JP6748569B2 - Object detection device - Google Patents

Description

The present invention relates to an object detection device that detects an object using an ultrasonic sensor.

Conventionally, an ultrasonic sensor is mounted on a moving body to detect an object existing around the moving body, and various controls for improving traveling safety of the moving body based on the detection result, for example, to a driver. In addition, notifications are made and the braking device is operated.

The object detection by the ultrasonic sensor is generally performed by performing envelope detection on the received wave received by the wave transmission/reception unit and determining that there is an object around the moving body when the detection threshold is exceeded (for example, Patent Document 1). reference). Patent Document 1 discloses detecting whether the state is an icing abnormality, a disconnection abnormality, or a normal state, based on the reverberation time after the ultrasonic wave transmission is stopped and the result of frequency analysis. As a result, when an abnormality occurs, it is possible to distinguish between icing and disconnection and perform a more precise abnormality determination.

JP 2001-221849 A

In the ultrasonic sensor, when foreign matter such as water or dirt adheres to the wave transmitting/receiving part that transmits the exploration wave and receives the reflected wave, the sensitivity decreases and the reflected wave is reflected even though it is reflected by the object. May be smaller than the detection threshold. In such a case, there is a concern that detection omission may occur and appropriate driving support control may not be performed. On the other hand, if the detection threshold is set to a low value, when foreign matter does not adhere to the sensor surface, it is unnecessary to detect the presence of an object based on noise due to road surface reflection and the like, which may cause unnecessary operation of driving assistance control. I'm worried.

The present invention has been made in view of the above problems, and an object thereof is to provide an object detection device capable of achieving both improvement in object detection performance based on reflected waves and suppression of unnecessary detection of an object. And

The present invention adopts the following means in order to solve the above problems.

The present invention uses an ultrasonic sensor (20) that transmits an ultrasonic wave from a vibrator and generates a received signal according to the vibration of the vibrator, and based on a reflected wave received by the ultrasonic sensor, a moving body ( The present invention relates to an object detection device for detecting an object existing around 10). The first configuration detects the object based on a beat detection unit that detects a beat state of reverberation after the ultrasonic wave is transmitted from the transducer, and a comparison between an amplitude of the reflected wave and a detection threshold value. An object detection unit and a threshold value setting unit that variably sets the detection threshold value based on a detection result of the beat state by the beat detection unit.

When foreign matter adheres to the sensor surface (specifically, the transmitting/receiving part that transmits the exploration wave and receives the reflected wave), the reverberation vibration occurs between the sensor surface and the normal time when the foreign matter does not adhere to the sensor surface. If a difference in characteristics appears and the reverberation waveform deviates from the normal state, it is estimated that there is an adhering substance in the transmitting/receiving unit. In view of this point, in the above-described configuration, the reverberation beat state is detected, and the detection threshold for determining the presence or absence of an object based on the reflected wave is variably set based on the detected beat state. With such a configuration, it is possible to detect an object based on a reflected wave by using a detection threshold value according to the sensitivity. As a result, both improvement of the object detection performance based on the reflected wave and suppression of unnecessary detection of the object can be achieved.

The figure which shows schematic structure of the object detection system of the vehicle of 1st Embodiment. The time chart explaining the wave transmission and wave reception of the ultrasonic sensor. The figure explaining the state where the beat disappears by reverberation. The time chart which shows the transition of the amplitude threshold when the beat does not occur. The flowchart which shows the process sequence of a reflected wave threshold value setting process. 6 is a flowchart showing a processing procedure of amplitude threshold setting processing. The flowchart which shows the process sequence of the object detection process based on a reflected wave. The figure which shows schematic structure of the object detection system of the vehicle of 2nd Embodiment. The time chart which shows the specific mode of the reverberation beat detection method. The flowchart which shows the process sequence of a reflected wave threshold value setting process. The time chart explaining the beat detection method based on reverberation frequency. The time chart explaining the beat detection method based on reverberation frequency. The schematic block diagram of the object detection system of the vehicle of a 3rd embodiment. The flowchart which shows the process sequence of a reflected wave threshold value setting process.

Hereinafter, embodiments will be described with reference to the drawings. In each of the following embodiments, the same or equivalent portions are denoted by the same reference numerals in the drawings, and the description of the portions having the same reference numeral is cited.

(First embodiment)
The object detection system of this embodiment is mounted on a vehicle as a moving body. The object detection system shown in FIG. 1 detects an object (for example, another vehicle or road structure) existing around the vehicle 10 by using a distance measurement result of an ultrasonic sensor 30 mounted on the vehicle 10. ..

The ultrasonic sensor 30 is a sensor that detects the presence or absence of an object existing around the vehicle and the distance to the object by transmitting an ultrasonic wave as an exploration wave and receiving a reflected wave reflected by the exploration wave by surrounding objects. is there. The ultrasonic sensor 30 is communicatively connected to a driving assistance ECU 40 that performs driving assistance control (for example, collision avoidance control) of the vehicle 10, and outputs object detection information based on a command from the driving assistance ECU 40. .. The object detection information includes information on the position, distance, and azimuth of an object existing around the vehicle 10.

The ultrasonic sensor 30 includes a wave transmission/reception unit 21 and a detection ECU 20 as an object detection device. The wave transmission/reception unit 21 has a vibrator, and one vibrator serves both as a wave transmitter and a wave receiver. The wave transmission/reception unit 21 is disposed, for example, on a front bumper and a rear bumper of the vehicle 10.

The detection ECU 20 includes a wave transmission unit 22, a wave reception unit 23, and a control unit 24, which realize a wave transmission/reception function. The wave transmission unit 22 generates a pulse signal by pulse-modulating a sine wave having a predetermined frequency in the ultrasonic region and outputs the pulse signal to the wave transmission/reception unit 21. The wave transmission/reception unit 21 vibrates the vibrator at a predetermined transmission cycle. , Output ultrasonic waves as exploration waves. The wave receiving unit 23 converts the vibration of the vibrator into an electric signal and outputs it as a wave receiving signal to the waveform processing unit 25.

The control unit 24 outputs a wave transmission/reception command signal to the wave transmission unit 22 and the wave reception unit 23 based on a command from the driving support ECU 40, and at the same time, outputs the object detection information recognized based on the reflected wave to the driving support ECU 40. Output to. The detection ECU 20 further includes a waveform processing unit 25, an amplitude measuring unit 26, and a frequency measuring unit 27, and realizes a function of generating object detection information together with the control unit 24.

As the waveform processing, the waveform processing unit 25 performs filter processing and amplification processing on the received signal and detects the envelope with the envelope detection circuit. The amplitude measuring unit 26 measures the amplitude value of the received wave (including reverberation and reflected wave). In this embodiment, the upper limit value of the amplitude value is set, and when the amplitude value is larger than the upper limit value, the amplitude value is fixed at the upper limit value Amax. The frequency measuring unit 27 measures the frequency of the received wave. For example, a point at which the voltage changes from a positive value to a negative value is a zero cross point, and the reciprocal of the time between the zero cross points is a frequency.

With reference to FIG. 2, a series of flow of wave transmission and wave reception of the ultrasonic sensor 30 will be described. The horizontal axis of FIG. 2 is time, and the vertical axis is the amplitude value A. In FIG. 2, the waveform is shown by envelope detection.

The wave transmission unit 22 outputs a pulse signal to the wave transmission/reception unit 21 in accordance with a control command from the control unit 24 from time t10 to time t11. As a result, the transducer of the wave transmission/reception unit 21 vibrates, and ultrasonic waves of a predetermined frequency are transmitted from the wave transmission/reception unit 21 (time t10 to t11). During the period (t11 to t12) after the time t11 at which the transmission ends, the reverberation of the transmission wave occurs. Reverberation occurs due to the mechanical inertial vibration of the vibrator continuing after the vibration for the transmission is stopped.

When the ultrasonic wave transmitted during the period from time t10 to time t11 is reflected by an object existing around the vehicle and received by the wave transmitting/receiving unit 21 as a reflected wave, a time corresponding to the distance to the object (see FIG. Then, the amplitude value A increases at time t13). The control unit 24 compares the amplitude value A of the reflected wave at this time with the amplitude threshold value Ath, and determines that there is an object when the amplitude value A is larger than the amplitude threshold value Ath. The shorter the distance between the vehicle 10 and the object, the earlier the reflected wave appears.

The amplitude threshold value Ath is a threshold value used for comparison with the amplitude calculated based on the received signal, and in the present embodiment, the end determination of reverberation, that is, the start when the received signal is acquired as a signal based on the reflected wave. A reverberation threshold Atha used for determination and a reflected wave threshold Athb used for object detection determination that detects an object by a reflected wave are provided. The detection ECU 20 determines that the reverberation has ended, based on the result of comparison between the amplitude value A of the received wave and the reverberation threshold Atha after the end of the wave transmission. If it is determined that the reverberation has ended, the process starts to read the reflected wave. In addition, the amplitude threshold value Ath is switched from the reverberation threshold value Atha to the reflected wave threshold value Athb along with the transition to the start of reading the reflected wave, and the object detection is performed using the reflected wave threshold value Athb.

Specifically, as shown in FIG. 2, it is determined that the reverberation has ended (time t12) when a predetermined delay time Ty elapses after the amplitude value A after the transmission falls below the reverberation threshold Atha (time t12), and the reflection Start loading waves. When it is determined that the reverberation has ended, the amplitude threshold Ath is switched from the reverberation threshold Atha to the reflected wave threshold Athb. At the time of the switching, in the present embodiment, the amplitude threshold value Ath is gradually decreased from the reverberation threshold value Atha to the reflected wave threshold value Athb, and then the reflected wave threshold value Athb is set to a constant value. After time t12, the amplitude value A of the reflected wave is compared with the amplitude threshold value Ath, and it is determined that an object is detected based on the threshold value A of the reflected wave exceeding the amplitude threshold value Ath. The reflected wave threshold Athb corresponds to the “detection threshold”.

In the reverberation part, a "beat" may occur due to a plurality of waves having different frequencies interfering with each other to generate a synthetic wave. That is, as shown in FIG. 2, the reverberation amplitude value A may fluctuate in the reverberation continuation period after the transmission is finished at time t11. In this system, the circuit configuration of the coil, the capacitor, and the like in the ultrasonic sensor 30 is designed so that a beat is generated due to reverberation when the ultrasonic sensor 30 is normal. Therefore, when the ultrasonic sensor 30 can normally detect an object, the reverberation waveform has a waveform that increases and decreases as shown in FIG.

Here, if foreign matter such as water or dirt adheres to the wave transmission/reception unit 21 of the ultrasonic sensor 30, the sensitivity decreases, so that the reflected wave of the object is actually received, The amplitude value A of the reflected wave may be smaller than the amplitude threshold value Ath. In order to eliminate the omission of detection due to such a decrease in sensitivity, it may be possible to design the amplitude threshold value Ath to be small. However, if the amplitude threshold value Ath is designed to be small, there is a possibility that an unnecessary object may be detected by noise due to road surface reflection or the like when the transmitting/receiving unit 21 is normal and there is no attached matter.

When foreign matter adheres to the wave transmitting/receiving unit 21 of the ultrasonic sensor 30, a difference in vibration characteristics of reverberation appears, and when the reverberation waveform deviates from the normal state, foreign matter adheres to the wave transmitting/receiving unit 21. It can be estimated that In the present embodiment, attention is paid to the reverberation beat state, and when the reverberation beat state is different from the normal state, it is considered that foreign matter is attached to the wave transmission/reception unit 21, and an object is easily detected in order to compensate for the decrease in sensitivity. The reflected wave threshold value Athb is to be changed to that side.

Specifically, as shown in FIG. 1, the detection ECU 20 detects the beat state of the reverberation of the transmitted wave, and the reflected wave threshold value based on the detection result of the beat state of the reverberation by the beat detection unit 28. Athb is set variably, and a threshold setting unit 29 that sets an amplitude threshold Ath is provided. The control unit 24 uses the amplitude threshold Ath set by the threshold setting unit 29 to detect an object based on the reflected wave. Hereinafter, the processes performed by the beat detection unit 28 and the threshold value setting unit 29 will be described in detail.

The slope of the amplitude value A during the period in which the reverberation amplitude value A tends to decrease differs between when the reverberation has a beat and when it does not. Specifically, when a beat occurs in the reverberation, as shown in FIG. 2, a period in which the amplitude value A of the reverberation monotonously decreases toward zero (hereinafter, referred to as “amplitude falling period Td”). The gradient of the amplitude value A in () is relatively steep. On the other hand, when no beat is generated due to reverberation, as shown in FIG. 3, the slope of the amplitude value A in the amplitude falling period Td is gentler than when the beat is generated. .. Focusing on this point, the beat detection unit 28 detects the presence or absence of reverberation beat based on the slope of the amplitude value A in the amplitude falling period Td.

Specifically, the beat detection unit 28 includes an inclination calculation unit 28a and a beat determination unit 28b, as shown in FIG. The inclination calculating unit 28a determines the amplitude value A of the amplitude falling period Td during the period during which the reverberation continues, more specifically, before the amplitude value A falls below the reverberation threshold Atha after transmitting the exploration wave. The absolute value of the slope (hereinafter referred to as “falling slope α”) is calculated. The falling slope α corresponds to the “amplitude slope”.

The beat determination unit 28b compares the falling slope α calculated by the slope calculation unit 28a with the beat determination value αth. Then, when the falling slope α is equal to or less than the beat determination value αth, that is, when the decrease of the amplitude value A when the reverberation is attenuated is slow, it is determined that no reverberation is generated. On the other hand, when the falling slope α is larger than the beat determination value αth, that is, when the decrease in the amplitude value A when the reverberation is attenuated is sharp, it is determined that the reverberation has a beat. The beat detection unit 28 outputs the detection result of the reverberation beat state to the threshold value setting unit 29.

In addition, when the reverberation has a beat, as shown in FIG. 2, the amplitude value A fluctuates in the period during which the reverberation continues, so that the amplitude value of the reverberation within one reverberation period. A period in which A tends to decrease appears multiple times. The beat detection unit 28 recognizes the slope of the amplitude value A at the last amplitude fall Ap by calculating the slope of the amplitude value A each time the amplitude value A decreases, and rewriting it each time. Beat determination is performed with the inclination α.

The threshold value setting unit 29 inputs the detection result of the reverberant beat state from the beat detector 28, and variably sets the reflected wave threshold Athb according to the reverberant beat state. The ultrasonic sensor 30 of the present embodiment is designed so that beats are generated by reverberation in a normal state where no foreign matter is attached to the wave transmission/reception unit 21, and the threshold value setting unit 29 is used when the reverberation beat state is normal. In this state, that is, when a beat occurs due to reverberation, the second threshold value Ath2 is set as the reflected wave threshold value Athb. When no beat is generated due to reverberation and the beat state of reverberation is different from the normal state, a first threshold value Ath1 (Ath1<Ath2) smaller than the second threshold value Ath2 is set as the reflected wave threshold value Athb. ..

Further, the threshold value setting unit 29 sets the amplitude threshold value Ath using the reflected wave threshold value Athb and the reverberation threshold value Atha set according to the beat state of reverberation. In the present embodiment, considering that the slope at the last amplitude fall Ap of the reverberation is different between the case where the beat occurs in the reverberation and the case where it does not, the amplitude threshold is set in accordance with the beat state of the reverberation. The decrease rate B when the reverberation threshold Atha is gradually changed to the reflected wave threshold Athb is variably set. The decrease rate B is the amount of change in the amplitude threshold value Ath per unit time, and is indicated by a positive value. That is, as the decrease rate B is larger, the amplitude threshold value Ath is decreased with a steeper slope.

In the present embodiment, the delay time Ty is variably set according to the beat state of the reverberation. When the reverberation causes the beat, the delay time Ty is set to the second delay time Ty2 and the beat occurs. If not, the second delay time Ty2 short has first delay time Ty1 than. When the reverberation has a beat, since the amplitude value A fluctuates up and down, it is possible that the amplitude value A once becomes smaller than the amplitude threshold value Ath and then exceeds the amplitude threshold value Ath again. Further, when the reverberation does not have a beat, it is desirable to move to the start of reading the reflected wave earlier as the reverberation extends. Therefore, by setting the delay time Ty according to the beat state of reverberation, the detection performance for short-distance objects is ensured while avoiding erroneous detection of objects due to reverberation.

Specifically, when a beat occurs due to reverberation, the amplitude threshold value Ath is set to the reverberation threshold value Atha in a predetermined period after the transmission of the exploration wave, as indicated by a dashed line in FIG. After that, at a time point (t12) after the second delay time Ty2 has passed since the amplitude value A fell below the reverberation threshold value Atha, the amplitude threshold value Ath is gradually changed from the reverberation threshold value Atha toward the second threshold value Ath2 at the second reduction rate B2. To a constant value with the second threshold value Ath2. As the second threshold value Ath2, a high amplitude value is set so that the presence of an object is not detected based on the reflected wave from the road surface reflection, and thereby unnecessary detection of the object is suppressed.

When no beat is generated due to reverberation, the amplitude threshold value Ath is set as the reverberation threshold value Atha in a predetermined period after the transmission of the exploration wave, as indicated by a dashed line in FIG. After that, at a time point (t21) after the first delay time Ty1 (Ty1<Ty2) has passed after the amplitude value A falls below the reverberation threshold value Atha, the amplitude threshold value Ath is changed from the reverberation threshold value Atha to the first threshold value at the first reduction rate B1. The value is gradually decreased toward Ath1 (Ath1<Ath2), and then the first threshold value Ath1 is set to a constant value. In a situation where no beat is generated due to reverberation and it is assumed that there is an adhering matter in the wave transmitting/receiving unit 21, the reflected wave threshold value Athb is set to be low to suppress detection omission of an object. I have to.

The threshold setting unit 29 outputs the set amplitude threshold Ath to the control unit 24. The ultrasonic wave transmitter/receiver 21 of the ultrasonic sensor 30 transmits ultrasonic waves at every transmission cycle Tc (for example, at intervals of several hundred milliseconds), and the amplitude threshold value Ath is set at each transmission cycle Tc. The control unit 24 compares the amplitude of the received wave (reverberation and reflected wave) input from the amplitude measurement unit 26 with the amplitude threshold value Ath input from the threshold value setting unit 29 to determine the end of reverberation and detect an object.

The driving assistance ECU 40 is mainly configured by a microcomputer including a CPU, various memories, etc., and performs driving assistance control of the vehicle 10 based on the object detection information acquired from the ultrasonic sensor 30. As the driving support control, a driver of the vehicle 10 is notified by an alarm sound so that the vehicle 10 does not come into contact with an object, or various controls such as braking control and steering control for avoiding contact with the object. To go. An outside air temperature sensor 41 that detects the outside air temperature is attached to the vehicle 10.

Next, the processing executed by the object detection device of this embodiment will be described with reference to the flowcharts of FIGS. 5 shows the processing procedure of the setting processing of the reflected wave threshold Athb, FIG. 6 shows the processing procedure of the setting processing of the amplitude threshold Ath, and FIG. 7 shows the processing procedure of the object detection processing by the reflected wave. These processes are executed by the detection ECU 20 at predetermined intervals after the transmission/reception unit 21 outputs a transmission command to transmit ultrasonic waves.

In FIG. 5, in step S 101, the reverberation is received by the wave receiving unit 23. In step S102, the falling slope α of the amplitude value A is calculated in the period before the received amplitude value A of the reverberation falls below the amplitude threshold value Ath.

In step S103, it is determined whether the falling slope α is larger than the beat determination value αth. If the falling slope α is larger than the beat determination value αth, the process proceeds to step S104, the second threshold value Ath2 is set as the reflected wave threshold value Athb, and this is stored in the storage unit.

On the other hand, when the falling slope α is less than or equal to the beat determination value αth, the process proceeds to step S105, and based on the outside air temperature information detected by the outside air temperature sensor 41, whether or not the outside air temperature has changed by a predetermined temperature or more. Is determined (temperature change determination unit). Here, an affirmative determination is made if the outside air temperature does not change rapidly beyond a predetermined temperature within a predetermined short time (for example, several minutes to several tens of minutes). A situation where a rapid temperature change occurs may occur when the vehicle 10 enters a space that is shielded from the outside, such as a garage, a tunnel, an indoor parking lot, or the like.

If the outside air temperature has not changed by the predetermined temperature or more, an affirmative decision is made in step S105, the operation proceeds to step S106, the first threshold value Ath1 is set as the reflected wave threshold value Athb, and this is stored in the storage unit. On the other hand, if the outside air temperature has changed by the predetermined temperature or more, the process proceeds to step S104, and the second threshold value Ath2 is set as the reflected wave threshold value Athb. In the case where the outside air temperature changes abruptly and largely, the cause of disappearance of the reverberation beat is considered not to be due to the adhesion of foreign matter to the wave transmitting/receiving unit 21, but to the temperature characteristic of the circuit in the ultrasonic sensor 30. This is because.

Next, the setting process of the amplitude threshold Ath will be described. In FIG. 6, in step S201, the transmitted wave and the reverberation are received by the wave receiving unit 23, and it is determined based on the amplitude value A whether the reverberation has ended. Specifically, it is determined whether or not the delay time Ty has elapsed since the amplitude value A after the transmission of the exploration wave fell below the amplitude threshold value Ath. The delay time Ty is set to the first delay time Ty1 when the beat does not occur due to reverberation, and is set to the second delay time Ty2 when the beat occurs due to reverberation. If it is determined that the reverberation has not ended, the process proceeds to step S202, and the amplitude threshold value Ath is set to the reverberation threshold value Atha.

If the affirmative determination is made in step S201, that is, if the reverberation has ended, the process proceeds to step S203, and it is determined whether or not the amplitude threshold Ath has decreased to the reflected wave threshold Athb. If the amplitude threshold value Ath is higher than the reflected wave threshold value Athb, an affirmative decision is made in step S203 and the operation proceeds to step S204 to gradually change the amplitude threshold value Ath at the reduction rate B. Specifically, when the beat does not occur in the reverberation, the value obtained by reducing the previous value of the amplitude threshold value Ath by the first reduction rate B1 is set as the current value, and when the beat occurs in the reverberation, The value obtained by reducing the previous value of the amplitude threshold value Ath by the second reduction rate B2 is set as the current value. On the other hand, when the amplitude threshold value Ath has decreased to the reflected wave threshold value Athb, the process proceeds to step S205, the amplitude threshold value Ath is held at the reflected wave threshold value Athb, and this routine is ended.

Next, the object detection processing by the reflected wave will be described. 7, in step S301, it is determined whether the reverberation has ended by the same processing as in step S201 of FIG. If it is determined that the reverberation has ended, the process proceeds to step S302, and the received wave is read as a reflected wave. In the following step S303, the amplitude threshold value Ath set in FIG. 6 is acquired, and the amplitude value A of the reflected wave is compared with the amplitude threshold value Ath. If the amplitude value A of the reflected wave is less than or equal to the amplitude threshold value Ath, the process proceeds to step S304 and it is determined that there is no object. On the other hand, when the amplitude value A of the reflected wave is larger than the amplitude threshold value Ath, the process proceeds to step S305 and it is determined that there is an object. Then, this process ends.

According to this embodiment described in detail above, the following excellent effects can be obtained.

Since the reflected wave threshold Athb is variably set based on the beat state of reverberation, it is possible to perform object detection based on the reflected wave using the reflected wave threshold Athb according to the presence/absence of attached matter in the wave transmitting/receiving unit 21. it can. This makes it possible to improve the object detection performance based on the reflected wave and suppress unnecessary detection of the object.

Specifically, when the reverberation beat state detected by the beat detection unit 28 is different from the normal state in which there is no deposit on the wave transmission/reception unit 21, the reflected wave threshold Athb is set on the side where an object is easily detected. The configuration was changed. According to this configuration, when there is no adhering matter on the wave transmitting/receiving unit 21, the reflected wave threshold value Athb is set to a high value, so that unnecessary object detection due to noise due to road surface reflection or the like can be suppressed. .. Further, when the wave transmitting/receiving unit 21 has an adhered substance, the reflected wave threshold value Athb is set to a low value, so that an object can be accurately detected in a situation where the sensitivity is lowered. Further, since the sensitivity is lowered due to the presence of the adhered matter, unnecessary object detection can be suppressed even if the reflected wave threshold value Athb is set to be low.

The reflected wave threshold value Athb is variably set based on the detection result of the reverberation beat state, provided that the outside air temperature has not changed by a predetermined temperature or more. When the outside air temperature changes by a predetermined temperature or more, it is considered that the reason why the reverberation beat state changes is not the presence of adhered matter in the wave transmitting/receiving unit 21, but the temperature characteristic of the circuit in the ultrasonic sensor 30. .. In other words, when the reverberation beat state changes in a situation where the outside air temperature has not changed by more than a predetermined value, it is highly probable that adhering matter is present in the wave transmitting/receiving unit 21. With the above configuration in consideration of this point, the accuracy of determining the presence/absence of an adhering matter on the wave transmitting/receiving unit 21 can be increased.

Focusing on the fact that the falling slope α of the amplitude of the reverberation wave varies depending on the reverberation beat state, the reverberation beat state is detected based on the falling slope α. According to this configuration, at least the slope of the amplitude value A needs to be calculated during the last period of the amplitude fall Ap, so that the reverberation beat state can be detected with a small processing load.

Focusing on the fact that the falling slope α of the amplitude when the reverberation decays differs depending on the reverberation beat state, the amplitude threshold value is changed from the reverberation threshold value Atha based on the detection result of the reverberation beat state by the beat detection unit 28. The decrease rate B, which is the amount of change per unit time when gradually changing to the reflected wave threshold value Athb, is variably set. Specifically, when the beat does not occur in the reverberation, the reduction rate B is set to be smaller than that in the case where the beat occurs in the reverberation. With such a configuration, in a situation where the reverberation is gradually attenuated, the amplitude threshold value Ath is also gently reduced, so that unnecessary detection of an object due to the reverberation can be suppressed. On the other hand, in a situation where the reverberation is steeply attenuated, the amplitude threshold value Ath is rapidly lowered, so that it is possible to improve the detection performance of an object existing at a short distance from the vehicle 10 and to accurately measure an object having a low reflectance. Can be detected.

The delay time Ty is variably set based on the detection result of the reverberation beat state by the beat detection unit 28. Specifically, the delay time Ty is set so that when the reverberation does not have a beat, the timing of starting acquisition of the received signal as a reflected wave is earlier than when the reverberation has a beat. It was configured to do. With such a configuration, in an unstable situation in which the amplitude of reverberation may increase again, it is possible to delay the start of detection of an object based on the reflected wave, and conversely, the reverberation is stably attenuated. In the situation where there is a situation, it is possible to shift to the detection start of the object based on the reflected wave earlier. Accordingly, it is possible to achieve both suppression of unnecessary detection by starting detection of an object while reverberation has not ended and improvement of detection performance of an object existing at a short distance from the vehicle 10.

(Second embodiment)
Next, the second embodiment will be described focusing on the differences from the first embodiment. In the first embodiment, the reverberation beat state is detected based on the falling slope α which is the absolute value of the slope of the falling part of the reverberation waveform. On the other hand, in the present embodiment, the beat state of reverberation is detected by detecting the frequency at which the amplitude value A of reverberation increases or decreases with a change of a predetermined value or more.

FIG. 8 is a schematic configuration diagram of the object detection system of this embodiment. Note that FIG. 8 shows a portion different from FIG. In FIG. 8, the beat detection unit 28 includes a fluctuation detection unit 28c and a beat determination unit 28d. The fluctuation detecting unit 28c determines the number of times the amplitude value A of the reverberation has increased or decreased by a fluctuation amount equal to or more than a predetermined value in the period before the amplitude value A falls below the amplitude threshold value Ath after transmitting the ultrasonic wave (hereinafter, “beat number δ ".) is measured. For example, as shown in FIG. 9, in the period after time t31 after the end of the transmission of the exploration wave, the number of appearances of the minimum point P in which the amplitude value A is below the fluctuation threshold Dth is counted, and the number of appearances is set as the beat number δ To do. The fluctuation threshold Dth is set to a value smaller than the upper limit Amax and larger than the reverberation threshold Atha.

The beat determination unit 28d compares the beat count δ detected by the fluctuation detection unit 28c with the beat determination value δth, and when the beat count δ is equal to or less than the beat determination value δth, the beat does not occur due to reverberation. judge. On the other hand, when the beat number δ is larger than the beat determination value δth, it is determined that the reverberation causes the beat. The threshold value setting unit 29 inputs the detection result of the reverberating beat state from the beat detecting unit 28, and variably sets the reflected wave threshold value Athb according to the presence or absence of the beat.

Next, the process of setting the reflected wave threshold Athb of the present embodiment will be described with reference to the flowchart of FIG. This process is executed by the detection ECU 20 at every predetermined cycle after the transmission/reception unit 21 outputs a transmission command to transmit an ultrasonic wave.

In FIG. 10, in step S401, the reverberation is received by the wave receiving unit 23. In step S402, the number of beats δ is calculated based on the reverberation amplitude value A in the period before the received reverberation amplitude value A falls below the reverberation threshold value Atha.

In step S403, it is determined whether or not the beat count δ is larger than the beat determination value δth. If the beat count δ is larger than the beat determination value δth, the process proceeds to step S404, the first threshold value Ath1 is set as the reflected wave threshold value Athb, and this is stored in the storage unit. On the other hand, if the number of beats δ is equal to or less than the beat determination value δth, the process proceeds to step S405, and it is determined whether the outside air temperature has changed by a predetermined temperature or more based on the outside air temperature information detected by the outside air temperature sensor 41. ..

If the outside air temperature has not changed by the predetermined temperature or more, the process proceeds to step S406, the first threshold value Ath1 is set as the reflected wave threshold value Athb, and this is stored in the storage unit. On the other hand, if the outside air temperature has changed by the predetermined temperature or more, the process proceeds to step S404, and the second threshold value Ath2 is set as the reflected wave threshold value Athb. After that, this processing ends. The reflected wave threshold value Athb set in the process of FIG. 10 is used in the setting process of the amplitude threshold value Ath shown in FIG. 6, and the amplitude value A of the reflected wave and the amplitude threshold value Ath are calculated by the object detection process of FIG. Object detection is performed based on the comparison result.

According to the second embodiment described in detail above, attention is paid to the fact that the frequency at which the amplitude of the reverberation wave increases and decreases varies depending on the beat state of the reverberation, and the reverberation beat based on the beat number δ representing the frequency. It is configured to detect the state. With this configuration, the reverberation beat can be directly detected, and the beat state can be detected more accurately. As a result, it is possible to set a more suitable reflected wave threshold Athb from the viewpoint of both suppressing unnecessary detection of an object and improving the detection performance of the object.

(Third Embodiment)
Next, the third embodiment will be described focusing on the differences from the first embodiment. In the first embodiment, the reverberation beat state is detected based on the falling slope α, but in the present embodiment, the beat state is detected based on the reverberation frequency.

The beat detection process based on the reverberation frequency will be described with reference to FIGS. 11 and 12. FIG. 11 shows a case where beats are generated by reverberation, and FIG. 12 shows a case where beats are not generated by reverberation. In FIG. 11 and FIG. 12, the upper part shows the transition of the amplitude value A of the composite wave, and the lower part shows the transition of the amplitude value A of each of the low frequency component and the high frequency component.

The reverberation beat is caused by a plurality of waves having different frequencies interfering with each other to generate a synthetic wave. When the beat is generated due to the reverberation, as shown in FIG. 11, the amplitude values A of the low frequency component and the high frequency component have substantially the same changes over time, and the frequency measuring unit 27 indicates that the high frequency component The frequency is measured. On the other hand, when the reverberation is shifted to the low frequency side and the frequency of the vibration of the low frequency component is measured by the frequency measuring unit 27, no reverberation beat is generated as shown in FIG. Focusing on this point, in the present embodiment, the beat state is detected based on the frequency of the reverberation.

FIG. 13 is a schematic configuration diagram of the object detection system of this embodiment. Note that FIG. 13 shows a portion different from FIG. The beat detection unit 28 inputs the reverberation frequency (hereinafter referred to as “reverberation measurement frequency fa”) measured after the completion of the exploration wave transmission command from the frequency measurement unit 27, and based on the input reverberation measurement frequency fa, It is determined whether or not the reverberation has a beat. In the present embodiment, frequency information indicating the relationship between the reverberation frequency at the reference temperature (for example, normal temperature) and the driving frequency is stored in the storage unit in advance, and the reverberation beat state is detected using the frequency information. To do. In the present embodiment, the ultrasonic sensor 30 is designed so that beats are generated by reverberation at the reference temperature, and in a normal state in which no foreign matter is attached to the wave transmitting/receiving unit 21, the reverberation frequency indicates the amplitude component of the amplitude component. The frequency of a large high frequency component (frequency higher than the driving frequency) is measured. The reference temperature is an ambient temperature when the vehicle is traveling normally, and may be set according to, for example, a shipping area.

Specifically, the beat detection unit 28 determines whether or not the relationship between the reverberation measurement frequency fa and the drive frequency is the same as the relationship between the reverberation frequency and the drive frequency at the reference temperature. If the relationship between the two is the same as at the reference temperature, it is determined that the beat is occurring in the reverberation part. On the other hand, when the relationship between the two is different from that at the reference temperature, it is determined that the beat does not occur in the reverberation part. The threshold value setting unit 29 inputs the detection result of the reverberating beat state from the beat detecting unit 28, and variably sets the reflected wave threshold value Athb according to the presence or absence of the beat.

Next, the process of setting the time threshold value Tth according to this embodiment will be described with reference to FIG. This process is executed by the detection ECU 20 at every predetermined cycle after the transmission/reception unit 21 outputs a transmission command to transmit an ultrasonic wave.

In FIG. 14, the reverberation is received by the wave receiving unit 23 in step S501. In step S502, the reverberation measurement frequency fa is acquired, and in step S503, it is determined whether the relationship between the reverberation measurement frequency fa and the drive frequency is the same as that at the reference temperature. If the relationship between the reverberation measurement frequency fa and the drive frequency is the same as at the reference temperature, the process proceeds to step S504, the second threshold value Ath2 is set as the reflected wave threshold value Athb, and this is stored in the storage unit. On the other hand, when the relationship between the reverberation measurement frequency fa and the driving frequency is not the same as the reference temperature, the process proceeds to step S505, and the outside air temperature changes by a predetermined temperature or more based on the outside air temperature information detected by the outside air temperature sensor 41. It is determined whether or not.

If the outside air temperature has not changed by the predetermined temperature or more, the process proceeds to step S506, the first threshold value Ath1 is set as the reflected wave threshold value Athb, and this is stored in the storage unit. On the other hand, if the outside air temperature has changed by the predetermined temperature or more, the process proceeds to step S504, and the second threshold value Ath2 is set as the reflected wave threshold value Athb. After that, this processing ends. The reflected wave threshold value Athb set in the process of FIG. 14 is used in the setting process of the amplitude threshold value Ath shown in FIG. 6, and the reflected wave amplitude value A and the amplitude threshold value Ath are calculated by the object detection process of FIG. Object detection is performed based on the comparison result.

According to the third embodiment described in detail above, focusing on the fact that the appearance of the reverberation frequency differs depending on the reverberation beat state, the reverberation beat state is detected based on the reverberation frequency. With this configuration, the reverberation frequency can be detected relatively easily using the reverberation frequency, and the reflected wave threshold value Athb can be variably set using the detection result, so that unnecessary detection of an object can be performed. It is possible to achieve both suppression and improvement in object detection performance.

(Other embodiments)
The present invention is not limited to the above embodiment, and may be implemented as follows, for example.

In the above-described embodiment, the case where the ultrasonic sensor 30 is designed to generate beats due to reverberation in a normal state has been described. However, an ultrasonic sensor designed to prevent beats due to reverberation under normal conditions is used. You may apply to the system provided. In this case, the reflected wave threshold value Athb is changed to the side where the object is easily detected when the state where the beat is not generated due to the reverberation is changed to the state where the beat is generated.

In the above-described embodiment, the presence or absence of reverberation beats is detected by the beat detection unit 28. However, the degree of beat strength is detected, and the reflected wave threshold Athb, the reduction rate B, and the delay time Ty are detected based on the detection results. It may be variably set. Specifically, when the reflected wave threshold value Athb is set according to the falling slope α, the larger the amount of deviation from the normal falling slope α, the easier the object is to detect the reflected wave threshold value Athb. Set to. Alternatively, when the reflected wave threshold value Athb is set according to the number of beats, the reflected wave threshold value Athb is set on the side where the object is more likely to be detected as the deviation amount from the normal beat number is larger. Further, the reflected wave threshold Athb may be variably set according to the outside air temperature and the temperature information of the sensor individual.

In the above-described embodiment, it is configured to determine whether the reverberation has ended, based on the result of comparison between the delay time Ty and the time after the amplitude value A falls below the amplitude threshold Ath after the end of transmission of the exploration wave. However, it may be configured to determine whether or not the reverberation has ended by counting the time from the end of transmission and comparing it with a threshold value. In this case, the threshold value of the time from the end of the transmission command is variably set based on the reverberation beat state.

In the third embodiment, frequency information indicating the relationship between the reverberation frequency at the reference temperature and the driving frequency is set in advance, and it is determined whether the relationship between the reverberation measurement frequency fa and the driving frequency is the same as at the reference temperature. Although the beat state of reverberation is detected by the determination, the beat state detection method based on the frequency of the reverberation is not limited to this. For example, the configuration may be such that it is determined whether the level of the reverberation frequency with respect to the drive frequency has changed within the period in which the reverberation occurs, and the beat state of the reverberation is detected based on the determination result. Specifically, when the reverberation measurement frequency fa transitions from a frequency higher than the drive frequency to a lower frequency within the period of reverberation, or when the reverberation measurement frequency fa transitions from a frequency lower than the drive frequency to a higher frequency. In this case, it is determined that no reverberation is generated. In addition, when the reverberation measurement frequency fa continues to be higher than the drive frequency within the reverberation period, it is determined that reverberation causes beat.

A plurality of detection methods may be combined to detect the reverberation beat state. For example, a configuration for detecting the reverberant beat state based on the falling slope α and the beat number δ, a configuration for detecting the reverberant beat state based on the falling slope α and the reverberation frequency, and the like can be given. With the configuration in which a plurality of detection methods are combined, the reverberation beat state can be detected more accurately.

In the first embodiment, the amplitude value A monotonically decreases while the amplitude value A monotonically decreases, that is, the beating determination is performed based on the recognition of the falling slope α at the amplitude falling Ap. For the increase/decrease change in the amplitude value A that occurs before the period, the beat determination may be performed based on the decrease amount of the amplitude per unit time.

In the above embodiment, the case where the detection ECU 20 of the ultrasonic sensor 30 functions as an object detection device has been described, but the ECU on the vehicle 30 side may function as an object detection device.

In the above-described embodiment, the object detection device mounted on the vehicle has been described as an example, but the object detection device may be mounted on a moving body such as a railway vehicle, a ship, an aircraft, or a robot.

-Each component described above is a conceptual one, and is not limited to the above embodiment. For example, the function of one component may be distributed to a plurality of components, or the function of a plurality of components may be realized by one component.

10... Vehicle (moving body), 20... Detection ECU (object detection device), 21... Wave transmission/reception unit, 28... Beat detection unit, 29... Threshold setting unit, 30... Ultrasonic sensor, 40... Driving support ECU.

Claims (5)

An ultrasonic sensor (30) that transmits ultrasonic waves from a vibrator and generates a received signal in accordance with the vibration of the vibrator is used, and based on the reflected wave received by the ultrasonic sensor, the surroundings of the moving body (10). An object detection device (20) for detecting an object existing in
A beat detection unit that detects a beat state of reverberation after the ultrasonic waves are transmitted from the vibrator,
An object detection unit that detects the object based on a comparison between the amplitude of the reflected wave and a detection threshold,
A threshold setting unit that variably sets the detection threshold based on the detection result of the beat state by the beat detection unit;
A temperature change determination unit that determines that the outside air temperature has not changed by a predetermined temperature or more,
Bei to give a,
The threshold setting unit, when it is determined by the temperature change determination unit that the outside air temperature has not changed by the predetermined temperature or more, the detection threshold based on the detection result of the beat state by the beat detection unit. An object detection device that is variably set . The object detection device according to claim 1, wherein the threshold value setting unit changes the detection threshold value to a side at which the object is easily detected when the beat state detected by the beat detection unit is different from the normal state. A slope calculator that calculates an amplitude slope as a reduction amount per unit time of the amplitude in a period in which the amplitude of the reverberation tends to decrease,
The beat detection unit detects the beat state based on the amplitude gradient calculated by the gradient calculation unit, an object detection apparatus according to claim 1 or 2. A fluctuation detecting unit for detecting a frequency at which the amplitude of the reverberation fluctuates by a predetermined amount or more,
The beat detection unit detects the beat state based on the frequency detected by the fluctuation detecting unit, the object detecting apparatus according to any one of claims 1-3. A frequency measuring unit for measuring the frequency of the reverberation,
The beat detection unit detects the beat state based on the frequency measured by the frequency measurement unit, the object detecting apparatus according to any one of claims 1-4.

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