Speed detecting device and method

Abstract

According to the present invention: a continuous sine wave signal is emitted toward an object serving as a target; a reflected wave comprising the sine wave signal reflected by the object is received; a frequency component of the sine wave signal that has been Doppler-shifted in accordance with the relative speed of a moving body and the object is extracted from the received reflected wave and output as a Doppler shift signal; a plurality of Doppler shift signals having a second duration are generated by cutting out, at a plurality of mutually different timings within a predetermined time period, a part of the Doppler shift signal having a predetermined first duration corresponding to the predetermined time period; a Doppler velocity for each of the Doppler shift signals having the first and second durations are calculated on the basis of the Doppler shift signals having the first and second durations; and the speed of the moving body in the current time period is determined on the basis of the calculated Doppler velocities of each of the Doppler shift signals having the first and second durations.

Description

Vehicle speed detection device and method

[0001] The present invention relates to a vehicle speed detection device and method, and is suitable for application to a vehicle speed detection device that detects the speed of a vehicle such as a railway vehicle.

[0002] In the railway business, safe running of vehicles and accurate train operation are important. For safe running of vehicles, monitoring of vehicle speed is essential, especially monitoring of vehicle speed in scenes such as stops at stations and curves. Also, in urban areas, train schedules are becoming more detailed, and monitoring of vehicle speed is also required for accurate train operation. In addition, in tunnels and subways, etc., since GPS (Global Positioning System) information cannot be obtained, accurate vehicle speed information is required for vehicle position detection.

[0003] Conventionally, for speed detection of railway vehicles, a method of measuring the rotation speed of wheels by a speed generator attached to the wheels and calculating the speed from the rotation speed of the wheels has been widely used. However, in this method, there is a problem that accurate speed may not be detected due to wheel spin. Therefore, in recent years, research and development of a speed detection method using millimeter waves has been advanced as a method for avoiding the influence of wheel spin and detecting accurate speed.

[0004] As such a speed detection method using millimeter waves, a method of irradiating a sine wave of millimeter waves from a speed detection device installed on a vehicle to a rail and detecting the speed from the Doppler shift amount of the sine wave reflected from the rail is disclosed in Patent Document 1.

[0005] JP-A-2014-21075, JP-A-2015-226297, JP-A-2006-337,025

[0006] However, according to this method, the Doppler shift amount changes according to the irradiation angle of the millimeter waves irradiated from the speed detection device to the rail. Therefore, in order to detect accurate vehicle speed, it is necessary to irradiate the rail with millimeter waves at a designed known irradiation angle and within a narrow angle range.

[0007] In this regard, for example, Patent Document 2 discloses an antenna that generates a narrow-angle beam capable of irradiating a narrow angular range, in which a patch antenna is formed on a substrate and a lens antenna is placed on top of it.

[0008] In this case, a large lens antenna is required to generate a narrow-angle beam in such an antenna. However, when applying this method to railway vehicles, it is difficult to install a large antenna because the space at the bottom of the vehicle directly above the rails is limited. For this reason, an antenna with a beam width is actually installed, but when a beam width is used, there is a problem in that a speed detection error occurs corresponding to the beam width.

[0009] As a method to suppress such velocity detection errors, for example, Patent Document 3 discloses a method of taking a moving average when performing a Fourier transform on the Doppler shift amount. However, this method has the problem that a delay equal to the time length required to calculate the moving average occurs in velocity detection.

[0010] This invention was made in consideration of the above points, and aims to propose a velocity detection device and method that can accurately detect the velocity of a moving object in real time by suppressing velocity detection errors caused by fluctuations in Doppler shift due to the influence of the antenna beam width.

[0011] To solve the above problems, the present invention provides a speed detection device for detecting the speed of a moving object, comprising: an antenna unit mounted on the moving object that emits a continuous sinusoidal wave signal toward a target object, receives the reflected wave of the sinusoidal wave signal at the target object, extracts the frequency components of the sinusoidal wave signal that have been Doppler-shifted according to the relative speed of the moving object and the target object from the received reflected wave object and outputs them as a Doppler-shifted signal; and a plurality of second timings obtained by cutting out a portion of the Doppler-shifted signal of a predetermined first time length corresponding to a predetermined time period within a predetermined time period, at a plurality of different timings. The system includes a cutting unit that generates the Doppler shift signal for a given time length, a Fourier transform unit that performs a Fourier transform on each of the first and second time length Doppler shift signals, a Doppler velocity detection unit that calculates the Doppler velocity for each of the first and second time length Doppler shift signals based on the Fourier transformed signals, and a velocity determination unit that determines the velocity of the moving object in the current time period based on the calculated Doppler velocity for each of the first and second time length Doppler shift signals.

[0012] Furthermore, the present invention relates to a speed detection method performed in a speed detection device for detecting the speed of a moving object, comprising: a first step of emitting a continuous sinusoidal wave signal toward a target object, receiving the reflected wave of the sinusoidal wave signal at the object, and extracting the frequency components of the sinusoidal wave signal that have been Doppler-shifted from the received reflected wave according to the relative speed of the moving object and the object, and outputting them as a Doppler-shifted signal; and a plurality of second time intervals obtained by cutting out a portion of the Doppler-shifted signal of a predetermined first time length corresponding to the time period at a plurality of different timings within a predetermined time period. The system includes a second step of generating a Doppler shift signal of a given time length, a third step of performing a Fourier transform on each of the first and second time length Doppler shift signals, a fourth step of calculating the Doppler velocity for each of the first and second time length Doppler shift signals based on the Fourier-transformed signals, and a fifth step of determining the velocity of the moving object in the current time period based on the calculated Doppler velocity for each of the first and second time length Doppler shift signals.

[0013] According to the velocity detection device and method of the present invention, the Doppler velocity calculated based on each Doppler shift signal of the second time length is reflected in the global Doppler velocity calculated based on the Doppler shift signal of the first time length to calculate the final Doppler velocity.

[0014] According to the present invention, a speed detection device and method can be realized that can accurately detect the speed of a moving object in real time.

[0015] (A) and (B) are schematic diagrams illustrating the vehicle speed detection principle according to this embodiment. These are waveform diagrams illustrating fading. These are diagrams illustrating update cycle data and update cycle partial data. This is a block diagram illustrating the configuration of the vehicle speed detection device according to this embodiment. (A) to (C) are waveform diagrams illustrating experimental results using the vehicle speed detection device according to this embodiment.

[0016] An embodiment of the present invention will be described in detail below with reference to the drawings.

[0017] (1) As shown in the principle diagram 1(A), we consider a vehicle speed detection device 3 that irradiates millimeter waves toward a target 1 such as the ground or rails and detects the speed of the vehicle 2 based on the reflected waves. Here, we assume that the vehicle speed detection device 3 is installed on the bottom of a vehicle 2 such as a railway vehicle.

[0018] The Doppler velocity Vdpr detected by this vehicle speed detection device 3 is given by the following equation, where θ is the angle between the vehicle speed Vcar and the direction of illumination. It can be expressed as follows. Note that "Doppler velocity" here refers to the velocity of the vehicle speed detection device 3 with respect to the direction of emission of millimeter waves.

[0019] In this vehicle speed detection device 3, if the transmitting antenna and receiving antenna for sending and receiving millimeter waves are separate, the calculation of the Doppler velocity Vdpr becomes complicated because the irradiation angle of the millimeter waves on the target 1 and the reception angle of the millimeter waves on the receiving antenna are different. Therefore, this problem can be solved by connecting the millimeter wave transmitting and receiving units with a circulator circuit and making the transmitting and receiving antennas common.

[0020] Furthermore, if the angular range of the millimeter waves irradiating target 1 is very narrow, like a pencil beam, then in (1), "θ" can be treated as a constant, and the Doppler velocity Vdpr is uniquely determined. However, as mentioned above, a huge antenna is required to generate a narrow-angle pencil beam.

[0021] However, considering the size of the antenna that can typically be installed on the bottom of vehicle 2, it is difficult to generate a narrow-angle pencil beam. In reality, the antenna will have a certain beam width, and therefore the range of millimeter waves illuminating target 1 will also have a certain degree of spread.

[0022] As shown in Figure 1(B), when the irradiation range R of the millimeter waves irradiated onto the target 1 has a range from θ-δ to θ+δ, the Doppler velocity Vdpr is detected by the vehicle speed detection device 3 with an error range corresponding to this range. For example, if the irradiation angle θ of the millimeter waves on the target 1 is 45 degrees and the beam width of the antenna is ±5 degrees, the detected Doppler velocity Vdpr will have an error range of -9% to +8% because the range of θ in cosθ is 40 to 50 degrees.

[0023] Furthermore, since the received waveform of the antenna is a superposition of waveforms with different Doppler shift amounts, a fading waveform like the one shown in Figure 2 is output from the antenna. This fading waveform is represented by the dashed line K in the figure. １ A momentary drop in amplitude occurs in the area enclosed by the box, making it difficult to detect the received waveform in such areas.

[0024] Therefore, in this embodiment, in order to avoid detection errors of the Doppler velocity Vdpr caused by the beam width of millimeter waves and undetected received waveforms due to fading, the vehicle speed detection device 3 uses all available data of the fading waveform acquired within the period in which it detects the vehicle speed Vcar (for example, 25 milliseconds, hereinafter referred to as the update period) (hereinafter referred to as the update period data), as well as data extracted from parts of this update period data at different timings (hereinafter referred to as update period partial data), to detect the vehicle speed Vcar.

[0025] Specifically, in this embodiment, as shown in Figure 3 for example, Fourier transforms are performed on "Data 1," which is the maximum amount of data available for data processing from all the fading waveform data acquired within the update cycle period, excluding the time spent storing the data in memory, and on "Data 2" to "Data 6," which are portions of "Data 1" extracted at different timings and with a time length sufficiently shorter than the time length of "Data 1."

[0026] Furthermore, based on the Fourier transform results of "Data 1" to "Data 6", the peak frequency is f ０ c is the speed of light, and f is the frequency of millimeter waves. ｄAs follows, Based on this, the Doppler velocity Vdpr' is calculated for each of the "Data 1" to "Data 6" values.

[0027] Furthermore, each Doppler velocity Vdpr' obtained in this way is weighted according to its reliability.

[0028] For example, in Figure 2, the dashed line K １ As shown in the area enclosed by the dashed line K, in places where instantaneous amplitude drops occur due to fading, signals with low received power due to a decrease in antenna gain at the millimeter-wave beam edge of target 1 are strongly affected. １ Using the data in the enclosed area will increase the error in the detected vehicle speed Vcar.

[0029] Therefore, in this embodiment, the Doppler velocity Vdpr' derived from the Fourier transform of the update cycle data ("Data 1" in Figure 3) and the Doppler velocity Vdpr' derived from partial data ("Data 2" to "Data 6" in Figure 3) extracted from the update cycle data at different timings are weighted with a magnitude corresponding to the peak power after the Fourier transform or the signal power before the Fourier transform.

[0030] Specifically, for example, in Figure 2, the dashed line K １ For the update cycle portion data that includes time periods when the received power is low, as shown in the enclosed area, the weight is reduced, while in Figure 2, the dashed line K ２ As shown in the enclosed area, the update cycle data that includes time periods when the received power is high is given a greater weight. This weighting helps to suppress errors associated with the antenna beamwidth and the effects of amplitude drops in the received signal due to fading.

[0031] Furthermore, since the vehicle speed Vcar changes continuously with time, tracking allows for the estimation of the vehicle speed Vcar for the next update cycle. A well-known tracking method uses a Kalman filter, which can be used to estimate the vehicle speed Vcar for the next update cycle. In addition to the Kalman filter, another method for estimating the vehicle speed Vcar is to estimate the vehicle speed Vcar for the next update cycle using the average value of past vehicle speed Vcars and acceleration information.

[0032] In this embodiment, the estimated value of the vehicle speed Vcar in the next update cycle, which is estimated by this tracking process, is also used to set the weight of the Doppler speed Vdpr' calculated based on the "Data 1" to "Data 6" described above.

[0033] Specifically, the vehicle speed Vcar for the next update cycle is estimated by tracking processing, and the Doppler speed Vdpr for the next update cycle is estimated using equation (1) based on this estimated value. The closer the Doppler speed Vdpr' obtained based on the Fourier transform results of "Data 1" to "Data 6" in Figure 3 is to the estimated value of this Doppler speed Vdpr (hereinafter referred to as the estimated Doppler speed), the higher the reliability of the Doppler speed Vdpr'. Therefore, in this embodiment, the closer the Doppler speed Vdpr' obtained based on the Fourier transform results is to the estimated Doppler speed based on the vehicle speed Vcar obtained by tracking processing for "Data 1" to "Data 6", the greater the weight given to "Data 1" to "Data 6".

[0034] In this embodiment, the final Doppler velocity Vdpr is calculated by taking the average of the weighted Doppler velocities Vdpr', and based on the calculated Doppler velocity Vdpr, the following equation is used: This detects the vehicle speed (Vcar).

[0035] As described above, the detection error of the vehicle speed Vcar caused by fluctuations in Doppler shift due to the influence of the antenna beam width can be suppressed within the update cycle. Below, a vehicle speed detection device according to this embodiment, which applies this principle, will be described.

[0036] (2) Configuration diagram of the vehicle speed detection device according to this embodiment FIG. 4 shows the vehicle speed detection device 10 according to this embodiment. This vehicle speed detection device 10 includes an antenna unit 11 installed at the bottom of the vehicle, and an arithmetic unit 12 that calculates the vehicle speed Vcar based on the output from the antenna unit 11.

[0037] The antenna unit 11 has, for example, a synthesizer 20 that generates a sine wave signal in the millimeter wave band of 76 GHz, and continuously emits the beam of the sine wave signal generated by the synthesizer 20 from a transmitting antenna 22 via an amplifier 21, and irradiates a target object 1 (FIG. 1(A)).

[0038] Further, the antenna unit 11 receives a part of the reflected wave obtained by the reflection of the beam of this sine wave signal by the target 1 with a receiving antenna 23. At this time, the received signal received by the receiving antenna 23 is a sine wave signal Doppler-shifted according to the relative speed between the target 1 and the vehicle speed detection device 10.

[0039] This received signal is down-converted by a mixer 25, which is a high-frequency converter, via an amplifier 24. Here, a sine wave signal generated by the synthesizer 20 is given as the local signal of the mixer 25. Therefore, from the mixer 25, a frequency component Doppler-shifted according to the relative speed between the vehicle 2 (FIG. 1) and the target object 1 (FIG. 1) among the reflected waves of the sine wave signal received by the receiving antenna 23 is output. In the following, this frequency component of the sine wave signal is called a Doppler shift signal.

[0040] Then, after the high-frequency components of the Doppler shift signal above a predetermined frequency are removed by a filter 26, they are converted into digital signals by an A / D (Analog / Digital) converter 27 and transmitted to the arithmetic unit 12.

[0041] In the arithmetic unit 12, the data of the Doppler shift signal given from the antenna unit 11 is stored in units of the update period for detecting the vehicle speed Vcar. Note that the data of the Doppler shift signal stored at this time is data for the maximum time length available for data processing excluding the time for storing the data in the memory as described above. Then, the data in units of the stored update period is given as update period data D1 to a Fourier transformer 31 provided corresponding to the update period data D1.

[0042] Also, the update period data D1 is given to each of a plurality of data extraction units 30 provided. Each data extraction unit 30 extracts a part of the update period data D1 at mutually different timings and with the same time length sufficiently shorter than the update period data D1, like the "data 2" to "data 6" described above with respect to FIG. 3. Further, each data extraction unit 30 outputs the above-described update period partial data D2 obtained by such extraction to a Fourier transformer 31 provided in association with itself.

[0043] Note that each update period partial data D2 may have a partial overlap in the time zone of the data with the update period partial data D2 at the timings before and after, as shown in FIG. 3, but a plurality of update period partial data D2 are generated so as to cover from the first time to the last time of the update period data D1. That is, the update period partial data D2 is generated such that all parts of the update period data D1 are dispersed and included in any one of the update period partial data D2.

[0044] The Fourier transformer 31 Fourier-transforms the given update period data D1 or update period partial data D2, and outputs the update period data (hereinafter referred to as Fourier-transformed update period data) D3 in the frequency domain or the update period partial data (hereinafter referred to as Fourier-transformed update period partial data) D4 in the frequency domain thus obtained to a Doppler speed detection unit 32 and a level detection unit 33 provided in association with itself.

[0045] The Doppler velocity detection unit 32 extracts the peak frequency from the Fourier transform update period data D3 or the Fourier transform update period partial data D4 provided by the Fourier transform 31, and calculates the Doppler velocity Vdpr' based on the extracted peak frequency using equation (2) above. The Doppler velocity detection unit 32 then outputs the calculated Doppler velocity Vdpr' to the weight calculation unit 35 and the multiplication circuit 36, respectively, which are provided in the weighting processing unit 34, in association with itself.

[0046] Furthermore, the level detection unit 33 detects the peak frequency power (hereinafter referred to as peak power) PV from the Fourier transform update period data D3 or the Fourier transform update period partial data D4 provided by the Fourier transform converter 31, and outputs the detected peak power PV to the weight calculation unit 35 provided in the weighting processing unit 34, associating it with itself.

[0047] Furthermore, as will be described later, each weight calculation unit 35 is given an estimated Doppler velocity EVdpr by the tracking velocity estimation unit 39, which is the estimated Doppler velocity EVdpr.

[0048] Thus, the weight calculation unit 35 calculates a weight W for the corresponding Fourier transform update period data D3 or Fourier transform update period partial data D4 based on the Doppler velocity Vdpr' provided by the corresponding Doppler velocity detection unit 32, the peak power PV provided by the corresponding level detection unit 33, and the estimated Doppler velocity EVdpr provided by the tracking velocity estimation unit 39, and outputs the calculation result to the multiplication circuit 36 ​​associated with the weight calculation unit 35.

[0049] Specifically, for example, the weight calculation unit 35, which is associated with the Fourier transform update cycle data D3, calculates the vehicle speed Vcar from the Doppler speed Vdpr detected by the Doppler speed detection unit 32 in the current update cycle using equation (3) above, and takes the calculated vehicle speed Vcar as S, and then the following equation This calculates the weight W for the update period data D3 after the Fourier transform, and outputs the calculated weight W to the corresponding multiplication circuit 36.

[0050] Furthermore, each weight calculation unit 35, which is associated with the updated period partial data D4 after the Fourier transform, is calculated using the following formula: This calculates the weight W for the corresponding Fourier transform-post-update period portion data D4, and outputs the calculated weight W to the corresponding multiplication circuit 36.

[0051] Incidentally, in equations (4) and (5) above, "Vdpr' - EVdpr" is the error between the estimated Doppler velocity EVdpr estimated by the tracking velocity estimation unit 39 and the corresponding Doppler velocity Vdpr' detected by the Doppler velocity detection unit 32. Therefore, in equations (4) and (5), the peak power PV is multiplied by the reciprocal of the error so that the larger the error, the smaller the weight W becomes.

[0052] The multiplication circuit 36 ​​multiplies the Doppler velocity Vdpr' provided by the corresponding Doppler velocity detection unit 32 by the weight W provided by the corresponding weight calculation unit 35, and outputs the multiplication result as the weighted detected Doppler velocity WVdpr' to the average value calculation unit 37. The average value calculation unit 37 also calculates the average value of the weighted detected Doppler velocity WVdpr' provided by each multiplication circuit 36, and outputs the calculation result as the final Doppler velocity Vdrp to the vehicle speed determination unit 38.

[0053] The vehicle speed determination unit 38 then calculates the vehicle speed Vcar for the current update cycle using equation (3) above, based on the Doppler speed Vdpr provided by the average value calculation unit 37, and outputs the calculated vehicle speed Vcar to the outside, as well as to the tracking speed estimation unit 39.

[0054] The tracking speed estimation unit 39 estimates the Doppler velocity in the next update cycle using an existing tracking method, for example, one that utilizes a Kalman filter. Specifically, it estimates the vehicle speed Vcar for the next cycle by inputting the vehicle speed Vcar provided by the vehicle speed determination unit 38 into the Kalman filter, and then estimates the Doppler velocity for the next cycle based on the estimated vehicle speed Vcar. The tracking speed estimation unit 39 then outputs the estimated Doppler velocity as the estimated Doppler velocity EVdpr to each weight calculation unit 35 of the weighting processing unit 34.

[0055] Based on this estimated Doppler velocity EVdpr, the weights of the Doppler velocity Vdpr' calculated based on the update cycle data D1 in the next update cycle, as well as the weights of the Doppler velocity Vdpr' calculated based on each update cycle partial data D2, are calculated as described above.

[0056] However, if the vehicle speed Vcar provided by the vehicle speed determination unit 38 is below a predetermined threshold speed (for example, 2 km / h), the tracking speed estimation unit 39 instructs the weight calculation unit 35 corresponding to the Fourier transform update period data D3 to set the weight W to "1", and instructs the weight calculation unit 35 corresponding to each Fourier transform update period partial data D4 to set the weight W to "0".

[0057] In addition, the tracking speed estimation unit 39 instructs the average value calculation unit 37 to output the weighted detected Doppler speed WVdpr', which is provided by the weight calculation unit 35 corresponding to the Fourier transform update period data D3, directly to the vehicle speed determination unit 38.

[0058] In this case, the weighted detected Doppler velocity WVdpr' provided by the multiplication circuit 36 ​​corresponding to the Fourier transform-post-update period data D3 is output directly to the vehicle speed determination unit 38 as the final Doppler velocity Vdrp, and the vehicle speed determination unit 38 calculates the vehicle speed Vcar based on this Doppler velocity Vdrp.

[0059] In the case of a low vehicle speed Vcar, the reason for providing the vehicle speed determination unit 38 with the weighted detected Doppler speed WVdpr calculated based on the Fourier transform update period data D3 as the final Doppler speed Vdrp is as follows:

[0060] When the vehicle speed Vcar is slow, the amount of Doppler shift is small. Also, the longer the data length of the update cycle data, the more the low-frequency region of the Doppler shift can be detected, making it possible to detect low vehicle speeds. Therefore, in this embodiment, when the vehicle speed Vcar determined by the vehicle speed determination unit 38 is low, the vehicle speed Vcar is calculated using only the Doppler speed Vdpr' detected based on the Fourier-transformed update cycle data D3, thereby effectively suppressing errors.

[0061] However, instead of setting the weight in the weight calculation unit 35 corresponding to each Fourier transform update period portion data D4 to "0", if the vehicle speed Vcar given by the vehicle speed determination unit 38 is a low speed below a predetermined threshold speed, the tracking speed estimation unit 39 may control each weight calculation unit 35 to increase the weight W calculated by equation (4) in the weight calculation unit 35 corresponding to the Fourier transform update period data D3, and decrease the weight W calculated by equation (5) in each weight calculation unit 35 corresponding to each Fourier transform update period portion data D4.

[0062] Figures 5(A) to 5(C) show examples of vehicle speed Vcar detection results when the beam width is ±5 degrees. Figure 5(A) shows the results of detecting the vehicle speed Vcar using the method of this embodiment, and the standard deviation error of the detected vehicle speed Vcar was approximately 0.12 km / h.

[0063] Figure 5(B) shows the results of detecting the vehicle speed Vcar using only the update cycle data D1. Compared with the results in Figure 5(A), the detected vehicle speed Vcar fluctuates, and the standard deviation error of the detected vehicle speed Vcar was 0.31 km / h.

[0064] Furthermore, Figure 5(C) shows the results of calculating the vehicle speed Vcar based on the simple average of the Doppler velocities Vdpr' calculated from the Fourier transform results of "Data 1" to "Data 6" in Figure 3, without weighting these Doppler velocities Vdpr'. Similar to Figure 5(B), a comparison with the results in Figure 5(A) reveals that the detected vehicle speed Vcar is fluctuating. The standard deviation error of the detected vehicle speed Vcar at this time was approximately 0.28 km / h.

[0065] From the results shown in Figures 5(A) to (C) above, it was confirmed that the error in the detected vehicle speed Vcar can be suppressed by weighting the Doppler speed Vdpr' calculated based on the update cycle data D1 and the Doppler speed Vdpr' calculated based on each update cycle partial data D2 with a weight W corresponding to the reliability of the update cycle partial data D2.

[0066] (3) Effects of this embodiment As described above, the vehicle speed detection device 10 of this embodiment generates update cycle partial data D2 by extracting a portion of the update cycle data D1 at different timings, and calculates the Doppler velocity Vdpr' based on the Fourier transformed update cycle data D3 and the Fourier transformed update cycle partial data D4 obtained by Fourier transforming the update cycle data D1 and the update cycle partial data D2, respectively. The vehicle speed detection device 10 also weights these calculated Doppler velocities Vdpr' with a weight W of a magnitude corresponding to their reliability, calculates the final Doppler velocity Vdpr based on each weighted Doppler velocity Vdpr', and determines the vehicle speed Vcar based on that Doppler velocity Vdpr.

[0067] According to the vehicle speed detection method of this embodiment, the Doppler speed Vdpr' calculated based on update cycle partial data D2, which has a shorter time duration, is reflected in the overall Doppler speed Vdpr' within the update cycle calculated based on update cycle data D1, thereby correcting the Doppler speed Vdpr' calculated based on update cycle data D1.

[0068] In this case, the global Doppler velocity Vdpr' within the update cycle, calculated based on the update cycle data D1, is greatly influenced by the update cycle partial data D2 from reliable time periods within the update cycle, whereas the fluctuations in the Doppler shift have only a small influence on the update cycle partial data D2 from less reliable time periods within the update cycle.

[0069] Therefore, the vehicle speed detection method of this embodiment can significantly suppress speed detection errors caused by fluctuations in Doppler shift resulting from the beam width of the sinusoidal signal emitted from the antenna unit 11. Furthermore, the vehicle speed detection method of this embodiment can calculate the vehicle speed Vcar for each update cycle within that update cycle, so there is no delay in detecting the vehicle speed Vcar. Thus, this vehicle speed detection method can accurately detect vehicle speed in real time.

[0070] (4) Other Embodiments In the embodiments described above, the present invention was described in the case where it is applied to a vehicle speed detection device for detecting the speed of a vehicle. However, the present invention is not limited to this and can be broadly applied to speed detection devices for detecting the speed of moving objects other than vehicles, such as elevators.

[0071] Furthermore, although the above-described embodiment mentions a case where the entire vehicle speed detection device 10 is mounted on the vehicle, the present invention is not limited to this, and the calculation unit 12 may be installed in a location other than the vehicle. In this case, the calculation unit 12 may be configured not as a single computer device, but as a distributed computing system composed of multiple computer devices.

[0072] Furthermore, although the above-described embodiment mentions a case where all update cycle portion data D2 are generated with the same time length, the present invention is not limited to this, and some or all of each update cycle portion data D2 may have different time lengths.

[0073] The present invention can be widely applied to speed detection devices of various configurations for detecting the speed of a moving object.

[0074] 10...Vehicle speed detection device, 11...Antenna unit, 12...Calculation unit, 30...Data extraction unit, 31...Fourier transformer, 32...Doppler velocity detection unit, 33...Level detection unit, 34...Weighting processing unit, 35...Weight calculation unit, 36...Multiplication circuit, 37...Average value calculation unit, 38...Vehicle speed determination unit, 39...Tracking speed estimation unit, D1...Update cycle data, D2...Update cycle partial data, D3...Update cycle data after Fourier transform, D4...Update cycle partial data after Fourier transform, PV...Peak voltage, Vcar...Vehicle speed, Vdpr, Vdpr'...Doppler velocity, W...Weight.

Claims

1. A speed detection device for detecting the speed of a moving object, comprising: an antenna unit mounted on the moving object that emits a continuous sinusoidal wave signal toward a target object, receives the reflected wave of the sinusoidal wave signal at the target object, extracts the frequency components of the sinusoidal wave signal that have been Doppler-shifted from the received reflected wave according to the relative speed of the moving object and the target object, and outputs them as a Doppler-shifted signal; an extraction unit that generates a plurality of Doppler-shifted signals of second time lengths by extracting a portion of the Doppler-shifted signal of a predetermined first time length corresponding to the time period at a plurality of different timings within a predetermined time period; a Fourier transform unit that performs a Fourier transform on each of the first and second time length Doppler-shifted signals; and a Doppler speed detection unit that calculates the Doppler velocity for each of the first and second time length Doppler-shifted signals based on the Fourier-transformed first and second time length Doppler-shifted signals. A speed detection device comprising a speed determination unit that determines the speed of the moving object in the current time period based on the Doppler velocity for each of the first and second time lengths of the Doppler shift signals calculated.

2. The speed detection device according to claim 1, wherein the first time length is the maximum time length for which the Doppler shift signal can be used within a predetermined time period, and each of the Doppler shift signals of the second time length is generated such that all parts of the Doppler shift signal of the first time length are distributed and included in any of the Doppler shift signals of the second time length.

3. The velocity detection device according to claim 2, further comprising a weighting processing unit that weights the Doppler velocity calculated based on the Doppler shift signal of the first time length and each of the Doppler velocities calculated based on each of the Doppler shift signals of the second time length, according to the reliability of the calculated Doppler velocities.

4. The speed detection device according to claim 3, further comprising a level detection unit that detects the peak voltages of the first and second time-length Doppler shift signals, respectively, which have been Fourier transformed, wherein the weighting processing unit weights each of the first and second time-length Doppler shift signals with a weight of a magnitude corresponding to the magnitude of the peak voltage of the Fourier-transformed Doppler shift signal.

5. The velocity detection device according to claim 3 or 4, further comprising a Doppler velocity estimation unit that estimates the Doppler velocity based on the velocity of the moving body determined by the velocity determination unit, wherein the weighting processing unit weights the corresponding Doppler shift signals of the first time length and the Doppler shift signals of the second time length by a weight corresponding to the difference between the Doppler velocity calculated by the Doppler velocity detection unit based on the Doppler shift signals of the first and second time lengths and the Doppler velocity estimated by the Doppler velocity estimation unit.

6. A speed detection method performed in a speed detection device for detecting the speed of a moving object, comprising: a first step of emitting a continuous sinusoidal wave signal toward a target object, receiving the reflected wave of the sinusoidal wave signal at the object, extracting the frequency components of the sinusoidal wave signal that have been Doppler-shifted from the received reflected wave according to the relative speed of the moving object and the object, and outputting them as a Doppler-shifted signal; a second step of generating a plurality of Doppler-shifted signals of second time lengths by cutting out a portion of the Doppler-shifted signal of a predetermined first time length corresponding to a predetermined time period at a plurality of different timings within a predetermined time period; a third step of performing a Fourier transform on each of the first and second time length Doppler-shifted signals; and a fourth step of calculating the Doppler velocity for each of the first and second time length Doppler-shifted signals based on the Fourier-transformed first and second time length Doppler-shifted signals. A speed detection method characterized by comprising a fifth step of determining the speed of the moving object in the current time period based on the Doppler velocity for each of the first and second time lengths of the Doppler shift signals that have been calculated.

7. The velocity detection method according to 6, characterized in that the first time length is the maximum time length for which the Doppler shift signal can be used within a predetermined time period, and each of the Doppler shift signals of the second time length is generated such that all parts of the Doppler shift signal of the first time length are distributed and included in any of the Doppler shift signals of the second time length.

8. The speed detection method according to claim 7, characterized in that, in the fourth step, the speed detection device weights the Doppler velocity calculated based on the Doppler shift signal of the first time length and each of the Doppler velocities calculated based on each of the Doppler shift signals of the second time length according to the reliability of the calculated Doppler velocities.

9. The speed detection method according to claim 7, characterized in that, in the fourth step, the speed detection device detects the peak voltages of the first and second time-length Doppler shift signals, respectively, which have been Fourier transformed, and weights the first and second time-length Doppler shift signals with a weight corresponding to the magnitude of the peak voltage of the Fourier-transformed Doppler shift signals.

10. The speed detection method according to 8 or 9, characterized in that the speed detection device estimates the Doppler velocity based on the determined velocity of the moving body, and in the fourth step, the speed detection device weights the Doppler velocity of the first time length and the Doppler shift signals of the second time length, respectively, with a weight corresponding to the difference between the Doppler velocity calculated based on the Doppler shift signals of the first and second time lengths and the estimated Doppler velocity.

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