JPS6314308B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic obstacle detection device, and an object of the present invention is to provide an ultrasonic obstacle detection device that can detect obstacles with high accuracy.

Conventionally, this type of device uses a transmitter to transmit tone burst-shaped ultrasonic waves and the time it takes for the reflected wave from an obstacle to be received by a receiver, which is calculated as the distance to the obstacle. It is being But in this case,
Since both the direct wave from the transmitter and the reflected wave are received by the receiver, the reflected wave from an obstacle in the nearby area overlaps with the direct wave, causing no obstruction in the nearby area. There is a dead zone where detection is not possible, and obstacles cannot be detected accurately.

Therefore, the present invention avoids the above-mentioned problems by switching the transmission signal from an ultrasonic signal to a Doppler radar signal when it comes to a nearby area.Hereinafter, an embodiment of the present invention will be described based on the drawings. explain.

1 is a signal generator that can switch and output a tone burst-like ultrasonic signal with a carrier frequency f ₀ and a Doppler radar signal [continuous wave] with a frequency f ₀ ; 2 is an amplifier; and 3 is a transmitter; The ultrasonic signal or Doppler radar signal is transmitted. 4
is a wave receiver, which receives the reflected wave transmitted from the wave transmitter 3 and reflected by an obstacle (not shown). 5 is an amplifier, and 6 is a tuning circuit tuned to the frequency f ₀ , into which the output of the receiver 4 via the amplifier 5 is input. 7 is a changeover switch 8, 9, 10
This timing circuit 7 also instructs switching between the ultrasonic signal and the Doppler radar signal of the signal generator. 11 is a detection circuit to which the output signal of the tuning circuit 6 is inputted via the changeover switch 8; 12 is a detection circuit that calculates the distance to an obstacle using the detection output of the detection circuit 11 and the transmission timing signal obtained from the signal generator 1; The first calculating unit 13 is a distance display device, which receives distance data from the first calculating unit 12 via the changeover switch 9, for example, and displays this distance data. 14 is a π/2 phase shifter to which the output signal of the signal generator 1 is input via the changeover switch 10, and delays the phase of the input signal by π/2. 15 is the first
The multiplier multiplies the output signal of the tuning circuit 6 input via the changeover switch 8 and the output signal of the signal generator 1 inputted through the changeover switch 10. 16 is a second multiplier which multiplies the output signal of the π/2 phase shifter 14 and the output of the tuning circuit 6 input via the changeover switch 8. Reference numerals 17 and 18 are low-pass filters connected to the outputs of the first and second multipliers 15 and 16, respectively. Reference numeral 19 inputs the output signals of the low-pass filters 17 and 18 to determine whether an obstacle is approaching or receding. 20 is an up/down counter which is instructed to go up or down by the output signal of the direction discrimination circuit 19, and uses the output of the first multiplier 15 as a counting input, and at an appropriate timing, the output of the timing circuit 7 determines the initial value. will be reset to 21 is a second arithmetic unit that calculates the distance to the obstacle by using the specified value preset in the setting circuit 22 and the count value of the up-down counter 20 as input signals, and the calculated distance data is used as the switching unit. A distance display 1 is used as a substitute for the distance data output from the first arithmetic unit 12 via a switch 9.
3 is input. 23 is a detection circuit that detects when the distance data of the first arithmetic unit 12 or the second arithmetic unit 21 has reached a specified distance, and the detection output is inputted to the timing circuit 7 as a switching instruction signal.

Next, the timing circuit 7 and the changeover switches 8, 9,
The detection operation will be explained in detail based on the relationship shown in FIG.

First, the timing circuit 7 instructs the signal generator 1 to output an ultrasonic signal, and the changeover switch 8 instructs the output of the tuning circuit 6 to be sent to the detection circuit 11 and the first multiplier 1.
5, the switch 9 is instructed to supply the distance data of the first arithmetic unit 12 to the distance display 13, and the switch 10 is instructed to turn off. Instruct. When the changeover switches 8, 9, and 10 are in the switching state, the ultrasonic signal emitted from the transmitter 3 and reflected is transmitted to the receiver 4.
The signal is received by the tuning circuit 6, the changeover switch 8, and the detection circuit 11, and then input to the first arithmetic unit 12. The first arithmetic unit 12 calculates the time required for the output signal of the detection circuit 11 to rise based on the transmission timing signal, converts this into distance data, and displays the calculated distance data via the changeover switch 9. The distance to the obstacle is displayed. Further, when an obstacle approaches and the distance data of the first arithmetic unit 12 reaches a specified distance, the detection circuit 23 detects this and sends a switching instruction signal to the timing circuit 7. The timing circuit 7 to which the switching instruction signal is input switches the output signal of the signal generator 1 from the ultrasonic signal to the Doppler radar signal,
The changeover switch 8 is set to a changeover state in which the output of the tuning circuit 6 is applied to the first and second multipliers 15 and 16, the changeover switch 9 is set to a changeover state to select the distance data of the second arithmetic unit 21, and the changeover switch 10 Turn on. By this mode reversal, the transmitter 3
The Doppler radar signal transmitted in place of the ultrasonic signal is reflected by an obstacle and similarly transmitted to the receiver 4.
After that, it is applied to the first and second multipliers 15 and 16 via the tuning circuit 6 and the changeover switch 8. Also, due to this mode inversion, a continuous wave is supplied from the signal generator 1 to the π/2 phase shifter 14 and the first multiplier 15 via the changeover switch 10, and the continuous wave is supplied to the second multiplier 16. A π/2 phase shifter 14 supplies a Doppler radar signal with a π/2 phase delay. The outputs of the first and second multipliers 15 and 16 in this operating mode are as follows.

Transmitting signal = A ₀ sinω ₀ t (however, ω ₀ = 2πf ₀ ) Receiving signal = Asin (ω ₀ t−T) π/2 phase shifter 14 output = A ₀ sin (ω ₀ t−π/2 ) First multiplier 15 output = A ₁ {cosT − cos (2ωt − T)} Second multiplier 16 output = −A ₁ {sinT + sin (2ωt − T)} These first and second multipliers When outputs 15 and 16 are passed through low-pass filters 18 and 17, respectively, the above equation becomes as follows.

Low-pass filter 17 output = A ₁ cosT Low-pass filter 18 output = -A ₁ sinT The component T in these two equations is an amount that varies depending on the position of the obstacle, and has a different sign when it approaches and when it moves away, so This is discriminated by the direction discrimination circuit 19 and the up-down counter 20 is switched between addition and subtraction. In the up-down counter 20, the first multiplier 15
The beats of the output beat signal are added or subtracted. Incidentally, the up-down counter 20 is reset to the initial value by the timing circuit 7 when the obstacle reaches a specified distance. In the second arithmetic unit 21, the calculated value of the up-down counter 20 [number of beats]
Based on n, the current distance L' to the obstacle is calculated using the following equation.

L'=L-nλ where L is the specified distance and λ is the wavelength of the Doppler radar signal in the air. This calculated distance
The distance data of L' is supplied to the distance display 13 via the changeover switch 9, and the distance is displayed. Here, if the obstacle returns to the point at the specified distance L after entering within the specified distance L, the detection circuit 23 detects this and generates a switching instruction signal to the timing circuit 7 again, and the Doppler Obstacles are detected by switching from radar signals to ultrasonic signals.

In this way, when an obstacle approaches the nearby area, the transmitted wave is switched from an ultrasonic signal to a Doppler radar signal wave, the Doppler frequency is counted, and the distance to the obstacle is calculated from the tone burst-shaped ultrasonic wave. It is also possible to detect obstacles in a nearby area that could not be detected by using acoustic signals alone due to direct wave effects.

As explained above, according to the present invention, there is provided a wave transmitting means that can freely transmit a tone burst-like ultrasonic signal and a Doppler radar signal by switching between them, and a wave reflected from an obstacle of a signal transmitted from the wave transmitting means. During the ultrasonic signal transmission period, the distance to the obstacle is calculated from the time from transmission to reception, and during the Doppler radar signal transmission period, the Doppler frequency is counted and the distance to the obstacle is calculated. a signal processing means for calculating the distance between the ultrasonic wave transmitter and the Doppler radar; In order to detect the distance to an obstacle within the specified distance by transmitting a Doppler radar signal, it is impossible to detect the object simply by using tone burst ultrasound due to the direct wave effect. It is possible to detect obstacles in a nearby area that has not been detected, improve detection performance, and improve reliability in detecting obstacles.

[Brief explanation of the drawing]

The drawing is a configuration diagram of an ultrasonic obstacle detection device according to an embodiment of the present invention. 1... Signal generator, 2... Amplifier, 3... Transmitter, 4... Receiver, 5... Amplifier, 6... Tuning circuit, 7... Timing circuit, 8, 9, 10... Changeover switch, 11...Detection circuit, 12...First arithmetic unit, 13...Distance display, 14...π/2 phase shifter, 15...First multiplier, 16...Second Multiplier, 17, 18...Low pass filter, 19...
... Direction discrimination circuit, 20 ... Up-down counter, 21 ... Second arithmetic unit, 22 ... Setting circuit,
23...Detection circuit.

Claims (1)

[Claims] 1. A wave transmitting means capable of transmitting signals by switching between a tone burst ultrasonic signal and a Doppler radar signal, and a wave receiving means receiving a reflected wave from an obstacle of the signal transmitted from the wave transmitting means; Signal processing means that calculates the distance to an obstacle during the ultrasonic signal transmission period from the time from transmission to reception, and calculates the distance to the obstacle by counting the Doppler frequency during the Doppler radar signal transmission period. and an instruction means for detecting that the detection distance during the ultrasound transmission signal transmission period has reached a specified distance and switching the transmission signal of the ultrasound transmission means from the ultrasound signal to the Doppler radar signal, An ultrasonic obstacle detection device that detects a distance to an obstacle within the specified distance by transmitting a Doppler radar signal.