JPH11346113A - Directional synthesis processing method - Google Patents

Abstract

(57) [Summary] To provide a directivity synthesis processing method having a high degree of freedom. An evaluation function used for evaluating an error when determining whether or not to execute a minute correction of a load / phase shift amount distribution is automatically switched in accordance with an error temporal change trend (112). The element relating to the minute correction is automatically selected in a random manner according to the temporal change trend of the error (106, 10).
8). The amount of the minute correction in the next cycle is changed according to the execution history of the minute correction reflecting the temporal change trend of the error (120).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a directivity synthesis process for determining a load / phase shift distribution in an element array such as an ultrasonic transducer array and an array antenna so as to conform to a desired directivity pattern (specification). About the method.

[0002]

2. Description of the Related Art An ultrasonic transducer array is
In general, as shown in FIG. 5, a plurality of transducers 10 are spatially dispersed and arranged, and each transducer 10 is connected by a coupling / distribution unit 12. When transmitting an ultrasonic signal from this array, a coupling / distribution unit 12
Input an electrical signal to the The coupling / distribution unit 12 distributes this signal to each of the transducers 10 in accordance with the weight (load) given to each of the transducers 10, and further performs a phase shift according to the phase shift amount given to each of the transducers 10. Let it. Each transducer 10 converts the supplied electric signal into an ultrasonic signal. Conversely, when receiving an ultrasonic signal with this array, the received ultrasonic signal is converted into an electric signal by each transducer 10 and supplied to the coupling / distribution unit 12. The combining / distributing unit 12 shifts the phase of the signal according to the above-described phase shift amount, combines the signals according to the above-described load (weighted addition), and supplies the combined signal to a receiver (not shown). Here, the phase shift function is a part of the function of the coupling / distribution unit 12, but this is for simplification of the description.

Since each of the vibrators 10 has a specific directivity determined by its structure and the like, the spatial arrangement of the vibrators 10 is given, and the load / phase shift amount of each of the vibrators 10, that is, By determining the load / phase-shift amount distribution in the ultrasonic transducer array, the directivity pattern of the ultrasonic transducer array can be determined. Accordingly, the load / phase shift amount distribution is based on the directivity of each oscillator 10 alone, the spatial arrangement of each oscillator 10, the directivity pattern (specification) to be realized, and the initial value of the load / phase shift amount distribution. Is determined, an ultrasonic transducer array having a directional pattern satisfying specifications can be designed. Also, regarding an array antenna having a configuration in which a plurality of antenna elements are spatially dispersed and coupled by a coupling / distributor, for example, “Directional synthesis of a waveguide slot array antenna by linear programming” (Hara et al., Vol.J66-B, N, July 1983.
o. As disclosed in 7) and the like, there is known a method of designing using linear programming. Since this method can be implemented by simulation using a computer, it is useful for automating the work of designing devices such as an ultrasonic transducer array and an array antenna (collectively referred to as an “element array” in the present application).

However, this method has a problem that the degree of freedom is generally lacking. First, the above-described method can be used as a design target only in an element array in which the shape, arrangement, and directivity of a single element (ultrasonic transducer, antenna element, etc.) all satisfy predetermined conditions. ing. Furthermore, there are restrictions on the specifications that can be given (directivity patterns that can be designed), and it is not possible for a design operator to give specifications as desired. Further, a condition (convergence determination condition) for detecting that the load / phase shift amount distribution has converged to the solution must be set strictly, and there is difficulty in changing the convergence determination condition. In addition, it is also possible to appropriately insert processing constraints into the simulation process.
Have difficulty. In addition, the solution may change depending on the initial settings such as the load / phase-shift amount distribution, or the solution may reach a local solution instead of the optimal solution.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method in which the shape, arrangement, and directivity of elements, the directivity that can be designed, the convergence judgment conditions, the constraints, and the like are loose and the degree of freedom is high. Is to provide. An object of the present invention is to provide a method that does not require strict initial settings, is easy to use, and easily reaches an optimal solution.

In the directivity synthesis processing method according to the present invention, a first step of executing a simulation relating to a directivity pattern, a second step of determining whether or not a minute correction is possible and executing the minute correction, and repeatedly executing the simulation It is assumed that a third step of determining whether or not to end is performed.

[0007] Among these steps, in the first step, a simulation for calculating the directivity pattern of the element array and its error with respect to a predetermined specification based on the second load / phase shift amount distribution is executed. The second here
The load / phase shift amount distribution is a load / phase shift amount distribution obtained by performing a minute correction to the first load / phase shift amount distribution.
The first load / phase shift amount distribution is an initially set load / phase shift amount distribution or a load / phase shift amount distribution obtained as a result of the previous simulation.

In the second step, when the error calculated based on the second load / phase shift amount distribution is smaller than the error already calculated based on the first load / phase shift amount distribution, that is, after performing a slight correction, Load / phase shift distribution (second load / phase shift distribution)
When it is found that the error becomes smaller by using, the second load / phase shift amount distribution up to that point is used as a new first load / phase shift amount distribution. Conversely, the second
When the error calculated based on the load / phase shift amount distribution is larger than the error calculated based on the first load / phase shift amount distribution, that is, when the load / phase shift amount distribution after performing the minute correction is used, the error is reduced. On the contrary, when it is found that the distribution becomes larger, the first load / phase shift amount distribution up to that point is used as it is as the first load / phase shift amount distribution.

Further, in the third step, the first load /
When the directivity pattern obtained by the simulation based on the phase shift amount distribution satisfies a predetermined specification, the first load / phase shift amount distribution at that time is output as a synthesis result. Conversely, when the specification is not satisfied, the above error is stored and the simulation is executed again. Therefore, the simulation in the first step is (in principle)
It is repeatedly executed until a directivity pattern satisfying the specifications is obtained. When such a directivity pattern is obtained, a load / phase shift amount distribution related to the directivity pattern is output.

One of the features of the present invention is that various processes related to the simulation are executed on the basis of an error with respect to the specification appearing in the calculation result of the directivity pattern due to the repetitive execution of the simulation, in particular, its fluctuation tendency. It is. For example, in the second step, the evaluation function used for evaluating the error is automatically switched in accordance with the fluctuation tendency that appears in the error due to the repeated execution of the simulation. By automatically selecting the element to be subjected to the minute correction, or automatically changing the amount of the minute correction, information on the tendency of variation of the error can be reflected in the simulation. As a result, the simulation is repeated in a direction that quickly converges on the solution, so that it is not necessary to strictly initialize the load / phase shift distribution and the like.
The degree of freedom in designing directivity and setting convergence determination conditions is increased.

[0011] The fluctuation tendency that appears in the error due to the repeated execution of the simulation can be derived by storing and processing the error calculated during the execution of the simulation. Specifically, the maximum value or average value from the errors calculated during the simulation is obtained and compared over a predetermined period in the past, thereby obtaining the fluctuation tendency of the errors. Alternatively, it is derived based on the stored error, for example, in the form of a change rate of the error. Preferably, the rate of change is calculated in a plurality of ways while changing the number of times on which the calculation is based, and the results are integrated to detect a change trend. As described above, the information that is the basis for deriving the change trend and the current situation does not directly depend on the shape, arrangement, directivity of a single element, and the like, so that the restrictions on these settings are relaxed.

Further, when selecting and determining the element to be subjected to the minute correction, first, the load / load according to the change trend of the error is determined.
A partial area to be corrected is specified from the phase shift amount distribution, and an element to be subjected to minute correction is selected and determined on a random basis from a plurality of elements generally related to the specified partial area. As described above, since the processing using the random numbers is employed in determining the element, the probability of reaching the local solution is reduced, and the optimum solution is easily reached.

Further, the convergence to the solution can be further expedited by increasing the amount of the minute correction when the error decreases with the minute correction and decreasing the amount when the error increases. In particular, even when the error is reduced due to the fine correction, if the error increases during the fine correction within the predetermined number of times before, the amount of the fine correction is maintained as before, and the Even when the error increases, if the error is reduced during the minute correction within the predetermined number of times before, if the amount of the minute correction is maintained as it is, the error fluctuation tendency can be further improved. It can be strongly reflected in the amount of the minute tendency, and the convergence to the solution can be further accelerated. In addition, an end condition using the amount of minute correction can be added. Specifically, even when the directivity pattern obtained by the simulation does not satisfy the specifications, when the amount of the minute correction is less than the predetermined value, the simulation is prevented from being executed again and the What is necessary is just to output the first load / phase shift amount distribution at the point in time as a synthesis result.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

First, a method according to one embodiment of the present invention is as follows.
As shown in FIG. 1, it can be realized using a computer or the like including the element single directivity calculation unit 14 and the directivity synthesis processing unit 16. The element single directivity calculation unit 14 generates element shape data indicating the shape and structure of each element, for example,
When an identification code (ID) associated with the type of the structure is given by the design worker, element directivity data indicating the directivity of the element alone is generated according to this data. The element single directivity data is composed of angle information and gain information so as to express directivity in a three-dimensional space, and is supplied to the directivity synthesis processing unit 16.

The directivity synthesizing unit 16 further provides, from the design operator, element array data indicating the position and relative positional relationship of each element in the three-dimensional space, and specifications regarding the directivity pattern to be realized. Directivity pattern data and load / phase-shift amount initial value data, which is a load / phase-shift amount distribution initially applied for repeating the simulation, are input. As shown in FIG. 2, the directivity synthesis processing unit 16 inputs these element single directivity data, element array data, directivity pattern data, and load / phase shift amount initial value data (1).
00), the simulation is repeatedly executed until a predetermined termination condition is satisfied (124, 126), and the resulting load / phase shift amount initial value data is output as a design result.

In FIG. 2, the load / phase shift amount distribution is slightly changed, and based on the load / phase shift amount distribution, the single element directivity data and the element array data, the directivity pattern of the element array and this directivity pattern are obtained. The simulation of calculating the error of the gender pattern with respect to the above specification (114) is repeatedly executed. The error calculated here is used to determine whether or not to adopt this minute correction (116). That is, in step 116, the error of the directivity pattern calculated based on the load / phase shift amount distribution before the minute change and the error of the directivity pattern calculated based on the load / phase shift amount distribution after the minute change are determined. Compare. If the latter is smaller than the former, the error with respect to the specification can be reduced by adopting the minute change. Therefore, the next time step 114 is executed, the minute change is made to use as the “load / phase shift amount distribution before the minute change”. (11
8). Otherwise, the slight change is not adopted, and the load / phase shift distribution used as the “load / phase shift amount distribution before the slight change” is continuously used as the “load / phase shift amount distribution before the slight change”. And

The error calculated in step 114 is stored and used as “error of the directivity pattern calculated based on the load / phase-shift amount distribution before the minute change” when the next step 114 is executed. Further, steps 114 and 11
In order to execute Step 6, it is necessary to provide in advance which element of which load / phase shift amount is to be corrected in the above-mentioned minute correction, how much the amount of the minute correction is to be made, how to evaluate the error, and the like. Must be kept. In the present embodiment, information indicating how the error appearing in the calculation result of the directivity pattern changes with the repetition of the simulation is derived based on the stored error, and based on the result, The target of the minute correction is appropriately changed and set as the simulation is repeated.

First, when determining the element to be subjected to the minute correction, the directivity synthesis processing unit 16 normalizes the load (102) and calculates three past error change rates. (104). That is, the degree to which the error has changed in the long term, the medium term, and the short term due to the repetition of the simulation according to step 114 is calculated based on the stored error. Directivity synthesis processing unit 16
Determines which part of the directivity pattern calculated in step 116 should be subjected to the minute correction based on the error change rate calculated in step 104 (10
6) Further, one or a plurality of elements are automatically and randomly selected from one or a plurality of elements related to the part, and the load / phase shift amount relating to the element is subjected to a minute correction. (108). In addition, the directivity synthesis processing unit 16 later executes steps 106 and 108 with information indicating which part of the directivity pattern is to be subjected to the minute correction or which element is to be subjected to the minute correction. Remember for future use. That is, by comparing the portion or the element related to the minute correction in the directivity pattern and the calculated error change rate, the portion or the element to be subjected to the minute correction this time is determined. . Furthermore, in order to avoid convergence to a local solution, the directivity synthesis processing unit 16 uses a random number as described above when selecting an element.

Next, the directivity synthesis processing unit 16 calculates the maximum value and the average value of the errors for each simulation from the stored past errors (110), and calculates these values in the latest predetermined number of simulations. According to how the maximum value and the average value change, one of the maximum value function and the average value function is selected, and step 10
The evaluation function is used to evaluate the error of the portion selected in 6 (112). The evaluation function selected here is a function used in step 116 to evaluate the magnitude of the error. Therefore, in the present embodiment, not only the element to be finely corrected but also the evaluation of the error reflects the past change trend of the error.

Further, in step 120 which is executed following steps 116 and 118, the directivity synthesis processing section 16
Changes the correction amount of the load / phase shift amount distribution based on the execution history of step 118. That is, the correction amount is increased when step 118 is executed continuously for a predetermined number of times or more in the latest simulation, and decreased when step 118 is not executed continuously for a predetermined number of times or more in the latest simulation. Therefore, in the present embodiment, the past change trend of the error can be reflected in the correction amount through the execution history of step 118.

The directivity synthesis processing unit 16 further calculates the maximum error in the current simulation based on the stored error (122), and when the calculated maximum error is smaller than a predetermined value (124), the correction amount Is smaller than the predetermined minute value ε (126), the repetition of the simulation is terminated. In addition, it is also possible to add constraints using four arithmetic operations, logarithmic operations, logical operations, and the like to the procedure shown in FIG.

FIG. 3 and FIG. 4 show examples of designing using the method according to the present embodiment. First, FIG.
In the directivity pattern shown as, data indicating a rectangular element having a size corresponding to の of the wavelength is used as element shape data, and elements are linearly arranged at intervals corresponding to 波長 of the wavelength as element array data. Data indicating that 20 arrays are arranged is further converted to directivity pattern data from -90 degrees to -1.
-34 dB or less in the 0 degree direction, 0 in the 0 to 20 degree direction
-3 dB, -20 to -23 dB in the direction of 30 to 70 degrees
When data indicating the specification B is given,
It is a directivity pattern based on a load / phase shift distribution finally obtained by repeating a simulation. As compared with the conventional linear programming method indicated by a broken line for comparison, it is understood that a directivity pattern closer to the specification is obtained. FIG. 4 is an example in which each data is given in accordance with the disclosure of “Optimal Design of Quasi-Ideal Beam Transducer” (Sasakura et al., Journal of the Ocean Acoustics Society, Vol. 17, No. 2), which is described in the article. It can be seen that characteristics close to the characteristics are obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a flow of an operation of a directivity synthesis processing unit according to the embodiment.

FIG. 3 is a diagram illustrating a synthesis example.

FIG. 4 is a diagram illustrating a synthesis example.

FIG. 5 is a block diagram showing a schematic configuration of an ultrasonic transducer array.

[Explanation of symbols]

14 element directivity calculation unit, 16 directivity synthesis processing unit.

Claims (16)

[Claims] 1. A second load / phase-shift amount distribution obtained by performing a minute correction on an initially set or first load / phase-shift amount distribution obtained in a previous simulation. A first step of executing a simulation for calculating the directivity pattern of the element array and its error with respect to a predetermined specification based on the load / phase shift amount distribution of
When the error calculated based on the load / phase shift amount distribution is smaller than the error calculated based on the first load / phase shift distribution, the second load / phase shift amount distribution is used. A second step of setting the first load / phase-shift amount distribution to the first load / phase-shift amount distribution; and a directivity obtained by the simulation based on the first load / phase-shift amount distribution. When the pattern satisfies a predetermined specification, the first load / phase-shift amount distribution at that time is output as a synthesis result. Otherwise, the error is stored and the simulation is executed again. In the directivity synthesis processing method, the evaluation function used for evaluating the error is automatically switched in the second step according to the fluctuation tendency that appears in the error with the repetitive execution of the simulation. Directivity synthesis processing method. 2. A second load / phase-shift amount distribution obtained by performing a minute correction on an initially set or a first load / phase-shift amount distribution obtained in a previous simulation. A first step of executing a simulation for calculating the directivity pattern of the element array and its error with respect to a predetermined specification based on the load / phase shift amount distribution of
When the error calculated based on the load / phase shift amount distribution is smaller than the error calculated based on the first load / phase shift distribution, the second load / phase shift amount distribution is used. A second step of setting the first load / phase-shift amount distribution to the first load / phase-shift amount distribution; and a directivity obtained by the simulation based on the first load / phase-shift amount distribution. When the pattern satisfies a predetermined specification, the first load / phase-shift amount distribution at that time is output as a synthesis result. Otherwise, the error is stored and the simulation is executed again. In the directivity synthesis processing method having the above, automatically selecting a portion related to the minute correction in the directivity pattern according to a fluctuation tendency that appears in the error due to the repeated execution of the simulation. A directional synthesis processing method characterized by the following. 3. The directivity synthesizing method according to claim 1, wherein a portion related to the minute correction in the directivity pattern is automatically selected according to a fluctuation tendency that appears in the error due to the repetitive execution of the simulation. A directional synthesis processing method characterized by the following. 4. A second load / phase-shift amount distribution obtained by performing a minute correction on a first load / phase-shift amount distribution obtained by an initial setting or a previous simulation. A first step of executing a simulation for calculating the directivity pattern of the element array and its error with respect to a predetermined specification based on the load / phase shift amount distribution of
When the error calculated based on the load / phase shift amount distribution is smaller than the error calculated based on the first load / phase shift distribution, the second load / phase shift amount distribution is used. A second step of setting the first load / phase-shift amount distribution to the first load / phase-shift amount distribution; and a directivity obtained by the simulation based on the first load / phase-shift amount distribution. When the pattern satisfies a predetermined specification, the first load / phase-shift amount distribution at that time is output as a synthesis result. Otherwise, the error is stored and the simulation is executed again. And a directivity synthesis processing method comprising: automatically selecting an element to be subjected to the minute correction according to a fluctuation tendency appearing in the error with the repetitive execution of the simulation. Synthetic processing method. 5. The directivity synthesis processing method according to claim 1, wherein an element to be subjected to the minute correction is automatically selected in accordance with a fluctuation tendency that appears in the error with the repetitive execution of the simulation. Characteristic directivity synthesis processing method. 6. The directivity synthesis method according to claim 4, wherein a partial area to be corrected is specified from the load / phase shift amount distribution in accordance with the change trend, and the partial area related to the specified partial area is specified. In general, a directivity synthesis method is characterized by randomly selecting, from a plurality of elements, an element to be subjected to the minute correction. 7. The directivity synthesis processing method according to claim 1, wherein a maximum value or an average value of errors calculated at the time of the simulation is obtained, and the obtained maximum value or average value is calculated over a past predetermined period. A directivity synthesis processing method characterized in that the fluctuation tendency is derived by comparing. 8. The directivity synthesis processing method according to claim 1, wherein the change trend is derived by calculating a change rate of the error. 9. The directivity synthesis processing method according to claim 8, wherein the change rate is calculated a plurality of times by changing the number of times of calculation, and the results are integrated to detect the change trend. A directional synthesis processing method characterized by the following. 10. A second load / phase-shift amount distribution obtained by performing a small correction on an initially set or first load / phase-shift amount distribution obtained in a previous simulation,
A first step of executing a simulation for calculating the directivity pattern of the element array and an error with respect to a predetermined specification based on the second load / phase shift amount distribution, and based on the second load / phase shift amount distribution; If the calculated error is smaller than the error already calculated based on the first load / phase-shift amount distribution, the second load / phase-shift amount distribution is used. Otherwise, the first load / phase-shift amount distribution is used. With the first load /
A second step of setting the phase shift amount distribution; and, when the directivity pattern obtained by the simulation based on the first load / phase shift amount distribution satisfies a predetermined specification, the first step at that time. A third step of outputting a load / phase-shift amount distribution as a synthesis result, and otherwise storing the error and executing the simulation again; and repeatedly executing the simulation. A method for automatically changing the amount of the minute correction according to the tendency of the error to appear. 11. The directivity synthesis processing method according to claim 10, wherein an evaluation function used for evaluating the error in the second step is determined according to a fluctuation tendency that appears in the error with the repetitive execution of the simulation. A directivity synthesis processing method characterized by automatically switching. 12. The directivity synthesizing method according to claim 10, wherein a part of the directivity pattern related to the minute correction is automatically included in the directivity pattern according to a fluctuation tendency that appears in the error due to the repetitive execution of the simulation. A directivity synthesis processing method characterized by selecting. 13. The directivity synthesis processing method according to claim 10, wherein an element to be subjected to the minute correction is automatically selected according to a fluctuation tendency which appears in the error with the repetitive execution of the simulation. Characteristic directivity synthesis processing method. 14. The directivity synthesis processing method according to claim 10, wherein the amount of the minute correction is increased when the error decreases with the minute correction, and is decreased when the error increases. Sex synthesis processing method. 15. The directivity synthesis processing method according to claim 14, wherein even when the error is reduced due to the fine correction, the error increases during the fine correction within a predetermined number of times before. In the case where the amount of the fine correction is maintained as before, and even when the error increases due to the fine correction, if the error is reduced during the fine correction within a predetermined number of times before, A directional synthesis processing method, wherein the amount of the minute correction is maintained as before. 16. The directivity synthesizing method according to claim 10, wherein the amount of the minute correction is a predetermined amount even when the directivity pattern obtained by the simulation does not satisfy the specifications. A directivity combining method comprising: when the value falls below a value, avoiding re-execution of the simulation and outputting the first load / phase shift amount distribution at that time as a combined result.