JPH0334710Y2 - - Google Patents

Description

[Detailed Description of the Invention] <<Field of the Invention>> This invention relates to an ultrasonic object detection device, and particularly to a detection technique when an object to be detected is located near the boundary of a detection area.

<Prior art and its problems> In ultrasonic object detection devices, in order to accurately detect the target object and avoid detecting objects other than the target object,
The detection area is set narrowly.

For example, when detecting an object on a conveyor belt, set a detection area with a width approximately equal to the width of the conveyor belt, and even objects on the sides of the conveyor belt (for example, walls or equipment) may be detected. I try not to.

By the way, the object to be detected may not be located at the center of the width of the detection area, but may be located at the end of the width. That is, if the object to be detected is located near the boundary area of the front end or rear end of the detection area, there is a possibility that the detection will be inaccurate. Therefore, conventionally, the object at the boundary of the detection area is detected by expanding the detection area as a whole in both the front end side and the rear end side.

However, in this conventional detection method, the detection area expands to areas where the target object is not present, so there is a high possibility that noise will be mixed in or unnecessary objects will be detected, making it difficult to detect the target object. On the other hand, there was a problem of inaccuracy.

<<Purpose of the invention>> The purpose of the invention is to provide an ultrasonic object detection device that can accurately detect objects by minimizing changes in the detection area.

<<Structure and Effects of the Invention>> In order to achieve the above object, the ultrasonic object detection device according to the invention includes a transducer that transmits ultrasonic waves and receives reflected ultrasonic waves, and defines an object detection area. a detection area signal generation circuit that generates a signal; a judgment circuit that judges whether the reflected ultrasonic wave received by the transducer is on the leading edge side or the trailing edge side of the detection area signal; The present invention is characterized by comprising a widening circuit that expands the detection area signal by a predetermined width to either the leading edge side or the trailing edge side based on the output.

According to this configuration, since the detection area signal is expanded only on either the leading edge side or the trailing edge side, the expansion width of the sensing area can be minimized, and noise contamination and detection of unnecessary objects are prevented. Therefore, the target object can be detected accurately.

<<Description of Embodiments>> Fig. 1 shows an ultrasonic object detection device according to an embodiment of this invention, and Figs. 2 and 3 are time charts showing the operation of the main parts of this embodiment device. .

This ultrasonic object detection device consists of a clock generator 1, a wave transmission/reception timing circuit 2, a wave transmitter/receiver 3 consisting of a wave transmitter for transmitting ultrasonic waves, and a wave receiver for receiving reflected ultrasonic waves, and settings. device 4, setting area signal generation circuit 5, two gate circuits 6 and 7, two signal generation circuits 8 and 9, two judgment detection circuits 1
0 and 11, two widening decision circuits 12 and 1
3, an amplifier 14, a detector 15, a received signal generation circuit 16, and a holder 17.

A clock generator 1 supplies a system clock a to each section and also outputs it to a wave transmitting/receiving timing circuit 2. In this embodiment, the system clock a is a clock whose period corresponds to 1 cm.

The wave transmission/reception timing circuit 2 is mainly composed of a decoder and a counter, and generates a wave transmission timing signal A, a wave reception timing signal C, and a pulse signal b. As shown in Figure 2, the pulse signal b is
It consists of 10 basic pulses _b0 to _b9 , each basic pulse has a pulse width of one clock cycle of system clock a, and is repeated every 10 clock cycles of system clock a. Further, as schematically shown in FIG. 3, the reception timing signal C consists of ten zone signals _Z0 to _Z9 , and each zone signal is created from the ten fundamental pulses _b0 to _b9 . In this example, the first zone signal Z ₀ is the timing for receiving reflected ultrasound from an object within a distance range of 0 to 10 cm, and similarly, the final zone signal Z ₉ is the timing for receiving reflected ultrasound from an object within a distance range of 90 to 10 cm.
This is the timing to receive reflected ultrasound from an object within a distance of 100 cm. The transmission timing signal A is created from the zone signal Z ₀ and the first half fundamental pulses (for example, b ₀ to b ₄ ).

The transmitter/receiver 3 has a transmitting section that receives a transmitting timing signal A.
In response, the ultrasonic wave A is transmitted, and the receiving section receives the reflected ultrasonic waves B and C. Reflected ultrasonic wave (b) indicates a reflected wave from an object, and reflected ultrasonic wave (c) indicates a reflected wave from a wall or the like.

The setting device 4 specifies which of the ten zone signals Z ₀ to _{Z 9} is to be used as the object detection area signal.

The setting area signal generation circuit 5 receives wave reception timing C.
Select the zone signal specified by the setter 4 from among the following. In this example zone signal Z ₅ is selected,
This is the setting area signal D in the signal generation circuits 8 and 9.
has been entered. This zone signal Z ₅ is 50-60cm
This is the timing to receive reflected waves from objects within a distance range of .

The gate circuits 6 and 7 output a signal c indicating the leading edge side of the setting area signal D and a signal d indicating the trailing edge side to the signal generating circuits 8 and 9, respectively. This signal c,
d is created by a combination of the basic pulses b ₀ to b ₉ . In this example, signal c is the fundamental pulse
is created from b ₀ and b ₁ , and the signal d is the fundamental pulse
It is created from b ₈ and b ₉ .

The signal generation circuits 8 and 9 each transmit wave timing #1
~ #4, the detection area signal E is created by delaying the setting area signal D by a predetermined clock period of the system clock a. In this embodiment, the system clock a is delayed by one clock cycle. This operation corrects errors due to time delays and the like that occur between the transmission timing A and the output of the received signal generation circuit 16.

Then, at wave transmission timing #1, the signal generation circuit 8 generates signal Q of the leading edge side signal F from the detection area signal E and the output signal c from the gate circuit 6, and also generates the detection area signal E, etc. Create a reception area signal 2 of width. This leading edge side signal is clocked from the rising edge of the detection area signal E to the system clock a.
It has a pulse width of one clock period. Further, the signal generation circuit 9 generates a signal ``nu'' of the trailing edge side signal G from the detection area signal E and the output d from the gate circuit 7, and also generates a reception area signal ``d'' having the same width as the detection area signal E. . The falling part of this trailing edge side signal N overlaps with the falling part of the detection area signal E, and the internal system clock a
It has a width of one clock period. The leading edge signal Q and the receiving area signal D are input to the judgment detection circuit 10, and the leading edge signal H is input to the J terminal of the flip-flop 18. The trailing edge side signal N and reception area signal D are determined by the judgment detection circuit 11.
The trailing edge signal N is input to the K terminal of the flip-flop 18. The flip-flop 18 receives the system clock a as its clock input, and outputs an intermediate region signal e indicating the interval from the falling edge of the leading edge signal F to the rising edge of the trailing edge signal G to the Q terminal at each wave transmission timing.

On the other hand, the reflected ultrasonic waves B and C received by the wave receiving section of the transducer 3 are input as received signals to a received signal generation circuit 16 via an amplifier 14 and a detector 15. The received signal generation circuit 16 includes a waveform shaping circuit and a bevel discrimination circuit, and when the detection output exceeds a predetermined level, the received signal H is determined by the detection circuits 10 and 11.
and output to AND gate 19.

First, at wave transmission timing #1, the target object is 50 cm
This shows a case where the received signal overlaps the rising edge of the detection area signal E within a distance range of ~51 cm. In this case, the determination detection circuit 10 determines that the received signal is on the leading edge side of the detection area signal E by comparison with the leading edge side signal Q. the result,
The determination detection circuit 10 captures the reception signal H using the reception area signal D having the same width as the detection area signal E, outputs it to the holder 17, and outputs the activation signal f to the width expansion determination circuit 12, A prohibition signal g is output to the widening determination circuit 13. The widening determining circuit 12 receives the activation signal f and outputs a widening command signal h to the signal generating circuit 8. In response to this widening command signal h, the signal generating circuit 8 expands the leading edge side of the detection area signal E by a predetermined width t (in this embodiment, one clock cycle of the system clock a) at the next wave transmission timing #2. At the same time, a leading edge signal L is created by extending the leading edge side of the leading edge signal Q by a predetermined width t.

At wave transmission timing #2, the target object is at the same location as at wave transmission timing #1. Therefore, the judgment detection circuit 10 is given the newly created reception area signal H and leading edge side signal R, so that the reception signal H is reliably detected and the holder 1
7 is output. Then, at the next transmission timing, if the timing of the received signal H is at the same position as the previous time, the received signal H will exist within the width of the newly created leading edge side signal R, so the widening command signal h does not disappear. That is, the signal generating circuit 8 successively outputs the receiving area signal E and the leading edge side signal R. After that, when the target object moves and it is detected that the received signal H is not within the width of the leading edge side signal li, the widening command signal h disappears and the signal generation circuit 8
In this step, a reception area signal D having the same width as the detection area signal E is created, and a leading edge side signal Q is created.

Next, at transmission timings #3 and #4, the target object is
This shows a case where the received signal H is in the range of 59 cm to 60 cm and is on the trailing edge side of the detection area signal E. First, at transmission timing #3, the received signal H is the detection area signal E.
This overlaps with the trailing edge side, and this is compared with the trailing edge signal N in the determination circuit 11, and it is determined that the received signal H is on the trailing edge side of the detection area signal E. As a result, the determination detection circuit 11 receives the reception signal H using the reception area signal having the same width as the detection area signal and outputs it to the holder 17, and also outputs the activation signal i to the width expansion determination circuit 13. A prohibition signal j is output to the widening determination circuit 12. In response to this, the widening determining circuit 13 outputs a widening command signal k to the signal generating circuit 9. At the next transmission timing #4, the signal generation circuit 9 generates a reception area signal T by adding a predetermined width t (one clock period of the system clock a in this embodiment) to the trailing edge side of the detection area signal E. At the same time, a trailing edge signal is created by adding a predetermined width t to the trailing edge of the trailing edge signal.

Then, at wave transmission timing #4, since the newly created reception area signal G and trailing edge side signal L are input, the determination detection circuit 12 receives the reception signal H from the reception area signal G and transfers it to the holder 17. Output to. Then, at the next wave transmission timing, if the timing of the received signal H is at the same position as the previous time, the received signal H is within the width of the newly created trailing edge side signal line, so a widening command is issued to the signal creation circuit 9. Signal k does not disappear. Thereafter, the action on the trailing edge side is similar to the action on the leading edge side.

The above explanation is for the case where the signal from the target object is in the 10% area on the leading edge side and the 10% area on the trailing edge side of the detection area signal E, and when the received signal is in the remaining 80% area in the middle. , is ANDed with the intermediate region signal e in the AND gate 19, and the holder 1
7 is now output.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an ultrasonic object detection device according to an embodiment of this invention, Fig. 2 is a time chart showing the operation of the wave transmitting/receiving timing circuit, and Fig. 3 is a main part of the device of the above embodiment. This is a time chart showing the operation. 1... Clock generator, 2... Wave transmitting/receiving timing circuit, 3... Transducer/receiver, 4... Setting device, 5...
Setting area signal generation circuit, 6, 7... gate circuit,
8, 9... Signal creation circuit, 10, 11... Judgment detection circuit, 12, 13... Widening determination circuit, 17...
Holder, A... Transmission timing signal, B... Transmission/reception ultrasonic wave, C... Receiving timing signal, D... Setting area signal, F... Leading edge side signal, G... Trailing edge side signal, H... ...Reception signal, I...Reception area signal, a
...System clock, b...Pulse signal, c...
...first half area signal, d...second half area signal, e...middle area signal, f, i...starting signal, g, j...prohibition signal, h, k...widening command signal, t...additional width, A...Transmitted ultrasound, B...Reflected ultrasound from the target object.

Claims (1)

[Scope of utility model registration request] a transducer that transmits ultrasonic waves and receives reflected ultrasonic waves, a detection area signal generation circuit that creates a signal that defines an object detection area, and a reflected ultrasonic wave received by the transducer that detects the object detection area A determination circuit for determining whether the signal is on the leading edge side or the trailing edge side; and a determination circuit for extending the detection area signal by a predetermined width to either the leading edge side or the trailing edge side based on the output of this determining circuit. An ultrasonic object detection device characterized by comprising a widened circuit.