JPH0529579B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for positioning the stop position of a conveyance vehicle. The present invention relates to a method for locating a stop position of a vehicle.

[Prior art]

Transport vehicles, especially unmanned guided vehicles, have made great progress in recent years as core equipment in factory automation.

A conventional automatic guided vehicle has a loading platform on its upper surface for placing an article to be transported, and transports the article to a station provided at each process. Then, the article is automatically transferred from the automatic guided vehicle to each station by a transfer device provided at the station.

On the other hand, the stopping accuracy of an unmanned guided vehicle is about ±10 mm in the direction of movement and the direction crossing it, and about ±1° in the rotation direction around the vertical axis, and the Since the relative stopping position accuracy depends on the stopping accuracy of the unmanned guided vehicle,
The value was similar to the above-mentioned stopping accuracy. Due to the error in the stopping accuracy, there is a discrepancy between the relative stopping position of the transfer device and the loading platform and the normal relative stopping position. When loading, it is necessary to provide the transfer device or the transport vehicle with a structure that eliminates the above-mentioned deviation, or to improve the stopping accuracy of the automatic transport vehicle.

As a known method for improving stopping accuracy, a plurality of hydraulic jacks are installed on an unmanned guided vehicle, a conical female hole is formed in the rod portion of the jack, and a hole is connected to the female hole at the regular stopping position on the floor of each station. A plurality of positioning protrusions each having a conical male portion having a matching shape are provided corresponding to the mounting position of the hydraulic jack,
When the automatic guided vehicle stops at a station, there is a method in which the hydraulic jacks are advanced and fitted onto respective positioning protrusions for positioning. As a result, the automatic guided vehicle is lifted from the floor and positioned at its normal stopping position.

[Problem to be solved by the invention]

However, in the above method, the positioning protrusion becomes an obstacle to traveling, and a large number of additional equipment such as a hydraulic power source is required, which increases the price and complicates the structure. Furthermore, since the above method performs positioning by contact between the female hole and the male part, the positioning accuracy deteriorates due to wear of the female hole and the male part, and dust is generated due to abrasion particles. It could not be used in environments with specified accuracy and cleanliness.

Further, since a transfer device is provided for each station, if the transfer device is provided with a structure to eliminate the above-mentioned deviation, a large number of such structures will be required, leading to an increase in the price of the entire system.

The present invention has been made in view of the above circumstances, and provides positioning means in three directions, two directions in a horizontal plane and a rotational direction around a vertical axis, on the loading platform, and detects and eliminates the above-mentioned deviation. Calculate the positioning correction value, and based on the calculated positioning correction value,
The purpose of the present invention is to provide a method for positioning a conveyance vehicle that allows positioning of the loading platform to position the relative stop position between the loading platform and the transfer device with a simple structure, non-contact, inexpensively, and with high accuracy. do.

[Means to solve the problem]

A method for positioning a transport vehicle according to the present invention is a method for positioning a transport vehicle that has a loading platform on which articles are placed, travels automatically, and stops at a positioning mark, in two directions in a horizontal plane and around a vertical axis. The transportation vehicle is provided with means for positioning the loading platform in three directions of the rotation direction of the vehicle, and a visual sensor for detecting the positioning mark, and the positioning means for positioning the loading platform in three directions of the rotation direction of the vehicle and a visual sensor for detecting the positioning mark are provided in the transport vehicle, and the positioning means for positioning the loading platform in three directions between the transport vehicle and the positioning mark are provided in the transport vehicle. The displacement amount in the three directions is calculated, and based on the displacement amount, a positioning correction value, which is the amount of movement in the three directions that should reduce the displacement amount in the loading platform, is calculated. The present invention is characterized in that the loading platform is moved by driving the directional positioning means.

[Effect]

In the present invention, positioning means in three directions is provided, and the amount of deviation between the positioning mark and the stop position of the conveyance vehicle is detected from the detection result by the visual sensor, and based on this, positioning correction values in the three directions are calculated to calculate the amount of deviation. Decreasing and positioning.

〔Example〕

Hereinafter, the present invention will be explained in detail based on drawings showing embodiments thereof.

FIG. 1 is a left side view of a conveyance vehicle according to the present invention, and the direction of travel of the conveyance vehicle is the direction indicated by a white arrow.

In the figure, reference numeral 1 indicates a pair of left and right drive wheels 2 (the right drive wheel is not shown) and four auxiliary wheels 3, 3 provided on the front, rear, left and right sides of the conveyance vehicle (the right auxiliary wheel is not shown).
The aircraft was supported by The drive wheels 2 are attached to the center of the fuselage 1 at an appropriate distance from the left and right, and each drive motor (not shown) is coaxially and directly connected to each drive motor.
The aircraft 1 is moved forward and backward by simultaneous driving. Further, the auxiliary wheels 3, 3 are rotatably mounted around the vertical axis of the fuselage body 1 at appropriate distances in the front, rear, left and right directions of the fuselage body 1.

A loading platform 4 for placing articles to be transported is provided on the upper part of the aircraft body 1, with its center being the same as that of the aircraft body 1, and the loading platform 4 is provided at the center of the aircraft body 1 in the traveling direction of the aircraft body 1. , positioning means 5x, 5y in each direction for positioning in each of three directions: a direction perpendicular to the traveling direction and a direction of rotation around the vertical axis of the aircraft body 1;
5θ, it is attached to the body 1 so as to be movable and rotatable in the three directions. Further, the positioning means 5x, 5y, and 5θ in each direction can be driven in the three directions separately by driving portions 6x, 6y, and 6θ in three directions.

On the other hand, visual sensors 7 _A and 7 _B using industrial TV cameras for detecting the stopping position of the aircraft 1 are installed at the front and rear of the center of the aircraft 1, facing downward at a distance L from the center of the aircraft 1, respectively. A black circle is drawn at the center of a white square on the floor 9 at the same interval as the visual sensors 7 _A and 7 _B to indicate the stopping position of each process.
The positioning marks 8, 8 are connected to the visual sensor _7A ,
7 _B detects the stopping position of the aircraft 1 by taking an image. In addition, the imaged positioning marks 8, 8
A positioning control device 9 is provided inside the fuselage 1 for applying a drive signal to each of the drive units 6x, 6y, and 6θ from the position.

FIG. 2 is a partially cutaway side view showing each positioning means equipped with a drive unit of the loading platform, and each positioning means 5x, 5y, 5θ is attached to the front and back of the central part of the fuselage 1, and is an inverted L-shaped vertical member. The base 57 is fastened to two brackets 12, 12, each having a rectangular flat plate fixed to the center, the longitudinal direction of which is perpendicular to the traveling direction of the fuselage 1.

The base 57 has a square flat plate shape with sides slightly shorter than the horizontal length of the loading platform, and has a cylindrical boss part above the center part, and a swing bearing 52 is attached to the boss part.
A drive motor 66θ using a stepping motor for turning is attached to the lower center of the rear part of the base 57 with its output shaft facing upward.
A flexible joint 61θ is attached to the tip of the drive motor 66θ.
An eccentric shaft 62θ having a predetermined eccentricity is connected to the output shaft through
Two ball bearings 63, which are eccentric cams, are installed at the upper end of θ.
θ, 63θ are fitted externally. Further, the base 57 has a lower mounting flange at the upper center of the rear part thereof, and a cylindrical bearing box 64θ is mounted coaxially with the drive motor 66θ, and the eccentric shaft 62θ is attached to the upper end of the bearing box 64θ. Two ball bearings 65θ fitted inside,
65θ, and the eccentric shaft 62θ
A rotating table 50θ, which will be described later, rotates around a swing bearing 52θ due to the amount of eccentricity.

The boss portion of a rotating table 50θ, which has a flat plate shape with approximately the same external shape as the base 57 and has a cylindrical boss portion facing downward at the center, is fitted into the inner ring of the swing bearing 52θ,
The rotating table 50θ is rotatable in a rotational direction (hereinafter referred to as the θ direction) about the vertical axis of the body 1 about the pivot bearing 52θ. Further, a cylindrical bearing box 64x having mounting flanges at the upper and lower ends is attached to the lower part of the center of the front part of the rotating table 50θ, and the lower mounting flange is attached in the front-rear direction (hereinafter referred to as the x direction). A drive motor 66x using a stepping motor for movement is mounted with its output shaft facing upward. At the tip of the drive motor 66x,
An eccentric shaft 62x having a predetermined eccentricity is connected to the drive motor output shaft via a flexible joint 61x, and two ball bearings, which are eccentric cams, are mounted at the upper end of the eccentric shaft 62x. 63x, 63x are fitted externally. The eccentric shaft 62x is supported by two ball bearings 65x, 65x fitted in the upper part of the bearing box 64x, and the moving table 50x, which will be described later, is moved in the x direction depending on the eccentricity of the eccentric shaft 62x. Move to. In addition, four moving guides 52x, 52x in the x direction, which are made of rails of linear guides and are appropriately spaced on the front, rear, left and right sides of the rotating table 50θ, are installed with their longitudinal directions substantially aligned with the x direction of the fuselage 1. It is being

FIG. 3 is an enlarged perspective view showing the mounting state of the eccentric cam of the driving means of the loading platform, and the ball bearings 63θ, 63θ, which are the eccentric cams, have a rectangular flat plate shape and have a square bar-shaped convex portion at one end. , a lower cam receiver 54θ having an oblong eccentric cam groove 59θ whose longitudinal direction is in the same direction as the convex portion in the center; and the lower cam receiver 54θ.
The upper cam receiver 53θ is fitted inside the upper cam receiver 53θ, which has an eccentric cam groove 58θ similar to the lower cam receiver 54θ placed on the upper side.
The lower cam receiver 54 is adjusted by adjusting screws 55θ, 55θ screwed together at appropriate intervals in the longitudinal direction of the 4θ convex portion.
With respect to θ, it is slidable in a direction perpendicular to the longitudinal direction of the eccentric cam groove. Also, the lower cam receiver 54θ
The upper cam bearing 53θ is the upper ball bearing 63θ of the two ball bearings 63θ, 63θ which are eccentric cams.
The outer ring of the lower ball bearing 63θ is pressed against the side surface of the eccentric cam groove 58θ of the upper cam receiver 53θ on the adjustment bolt 55θ side, and the outer ring of the lower ball bearing 63θ is pressed against the side surface of the eccentric cam groove 59θ of the lower cam receiver 54θ on the side opposite to the adjustment bolt 55θ. It is adjusted by an adjustment bolt 55θ so that it is pressed against the side surface, thereby applying a preload to each outer ring. After this adjustment is completed, the lock nut 56θ locks the adjustment bolt 55θ from rotating. The lower cam receiver 54θ and the upper cam receiver 53θ are attached to the rear center of the rotating table 50θ.

On the other hand, the moving guide 5 attached to the rotating table 50θ
2x, 52x..., and the moving guides 52x,
Four upper guides 51x, 51x... are formed using rolling parts of linear guides that roll against 52x...
is attached to the lower part of the moving table 50x, and the moving table 50
x can be freely rolled in the x direction with respect to the rotating table 50θ.

The moving table 50x has a flat plate shape having approximately the same external shape as the rotating table 50θ, and a cylindrical bearing box 64y having mounting flanges at the upper and lower parts is attached to the lower left center of the moving table 50x. There is. In addition, the lower mounting flange has a direction perpendicular to the direction of travel,
That is, a drive motor 66y using a stepping motor for moving the body 1 in the left-right direction (hereinafter referred to as the y-direction) is mounted with its output shaft facing upward. A flexible bearing 6 is attached to the tip of the drive motor 66y.
An eccentric shaft 62y having a predetermined eccentricity is connected to the output shaft of the drive motor 66y via 1y, and two ball bearings, which are eccentric cams, are attached to the upper end of the eccentric shaft 62y. 63y, 63y are fitted externally. The eccentric shaft 62y is supported by two ball bearings 65y, 65y fitted in the upper part of the bearing box 64y, and the moving table 50y, which will be described later, is moved in the y direction depending on the eccentricity of the eccentric shaft 62y. Move to. In addition, above the center of the front part of the moving table 50x, there is a rotating table 5.
The upper cam receiver 53 has the same structure as the upper cam receiver 53θ and the lower cam receiver 54θ installed at 0θ.
x and the lower cam receiver 54x are connected to the eccentric cam groove 58.
It is attached with the longitudinal direction of x, 59x as the y direction. Furthermore, there are four y-direction moving guides 52y, 52y, which are appropriately spaced apart from each other on the front, rear, left, and right sides of the upper side of the moving table 50x, and are formed by using the rail portions of linear guides.
is installed. And four upper guides 51y, 51y using rolling parts of linear guides.
... are attached to the lower part of the rectangular plate-shaped moving table 50y so as to engage with the moving guides 52y, 52y, etc., making the moving table 50y freely rollable in the y direction. In addition, at the lower center of the left side of the moving table 50y, an upper cam receiver 53y and a lower cam receiver 54y, which are engaged with the ball bearings 63y and 63y and have the same structure as the upper cam receiver 53θ and the lower cam receiver 54θ, are located on the eccentric side. The longitudinal direction of the cam grooves 58y and 59y is the x direction, and the upper and lower cam receivers 53[theta] and lower cam receivers 54[theta] are installed with their upper and lower sides reversed. A loading section 41 for loading articles constituting the loading platform 4 is attached to the upper part of the moving platform 50y.

FIG. 4 is a block diagram showing the configuration of the positioning control device for a conveyance vehicle according to the present invention, and the positioning control device 9 is a positioning device for detecting the positions of the positioning marks 8, 8 imaged by the visual sensors _7A , _7B . The detection unit 91 detects the center positions P _A , P _B of the field of view of the visual sensor and the center positions P _A ′, of the detected positioning marks 8 , 8 .
Positioning correction values Δx, Δy, Δθ in the x direction, y direction, and θ direction for calculating the deviation from P _B ′ and positioning the loading platform 4 of the conveyance vehicle in a direction that eliminates the deviation amount based on the calculated deviation. The positioning correction value calculation unit 92 calculates the positioning correction values Δx, Δy, Δθ and the respective drive motors 66x, 66y, 6.
The relationship between the number of pulses given to 6θ and the number of pulses applied to each drive motor 66x, 66y, 66θ
A motor drive unit 93 is provided to provide a predetermined number of pulses Lx, Ly, and Lθ to the motor.

Next, a method for controlling a conveyance vehicle and calculating a positioning correction value at a stop position according to the present invention will be explained. The positioning correction values Δx, Δy, and Δθ are determined by the driving parts 6x, 6y, and 6θ of the loading platform in order to match the center position G of the loading platform 4 and its x direction with the intermediate position G' of the positioning marks 8, 8 and their installation direction. This eliminates the above deviation.

FIG. 5 is a flowchart showing the control flow of the method for positioning the conveyance vehicle, which is the main part of the present invention, and FIG. 6 is a diagram explaining the method for calculating the positioning correction value. The guide device automatically travels toward a station provided in each process, and stops at a position where the black circle at the center of the positioning marks 8, 8 can be seen by the visual sensors _7A , _7B . When the conveyance vehicle stops, the positioning marks 8, 8 are imaged by the visual sensors _7A , _7B , and based on the imaging results, the position detection unit 91 determines the installation direction with the intermediate position G' between the positioning marks 8, 8 as the origin. _{The distances d XA , d YA , d XB , dYB}
seek. The positioning correction value calculation unit 92 calculates the distances d _XA , d _XB , and
Using d _YA and d _YB , positioning correction values Δx, Δy, and Δθ are calculated using a calculation method described later. Then, each positioning correction value Δx, Δy, Δθ is determined by the motor drive unit 93.
are converted into required pulses Lx, Ly, Lθ for each drive motor, and the required pulse numbers Lx, Ly, Lθ are output to each drive motor 66x, 66y, 66θ.

The loading platform 4 is thereby positioned.

On the other hand, the calculation of each positioning correction value Δx, Δy, Δθ is as follows:
When the center of gravity of the positioning markers 8, 8 is captured within the field of view of the optical sensors _7A , _7B indicated by the two-dot chain lines in Fig. 6, the distances _dXA , _dYA , _dXB , _dYB can be determined. . Using the determined distances, positioning correction values Δx, Δy, and Δθ are determined using the following equations.

_{ΔX ＝ d XA + d _ _ _ _ _ _} ^-1 (d _Y / 2L) = sin ^-1 (d _YA - d _YB / 2L) ...(3) However, 2L: Installation distance of positioning signs 8 and 8 Each positioning correction value according to equations (1) to (3) above Δx,
Find Δy, Δθ, and calculate each positioning correction value Δx, Δy, Δθ
The predetermined number of pulses Lx, Ly, Lθ corresponding to the
By driving 6Y and 66θ, the loading platform 4 is positioned at the normal stop position. The amount of movement and rotation in the three directions due to the amount of eccentricity is a sufficiently large value (in this example, ±15 mm in the x direction, ±15 mm in the y direction,
±20 mm in the direction and ±2° in the θ direction), so even if the stopping accuracy of the transport vehicle is not sufficient, the relative positional accuracy between the loading platform and the transfer device can be ±1 in the x and y directions.
It became possible to keep the mm and θ directions within the allowable values.

Furthermore, in this embodiment, an eccentric cam using a ball bearing is used, and a preload is applied to its outer ring, so the structure of the positioning means is simplified and play between the eccentric cam and the eccentric cam groove can be suppressed. This enabled smooth positioning.

In this embodiment, an eccentric cam mechanism is used as a positioning means, but the present invention is not limited to this. Positioning means in the three directions of the x direction, y direction, and θ direction such as a rack pinion, a ball screw, etc. Any mechanism that makes it possible may be used. Further, in this embodiment, a positioning mark with a black circle drawn at the center of a white square was used as the positioning mark, but any mark can be used as long as it can be detected by an optical sensor.

Further, in this embodiment, the visual sensor is provided at an equal distance from the center of the aircraft body, but the present invention is not limited to this. Needless to say, it may be provided at any position.

Further, in this embodiment, a stepping motor is used as the drive motor, but the present invention is not limited to this, and any motor capable of position control, such as a servo motor with an encoder, may be used.

〔effect〕

As described in detail above, in the method for positioning a conveyance vehicle according to the present invention, the loading platform on which the article is placed is provided with positioning means that can position the article with high precision in two directions in the horizontal plane and in three directions in the rotational direction around the vertical axis. A visual sensor detects the amount of deviation between the predetermined stop position and the stop position of the conveyance vehicle, and based on that, 3
Since the positioning correction value in the direction is determined and the loading platform is positioned, it has excellent effects such as providing a transportation vehicle positioning method that can accurately position the loading platform in a non-contact manner with a simple structure and at low cost. play.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a left side view of a conveyance vehicle according to the present invention, and FIG. 2 is a partially cutaway side view showing a means for positioning a loading platform.
Figure 3 is an enlarged perspective view showing the installation state of the eccentric cam;
FIG. 4 is a block diagram showing the configuration of the positioning control device of the present invention, FIG. 5 is a flowchart showing the flow of control, and FIG. 6 is a diagram showing the method of calculating positioning values. 1... Airframe, 5x... x direction positioning means, 5y...
y direction positioning means, 5θ...θ direction positioning means.

Claims (1)

[Scope of Claims] 1. A method for positioning a transport vehicle that has a loading platform on which articles are placed and that travels automatically and stops at a positioning mark, the method comprising: two directions in a horizontal plane and a rotation direction around a vertical axis; A means for positioning the loading platform in three directions and a visual sensor for detecting the positioning mark are provided in the transport vehicle, and a deviation between the transport vehicle and the positioning mark in the three directions is determined based on the detection result of the visual sensor. Based on the amount of deviation, calculate a positioning correction value that is the amount of movement in the three directions that should reduce the amount of deviation in the loading platform, and based on the positioning correction value, positioning means in the three directions. A method for positioning a conveyance vehicle, characterized in that a loading platform is moved by driving.