JP2006347403A - Relative velocity calculation device and inter-vehicle distance controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a relative speed calculation device and an inter-vehicle distance controller for making compatible both the reduction of noise included in a relative speed calculation value and the reduction of a response delay generated when filtering the relative speed calculation value. <P>SOLUTION: This relative speed calculation device is provided with an inter-vehicle distance detection means 100 for detecting inter-vehicle distance information between an own vehicle and the other vehicle traveling ahead or behind the own vehicle and a relative speed calculation means 108 for calculating the relative speed information of the own vehicle and the other vehicle in each arithmetic period(for example, 20 milli-second) preliminarily set based on the inter-vehicle distance information. The relative speed calculation means 108 calculates relative speed information based on the inter-vehicle distance information inputted in the arithmetic period n and the inter-vehicle distance information inputted in an arithmetic period (n-r) prior to the arithmetic period n by the number r (r=15, for example) of prescribed periods. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is suitable for use in an auto-cruise control device or the like for automatically driving a vehicle at a predetermined speed, and a relative speed calculation device between the host vehicle and another vehicle, and an inter-vehicle distance set using the relative speed. The present invention relates to an inter-vehicle distance control device that maintains the above.

  In recent years, the technology and relative speed for calculating the relative speed between the vehicle and the object based on the inter-vehicle distance information between the vehicle and the object in front of the vehicle (preceding vehicle) or the object behind the vehicle (following vehicle). For example, an auto cruise device that automatically drives a vehicle at a set speed at a set speed to maintain a distance between the vehicle and the preceding vehicle at a predetermined distance has been developed. Those with the added are put into practical use.

  In such an auto cruise device with an inter-vehicle distance control function, the presence or absence of a preceding vehicle and the preceding vehicle are detected or detected when there is a preceding vehicle, and are set when no preceding vehicle is detected. When the preceding vehicle is detected, the inter-vehicle distance control is performed to maintain the inter-vehicle distance at a predetermined distance based on the detected inter-vehicle distance information.

  In this inter-vehicle distance control, feedback control for accelerating or decelerating the host vehicle may be performed so that the detected inter-vehicle distance information becomes a target inter-vehicle distance (predetermined distance). Although the target inter-vehicle distance can be set to a fixed distance in the simplest case, it is preferable to set a target inter-vehicle distance (predetermined distance) according to the vehicle speed of the host vehicle. In this case, of course, the target inter-vehicle distance is set larger as the vehicle speed of the host vehicle is higher.

In addition, a technique using the relative speed between the host vehicle and the preceding vehicle for such inter-vehicle distance control has been proposed (see, for example, Patent Documents 1 and 2).
For example, Patent Document 1 discloses a technique for controlling the vehicle speed of the host vehicle based on the difference between the inter-vehicle distance information between the host vehicle and the preceding vehicle and the target inter-vehicle distance and the relative speed between the host vehicle and the preceding vehicle. Has been.

In such an inter-vehicle distance control device, the inter-vehicle distance between the host vehicle and the preceding vehicle is detected by an inter-vehicle distance sensor such as a laser radar or a camera.
The relative speed information between the host vehicle and the preceding vehicle can be obtained by calculating the rate of change of the inter-vehicle distance. Generally, the inter-vehicle distance information is differentiated every predetermined calculation cycle (here, 20 milliseconds). Thus, relative speed information (relative speed calculation value) is calculated.

  However, the inter-vehicle distance information detected by the inter-vehicle distance detection sensor and the relative speed calculation value calculated by differentiating the inter-vehicle distance information are greatly affected by noise and the like, so the inter-vehicle distance control by the ECU becomes unstable. . Therefore, the ECU uses a signal value smoothed by performing a filtering process on these signals with a predetermined filter coefficient.

A low-pass filter (LPF) is used for the filter processing, and the LPF performs a filter operation based on a predetermined filter coefficient every predetermined operation period (for example, 20 milliseconds).
In the LPF, filter coefficients a and b satisfying (a + b = 1, a> 0, b> 0) are set, and the filtered signal value F (n−1) calculated by the LPF one calculation cycle before is input. The filtered signal value F (n) is calculated by adding the signal value (pre-filter signal value) L (n) multiplied by the filter coefficients a and b, respectively [F ( n) = aF (n−1) + bL (n)].

Thereby, the noise (minute change) included in the pre-filter signal value is cut or suppressed by the filter processing by the LPF, and the post-filter signal value has a smooth variation characteristic.
The post-filter signal value filtered by the LPF is cumulatively affected by the pre-filter signal value in each previous period, but this effect is greater as the pre-filter signal value near that point in time, The smaller the pre-filter signal value from that point, the smaller.

  At this time, the value of the filter coefficient a that is multiplied by the filtered signal value F (n−1) before one calculation cycle is increased (the value of the filter coefficient b that is multiplied by the input signal value L (n) is decreased) (filter) Since the noise in the input signal value L (n) in the calculation cycle is more strongly suppressed in the calculated filtered signal value, noise with a large amplitude can be removed.

However, if the value of the filter coefficient a is increased in this way, the latest input signal value L (n) is neglected. For example, when the pre-filter signal value L (n) varies as shown in FIG. The response delay ΔT until the fluctuation of the signal value before filtering is reflected in the value of the signal value after filtering becomes large.
Conversely, if the value of the filter coefficient a is set to be small (the value of the filter coefficient b is set to be large) (also referred to as making the filter lighter), the response delay ΔT can be reduced, but if the noise amplitude is large, the noise Cannot be removed sufficiently, and the inter-vehicle distance control becomes unstable.

Therefore, the values of the filter coefficients a and b are set to values that can remove noise reliably, and at the same time, can reduce noise more than a certain level while suppressing the response delay within the allowable limit with respect to fluctuations in the signal value before filter. It is desirable to do.
JP 2004-127926 A JP 2000-285395 A

  However, the relative speed calculation value calculated by differentiating the inter-vehicle distance information amplifies the noise included in the inter-vehicle distance information. Therefore, in the conventional relative speed calculation method, as shown in FIG. If the above-described filter coefficient a is set to be somewhat large so that it can be removed (filter coefficient b is small), a large response delay (ΔT) is generated that is not acceptable as shown in FIG. It will be.

As described above, according to the conventional technique, when the filter process is performed so as to remove the noise of the relative speed calculation value, the response delay of the relative speed calculation value after the filter becomes large, and thus the inter-vehicle distance control by the ECU is delayed. As a result, it is difficult to simultaneously eliminate noise and avoid response delay.
The present invention has been devised in view of such problems, and can be suitably used for an auto cruise control device or the like, and can suppress noise included in a relative speed calculation value calculated based on inter-vehicle distance information, It is an object of the present invention to provide a relative speed calculation device and an inter-vehicle distance control device using a relative speed, which can simultaneously reduce response delay that occurs when filtering a calculated value.

  In order to achieve the above-described object, the relative speed calculation device according to the first aspect of the present invention is an inter-vehicle distance detection unit that detects inter-vehicle distance information between the host vehicle and another vehicle traveling in front of or behind the host vehicle. And a relative speed calculation means for calculating relative speed information between the host vehicle and the other vehicle for each preset calculation cycle based on the inter-vehicle distance information. The calculation means calculates the relative speed information based on the inter-vehicle distance information input in the calculation cycle n and the inter-vehicle distance information input in the previous calculation cycle (n−r) by a predetermined number of cycles r. It is characterized by that.

According to a second aspect of the present invention, there is provided a relative speed calculation apparatus according to the first aspect of the present invention, further comprising a filter means for filtering the relative speed information calculated by the relative speed calculation means.
According to a third aspect of the present invention, there is provided the relative speed calculation device according to the first or second aspect, wherein the relative speed calculation means is configured to determine, for each calculation cycle, the inter-vehicle distance information input in the calculation cycle n and a predetermined distance. The relative speed information is calculated by dividing the difference from the inter-vehicle distance information input in the calculation cycle (n−r) before the cycle by the time corresponding to the predetermined number of cycles r.

  According to a fourth aspect of the present invention, in the relative speed calculation device according to the first aspect of the present invention, the cycle of the calculation cycle is 10 to 40 milliseconds, and the predetermined cycle number r is 5 to 50, and the relative speed calculation means is input in the calculation cycle (n−r) before the inter-vehicle distance information input in the calculation cycle every calculation cycle and the predetermined number of cycles r. The relative speed information is calculated by dividing a difference from the inter-vehicle distance information by a time corresponding to the predetermined period number r.

If the calculation cycle is shortened, high-precision control can be performed if inter-vehicle distance control is performed according to the calculation cycle, but the frequency of calculation and control becomes high, which imposes a heavy burden on the controller system. On the other hand, if the calculation cycle is lengthened, the frequency of calculation and control can be kept low, but the accuracy of control is reduced. From such a viewpoint, the calculation cycle is set to 10 to 40 milliseconds.
Further, if the time corresponding to the predetermined number of cycles r is too long, the response delay with respect to the actual relative speed becomes too large, and if it is too short, the effect of suppressing the amplitude of the noise of the relative speed calculated value is reduced. Sets the value of r so that the time corresponding to the predetermined number of cycles r is in the range of about 200 milliseconds to 500 milliseconds.

  According to a fifth aspect of the present invention, there is provided a relative speed calculation device according to any one of the first to fourth aspects, wherein the inter-vehicle distance filter means filters the inter-vehicle distance information detected by the inter-vehicle distance detection means. The relative speed calculation means calculates the relative speed information based on the filtered inter-vehicle distance information filtered by the inter-vehicle distance filter means.

  According to a sixth aspect of the present invention, there is provided an inter-vehicle distance control device according to the present invention, which detects an inter-vehicle distance between acceleration / deceleration means for accelerating or decelerating the own vehicle and a preceding vehicle traveling in front of the own vehicle. Distance detecting means, relative speed calculating means for calculating a relative speed between the host vehicle and the preceding vehicle for each predetermined calculation cycle based on the inter-vehicle distance information detected by the inter-vehicle distance detecting means, and the relative speed Based on the relative speed information filtered by the filter means and the inter-vehicle distance information detected by the inter-vehicle distance detection means, the own vehicle and the preceding vehicle are filtered. And an acceleration / deceleration control means for controlling the operation of the acceleration / deceleration means so that the inter-vehicle distance becomes a predetermined target value. Based 該車 distance information to 該車 distance information entered only in the previous calculation cycle (n-r) predetermined cycle number r, is characterized by calculating the said relative velocity.

  Therefore, according to the relative speed calculation apparatus of the first aspect of the present invention, when calculating the relative speed information in the calculation cycle n, the inter-vehicle distance information of the calculation cycle n and the calculation cycle (n Since the relative speed information is calculated based on the inter-vehicle distance information of -r), by calculating the change rate of the inter-vehicle distance information in a longer time than the conventional one, the noise included in the calculated relative speed calculated value is calculated. The amplitude can be suppressed.

  According to the relative speed calculation apparatus of the present invention as set forth in claim 2, in addition to the effect of claim 1, the relative speed information calculated by the relative speed calculation means can be filtered to obtain stable relative speed information. In addition, when the filter processing is performed, noise is sufficiently suppressed even with a relatively light filter, so that the relative speed can be calculated with high responsiveness to the actual relative speed fluctuation.

According to the relative speed calculation apparatus of the present invention as set forth in claim 3, in addition to the effect of claim 1 or 2, the inter-vehicle distance information in the calculation cycle n and the inter-vehicle distance in the calculation cycle (n−r) before the predetermined cycle. Since the relative speed can be calculated by dividing the difference from the information by the r calculation cycle, the relative speed can be obtained easily and reliably.
According to the relative speed calculation apparatus of the present invention as set forth in claim 4, in addition to the effects of claims 1 to 3, the current calculation cycle and 5 to 50 cycles for each calculation cycle of 10 to 40 milliseconds. The relative speed information is calculated by dividing the difference from the inter-vehicle distance information input before the calculation cycle number r by the time corresponding to the calculation cycle number r. Relative speed information can be calculated without delay, and the amplitude of noise included in the calculated relative speed information can be suppressed.

Further, according to the relative speed calculation device of the present invention described in claim 5, in addition to the effects of claims 1 to 4, the relative speed information is calculated based on the inter-vehicle distance information in which the noise is reduced by performing the filtering process. Furthermore, the amplitude of noise included in the calculated relative speed can be reduced.
According to the inter-vehicle distance control device of the present invention as set forth in claim 6, the relative speed calculation means calculates the relative speed using the inter-vehicle distance information when the predetermined number of cycles are traced back, and further filters this. Since the noise is removed, the filter can be set lighter than usual, and a good relative speed with less noise and delay can be obtained. Therefore, stable acceleration / deceleration control with good responsiveness is possible, and it is possible to perform inter-vehicle distance control with little unnecessary acceleration / deceleration.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 3 are for explaining an inter-vehicle distance control device including a relative speed calculation device according to an embodiment of the present invention. FIG. 1 is a block diagram showing the configuration, and FIG. 2 is an inter-vehicle distance information. FIG. 3 is a circuit diagram schematically showing an arithmetic circuit for filtering relative speed information and an arithmetic circuit for calculating relative speed, and FIG. 3 shows relative speed information (differential value of inter-vehicle distance information) and post-filter signal value in this embodiment. It is a graph which shows a time-dependent change.

  In the present embodiment, the relative speed calculation device and the inter-vehicle distance control device of the present invention are applied to an auto cruise control device. In this auto-cruise control device, when there is no preceding vehicle ahead of the host vehicle or when the inter-vehicle distance D between the host vehicle and the preceding vehicle is sufficiently wider than the inter-vehicle distance control start threshold Ds, the vehicle is set at the set vehicle speed V0. When the vehicle is automatically driven at a constant speed (constant speed control mode) and the inter-vehicle distance D is shorter than the inter-vehicle distance control start threshold Ds, the host vehicle is accelerated or decelerated so that the inter-vehicle distance D maintains the target inter-vehicle distance Dt. Then, the inter-vehicle distance is controlled (inter-vehicle distance control mode).

The inter-vehicle distance control start threshold Ds may be set to the detection limit value of the inter-vehicle distance sensor or may be set to be shorter than the detection limit value.
As shown in FIG. 1, the auto cruise control device according to the present embodiment includes an ECU (electronic control device) 150 including a memory (ROM, RAM) and a CPU, an inter-vehicle distance detection means (inter-vehicle distance sensor) 100, a vehicle speed. A sensor 101, a brake switch 102, a throttle opening sensor 103, and an operation switch 104 are provided, and a throttle actuator 105 and a brake actuator 106 as acceleration / deceleration means are further provided.

The input side of the ECU 150 is connected to an inter-vehicle distance detecting means 100, a vehicle speed sensor 101, a brake switch 102, a throttle opening sensor 103, and an operation switch 104. On the output side of the ECU 150, a throttle actuator 105 and a brake actuator 106 are connected. It is connected.
A vehicle speed sensor 101, a brake switch 102, and a throttle opening sensor 103 are sensors for detecting information on the traveling speed of the host vehicle, on / off of a brake pedal (not shown), and the opening of a throttle valve, respectively. The operation switch 104 is a switch for instructing the ECU 150 to start auto-cruise control. When the driver turns on the operation switch 104, the traveling vehicle speed at that time is set to the set vehicle speed V0 and the auto-cruise control is started. It is like that. The operation switch 104 is also provided with a function that can increase or decrease the set vehicle speed V0 during auto-cruising.

In addition, the auto-cruise control can be released by turning off the operation switch 104, but the auto-cruise control is also released by the brake operation detected from the signal of the brake switch 102.
The inter-vehicle distance detection means (inter-vehicle distance sensor) 100 is a sensor that detects the presence of an object (preceding vehicle) ahead of the host vehicle and the inter-vehicle distance between the host vehicle and the preceding vehicle, for example, using a laser radar or the like. The inter-vehicle distance information is output as a voltage value signal. Here, the detection limit value of the inter-vehicle distance sensor 100 is 150 meters, and when there is no preceding vehicle or the inter-vehicle distance is equal to or greater than the detection limit value, the inter-vehicle distance detection means sets the detection limit value (150 meters) to the inter-vehicle distance. It is output as distance information.

The ECU 150 includes, as functional elements, an inter-vehicle distance LPF 107, a differentiation circuit (relative speed calculating means) 108, a relative speed LPF (low-pass filter as a filter means) 109, a target inter-vehicle distance setting means 110, a target vehicle speed calculating means (target vehicle speed setting means). ) 111 and acceleration / deceleration control means 112.
The inter-vehicle distance detection signal input from the inter-vehicle distance detection means 100 to the ECU 150 is filtered by the inter-vehicle distance LPF 107. As a result, minute fluctuations (noise) included in the inter-vehicle distance detection signal (inter-vehicle distance information) are removed and converted into a stable signal value (filtered inter-vehicle distance information D) with less unnecessary fluctuations. The filtered inter-vehicle distance information D is input to the target vehicle speed calculation unit 111.

The filtered inter-vehicle distance information D filtered by the inter-vehicle distance LPF 107 is also input to a differentiating circuit (relative speed calculating means) 108. The differentiating circuit 108 performs a differentiation process on the input post-filter distance information, and calculates relative speed information (relative speed calculation value) from the rate of change of the post-filter distance information.
Then, the calculated relative speed calculated value is input to the relative speed LPF 109 for filtering. As a result, minute fluctuations (noise) included in the relative speed calculation value output from the differentiating circuit 108 are removed and converted to a stable signal value (filtered relative speed information) ΔV with little unnecessary fluctuation.

Details of the filtering process and the calculation of the relative speed information will be described later.
The target inter-vehicle distance setting means 110 stores a target inter-vehicle distance as a map corresponding to the vehicle speed V of the host vehicle, and based on the vehicle speed V of the host vehicle input from the vehicle speed sensor 101 using this map. Thus, a target inter-vehicle distance (target inter-vehicle distance) D0 is set.

When the inter-vehicle distance (filtered inter-vehicle distance information) D input from the inter-vehicle distance LPF 107 is equal to or greater than the inter-vehicle distance control start threshold Ds, the target vehicle speed calculation unit 111 indicates that there is no preceding vehicle ahead of the own vehicle or the own vehicle And the preceding vehicle is determined to be sufficient, the set vehicle speed V0 is set to the target vehicle speed Vt and sent to the acceleration / deceleration control means 112 (constant speed mode).
When the inter-vehicle distance D is smaller than the inter-vehicle distance control start threshold Ds, the inter-vehicle distance (filtered inter-vehicle distance) Dn input from the inter-vehicle distance LPF 107 in the calculation cycle n, and the relative speed input from the relative speed LPF 109 ( Based on the filtered relative speed information) ΔVn, the target inter-vehicle distance Dtn input from the target inter-vehicle distance setting means 110, and the vehicle speed Vn of the host vehicle input from the vehicle speed sensor 102, Vtn = Vn + a (Dn−Dtn) + bΔVn.・ (A)
To calculate the target vehicle speed Vtn. However, when the calculated target vehicle speed Vtn is larger than the set vehicle speed V0, the set vehicle speed V0 is set to the target vehicle speed Vt. The target vehicle speed Vtn set in this way is input to the acceleration / deceleration control means 112 at each calculation cycle.

The relative speed ΔV is positive in the direction in which the distance between the host vehicle and the preceding vehicle increases.
The acceleration / deceleration control means 112 performs feedback control for accelerating or decelerating the host vehicle so that the vehicle speed V of the host vehicle input from the vehicle speed sensor 101 becomes the target vehicle speed Vt. Thus, in the constant speed mode, the own vehicle travels at the set vehicle speed V0, and in the inter-vehicle distance control mode, the inter-vehicle distance between the own vehicle and the preceding vehicle is maintained at the target inter-vehicle distance D0.

Next, filter processing in the inter-vehicle distance LPF 107 and the relative speed LPF 109 and calculation of the relative speed in the relative speed calculation means (differential circuit) 108 will be described with reference to FIG.
As shown in FIG. 2, the inter-vehicle distance LPF 107 includes a signal recognition unit 201, a first amplifier 202, a second amplifier 203, a delay element 204, and an adder circuit 205.

The signal (voltage value) of the inter-vehicle distance information detected by the inter-vehicle distance sensor 100 is first input to the signal recognition unit 201 of the inter-vehicle distance LPF 107, and the signal recognition unit 201 is every 1 calculation cycle (here, 20 milliseconds). The input inter-vehicle distance detection signal value is recognized, and the recognized value is output as the inter-vehicle distance detection signal value L ₁ (n).
The first amplifier 202 is interposed between the delay element 204 and the adder circuit 205, and the second amplifier 203 is interposed between the signal recognition unit 201 and the adder circuit 205, respectively. The amplifier 203 outputs values obtained by multiplying the input signal values by the set filter coefficients a ₁ and b ₁ (where a ₁ + b ₁ = 1, a ₁ > 0, b ₁ > 0). ing.

The filter coefficients a ₁ and b ₁ are values set in advance so that a minute change (noise) of the inter-vehicle distance detection signal value L ₁ (n) can be sufficiently removed. In this case, the larger the filter coefficient a ₁ (the smaller the filter coefficient b ₁ ) is, the larger noise can be removed, but the response delay with respect to the change in the inter-vehicle distance detection signal value L ₁ (n) increases, so the filter coefficients a ₁ , b The value of ₁ is set to such a value that the noise can be surely removed, and at the same time, the response delay to the change in the inter-vehicle distance detection signal value L ₁ (n) does not become so large.

  The adder circuit 205 receives signal values from the first amplifier 202 and the second amplifier 203, and the adder circuit 205 adds the values of the input signal values and outputs the sum. The delay element 204 is interposed between the adder circuit 205 and the first amplifier 202, and the delay element 204 converts the signal value input from the adder circuit 205 (that is, the inter-filter distance information) into one calculation cycle (20 mm). (Second) is output with a delay.

Therefore, the inter-vehicle distance detection signal value L ₁ (n) input from the signal recognition unit 201 to the second amplifier 203 is converted into a signal value b ₁ L ₁ (n) obtained by multiplying the filter coefficient b ₁ by the second amplifier 203. Is input to the adder circuit 205, and the first amplifier 202 is supplied with the post-filter signal value F ₁ (n−1) before one operation cycle from the delay element 204, and is input with the post-filter signal value one operation cycle before. F ₁ (n−1) is converted to a signal value a ₁ F ₁ (n−1) obtained by multiplying the filter coefficient a ₁ by the first amplifier 202 and input to the adder circuit 205.

The adder circuit 205 adds the signal value a ₁ F ₁ (n−1) input from the first amplifier 202 and the signal value b ₁ L ₁ (n) input from the second amplifier 203 and adds them. The signal value a ₁ F ₁ (n−1) + b ₁ L ₁ (n) is output.
That is, when viewed as the entire inter-vehicle distance LPF 107, the inter-vehicle distance detection signal value L ₁ (n) input from the inter-vehicle distance sensor 100 is expressed as F ₁ (n) = a ₁ F ₁ (n−1) + b ₁ L ₁ (n ) ... (B)
And output from the inter-vehicle distance LPF 107.

The filtered inter-vehicular distance information filtered at the inter-vehicle distance LPF 107 for each calculation cycle is input to the differentiating circuit (relative speed calculating means) 108 and the target vehicle speed setting means 111.
The differentiation circuit 108 includes a delay element 206, an addition circuit 207, and a division circuit 208.

In the calculation cycle n, the filtered inter-vehicle distance information F ₁ (n) input from the inter-vehicle distance LPF 107 to the differentiating circuit 108 is input to the delay element 206 and the adding circuit 207 of the differentiating circuit 108.
The delay element 206 is configured to delay the inputted post-filter inter-vehicle distance information by 10 to 25 computation cycles (here, 15 computation cycles) and output the delayed post-filter inter-vehicle distance information F ₁ ( n-15) is input to the adder circuit 207 after inverting the sign.

Then, the adder circuit 207 adds the filtered inter-vehicle distance information F ₁ (n) input in the arithmetic cycle n and the post-filter inter-vehicle distance information −F ₁ (n−15) 15 arithmetic cycles before reversing the positive / negative. Output the signal value.
The signal output from the adder circuit 207 is input to the divider circuit 208, and a value divided by a time corresponding to 15 calculation cycles (ie, 300 milliseconds) is output.

That is, assuming that the differentiation circuit 108 as a whole, L ₂ (n) = [F ₁ (n) −F ₁ (n−15)] / 15 calculation cycle (C)
As a result, the relative speed calculation value L ₂ (n) in the calculation cycle n is output.
Incidentally, in the next calculation cycle (n + 1), the differentiating circuit 108 determines that L ₂ (n + 1) = [F ₁ (n + 1) −F ₁ (n−14)] / 15 calculation cycle (C ′).
Will be output. That is, in the differentiating circuit 108, the filtered inter-vehicular distance information input in the current arithmetic cycle for each arithmetic cycle (20 milliseconds), and the filtered inter-vehicle distance information input 15 arithmetic cycles before the current arithmetic cycle, A signal value obtained by dividing the difference by a time (300 milliseconds) corresponding to 15 calculation cycles is output.

The signal value calculated in the differentiation circuit 108 in this way indicates the rate of change of the inter-vehicle distance information (filtered inter-vehicle distance information), that is, the speed difference (relative speed) between the host vehicle and the preceding vehicle. That is, the differentiating circuit 108 calculates a relative speed calculation value for each calculation cycle and inputs it to the relative speed LPF 109.
The configuration of the relative speed LPF 109 is substantially the same as the configuration of the inter-vehicle distance LPF 107, and includes a first amplifier 209, a second amplifier 210, a delay element 211, and an adder circuit 212. However, since the relative speed calculated value L ₂ (n) is already input to the relative speed LPF 109 for each calculation period, the relative speed LPF 109 includes means for recognizing a signal for each calculation period like the signal recognition unit 201 in the inter-vehicle distance LPF 107. There is no need.

The first amplifier 209 and the second amplifier 210 multiply the input signal values by set filter coefficients a ₂ and b ₂ (where a ₂ + b ₂ = 1, a ₂ > 0, b ₂ > 0), respectively. A value is output.
The filter coefficients a ₂ and b ₂ are set in advance so as to sufficiently remove a minute change (noise) of the relative speed calculation value L ₂ (n) corresponding to the relative speed calculation value L ₂ (n). According to the present invention, the amplitude of noise included in the relative speed calculation value L ₂ (n) is suppressed as compared with the conventional one, so that the filter coefficient a ₂ is small (the filter coefficient b ₂ is large). ) Set so that the response delay to the change of the relative speed calculation value L ₂ (n) does not become large.

Therefore, the relative speed calculated value L ₂ (n) input from the differentiating circuit 108 in the calculation cycle n is F ₂ (n) = a ₂ F ₂ (n−1) + b ₂ L ₂ (n) in the relative speed LPF 109. ... (D)
And the filtered signal value F ₂ (n) is output.
Since the inter-vehicle distance control device (particularly the differentiation circuit 108) according to an embodiment of the present invention is configured in this manner, the difference between the inter-vehicle distance information in the current calculation cycle and the inter-vehicle distance information before 15 calculation cycles is calculated. Since the calculation is performed by dividing by a time corresponding to 15 calculation cycles (300 milliseconds), the range of variation (noise) in the calculated relative speed calculation value can be suppressed small (see FIG. 3).

This also makes it possible to sufficiently remove noise contained in the calculated relative speed even if the filter coefficient a ₂ set in the relative speed LPF 109 is set to a small value (b ₂ is set to a large value). Therefore, by setting the filter lighter than usual, a configuration with less response delay can be achieved.
In addition, since the differentiating circuit 108 calculates the relative speed calculation value every calculation cycle (20 milliseconds), the relative speed calculation value can be calculated without delaying the actual relative speed with respect to the change.

Therefore, the relative speed calculation device according to the present embodiment can reduce the response delay ΔT of the filtered relative speed information F ₂ (n) with respect to the relative speed calculation value L ₂ (n) as shown in FIG. While the noise included in the speed calculation value L ₂ (n) is reliably removed, the response delay ΔT is small and stable relative speed information (filtered signal value) can be calculated. In addition, since the relative speed obtained in this way is input to the target vehicle speed calculation unit 111, the inter-vehicle distance control device in the present embodiment does not cause the target vehicle speed calculation unit 111 to be delayed with respect to the actual relative speed change. Since the stable target vehicle speed Vt is set, the acceleration / deceleration control means 112 can stabilize the vehicle by accelerating or decelerating the vehicle, and can perform inter-vehicle distance control with good responsiveness.
[Others]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

For example, in the above-described embodiment, the calculation cycle related to the filter processing and the differentiation processing is one calculation cycle of 20 milliseconds, but the time of one calculation cycle is not limited to this.
However, if the calculation cycle is set longer than about 40 milliseconds, the frequency of calculation and control is reduced, so the load on the CPU and the like is reduced. However, the accuracy (data density) of the relative speed calculation value is reduced, and the target vehicle speed is set. The accuracy of control in the means 111 and the acceleration / deceleration control means 112 becomes coarse, and the response delay of the relative speed calculation value with respect to the actual relative speed also increases.

If the calculation cycle is set shorter than about 10 milliseconds, the control accuracy and the relative speed calculation responsiveness are improved. However, the calculation and control frequency per hour is excessive, and the load on the CPU is increased. Too big.
For this reason, the length of the calculation cycle is set in the range of 10 to 40 milliseconds so as not to increase the response delay of the relative speed calculation value and deteriorate the control accuracy while suppressing the load on the calculation process. Is preferred.

Further, in the embodiment, the time that the delay element 206 of the differentiating circuit 108 delays (that is, the time corresponding to the predetermined period number r) is not limited to this.
However, if the time corresponding to the predetermined period number r is too long, the relative speed calculation value response delay with respect to the actual relative speed becomes large. Moreover, if the time corresponding to the predetermined number of cycles r is too short, noise included in the relative speed calculation value cannot be sufficiently suppressed. For this reason, it is preferable to set the time corresponding to the predetermined number of cycles r in the range of 200 milliseconds to 500 milliseconds.

For example, when one calculation cycle is set to 10 milliseconds, the value of the predetermined cycle number r is set in the range of 20 to 50, and when one calculation cycle is set to 20 milliseconds, the value of the predetermined cycle number r is set. Is set in the range of 10 to 25, and when one calculation cycle is set to 40 milliseconds, the value of the predetermined cycle number r is preferably set in the range of 5 to 12.
In the above-described embodiment, the target vehicle speed setting unit 111 calculates the target vehicle speed using the filtered relative speed information. However, the use of the filtered relative speed information that is the output of the relative speed calculation device is not limited to this. Absent.

  For example, even if the target vehicle speed based on the relative speed information is not set and the acceleration or deceleration of the host vehicle is feedback controlled by throttle control based on the target inter-vehicle distance and the detected inter-vehicle distance, the relative speed is negative. In the case where the absolute value is considerably large (that is, when the vehicle approaches the preceding vehicle rapidly), for example, the vehicle may not be sufficiently decelerated only by the throttle control. If the value is negative and the absolute value is greater than or equal to a predetermined value, the driver may be warned or the vehicle may be decelerated by braking.

  In the above-described embodiment, the detected inter-vehicle distance and the calculated relative speed are each filtered to remove noise. However, like the relative speed calculation means in the present invention, the current inter-vehicle distance and a predetermined calculation are performed. By calculating the relative speed by paying attention to the difference from the inter-vehicle distance before the cycle, if the noise is sufficiently suppressed and the response delay is also sufficiently suppressed, the inter-vehicle distance LPF (inter-vehicle distance filter means) and the relative Either or both of the speed LPFs (filter means) may be omitted.

  In particular, it is conceivable that a sufficient effect can be obtained without using the relative speed LPF if the calculated relative speed is calculated based on the filtered inter-vehicle distance information in which noise is suppressed by the inter-vehicle distance LPF.

It is a block diagram which shows the structure of the auto-cruise control apparatus to which the relative speed calculation apparatus and the inter-vehicle distance control apparatus which concern on one Embodiment of this invention are applied. FIG. 3 is a circuit diagram schematically showing an arithmetic circuit related to filter processing of inter-vehicle distance information and relative speed information and an arithmetic circuit related to relative speed calculation according to an embodiment of the present invention. It is a graph which shows an example of a time-dependent change of relative speed information (differential value of distance information between vehicles) and a signal value after a filter concerning one embodiment of the present invention. It is a graph which shows an example of the time-dependent change of the signal value before a filter regarding the relative speed information used for the conventional inter-vehicle distance control apparatus, and the signal value after a filter.

Explanation of symbols

100 Inter-vehicle distance detection means (inter-vehicle distance sensor)
101 Vehicle speed sensor 102 Brake switch 103 Throttle opening sensor 104 Operation switch 105 Throttle actuator 106 Brake actuator 107 Distance between vehicles LPF
108 Differentiation circuit 109 Relative speed LPF (filter means)
110 Relative speed recognition means 111 Target inter-vehicle distance setting means 112 Acceleration / deceleration control means 150 ECU
201 Signal recognition unit 202 First amplifier (distance between vehicles)
203 Second amplifier (distance between vehicles)
204 Delay element (distance between vehicles)
205 Adder circuit (distance between vehicles)
206 Delay element (differential circuit)
207 Adder circuit (differential circuit)
208 Divider 209 First Amplifier (Relative Speed)
210 Second amplifier (relative speed)
211 Delay element (relative speed)
212 Adder circuit (relative speed)

Claims (6)

An inter-vehicle distance detecting means for detecting inter-vehicle distance information between the own vehicle and another vehicle traveling in front of or behind the own vehicle;
In a relative speed calculation device comprising: relative speed calculation means for calculating relative speed information between the host vehicle and the other vehicle for each preset calculation cycle based on the inter-vehicle distance information;
The relative speed calculation means is configured to calculate the relative speed information based on the inter-vehicle distance information input in the calculation cycle n and the inter-vehicle distance information input in the calculation cycle (n−r) preceding the predetermined cycle number r. Relative speed calculation device characterized by calculating. 2. The relative speed calculation apparatus according to claim 1, further comprising filter means for filtering the relative speed information calculated by the relative speed calculation means. The relative speed calculation means calculates, for each calculation cycle, the difference between the inter-vehicle distance information input in the calculation cycle n and the inter-vehicle distance information input in the calculation cycle (n−r) before the predetermined cycle. 3. The relative speed calculation device according to claim 1, wherein the relative speed information is calculated by dividing by a time corresponding to the number of periods r. The cycle of the calculation cycle is 10 to 40 milliseconds, the predetermined cycle number r is 5 to 50, and the relative speed calculation means calculates the inter-vehicle distance information input in the calculation cycle every calculation cycle. The relative speed information is calculated by dividing the difference from the inter-vehicle distance information input in the previous calculation cycle (n−r) by the predetermined cycle number r by the time corresponding to the predetermined cycle number r. The relative speed calculation apparatus according to claim 1, wherein the relative speed calculation apparatus is characterized. An inter-vehicle distance filter means for filtering the inter-vehicle distance information detected by the inter-vehicle distance detection means;
5. The relative speed calculation unit calculates the relative speed information based on the filtered inter-vehicle distance information filtered by the inter-vehicle distance filter unit. 6. Relative speed calculation device. Acceleration / deceleration means for accelerating or decelerating the vehicle;
An inter-vehicle distance detecting means for detecting an inter-vehicle distance between the host vehicle and a preceding vehicle traveling in front of the host vehicle;
A relative speed calculating means for calculating a relative speed between the host vehicle and the preceding vehicle for each preset calculation cycle based on the inter-vehicle distance information detected by the inter-vehicle distance detecting means;
Filter means for filtering the relative speed information calculated by the relative speed calculation means;
Based on the relative speed information filtered by the filter means and the inter-vehicle distance information detected by the inter-vehicle distance detection means, the acceleration / deceleration means is set so that the inter-vehicle distance between the host vehicle and the preceding vehicle becomes a predetermined target value. An inter-vehicle distance control device comprising acceleration / deceleration control means for controlling the operation of
The relative speed calculation means calculates the relative speed based on the inter-vehicle distance information input in the calculation cycle (n−r) preceding the inter-vehicle distance information input in the calculation cycle n by a predetermined cycle number r. A vehicle-to-vehicle distance control device.

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