JP7452127B2 - Autonomous mobile device and autonomous mobile device control method - Google Patents

Description

The present invention relates to an autonomous mobile device and a method of controlling an autonomous mobile device.

In recent years, autonomous mobile devices that move autonomously, such as automated guided vehicles and autonomous mobile robots, have become widespread. Autonomous mobile devices may fall over due to slopes or differences in road surfaces. Therefore, an inclination that allows the autonomous mobile device to run is set in advance, and the autonomous mobile device avoids slopes that exceed the inclination.
BACKGROUND ART As an autonomous mobile device that detects road surface conditions and performs autonomous travel, there is a technique described in Patent Document 1, for example. This technology corrects the surrounding information of the autonomous mobile device detected by the surrounding information acquisition sensor based on the inclination state of the autonomous mobile device detected by the inclination sensor. This technology eliminates detection and performs driving control based on accurate surrounding information.

Japanese Patent Application Publication No. 2016-139389

In the above-mentioned conventional autonomous mobile device, the slope at which it is allowed to run is set in advance, but the slope at which the autonomous mobile device falls varies depending on the center of gravity and how the wheels are assembled, and the slope at which the autonomous mobile device falls depends on the permissible slope set in advance. It cannot be determined whether this is sufficient.
Additionally, if the allowable inclination is set with sufficient margin for the inclination at which the autonomous mobile device will actually fall, the range in which it can run will be restricted, making it difficult for the autonomous mobile device to fully demonstrate its performance. I can't.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an autonomous mobile device and a method for controlling the autonomous mobile device that can appropriately set an allowable inclination that allows travel and fully exhibit performance.

In order to solve the above problems, an autonomous mobile device according to one aspect of the present invention is provided with a pair of left and right wheels, a motor that rotates the wheels, a motor that rotates the wheels, and a motor that rotates the wheels. Using a vehicle body that can run in any direction, a current detection unit that detects a motor current flowing through the motor, and the motor current detected by the current detection unit, an overturning limit angle that is an angle at which the vehicle body overturns is determined. The vehicle includes an overturning limit angle estimating section for estimating the overturning limit angle, and a traveling control section for controlling the traveling of the vehicle body based on the overturning limit angle estimated by the overturning limit angle estimating section.
In this way, since the overturning limit angle is estimated based on the motor output, it is possible to appropriately estimate the overturning limit angle, which changes depending on the center of gravity and how the wheels are assembled. Therefore, it becomes possible to appropriately set the allowable inclination that allows the autonomous mobile device to travel, and it becomes possible to fully demonstrate its performance.

Moreover, in the above autonomous mobile device, the motor may be a direct drive motor. In this case, since a speed reducer is not used, the motor output can be detected with high precision from the motor current.
Furthermore, in the above autonomous mobile device, the tipping limit angle estimating unit includes a center of gravity estimating unit that estimates a center of gravity position of the vehicle body based on a ratio of loads of the left and right wheels, and the center of gravity position estimated by the center of gravity estimating unit The tipping limit angle may be estimated based on the center of gravity position and the distance between the centers of the wheels.
In this case, the position of the center of gravity of the vehicle body can be appropriately estimated, and the overturning limit angle can be estimated with high accuracy.

Further, in the above autonomous mobile device, the center of gravity estimating unit includes a first unit that estimates a center of gravity position of the vehicle body in the left-right direction based on the ratio of the loads estimated when the vehicle body runs on a horizontal road surface. the ratio of the load estimated when the vehicle body is run on a road surface inclined in the left-right direction, and the center-of-gravity position in the left-right direction estimated by the first center-of-gravity estimator. and a second center of gravity estimating section that estimates the height of the center of gravity of the vehicle body based on the height of the center of gravity of the vehicle body.
In this case, the position of the center of gravity in the left-right direction and the height of the center of gravity in the vertical direction of the vehicle body can be appropriately estimated.
Further, in the above autonomous mobile device, the center of gravity estimating unit estimates the load applied to the wheels by estimating the output shaft torque of the motor based on the motor current detected by the current detecting unit, and The center of gravity position of the vehicle body may be estimated based on the ratio of the loads of the wheels.
In this case, the position of the center of gravity of the vehicle body can be appropriately estimated, and the overturning limit angle can be estimated with high accuracy.

Furthermore, the above autonomous mobile device further includes a tilt detection section that detects a tilt state of the vehicle body, and the travel control section determines whether the vehicle body is tilted based on the tilt state of the vehicle body detected by the tilt detection section. If it is determined that the inclination exceeds the allowable angle set according to the overturning limit angle estimated by the overturning limit angle estimating unit, it is determined that the direction of travel is impossible, and the road surface existing in the direction of travel is determined to be impossible. The vehicle body may be controlled to travel in order to avoid the area. In this case, since the overturning margin can be determined based on the inclination state of the vehicle body, it is possible to appropriately determine whether or not the vehicle can run on the road surface on which the vehicle body has run aground.
Further, in the above autonomous mobile device, the inclination detection unit estimates the load applied to the wheels by estimating the output shaft torque of the motor based on the motor current detected by the current detection unit, and estimates the load applied to the wheels. The inclination state of the vehicle body may be detected based on the ratio of the loads of the wheels. In this case, it is possible to appropriately detect a gentle slope or running onto a bank, and it is possible to appropriately determine whether or not the vehicle can run on the road surface on which the vehicle has run.

The autonomous mobile device further includes a peripheral information acquisition unit that acquires peripheral information of the vehicle body, and the travel control unit controls the vehicle progress based on the peripheral information of the vehicle body detected by the peripheral information acquisition unit. If it is determined that there is a road surface with an inclination that exceeds the allowable angle set according to the tipping limit angle estimated by the tipping limit angle estimation unit in the direction, it is judged that the direction of travel is impossible, and the direction of travel is determined to be impossible. The vehicle body may be controlled to travel in order to avoid the road surface area that exists in the vehicle.
In this case, before the vehicle body runs onto a road surface with an inclination exceeding the allowable inclination, it is possible to avoid the road surface. Therefore, overturning of the vehicle body can be reliably avoided.

Furthermore, in the above autonomous mobile device, when the travel control unit determines that travel is not possible in the travel direction, the travel control unit causes the vehicle body to travel a predetermined distance in a direction opposite to the travel direction, and The driving route may be reset to avoid the road surface area that exists in the area. In this case, it is possible to appropriately set a travel route that avoids road surface areas where travel is impossible.

Further, a control method for an autonomous mobile device according to one aspect of the present invention includes a pair of left and right wheels, a motor that is provided corresponding to the pair of left and right wheels, and a motor that rotates the wheels, and a motor that rotates the wheels in an arbitrary direction. A method for controlling an autonomous mobile device, comprising: detecting a motor current flowing through the motor; and detecting an overturning angle, which is an angle at which the vehicle body overturns, using the detected motor current. The method includes a step of estimating a limit angle, and a step of controlling travel of the vehicle body based on the estimated tipping limit angle.
In this way, since the overturning limit angle is estimated based on the motor output, it is possible to appropriately estimate the overturning limit angle, which changes depending on the center of gravity and how the wheels are assembled. Therefore, it is possible to appropriately set the allowable inclination that allows the autonomous mobile device to travel, and it is possible to fully demonstrate its performance.

Furthermore, a control method for an autonomous mobile device according to one aspect of the present invention includes a pair of left and right wheels, a motor that is provided corresponding to the pair of left and right wheels, and that rotates the wheels, and a motor that rotates the wheels in an arbitrary direction. A method of controlling an autonomous mobile device comprising: a vehicle body capable of traveling on a vehicle body; The method includes the steps of estimating the overturning limit angle based on the center-to-center distance of the wheels, and controlling the vehicle body to travel based on the estimated overturning limit angle.
In this way, since the overturning limit angle is estimated based on the ratio of the loads of the left and right wheels, it is possible to appropriately estimate the overturning limit angle, which changes depending on the center of gravity and how the wheels are assembled. Therefore, it is possible to appropriately set the allowable inclination that allows the autonomous mobile device to travel, and it is possible to fully demonstrate its performance.

According to one aspect of the present invention, it is possible to appropriately set the permissible inclination that allows running, and to exhibit high running performance.

FIG. 1 is a diagram showing a schematic configuration of an autonomous mobile system. FIG. 2 is a functional block diagram of the travel control device and the motor drive device. FIG. 3 is a flowchart illustrating the operation of the autonomous mobile device. FIG. 4 is a flowchart showing the calibration processing procedure. FIG. 5 is a diagram illustrating the relationship between the load applied to the wheel and the position of the center of gravity. FIG. 6 is a diagram showing the load applied to the wheels. FIG. 7 is a diagram illustrating a method for calculating the center of gravity position. FIG. 8 is a diagram showing the overturning limit angle. FIG. 9 is a flowchart showing the running operation processing procedure. FIG. 10 is a functional block diagram of a travel control device and a motor drive device in the second embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
Note that the scope of the present invention is not limited to the following embodiments, and can be arbitrarily modified within the scope of the technical idea of the present invention.

(First embodiment)
FIG. 1 is a diagram showing a schematic configuration of an autonomous mobile system 100 including an autonomous mobile device (self-propelled vehicle) 1 in this embodiment.
As shown in FIG. 1, the autonomous mobile system 100 includes a self-propelled vehicle 1, an external computer 70, and an access point 72. The self-propelled vehicle 1 can be an automated guided vehicle (AGV) that autonomously travels within a factory or the like without a user performing a driving operation. The self-propelled vehicle 1 can communicate via wireless communication with an external computer 70 operated by a user via an access point 72 . The wireless communication standard is not particularly limited.
In this embodiment, a case will be explained in which the self-propelled vehicle 1 is an AGV, but the self-propelled vehicle 1 may be a differential two-wheel drive self-propelled body having wheels (drive wheels) using a motor as a drive source. For example, it may be an autonomous mobile robot capable of autonomous travel.

The self-propelled vehicle 1 includes wheels 2, auxiliary wheels 3, and a vehicle body 4, as shown in FIG. The wheels 2 and the auxiliary wheels 3 are rotatably supported by the vehicle body 4.
The wheels 2 are drive wheel units having a configuration in which tires are attached to a direct drive motor (DD motor) 5 having no reduction gear (structure), and rotate using the DD motor 5 as a drive source. The self-propelled vehicle 1 (vehicle body 4) is a differential two-wheel drive type moving device using a pair of left and right wheels 2 as driving wheels. The auxiliary wheels 3 are attached to the four corners of the vehicle body 4. Note that the number and mounting positions of the auxiliary wheels 3 are not limited to the configuration shown in FIG. 1.

The self-propelled vehicle 1 also includes a motor drive device 6 that drives the DD motor 5, as shown in FIG. The motor drive device 6 includes a drive circuit including a motor driver. The motor drive device 6 inputs a speed command value output from a travel control device 10, which will be described later, and drives and controls the DD motor 5 based on the speed command value.
The motor drive device 6 also includes a current sensor 63 (see FIG. 2) that detects the motor current of the DD motor 5. Further, the motor drive device 6 may include an inclination sensor 64 (see FIG. 2) that detects the inclination state of the self-propelled vehicle 1. Here, the tilt sensor 64 can be, for example, an acceleration sensor or a gyro sensor.

Further, the self-propelled vehicle 1 may include a plurality of laser range finders (LRF) 7 attached to the vehicle body 4, as shown in FIG. The LRF 7 is a sensor that measures the distance based on the time it takes for the laser to emit a laser beam, reflect it off an object, and return. The LRF 7 is a surrounding information acquisition sensor that acquires surrounding information of the self-propelled vehicle 1 by irradiating the circumference of the self-propelled vehicle 1 with a fan-shaped laser and measures the distance to surrounding objects.
Note that the number of LRFs 7 installed and their mounting positions are not limited to the configuration shown in FIG. 1. Further, the surrounding information acquisition sensor is not limited to LRF, and may be, for example, an ultrasonic sensor, a camera (CCD camera, CMOS camera), or the like.

The self-propelled vehicle 1 also includes a travel control device 10 that controls travel of the self-propelled vehicle 1, as shown in FIG. The travel control device 10 is a host device such as a board PC. The travel control device 10 has a wireless communication function, and receives operation commands input by a user from an external computer 70 via an access point 72, and transmits travel logs of the self-propelled object 1 to the external computer 70. can do. Here, the operation command that the travel control device 10 receives from the external computer 70 includes destination information, travel route information, etc. of the self-propelled vehicle 1.
For example, the travel control device 10 generates map information of an area in which the self-propelled vehicle 1 can travel based on surrounding information acquired by the LRF 7, and determines the traveling direction of the self-propelled vehicle 1. Then, the travel control device 10 generates a speed command value for traveling in the determined traveling direction, and outputs the generated speed command value to the motor drive device 6 as an operation command.

In this embodiment, in order to prevent the self-propelled vehicle 1 from running onto a road surface that is inclined in the left-right direction and overturning, the self-propelled vehicle 1 estimates the limit angle at which the self-propelled vehicle 1 will overturn (the overturning limit angle), Based on the tipping limit angle, travel control is performed to avoid slopes and steps that could result in a tipping position. Note that a road surface that is inclined in the left-right direction is a road surface on which the self-propelled vehicle 1 is inclined in the left-right direction when the self-propelled vehicle 1 is placed on it, and is a road surface that has a predetermined inclination in the left-right direction, or a road surface that is in contact with the left and right wheels. This includes steps with different ground heights.
In this embodiment, the self-propelled vehicle 1 uses the output of the DD motor 5, which is the drive source of the wheels 2, to estimate the overturning limit angle. Specifically, the ratio of the loads applied to the left and right wheels 2 is estimated by estimating the output shaft torque of the DD motor 5 from the motor current of the DD motor 5, and the center of gravity of the self-propelled vehicle 1 is determined using the estimated load ratio. Estimate location. Then, based on the position of the center of gravity of the self-propelled vehicle 1 and the distance between the centers of the wheels 2, the overturning limit angle is estimated.

FIG. 2 is a functional block diagram of the travel control device 10 and the motor drive device 6.
As shown in FIG. 2, the travel control device 10 includes an overturning limit angle estimating section 11, a route determining section 12, and an operation command section 13. The motor drive device 6 includes a forward/backward determining section 61 and a drive control section 62. Note that the motor drive device 6 includes the current sensor 63 and the tilt sensor 64 as described above.

The overturning limit angle estimation unit 11 estimates the overturning limit angle of the self-propelled vehicle 1 and outputs the estimated overturning limit angle to the motor drive device 6 . Specifically, the overturning limit angle estimation unit 11 estimates the center of gravity position of the self-propelled vehicle 1, and calculates the overturning limit angle based on the estimated center of gravity position and the distance between the centers of the left and right wheels 2 (tread width). presume.
Here, the position of the center of gravity in the left-right direction of the self-propelled vehicle 1 can be estimated based on the load ratio applied to the left and right wheels 2 when the self-propelled vehicle 1 is traveling on a flat road surface with no inclination. In addition, the height of the center of gravity of the self-propelled vehicle 1 is determined by the load ratio applied to the left and right wheels 2 when the self-propelled vehicle 1 is running on a road surface that is inclined in the left-right direction, and the center of gravity of the self-propelled vehicle in the left-right direction. It can be estimated based on the location. The method for estimating the tipping limit angle will be described in detail later.

The route determining unit 12 determines the traveling direction of the self-propelled vehicle 1 based on travel route information input by the user. At this time, the route determining unit 12 may detect obstacles based on the surrounding information acquired by the surrounding information acquisition sensor (LRF) 7, and may determine the traveling direction so as to avoid the detected obstacles.
Alternatively, the route determining unit 12 may estimate the self-position of the self-propelled vehicle 1, determine a travel route from the current position to the destination input by the user, and determine the traveling direction of the self-propelled vehicle 1. good. Any method can be used to estimate the self-position. For example, the self-position may be estimated using surrounding information acquired by the LRF 7. In addition, the self-position may be estimated using a signal emitted by a beacon etc. installed in the building or a GPS signal, or the rotational speed information of the left and right wheels 2 may be used to determine the moving direction of the self-propelled vehicle 1 and the starting point. The self-position may be estimated by calculating the moving distance.
The motion command section 13 generates a speed command value for each of the left and right wheels 2 to proceed in the direction of travel determined by the route determination section 12, and outputs this to the motor drive device 6 as a motion command.

The advance/retreat determining section 61 determines whether or not the road surface existing in the traveling direction is a road surface on which the vehicle can run, based on the overturning limit angle estimated by the overturning limit angle estimating section 11 . Specifically, if the forward/backward determining unit 61 determines that the inclination of the self-propelled vehicle 1 exceeds the permissible angle set according to the overturning limit angle based on the inclination state of the self-propelled vehicle 1, It is determined that the direction is impossible to travel.
Here, the tilted state of the self-propelled vehicle 1 can be calculated from the load ratio applied to the left and right wheels. Note that the tilting state of the self-propelled vehicle 1 may be detected by the tilt sensor 64. If the advance/retreat determining unit 61 determines that the traveling direction is impossible, it instructs the route determining unit 12 to reset the traveling route.

The drive control unit 62 drives and controls the left and right DD motors 5 so that the left and right wheels 2 rotate according to the speed command values, respectively, and causes the self-propelled vehicle 1 to travel.
In FIG. 2, the route determining section 12, the motion commanding section 13, the advance/retreat determining section 61, and the drive control section 62 correspond to the travel control section. Further, the current sensor 63 corresponds to a current detection section, and the tilt sensor 64 corresponds to a tilt detection section.

Next, the operation of the self-propelled vehicle 1 will be explained based on FIG. 3.
The process shown in FIG. 3 is started at the timing when the user presses a button or the like (not shown) instructing to start the self-propelled body 1 after loading luggage or the like onto the self-propelled vehicle 1. However, the start timing of the process in FIG. 3 is not limited to the above.
First, in step S1, the travel control device 10 acquires parameters input by the user by operating the external computer 70. The parameters include various information necessary for calibration (step S2) and traveling operation (step S3) of the self-propelled vehicle 1, which will be described later.

In step S2, the travel control device 10 performs the calibration process shown in FIG. 4 to estimate the overturning limit angle of the self-propelled vehicle 1.
In step S21 of FIG. 4, the operation command unit 13 (see FIG. 2) outputs an operation command to the motor drive device 6 so that the self-propelled vehicle 1 travels back and forth on a horizontal road surface. At this time, the operation command unit 13 may confirm that the horizontal state of the self-propelled vehicle 1 is detected by the inclination sensor 64, and then cause the self-propelled vehicle 1 to travel at a predetermined speed. Then, in step S22, the overturning limit angle estimating unit 11 estimates the weight of the self-propelled vehicle 1 ((W _L + W _R ) described later), and estimates the output shaft of the DD motor 5 used for the left and right wheels 2. The position of the center of gravity of the self-propelled vehicle 1 in the left-right direction is estimated from the difference in torque.
The output shaft torque of the motor can be calculated based on the motor current. In this embodiment, since the motor used for the wheel 2 is a DD motor, the relationship between the motor current i and the output shaft torque τ can be expressed by the following equation.
i=(1/Kt)・τ……(1)
Here, Kt is a torque constant.

In this way, by detecting the motor current i of the DD motor 5 used in the wheel 2, the output shaft torque τ of the DD motor 5 can be detected.
If the center of gravity of the self-propelled vehicle 1 is not biased in the left-right direction, the left and right output shaft torques are equal. Therefore, the overturning limit angle estimation unit 11 can estimate the loads W _L and W _R based on the left and right output shaft torques, and estimate where the center of gravity of the self-propelled vehicle 1 is located in the left and right direction. . For example, as shown in FIG. 5, since the loads W _L and W _R can be estimated from the output shaft torque, the distances a and b can be determined from the balance of moments around the center of gravity G. Here, the distance a is the distance between the grounding point of the left wheel 2L and the intersection point where a line g extending vertically from the center of gravity G intersects with the grounding surface. Further, the distance b is the distance between the grounding point of the right wheel 2R and the intersection point.

In step S23, the operation command unit 13 outputs an operation command to the motor drive device 6 so that the self-propelled vehicle 1 makes a sharp turn on the spot with the center of the vehicle body as an axis on a horizontal road surface, The process moves to step S24. In step S24, the overturning limit angle estimation unit 11 estimates the moment of inertia of the self-propelled vehicle 1.
In step S25, the operation command unit 13 outputs an operation command to the motor drive device 6 so that the self-propelled vehicle 1 runs on a road surface inclined in the left-right direction, and the process proceeds to step S26. In step S26, the overturning limit angle estimating unit 11 calculates the overturning limit angle of the self-propelled vehicle 1, and ends the calibration process of FIG. 4. Note that if the center of gravity position is near the center in the left-right direction, an overturning limit angle may be allowed, and if it is biased to either side, the overturning limit angle is calculated for each of rightward and leftward inclinations.

Hereinafter, the method of calculating the overturning limit angle in step S26 will be specifically explained.
The output shaft torque of the motor consists of the load moment of inertia of the tires and the friction torque from the road surface. The load moment of inertia of a tire can be calculated from its structure, and the friction torque is proportional to the load applied to the tire. Therefore, the load applied to the wheel 2 can be estimated from the output shaft torque of the left and right wheels calculated based on the motor current.
For example, as shown in FIG. 6, when the self-propelled vehicle 1 is driven on a step so as to be tilted in the roll direction, the load _WR applied to the right wheel 2R is larger than the load _WL applied to the left wheel 2L. The ratio of the loads _WR and _WR applied to the left and right wheels 2L and 2R at this time is equal to the ratio of the distances a and b shown in FIG.
W _L /W _R =b/a……(2)
Here, the distance a is a line extending vertically from the grounding point 44 of the left wheel 2L and the center of gravity G when the self-propelled vehicle 1 is riding on the inclined surface 43 at an angle θ with respect to the horizontal surface 42 (Fig. 7 This is the distance between the intersection point 45 where the straight line vv) intersects with the inclined surface 43. Further, the distance b is the distance between the grounding point 46 of the right wheel 2R and the intersection 45.

In step S26 of FIG. 4, the overturning limit angle estimating unit 11 uses the load ratio applied to the left and right wheels 2L, 2R when the self-propelled vehicle 1 is running on a road surface inclined in the left-right direction. The position of the center of gravity G of the vehicle 1 (height h of the center of gravity in FIG. 7) is estimated, and the overturning limit angle is estimated based on the estimated position of the center of gravity G.
First, the overturning limit angle estimating unit 11 uses the inclination sensor 64 to detect the inclination θ of the self-propelled vehicle 1 when the self-propelled vehicle 1 is traveling on a road surface that is inclined in the left-right direction. Note that if the angle of the road surface is known, it is not necessary to detect the inclination θ by the inclination sensor 64. Then, as shown in FIG. 7, the overturning limit angle estimating unit 11 calculates the inclination θ of the self-propelled vehicle 1, the load ratio (distance a, b) applied to the left and right wheels 2L, 2R, and the left-right direction of the self-propelled vehicle 1. The center of gravity height h of the self-propelled vehicle 1 is estimated based on the center of gravity position (straight line gg in FIG. 7). Here, the position of the center of gravity of the self-propelled vehicle 1 in the left-right direction is estimated in step S22 of FIG. 4. That is, the tipping limit angle estimating unit 11 estimates the intersection of the straight line gg and the straight line vv shown in FIG. 7 as the position of the center of gravity G, and estimates the height h of the center of gravity of the self-propelled vehicle 1.

Next, the overturning limit angle estimation unit 11 estimates the overturning limit angle of the self-propelled vehicle 1 using the position of the center of gravity in the left-right direction and the height h of the center of gravity of the self-propelled vehicle 1 .
The overturning limit angle of the self-propelled vehicle 1 is the angle at which the load applied to one wheel becomes zero, and as shown in FIG. 8, the overturning limit angle θ _R of the self-propelled vehicle 1 to the right is the This is the inclination of the self-propelled vehicle 1 when the center of gravity G is located directly above the grounding point 46 of the right wheel 2R.
In other words, the rightward overturning limit angle θ _R is determined by the distance L _R in the left-right direction of the self-propelled vehicle 1 from the center of gravity G to the grounding point 46 of the right wheel 2R, and the height h of the center of gravity of the self-propelled vehicle 1. It can be estimated based on Similarly, the leftward overturning limit angle θ _L (not shown) is determined by the distance L _L in the left-right direction of the self-propelled vehicle 1 from the center of gravity G to the grounding point 44 of the left wheel 2L, and the height of the center of gravity of the self-propelled vehicle 1. It can be estimated based on h. Here, the sum of the distances L _L and L _R is equal to the distance (tread width) L between the left and right wheels 2L and 2R of the self-propelled vehicle 1.

For example, if the center of gravity of the self-propelled vehicle 1 is not biased in the left-right direction, the rightward overturning limit angle θ _R of the self-propelled vehicle 1 can be expressed by the following equation.
θ _R = tan ^-1 (L _R /h) = tan ^-1 (L/2h) ...... (3)
In step S26, the center of gravity height h may be estimated a plurality of times, and the final tipping limit angle estimation result may be obtained based on the plurality of estimation results of the center of gravity height h. In this case, the inclination angle of the road surface on which the self-propelled vehicle 1 travels may be made different each time.
The processing in FIG. 4 corresponds to the function of the center of gravity estimating section, and in detail, the processing in steps S21 and S22 corresponds to the function of the first center of gravity estimating section, and the processing in steps S25 and S26 corresponds to the function of the second center of gravity estimating section. It corresponds to the function of the center of gravity estimator.

Returning to FIG. 3, in step S3, the motor drive device 6 drives and controls the DD motor 5 based on the operation command from the travel control device 10, and causes the self-propelled vehicle 1 to travel toward the destination. At this time, the motor drive device 6 executes the traveling operation process shown in FIG. 9 .
In step S31 in FIG. 9, the advance/retreat determining unit 61 determines whether or not the traveling direction is possible while the self-propelled vehicle 1 is traveling based on the operation command from the travel control device 10.
Specifically, the advance/retreat determining unit 61 estimates the load ratio applied to the left and right wheels by estimating the output shaft torque of the DD motor 5 from the motor current detected by the current sensor 63, and determines the tilting state of the self-propelled vehicle 1. Detect. Then, if the forward/backward determining unit 61 determines that the inclination of the self-propelled vehicle 1 exceeds the permissible angle set according to the overturning limit angle based on the inclination state of the self-propelled vehicle 1, the traveling direction is It is determined that it is impossible.

Here, the allowable angle is set to a value less than the overturning limit angle of the self-propelled vehicle 1. Further, the allowable angles are set for each of the left and right sides according to the rightward overturning limit angle θ _R and the leftward overturning limit angle θ _L . If the self-propelled vehicle 1 is tilted to the right, it is determined whether or not the self-propelled vehicle 1 can run in the forward direction based on the permissible angle set according to the rightward overturning limit angle θ _R , and the self-propelled vehicle 1 If the vehicle is tilted to the left, it is determined whether or not the vehicle can travel in the forward direction based on the permissible angle set according to the leftward overturning limit angle θ _L.
Note that the tilting state of the self-propelled vehicle 1 may be detected by the tilt sensor 64. By using the tilt sensor 64, the tilted state of the self-propelled vehicle 1 can be easily detected.

When the advance/retreat determining unit 61 determines in step S31 that the traveling direction is travelable, the process proceeds to step S32, where the self-propelled vehicle 1 is controlled to move forward, and the process proceeds to step S33. Note that the description will be made assuming that the traveling direction is the forward direction of the self-propelled vehicle 1.
In step S33, the motor drive device 6 determines whether the self-propelled vehicle 1 has reached the destination. For example, when the motor drive device 6 receives an operation command to stop the self-propelled vehicle 1 from the travel control device 10, it can determine that the destination has been reached. Then, if the motor drive device 6 determines that the self-propelled vehicle 1 has not reached the destination, the process returns to step S31, and if it determines that the self-propelled vehicle 1 has reached the destination, the motor drive device 6 returns the self-propelled vehicle 1 to step S31. 1 is stopped, and the traveling operation process of FIG. 9 is completed.

On the other hand, if the advance/retreat determining unit 61 determines in step S31 that traveling is not possible in the traveling direction, the process proceeds to step S34, and travel control is performed so that the self-propelled vehicle 1 travels a predetermined distance in the opposite direction to the traveling direction. do. Here, since the traveling direction of the self-propelled vehicle 1 is the forward direction of the self-propelled vehicle 1, in this step S24, travel control is performed to move the self-propelled vehicle 1 backward by a predetermined distance.
In step S35, the advance/retreat determining section 61 transmits an instruction to reset the traveling route of the self-propelled vehicle 1 to the route determining section 12 of the traveling control device 10, and the process returns to step S31. As a result, the route determining unit 12 resets the travel route for heading to the destination while avoiding the road surface area existing in the traveling direction of the self-propelled vehicle 1, and the operation command unit 13 resets the travel route on the re-set travel route. An operation command for traveling along the road is output to the motor drive device 6. Note that if the motor drive device 6 is capable of resetting the travel route, the motor drive device 6 may reset the travel route.

As described above, in this embodiment, before the self-propelled vehicle 1 is actually used, the inclination (overturn limit angle) of the self-propelled vehicle 1 until it falls is estimated through calibration processing. When the self-propelled vehicle 1 is actually used, travel control is performed based on the estimated overturning limit angle. Specifically, the tilting state of the self-propelled vehicle 1 is detected by estimating the load applied to the left and right wheels from the motor current, and the margin of tilt before the self-propelled vehicle 1 falls is determined. In other words, if it is determined that the inclination of the self-propelled vehicle 1 exceeds the permissible angle set according to the overturning limit angle, it is determined that the direction of travel is impossible, and the road surface area existing in the direction of travel is determined to be Control your driving to avoid this.

In this way, since the margin of inclination from the motor output to the point of overturning is determined, it is possible to appropriately determine whether or not the self-propelled vehicle 1 is running onto a road surface where there is a possibility of overturning. Therefore, driving control can be appropriately performed to prevent the self-propelled vehicle 1 from falling over while driving.
As a method of determining whether or not the vehicle can run, there is a method of detecting the inclination using a surrounding information acquisition sensor, an inclination sensor, etc., but if the inclination is gently different on the left and right sides, there is a risk that the vehicle may run onto the bank. In this embodiment, since the load on the left and right wheels is estimated using the motor output, it is possible to appropriately detect a gentle slope or running onto a bank, and it is possible to appropriately determine whether it is possible to drive on the road surface on which the vehicle has run. can.
If the vehicle cannot travel in the direction of travel, the self-propelled vehicle 1 can be moved backwards and a travel route that avoids road areas existing in the direction of travel can be re-established. In this case, since the traveling route can be reset using the position where the self-propelled vehicle 1 has been moved backward as the starting point, it is possible to appropriately set a traveling route that avoids road surface areas where it is impossible to travel.

Furthermore, in this embodiment, motor current is used when estimating the overturning limit angle. Specifically, the load applied to the wheels 2 is estimated by estimating the output shaft torque of the DD motor 5 based on the motor current, and the center of gravity position of the self-propelled vehicle 1 is determined based on the ratio of the loads of the left and right wheels 2. Estimate. Then, the tipping limit angle is estimated based on the estimated center of gravity position and the center-to-center distance of the wheels 2.
In this way, since the motor output is used, it is possible to appropriately estimate the overturning limit angle, which changes depending on the center of gravity and how the wheels are assembled.

In conventional autonomous mobile devices, the allowable incline that the vehicle is allowed to travel on is set in advance, and the allowable incline is usually set with enough margin to accommodate changes such as a rise in the center of gravity. . However, if the allowable inclination is set with a sufficient margin in relation to the actual overturning limit angle, even if the road surface is drivable, it may be determined that it is impossible to drive and avoid the situation. Unable to fully demonstrate performance.
In contrast, in the present embodiment, even if the center of gravity changes due to loading cargo on the self-propelled vehicle 1, the position of the center of gravity of the self-propelled vehicle 1 can be appropriately estimated, so that the self-propelled vehicle 1 can move easily. It becomes possible to appropriately set the permissible inclination that allows for this, depending on the actual overturning limit angle. In other words, it is possible to set the range of permissible inclination to be larger than that of the prior art, and it is possible to fully demonstrate the performance.

Furthermore, in this embodiment, a direct drive motor (DD motor) can be used as a drive source for rotating the wheels. In this case, since a speed reducer is not used, the relationship between the motor current i and the output shaft torque τ can be expressed by the above equation (1).
On the other hand, in the case of a servo motor+reducer configuration, the relationship between the motor current i and the output shaft torque τ is expressed by the following equation.
i=(1/η・Kt)・τ……(4)
Here, η is the reduction ratio.
By using a DD motor as a drive source to rotate the wheels, the motor current i for a certain output shaft torque τ becomes large, and the effects of motor switching and surrounding noise are reduced, improving detection accuracy. can. In other words, compared to a configuration using a servo motor + reducer, it is possible to estimate the motor output shaft torque τ from the motor current i with high accuracy, and as a result, the overturning limit angle can be estimated and the tilting state of the self-propelled vehicle 1 can be estimated. can be detected with high precision. Therefore, travel control for preventing the self-propelled vehicle 1 from falling can be appropriately performed.

(Second embodiment)
Next, a second embodiment of the present invention will be described.
In the first embodiment described above, a case has been described in which it is determined whether the vehicle can travel in the traveling direction based on the tilt state detected by the current sensor or the tilt sensor. In this second embodiment, a case will be described in which it is determined whether or not the vehicle can travel in the traveling direction based on surrounding information detected by a surrounding information acquisition sensor.

FIG. 10 is a functional block diagram of the travel control device 10 and the motor drive device 6 in this embodiment. In FIG. 10, parts having the same configuration as those in FIG. 2 are designated by the same reference numerals as in FIG. 2, and the following description will focus on parts with different configurations.
As shown in FIG. 10, the travel control device 10 includes an overturning limit angle estimating section 11, a route determining section 12, an operation command section 13, and a forward/retreat determining section 14. The motor drive device 6 includes a drive control section 62.

Similar to the advance/retreat determining section 61 in the first embodiment described above, the advance/retreat determining section 14 determines whether the road surface existing in the traveling direction is a road surface on which the vehicle can run, based on the overturn limit angle estimated by the overturn limit angle estimator 11. Determine whether or not. However, the advance/retreat determining section 14 differs from the advance/retreat determining section 61 in that it uses peripheral information detected by the peripheral information acquisition sensor (LRF) 7 to determine whether or not the vehicle can travel in the traveling direction.
Note that the laser range finder (LRF) 7 in FIG. 10 corresponds to a peripheral information acquisition unit, unlike the application of the first embodiment (obstacle detection and self-position estimation).

That is, in step S31 of FIG. 9, the advance/retreat determining unit 14 detects the inclination of the road surface existing in the traveling direction of the self-propelled vehicle 1 based on the surrounding information acquired by the LRF 7. If it is determined that there is a road surface in the direction of travel of the self-propelled vehicle 1 that has an inclination exceeding the allowable angle set according to the overturn limit angle, it is determined that the direction of travel is impossible, and the process moves to step S34. do.

As in the first embodiment described above, in the case of a configuration in which the current sensor 63 and the tilt sensor 64 are used to detect the inclination of the self-propelled vehicle 1 and determine whether or not the self-propelled vehicle 1 can travel in the traveling direction, the self-propelled vehicle 1 actually Judgment cannot be made unless you run onto a slope or step. On the other hand, in this embodiment, the height and slope state of the road surface existing in the traveling direction of the self-propelled vehicle 1 can be acquired using the LRF 7, so that the self-propelled vehicle 1 runs onto a road surface with an inclination. It is possible to determine whether or not the vehicle can be driven beforehand. Therefore, it is possible to avoid in advance road surface areas having inclinations exceeding the permissible angle.

In addition, in this embodiment, when it is determined in step S31 of FIG. 9 that the traveling direction is impossible, the self-propelled vehicle 1 is moved backward in step S34, and then the traveling route is reset in step S35. explained. However, the process of step S34 may be omitted. That is, if it is determined that the traveling direction is impossible, the traveling route may be reset without moving the self-propelled vehicle 1 backward.

(Modified example)
In each of the embodiments described above, a case has been described in which the motor that rotates the wheel 2 is a direct drive motor (DD motor). However, a configuration using a servo motor and a reduction gear may also be used. However, as described above, the DD motor is preferable because it has better detection accuracy of the output shaft torque of the motor.
Further, each of the above embodiments can be implemented in combination. That is, the determination of whether or not the vehicle can travel in the direction of travel based on the surrounding information acquired by the LRF 7 and the determination of whether or not the vehicle can travel in the direction of travel based on the inclination information of the self-propelled vehicle 1 may be performed in combination. In this case, it becomes possible to more reliably avoid overturning of the self-propelled vehicle 1.
Furthermore, the same overturning limit angle estimating unit 11 as in the first embodiment can be applied to the longitudinal direction (uphill running or downhill running) of the self-propelled vehicle 1.

DESCRIPTION OF SYMBOLS 1...Autonomous moving device (self-propelled vehicle), 2...Wheel, 3...Auxiliary wheel, 4...Vehicle body, 5...Direct drive motor (DD motor), 6...Motor drive device, 7...Laser range finder, 10...Travel control Device, 11... Falling limit angle estimating unit, 12... Route determining unit, 13... Movement command unit, 14... Advance/retreat determining unit, 61... Advance/retreat determining unit, 62... Drive control unit, 63... Current sensor, 64... Inclination sensor

Claims (10)

A pair of left and right wheels,
a motor that is provided corresponding to the pair of left and right wheels and rotates the wheels;
a vehicle body that can run in any direction with the wheels;
a current detection unit that detects a motor current flowing through the motor;
an overturning limit angle estimation unit that estimates a overturning limit angle, which is an angle at which the vehicle body overturns, using the motor current detected by the current detection unit;
a travel control section that controls traveling of the vehicle body based on the overturn limit angle estimated by the overturn limit angle estimation section;
a tilt detection unit that detects a tilt state of the vehicle body,
The travel control section includes:
Based on the inclination state of the vehicle body detected by the inclination detection unit, it is determined that the inclination of the vehicle body exceeds a permissible angle set according to the overturn limit angle estimated by the overturn limit angle estimation unit. In this case, the autonomous mobile device determines that the vehicle cannot travel in the direction of travel, and controls the vehicle body to avoid a road surface area existing in the direction of travel . The autonomous mobile device according to claim 1, wherein the motor is a direct drive motor. The tipping limit angle estimating unit includes:
comprising a center of gravity estimating unit that estimates a center of gravity position of the vehicle body based on a ratio of loads of the left and right wheels;
The autonomous mobile device according to claim 1 or 2, wherein the overturning limit angle is estimated based on the center-of-gravity position estimated by the center-of-gravity estimation unit and the center-to-center distance of the wheels. The center of gravity estimating unit is
a first center of gravity estimating unit that estimates a center of gravity position of the vehicle body in the left-right direction based on the ratio of the loads estimated when the vehicle body is running on a horizontal road surface;
of the vehicle body based on the ratio of the loads estimated when the vehicle body is run on a road surface inclined in the left-right direction and the center of gravity position in the left-right direction estimated by the first center of gravity estimating section. The autonomous mobile device according to claim 3, further comprising a second center of gravity estimating section that estimates the height of the center of gravity. The center of gravity estimating unit estimates the load applied to the wheel by estimating the output shaft torque of the motor based on the motor current detected by the current detecting unit,
The autonomous mobile device according to claim 3 or 4, wherein the center of gravity position of the vehicle body is estimated based on a ratio of loads between the left and right wheels. The inclination detection section is
The load applied to the wheels is estimated by estimating the output shaft torque of the motor based on the motor current detected by the current detection section, and the tilting state of the vehicle body is determined based on the ratio of the loads of the left and right wheels. The autonomous mobile device according to any one of claims 1 to 5, wherein the autonomous mobile device detects. further comprising a peripheral information acquisition unit that acquires peripheral information of the vehicle body,
The travel control section is
Based on the surrounding information of the vehicle body detected by the surrounding information acquisition unit, there is a road surface in the direction of travel that has an inclination exceeding a permissible angle set according to the overturning limit angle estimated by the overturning limit angle estimating unit. If it is determined that the vehicle is traveling in the direction of travel, the vehicle body is determined to be unable to travel in the direction of travel, and the vehicle body is controlled to travel in order to avoid a road surface area that exists in the direction of travel. The autonomous mobile device described. The travel control section includes:
If it is determined that the traveling direction is impossible, the vehicle body is caused to travel a predetermined distance in a direction opposite to the traveling direction, and a traveling route that avoids a road surface area existing in the traveling direction is reset. An autonomous mobile device according to any one of claims 1 to 7. A method for controlling an autonomous mobile device comprising a pair of left and right wheels, a motor that is provided corresponding to the pair of left and right wheels and rotates the wheels, and a vehicle body that can travel in any direction using the wheels. hand,
detecting a motor current flowing through the motor;
estimating an overturning limit angle, which is an angle at which the vehicle body overturns, using the detected motor current;
controlling the traveling of the vehicle body based on the estimated overturning limit angle;
Detecting a tilted state of the vehicle body,
In the step of controlling the traveling of the vehicle body,
Based on the detected tilt state of the vehicle body, if it is determined that the tilt of the vehicle body exceeds an allowable angle set according to the overturning limit angle, it is determined that the traveling direction is impossible. A method for controlling an autonomous mobile device, characterized in that the vehicle body is controlled to travel in order to avoid a road surface area that exists in the direction of travel . A method for controlling an autonomous mobile device comprising a pair of left and right wheels, a motor that is provided corresponding to the pair of left and right wheels and rotates the wheels, and a vehicle body that can travel in any direction using the wheels. hand,
estimating the position of the center of gravity of the vehicle body based on the ratio of the loads of the left and right wheels;
estimating a tipping limit angle based on the estimated center of gravity position and the center-to-center distance of the wheels;
controlling the traveling of the vehicle body based on the estimated overturning limit angle;
Detecting a tilted state of the vehicle body,
In the step of controlling the traveling of the vehicle body,
Based on the detected tilt state of the vehicle body, if it is determined that the tilt of the vehicle body exceeds an allowable angle set according to the overturning limit angle, it is determined that the traveling direction is impossible. A method for controlling an autonomous mobile device, characterized in that the vehicle body is controlled to travel in order to avoid a road surface area that exists in the direction of travel .

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