JP2006142966A - Obstacle discriminating device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an obstacle discriminating device for a vehicle capable of discriminating accurately a human body from other electric conductive objects. <P>SOLUTION: The obstacle discriminating device for the vehicle is equipped with a sensor 2 fed with a current from an AC power supply 1 and including an in-vehicle AC impedance circuit 21 in which AC impedance varies in compliance with the degree of the approach of an approaching conductor and a discrimination part 3 to sense the approaching conductor or discriminate its sort on the basis of an electricity quantity varying in accordance with an AC impedance change taken out of the AC impedance circuit 21, wherein the AC power supply 1 feeds a current to the AC impedance circuit 21 with an AC voltage having a frequency approximately equal to the resonance frequency of an electric equivalent model of a human body including a resistance component and a capacitance component. This enables the discrimination of the electricity quantity emitted from the AC impedance circuit 21 when a human body approaches from the electricity quantity when any other conductor including an electric conductive resin approaches, and the discrimination part 3 can discriminate accurately whether the approaching conductor is a human body or not. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for discriminating the approach of an obstacle to a vehicle and its type, and more particularly to an apparatus for detecting the approach of a pedestrian.

  In recent years, for the purpose of protecting pedestrians, in order to protect pedestrians, if an obstacle discriminating device is attached to the vehicle bumper part, it is determined whether or not the collision target is a pedestrian at the time of a vehicle collision. Techniques for operating these devices (for example, hoods and cowl airbags) have been proposed, and their practical application has been studied.

  As a pedestrian discrimination technique that precedes, Patent Documents 1 and 2 describe the capacitance between a pedestrian and a conductor based on a change in capacitance between a collision target that is a conductor and an electrode plate of a sensor. A method of detecting the approach of a conductive approaching body that detects the difference electrically (capacitance approaching body detection system) is proposed.

On the other hand, the present applicant has proposed a detection method in Patent Document 3 that discriminates a human body from other objects based on a difference in electrical characteristics that occur when a human body, a metal, or a resin object approaches or collides. That is, the detection equivalent model proposed by the present applicant is that the human body has a change in capacitance, the metal has a change in magnetic flux, and the resin as an insulator has a capacitance as electrical characteristics that occur when each detected object approaches. The approaching object is discriminated by using the fact that there is no change in both the magnetic flux and the magnetic flux.
JP 2000-177514 A JP 2000-326808 A Japanese Patent Laid-Open No. 2004-256023

  However, the resin that may approach or collide with the vehicle is not limited to an insulating resin, and may be a resin having conductivity such as a resin that has been subjected to metallic coating. Here, the conductive resin is different from the insulating resin in that the capacitance changes similarly to the human body, and a similar change in electrical characteristics occurs when approaching the human body. Therefore, the conventional detection model described above has a problem that it is difficult to distinguish between an object approaching and colliding with a vehicle being a human body and a conductive resin.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a vehicle obstacle discriminating apparatus capable of accurately discriminating between a human body and other conductive objects.

  Hereinafter, each means suitable for solving the above-described problems will be described with additional effects and the like as necessary.

1. A sensor unit including an in-vehicle AC impedance circuit that is fed from an AC power source and whose AC impedance changes according to the degree of proximity of the approaching conductor;
A discriminating unit that discriminates the detection of the approaching conductor or the type thereof based on the amount of electricity that changes in accordance with the change in the AC impedance taken from the AC impedance circuit;
In the vehicle obstacle determination device comprising:
The AC power supply has a large difference in frequency characteristics of the electrical equivalent model between the human body and another conductor due to the difference in the resistance component and the capacitance component in the electrical equivalent model of the conductor including the resistance component and the capacitance component. An obstacle determination device for a vehicle, wherein an AC voltage having an appearing frequency is supplied to the AC impedance circuit.

  According to the means 1, in the electrical equivalent model of the conductor in which the AC power source includes the resistance component and the capacitance component, the frequency characteristics of the electrical equivalent model between the human body and other conductors due to the difference in the resistance component and the capacitance component. The AC voltage with a frequency that greatly shows the difference is fed to the vehicle-mounted AC impedance circuit in which the AC impedance contained in the sensor unit changes according to the degree of proximity of the approaching conductor, and the AC is extracted from the AC impedance circuit by the discriminating unit Detection of the approaching conductor or its type is determined based on the amount of electricity that changes in accordance with the impedance change. Note that the approaching conductor referred to here refers to an object having a specific resistance smaller than the electric insulator level. Therefore, the human body and the conductive resin are included in the approaching conductor referred to herein.

  That is, the present invention focuses on the resistance component / capacitance component of a conductive object including a human body itself, and when an object approaches or collides, the difference between the resistance component / capacitance component appears as a difference in frequency characteristics. It is used. In the electrical equivalent model of a conductor in which the drive frequency of the AC power source that feeds the AC impedance circuit included in the sensor unit includes a resistance component and a capacitance component, the human body and other conductors differ depending on the resistance component and the capacitance component. By setting the frequency at which the difference in the frequency characteristics of the electrical equivalent model appears greatly, the amount of electricity output from the AC impedance circuit when approaching the human body and the amount of electricity when approaching other conductors including conductive resin Therefore, the determination unit can accurately determine whether or not the approaching conductor is a human body.

  2. 2. The vehicle fault according to claim 1, wherein the AC power source supplies an AC voltage having a frequency substantially equal to a resonance frequency of an electrical equivalent model of a human body including a resistance component and a capacitance component to the AC impedance circuit. Object discrimination device.

  According to the means 2, the AC power supply has an AC voltage having a frequency substantially equal to the resonance frequency of the electrical equivalent model of the human body including the resistance component and the capacitance component, and the AC impedance included in the sensor unit is the degree of proximity of the approaching conductor. The vehicle-mounted AC impedance circuit that changes according to the power is fed, and the determination unit detects the approaching conductor or determines its type based on the amount of electricity that changes according to the AC impedance change taken out from the AC impedance circuit. The drive frequency of the AC power source that supplies power to the AC impedance circuit included in the sensor unit is set to a frequency that is substantially equal to the resonance frequency of the electrical equivalent model of the human body including the resistance component and the capacitance component. Since the difference in resonance characteristics from the conductive object is the largest, the determination unit can determine whether or not the approaching conductor is a human body very accurately.

  3. The determination unit sets a threshold value in advance between an output value at the time of approaching a human body and an output value at the time of approaching another conductor with respect to the amount of electricity output from the AC impedance circuit, and the approaching conductivity is determined based on the threshold value. The vehicle obstacle discriminating device according to means 1 or 2, characterized in discriminating whether or not the body is a human body.

  According to the means 3, the discriminating unit approaches the electrical quantity output from the AC impedance circuit based on a threshold value set in advance between the output value when the human body approaches and the output value when the other conductor approaches. Whether or not the conductor is a human body can be accurately determined by a simple process.

  According to the present invention, the drive frequency of the AC power source that supplies power to the AC impedance circuit included in the sensor unit is different from the resistance component and the capacitance component in the electrical equivalent model of the conductor including the resistance component and the capacitance component. By setting the frequency at which the difference in frequency characteristics of the electrical equivalent model between the human body and other electrical conductors appears to be large, the electrical quantity output from the AC impedance circuit when approaching the human body and other electrical conductors including conductive resin Since the amount of electricity at the time of approach can be distinguished, the determination unit can accurately determine whether or not the approaching conductor is a human body.

  An embodiment embodying the vehicle obstacle determination device of the present invention will be specifically described with reference to the drawings.

  As shown in FIG. 1, the vehicle obstacle determination device of the present embodiment includes an AC power source 1, a sensor unit 2, and a determination unit 3.

  The AC power supply 1 is a low output impedance sine wave oscillator, and supplies an AC voltage Vi to an AC impedance circuit 21 included in the sensor unit 2.

  The sensor unit 2 includes an AC impedance circuit 21, a voltage drop detection resistor 22 connected in series to the AC impedance circuit 21, and a grounding capacitor 23 that is also connected in series to the AC impedance circuit 21. The AC impedance circuit 21 includes a coil 211 disposed in a vehicle bumper (not shown), a resistance element 213 connected in series with the coil 211, and a capacitor 212 connected in parallel with the coil 211 and the resistance element 213. The coil 211 is provided as a member for detecting a change in magnetic flux, and it is preferable to provide an electrode (not shown) as a member for detecting a change in capacitance. However, instead of the electrode, a part of the coil 211 is used for detecting a capacitance. It can also be used as a member.

  The AC power supply 1 is connected to one end of an AC impedance circuit 21, and the other end of the AC power supply 1, the voltage drop detection resistor 22, and the other end of the grounding capacitor 23 are grounded. The voltage drop of the voltage drop detection resistor 22 is input to the determination unit 3. What is important here is that the oscillation frequency f of the AC power source 1 (the driving frequency of the AC impedance circuit 21) is the difference between the resistance component and the capacitance component in an electrical equivalent model of a conductor including a resistance component and a capacitance component. Therefore, the frequency at which the difference in the frequency characteristics of the electrical equivalent model greatly appears between the human body and another conductor (here, as an example, a frequency substantially equal to the resonance frequency of the electrical equivalent model of the human body). The discriminating unit 3 rectifies and smoothes the voltage drop of the voltage drop detection resistor 22, that is, the output voltage Vo, converts the amplitude into a digital signal and takes it into the microcomputer, and this microcomputer detects the type of obstacle and its approach. Then, the determination / detection result is sent as a determination signal to a control device of a pedestrian protection device (not shown). The circuit configuration of this type of discriminating unit 3 itself is well known and will not be described. Of course, it is obvious that the determination unit 3 may be configured by a hardware circuit.

  Here, an electrical equivalent model of the detected object itself which is an obstacle focused on in the present invention will be described. As the equivalent model of the detected object itself, there are three patterns of equivalent models Z1 to Z3 shown in FIGS. The equivalent model Z1 shown in FIG. 2A is formed by connecting a resistance component, a capacitance component, and a series component of a resistance component and a capacitance component in parallel. The equivalent model Z2 shown in FIG. 2B is a case where a resistance component and a capacitance component are connected in parallel, and the series component can be ignored with respect to the equivalent model Z1. The equivalent model Z3 shown in FIG. 2C is a case where a resistance component and a capacitance component are connected in series, and a parallel component can be ignored with respect to the equivalent model Z1.

  Next, frequency characteristics in the equivalent model of the detected object will be described. Here, for the sake of simplicity, a calculation example of the frequency characteristic in the equivalent model Z3 is shown in FIG. FIG. 3 shows changes in frequency characteristics when the detected object [1] (resistance value 1 kΩ), the detected object [2] (resistance value 5 kΩ) and the detected object [3] (resistance value 100 kΩ) approach the sensor unit 2. It is obtained by calculation. If the resistance component of the detected object is different, the trajectory of the resonance characteristics varies depending on the difference in the capacitance component (combination of the capacitance between the sensor unit and the detected object, and the capacitance between the detected object and the ground). The changed waveform is uniquely determined and does not coincide with the waveform of other detected objects. Therefore, for example, a detected object [1] having a resistance value equivalent to a human body (1 kΩ) is included in the region A shown in FIG. 3, but a detected object [2] (resistance value 5 kΩ) having a resistance value higher than that is detected. The object [3] (resistance value 100 kΩ) is not included in the A region.

  In the vehicle obstacle determination device of the present embodiment, the AC power source 1 drives the AC impedance circuit 21 of the sensor unit 2 at a frequency B substantially equal to the resonance frequency of the electrical equivalent model of the human body, and the determination unit 3 includes the human body. Based on a threshold value set in advance between the voltage input / output ratio (the vertical axis component Vo / Vi in FIG. 3) as the output value when approaching and the voltage input / output ratio as the output value when approaching another conductor The human body and other conductive objects can be accurately discriminated by simple processing. Specifically, in FIG. 3, when the input / output ratio (Vo / Vi) is equal to or greater than the threshold, it is determined that the body is a human body, and when the input / output ratio is less than the threshold, it is determined that the conductor is other than the human body. . On the other hand, since the resistance component is not considered in the conventional model, it is clear that the above characteristics cannot be expressed, and the human body is separated from other conductors including conductive resin as in this embodiment. It is impossible to do. In the present embodiment, the drive frequency of the AC power source 1 is set to a frequency B that is substantially equal to the resonance frequency of the electrical equivalent model of the human body, which is the frequency at which the difference in resonance characteristics between the human body and other conductive objects is greatest. Since it is set, the human body and other conductive objects can be distinguished very accurately.

  Here, FIGS. 4A to 4C show actual measurement examples of the transition of the frequency characteristics due to the approach of various detection objects. 4A is an example of actual measurement of characteristics by a human body, FIG. 4B is an example of actual measurement of characteristics by a resin bumper subjected to metallic coating, and FIG. 4C is an example of actual measurement of characteristics by a rubber pylon. Respectively. The other two types of conductive resins have a large resistance value (5 kΩ and 100 kΩ, respectively) with respect to the human body, and the output amplitude change amount at the frequency B is smaller than that of the human body. It is understood that the human body and other objects can be separated by using.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the example in which the drive frequency of the AC power supply 1 is set to the frequency B substantially equal to the resonance frequency of the electrical equivalent model of the human body has been described, but the present invention is not limited to this. That is, the driving frequency of the AC power source 1 is a frequency at which a difference in the frequency characteristics of the electrical equivalent model greatly appears between the human body and another conductor due to the difference in the resistance component and the capacitance component in the electrical equivalent model of the conductor (for example, If the frequency is set within a predetermined range centering on the resonance frequency of the electrical equivalent model of the human body, it is possible to accurately distinguish the human body from other conductive objects.

  The present invention is applicable to various vehicle obstacle discriminating devices having a sensor unit including an AC impedance circuit.

1 is an equivalent circuit diagram illustrating an overall configuration of a vehicle obstacle determination device according to an embodiment of the present invention. It is a figure which shows the equivalent model Z1-Z3 of a detected object. It is a figure which shows the example of calculation of transition of the frequency characteristic in the equivalent model Z3. It is a figure which shows the actual measurement example of transition of the frequency characteristic by the approach of various detection objects, (a) is the actual measurement example of the characteristic by the human body, (b) is the actual measurement example of the characteristic by the resin bumper subjected to metallic coating, (C) has shown the example of the measurement of the characteristic by a rubber pylon, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Sensor part 3 Discriminating part 21 AC impedance circuit Z, Z1-Z3 Electrical equivalent model of detected object

Claims (3)

A sensor unit including an in-vehicle AC impedance circuit that is fed from an AC power source and whose AC impedance changes according to the degree of proximity of the approaching conductor;
A discriminating unit that discriminates the detection of the approaching conductor or the type thereof based on the amount of electricity that changes in accordance with the change in the AC impedance taken from the AC impedance circuit;
In the vehicle obstacle determination device comprising:
The AC power supply has a large difference in frequency characteristics of the electrical equivalent model between the human body and another conductor due to the difference in the resistance component and the capacitance component in the electrical equivalent model of the conductor including the resistance component and the capacitance component. An obstacle determination device for a vehicle, wherein an AC voltage having an appearing frequency is supplied to the AC impedance circuit.   2. The vehicle according to claim 1, wherein the AC power supply supplies an AC voltage having a frequency substantially equal to a resonance frequency of an electrical equivalent model of a human body including a resistance component and a capacitance component to the AC impedance circuit. Obstacle discrimination device.   The determination unit sets a threshold value in advance between an output value at the time of approaching a human body and an output value at the time of approaching another conductor with respect to the amount of electricity output from the AC impedance circuit, and the approaching conductivity is determined based on the threshold value. The vehicle obstacle determination device according to claim 1 or 2, wherein the vehicle determines whether the body is a human body.

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