JP3214932B2 - Distance / speed prediction device - Google Patents

Abstract

PURPOSE:To evaluate the degree of risk on collision with a constant threshold value even when the angle of the base line of collision against the normal line is large (oblique collision) by calculating the constituent of the relative speed perpendicular to the base line from the detected output of a sensor. CONSTITUTION:Distance/speed sensors 1, 2 having light projection sections and light reception sections are provided on a moving body 3 at an interval of the base line length, and light beams 4, 5 are emitted from the sensors 1, 2 to cross each other. An obstacle 6 approaches the moving body 3 at the speed vector V, and it gets into contact with the light beam 4 at a point P when it is moved to the position 7. The scattered light is received by the sensors 1, 2 at the point P, and distances of the point P from both ends of a base line AB and constituents V1, V2 of the speed vector V in the directions of the sensors 1, 2 are measured. When the relative speed constituent VY=Vcostheta2 perpendicular to the base line AB exceeds the preset value Vth, a life protecting device such as an air bag or a pre-tension must be activated. The speed constituent VY (degree of risk) is obtained from measured parameters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance / speed prediction device, for example, a distance / speed prediction device suitable for a vehicle collision prediction sensor. The present invention relates to a distance / speed prediction device that generates a start signal of a protection device.

[0002]

2. Description of the Related Art Conventionally, as a vehicle collision prediction sensor,
Although rear-end collision prevention during traffic congestion and back sensors during reverse are known, it is generally known whether a collision is dangerous to the life of the driver or passenger, relative speed to the obstacle, weight of the obstacle, It depends on the way of collision, etc., and it is often difficult to know these before the collision. As a conventional method for measuring the strength of an impact after a collision, a mechanical acceleration sensor is known. When this measured value exceeds a certain threshold value, a life protection device such as an airbag or a pretension is activated to mitigate the impact in the event of a collision.

Many methods for predicting the danger of a collision before a collision have been proposed in many cases, and many of them are based on the assumption that the inter-vehicle distance is long as seen in a rear-end collision prevention device. However, detection of the danger of collision between a moving object and an obstacle in a close state immediately before the collision and the relative speed play an important role in determining whether to activate the life protection device.

The present applicant has already shown a method for obtaining an evaluation value relating to the risk of collision and a speed immediately before the collision in the collision prediction device of Japanese Patent Application No. 4-8531. FIG. 8 illustrates this principle. In the figure, point P is an obstacle, and A,
B is distance / speed measurement means provided at both ends of the moving object. V is the relative speed between the moving object and the obstacle, V ₁ , V ₂
The distance and speed measuring means A, the velocity component in the direction B, the point a theta P is A, the angle, the angle forming the theta ₁ is a V and V ₁ tensioning against B, L the length of the base line AB, A , B to the point P are L ₁ and L ₂ . The risk of collision is high when θ ₁ ≦ θ, and decreases as θ ₁ > θ. This can be expressed as follows using measured parameters.

V ₁ = Vcos θ ₁ , V ₂ = Vcos (θ
₁₋ θ), V ₂ + V ₁ = 2V cos (θ ₁ −θ / 2) cos (θ /
2) V ₂ −V ₁ = 2V sin (θ ₁ −θ / 2) sin (θ /
2) If (V ₂ −V ₁ ) / (V ₂ + V ₁ ) = K, θ ₁ = tan ⁻¹ {K / tan (θ / 2)} + θ / 2 Therefore, the condition of θ ₁ ≦ θ is K ≦ tan ² (θ / 2)
It is expressed as Alternatively, in consideration of the ^{sign, | K | ≦ tan 2 (} θ / 2) ··· (1) _{^{However, θ = cos -1 (L 1}} 2 + L 2 2 -L 2) / 2L 1 L 2 ·· (2) K = (V ₂ −V ₁ ) / (V ₂ + V ₁ ) (3) The true relative speed V is given by the following equation.

V = (V ₁ ² + V ₂ ² -2 V ₁ V ₂ cos θ) ^1/2 / sin θ (4) When the relative speed V exceeds a certain set value V _th , an airbag, a pretension, etc. It is necessary to activate the life-protection device. That is, V ≧ V _th (5) In other words, from the known amount L and the parameters L ₁ , L ₂ , V ₁ , V _{2 of} the measured distance / speed, (2),
Calculate θ, K, and V using equations (3) and (4),
The risk of collision can be determined by checking whether the inequalities (1) and (5) are satisfied. By using these information and the information of the impact sensor after the collision and obtaining a signal for activating the life protection device through a logic circuit means (not shown), it is highly accurate whether the life protection device should be started or not. Information can be obtained.

[0007]

The above-mentioned application has the following disadvantages. The threshold value V
_th is determined for a component of the velocity V perpendicular to the base line AB. For this reason, the threshold value V _th is substantially constant for the collision at an angle close to the perpendicular to the base line AB, but corresponds to the magnitude of the angle in the case of an oblique collision with a large angle with respect to the normal line of the base line. _Vth needs to be changed.

The present invention has been made in view of such a situation, and the present invention is not limited to a case where a collision between a moving object and an obstacle in a close state immediately before a collision has a large angle with respect to a normal to a base line. It is an object of the present invention to provide a distance / speed prediction device that evaluates the risk of collision based on a threshold value and generates a start signal for a life protection device.

[0009]

SUMMARY OF THE INVENTION To this end, the present invention provides an obstacle detecting / projecting / receiving unit which is disposed at a distance of a base line from a moving body, and the light beam crosses from the projecting unit so as to intersect each other. And a distance / speed detecting means for detecting the distance between the moving object and the obstacle and the relative speed of the two, and receiving the reflected light from the obstacle by the light receiving unit, and detecting the distance / speed detecting means from the detection output of the distance / speed detecting means. Calculating means for calculating a component perpendicular to a base line of the relative speed. Further, the present invention has an obstacle detecting / projecting light receiving / receiving section which is arranged at a distance of a base line from the moving body, and emits a light beam so as to intersect with each other from the light emitting section and reflects the light from the obstacle. Distance / speed detecting means for receiving light at the light receiving unit and detecting the distance between the moving body and the obstacle and the relative speed of both, and a component perpendicular to the base line of the relative speed from the detection output of the distance / speed detecting means. Calculating means for calculating the relative speed component perpendicular to the baseline with a predetermined threshold value, and calculating means for determining whether to generate an activation signal for the life protection device according to the comparison result. It is characterized by having.

[0010]

According to the present invention, a relative speed component perpendicular to the base line between the moving object and the obstacle is obtained from the distance between the moving object and the obstacle detected by using the two distance / speed detecting means and the relative speed between the two. calculates V _Y, V _Y and is obtained by adapted to compare the predetermined threshold V _th, the constant even when the angle is large oblique impact against the baseline of the moving body threshold V
_th can be adopted, and the life protection device can be activated when V _Y exceeds V _th .

[0011]

FIG. 1 shows a conceptual diagram of the present invention. In FIG. 1, distance / speed sensors 1 and 2 are arranged at two points A and B with AB as a base line and point P as an obstacle. V, V ₁ , V ₂ ,
8, θ and θ ₁ are determined as shown in FIG. 1, a perpendicular PH is lowered from the point P to the base line AB, and a relative velocity component Vcos θ ₂ perpendicular to the base line AB is used as an evaluation amount instead of the velocity vector V. With this selection, the threshold V _th is substantially constant even when the angle of the base line with respect to the normal is large.
Can be compared.

FIG. 2 shows a first embodiment of the present invention. In FIG. 2, distance / speed sensors 1 and 2 having a light projecting unit and a light receiving unit are provided on a moving body 3 at intervals of a base line length L, and collimated coherent light is output from the distance / speed sensors 1 and 2. The beams 4, 5 are emitted so as to intersect each other. As the base length L, a relatively long distance of about 1 to 2 m is used. Numeral 6 denotes an obstacle, which approaches the moving body 3 with a velocity vector V, moves to a position represented by 7 and contacts the light beam 4 at a point P, and V ₁ , V ₂ , θ ₁ , θ ₂ are It is determined as shown in FIG. The scattered light at the point P is received by the distance / speed sensors 1 and 2 at both ends of the base line AB, and the distances L ₁ and L ₂ from both ends of the base line AB at the point P and the distance / speed sensors 1 and ₂ of the speed vector V are detected. Components V ₁ and V _{2 in the} direction are measured. Assuming that the angles of the point P with respect to both ends of the base line AB are α and β, the relative velocity component V _Y = Vcos θ ₂ perpendicular to the base line AB is expressed by the following equation.

[0013] _{V Y = Vcosθ 2 ··· (6} ) _{However, θ 2 = θ 1 + α} -π / 2 α = sin -1 (L 2 sinθ / L) θ 1 = tan -1 (K / tan (θ / 2)) + θ / 2 K = (V 2 -V 1) / (V 2 + V 1) θ = cos -1 (L 1 2 + L 2 2 -L 2) / 2L 1 L 2 V = (V 1 2 ^{_{+ V 2 2 -2V 1 V 2}} cosθ) 1/2 / s
inθ When the relative speed V _Y exceeds a certain set value V _th , it becomes necessary to activate a life protection device such as an airbag or a pretension. That is, V _Y ≧ V _th (7) Accordingly, θ, K, and V are obtained from the known amount L and the parameters L ₁ , L ₂ , V ₁ , and V _{2 of} the measured distance and speed, and θ The risk of collision can be determined by calculating ₁ , θ ₂ and α, finding V _Y from equation (6), and seeing whether or not the inequality equation (7) is satisfied.

FIG. 3 is a diagram showing functional blocks of the first embodiment of the present invention and showing a processing flow. In FIG. 3, reference numeral 20 denotes a distance / speed measuring means, and 21 denotes (θ, K,
V) calculating means 23, (θ ₁ , θ ₂ , α) calculating means, 2
4 is a vertical relative velocity component (V _Y ) calculating means, 22 and 30 are discriminating means, 25 is a logic circuit, 26 is an impact sensor, 27 is a warning signal generating means, and 28 is a starting signal generating means for the life protection device. Represent.

The measured value L is obtained by the distance / speed measuring means 20.
_{1, L 2, V 1,} V 2 are detected, the measured value (theta,
K, evaluated amount theta by V) calculation means 21, K, V is calculated, further _{(θ 1, θ 2, α} ) by calculating means 23, theta
₁ , α, θ ₂ are calculated. Next, the relative velocity component V _Y = Vcos θ ₂ perpendicular to the base line AB is calculated by the vertical relative velocity component (V _Y ) calculation means 24 based on the equation (6), and the calculated V _Y is determined by the determination means 30. _Is compared with a predetermined threshold value _Vth . If it exceeds this, the output signal of the impact sensor 26 and the determination means 22
With reference to the comparison result between the evaluation amount K and C = tan ² (θ / 2), the activation signal of the life protection device is turned ON through the activation signal generating means 28 according to the logical operation by the logic circuit 25.

The logic operation of the logic circuit 25 will be described with reference to FIGS. In FIG. 4, the determining means 22, 30
If both are satisfied as a result of the determination in step 2, the logical product of the results is taken, and the result is compared with the impact sensor output signal α after the collision.
Comparison determination alpha ≧ alpha with aging predicted value alpha ₁ at time t _{1
If 1} is YES, a logical product of this is taken and the activation signal of the life protection device is turned ON. Further, if the comparison determining alpha ≧ alpha ₁ is NO, then the comparison and determination alpha ≧ alpha ₂ with aging predicted value alpha ₂ at time t ₂ of the alpha, YES if, this and K ≦
C, a logical operation is performed by the logical operation circuit RC with the logical sum of the comparison determination signal of V _Y ≧ V _th to determine whether or not the activation signal of the life protection device is turned ON. If this result is negative, the process further waits for a comparison α ≧ α ₃ to be compared with the temporal change predicted value α ₃ at time t ₃ . If this result is YES, the activation signal of the life protection device is turned ON even if both the comparison determination signals of K ≦ C and V _Y ≧ V _th are NO. If α <α _3, start-up signal is not issued. FIG. 5 schematically shows the initial temporal change of the shock sensor output signal α after the collision. Specifically, t ₃ represents the shortest time in which the life protector can be activated by the impact sensor alone, and is usually selected within 20 ms. Further, t ₁ and t ₂ are, for example, 1 respectively.
Preferably, it is selected within 0 ms and 15 ms. The shock sensor output signal α ₃ is, for example, 12 mp in an airbag.
h (about 20 km / h).

The logical operation circuit RC, measurements alpha _2m at time t ₂ of the shock sensor output signal alpha after the collision, and, K, V _Y
Is a comparison of a kind of weighted average value of the measured values K _2m and V _2m at the same time with a predetermined set value. For example, using f (α _2m ), g (K _2m ), and h (V _2m ) as evaluation functions corresponding to the respective measurement values, the evaluation value ε is given by: ε = a ₁ f (α _2m ) + a ₂ g (K _2m ) + A ₃ h (V _2m ), and the obtained ε is set to a predetermined set value ε _0.
Compare with Here, a ₁ , a ₂ , and a ₃ are coefficients for obtaining a weighted average value, and are selected as a ₁ + a ₂ + a ₃ = 1. Evaluation function f (α _2m ), g (K _2m ),
Specific examples of h (V _2m ) are as follows: f (α _2m ) = f (α _{2 m} / α ₂ ) = 1 if 0.9 ≦ α _2m / α ₂ <1.0 0.5 if 0.8 ≦ α _2m / Α ₂ <0.90 if α _2m / α ₂ <0.8 g (K _2m ) = g (K / C) = 1 if 1.0 ≦ K / C <3.0 0.5 if 3. 0 ≦ K / C <6.0 0 if 6.0 ≦ K / Ch (V _2m ) = h (V _2m / V _th ) = 1 if 0.9 ≦ V _2m / V _th <1.0 0.0. 5 if 0.8 ≦ V _2m / V _th <0.90 if V _2m / V _th <0.8 Also, as numerical examples of the coefficients a ₁ , a ₂ and a ₃ , a ₁ = 0.5, a ₂ = 0.2, a ₃ = 0.3 The evaluation value ε is obtained from the evaluation function and the coefficient determined as described above, and is compared with a predetermined setting value ε ₀ . If ε ₀ ≦ ε, the activation signal of the life protection device is turned ON. As ε ₀ , for example, a numerical value of about 0.85 to 1.0 is selected.

In this embodiment, the base line A of the relative speed with respect to the obstacle at the closest distance such as within 1 m from the base line AB of the moving object.
Although the case where the component perpendicular to B is determined is considered, it is possible to search for an obstacle farther by appropriately selecting the intersection angle of the light beams. In addition, the description has been made with the mind that two identical light beams are radiated at the same time. However, the band-pass filters are lit alternately in time series or radiate simultaneously, but are amplitude-modulated at different frequencies and correspond to the respective light beams. And the signal processing shown in the above flow may be performed in parallel.

The feature of the present embodiment is that the component perpendicular to the base line AB of the relative speed with respect to the obstacle can be accurately measured at the closest distance with a simple configuration such as a single light beam crossing each other.

When the existence of an obstacle is confirmed and the parameters of distance and speed are measured, the possibility of collision is extremely high, but the mass of the obstacle is large enough to require activation of the life protection device. It is difficult to predict the mass of an obstacle using a known light, microwave, or ultrasonic wave as a means for measuring the distance / velocity parameter. Relying on this prediction. Then, using the criteria of K ≦ C and V _Y ≧ V _th , it is possible to output the activation signal of the life protection device after the collision as early as possible within the maximum time t ₃ required for life support, In the earliest case, it is possible to issue an activation signal within 10 ms after the collision and to make the inflation time of the airbag longer, which can contribute to improvement of safety.

FIG. 6 shows a second embodiment of the present invention. First
In this embodiment, single light beams intersecting each other are emitted from both ends of the base line AB. In this embodiment, light beams intersecting each other are emitted from both ends of the base line AB. In FIG. And a pair of light beams 12 and 13. A straight line indicated by a dotted line means that a predetermined distance _Yth from the base line AB is set as the monitoring distance. In other words, if the position P where the obstacle 6 first comes into contact with one of the light beams 10 and 11 is within the distance _Yth , the light beam is switched to the other light beam emitted from the same distance / speed sensor. Again to confirm the danger. For example, if the point at which the light beam 10 first contacts the light beam is within the monitoring distance _Yth , this means that the light beam 10 is cut to 11 and the measurement is attempted again.

FIG. 7 shows a specific configuration and processing flow. FIG. 7 is a partial modification of the processing flow of FIG. 3, and only the modified part will be described. When an obstacle comes into contact with the light beam, the distance / velocity measuring means 20 uses L ₁ , L ₂ , V
₁ and V ₂ are measured, and the evaluation quantities θ, K and V are calculated by the (θ, K, V) calculating means 21 and further (θ ₁ , θ ₂ ,
α) The calculation means 23 calculates θ ₁ , α, θ ₂ ,
The calculation unit 24 calculates the relative velocity component V _Y perpendicular to the base line AB.
Is calculated and compared with a predetermined threshold value V _th by the determination means 30. At the same time, the discriminating means 32 determines the magnitude of the distance Y from the base line AB of the contact point P and the monitoring distance _Yth. If the result is YES, the light beam switching circuit 33 is operated to repeat the above processing again. Again a result, the calculation of V _Y by calculating means 24, is performed processing up compared with the threshold V _th, the judgment result of the light beam is switched before and after the determination means 30, the shock sensor 26, the result of the determination means 23 In consideration of the above, the logic circuit 31 determines whether or not to activate the life protection signal.

Although various determination mechanisms are conceivable, one example is to take an arithmetic mean of two measurements such as (V _y1 + V _y2 ) / 2 ≧ V _th (8). The calculation of the distance Y is performed by, for example, the following equation.

Y = (L ₁ L ₂ sin θ) / L (9) Next, features of the present embodiment will be described. In FIG. 6, a double light barrier is formed by switching between the two light beams 10 and 11, and it is detected that an obstacle has approached a preset monitoring distance _Yth. As shown, it is possible to double the accuracy of the measurement.

This embodiment can be modified as follows. In FIG. 6, light beams are radially emitted from each of the base lines AB.
Although the main beam is emitted, it is possible to increase the number of the beams or to make the emission angle of a single light beam variable so as to equivalently have the same role as a plurality of light beams.

[0026]

As described above, according to the present invention, by measuring the speed of an obstacle immediately before a collision, in particular, the speed component perpendicular to the baseline, the evaluation criterion V _th is determined with respect to the normal to the baseline. In the case of an oblique collision having a large angle, it is possible to adopt a substantially constant value, and it is possible to accurately measure in real time with a simple configuration, and the speed component exceeds a predetermined threshold. In such a case, an activation signal for the life protection device can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a diagram illustrating a first embodiment.

FIG. 3 is a diagram illustrating a configuration and a processing flow of the first embodiment.

FIG. 4 is a diagram illustrating a logic circuit according to the first embodiment.

FIG. 5 is a diagram illustrating an output signal of an impact sensor.

FIG. 6 is a diagram illustrating a second embodiment.

FIG. 7 is a diagram illustrating the configuration and processing flow of a second embodiment.

FIG. 8 is an explanatory view of the principle of the collision prediction device of the prior application.

[Explanation of symbols]

1, 2 distance / speed sensor 4, 5 light beam 3 moving object 6, 7 obstacle 20 distance / speed measuring means 21 (θ, K, V) calculating means 23 (θ ₁ , θ ₂ , Α) calculating means 24 ... vertical relative velocity component (V _Y ) calculating means 22, 30, 32 ... discriminating means 25, 31 ... logic circuit 26 ... impact sensor 27 ... warning signal generating means 28 ... starting signal generating means 33 ... light Beam switching circuit

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-49-116746 (JP, A) JP-A-48-74985 (JP, A) JP-A-6-160527 (JP, A) JP-A-5-160527 197428 (JP, A) JP-A-49-92734 (JP, A) JP-A-53-4932 (JP, A) JP-B-52-9895 (JP, B2) JP-B-54-9036 (JP, B1)

Claims (2)

(57) [Claims] An obstacle detecting light-projecting / light-receiving unit is disposed at a distance of a base line from a moving body, and a light beam is emitted from the light-projecting unit so as to intersect with each other and reflected light from the obstacle. And a distance / speed detecting means for detecting the distance between the moving body and the obstacle and the relative speed of both, and a component perpendicular to the base line of the relative speed from the detection output of the distance / speed detecting means. A distance / velocity prediction device, comprising: a calculation means for calculating. 2. A light-emitting device according to claim 1, further comprising: an obstacle detecting light projecting / receiving unit disposed at a distance from the moving body by a base line length. And a distance / speed detecting means for detecting the distance between the moving body and the obstacle and the relative speed of both, and a component perpendicular to the base line of the relative speed from the detection output of the distance / speed detecting means. Calculating means for calculating, comparing means for comparing a relative speed component perpendicular to the base line with a predetermined threshold value, and calculating means for determining whether to generate a start signal for the life protection device according to the comparison result. A distance / speed prediction device, comprising: