JP4170112B2 - Obstacle discrimination device for vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an obstacle discrimination device for a vehicle for detecting or discriminating an object that collides with, for example, a vehicle bumper.
[0002]
[Prior art and its problems]
Pedestrian protection technology that activates a device to protect pedestrians when it is determined whether or not the collision target is a pedestrian at the time of a vehicle collision has been proposed, and its practical application has been studied. For this reason, a pedestrian discrimination technique is desired.
[0003]
As a prior art pedestrian discrimination technique, Patent Documents 1 and 2 describe walking based on a change in capacitance between a collision target that is a conductor (including a resistor in this specification) and an electrode plate of a sensor. Has proposed a capacitive collision target discrimination technique that electrically detects the difference in capacitance between a person and a conductor.
[0004]
[Patent Document 1]
JP 2000-177514 A [Patent Document 2]
Japanese Patent Laid-Open No. 2000-326808 [0005]
[Problems to be solved by the invention]
However, in the above-described conventional electrostatic capacity type collision object discrimination technology, the difference in electrostatic capacity between the human body and the metal body is not so large, and the inclination of the sensor output is in the same direction. There was a drawback that it was difficult to separate from humans depending on the type. Further, since it is necessary to operate at a high frequency in order to increase the output change accompanying the capacitance change, there is a problem that the influence of the high frequency noise superimposed on the circuit output and the influence of the parasitic capacitance are large.
[0006]
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 having excellent detection accuracy while suppressing the complexity of the circuit configuration.
[0007]
[Means for Solving the Problems]
The vehicle obstacle discriminating device of the present invention includes 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 approaching degree of the approaching conductor, and is extracted from the AC impedance circuit. In the vehicle obstacle discrimination device comprising:
The AC impedance circuit includes a coil as an inductance element, and the determination unit makes the determination based on an inductance change of the coil caused by the approaching conductor approaching the coil. Note that the approaching conductor referred to here is an object having a specific resistance smaller than the electrical insulator level, and includes an at least human body level specific resistance and a specific resistance smaller than that. Therefore, the human body and the metal body are included in the approaching conductor referred to here.
[0008]
That is, according to the present invention, the approaching conductor that has a predetermined specific resistance and approaches the vehicle (the sensor unit thereof) changes the approaching conductivity based on the phenomenon of changing the inductance of the coil (ie, the inductance element) of the sensor unit. Detection of body approach or discrimination of its type. More specifically, when an approaching conductor made of a metal body approaches the coil, the inductance of the coil decreases due to an eddy current induced in the metal body. As a result, when the approaching conductor is composed of a metal body having a conductivity much lower than that of the human body, the reduction of the inductance of the approaching conductor is larger than that of the human body, and this corresponds to eddy current loss. The resistance value of the equivalent resistor connected in parallel with the coil to be reduced is also reduced. As a result, the close proximity of the metal body to the coil greatly reduces the reduction of the AC impedance of the coil compared to the close proximity of the human body, so that the metal body and the human body can be discriminated based on this.
[0009]
In the apparatus of the present invention, the AC impedance circuit further includes an electric quantity detection impedance element connected in series with the coil, and the determination unit determines an inductance change of the coil as a voltage of the electric quantity detection impedance element. Detect based on descent. In this way, it is possible to easily detect the presence or absence of a decrease in the AC impedance of the coil.
[0010]
Further , in the apparatus of the present invention, the determination unit determines a metal body as the approaching conductor based on an increase in voltage drop of the electrical quantity detection impedance element mainly caused by a change in inductance of the coil. Thereby, it is possible to easily detect whether or not the AC impedance of the coil is reduced.
[0011]
In the apparatus of the present invention, one end of the coil is further grounded through the impedance detecting element for electric quantity, and the determination unit is mainly caused by a change in parasitic capacitance connected in parallel to the impedance element for detecting electric quantity. The person as the approaching conductor is discriminated based on a change in voltage drop of the impedance detecting element for detecting electric quantity.
[0012]
More specifically, as described above, the reduction of the AC impedance of the coil due to the approach of the human body is much smaller than that of the metal body, but the capacitance C of the AC impedance circuit to the human body is relatively large because the surface area of the human body is relatively large. . Although this capacitance C can be equivalent to existing between both ends of the AC impedance circuit and GND, the capacitance C on the side fed from the AC power supply of both ends of the AC impedance circuit is charged from the AC power supply. Therefore, it can be ignored, and the capacitance C connecting the connection point between the AC impedance circuit and the impedance detecting element for detecting the quantity of electricity and GND increases. Since the electrostatic capacitance C is connected in parallel with the impedance detecting element for electric quantity, the AC impedance of the impedance element for detecting electric quantity is lowered, and as a result, the voltage drop of the impedance element for detecting electric quantity is lowered. Accordingly, the approach of the human body to the AC impedance circuit can be detected by the voltage drop of the electrical quantity detection impedance element. If the metal body has an area equivalent to that of the human body, the capacitance C is connected in parallel with the impedance detection element for the amount of electricity as in the case of the human body. Since the increase in the voltage drop of the electrical quantity detection impedance element due to the reduction of the AC impedance of the coil is more dominant than the voltage drop of the electrical quantity detection impedance element due to this capacitance C, the voltage drop of the electrical quantity detection impedance element Will increase.
[0013]
In a preferred aspect, the discriminating unit determines that the approaching conductor is a metal body due to an increase in the voltage drop of the electric quantity detection impedance element, and that the approaching conductor is due to a decrease in the voltage drop of the electric quantity detection impedance element. Judge as human. Thereby, since the direction of the voltage change of the impedance element for electric quantity detection is reversed by the approach of a human and the approach of a metal body, both can be distinguished well.
[0014]
In a preferred aspect, the AC impedance circuit includes a capacitor connected in parallel with the coil, and the AC power supply supplies an AC voltage having a frequency substantially equal to a parallel resonance frequency of the coil and the capacitor to the AC impedance circuit. To do. This makes it possible to set the combined AC impedance of the coil and the capacitor very high when neither the metal body nor the human approaches the AC impedance circuit, and the AC impedance of the coil due to the approach of the metal body. The rate of change of this synthetic AC impedance due to the change can be increased, and the metal body detection sensitivity can be improved.
[0015]
In a preferred aspect, the AC impedance circuit includes a resistance element connected in parallel with the coil and the capacitor. In this way, the impedance of the AC impedance circuit in a state where the metal body or the human body is not approaching can be easily set to an optimum level with respect to the AC impedance of the impedance element for detecting electric quantity by the resistance value of the resistance element. Can be prescribed.
[0016]
In a preferred aspect, since the electrical quantity detection impedance element is formed of a resistance element, it is easy to determine the AC impedance value of the electrical quantity detection impedance element.
[0017]
In a preferred aspect, the sensor has another sensor for detecting the approach of the detection target, and the discrimination unit detects the approach to the detection target even though the other sensor detects the approach of the detection target. When the change in voltage drop is small, it is determined that the detection target is an insulator. In addition, as said other sensor, an ultrasonic sensor, a pressure sensor, etc. are employable, for example. If it does in this way, it can discriminate | determine that the to-be-detected target which collided or approached is not a metal body or a human body.
[0018]
In a preferred aspect, the axial center of the coil is arranged in the direction in which the approaching conductor exists. In this way, the sensitivity of the coil can be improved.
[0019]
In a preferred aspect, a connection point between the coil and the capacitor and the impedance detecting element for detecting the quantity of electricity is connected to an electrode plate extending substantially at right angles to the assumed direction of the approaching conductor. The electrode plate preferably has a large area. If it does in this way, the decreasing rate of the impedance element for electric quantity detection by the approach of a human body can be improved, and a human body detection sensitivity can be improved.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the vehicle obstacle determination device of the present invention will be described with reference to FIG.
(Description of circuit configuration)
Reference numeral 1 denotes an AC power source which is a low output impedance sine wave oscillator, 2 denotes a sensor unit, and 3 denotes a discrimination unit. The sensor unit 2 includes an AC impedance circuit 21 and a voltage drop detection resistor 22 connected in series with each other. The AC impedance circuit 21 is formed by connecting a coil 211 embedded in a bumper 4 of a vehicle, a capacitor 212, and a resistance element 213 in parallel. 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 and the other end of the voltage drop detection resistor 22 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 resonance frequency of the parallel LC circuit composed of the coil 211 and the capacitor 212 is the oscillation frequency of the AC power supply 1. The discriminating unit 3 rectifies and smoothes the voltage drop of the voltage drop detection resistor 22, converts the amplitude into a digital signal and takes it into the microcomputer, and the microcomputer detects the type of the obstacle 5 and its approach. 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.
(Explanation of obstacle separation process)
A method for discriminating the proximity obstacle 5 and an approach detection method using this circuit will be described with reference to FIGS. In these figures, L is the inductance of the coil 211, C is the capacitance of the capacitor 212, R is the resistance value of the resistance element 213, Ro is the resistance value of the voltage drop detection resistor 22, Vi is the output voltage of the AC power supply 1, Vo is a voltage drop of the voltage drop detection resistor 22 and is an output voltage of the sensor unit 2.
[0021]
FIG. 2 shows the case where the proximity obstacle 5 is an electrical insulator. The capacitor 212 may be provided separately from the coil 211, but may be a stray capacitance of the coil 211. The resistor R may be provided separately from the coil L, but may be an internal resistance of the coil L itself. The sensing part of the object is a coil 211. Since the combined AC impedance of this LC parallel resonant circuit can theoretically be considered as infinite, the AC impedance of the AC impedance circuit 21 can be considered as the resistance value R. When the proximity obstacle 5 approaching the coil 211 is an electrical insulator, the proximity obstacle 5 does not affect the sensor unit 2 electrically, so that the output voltage Vo is output as is well known. The voltage Vi is determined by the resistance voltage dividing ratio between the resistance value R and the resistance value Ro.
[0022]
Here, if the approach of the proximity obstacle 5 is detected by an ultrasonic sensor or the like, the output voltage Vo of the sensor unit 2 does not change regardless of this approach, so the proximity obstacle 5 is not an electrical insulator, that is, a human being. Can be determined.
[0023]
FIG. 3 shows a case where the proximity obstacle 5 is a metal body such as aluminum. In this case, an eddy current flows through the metal body due to the approach of the metal body, the inductance of the coil 211 decreases, and the AC impedance of the LC resonance circuit decreases from theoretical infinity to a predetermined value. The AC impedance of the AC impedance circuit 21 is further reduced from the original value which is the resistance value of the resistance element 213. Due to the combined AC impedance of the AC impedance circuit 21, the voltage drop of the voltage drop detection resistor 22 that forms an impedance voltage dividing circuit therewith, that is, the output voltage Vo increases. That is, it can be determined that the metal body has approached when the output voltage Vo increases.
[0024]
FIG. 4 shows a case where the proximity obstacle 5 is a human body. Since the human body has a remarkably large specific resistance (two or more digits) compared to the metal body, the eddy current caused by the coil 211 can be almost ignored, and the parallel resonance state of the AC impedance circuit 21 is not destroyed, and the AC impedance The LC component of the circuit 21 can be ignored approximately. On the other hand, since the surface area of the human body is large, the capacitance C1 between the human body and the coil 21 (in terms of circuit, the connection point between the coil 21 and the voltage drop detection resistor 22) increases. Here, if the ground capacitance of the human body is C2, the connection point is grounded through a series circuit of the capacitances C1 and C2. As a result, this series-connected capacitance is connected in parallel to the voltage drop detection resistor 22 and their combined AC impedance is reduced, so that the voltage drop of the voltage drop detection resistor 22, that is, the output voltage Vo is reduced. That is, when the output voltage Vo decreases, it can be determined that the human body has approached. In the case of approaching the metal body shown in FIG. 3, for example, if this metal body is grounded, a large capacitance C1 is connected in parallel with the voltage drop detection resistor 22. In the case of approach, since the reduction of the AC impedance of the AC impedance circuit 21 is more dominant, the influence of the voltage drop reduction of the voltage drop detection resistor 22 due to the reduction of the capacitance C1 can be ignored. When the metal body is not grounded, the voltage drop reduction of the voltage drop detection resistor 22 is further reduced.
[0025]
FIG. 5 shows a calculation example of a change in the output voltage Vo when a human body, a metal, and an electrical insulator (other object) approach the coil 211, and FIG. 6 shows an actual measurement example.
[0026]
Next, as a comparative example, a graph showing a change in the AC impedance of the capacitance sensor unit and a change in the output voltage Vo when the electric insulator, metal body, and human body approach the capacitor C as a conventional capacitance sensor. A description will be given with reference to FIGS.
[0027]
FIG. 7 shows a case where the electrical insulator approaches, in which case the output voltage Vo does not naturally change. FIG. 8 shows a case where the ground metal body approaches, and in this case, since the capacitance C1 is connected in parallel to the voltage drop detection resistor Ro, a voltage drop of the voltage drop detection resistor 22 occurs, and the output voltage Vo decreases. FIG. 9 shows a case where a person approaches. In this case, since the capacitances C1 and C2 connected in series are connected in parallel to the voltage drop detection resistor Ro as described above, it is as much as in the case of approaching a metal body. However, the voltage drop of the voltage drop detection resistor 22, that is, the output voltage Vo is lowered. FIG. 10 shows a calculation example of the change in the output voltage Vo when the human body, the metal, and the electrical insulator (other object) approach the coil 211 by the capacitance sensor. From the comparison between FIG. 5 and FIG. 10, it is understood that the sensor of this embodiment can provide excellent discrimination accuracy because the influence of the separation of the human body and the metal body on the output voltage Vo is opposite. .
(Modification 1)
The deformation mode will be described below.
In the above embodiment, the metal body is made of a material having a small relative permeability and low electrical resistance, such as aluminum. However, if the metal body is a material having a large relative permeability and high electrical resistance, an inductance caused by an increase in eddy current loss is used. The inductance increases due to a decrease in the magnetic resistance of the magnetic circuit of the coil due to the metal body having a relative permeability larger than the decrease in.
[0028]
However, in the above embodiment, since the coil 21 forms a parallel resonance circuit, the combined AC impedance of the LC resonance circuit is limited from theoretical infinite to finite regardless of whether the coil inductance increases or decreases. Thus, the combined AC impedance value of the AC impedance circuit 21 decreases. That is, according to the above embodiment, since the parallel LC resonance circuit is employed, the metal body can be distinguished from the human body with high accuracy.
(Modification 2)
Other modifications will be described below.
[0029]
In this modification, the coil 211 wound around the bobbin 210 in FIG. 1 has a short axis and a large radius, and is opened forward. In this way, since the magnetic flux formed by the coil 211 can easily reach the target, the metal body detection sensitivity is improved. Reference numeral 100 denotes a metal cylinder having openings at both ends surrounding the coil 211. The metal cylinder 100 can reduce the sensitivity of the coil 211 in the radial direction of the coil 211 and can relatively improve the forward sensitivity. A metal plate 101 is connected to a connection point between the coil 211 and the voltage drop detection resistor 22, and extends in the vertical and horizontal directions. In this way, the capacitance C1 between the metal plate 101 and the human body in front of the metal plate 101 can be increased, and the human body detection sensitivity can be improved.
[0030]
(Modification 3)
In the above embodiment, the coil 213 of the AC impedance circuit 21 is grounded to the front bumper of the vehicle, but it may be provided at another part. A plurality of front bumpers may be provided at various positions.
[Brief description of the drawings]
FIG. 1 is a schematic circuit diagram showing an embodiment of the present invention.
FIG. 2 is an equivalent circuit diagram showing a case where an electrical insulator approaches the circuit of FIG.
FIG. 3 is an equivalent circuit diagram showing a case where a metal body approaches the circuit of FIG.
4 is an equivalent circuit diagram showing a case where a human body approaches the circuit of FIG.
FIG. 5 is a characteristic diagram showing output characteristics (calculation example) by the circuit of FIG. 1;
6 is a characteristic diagram showing output characteristics (measurement example) by the circuit of FIG. 1. FIG.
FIG. 7 is an equivalent circuit diagram showing a case where an electrical insulator approaches a conventional capacitance sensor.
FIG. 8 is an equivalent circuit diagram showing a case where a metal body approaches a conventional capacitance sensor.
FIG. 9 is an equivalent circuit diagram illustrating a case where a human body approaches a conventional capacitance sensor.
FIG. 10 is a characteristic diagram showing output characteristics (calculation example) of a conventional capacitance sensor.
FIG. 11 is a schematic circuit diagram showing a modification.
[Explanation of symbols]
1 AC power supply 2 Sensor unit 3 Discrimination unit 21 AC impedance circuit 22 Voltage drop detection resistor 211 Coil 212 Capacitor 213 Resistance element

Claims (8)

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 approaching degree of the approaching conductor,
A discriminating unit for discriminating the detection of the approaching conductor or its type based on the amount of electricity that changes in accordance with the change in the AC impedance taken out from the AC impedance circuit;
In the vehicle obstacle determination device comprising:
The AC impedance circuit includes a coil as an inductance element,
The determination section, to name the detection or determination on the basis of the inductance variation of the coil due to the approach of the proximity conductor to said coil,
Before SL AC impedance circuit has the coil and connected in series electrically amount detecting impedance element,
The discriminating unit detects a change in inductance of the coil based on a voltage drop of the impedance detecting element for detecting electric quantity ,
Before SL discrimination unit discriminates the metal member as the approaching conductor based on the increase in the voltage drop of the electric quantity detecting impedance element mainly caused by the inductance variation of the coil,
One end of the previous SL coil is grounded through the electric quantity detecting impedance element,
The discriminating unit discriminates a person as the approaching conductor based on a decrease in voltage drop of the electric quantity detection impedance element mainly caused by a change in parasitic capacitance connected in parallel to the electric quantity detection impedance element. An obstacle discriminating apparatus for a vehicle , characterized in that: The vehicle obstacle determination device according to claim 1 ,
The determination unit determines that the approaching conductor is a metal body due to an increase in the voltage drop of the electric quantity detection impedance element and that the approaching conductor is a human due to a decrease in the voltage drop of the electric quantity detection impedance element. An obstacle discriminating apparatus for a vehicle characterized by the above. In the vehicle obstacle determination device according to claim 1 or 2 ,
The AC impedance circuit has a capacitor connected in parallel with the coil,
The vehicle obstacle determination device, wherein the AC power supply supplies an AC voltage having a frequency substantially equal to a parallel resonance frequency of the coil and the capacitor to the AC impedance circuit. The vehicle obstacle determination device according to claim 3 ,
The AC impedance circuit is a vehicle obstacle determination device having a resistance element connected in parallel with the coil and a capacitor. The vehicle obstacle determination device according to claim 4 ,
The electric quantity detection impedance element is a vehicle obstacle determination device including a resistance element. The vehicle obstacle determination device according to claim 1 ,
It has other sensors that detect the approach of the detection target,
The determination unit determines that the detection target is an insulator when a change in voltage drop of the impedance detection element for electric quantity is small even though another sensor detects the approach of the detection target. Obstacle discrimination device for vehicles. The vehicle obstacle determination device according to claim 3 ,
The obstacle detection device for a vehicle, wherein an axis of the coil is arranged in a direction in which the approaching conductor is present. The vehicle obstacle determination device according to claim 3 ,
An obstacle discriminating apparatus for a vehicle, wherein a connection point between the coil and the capacitor and the impedance detecting element for detecting an electrical quantity is connected to an electrode plate extending substantially at right angles to a direction in which the approaching conductor is present.

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