JPH05312941A - Ultrasonic distance measuring apparatus for obtaining central position of target - Google Patents

Abstract

PURPOSE:To obtain an ultrasonic distance measuring apparatus, which is mounted on a moving body, transmits and receives ultrasonic waves to and from a target from the moving body to the direction of the side surface thereof and can obtain the central position of the target based on the sequentially measured distance data to the target. CONSTITUTION:Ultrasonic-wave transmitting means 1 and 3 transmit ultrasonic waves in the direction perpendicular to the moving direction of a moving body. Pairs of ultrasonic-wave receiving means 2A and 4A and 2B and 4B individually receive the reflected waves of the transmitted ultrasonic wave at positions on both sides, which are separated at an equal distance in the moving direction of the moving body and the opposite direction of the moving direction from the position of the transmission of the ultrasonic waves. A pair of distance measuring parts 6A and 6B individually measure the distance to the target based on the time between the transmitting time of the ultrasonic wave and the receiving time of a pair of the ultrasonic waves. An arithmetic processing part 7 computes the central position of the target based on the difference data of a pair of the measured distance data. These parts are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mounted on a moving body, transmits and receives ultrasonic waves from a moving moving body to a target in the side direction thereof, and detects the distance from the target to the target. The present invention relates to an ultrasonic distance measuring device that obtains the center position of a target.

[0002]

2. Description of the Related Art At present, unmanned transfer robots for carrying parts and luggage are used in factories and warehouses. The purpose of this unmanned transfer robot is to transfer articles from a certain point to a destination. In this case, an identification target (for example, a signal generation target that generates an identification signal) is provided in advance at a specific position on the traveling route (for example, a passage at a crossroad or the vicinity thereof), and the mobile robot uses the built-in sensor to identify the identification target. In many cases, a target is detected to recognize that the target is at the specific position, and the robot reaches the destination while calibrating the position and traveling direction of the robot. This is because the accumulated error of the position and orientation of the robot calculated based on the orientation sensor and the distance sensor incorporated therein increases as the mobile robot travels, so that the calibration is performed at predetermined intervals. However, in the case of a floor-working robot such as a robot that cleans the floor surface or a robot that trowels cement on the floor surface, sweeps all the given areas without overlapping and overlapping. Since the original purpose is to move and work, the provision of the identification target on the traveling route or in the vicinity thereof not only increases the cost but also causes a part of the work area to be an unworked part. Or the collision avoidance operation with the identification target is required, which is not preferable.

Therefore, even if a specific identification target that generates the above-mentioned identification signal is not provided on the traveling route or in the vicinity thereof, the position of the known target on the work site of the mobile body such as a mobile robot can be accurately determined. It is desirable to be able to measure and calibrate one's own azimuth and position in the absolute coordinate system set relatively to the real plane with reference to the measured target position. Therefore, there has conventionally been a demand for using a target such as a pillar protruding from the wall surface of a work site as a reference target and accurately measuring the center position of the reference target. For this reason,
Conventionally, while moving a mobile body such as a mobile robot in parallel with a wall surface, an ultrasonic distance measuring device mounted on the mobile body is used to transmit / receive ultrasonic waves to / from a wall surface in a lateral direction of the mobile body. The distance to was measured sequentially, and the position where the measured distance became short, that is, the protrusion from the wall surface was measured as the position of the column. However, in this case, the positions of the starting point and the ending point of the pillar are unclear and cannot be specified in many cases, so
Until now, it was difficult to accurately determine the center position of a reference target such as a pillar. This will be described below by an actual measurement example.

FIG. 5 is a block diagram showing a configuration of a conventional ultrasonic distance measuring apparatus. In the figure, reference numeral 1 is an ultrasonic wave transmitting sensor such as a piezoelectric vibrator, 2 is a wave receiving sensor having similar elements, Reference numeral 3 is an ultrasonic wave transmitting unit, and 4 is an ultrasonic wave receiving unit.
42), a detector 43, and a comparator 44.
Reference numeral 5 is a timing control unit, and 6 is a distance measuring unit. FIG. 6 is a waveform diagram for explaining the operation of the apparatus of FIG. Figure 7
FIG. 6 is a diagram showing a positional relationship in a horizontal plane between a moving body equipped with the device of FIG. 5, a wall surface, and a pillar, in which a reflected wave of an ultrasonic wave transmitted from the wave transmission sensor 1 is received on a side surface of the moving body during traveling. The state of being received by the wave sensor 2 is shown.

The operation of FIG. 5 will be described with reference to FIGS. 6 and 7. The ultrasonic wave transmitting unit 3 generates a predetermined frequency (for example, 2) by the transmission gate signal (see (a) in FIG. 6) generated by the timing control unit 5 in FIG.
A transmission drive signal of 0 kHz (see (b) of FIG. 6) is supplied to the wave transmission sensor 1 to drive it. When driven, the wave transmission sensor 1 transmits an ultrasonic wave having a predetermined beam directivity characteristic toward a wall surface. Here, when the traveling direction of the moving body and the wall surface are substantially parallel as in the positional relationship of FIG. 7, the transmitted ultrasonic waves are reflected from the wall surface. Then, a part of this reflected wave is received by the wave receiving sensor 2, and the reception signal converted to an electric signal (see (c) of FIG. 6) is supplied to the ultrasonic wave reception unit 4. The ultrasonic wave receiving unit 4 amplifies the received signal with the built-in amplifier 41, and then detects it with the detector 43 through the BPF 42 having a predetermined pass band before and after the transmission frequency as a center, and the detected signal (see FIG. 6). (See (d)) is compared with a predetermined threshold value by the comparator 44, and the binarized signal exceeding the threshold value is output as a detection signal (see (e) in FIG. 6). Then, the distance measuring unit 6 counts a time T (see (f) in FIG. 6) from the rising time of the transmission gate signal to the rising time of the detection signal by a built-in counter.
Then, distance data from the counting time T and the ultrasonic wave propagation velocity in the air to the target is calculated and output.

FIGS. 8 and 9 are views showing distance data examples 1 and 2 in the vicinity of a column, which are measured while the moving body of FIG. 7 is moving. The horizontal axis in the figure represents the measurement time, but when the moving speed is constant, it is equivalent to the coordinate position of the moving body (the coordinate position on the horizontal axis). The vertical axis is the measured distance data. In FIG. 8, the ultrasonic distance measuring device catches the pillar near the change point D and detects that the pillar ends near the change point E. However, the data before and after the change points D and E are detected. The starting and ending points of the columns are not very accurate due to the large variability in. In FIG. 9, due to the influence of the end face of the column, a complicated measurement result is obtained, and the starting point and the ending point of the column cannot be clearly specified. Therefore, the center of the pillar cannot be calculated accurately.

[0007]

In the conventional ultrasonic distance measuring device as described above, the ultrasonic distance measuring device is mounted on a moving body, and ultrasonic waves are transmitted and received from the moving moving body to the wall surface in the side direction thereof. , When the center position of a target such as a pillar projecting from the wall is sequentially measured and the center position of the target projecting from the wall is determined, the correct center position cannot be determined because the starting point and the end point of the projecting target cannot be specified. There was a problem. The present invention has been made to solve such a problem, and is mounted on a moving body, transmits and receives ultrasonic waves from a moving moving body to a target in the lateral direction, and sequentially transmits to the target. An object of the present invention is to obtain an ultrasonic distance measuring device capable of obtaining the center position of the target from the distance information.

[0008]

An ultrasonic distance measuring apparatus for determining the center position of a target according to claim 1 of the present invention is mounted on a moving body, and the target in the lateral direction from the moving moving body. In the ultrasonic distance measuring device for sequentially transmitting and receiving ultrasonic waves to sequentially measure the distance to the target, ultrasonic wave transmitting means for transmitting ultrasonic waves in a direction perpendicular to the moving direction of the moving body, and the ultrasonic wave transmitting means. Are installed at positions on both sides of the moving body at the same distance in the moving direction of the moving body and the opposite direction thereof,
A pair of ultrasonic wave receiving means for individually receiving the ultrasonic waves transmitted from the ultrasonic wave transmitting means and reflected from the target object, a transmission wave generation time by the ultrasonic wave transmitting means, and a pair of ultrasonic wave receiving means, respectively. A pair of distance measuring means for measuring the distance to the target respectively from the time between the obtained received wave detection time and the difference data of the pair of distance information respectively obtained from the pair of distance measuring means are sequentially calculated. A calculation processing unit that calculates the center position of the target from the change rate data of the sequentially calculated difference data is provided.

An ultrasonic distance measuring apparatus for determining the center position of a target according to claim 2 of the present invention is the ultrasonic distance measuring apparatus according to claim 1, wherein a difference between a pair of distance information obtained from each of the pair of distance measuring means. A subtractor that sequentially calculates data,
A memory for storing difference data sequentially obtained from the subtractor, a differentiator for calculating a change rate per unit time of the difference data read from the memory, and a vicinity of an inflection point of the change rate data obtained from the differentiator. Start the measurement of an average value calculator that calculates the average value of only the data, and two intersections where the difference data read from the memory intersects the reference level with the average value calculated by the average value calculator as the reference level. The first intersection that intersects from the point side and the second intersection that intersects from the measurement end point side
And a center position calculator for calculating the midpoint between the first and second intersections as the center position of the target.

[0010]

In the invention according to claim 1, ultrasonic waves are transmitted and received from the moving body mounted on the moving body to the target in the lateral direction, and the distance to the target is successively measured. In the ultrasonic distance measuring device, the ultrasonic wave transmitting means transmits an ultrasonic wave in a direction perpendicular to the moving direction of the moving body. The pair of ultrasonic wave transmitting means are installed at positions on both sides at equal distances from the ultrasonic wave transmitting position in the moving direction of the moving body and in the opposite direction, and are transmitted by the ultrasonic wave transmitting means and reflected from the target. The received ultrasonic waves are individually received. A pair of distance measuring means, the transmission wave generation time by the ultrasonic transmission means,
The distance to each of the targets is measured from the time between the reception wave detection times obtained from the pair of ultrasonic wave reception means. The arithmetic processing means sequentially calculates the difference data of the pair of distance information obtained from the pair of distance measuring means, and calculates the center position of the target from the change rate data of the sequentially calculated difference data.

In the invention according to claim 2, in the invention according to claim 1, the arithmetic processing means includes a subtracter, a memory, a differentiator, an average value calculator, and a center position calculator. The subtractor successively calculates the difference data of the pair of distance information obtained from the pair of distance measuring means, and the memory stores the difference data successively obtained from the subtractor. The differentiator calculates the change rate per unit time of the difference data read from the memory, and the average value calculator calculates the average value of only the data near the inflection point of the change rate data obtained from the differentiator. The center position calculator uses the average value calculated by the average value calculator as a reference level, and intersects two intersections at which the difference data read from the memory intersects with the reference level, from the measurement start point side. And the second intersection point intersecting from the measurement end point side,
The midpoint between the intersection and the second intersection is calculated as the center position of the target.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an ultrasonic distance measuring apparatus for determining the center position of a target according to the present invention.
1 is an ultrasonic wave transmitting sensor, 2A is a # 1 receiving sensor, 2B
Is a # 2 wave receiving sensor, and their arrangement will be described with reference to FIG. 3 is an ultrasonic transmitter, 5 is a timing controller,
Each is the same device as in FIG. Reference numerals 4A and 4B denote # 1 and # 2 ultrasonic wave reception units provided for each of the wave receiving sensors. The two ultrasonic wave receiving units 4A and 4B are the same devices as the ultrasonic wave receiving unit 4 of FIG. 5, and each include an amplifier 41, a BPF 42, a detector 43, and a comparator 44. 6A and 6B are # 1 and # 2 distance measuring units, respectively, which are the same devices as the distance measuring unit 6 in FIG.
Reference numeral 7 in FIG. 1 denotes an arithmetic processing unit according to the present invention, which internally includes a subtractor 71, a memory 72, a differentiator 73, an average value calculator 74, and a center position calculator 75. Also, the above 71 to 7
5 shows an example in the case of being provided as a device for each function of the arithmetic processing to be executed, and as actual hardware, for example, a microprocessor (CPU), a ROM storing a control program, and data RA for temporary storage
The arithmetic processing unit 7 can be configured by M, a data input / output interface, and the like. In addition, the ultrasonic distance measuring device according to the present invention is configured by the devices 1 to 7,
Mounted on a mobile unit.

FIG. 2 is a diagram showing the positional relationship in the horizontal plane between the moving body equipped with the apparatus of FIG. 1, the wall surface and the pillar. In the figure, the wave-transmitting sensor 1 is provided approximately at the center of the side surface of the moving body.
Is installed, and a distance d equal to the front (direction of travel) and the rear
A # 1 wave receiving sensor 2A and a # 2 wave receiving sensor 2B are installed with a space in between. Therefore, the # 2 wave receiving sensor 2B, the wave transmitting sensor 1 and the # 1 wave receiving sensor 2A are arranged on the same straight line, and the wave transmitting sensor 1 is superposed in a direction perpendicular to the arrangement direction of the sensors (that is, the traveling direction of the moving body). Send sound waves. At the position of the moving body shown in FIG. 2, the # 1 wave receiving sensor 2A mainly receives the reflected wave from the pillar, and the # 2 wave receiving sensor 2B mainly receives the reflected wave from the wall surface. Shows. However, at the position where the moving body has advanced a little further, both the # 1 and # 2 wave receiving sensors 2A and 2B are in a state of mainly receiving the reflected wave from the wall surface. The sensor interval d in FIG. 2 is selected so that the detection distance and the detection angle are optimal depending on the transmission / reception frequency of ultrasonic waves, directional characteristics, and the like. In this embodiment, d = 25 cm is selected as the optimum interval when the ultrasonic transmission / reception frequency is 25 kHz.

FIG. 3 is an explanatory diagram of difference data between a pair of distance measurement information according to the present invention, and FIG. 4 is an explanatory diagram of arithmetic processing in the arithmetic processing unit of FIG. The horizontal axis of FIGS. 3 and 4 is the measurement time (equivalent to the coordinate position when the moving body is at a constant speed), and the vertical axis is the distance difference data or its differential value.
The ultrasonic distance measuring device of FIG. 1 is mounted on a moving body, and sequentially transmits ultrasonic waves from a wave transmission sensor 1 provided on a side surface of the moving body while moving in parallel with a wall surface as in the positional relationship shown in FIG. Send. The wave transmitting sensor 1 and the # 1 and # 2 wave receiving sensors 2A and 2B provided before and after the traveling direction respectively receive reflected waves from the wall surface, and these two received signals correspond to # 1 and # 2, respectively. As a result of being individually received and measured by the ultrasonic wave receiving unit and the # 1 and # 2 distance measuring units 6A and 6B, two distance data D are obtained as distance data to the wall surface.
_A and D _B are obtained.

Now, the two distance data D _A and D _B
Focusing on the difference data ΔD = D _B −D _A , the relative positions of the moving body, the wall surface, and the column are (a) the two receiving sensors 2A.
The value of the difference data ΔD is small at the positions where both and 2B receive the reflected wave from the wall surface or the column. However, there is a difference in the distance data between the wall surface and the pillar. (B) The absolute value of ΔD is large at the position where one wave receiving sensor receives the reflected wave from the column and the other wave receiving sensor receives the reflected wave from the wall surface (for example, the position in FIG. 2). However, there are two types of polarity, positive and negative. Therefore, when the side surface of the moving body changes to a wall surface, a pillar, or a wall surface, the relative position becomes (a), (b), (a),
Since it changes in the order of (b) and (a), the difference data ΔD changes as shown in FIG. The black circles in FIG. 3 are difference data in the case where the moving body moves substantially parallel to the wall surface, and the curve connecting the black circles has a reverse polarity with a value of 0 as a boundary. The white circles in FIG. 3 indicate the case where the moving body is slightly displaced from the parallel movement and moves at a certain angle with the wall surface, and the curve connecting the white circles may not cross a value of 0.

The arithmetic processing unit 7 of FIG. 1 outputs distance data D _A and D _B from the # 1 and # 2 distance measuring units 6A and 6B, respectively.
(1) First, the subtracter 71 causes the distance difference data ΔD = D.
Sequentially calculating a _B -D _A, and temporarily stores the sequentially calculated difference data in the memory 72. (2) Next, the differentiator 73 sequentially reads the difference data temporarily stored in the memory 72, and obtains a change rate of how much the difference data increases or decreases in a unit time. This calculation is to calculate the differential value of the difference data. FIG. 4A is a difference data curve formed by connecting white circles in the case of being slightly deviated from the parallel movement, and FIG. 4B is a differential value of the difference data. (3) Next, the average value calculator 74 only determines the vicinity of the inflection point of the differential value data calculated by the differentiator 73 (that is, the portion where the differential value does not increase or decrease near the peak value in FIG. 4B). The average value of the data is calculated, and this average value is used as the reference level. FIG. 4 (c) shows this reference level,
When the moving body is not parallel to the target and moves at an angle, the level value is determined by the angle. (4) Next, the central position calculator 75 measures two intersections at which the difference data curve connecting the difference data read from the memory 72 intersects with the reference level, and an intersection A from the measurement start point to the end point. The intersection point B from the end point to the start point is obtained, the midpoint C between the intersection points A and B is calculated, and the position of the midpoint C is set as the center position of the pillar. Then, the target center position information is output.

[0017]

As described above, according to the present invention, ultrasonic waves are transmitted and received from a moving moving object mounted on a moving object to a target in the lateral direction of the moving object to determine the distance to the target. In the ultrasonic distance measuring device for sequentially measuring, the ultrasonic wave is transmitted in a direction perpendicular to the moving direction of the moving body, and the reflected wave of the transmitted ultrasonic wave is moved from the position of the ultrasonic wave transmission to the moving direction of the moving body. Individually received at positions on both sides equally spaced in the opposite direction, sequentially calculating the difference data of a pair of distance information measured from the time between the transmission and reception signals of the ultrasonic wave,
Since the center position of the target is calculated from the change rate data of the difference data, for example, the center position of the target such as a pillar protruding from the wall surface by the floor sweep robot is accurately determined, and the center of the target is calculated. Using the position as the reference position, the effect that the moving body can calibrate its own position and azimuth is obtained.

According to the present invention, the average value is calculated only for the data in the vicinity of the inflection point of the differential value of the differential data of the pair of distance information, and the average value is used as the reference level, and the difference data is used as the reference level. Two intersections intersecting are obtained as a first intersection intersecting from the measurement start point side and a second intersection intersecting from the measurement end point side, and a midpoint between the first intersection and the second intersection is determined. Since it is calculated as the center position of the target, there is an effect that the center position of the target can be accurately obtained even when the moving body moves at a certain angle instead of parallel to the surface of the target such as the pillar. ..

[Brief description of drawings]

FIG. 1 is a block diagram of an ultrasonic distance measuring apparatus for determining a center position of a target according to the present invention.

FIG. 2 is a diagram showing a positional relationship in a horizontal plane between a moving body equipped with the apparatus of FIG. 1, a wall surface and a pillar.

FIG. 3 is an explanatory diagram of difference data between a pair of distance measurement information according to the present invention.

4 is an explanatory diagram of a calculation process in a calculation processing unit in FIG.

FIG. 5 is a block diagram showing a configuration of a conventional ultrasonic distance measuring device.

6 is a waveform chart for explaining the operation of FIG.

FIG. 7 is a diagram showing a positional relationship in a horizontal plane between a moving body equipped with the apparatus of FIG. 5, a wall surface and a pillar.

8 is a diagram showing a distance data example 1 in the vicinity of a column measured while the moving body in FIG. 7 is moving.

FIG. 9 is a diagram showing a distance data example 2 in the vicinity of a column measured while the moving body in FIG. 7 is moving.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 wave transmission sensor 2A, 2B # 1 and # 2 wave reception sensor 3 ultrasonic wave transmission section 4A, 4B # 1 and # 2 ultrasonic wave reception section 5 timing control section 6A, 6B # 1 and # 2 distance measurement section 7 arithmetic processing Part 71 Subtractor 72 Memory 73 Differentiator 74 Average Value Calculator 75 Center Position Calculator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kyoyuki Takeuchi 2-16-46 Minami-Kamata, Ota-ku, Tokyo Tokimec Co., Ltd.

Claims (2)

[Claims] 1. An ultrasonic distance measuring device mounted on a moving body, which transmits and receives ultrasonic waves to and from a moving moving body to a target in a lateral direction thereof, and successively measures a distance to the target. An ultrasonic wave transmitting means for transmitting ultrasonic waves in a direction perpendicular to the moving direction of the moving body, and is installed at positions on both sides that are equidistant from the position of the ultrasonic wave transmitting in the moving direction of the moving body and the opposite direction thereof, A pair of ultrasonic wave receiving means for individually receiving the ultrasonic waves transmitted by the ultrasonic wave transmitting means and reflected from the target, a transmission wave generation time by the ultrasonic wave transmitting means, and a pair of ultrasonic wave receiving means, respectively. A pair of distance measuring means for measuring the distance to the target respectively from the time between the obtained received wave detection time and a pair of distance information difference data obtained from the pair of distance measuring means are sequentially calculated. , The Ultrasonic measuring device for determining the center position of the target object, characterized in that an arithmetic processing means for calculating the center position of the target object from the change rate data of the difference data that is next calculated. 2. A subtracter for sequentially calculating difference data of a pair of distance information respectively obtained from the pair of distance measuring means, a memory for storing difference data successively obtained from the subtractor, and a memory read from the memory. A differentiator for calculating the change rate of the difference data per unit time, an average value calculator for calculating the average value of only the data near the inflection point of the change rate data obtained from the differentiator, and the average value calculator With the calculated average value as the reference level,
Two intersections at which the difference data read from the memory intersects with the reference level are obtained as a first intersection intersecting from the measurement start point side and a second intersection intersection from the measurement end point side, and the first intersection point is obtained. The ultrasonic measurement apparatus for determining the center position of a target according to claim 1, further comprising arithmetic processing means including a center position calculator that calculates a center point between the second intersection and the center position of the target.