JP7561536B2 - Automated guided vehicles - Google Patents

Description

The present invention relates to an automated guided vehicle.

Patent Document 1 discloses an automated guided vehicle 10 that enters a pallet 20 having flat legs 22a, 22b formed integrally on both sides of the lower part of a stand 21 on which a heavy object is placed, and transports the pallet 20 loaded onto the loading platform. Pallet guide sensors 12 that detect pallet guides 26 affixed to the underside of the stand 21 of the pallet 20 are provided at the front and rear of the loading platform of the automated guided vehicle 10, and pallet side guide sensors 15 that detect the distance to the legs 22a, 22b of the pallet 20 are provided at both ends of the loading platform of the automated guided vehicle 10.

When the automated guided vehicle 10 enters the pallet 20, the pallet guide sensor 12 detects the pallet guide 26, and the pallet side guide sensor 15 detects the distance to the legs 22a, 22b, thereby determining the positional relationship between the automated guided vehicle 10 and the pallet 20, and steering the automated guided vehicle 10 so that the center line of the automated guided vehicle 10 coincides with the center line of the pallet 20. This allows the automated guided vehicle 10 to accurately enter the pallet 20 without an operator having to steer the automated guided vehicle 10.

JP 2001-209432 A (for example, paragraphs 0010-0025, Figures 1 and 2)

However, in Patent Document 1, it is necessary to provide pallet guides 26 on all pallets 20 and a pallet guide sensor 12 on the automated guided vehicle 10. This increases the effort and cost required to install these. Also, to reduce the weight of the pallet 20, it is possible to provide multiple legs 22a, 22b of the pallet 20 in a truss or lattice shape rather than a flat plate shape. In such a case, the pallet side guide sensor 15 repeatedly detects and does not detect the distance as the automated guided vehicle 10 approaches the pallet 20, which causes the problem that it is not possible to continuously detect the distance to the legs 22a, 22b.

The present invention was made to solve the above-mentioned problems, and aims to provide an automated guided vehicle that can enter a pallet at low cost and accurately, even when the pallet has multiple legs.

In order to achieve this object, the automated guided vehicle of the present invention enters beneath a platform of a pallet having a platform supported by a plurality of legs provided on both sides thereof, and loads and transports the pallet by raising a loading platform beneath the platform, and includes an approach sensor that measures the distance and direction to surrounding objects and is provided on the approach direction side of the pallet, a lateral sensor that measures the distance and direction to surrounding objects and is provided on a lateral side in the approach direction, and a sensor that measures the distance and direction to surrounding objects and is provided on a lateral side in the approach direction when the automated guided vehicle enters the pallet or leaves the pallet. In this case, the system is equipped with leg detection means which detects the legs of the pallet from measurement data by the entry sensor when the side sensor is located outside the pallet, and detects the legs of the pallet from measurement data by the side sensor when the side sensor is located inside the pallet , center line calculation means which calculates a center line between both legs of the pallet from the legs of the pallet detected by the leg detection means, and steering angle calculation means which calculates a steering angle of the unmanned guided vehicle so as to reduce the amount of deviation between the center line between both legs of the pallet calculated by the center line calculation means and the center line of the unmanned guided vehicle.

According to the automated guided vehicle described in claim 1, when the automated guided vehicle enters below a pallet or leaves the pallet, the legs of the pallet are detected from the measurement data measured by the entry sensor or side sensor, and the steering angle of the automated guided vehicle is calculated based on the detected legs of the pallet. This eliminates the need to provide guides or the like on the pallet for position control when the automated guided vehicle enters or leaves the pallet, and to provide a sensor on the automated guided vehicle to read the guides, thereby reducing the costs of the automated guided vehicle and the pallet.

The entry sensor and side sensor measure the distance and direction to surrounding objects, so even if the pallet has multiple legs and there is a gap between each pair of legs, the position of the pallet legs within the detection range of the entry sensor and side sensor can be continuously detected. This has the effect of allowing the automated guided vehicle to accurately enter or leave the pallet.

Furthermore, when the side sensor is located outside the pallet, the legs of the pallet are detected by the measurement data from the entry sensor, and when the side sensor is located inside the pallet, the legs of the pallet are detected by the measurement data from the side sensor. When the side sensor is located outside the pallet, the entry sensor faces the legs of the pallet, so a large number of legs on the pallet can be detected. In this way, based on the large number of pallet legs detected by the entry sensor, the position between both legs of the pallet can be calculated more accurately.

On the other hand, when the side sensor is located inside the pallet, the legs of the pallet face the side sensor, and in such a case, a large number of the pallet legs are detected by the side sensor. In this way, based on the large number of pallet legs detected by the side sensor, it is possible to more accurately calculate the position between the two legs of the pallet, even when the automated guided vehicle is located inside the pallet.

Furthermore, a steering angle of the automated guided vehicle is calculated to reduce the amount of deviation between the center line of the automated guided vehicle and the center line of the pallet calculated from the detected pallet legs. This allows the automated guided vehicle to travel along the center of the pallet, which has the effect of suppressing contact between the automated guided vehicle 1 and the pallet, especially the legs of the pallet.

According to the automated guided vehicle of claim 2 , in addition to the effects of the automated guided vehicle of claim 1 , the following effect is achieved. The center line between both legs of the pallet is calculated based on the innermost position of the legs of the pallet. In other words, since the center line is calculated based on the narrowest position between both legs of the pallet, it is possible to prevent contact between the automated guided vehicle and the legs of the pallet.

According to the automated guided vehicle of claim 3 , in addition to the effects of the automated guided vehicle of claim 1 or 2 , the following effect is achieved. The midpoint between each pair of left and right pallet legs is calculated, and the center line between both pallet legs is calculated based on the calculated midpoint. By calculating the steering angle of the automated guided vehicle based on this center line, the automated guided vehicle can travel along the midpoint between the left and right pair of pallet legs, which has the effect of suitably suppressing contact between the automated guided vehicle and the pallet legs.

According to the automated guided vehicle of claim 4 , in addition to the effects of the automated guided vehicle of claim 3 , the following effect is achieved. A plurality of straight lines are calculated connecting the midpoints of the left and right pairs of pallet legs, which are closer to the automated guided vehicle, with the other midpoints, and the center line between both pallet legs is calculated by averaging the calculated straight lines. That is, since the center line is calculated from the midpoint closest to the automated guided vehicle, i.e., the midpoint of the pallet legs when the automated guided vehicle is passing or about to pass, and the midpoint of the other pallet legs, by calculating the steering angle based on this center line, there is an effect that contact between the automated guided vehicle and the pallet legs can be more suitably suppressed while keeping the change in steering angle small.

The automated guided vehicle according to claim 5 has the following effect in addition to the effect of the automated guided vehicle according to any one of claims 1 to 4. The number of legs of a pallet passing in front of the side sensor is counted, and the position of the automated guided vehicle within the pallet is detected from the measured number of legs of the pallet. This has the effect of reducing the costs of the automated guided vehicle and pallets, since the position of the automated guided vehicle within the pallet can be grasped without providing a marker or the like indicating the position of the automated guided vehicle on the pallet and a sensor or the like for detecting the marker or the like on the automated guided vehicle.

1A is a diagram showing an automated guided vehicle and a pallet, and FIG. 1B is a diagram showing the automated guided vehicle and the pallet in the direction of arrow Ib. 1A is a diagram showing a state in which an automated guided vehicle is about to enter a pallet, and FIG. 1B is a diagram showing a state in which the automated guided vehicle has entered the pallet. FIG. 2 is a diagram illustrating steering control of an automated guided vehicle. FIG. 2 is a block diagram showing an electrical configuration of the automated guided vehicle. 13 is a flowchart of a pallet entry/exit process. 13A is a flowchart of front and rear detection processing, and FIG. 13B is a flowchart of side detection processing. 13A is a flowchart of a center line selection process, and FIG. 13B is a flowchart of a velocity calculation process.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings. First, the configuration of an automated guided vehicle 1 in this embodiment will be described with reference to FIG. 1. FIG. 1(a) is a diagram showing the automated guided vehicle 1 and a pallet 50, and FIG. 1(b) is a diagram showing the automated guided vehicle 1 and the pallet 50 in the direction of arrow Ib. The direction of arrow F in FIGS. 1 and 2 indicates the traveling direction of the automated guided vehicle 1. In this embodiment, the longitudinal direction of the automated guided vehicle 1 is defined as "front and rear", and the left side of FIG. 1(a) is tentatively defined as the front.

The automated guided vehicle 1 is a vehicle that travels automatically while carrying a pallet 50 carrying a load W, and includes a vehicle body 2, a travel device 3, an entrance sensor 4a, and a lateral sensor 4b. The travel device 3 is a device that causes the automated guided vehicle 1 to travel, and is disposed at each of the four corners of the automated guided vehicle 1 when viewed from above.

The entry sensor 4a is a sensor that measures the distance and direction to surrounding objects, and is provided at the front and rear of the automated guided vehicle 1. In this embodiment, of the front and rear entry sensors 4a, the entry sensor 4a on the entry direction side to the pallet 50 is referred to as the "entry sensor 4a1", and the entry sensor 4a on the opposite side to the entry direction to the pallet 50 is referred to as the "entry sensor 4a2". The side sensor 4b is a sensor that measures the distance and direction to surrounding objects, and is provided on one side of the automated guided vehicle 1 (the left side of the traveling direction in FIG. 1(a) in this embodiment). The entry sensor 4a and the side sensor 4b measure the distance and direction between the entry sensor 4a and the object by irradiating the surroundings with laser light L (see FIG. 2). The position where the entry sensor 4a is provided is not limited to both the front and rear of the automated guided vehicle 1, but may be only the front side or only the rear side of the automated guided vehicle 1. Furthermore, the location of the side sensor 4b is not limited to the left side in the direction of travel, but may be on the right side or on both sides of the automated guided vehicle 1.

The pallet 50 loaded on the automated guided vehicle 1 has legs 51 and a base 52. The legs 51 are columnar members provided on both sides of the pallet 50. Six legs 51 are provided on each side of the pallet 50, and the six legs 51 are joined to form a truss structure. The base 52 is joined to the tops of the legs 51 on both sides, and is a flat member for carrying the load W. Note that the number of legs 51 is not limited to six, and may be six or more or less depending on the overall length of the base 52 and the mass of the load W to be carried.

When loading a pallet 50, the automated guided vehicle 1 lowers its vehicle height and enters below the platform 52. After entering a specified position on the pallet 50, it stops traveling and the vehicle height of the automated guided vehicle 1 is raised, so that the pallet 50 is loaded onto the loading platform formed on the upper surface of the vehicle body 2. On the other hand, when the loaded pallet 50 is to be unloaded from the automated guided vehicle 1 and removed from the pallet 50, the vehicle height of the automated guided vehicle 1 is lowered, the pallet 50 is removed from the loading platform of the vehicle body 2, and with the vehicle height lowered, the automated guided vehicle 1 travels in the opposite direction from the direction in which it entered the pallet 50, allowing the automated guided vehicle 1 to leave the pallet 50.

In this embodiment, when the automated guided vehicle 1 approaches the pallet 50 and leaves the pallet, the legs 51 of the pallet 50 are detected from measurement data based on the distance and direction to surrounding objects measured by the approach sensor 4a and the side sensor 4b, and the automated guided vehicle 1 is steered based on the detected position of the legs 51. The detection of the legs 51 by the approach sensor 4a and the side sensor 4b and the steering method of the automated guided vehicle 1 are described using Figures 2 and 3.

Figure 2(a) shows the state in which the automated guided vehicle 1 is about to enter the pallet 50, and Figure 2(b) shows the state in which the automated guided vehicle 1 has entered the pallet 50. In Figure 2, for the sake of explanation, the illustration of the platform 52 of the pallet 50 is omitted, and the parts of the legs 51 that are detected by the entry sensor 4a and the side sensor 4b are shown in bold lines, and the parts that are not detected are shown in dashed lines.

First, as shown in FIG. 2(a), when the automated guided vehicle 1 is located outside the pallet 50, the legs 51 are detected by the entry sensor 4a1 facing the pallet 50. Since the entry sensor 4a1 facing the pallet 50 detects a large number of legs 51 of the pallet 50, the positions of the legs 51 can be accurately detected.

In this embodiment, the positions of the legs 51 of the pallet 50 are expressed as "relative positions" with the center of the automated guided vehicle 1 in a top view as the reference position (i.e., origin (0,0)) and the front-rear and left-right directions of the automated guided vehicle 1 as coordinate axes. Conversion of the measurement data measured by the entrance sensor 4a and the side sensor 4b into relative positions is a well-known technique, so a description thereof will be omitted. The reference position is not limited to the center of the automated guided vehicle 1 in a top view, but may be another part of the automated guided vehicle 1, such as the center at the front end of the automated guided vehicle 1. Furthermore, the positions of the legs 51 of the pallet 50 are not limited to being expressed as relative positions, but may be expressed as "absolute positions" with a specific point as the reference position.

When the legs 51 of the pallet 50 are detected, pairs of legs 51 on both sides are formed from the detected legs 51. Specifically, among the detected legs 51, legs 51 that are at approximately the same position in the longitudinal direction of the pallet 50 are grouped as a pair of legs 51. The innermost positions PpL and PpR of the pair of legs 51 are obtained, and the center line Pc of the legs 51 on both sides is calculated based on the midpoint Cc of the line connecting these positions PpL and PpR. The automated guided vehicle 1 is then steered based on the center line Pc. The specific steering method for the steering angle θv will be described later with reference to FIG. 3.

On the other hand, when the automated guided vehicle 1 is located inside the pallet 50, the legs 51 are detected using the side sensors 4b, as shown in FIG. 2(b). When the automated guided vehicle 1 is located inside the pallet 50, the side sensors 4b face the legs 51, so that a large number of legs 51 are detected by the side sensors 4b. This allows the positions of the legs 51 to be detected accurately.

Since only one of the legs 51 on both sides is detected by the lateral sensor 4b, a center line Pc similar to that shown in FIG. 2(a) is calculated from the detected leg 51. Specifically, the position of the leg 51 detected by the lateral sensor 4b is moved (offset) inward from the legs 51 on both sides by a distance Lp/2, which is half the distance Lp between the legs 51 on both sides stored in the pallet data 11b described later, to obtain the midpoint Cc between them, and the center line Pc is calculated based on the obtained midpoint Cc.

In this embodiment, the stopping position of the automated guided vehicle 1 within the pallet 50, i.e., the position where the pallet 50 is loaded onto the body 2 of the automated guided vehicle 1, is the midpoint between the third leg 51a and the fourth leg 51b from the entry direction side of the automated guided vehicle 1 (i.e., the position of the automated guided vehicle 1 in FIG. 2(b)). Therefore, in this embodiment, the position of the automated guided vehicle 1 within the pallet 50 is determined from the number of legs 51 that pass directly in front of the side sensor 4b (passing leg position memory 12h, which will be described later in FIG. 4).

Specifically, when the automated guided vehicle 1 enters the pallet 50, the number of legs 51 before entering the pallet 50 is set to 0, and each time a leg 51 passes directly in front of the side sensor 4b, one is added. In other words, when the automated guided vehicle 1 enters the pallet 50, the position of the automated guided vehicle 1 within the pallet 50 is determined based on the number of legs 51 that have passed after entering the pallet 50.

On the other hand, when the automated guided vehicle 1 leaves the pallet 50, the number of legs 51 at the stopping position within the pallet 50 (i.e., between legs 51a and 51b) is three, and one is subtracted each time a leg 51 passes directly in front of the side sensor 4b. In other words, when the automated guided vehicle 1 leaves the pallet 50, the position of the automated guided vehicle 1 within the pallet 50 is determined based on the number of legs 51 until it leaves the pallet 50.

In this way, the position within the pallet 50 is determined based on the number of legs 51 that pass the lateral sensor 4b. This makes it possible to easily determine the position of the automated guided vehicle 1 within the pallet 50 without providing a marker or the like indicating the position of the automated guided vehicle 1 within the pallet 50 and providing the automated guided vehicle 1 with a sensor or the like for detecting the marker or the like. This allows the costs of the automated guided vehicle 1 and the pallet 50 to be reduced.

Next, referring to Figure 3, we will explain the steering method of the automated guided vehicle 1 from the center line Pc of the pallet 50 described in Figures 2(a) and (b).

Figure 3 is a diagram explaining the steering control of the automated guided vehicle 1. At the front and rear ends of the automated guided vehicle 1, virtual detection areas Dp are provided to detect the amount of deviation between the center line Lc of the automated guided vehicle and the center line Pc of the pallet 50. The steering angle θv of each traveling device 3 is calculated based on the amount of deviation df, dr between the center line Lc of the automated guided vehicle and the center line Pc of the pallet 50 detected in the front and rear detection areas Dp.

Specifically, first, a virtual origin Cf is set on the center line Lc at a position that is a predetermined distance Lip rearward from the center position of the front detection area Dp in a top view, and a virtual origin Cr is set at a position that is a distance Lip rearward from the center position of the rear detection area Dp in a top view. Then, a straight line is drawn that is perpendicular to the line segment connecting the virtual origin Cf and the position Gf of the center line Pc of the pallet 50 in the front detection area Dp, i.e., the position corresponding to the deviation amount df from the center line Lc, and that faces the rear side of the vehicle body 2. A straight line is drawn that is perpendicular to the line segment connecting the detection position Gr of the center line Pc in the rear detection area Dp, i.e., the position corresponding to the deviation amount dr from the center line Lc, and that faces the front side of the vehicle body 2. The intersection of these straight lines is the turning center C.

A circular arc-shaped turning path R is generated that is centered on the turning center C and passes through the center of the traveling device 3. The angle θv between the tangent direction at the center of each traveling device 3 on the turning path R and the direction V toward the traveling direction of the automated guided vehicle 1 is set as the steering angle θv.

Note that FIG. 3 only illustrates the steering angle θv of the traveling device 3 at the upper right when viewed from above the automated guided vehicle 1, but the calculation method for the steering angle θv for the other traveling devices 3 is similar, so it is not illustrated. Each traveling device 3 is steered and controlled so that the orientation of each traveling device 3 matches the steering angle θv calculated for it.

Next, the electrical configuration of the automated guided vehicle 1 will be described with reference to FIG. 4. FIG. 4 is a block diagram showing the electrical configuration of the automated guided vehicle 1. The automated guided vehicle 1 is equipped with a CPU 10, a flash ROM 11, and a RAM 12, which are each connected to an input/output port 14 via a bus line 13. The above-mentioned entry sensor 4a (entry sensors 4a1, 4a2), side sensor 4b, traveling device 3, and communication device 15 that transmits and receives information to and from external devices are each connected to the input/output port 14. Note that multiple traveling devices 3 are provided on the automated guided vehicle 1, but in FIG. 4, they are collectively represented as one traveling device 3.

The CPU 10 is a calculation device that controls each part connected to the bus line 13 and the input/output port 14. The flash ROM 11 is a rewritable non-volatile memory that stores a control program 11a, pallet data 11b, and stopping speed gain data 11c. The control program 11a is a program that causes the CPU 10 to execute the pallet entry/exit process of FIG. 5.

The pallet data 11b stores various information about the pallet 50, specifically, the distance Lp between the legs 51 of the pallet 50, the distance between the position of each leg 51 and the stopping position of the automated guided vehicle 1, the overall length and overall width of the pallet 50, etc. The stopping speed gain data 11c stores a gain value for calculating a speed according to the distance (remaining distance) between the automated guided vehicle 1 and its stopping position within the pallet 50 when the automated guided vehicle 1 travels within the pallet 50. The speed according to the position of the automated guided vehicle 1 is calculated by multiplying the distance between the automated guided vehicle 1 and the stopping position of the pallet 50 by the gain value stored in the stopping speed gain data 11c.

The RAM 12 is a memory for rewriting various work data and flags when the CPU 10 executes the control program 11a, etc., and includes a steering angle memory 12a in which the steering angle θv of each traveling device 3 is distinguished and stored, a speed memory 12b in which the traveling speed of the automatic guided vehicle 1 is stored, a front-rear centerline memory 12c in which the centerline Pc calculated based on the entry sensor 4a is stored, and a side centerline memory 12c in which the centerline Pc calculated based on the side sensor 4b is stored. 12d, a center line memory 12e that stores the center line Pc used to calculate the steering angle θv, a front and rear pair number memory 12f that stores the number of pairs of legs 51 of the pallet 50 detected by the entry sensor 4a, a lateral leg number memory 12g that stores the number of legs 51 of the pallet 50 detected by the lateral sensor 4b, a passing leg position memory 12h, and a remaining distance memory 12i that stores the distance between the position of the AGV 1 and the stopping position of the AGV 1 within the pallet 50.

The passing leg position memory 12h stores the number of legs 51 of the pallet 50 according to the position of the automated guided vehicle 1 within the pallet 50. Specifically, the passing leg position memory 12h stores the number of legs 51 that have passed directly in front of the side sensor 4b, and as described above, when the automated guided vehicle 1 enters the pallet 50, the initial value of the passing leg position memory 12h is set to 0, and 1 is added to the passing leg position memory 12h each time the automated guided vehicle 1 passes directly in front of the side sensor 4b. On the other hand, when the automated guided vehicle 1 leaves the pallet 50, the initial value of the passing leg position memory 12h is set to 3, which is the stopping position of the automated guided vehicle 1 within the pallet 50, and 1 is subtracted from the passing leg position memory 12h each time the automated guided vehicle 1 passes directly in front of the side sensor 4b.

Next, the processing executed by the CPU 10 of the automated guided vehicle 1 will be described with reference to Figures 5 to 7. Figure 5 is a flowchart of the pallet entry/exit processing. The pallet entry/exit processing is executed when the operation mode for the automated guided vehicle 1 received from a higher-level process controller (not shown) via the communication device 15 is "pallet entry", which instructs the automated guided vehicle 1 to enter the pallet 50, or "pallet exit", which instructs the automated guided vehicle 1 to exit the pallet 50.

The pallet entry/exit process begins with an initialization process (S1). In the initialization process of S1, in particular, "0" is set in the front and rear pair number memory 12f and the lateral leg number memory 12g, and as described above, "0" is set in the passing leg position memory 12h when the automated guided vehicle 1 is to enter the pallet 50, and "3" is set in the passing leg position memory 12h when the automated guided vehicle 1 is to leave the pallet 50. The initialization process of S1 also sets the other memory values in the RAM 12 to their respective initial values.

After processing S1, it is confirmed whether the current position of the automated guided vehicle 1 has reached the stop position (S2). The stop position confirmed in processing S2 is the stop position described above, i.e., the midpoint between the third leg 51a and the fourth leg 51b from the entry direction on the pallet 50 (see FIG. 2(b)), when the automated guided vehicle 1 is to enter the pallet 50, and is a position outside the pallet 50 specified by the upper process controller when the automated guided vehicle 1 is to leave the pallet 50.

In the process of S2, if the current position of the automated guided vehicle 1 has not reached the stop position (S2: No), the front/rear side detection process (S3) is executed. Now, the front/rear side detection process will be described with reference to FIG. 6(a).

Figure 6 (a) is a flowchart of the front/rear side detection process. The front/rear side detection process is a process for calculating the center line Pc and the number of pairs of legs 51 of the pallet based on the approach sensor 4a. The front/rear side detection process first checks the operating mode instructed by the upper process controller (S20).

In the process of S20, if the operating mode is pallet entry (S20: "pallet entry"), of the front and rear entry sensors 4a, the front entry sensor 4a of the automated guided vehicle 1 is set as the sensor that measures the measurement data (S21), and in the process of S20, if the operating mode is pallet departure (S20: "pallet departure"), the rear entry sensor 4a is set as the sensor that measures the measurement data (S22). Hereinafter, in the front and rear detection process, the entry sensor 4a set in the processes of S21 and S22 is referred to as the "target sensor".

That is, by the processing of S21 and S22, of the entry sensors 4a at the front and rear of the automated guided vehicle 1, the entry sensor 4a facing the leg 51 of the pallet 50 is set as the "target sensor". When entering the pallet 50, of the entry sensors 4a provided at the front and rear of the automated guided vehicle 1, the entry sensor 4a closest to the pallet 50 is set as the target sensor, so that the legs 51 of the pallet 50 can be detected more accurately. On the other hand, when leaving the pallet 50, the entry sensor 4a1 in FIG. 2(a) is set as the target sensor in the processing of S22, so that the number of legs 51 of the pallet 50 detected by the entry sensor 4a1 can be gradually increased as the automated guided vehicle 1 travels.

After the processes of S21 and S22, measurement data is acquired from the target sensor (S23), and all pairs of legs 51 of the pallet 50 described above are detected from the acquired measurement data (S24). Thereafter, it is confirmed whether pairs of legs 51 of the pallet 50 have been detected by the process of S24 (S25).

If a pair of legs 51 is detected in the process of S25 (S25: Yes), the midpoint Cc of each detected pair of legs 51 is obtained (S26). Specifically, the measurement data corresponding to each detected pair of legs 51 is converted to the relative position described above in FIG. 2, and then the midpoint Cc of the line connecting the innermost positions of the pair of legs 51 is obtained for each pair of legs 51.

After the process of S26, the center line Pc of the pallet 50 is calculated from the midpoints Cc of each acquired pair of legs 51 and stored in the front-rear center line memory 12c (S27). Specifically, of the midpoints Cc of the acquired pairs of legs 51, the straight lines between the midpoint Cc closest to the automated guided vehicle 1 and all other midpoints Cc are calculated, and the calculated straight lines are averaged to calculate the center line Pc, which is stored in the front-rear center line memory 12c.

After processing in S27, the number of pairs of legs 51 detected in processing in S25 is obtained and stored in the front and rear pair number memory 12f (S28).

If a pair of legs 51 is not detected in the process of S25 (S25: No), or after the process of S28, the front and rear side detection process ends.

Returning to FIG. 5, after the front/rear detection process in S3, the side detection process (S4) is executed. Now, the side detection process will be explained with reference to FIG. 6(b).

Figure 6 (b) is a flowchart of the lateral detection process. The lateral detection process is a process for calculating the center line Pc and the number of legs 51 that the lateral sensor 4b has passed, based on the lateral sensor 4b.

The lateral detection process first acquires measurement data from the lateral sensor 4b (S40). After the process of S40, all legs 51 of the pallet 50 are detected from the acquired measurement data (S41). After the process of S41, it is confirmed whether the legs 51 have been detected (S42).

In the process of S42, if a leg 51 is detected (S42: Yes), the midpoint Cc of the pallet 50 is calculated from each detected leg 51 (S43). Specifically, the measurement data corresponding to each detected leg 51 is converted to the relative position described above in FIG. 2, and the innermost position of each leg 51, i.e., the position toward the center of the pallet 50, is obtained, and a position moved from that position toward the inside of the legs 51 on both sides by half the distance Lp/2 between the left and right legs 51 of the pallet 50 stored in the pallet data 11b is set as the midpoint Cc of each leg 51.

After the process of S43, the center line Pc of the pallet 50 is calculated from the midpoints Cc calculated in the process of S43 and stored in the side center line memory 12d (S44). Specifically, similar to the process of S27 in FIG. 6(a), the center line Pc is calculated by averaging the calculated straight lines between the midpoint Cc closest to the automated guided vehicle 1 and all the other midpoints Cc, out of the midpoints Cc calculated in the process of S43, and the calculated straight lines are averaged to calculate the center line Pc, which is stored in the side center line memory 12d.

After the process of S44, the number of legs 51 detected in the process of S42 is obtained and stored in the side leg number memory 12g (S45). After the process of S45, it is confirmed whether there is a leg 51 located directly in front of the side sensor 4b among the legs 51 detected in the process of S42 (S46). Specifically, the distance corresponding to the direct front of the side sensor 4b (0 degrees) in the measurement data acquired by the side sensor 4b is confirmed, and if the position of the leg 51 closest to the traveling direction can be detected, for example, if the distance corresponding to the direct front of the side sensor 4b changes from 10 m or more to 1 m or less, it is determined that there is a leg 51 located directly in front of the side sensor 4b. In the process of S46, if there is a leg 51 located directly in front of the side sensor 4b (S46: Yes), the operation mode instructed by the upper process controller described above is confirmed (S47).

In the process of S47, if the operation mode is pallet entry (S47: "pallet entry"), 1 is added to the passing leg position memory 12h (S48), and if the operation mode is pallet departure (S47: "pallet departure"), 1 is subtracted from the passing leg position memory 12h (S49).

If a leg 51 is not detected in the process of S42 (S42: No), if a leg 51 is not located directly in front of the side sensor 4b in the process of S46 (S46: No), or after the processes of S48 and S49, the side detection process ends.

Returning to FIG. 5, after the lateral detection process of S4, it is confirmed whether the number of pairs of legs 51 in the front and rear pair number memory 12f is 2 or more, or the number of legs 51 in the lateral leg number memory 12g is 2 or more (S5). In the process of S5, if the number of pairs of legs 51 in the front and rear pair number memory 12f is 2 or more, or the number of legs 51 in the lateral leg number memory 12g is 2 or more (S5: Yes), it can be determined that a pair of legs 51 has been detected by the entry sensor 4a or the lateral sensor 4b, and the center line Pc has been calculated by the process of S3 or S4, and in such a case, the center line selection process (S6) is executed. Here, the center line selection process will be explained with reference to FIG. 7(a).

Figure 7 (a) is a flowchart of the center line selection process. The center line selection process is a process for selecting the center line Pc used to calculate the steering angle θv of the traveling device 3 from either the front-rear center line memory 12c or the lateral center line memory 12d depending on the number of legs 51 in the lateral leg number memory 12g. The center line selection process first checks whether the number of legs 51 in the lateral leg number memory 12g is 2 or more (S60).

In the process of S60, if the number of legs 51 in the lateral leg number memory 12g is less than two (S60: No), the value of the anterior-posterior centerline memory 12c is set in the centerline memory 12e (S61); on the other hand, if the number of legs 51 in the lateral leg number memory 12g is two or more (S60: Yes), the value of the lateral centerline memory 12d is set in the centerline memory 12e (S62).

Specifically, in the process of S60, if the number of legs 51 in the lateral leg number memory 12g is less than 2 (S60: No), this is the case when the number of legs 51 detected by the lateral sensor 4b in the lateral detection process of S4 (FIG. 6(b)) is small, while many pairs of legs 51 are detected by the entry sensor 4a in the front and rear detection process of S3 (FIG. 6(a)). That is, this is the case before the automated guided vehicle 1 (particularly the lateral sensor 4b) enters the pallet 50 or has just entered the pallet 50, or immediately before or after the automated guided vehicle 1 leaves the pallet 50.

In such a case, while the front entry sensor 4a faces the legs 51 of the pallet 50, the side sensor 4b does not face the legs 51 of the pallet 50, so the number of pallet legs 51 detected by the front entry sensor 4a can be greater than the number of legs 51 detected by the side sensor 4b. Therefore, by setting the front-to-rear centerline memory 12c calculated from the front entry sensor 4a, which is calculated from more pallet legs 51, in the centerline memory 12e, a more accurate centerline Pc calculated from more pallet legs 51 can be set in the centerline memory 12e.

On the other hand, in the process of S60, if the number of legs 51 in the side leg number memory 12g is two or more (S60: Yes), this means that there are few pairs of legs 51 detected by the entry sensor 4a in the front and rear detection process of S3, while there are many pairs of legs 51 detected by the side sensor 4b in the side detection process of S4. In other words, this is the case when the automated guided vehicle 1 is positioned within the pallet 50 after a while has passed since it entered the pallet 50, or when the automated guided vehicle 1 has just begun to leave the pallet 50 and is now in that state.

In such a case, while there are few legs 51 of the pallet 50 facing the front entry sensor 4a, the side sensor 4b faces the legs 51 of the pallet 50, so many legs 51 can be detected by the side sensor 4b. Therefore, by setting the side centerline memory 12d from the side sensor 4b to the centerline memory 12e, even when the automated guided vehicle 1 is moving inside the pallet 50, a more accurate centerline Pc calculated from many pallet legs 51 can be set in the centerline memory 12e.

After processing S61 or S62, the center line selection process ends.

Return to FIG. 5. After the center line selection process of S6, the method described in FIG. 3 is used to calculate the turning center C based on the deviations df, dr between the virtual origins Cf, Cr of the automated guided vehicle 1 and the center line Pc of the center line memory (S7), and the steering angle θv of each traveling device 3 is calculated based on the turning center C and stored in the steering angle memory 12a (S8). After the process of S8, a speed calculation process (S9) is executed. The speed calculation process will now be described with reference to FIG. 7(b).

Figure 7 (b) is a flow chart of the speed calculation process. The speed calculation process is a process for setting the travel speed of the automatic guided vehicle 1 according to the position of the automatic guided vehicle 1 within the pallet 50. The speed calculation process first checks the operation mode instructed by the upper process controller (S70). In the process of S70, if the operation mode is pallet entry (S70: "pallet entry"), it is checked whether the number of legs 51 in the passing leg position memory 12h is 3 (S71). As described above, the stopping position within the pallet 50 is the midpoint between the third leg 51a and the fourth leg 51b (both see Figure 2 (b)) from the entry direction side of the automatic guided vehicle 1, so in the process of S71, it is checked whether the third leg 51a before the stopping position has been passed.

In the process of S71, if the number of legs 51 in the passing leg position memory 12h is 3 (S71: Yes), the remaining distance to the stop position is calculated from the number of legs 51 in the passing leg position memory 12h and stored in the remaining distance memory 12i (S72). Specifically, since the pallet data 11b stores the distance from the position of each leg 51 of the pallet 50 to the stop position in the traveling direction of the automated guided vehicle 1, the distance to the stop position corresponding to the number of legs 51 in the passing leg position memory 12h is obtained from the pallet data 11b and stored in the remaining distance memory 12i. At this time, if the automated guided vehicle 1 is positioned midway between adjacent legs 51, the travel distance from the leg 51 detected immediately before is subtracted from the remaining distance memory 12i.

After processing in S72, a speed is set in the speed memory 12b, which is the remaining distance in the remaining distance memory 12i multiplied by the gain value of the stop speed gain data 11c (S73).

That is, when the automated guided vehicle 1 enters the pallet 50 and stops, the remaining distance between the automated guided vehicle 1 and the stopping position within the pallet 50 is calculated based on the number of legs 51 in the passing leg position memory 12h, and the traveling speed is controlled according to the remaining distance. Therefore, by providing markers or the like for controlling the traveling speed of the automated guided vehicle 1 within the pallet 50 and controlling the traveling speed of the automated guided vehicle 1 without providing a sensor or the like for detecting the markers or the like on the automated guided vehicle 1, the costs of the automated guided vehicle 1 and the pallet 50 can be reduced.

In the process of S70, if the operation mode is pallet removal (S70: "pallet removal"), or in the process of S71, if the number of legs 51 in the passing leg position memory 12h is not 3 (S71: No), it is not the timing to stop the automated guided vehicle 1, so the running speed set by the upper process controller is set in the speed memory 12b (S74). After the process of S73 or S74, the speed calculation process ends.

After the speed calculation process of S9, the automatic guided vehicle 1 is caused to travel by operating each travel device 3 according to the steering angle θv in the steering angle memory 12a and the travel speed in the speed memory 12b (S10). After the process of S10, the current position of the automatic guided vehicle 1 is corrected by the travel distance according to the travel process of S10 (S11). At this time, if the automatic guided vehicle 1 is traveling within a pallet 50, the current position of the automatic guided vehicle 1 may be further corrected using the position of the automatic guided vehicle 1 within the pallet 50 according to the number of legs 51 in the passing leg position memory 12h and the pallet data 11b. After the process of S11, the processes from S2 onwards are repeated.

In the process of S2, if the current position of the automated guided vehicle 1 reaches the stop position (S2: Yes), the automated guided vehicle 1 stops traveling (S12). In addition, in the process of S5, if the number of pairs of legs 51 in the front and rear pair number memory 12f and the number of legs 51 in the side leg number memory 12g are both smaller than 2 (S5: No), it is determined that there is an abnormal state in which the number of legs 51 cannot be detected sufficiently by the entry sensor 4a and the side sensor 4b, such as when the entry sensor 4a or the side sensor 4b is broken. In such a case, the upper process controller is notified that an abnormality has occurred (S13), and the automated guided vehicle 1 stops traveling by the process of S12. After the process of S12, the pallet entry/exit process is terminated.

As described above, when the automated guided vehicle 1 is located outside the pallet 50, the legs 51 of the pallet 50 are detected based on the measurement data of the entry sensor 4a, the center line Pc is calculated based on the detected legs 51, and the steering angle θv of the traveling device 3 is calculated based on the calculated center line Pc. On the other hand, when the automated guided vehicle 1 is located inside the pallet 50, the legs 51 of the pallet 50 are detected based on the measurement data of the lateral sensor 4b, and the center line Pc and steering angle θv are calculated based on the detected legs 51.

This eliminates the need to provide a magnetic guide or the like on the pallet 50 and a sensor to read the magnetic guide or the like on the automated guided vehicle 1 for position control when the automated guided vehicle 1 enters the pallet 50 or leaves the pallet 50, thereby reducing the costs of the automated guided vehicle 1 and the pallet 50. Here, the entry sensor 4a and the side sensor 4b measure the distance and direction to surrounding objects, so even if the pallet 50 has multiple legs 51 arranged in a truss shape and there is a gap between the legs 51, the position of the legs 51 within the detection range of the entry sensor 4a and the side sensor 4b can be continuously detected. This allows the automated guided vehicle 1 to accurately enter the pallet 50 or leave the pallet 50.

In addition, when calculating the center line Pc of the pallet 50 in the process of S27 in FIG. 6(a), the midpoint Cc of the line connecting the innermost sides of each pair of legs 51 of the pallet 50 is used. As a result, the center line Pc is calculated based on the narrowest position between both legs of the pallet 50, so that the automated guided vehicle 1 can enter or leave the pallet 50 while preventing contact between the automated guided vehicle 1 and the legs 51 of the pallet 50.

Furthermore, when calculating the center line Pc, all straight lines connecting the intermediate point Cc closest to the automated guided vehicle 1 and the other intermediate points Cc are calculated, and the center line Pc of the pallet 50 is calculated by averaging the calculated straight lines. In other words, the center line Pc is calculated from the intermediate point Cc closest to the automated guided vehicle 1, i.e., the intermediate point Cc of the legs 51 of the pallet 50 while the automated guided vehicle 1 is passing or about to pass, and the intermediate points Cc of the other legs 51. Therefore, by calculating the steering angle θv of the traveling device 3 based on this center line Pc, it is possible to more appropriately suppress contact between the automated guided vehicle 1 and the legs 51 while keeping the change in the steering angle θv small.

The present invention has been described above based on the embodiments, but the present invention is in no way limited to the above-mentioned embodiments, and it can be easily imagined that various improvements and modifications are possible within the scope of the invention without departing from its spirit.

In the above embodiment, the legs 51 of the pallet 50 are configured in a truss shape, but this is not limited to this. For example, the legs 51 may be configured in the shape of approximately vertical columns, or the legs 51 may be configured in a lattice shape.

The legs 51 may also be formed in a wall shape, and one wall-shaped leg 51 may form both sides of the pallet 50. In this case, instead of obtaining the position of the automated guided vehicle 1 on the pallet 50 based on the number of legs 51 in the lateral leg number memory 12g and the number of legs 51 in the passing leg position memory 12h in the process of S60 in FIG. 7(a) or the process of S71 in FIG. 7(b), the position of the automated guided vehicle 1 on the pallet 50 may be obtained based on the distance until or after the automated guided vehicle 1 enters the pallet 50, or the distance until or after the automated guided vehicle 1 leaves the pallet 50, and steering control and speed control may be performed.

In the above embodiment, in the process of S26 in FIG. 6(a), the midpoint Cc of the line connecting the innermost points of each detected pair of legs 51 was obtained. The method of obtaining the midpoint Cc is not limited to this, and for example, as in the process of S43 in FIG. 6(b), the position of one leg 51 in each detected pair of legs 51 may be moved a distance Lp/2 toward the center of the pallet 50, and the midpoint Cc of each leg 51 may be the position obtained.

In the above embodiment, in the process of S27 in FIG. 6(a) and the process of S44 in FIG. 6(b), the center line Pc is calculated by calculating all straight lines between the intermediate point Cc closest to the automated guided vehicle 1 and the other intermediate points Cc among the acquired intermediate points Cc, and averaging the calculated straight lines. However, this is not limited to the above, and for example, the center line Pc may be calculated based on intermediate points Cc other than the intermediate point Cc closest to the automated guided vehicle 1, or the center line Pc may be calculated by connecting the intermediate point Cc closest to the automated guided vehicle 1 and the intermediate point Cc farthest from the automated guided vehicle 1.

In addition, the center line Pc is not limited to being calculated by averaging all the straight lines based on the midpoints Cc. For example, the center line Pc may be calculated using a specific straight line selected from the straight lines based on the midpoints Cc, or may be calculated using a straight line randomly selected from the straight lines based on the midpoints Cc. Alternatively, the center line Pc may be calculated from all the midpoints Cc using the least squares method.

In the above embodiment, in the centerline selection process of FIG. 7(a), the centerline Pc is selected from either the front-rear centerline memory 12c or the lateral centerline memory 12d according to the number of legs 51 in the lateral leg number memory 12g. However, this is not limited to the above, and the centerline Pc may be selected according to the number of legs 51 in the lateral leg number memory 12g and the number of pairs of legs 51 in the front-rear pair number memory 12f. In this case, for example, if the number of pairs of legs 51 in the front-rear pair number memory 12f is greater than 1 or the number of legs 51 in the lateral leg number memory 12g is less than 2, the value of the front-rear centerline memory 12c is set in the centerline memory 12e (i.e., S61 in FIG. 7(a)), and if the number of pairs of legs 51 in the front-rear pair number memory 12f is 1 or less and the number of legs 51 in the lateral leg number memory 12g is 2 or more, the value of the lateral centerline memory 12d is set in the centerline memory 12e (i.e., S62 in FIG. 7(a)). Also, the center line Pc may be selected based only on the number of pairs of legs 51 in the front and rear pair number memory 12f.

Furthermore, in the centerline selection process of FIG. 7(a), the centerline Pc is selected from either the anterior-posterior centerline memory 12c or the lateral centerline memory 12d, but this is not limited thereto, and the centerline Pc from either the anterior-posterior centerline memory 12c or the lateral centerline memory 12d may always be set in the centerline memory 12e, or the centerline Pc obtained by averaging the centerline Pc of the anterior-posterior centerline memory 12c and the centerline Pc of the lateral centerline memory 12d may always be set in the centerline memory 12e.

In the above embodiment, in the processes of S7 and S8 in FIG. 5, the turning center C and the steering angle θv of each traveling device 3 are calculated based on the center line Pc of the center line memory 12e. The calculation of the turning center C and the steering angle θv is not limited to being based on the center line Pc. For example, the turning center C and the steering angle θv may be calculated based on a straight line deviated from the center of the pallet 50, or the turning center C and the steering angle θv may be calculated based on a curved or straight path calculated to avoid contact between the automated guided vehicle 1 and each leg 51.

In the above embodiment, in the process of S46 in FIG. 6(b), it is confirmed whether there is a leg 51 located directly in front of the side sensor 4b, but it is not limited to this, and it may be confirmed whether there is a leg 51 in a position shifted from directly in front of the side sensor 4b. In this case, when the side sensor 4b and the leg 51 form a predetermined relative angle (e.g., 20 degrees), it may be determined that the leg 51 is located in a position shifted from directly in front of the side sensor 4b.

In the above embodiment, an unmanned guided vehicle 1 was used for explanation, but this is not limited thereto, and the present invention may be applied to, for example, a unit carrier, etc.

In the above embodiment, the control program 11a is stored in the flash ROM 11. However, the control program 11a may be stored and executed in a semiconductor memory other than the flash ROM 11, such as a RAM card, an optical disk such as a DVD, or a magnetic medium such as a hard disk drive, or the control program 11a may be stored in a server on a network (such as the Internet or an intranet) and downloaded from the server for execution.

The numerical values given in the above embodiment are merely examples, and it is of course possible to adopt other numerical values.

1 Automatic guided vehicle 4a Entry sensor 4b Side sensor 50 Pallet 51 Leg 52 Base Cc Midpoint Pc Center line S8 Steering angle calculation means S24, S25, S41, S42 Leg detection means S27, S44 Center line calculation means S26, S43 Midpoint calculation means S48, S49 Pallet passing number measurement means S71 Position detection means

Claims (5)

An automated guided vehicle that enters below a platform of a pallet having a plurality of legs provided on both sides and a platform supported by the legs, and loads and transports the pallet by lifting a loading platform below the platform,
An approach sensor that measures the distance and direction to surrounding objects and is provided on the approach direction side to the pallet;
A lateral sensor that measures a distance and a direction to a surrounding object and is provided on a lateral side in the approach direction;
a leg detection means for detecting a leg of the pallet based on measurement data from the entry sensor when the side sensor is located outside the pallet, and detecting a leg of the pallet based on measurement data from the side sensor when the side sensor is located inside the pallet, when the automated guided vehicle enters or leaves the pallet ;
a centerline calculation means for calculating a centerline between both legs of the pallet from the legs of the pallet detected by the leg detection means;
This unmanned guided vehicle is characterized by having a steering angle calculation means for calculating a steering angle of the unmanned guided vehicle so as to reduce the amount of deviation between the center line between both legs of the pallet calculated by the center line calculation means and the center line of the unmanned guided vehicle. 2. The automated guided vehicle according to claim 1 , wherein the center line calculation means calculates the center line between both legs of the pallet based on the innermost positions of the legs of the pallet detected by the leg detection means. The leg detection means detects a pair of left and right legs of a plurality of pallet legs provided on both sides of the pallet,
a midpoint calculation means for calculating a midpoint between each pair of left and right pallet legs detected by the leg detection means;
3. The automated guided vehicle according to claim 1 , wherein the center line calculation means calculates a center line between both legs of the pallet based on the midpoint of the left and right pair of legs of the pallet calculated by the midpoint calculation means. The center line calculation means
an individual center line calculation means for calculating a plurality of straight lines connecting the midpoints of the left and right pairs of pallet legs calculated by the midpoint calculation means, the midpoints being closer to the automatic guided vehicle, and the other midpoints;
4. An automated guided vehicle according to claim 3 , further comprising center line averaging means for calculating a center line between both legs of the pallet by averaging the straight lines calculated by the individual center line calculation means. a pallet passing number measuring means for measuring the number of legs of the pallet passing in front of the side sensor;
An automated guided vehicle as described in any one of claims 1 to 4 , characterized in that it is further equipped with a position detection means for detecting the position of the automated guided vehicle within the pallet from the number of pallet legs measured by the pallet passing number measurement means.

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