JPS60209191A - Radar device for vehicle - Google Patents

Abstract

PURPOSE:To reduce the power consumption of a radar part by controlling the operation and stop of a transmitting means according to whether an operation control means receives a reflected signal of an electromagnetic wave from the transmitting means or not. CONSTITUTION:The transmitting means 31 sends out the electromagnetic wave. A receiving means 33 receives the reflected signal from the sent electromagnetic wave from a reflecting body. A distance arithmetic means 35 operates the distance to the reflecting body on the basis of the propagation delay time from the transmission to the reception of the electromagnetic wave. The operation control means 37 controls the operation and stop of the means 31 according to whether the reflected signal is received or not. Then, laser light is outputted M times to check whether the frequency (m) of the detection of the reflected wave is less than M and more than M/2; when the frequency (m) is within the range, the mean distance of (m) detected distances is calculated and distance data is outputted. The distance data is made ineffective unless M>=m>=M/2, and a signal processing circuit supplies an inhibition instruction signal to a pulse modulator to stop the output of a laser M times, reducing the power consumption and heat generation.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is directed to, for example, receiving a reflected signal of electromagnetic waves sent in the direction of travel of a vehicle and detecting the time from when the electromagnetic waves are sent to when they are received. The present invention relates to a vehicle radar device that measures the distance to a reflector by reducing power consumption.

[Technical Background of the Invention] By attaching a radar device to a vehicle, for example, it is possible to detect obstacles existing in the direction of travel of the vehicle to ensure safe driving, or to detect the distance between the preceding vehicle and your own troops. A system has been proposed that controls the own vehicle to always maintain a safe distance between vehicles and drive safely. (Unexamined Japanese Patent Publication No. 58-20352
4> FIG. 1 shows an example of such a vehicle radar device. This vehicle radar device is an optical radar device that uses a laser as an electromagnetic wave, and has a repetition period Tp of about 100 us1 as shown in FIG. Pulse width T
A pulse signal with w of approximately 2 Q ns and peak value ■0 is supplied to the light emitting element 9 of the light transmitter 7, and the light emitting element 9 is driven by high-speed pulse modulation, and the light emitting element 9 emits a pulse with a wavelength λ and a pulse width Tw. It outputs light Lt. Note that as the light emitting element 9,
For example, laser diodes that generate infrared radiation are used. The pulsed light Lt output from the light emitting element 9 is -
The light is focused by the lens 511, shaped into a beam with a divergence angle θt, and then radiated in the direction of travel of the vehicle.

The pulsed light Lt emitted in this way is reflected by an object in front, for example, a preceding vehicle, and is collected by a lens 15 with a large diameter constituting the light receiver 13 as a weak reflected light lr as shown in FIG. After the light passes through an optical filter 17 that removes backward noise composed of disturbance light such as sunlight and artificial lighting, it enters the light-receiving surface of the light-receiving element 19 located at the focal point of the lens 15. The light receiving element 19 photoelectrically converts this incident reflected light and outputs a reflected signal C in the form of a high-speed minute pulse as shown in FIG. This reflected signal C is amplified to a predetermined level by a wideband amplifier 21 and shaped, and then becomes a high-speed pulse signal d and is supplied to a signal processing circuit 23.

On the other hand, the signal processing circuit 23 is supplied with a trigger signal synchronized with the pulse signal a from the pulse modulator 5.
The propagation delay time τ is calculated based on the time relationship of the high-speed pulse signal d from 1 to 1, and the distance R to the object is calculated from this propagation delay time τ using the following equation.

R=,c・τ/2 Here, C is the speed of light, which is C-3×108IIl/S.3 [Problems with Background Art] By the way, during the measurement of the vehicle radar device, It operates continuously regardless of the presence or absence of an object. but,
In this way, continuously operating the radar device using power from the battery even though there is no object is
This is not desirable from the viewpoint of reducing battery power consumption due to an increase in on-vehicle loads in recent years. In particular, laser diodes are used in the vehicle radar equipment mentioned above, but it is well known that the operating power consumption of laser diodes is relatively large, and unnecessary continuous operation reduces battery power consumption. I can't figure it out.

[Objective and Summary of the Invention] The present invention has been made in view of the above, and an object thereof is to provide a vehicle radar device with reduced power consumption.

In order to achieve the above object, the present invention is provided in a vehicle as shown in FIG. In the vehicle radar device, the operation control means 37 operates and stops the transmitting means 31 depending on whether or not the reflected signal is received. The gist is that it is possible to control the

[Example] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 4 shows an embodiment of the present invention.

The vehicle radar device shown in this figure is the same as that shown in FIG. 1 except that the configuration and operation of the pulse modulator 25 and signal processing circuit 27 are different from those shown in FIG. Therefore, the same components are given the same reference numerals and their explanations will be omitted.

That is, the pulse modulator 25 shown in FIG. It is configured not to output signal a. Therefore, this prohibition command signal e is transmitted to the pulse modulator 2.
While the light is being supplied to the light emitting element 5, the light is not output from the light emitting element 9. It should be noted that the trigger signal S is applied to the pulse modulator 25 even while the prohibition command signal e is being supplied to the pulse modulator 25.
and is supplied to the signal processing circuit 27.

Next, the signal processing circuit 27 will be explained using FIGS. 5 and 6.

FIG. 5 is a diagram that does not show the waveforms of each signal, and as shown in this diagram, even though the light emitting element 9 was driven by the pulse signal a from the pulse modulator 25 and the laser beam was sent out, If even one reflected pulse signal d is not received from the wideband amplifier 21, a prohibition command signal e having a duration corresponding to N times the period of the trigger signal is sent from the signal processing circuit 27 to the pulse modulator. 25, and while the prohibition command signal e is being supplied, the output of the pulse signal a from the pulse modulator 25 is stopped, thereby stopping the output of the laser.

FIG. 6 is a flowchart showing the operation of the signal processing circuit 27 for generating the prohibition command signal e. Although it is possible for the signal processing circuit 27 to use a microcomputer to achieve such an effect, it can also be easily achieved using wired logic without using a microcomputer.

In FIG. 6, the first step is to clear the cursor (step 100). This counter (2) is for counting the number of trigger signals (i) and determining the duration of the inhibition command signal (e) when the reflected pulse signal (d) is not received. next,
The trigger signal S output in synchronization with the pulse signal a that drives the light emitting element 9 is detected, and when the trigger signal S is received, it is determined whether the content of the counter ■ is greater than or equal to "1" or not. Check (steps 110.120). Initially, the content of counter 1 is rOJ, so it is checked whether there is a reflected pulse signal d (step 130). Here, when the reflected pulse signal d is received, the counter 2 is cleared and the prohibition command signal e is set to low (L) level (steps 140 and 150). That is, while the reflected pulse signal d is being received in this way, Karatan ■ is always cleared to rOJ. Steps 1'l0-150 are repeated, and the distance to the reflector is detected by the reflected pulse signal d.

However, when performing such repetitive movements,
For example, if the vehicle in front moves away and the reflector disappears, the reflected pulse signal d disappears, so step 1
As a result of the determination of the presence or absence of the reflected pulse signal d in step 30, the process proceeds from step 130 to step 160, where the count value 2 is incremented and it is checked whether the contents of the counter 2 are greater than N (step 170). Counter ■
If the content of is less than or equal to N, the prohibition command signal e is high (H).
This high (H) level prohibition command signal e is supplied to the pulse modulator 25, and the pulse modulator 25 is controlled so as not to output the pulse signal a (step 180). As a result, the light emitting element 9 does not output laser light. In step 180, when the prohibition command signal e is set to a high (+-1) level, the process returns to step 110, detects the next trigger signal, and again checks whether the content of the counter e is greater than or equal to "1". To check. Once, while there is no reflected pulse signal d and the prohibition command signal e is set to a high level, the contents of the counter ■ are a value of "1" or more, so the process proceeds from step 120 to step 160.
The prohibition command signal e remains high (H) until the counter ``■'' is incremented and the contents of the counter
> level continues to be set (steps 170, 180)
.

In this way, the counter ■ is incremented every time the trigger signal I is generated, and when the contents of the counter ■ become larger than N, the process proceeds to step 140 as a result of the judgment in step 170, and the contents of the counter ■ are cleared. and sets the prohibition command signal e to low (L) level (step 1
50). As a result, the pulse modulator 25 starts outputting the pulse signal a again, and the light emitting element 9 outputs laser light again, and obstacles and preceding vehicles are detected. In steps 140 and 150, when the contents of the counter 2 are cleared and the prohibition command signal e becomes low (L) level, the process returns to step 110 and the same operation is repeated thereafter.

FIG. 7 shows a flowchart 17-- showing another embodiment of the present invention.
The block configuration of the vehicle radar device of this embodiment is the same as that shown in FIG.

The embodiment shown in FIG. 7 emits a laser, calculates the ratio of the number of times reflected light is detected, and decides to stop outputting the laser if this ratio is lower than a predetermined value. . Therefore, in this embodiment, even when the level of reflected waves from reflectors such as obstacles and preceding vehicles is relatively low and reflected waves cannot be detected at times, the number of times reflected waves are detected is greater than or equal to a predetermined value. If it is within a predetermined range, it is determined that there is a reflector and the laser beam continues to be output.
If the number of times a reflected wave is detected is less than a predetermined value or outside a predetermined range, it is determined that there is no reflector and the laser output is stopped to reduce power consumption and heat generation.

In FIG. 7, first, the laser is emitted M times, the reflected light corresponding thereto is detected, and the number of times of detection is set as ■ (steps 210 and 220). Next, as shown in step 230, it is checked whether the number of detections m is less than or equal to M and greater than or equal to M/2 (M≧m≧M/2). If the number of detections l is within this range, the average distance of the number of times detected is calculated and used as distance data (step 240). onwards,
These steps 210 to 240 are repeatedly executed.

However, in step 230, if the number of detections m is not within the range of M≧m≧M/2, the distance data is invalidated, and the prohibition command signal e is supplied from the signal processing circuit 27 to the pulse modulator 25 to The output is stopped M times (step 25.0.260) to reduce power consumption and heat generation.

[Effects of the Invention] As explained above, according to the present invention, when a reflected signal cannot be received because there are no obstacles or reflectors of the preceding vehicle, the operation of the transmitting means is stopped. Therefore, power consumption by the radar section can be reduced.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a conventional vehicle radar device, FIG. 2 is an operation waveform diagram of the device in FIG. 1, FIG. 3 is a complaint correspondence diagram, and FIG. A block diagram of the radar device, Fig. 5 is an operation waveform diagram of Fig. 4, and Fig. 6 is an operation waveform diagram of Fig. 4.
FIG. 7 is a flowchart showing the operation of another embodiment of the present invention. 31... Transmitting means 33... Receiving means 35... Distance calculation means 37... Operation control means Fig. 5 - Fig. 6 Fig. 7

Claims (1)

[Scope of Claims] (1) A transmitting means for transmitting an electromagnetic wave, a receiving means for receiving a reflected signal of the transmitted electromagnetic wave by a reflector, and a transmitting means for receiving a reflected signal of the transmitted electromagnetic wave by a reflector based on the propagation delay time from transmitting the electromagnetic wave to receiving the electromagnetic wave. 1. A vehicle radar device comprising: a distance calculation means for calculating a distance to a vehicle; and an operation control means for controlling operation and stop of the transmission means depending on whether or not the reflected signal is received. (2) The vehicle according to claim 1, wherein the operation control means stops the operation of the transmitting means for a predetermined period of time once it detects that no reflected signal has been received. radar equipment. (3) When the operation control means detects that the number of times the reflected signal is received within a predetermined time period does not reach a predetermined number of times, the operation of the transmission means is stopped for the predetermined time period. The vehicle radar device described in .