JP5741508B2 - Distance and speed measuring device - Google Patents

Description

  The present invention relates to a distance / velocity measuring device that transmits a pulsed transmission wave and receives the reflected wave to measure the distance and speed of a target reflecting the transmission wave.

  An apparatus for transmitting a pulsed transmission wave, receiving the reflected wave, and measuring the time difference from the transmission timing of the transmission wave to the reception timing of the reflected wave to determine the distance from the target reflecting the transmission wave Are known.

  In this type of device, as one of the methods for measuring the time difference from the transmission timing to the reception timing (the timing at which the received signal reaches the maximum voltage), the timing at which the received signal becomes larger than a predetermined threshold is set to the previous timing, and then to the predetermined timing. The time difference from the transmission timing to the previous timing and the time difference from the transmission timing to the subsequent timing are individually measured with a timer, etc. Some estimate the time difference to the timing (see, for example, Patent Document 1).

  Also, every time a transmission wave is transmitted, the received signal is sampled at a predetermined interval for a predetermined period, and based on the result of performing similar sampling for a plurality of transmission waves, the same time with reference to the transmission timing of the transmission wave By adding (integrating) the sampled values sampled at the same time, an integrated sampling value corresponding to the sampling value of the integrated signal (which reduces the noise of the received signal) obtained by integrating multiple received signals is obtained, and the integration is performed. There is also one that obtains reception timing from a sampling value (see, for example, Patent Document 2).

Hereinafter, the former is referred to as a one-shot ranging method, and the latter is referred to as an integral ranging method.
Further, the received light signal is binarized using a threshold value set in accordance with the intensity of the background light, and the binarized signal is sampled by two kinds of methods (level sampling and edge sampling) to obtain the received signal. It is described that a method to be used is switched according to a parameter related to S / N, and a time difference from transmission to reception is obtained in accordance with one of the sampling results, and thus a distance to an object reflecting the transmission wave is obtained ( (See Patent Document 3).

  As parameters related to S / N, specifically, an elapsed time from transmission (S / N is large for a short distance) or pre-range measurement before actual distance measurement is performed. It has been proposed to use a detected signal level (S / N is large if the signal level is high) or the like.

JP-A-9-236661 JP 2005-257405 A Special table 2007-4606

  By the way, in the one-shot ranging method, the time resolution (and distance resolution) is determined by the operation clock of the timer that measures the time difference from the transmission timing to the previous timing and the subsequent timing. Therefore, high accuracy is achieved by using a high-speed operation clock. Measurement is possible. However, there is a problem that the measurement result cannot be obtained when the reflection intensity from the target is weak and only a reception signal lower than a predetermined threshold (a reception signal of the same level as the noise level) can be obtained.

  On the other hand, since the S / N of the received signal can be improved by the integration effect in the integral ranging method, the measurement result can be obtained even for a received signal lower than a predetermined threshold that is buried in noise. However, the time resolution (and hence the distance resolution) is determined by the sampling interval of the received signal, and the sampling interval cannot be made as high as the operation clock, so that there is a problem that the detection accuracy is inferior compared to the one-shot ranging method. is there. Even if the integration ranging method can achieve the same detection accuracy as the one-shot ranging method, in that case, the amount of sampled data becomes enormous, and the scale of the device for storing the data There is a problem that the amount of data processing increases.

  In addition, when the above-described device is used as, for example, a vehicle collision prevention (PCS) sensor, it is necessary to detect not only the distance to the target but also the speed (relative speed) of the target. It is desirable that the distance from the target is reliably obtained at regular time intervals, and further, since it is used for safety-related control, it is desirable that the detection result be obtained with the highest possible accuracy.

  It is also conceivable to apply the idea described in Patent Document 3 by switching between the two types of distance measuring methods. However, for example, in-vehicle radar devices need to detect various types of objects from stationary objects to moving objects, and not only the reflection characteristics differ from object to object but also the same object. However, the reflection intensity varies depending on the reflection position. In addition, the relative positional relationship with the object changes greatly in a short time, and the reflection position on the object frequently changes accordingly.

  In other words, in the method of switching according to the elapsed time from transmission, the actual reflection intensity is not considered at all, and in the method of switching according to the result of the pre-ranging, the situation is different between the pre-ranging and the actual ranging. It may have changed. Therefore, there is a case in which neither method can select an accurate distance measurement method, and there is a problem in that the accuracy of the measurement result of distance and speed is lowered.

  Furthermore, while the technique described in Patent Document 3 performs different sampling on a signal obtained by binarizing a received signal, both the one-shot ranging method and the integral ranging method are both The processing is executed using the result of sampling the received signal as it is without binarizing. Therefore, there has been a problem that an apparatus that switches between the one-shot distance measurement method and the integral distance measurement method cannot be realized simply by applying the technique described in Patent Document 3.

  In order to solve the above-described problems, the present invention provides a distance and speed measuring device capable of obtaining the distance (and thus the speed) from the target reflecting the transmitted wave with the highest possible accuracy for each measurement period. For the purpose.

  In the distance / velocity measuring device of the present invention, the transmitting / receiving means irradiates the pulsed transmission wave a plurality of times for each preset measurement period, receives the reflected wave of the transmission wave, and determines the intensity of the reflected wave. A received signal is generated.

  However, the transmission interval Tw of the transmission wave is set to be equal to or longer than the time required for the transmission wave to reciprocate the maximum detection distance specified by the device, and the number of transmission waves is N and the measurement cycle is Tcycl. > N × Tw is set (see FIG. 2).

  Then, the first ranging means calculates the elapsed time from the transmission timing of the transmission wave to the timing at which the reception signal corresponding to the transmission wave crosses a preset detection threshold for any one of the plurality of transmission waves. Based on the measurement result, a first distance measurement value representing a distance to a reflection target that is a target reflecting the transmission wave is obtained for each measurement period. Note that the timing of crossing the detection threshold includes a timing of changing from a signal level equal to or lower than the detection threshold to a signal level higher than the detection threshold, and a timing of changing from a signal level higher than the detection threshold to a signal level equal to or lower than the detection threshold.

  In addition, the second ranging means has, for each of the plurality of transmission waves, a maximum measurement period set to be equal to or longer than a time required for the transmission wave to reciprocate a preset maximum detection distance from the transmission timing of the transmission wave. During this period, the received signal is sampled at a preset sampling interval, and the reflection target is calculated based on the integrated sampling value obtained by adding the sampling values sampled at the same time with reference to the transmission timing of each transmission wave. A second distance value representing the distance up to is obtained for each measurement period.

  That is, the integrated sampling value corresponds to a sampling value of an integrated signal obtained by adding a plurality of received signals at the same timing with reference to the transmission timing. Note that the integrated signal has a reduced noise and an improved S / N compared to the original received signal.

  Then, the distance calculation means calculates a target distance representing a distance from the reflective target for each measurement cycle using at least one of the first distance value and the second distance value, The speed calculation means calculates the speed of the reflective target for each measurement period based on the distance calculated by the distance calculation means.

  According to the distance / velocity measuring apparatus of the present invention configured as described above, the first distance measuring means obtains the first distance value with high accuracy by the first distance measuring means when the received signal is larger than the detection threshold. If the received signal is below the detection threshold, the second distance value by the second distance measuring means can be obtained, although the accuracy is inferior to the first distance value. For this reason, by appropriately selecting the first distance value and the second distance value, the target distance can be obtained with the highest possible accuracy for each measurement cycle, and further, based on the target distance. The speed of the target can be determined with the highest possible accuracy.

  Further, according to the distance and speed measuring apparatus of the present invention, the first distance measuring means uses a plurality of transmission waves (however, any one), and the second distance measuring means is the first distance measuring means. Since the processing is executed using the same plurality of transmission waves (but all), the first distance value and the second distance value obtained using the received signals obtained almost simultaneously within the same measurement period Can be used to determine the target distance and speed. For this reason, even when the surrounding situation (relative positional relationship with the object) to be detected changes in a short time, an accurate detection result can be obtained.

  Incidentally, the first distance measuring means has, as detection threshold values, a lower threshold value set to a value larger than the noise level of the received signal and an upper threshold value set to a value larger than the lower threshold value. If the threshold value is exceeded, the first threshold value may be determined by using the upper threshold value as the detection threshold value, and if the received signal is equal to or lower than the upper threshold value, the lower threshold value may be used as the detection threshold value. The upper threshold value is desirably a value that ensures that the accuracy of the first distance measurement value is higher than the accuracy of the second distance measurement value.

  In this case, the distance calculation means, for example, the first distance value when the received signal is larger than the upper threshold value, the second distance value when the received signal is smaller than the lower threshold value, and the received signal is greater than or equal to the lower threshold value and smaller than or equal to the upper threshold value. In this case, it is conceivable to obtain an average value of the first distance value and the second distance value as the target distance.

  By using the average value of the first distance value and the second distance value in this way, the target distance value changes rapidly when the distance measuring means used for calculating the target distance is switched. That is, the occurrence of distance jumps can be suppressed.

  Here, the average value of the first distance value and the second distance value may be a simple average value or a weighted average value. When the weighted average value is used, the higher weight may be set so as to increase in accordance with the accuracy of the first distance value and the accuracy of the second distance value.

  As the detection threshold, only one of the upper threshold and the lower threshold is used. When the received signal exceeds the detection threshold, the first distance measurement value is used. When the received signal is less than the detection threshold, the second threshold is used. The distance measurement value may be the target distance.

  In the distance / speed measuring apparatus of the present invention, the speed calculating means may be configured to calculate the speed using a time series filter. Here, the case where the target distance obtained by the distance calculation means is the first distance value is the first state, and the case where the target distance is the average value of the first distance value and the second distance value is the second state. The case of the second distance measurement value is set as the third state.

In this case, the target distance obtained by the distance calculating means when the transition from the first state to the third state or from the third state to the first state is made without passing through the second state has low reliability. It may be configured to calculate the speed as a thing.

  Thus, even when the detection result of the target distance changes greatly when the target distance is switched from the first distance value to the second distance value or from the second distance value to the first distance value, It is possible to prevent the calculation result of from changing significantly unnaturally. As a result, the stability of various controls using the speed calculation result can be improved.

  Furthermore, when the time series filter is a Kalman filter, the reliability of the target distance may be adjusted by increasing or decreasing the Kalman gain. In this case, the speed is calculated on the assumption that the reliability of the observed value (the newly calculated target distance) is lower as the Kalman gain is decreased.

  The unit time when the first distance measuring unit measures the elapsed time is preferably shorter than the sampling interval when the second distance measuring unit performs sampling.

The block diagram which shows the whole structure of a distance and speed measuring apparatus. FIG. 4 is a timing chart showing transmission timing signals and operation timings of respective units of the apparatus. Explanatory drawing for understanding the waveform of the received signal with respect to one pulse signal and the operation of the one-shot distance measuring circuit and the integral distance measuring circuit. Explanatory drawing which shows the relationship between the signal level (reflection intensity) of a received signal, the effective area | region of one-shot ranging and integral ranging, and the precision of the distance calculated | required by one-shot ranging circuit or integral ranging circuit. It is a state transition diagram regarding the calculation state of a target distance. The flowchart which shows the content of the target detection process. Explanatory drawing which illustrated the acquisition method of distance measurement data, and the calculation method of distance data according to the acquisition state for every measurement period.

Embodiments of the present invention will be described below with reference to the drawings.
<Overall configuration>
The distance and speed measuring device 1 to which the present invention is applied is mounted on a vehicle, detects various targets existing in front of the vehicle, and generates information (distance, relative speed, etc.) on the detected target. It is.

  As shown in FIG. 1, the distance / speed measuring device 1 reflects a laser beam and a light emitting unit 10 that irradiates a pulsed laser beam (transmitted wave) toward an irradiation area in front of the vehicle according to a transmission timing signal ST. The light receiving unit 20 that receives the reflected light (reflected wave) from the target and converts it into electrical signals (reception signals) R1 to R4 corresponding to the received light intensity, and the transmission timing signal ST supplied to the light emitting unit 10 are generated. At the same time, based on the received signals R1 to R4 supplied from the light receiving unit 20, the distance measuring unit 30 that measures the distance from the target (reflecting target) that reflects the laser beam, and the measurement result of the distance measuring unit 30 And a signal processing unit 40 for detecting a target existing in the irradiation region and generating information (distance, speed, etc.) regarding the target.

<Light emitting part>
In accordance with the transmission timing signal ST, the light emitting unit 10 has a light emitting element 11 composed of a laser diode or the like that generates laser light, and an irradiation range of the laser light emitted from the light emitting element 11 so that the laser light is irradiated onto the irradiation region. It consists of a collimating lens 12 to be adjusted.

<Light receiver>
The light receiving unit 20 condenses the reflected light coming from the irradiation region, and generates a plurality of electric signals having a voltage value corresponding to the intensity of the reflected light received through the condensing lens 21 (this embodiment). In order to amplify the light receiving signal of each light receiving element constituting the light receiving element group 22 individually, an amplification composed of a plurality of amplifier circuits provided for each light receiving element. It consists of a circuit group 23 and the like.

  The light receiving elements constituting the light receiving element group 22 are arranged in a line along the vehicle width direction (horizontal direction) so that each receives reflected light coming from different directions in the horizontal plane in the irradiation range. Has been placed.

  Hereinafter, the combination of the light receiving element and the amplifier circuit is referred to as light receiving channels CH1 to CH4. That is, the amplified signal output from each light receiving channel CHi (i = 1 to 4) becomes the reception signal Ri.

<Ranging unit>
The distance measuring unit 30 is provided for each of the received signals R1 to R4 and the control circuit 31 that generates the transmission timing signal ST, and is obtained by two types of distance measuring methods based on each received signal Ri and the transmission timing signal ST. A plurality of distance measuring circuits 32a to 32d, each generating a distance measurement value, are provided. However, since the distance measuring circuits 32a to 32d have the same configuration, the distance measuring circuit 32 will be referred to as a distance measuring circuit 32 in the following unless it is necessary to distinguish them.

  As shown in FIG. 2, the control circuit 31 generates a periodic signal representing a measurement cycle Tcycl (Tcycl = 33 ms in the present embodiment), and generates a transmission timing signal ST in synchronization with this periodic signal. Specifically, the transmission timing signal ST includes N (N = 100 in the present embodiment) pulse signals that are output every measurement cycle Tcycl. In addition, the pulse signal has a time interval Tw (this embodiment) sufficiently longer than the maximum measurement period (0.33 μs in this embodiment) required for the laser beam to reciprocate the maximum detection distance (50 m in this embodiment) of the apparatus 1. In the form, Tw = 18 μs). However, Tcycl, N, and Tw are not limited to the exemplified values, and may be set to satisfy Tcycl> N × Tw at a minimum.

  Returning to FIG. 1, the distance measuring circuit 32 measures the distance using an arbitrary one (for example, the 50th) of the N pulse signals irradiated every measurement cycle Tcycl, and obtains the first distance value. A one-shot distance measuring circuit 321 to be generated and an integral distance measuring circuit 322 for measuring a distance by using all the N pulse signals and generating a second distance value are provided. The distance measuring circuit 32 outputs both the first distance value and the second distance value at every measurement cycle Tcycl by always operating both the one-shot distance measuring circuit 321 and the integral distance measuring circuit 322. Is configured to do.

<One-shot ranging circuit>
As shown in FIG. 3, in the one-range ranging circuit 321, the timing when the reception signal Ri exceeds the detection threshold (that is, crosses) is the previous timing, and then the reception signal Ri falls below the detection threshold (that is, crosses) The timing is the later timing, the elapsed time Tf from the transmission timing to the previous timing, and the elapsed time Tb from the transmission timing to the subsequent timing are measured by a timer, and the intermediate timing between the previous timing and the subsequent timing is received timing ( The average value of both elapsed times Tf and Tb is calculated as the elapsed time Tr (= {Tf + Tb} / 2) from the transmission timing to the reception timing. Further, a value obtained by converting the elapsed time Tr into a distance is output as a first distance measurement value.

However, in the one-shot distance measuring circuit 321, two types of threshold values are prepared as detection threshold values, and the larger one is referred to as an upper threshold value and the smaller one is referred to as a lower threshold value.
In other words, the one-shot distance measuring circuit 321 includes four timers (first to fourth timers) that start timing at the transmission timing of the pulse signal to be used (rising edge of the transmission timing signal ST). However, the LSB (unit time) of the first to fourth timers coincides with the cycle of the operation clock for operating the timer, and is set to 0.125 ns in this embodiment.

  Among these, the first timer stops timing when the received signal Ri smaller than the lower threshold exceeds the lower threshold, and the second counter measures time when the received signal Ri smaller than the upper threshold exceeds the upper threshold. The third counter stops timing when the received signal Ri greater than the upper threshold falls below the upper threshold, and the fourth counter counts timing when the received signal Ri greater than the lower threshold falls below the lower threshold. Is configured to stop.

  When the received signal Ri exceeds the upper threshold, the first distance value is obtained using the time value (elapsed time Tf) of the second timer and the time value (elapsed time Tb) of the third timer, When the received signal Ri exceeds the lower threshold and is equal to or lower than the upper threshold, the first distance value is obtained using the time value (elapsed time Tf) of the first timer and the time value (elapsed time Tb) of the fourth timer. When the received signal Ri is equal to or lower than the lower threshold value, the first distance measurement value is “no data”.

  Note that the elapsed time Tr before conversion into the first distance measurement value is, for example, a period during which the reception signal Ri exceeds the detection threshold (Tb) in consideration of distortion generated in the reception signal Ri when the amplifier circuit is saturated. The correction may be made according to the length of -Tf).

An apparatus for realizing such a one-shot distance measurement method is described in detail in, for example, Japanese Patent Application Laid-Open No. 9-236661, and the description thereof is omitted here.
<Integral distance measuring circuit>
On the other hand, the integral distance measuring circuit 322 executes the following processing.

  First, for each of the N pulse signals, reception is performed at a predetermined sampling interval Tsmpl (Tsmpl = 25 ns in the present embodiment) until the time required for the laser beam to reciprocate the maximum detection distance from the transmission timing elapses. The signal Ri is sampled.

An integrated sampling value is obtained by adding the sampling values sampled at the same time with reference to the transmission timing.
Then, a value obtained by multiplying the peak value of the integrated sampling value by a coefficient (0.5 in this embodiment) that is larger than 0 and smaller than 1 is set as a detection threshold (50% threshold), and is set. The same timing as in the case of one-range ranging is detected using the detected threshold, and the sampling value corresponding to the previous timing and the subsequent timing is the number from the transmission timing (the previous timing is the Mfth and subsequent timing). And the elapsed time Tf from the transmission timing to the previous timing and the elapsed time Tb from the transmission timing to the subsequent timing are calculated using the equations (1) and (2).

Tf = Mf × Tsmpl (1)
Tb = Mb × Tsmpl (2)
In the following, as in the case of the one-shot distance measuring circuit 321, the elapsed time Tr from the transmission timing to the reception timing is obtained based on the elapsed times Tf and Tb, and the elapsed time Tr converted into the distance is the second distance measurement. Output as a value. An apparatus that realizes such an integral distance measuring method is described in detail in, for example, Japanese Patent Application Laid-Open No. 2005-257405, and the description thereof is omitted here.

  However, when the reception signal Ri exceeding the upper threshold value is input to the integral ranging circuit 322, the integral sampling value exceeds the measurement voltage range in the circuit 322, and the accuracy of the second ranging value is reduced. The processing is stopped and the second distance value is set to “no data”.

  As shown in FIG. 4, the one-shot distance measuring circuit 321 obtains a distance measurement value when the reflection intensity is equal to or higher than the lower threshold, and the greater the reflection intensity (the signal level of the reception signal Ri), the better the distance accuracy. In addition, the distance measurement accuracy of the integral distance measuring circuit 322 deteriorates when the reflection intensity is high enough to saturate the amplifier circuit 23 or when the reflection intensity is low enough to be less than the average level of noise.

  The lower threshold used in the one-shot distance measuring circuit 321 is set to a value obtained by adding a preset margin to the average noise level of the received signal (100 mV in this embodiment), and the upper threshold is set to one. The accuracy of the measurement result (first distance value) by the source distance measurement is set to a value (500 mV in the present embodiment) that exceeds the accuracy of the measurement result (second distance value) by the integral distance measurement.

  In the following, areas where the reflection intensity is below the average noise level are undetected areas, areas above the average noise level and below the upper threshold are integrated ranging effective areas, and areas above the lower threshold are measured once. The effective distance area, the area where the integrated distance measurement area and the one-time distance measurement area overlap is referred to as an intermediate area.

  That is, in the undetected area (area X in the figure), a distance measurement value cannot be obtained, and in the integrated distance measuring effective area (area A in the figure) excluding the intermediate area, measurement by the single distance measuring circuit 321 is performed. Since the distance is impossible, only the second distance value can be obtained. Further, in the one-shot distance measurement effective area (area C in the figure) excluding the intermediate area, the first distance measurement value has higher distance accuracy than the second distance measurement value, and the intermediate area (area B in the figure). Then, the second distance value has higher distance accuracy than the first distance value.

  For this reason, when the signal level of the reception signal Ri belongs to the region A, the second distance value generated by the integral distance measuring circuit 322 is used as distance data. This state is referred to as an “integration only” state (an example of the third state in the present invention). Further, when the signal level of the reception signal Ri belongs to the region C, the first distance measurement value (however, the upper threshold value is used) generated by the one-shot distance measurement circuit 321 is used as the distance data. This state is referred to as a “one-shot” state (an example of the first state in the present invention). When the signal level of the reception signal Ri belongs to the area B, the value obtained from the first distance value (however, using the lower threshold) and the second distance value generated by the distance measuring circuits 321 and 322 is the distance data. Used. This state is referred to as a “one-shot integration coexistence” state (an example of a second state in the present invention). Further, the state where the signal level of the reception signal Ri is in the region X and the distance data cannot be obtained is the “undetected” state, and the signal level of the reception signal Ri is outside the region X and the distance data can be obtained. Is called “detected” state.

  The level change of the reception signal Ri (reflection intensity) is not always continuous. For example, as shown by a dotted line in the state transition diagram of FIG. May change from region to region A, and a transition occurs between arbitrary states.

  For example, when the detection target is a vehicle, the reflection intensity varies greatly depending on whether the reflection position is a body or a reflector attached to the body. Moreover, the relative positional relationship between the vehicle to be detected and the host vehicle frequently changes depending on their behavior (relative speed, steering operation, vibration, etc.), and the reflection position on the vehicle also frequently changes. Such a sudden level change occurs.

<Signal processing unit>
Returning to FIG. 1, the signal processing unit 40 includes a well-known microcomputer mainly composed of a CPU, a ROM, and a RAM, and ranging data (first measurement) supplied from the ranging unit 30 for each light receiving channel CHi. The target is detected according to the distance value D1 and the second distance value D2), and at least the target detection process for obtaining the distance and relative speed from the detected target is executed.

Here, the detail of the target detection process which the signal processing part 40 performs is demonstrated along the flowchart shown in FIG.
This process is started every time distance measurement data is calculated by the distance measurement circuit 32, that is, every measurement cycle Tcycl.

  When this processing is started, one light receiving channel CHi that has not been subjected to the processing (S120 to S160) described later is set as a selected channel, and distance measurement data for the selected channel is acquired (S110), and a first distance value D1 is obtained. Is calculated (that is, “no data”) (S120), and whether the second distance value D2 is calculated (that is, “no data”) (S130, S135). Judging.

  When the first distance value D1 is calculated but the second distance value D2 is not calculated (S120: YES and S130: NO), that is, the calculation state of the distance measurement data is “only one shot”. In the state, the first distance value D1 is set as the distance data D (= D1) of the selected channel as it is (S140).

  When both the first distance value D1 and the second distance value D2 are calculated (S120: YES and S130: YES), that is, when the distance measurement data calculation state is the “one-shot integration coexistence” state, According to the equation (3), the distance data D of the selected channel is obtained by a weighted average (S150).

D = (1−α) × D1 + α × D2 (3)
However, α is a weighted average weight, and 0.3 is used in this embodiment. Α is smaller than 0.5 if the accuracy of the first distance value D1 is better according to the distance accuracy of the first distance value D1 and the second distance value in the intermediate area. If the accuracy of the second distance value D2 is better, a value larger than 0.5 may be set. Here, the first distance value D1 is set to be approximately twice as accurate as the second distance value D2.

  When the first distance value D1 has not been calculated (S120: NO and S135: YES), that is, when the distance measurement data calculation state is “integration only”, the second distance value D2 is directly selected as the selected channel. Distance data D (= D2) (S160).

That is, the distance data D is selectively calculated based on at least one of the first distance value D1 and the second distance value D2.
If neither the first distance value D1 nor the second distance value D2 has data, that is, if the distance measurement data calculation state is “undetected”, the distance data D is not calculated. Proceed to the next step without data.

  When the processes of S110 to S160 are completed, the distance measurement data calculation state is stored according to the processing result (S170). That is, when the distance data D is calculated by S140, the state is “only one shot”, when the distance data D is calculated by S150, the “one-shot integration coexistence” state, and when the distance data D is calculated by S160. In the case of “Integration only” state, and “Non-detection” state in any case, “Undetected” state is stored.

  Then, it is determined whether or not the processing of S120 to S170 has been executed for all the light receiving channels CH1 to CH4 (S180). If there is an unprocessed light receiving channel CHi (S180: NO), the processing returns to S110 and is not processed. The same processing is executed with the light receiving channel CHi as the selected channel.

  On the other hand, if the processing of S120 to S170 has been executed for all the light receiving channels CH1 to CH4, the distance data D calculated for each light receiving channel CHi is clustered, each cluster is detected as a target, and each target is detected. Then, the distance to the target and the calculation state are set (S190).

  When the target is detected by a single light receiving channel CHi, the detection result (distance data D and calculation state) in the light receiving channel CHi is inherited as the distance from the target and the calculation state. On the other hand, when the target is detected across a plurality of light receiving channels CHi, the distance data D and the calculation state obtained in the calculation state with the highest distance accuracy are inherited as the distance to the target and the calculation state. To do. However, the distance accuracy in each calculation state is assumed to be highest for “only one shot” and lowest for “only integration”.

  Next, for each detected target, the current state is changed from the previous state based on the calculation state (previous state) set in the previous cycle for the same target and the calculation state (current state) set in the process of S190. Whether the state transition to is a transition from "only one" to "only integration", or a transition from "only integration" to "only one" (hereinafter collectively referred to as "specific transition") If it is not a specific transition, the process of calculating the relative speed is executed assuming that the reliability of the distance set in the process of S190 (hereinafter also referred to as “observed value”) is normal. (S210) If it is a specific transition, a process of calculating the relative speed is executed assuming that the reliability of the observed value is low (S220).

  In S210 and S220, the relative speed is calculated using a time series filter (for example, Kalman filter). The reliability of the observed value can be adjusted by increasing or decreasing the Kalman gain in the case of a Kalman filter, for example. Specifically, reducing the Kalman gain reduces the reliability of the observed value.

Finally, the current state set in S190 for each target is stored as the previous state (S230), and this process ends.
<Action>
Here, FIG. 7 shows the data acquisition status of the first distance measurement value (measurement result of one-shot distance measurement) D1 and the second distance measurement value (measurement result of integrated distance measurement) D2, and the data acquisition status. It is explanatory drawing which illustrated the calculation method of the obtained distance data D for every measurement period.

  Even if data omission occurs in any of the distance measurement circuits 321 and 322, the distance data D based on the measurement result in the distance measurement circuit 32 is obtained for each measurement period without being compensated by interpolation processing or the like. Recognize.

  In addition, without going through the “one-shot integration coexistence” state, a transition is made directly from the “one-shot only” state to the “integration-only” state, or from the “integration-only” state to the “one-shot-only” state (in the figure). When the relative velocity is calculated using the time series filter, an operation that reduces the reliability of the observed value is performed.

<Effect>
As described above, in the distance / speed measuring apparatus 1, when the one-shot distance measuring circuit 321 and the integral distance measuring circuit 322 are operated simultaneously in parallel, and the received signal Ri belongs to the region C where it is larger than the upper threshold value, When the first ranging value D1 belongs to the region A where the received signal Ri is lower than the lower threshold, the second measured value D2 is both when the received signal Ri belongs to the region B larger than the lower threshold and lower than the upper threshold. A weighted average value of the distance measurement values D1 and D2 is generated as the distance data D.

  Therefore, according to the distance / speed measuring apparatus 1, even when the one-range distance measuring circuit 321 cannot obtain the first distance value D1, or when the accuracy of the first distance value D1 is lowered, the integral distance measurement is performed. By using the second distance value D2 obtained by the circuit 322, the distance data D (and hence the target distance) can be obtained with the highest possible accuracy for each measurement cycle Tcycl. Based on the target distance, the relative speed with the target can be obtained with the highest possible accuracy.

  Further, by using the weighted average value of both distance measurement values D1 and D2, when the distance measurement circuits 321 and 322 used for calculating the distance data D are switched, the distance data D changes rapidly, that is, the distance The occurrence of jumps can be suppressed.

As a result, it is possible to improve the reliability of various vehicle controls executed based on the distance and relative speed with the target detected by the distance / speed measuring device 1.
In addition, according to the distance / speed measuring device 1, since the reliability of the observation value (distance data D) when calculating the relative speed is adjusted according to the state transition of the calculation state, the reception intensity is rapidly increased. Even if the observed value suddenly switches from the first distance value D1 to the second distance value D2 or from the second distance value D2 to the first distance value D1, the calculation result of the relative speed is not good. It can suppress that it changes naturally naturally. As a result, the stability of various controls that use the calculation result of the relative speed can be improved.

  Further, according to the distance / speed measuring device 1, among the plurality of transmission waves transmitted for each measurement cycle, the one-shot distance measuring circuit 321 uses one and the integral distance measuring circuit 322 uses all. In order to execute the process, the first distance value and the second distance value are obtained based on the received signals obtained almost simultaneously within the same measurement period. For this reason, even when the surrounding situation (relative positional relationship with the object) to be detected changes in a short time, an accurate detection result can be obtained.

By the way, such a distance and speed measuring device 1 can be suitably used as, for example, a vehicle collision prevention (PCS) sensor.
That is, when used as a sensor for PCS, it is necessary to detect not only the distance to the target but also the speed (relative speed) of the target. For this purpose, the distance from the target is set at regular time intervals. This is because it is desirable to reliably obtain the detection result, and furthermore, since it is used for safety-related control, it is desirable to obtain a detection result with the highest possible accuracy.

<Other embodiments>
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it can implement in various aspects.

  For example, in the above embodiment, when the distance data D is obtained by the weighted average of the first distance value D1 and the second distance value D2, a fixed value is used as the weight α. It may be changed.

  In the above embodiment, two types of threshold values (upper threshold value and lower threshold value) are used as detection threshold values used in the one-shot distance measuring circuit 321. However, three or more threshold values may be used, or a single threshold value may be used. May be.

  In the above embodiment, when a target is detected across a plurality of light receiving channels CHi, the distance data D obtained in the calculation state with the highest distance accuracy and the calculation state are represented by the distance and calculation state of the target. However, it is not limited to this. For example, the distance data D and the calculation state of the light receiving channel CHi located at the center of the plurality of receiving channels CHi may be employed.

  In the above embodiment, the time series filter is used for calculating the relative speed. However, the differential value of the distance data D may be used as it is as the relative speed.

  DESCRIPTION OF SYMBOLS 1 ... Distance and speed measuring device 10 ... Light emitting part 11 ... Light emitting element 12 ... Collimating lens 20 ... Light receiving part 21 ... Condensing lens 22 ... Light receiving element group 23 ... Amplifier circuit group 0 ... Distance measuring part 31 ... Control circuit 32 (32a) ˜32d) Distance measuring circuit 40 Signal processing unit 321 Single shot distance measuring circuit 322 Integral distance measuring circuit

Claims (6)

Transmission / reception means (10, 20) for irradiating a pulsed transmission wave a plurality of times for each preset measurement period, receiving a reflected wave of the transmission wave, and generating a reception signal indicating the intensity of the reflected wave; ,
Based on the result of measuring the elapsed time from the transmission timing of the transmission wave to the timing at which the received signal corresponding to the transmission wave crosses a preset detection threshold for any one of the plurality of transmission waves First distance measuring means (321) for obtaining a first distance value representing a distance to a reflective target that is a target reflecting the transmission wave for each measurement period;
For each of the plurality of transmission waves, the transmission timing of each transmission wave is set in advance for a maximum measurement period that is set longer than the time required for the transmission wave to reciprocate a preset maximum detection distance. The received signal is sampled at a sampling interval, and the distance to the reflecting target is calculated based on the integrated sampling value obtained by adding the sampling values sampled at the same time with the transmission timing of each transmission wave as a reference. Second distance measuring means (322) for obtaining a second distance value to be expressed for each measurement period;
A distance calculation means (40, S120 to S120) that calculates a target distance representing a distance from the reflective target for each measurement period by using at least one of the first distance value and the second distance value. S160)
Based on the distance calculated by the distance calculating means, speed calculating means (40, S190 to S220) for calculating the speed of the reflecting target for each measurement period;
Equipped with a,
The first distance measuring means has, as the detection threshold, a lower threshold set to a value larger than a noise level, and an upper threshold set to a value larger than the lower threshold, and the received signal is the upper threshold If the threshold value exceeds the upper threshold value as the detection threshold value, and the received signal is equal to or lower than the upper threshold value, the lower threshold value is used as the detection threshold value to obtain the first distance measurement value.
The distance calculation means includes the first distance value when the received signal is larger than the upper threshold, the second distance value when the received signal is smaller than the lower threshold, and the received signal is equal to or larger than the lower threshold. A distance / velocity measuring apparatus characterized in that an average value of the first distance measurement value and the second distance measurement value is obtained as the target distance when it is equal to or less than the upper threshold . A case where the target distance obtained by the distance calculating means is the first distance value is the first state, and a case where the target distance is an average value of the first distance value and the second distance value. 2 states, the case where the second distance measurement value is the third state,
The velocity calculation means, when calculating the velocity using the sequence filters, without the expiration of the second state, a direct transition the said third state or from the third state from the first state to the first state The distance / speed measuring apparatus according to claim 1 , wherein the speed is calculated assuming that the target distance obtained by the distance calculating means has low reliability. The distance / velocity measuring apparatus according to claim 2 , wherein the time series filter is a Kalman filter, and the reliability of the target distance is adjusted by increasing or decreasing a Kalman gain. The distance / speed measuring device according to claim 1 , wherein an average value of the first distance measurement value and the second distance measurement value is calculated by a weighted average. Wherein the first distance measuring means unit time for performing the measurement of the elapsed time, any one of claims 1 to 4 wherein the second distance measuring means is equal to or shorter than the sampling interval of the time of performing sampling The distance and speed measuring device according to item 1. Transmission / reception means (10, 20) for irradiating a pulsed transmission wave a plurality of times for each preset measurement period, receiving a reflected wave of the transmission wave, and generating a reception signal indicating the intensity of the reflected wave; ,
Based on the result of measuring the elapsed time from the transmission timing of the transmission wave to the timing at which the received signal corresponding to the transmission wave crosses a preset detection threshold for any one of the plurality of transmission waves First distance measuring means (321) for obtaining a first distance value representing a distance to a reflective target that is a target reflecting the transmission wave for each measurement period;
For each of the plurality of transmission waves, the transmission timing of each transmission wave is set in advance for a maximum measurement period that is set longer than the time required for the transmission wave to reciprocate a preset maximum detection distance. The received signal is sampled at a sampling interval, and the distance to the reflecting target is calculated based on the integrated sampling value obtained by adding the sampling values sampled at the same time with the transmission timing of each transmission wave as a reference. Second distance measuring means (322) for obtaining a second distance value to be expressed for each measurement period;
Distance calculating means (40, S120 to S160) for selectively calculating a target distance representing a distance from the reflective target based on at least one of the first distance value and the second distance value;
Based on the distance calculated by the distance calculating means, speed calculating means (40, S190 to S220) for calculating the speed of the reflecting target for each measurement period;
Equipped with a,
The first distance measuring means has, as the detection threshold, a lower threshold set to a value larger than a noise level, and an upper threshold set to a value larger than the lower threshold, and the received signal is the upper threshold If the threshold value exceeds the upper threshold value as the detection threshold value, and the received signal is equal to or lower than the upper threshold value, the lower threshold value is used as the detection threshold value to obtain the first distance measurement value.
The distance calculation means includes the first distance value when the received signal is larger than the upper threshold, the second distance value when the received signal is smaller than the lower threshold, and the received signal is equal to or larger than the lower threshold. A distance / velocity measuring apparatus characterized in that an average value of the first distance measurement value and the second distance measurement value is obtained as the target distance when it is equal to or less than the upper threshold .