JPH0522191B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an ultrasonic obstacle detection device that uses ultrasonic waves to detect obstacles existing behind, for example, an automobile.

[Prior art]

Conventionally, ultrasonic waves have been used to detect obstacles in the blind spot at the rear of a car, for example, and if the distance to the obstacle is within a dangerous area, a warning is sounded with a buzzer, etc., and the location of the obstacle is displayed. There is an ultrasonic obstacle detection device that performs the following (for example, Japanese Patent Laid-Open No. 57-74246).

Figure 1 is a diagram showing the general circuit configuration of a conventional device of this type. The distance to obstacles is detected.

That is, the timing signal generating circuit 1 generates a timing signal A having a period of T and a pulse width of t as shown in FIG. 2a, and supplies it to the oscillator 2. A carrier signal B of a frequency is generated, and the ultrasonic transmitting element 3 is driven by this signal B to cause the transmitting element 3 to emit an ultrasonic wave. Then, this ultrasonic wave is sent to the transmitting element 3
It is reflected by an obstacle in front of the ultrasonic wave and enters the ultrasonic receiving element 4. In this case, in addition to the waves reflected by the obstacle (main rope waves), side rope waves directly propagating from the transmitting element 3 to the receiving element 4 are incident on the receiving element 4 . Therefore, the receiving element 4 outputs an ultrasonic reception signal C consisting of a side lobe wave signal and an obstacle detection wave signal as shown in FIG. 2c. This received signal C is amplified by an amplifier 5 and input to a waveform shaping circuit 6. Then, the waveform shaping circuit 6 removes the side lobe wave signal unrelated to distance detection from the amplified ultrasonic reception signal, extracts only the obstacle detection wave signal, and outputs the second wave signal.
As shown in FIG. d, a pulse signal D synchronized with the generation timing of the obstacle detection wave signal is generated and supplied to the distance determination circuit 7. Then, the distance determination circuit 7 calculates the distance to the obstacle based on the timing difference τ between the timing signal A and the pulse signal D, determines whether this distance is within the danger area, and calculates the distance to the obstacle. The display device 8 displays the location and location, and the alarm device 9 emits an alarm sound if the location is in a dangerous area. This makes it possible to prevent collisions with obstacles.

However, in the above configuration, if foreign matter such as snow or mud adheres to either the transmitting element or the receiving element, the transmitting/receiving efficiency decreases and the detectable distance becomes shorter, or if the transmitting/receiving efficiency decreases significantly, it may be detected as an obstruction. There may be cases where there is no received wave even though there is a signal, in other words, it is determined that there is no obstacle.
A problem has arisen in which functions are no longer performed properly and reliability is poor.

Therefore, as a solution to this problem, a system has been proposed that includes a self-check means that detects the deterioration in the performance of the transmitting and receiving elements and notifies the driver. Since the system issues an alarm only when the level has reached a certain level or lower, it has the disadvantage that it cannot provide an effective effect on functional deterioration that does not reach a predetermined level or lower. Furthermore, since the self-check operation is performed when the power is turned on, it is not possible to detect any functional deterioration that occurs before the next self-check operation, and in any case, there is a high possibility that foreign matter such as snow or mud may adhere to the device. There was a problem that it could not be an effective solution for things used in places.

[Purpose of the invention]

An object of the present invention is to provide an ultrasonic obstacle detection device that can accurately detect obstacles even when foreign matter such as snow or mud is attached.

[Summary of the invention]

The present invention utilizes the fact that the propagation path of sidelobe waves propagating from a transmitting element to a receiving element is always constant, and the reception level is also constant as long as the performance of the transmitting and receiving element is kept constant. It is configured to detect the reception level of sidelobe waves and adjust the ultrasonic transmission gain or reception sensitivity so that this detection level is always kept constant.

[Embodiment of the Invention] FIG. 3 is a circuit diagram showing an embodiment of the present invention, in which a side lobe wave extraction circuit 1 is added to the configuration of FIG. 1.
0, level determination circuit 11, amplification gain switching circuit 1
2. Amplification gain determination circuit 13, functional deterioration notification circuit 1
4 has been added, and the same parts as in FIG. 1 are represented by the same symbols.

In such a configuration, the side lobe wave extraction circuit 10 receives the ultrasonic reception signal amplified by the amplifier 5, removes the obstacle detection wave signal contained in the signal, extracts only the side lobe wave signal, and determines the level. The signal is supplied to the determination circuit 11. Then, the level judgment circuit 11 compares the voltage level V _S of the input side lobe wave signal with the normal voltage level V _S0 , and if V _S < V _S0 , a decrease in sensitivity has occurred due to adhesion of foreign matter, etc. The amplification gain switching control signal is sent to the amplification gain switching circuit 12, and the amplification gain of the amplifier 5 is adjusted so that V _S =V _S0 .
As a result, the received voltage level of the sidelobe wave signal is kept constant, and the decrease in sensitivity is compensated for by increasing the amplification gain, making it possible to detect obstacles with the same accuracy as in normal conditions.

On the other hand, the amplification gain determination circuit 13 monitors the switching state of the amplification gain by the switching circuit 12, and if the amplification gain of the amplifier 5 is not controlled to the maximum gain but does not become V _S =V _S0 , It is determined that the performance of the transmitting/receiving element has deteriorated significantly or that a failure has occurred in the circuit system, and the functional deterioration notification circuit 14 is activated to notify the driver of the functional deterioration.

In this way, in this embodiment, a functional deterioration that does not result in a complete failure of the circuit system is automatically compensated for by the control that keeps the reception level of the sidelobe wave constant, and the limit of compensation is exceeded. If this happens, the driver will be notified, so even under conditions of use where foreign objects such as snow are present, the system can detect obstacles in the same way as under normal conditions, maintaining high reliability. I can do it.

In this embodiment, the amplification gain of the amplifier 5 is adjusted to compensate for the functional decline, but as shown in FIG. An oscillator power determination circuit 16 is provided in place of the amplification gain determination circuit 13, and the voltage of the carrier wave generated from the oscillator 2 is adjusted to change the ultrasonic transmission gain, thereby compensating for the functional decline and exceeding the compensation limit. This may be determined by the oscillator power switching circuit 16.

Further, as shown in FIG. 5, an amplification gain switching circuit 5
A threshold switching circuit 17 is provided in place of
In addition, a threshold voltage determination circuit 18 is provided in place of the amplifier gain determination circuit 13 to determine the threshold level of the waveform shaping operation in the waveform shaping circuit 6.
If V _S <V _S0 , the functional degradation may be compensated for by lowering the voltage, and the threshold voltage determination circuit 18 may determine that the compensation limit has been exceeded.

Furthermore, this is the judgment circuit 13, 16, 18
If another criterion for detecting a state immediately before exceeding the compensation limit is added as a judgment criterion, and an advance notice of functional deterioration is issued based on this criterion, the device can be made even more reliable. According to the ultrasonic obstacle detection device configured in this way, the sidelobe signal, which is originally desirable to be absent, is actively used to adjust the ultrasonic transmission gain or reception sensitivity, and the device detects foreign objects such as snow. Even under such usage conditions, obstacles can be detected in the same way as under normal conditions.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a decline in the obstacle detection function due to performance deterioration of the ultrasonic transmitting/receiving element or a decline in the obstacle detection function due to the adhesion of foreign matter such as snow can be automatically prevented. This has the excellent effect of being able to detect obstacles with the same accuracy as under normal conditions and maintaining high reliability.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of a conventional ultrasonic obstacle detection device, FIG. 2 is a waveform diagram for explaining its operation, FIG. 3 is a circuit diagram showing an embodiment of the present invention, and FIG. 5 and 5 are circuit diagrams showing other embodiments of the present invention, respectively. 1... Timing signal generation circuit, 2... Oscillator, 3
...Ultrasonic transmitting element, 4... Ultrasonic receiving element, 5...
Amplifier, 6... Waveform shaping circuit, 7... Detection distance judgment circuit, 8... Display, 9... Alarm, 10... Side lobe wave extraction circuit, 11... Level judgment circuit, 12... Amplification gain switching circuit, 13... Amplification gain Judgment circuit, 14
...Function deterioration notification circuit, 15...Oscillator power switching circuit, 17...Threshold switching circuit.

Claims (1)

[Claims] 1. In an ultrasonic obstacle detection device that emits ultrasonic waves from an ultrasonic transmitting element and detects obstacles in the emission direction using an ultrasonic receiving element, the ultrasonic waves directly propagate from the ultrasonic transmitting element to the ultrasonic receiving element. a level detection circuit that detects the reception level of the sidelobe wave; an adjustment circuit that adjusts the transmission gain or reception sensitivity of the ultrasonic wave according to the detected reception level;
An ultrasonic obstacle detection device equipped with an alarm that issues an alarm when the adjustment of this adjustment circuit exceeds a limit.