JPS61162767A - Obstacle detector for vehicle - Google Patents

Abstract

PURPOSE:To prevent misdetection of an obstacle due to perspective, by dividing a display unit into several area so as to changes the amplification factor of a received wave signal with a gain amplification circuit for each of measuring time ranges corresponding to the area. CONSTITUTION:A display unit 14 is divided into a plurality of areas 14a-14d in proportion to the distance to an obstacle 6. Then, the amplification factor of a received wave signal of a gain amplification circuit 11 is changed with a microcomputer 1 for each of measuring time ranges corresponding to the areas 14a-14d. The microcomputer 1 compares peak value of the received wave signal with a reference value to judge the presence of the obstacle 6 for each of the areas 14a-14d of the display unit 14 and shows the results on the display unit 14. This can eliminate misdetection of the obstacle 6 due to the perspective while enabling accurate detection of the position of the obstacle 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an obstacle for a vehicle that transmits an ultrasonic pulse in a detection direction and measures the distance to the obstacle based on the time difference between the pulse and the pulse reflected from the obstacle. The present invention relates to a detection device.

BACKGROUND OF THE INVENTION Conventionally, a device for detecting obstacles behind or on the sides of a vehicle body using ultrasonic waves is known, for example, from Japanese Patent Application Laid-Open No. 57-22944. This device consists of a transmitting/receiving sensor that transmits and receives the ultrasonic sensor, an amplifier that amplifies the received wave signal, a comparison detector that receives the output signal of the amplifier and compares it with a preset reference signal, and each comparison detector. and a connected display.

By the way, the level of the received wave signal changes exponentially depending on the distance from the vehicle to the obstacle, so for example, the received wave from a distance is amplified greatly, and the received wave from nearby is amplified small or not at all. need to be done. However, in conventional vehicle obstacle detection devices, the degree of amplification is not adjusted depending on the distance, so there is a risk of erroneous detection because the received wave signal level differs significantly depending on the distance of the obstacle. Furthermore, conventional display devices have multiple indicators such as blue, yellow, and red, but each indicator only displays the approximate location i of the obstacle.
In addition, each display requires a separate comparison detector, so if you want to accurately detect the position of an obstacle, you will need not only a display but also a large number of comparison detectors, which makes it difficult to accurately detect obstacles. accurate position detection was impossible.

Purpose of the Invention The present invention has been made in view of such conventional problems.
The purpose is to provide an obstacle detection device for a vehicle that can eliminate false detection of obstacles due to distance and distance and can accurately detect the position of the obstacle.

Structure of the Invention In order to achieve the above object, the present invention divides a display device into a plurality of regions in proportion to the distance to an obstacle, and uses a gain amplifier circuit to collect received wave signals for each measurement time period corresponding to each region. By changing the amplification degree of the obstacle, a received wave signal of a substantially constant level can be obtained regardless of the distance of the obstacle. The peak value of the received wave signal is then compared with a reference value by a microcomputer, the presence of an obstacle is determined for each area of the display device, and the result is displayed on the display device.

, Description of Embodiments FIG. 1 shows the overall configuration of an obstacle detection device according to the present invention, in which 1 is a micro combinator which executes digital calculation processing by software according to a predetermined program, and 2 is a micro combinator with a frequency of, for example, 40. 3 is an AND circuit that combines a signal with a pulse width of 300xa generated by the microcomputer 1 and the carrier wave of the fundamental wave generator 2; 4 is an AND circuit that amplifies the output of the AND circuit 3; an amplifier; 5 is a transmitting sensor such as a piezoelectric element that transmits the ultrasonic pulse amplified by the amplifier 4; 6 is an obstacle; 7 is a receiving sensor that receives reflected waves reflected by the obstacle; 8 is a receiving sensor that receives a received wave signal; Amplifier 9 has a frequency of 40
Bandpass filter that passes only KHz waves, 10
11 is a programmable gain amplifier circuit (hereinafter referred to as PG) that performs amplification according to the reception timing by the micro combinator 1.
12 is a tracking (referred to as A) which operates based on instructions from the microcomputer 1 and outputs the input as it is.
A programmable peak hold circuit that can obtain three states: a peak hold state in which the peak value of the received wave signal is maintained, and a hold state in which this value is maintained for a certain period of time (the time during which the AD converter described below operates).
13 is an AD converter which converts an analog signal from the PPH 12 into a digital signal and sends it to the microcomputer 1. 14 is a display device that displays the position of an obstacle according to a command from the microcomputer 1.

As shown in FIG. 2, the display device 14 is divided into, for example, four regions 14a to 14d, and each region has a length proportional to the distance from the vehicle to the obstacle 6. That is, in the region 14a, the distance from the vehicle to the obstacle is 0 to
The range is 0.5 m, the region 14b is 0.5 to 1.0 m, the region 14G is 1.0 to 1.5 m, and the region 14d is 1.5 to 2.0 m. The range of Om is shown. Since the relationship between the distance from the vehicle to the obstacle 6 and the time T from transmission to reception (hereinafter referred to as measurement time) is expressed as L - speed of sound x T/2, each area of the display device 14 14a~
14d can be made to correspond to measurement time periods T and -T, respectively.

FIG. 3 shows an example of signal processing at measurement times T and -T. In FIG. , a received wave signal of a substantially constant level is obtained from a certain obstacle regardless of its distance.

In addition, PPH12 tracks each measurement time period.
Repeat the three states of peak hold and hold, and perform PCA
The peak value of the received wave signal amplified by II is held for a certain period of time. The AD converter 13 operates only during the hold state of the PPH 12, converts the peak value into a digital signal, and sends it to the microcomputer 1, for example during the measurement time period T.

When the receiving sensor 5 detects a received wave, the received wave is detected by the wave detector 10, and the PCA II gives a T
3, and while the PPH 12 holds the peak value of this wave, the AD converter 13 converts it into a digital signal, and the microcomputer 1 compares this digital signal with a reference value to detect obstacles. The third area 14c of the display device 14 is turned on. Thereby, it can be determined that an obstacle exists within a range of 1.0 to 1.5 m from the vehicle.

The operation of the microcomputer 1 will be explained according to the flowcharts shown in FIGS. 4 to 6.

First, in the main routine shown in Fig. 4, when started, initial settings necessary for arithmetic processing such as RAM clearing and flag resetting are performed, and then the counter is cleared and the counter value is set to 0, and the PPH12 is placed in the tracking state. , generates a pulse width signal of 300 μs. Then, set the interrupt flag to O to disable interrupts, set the gain of PGALI according to the reception timing, put the PPH12 in the peak hold state, and then hold the PPH12 for a certain period of time, for example, 2.5μ.
The display routine shown in FIG. 6 is executed in parallel with this waiting time. Thereafter, the PPH 12 is put into a hold state, the AD converter 13 is started, and the AD conversion routine shown in FIG. 5 is executed. After the AD conversion is completed, 1 is added to the counter, and if the counter value is less than 4 (when the number of areas on the display device 14 is 4), the operation after the pulse generation is repeated, and when the counter value reaches 4, the initialization is started. Return to the behavior after setting.

In the AD conversion routine shown in FIG. 5, first, the memory of the area (or measurement time period) in which the AD value converted into a digital signal by the AD converter 13 is to be saved is specified, and after the AD value is saved in this memory, an interrupt Set the flag to 1 to enable interrupts and return to the main routine. In other words, this A
The D conversion routine stores AD values one by one in separate memories corresponding to each area.

In the display routine shown in FIG. 6, the timer is first updated, then the AD value retrieved from the memory is compared with the reference level, and if the AD value is higher than the reference level, the corresponding area of the display device 14 is Turn it on. When the determination of one area is completed, the determination of the next area is repeated, and when the determination of all areas is completed, the process returns to the main routine.

In addition, in the above embodiment, the AD converter 13
After converting the analog signal from PPH 12 into a digital signal, the microcomputer 1 determines the obstacle. However, the AD converter 13 is removed, and the microcomputer 1 directly compares the analog signal from the PPH 12 with a reference value to determine the obstacle. You can judge things. Further, in the above embodiment, the transmitting sensor 5 and the receiving sensor 7 are fixed and obstacle detection is performed in one direction, but the present invention can also be applied to a system in which the transmitting/receiving sensor is used for scanning.

Effects of the Invention As is clear from the above explanation, according to the present invention, the display device is divided into a plurality of regions in proportion to the distance to the obstacle, and the gain amplifier circuit receives signals for each measurement time period corresponding to each region. Since the degree of amplification of the wave signal is changed, a received wave signal of a substantially constant level can be obtained regardless of the distance of the obstacle, and erroneous detection due to the distance of the obstacle can be prevented. In addition, the peak value of the received wave signal is maintained by a peak hold circuit, and this peak value is compared with a reference value by a microcomputer to determine the presence of an obstacle for each area of the display device, so the position of the obstacle can be accurately determined. can be displayed.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a vehicle obstacle detection device according to the present invention, FIG. 2 is a system diagram of a display device, and FIG. 3 is a chart diagram. 1... Microcomputer, 5... Transmission sensor,
7...Reception sensor, 11...Gain amplifier circuit (P
GA), 12...Peak hold circuit (PPH)
, 14-...display device, 14a-14d...area. Applicant Daihatsu Motor Co., Ltd. Agent Patent Attorney Hidetaka Tsutsui Figure 1 Figure 3 T; Niu・ν King PH; Peak Hold
H; Hold ADC: AD converter t1 to Figure 4 Figure 5

Claims (1)

[Claims] (1) In a vehicle obstacle detection device that detects the distance from the vehicle to the obstacle based on the time difference between the transmission time of the ultrasonic wave and the reception time of the reflected wave from the obstacle, it is proportional to the distance from the vehicle to the obstacle. a display device that is divided into a plurality of regions, a gain amplifier circuit that amplifies a different received wave for each region of the display device, and a peak that holds the peak value of the amplified received wave signal in each region. The present invention is equipped with a hold circuit and a microcomputer that compares the peak value with a reference value to selectively blink each area of the display device, and also sets the gain of the gain amplifier circuit and commands the operation of the peak hold circuit. Features of vehicle obstacle detection device.