JP5784179B1 - Ultrasonic distance measuring device and ultrasonic distance measuring method - Google Patents

Abstract

Ultrasonic distance measuring device and ultrasonic distance measuring device capable of accurately detecting the temperature of an external medium outside the device and measuring the distance to a target object with high accuracy while suppressing an increase in device size Get the way. The temperature sensor (4) is built in the apparatus to reduce the size, and the internal temperature detected by the built-in temperature sensor (4) is determined between the temperature sensor (4) and an external medium. It is possible to estimate the external medium temperature (Ta) with high accuracy by performing correction based on at least one of the heat resistance (Rca) and the heat generation amount (P) of the device and the heat capacity (C) of the device. ing. [Selection] Figure 1

Description

  The present invention relates to an ultrasonic distance measuring device and an ultrasonic distance measuring method for measuring a distance to a target object using an ultrasonic signal.

  Conventionally, the delay time from when an ultrasonic signal is transmitted toward the target object until the ultrasonic signal reflected by the target object is received is measured, and the target object is measured based on the measured delay time and the sound speed. There is an apparatus for measuring the distance (see, for example, Patent Document 1).

  In the related art described in Patent Document 1, the outside air temperature that is the temperature outside the apparatus is accurately detected in order to calculate the speed of sound, which is one of the parameters for measuring the distance to the target object. is necessary. Therefore, in the prior art described in Patent Document 1, a temperature sensor for detecting the outside air temperature is provided outside the apparatus.

JP 2001-108745 A

However, the prior art has the following problems.
In the prior art described in Patent Document 1, since the temperature sensor is provided outside the apparatus, there is a problem that the apparatus size increases. That is, there is a problem that it is difficult to detect the outside air temperature with high accuracy and to suppress the increase in the size of the apparatus.

  The present invention has been made in order to solve the above-described problems. In addition to suppressing the increase in the size of the apparatus, the external medium temperature outside the apparatus is accurately detected, and the distance to the target object is increased. It is an object of the present invention to obtain an ultrasonic distance measuring device and an ultrasonic distance measuring method capable of measuring with high accuracy.

  The ultrasonic distance measuring device according to the present invention measures a delay time from when an ultrasonic signal is transmitted toward a target object to when an ultrasonic signal reflected by the target object is received, and the measured delay time and sound velocity are measured. An ultrasonic distance measuring device that is a device that measures a distance to a target object based on the above, a temperature sensor that is built in the device and detects the internal temperature of the device, which is the internal temperature of the device, and a temperature sensor The external temperature of the external medium by correcting the internal temperature detected by the temperature sensor based on the thermal resistance between the external medium and the external medium existing outside the apparatus, and at least one of the calorific value of the apparatus and the heat capacity of the apparatus. A control unit that estimates an external medium temperature that is a temperature, calculates a sound speed based on the estimated external medium temperature, and measures a distance to the target object based on the delay time and the calculated sound speed. It is.

  The ultrasonic distance measuring method according to the present invention is an ultrasonic distance measuring method executed by an apparatus for measuring a distance to a target object using an ultrasonic signal, and transmits the ultrasonic signal toward the target object. A delay time measuring step for measuring a delay time until receiving an ultrasonic signal reflected by the target object, a temperature sensor installed inside the apparatus and detecting an internal temperature of the apparatus, and an external existing outside the apparatus The external medium temperature, which is the temperature of the external medium, is estimated by correcting the internal temperature detected by the temperature sensor based on the thermal resistance between the medium and at least one of the heat generation amount of the apparatus and the heat capacity of the apparatus. The sound velocity is calculated based on the external medium temperature estimation step and the external medium temperature estimated in the external medium temperature estimation step, and is calculated with the delay time measured in the delay time measurement step. A distance measuring step of measuring the distance to the target object based on the sound velocity, are those comprising a.

  According to the present invention, it is possible to reduce the size by incorporating a temperature sensor inside the apparatus, and to determine the internal temperature of the apparatus detected by the incorporated temperature sensor, the thermal resistance between the temperature sensor and the external medium, and the apparatus By correcting based on at least one of the heat generation amount and the heat capacity of the apparatus, a configuration for estimating the external medium temperature with high accuracy is provided. As a result, an ultrasonic distance measuring device and an ultrasonic distance measuring device that can accurately detect the temperature of the external medium outside the device and measure the distance to the target object with high accuracy while suppressing the increase in size of the device. You can get the method.

It is a block diagram which shows the outline of the ultrasonic distance measuring apparatus in Embodiment 1 of this invention. The time variation of the temperature T _s to the temperature sensor built in the ultrasonic distance measuring device according to the first embodiment of the present invention detects an explanatory diagram showing. In Embodiment 2 of this invention, it is explanatory drawing which shows the relationship between a wind speed and thermal resistance _Rca . It is a block diagram which shows the outline of the ultrasonic distance measuring device in a prior art.

  Hereinafter, an ultrasonic distance measuring device and an ultrasonic distance measuring method according to the present invention will be described with reference to the drawings according to a preferred embodiment. In the description of the drawings, the same reference numerals are assigned to the same elements, and duplicate descriptions are omitted.

Embodiment 1 FIG.
First, in order to clarify the technical features of the ultrasonic distance measuring device of the present invention, the problems of the prior art newly noticed by the present inventor will be described with reference to FIG. FIG. 4 is a configuration diagram showing an outline of an ultrasonic distance measuring device in the prior art.

  The ultrasonic distance measuring device in FIG. 4 includes an ultrasonic sensor 101, an ultrasonic sensor measurement correction unit 102, and a temperature sensor 103.

The ultrasonic sensor 101 measures a delay time _Td from when an ultrasonic signal is transmitted toward a target object (not shown) to when an ultrasonic signal reflected by the target object is received, and the measured delay time. _Td is output to the ultrasonic sensor measurement correction means 102.

Unlike the present invention, the temperature sensor 103 is not built in the apparatus (inside the ultrasonic sensor 101) but is provided outside the apparatus (outside the ultrasonic sensor 101). to detect the T _a. Further, the temperature sensor 103 outputs the detected outside air temperature _Ta to the ultrasonic sensor measurement correction unit 102.

Ultrasonic sensors measure correcting unit 102 on the basis of the air temperature T _a input from the temperature sensor 103, calculates the speed of sound c in accordance with the following equation (1).

Subsequently, the ultrasonic sensor measurement correction unit 102 calculates the distance R to the target object according to the following equation (2) based on the delay time _Td input from the ultrasonic sensor 101 and the calculated sound velocity c. calculate.

Here, as shown in the above equation (2), the distance R is proportional to the sound speed c. Therefore, in order to improve the measurement accuracy of the distance R, it is necessary to accurately grasp the sound speed c. For this purpose, as can be seen from the above equation (1), it is necessary to accurately detect the outside air temperature T _a.

Therefore, in the prior art, in order to detect the outside air temperature _Ta with high accuracy, the outside air temperature _Ta is directly detected by providing the temperature sensor 103 outside the apparatus. In other words, if a built-in temperature sensor 103 into the apparatus, can not be precisely detected outside air temperature T _a, although there is a disadvantage that apparatus size becomes large, had to be provided with a temperature sensor 103 to the outside of the apparatus .

The present inventors, in a case where a built-in temperature sensor 103 into the apparatus, the air temperature T _a as a factor that can not be accurately detected, and considered as follows.

That is, first, when an internal temperature sensor 103 in the apparatus, since they produce a delay with respect to changes in the air temperature T _a by the heat capacity possessed by the ultrasonic sensor 101 can not accurately detect the air temperature T _a. Further, the second, if a built-in temperature sensor 103 into the apparatus, between the temperature of the outside air temperature T _a and the temperature sensor 103 is detected by the apparatus, according to the thermal resistance between the outside air temperature sensor 103 resulting temperature difference, since the heat resistance is changed by the outside air in the wind speed can not be precisely detected outside air temperature T _a.

  In the present invention, based on the above considerations, the temperature detected by the temperature sensor will be described later even if the temperature sensor is built in the device to suppress an increase in the size of the device. An ultrasonic distance measuring device capable of accurately estimating the outside air temperature outside the device by performing such correction is provided.

  Next, the ultrasonic distance measuring apparatus according to the first embodiment will be described with reference to FIG. FIG. 1 is a configuration diagram showing an outline of an ultrasonic distance measuring apparatus according to Embodiment 1 of the present invention. In addition, the ultrasonic distance measuring apparatus in this invention is mounted in vehicles, such as a motor vehicle, for example, and can measure the distance with a front obstruction accurately using an ultrasonic wave.

  The ultrasonic distance measuring device in FIG. 1 includes a case 1 (housing), a CPU 2 (control unit), an ultrasonic transducer 3 and a temperature sensor 4. As shown in FIG. 1, the CPU 2, the ultrasonic transducer 3 and the temperature sensor 4 are built in the apparatus (contained in the case 1).

  The operation of the ultrasonic transducer 3 is controlled by the CPU 2. The ultrasonic transducer 3 transmits an ultrasonic signal toward a target object (not shown) based on operation control by the CPU 2. The ultrasonic signal reflected by the target object is received by the ultrasonic transducer 3, converted into an electric signal, and then input to the CPU 2.

Temperature sensor 4, as described above, are incorporated in the device interior (the case 1), (and later referred to as the device internal temperature T _s) within the device temperature is detected and outputs the detection result to CPU2 To do.

The CPU 2 measures a delay time _Td from when the ultrasonic transducer 3 transmits the ultrasonic signal toward the target object to when the ultrasonic signal reflected by the target object is received. Further, CPU 2, by correcting the device internal temperature T _s to the temperature sensor 4 detects (in hereinafter referred to as the external medium temperature T _a) outside the device temperature of the external medium present in (case 1 outside) the estimated To do.

Subsequently, CPU 2 is estimated based on an external medium temperature _{T a,} and calculates the speed of sound c in accordance with the above equation (1). Further, the CPU 2 calculates a distance R to the target object according to the above equation (2) based on the measured delay time _Td and the calculated sound speed c.

Next, the estimation of the external medium temperature _{T a} by CPU 2, will be described with reference to FIG. Figure 2 is an explanatory view showing a time variation of the temperature T _s to the temperature sensor built in the ultrasonic distance measuring device according to the first embodiment of the present invention detects.

In the first embodiment, the case where the external medium existing outside the apparatus is air (outside air) will be described as an example. In this case, it referred to as air temperature T _a is here an external medium temperature T _a. In addition, it is assumed that the thermal resistance between the temperature sensor 4 and the external medium (here, outside air) is R _sa , the heat capacity of the device is C, and the heat generation amount of the device is P. Further, each of the thermal resistance R _sa , the heat capacity C, and the calorific value P is known by measurement or the like by a prior experiment, and is preset in the CPU 2 as a thermal characteristic parameter.

First, with respect to the relationship among the device internal temperature T _s , the outside air temperature T _a , the heat capacity C, and the heat resistance R _sa , the following equation (3) is established from Newton's law of cooling. In addition, t in the following formula (3) is time.

Further, regarding the relationship among the apparatus internal temperature T _s , the heat capacity C, and the heat generation amount P, the following formula (4) is established by applying the law of energy conservation with respect to sensible heat.

  Subsequently, the following equation (5) is obtained by combining the above Newton's law of cooling and the law of energy conservation.

  Further, in the above equation (5), the differential equation d / dt is replaced with the Laplace operator s and rearranged, thereby obtaining the following equation (6).

Further, the above equation (6) represents the response as shown in FIG. 2, that is, the input is T _a + R _sa · P and the first order lag response of the time constant CR _sa . FIG. 2 shows a case where T _a + R _sa · P is constant. Further, for the first-order lag response expressed by the above equation (6), the Laplace inverse transform is performed on the above equation (6) to obtain the following equation (7).

In the above equation (7), T _s (0) is the temperature detected by the temperature sensor 4 at time t = 0. Also, outside air temperature T _a, the thermal resistance R _sa between the temperature sensor 4 and the outside _air, and each of the heating value P, a variation in the extent that can be regarded as a constant value in the sampling period t _s which will be described later is small assumption doing.

Further, CPU2 is configured to sample the device internal temperature _{T s} to the temperature sensor 4 is detected by the sampling period _{t s,} a value which is sampled k-th by CPU2 and _T s (k). Here, without losing generality, in the above equation (7), T _s (0) is replaced with T _s (k−1), and T _s (t) is replaced with T _s (k). Equation (8) is obtained.

The above equation (8) is the correction amount represented by (* 1) with respect to the device internal temperature T _s (k) detected by the temperature sensor 4 sampled k-th by the CPU 2, and (* 2) This means that the outside air temperature _Ta is estimated by using the correction amount expressed by the following equation. Hereinafter, the correction amount represented by (* 1) is referred to as a first correction amount based on the thermal resistance R _sa and the heat generation amount P, and the correction amount represented by (* 2) is referred to as the thermal resistance. This is referred to as a second correction amount based on R _sa and the heat capacity C. Further, the second correction amount represented by (* 2) is calculated based on the time change of the apparatus internal temperature T _s .

Thus, CPU 2 has a thermal resistance R _sa, heating amount based on the P and the heat capacity C, by correcting the device internal temperature T _s to the temperature sensor 4 detects, estimates the ambient temperature T _a. Specifically, CPU 2, to the apparatus internal temperature T _s to the temperature sensor 4 detects, with subtracts the first correction amount, by adding the second correction amount, to estimate the outside air temperature T _a.

Also, by following a delay in the device internal temperature T _s that is detected by the temperature sensor 4 to a change in air temperature T _a by the heat capacity C, ambient temperature by adding the second correction amount related to the heat capacity C T _a Can be estimated with high accuracy.

In the above equation (8), the case where the outside air temperature _Ta is estimated using both the first correction amount and the second correction amount is exemplified, but either the first correction amount or the second correction amount is used. it may be estimated the air temperature T _a with. Needless to say, even if the above equation (8) is modified and calculated as in the following equation (9), for example, the same operation as in the first embodiment is performed.

Further, CPU 2 is, in this manner estimating the outside air temperature T _a, and calculates the speed of sound c in accordance with the above equation (1), a delay time measured T _d, based on the calculated speed of sound c, the above equation ( The distance R to the target object is calculated according to 2).

  As described above, according to the first embodiment, the temperature inside the device detected by the temperature sensor built in the device is at least the thermal resistance between the temperature sensor and the external medium, the amount of heat generated by the device, and the heat capacity of the device. The external medium temperature is estimated by performing correction based on one of them.

  Specifically, the external medium temperature is obtained by subtracting the first correction amount based on the thermal resistance between the temperature sensor and the external medium and the heat generation amount of the apparatus from the internal temperature detected by the temperature sensor. presume. Further, the external medium temperature is estimated by adding a second correction amount based on the thermal resistance between the temperature sensor and the external medium and the heat capacity of the apparatus to the apparatus internal temperature detected by the temperature sensor.

  As a result, it is possible to accurately detect the external medium temperature outside the apparatus and measure the distance to the target object with high accuracy while suppressing the increase in the size of the apparatus.

Embodiment 2. FIG.
In the first embodiment, the case where the external medium temperature _Ta is estimated without considering the flow rate of the external medium has been described. In the second embodiment of the present invention, a case where the external medium temperature _Ta is estimated in consideration of the flow rate of the external medium will be described. In the second embodiment, as in the first embodiment, the external medium existing outside the apparatus is air (outside air) and the ultrasonic distance measuring device is mounted on the vehicle. I will explain. In this case, the flow rate of the external medium corresponds to the wind speed of the outside air.

Here, when considering the flow rate of the external medium, attention is paid to the thermal resistance R _sa between the temperature sensor 4 and the outside air. In this case, the thermal resistance R _sa is further decomposed into a thermal resistance R _sc between the temperature sensor 4 and the case 1 and a thermal resistance R _ca between the case 1 and the outside air. That is, it is expressed as the following formula (10).

FIG. 3 is an explanatory diagram showing the relationship between the wind speed and the thermal resistance R _{ca in} the second embodiment of the present invention. As shown in FIG. 3, it is known that the thermal resistance R _ca between the case 1 and the outside air changes depending on the wind speed of the outside air. More precisely, the thermal resistance R _ca is the relative flow rate (relative speed) between the case 1 and the external medium, that is, if the case 1 is mounted on the vehicle, the vehicle speed (own vehicle speed) and the wind speed of the outside air. Varies with relative flow rate.

  The ultrasonic distance measuring device according to the second embodiment further includes a relative flow velocity acquisition unit that acquires the relative flow velocity between the device and the external medium. Here, regarding a specific example of the relative flow velocity acquisition unit, assuming that the case 1 is mounted on a vehicle, a vehicle speed acquisition unit that acquires the vehicle speed as a device movement speed acquisition unit that acquires the movement speed of the case 1 ( For example, a vehicle speed sensor or the like is provided. Furthermore, a wind speed acquisition unit (for example, a wind speed sensor) that acquires the wind speed is provided as an external medium flow rate acquisition unit that acquires the flow rate of the external medium. And a relative flow velocity acquisition part is acquired by calculating a relative flow velocity based on the acquisition result by a vehicle speed acquisition part and a wind speed acquisition part. The relative flow rate acquisition unit may acquire the relative flow rate by causing the external device or the like to detect the relative flow rate and receiving the detection result by the relative flow rate acquisition unit.

The relationship between the wind speed and the thermal resistance R _ca in FIG. 3 is known in advance through experiments and is set in the CPU 2 in advance. In addition, as shown in FIG. 1, the vehicle speed information is input from the vehicle to the CPU 2 (relative flow velocity acquisition unit). Specifically, what is necessary is just to comprise so that the own vehicle speed which the vehicle speed acquisition part acquired may be input into CPU2.

  In the second embodiment, the CPU 2 regards the input host vehicle speed as equivalent to the relative flow velocity between the vehicle and the outside air, that is, the wind speed. This eliminates the need for a separate wind speed acquisition unit such as a wind speed sensor.

Further, CPU 2 is configured to sample a vehicle speed the vehicle speed acquiring unit is acquired at a sampling period t _s, according to the relationship between the preset wind speed and the thermal resistance R _ca, sampled in k-th The thermal resistance R _ca corresponding to the host vehicle speed is calculated, and this is set as the kth thermal resistance value R _ca (k).

Here, each of the heat capacity C, the thermal resistance R _sc between the temperature sensor 4 and the case 1, and the heat generation amount P is known by measurement by a prior experiment or the like, and is preset in the CPU 2.

Further, CPU 2 is lower is derived from the above equation (9) and the above equation (10) according to (11), to estimate the outside air temperature _{T a.}

As described above, the CPU 2 calculates the thermal resistance R _ca corresponding to the relative flow velocity (here, the vehicle speed) according to the relative flow velocity between the case 1 and the outside air (here, considered to be equivalent to the own vehicle speed). Thus, the outside air temperature _Ta is estimated by changing the thermal resistance _Rsa between the temperature sensor and the external medium.

Furthermore, CPU 2, if this estimated outside air temperature T _a, and calculates the speed of sound c in accordance with the above equation (1), a delay time measured T _d, based on the calculated speed of sound c, the above equation ( The distance R to the target object is calculated according to 2).

  As described above, according to the second embodiment, the relative flow velocity acquisition unit that acquires the relative flow velocity between the apparatus and the external medium in consideration of the flow velocity of the external medium (more strictly, the relative flow velocity between the apparatus and the external medium) is provided. In addition, the thermal resistance between the temperature sensor and the external medium is changed based on the acquired relative flow velocity.

  The case is mounted on the vehicle, and further includes a vehicle speed acquisition unit that acquires the vehicle speed of the vehicle as a relative flow velocity acquisition unit, and changes the thermal resistance using the vehicle speed acquired by the vehicle speed acquisition unit as a relative flow velocity.

Thereby, for example, if the external medium is air (outside air), the thermal resistance R _ca between the temperature sensor and the external medium is calculated using the thermal resistance R _ca calculated according to the relationship between the wind speed and the thermal resistance R _{ca. Since} the outside air temperature is estimated by changing _sa , the outside air temperature can be estimated more accurately than in the first embodiment. In addition, if the device is mounted on a vehicle, the thermal resistance _Rca is calculated _assuming that the vehicle speed is the wind speed, so there is no need to provide an external wind speed sensor or the like, and the size can be reduced and the cost can be reduced. can do.

  In the first and second embodiments, the calorific value P is set to a known value by a prior experiment or the like, but by measuring the voltage applied to the ultrasonic distance measuring device and the current flowing through the device. In addition, a heat generation amount detection unit that detects the heat generation amount P may be provided separately. In this case, the above equation (11) can also be calculated using the heat generation amount P detected by the heat generation amount detection unit.

  In the first and second embodiments, the case where the external medium is air has been described as an example. However, the present invention is not limited to this, and the present invention can be applied to a medium other than air (for example, water). The same effect as when the external medium is air can be obtained.

  1 Case, 2 CPU, 3 Ultrasonic transducer, 4 Temperature sensor, 101 Ultrasonic sensor, 102 Ultrasonic sensor measurement correction means, 103 Temperature sensor.

Claims (7)

Measure the delay time from the transmission of the ultrasonic signal toward the target object to the reception of the ultrasonic signal reflected by the target object, and the target object based on the measured delay time and the sound speed An ultrasonic distance measuring device which is a device for measuring the distance of
A temperature sensor that is built in the device and detects a device internal temperature that is a temperature inside the device; and
The device internal temperature detected by the temperature sensor based on a thermal resistance between the temperature sensor and an external medium existing outside the device, and at least one of a calorific value of the device and a heat capacity of the device. By correcting, the external medium temperature, which is the temperature of the external medium, is estimated, the sound speed is calculated based on the estimated external medium temperature, and the target object is calculated based on the delay time and the calculated sound speed. A control unit for measuring the distance of
An ultrasonic distance measuring device comprising: The ultrasonic distance measuring device according to claim 1,
The controller is
An ultrasonic distance measuring device that estimates the external medium temperature by subtracting a first correction amount based on the thermal resistance and the heat generation amount from the internal temperature detected by the temperature sensor. In the ultrasonic distance measuring device according to claim 1 or 2,
The controller is
An ultrasonic distance measuring device that estimates the external medium temperature by adding a second correction amount based on the thermal resistance and the heat capacity to the internal temperature detected by the temperature sensor. In the ultrasonic distance measuring device according to claim 3,
The controller is
An ultrasonic distance measuring device that calculates the second correction amount based on a temporal change in the temperature inside the device detected by the temperature sensor. In the ultrasonic distance measuring device according to any one of claims 1 to 4,
A relative flow velocity acquisition unit for acquiring a relative flow velocity between the device and the external medium;
The controller is
An ultrasonic distance measuring device that changes the thermal resistance based on the acquired relative flow velocity. In the ultrasonic distance measuring device according to claim 5,
The device is mounted on a vehicle;
As the relative flow velocity acquisition unit, further comprising a vehicle speed acquisition unit for acquiring the vehicle speed of the vehicle,
The controller is
An ultrasonic distance measuring device that changes the thermal resistance using the vehicle speed acquired by the vehicle speed acquisition unit as the relative flow velocity. An ultrasonic distance measuring method executed by an apparatus for measuring a distance to a target object using an ultrasonic signal,
A delay time measuring step of measuring a delay time from transmission of an ultrasonic signal toward a target object to reception of the ultrasonic signal reflected by the target object; and
Based on a thermal resistance between a temperature sensor that is installed inside the device and detects an internal temperature of the device and an external medium existing outside the device, and based on at least one of a heat generation amount of the device and a heat capacity of the device An external medium temperature estimation step for estimating an external medium temperature that is a temperature of the external medium by correcting the internal temperature of the apparatus detected by the temperature sensor;
Wherein calculating the sound speed based on the external medium temperature estimated by the external medium temperature estimating step, measuring a distance to the target object based on said sound velocity calculated and the delay time measured by said delay time measuring step A distance measuring step to
An ultrasonic distance measuring method comprising:

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