JPH06300833A - Ultrasonic type device for detecting distance - Google Patents

Abstract

PURPOSE:To prevent a false detecting operation due to lowering of a reception sensitivity level caused by an external cause and thereby to improve accuracy of measurement in the case when a distance measurement such as detection of a ground height is executed by an ultrasonic sensor. CONSTITUTION:A reception signal of a receiver 7b of an ultrasonic sensor 7 receiving an ultrasonic wave transmitted from a transmitter 7a and reflected by an object of detection is inputted to CPU 10 through the intermediary of a time-based sensitivity regulating circuit 11 of which the reception amplification degree is so designed as to increase with passage of time from the transmission of the ultrasonic wave. Thereby the reception signal of a reflected wave from the object of detection located at a position near the ultrasonic sensor 7 is not amplified, while the reception signal of the reflected wave from the object located at a position far from the sensor is amplified, and computation of a time value for measuring a distance can be executed exactly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can detect the ground height of a pre-mowing treatment device in a combine, the ground height of a tilling work machine pulled by a tractor, and the ground height of a work vehicle of a construction machine. Therefore, the ultrasonic waves emitted from the transmitter mounted on these traveling aircraft are reflected by the object to be detected, and the receiver receives the reflected wave, and the control unit measures the distance to the object to be detected. The present invention relates to an ultrasonic distance detecting device for doing so.

[0002]

2. Description of the Related Art As a cutting height detecting device in a combine, which has been widely used in the past, a mechanical sensor having a contact portion that comes into contact with the ground is damaged by a foreign matter of the root of a grain stem hitting the contact portion. There was a drawback that it was easy to do. On the other hand, recently, as disclosed in JP-A-58-142279, a non-contact type ultrasonic sensor is often used.

In Japanese Patent Publication No. Sho 63-32410, ultrasonic waves from a transmitter are reflected by a supporting member of a machine or the like located near the ultrasonic sensor, and the ultrasonic waves are received by a receiver to be detected. May be confused with the waves received from objects,
Since it may cause control malfunction, on the output side of the receiver,
It is proposed to provide a comparator (signal comparator) that changes so that the sensing level decreases with the passage of time from the time of transmitting ultrasonic waves.

[0004]

With this configuration, the magnitude of the reference signal of a constant voltage output from the reference value generator and the detection signal from the receiver that receives the reflected wave at the object to be detected is determined as described above. Comparison is made by the comparator, and only the one in which the detection signal is larger than the value of the reference signal is outputted from the comparator. In other words, the reference value generator and the comparator should be a kind of filter device for the detection signal, the reference value is a threshold, this threshold is the time elapsed from the time of transmission of ultrasonic waves. It changes so that it becomes smaller with.

However, if the sensitivity level is simply reduced over time as in the prior art, for example, an ultrasonic sensor is provided near the ground, and the time from transmission to reception is short. In this case, it is necessary to use a receiver having a high sensitivity level for detection because the discrimination must be made at a portion having a large threshold value.
In addition, when the sensitivity level of the detection signal received by the receiver fluctuates low (high), such as when the condition of the field scene changes due to movement from a hard soil surface to a soft soil surface, Even if the height from the normal rotation of the ultrasonic wave to the ground is the same, the points that exceed the above threshold will be different, and an error will occur in the measurement result of the ground height, resulting in an incorrect judgment in cutting height control. There was a problem that I would be defeated.

In other words, if the level of the received signal at the receiver decreases (rises) due to some external cause, there is a problem that an error occurs in the distance detection to the object to be detected.
Contrary to the above-mentioned prior art, the present invention amplifies the output signal (detection signal) from the receiver and then determines the presence or absence of the object to be detected, and the amplification degree is small when the ultrasonic wave is transmitted. However, by increasing the amplification over time, the adverse effect of the detection signal of the reflected wave from the one located near the transmitter is removed without being affected by external causes, and the detected object is detected. Eliminating erroneous determination of distance measurement to an object is a technical problem to be solved.

[0007]

In order to solve the above-mentioned problems, the present invention provides a receiver with a reflected wave obtained by reflecting an ultrasonic wave emitted from a transmitter mounted on a traveling machine body of a work vehicle on an object to be detected. In the ultrasonic distance detecting device for receiving and measuring the distance from the received signal to the object to be detected by the control unit, the received signal from the receiver is changed with the passage of time from the time of ultrasonic wave transmission. It is configured to be input to the control unit via a temporal sensitivity adjustment circuit that is designed to increase the reception amplification degree accordingly.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described. FIG. 1 is a side view of the combine, FIG. 2 is a front view thereof, and the hydraulic pressure shown in FIG. The cutting pretreatment device 2 is mounted via a cylinder 9 so as to be movable up and down. The cutting pretreatment device 2 has a grain culm raising device 3 in which the lower end is inclined forward and the upper end is inclined rearward, and a portion in front of the lower end. It comprises a grass body 4, a cutting blade 5 at the lower rear of the grain culm raising device 3, and a grain culm transporting device 6.

The ultrasonic sensor 7 in the ultrasonic distance detecting device of this embodiment is arranged on a bracket (not shown) provided on the back side of the grain culm raising device 3, and as shown in FIG. The ultrasonic sensor 7 is arranged so that the transmitting portion (horn portion) of the transmitter 7a and the receiving portion of the receiver 7b face the ground 8. FIG. 3 shows an embodiment of the ultrasonic detecting device of the present invention and its control unit. Reference numeral 10 is a central processing unit (CP) as a control unit in the ultrasonic distance detecting device.
In U), although not shown, a read-only memory (ROM) in which a control program is stored and a readable / writable memory (RA) in which various detection values, data, etc. are temporarily stored
M), an interface, a bus, etc., and ultrasonic waves are transmitted to the transmitter 7a of the ultrasonic sensor 7 at an appropriate time interval T1 via the transmitting circuit 15 in response to a command from the CPU 10 to detect an object or the like. The reflected wave reflected is the receiver 7
Then, the detection signal is input to the CPU 10 via the temporal sensitivity adjusting circuit 11 of the present invention.

Further, another upper central processing unit (CPU) 12 is connected to the CPU 10, and in the CPU 10,
An output signal is output to the upper CPU 12 according to the calculated distance.
To the drive circuit 13, and the electromagnetic solenoid of the hydraulic switching valve 14 is operated in response to the output from the drive circuit 13 to move the pre-cutting device 2 up and down. The hydraulic cylinder 9 for is operated.

The upper CPU 12 also receives signals from other sensors and control switches in the combine, and also controls the drive of the pre-mowing processing device according to the vehicle speed, the threshing load, and the like. Next, the CPU 10 and the time sensitivity adjustment circuit 11
The control will be described. The drive circuit 11 is operated by the drive pulse P1 (see FIG. 4) output from the CPU 10 and the oscillator 7a outputs the oscillation wave P2 in the duty interval T2 at every predetermined time interval T1. In the receiver 7b, the transmitted wave P2 from the transmitter 7a is reflected on the ground 8 and outputs a received wave P3.

When the output signal P3 from the receiver 7b is input to the time sensitivity adjusting circuit 11, here, as shown in FIG. 5, the amplification degree increases with the lapse of time from the emission start time To of the oscillation wave P2. Time course amplification characteristic curve X1
After amplifying the input signal (detection signal) at
Output to. In FIG. 5, the horizontal axis represents time (msec.), The vertical axis represents amplification (dB), and the scale below the horizontal axis is distance (cm) conversion at room temperature (20 ° C.). Further, the ambient temperature may be detected by the temperature sensor 16, and the time-dependent amplification characteristic curve having different amplification degrees may be appropriately applied depending on the temperature section.

Thus, the output signal P from the receiver 7b
When 3 is output as the detection signal P4 via the time sensitivity adjusting circuit 11, the receiver 7b receives an obstacle located near the transmitter 7a, for example, a reflected wave reflected by the frame of the pre-cutting device 2 or the like. Since the time to reach is short, the detection signal P4 is hardly amplified, and the time T3 until the reflected wave reflected from the location of the detected object necessary for detecting the cutting height such as the ground is received by the receiver 7b. Is long, it can be sufficiently amplified by the time sensitivity adjusting circuit 11 and output as the detection signal P4.

In FIG. 6, since there are few irregular reflections on the ground 8,
In the case where the detection signal curve P4 from the time sensitivity adjusting circuit 11 has one peak value, in this case, the points where the detection signal P4 becomes equal to or higher than the constant level (threshold value) H are T4 and T5. Since there are two time points, as the time value Tm for measuring the distance from the ultrasonic sensor 7 to the ground, the calculation of Tm = ((T5-T4) / 2) + T4 is C
It is executed by the PU 10.

Incidentally, in the prior art, the time value corresponding to the distance is set at the time when the detection signal P4 first becomes equal to or higher than a constant level (threshold value) H. However, when such a judgment is made, the reflection from the ground is reflected. Even if it is a sharp sawtooth detection signal with a large peak value, it may be erroneously determined to be the ground. Therefore, the time difference of (T5-T4) is T6.
Within the range (T6 = 0.8 msec. In the embodiment), the above-mentioned Tm
Execute the average value calculation of.

Further, as shown in FIG. 7, the detection signal curve P
When 5 has two or more peak values such as a double hump, or when a high-level detector signal of a plateau continues, the time interval of the section (T5-T4) above the threshold value H is generally the above-mentioned. T6 × 2 (in the embodiment, T6 × 2 = 1.6 msec. Or more, so the time value Tm for measuring the distance from the ultrasonic sensor 7 to the ground is Tm = T4 + T6
The calculation is performed such that (the time when the detection signal curve P5 first exceeds the threshold value H and an appropriate time (dummy time) T6 is added).

As described above, of the detection signals output from the time sensitivity adjusting circuit 11, the time value as the one converted into the distance to the object to be detected is determined by the threshold value H having a constant magnitude. Controlling to 1 has the effect that threshold value setting and digital change thereof can be extremely easily performed. Further, in order to prevent the CPU 10 from erroneously determining that it is a detection target when the receiver 7b receives an erroneous signal or when the distance from the ultrasonic sensor 7 to the object to be detected is too short, the flowchart of FIG. As shown, the absolute value (T4
-T5) is within T6, and when the time when the threshold value H is first exceeded is in the time zone in which the amplification degree is appropriately small in the time-lapse amplification characteristic curve X1 (T4≤T9) (step S2, no), A signal indicating that the sensor is abnormal is output to the CPU 12 (step S3). In this case, other processing is executed (step S4), and in other cases,
The calculation of the time value Tm is executed (step S5), and the result is output to the CPU 12.

Then, the relationship between the calculated time value Tm and the distance is stored in advance in the ROM as a look-up table such as a relational expression by an experiment, and the CPU 12 sets the distance from the time value Tm and the look-up table. Calculate L. In the embodiment, the vertical distance between the lower end surface of the mowing pretreatment device 2 and the ground 8 or the vertical distance from the mowing blade 5 to the ground 8 is the distance required for control.

The CPU 12 outputs a predetermined up / down command signal to the drive circuit 13 according to the calculated distance, and operates the electromagnetic solenoid of the hydraulic pressure switching valve 14 according to the output from the drive circuit 13, The hydraulic cylinder 9 for raising and lowering the pre-mowing treatment device 2 is operated.

[0020]

As described above, according to the present invention, the reflected wave obtained by reflecting the ultrasonic wave emitted from the transmitter mounted on the traveling machine body of the work vehicle on the object to be detected is received. In the ultrasonic distance detecting device for receiving and measuring the distance from the received signal to the object to be detected by the control unit, the received signal from the receiver is changed with the passage of time from the time of ultrasonic wave transmission. The output signal (detection signal) from the receiver is configured to be input to the control unit via the temporal sensitivity adjustment circuit that is designed to increase the reception amplification.
It is to determine the presence or absence of the detected object after amplifying
By reducing the amplification level when transmitting ultrasonic waves and increasing the amplification level over time, it is possible to avoid being affected by external causes such as changes in the state of the field and at a position close to the transmitter. It is possible to eliminate the adverse effect of the detection signal of the reflected wave from the above, eliminate the erroneous judgment of the distance measurement to the object to be detected, and to perform the distance detection with high accuracy at all times.

[Brief description of drawings]

FIG. 1 is a side view of a combine.

FIG. 2 is a front view of the combine.

FIG. 3 is a functional block diagram of control means.

FIG. 4 is a time chart of a transmitted wave and a received wave of the ultrasonic sensor.

FIG. 5 is a time-dependent amplification characteristic curve diagram in the time sensitivity adjustment circuit.

FIG. 6 is an explanatory diagram of an output signal from the time sensitivity adjustment circuit.

FIG. 7 is an explanatory diagram of an output signal from another time sensitivity adjustment circuit.

FIG. 8 is a flowchart of control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Traveling machine 2 Pre-cutting processing apparatus 3 Grain culm raising apparatus 4 Grass cutting body 5 Cutting blade 7 Ultrasonic sensor 7a Transmitter 7b Receiver 9 Hydraulic cylinder 10 CPU 11 Time sensitivity adjustment circuit 12 Upper CPU 13 Amplification circuit 14 Hydraulic switching valve

Claims (1)

[Claims] 1. A receiver receives a reflected wave obtained by reflecting an ultrasonic wave emitted from a transmitter mounted on a traveling machine body of a work vehicle on the object to be detected, and from the received signal, the object to be detected is detected by a controller. In an ultrasonic distance detecting device for measuring the distance to, the received signal from the receiver is adjusted in time sensitivity such that the reception amplification degree increases with the passage of time from the time of transmitting the ultrasonic wave. An ultrasonic distance detecting device, characterized in that it is configured to be input to the control unit via a circuit.