JPH03148083A - Ultrasonic obstacle sensor - Google Patents

Abstract

PURPOSE:To judge obstacles on a road in the range from a low speed to a high speed effectively based on reflected waves by providing a vehicle-speed detecting means, two timing-command means, an ultrasonic-wave-signal generating and receiving means, a judging-signal generating means, a comparing means and the like. CONSTITUTION:A timing-command means 1 supplies an ultrasonic-wave-pulse command signal V0 to an ultrasonic-wave-signal generating means 3 for a specified time at every specified interval based on the vehicle speed pulse signal from a vehicle-speed detecting means 9. The means 2 drives an ultrasonic-wave transmitting means 3 with a driving signal V1. The means 3 projects the ultrasonic pulses on a road surface (a) at the slant forward part. An ultrasonic-wave receiving means 4 receives a reflected wave V2 from the road surface. A received-signal processing means 5 amplifies the signal V2 and performs AM detection. An AM detected signal V30 is outputted into a comparing circuit 8. A second timing command means 6 operates a judging-signal generating means 7 with the signal V0 as a trigger. The signals V30 from the means 5 is compared with judging signals V5 and V6 from the means 7 in the comparing circuit 8, and a detected signal V7 is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic obstacle sensor used in automobiles and the like.

In particular, the present invention relates to an ultrasonic obstacle sensor for an automobile suspension control device that senses the road surface condition in advance to alleviate shock to the vehicle body.

[Prior Art] As a conventional obstacle sensor using ultrasonic waves, there is, for example, a device for detecting obstacles around a vehicle disclosed in Japanese Patent Publication No. 1-30436.

Furthermore, there is a suspension device disclosed in, for example, Japanese Unexamined Patent Publication No. 62-131813, which detects the road surface condition in front of the vehicle in advance and alleviates shock to the vehicle body.

Conventionally, when attempting to detect objects (obstacles) using ultrasonic waves, most methods use ultrasonic waves to calculate the distance to surrounding objects. Various methods have been proposed to accurately measure .

However, with this method, reflected waves from the road surface ahead are also detected as obstacles, so measures must be taken to avoid detecting reflected waves from the road surface, for example by changing the directionality of the horn. On the other hand, there are currently no proposals for signal processing that actively detects only the reflected wave signal from the road surface and effectively detects obstacles on the road from that signal. be.

Furthermore, since the main purpose of conventional devices was to use them when driving at low speeds such as in parking lots, even if the transmission period T of ultrasonic pulses is long, the distance the vehicle moves during that period is D = V. , xT, the smaller the vehicle speed v8, the smaller the distance, so there was no need to worry about the car traveling a long distance quickly and colliding with an obstacle before it was detected. However, as the vehicle speed increases, the transmission period T cannot be shortened to less than the round trip time of the ultrasonic wave by waiting for the reflected wave of one pulse to arrive and then emitting the next pulse as in conventional pulse transmission. Therefore, there was a contradiction that the distance could not be reduced. In other words, when trying to detect reflected waves of ultrasonic waves from obstacles, in order to ensure the strength of the reflected waves and further eliminate the influence of received ultrasonic waves at unnecessary times, detection is performed by intermittent pulse transmission. This method is desirable, but when the vehicle speed increases while driving, waiting for the ultrasonic round trip time before emitting the next pulse has the problem that obstacles cannot be detected in time.

On the other hand, a method has been proposed in which continuous waves are emitted onto the road ahead and the received waves are continuously observed to detect obstacles on the road, but continuous waves have a number of drawbacks, including the following.

■ Due to the heat generated by the transmitter, the energy of the ultrasound cannot be increased.

■ Affected by interference between transmitting and receiving waves and standing waves.

■ It is difficult to distinguish between reflected waves from the road ahead and other signals.

■ There is no way to distinguish between factors other than unevenness that change the intensity of reflected waves, such as wind and temperature fluctuations.

[Problem to be solved by the invention] In the conventional ultrasonic obstacle sensor as described above, reflected waves from the road surface are also detected as obstacles, so the problem is that the directivity of the horn must be devised. was there.

Furthermore, when the vehicle speed changes, especially at high speeds, there is a problem in that obstacles cannot be detected.

Furthermore, when continuous waves are irradiated, there are problems such as the inability to increase the energy of the ultrasonic waves due to the heat generated by the transmitter.

This invention was made to solve the above-mentioned problems. Ultrasonic waves with different transmission cycles depending on the vehicle speed are emitted in pulses onto the road surface diagonally ahead, and the reflected waves can be used to detect obstacles on the road at low speeds. The object of the present invention is to obtain an ultrasonic obstacle sensor that can effectively distinguish and discriminate over a wide range up to high speeds.

[Means for Solving the Problems] The ultrasonic obstacle sensor according to the present invention includes the following means.

(i) Vehicle speed detection means for detecting the speed of the vehicle.

(ii) Timing command means for generating a command signal for intermittently generating ultrasonic waves based on the output of the vehicle speed detection means.

(iii) Ultrasonic signal generating means for generating an ultrasonic signal based on the command signal.

(iv) Ultrasonic transmitting means for transmitting the ultrasonic waves to the road surface based on the ultrasonic signals.

(V) Ultrasonic receiving means for receiving the reflected waves of the ultrasonic waves and generating a received signal.

(vi) Received signal processing means for performing AM detection on the received signal and outputting an AM detected signal.

(vii) second timing command means for generating a timing pulse signal based on the output of the vehicle speed detection means and the command signal;

(咄), Discrimination signal generating means for generating a discrimination signal based on the timing pulse signal.

(ix>, a comparison circuit that compares the AM detection signal and the discrimination signal and outputs a detection signal of an obstacle on the road surface;

[Operation] In the present invention, the speed of the vehicle is detected by the vehicle speed detection means, and the timing command means generates a command signal for intermittently generating ultrasonic waves based on the output of the vehicle speed detection means.

Furthermore, the ultrasonic signal generating means generates an ultrasonic signal based on the command signal, and the ultrasonic transmitting means transmits the ultrasonic wave to the road surface based on the ultrasonic signal.

Furthermore, the ultrasonic receiving means receives the reflected wave of the ultrasonic wave to generate a received signal, and the received signal processing means performs AM detection on the received signal and outputs an AM detected signal.

Furthermore, the second timing command means generates a timing pulse signal based on the output of the vehicle speed detection means and the command signal, and the discrimination signal generation means generates a discrimination signal based on the timing pulse signal.

Then, the comparison circuit compares the AM detection signal and the discrimination signal, and outputs a detection signal of the obstacle on the road surface.

[Embodiment] The structure of an embodiment of the present invention will be described with reference to FIGS. 1, 2, 3, 4, and 5.

FIG. 1 is a block diagram showing an embodiment of the present invention.7 In FIG. 1, an embodiment of the present invention includes a timing command means (1) and a An ultrasonic signal generating means (2), an ultrasonic transmitting means (3) such as an ultrasonic microphone connected to the ultrasonic signal generating means (2) and installed near the bumper of the car body, and a bumper of the car body as well. An ultrasonic receiving means (4) such as an ultrasonic microphone installed nearby, a received signal processing means (5) connected to the ultrasonic receiving means (4), and a timing command means (1) connected to the ultrasonic receiving means (4). a second timing command means (6); and a second timing command means (6).
a comparison circuit (8) connected to the received signal processing means (5) and the discrimination signal generation means (7), a timing command means (1), and a received signal processing means. (5) and vehicle speed detection means (9) connected to the second timing command means (6).

FIG. 2 shows a timing command means (
1) and a circuit diagram showing vehicle speed detection means (9).

In FIG. 2, the timing command means (1) is, for example, a Hitachi HD63BOIY microcomputer (10
), a crystal oscillator (11) connected to this microcomputer (10), and a microcomputer (10)
The starting circuit (12) is connected to the starting circuit (12).

The starting circuit (12) is composed of a self-resetting normally open starting switch (13) installed in the driver's seat of the automobile, and a shaping circuit (14) connected to this starting switch (13). There is.

The vehicle speed detection means (9) also includes a rotating magnet (90) that rotates in accordance with the rotation of the wheels, a reed switch (91), and a resistor (92) connected to the reed switch (91).
), and a waveform shaping circuit (93) connected to a reed switch (91) and a resistor (92).

FIG. 3 shows an ultrasonic signal generating means (
2) is a circuit diagram showing 2).

In FIG. 3, the ultrasonic signal generating means (2) includes an ultrasonic oscillation circuit (20) and a microcomputer (1) of the ultrasonic oscillation circuit (20) and the timing command means (1).
0) and this NAND gate I (21) connected to
Inverter (22) connected to AND gate (21)
and the amplifier circuit (2) connected to this inverter (Z2).
3) and a step-up transformer (24) connected to this amplifier circuit (23).

FIG. 4 shows a received signal processing means (5) of an embodiment of the present invention.
) is a circuit diagram showing.

In FIG. 4, the received signal processing means (5) includes an amplifier circuit (50) connected to the ultrasonic receiving means (4) and an AM detection variable amplifier circuit (5) connected to the amplifier circuit (50).
1).

Note that the AM detection variable amplifier circuit (51) is the amplifier circuit (5
AM detection circuit connected to 0) and vehicle speed detection means (9)
PET (52) connected to AM test 10 wave circuit and variable amplifier circuit (52) connected to FET (52).
53).

FIG. 5 is a circuit diagram showing the second timing command means (6) and discrimination signal generation means (7) of one embodiment of the present invention.

In FIG. 5, the second timing command means (6) is
The microcomputer (1) of the timing command means (1)
0) monostable multipulse generator circuit (60) connected to
, a pulse correction circuit (61) connected to the vehicle speed detection means (9) and consisting of an FET and a resistor;
61) and a monostable multipulse generating circuit (62) connected to the monostable multipulse generating circuit (60), and a monostable multipulse generating circuit (63) connected to this monostable multipulse generating circuit (62). It is composed of.

Further, the discrimination signal generating means (7) includes a charging circuit (70) connected to the monostable multi-pulse generating circuit (63) and a discharging circuit (71) connected in parallel to the charging circuit (70).
and a capacitor (72) connected to a charging circuit (70) and a discharging circuit (71).

Next, the operation of the above embodiment will be explained with reference to FIGS. 6 and 7.

FIG. 6 is a timing chart showing signal waveforms of various parts in an embodiment of the present invention at low speeds, and FIG. 7 is a timing chart showing signal waveforms of various parts in an embodiment of the invention at high speeds.

In Fig. 6, vo is a command signal, vl is a drive signal,
2 is a received signal that is a reflected wave from a road surface with no large obstacles, v2* is a received signal that is a reflected wave from a road surface that has obstacles, v3o is an AM detection signal, V 4 s + V
4b and ■ are timing pulse signals, v5 and v6 are discrimination signals, and ■ is a detection signal.

The period 1+ of the received signal V2 described above is a direct wave or an unnecessary reflected wave component due to wraparound, and can be improved by improving the layout, directivity, and holding of the ultrasonic microphone.

At time t, the ultrasonic transmitting/receiving means are adjacent and the directivity is also between the paths.
In this case, it corresponds to the round trip time of the detected shortest path sb shown in FIG.

Similarly, t8 is the central route Sa, and tc is the farthest route Sc.
If the speed of sound is C, then t,=2sa/C1 tb=2Sb/C1 te=2Sc/C.

First, the vehicle speed detection means (9) is a reed switch (91).
and a resistor (92) to generate a vehicle speed pulse signal corresponding to the rotation of the wheels, which is waveform-shaped and output by a waveform shaping circuit (93).

The timing command means (1) generates a command signal V shown in FIG. 6 for transmitting pulses of ultrasonic waves for a predetermined time at predetermined intervals based on the vehicle speed pulse signal of the vehicle speed detecting means (9). is supplied to the ultrasonic signal generating means (2).

This timing command means (1) may be configured by a programmable timer built into the microcomputer (10), or can be easily realized using a commercially available timer IC. The activation switch (13) of the timing command means (1) generates a low level signal when it is temporarily closed, and the shaping circuit (14) inverts and shapes the low level signal and generates it as a activation signal. The microcomputer (10) is activated by receiving a constant voltage from a constant voltage circuit in response to power supply from a DC power supply, and generates a series of clock signals based on the oscillation action of a crystal oscillator (1). , in response to each of these clock signals, executes a computer program stored therein in advance and outputs a command signal v0.

The ultrasonic signal generating means (2) generates a command signal V. Based on this, the ultrasonic transmitting means (3) is driven by a drive signal v shown in FIG. 6, which has a predetermined time, a predetermined voltage, and a predetermined frequency.

This ultrasonic signal generation means (2) includes an ultrasonic oscillation circuit (2
0) at a predetermined high frequency is applied to the inverter (22) through the NAND gate (21) while the command signal v0 is being generated from the microcomputer (10). The ultrasonic pulses sequentially generated from 22) are transmitted to an amplification circuit (23
) is amplified as a series of oscillation pulses, and the voltage is boosted by 13 4 by a step-up transformer (24) and applied to the ultrasound transmitting means (3).

The ultrasonic transmitting means (3) irradiates ultrasonic pulses onto the road surface below diagonally in front of the vehicle, and the ultrasonic receiving means (4) receives a received signal V2 (V2'') which is a reflected wave from the road surface.

These ultrasonic transmitting means (3) and ultrasonic receiving means (4)
From the directional characteristics of
It will disappear at time t6, which corresponds to tc.

The change in intensity between them is determined by the directivity and geometric layout.

As shown in FIG. 6, the waveform becomes a substantially mountain-shaped waveform that peaks at time t8.

The received signal V2' shown in FIG. 6 shows an observed waveform when an obstacle O is present on the road surface. The reflected wave component from the obstacle O is observed to be superimposed on the approximately mountain-shaped observed waveform of only the road surface. At time t2, the ultrasonic transmitting/receiving means (
3) and (4) correspond to the round trip time of the shortest route to and from the obstacle 0.

If we consider a case where an obstacle ○ is stationary on the road and a car equipped with an ultrasonic obstacle sensor is traveling along the road and gets too close to the obstacle 0, it captures the obstacle 0 at time tc, After passing through the time point 〇 and being captured at time tb, it becomes undetectable, and then the car goes too far over obstacle 0, and time t2 changes from 1 cm + 1ゎ to t.

Next, the peak of the reflected wave corresponding to the obstacle O is determined at each time t
It is approximately equivalent to the value obtained by multiplying the reflected wave intensity from the road surface according to the time shown in 2 by a predetermined multiplication factor, so if you trace the peak of obstacle ○ according to time t2, the intensity of the reflected wave only from the road surface It can be seen that it becomes a mountain shape as in the case of .

The received signal processing means (5) amplifies the received signal v2 (v2'), performs AM detection, and outputs an AM detected signal 3 in order to easily process the received level.

If the road surface is flat, the AM detection signal ■, is the received wave V, only from the road surface. , and if the obstacle O is on the road surface, the component of the received wave V3fBl corresponding to the obstacle O is also superimposed, and A
As the M detection signal, V3''tV3+A+10Vs++z is obtained.

This received signal processing means (5) masks the signal in the unnecessary signal section t2 at the same time as AM detection, so tb~tc
Only the signal in the necessary section is subjected to AM detection, and an AM detection signal (3) is obtained.

Then, the AM detection signal V is amplified in accordance with the vehicle speed by a variable amplifier circuit (53) whose amplification degree is controlled by controlling the gate voltage of the FET (52) using the vehicle speed pulse signal ζ. is output to the comparison circuit (8).

On the other hand, the second timing command means (6) outputs a command signal V
With o as a trigger, t, ~t until the next cycle
c, or use the timing pulse signal v4.c shown in FIG. .

V4b and Vae are created and the discrimination signal generating means (7) is activated.

This second timing command means (6) is a programmable timer of a microcomputer (10) and receives a command signal V. Alternatively, a monostable multi-bi-break circuit may be constructed using a timer IC that is triggered by this command signal Y0 and outputs a pulse signal with a predetermined time width.

Timing pulse signal V4. thus obtained. The time width of V4b and V4e corresponds to tb/2, and the time width of V4e corresponds to t-tb.

The discrimination signal generating means (7) generates a timing pulse signal V.
Corresponding to L-+H of a c, a discrimination signal (charging voltage signal) v5 which monotonically increases until a predetermined elapsed time is generated by the charging port F#r (70) and the capacitor (72). After the discrimination signal v5 shows the maximum value at time t, when the timing pulse signal V4c switches from H to L, the discriminating signal v5 reaches the minimum value at time tc by the discharge circuit (71) and the capacitor (72). , a discharge waveform is created and a discrimination signal (discharge voltage signal) V6 is generated.

The comparison circuit (8) receives the AM detection signal V from the received signal processing means (5). and the discrimination signals v5 and v6 from the discrimination signal generating means (7) are compared to output a detection signal (2). Next, a case in which the vehicle is traveling at a high speed exceeding a predetermined speed will be described with reference to FIG. 7.

Since the vehicle speed is fast, the command signal V of the timing command means (1). As shown in FIG. 7, the repetition period is shortened to the central time t of arrival of the reflected wave, which is a shorter time t6.

In FIG. 7, the received signal v2 of the reflected wave shows an example of only a road surface without a large obstacle, and the received signal v2 shows an example of the waveform when passing over a large obstacle.

The times t1, t5, and tc of the received signal V, although there are some fluctuations as the vehicle speed increases, basically inherit the characteristics and quality explained in FIG. It's not something that changes.

V in Figure 7. is an AM signal that has properly amplified the AM detection waveform.
It is a detection signal.

The timing pulse signals V4a, V4b, and V4c from the second timing command means (6) have an output time width t5 even if the trigger interval changes due to a change in the command signal v0.
/2, tb/2.1, -1, are maintained substantially constant, so a waveform as shown in FIG. 7 is output.

The discrimination signal generating means (7) generates a timing pulse signal V.
4c, the command signal ■ is periodic as shown in FIG. Since the delay time tb or t is maintained approximately constant based on the A, M detection signals V,. It outputs discrimination signals v5 and V6 (charging voltage signal and discharging voltage signal) with almost no phase shift. Therefore, the comparison circuit (8) can perform stable comparison and output the detection signal v7.

Furthermore, even if an unavoidable shift in the transmission time of transmitting and receiving ultrasonic waves occurs as the vehicle speed increases, this is a value that can be known in accordance with the vehicle speed, so for example, the second timing command means (6 It goes without saying that by controlling the pulse correction circuit (61) of ) by the vehicle speed detection means (9), it is possible to more accurately match the delay time and the transmission time difference as necessary.

An embodiment of the present invention, as described above, changes the transmission interval of ultrasonic pulses to become shorter at high speed, and
Even before and after changing the pulse transmission interval, it operates to generate a discrimination signal that is synchronized with the repetition period of the received reflected wave signal and has a delay time equivalent to the arrival time delay from transmission to reception of ultrasonic waves. Timing command means (1)
, a second timing command means (6), a discrimination signal generation means (7), and the like.

Therefore, at low speeds, ultrasonic waves are transmitted and received at sufficiently long transmission intervals to ensure the arrival of the transmitted ultrasonic pulses, and by generating a discrimination signal that matches the transmission timing and comparing the levels of the received signals, It is possible to effectively utilize the technical advantages of the pulse transmission method.

On the other hand, at high speeds, by changing to a short pulse interval that does not wait for the reflected wave to arrive, which is necessary to prevent detection errors,
In addition to preventing detection failures at high speeds, the round trip time from transmission to reception basically does not change significantly even at high speeds, so there is a nearly constant delay time regardless of changes in transmission timing. By generating a periodic discrimination signal and comparing the level of the received signal, it is possible to provide an ultrasonic obstacle sensor that is ideal for in-vehicle use and does not lose the advantages of the pulse transmission method even at high speeds. .

In the above embodiment, the timing command means (1) was composed of a microcomputer (10) etc., and the second timing command means (6) and the discrimination signal generation means (7) were composed of individual circuits. Similar operation can be expected even if all of the circuits are configured with microcomputers.

Further, in the above embodiment, the discrimination signal generating means (7) is configured with a charging circuit and a discharging circuit using an analog CR, and the discrimination signal (comparison voltage) of a monotonically increasing or monotonically decreasing chevron is explained. It goes without saying that the intended purpose can also be achieved by employing a discrimination signal constructed by a microcomputer and rising and falling on a staircase.

Furthermore, in the above embodiment, the discrimination signal generating means (7) is constructed of two electronic circuits, but as long as different predetermined discrimination signals (comparison 2 voltage) are generated before and after a predetermined elapsed time, other electronic circuits can be used. The circuit configuration may be a single circuit, for example.

Furthermore, in the above embodiment, the ultrasonic transmitting means (3) and the ultrasonic receiving means (4) are configured separately, but even if a single ultrasonic microphone is used in a time-sharing manner, the intended purpose can still be achieved. It is not even possible to achieve this.

Furthermore, in the above embodiment, the delay time t is determined by the discrimination signal v
6 was kept constant before and after switching, but as shown in Fig. 6,
Discrimination signal (comparison voltage) vs, V6 and AM detection signal V30
are both regular periodic waveforms, so t, b and tbf:N
Since the effect is the same even if there is a difference in delay time from Xt, +, the second timing command means (6) uses the command signal V thus changed. It goes without saying that the same effect can be obtained by outputting . In other words, even if they do not match,
It is fine as long as it is reasonable. This command signal ■. The change has been explained in two steps, but it goes without saying that the same effect can be obtained even if the change is made in multiple steps.

[Effects of the Invention] As explained above, this invention provides a vehicle speed detection means for detecting the speed of a vehicle, and a timing for generating a command signal for intermittently generating ultrasonic waves based on the output of the vehicle speed detection means. a command means, an ultrasonic signal generating means for generating an ultrasonic signal based on the command signal, an ultrasonic transmitting means for transmitting the ultrasonic wave to a road surface based on the ultrasonic signal, and a reflected wave of the ultrasonic wave. ultrasonic receiving means for receiving and generating a received signal, received signal processing means for performing AM detection on the received signal and outputting an AM detected signal, and generating a timing pulse signal based on the output of the vehicle speed detecting means and the command signal. a second timing command means for generating a discrimination signal; a discrimination signal generation means for generating a discrimination signal based on the timing pulse signal; and a detection signal for the obstacle on the road surface by comparing the AM detection signal and the discrimination signal. Since it is equipped with a comparison circuit that outputs a This has the effect of being able to be distinguished and discriminated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing timing command means and vehicle speed detection means of an embodiment of the invention, and FIG. 3 is a circuit diagram showing an embodiment of the invention. FIG. 4 is a circuit diagram showing the received signal processing means according to an embodiment of the present invention; FIG. 5 is a circuit diagram showing the second timing command means and discrimination signal generation means according to the embodiment of the present invention. 6 is a timing chart showing signal waveforms of various parts at low speed in an embodiment of the present invention; FIG. 7 is a timing chart showing signal waveforms of each part at high speed in an embodiment of this invention. It is a chart diagram. In the figure, (1) ... timing command means, (2) ...
Ultrasonic signal generating means, (3) ... Ultrasonic transmitting means, (4) ... Ultrasonic receiving means, (5) ... Received signal processing means, (6) (7) (8) (9 ) In addition, is shown. ...second timing command means, ...discrimination signal generation means, comparison circuit, ...vehicle speed detection means.

Claims (1)

[Claims] A vehicle speed detection means for detecting the speed of the vehicle; a timing command means for generating a command signal for intermittently generating ultrasonic waves based on the output of the vehicle speed detection means; and a timing command means for generating an ultrasonic signal based on the command signal. an ultrasonic signal generating means, an ultrasonic transmitting means for transmitting the ultrasonic wave to the road surface based on the ultrasonic signal, an ultrasonic receiving means for receiving the reflected wave of the ultrasonic wave and generating a received signal, and an AM method for transmitting the received signal. Detected AM
Received signal processing means for outputting a detection signal; second timing command means for generating a timing pulse signal based on the output of the vehicle speed detection means and the command signal; and a discrimination signal for generating a discrimination signal based on the timing pulse signal. An ultrasonic obstacle sensor comprising a generating means and a comparison circuit that compares the AM detection signal and the discrimination signal and outputs a detection signal of the obstacle on the road surface.