JP2023047537A - Autonomous moving body - Google Patents

Abstract

To provide an autonomous moving body capable of reducing a risk of overturning in abrupt braking during traveling even when a center of gravity deviates due to placement of a cargo.SOLUTION: An autonomous moving body 10 includes a moving body main body 11, plural drive wheels 12 provided in the moving body main body 11, a traveling drive device for driving the drive wheels 12, and a control device for controlling the traveling drive device, and can travel and turn in all directions. Further, the autonomous moving body includes drive motors provided in the respective drive wheels 12, a cargo bed 13 provided in the moving body main body 11, and a torque detection unit for detecting a torque of each of the drive motors. The control device obtains a difference of torque which is derived from deviation of a center of gravity Gw of a cargo W on the cargo bed 13, on the basis of the torque of the drive motors detected by the torque detection unit. When the difference of the torque is equal to or larger than a predesignated threshold, the control device controls the traveling drive device so that the drive wheel 12 of the drive motor having a small torque is headed in an advancing direction of the moving body main body 11 along with the turning of the moving body main body 11.SELECTED DRAWING: Figure 5

Description

The present invention relates to an autonomous mobile body.

As a conventional technology related to an autonomous mobile body, for example, a load-carrying robot disclosed in Patent Document 1 is known. The load-carrying robot disclosed in Patent Document 1 has two wheels, a body, an attitude sensor, an actuator, a moving device, and a control section. The two wheels are respectively connected to two coaxially arranged axles and rotatably supported. The aircraft has a loading platform on which luggage can be loaded. The attitude sensor detects the attitude of the aircraft. The actuator rotates the two wheels based on the detection result of the attitude sensor, and generates a force that maintains the attitude of the aircraft. The moving device is capable of moving the loading platform with respect to the fuselage. The control device controls the operation of the moving device to move the load mounted on the carrier of the aircraft in the direction of stabilizing the posture of the aircraft.

According to the cargo transport robot disclosed in Patent Document 1, a belt conveyor is arranged on the loading platform of the cargo transport robot, and by moving the cargo in the posture stabilization direction, the combined center of gravity position is always near the design position. corrective action is performed. As a result, the cargo transport robot can prevent horizontal imbalance when loading cargo, and can realize stable cargo transportation.

JP 2006-123854 A

However, the load carrying robot disclosed in Patent Document 1 moves the load in the direction in which the posture is stabilized. and a height sensor that Therefore, this type of load carrying robot has the problem that the manufacturing cost increases and the control for stabilizing the posture of the load becomes complicated. In addition, there is a risk that this type of cargo transport robot will topple over when it is suddenly braked while traveling.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce the risk of overturning in the direction of travel due to sudden braking during travel even if the center of gravity is biased due to the placement of a load. It lies in the provision of mobile units.

In order to solve the above problems, the present invention provides a mobile body, a plurality of drive wheels provided on the mobile body, a travel drive device for driving the drive wheels, and a control system for controlling the travel drive device. an autonomous mobile body capable of traveling and turning in all directions, comprising: a drive motor provided for each of the plurality of drive wheels; a cargo bed provided on the mobile body; and a torque detection unit for detecting torque, wherein the control device obtains a difference in torque caused by unevenness of the load on the loading platform based on the torque of the drive motor detected by the torque detection unit, and detects the torque. When the difference is equal to or greater than a preset threshold value, the traveling drive device is controlled such that the drive wheels of the drive motor with small torque are oriented toward the moving direction of the moving body due to the turning of the moving body. Characterized by

In the present invention, when a load is placed on the loading platform, the torque detection unit detects the torque of the drive motor, and the control device detects the torque generated by the deviation of the combined center of gravity of the center of gravity of the autonomous moving body and the center of gravity of the load. Look for differences. When the difference in torque is equal to or greater than a preset threshold value, the control device controls the traveling drive device so that the drive wheels of the drive motor with smaller torque move toward the traveling direction due to the turning of the mobile body. Since the drive wheels of the drive motor with small torque are directed toward the direction of travel, the combined center of gravity of the center of gravity of the autonomous mobile body and the center of gravity of the load is not located on the side of the travel direction of the main body of the mobile body. As a result, even if sudden braking is performed while the autonomous mobile body is running, the risk of the autonomous mobile body tipping over in the traveling direction can be reduced. In addition, since it is possible to determine whether or not the center of gravity of the load is biased by the torque of the drive motor, there is no need to separately provide means for determining whether or not the center of gravity of the load is biased, and manufacturing costs can be reduced.

Further, in the autonomous moving body described above, the control device may be configured to obtain the difference in the torque by turning the moving body main body after stopping traveling or turning the moving body main body before starting traveling.
In this case, the control device obtains the torque difference by turning after the moving body stops running or by turning before starting running of the moving body body. It is possible to reduce the risk of the autonomous mobile body overturning in the direction of travel.

Further, in the above-described autonomous mobile body, the control device may be configured to obtain the difference in the torque as the mobile body travels.
In this case, it is possible to determine the difference in the torque of the drive motor while the mobile body is traveling without stopping the traveling of the mobile body. be able to.

Further, in the autonomous moving body, the range on the traveling direction side from the center of the moving body body is defined as the traveling direction side range, and the range on the side opposite to the traveling direction side from the center of the moving body body is the opposite direction side range. and, when the difference in torque is equal to or greater than a preset threshold, the drive wheels of the drive motor having the small torque are positioned from the opposite direction side range to the advancing direction side range. The travel drive device may be controlled.
In this case, when the difference in torque is equal to or greater than a preset threshold value, the control device positions the drive wheels of the drive motor with small torque from the opposite direction side range to the advancing direction side range due to turning of the moving body main body. For this reason, the composite center of gravity of the center of gravity of the autonomous mobile body and the center of gravity of the load is not located in the range on the traveling direction side of the body of the mobile body. It can reduce the risk of body falls.

ADVANTAGE OF THE INVENTION According to this invention, the autonomous mobile body which can reduce the risk of overturning by sudden braking during driving|running|working can be provided, even if the center of gravity is biased by placing a load.

1 is a schematic side view of an autonomous mobile body according to an embodiment of the present invention; FIG. 1 is a schematic plan view of an autonomous mobile body according to an embodiment of the present invention; FIG. 1 is a configuration diagram showing a schematic configuration of an autonomous mobile body according to an embodiment of the present invention; FIG. FIG. 10 is a flow chart showing control of turning of the mobile body based on the bias of the load on the loading platform of the autonomous mobile body; (a) is a plan view showing a state in which the center of gravity of the load is located on the traveling direction side, and (b) is a plan view showing a state in which the center of gravity of the load is located on the opposite side of the traveling direction due to turning. (a) is a side view of the autonomous mobile body suddenly braked with the center of gravity of the load positioned on the opposite side of the traveling direction, and (b) is a side view of the autonomous mobile body suddenly braked with the center of gravity of the load positioned on the traveling direction side. 1 is a side view of an autonomous mobile body. FIG. FIG. 11 is a flowchart showing control of turning of a mobile body of an autonomous mobile body according to a modification;

An autonomous mobile body according to an embodiment of the present invention will be described below with reference to the drawings. The autonomous mobile body of this embodiment is an autonomous mobile body for transporting cargo that unmannedly transports cargo.

As shown in FIGS. 1 and 2 , the autonomous mobile body 10 includes a mobile body body 11 having a plurality of drive wheels 12 . A loading platform 13 is provided on the top of the mobile body 11 . The drive wheels 12 are omnidirectional wheels. An omnidirectional wheel is a wheel that rotates integrally with an axle (not shown) and that can move in the direction of the axis A of the axle, for example, an omni wheel. In this embodiment, the mobile body 11 is provided with four drive wheels 12 . When distinguishing the four drive wheels 12, they are referred to as a first drive wheel 12A, a second drive wheel 12B, a third drive wheel 12C, and a fourth drive wheel 12D. The first driving wheel 12A and the second driving wheel 12B are driving wheels on the front side of the mobile body 11, and the third driving wheel 12C and the fourth driving wheel 12D are driving wheels on the rear side of the mobile body 11. is a circle.

The autonomous moving body 10 can move in all directions while maintaining the orientation of the moving body main body 11 by controlling the number of rotations and the direction of rotation of the driving wheels 12 . In addition, the autonomous mobile body 10 can move while changing the orientation of the mobile body 11, and can also change the orientation of the mobile body 11 without moving. It is possible to perform a super pivot turn, which is a turn. As shown in FIG. 2, the center P of the mobile body 11 is the center of the pivot turn. It should be noted that the term “omnidirectional” as used herein refers to the moving direction on the road surface or floor surface on which the mobile body 11 travels.

A loading platform 13 provided on the upper portion of the moving body main body 11 is formed of a substantially rectangular flat surface. The longitudinal direction of the loading platform 13 forms an angle of 45° with the axis A of each axle. In FIGS. 1 and 2, the load W is indicated by a phantom line. The cargo W may be placed directly on the cargo bed 13, or a storage box such as a folding container box or cardboard box capable of accommodating articles may be placed on the cargo bed 13 as the cargo W.

As shown in FIG. 3 , the autonomous mobile body 10 includes a travel drive device 14 that drives drive wheels 12 . The travel drive device 14 includes a drive motor 15 for rotating the drive wheels 12 and a motor driver 16 for driving the drive motor 15 . A drive motor 15 and a motor driver 16 are provided for each drive wheel 12 . Therefore, the number of drive motors 15 and motor drivers 16 is the same as the number of drive wheels 12 . A motor driver 16 controls the rotation speed of the drive motor 15 according to a command from the control device 17 . The control device 17 can control the traveling direction of the mobile body 11 by controlling the rotation speed of the drive motor 15 via the motor driver 16 . Also, the motor driver 16 can detect the value of the current flowing through the drive motor 15 , and the torque of the drive motor 15 can be detected from the value of the current flowing through the drive motor 15 . Therefore, the motor driver 16 corresponds to a torque detection section that detects the torque of the drive motor 15 . The torque of the drive motor 15 is torque in rotation about the axis A as the center of rotation. Incidentally, the motor driver 16 always detects the current value of the driving motor 15 .

A sensor 18 and a control device 17 are mounted on the mobile body 11 . As the sensor 18, a sensor capable of causing the control device 17 to detect an obstacle is used. The sensor 18 of this embodiment is a laser range finder (LRF). A laser range finder is a range finder that measures the distance by irradiating a laser around and receiving the reflected light reflected from the part hit by the laser. In this embodiment, a two-dimensional laser range finder that irradiates a laser while changing the irradiation angle in the horizontal direction is used.

In this embodiment, as shown in FIGS. 1 and 2, sensors 18 are provided on the front and rear surfaces of the mobile body 11, respectively. When distinguishing between the sensors 18, one sensor 18 is referred to as the first sensor 18A and the other sensor 18 is referred to as the second sensor 18B. In this embodiment, one of the first sensor 18A and the second sensor 18B is positioned on the traveling direction side, and the other is positioned on the opposite side of the traveling direction. For example, in FIGS. 1 and 2, the first sensor 18A faces the front side of the autonomous mobile body 10 in the traveling direction, and the second sensor 18B faces the rear side, which is the opposite side of the traveling direction. In this case, when the autonomous mobile body 10 travels forward, the first sensor 18A emits laser light L and the second sensor 18B does not operate. 1 and 2, the traveling direction of the autonomous mobile body 10 is indicated by an outline arrow. Although not shown, when the autonomous mobile body 10 travels forward with the second sensor 18B facing the front of the autonomous mobile body 10, the second sensor 18B emits a laser beam, and the first sensor facing the rear 18A does not work. In the present embodiment, as shown in FIG. 2, the range on the traveling direction side from the center P of the moving body main body 11 is defined as the traveling direction side range, and the range on the side opposite to the traveling direction side from the center P of the moving body main body 11 is the opposite direction side range.

As shown in FIG. 3, the control device 17 includes a CPU 20 and a storage section 21 including RAM, ROM, and the like. The controller 17 may comprise dedicated hardware, such as an application specific integrated circuit (ASIC), for performing at least some of the various processes. Controller 17 may be configured as a circuit including one or more processors operating according to a computer program, one or more dedicated hardware circuits such as ASICs, or combinations thereof.

The storage unit 21 stores program codes or commands configured to cause the CPU 20 to execute processing. The storage unit 21 stores various programs for controlling the mobile body 11, and also stores an environment map related to the mobile space in which the mobile body 11 moves. The environment map is a map created while the mobile body 11 moves in the mobile space. A technique for estimating the self-location of the mobile body 11 using an environment map is called SLAM (Simultaneous Localization and Mapping). Storage 21, or computer-readable media, includes anything accessible by a general purpose or special purpose computer.

An operation unit 22 for operating the autonomous mobile body 10 is connected to the control device 17 . The operation unit 22 has a plurality of buttons (not shown) that can be operated to issue various instructions including a travel instruction to the autonomous mobile body 10 . Also, although not shown, the autonomous mobile body 10 is equipped with an annunciator. The alarm device is a device that issues an alarm to the surroundings when a specific condition is met, for example, when the autonomous mobile body 10 turns in the vicinity of the operator, and is controlled by the control device 17 . The alarm issued by the alarm is by sound or light.

By the way, when the load W is placed on the loading platform 13 , the composite center of gravity of the center of gravity of the autonomous mobile body 10 and the center of gravity of the load W is higher than the center of gravity of the autonomous mobile body 10 . Then, if the center of gravity of the load W is biased in the traveling direction side range, the combined center of gravity of the autonomous mobile body 10 and the center of gravity of the load W is higher than the center of gravity of the autonomous mobile body 10 and the traveling direction side range Located in The higher the combined center of gravity and the more biased towards the travel direction side range, the higher the risk of overturning due to sudden braking during running. Therefore, in the present embodiment, when the center of gravity of the load W is biased, the storage unit 21 of the control device 17 stores a program for turning the autonomous mobile body 10 according to the bias of the load W on the loading platform 13. stored. A procedure for turning the autonomous mobile body 10 according to the bias of the load W on the loading platform 13 is shown in the flow chart of FIG.

As shown in FIG. 4, first, the control device 17 determines whether or not the autonomous mobile body 10 has stopped (step S01). When the control device 17 determines that the autonomous mobile body 10 has stopped, the control device 17 turns the autonomous mobile body 10 to one side (step S02). If it is determined in step S01 that the autonomous mobile body 10 has not stopped, step S01 is repeated. Next, the current value of the driving motor 15 when the autonomous mobile body 10 turns is detected (step S03). At step S03, each motor driver 16 detects the value of the current flowing through each drive motor 15 respectively. Next, the torque of each drive motor 15 is calculated based on each current value (step S04). The turning for the detection of the current value is limited turning, and the turning angle may be about 10°, for example, within a range where the torque of each drive motor 15 can be calculated.

Next, the control device 17 determines whether or not the torque ratio R as the torque difference of the drive motor 15 is equal to or greater than the threshold value Rth (R≧Rth) (step S05). As the ratio R of the torque of the drive motor 15 of the four drive wheels 12A to 12D in the autonomous mobile body 10, the torque T1 of the drive motor 15 of the first drive wheel 12A and the drive motor 15 of the second drive wheel 12B and the ratio R (T1/T2) between the torque T2 of the drive motor 15 for the first drive wheel 12A and the torque T3 of the drive motor 15 for the third drive wheel 12C (T1/T3 ), the ratio R (T1/T4) between the torque T1 of the drive motor 15 for the first drive wheel 12A and the torque T4 of the drive motor 15 for the fourth drive wheel 12D, and the drive of the second drive wheel 12B The ratio R (T2/T3) between the torque T2 of the motor 15 and the torque T3 of the drive motor 15 for the third drive wheel 12C, the torque T2 of the drive motor 15 for the second drive wheel 12B, and the fourth drive A ratio R (T2/T4) between the torque T4 of the drive motor 15 for the wheel 12D, the torque T3 of the drive motor 15 for the third drive wheel 12C, and the torque T4 of the drive motor 15 for the fourth drive wheel 12D. and the ratio R(T3/T4).

The torque ratio R to be determined in this embodiment is the ratio R (T1/ T4). Similarly, the control device 17 determines whether the ratio R (T2/T3) between the torque T2 of the drive motor 15 of the second drive wheel 12B and the torque T3 of the third drive wheel 12C is equal to or greater than the threshold value Rth. . That is, the torque ratio R to be determined is the torque ratio between the drive motor 15 for the front drive wheel 12A (12B) and the drive motor 15 for the rear drive wheel 12C (12D). Note that both the torque ratio R (T1/T4) and the torque ratio R (T2/T3) may be calculated, or either one of the torque ratios R may be calculated. When the center of gravity of the load W on the loading platform 13 is biased, the drive motor 15 of the drive wheel 12 near the center of gravity of the load W has a large torque T during turning, and the drive motor 15 of the drive wheel 12 far from the center of gravity of the load W Torque T during turning becomes smaller. Note that the threshold value Rth is a preset value and is stored in the storage unit 21 .

In step S05, when the control device 17 determines that the torque ratio R is equal to or greater than the threshold value Rth (R≧Rth), the driving wheels 12 of the driving motor 15 with small torque are moved to the traveling direction side so as to change the direction of the loading platform 13. to one side (step S06). Specifically, the autonomous moving body 10 is rotated by 180° so that the center of gravity of the load W on the loading platform 13 is positioned in the range on the traveling direction side to the state in which the center of gravity of the load W is positioned in the range on the opposite direction side. Let At this time, the annunciator may issue an alarm along with turning. When the rotation of the autonomous mobile body 10 is completed, the process returns to step S01. If the controller 17 determines in step S05 that the ratio R of the torque of the drive motor 15 is not equal to or greater than the threshold Rth (R<Rth), the motor is turned in the opposite direction to the turning direction for detecting the current value. It is made to turn, and the autonomous mobile body 10 is returned to the original position before the limited turning (step S07).

Next, operation|movement of the autonomous mobile body 10 of this embodiment is demonstrated. The autonomous mobile body 10 emits a laser beam from the sensor 18, estimates its own position, creates an environmental map, and travels. The control device 17 performs obstacle avoidance processing to keep the distance between the autonomous mobile body 10 and the obstacle at a predetermined value or more so that the autonomous mobile body 10 and the obstacle do not come into contact with each other.

When the autonomous mobile body 10 arrives at the workplace where a worker (not shown) handles the load W, the autonomous mobile body 10 waits near the worker. As shown in FIG. 5A, in the autonomous mobile body 10, the first sensor 18A faces the direction of travel. The worker places the load W on the loading platform 13 and completes the cargo handling work. Then, the worker presses the button of the operation unit 22 of the autonomous mobile body 10 after finishing the cargo handling work, and instructs the autonomous mobile body 10 to start traveling.

By the way, for example, as shown in FIG. 5(a), the center of gravity Gw of the load W placed on the loading platform 13 may be biased toward the traveling direction side range. In this case, the position of the composite center of gravity (not shown) of the center of gravity Gv of the autonomous mobile body 10 and the center of gravity Gw of the load W in plan view is located in the traveling direction side range from the center of the autonomous mobile body 10 . Therefore, the load received by each driving wheel 12 differs according to the position of the combined center of gravity. Once the autonomous mobile body 10 moves (including minute movements when handling the load W) and stops while the center of gravity Gw of the load W is biased, it turns to detect the current value of the drive motor 15 . At this time, since the combined center of gravity of the center of gravity Gv of the autonomous mobile body 10 and the center of gravity Gw of the load W is located in the traveling direction range, the drive motor 15 closer to the combined center of gravity and the drive motor farther from the combined center of gravity There is a difference in torque from 15.

When the torque ratio R of the drive motor 15 is equal to or greater than the threshold value Rth, the autonomous mobile body 10 is rotated by 180°. As shown in FIG. 5B, in the autonomous mobile body 10 after turning, the composite center of gravity of the center of gravity Gv of the autonomous mobile body 10 and the center of gravity Gw of the load W and At this time, the second sensor 18B of the moving body 11 is positioned on the traveling direction side, but when the moving body 11 turns 180° to one side, the second sensor 18B becomes the sensor 18 for detecting an obstacle ahead, Since the first sensor 18A faces the rear, it stops operating. Then, the autonomous mobile body 10 starts autonomous traveling toward the destination while detecting an obstacle ahead by the second sensor 18B.

As shown in FIG. 6( a ), even if the autonomous mobile body 10 suddenly brakes during autonomous travel, the combined center of gravity is located in the opposite direction range, which is the opposite side of the traveling direction, so the load W and the autonomous mobile body 10 does not overturn in the direction of travel. Note that if the center of gravity Gw of the load W is biased to the traveling direction side range without performing a 180° turn, the combined center of gravity of the center of gravity Gv of the autonomous mobile body 10 and the center of gravity Gw of the load W is It is located higher than the center of gravity Gv and in the traveling direction side range. As shown in FIG. 6B, the higher the composite center of gravity and the more biased toward the traveling direction side range, the higher the risk of overturning the autonomous mobile body 10 in the traveling direction side due to the moment generated by sudden braking during traveling. .

When the torque ratio R of the drive motor 15 is not equal to or greater than the threshold value Rth, the autonomous mobile body 10 turns in the direction opposite to the turning direction for detecting the current value, and the autonomous mobile body 10 returns to the original position. Then, the autonomous mobile body 10 starts autonomous traveling toward the destination while detecting obstacles in the traveling direction by the first sensor 18A.

The autonomous mobile body 10 of this embodiment has the following effects.
(1) When the load W is placed on the loading platform 13, the motor driver 16 detects the torque of the drive motor 15, and the control device 17 synthesizes the center of gravity Gv of the autonomous mobile body 10 and the center of gravity Gw of the load W. A torque ratio R is obtained as a torque difference caused by the deviation of the center of gravity. When the torque ratio R is equal to or greater than a preset threshold value Rth, the control device 17 controls the traveling drive device so that the drive wheels 12 of the drive motor 15 with small torque are directed toward the direction of travel by turning the main body 11 of the mobile body. 14. Since the drive wheels 12 of the drive motor 15 with small torque are directed toward the direction of travel, the combined center of gravity of the center of gravity Gv of the autonomous mobile body 10 and the center of gravity Gw of the load W is not located on the side of the travel direction of the main body 11 of the mobile body. As a result, even if sudden braking is performed while the autonomous mobile body 10 is running, it is possible to reduce the risk of the autonomous mobile body 10 overturning in the traveling direction. In addition, since it is possible to determine whether or not the center of gravity Gw of the load is biased by the torque of the drive motor 15, there is no need to separately provide means for determining whether or not the center of gravity Gw of the load W is biased. Manufacturing costs can be suppressed.

(2) Since the control device 17 obtains the torque ratio R by turning after the autonomous mobile body 10 stops running or turning before the autonomous mobile body 10 starts running, Even if sudden braking is performed later, the risk of overturning of the autonomous mobile body 10 in the traveling direction can be reduced.

(3) The control device 17 can determine the difference in the torque of the drive motor 15 by the travel of the autonomous mobile body 10 without stopping the travel of the autonomous mobile body 10. It is possible to determine whether or not the center of gravity Gw of W is biased.

(4) Since the rotation of the moving body body 11 after the movement is stopped is within a turning range in which the torque of the driving motor 15 can be detected, the torque of the driving motor 15 can be detected by the limited turning of the moving body body 11. can. Therefore, it is possible to reduce the energy consumption required to determine the unevenness of the load W on the loading platform 13 .

(5) In the present embodiment, the range on the traveling direction side from the turning center P of the moving body main body 11 is defined as the traveling direction side range, and the range on the side opposite to the traveling direction side from the turning center P of the moving body main body 11. is the opposite direction side range. When the torque difference is equal to or greater than a preset threshold value, the control device 17 controls the travel drive device 14 so that the drive wheels 12 of the drive motor 15 with small torque are positioned from the opposite direction side range to the advancing direction side range. do. Therefore, when the torque ratio R is equal to or greater than a preset threshold value Rth, the control device 17 causes the driving wheels 12 of the drive motor 15 with small torque to move from the range on the opposite direction side to the range on the advancing direction side due to turning of the mobile body 11 . Located in For this reason, the combined center of gravity of the center of gravity Gv of the autonomous mobile body 10 and the center of gravity Gw of the load W is not located in the traveling direction side range of the mobile body 11, and even if the autonomous mobile body 10 is suddenly braked while traveling, The risk of overturning of the autonomous mobile body 10 in the traveling direction can be reduced.

(Modification)
Next, a modified example will be described. The autonomous moving body 10 according to the modification obtains the current value of the driving motor 15 and the torque of the driving motor 15 not only by turning after stopping but also by turning the moving body main body 11 during movement. Turning during movement corresponds to the case where the autonomous mobile body 10 travels on a turning route during movement to change course. In this case, the autonomous moving body 10 is turned according to the bias of the load W on the loading platform 13 according to the flowchart shown in FIG.

In the flow chart shown in FIG. 7, the control device 17 determines whether or not the autonomous mobile body 10 is traveling along a turning route (hereinafter referred to as a "specific turning route") (step S101). Since the control device 17 can detect that the autonomous mobile body 10 is turning during movement, it can determine whether or not the autonomous mobile body 10 is traveling on a specific turning route. In the specific turning path, turning is performed to change the traveling direction, so the torque indicating the bias of the center of gravity Gw of the load W of the drive motor 15 can be obtained. Next, the current value of the drive motor 15 in the specific turning path is detected (step S102). Incidentally, the motor driver 16 always detects the current value of the driving motor 15 . If it is determined in step S101 that the autonomous mobile body 10 is not traveling on the specific turning route, step S101 is repeated.

When the control device 17 determines whether or not the autonomous mobile body 10 is traveling along the specific turning path, it calculates the torque based on the detected current value (step S103). Next, it is determined whether or not the torque ratio R of the drive motor 15 is equal to or greater than the threshold value Rth (R≧Rth) (step S104). When the control device 17 determines that the torque ratio R is equal to or greater than the threshold value Rth (R≧Rth), when the autonomous mobile body 10 stops, the drive wheels 12 of the drive motor 15 with small torque move from the range on the opposite direction side. The autonomous mobile body 10 is reversed (turned) so as to head toward the traveling direction side range (step S105). When the controller 17 determines in step S105 that the torque ratio R of the drive motor 15 is not equal to or greater than the threshold Rth (R<Rth), the process returns to step S101.

In this modification, it is possible to determine whether or not the center of gravity Gw of the load W on the bed 13 is biased by turning after stopping, and also whether or not the center of gravity Gw of the load W is biased on the bed 13 on a specific turning path during movement. When the torque ratio R is equal to or greater than the threshold value Rth (R≧Rth) and the drive motor 15 stops after movement, the drive wheels 12 of the drive motor 15 with small torque are reversed (turned) in one direction toward the traveling direction. ).

The present invention is not limited to the above-described embodiments (including modifications), and various modifications are possible within the scope of the invention. For example, the following modifications may be made.

O In the above-mentioned embodiment (including the modification), the autonomous mobile body provided with four driving wheels was illustrated, but the driving wheels are not limited to four wheels. Three or more drive wheels may be provided.
(circle) although the ratio of a torque was used as a torque difference in said embodiment (a modification is included), it is not restricted to this. The torque difference may be, for example, a torque difference (amount). In this case, a threshold is set for the torque difference.
(circle) although said embodiment (including a modified example) presupposed that it turns after stopping in order to discriminate|determine the presence or absence of the bias|inclination of the gravity center of load, it is not restricted to this. For example, it may be determined whether or not the center of gravity of the load is biased only on a specific turning path during movement.
O In the above-described embodiments (including modifications), the turning direction is set to one after stopping in order to determine whether or not the load is uneven, but the present invention is not limited to this. The turning after stopping may be in the other direction. Also, the turning direction for changing the direction of the loading platform may be either one or the other.
O In the above-described embodiments (including modifications), the difference in the torque of the drive motor is obtained when a load with a biased center of gravity is placed on the platform, but the present invention is not limited to this. For example, even if a load whose center of gravity is not biased is placed at a biased position on the loading platform, and the combined center of gravity of the center of gravity of the autonomous mobile body and the center of gravity of the load is located in the range on the traveling direction side, the torque of the drive motor difference is required.
○ In the above embodiments (including modifications), when the autonomous moving body turns 180° in one direction so that the drive wheels of the drive motor with small torque move from the opposite direction side range of the moving body main body to the traveling direction side range, However, it is not limited to this. For example, the autonomous mobile body may turn in one direction or in the other direction within a range of 90 to 180 degrees, and the driving wheels of the drive motor with small torque are positioned in the traveling direction range after turning. do it.
(circle) in said embodiment (a modification is included), although the autonomous mobile body avoided the obstacle by a sensor and autonomously traveled, it does not restrict to this. For example, the autonomous mobile body may set an obstacle that satisfies a specific condition among the obstacles detected by the sensor as an obstacle to be followed instead of being regarded as an obstacle. In this case, the sensor corresponds to the object to be tracked, and the object to be tracked may be, for example, a worker who handles cargo with respect to the autonomous mobile body.

10 Autonomous moving body 11 Moving body main body 12 (12A, 12B, 12C, 12D) Drive wheel 13 Bed 14 Travel drive device 15 Drive motor 16 Motor driver (torque detection unit)
17 control device 18 (18A, 18B) sensor 20 CPU
21 storage unit 22 operation unit A axis (axle)
R Ratio Rth Threshold T1, T2, T3, T4 Torque W Load

Claims (4)

a mobile body;
a plurality of drive wheels provided on the mobile body;
a travel drive device that drives the drive wheels;
a control device that controls the traveling drive device,
In an autonomous mobile body that can run and turn in all directions,
a drive motor provided for each of the plurality of drive wheels;
a loading platform provided on the moving body main body;
a torque detection unit that detects the torque of the drive motor,
The control device obtains a difference in torque caused by unevenness of the load on the loading platform based on the torque of the drive motor detected by the torque detection unit,
When the difference in torque is equal to or greater than a preset threshold value, the traveling drive device is controlled so that the drive wheels of the drive motor having a small torque are oriented toward the moving direction of the moving body due to turning of the moving body. An autonomous mobile body characterized by: 2. The autonomous mobile body according to claim 1, wherein the control device obtains the difference in torque when the mobile body turns after it stops traveling or when it turns before it starts traveling. 2. The autonomous mobile body according to claim 1, wherein the control device obtains the difference in the torque from the running of the mobile body body. The range on the traveling direction side from the center of the moving body main body is defined as the traveling direction side range,
The range on the side opposite to the traveling direction side from the center of the moving body main body is defined as the opposite direction side range,
The control device is
When the difference in torque is equal to or greater than a preset threshold value, the travel drive device is controlled such that the drive wheels of the drive motor having the small torque are positioned from the opposite direction side range to the traveling direction side range. The autonomous mobile body according to any one of claims 1 to 3, characterized in that:

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