JPS58156872A - Ultrasonic measuring device of distance - Google Patents

Abstract

PURPOSE:To eliminate the influence of an external noise and secondary reflection and to improve stability and reliability, by varying the period of ultrasonic wave pulse transmission according to the distance to an object, etc., and summing up received signals plural times and extracting signals higher than a prescribed level. CONSTITUTION:A pulse controller 1 which operates corresponding to the value of a counter 11 for counting distance controls a transmission pulse generator 3 to adjust the period of ultrasonic wave pulse transmission so that the longer the distance, the longer the period. The reflected pulse of the transmitted pulse from an obstacle 7 is received plural times and applied through shift registers 9a,9b... to an adder 9; and a sum output having a pulse level greater than the prescribed value is supplied through a pulse level detector 10 to the counter 11 as a counting stop signal. This constitution performs distance measurement free of the influence of an external noise. Further, while the distance is unchanged, the period of the transmitted pulses is varied at random to eliminate the influence of secondary reflection similarly. Thus, the stability and reliability of an ultrasonic wave distance measuring device are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic distance measuring device that continuously measures the distance to an object in front using ultrasonic waves, and eliminates the effects of external noise, secondary reflections from objects, etc. It has been improved in terms of stability and reliability. The present invention will be explained below based on the drawings.

The pulse controller in Fig. 1 (1) controls the ultrasonic transmission pulse by
control for shooting. This control determines the next measurement distance range according to the previously measured distance to the obstacle,
The repetition period T of ultrasonic wave generation is controlled. Furthermore, within the determined measurement distance range, the repetition period T is randomly varied by several clocks. However, in the initial state, the repetition period is the maximum measurement distance range. In order to perform such transmission control, the pulse controller (1) is in direct control with the clock generator (2) and the transmission pulse generator (3). The thus generated transmission pulses are radiated into space as ultrasonic waves by the amplifier (4), the transformer (5), and the converter (6). When this hits an obstacle, the reflected wave is received by the converter (6), becomes a received pulse by the transformer (5)', and the width detector (8), and is shifted by 9a to 9n forming the memory circuit. - Enter the register. Note that the converters in (6) and (6)' above can also be used. Each shift register has an ultrasonic repetition period T
It is composed of flip-flops, etc. with the number of stages corresponding to the shift pulse inputted in the clock pulse generator, and uses the time and start time when the transmission pulse is emitted, and performs the shift operation using the shift pulse CL1 of the clock pulse generator in (2). There is. At this time, when the received pulse from the amplified detector (8) is processed to make it into a pulse with a shift pulse width or more, and then inputted into the input of the shift register 9a (that is, when "1" is input), The instantaneous shift register records "1" and is shifted by the shift pulse CL1. When one cycle of transmission ends, ``1'' is displayed in 9a only in the area corresponding to the distance of the received pulse.
(see 201 in FIG. 2). In the next transmission cycle, the state is stored in
Since the data shown in 9a is entered, the data previously entered in 9a is shifted and entered into the next shift register 9b. In this way, the data is stored in the next to 9n shift registers.

Since the received pulse includes not only the reflected pulse from the object but also the pulse due to noise etc., for example, 202 in Fig. 2,
Take the correlation N times obtained from the above suffu and register,
The contents of each shift register are shifted and extracted in order to emphasize reflected signals from objects and remove random reflected waves due to noise. Then, the output of each shift register (Fig. 1 (a) to (n)) can be obtained, but
If these are added one after another using, for example, an analog adder, the contents of each shift register will be duplicated and an added signal will be obtained, as shown in FIG. 2 400. Therefore, in order to extract only the large pulses with good correlation, the pulse level detector shown in Fig. 1 (10) is used to superimpose N pulses.
A threshold level S corresponding to this is set, and pulses with a voltage higher than this level are extracted. (See Figure 2 400)
. Then, if the counter in Fig. 1 (11) is stopped with this pulse (the start pulse of the counter is input from the transmitting pulse generator (3) when the transmitting pulse is generated, the distance measurement clock pulse CL2 is counted. ), the contents of the counter represent the distance to the object. On the other hand, since the transmission repetition period is changed according to the measured distance, the reflected wave from a distant object comes within a certain distance within the second and subsequent repetition periods, and the correlation is established by adding N times. There is a possibility that it can be taken. In order to eliminate this and further reduce the effects of noise and secondary reflections, the repetition period of the transmitted pulse is randomly varied by several clock pulses each time even at a fixed measurement distance, as shown in Figure 3. Send. It is also effective to change the values in a fixed order rather than randomly. In this way, reflected waves from a distance or secondary and tertiary reflected waves can no longer be correlated by the overlapping circuit, and can be effectively removed. At the same time, the contents of the counter are indicated on the display shown in Figure 1 (12), and at the same time, the alarm generator shown in Figure 1 (13) generates an audible sound at a period or frequency corresponding to the distance to express the distance in sound. , it is possible to set an alarm to sound at a higher pitch when the vehicle reaches a predetermined closest approach distance. Note that the distance information from the counter is sent to the pulse controller (1) in order to determine the next measurement distance range.

The first feature of distance measurement in the present invention is that the next distance measurement range is determined according to the measured distance.

The second feature is that even at a certain distance, the synchronization T is repeatedly changed randomly, and overlapping circuits are combined to eliminate various noises.

Third, by superimposing received data obtained several times, random reflected components such as noise generated from automobiles and the like are removed, improving the reliability and stability of the device.

By adding the above improvements, even if many users use the same frequency at the same time, there will be no interference between them, and the device can stably measure the distance between objects and has the necessary distance accuracy and resolution. was completed.

FIG. 4 shows an embodiment in which one, two or three converters (6) shown in FIG. 1 are attached to the rear of an automobile.

When the power is turned on, the device enters its initial state and generates transmission pulses at a repeating cycle within the maximum distance range. When an obstacle is measured, it is displayed and at the same time the distance is notified with a repeating audible tone corresponding to the measured distance. As drivers become accustomed to the system, they will be able to determine the approximate distance at a given time just by listening to the sound, and will be able to get a sense of distance without looking at the display. When the set closest distance is reached, a high-pitched alarm is sounded to alert the driver and pedestrians. In this way, it can be useful for detecting obstacles and preventing collisions when the vehicle is moving backwards.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the ultrasonic distance measuring device of the present invention,
Figures 2 and 3 are diagrams for explaining the operation of Figure 1, and Figures 4 (a), (b), and (c) show examples in which the device in Figure 1 is installed in a car. Figure shown, patent applicant Kazuo Okada Suzuki ■

Claims (3)

[Claims] (1) Ultrasonic waves of a predetermined time width are generated intermittently, and the repetition period of this ultrasonic wave is made longer when the measured distance to the object is long, and shortened when the measured distance is short, and the repetition period is set to a constant value. The measurement distance is also changed randomly, and the received signals from which the ultrasonic waves hit an object and are reflected are added up multiple times, and only the signals above a predetermined level are extracted and used as the received signals, and the ultrasonic waves are generated. A method of measuring the distance to an object based on the time taken until the received signal is generated. (2) A pulse controller that determines the transmission repetition period of ultrasonic waves according to the distance to the detected object and randomly changes the transmission repetition period even at a fixed distance; a clock pulse generator and a transmitting pulse generator, a first converter for converting the output of the transmitting pulse generator into ultrasonic waves, a second converter for receiving the ultrasonic waves, and an output of the second converter; A plurality of memory circuits that sequentially store data after width detection, an adder circuit that adds the outputs of the plurality of memory circuits, a pulse level detector that determines whether the output of the adder circuit is above a predetermined level, and an ultrasonic wave. An ultrasonic distance measuring device consisting of a counter that measures the time from when a transmission pulse is generated until a pulse level detector generates an output, and a display that displays the counted value of the counter audibly or optically. (3) The ultrasonic distance measuring device according to claim 2, wherein the first converter converts the output of the pulse generator into ultrasonic waves, and the second converter receives the ultrasonic waves.