinity of the time discrete with the maximum accumulated sum is determined, and depending on this sum of the accumulated sums, enter the range estimate is a correction equal in absolute value and inverse in sign to the corresponding estimate bias determined during calibration.

On figa, b are examples of filling the data array after accumulation, respectively, with a signal-to-noise ratio of 1 and 10.

Figure 2 presents an example of the dependence of the delay estimate on the signal amplitude and its bias.

The analysis of the proposed method for the two-level accumulation mode with the following initial data.

Accumulation volume N = 200 cycles.

The ratio of the signal amplitude to the standard deviation σ of noise from 1 to 200.

The levels of the first and second analog thresholds are respectively + σ and -σ.

The duration of the signal at the base is t _and = 6ΔT, where ΔT is the duration of the time samples.

The duration of the leading edge of the signal t _fr = 2ΔT.

In this example, the delay of the reflected signal is determined as the first initial moment [5] of the array of accumulated sums, and the range estimate R is formed according to the dependence R = cT _s / 2, where c is the speed of light.

As follows from figa, b, the estimate of the delay of the received signal by the proposed method (shown by the index on the time axis) changes its position in a wide range of amplitudes of the received signal (with a signal-to-noise ratio from threshold to the level of overflow of the drive channels in several adjacent time samples ) by about 0.5 time samples. For the considered example, the dependence of the required correction on the sum of the accumulated sums S _S in the vicinity of the k-th time discrete in which the accumulated sum S _{k is} maximum is obtained.

The corrected range estimate R * = R + Δr is practically independent of the signal-to-noise ratio S in a wide dynamic range of 0.2 <S <100. In this example

where R is the uncorrected range estimate;

Δr is the correction;

S _k is the current accumulated sum in the k-th time discrete, the largest in comparison with the accumulated sums in the adjacent time discrete;

S _{k max} - the maximum possible value of the accumulated amount;

a is the coefficient determined previously during calibration;

S _S - the amount of accumulated amounts;

S _j - the accumulated amount in the j-th time discrete;

j is the current index;

S ₀ - coefficient determined previously during calibration.

In Fig. 2, the correction area is limited to S ~ 20, because, firstly, this corresponds to the maximum value S _S taken into account when forming the estimate (7), and, secondly, when the signal-to-noise ratio> 10-20 generate a range estimate not by the accumulated array, but by direct temporary fixation of the received signal.

Compared with the methods of radar range determination, which do not take into account the correction for the value of the received signal, the proposed method allows several times to reduce the systematic error of range measurement. In the above example, this allows us to reduce the systematic error by about an order of magnitude, so that the real range measurement error can be reduced to 0.05 m with a time discrete of 6.67 ns, which corresponds to a clock frequency of 150 MHz and a resolution of 1 m in range. this standard error of the measurement of the range δ _R in the sensing series N = 200 cycles and the discrete range ΔR = 1 m is

Thus, the proposed method of radar range measurement allows for a higher accuracy of range measurement in a wide range of amplitudes of the received signals.

Information sources

1. V.A. Volokhatyuk, V.M. Kochetkov, P.P. Krasovsky "Optical location issues." - M.: Soviet Radio, 1971, p. 177.

2. International application WO 2005/006016 - prototype.

3. Ya. D. Shirman, VN Manzhos "Theory and technique of processing radar information against the background of interference." - M.: Radio and Communications, 1981, pp. 81-83.

4. V.E. Gmurman "Probability Theory and Mathematical Statistics." - M.: Higher School, 1977, p. 281.

5. I. N. Bronstein, K. A. Semendyaev, “A Handbook of Mathematics for Engineers and Students of Technical Universities”. - M.: Science, 1986, p. 466.

Claims (1)

A method of radar-ranging determination of the distance to a target by the method of incoherent accumulation, including a series of cycles, in each of which a laser probe pulse is sent to the target, the time is quantized to discretes, the reflected pulse is received, the hypothesis of the absence or presence of a signal is generated by threshold transformation in each time sample the received mixture of signal and noise, the formation of the corresponding number hypothesis and the accumulation of the generated numbers in the form of sums for each time discrete, at the end of a series of cycles in Allocate those time samples in which the accumulated sum exceeds a predetermined number, from these accumulated sums form an estimate of the distance to the target, characterized in that they pre-calibrate, during which the true value of the distance to the target is determined, the amplitude of the pulses reflected by the target is changed within the working dynamic range, for each value of the amplitude, an estimate of the range, its displacement relative to the true value and the sum of the accumulated sums in time discrete in the vicinity time samples with the maximum accumulated amount, and in the working range determination after the formation of the range, the sum of the accumulated sums in the time discs in the vicinity of the time samples with the maximum accumulated sum is determined, and, depending on this sum of the accumulated sums, a correction is introduced into the range estimate, equal in absolute value and opposite in sign to the corresponding bias of the estimate determined during calibration.

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