JP2019113359A - Obstacle detection sensor - Google Patents

Abstract

To provide a distance measuring device with which it is possible to make measurement with high accuracy irrespective of road surface conditions.SOLUTION: A distance measuring device 100 comprises: a control unit 1 for determining a detection condition for an obstacle 91 on a road 92; a TOF sensor unit 3 for oscillating an oscillatory wave and receiving the reflected wave of the oscillated oscillatory wave and thereby acquiring distance information; a vehicle-side communication unit 2 for communicating with the outside and acquiring road surface information; and a vehicle-side storage unit 4 in which detection related information for identifying the obstacle 91 is stored on the basis of the distance information. The control unit 1 compares the detection related information read out from the vehicle-side storage unit 4 with the distance information and road surface information acquired from the TOF sensor unit 3 and the vehicle-side communication unit 2 and determines a detection condition.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an obstacle detection sensor provided with a TOF distance sensor.

  In Patent Document 1, ultrasonic distance is measured by so-called Time-Of-Flight (TOF) method, in which ultrasonic waves are transmitted and their reflected waves are received to measure the distance to a reflective object. The device is described.

  The ultrasonic distance measuring device described in this patent document 1 modulates the frequency, phase, etc. of the pulse signal to transmit the burst wave of the ultrasonic wave to which the identification signal (modulated signal) is added, and the identification signal is information The distance can be determined with high accuracy by receiving the reflected wave of the ultrasonic wave, and the like, and correlating the signal with the transmitted modulated signal.

  In Patent Document 2, a distance measurement device (ultrasonic sonar) is attached to a vehicle, and a vehicle periphery monitor that detects an obstacle present around the vehicle by receiving a reflected wave of ultrasonic waves transmitted from the ultrasonic sonar. The device is described. Further, in such a vehicle periphery monitoring device, a need for improving the detection performance of an obstacle present around the vehicle is described.

JP, 2005-249770, A JP, 2011-12416, A

The road on which the vehicle travels includes obstacles that cause so-called travel and unevenness of the road surface that does not hinder travel (for example, depressions and bumps on the road surface, and the presence of gravel and stone rollers).
The ultrasonic distance measuring device described in Patent Document 1 can accurately obtain the distance by distinguishing the reflection wave of the ultrasonic wave oscillated by the self and the other ultrasonic waves according to the presence or absence of the identification signal. . However, even if the identification signal is given to the oscillating ultrasonic wave, the obstacle on the road and the unevenness of the road surface can not be distinguished depending on the identification signal. This is because the identification signal is also included in the reflected wave due to the unevenness of the road surface.
Therefore, just obtaining the distance information accurately does not sufficiently satisfy the need for improvement in the detection performance of obstacles existing around the vehicle as exemplified in Patent Document 2.
Therefore, it is desirable to provide an obstacle detection sensor that can perform measurement with high accuracy regardless of the state of the road surface.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an obstacle detection sensor capable of performing measurement with high accuracy regardless of the state of a road surface.

The characteristic configuration of the obstacle detection sensor according to the present invention for achieving the above object is
A control unit that determines a detection condition of an obstacle on a road, a distance sensor unit that oscillates a vibration wave and receives distance information by receiving a reflection of the oscillated vibration wave;
A communication unit that communicates with the outside to acquire road surface information;
A storage unit storing detection related information for identifying the obstacle based on the distance information;
The control unit determines the detection condition by comparing the detection relation information read from the storage unit with the distance information and the road surface information acquired from the distance sensor unit and the communication unit. .

  According to the above configuration, the so-called TOF type distance sensor unit oscillates (transmits) an oscillating wave such as an ultrasonic wave or light and receives (reflects) a reflected wave of the oscillated oscillating wave, that is, When continuing acquisition of information related to the unevenness of the road surface and the presence of obstacles as TOF information acquired from the reflected wave, the control unit acquires detection related information recorded in advance in its own storage unit and the information acquired from the outside The detection condition of the obstacle on the road currently measured may be determined by comparing the road surface information about the road currently measured and the distance information acquired for the distance sensor unit to detect the obstacle. it can. Here, the road surface information is information on what kind of unevenness the road surface of the road is.

That is, the control unit can determine (change) the detection condition of the obstacle according to the state of the unevenness of the road surface currently measured. For example, in the case of a paved road with little unevenness, even if a weak reflected wave is received, the reflected wave is not caused by the unevenness of the road but the detection condition is changed so as to be judged as an obstacle. It becomes possible. Moreover, if it is a gravel road with big unevenness, even if it receives a somewhat large reflected wave, the said reflected wave is unevenness of a road, and it is possible to change detection conditions so that it is judged that it is not due to an obstacle. become.
Therefore, according to the above configuration, it is possible to provide an obstacle detection sensor capable of performing measurement with high accuracy regardless of the state of the road surface, such as appropriately identifying and detecting road irregularities and obstacles.

The further characteristic configuration of the obstacle detection sensor according to the present invention is
The communication unit communicates with a road information server having an external storage unit storing the road surface information, and the control unit acquires the road surface information from the external storage unit.

According to the above configuration, the control unit can acquire the road surface information from the external storage unit, that is, the storage device of the road information server that is external to the control unit.
Therefore, the obstacle detection sensor can acquire the necessary and sufficient amount of information about the road currently being measured from the outside without having the storage device with a large capacity. In addition, the obstacle detection sensor can easily use the latest road information that will be sequentially updated on the road information server.
Therefore, according to the above configuration, it is possible to provide an obstacle detection sensor placement that can perform measurement with high accuracy even if the condition of the road changes after manufacturing the obstacle detection sensor.

The further characteristic configuration of the obstacle detection sensor according to the present invention is
The control unit transmits the distance information from the communication unit to the road information server, and causes the road information server to record the distance information in the external storage unit.

Usually, most of the distance information acquired by the distance sensor unit is probability distance information with the road surface. Therefore, if the distance information acquired by the distance sensor unit is accumulated, the distance information to the obstacle included in the distance information is relatively diluted, and the information on the distance to the measured road surface, that is, the unevenness of the road surface Information about the becomes dominant. That is, the accumulated distance information becomes information approximate to road surface information.
Therefore, according to the above configuration, the distance information acquired by the distance sensor unit, that is, the latest road surface information acquired by the distance sensor unit is stored in the storage unit of the road information server, and the road surface information of the road information server is updated. Can.

The further characteristic configuration of the obstacle detection sensor according to the present invention is
The control unit transmits the acquired distance information to the road information server when the acquired distance information changes a predetermined distance or more with respect to the distance information transmitted to the road information server immediately before that. The point is to

For example, assuming that the distance information acquired by the distance sensor unit is always transmitted to the road information server, the amount of communication increases, which may cause congestion in the communication network.
Therefore, according to the above configuration, when the control unit acquires distance information, the acquired distance information changes the distance information transmitted immediately to the road information server immediately before, that is, finally, a predetermined change or more. The amount of communication can be reduced by transmitting the acquired distance information to the road information server so that communication does not occur if there is no change above the predetermined level.
Therefore, it is possible to update the information of the road information server by the necessary amount while avoiding an increase in the amount of communication and avoiding congestion of the communication network.

The further characteristic configuration of the obstacle detection sensor according to the present invention is
It has an environmental sensor unit that acquires environmental values,
The control unit corrects the distance information based on an environmental value acquired by the environmental sensor unit.

  The characteristics such as the propagation velocity of the vibration wave, in particular, the sound velocity of the ultrasonic wave, fluctuates according to the environmental value which is information of the environment such as ambient temperature, humidity and pressure. Therefore, according to the above configuration, it is possible to accurately obtain the characteristic of the vibration wave, for example, the sound velocity of the ultrasonic wave, based on the environmental value acquired by the environment sensor unit, and acquire the corrected accurate distance information.

The further characteristic configuration of the obstacle detection sensor according to the present invention is
The communication unit communicates with an environmental information server that distributes environmental values;
The control unit acquires an environmental value from the environmental information server, and corrects the distance information based on the environmental value.

  The characteristics such as the propagation velocity of the vibration wave, in particular, the sound velocity of the ultrasonic wave, fluctuates according to the environmental value which is information of the environment such as ambient temperature, humidity and pressure. Therefore, according to the above configuration, it is possible to accurately obtain the characteristic of the vibration wave, for example, the sound velocity of the ultrasonic wave, based on the environmental value acquired from the environment information server, and acquire the corrected accurate distance information.

The further characteristic configuration of the obstacle detection sensor according to the present invention is
The road information server is provided by cloud computing.

According to the above configuration, the road information of the road information server can be shared and stored by a plurality of road information servers existing on the network while being shared by a large number of obstacle detection sensors connected by the network. Moreover, the road information of the road information server can be updated by the many obstacle detection sensors.
Thus, road information across the road network can be shared by multiple obstacle detection sensors while maintaining state of the art. Also, multiple road information servers can be shared for safe storage and update. That is, the obstacle detection sensor can acquire the latest road information and can improve the distance measurement performance.

Illustration of the configuration of the distance measuring device An explanatory view of the configuration of the control unit and the TOF sensor unit A diagram of the waveform modulated by the phase modulation method A diagram of the waveform modulated by the amplitude modulation method Explanation of the waveform modulated by the frequency modulation method A diagram of a waveform modulated by simultaneously using a phase modulation scheme and an amplitude modulation scheme Illustration of distance measurement by TOF method An illustration of avoiding false positives Explanation of the change of detection condition Flow chart of judgment whether to transmit distance information to road information server

  A distance measuring device 100 used as an obstacle detection sensor according to an embodiment of the present invention will be described based on FIGS. 1 to 10.

[Description of Summary]
FIG. 1 is a schematic view illustrating a schematic configuration of a vehicle 200 on which the distance measuring device 100 is mounted.
The distance measuring device 100 is a distance measuring device that measures the distance to the object 9 by receiving and measuring the reflection wave of the modulated ultrasonic wave and acquiring distance information.
In the present embodiment, the distance measuring device 100 functions as an obstacle detection sensor that can distinguish the obstacle 91 and the unevenness 93 of the road 92 by measuring the distance to the object 9. The distance measuring device 100 is mounted on, for example, the vehicle 200, recognizes the presence of the obstacle 91, grasps the distance to the obstacle 91, and obtains the information from the control unit 1 in the driver's seat of the vehicle 200. The driver is notified via a display unit (not shown) or the like.

  As shown in FIG. 1, the distance measuring device 100 includes a TOF sensor unit 3 (an example of a distance sensor unit), a vehicle communication unit 2 (an example of a communication unit) that communicates with the Internet N which is an external network, and an object 9 includes, as main components, a vehicle-side storage unit 4 (an example of a storage unit) that stores detection relation information for identifying 9 and a control unit 1 that performs operation control of the distance measuring device 100 and the vehicle 200 .

  In the present embodiment, at least the storage server 7, the road information server 61, and the environment information server 63 are connected to the Internet N which is an external network viewed from the vehicle 200.

[Detailed description]
[About the Internet and Cloud Computing]
The internet N is a network through which the vehicle 200 can communicate with various servers and other vehicles 300 via the public communication antenna 60. The public communication antenna 60 is, for example, a base station of a mobile telephone network.
At least the storage server 7, the road information server 61, and the environment information server 63 are connected to the Internet N, and each server can independently communicate with other servers, vehicles 200, etc. .

  The road information server 61 is a server that manages road surface information (road surface information) of the road on which the vehicle 200 and the other vehicle 300 are supposed to travel, and distance information acquired by the vehicle 200 and the other vehicle 300. And a central processing unit (not shown) for program calculation and analysis.

  In the present embodiment, the road information server 61 does not locally include a storage unit that stores (stores) road surface information and distance information, but a storage server having a storage device such as a hard disk (hereinafter referred to as an external storage unit 70). 7 is used as a storage unit. In the present embodiment, the road information server 61 has a road surface information DB 71 storing road surface information and a distance information DB 72 in the external storage unit 70 of the storage server 7. That is, the road information server 61 has the road surface information DB 71 and the distance information DB 72 in the cloud storage storage server 7.

  In the road information server 61 and the storage server 7, a plurality of electronic computers connected on the Internet N virtually function as one server, or a plurality of types of virtual servers are constructed on one electronic computer. It functions as a so-called cloud.

  In the distance information DB 72, information concerning the unevenness of the road is stored. For example, the distance information transmitted from the vehicle 200 or another vehicle 300 is stored.

Road surface information is stored in the road surface information DB 71. The road surface information is information obtained by analyzing a large amount of distance information (so-called big data) stored in the distance information DB 72 on the cloud, for example, by the central processing unit of the road information server 61 and classifying the state of each road ( Road surface information is stored.
The road surface information DB 71, for example, classifies and stores road surface information indicating that a certain road is a well-paved road, a damaged paved road, a gravel road, unpaved road, and the like. The specific description will be described later.

  The road surface information is not limited to the above example, and the road surface material is asphalt, concrete, etc., and the road surface condition is below freezing temperature, frozen, wet, etc. It may include other detailed information such as temperature and condition.

The environment information server 63 is a server that manages weather information around the road on which the vehicle 200 and other vehicles 300 are supposed to travel, and distributes the weather information in response to a request from the vehicle 200 or the like.
The environment information server 63 can deliver at least an environmental value such as temperature and humidity information among the weather information to the vehicle 200 and the like. In the present embodiment, the environment information server 63 can deliver information on atmospheric pressure in addition to air temperature and humidity as an environmental value.
Although not shown, the environment information server 63 also uses the storage server 7 as a storage unit for storing weather information, as the road information server 61 does.

[Configuration of TOF sensor]
As shown in FIG. 2, the TOF sensor unit 3 includes a piezoelectric element 31 for oscillating an ultrasonic wave, an oscillator 34 for oscillating a fundamental wave of an ultrasonic wave oscillated by the piezoelectric element 31, and a fundamental wave (carrier wave) oscillated by the oscillator 34. And a detector 35 that demodulates the reflected wave received by the piezoelectric element 31 to obtain a demodulated signal. The TOF sensor unit 3 transmits ultrasonic waves from the piezoelectric element 31 and receives reflected waves of the ultrasonic waves by the piezoelectric element 31 to measure a distance to a reflective object, so-called time-of-flight (time-of-flight). It is a sensor unit for performing the TOF method.

The piezoelectric element 31 is a device that oscillates and receives ultrasonic waves.
The piezoelectric element 31 includes a vibrator (not shown) that is displaced according to the applied voltage, and generates an electromotive force according to the displacement when a mechanical force such as vibration energy is applied. It is a unit of a so-called ultrasonic transducer.
Since the vibrator of the piezoelectric element 31 resonates at a predetermined frequency (wavelength), normally, the frequency (or wavelength) that is the center of the oscillating ultrasonic wave and the frequency (or wavelength) that is the center of the ultrasonic waves that can be received ) Will be the same.
The resonance frequency of the piezoelectric element 31 of the present embodiment is 40 kHz.

  In the present embodiment, the piezoelectric element 31 oscillates an ultrasonic wave in response to a change in voltage applied from the modulator 32. In addition, the piezoelectric element 31 can receive external vibration, for example, an ultrasonic wave oscillated by the piezoelectric element 31 itself.

In the present embodiment, the piezoelectric element 31 repeats continuous vibration (vibration to which a voltage is applied) and stop for a predetermined time. The piezoelectric element 31 can receive external vibration (ultrasound) when the vibration is stopped. In other words, when receiving external vibration, the application of the voltage is stopped.
The vibration received by the piezoelectric element 31 is converted into a voltage signal by the piezoelectric element 31 and transmitted to the detector 35.

  That is, in the present embodiment, a unit of one ultrasonic transducer is used as the piezoelectric element 31, and when oscillating an ultrasonic wave corresponding to a modulation wave, the piezoelectric element 31 is used as an oscillating element and receives surrounding ultrasonic waves. At the same time, the same piezoelectric element 31 is used as a receiving element.

The oscillator 34 is a frequency generator that oscillates a fundamental wave for vibrating the piezoelectric element 31. The fundamental wave oscillated by the oscillator 34 is used as a carrier in this embodiment.
In the present embodiment, the oscillator 34 generates a predetermined frequency based on the basic vibration of a quartz vibrator (not shown) vibrating at a predetermined frequency, and supplies the generated frequency to the modulator 32 as a carrier wave.

  The modulator 32 is a modulation circuit (not shown) that modulates the fundamental wave oscillated by the oscillator 34 (hereinafter, may be simply referred to as modulation) and transmits the modulation wave to the piezoelectric element 31. 31 has a circuit (not shown) for generating a voltage for driving 31.

  In the present embodiment, the modulator 32 uses the fundamental wave oscillated by the oscillator 34 as a carrier wave, modulates the fundamental wave according to the signal oscillated by the pulse generator 15, and generates a modulated wave including signal information. . Then, the modulator 32 drives the piezoelectric element 31 by applying the modulation wave to the piezoelectric element 31 as a wave of voltage, that is, a voltage in which the magnitude of the phase or amplitude is changed. The piezoelectric element 31 vibrates in response to the voltage applied from the modulator 32, and oscillates a modulated ultrasonic wave, that is, an ultrasonic wave including signal information.

The modulator 32 can modulate by a modulation method according to the instruction of the control unit 1.
In the present embodiment, the modulator 32 is configured to oscillate a modulation wave according to an instruction from the control unit 1 by using any one or a combination of a phase modulation method, an amplitude modulation method, and a frequency modulation method.
The modulator 32 includes a modulation circuit (not shown) corresponding to a phase modulation scheme, an amplitude modulation scheme, a frequency modulation scheme, and a scheme combining these in the inside of the modulator 32.

  Note that the phase modulation method referred to in the present embodiment refers to a method of modulating a digital signal by changing the phase of a carrier wave and expressing it, that is, phase modulation and transmitting it, and also PSK (phase-shift keying) be called.

An example of a waveform at the time of modulating by a phase modulation system is shown in FIG.
In this embodiment, as shown in FIG. 3, the same phase as the carrier wave represents a binary 1 and the phase shifted by π from the carrier wave represents a binary zero.

Further, the amplitude modulation method in the present embodiment refers to a method in which a digital signal is modulated by expressing it as a difference in carrier wave amplitude, that is, amplitude modulation, and is also called ASK (amplitude shift keying).
In the present embodiment, of the continuous waves, a relatively large amplitude represents a binary 1 and a relatively small amplitude represents a binary zero.

FIG. 4 shows an example of the waveform when modulated by the amplitude modulation method.
In FIG. 4, with respect to a relatively large amplitude representing a binary one, modulation control is performed with a 50% amplitude as a target amplitude in the case of representing a binary zero, where the amplitude is 100%. In the case of an amplitude of 75 percent or less, which is an average value of percent and 50 percent, a binary zero is assumed to be represented.

  Further, the frequency modulation method referred to in the present embodiment refers to a method of modulating a digital signal with a difference in carrier wave frequency, that is, frequency modulation, and is also called FSK (frequency shift keying).

An example of a waveform at the time of modulating by a frequency modulation system is shown in FIG.
In the present embodiment, the same frequency as the carrier wave can represent a binary 1 and can represent binary zeros if the frequency is changed by a predetermined magnitude than the carrier wave. For example, in the case of FIG. 5, the same frequency as the carrier represents a binary 1 and the case where the frequency is smaller than the carrier by a predetermined magnitude represents a binary zero.

  In the present embodiment, hereinafter, the modulator 32 modulates and outputs a modulation wave by a modulation method in which the modulation is simultaneously performed using two modulation methods of the phase modulation method and the amplitude modulation method simultaneously, and the piezoelectric element 31 is converted to the modulation wave. The case where the corresponding ultrasonic wave is oscillated will be described as an example.

The waveform W in FIG. 6 illustrates an example of the waveform of the ultrasonic wave when the piezoelectric element 31 oscillates the ultrasonic wave modulated using the phase modulation method and the amplitude modulation method simultaneously.
In the case of FIG. 6, the pulse generator 15 transmits a pulse signal (shown in the upper table of FIG. 6) including an 8-bit code of [11111000] in order from the most significant bit. The modulator 32 distributes and modulates the amplitude modulation method and the phase modulation method alternately for each bit in the order of the upper bit to the lower bit. Furthermore, the piezoelectric element 31 (see FIG. 1) oscillates an ultrasonic wave of a waveform W as an ultrasonic wave corresponding to the modulated modulation wave.
Note that FIG. 6 exemplifies a case where the modulator 32 modulates the burst length of the portion concerned with a half of the part representing 1 according to the amplitude modulation method, when the modulator 32 represents zero in the amplitude modulation method. doing.

  The detector 35 shown in FIG. 2 is a functional unit having a demodulation function for demodulating the vibration received by the piezoelectric element 31 to obtain a demodulated signal. In the present embodiment, the vibration received by the piezoelectric element 31 is an ultrasonic wave, and in particular, a reflected wave of the ultrasonic wave oscillated by the piezoelectric element 31.

In the present embodiment, the detector 35 has a demodulation circuit that functions as a demodulation unit that supports phase modulation, amplitude modulation, and frequency modulation.
The detector 35 transmits the demodulated signal thus demodulated to the comparator 17 of the control unit 1. The controller 1 having received the demodulated signal determines the type of the demodulated signal, and recognizes the signal contained in the demodulated signal.

[Configuration of Vehicle-side Communication Unit]
The vehicle side communication unit 2 is a functional unit for the vehicle 200 and the distance measurement device 100 to communicate with an external network as shown in FIG. In the present embodiment, the vehicle communication unit 2 is connected to the Internet N via the on-vehicle antenna 20 and a public communication antenna 60 connected to the so-called Internet N. The vehicle side communication unit 2 can communicate with the road information server 61 connected to the Internet N and the environment information server 63 via the Internet N.

[Configuration of Storage Unit]
The vehicle-side storage unit 4 is a storage device for storing and reading various information used by the vehicle 200 and the distance measuring device 100 as shown in FIG.
In the present embodiment, the vehicle-side storage unit 4 stores map information DB 41 storing information on the road network on which the vehicle 200 is supposed to travel, and the control unit 1 controls the obstacle 91 based on distance information with the object 9. , A temporary storage DB 49 for temporarily storing road surface information acquired from the road information server 61 and distance information acquired by the TOF sensor unit 3, and a control unit 1 Has a program DB in which a basic program for executing various operations is stored.

  In the map information DB 41, information of a road map which can specify the road 90 at least from the latitude and longitude is recorded.

  Detection relationship information for identifying the obstacle 91 and the unevenness 93 of the road 92 based on the distance information is stored in the measurement condition DB 42 according to the state of the road surface of the road. For example, it is possible to store detection related information corresponding to each road 90 being a well-paved road, a damaged paved road, a gravel road, or an unpaved road.

[Configuration of control unit]
As shown in FIG. 1, the control unit 1 is an ECU (engine control unit) of the vehicle 200, and has a function of controlling the entire distance measuring device 100 in the present embodiment.
As shown in FIG. 2, the control unit 1 has a CPU 10 which is a central processing unit as a core mechanism. The control unit 1 further includes a pulse generator 15 and a comparator 17.

The pulse generator 15 is a signal generator that generates a signal including a predetermined code. The pulse generator 15 is configured to generate, as an identification signal, a signal including a predetermined code (a unique code string or a code string serving as an identification ID) unique to the distance measuring device 100.
In the present embodiment, the pulse generator 15 supplies (transmits) the generated identification signal to the modulator 32 as the control unit 1.
The pulse generator 15 operates to generate a signal including a predetermined code in accordance with an operation command transmitted from the CPU 10.

The pulse generator 15 generates a signal having a predetermined bit length and a binary code of a predetermined bit arrangement.
For example, an 8-bit bit length can be selected as the predetermined bit length.
An arbitrary arrangement may be selected as the predetermined bit arrangement.

The pulse generator 15 outputs each bit in a predetermined bit length as a pulse signal (pulse on / off). When the pulse generator 15 generates a pulse at a predetermined timing (pulse on), the pulse at the predetermined timing means 1 in binary, and when the pulse is not generated at a predetermined timing (pulse off), the predetermined timing Means zero.
When the bit length is 8 bits, the pulse generator 15 outputs a signal of a combination of on and off of 8 pulses.

Hereinafter, the state in which the pulse generator 15 generates a pulse at a predetermined timing will be referred to as a code 1. Further, a state in which the pulse generator 15 does not emit a pulse at a predetermined timing is defined as a code zero.
Also, when simply referred to as a pulse, it means either sign 1 or sign zero.
Moreover, when calling it a pulse signal, the combination of several pulses is meant.

The predetermined timing at which the pulse generator 15 emits a pulse can be synchronized with, for example, the timing (for example, period) of the fundamental wave oscillated by the oscillator 34.
In the present embodiment, the oscillator 34 is synchronized with the period of the fundamental wave to be oscillated. Specifically, in principle, one pulse is emitted at every eight-wave oscillation timing (eight periods). There is.

The comparator 17 is an operation unit for comparing the code included in the signal (demodulated signal) acquired from the detector 35 of the TOF sensor unit 3 with the code of the pulse generator 15 to determine coincidence or non-coincidence.
The comparator 17 transmits the result of the determination (hereinafter, referred to as a determination result) to the CPU 10.

  The CPU 10 is a functional unit that executes functions other than the pulse generator 15 and the comparator 17 in the control unit 1 and is an arithmetic unit that operates according to a program stored in the program DB 43 (see FIG. 1) of the vehicle storage unit 4. It is.

The CPU 10 serves as the control unit 1 to calculate the distance to the object 9 based on the determination result obtained from the comparator 17 and the timing at which the determination result is obtained.
In addition, the CPU 10 as the control unit 1 includes detection relation information recorded in advance in the measurement condition DB 42, road surface information about the currently measured road acquired from the road surface information DB 71 via the road information server 61, and TOF The detection condition of the obstacle 91 on the road currently measured can be determined by comparing the distance information acquired for the sensor unit 3 to detect the obstacle 91.

As a detection condition, for example, when a reflected wave having a peak exceeding a predetermined threshold is received, the reflected wave can be defined as a reflected wave from the obstacle 91.
Then, for example, the predetermined threshold in the case of the unpaved road can be set to a threshold larger than the predetermined threshold in the case of the well-paved road.
The reception of the reflected wave, the distance measurement, and the detection of the obstacle 91 will be described later.

  In the present embodiment, the road currently being measured (the road currently being traveled) is acquired by the navigation unit 5, which is a car navigation device having, for example, a so-called GPS (Global Positioning System). The control unit 1 acquires GPS information including latitude and longitude information from the navigation unit 5 and the control unit 1 reads out map information stored in the map information DB 41, and the control unit 1 performs GPS information and map information. It can identify by contrasting with.

[Description of operation]
[Basic explanation of obstacle detection operation]
Below, detection operation of obstacle 91 and distance measurement by distance measuring device 100 is explained.
In the present embodiment, the distance measuring device 100 measures the distance by the so-called Time-Of-Flight (TOF) method.

FIG. 7 illustrates a graph explaining the basic concept of distance information based on the TOF method and distance information based on the TOF method.
The horizontal axis of the graph of FIG. 7 means the passage of time.
The vertical axis of the graph of FIG. 7 means the magnitude of the amplitude.
The line E1 is an envelope of the amplitude of the vibration of the piezoelectric element 31, and is an example of distance information in the present embodiment.
In the present embodiment, the piezoelectric element 31 oscillates the modulated ultrasonic wave as described above.

The piezoelectric element 31 is driven by the modulator 32 for the oscillation time T1 at predetermined intervals.
In FIG. 7, after the piezoelectric element 31 is driven by the modulator 32 for oscillation time T1 to vibrate (forced oscillation), vibration due to inertia is continued for reverberation time T2 (so-called reverberation), and then external vibration The figure shows the case of receiving a signal.

In the case of FIG. 7, the piezoelectric element 31 receives the vibration peak P1 having a magnitude exceeding the predetermined threshold Th1 after time Tp since the drive of the piezoelectric element 31 is started. The vibration peak P1 is usually the peak of the reflected wave from the obstacle 91 (see FIG. 1).
The threshold Th1 is a value for identifying a small reflected wave from the road 90 accompanying the unevenness of the road and a reflected wave from the obstacle 91. The threshold value Th1 is an example of detection relation information in the case where the road 90 is a paved road well paved, and is a value stored in advance in the measurement condition DB 42 in the present embodiment.

  In the present embodiment, a reflected wave having a peak exceeding the threshold Th1 is defined as a reflected wave from the obstacle 91. On the other hand, a reflected wave having a peak not exceeding the threshold Th1 is generally defined as a reflected wave generated by the unevenness of the road 90.

When the distance to the obstacle 91 is measured by the TOF method, the start point of the vibration peak P1 may be recognized as the start point of the reception of the reflected wave.
The start point of the vibration peak P1 is illustrated in FIG. 7 as a point going back from the time Tp by the time ΔT. Usually, the length of time ΔT is equal to the oscillation time T1. In other words, the time Tf required for receiving the reflection wave of the ultrasonic wave oscillated by the piezoelectric element 31 can be obtained by subtracting the oscillation time T1 from the time Tp.

  For example, in the case of FIG. 7, the time from the time when driving of the piezoelectric element 3 is started (zero) to the time when time .DELTA.T goes back from the time when time Tp indicating the vibration peak P1 is reached corresponds to time Tf. . Alternatively, the time from the time when the oscillation time T1 is reached to the time when the time Tp indicating the vibration peak P1 is reached is also the same time length as the time Tf.

  As described above, in the present embodiment, the line E1 (the envelope of the amplitude of the vibration of the piezoelectric element 31) is an example of the distance information. The line E1 is stored in the temporary storage DB 49 by the control unit 1 as numerical data acquired from the amplitude of the vibration of the piezoelectric element 31 in the present embodiment.

The reflected wave received by the piezoelectric element 31 is demodulated by the detector 35, and the extracted demodulated signal is transmitted to the comparator 17 of the control unit 1.
Here, the reflected wave of the ultrasonic wave oscillated by the piezoelectric element 31 has information including a predetermined code. Therefore, the signal demodulated and extracted by the detector 35 contains the predetermined code generated by the pulse generator 15. Therefore, if the determination result of the comparator 17 matches, the control unit 1 recognizes that the reflected wave is a reflected wave of the ultrasonic wave oscillated by the piezoelectric element 31, and detects the presence of the obstacle 91. Can. Then, the control unit 1 can obtain the time Tf, and obtain the distance to the obstacle 91 by multiplying the sound speed by half the time Tf.

  Here, since the speed of sound is a characteristic that fluctuates due to the air temperature, humidity, atmospheric pressure and the like around the vehicle 200, in the present embodiment, the air temperature and humidity acquired by the environment sensor unit 8 included in the vehicle 200 by the control unit 1 The velocity of sound in the environment in which the vehicle 200 is traveling is accurately determined based on an environmental value which is information on the environment such as air pressure. Thus, the control unit 1 can acquire accurate distance information in which the fluctuation of the environmental value is corrected.

  In addition, when a failure occurs in the environment sensor unit 8 and the environment value can not be acquired, the control unit 1 causes the vehicle communication unit 2 to communicate with the environment information server 63, and the environment value from the environment information server 63 To accurately determine the velocity of sound under the environment in which the vehicle 200 is traveling. Thereby, even when a failure occurs in the environment sensor unit 8, the control unit 1 can acquire accurate distance information in which the fluctuation of the environmental value is corrected.

[Avoiding False Detection]
It supplements about the case where the determination result of the comparator 17 is incoincidence.
FIG. 8 illustrates, in addition to the line E1 shown in FIG. 7, the incidence of an ultrasonic wave having a vibration peak P2 as a line Ef. In this line Ef, for example, the piezoelectric element 31 receives an ultrasonic wave or a reflected wave emitted from another distance measuring device mounted on another vehicle 300 (see FIG. 1) or the like.

In the case shown in FIG. 8, the ultrasonic wave having the vibration peak P2 does not include a signal including a predetermined code. Therefore, even when the vibration peak P2 exceeds the threshold value Th1, the comparator 17 determines the non-coincidence, so the control unit 1 causes the piezoelectric element 31 to oscillate the ultrasonic wave having the vibration peak P2 received by the piezoelectric element 31. It can be recognized that it is not a reflected wave of ultrasonic waves.
As described above, by oscillating and receiving an ultrasonic wave containing a predetermined code, the control unit 1 can avoid erroneous detection and improve the measurement performance of the distance measuring device 100. it can.

[Supplementary explanation of road surface information]
The road surface information stored in the road surface information DB 71 is supplemented based on FIG.
For example, a well paved road is flat. Therefore, as illustrated in FIG. 7, it is assumed that a road which can obtain distance information such that small reflected waves are not detected and small reflected waves are continuously detected is a well-paved road. The road surface information DB 71 is stored.

  In addition, damaged pavements are often found to be uneven. Therefore, a road where a small reflected wave is sometimes recognized and a small reflected wave is continuously detected is stored in the road surface information DB 71 as, for example, a damaged paved road.

  In the case of gravel roads, there is a continuously large unevenness. Therefore, a road on which a non-small reflected wave is continuously detected is stored in the road surface information DB 71 as, for example, a gravel road.

  In the case of unpaved roads, large irregularities exist. Therefore, a road on which a non-small reflected wave or a somewhat large reflected wave is detected irregularly is stored as the unpaved road in the road surface information DB 71, for example.

[About change of detection condition]
The change of the detection condition will be described.
Similar to the line E1 shown in FIG. 7, the line E2 shown in FIG. 9 is an envelope of the amplitude of the vibration of the piezoelectric element 31, but unlike the line E1 shown in FIG. Together with the vibration peak P1 of the reflected wave from the vibration wave P. Each of the reflected wave having the vibration peak P1, the vibration peak P3 and the vibration peak P4 has information including a predetermined code.

Further, FIG. 9 shows the threshold Th1 and the threshold Th2 larger than the threshold Th1.
Here, as described above, the threshold Th1 is a threshold in the case of a well-paved pavement.
Moreover, threshold value Th2 is a threshold value in the case of an unpaved road.
Similarly to the threshold Th1, the threshold Th2 is also a value stored in advance in the measurement condition DB 42 in the present embodiment, and is an example of detection relation information in the present embodiment.

  In FIG. 9, the vibration peak P1 is at a position larger than the threshold Th2 and the threshold Th1. The vibration peak P3 is at a position larger than the threshold Th1 and at a position smaller than the threshold Th2. The vibration peak P4 is at a position smaller than the threshold Th1.

  As described above, since the reflected wave having the vibration peak P1, the vibration peak P3 and the vibration peak P4 respectively has information including a predetermined code, the vibration peak P1, the vibration peak P3 and the vibration peak P4 It is considered that the reflected waves having x are each a reflected wave of the ultrasonic wave oscillated by the piezoelectric element 31. Therefore, in the example of FIG. 9, it is a problem whether the vibration peak P3 and the vibration peak P4 are the reflected waves of the obstacle 91 or the reflected waves due to the unevenness 93 of the road 92.

Therefore, in the present embodiment, the control unit 1 can perform measurement with high accuracy regardless of the state of the road surface by selecting the threshold value corresponding to the road 90 currently being measured as follows.
At the time of measurement, the control unit 1 first acquires road surface information on the road currently being measured (traveled) from the road information server 61.

When the control unit 1 acquires, for example, information that the road 92 is a well-paved road as the road surface information, the control unit 1 compares the road surface information with the detection related information read from the measurement condition DB 42. Threshold Th1 is selected.
Next, the control unit 1 compares the threshold value Th1 with the line E2 as distance information.
In the case of FIG. 9, since the vibration peak P3 is larger than the threshold value Th1, it is determined that the reflected wave of the obstacle 91 is generated. On the other hand, since the vibration peak P3 is smaller than the threshold Th1, the vibration peak P3 is determined to be the unevenness 93 on the surface of the road 92.

On the other hand, when the control unit 1 acquires information that the road 92 is an unpaved road as the road surface information, the control unit 1 compares the road surface information with the detection related information read from the measurement condition DB 42. Threshold Th2 is selected.
Next, the control unit 1 compares the threshold value Th2 with the line E2 as distance information.
In the case of FIG. 9, since the vibration peak P3 and the vibration peak P4 are smaller than the threshold value Th2, it is determined to be the unevenness 93 on the surface of the road 92.

  Thus, the road surface information about the road 92 currently being measured is acquired from the road information server 61, the road surface information is compared with the detection relation information and the distance information, and the appropriate threshold is set (selected). Therefore, regardless of the road surface condition of the road 92, the measurement performance of the distance measuring device 100 can be measured with high accuracy regardless of the road surface condition, such as identifying and detecting the unevenness 93 of the road 92 and the obstacle 91. Can be improved.

[About transmission of distance information]
In the present embodiment, the control unit 1 transmits distance information to the road information server 61, and stores the distance information in the distance information DB 72. Specifically, the road information server 61 is configured to store the received distance information in the distance information DB 72 of the storage server 7 based on the request from the control unit 1.
Furthermore, in the present embodiment, when the acquired distance information changes a predetermined distance or more with respect to the distance information transmitted to the road information server 61 immediately before that, the control information is acquired immediately before that. While transmitting to the road information server 61, it is stored in the temporary storage DB 49.

  In the present embodiment, when acquiring the distance information (hereinafter referred to as latest information), the control unit 1 reads the distance information (hereinafter referred to immediately before information) transmitted to the road information server 61 immediately before from the temporary storage DB 49. Then, the control unit 1 compares the latest information with the immediately preceding information, and transmits the latest information to the road information server 61 if the latest information changes from the immediately preceding information by a predetermined amount or more. . On the other hand, the control unit 1 compares the latest information with the immediately preceding information, and does not transmit the latest information to the road information server 61 unless the latest information changes from the immediately preceding information by a predetermined amount or more. It has become like.

  Here, examples of the change more than a predetermined amount from the previous information include, for example, increase or decrease of the number of detected vibration peaks, increase or decrease of the average value of the detected amplitude, and the like.

  As described above, by transmitting the latest information to the road information server 61 only when the latest information changes with respect to the immediately preceding information, the amount of communication can be reduced. In addition, it is possible to update the information of the road information server by the necessary amount while avoiding an increase in the amount of communication and avoiding congestion of the communication network.

Hereinafter, the determination procedure as to whether the control unit 1 transmits the latest information to the road information server 61 will be described according to the flowchart of FIG.
When the piezoelectric element 31 of the distance measuring device 100 oscillates (step # 01), the control unit 1 acquires the latest information (step # 02).

  If the oscillation in step # 01 is the first oscillation after the start of traveling of the vehicle 200 (step # 03: Yes), the control unit 1 causes the vehicle communication unit 2 to update the road information server 61 with the latest information. The transmission is made (step # 06), and the latest information is stored in the temporary storage DB 49 (step # 07), and the determination is ended (step # 08).

If the oscillation of step # 01 is not the first oscillation (step # 03: No), the process proceeds to step # 04, and immediately preceding information is read out from the temporary storage DB 49 (step # 04).
When the latest information is different from the previous information by a predetermined amount or more, the process proceeds to step # 06.

  If the latest information does not differ from the previous information by a predetermined amount or more, the process proceeds to step # 08 and the determination is ended (step # 08).

  As described above, it is possible to provide a distance measurement device in which the measurement performance of distance measurement is improved.

[Another embodiment]
(1) In the above embodiment, although the resonance frequency of the piezoelectric element 31 is 40 kHz, the resonance frequency of the piezoelectric element 31 is not limited to this, and can be arbitrarily set in a sound range (frequency band) exceeding the audible range of human beings . Note that the range beyond the audible range of human beings refers to the range of ultrasonic waves in a frequency band of, for example, 20 kHz or more.

(2) In the above embodiment, the case where the modulator 32 modulates by simultaneously using two modulation methods of the phase modulation method and the amplitude modulation method has been described.
However, in addition to the two modulation methods of the phase modulation method and the amplitude modulation method, the modulator 32 may further modulate using a frequency modulation method simultaneously.
Alternatively, the modulator 32 may perform modulation using any one of a phase modulation method, an amplitude modulation method, and a frequency modulation method.

(3) In the above embodiment, the control unit 1 transmits the distance information to the road information server 61, and the road information server 61 receives the distance information as the distance information of the storage server 7 based on the request from the control unit 1. The case of storing in the DB 72 has been described.
However, if the control unit 1 transmits the distance information to the road information server 61, the road information server 61 voluntarily stores the distance information in the distance information DB 72 of the storage server 7 (without request from the control unit 1). You can also

(4) In the above embodiment, as the predetermined bit length, the case where the bit length is 8 bits is described.
However, the setting of the bit length is optional, and the bit length necessary for interference prevention can be selected. For example, the bit length may be 16 bits.

(5) In the above embodiment, when the acquired distance information changes by a predetermined amount or more with respect to the distance information transmitted to the road information server 61 immediately before, the distance acquired immediately before the control The case where information is transmitted to the road information server 61 is illustrated.
However, the control unit 1 can also transmit the acquired distance information to the road information server 61 each time it is acquired. Also, the control unit 1 obtains the acquired distance information. A plurality of times may be collectively sent to the road information server 61 for each of a plurality of times of acquisition.

(6) In the said embodiment, the case where the TOF sensor part 3 was equipped with the piezoelectric element 31 which oscillates an ultrasonic wave was illustrated.
However, instead of the piezoelectric element 31, a light emitting device such as an LED that emits light or a device that oscillates an electromagnetic wave such as a terahertz wave may be provided.

(7) In the above embodiment, in the description of the change of the detection condition, the control unit 1 selects the threshold value Th1 when acquiring information that the road 92 is a well paved road as the road surface information, The example which selects threshold value Th2 when acquiring the information that road 92 is an unpaved road was explained.
However, in addition to the information indicating that the road is a well-paved road and the information indicating that the road is a non-paved road as the road surface information, the control unit 1 also states that the information is a damaged paved road or a gravel road. More detailed road surface information can also be obtained. In this case, individual threshold values can be set corresponding to the respective detailed road surface information and stored in advance in the measurement condition DB 42. Then, these thresholds can be switched and selected in correspondence with the acquired detailed road surface information.

(8) In the above embodiment, as the control unit 1, the CPU 10 detects the detection relation information recorded in advance in the measurement condition DB 42 and the road currently measured, which is obtained from the road surface information DB 71 via the road information server 61. The case where the detection condition of the obstacle 91 on the road currently measured is compared with the road surface information of the above and the distance information which the TOF sensor part 3 acquired to detect the obstacle 91 is compared is illustrated. Moreover, the said road surface information illustrated that it was the information which classified the state of the road.
However, instead of acquiring road surface information, which is information obtained by classifying the state of a road, from the road surface information DB 71 via the road information server 61, the control unit 1 is assumed to acquire it if it measures the road currently being measured. It is also possible to acquire the ideal distance information (information of the reflected wave assumed to be received by the piezoelectric element 31) as road surface information.

(9) In the above embodiment, when the code is represented, for example, in the case of the phase modulation scheme, the same phase as the carrier represents a binary 1 and the phase shifted by π from the carrier represents a binary zero; The case where the minimum unit is two values was illustrated.
However, how to represent the code is not limited to the above example. The code can use other scale numbers, for example, decimal numbers in addition to binary numbers. In addition, modulation exceeding two values can be performed in each modulation method.

  Specifically, for example, in the case of the phase modulation method, the same phase as the carrier represents a decimal number (0), and thereafter the carrier and the phase shifted by π / 4 deviate one decimal number by π / 2. The phase may be expressed by four values such that the phase of 2 is a decimal number and the phase shifted by 3π / 4 is a decimal number 3. In this case, not a decimal number but a binary number may be used as in the above embodiment. For example, it represents the binary 00 in the same phase as the carrier, and thereafter, the binary 01 with a phase shifted by π / 4 and the carrier 10 with a binary 10 with a phase shifted by π / 2 by 3π / 4 The shifted phase can be made to represent a binary 11;

  Similarly, in the case of the amplitude modulation system and the frequency modulation system, other scale numbers other than binary numbers can be adopted, and modulation exceeding two values can also be performed. For example, in the case of the amplitude modulation method, four stages of amplitude gradations are set, and binary numbers 00, 01, 10, 11 or decimal numbers 0, 1, 2, 3 are represented. It can also be done. In addition, it is possible to set more levels and represent more than four values. Similarly, in the case of the frequency modulation method, it is also possible to set multi-step size frequency change to the carrier wave and represent multiple values.

(10) In the above embodiment, when modulation is performed by the amplitude modulation method, 50% of the amplitude of the binary number is assumed to be 100% when the amplitude is 100% with respect to the relatively large amplitude representing the binary 1 The case where modulation control is performed as a target amplitude in the case of representing zero, and an amplitude of 75% or less, which is an average value of 100% and 50%, is assumed to represent binary zero.
However, in the case where modulation is performed only by the amplitude modulation method, in the case of representing a binary zero, modulation control of the zero percent amplitude may be performed as a target amplitude in the case of representing a binary zero. In this case, for example, in the case of an amplitude of 50 percent or less, which is an average value of 100 percent and zero percent, binary zero may be represented.

(11) In the above embodiment, the TOF sensor unit 3 includes the piezoelectric element 31 that oscillates the ultrasonic wave, the oscillator 34 that oscillates the fundamental wave of the ultrasonic wave oscillated by the piezoelectric element 31, and the fundamental wave that the oscillator 34 oscillates. The modulator 32 can be modulated by a modulation method according to an instruction of the control unit 1, and the modulator 32 can be a phase modulation method, an amplitude modulation according to an instruction of the control unit 1. The case where the modulation wave is oscillated by any one of the method and the frequency modulation method or the combination thereof is illustrated.
However, the TOF sensor unit 3 does not necessarily have to include the modulator 32, and the modulator 32 does not necessarily have to oscillate the modulation wave. For example, the TOF sensor unit 3 can also oscillate an ultrasonic wave corresponding to the fundamental wave from the piezoelectric element 31.

  Note that the configurations disclosed in the above-described embodiment (including the other embodiments, and the same hereinafter) can be applied in combination with the configurations disclosed in the other embodiments as long as no contradiction arises. The embodiment disclosed in the present specification is an exemplification, and the embodiment of the present invention is not limited thereto, and can be appropriately modified without departing from the object of the present invention.

  The present invention is applicable to a distance measuring device.

1: Control unit 2: Vehicle-side communication unit 3: TOF sensor unit (distance sensor unit)
4: Vehicle-side storage unit 5: Navigation unit 7: Storage server 8: Environment sensor unit 9: Object 10: CPU
15: pulse generator 17: comparator 20: vehicle antenna 31: piezoelectric element 32: modulator 34: oscillator 35: detector 60: antenna for public communication 61: road information server 63: environment information server 70: external storage unit 90 : Road 91: Obstacle 92: Road 93: Irregularity 100: Distance measuring device 200: Vehicle 300: Vehicle DB 41: Map information DB 42: Measurement condition DB 43: Temporary storage DB 71: Road surface information DB 72: Distance information E1: Line E2: Line Ef : Line N: Internet P1: Vibration peak P2: Vibration peak P3: Vibration peak P4: Vibration peak T1: Oscillation time T2: Reverberation time Th1: Threshold value Th2: Threshold value W: Waveform

Claims (7)

A control unit that determines a detection condition of an obstacle on a road, a distance sensor unit that oscillates a vibration wave and receives distance information by receiving a reflection of the oscillated vibration wave;
A communication unit that communicates with the outside to acquire road surface information;
A storage unit storing detection related information for identifying the obstacle based on the distance information;
The control unit compares the detection relation information read from the storage unit with the distance information and the road surface information acquired from the distance sensor unit and the communication unit to determine the detection condition. Sensor.   The obstacle detection sensor according to claim 1, wherein the communication unit communicates with a road information server having an external storage unit storing the road surface information, and the control unit acquires the road surface information from the external storage unit.   The obstacle detection sensor according to claim 2, wherein the control unit transmits the distance information from the communication unit to the road information server, and causes the road information server to record the distance information in the external storage unit.   The control unit transmits the acquired distance information to the road information server when the acquired distance information changes a predetermined distance or more with respect to the distance information transmitted to the road information server immediately before that. The obstacle detection sensor according to claim 3. It has an environmental sensor unit that acquires environmental values,
The obstacle detection sensor according to any one of claims 2 to 4, wherein the control unit corrects the distance information based on an environmental value acquired by the environmental sensor unit. The communication unit communicates with an environmental information server that distributes environmental values;
The obstacle detection sensor according to any one of claims 2 to 5, wherein the control unit acquires an environmental value from the environmental information server and corrects the distance information based on the environmental value.   The obstacle detection sensor according to any one of claims 2 to 6, wherein the road information server is provided by cloud computing.

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