JPH0815430A - Detector for vehicle ground speed - Google Patents

Abstract

PURPOSE:To judge advance and reverse movements accurately with respect to a detector for vehicle ground speeds, which detects the ground speed based on a Doppler frequency. CONSTITUTION:First transmitter and receiver 1a and 1b are provided in the slant state toward the front side of the advancing direction of a vehicle, and second transmitter and receiver 2a and 2b are provided in the slant state toward the rear side of the advancing direction. First transmitting and receiving circuits 4 and 6 are provided in correspondence with the first transmitter and receiver 1a and 1b, and second transmitting and receiving circuits 5 and 7 are provided in correspondence with the second transmitter and receiver 2b. A first mixing circuit 8 and a first front/rear judging circuit 10 are provided in correspondence with the first transmitting and receiving circuits 4 and 6. A second mixing circuit 9 and a second front/rear judging circuit 11 are provided in correspondence with the second transmitting and receiving circuits 5 and 7. A CPU 12 judges the advancing direction of the vehicle based on the output signals of the front/rear judging circuits 10 and 11 of the system, wherein the greater Doppler signal is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground vehicle speed detecting device, and more particularly to a ground vehicle speed detecting device for detecting a ground vehicle speed based on a Doppler shift frequency.

[0002]

2. Description of the Related Art Conventionally, as a device for detecting the moving speed of a moving body, a device for emitting a transmission signal of a predetermined frequency and receiving a reflected wave thereof, based on a Doppler shift frequency detected as a frequency difference between the transmission and reception signals There is known a device that calculates a moving speed.

For example, Japanese Unexamined Patent Publication No. 62-100768 discloses a device for detecting the moving speed of a ship based on this principle. This device emits an ultrasonic signal of a predetermined frequency from the hull toward the sea surface, and tries to detect the ship speed based on the Doppler shift frequency superimposed on the reflected wave. In order to suppress the above, one set of ultrasonic transceivers is arranged in front of and behind the hull.

In this case, more information can be obtained regarding the Doppler shift frequency than in the case where only one set of transceivers is provided in front of the hull or at the rear of the hull, and the detection accuracy of the ship speed can be improved. Is.

By the way, the Doppler shift frequency superimposed on the received signal is influenced by the condition of the reflection path of the transmitted / received signal. For example, in the device described in the above publication, when the condition of the sea surface changes, the Doppler shift frequency changes with the change. Therefore, a Doppler shift frequency that does not correspond to the actual ship speed may be detected.

In particular, when the ship speed is very low, a Doppler shift frequency corresponding to the ship speed in the direction opposite to the actual traveling direction may occur. On the other hand, the value of the Doppler shift frequency itself is always detected as a positive value regardless of the traveling direction of the hull.Therefore, simply averaging the detected Doppler shift frequency will detect a larger ship side than it actually is. Occurs.

Therefore, in the device disclosed in the above publication, the polarity of the Doppler shift frequency, that is, whether the Doppler shift occurs in the positive direction or the negative direction with respect to the frequency of the transmission signal. In consideration of the above, when averaging the detected Doppler shifts, the positive Doppler shifts are added and the negative Doppler shifts are subtracted to detect the moving speed corresponding to the ship speed.

[0008]

However, since the above-mentioned conventional device has a structure in which one set of transmitters and receivers are provided in front of and behind the hull, and the above-mentioned processing is performed on each of the received signals obtained, For example, when the ship speed is extremely low and the hull is pitched, Doppler shifts indicating different traveling directions may be detected by the transmitters and receivers arranged in the front and rear.

In this case, it is not possible to specify which detection result should be prioritized by the above-mentioned conventional apparatus, and such a situation may occur relatively frequently when traveling at a very slow speed. However, after all, it was practically difficult to detect the moving speed when traveling at a very low speed by the above conventional device.

The present invention has been made in view of the above points, and the Doppler shift frequencies are respectively set for the transmitter / receiver inclined forward in the traveling direction and the transmitter / receiver inclined rearward in the traveling direction. Detecting and determining the traveling direction based on the received signal with the larger Doppler shift frequency, or by setting the frequency of the transmitting signal that is emitted from the transmitter inclined in the traveling direction forward or backward. Add or subtract frequencies to form a comparison frequency,
An object of the present invention is to provide a ground vehicle speed detecting device that solves the above-mentioned problems by calculating the vehicle speed based on the difference between the comparison frequency and the frequency of the received signal.

[0011]

1 and 2 show the principle configuration of a ground vehicle speed detecting device for achieving the above object.
That is, the above object is to provide a ground vehicle speed detecting device for detecting a ground vehicle speed based on the Doppler shift frequency as shown by a solid line in FIG. 1, and to provide a first transmitter M1a inclined forward with respect to the vehicle traveling direction. And a first receiver M1b,
A second transmitter M2a and a second receiver M2b, which are inclined rearward with respect to the vehicle traveling direction, and the first transmitter M1a.
Frequency of the transmission signal transmitted by the first receiver M1b
Received by the second receiver M2b and the DS1 detection means M3 for detecting the difference between the frequency of the received signal received by the receiver and the first Doppler shift frequency, the frequency of the transmitted signal transmitted by the second transmitter M2a, and the second receiver M2b. DS2 detecting means M4 for detecting a difference from the frequency of the received signal as a second Doppler shift frequency, and DS comparing means M for comparing the first Doppler shift frequency and the second Doppler shift frequency.
5 and the result of comparison by the DS comparison means M5, the first
The traveling direction determination means M6 for determining the traveling direction of the vehicle based on a reception signal which is recognized to have a large Doppler shift frequency among reception signals received by the receiver M1b and the second receiver M2b. This is achieved by the ground vehicle speed detection device.

Further, as shown by a solid line and a broken line in FIG.
The ground speed detecting device according to claim 1, wherein the D
As a result of the comparison by the S comparing means M5, when it is recognized that the first Doppler shift frequency is higher than the second Doppler shift frequency, the first Doppler shift frequency and the second Doppler shift frequency are compared. If the second Doppler shift frequency is found to be higher than the first Doppler shift frequency as a result of comparison by the climbing deviation detection means M7 for detecting deviation and the DS comparison means M5, the second Doppler shift frequency is detected. Downward deviation detecting means M8 for detecting a deviation between the shift frequency and the first Doppler shift frequency, and based on the detection results of the ascending deviation detecting means M7 and the downward deviation detecting means M9 within a predetermined time, The ground vehicle speed detection device according to claim 2, further comprising a slope determination means M9 for performing slope determination, based on the Doppler shift frequency. It is effective to make the road determination.

Further, the above-mentioned purpose is as shown in FIG.
A ground vehicle speed detection device including a transmitter M11 that emits a transmission signal of a predetermined frequency supplied from the transmission signal generation means M10 to a road surface, and a receiver M12 that receives a reflected wave of the transmission signal from the road surface as a reception signal. In the above, the comparison frequency forming means M13 for forming a comparison frequency by adding or subtracting a predetermined frequency to the frequency of the transmission signal generated by the transmission signal generating means M10 and the difference between the frequency of the reception signal and the comparison frequency are calculated. It is also achieved by the ground vehicle speed detection device according to claim 3, further comprising a pseudo DS detection means M14 for detecting as a pseudo Doppler shift frequency and a ground vehicle speed calculation means M15 for detecting a ground vehicle speed based on the pseudo Doppler shift frequency.

[0014]

In the invention according to claim 1, the DS1 detecting means M3 includes the first transmitter M1a and the first receiver M.
The Doppler shift frequency formed with 1b is detected. On the other hand, the DS2 detection means M4 detects the Doppler shift frequency formed between the second transmitter M2a and the second receiver M2b.

By the way, the Doppler shift frequency detected corresponding to the vehicle is detected within an appropriate frequency band around the actual vehicle speed. Therefore, for example, when the vehicle is moving forward at a slight speed, the Doppler shift frequency indicating that the vehicle is temporarily moving backward may be detected.

On the other hand, the Doppler shift frequency to be superimposed on the reception signal received by the first receiver M1b, and the second Doppler shift frequency.
The Doppler shift frequency superimposed on the reception signal received by the receiver M2b is not necessarily the same, and there is a case where a larger Doppler shift frequency is likely to be superimposed on one reception signal depending on the vehicle attitude or the like. is there.

In this case, in determining the traveling direction of the vehicle, it is preferable to use a received signal on which a larger Doppler shift frequency is superimposed, that is, to use a received signal for detecting a higher vehicle speed. This is advantageous in preventing erroneous determination of the traveling direction.

On the other hand, the DS comparison means M5 is
The first Doppler shift frequency detected by the DS1 detection means M3 and the second Doppler shift frequency detected by the DS2 detection means M4 are compared.

Based on the comparison result, the traveling direction judging means M6 selects the received signal on which the larger Doppler shift frequency is superimposed to judge the traveling direction of the vehicle. Therefore, the traveling direction determination means M6
The determination result of is accurately matched with the actual traveling direction.

According to the second aspect of the present invention, the irradiation angle of the transmission signal emitted from the first transmitter M1a becomes more perpendicular to the road surface as the nose of the vehicle dives on a downhill road or the like. On the other hand, the irradiation angle of the transmission signal emitted from the second transmitter M2a becomes more perpendicular to the road surface as the nose of the vehicle lifts on an uphill road or the like.

In this case, the first transmitter M1
a, the second transmitter M1b, and the first receiver M1
b, the second receiver M2b has directivity with respect to the transmission / reception signal, and the more vertically the transmission signal is emitted, that is, the more the reception signal is reflected vertically from the road surface, the more the Doppler shift frequency is superimposed in the reception signal. The smaller the component.

Therefore, when the vehicle is traveling on an uphill road, the first Doppler shift frequency is large on average, while when the vehicle is traveling on a downhill road, the above-mentioned first Doppler shift frequency is on average. A large second Doppler shift frequency is detected.

On the other hand, the climb deviation detecting means M7
Detects the deviation when the first Doppler shift frequency is larger than the second Doppler shift frequency, and the downlink deviation detecting means M8 determines that the second Doppler shift frequency is the first Doppler shift frequency. If it is larger than the Doppler shift frequency, the deviation is detected.

Therefore, when the vehicle is traveling on an uphill road, the deviation between the first and second Doppler shift frequencies is mainly detected by the uphill deviation detecting means M7, and the vehicle is traveling on a downhill road. In this case, the deviation between the first and second Doppler shift frequencies is mainly detected by the downlink deviation detecting means M8.

Then, the slope judging means M9 compares the detection result of the ascending deviation detecting means M7 with the detection result of the descending deviation detecting means M8 over a predetermined period, and as a whole, the first Doppler shift frequency is the first. If it is recognized that it is larger than the Doppler shift frequency of 2, it is determined that the traveling road is an uphill road, and conversely, the first Doppler shift frequency is the second
If it is recognized that the whole is smaller than the Doppler shift frequency of, the traveling road is determined to be a downhill road.

In this case, the determination result of the slope determining means M9 appropriately reflects the vehicle attitude on the uphill road or the downhill road, and as a result, the highly accurate slope determination can be performed.

In the invention described in claim 3, the transmitter M11 receives a signal supplied from the transmission signal generating means M10 and transmits a transmission signal of a predetermined frequency. Then, the receiver M12 receives the reception signal on which the Doppler shift frequency corresponding to the vehicle speed is superimposed.

On the other hand, the comparison frequency forming means M13 is
A predetermined frequency is added to or subtracted from the frequency of the transmission signal to form the comparison frequency. As a result, even when no Doppler shift frequency is superimposed on the received signal, an appropriate frequency difference is generated between the frequency of the received signal and the comparison frequency.

The pseudo DS detecting means M14 detects the difference between the frequency of the received signal and the comparison frequency, and supplies the value as the pseudo Doppler shift frequency to the ground vehicle speed calculating means M15.

In this case, the frequency of the received signal always changes in the region smaller than the comparison frequency or in the region always exceeding the comparison frequency regardless of whether the vehicle is moving forward or backward, and the pseudo Doppler shift frequency is , Shows a continuous increase and decrease with respect to changes in vehicle speed, including forward and backward movements of the vehicle.

In the ground vehicle speed calculating means M15, the Doppler shift superimposed on the reception signal is generated in the positive direction or in the negative direction with respect to the frequency of the transmission signal. Directly from the pseudo Doppler shift frequency, without considering
Vehicle speed calculation including forward / backward movement of the vehicle is performed.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a block diagram of a ground vehicle speed detecting device according to an embodiment of the present invention.

In the figure, a first transmitter 1a and a first receiver 1b are ultrasonic transmitters / receivers which are provided in a tilted manner in front of the vehicle. Further, the second transmitter 2a and the second receiver 2b are ultrasonic transmitters / receivers that are provided to be inclined toward the rear of the vehicle.

Here, these first transceivers 1a, 1b,
And the second transmitter / receiver 2a, 2b respectively includes the first and second transceivers.
The reflected wave of the transmission signal emitted from the transmitters 1a and 2a toward the road surface 3 is the first or second receiver 1 as the reception signal.
The positional relationship between the two is adjusted so that they are propagated to b and 2b.

A first transmission circuit 4 and a second transmission circuit 5 are connected to the first and second transmitters 1a and 2a, respectively. The first and second transmission circuits 4 and 5 are circuits that generate a transmission signal of a predetermined frequency, and an oscillation circuit that generates a reference frequency, a frequency dividing circuit that converts the oscillation signal into a predetermined frequency, and a signal after frequency division. Is constituted by an amplifier circuit or the like for amplifying to a predetermined output.

On the other hand, a first receiving circuit 6 or a second receiving circuit 7 is connected to the first and second receivers 1b and 2b, respectively. These first and second receiving circuits are circuits for amplifying the received signals received by the first and second receivers 1b, 2b into a signal-processable state, and include a bandpass filter and an amplifying circuit. Composed.

Further, the first receiving circuit 6 and the second receiving circuit 7
Are respectively connected to the first mixing circuit 8 or the second mixing circuit 9. Furthermore, the first mixing circuit 8
A signal having the same frequency as the transmission signal in each system is supplied from the first transmission circuit 4 or the second transmission circuit 5 to the second mixing circuit 9.

Here, as shown in FIG. 4, the first mixing circuit 8 receives the transmission signal from the first transmitter 1a and the first transmission signal.
A mixing unit 8a that mixes with the received signal received by the receiver 1b to generate a signal including a low frequency component corresponding to the frequency difference between the two, passing only the low frequency component from the mixed signal, and It is a circuit including an LPF / amplifier 8b for amplification and a comparator 8c for converting an output signal of the LPF / amplifier 8b into a pulse signal.

In this case, in the mixing section 8a, the Doppler shift frequency (hereinafter, referred to as the Doppler shift frequency) superimposed on the received signal while the signal is transmitted and received between the first transmitter 1a and the first receiver 1b.
A signal including a low frequency component corresponding to the first Doppler shift frequency is formed, and therefore the comparator 8c outputs a pulse signal generated in a cycle corresponding to the first Doppler shift frequency (hereinafter , This signal is referred to as the first Doppler signal).

The configuration of the second mixing circuit 9 is also the same as that of the first mixing circuit 8 described above. Therefore, from the second mixing circuit 9, the second transmitter 2a and the second receiver 2b are connected.
The Doppler shift frequency (hereinafter referred to as the second
A pulse signal generated in a cycle corresponding to the Doppler shift frequency) is output (hereinafter, this signal is referred to as a second Doppler signal).

In the present embodiment, the first front-back determination circuit 10 is connected to the first transmission circuit 4 and the first reception circuit 6.
However, a second front-back determination circuit 11 is connected to the second transmission circuit 5 and the second reception circuit 7, respectively.

The first front-rear determination circuit 10 determines whether the vehicle is moving forward or backward based on the signal supplied from the first transmitting circuit and the signal supplied from the first receiving circuit 6. Further, it is a circuit that issues a forward / backward determination signal (hereinafter referred to as a first front / rear determination signal) according to the determination result. Specifically, as shown in FIG. 5, the signal supplied from the first receiving circuit 6 is F F / V converter 10a for V / V conversion, F / V for F / V conversion of the signal supplied from the first transmission circuit 4
V converter 10b and F / V converters 10a and 10 thereof
This is realized by the forward / backward determination comparator 10c that compares the value of b.

That is, while the vehicle is running, the first
In the process in which the transmission signal emitted from the transmitter 1a reaches the first receiver 1b, the Doppler shift frequency fd corresponding to the vehicle speed is superimposed on the reception signal.

When the vehicle travels leftward in FIG. 1 (forward direction), the Doppler shift frequency fd is superimposed in the direction of increasing the frequency of the received signal as shown in FIG. On the other hand, a reception signal having a center frequency of F + fd is detected, and when the vehicle travels to the right in FIG. 1 (reverse direction), a reception signal having a center frequency of F-fd is received as shown in FIG. The signal is detected.

Here, as shown in FIGS. 6A and 6D, the frequency spread is formed in the received signal at the first position.
This is due to various factors such as the directivity of the transmitter 1a having a certain degree of spread and the influence of the road surface condition when the transmission signal is diffusely reflected on the road surface.
When the / V conversion is performed, the output voltage becomes a voltage corresponding to the average frequency of the received signal, that is, a voltage corresponding to the frequency F + fd or F-fd.

Therefore, in this embodiment, the output terminal of the F / V converter 10a shown in FIG. 5 is indicated by a broken line in FIG. 6 (B) or FIG. 6 (E) corresponding to the traveling direction of the vehicle. On the other hand, a voltage appears, and at the output terminal of the F / V converter 10b, the voltage indicated by the solid line in FIGS. 6B and 6E stably appears in any case.

Therefore, the forward / reverse determination comparator 10c for comparing the output voltage of the F / V converter 10a with the output voltage of the F / V converter 10b indicates that the vehicle is moving forward and the Doppler shift fd is in the positive direction. If it occurs in Figure 6
As shown in FIG. 6C, a “low” level signal is output, and when the vehicle is moving backward and the Doppler shift fd is in the negative direction, a “high” level signal is output as shown in FIG. 6 (F). It will be output respectively.

In this case, these "low" and "high" signals form the above-mentioned first forward / backward determination signal, and it is monitored whether the signal is "high" level or "low" level. As a result, forward / backward determination based on the reception signal received by the first receiver 1b can be realized.

Further, the second front-back determination circuit 11 has the above-mentioned first
It is a circuit having substantially the same hardware configuration as the front-back determination circuit 10, and the vehicle is moving forward or backward based on the signal supplied from the second transmitting circuit and the signal supplied from the second receiving circuit 7. It is a circuit that determines whether or not the vehicle is moving, and further outputs a forward / backward determination signal (hereinafter referred to as a second front / back determination signal) according to the determination result.

However, in response to the fact that the second transceivers 2a and 2b are provided so as to be inclined rearward in the traveling direction, when the vehicle moves forward, the received signal whose center frequency is F-fd is Since the received signals having the center frequency of F + fd are formed when moving backward, the connection between the forward / backward determination comparator and the two F / V converters is of a polarity opposite to that of the configuration shown in FIG.

Therefore, the second front / back determination circuit 11 also
A "low" level signal is output when the vehicle is moving forward, and a "high" level signal is output when the vehicle is moving backward. By monitoring the values, the forward / backward movement based on the received signal received by the second receiver 2b is performed. The judgment can be realized.

Here, the above-mentioned first mixing circuit 8,
The second mixing circuit 9, the first front-rear determination circuit 10, and the second front-rear determination circuit 11 are connected to the arithmetic unit (CPU) 12. Then, the CPU 12 performs forward / backward determination, slope determination, and slope gradient value calculation based on these output signals. Hereinafter, the specific operation of the CPU 12 and the characteristic operation of the ground vehicle speed detecting device according to the present embodiment will be described.

FIG. 7 is a flowchart showing an example of a routine executed by the CPU 12 to make a forward / backward determination. Here, the CPU 12 includes the first front-back determination circuit 1 as described above.
The first and second forward / backward determination signals are supplied from 0 and the second front / rear determination circuit 11, respectively. The ground vehicle speed detection device of this embodiment is characterized in that these two forward / backward determination signals are appropriately selected and used according to the logic described later.

That is, when the routine shown in FIG. 7 is started, first, at step 100, the first mixing circuit 8 is started.
The first Doppler signal DS1 output from the second mixing circuit 9 is read, and then the second Doppler signal DS2 output from the second mixing circuit 9 is read in step 102.

Next, at step 104, the above-mentioned pole read DS1 and DS2 are compared, and DS1 ≧ DS
It is determined whether or not 2 holds. That is, when determining the traveling direction of the vehicle, as described above, the frequency F of the transmission signal,
The frequency of the received signal is compared and the Doppler shift frequency f
It is necessary to judge whether d is superposed in the direction of increasing the frequency or superposed in the direction of decreasing the frequency.

The frequency of the received signal is as shown in FIG.
As described above, there is a certain extent of spread as shown in (D), but as in this embodiment, the frequency F of the transmission signal is compared with the center frequency F + fd or F-fd of the reception signal to determine the traveling direction. When making a determination, naturally, a larger fd is advantageous in preventing erroneous determination.

Therefore, when a signal indicating forward and backward movement of the vehicle is output from the first front / rear determination circuit 10 and the second front / rear determination circuit 11 as in the present embodiment, the received signal on which a larger Doppler shift frequency is superimposed is received. The judgment result based on the above should be used with priority.

Therefore, in step 104, D
When it is determined that S1 ≧ DS2 is established, it is determined that forward / backward determination should be performed based on the first forward / backward signal output from the first front / rear determination circuit 10, and the step 1
In step 106, the value FR1 of the first forward / backward movement determination signal is read, FR1 is stored as the forward / backward movement determination output TFR in the subsequent step 108, TFR is further output in step 110, and this processing is ended.

In step 104, DS1
When it is determined that ≧ DS2 is not established, it is determined that the forward / backward determination should be performed based on the second forward / backward signal output from the second front / rear determination circuit 11, and step 1
In step 12, the value FR2 of the second forward / backward movement determination signal is read, FR2 is stored as the forward / backward movement determination output TFR in the subsequent step 114, and the processing of step 110 is executed to end this routine.

In this case, the forward / backward determination output TFR is always based on the signal that is advantageous for preventing the erroneous detection of the forward / backward determination from the two received signals having different detection paths. Therefore, according to the ground vehicle speed detection apparatus of the present embodiment, the traveling direction of the vehicle can be accurately determined even in the situation where the first forward / backward determination signal and the second forward / backward determination signal output different determination results. Is possible.

In this embodiment, the first mixing circuit 8 is connected to the above-mentioned DS1 detecting means M3, the second mixing circuit 9 is connected to the above-mentioned DS2 detecting means M4, and the first and second front-back determination circuits 10 and 11 are provided. And the CPU 12 to the above-mentioned traveling direction determination means M6, and the CPU 12 to the above-mentioned DS.
Each corresponds to the comparison means M5.

By the way, the above-described effects of the ground vehicle speed detecting device of this embodiment are effective when a steady difference occurs between the first Doppler shift frequency DS1 and the second Doppler shift frequency DS2.

That is, the first transceivers 1a, 1b and the second
The transmitters / receivers 2a and 2b are different from each other only in the inclination direction, and should be originally detected as DS1 = DS2. In such a situation, there is no superiority or inferiority to the determination accuracy of the forward / backward determination between the first forward / backward determination signal and the second forward / backward determination signal, and any forward / backward determination signal can be used to determine the forward / backward determination. There should be no significant difference in accuracy.

However, the first transceivers 1a, 1b,
The second transceivers 2a and 2b have directivity with respect to the transmission and reception sensitivity, and there is a difference between the elevation angles of the first transceivers 1a and 1b with respect to the road surface and the elevation angles of the second transceivers 2a and 2b with respect to the road surface. If so, the result is a difference between DS1 and DS2.

That is, FIG. 8 shows the directivity of the first transmitter 1a. As shown in FIG. 8, the transmission signal is output with great intensity in the vertical direction. On the other hand, the reason why the Doppler shift is superimposed on the received signal is that the propagation paths of the transmitted signal and the received signal are expanded and contracted microscopically as the vehicle moves. Specifically, in FIG. This is because the transmission distance L of the transmission signal traveling at the irradiation angle θ expands or contracts by the change in the horizontal component L sin θ.

Therefore, the larger the horizontal component L sin θ of the propagation path L, that is, the larger the irradiation angle θ,
A large Doppler shift is superimposed on the signal propagating along the propagation path. Then, the more the intensity of the transmission signal emitted from the first transmitter 1a is concentrated in the direction in which the irradiation angle θ is large, the larger the Doppler shift is detected in the reception signal received by the first receiver 1b.

That is, when the inclination angle of the first transmitter 1a with respect to the road surface normal is θa, the relationship between the first Doppler shift frequency DS1 and θa is as shown in FIG. There is a rising relationship and the inclination angle θa
The larger DS1 is, the larger DS1 is detected.

Therefore, the vehicle attitude changes while the vehicle is running, and the inclination angles of the first transceivers 1a and 1b and the second transceiver 2 are changed.
If there is a difference between the inclination angles of a and 2b, there will be a difference in the sizes of DS1 and DS2.
Since superiority or inferiority in detection accuracy occurs between the forward / backward movement determination signal and the second forward / backward movement determination signal, the function of the above-described embodiment works effectively.

By the way, the relationship between the above-mentioned tilt angle of the first transceiver and DS1, and the tilt angle of the second transceiver and DS2.
By using the relationship with, it is possible to accurately perform slope determination.

That is, in the vehicle, the wheels and the vehicle body are connected by the suspension mechanism in order to absorb the traveling vibration. Therefore, if the vehicle is traveling on a flat road in the neutral position, a lift occurs on the vehicle body nose on an uphill road where the center of gravity shifts to the rear, while on the downhill road where the center of gravity shifts to the front, Dive occurs on the nose.

Therefore, the slope of the running road and the DS
1 and DS2, as shown in FIG. 10 (A), when the road surface is flat, the relationship of DS1 = DS2 is established (see FIG. 10 (B)), and as shown in FIG. 11 (A). When the road surface is an uphill road, the relationship of DS1> DS2 is established as a whole (see FIG. 11 (B)), and FIG. 12 (A).
When the road surface is a downhill road as shown in Fig.
The relationship of 1 <DS2 is established (see FIG. 12B).

Therefore, if DS1 and DS2 are compared over a predetermined period while the vehicle is running and the magnitude relationship between them is grasped, the relationship corresponds to the slope condition of the road surface, and a high grade hill judgment can be made. It can be realized.

FIG. 13 shows the CPU 12 according to such a principle.
6 is a flowchart of an example of a routine that is executed to perform slope determination. The CPU 12 executes this routine to implement the ground vehicle speed detecting device according to the second embodiment of the present invention.

When the routine shown in FIG. 13 is started, first, in step 200, the counter COUNT for counting the number of times of measurement is incremented, and then in step 202,
At 204, DS1 and DS2 are read respectively. Then, in step 206, it is determined whether DS1 ≧ DS2 is satisfied to determine an instantaneous road surface gradient.

As a result, when DS1 ≧ DS2 is established, it is highly possible that the situation shown in FIG.
In step 208, the deviation between DS1 and DS2 is calculated as the climbing deviation DSU, and in step 210, the cumulative value DU of the climbing deviation is calculated.

On the other hand, in step 206, DS
If it is determined that 1 ≧ DS2 is not established, it is highly possible that the situation shown in FIG.
Proceed to step 12, and move the deviation between DS2 and DS1 to the down deviation DSD.
Further, in step 214, the cumulative value DD of the downlink deviation is calculated.

After these processes are completed, it is then determined in step 216 whether COUNT has reached the predetermined value N. If COUNT ≧ N is not satisfied, a sufficient number of calculation is still required to perform the slope determination. It is determined that the process has not been performed, and thereafter, the process of shifting to step 200 is repeatedly executed. If CPUNT ≧ N is satisfied, it is determined that the calculation of the predetermined number of times is completed, and then the process proceeds to step 218.

At step 218, it is judged whether the deviation between the average value "DU / N" of the climbing deviation and the average value "DD / N" of the descending deviation exceeds a predetermined judgment value TH. If the above conditions are not satisfied, the routine proceeds to step 220, where the deviation between the average value "DD / N" of the downward deviation and the average value "DU / N" of the upward deviation exceeds a predetermined judgment value TH. To determine.

Here, the condition "(D
The condition of (U / N)-(DD / N)> TH "is satisfied when the climb deviation DU exceeds the predetermined level and is detected unevenly. In this case, the state of FIG. It can be determined that the climbing slope has continued for a predetermined period.

On the other hand, the condition "(DD
/ N)-(DU / N)> TH "is satisfied when the downward deviation DD is detected in excess of a predetermined level, and in this case, the state of FIG. It can be determined that the slope has continued for a predetermined period.

Therefore, if the condition of step 218 is satisfied, the process proceeds to step 222 and a judgment that the road is an uphill road is output, while if it is judged in step 220 that the condition is satisfied, then The process proceeds to step 228 to output the determination that the road is a downhill road. If none of these conditions is satisfied, it is determined that the traveling road is a flat road, and COUNT is set to "0" in step 234.
To reset the process to the end.

By the way, in this embodiment, after the judgment of the gradient direction of the traveling road is completed, the slope gradient is calculated based on the uphill slope DD and the downhill slope DU, and step 222 is executed as described above. If so, then in step 224, the ascending deviation DU and the descending deviation D
The average value of the D differences is stored as the Doppler shift difference average value UF, and the slope gradient is calculated based on the UF in step 226, and then the process proceeds to step 234.

When step 228 is executed, the average value of the difference between the down deviation DD and the up deviation DU is stored in step 230 as the Doppler shift difference average value DF, and then based on DF in step 232. After performing the processing to calculate the slope gradient, step 23
Go to 4.

Here, the relationship between the UF and DF and the road surface gradient can be experimentally grasped in advance according to the suspension characteristics of the vehicle, and in this embodiment,
The map stored in the relation is used for the above steps 226 and 232.
The slope gradient will be obtained by referring to.

As a result, according to this embodiment, the first Doppler shift frequency DS1 detected by the first transceivers 1a and 1b and the second Doppler shift frequency DS2 detected by the second transceivers 2a and 2b are set. Based on this, it is possible to accurately detect the gradient direction and the magnitude of the gradient of the traveling road surface, and it is possible to further enhance the usefulness as a ground vehicle speed detection device.

In this embodiment, the CPU 12 executes the step 206 in FIG. 13 so that the D
The S comparing means M5 executes the steps 208, 210 and 216, the climb deviation detecting means M7 executes the steps 212, 214 and 216, the down deviation detecting means M8, and the steps 218 and 22.
By executing 0, 222, and 228, the slope determining means M9 is realized.

Next, an embodiment of the invention described in claim 3 will be described.

FIG. 14 is a block diagram of a ground vehicle speed detecting device which is an embodiment of the invention described in claim 3. In the figure, a transmitter 21 and a receiver 22 are arranged to transmit and receive an ultrasonic signal of a predetermined frequency through the road surface 3, and the traveling direction is the same as that of the second transceivers 2a and 2b described above. A certain inclination is given to the rear.

The transmitter 21 includes an amplifier 23 and a frequency divider 2
4 and an oscillator 25 are connected to the transmission system.
Here, the frequency divider 24 is a circuit that appropriately divides the frequency f ₀ signal supplied from the oscillator 25 and outputs the signal. In the present embodiment, the frequency fs signal is supplied to the amplifier 23. Further, it has a function of supplying a signal of frequency fc (= fs + Δfs) to a mixing circuit 27 described later.

The receiver 22 is connected to a receiving system including an amplifier 26, a mixing circuit 27, and a low pass filter (LPF) 28. Here, the mixing circuit 27
Is a circuit for generating a signal including the frequency difference between the two supplied signals as a low frequency component. In this embodiment, the received signal of the frequency fr supplied through the amplifier 26 and the above-mentioned separated signal are separated. Frequency fc supplied from the frequency divider 24
A signal including the frequency difference fc−fr = fd ′ of the signal of 1 as the low frequency component is generated.

Therefore, at the output terminal of the LPF 28 for extracting only the low frequency component from the output signal of the mixing circuit 28, a signal varying at the frequency fd '= fc-fr appears.

By the way, FIG. 15 shows signals of various frequencies handled in the ground vehicle speed detecting device of this embodiment as spectrum intensities. FIG. 15A shows the frequency fd of the received signal when the vehicle is moving forward. FIG. 3B shows a state in which the Doppler shift is superimposed, and FIG. 6B shows a state in which the Doppler shift of the frequency fd is superimposed on the received signal when the vehicle moves backward.

In this case, the Doppler shift fd can be detected as a difference between the frequency fs of the transmission signal and the frequency fr of the reception signal, and the vehicle moves forward (the vehicle speed is positive) as shown by the broken line in FIG. Regardless of (the vehicle speed is negative), the value is proportional to the absolute value of the vehicle speed. Therefore, if the mixing circuit 27 transmits the transmission signal of the frequency fs and the frequency fr.
If the received signal is mixed with the received signal, the LPF 28 outputs a signal without distinction between forward and backward movements.

On the other hand, from the frequency dividing circuit 24 to the mixing circuit 2
When the frequency fc of the comparison signal supplied to 7 and the frequency fr of the received signal are compared, the difference fd 'between them is Δfs + fd when the vehicle is moving forward as shown in FIG. As shown in, when the vehicle moves backward, Δfs-f
It can be expressed as d, and can be understood as a variable that continuously changes with respect to the positive or negative of the vehicle speed, as shown by the solid line in FIG. 16, in relation to the vehicle speed.

In this case, the signal output from the LPF 28 is a pseudo Doppler signal which can be continuously treated before and after the vehicle speed "0" and the Doppler shift fd is reflected, and its frequency fd 'must be detected. Thus, it becomes possible to detect the vehicle speed including the traveling direction of the vehicle.

In this sense, the ground vehicle speed detecting device of the present embodiment can easily and reliably perform forward / backward judgment as compared with a device which mixes the transmission signal of the frequency fs and the reception signal of the frequency fr as they are. It has the advantage of

Further, the pseudo Doppler shift frequency fd 'in this embodiment has a value around Δfs in the vicinity of the vehicle speed "0", and becomes a relatively high frequency signal even when the vehicle speed is extremely low. Therefore, as compared with the case where the Doppler shift frequency fd is directly monitored, it is possible to detect a large number of amplitude fluctuations within a predetermined sampling time. In this sense, the ground vehicle speed detection device of this embodiment also has an advantage that it is effective for improving the vehicle speed detection accuracy at low speeds.

By the way, in this embodiment, the LPF2
When a pseudo Doppler signal is obtained as the output signal of 8,
From the viewpoint of facilitating the handling as an electric signal, the signal is F / V converted into a signal representing a vehicle speed at 0 to 5 V (hereinafter referred to as a vehicle speed signal).

In this case, in order to increase the resolution of the vehicle speed signal, it is easiest to widen the voltage variation range (0 to 5 V), but since it is necessary to send and receive signals to and from other electronic devices, Such changes are virtually impossible.

Therefore, in this embodiment, as shown in FIG.
As indicated by a broken line therein, an F / V converter 29 that generates a voltage signal corresponding to the vehicle speed based on the pseudo Doppler signal, and a frequency divider 24 based on the output signal of the F / V converter 29 Dividing ratio switch 3 that issues a command to change the dividing ratio
By setting 0, Δfs is changed according to the vehicle speed to improve the resolution of the vehicle speed signal.

That is, FIG. 17 shows Δ in the present embodiment.
An example of the pseudo Doppler shift frequency fd ″ when fs is appropriately switched is shown. As shown in the figure, in the present embodiment, Δfs changes from 20 kHz to −10 kHz as the vehicle speed increases. The normal vehicle speed range (-
At 50 km / h to 200 km / h), fd ″ is always within the range of 5 kHz to 15 kHz.

In this case, for example, as shown in FIG. 16, in order to cover the normal vehicle speed range, the resolution is about three times as high as that in the case where the pseudo Doppler shift frequency fd 'changes in a width of about 0 to 30 kHz. It will be improved.

That is, if the F / V converter 29 and the frequency division ratio switch 30 are additionally provided in the ground vehicle speed detecting apparatus of the present embodiment, the accuracy of vehicle speed detection at low speed running can be improved. In addition to this, it is possible to obtain the effect that the detection accuracy can be improved in the entire vehicle speed range.

In this embodiment, the amplifier 23
F of the shaker 25 and the frequency divider 24 ₀To fs
A part of the frequency divider 24 is provided in the transmission signal generating means M10 described above.
Out of f₀Is divided into fc (= fs + Δfs)
The above-mentioned comparison frequency forming means M13 includes a mixing circuit.
27 and lpf28 are added to the pseudo DS detecting means M14 described above.
Each is equivalent.

[0105]

As described above, according to the first aspect of the present invention, the reception signal received by the first receiver which is inclinedly arranged in front of the vehicle and the inclined signal is arranged rearward of the vehicle. It is determined which of the received signals received by the second receiver has a larger Doppler shift frequency,
According to the determination, the traveling direction of the vehicle can be determined based on the received signal on which the larger Doppler shift frequency is superimposed among the two received signals.

Therefore, according to the present invention, even when the vehicle is traveling at a very low speed, even when the Doppler shift frequency indicating the traveling direction different from the actual traveling direction is easily detected by one of the receivers, it is stable and accurate. It is possible to determine a proper traveling direction.

According to the second aspect of the present invention, the first Doppler shift frequency becomes higher than the second Doppler shift frequency as the nose of the vehicle lifts, and the first doppler shift frequency becomes higher as the nose of the vehicle dives. Corresponding to the fact that the Doppler shift frequency of 2 becomes larger than the first Doppler shift frequency, the possibility that the road surface on which the vehicle is running is an uphill road is taken as an uphill deviation, and the possibility that it is a downhill road is taken as a downhill deviation. Each is detected. Then, by comparing the deviations over a predetermined period, it is possible to perform the slope determination more accurately while enjoying the same effect as that of the invention described in claim 1.

Further, according to the third aspect of the present invention, a pseudo frequency which is grasped as a difference between the comparison frequency and the reception signal frequency is formed by subtracting the predetermined frequency from the addition frequency of the transmission signal to form a comparison frequency. The vehicle speed is calculated based on the Doppler shift frequency. For this reason,
It is possible to uniquely calculate the vehicle speed from the pseudo Doppler shift frequency including the reverse, and it is possible to easily and accurately determine the traveling direction of the vehicle and detect the vehicle speed even when traveling at a very low speed. .

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of the invention according to claims 1 and 2. FIG.

FIG. 2 is a principle configuration diagram of the invention according to claim 3;

FIG. 3 is a block configuration diagram of a ground vehicle speed detecting device that is an embodiment of the invention described in claims 1 and 2.

FIG. 4 is a block configuration diagram of a mixing circuit in an embodiment of the invention described in claims 1 and 2.

FIG. 5 is a block configuration diagram of a front-back determination circuit in an embodiment of the invention described in claims 1 and 2.

FIG. 6 is a diagram for explaining the operation of the front-back determination circuit in one embodiment of the invention described in claims 1 and 2;

FIG. 7 is a flowchart of an example of a routine executed by a CPU to implement the invention of claim 1.

FIG. 8 is a diagram for explaining directivity of a transmitter.

FIG. 9 is a characteristic diagram showing a relationship between a transmitter inclination angle θa and a detected Doppler shift frequency DS1.

FIG. 10 is a diagram for explaining Doppler shift frequency characteristics on a flat road.

FIG. 11 is a diagram for explaining Doppler shift frequency characteristics on an uphill road.

FIG. 12 is a diagram for explaining Doppler shift frequency characteristics on a downhill road.

FIG. 13 is a flowchart of an example of a routine executed by a CPU to implement the invention of claim 2;

FIG. 14 is a block configuration diagram of a ground vehicle speed detecting device which is an embodiment of the invention described in claim 3;

FIG. 15 is a diagram showing a frequency spectrum of a signal handled by the ground vehicle speed detection device which is an embodiment of the present invention.

FIG. 16 is a diagram for explaining an example of the operation of the ground vehicle speed detection device according to the third embodiment of the invention.

FIG. 17 is a diagram for explaining another example of the operation of the ground vehicle speed detecting device according to the third embodiment of the invention.

[Explanation of symbols]

 M1a, 1a 1st transmitter M1b, 1b 1st receiver M2a, 2a 2nd transmitter M2b, 2b 2nd receiver M3 DS1 detecting means M4 DS2 detecting means M5 DS comparing means M6 advancing direction determining means M7 climbing deviation detecting means M8 Downward deviation detecting means M9 Slope judging means M10 Transmission signal generating means M11,21 Transmitter M12,22 Receiver M13 Comparison frequency forming means M13 M14 Pseudo DS detecting means M15 Ground vehicle speed calculating means 8 First mixing circuit 9 Second mixing circuit 10 1st front-back determination circuit 11 2nd front-back determination circuit 12 CPU 24 frequency divider 27 mixing circuit 28 low-pass filter (LPF) DS1 1st Doppler shift frequency DS2 2nd Doppler shift frequency FR1 1st forward / backward determination value FR2 2nd forward Reverse judgment value TRF Forward / backward judgment output SU, DSD Doppler shift frequency deviation DU climb deviation DD down deviation

Claims (3)

[Claims] 1. A ground vehicle speed detecting device for detecting a ground vehicle speed based on a Doppler shift frequency, comprising: a first transmitter and a first receiver which are inclined forward with respect to a vehicle traveling direction; On the other hand, a second transmitter and a second receiver which are inclined rearward, and a difference between the frequency of the transmission signal transmitted by the first transmitter and the frequency of the reception signal received by the first receiver are calculated. DS1 detecting means for detecting as a first Doppler shift frequency; a difference between a frequency of a transmission signal transmitted by the second transmitter and a frequency of a reception signal received by the second receiver; And a DS2 detecting means for comparing the first Doppler shift frequency with the second Doppler shift frequency, and a result of the comparison by the DS comparing means, the first receiver and A vehicle ground speed detection device, comprising: a traveling direction determination means for determining a traveling direction of the vehicle based on a reception signal recognized as having a high Doppler shift frequency among reception signals received by the second receiver. 2. The ground vehicle speed detecting device according to claim 1, wherein, when it is recognized that the first Doppler shift frequency is higher than the second Doppler shift frequency as a result of comparison by the DS comparing unit, As a result of the comparison by the climbing deviation detecting means for detecting a deviation between the first Doppler shift frequency and the second Doppler shift frequency, and the DS comparing means, the second Doppler shift frequency is the first Doppler shift frequency. Downward deviation detecting means for detecting a deviation between the second Doppler shift frequency and the first Doppler shift frequency when it is recognized to be larger, and the ascending deviation detecting means and the downward deviation detection within a predetermined time. A ground vehicle speed detecting device comprising: a slope determining means for determining a slope of a traveling road based on a detection result of the means. . 3. A vehicle ground speed including a transmitter that emits a transmission signal of a predetermined frequency supplied from the transmission signal generating means to a road surface, and a receiver that receives a reflected wave of the transmission signal from the road surface as a reception signal. In the detection device, a comparison frequency forming means for forming a comparison frequency by adding or subtracting a predetermined frequency to the frequency of the transmission signal generated by the transmission signal generating means, and a difference between the frequency of the reception signal and the comparison frequency. A ground vehicle speed detection device comprising: a pseudo DS detection means for detecting as a pseudo Doppler shift frequency; and a ground vehicle speed calculation means for detecting a ground vehicle speed based on the pseudo Doppler shift frequency.