JPH02203291A - Ultrasonic doppler speedometer - Google Patents

Abstract

PURPOSE:To reduce the influence of an external noise and to improve reliability by using periodic pulses with specific width which are the output signal of a periodic pulse generator as a control signal and outputting a high-frequency signal to an ultrasonic transmitter intermittently. CONSTITUTION:The high frequency signal 101 generated by a high frequency generator 1 is converted into an intermittent wave 103 by a gate circuit 3 which uses the periodic pulses 102 generated by the periodic pulse generator 2 as the control signal. When the intermittent wave 103 is applied to the ultrasonic wave transmitter 4, an ultrasonic wave S1 which is sent 4 is an intermittent wave. Consequently, a reflected wave S2 that an ultrasonic wave receiver 5 receives and a received signal 104 which is converted into an electric signal are intermittent waves. The pulses 102 are delayed by a delay circuit 5 by the time of the reception 5 of the ultrasonic wave S1 after reflection and the delayed periodic pulses 105 are used as the control signal to control the conduc tion of the signal 104 by a gate circuit 7, so that an electric signal 106 is input ted to a mixer 9 only when the signal 104 which is an intermittent wave is inputted. Therefore, noises which are inputted while the signal 104 is absence are cut.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic Doppler speedometer that uses the Doppler effect of ultrasonic waves to determine the running speed of a vehicle.

(Prior art) Conventional methods for measuring vehicle speed are generally based on the rotational speed of the wheels, but since this method is based on a mechanical structure, it deteriorates over time and When using wheels, there is a problem that a large error occurs in the speed measured.To solve this problem, the vehicle emits ultrasonic waves and receives the reflected waves that hit the road, and the frequency of this received signal is An ultrasonic Doppler speedometer that utilizes the relationship that the difference between the frequency of the above-mentioned transmitted ultrasonic wave and the frequency of the transmitted ultrasonic wave is proportional to the traveling speed of the vehicle is sometimes used.

FIG. 5 is a block diagram showing an example of a conventional ultrasonic Doppler speed needle. The ultrasonic Doppler speedometer 30 is mounted on the vehicle, and includes a high frequency generator 1 and an ultrasonic transmitter 4.
, an ultrasonic receiver 5, an amplifier 31, and a computing unit 32. H sound wave range from tens of KHz to hundreds of K
A high frequency signal having a frequency of fo generated by a high 1 wave generator 1 which oscillates an electric signal having a frequency of Hz is applied to an ultrasonic transmitter 4 to generate a transmission wave S, which is oscillated toward the road surface 20. . Here, since the speed needle is mounted on the vehicle, it moves at the same traveling speed V as the vehicle. The reflected wave S3 reflected by the road surface 20 is received by the ultrasonic receiver 5, converted into an electric signal, amplified by the amplifier 31, and generated by the arithmetic unit 32. The Doppler frequency f, which is the difference between the received signal fl and the above-mentioned r range, is obtained by mixing the received signal fl with the electric signal generated by the signal fl. Since this Doppler frequency [4 is proportional to the vehicle running speed ■, the running speed ■ can be determined from the Doppler frequency f4.

[Problem to be solved by the invention]

In the prior art described above, both the transmitted wave S and the received wave St are continuous waves, and the operations of the amplifier 31 and the arithmetic circuit 32 are also performed continuously. For this reason, there is no way to prevent noise from entering the ultrasonic receiver 5, and there is a problem that the speed ■ calculated by the calculator 32 may be far from the actual value, resulting in a measurement result with a large error. There is. Particularly, in vehicles, the external noise of sound waves is large, and although the noise in the ultrasonic frequency band is far less than that in the audible band, it may not be negligible.

It is an object of the present invention to solve the above problems and provide an ultrasonic Doppler speed needle for vehicles that is less susceptible to the effects of external noise and has high reliability.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, there is provided a high frequency generator that generates an electric signal of a constant frequency, and an output signal of the high frequency generator is applied to transmit an ultrasonic wave as a transmission wave into the air. an ultrasonic transmitter, an ultrasonic receiver that receives an ultrasonic wave as a reflected wave of the transmitted wave and converts it into an electric signal as a received signal, an amplifier that amplifies the received signal, and the ultrasonic receiver An ultrasonic Doppler velocimeter comprising a mixing circuit for determining the frequency of the difference between the frequency of the received ultrasonic wave and the frequency of the output signal of the high frequency generator,
A periodic pulse generator that generates a pulse of a predetermined width in a constant liI period, and a periodic pulse as an output signal of this periodic pulse generator is used as a control signal to intermittently output the high frequency signal and apply it to the ultrasonic transmitter. a gate circuit; a delay circuit that uses the periodic pulse as an input signal and outputs a periodic pulse delayed by a predetermined time; and a gate that intermittently passes the received signal or the output signal of the amplifier using the output signal of the delay circuit as a control signal. A determination circuit for determining the validity of the output signal of the mixing circuit is provided.

[Operation] In the configuration of the present invention, a sine wave high frequency signal generated by a high frequency generator is converted into an intermittent wave by a gate circuit using a periodic pulse generated by a periodic pulse generator as a control signal, and this intermittent wave is When applied to a sonic wave transmitter, the ultrasonic wave emitted by the ultrasonic transmitter also becomes an intermittent wave, and accordingly, the reflected wave received by the ultrasonic receiver and the received signal converted into an electric signal also become an intermittent wave.0 period pulse A delay circuit delays the ultrasonic wave emitted by the ultrasonic transmitter by the time it is reflected and received by the ultrasonic receiver, and a gate circuit uses this delayed periodic pulse as a control signal to process the received signal or this reception. When the conduction of the amplified output signal is controlled, the electric signal is input to the mixer only when the received signal, which is an intermittent wave, is input. Therefore, the noise that enters during the period when there is no received signal is cut out, so it does not affect the measurement results.Also, the mixer can calculate the frequency difference between the received signal and the high-frequency signal generated by the high-frequency generator. The Doppler frequency proportional to the running speed of the vehicle is determined by the method, but when there is noise mixed in during the measurement period and the judgment circuit determines that there is an abnormality in the output signal of the mixer, this signal is calculated from the measured value. By excluding this, highly reliable measurement results with less noise influence can be obtained.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention. In this figure, a high frequency generator l generates an electric signal 101 as a continuous wave signal with a frequency f, and a zero period pulse generator 2 generates a periodic pulse 10 having a predetermined period and time width.
Outputs 2. Since the gate circuit 3 uses the electric signal 102 as a control n signal and passes the electric signal 101 only when the electric signal 102 is not zero, the electric signal 103 as an output signal of the gate circuit 3 is a high-frequency signal for the same time width as the electric signal 102. It becomes a certain intermittent wave. Electrical signal 1 which is this intermittent wave
The ultrasonic transmitter 4 to which 03 is applied also emits an intermittent ultrasonic wave S, and this emitted wave Sl hits the road surface 2.
0 and the ultrasonic receiver 5 receives a part of the reflected wave St. Since the 0 emitted wave Sl is an intermittent wave, this received wave St
Similarly, it becomes an intermittent wave. The relationship between such electrical signals will be explained in more detail.

FIG. 2 is a waveform diagram showing the waveform of the electrical signal.

The electrical signal 101 is a sine wave signal with a constant imaging width. The frequency f0 of this electrical signal 101 is 100K) (approximately z).The electrical signal 102 is an output signal of the periodic pulse generator 2, and is a square wave pulse with a period T and a time width t.

The electric signal 103 is an output signal of the gate circuit 3, and is a high frequency signal that lasts for a time width t and is an intermittent wave that is repeated mX1iT. The gate circuit 3 passes the electrical signal 101 when the electrical signal 102 is not zero and cuts it off when the electrical signal 102 is zero, so the electrical signal 103 which is the output signal of the gate circuit 3
is an intermittent wave whose envelope is the waveform of the electrical signal 102.

The electric signal 104 is a signal received by the ultrasonic receiver, and is delayed from the electric signal 103 by 111 minutes, which is the time it takes for the ultrasonic wave to reflect on the road surface 20 and return. This figure simulatively shows a state in which noise N is superimposed between the second and third pulses, and noise N2 is superimposed within the third pulse. Since the required strength of the electric signal can be obtained by amplifying it, the magnitude of the amplitude of the electric signal in this figure has no meaning.

The electrical signal 105 is the output signal of the delay circuit 6, and is delayed by the aforementioned time of 111 minutes with respect to the electrical signal 103, so it is synchronized with the electrical signal 104. Since the gate circuit 7 is controlled by this electric signal 105 and the received signal is passed only when the electric signal 105 is not zero, the input signal of the amplifier 8,
Furthermore, the noise N1 contained in the electrical signal 104 is removed from the electrical signal 106 as an output signal. However, the noise N2 picked up during the time width td is amplified and output as is.

The period T may be any time interval necessary to actually continuously measure the running speed of the vehicle, and it may be measured at most several times in one second, so the period T is a fraction of a fraction of the time. Seconds. In addition, the time width td only needs to be the time required for the mixing circuit 9 and the judgment circuit 1O (described later) to operate normally, and the number 1118ee is sufficient, so in the end, most of the noise is expressed as the noise N. It is cut without being amplified by the amplifier 8 and has no effect on the measurement results.

Figure 3 shows the electrical signal 10 when no noise is mixed in. FIG. 2 is a diagram showing the frequency distribution of FIG. As shown in this figure, the frequency distribution of the electrical signal when no noise is mixed becomes a mountain shape centered on the Doppler frequency fd.

FIG. 4 is a diagram showing the frequency distribution of the electrical signal 107 when noise N is mixed. In general, high frequencies are easily mixed in with noise, so the frequency distribution of noise has many high frequency components, and includes many frequency components higher than the Doppler frequency fd, and in particular, the peak point of the distribution is not only the 21 points of the Doppler frequency fd. Furthermore, it has the characteristic that peak points also occur at 22 points with high frequencies.

The determination circuit 9 captures the characteristics of the electrical signal 107 when such noise is mixed in, and determines when there are multiple peak points in the frequency distribution or when a peak point occurs at a frequency higher than a preset frequency. This will be considered an abnormality and will not be used as a measurement result for running speed.

In this manner, the determination circuit 9 removes abnormal signals caused by noise, thereby making it possible to obtain a speed U that measures the traveling speed with high reliability.

〔Effect of the invention〕

As described above, this invention converts a high frequency signal of a sine wave generated by a high frequency generator into an intermittent wave, and when this intermittent wave is applied to an ultrasonic transmitter, the ultrasonic wave transmitted by the ultrasonic transmitter also becomes an intermittent wave. Since the reflected wave reflected from the road surface also becomes an intermittent wave, the received signal also becomes an intermittent wave. By amplifying only when there is a received signal, taking into account the time required for the ultrasonic receiver to travel back and forth, noise that enters during the period between intermittent waves is suppressed and does not affect the measurement results. By finding the difference in frequency between the signal and the high-frequency signal generated by the high-frequency generator, the Doppler frequency, which is proportional to the vehicle's running speed, can be found. When it is determined that there is an abnormality in the output signal of the sensor, this signal is excluded from the measured values, resulting in highly reliable measurement results with less influence of noise. In this way, by making the transmitted ultrasonic wave an intermittent wave and providing a determination circuit, it is possible to construct an ultrasonic Doppler velocimeter with high axial compensation of measurement results.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
3 is a waveform diagram for explaining the operation, FIG. 3 is a frequency distribution diagram during normal operation, FIG. 4 is a frequency distribution diagram when noise is mixed in, and FIG. 5 is a conventional block configuration diagram. ... High frequency generator, 2... Periodic pulse generator, 7.
... Gate circuit, 4 ... Ultrasonic transmitter, ... Ultrasonic receiver, 6 ... Delay circuit, 31 ... Amplifier, 9 Mixer, 10 ... Judgment circuit, 0.40. ...Ultrasonic Doppler speedometer. Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1) A high frequency generator that generates an electrical signal of a constant frequency;
An ultrasonic transmitter to which the output signal of the high frequency generator is applied and transmits an ultrasonic wave into the air as an emitted wave, and an ultrasonic transmitter that receives the ultrasonic wave as a reflected wave of the emitted wave and converts it into an electric signal as a received signal. an ultrasonic receiver for converting, an amplifier for amplifying the received signal, and a mixing circuit for determining the frequency of the difference between the frequency of the ultrasonic wave received by the ultrasonic receiver and the frequency of the output signal of the high frequency generator. The ultrasonic Doppler velocimeter is equipped with a periodic pulse generator that generates pulses of a predetermined width at a constant period, and a periodic pulse as an output signal of the periodic pulse generator, which intermittently outputs the high frequency signal as a control signal. a gate circuit that applies the signal to the ultrasonic transmitter, a delay circuit that uses the periodic pulse as an input signal and outputs a periodic pulse delayed by a predetermined time, and uses the output signal of the delay circuit as a control signal to control the received signal or the amplifier. An ultrasonic Doppler velocimeter comprising: a gate circuit that intermittently passes an output signal; and a determination circuit that determines the validity of the output signal of the mixing circuit.