JP2884219B2 - Ultrasonic sensor system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic sensor system that emits ultrasonic waves into a monitoring area and detects the presence or absence of an object in the monitoring area based on the presence or absence of a reflected wave from the monitoring area.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 5, a plurality of ultrasonic sensor units 1 are connected to a single control unit 2.
There is an ultrasonic sensor system that controls and detects by using an ultrasonic sensor. In this system, a transmission command signal periodically generated from the transmission command signal generation 24 of the control unit 2 is transmitted to each ultrasonic sensor unit 1 through a transmission signal line LS commonly connected to each ultrasonic sensor unit 1. Is output to the oscillator 11b of the ultrasonic transmission control unit 11 of the transmission circuit 11 having received the oscillation signal from the oscillator 11b.
“a” generates a tone burst wave and causes the ultrasonic transducer S to emit ultrasonic waves of a pulse train toward a monitoring area. Then, when an object such as a human body or an automobile exists in the monitoring area, the reflected wave reflected by the object is received by the ultrasonic transducer S.

The received signal is amplified by an amplifier circuit 13a of an ultrasonic wave reception controller 13, detected by a detection circuit 13b, and further, a reflected pulse detection circuit 14 determines the presence or absence of a reflected pulse. . The reflected pulse detection circuit 14 outputs a reflected pulse detection signal only when it is determined that a reflected wave is present, and turns on the transistor TR1 of the voltage dividing circuit 15.
On the other hand, the voltage of the reception signal line LR is pulled up to the reference voltage Vc via the reference resistor R0. However, in the ultrasonic sensor unit 1 that has determined that there is a reflected wave, the transistor TR1 is turned on as described above. Then, the receiving signal line LR is short-circuited to ground via the resistor r. That is,
The resistor r is connected to the reference resistor R0 to close the voltage dividing circuit 15, and the total resistance of the resistor voltage dividing circuit 15 formed at this time is such that the resistance r is the same as the resistance of all the ultrasonic sensor units 1. Since the value is used, the value becomes smaller corresponding to the number of the ultrasonic sensor units 1 that have detected the reflected pulse. Therefore, the voltage level discrimination circuit 21 determines the voltage drop at the connection point of the reception signal line LR with the reference resistor R0, and the ultrasonic sensor unit number determination circuit 22 refers to the reference table to the determined voltage level. Then, the number of the ultrasonic sensor units 1 that have detected the object is calculated, and the calculated number is displayed on, for example, a display (not shown).

However, in the above-described ultrasonic sensor system, the transmission signal line LS and the reception signal line LR have two components.
If the number of ultrasonic sensor units increases, the above two types of signal lines LS and LR must be wired to each of the ultrasonic sensor units, which increases the number of wirings and the system configuration. There are drawbacks such as increased complexity.

In such a system, when an ultrasonic sensor unit that has received a reflected pulse is present, a resistor r having the same resistance value is connected to a reference resistor R0 via a reception signal line LR, and a voltage dividing circuit is provided. Since 15 is formed, the voltage input to the voltage level discrimination circuit 21 does not accurately change in accordance with the number of ultrasonic sensor units 1 that have detected the object, but changes non-linearly. for that reason,
As the number of ultrasonic sensor units that detect an object increases, there has been a problem that the accuracy of discriminating the number decreases.

[0006]

SUMMARY OF THE INVENTION The present invention proposed in view of the above circumstances connects a single control unit and a number of ultrasonic sensor units with signal lines, and generates reflected pulses on the control unit side. A first object of the ultrasonic sensor system capable of discriminating the number of the detected ultrasonic sensor units is to perform the discrimination of the number with high accuracy, and a second purpose is to perform the discrimination of the number accurately and a signal line. To reduce the number of devices, to reduce the size and simplification of the system, and to reduce the cost.

[0007]

An ultrasonic sensor system according to the present invention proposed to achieve the above object has a plurality of ultrasonic sensor units connected in parallel to transmission and reception signal lines, The other end of each of these signal lines is connected to a control unit, and in each of the ultrasonic sensor units, an ultrasonic transmission control unit is connected to the transmission signal line except for a transmission command signal discriminating circuit. Receiving the transmission command signal output from the control unit via the control unit and emitting an ultrasonic pulse, the control unit pulls up the reception signal line via a reference resistor, and When the reflected pulse detection circuit of the sensor unit outputs the reflected pulse detection signal through the signal line for reception, the shared voltage of the reference resistance of the signal line for reception is changed. A voltage level discriminating circuit that detects and discriminates by a differential amplifier circuit, and the number of ultrasonic sensor units that discriminates the number of ultrasonic sensor units that have detected reflected pulses according to the voltage level detected by the voltage level discriminating circuit. And a determination circuit.

According to a second aspect of the present invention, a plurality of ultrasonic sensor units are connected in parallel to a common signal line, and the other end of the signal line is connected to a control unit. Each includes a transmission command signal discriminating circuit that detects a transmission command signal output from the control unit via the signal line, and drives an ultrasonic transmission control unit, and the control unit includes the signal line. When the reflected pulse detection circuit of the ultrasonic sensor unit outputs a reflected pulse detection signal, the shared voltage of the reference resistance of the common signal is detected by a differential amplifier circuit. And a voltage level discriminating circuit configured to discriminate the reflected pulse according to the voltage level detected by the voltage level discriminating circuit. It has a configuration including an ultrasonic sensor unit number discriminating circuit for discriminating the number of waves sensor unit.

According to a third aspect of the present invention, the sensor unit number discriminating circuit has a gate signal generating circuit for outputting a gate signal having a predetermined width after the transmission command signal is output from the control unit. While the gate signal is being output, the change value of the voltage level is detected,
The configuration is such that the number of ultrasonic sensor units that have detected reflected pulses is determined, thereby realizing a system that is effective as a noise countermeasure against variations in the reception time of reflected pulses of the ultrasonic sensor unit.

[0010]

According to the ultrasonic sensor system of the present invention, when the reflected pulse detection signal of the ultrasonic sensor unit is output through the receiving signal line, the voltage determination circuit of the control unit outputs the signal. The shared voltage of the reference resistance of the line is detected and determined by the differential amplifier circuit. Therefore, the output voltage obtained as a reflected pulse detection signal from the signal line changes linearly according to the number of ultrasonic sensor units that have detected an object, so that accurate determination can be made even when the number of sensor units increases. it can.

According to the ultrasonic sensor system of the second aspect of the present invention, the same signal line is used to transmit a transmission command signal from the control unit to each ultrasonic sensor unit, and the same signal line is used. Using the signal line, the ultrasonic sensor unit that has received the reflected pulse can return an output signal to the control unit.
At this time, the output voltage obtained as a reflected pulse detection signal from the signal line changes linearly according to the number of ultrasonic sensor units that have detected the object.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an ultrasonic sensor system according to an embodiment of the present invention. In FIG. 1, the same or equivalent components as those shown in FIG. The resistance r for short-circuiting and grounding the receiving signal line LR when each ultrasonic sensor unit 1 receives a reflected pulse has the same value in all the sensor units 1.

The difference from FIG. 5 is that the voltage level discriminating circuit 2A is constituted by a differential amplifier circuit, and the differential amplifier circuit 2A is constituted by using an operational amplifier OP. When the reflection pulse detection circuit 14 outputs the reflection pulse detection signal through the reception signal line LR, the shared voltage of the reference resistor R0 of the reception signal line LR is detected. Here, assuming that the potentials at both ends of the reference resistor R0 applied to each terminal of the operational amplifier OP are E1 and E2,
The output voltage EO of the operational amplifier OP is expressed by the following equation: EO = [(R4 + R6) ６ (R5 + R7)] × (R7 / R4) E2-R6 / R4E1. Here, R4 = R5, R6 = R7
EO = R6 / R4. (E1-E2).

That is, in such a differential amplifier circuit 2A, the difference between the potentials E1 and E2 across the reference resistor R0 is expressed by R
A voltage amplified by 6 / R4 times, that is, a voltage EO proportional to the difference between the potentials E1 and E2 across the reference resistor R0 is obtained. Therefore, in such a differential amplifier circuit 2A, the output voltage EO corresponds to the increase of the current flowing through the voltage dividing circuit 15, and is linearly proportional to the number of the ultrasonic sensor units 1 detecting the reflected pulse. Since the number of ultrasonic sensors changes, the number of ultrasonic sensor units 1 can be determined with high accuracy even when the number of ultrasonic sensor units 1 increases.

The ultrasonic sensor unit 1 detects a transmission command signal a output from the transmission command signal generation circuit 24 of the control unit 2 via the transmission signal line LS,
A transmission command signal discriminating circuit 12 for driving the ultrasonic transmission control unit 11 is provided. Transmission command signal generation circuit 24
Outputs a high-level transmission command signal a to turn on the transistor TR2 to lower the voltage of the reception signal line LR to a predetermined level or less, and to transmit the transmission command signal a to the gate signal generation circuit 23 as an activation signal. Output as

The gate signal generation circuit 23 transmits a transmission command signal a
Outputs a gate signal d of a predetermined width from the point in time when. The ultrasonic sensor unit number discriminating circuit 22 detects the change value of the voltage level of the voltage level discriminating circuit 2A while the gate signal d is being output, and reflects the reflected pulse while referring to this voltage with the reference table 22a. The number of the ultrasonic sensor units that have detected the data is determined, and the determined data is displayed on, for example, a display (not shown).

FIG. 2 is a circuit diagram showing the transmission command signal discriminating circuit 12. As shown in FIG. This transmission command signal determination circuit 12
When the transmission command signal a is not output from the control unit 2, a voltage obtained by dividing the input voltage Vin supplied from the transmission signal line LS by the two resistors R2 and R3 always turns on the transistor TR3. Is set to be equal to or greater than the value, and the transistor TR3 is turned on.
The inverting circuit NOT outputs a high-level output voltage Vout, so that the ultrasonic wave transmission controller 11 is not driven. On the other hand, when the transmission command signal a is output and the transistor TR2 is turned on, the input voltage Vin becomes the GND level equal to or lower than the predetermined value, the transistor TR3 is turned off, and the inverting circuit NOT outputs the low-level output voltage Vout And drives the ultrasonic wave transmission controller 11.

FIGS. 3A to 3C are time charts showing the basic operation described above. When the transmission command signal a is output and the transistor TR2 is turned on, the reception signal line L
Since the voltage b of R is lower than the lower limit setting voltage Vth2, the output voltage c from the transmission command signal discriminating circuit 12 becomes close to the GND bell as described above, and drives the ultrasonic transmission control unit 11. After a slight delay time td, the gate signal generation circuit 23
Outputs a gate signal d having a predetermined width t, while the ultrasonic sensor unit number discriminating circuit 22 detects the change in the voltage level while the gate signal d is being output during t. That is, the voltage level discriminating circuit 2A detects the shared voltage of the reference resistor R0 of the receiving signal line LR by detecting the reflected pulse, and the voltage level at this time is stored in the reference table 22a prepared in advance by the number discriminating circuit 22. For example, the number of the ultrasonic sensor units that have received the reflected pulse is determined by reference.

FIG. 4 is a block diagram showing an ultrasonic sensor system according to another embodiment of the present invention. This embodiment differs from FIG. 1 in that the control unit 2 and each ultrasonic sensor unit 1 are connected by a common signal line L for transmission and reception. The ultrasonic sensor unit 1 detects the transmission command signal a output from the transmission command signal generation circuit 24 of the control unit 2 via the common signal line L, and drives the ultrasonic transmission control unit 11. A transmission command signal determination circuit 12 is provided.

The ultrasonic sensor unit 1 detects a transmission command signal a output from the transmission command signal generating circuit 24 of the control unit 2 via a common signal line L,
A transmission command signal discriminating circuit 12 for driving the ultrasonic transmission controller 11 is provided. The basic operation is the same as that of the system shown in FIG. According to such a system, the number of signal lines can be simplified and reduced, and the output voltage is proportional to the number of operating ultrasonic sensor units 1, so that the number can be accurately determined.

[0021]

As can be understood from the above description, according to the ultrasonic sensor unit of the first aspect of the present invention, since the voltage level discriminating circuit is constituted by the differential amplifier circuit, A voltage output that changes linearly in proportion to the number of operating sensor units 1 can be obtained, and therefore, even when the number of operating sensor units 1 increases, it is possible to determine with high accuracy.

According to the ultrasonic sensor unit of the second aspect, a voltage output that changes linearly in proportion to the number of operating ultrasonic sensor units 1 can be obtained, and the control unit is used for both transmission and reception. The number of ultrasonic sensor units can be greatly reduced when the number of ultrasonic sensor units is increased, and the system is simplified, wiring work is reduced, and costs are reduced. I can plan.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an ultrasonic sensor system according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific configuration of a transmission command signal determination circuit.

FIG. 3 is a time chart showing a basic operation of a part (a) to (d) of FIG. 1;

FIG. 4 is a block diagram showing an ultrasonic sensor system according to another embodiment of the present invention.

FIG. 5 is a block diagram showing a conventional ultrasonic sensor system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultrasonic sensor unit 2 Control unit 2A Voltage level discrimination circuit (differential amplification circuit) 11 Ultrasonic wave transmission control part 12 Transmission command signal discrimination circuit 13 Ultrasonic wave reception control part 14 Reflection pulse detection circuit 15 Resistance voltage dividing circuit 22 ultrasonic sensor unit number discrimination circuit 23 gate signal generation circuit 24 transmission command signal generation circuit L common signal line LS transmission signal line LR reception signal line

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01S 3/80-3/86 G01S 7/52-7/64 G01S 15/00-15/96

Claims (3)

(57) [Claims] 1. A method for transmitting a plurality of ultrasonic sensor units,
While connected in parallel to the signal lines for reception, the other end of each of these signal lines was connected to the control unit, and were simultaneously driven by the transmission command signal output from the control unit through the signal line for transmission. When the ultrasonic sensor unit detects and determines the reflected pulse,
An ultrasonic sensor system configured to output a reflected pulse detection signal and return it to the control unit via a reception signal line, wherein each of the ultrasonic sensor units includes: An ultrasonic transmission control unit for emitting an ultrasonic pulse in response to a transmission command signal output from the control unit, and an ultrasonic wave for detecting a reflected pulse with respect to the ultrasonic pulse emitted from the ultrasonic transmission control unit When the ultrasonic wave reception control unit detects a reflected pulse, the ultrasonic wave reception control unit is configured to include a reflected pulse detection circuit that short-circuits the reception signal line to a ground via a predetermined resistor. The control unit pulls up the reception signal line via a reference resistor, and the reflected pulse detection circuit of the ultrasonic sensor unit receives the reception signal line. When the reflected pulse detection signal is output through the credit signal line, the differential amplifier circuit detects and determines the shared voltage of the reference resistance of the receiving signal line, and the voltage level determination circuit detects the voltage. An ultrasonic sensor unit configured to determine the number of ultrasonic sensor units that have received the reflected pulse in accordance with the voltage level. 2. A plurality of ultrasonic sensor units are connected in parallel to a common signal line, the other end of the signal line is connected to a control unit, and a transmission command signal output from the control unit through the signal line. An ultrasonic sensor system configured to output a reflected pulse detection signal through the signal line when the ultrasonic sensor units driven at the same time detect and determine a reflected pulse, wherein each of the ultrasonic sensor units An ultrasonic wave transmission control unit that emits an ultrasonic pulse, an ultrasonic wave reception control unit that detects a reflected pulse with respect to the ultrasonic pulse emitted from the ultrasonic wave transmission control unit, and via the signal line A transmission command signal discriminating circuit that detects a transmission command signal output from the control unit and drives an ultrasonic transmission control unit A reflection pulse detection circuit for short-circuiting the signal line via a predetermined resistor when the ultrasonic wave reception control unit detects a reflection pulse, and the control unit includes the signal line Is pulled up via a reference resistor, and when the reflected pulse detection circuit of the ultrasonic sensor unit outputs a reflected pulse detection signal, a shared voltage of the reference resistor of the common signal is detected by a differential amplifier circuit. A voltage level discriminating circuit configured to discriminate the number of ultrasonic sensor units that have received reflected pulses according to the voltage level detected by the voltage level discriminating circuit. An ultrasonic sensor system configured to include a circuit. 3. The sensor unit number discriminating circuit includes a gate signal generating circuit for outputting a gate signal having a predetermined width after the transmission command signal is output from the control unit, and outputting the gate signal. While being
The ultrasonic sensor system according to claim 1, wherein the change in the voltage level is detected to determine the number of ultrasonic sensor units that have detected the reflected pulse.