DE102018220001A1 - Object detecting device - Google Patents

Abstract

In an object detection apparatus mounted on a vehicle and detecting an object outside the vehicle, frequency determining means (11) compares frequencies of a reference stored wave and a received wave to determine whether the received wave is a reflected wave of an ultrasonic wave, which was sent by a transmitter (1). When the received wave is a reflected wave of the ultrasonic wave, a distance calculating means (9) calculates a distance to an object reflecting the ultrasonic wave on the basis of the received wave. The frequency determining means calculates a degree of coincidence (M) between the reference wave and the received wave based on a frequency difference between the reference wave and the received wave and at least one weighting factor that changes with time, and determines whether based on the calculated degree of coincidence the received wave is a reflected wave of the ultrasonic wave emitted from the transmitter.

Description

background

Technical area

The present invention relates to an object detection apparatus.

State of the art

With respect to an object detection apparatus mounted on a vehicle and detecting an obstacle, there has been proposed a technique in which a frequency of an ultrasonic wave, which is a test wave, is changed with time and a frequency of a received wave is compared with the frequency of the test wave to avoid interference with an ultrasonic wave emitted by another vehicle traveling in the vicinity of the vehicle (see, for example, US Pat EP 2 373 434 B). The vehicle that carries the object detection device is hereinafter referred to as a separate vehicle.

A microphone used in an ultrasonic sensor has a narrow band and a low tracking ability. It may take time for frequency characteristics of transmitted waves to appear in frequency characteristics of the received waves. Thus, it is necessary to change the frequency of the transmitted wave over a long period of time in order to obtain complete frequency characteristics from the received waves.

However, increasing the time period during which ultrasonic waves are emitted is likely to cause interference between multiple reflected waves, which may result in lower accuracy of detection of frequency characteristics of the received waves.

In view of this, it is desirable to provide an object detecting apparatus which can prevent a decrease in the accuracy of detection of frequency characteristics of received waves in a case of interference between the reflected waves.

Summary

One aspect of the invention provides an object detection apparatus mounted on a vehicle and detecting an object outside the vehicle. The object detecting device includes: a transmitter configured to emit an ultrasonic wave; a receiver configured to receive an ultrasonic wave; a reference wave memory configured to store a reference wave whose frequency changes in accordance with a similar change pattern as a change of a frequency of a transmitted wave; a frequency determination device configured to compare frequencies of the reference wave and a received wave with each other to determine whether the received wave is a reflected wave of the ultrasonic wave emitted from the transmitter; a distance calculating means configured when the frequency determining means determines that the received wave is a reflected wave of the ultrasonic wave emitted by the transmitter to calculate a distance to an object reflecting the ultrasonic wave based on the received wave; wherein the frequency determining means is adapted to calculate a degree of coincidence between the reference wave and the received wave based on a frequency difference between the reference wave and the received wave and at least one weighting factor that changes with time, and based on the calculated degree of coincidence determine whether the received wave is a reflected wave of the ultrasonic wave emitted from the transmitter.

In a case where interference occurs between reflected waves of a test wave, resulting in a shift of a frequency change between the reference wave and the reflected waves, a change in the weighting factor with time and an increase in the weighting factor applied to a time interval may be applied in which the frequencies of the reflected waves are less influenced by the interference, will reduce an influence of such a shift of the frequency change. This configuration can prevent a reduction in the accuracy of detection of frequency characteristics in a case where interference occurs between reflected waves of a test wave.

Another aspect of the invention provides an object detection apparatus mounted on a vehicle and detecting an object outside the vehicle. The object detecting device includes: a transmitter configured to emit an ultrasonic wave; at least one receiver configured to receive an ultrasonic wave; a reference wave memory configured to store a reference wave whose frequency changes in accordance with a similar change pattern as a change of a frequency of a transmitted wave; a frequency determination device configured to compare frequencies of the reference wave and a received wave with each other to determine whether the received wave is a reflected wave of the ultrasonic wave emitted from the transmitter; a distance calculating device designed when the frequency determining means determines that the received wave is a reflected wave of the ultrasonic wave emitted by the transmitter to calculate a distance to an object reflecting the ultrasonic wave based on the received wave; and a relative velocity determining means configured to calculate a relative velocity of the object based on the received wave; wherein the frequency determining means is arranged to determine that a first wave, which is an ultrasonic wave first received by the at least one receiver after the transmitter has transmitted an ultrasonic wave, is a reflected wave of the ultrasonic wave emitted from the transmitter has been to compare frequencies of the reference wave and the received wave on the assumption that a relative speed of the object remains equal to a relative speed, which is calculated on the basis of the first wave by the relative speed determining means until a predetermined period has elapsed after detection of the first wave ,

In a case where an interference occurs between reflected waves of a test wave, resulting in a shift of a frequency change between the reference wave and the reflected waves, determining whether the second wave or subsequent waves received after receiving the first wave, is a reflected wave of the ultrasonic wave emitted from the transmitter; relying on the relative velocity of the object calculated on the basis of the first wave can reduce an influence of such a shift of the frequency change. In a case where interference occurs between reflected waves of a test wave, this configuration may prevent a reduction in accuracy of detection of frequency characteristics.

list of figures

• 1 Fig. 10 is a block diagram of an object detection apparatus according to a first embodiment of the present invention;
• 2 Fig. 10 is an illustration of a calculation of a degree of agreement using a frequency scale factor;
• 3 is an example of a weighting factor in the first embodiment;
• 4 Fig. 10 is a flowchart of an object detection processing;
• 5 FIG. 10 is an example of a degree of agreement for an up-chirp signal in a comparative example; FIG.
• 6 is an example of a degree of agreement for an up-chirp signal in the first embodiment;
• 7 FIG. 10 is an example of a weighting factor according to a second embodiment of the present invention; FIG.
• 8th is an example of a degree of agreement for an up-chirp signal in the second embodiment;
• 9 Fig. 10 is a block diagram of an object detection apparatus according to a third embodiment of the present invention;
• 10 FIG. 13 is an illustration of determining a shape of an object according to the third embodiment; FIG.
• 11 Fig. 10 is an illustration of determining a shape of an object according to a fourth embodiment of the present invention;
• 12 Fig. 10 is an illustration of determining a shape of an object in the fourth embodiment;
• 13 FIG. 10 is an example of a weighting factor according to a fifth embodiment of the present invention; FIG.
• 14 FIG. 15 is an example of an amplitude of a reflected wave of an object located at a short distance in the fifth embodiment; FIG.
• 15 Fig. 10 is a block diagram of an object detection apparatus according to a sixth embodiment of the present invention;
• 16 FIG. 10 is an illustration of calculating a degree of coincidence according to a comparative example; FIG.
• 17 Fig. 12 is an illustration of calculating a degree of coincidence in the sixth embodiment;
• 18 is an example of a reception time of a reflected wave;
• 19 Fig. 11 is an illustration of detecting a reception time of a reflected wave;
• 20 Fig. 10 is an illustration of calculating a degree of matching using a frequency offset;
• 21 FIG. 10 is an example of a weighting factor according to another embodiment of the present invention; FIG. and
• 22 FIG. 10 is an example of a weighting factor according to another embodiment of the present invention.

Description of specific embodiments

Hereinafter, various embodiments of the present invention will be described with reference to the accompanying drawings. Substantially common elements or steps in the embodiments are denoted by the same reference numerals and will not be described again.

First embodiment

Hereinafter, a first embodiment will be described. An object detecting device of the present embodiment is an ultrasonic sonar device. The object detection device is mounted on a vehicle and detects an object outside the vehicle.

As it is in 1 is shown, the object detecting device includes a microphone 1 , a transmission circuit 2 , a pulse generator 3 and a controller 4 , The object detection apparatus also includes a receiving circuit 5 , a signal processor 6 , an amplitude generator 7 , an amplitude determining device 8th , a distance determination device 9 , a frequency generator 10 , a frequency determining device 11 and a reference wave memory 12 , The control 4 , the signal processor 6 and the like are formed as a known microcomputer including a central processing unit (CPU), a read only memory (ROM) and a random access memory (RAM), an I / O unit, and the like, and various kinds of processing such as For example, arithmetic processing is performed in accordance with programs stored in the ROM or the like.

The microphone 1 , which corresponds to a transmitter, is disposed on an outer surface of the vehicle and transmits to the outside of the vehicle an ultrasonic wave, which is a test wave for detecting an object. More precisely, the microphone contains 1 a piezoelectric element (not shown) in which a piezoelectric layer is disposed between two opposing electrodes. The two electrodes are connected to the transmission circuit 2 connected. When an AC voltage (AC voltage) from the transmission circuit 2 is applied and the piezoelectric layer deforms or changes shape, becomes an ultrasonic wave from the microphone 1 sent out to the outside of the vehicle.

The transmission circuit 2 converts an input signal into an analog voltage using digital-to-analog conversion (D / A conversion) and outputs the analog voltage. The pulse generator 3 which generates a pulse signal is connected to the transmission circuit 2 connected. The transmission circuit 2 D / A converts a pulse signal from the pulse generator 3 is input to an AC voltage and applies the AC voltage to the microphone 1 on.

In accordance with a wave transmission instruction from the controller 4 generates the pulse generator 3 a pulse signal containing a chirp signal whose frequency changes over time in accordance with a predetermined pattern. Thus, a test wave containing a chirp signal whose frequency changes over time is picked up by the microphone 1 sent out. Besides, the microphone is 1 designed to emit test waves in multiple patterns containing different types of chirp signals. A pattern of a test wave is determined according to a wave transmission instruction issued by the controller 4 to the pulse generator 3 is transmitted.

In particular, when a shaft send instruction for a first pattern from the controller 4 to the pulse generator 3 is transmitted, generates the pulse generator 3 a pulse signal whose frequency increases monotonically with time. Thus, a first test wave, which includes an up-chirp signal whose frequency increases over time, is picked up by the microphone 1 sent out.

In particular, when a shaft send instruction for a second pattern from the controller 4 to the pulse generator 3 is transmitted, generates the pulse generator 3 a pulse signal whose frequency decreases monotonically with time. Thus, a second test wave, which includes a chirp down signal whose frequency decreases over time, is picked up by the microphone 1 sent out.

Assuming that fo is a resonant frequency of the microphone 1 represents, the pulse generator starts 3 a sweep of the frequency of the pulse signal from a frequency different from the resonance frequency fo. In particular, the pulse generator leads 3 passing the frequency of the pulse signal between a frequency lower than the resonance frequency fo and a frequency higher than the resonance frequency fo.

The microphone 1 is configured to emit and receive an ultrasonic wave and to output a voltage corresponding to a sound pressure of the received ultrasonic wave. In particular, the two electrodes of the piezoelectric element that are in the microphone 1 is included, also with the receiving circuit 5 connected. Accordingly, a voltage that is applied between the two electrodes when the microphone 1 receives an ultrasonic wave and the piezoelectric layer changes shape, in the receiving circuit 5 entered. The Receive circuit 5 A / D converts the voltage coming from the microphone 1 is input, converts to a digital signal and outputs the digital signal.

The signal processor 6 detects a frequency and an amplitude of a received wave by orthogonal demodulation using the signal provided by the receiving circuit 5 generated by the A / D conversion.

In particular, the signal processor calculates 6 A _r corresponding to A _r = (I ² + Q ² ) ^1/2 , where A _{r represents} the amplitude of the received wave. In addition, the signal processor calculates 6 P corresponding to P = arctan (Q / I), where P represents a phase of the received wave. In addition, the signal processor calculates 6 f _r corresponding to f _r = 1 / (2π) · dP / dt + f _p , where f _r represents the frequency of the received wave and fp represents the frequency of the pulse signal received by the pulse generator 3 is produced.

I represents a magnitude of a signal obtained by multiplying an output of the receiving circuit 5 with sin (2πf ₀ t) and subsequent removal of components whose frequency is equal to or greater than 2fo is obtained. In addition, Q represents a magnitude of a signal obtained by multiplying an output of the receiving circuit 5 with cos (2πf ₀ t) and then removing a component whose frequency is equal to or greater than 2fo. Furthermore represented t the time.

The amplitude generator 7 generates an envelope of amplitude A _r based on the amplitude A _r generated by the signal processor 6 is calculated. The amplitude determination device 8th determined at each time a sample is sampled based on the waveform produced by the amplitude generator 7 it is generated whether the amplitude A _{r is} equal to or greater than a predetermined threshold value.

The distance determination device 9 calculates a distance from an object outside the vehicle that has reflected a test wave, based on a time duration from a time when the microphone is turned on 1 the test wave emits, up to a time when the microphone 1 receives a reflected wave. The distance determination device 9 then determines whether the calculated distance is equal to or less than a predetermined value. In the present embodiment, a timing at which the amplitude of the received wave becomes equal to or greater than a threshold is called a wave reception time. The distance determination device 9 calculates a distance d corresponding to D = c · T / 2, where c represents the speed of sound, T the time duration from the time when the microphone is 1 sends out the test wave, represents up to the time of reception, and D represents the distance from the object.

The frequency generator 10 generates a waveform having the frequency f _r based on the frequency f _r that from the signal processor 6 is calculated.

The frequency determining device 11 determines if the ultrasonic wave coming from the microphone 1 is received, a reflected wave of the test wave is that of the microphone 1 based on whether the output signal of the receiving circuit 5 contains a signal that changes in accordance with a pattern generated by the controller 4 is specified.

Based on the waveform generated by the frequency generator 10 is generated, the frequency determining means detects 11 in particular, a chirp signal contained in the ultrasonic wave transmitted through the microphone 1 Will be received. In a case where the microphone 1 has sent out a first test wave determines the frequency determination device 11 in that the received wave is a reflected wave of the test wave coming from the microphone 1 was emitted when the detected chirp signal is an up-chirp signal. In a case where the microphone 1 has sent out a second test wave determines the frequency determining device 11 in that the received wave is a reflected wave of the test wave coming from the microphone 1 was emitted when the detected chirp signal is a down chirp signal.

Before the frequency of the received wave changes like a chirp signal contained in the pulse signal, the frequency of the received wave changes in a direction opposite to that of a frequency of the chirp signal or changes slower than the frequency of the chirp signal. This probably comes from the fact that when the transmission circuit 2 applying an AC voltage to the microphone 1 starts, the microphone 1 starts with a frequency that is close to the resonant frequency, easy to vibrate, and a certain amount of time is needed until the microphone 1 its vibration starts at the frequency of the pulse signal.

For example, if the microphone 1 sends out a first test wave containing an up-chirp signal as shown in FIG 5 is shown, a signal whose frequency increases monotonically more slowly than that of the pulse signal appears before Up-chirp signal that changes in a similar way to the pulse signal. On the other hand, a signal whose frequency decreases monotonically appears before the up-chirp signal which changes similarly to the pulse signal.

If the microphone 1 sends out a second test wave containing a chirp down signal as shown in FIG 6 4, a signal whose frequency increases monotonically appears before the down-chirp signal which changes similarly to the pulse signal. On the other hand, a signal whose frequency decreases monotonically slower than that of the pulse signal appears before the down-chirp signal, which changes similarly to the pulse signal.

Thus, in the present embodiment, using a chirp signal included in the received wave and a signal preceding the chirp signal, a determination is made on the received wave. In particular, the reference wave memory stores 12 for each chirp signal, a reference wave corresponding to the chirp signal and a signal preceding the chirp signal. The frequency determining device 11 determines a chirp signal contained in the received wave by comparing a waveform derived from the frequency generator 10 is transmitted, with a waveform of the reference wave, in the reference shaft memory 12 is stored.

As the waveform of the reference wave corresponding to the up-chirp signal, the frequency determining means uses 11 For example, a waveform whose frequency increases more slowly than that of the pulse signal, that of the pulse generator 3 is generated, and then increases at the same rate of change as the pulse signal. In addition, the frequency determining device uses 11 For example, a waveform whose frequency decreases and then increases at the same rate of change as the pulse signal.

As a waveform of the reference wave corresponding to the down-chirp signal, the frequency-determining means uses 11 For example, a waveform whose frequency decreases slower than that of the pulse signal, that of the pulse generator 3 is generated, and then reduced at the same rate of change as that of the pulse signal. In addition, the frequency determining device uses 11 For example, a waveform whose frequency increases and then decreases at the same rate of change as that of the pulse signal.

Thus, reference waves containing frequency change patterns similar to those of the transmitted waves become in the reference wave memory 12 saved. If a degree of agreement between the waveform provided by the frequency generator 10 is generated and the reference wave becomes equal to or larger than a predetermined reference value, the frequency determining means determines 11 in that the received wave contains a chirp signal.

In the present embodiment, the frequency determining means obtains 11 the degree of agreement using a frequency scale factor. 2 provides a method for obtaining the degree of agreement for an up-chirp signal by approximating a frequency R (t) the reference wave to a frequency fr (t) of the received wave using the frequency scale factor and evaluating a correlation between k · R (t) and f _r (t) where R (t) represents the frequency of the reference wave and k represents the frequency scale factor.

In the present embodiment, the frequency determining means calculates 11 a degree of agreement M on the basis of a difference between k · R (t) and f _r (t) and a weighting factor m which changes over time and uses the calculated degree of matching M to determine if the received wave contains a chirp signal. As it is in 3 is shown, in the present embodiment, the weighting factor used for a time interval corresponding to the first half of the reference wave is set larger than a time interval corresponding to the second half of the reference wave. Thus, a difference between k · R (t) and f _r (t) on the time interval corresponding to the first half of the reference wave, the degree of agreement to a large extent M influence. Therefore, despite a difference between k · R (t) and f _r (t) on the time interval corresponding to the second half of the reference wave, a chirp signal in the case of a small frequency difference between k · R (t) and f _r (t) on the time interval corresponding to the first half of the reference wave are detected.

If it is assumed that N represents the number of samples and σ represents a standard deviation becomes the sum of the square errors e expressed as follows: $$\text{e}=\left({\displaystyle \underset{\text{i}=1}{\overset{\text{N}}{\Sigma }}{\text{m}}_{\text{i}}}\right){\sigma }^2={\displaystyle \underset{\text{i}=1}{\overset{\text{N}}{\Sigma }}{\text{m}}_{\text{i}}}{\left({\text{f}}_{\text{i}}-{\text{kR}}_{\text{i}}\right)}^2$$

The sum of the square errors e is minimal if the following equation holds: $$\frac{\mathrm{\partial }\text{e}}{\mathrm{\partial }\text{k}}=0$$

Then k is expressed by: $$\text{k}=\frac{{\displaystyle \underset{\text{i}=1}{\overset{\text{N}}{\Sigma }}{\text{m}}_{\text{i}}{\text{f}}_{\text{i}}\cdot {\text{R}}_{\text{i}}}}{{\displaystyle \underset{\text{i}=1}{\overset{\text{N}}{\Sigma }}{\text{m}}_{\text{i}}{\text{<figure-callout id="2" label="R i" filenames="DE102018220001A1\_0010.png,DE102018220001A1\_0019.png" state="{{state}}">R </figure-callout>}}_{\text{i}}^{}}}$$

The sum of the square errors e is by inserting k in equation (1). A degree of agreement M is done by inserting the sum of squared errors e obtained as above, obtained in the following equation (4): $$\text{M}=\frac{1}{\sigma }=\sqrt{\frac{{\displaystyle \underset{\text{i}=1}{\overset{\text{N}}{\Sigma }}{\text{m}}_{\text{i}}}}{\text{e}}}$$

Similarly, a degree of agreement M for the down-chirp signal using the reference chord for the down-chirp signal.

The frequency determining device 11 compares the degree of agreement M with a predetermined threshold and determines that the received wave contains a chirp signal when the degree of matching M is greater than the threshold. In particular, the frequency determination device determines 11 in that the received wave contains an up-chirp signal when the degree of agreement M is greater than the threshold for the up-chirp signal, and determines that the received wave contains a down-chirp signal when the degree of coincidence M for the chirp down signal is greater than the threshold.

Then the frequency determining device compares 11 the degree of agreement M for the up-chirp signal with the degree of agreement M for the down-chirp signal and determines that the received wave contains an up-chirp signal and a down-chirp signal, respectively, whichever has a higher degree of matching M having.

Thus, the frequency determining means evaluates 11 after multiplying by R (t) with the frequency scale factor k so that there is a difference between R (t) and f _r (t) is reduced, a correlation between k · R (t) and f _r (t) , When the frequency of the received wave changes similar to the frequency of the reference wave, the frequency determining means determines 11 that the ultrasonic wave passing through the microphone 1 is received, a reflected wave of the test wave is that of the microphone 1 was sent out.

The frequency determining device 11 determines whether interference of the received waves occurs. When it is determined that interference of the received waves occurs, the frequency determining means calculates 11 a degree of agreement M using the weighting factor, as in 3 is shown. When it is determined that no interference of the received waves occurs, the frequency determining means calculates 11 a degree of agreement M using a constant weighting factor, rather than using the weighting factor, which changes over time.

In a case where two peaks or peaks of the waveform passing through the amplitude generator 7 is generated, determines the frequency determining means 11 in that interference of the received waves occurs when the frequency of the received wave changes in the course of time between the two peaks such that a magnitude of a change in the frequency of the received wave per unit time is greater than a predetermined value. When the frequency of the received wave changes in the course of time between the two peaks such that a magnitude of a change in the frequency of the received wave per unit time is equal to or smaller than the predetermined value, the frequency determining means determines 11 in that no interference of the received waves occurs.

A result of the determination made by the frequency determining device 11 is performed is to the distance determination means 9 transfer. Only if the frequency determining device 11 determines that the ultrasonic wave passing through the microphone 1 is received, a reflected wave of the test wave is that of the microphone 1 has been sent out, the distance determining means calculates 9 a distance from the object and determines whether the calculated distance is equal to or less than a predetermined threshold. A result of the determination made by the distance determiner 9 is performed is transmitted to an ECU (not shown). When the distance determining means 9 determines that the distance from the object is equal to or smaller than the predetermined value, a notification of a driver of the vehicle in that the object is arranged at a distance that is closer than the predetermined distance, an automatic braking and the like is performed.

The object detecting apparatus of the present embodiment is configured as shown in FIG 4 Periodically perform processing shown to capture an object.

In step S1 represents the controller 4 a change pattern of the frequency of the transmitted wave on up-chirping or down-chirping.

In step S2 , the step S1 follows, the object detection device transmits and receives ultrasonic waves. Especially if the controller 4 a wave transmit instruction to the pulse generator 3 in response to adjusting the chirp signal in step S1 transmits, starts the pulse generator 3 generating a pulse signal. When the transmission circuit 2 the pulse signal generated by the pulse generator 3 is generated, in an AC voltage D / A converts and the AC voltage to the microphone 1 applies, an ultrasonic wave, which is a test wave, from the microphone 1 sent out. In this case, the pulse generator changes 3 according to the wave transmission instruction from the controller 4 in the course of time, a frequency of the pulse signal to be generated. Thus, a first test wave or a second test wave from the microphone 1 sent out.

When the test wave is reflected from an object outside the vehicle and the microphone 1 receives a reflected wave of the test wave, a voltage changes between the two electrodes of the piezoelectric element that is in the microphone 1 is included. The voltage is in the receiving circuit 5 input, and the receiving circuit 5 A / D converts the input voltage.

In step S3 , the step S2 follows, the signal processor detects 6 an amplitude and a phase of a received wave by orthogonal demodulation using the signal provided by the receiving circuit 5 generated by the A / D conversion. The signal processor 6 calculates a frequency from the detected phase of the received wave.

The amplitude generator 7 generates an envelope having an amplitude based on the amplitude produced by the signal processor 6 is detected. The amplitude determination device 8th determined on the basis of the waveform generated by the amplitude generator 7 is generated whether the amplitude of the received wave is equal to or greater than a predetermined threshold, and transmits a result of the determination to the distance determining means 9 , The frequency generator 10 generates a waveform having a frequency based on the frequency generated by the signal processor 6 is detected.

In step S4 , the step S3 follows determines the frequency determining device 11 based on the waveform generated by the frequency generator 10 it is generated whether an interference of the received waves occurs.

In step S5 , the step S4 follows, represents the frequency determination device 11 a weighting factor in response to the determination result in step S4 on. When in step S4 it is determined that interference of the received waves occurs, the frequency determining means updates 11 Weight factor setting information for calculating a degree of coincidence M using the weighting factor, which changes over time. When in step S4 it is determined that no interference of the received waves occurs, the frequency determining means updates 11 Weight factor setting information for calculating a degree of coincidence M using a constant weighting factor.

In step S6 , the step S5 follows, receives the frequency determining device 11 a degree of matching by comparing the waveform generated by the frequency generator 10 is generated, with a waveform of the reference wave, in the reference shaft memory 12 is stored, and detects a chirp signal contained in the received wave.

If the microphone 1 emits a first test wave and an up-chirp signal is detected from the received wave, the frequency determining means determines 11 in that the received wave is a reflected wave of the test wave. If the microphone 1 sends out a second test wave and detects a chirp down signal from the received wave, determines the frequency determining means 11 in that the received wave is a reflected wave of the test wave.

In some cases, an ultrasonic wave passing through the microphone 1 is received, for example, in addition to a reflected wave of the test wave passing through the microphone 1 is emitted, containing an ultrasonic wave, which is emitted by another vehicle. As described above, by applying a characteristic to the frequency of the test wave and comparing a change in the frequency of the received wave with a change in the frequency of the test wave to determine whether the received wave is a reflected wave of the test wave the microphone 1 was emitted, interference is avoided, and the accuracy of detection of an object is improved.

In step S7 , the step S6 follows determines the distance determining means 9 whether an object is present in the environment of the vehicle. In particular, the distance determination means calculates 9 on the basis of a result of the determination made by the amplitude determining means 8th is performed, a distance from the object outside the vehicle, which is the Test wave has reflected. When from the frequency determining device 11 in step S6 it is determined that the received wave is a reflected wave of the test wave received from the microphone 1 has been transmitted, and the distance from the object detected by the distance determining means 9 has been calculated equal to or smaller than a predetermined value, the distance determining means determines 9 in that an object is present in the environment of the vehicle.

When in step S7 is determined that an object is present in the environment of the vehicle, the driver is in step S8 notifies by means of a monitor, buzzer or the like (not shown) that the object is located at a distance closer than the predetermined distance. Then the process flow ends. When in step S7 is determined that no object is present in the environment of the vehicle, the process flow ends without providing a message to the driver.

The present embodiment can achieve the following advantages. A microphone used in an ultrasonic sensor has a narrow band and a low tracking ability. It may take time for frequency characteristics of transmitted waves to appear in frequency characteristics of the received waves. Thus, it is necessary to change the frequency of the transmitted wave over a long period of time in order to obtain complete frequency characteristics from the received waves.

However, an increase in a period of time during which ultrasonic waves are emitted is likely to result in interference between a plurality of reflected waves, which may result in deterioration of the accuracy of detection of the frequency characteristics of the received waves. For example, in a case where an object having a specific height, for example, a wall, exists in the vicinity of the vehicle, interference between an ultrasonic wave coming from a portion of a surface of the object at a positional height with the microphone 1 and an ultrasonic wave reflected from a portion of the surface of the object near the earth, at the microphone 1 occur. Such interference is likely to occur in the presence of a wall or power pole, spaced by a distance equal to or greater than 3 m is present from the vehicle. As the period of time during which ultrasonic waves are emitted increases, it is more difficult to separate and detect reflected waves reflected from multiple objects.

It is assumed that a first wave is an ultrasonic wave, the first of the microphone 1 is received after the emission of a test wave, and a second wave is an ultrasonic wave, which is subsequently emitted by the microphone 1 Will be received. In a case where interference occurs between the second half of the first wave and the first half of the second wave, as shown in FIG 5 is shown, a frequency difference between the second half of the first wave and a chirp signal included in the test wave increases. In such a case, setting the weighting factor to a constant or fixed value may result in a lower degree of matching, as shown in FIG 5 is shown, which can reduce the accuracy of detecting a chirp signal. In the graphics of the degree of agreement, which in the 5 and 6 are shown, the dashed line represents a threshold used to detect a chirp signal.

In the present embodiment, a weighting factor that changes with time is used so that the weighting factor used for a time interval corresponding to the first half of the first wave is set to be greater than a time interval that is corresponds to the second half of the first wave, in which an interference probably occurs. Therefore, when the first wave is compared with the reference wave to calculate a degree of coincidence, a frequency difference on the time interval corresponding to the first half of the first wave, which is less susceptible to interference with the second wave, becomes larger in weight factor Weighted compared to the time interval corresponding to the second half of the first wave. As it is in 6 is shown, the degree of coincidence between the first shaft and the reference shaft exceeds the threshold, enabling accurate detection of the chirp signal.

As described above, in the present embodiment, in the case where interference between reflected waves occurs, a decrease in the accuracy of detecting the frequency characteristics of the received waves can be prevented. Thus, interference with ultrasonic waves emitted from other vehicles traveling in the vicinity of the own vehicle can be avoided, and the accuracy in detection of an object can be improved.

In addition, in the present embodiment, the object detecting device alternates between a constant weighting factor and a weighting factor that changes with time, depending on whether interference occurs. This configuration can reduce the accuracy of the Improve detection of a chirp signal when no interference occurs.

Second embodiment

Hereinafter, a second embodiment will be described. The present embodiment differs from the first embodiment only in that the weighting factor is modified. Thus, only the differences from the first embodiment will be described.

As it is in 7 is shown, in the present embodiment, the weighting factor used for a time interval corresponding to the second half of the reference wave is set larger than the weighting factor used for a time interval corresponding to the first half of the reference wave. A frequency difference on the time interval corresponding to the second half of the reference wave can to a great extent a degree of coincidence M in comparison to the time interval corresponding to the first half of the reference wave. Therefore, in spite of a frequency difference between the received wave and the reference wave on the time interval corresponding to the first half of the reference wave, a chirp signal can be detected in the case of a small frequency difference on the time interval corresponding to the second half of the reference wave.

In a case where there is a frequency difference between the second shaft and the reference shaft at a time interval corresponding to the first half of the reference shaft, as shown in FIG 5 is shown, a high degree of matching is obtained since there is a small frequency difference between the second wave and the reference wave at a time interval corresponding to the second half of the reference wave as shown in FIG 8th which enables detection of a chirp signal from the second wave.

As described above, in the present embodiment, a weighting factor that changes with time is used so that the weighting factor used for a time interval corresponding to the second half of the reference wave is set larger than the weighting factor is used for a time interval corresponding to the first half of the reference wave. Therefore, when the second wave is compared with the reference wave to calculate a degree of coincidence therebetween, a frequency difference on the time interval corresponding to the second half of the reference wave, which is less susceptible to interference with the first wave, becomes larger in weighting factor weighted in comparison to the time interval corresponding to the first half of the reference wave. The degree of coincidence between the second wave and the reference is thus calculated, allowing accurate detection of the chirp signal.

Third embodiment

Hereinafter, a third embodiment will be described. The present embodiment differs from the first embodiment only in that the weighting factor is modified. Thus, only the differences from the first embodiment will be described.

In the present embodiment, a plurality of weighting factors are set. The frequency determining device 11 is designed to use different weighting factors for the first and second waves when receiving multiple ultrasonic waves at different times.

Specifically, the weighting factors include a first weighting factor, which is the weighting factor in the first embodiment, and a second weighting factor, which is a weighting factor in the second embodiment. The frequency determining device 11 is designed to switch between the first and second weighting factors over time.

The frequency determining device 11 For example, it may normally use the first weighting factor and use the second weighting factor only for a period of time from a time when the degree of coincidence has a peak to a time when the predetermined time has elapsed. If the second wave is the microphone 1 reached within this period, the frequency determining device 11 also use the first weighting factor for the first wave and the second weighting factor for the second wave. When the predetermined time has elapsed since the time at which the degree of coincidence has peaked, the frequency determining means 11 change from the first weighting factor to the second weighting factor.

In order to reduce a processing load when multiple weighting factors are used, preferably, a sum of the weighting factors, that is, m1 + ... + mN, may take the same value at different times.

By thus switching between the weighting factors, a frequency difference between the first shaft and the reference shaft at a time interval corresponding to the first half of the first shaft and a frequency difference between the second shaft and the reference shaft a time interval corresponding to the second half of the second wave, weighted with a large weighting factor to calculate a degree of coincidence, wherein the first half of the first wave and the second half of the second wave are less susceptible to interference. Therefore, a chirp signal can be detected from the first and second shafts. In addition, the occurrence of multiple peaks of the coincidence degree with respect to the first wave can be prevented.

With this configuration, in a case where it is difficult to separate and detect the first and second waves, for example, in a case where a time difference between a time when the first wave is detected and a time, to which the second wave is detected equal to or less than 1 ms, the first and second waves are separated and detected.

As it is in 9 is shown, the object detecting apparatus of the present embodiment further includes a shape determining means 13 , The shape determination device 13 is configured to determine, based on distances from an object calculated from the first and second waves, whether an object has a shape with a particular height.

The shape determination device 13 In the present embodiment, it is arranged to form a shape of the detected object according to a method described in 10 is shown to determine. That is, assuming that H is a mounting height of the microphone 1 represents D ₁ represents a distance to the object obtained from the first wave, and D ₂ represents a distance to the object obtained from the second wave determines the shape determining means 13 that the object 100 has a shape with a specific height when a difference between D ₂ ² and D ₁ ² + H ^{2 is} equal to or smaller than a predetermined value, whereby D ₂ ² ≈D ₁ ² + H ² . If the difference between D ₂ ² and D ₁ ² + H ^{2 is} greater than the predetermined value, the shape determining means determines 13 that the object 100 has no shape with a special height.

If it is assumed that L ₁ represents a path that travels an ultrasonic wave during a period from a transmission of a test wave to a reception of the first wave, which is a reflected version of the test wave, and L ₂ D ₁ = L _1/2 D ₂ = L ₂ represents a distance which defines an ultrasonic wave during a period from a sending same test wave to a reception of a second shaft that is a reflected version of the same test wave, the following equations hold / 2. If D ₂ ² ≈ D ₁ ² + H ² is considered, therefore, applies L ₂ ^2/4 ≈ ₁ L ^2/4 + H ^2.

Detecting a chirp signal and calculating distances to an object from the first and second waves enables determination of a shape of the object. When the detected object is determined to be an object, for example, a wall that is likely to contact the own vehicle, a determination as to whether to perform automatic braking can be made even faster, which makes contact between the own vehicle and the vehicle Object can prevent.

Fourth embodiment

Hereinafter, a fourth embodiment will be described. The present embodiment differs from the third embodiment only in that the transmitter and the receiver are modified in configuration. Thus, only the differences from the third embodiment will be described.

The object detecting apparatus of the present embodiment includes two microphones 1 , One of the two microphones 1 emits an ultrasonic wave. Both microphones 1 then receive the reflected waves to determine a shape of an object that reflects the ultrasonic wave.

More specifically, the object detecting apparatus of the present embodiment determines a shape of an object according to a method as shown in FIGS 11 and 12 is shown. In the 11 and 12 sends the microphone 1a an ultrasonic wave out, and the microphones 1a . 1b receive their reflected waves. In addition, Ha and Hb represent mounting heights of the respective microphones 1a . 1b , Since represents a distance between the microphone 1a and a wall as the object 100 , Db represents a distance between the microphone 1b and the wall, and W represents a distance between the microphones 1a . 1b in a horizontal direction along the object 100 , Then, the distances L ₁ and L ₂ can be expressed as follows: L ₁ = ((D _a + D _b ) ² + W ² + (H _a -H _b ) ² ) ^1/2 and L ₂ = ((D _a + D _b ) ² + W ² + (H _a + H _b ) ² ) ^1/2 . Therefore, the following equation holds: L ₂ ² - L ₁ ² = 4H _a H _b . The shape determination device 13 determines that the object 100 has a shape with a specific height when a difference between (L ₂ ² - L ₁ ² ) and 4H _a H _{b is} equal to or smaller than a predetermined value and L ₂ ² - L ₁ ² ≈ 4H _a H _b holds.

Fifth embodiment

Hereinafter, a fifth embodiment will be described. The present embodiment differs from the first embodiment only in that the weighting factor is modified. Thus, only the differences from the first embodiment will be described.

In the present embodiment, one of two weighting factors is selected in response to a distance to an object to be detected. As it is in 13 is shown, each of the two weighting factors is divided into two parts by a reference value indicated by a dashed-dotted line. For each of the two weighting factors, a portion of the weighting factor where the weighting factor is equal to or greater than the reference value is preceded by another portion of the weighting factor where the weighting factor is less than the reference value.

The two weighting factors include a weighting factor for a short range and a weighting factor for a long range. A period during which the weighting factor for a short range is equal to or greater than the reference value is longer than a period during which the weighting factor for a long range is equal to or greater than the reference value. Therefore, when the weighting factor is used for a short range, a frequency difference is weighted with a large weighting factor used for a time interval corresponding to a large part of the first half of the reference wave, thereby calculating a degree of coincidence.

As it is in 14 is shown, interference between the first and second waves is less likely to occur when an object such as a wall or the like is disposed in the vicinity of the own vehicle than when the object is located away from the own vehicle. Therefore, when an object located near the own vehicle is detected, a frequency difference is weighted with a larger weighting factor used for a time interval corresponding to a large part of the first half of the first wave, thereby improving the accuracy of the first Detecting a chirp signal for the first wave is increased while the influence of interference between the first and second waves is reduced.

Sixth embodiment

Hereinafter, a sixth embodiment will be described. The present embodiment differs from the third embodiment only in that the method for detecting a chirp signal is modified. Thus, only the differences from the third embodiment will be described.

As it is in 15 is shown, the object detecting apparatus of the present embodiment also includes a relative speed determining means 14 , which is designed to calculate a relative speed of an object based on a received wave.

The frequency determining device 11 gives the frequency scale factor k calculated using equation (3) to the relative velocity determining means 14 out. The relative speed determination device 14 calculates a relative speed .DELTA.v of the object according to the following equation (5). $$\Delta \text{v}=\frac{\text{k}-1}{\text{k}+1}\text{c}$$

The relative speed determination device 14 calculates a relative velocity of the object in step S6 the 4 , The frequency determining device 11 estimates a relative velocity at a time when the degree of coincidence has a peak as a relative velocity of the object. In the present embodiment, a speed of the object with which the object is the microphone 1 approximates, as a relative velocity of the object calculated.

When it is determined that the first wave is a reflected wave of the ultrasonic wave coming from the microphone 1 has been sent out, the frequency estimator estimates 11 in that the relative velocity of the object remains almost equal to a relative velocity of the object, which is based on the first wave by the relative velocity determining means 14 is calculated until a predetermined period has elapsed after detection of the first wave. On the basis of the estimated relative speed, the frequency determining means compares 11 Frequencies of the reference wave and the received waves with each other. For each wave from the second wave and the subsequent waves received after the reception of the first wave, the frequency determining means calculates 11 a degree of agreement M by inserting the frequency scale factor k calculated for the first wave into the equation (1) and then using the equation (4).

The predetermined time is with .DELTA.T1 designated. A length of .DELTA.T1 can be set, for example, as follows.

This means, .DELTA.T1 is changed, calculating a distance based on the first wave. In particular, when the first wave is a reflected wave from an object at a short distance to the microphone 1 is arranged, a period of time increases from a reception of the first wave by the microphone 1 until a reception the second wave. Therefore increases .DELTA.T1 with a reduction of a distance to the object calculated on the basis of the first wave.

In addition, changes .DELTA.T1 in response to the amplitude of the first wave. In particular, as the amplitude of the first wave increases, a length of time increases until the amplitude drops, and thus, interference with the second wave is more likely to occur. Therefore, will .DELTA.T1 increases with an increase in the amplitude of the first wave.

When the mounting height of the microphone 1 increases, also increases a difference between distances that the first and second waves to the microphone 1 which results in an increase in a reception time difference between the first and second waves. Therefore, will .DELTA.T1 with an increase in the mounting height of the microphone 1 elevated.

As it is in 16 2, an interference between reflected waves may interfere with a phase due to a synthesis of reflected wave waveforms, which may result in a lower accuracy of detection of a frequency over a time interval of the second half of the first wave and the first half of the second wave equivalent. In addition, when the amplitude of the second wave drops after the end of the chirp, a V-shaped change of the frequency may occur. Thus, the accuracy of detecting the frequency of the second wave at a time interval corresponding to the second half thereof can be reduced as compared with the accuracy in detecting the frequency of the first wave. Thus, the degree of coincidence outside the first and second waves may have a peak, which may lead to false detection.

In the present embodiment, the relative velocity of the object used to calculate a degree of coincidence is fixed to the relative velocity calculated based on the first wave until a predetermined time has elapsed after detection of the first wave. With this configuration, the degree of matching is less likely to have a peak outside of a time interval corresponding to the first and second waves, as in FIG 17 is shown, which can prevent error detection.

modifications

The present invention is not limited to the above embodiments, but may be appropriately modified within the scope of the claims.

For example, in the first embodiment, the reception time is a timing at which the amplitude of the received wave becomes equal to or greater than the predetermined threshold. In an alternative embodiment, the in 18 is shown, represents the time t1 a reception time of the first wave that is a predetermined period of time before a time when the degree of coincidence for the first wave has a peak, and the time t2 represents a reception time of the second wave, which is the same predetermined time period before a time when the degree of coincidence for the second wave has a peak. This predetermined time is with .DELTA.T2 designated. As it is in 19 For example, it is assumed that a check wave from the microphone 1 is transmitted to an object at a predetermined distance to the microphone 1 and a received wave of the test wave at the microphone 1 Will be received. The duration .DELTA.T2 may be a period of an increase in the voltage between electrodes of the microphone 1 up to a peak of the degree of agreement M his. The duration .DELTA.T2 can be set individually for each of the up-chirp signal and the down-chirp signal and can be used in the distance determination device 9 an individual object detection device are stored.

Even if an amplitude of a reflected wave changes, a time period from a start of reception of the reflected wave to the peak of the degree of matching is less likely to change. Thus, as compared with the method of detecting the wave reception time by comparing the amplitude with the threshold, a decrease in the accuracy of detection of the wave reception time caused by the change in the amplitude of the reflected wave can be prevented.

In the first embodiment, the degree of matching is calculated by using the frequency scale factor. In an alternative embodiment, a degree of matching may be calculated using a frequency offset. As it is in 20 can be shown, a degree of matching by approximating a frequency R (t) the reference wave to a frequency f _r (t) the received wave using .delta.f and evaluating a correlation between R (t) + Δf and f _r (t), wherein R (t) represents the frequency of the reference wave and .delta.f represents the frequency offset.

$$\frac{\partial \text{E}}{\mathrm{\partial }\left(\Delta \text{f}\right)}=0$$

$$\Delta \text{f}=\frac{{\displaystyle \sum _{\text{i}=1}^{\text{N}}\left({\text{m}}_{\text{i}}{\text{f}}_{\text{i}}-{\text{m}}_{\text{i}}{\text{R}}_{\text{i}}\right)}}{{\displaystyle \sum _{\text{i}=1}^{\text{N}}{\text{m}}_{\text{i}}}}$$

$$\Delta \text{v}=\frac{\text{c}\Delta \text{f}}{2{\text{f}}_{\text{o}}+\Delta \text{f}}$$

In particular, the sum of the square errors e as shown in equation (6), and when the sum of the quadratic errors E is minimized, that is, when equation (7) holds, the frequency offset is .delta.f as shown in equation (8). The Degree of agreement M by substituting equation (8) into equation (6), the sum of the square errors e and inserting the sum of the quadratic errors E obtained in equation (4). The relative speed .DELTA.v is as shown in equation (9). The resonance frequency fo of the microphone 1 is used as a reference frequency. A different frequency than the reference frequency can be used. For example, a center frequency of one pass of the pulse signal may be used as the reference frequency. $$\text{e}=\left({\displaystyle \underset{\text{i}=1}{\overset{\text{N}}{\Sigma }}{\text{m}}_{\text{i}}}\right){\sigma }^2={\displaystyle \underset{\text{i}=1}{\overset{\text{N}}{\Sigma }}{\text{m}}_{\text{i}}}{\left({\text{f}}_{\text{i}}-{\text{R}}_{\text{i}}-\Delta \text{f}\right)}^2$$

$$\frac{\partial \text{e}}{\mathrm{\partial }\left(\Delta \text{f}\right)}=0$$

$$\Delta \text{f}=\frac{{\displaystyle \underset{\text{i}=1}{\overset{\text{N}}{\Sigma }}\left({\text{m}}_{\text{i}}{\text{f}}_{\text{i}}-{\text{m}}_{\text{i}}{\text{R}}_{\text{i}}\right)}}{{\displaystyle \underset{\text{i}=1}{\overset{\text{N}}{\Sigma }}{\text{m}}_{\text{i}}}}$$

$$\Delta \text{v}=\frac{\text{c}\Delta \text{f}}{2{\text{f}}_{\text{O}}+\Delta \text{f}}$$

20 provides a method for obtaining a degree of agreement M for the up-chirp signal. Similarly, a degree of agreement M for the down-chirp signal using the reference chord for the down-chirp signal.

When the frequency offset is used in the sixth embodiment, a degree of agreement M for the second wave and other recently received waves using .delta.f obtained for the first wave until a predetermined time has elapsed after detection of the first wave.

In an alternative embodiment, a degree of agreement M be calculated using another equation for weighting a frequency difference. In the first embodiment, the weighting factor decreases over time. In the second embodiment, the weighting factor increases with the passage of time. In an alternative embodiment, a weighting factor may be used that changes in other ways. In an alternative embodiment to the first embodiment, which in 21 For example, the weighting factor increases to a peak within a time interval corresponding to the first half, and then decreases. In an alternative embodiment to the second embodiment, which in 22 is shown, the weighting factor decreases to a peak and then decreases during a time interval corresponding to the second half. As it is in 3 In addition, in the first embodiment, the weighting factor is zero during a time interval corresponding to a part of the second half, and in the second embodiment, the weighting factor is zero during a time interval corresponding to a part of the first half it in 7 is shown. In an alternative embodiment of the respective first and second embodiments, the weighting factor may be greater than zero during a time interval corresponding to the former and the latter half. In an alternative embodiment to the first embodiment, a weighting factor equal to zero during a time interval equal to the entire second half may be used. In an alternative embodiment to the second embodiment, the weighting factor may be used, which is equal to zero during a time interval corresponding to the entire first half, as shown in FIG 22 is shown to compare the second half of the reference wave whose frequency changes in the same way as the frequency of the received wave.

The weighting factor of the first embodiment and the weighting factor of the second embodiment may be used to calculate a degree of coincidence. Computational results obtained during a sweep time of the frequency of the pulse signal may be buffered. A determination as to whether a chirp signal is included in the received signal may be made based on a higher degree of agreement from the buffered match levels. This configuration can increase the accuracy of detecting a chirp signal in the case of a low signal-to-noise ratio for the first wave or a wide interference range.

In an alternative embodiment to the respective first to fifth embodiments, a weighting factor that changes with time and a weighting factor that takes a fixed value may be used to calculate a degree of coincidence. A determination as to whether a chirp signal is included in the received signal may be made based on a higher degree of agreement from the degree of agreement calculated using the weighting factor that changes with time and the degree of matching using of the weighting factor which assumes a fixed value.

In an alternative embodiment to the fifth embodiment, three or more weighting factors may be used. In such an embodiment, use of a weighting factor set so that a period of time during which the weighting factor is equal to or greater than a reference value increases as a distance to an object to be detected decreases, the accuracy of detection of a Increase chirp signal.

In an alternative embodiment to the sixth embodiment, the object detecting device as in the fourth embodiment, two microphones 1 contain. In such an embodiment, the object detection device may be configured to include a component of a relative velocity of an object that corresponds to a velocity at which the object approaches the midpoint of a line segment, that is, the two microphones 1 connects, capture. In an alternative embodiment to the sixth embodiment, in which the object detection device comprises a plurality of microphones 1 contains, the mounting heights of the two microphones 1 be different, and .DELTA.T1 can for the respective microphones 1 be set differently. For each of the microphones 1 can, for example .DELTA.T1 with an increase in a mounting height of the microphone 1 increase.

In an alternative embodiment to the sixth embodiment .DELTA.T1 Each time a reflected wave is detected, it can be reset, and a relative speed can be fixed until the predetermined period of time .DELTA.T1 has passed after a last detection of a reflected wave. The frequency determining device 11 may be designed, for example, when the second wave before a lapse of the predetermined period of time .DELTA.T1 is detected after detecting the first wave to determine the presence or absence of a chirp signal in the second wave, wherein the relative velocity is fixed until the predetermined period of time .DELTA.T1 has elapsed after detection of the second wave. If the third signal is the microphone 1 within this .DELTA.T1 reached determines the frequency determining device 11 the presence or absence of a chirp signal in the third wave, the relative velocity being fixed until the predetermined time period .DELTA.T1 has passed after a detection of the third wave. In a case where there are several obstacles and the microphone 1 from these receives a number of reflected waves, such resetting of .DELTA.T1 improve the accuracy of detecting a chirp signal. In such an embodiment, in the .DELTA.T1 it is even before a lapse of .DELTA.T1 after a last reception of a reflected wave, it is allowed to return to a normal detection method in which the relative speed is not fixed when a predetermined period has elapsed after a fall in the amplitude of the received wave.

In an alternative embodiment, only one weighting factor may be used such that the weighting factor used for a time interval corresponding to the second half thereof is greater than the weighting factor used for a time interval corresponding to the first half thereof.

In an alternative embodiment to the sixth embodiment, as in the first embodiment, only one weighting factor may be used such that the weighting factor used for a time interval corresponding to its first half is greater than the weighting factor used for a time interval which corresponds to the second half thereof. In an alternative embodiment to the sixth embodiment, the weighting factor may be changed as in the third embodiment in response to a distance to an object to be detected. In an alternative embodiment to the sixth embodiment, the weighting factor may be a fixed value. In such an embodiment, the use of a fixed relative velocity may reduce an influence of interference and increase the accuracy of detection of a chirp signal.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2373434 [0002]

Claims (30)

An object detection device mounted on a vehicle and detecting an object outside the vehicle, the object detection device comprising: a transmitter (1) configured to emit an ultrasonic wave; a receiver (1) configured to receive an ultrasonic wave; a reference wave memory (12) configured to store a reference wave whose frequency changes in accordance with a similar change pattern as a change of a frequency of a transmitted wave; frequency determining means (11) adapted to compare frequencies of the reference wave and a received wave to determine whether the received wave is a reflected wave of the ultrasonic wave emitted by the transmitter; a distance calculating means (9) arranged when the frequency determining means determines that the received wave is a reflected wave of the ultrasonic wave emitted from the transmitter, a distance to an object reflecting the ultrasonic wave, based on the received wave to calculate, wherein the frequency determining means is adapted to calculate a degree of coincidence between the reference wave and the received wave based on a frequency difference between the reference wave and the received wave and at least one weighting factor that changes with time, and based on the calculated degree of coincidence determine whether the received wave is a reflected wave of the ultrasonic wave emitted from the transmitter. Object detection device according to Claim 1 wherein the at least one weighting factor that changes over time is set such that a value that the at least one weighting factor assumes in a time interval corresponding to the first half of the reference wave is greater than a value that the at least one weighting factor assumes a weighting factor in a time interval corresponding to the second half of the reference wave. Object detection device according to Claim 1 wherein the at least one weighting factor that changes over time is set such that a value that the at least one weighting factor assumes in a time interval corresponding to the second half of the reference wave is greater than a value that the at least one weighting factor assumes a weighting factor in a time interval corresponding to the first half of the reference wave. Object detection device according to Claim 1 wherein the at least one weighting factor comprises a plurality of weighting factors, and when the receiver has serially received a plurality of ultrasonic waves, the frequency determining means is adapted to a different weighting factor for a respective wave from a first wave that is an ultrasonic wave first received by the receiver , and a second wave, which is an ultrasonic wave, which is subsequently received by the receiver. Object detection device according to Claim 4 wherein a first weighting factor among the weighting factors is set such that a value adopted by the first weighting factor in a time interval corresponding to the first half of the reference wave is greater than a value taken by the first weighting factor in a time interval that is second half of the reference wave, a second weighting factor is set from the weighting factors such that a value that the second weighting factor assumes in a time interval corresponding to the second half of the reference wave is greater than a value that is the second weighting factor in a time interval which corresponds to the first half of the reference wave, and the frequency determining means is adapted to use the first weighting factor for the first wave and the second weighting factor for the second wave. Object detection device according to Claim 5 wherein the frequency determining means is arranged to use the second weighting factor after elapse of a predetermined period of time after detecting the first wave. Object detection device according to Claim 5 wherein the frequency determining means is adapted to use the second weighting factor until a predetermined period of time has passed after detection of the first wave. Object detection device according to Claim 1 wherein the at least one weighting factor comprises a plurality of weighting factors, each of the weighting factors assuming a value equal to or greater than a reference value over a specific time interval, and taking a value smaller than that on a time interval following the specific time interval Is reference value, and the frequency determining means is adapted to use the weighting factor whose specific time interval is longer as a distance to an object to be detected decreases. Object detection device according to Claim 1 wherein the at least one weighting factor comprises a plurality of weighting factors, a first weighting factor is set from the weighting factors such that the first weighting factor used for a time interval corresponding to the first half of the reference wave is greater than the weighting factor that is for a time interval is used, which corresponds to the second half of the reference wave, a second weighting factor is set from the weighting factors such that the second weighting factor used for a time interval corresponding to the second half of the reference wave is greater than the weighting factor that is for a Time interval is used, which corresponds to the first half of the reference wave, and the frequency determining means is adapted to a degree of agreement between the reference wave and the received wave using each of the first weighting factor and the second weighting factor z u and calculate, on the basis of a higher degree of agreement, the degree of agreement calculated using the first weighting factor and the degree of agreement calculated using the second weighting factor to determine whether the received wave is a reflected wave of the ultrasonic wave was sent by the transmitter. Object detection device according to one of Claims 4 to 9 in which a sum of the weighting factors takes the same value at different times. Object detection device according to one of Claims 1 to 10 wherein the frequency determining means is adapted to switch between the at least one weighting factor, which changes over time, and the at least one weighting factor, which has a constant value. Object detection device according to Claim 11 wherein the frequency determining means is arranged when the receiver has serially received a plurality of ultrasonic waves and interference occurs between the ultrasonic waves received by the receiver to use the at least one weighting factor which changes with time. Object detection device according to one of Claims 1 to 10 wherein the frequency determining means is arranged to calculate a degree of coincidence between the reference wave and the received wave using the at least one weighting factor that changes with time and a constant weighting factor instead of the at least one weighting factor, and based on a higher degree of matching the degree of matching calculated using the at least one weighting factor that changes with time and the degree of matching calculated using the constant weighting factor to determine whether the received wave is a reflected wave of the ultrasonic wave was sent by the transmitter. Object detection device according to one of Claims 1 to 12 wherein the frequency determining means is arranged when there are two peaks of receiving wave amplitudes and the receiving wave frequency changes in the course of time between the two peaks such that a magnitude of change of the receiving wave frequency per unit time is larger than a predetermined value to determine that a Interference between the two received waves occurs. Object detection device according to Claim 14 wherein the frequency determining means is adapted, when it is determined that an interference between two received waves occurs, to use the weighting factor which takes a smaller value on a time interval at which an interference between the two received waves occurs than at the other time interval , Object detection device according to Claim 14 wherein the frequency determining means is arranged when it is determined that interference occurs between two ultrasonic waves received from the receiver, using the at least one weighting factor that changes with time, and when it is determined that there is no interference between two ultrasonic waves that are received by the receiver occur using a constant weighting factor instead of the at least one weighting factor that changes over time. An object detection device mounted on a vehicle and detecting an object outside the vehicle, the object detection device comprising: a transmitter (1) configured to emit an ultrasonic wave; at least one receiver (1) configured to receive an ultrasonic wave; a reference wave memory (12) configured to store a reference wave whose frequency changes in accordance with a similar change pattern as a change of a frequency of a transmitted wave; frequency determining means (11) adapted to compare frequencies of the reference wave and a received wave to determine whether the received wave is a reflected wave of the ultrasonic wave emitted by the transmitter; a distance calculating means (9) arranged when the frequency determining means determines that the received wave is a reflected wave of the ultrasonic wave emitted from the transmitter, a distance to an object reflecting the ultrasonic wave, based on the received wave to calculate; and a relative speed determining means (14) configured to calculate a relative speed of the object based on the received wave; wherein the frequency determining means is adapted to determine that a first wave, which is an ultrasonic wave received first by the at least one receiver after the transmitter has transmitted an ultrasonic wave, is a reflected wave of the ultrasonic wave received from the transmitter was sent out to compare frequencies of the reference wave and the received wave on the assumption that a relative velocity of the object remains equal to a relative velocity calculated on the basis of the first wave by the relative velocity determining means until a predetermined period of time (ΔT1) after detection of first wave has passed. Object detection device according to Claim 17 wherein the frequency determining means is adapted to calculate a degree of coincidence between the reference wave and the received wave based on a frequency difference between the reference wave and the received wave and at least one weighting factor that changes with time, and based on the calculated degree of matching to determine whether the received wave is a reflected wave of the ultrasonic wave emitted by the transmitter. Object detection device according to Claim 17 or 18 wherein the at least one weighting factor includes a plurality of weighting factors, and when the receiver has received a plurality of ultrasonic waves, the frequency determining means is configured to have a different weighting factor for a respective one of the first wave and an ultrasonic wave after receiving the first wave from the at least one Receiver was received to use. Object detection device according to Claim 19 wherein the reference wave has a portion whose frequency changes in the same manner as the frequency of the transmitted wave and a portion whose frequency changes other than the frequency of the transmitted wave when the receiver has serially received a plurality of ultrasonic waves Frequency determining means is adapted to compare only the portion whose frequency changes in the same manner as the frequency of the transmitted wave, with ultrasonic waves, which are received after receiving the first wave. Object detection device according to one of Claims 17 to 20 wherein the frequency determining means is adapted to change a length of the predetermined time period (ΔT1) in response to the distance to the object calculated by the distance calculating means based on the first wave. Object detection device according to Claim 21 wherein the frequency determining means is adapted to increase the length of the predetermined time period (ΔT1) with a reduction in a distance to the object calculated by the distance calculating means based on the first wave. Object detection device according to one of Claims 17 to 22 wherein the frequency determining means is adapted to change a length of the predetermined time period (ΔT1) in response to the amplitude of the first wave. Object detection device according to Claim 23 wherein the frequency determining means is adapted to increase the length of the predetermined time period (ΔT1) with an increase in an amplitude of the first wave. Object detection device according to one of Claims 17 to 24 wherein the at least one receiver comprises a plurality of receivers arranged at different mounting heights on the vehicle, and the frequency determining means is arranged to assume, for each of the receivers, that the relative speed of the object remains equal to a relative speed calculated by the relative speed determining means a different predetermined period of time (ΔT1) has elapsed after detection of the first shaft. Object detection device according to Claim 25 wherein the frequency determining means is arranged to increase the time duration (ΔT1) for each of the receivers with an increase in a mounting height of the receiver. Object detection device according to one of Claims 17 to 26 wherein the frequency determining means is arranged, assuming that a relative speed of the object remains equal to a relative speed calculated on the basis of the last received wave by the relative speed determining means, until the predetermined time period (ΔT1) elapsed after a last detection of the received wave is to compare frequencies of the reference wave and the subsequent received wave. Object detection device according to Claim 27 wherein the frequency determining means is arranged, assuming that a relative speed of the object remains equal to a relative speed calculated on the basis of the last received wave by the relative speed determining means, until the predetermined time period (ΔT1) elapsed after a last detection of a received wave is and until a predetermined period of time after a fall in the amplitude of the received wave to below a predetermined value, to compare frequencies of the reference wave and the subsequently received wave. Object detection device according to one of Claims 17 to 28 further comprising a shape determining means (13) adapted to determine a shape of an object to be detected, the transmitter and the at least one receiver being integrated with one another, when it is assumed that L _{1 represents} a path containing an ultrasonic wave during a period of time from a transmission of the ultrasonic wave by the transmitter to a reception of the first wave by the at least one receiver, L _{2 represents} a distance that the ultrasonic wave during a period from a transmission of the ultrasonic wave by the transmitter to a reception of the second Wave, which is subsequently received by the at least one receiver, and H represents a mounting height of the transmitter and the at least one receiver, the shape determining means is arranged when a difference between L ₂ ^2/4 and L ₁ ^2/4 + H ^{2 is the} same or less than a predetermined value is to be determined immense, that the object has a shape with a special height. Object detection device according to one of Claims 17 to 28 further comprising a shape determiner (13) configured to determine a shape of an object to be detected, wherein, assuming that L _{1 represents} a distance representing an ultrasonic wave during a period of time from emission of the ultrasonic wave by the transmitter until reception of the first wave by the at least one receiver, L _{2 represents} a distance which the ultrasonic wave receives during a period from a transmission of the ultrasonic wave by the transmitter to a reception of a second wave subsequently from the at least one receiver For example, when Ha represents an installation height of the transmitter and Hb represents a mounting height of the at least one receiver, the shape determination device is designed to determine when a difference between L ₂ ² -L ₁ ² and 4HaHb is equal to or smaller than a predetermined value, that the object has a shape with a has special height.

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