JP2009216415A - Distance measuring system and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To self-diagnose faults and increase reliability as a system. <P>SOLUTION: A pulse radar 1 transmits a transmission pulse to the outside and receives the transmission pulse reflected by a target as a reception waveform. A determination section 2 calculates an estimated value of the reception waveform received by the pulse radar 1 on a real waveform space using predetermined estimating operation on the basis of the difference between a normal waveform received under the condition that the pulse radar 1 is not broken down and an abnormal waveform received under the condition that the pulse radar 1 is broken down. The determination section 2 performs fail determination by comparing the calculated estimated value to a predetermined threshold. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a ranging system, and more particularly to failure diagnosis using an equivalent time sampling pulse radar.

  In a general equivalent time sampling pulse radar (hereinafter referred to as pulse radar), a distance is calculated based on a round-trip propagation time until a transmitted pulse signal is reflected by a target to be measured and received. For example, Patent Document 1 discloses a pulse radar that transmits a pulse to the outside in a wide band and samples a received waveform received in the wide band with a wide band sampling pulse.

Japanese National Patent Publication No. 10-511182

  Such a pulse radar is incorporated in a distance measuring system such as a back sensor for an automobile or a parking assistance system. However, if the pulse radar itself has a circuit defect or the like, the influence directly affects the subsequent application side, which causes a reduction in the reliability of the entire system.

  The present invention has been made in view of such circumstances, and an object of the present invention is to perform a self-diagnosis of a failure and improve the reliability of the system.

  In order to solve this problem, the first invention provides a distance measuring system. This ranging system includes a pulse radar and a determination unit. The pulse radar transmits a transmission pulse to the outside and receives the transmission pulse reflected by the target. The determination unit uses the evaluation calculation set in advance based on the difference between the normal waveform received when the pulse radar is not broken and the abnormal waveform received when the pulse radar is broken. The evaluation value of the received waveform received by is calculated on the actual waveform space. Then, the determination unit performs a failure determination by comparing the calculated evaluation value with a preset threshold value.

  Here, in the first invention, it is preferable that the determination unit calculates an evaluation value based on an integrated average value of the received waveform received by the pulse radar. The determination unit may calculate the evaluation value based on a timing interval at which the received waveform received by the pulse radar passes the reference value. Furthermore, the determination unit may calculate the evaluation value based on the peak time of the received waveform received by the pulse radar.

  The second invention provides a distance measuring method. This distance measuring method has first to third steps. In the first step, a transmission pulse is transmitted to the outside, and the transmission pulse reflected by the target is received. The second step uses an evaluation calculation set in advance based on the difference between the normal waveform received when the pulse radar is not broken and the abnormal waveform received when the pulse radar is broken, In the first step, the evaluation value of the received waveform received by the pulse radar is calculated on the actual waveform space. In the third step, the fail evaluation is performed by comparing the calculated evaluation value with a preset threshold value.

  According to the present invention, the evaluation value of the received waveform received by the pulse radar is calculated in the actual waveform space, and the fail determination is performed by comparing the calculated evaluation value with a preset threshold value. . Thereby, the reliability as a system can be improved.

(Ranging system)
FIG. 1 is a configuration diagram of a distance measuring system 10 according to the present embodiment. Note that the distance measuring system 10 of the present embodiment is assumed to be mounted on a vehicle such as an automobile, and detects, for example, objects around the vehicle during back travel. The ranging system 10 includes a pulse radar 1 and a determination unit 2.

  The distance measuring system 10 is also provided with a speaker (not shown) for performing an alarm according to the distance, but since it is not directly related to the present invention, further explanation is omitted. Not only the speaker but also an output circuit that transmits the result of the distance measuring system 10 to the driver is sufficient. Therefore, the present invention is not limited to such an audio unit, and may be a video unit such as a display. In addition, since the system detects an object around the vehicle during back travel, the ranging system 10 is also connected to a switch (not shown) for back travel, and this switch is turned on / off sequentially. To detect.

  The pulse radar 1 transmits a transmission pulse to the outside, and receives the transmission pulse reflected by the target. The pulse radar 1 is a general equivalent time sampling pulse radar, and the distance is calculated based on the round-trip propagation time until the transmitted pulse signal is reflected by the target to be measured and received. Therefore, the pulse radar 1 is mainly composed of a transmission antenna 1a for transmitting pulses to the outside and a reception antenna 1b for receiving pulses from the outside.

  The transmission pulse reflected by the target becomes a reception waveform expanded on the time axis by performing equivalent time sampling. In the present embodiment, the received waveform for one frame (for one period) is received as 200 real-valued data from “0” to “255” through analog / digital conversion. In this embodiment, the interval of one frame is 25 ms.

  In the present embodiment, the transmitting antenna 1a and the receiving antenna 1b are provided as separate bodies, but the present invention only needs to be able to receive and transmit the pulse radar 1. Therefore, the transmitting antenna 1a and the receiving antenna 1b may be integrally formed antennas. In that case, the pulse radar 1 is configured to separate the pulse at the time of transmission and the pulse at the time of reception in terms of time or frequency.

  The determination unit 2 performs a fail determination. “Fail” refers to a state in which normal distance measurement cannot be performed. “Fail determination” refers to determining whether normal distance measurement is possible. That is, the determination unit 2 determines whether normal ranging can be performed based on the received waveform received by the pulse radar 1.

  The fail determination uses an evaluation calculation set in advance based on a difference between a normal waveform received when the pulse radar 1 is not broken and an abnormal waveform received when the pulse radar 1 is broken. The normal waveform may be a waveform set in advance before shipment, that is, when the ranging system 10 is manufactured, or may be a waveform received by the pulse radar 1 after shipment, that is, the state in which the ranging system 10 can be regarded as normal. .

  The determination unit 2 calculates an evaluation value of the received waveform received by the pulse radar 1 at the present time in the actual waveform space based on a preset evaluation calculation. And the determination part 2 performs a failure determination by comparing the evaluation value calculated by this, and the threshold value separately preset beforehand. The determination result is output as a reference flag to a subsequent processing unit (not shown), and the received waveform received by the pulse radar 1 is appropriately processed.

Examples of the evaluation calculation performed by the determination unit 2 include the following three criteria. The fail determination of the present embodiment is sufficient if at least one of these criteria is used. When combining a plurality of criteria, the determination unit 2 performs flag management using bits in order to identify specific errors. Thereby, the reference flag output from the determination unit 2 is also composed of a plurality of bits and can include a plurality of error contents.
(1) Fail determination based on integral average value (2) Fail determination based on passage timing (3) Fail determination based on peak time

(1) Fail determination based on integrated average value Fail determination based on the integrated average value is obtained by integrating the received waveform and averaging the integrated value in time units as an evaluation value. Whether or not distance measurement is possible is evaluated based on whether or not the evaluation value is included in a range defined by a predetermined threshold value.

  FIG. 2A shows a received waveform when the cable constituting the pulse radar 1 is disconnected or disconnected. In this case, first, the received waveform is integrated with the intermediate value (“128” in this embodiment) as the central axis. Then, as shown in FIG. 5B, the integral value is divided by the time unit (integration interval), that is, the area of the region formed by the central axis and the received waveform is equalized by the unit time. As a result, the height (voltage) of the re-formed rectangular area becomes the integral average value A. If the integrated average value A is low (close to the central axis) and falls between the threshold values t1 and t2 (t1 <A <t2), it is normal that the antenna cable is disconnected or the circuit is short-circuited. Judge that distance measurement is not possible.

  FIG. 3A shows a reception waveform when a circuit constituting the pulse radar 1 is short-circuited. In this case, first, the received waveform is integrated with the intermediate value as the central axis. Then, as shown in FIG. 5B, the integral value is divided by the time unit. As a result, the height (voltage) of the formed rectangular region becomes the integral average value A. If the integrated average value A is high (far from the central axis) and falls below the threshold T1 or exceeds the threshold T2 (A <T1, T2 <A), normal distance measurement cannot be performed because the circuit is short-circuited. Judge. Depending on the short-circuit state, the +-(plus or minus) of the received waveform may be reversed, so the determination range is divided into two.

(2) Fail determination based on passage timing When there is an abnormality in the transmission system or the reception system in the pulse radar 1, a reception waveform with a disordered period may be observed as shown in FIG. Since the cycle of the reference waveform is defined by the circuit constant and the external environment, a system failure is detected by distinguishing this state from the reference waveform.

  In the fail determination based on the passage timing, a point at which the received waveform passes a predetermined reference value is checked. Then, based on the length (interval) between two adjacent points, the periodic disturbance is detected. Specifically, when the received waveform shows a waveform as shown in FIG. 4A, first, the interval in which the received waveform passes the intermediate value (“128” in the present embodiment) is P0, P1, P2,. It is defined as P8 (FIG. 4B). Next, it is compared whether or not the time of each section P is included in a predetermined range (lower limit value Smin to upper limit value Smax). When Smin ≦ P ≦ Smax, the section P is a normal section, and when it is not satisfied, it is an abnormal section. This check is performed over the entire range, and if the total length of the abnormal sections is equal to or greater than a threshold value, an abnormality is detected. In the section P0 including the start point of the received waveform, it may start in the middle of the cycle, and in the section P8 including the end point of the received waveform, it may be interrupted in the middle of the cycle, so in these sections P0 and P8 Only the comparison with the upper limit value Smax is limited (the lower limit value Smin is not considered).

(3) Fail determination based on peak time When this pulse radar is used as a back sensor, for example, circuit constants are set in advance in consideration of the influence of the vehicle body. However, when the rear gate is opened, the signal directly reaching the receiving antenna from the transmitting antenna increases, and the received waveform as shown in FIG. 5A, that is, the absolute value of the amplitude exceeds the upper limit value MAX or the lower limit value LOW. A state is observed. By distinguishing such a state from the reference waveform, a system failure or a rear gate opening is detected.

  In the fail determination based on the peak time, an evaluation value is used for the total value obtained by summing the sections in which the voltage (amplitude) of the received waveform is the minimum value or the maximum value. Then, by comparing this evaluation value with a threshold value, it is evaluated whether or not the distance can be normally measured. Specifically, when the received waveform shows a waveform as shown in FIG. 5A, first, the received waveform has a maximum value (“255” in this embodiment) or a minimum value (“0” in this embodiment). The sections shown are defined as S0, S1, and S2 (FIG. 5B). Next, a value (S0 + S1 + S2) obtained by summing the time of each section S is compared with a threshold value, and if the total value is less than the threshold value, it is normal. Is not possible).

  Thus, according to the present embodiment, the determination unit 2 calculates the evaluation value of the received waveform received by the pulse radar 1 on the actual waveform space, and the calculated evaluation value and a preset threshold value. Fail determination is performed by comparing the value. Thereby, the reliability as a system can be improved. In addition, although the determination part 2 of this embodiment was a unit (hardware) which comprises the ranging system 10, this invention is not limited to this, The program which has the function similar to the determination part 2 is stored in a computer. It can also be realized by executing.

Configuration diagram of ranging system Illustration of fail judgment based on integral average value Illustration of fail judgment based on integral average value Fail judgment based on the reference timing Fail judgment based on peak time

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pulse radar 1a Transmission antenna 1b Reception antenna 2 Judgment part 10 Ranging system

Claims (5)

In the ranging system,
A pulse radar that transmits a transmission pulse to the outside and receives the transmission pulse reflected by the target; and
Using the evaluation calculation set in advance based on the difference between the normal waveform received when the pulse radar is not broken and the abnormal waveform received when the pulse radar is broken, the pulse radar A determination unit that calculates an evaluation value of a received waveform on a real waveform space, and performs a fail determination by comparing the calculated evaluation value with a preset threshold value, Distance measuring system. The determination unit
The distance measuring system according to claim 1, wherein the evaluation value is calculated based on an integrated average value of the received waveform received by the pulse radar. The determination unit
The ranging system according to claim 1 or 2, wherein the evaluation value is calculated based on a timing interval at which the received waveform received by the pulse radar passes a reference value. The determination unit
The ranging system according to any one of claims 1 to 3, wherein the evaluation value is calculated based on a peak time of the received waveform received by the pulse radar. In ranging method,
A first step of transmitting a transmission pulse to the outside and receiving the transmission pulse reflected by the target;
Using the evaluation calculation set in advance based on the difference between the normal waveform received when the pulse radar is not broken and the abnormal waveform received when the pulse radar is broken, the first A second step of calculating an evaluation value of a received waveform received by the pulse radar in a step on an actual waveform space;
A distance measuring method comprising: a third step of performing a fail determination by comparing the calculated evaluation value with a preset threshold value.

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