JP7330544B2 - Moving body and control method - Google Patents

Description

The present invention relates to a moving object and control method. This application claims priority from US Provisional Patent Application No. 62/960,699 filed in the US on January 14, 2020, the contents of which are hereby incorporated by reference.

2. Description of the Related Art In recent years, the development of autonomous mobile bodies (eg, autonomous mobile robots) such as unmanned vehicles has been active. In the case of an unmanned vehicle traveling on a roadway, there are fixed places and rules to operate, such as roads, lanes, traffic lights, and the like. On the other hand, there are also robots that must move around static and dynamic obstacles without special guidance in an environment where humans come and go. For example, security/guidance robots, cleaning robots, luggage-carrying robots, and personal mobility (transporting a single person). In the case of a robot that moves in such an environment where humans come and go, a flexible movement control that can move in a more complicated environment without interfering with human activity is required.
A robot that moves in an environment where humans come and go has size and shape restrictions. For example, indoors, it is better for robots to be able to use doors, elevators, etc. that humans use, so the width of the robot must be less than the width of the human body. In addition, since the vehicle runs in an environment where humans exist, it must have a certain height that is easily recognized by humans. Therefore, security/guidance robots and the like often have a vertically elongated shape that conforms to the human body shape.

For this reason, robots that move in an environment where people come and go are often configured with a differential two-wheel mechanism that is not complicated and can be easily downsized. The two-wheel differential mechanism attaches two left and right wheels to the robot, drives them independently, and changes the direction of the course by creating a difference in the rotational speed of the left and right wheels. For example, Patent Literature 1 discloses a mobile system that moves with a differential two-wheel mechanism.

Japanese Patent Application Laid-Open No. 2019-105901

In environments where people come and go, there are static obstacles such as desks, chairs, and walls, and dynamic obstacles such as walking humans. For this reason, the robot needs to avoid moving obstacles quickly and change its movement path. However, in the two-wheel differential mechanism, even if the wheel rotation speed of the left and right wheels is changed while the motor is operating at high speed, the response is slow and the vehicle can only make a wide turn slowly.
When considering the operation of robots in spaces where people gather and disperse, the inventors found that it is difficult to avoid obstacles in spaces where people gather and that this increases the frequency of stopping mobile robots. I found a problem.
In addition, this problem is that the ability to follow the target trajectory of the mobile robot equipped with two differential wheels depends on the control by the motor, and due to the characteristics of the DC motor, the torque decreases at high rotation speeds. It has been found that the factor is the structural problem that the ability to follow the trajectory is degraded.
Due to these issues, robots are not currently operating in densely populated spaces such as city centers.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a moving body and control method capable of improving the ability to follow a target trajectory.

(1) One aspect of the present invention is an autonomous mobile body, which includes a main body, two drive wheels driven by an electric motor to move the main body, and a difference in rotational angular velocity between the drive wheels. A differential mechanism that turns the main body by means of, a steering mechanism that changes the steering angle of the driving wheels for each driving wheel, and a control that simultaneously controls the differential mechanism and the steering mechanism along a target trajectory wherein the control unit determines a target azimuth angular velocity of the drive wheels so as to eliminate an orientation error between a first target point on the target trajectory and an orientation of the main body, and determines a second target on the target trajectory. A target rudder angle of the driving wheels is determined toward a point, and the azimuth error, the target azimuth angular velocity and the target rudder angle are set, the azimuth error is α, the first target point is (xt1, yt1), and the second target point is (xt2, yt2), where Ψ is the yaw angle, ωd is the target yaw rate, L is the tracking length, v is the forward speed, and δ is the rudder steering angle (steer angle). decide according to
α = arctan ((yt1-y)/(xt1-x))-Ψ (1)
ωd=(1/L)vα (2)
δ = arctan ((yt2-y)/(xt2-x))-Ψ (3)
It is mobile.
(2) In one aspect of the present invention, in the moving body according to (1) above, the differential mechanism changes a steering angle with a position within the contact surface of the driving wheel as a turning center for each of the driving wheels. Let
( 3 ) In one aspect of the present invention, in the mobile object according to ( 1 ) above, the control unit includes route information indicating a target route of the mobile object, a moving speed of the driving wheels, and a turning speed of the main body. and the steering angle of the driving wheels, the target rotational angular velocity of the driving wheels and the target steering angle of the driving wheels are calculated.
( 4 ) In one aspect of the present invention, in the moving body according to any one of (1) to ( 3 ) above, the projected area of the main body when viewed in the movement direction is the above-described Larger than the projected area of the main body.
( 5 ) In one aspect of the present invention, in the mobile body according to any one of (1) to ( 4 ) above, the height is longer than the width of the shaft that connects the two drive wheels.
( 6 ) In one aspect of the present invention, the moving body according to any one of (1) to ( 5 ) above further includes an attitude control device that controls the attitude of the main body.
( 7 ) One aspect of the present invention is a method for controlling an autonomous mobile body, in which a control unit adjusts the rotational angular velocities of two driving wheels based on course information indicating a target course to a differential mechanism . turning the main body by applying a difference; causing the steering mechanism to change the rudder angle of each of the drive wheels based on the course information ; simultaneously controlling the differential mechanism and the steering mechanism along a trajectory; and determining a target steering angle of the driving wheels toward the second target point on the target trajectory; , the heading error is α, the first target point is (xt1, yt1), the second target point is (xt2, yt2), Ψ is the yaw angle, ωd is the target yaw rate, L is the tracking length, v is the forward speed, and δ is Determining the turning angle (steer angle) of the rudder according to formulas (1) to (3);
α = arctan ((yt1-y)/(xt1-x))-Ψ (1)
ωd=(1/L)vα (2)
δ = arctan ((yt2-y)/(xt2-x))-Ψ (3)
is a control method having

According to the embodiments of the present invention, it is possible to provide a moving body and control method capable of improving the ability to follow a target trajectory.

1 is a schematic diagram of a moving object according to an embodiment of the present invention; FIG. It is a figure which shows an example of the driving method of the moving body which concerns on this embodiment. 1 is a block diagram showing a mobile object according to an embodiment; FIG. It is a figure which shows an example of operation|movement of the mobile body which concerns on this embodiment. It is a figure which shows an example of the trajectory tracking performance of a moving body. It is a figure which shows an example of the track|trajectory tracking performance of the moving body which concerns on this embodiment. It is a figure which shows an example of steering angle control of the mobile body which concerns on this embodiment. figure It is a figure for demonstrating an example of a model formula. It is a figure for demonstrating an example of a model formula. FIG. 4 is a diagram showing an example of a trajectory of a moving object; It is a figure which shows an example of the locus|trajectory of the mobile body which concerns on this embodiment. It is a figure which shows the other example of the moving body which concerns on this embodiment. FIG. 11 is an external view of a moving object according to a modification of the embodiment; It is a figure which shows the moving body which concerns on the modification of embodiment. It is a figure which shows an example of operation|movement of the mobile body which concerns on the modification of embodiment. FIG. 4 is a diagram for explaining example 1 of acceleration that a moving body receives; FIG. 10 is a diagram for explaining Example 2 of acceleration received by a moving body; FIG. 11 is a diagram for explaining Example 3 of acceleration received by a moving body; It is a figure for demonstrating an example of the attitude|position angle of a mobile body.

Next, a moving body and a control method according to this embodiment will be described with reference to the drawings. The embodiments described below are merely examples, and embodiments to which the present invention is applied are not limited to the following embodiments.
In addition, in all the drawings for explaining the embodiments, the same reference numerals are used for the parts having the same functions, and repeated explanations are omitted.
In addition, "based on XX" in the present application means "based on at least XX", and includes cases based on other elements in addition to XX. Moreover, "based on XX" is not limited to the case of using XX directly, but also includes the case of being based on what has been calculated or processed with respect to XX. "XX" is an arbitrary element (for example, arbitrary information).

(embodiment)
(moving body)
FIG. 1 is a schematic diagram of a moving body according to one embodiment of the present invention. The moving object 100 according to the present embodiment autonomously travels along a preset route or an automatically generated route following a given speed profile or an automatically generated speed profile. An example of the mobile object 100 is a robot.
The moving body 100 includes a main body 105 , a controller 130 and a drive mechanism 140 .
The main body 105 is a housing of the moving body 100 and houses the controller 130 and the drive mechanism 140 . An example of the shape of the main body 105 is a body of revolution (ellipse) obtained when an ellipse is placed with its long axis perpendicular to the horizontal plane (ground) and rotated about its long axis as the axis of rotation. The main body 105 has an elliptical shape when viewed in the movement direction, and a circular shape when viewed vertically. The height of the main body 105 is, for example, 1 m or more. The projected area of the main body 105 when viewed in the moving direction is larger (wider) than its projected area when viewed vertically. By configuring in this way, when traveling in an environment where humans are present, it can be easily recognized by humans.

A drive mechanism 140 moves the body 105 . The drive mechanism 140 includes two drive wheels and a steering angle mechanism.
Each of the two drive wheels is driven by a different power, such as an electric motor. In this embodiment, as an example, the case where each of the two drive wheels is driven by different electric motors will be described.
The height of the moving body 100 is longer than the width connecting the two driving wheels (the length of the line connecting the two driving wheels).
The steering angle mechanism changes the traveling direction of the moving body 100 .
In FIG. 1, the Y-axis is the direction of the line connecting the two drive wheels, the Z-axis is the longitudinal direction of the moving body 100, and the X-axis is the direction perpendicular to the Y and Z axes. The vertically upward direction in the longitudinal direction of the moving body 100 is the positive direction of the Z axis.
Controller 130 controls each of the two drive wheels. When the main body 105 is turned, the controller 130 provides a difference in rotational speed between the drive wheels. That is, the controller 130 controls each of the two drive wheels to have different rotation speeds when turning the main body 105 . The controller 130 causes the steering angle mechanism to change the steering angle of each driving wheel. That is, when the main body 105 is turned, the controller 130 controls each of the two drive wheels to have different steering angles with respect to the steering angle mechanism.

FIG. 2 is a diagram showing an example of a method for driving a moving object according to this embodiment.
FIG. 2 is a schematic diagram of the drive mechanism 140 of the moving body 100 viewed from the positive side of the Z axis. As described above, the drive mechanism 140 includes two drive wheels (drive wheel A and drive wheel B) and a steering angle mechanism. The two drive wheels are driven by different electric motors. The length connecting the two driving wheels is, for example, within 1 m. With this configuration, the moving body 100 can also use doors, elevators, and the like that are used by humans. The minimum turning radius of the moving body 100 is, for example, within 0.5 m. In the following description, clockwise rotation is assumed to be positive for angles.
The top view of FIG. 2 shows the state of the driving wheels when the moving body 100 moves in the positive direction of the X axis. The top view of FIG. 2 shows the main body 105, drive wheel A, drive wheel B, axle γ and axle α. When the movable body 100 moves in the positive direction of the X axis, the axle γ is oriented in the same direction as the axis α. Axis α preferably passes near the center of gravity of main body 105 .
The second diagram from the top in FIG. 2 illustrates the state of the driving wheels when the moving body 100 moves rightward, in other words, in the positive direction of the Y axis. When the moving body 100 moves in the positive direction of the Y-axis, the controller 130 controls the angle between the direction perpendicular to the axis α on the driving wheels A and the X-axis to be an angle a, and the driving wheels B on the axis α. The angle between the vertical direction and the X-axis is controlled to angle b. When moving the moving body 100 in the positive direction of the Y axis, the controller 130 individually sets the angles a and b. The angle a is set with the turning center at a position within the plane where the drive wheels A contact the ground (hereinafter referred to as the "ground plane"). The angle b is set with the position in the ground plane where the drive wheel B touches the ground as the turning center. Note that the ground contact surface is a place where the driving wheels come into contact with the horizontal surface when the mobile body is placed on the horizontal surface, and means a ground contact point or its vicinity.

The third diagram from the top in FIG. 2 illustrates the state of the drive wheels when the moving body 100 moves leftward, in other words, in the negative direction of the Y axis. When the movable body 100 moves in the negative direction of the Y axis, the controller 130 controls the angle formed between the direction perpendicular to the axis α on the driving wheels A and the X axis to be an angle −c, and the angle on the driving wheels B on the axis α The angle between the direction perpendicular to and the X-axis is controlled to angle -d. When moving the moving body 100 in the negative direction of the Y axis, the controller 130 sets the angle -c and the angle -d individually. The angle -c is set with the position in the ground plane where the driving wheel A touches the ground as the turning center. The angle -d is set with the position in the ground plane where the drive wheel B contacts the ground as the turning center.
The bottom diagram of FIG. 2 is a diagram showing that the moving object 100 may further include wheels. The drive mechanism 140 comprises one or more wheels C omnidirectionally movable in a direction perpendicular to the axis α. The example shown in the bottom diagram of FIG. 2 shows a case where wheels C1 and C2 capable of omnidirectional movement are provided at two locations across the Y-axis in a direction perpendicular to the axis α. Although the case where the wheel C1 and the wheel C2 are provided has been described here, either the wheel C1 or the wheel C2 may be provided. By configuring in this way, the traveling of the moving body 100 can be stabilized.

FIG. 3 is a block diagram showing a moving body according to this embodiment. As described above, the moving body 100 according to this embodiment includes the main body 105, the controller 130, and the drive mechanism 140. As shown in FIG.
The controller 130 includes a control device 131 and a travel condition acquisition section 132 .
The drive mechanism 140 includes an electric motor 141-1, an electric motor 141-2, encoders 142-1 and 142-2, a steering mechanism 143-1, and a steering mechanism 143-2.
The electric motor 141-1 acquires the control information output by the control device 131. FIG. The electric motor 141-1 drives the driving wheels A based on the acquired control information.
The electric motor 141-2 acquires the control information output by the control device 131. FIG. The electric motor 141-2 drives the driving wheels B based on the acquired control information.
Encoder 142-1 detects rotational speed n1 of electric motor 141-1. Encoder 142-1 outputs information indicating rotational speed n1 of electric motor 141-1 to traveling condition acquiring unit 132. FIG.
Encoder 142-2 detects rotational speed n2 of electric motor 141-2. Encoder 142-2 outputs information indicating rotation speed n2 of electric motor 141-2 to traveling condition acquisition unit 132.
The steering mechanism 143-1 includes a steering actuator (not shown) for changing the steering angle of the drive wheels A. FIG. The steering mechanism 143-1 changes the steering angle of the steering actuator of the drive wheels A so that the vehicle follows a preset route or an automatically generated route. The steering mechanism 143-1 acquires information indicating the steering angle of the driving wheels A (hereinafter referred to as “target steering angle A”) output from the control device 131. FIG. The steering mechanism 143-1 changes the steering angle of the steering actuator for the driving wheels A based on the acquired information indicating the target steering angle A. FIG.
The steering mechanism 143-2 includes a steering actuator (not shown) for changing the steering angle of the driving wheels B. FIG. The steering mechanism 143-2 changes the steering angle of the steering actuator for the drive wheels B so that the vehicle follows a preset route or an automatically generated route. The steering mechanism 143-2 acquires information indicating the steering angle of the drive wheels B (hereinafter referred to as “target steering angle B”) output from the control device 131. FIG. The steering mechanism 143-2 changes the steering angle of the steering actuator for the driving wheels B based on the acquired information indicating the target steering angle B. FIG.

Traveling condition acquisition unit 132 is connected to encoder 142 - 1 , encoder 142 - 2 , steering mechanism 143 - 1 , steering mechanism 143 - 2 and controller 131 . Traveling condition acquisition unit 132 acquires information indicating rotation speed n1 of electric motor 141-1 output from encoder 142-1. The traveling condition acquisition unit 132 acquires information indicating the rotation speed n2 of the electric motor 141-2 output from the encoder 142-2. The driving condition acquisition unit 132 acquires information indicating the steering angle (steer angle) δ1 of the drive wheels A output from the steering mechanism 143-1. The driving condition acquisition unit 132 acquires information indicating the steering angle (steer angle) δ2 of the drive wheels B output from the steering mechanism 143-2.
Based on the acquired information indicating the rotational speed n1 of the electric motor 141-1, the traveling condition acquisition unit 132 determines the forward speed V1 of the driving wheels A of the moving body 100 and the turning speed ω1 that is the speed at which the moving body 100 is turned. and Based on the acquired information indicating the rotational speed n2 of the electric motor 141-2, the traveling condition acquisition unit 132 determines the forward speed V2 of the drive wheel B of the moving body 100 and the turning speed ω2 that is the speed at which the moving body 100 is turned. and
The driving condition acquisition unit 132 transmits the derived information indicating the forward speed V1 and the turning speed ω1 of the driving wheel A, the information indicating the forward speed V2 of the driving wheel B, and the information indicating the turning speed ω2 to the control device 131. Output. The driving condition acquisition unit 132 outputs the acquired information indicating the steering angle δ1 of the drive wheels A and the acquired information indicating the steering angle δ2 of the drive wheels B to the control device 131 .

The control device 131 includes a steering angle control section 135 and a rotational angular velocity control section 136 .
The steering angle control unit 135 receives the information indicating the forward speed V1 and the turning speed ω1 of the drive wheels A and the information indicating the forward speed V2 and the turning speed ω2 of the driving wheels B output by the driving condition acquisition unit 132. , the information indicating the steering angle .delta.1 of the driving wheel A and the information indicating the steering angle .delta.2 of the driving wheel B are acquired. The steering angle control unit 135 uses the obtained information indicating the forward speed V1 of the drive wheels A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the driving wheels B, the information indicating the turning speed ω2, and the acquired information indicating the turning speed ω2 of the driving wheels A. Based on the information indicating the angle δ1 and the information indicating the steering angle δ2 of the driving wheels B, the steering angle of the driving wheels A (hereinafter referred to as "target steering angle A") and the steering angle of the driving wheels B (hereinafter referred to as "target steering angle B”). The steering angle control unit 135 outputs information indicating the derived target steering angle A to the steering mechanism 143-1, and outputs information indicating the derived target steering angle B to the steering mechanism 143-2.
The rotation angular velocity control unit 136 receives the information indicating the forward speed V1 and the turning speed ω1 of the drive wheels A and the information indicating the forward speed V2 and the turning speed ω2 of the driving wheels B output by the driving condition acquisition unit 132. , the information indicating the steering angle .delta.1 of the driving wheel A and the information indicating the steering angle .delta.2 of the driving wheel B are obtained. The rotation angular velocity control unit 136 controls the obtained information indicating the forward speed V1 of the driving wheels A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the driving wheels B, the information indicating the turning speed ω2, and the acquired information indicating the turning speed ω2 of the driving wheels A. Based on the information indicating the angle δ1 and the information indicating the steering angle δ2 of the driving wheels B, the rotational angular velocity of the driving wheels A (hereinafter referred to as "target rotational angular velocity A") and the rotational angular velocity of the driving wheels B (hereinafter referred to as "target rotational angular velocity B”). The rotation angular velocity control unit 136 outputs control information for controlling at the derived target rotation angular velocity A to the electric motor 141-1, and outputs control information for controlling at the target rotation angular velocity B to the electric motor 141-2.
In the control device 131, the steering angle control unit 135 outputs information indicating the target steering angle A to the steering mechanism 143-1 and outputs information indicating the target steering angle B to the steering mechanism 143-2, and rotation angular velocity control. The control for outputting the control information for the control at the target rotational angular velocity A by the unit 136 to the electric motor 141-1 and the control information for controlling at the target rotational angular velocity B to the electric motor 141-2 are performed at the same time.
In the control device 131, the steering angle control unit 135 outputs information indicating the target steering angle A to the steering mechanism 143-1 and outputs information indicating the target steering angle B to the steering mechanism 143-2, and rotation angular velocity control. The control in which the unit 136 outputs control information for controlling at the target rotational angular velocity A to the electric motor 141-1 and outputs control information for controlling at the target rotational angular velocity B to the electric motor 141-2 means that the moving object 100 is It can be done at arbitrary timing while driving.

(movement of moving body)
FIG. 4 is a diagram showing an example of the motion of the moving object according to this embodiment. Processing when the moving body 100 follows the target trajectory will be described with reference to FIG. 4 .
(Step S1-1)
Traveling condition acquisition unit 132 acquires information indicating rotation speed n1 of electric motor 141-1 output from encoder 142-1. The traveling condition acquisition unit 132 acquires information indicating the rotation speed n2 of the electric motor 141-2 output from the encoder 142-2.
(Step S2-1)
The driving condition acquisition unit 132 acquires information indicating the steering angle (steer angle) δ1 of the drive wheels A output from the steering mechanism 143-1. The driving condition acquisition unit 132 acquires information indicating the steering angle (steer angle) δ2 of the drive wheels B output from the steering mechanism 143-2.
(Step S3-1)
Based on the acquired information indicating the rotational speed n1 of the electric motor 141-1, the traveling condition acquisition unit 132 determines the forward speed V1 of the driving wheels A of the moving body 100 and the turning speed ω1 that is the speed at which the moving body 100 is turned. and Based on the acquired information indicating the rotational speed n2 of the electric motor 141-2, the traveling condition acquisition unit 132 determines the forward speed V2 of the drive wheel B of the moving body 100 and the turning speed ω2 that is the speed at which the moving body 100 is turned. and
(Step S4-1)
The driving condition acquisition unit 132 transmits the derived information indicating the forward speed V1 and the turning speed ω1 of the driving wheel A, the information indicating the forward speed V2 of the driving wheel B, and the information indicating the turning speed ω2 to the control device 131. Output. The driving condition acquisition unit 132 outputs the acquired information indicating the steering angle δ1 of the drive wheels A and the acquired information indicating the steering angle δ2 of the drive wheels B to the control device 131 .
The steering angle control unit 135 receives the information indicating the forward speed V1 and the turning speed ω1 of the drive wheels A and the information indicating the forward speed V2 and the turning speed ω2 of the driving wheels B output by the driving condition acquisition unit 132. , the information indicating the steering angle .delta.1 of the driving wheel A and the information indicating the steering angle .delta.2 of the driving wheel B are obtained. The steering angle control unit 135 uses the obtained information indicating the forward speed V1 of the drive wheels A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the driving wheels B, the information indicating the turning speed ω2, and the acquired information indicating the turning speed ω2 of the driving wheels A. Based on the information indicating the angle δ1 and the information indicating the steering angle δ2 of the driving wheels B, the target steering angle A of the driving wheels A and the target steering angle B of the driving wheels B are derived.

(Step S5-1)
The steering angle control unit 135 outputs information indicating the derived target steering angle A to the steering mechanism 143-1, and outputs information indicating the derived target steering angle B to the steering mechanism 143-2.
The steering mechanism 143-1 acquires information indicating the target steering angle A of the drive wheels A output by the control device 131. FIG. The steering mechanism 143-1 changes the steering angle of the steering actuator for the driving wheels A based on the acquired information indicating the target steering angle A. FIG.
The steering mechanism 143-2 acquires information indicating the target steering angle B of the drive wheels B output by the control device 131. FIG. The steering mechanism 143-2 changes the steering angle of the steering actuator for the driving wheels B based on the acquired information indicating the target steering angle B. FIG.
(Step S6-1)
The rotation angular velocity control unit 136 receives the information indicating the forward speed V1 and the turning speed ω1 of the drive wheels A and the information indicating the forward speed V2 and the turning speed ω2 of the driving wheels B output by the driving condition acquisition unit 132. , the information indicating the steering angle .delta.1 of the driving wheel A and the information indicating the steering angle .delta.2 of the driving wheel B are obtained. The rotation angular velocity control unit 136 controls the obtained information indicating the forward speed V1 of the driving wheels A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the driving wheels B, the information indicating the turning speed ω2, and the acquired information indicating the turning speed ω2 of the driving wheels A. Based on the information indicating the angle .delta.1 and the information indicating the steering angle .delta.2 of the driving wheel B, the target rotational angular velocity A of the driving wheel A and the target rotational angular velocity B of the driving wheel B are derived. The rotation angular velocity control unit 136 outputs control information for controlling at the derived target rotation angular velocity A to the electric motor 141-1, and outputs control information for controlling at the target rotation angular velocity B to the electric motor 141-2.
(Step S7-1)
The electric motor 141-1 acquires the control information output by the control device 131. FIG. The electric motor 141-1 drives the driving wheels A based on the acquired control information.
The electric motor 141-2 acquires the control information output by the control device 131. FIG. The electric motor 141-2 drives the driving wheels B based on the acquired control information.

(moving body performance)
The trajectory tracking performance of the moving body 100 will be described. In order to compare the trajectory tracking performance of a conventional moving body (differential two-wheeled vehicle with steering) and the moving body 100, a simulation based on a model formula was performed. Here, as an example, a trajectory tracking result of a differential two-wheel type bogie based on the Pure Pursuit law is shown. Trajectory tracking of differential two-wheeled carts by the Pure Pursuit law is commonly used in the field of robotics. The Pure Pursuit law is a method of chasing a target (carrot) on an orbit. The method of chasing carrots in orbit is also called carrot seek. In this simulation, the motion model of the robot is set to a differential two-wheel type trolley, and the distance to the target (carrot) is set to 2 [m]. The target speed was 3 [m/s] (approximately 11 [km/h]), which was considerably faster than a general walking speed and was set to a speed at which the subject would trot.
FIG. 5 is a diagram showing an example of trajectory tracking performance of a moving object. In FIG. 5, the horizontal axis is the x-coordinate and the vertical axis is the y-coordinate. In FIG. 5, a target trajectory (hereinafter referred to as "target trajectory") is indicated by a thick line, and a trajectory of a conventional moving body is indicated by a thin line. The target trajectory includes a small avoidance action with an amplitude of 1 [m] and a period of about 6 [m]. By assuming such a trajectory, it can be assumed that crowds will be avoided. The target trajectory is determined by the ever-changing future position of the dynamic obstacle (person). Therefore, the inability of the moving body to follow the target trajectory means that the moving body collides with a dynamic obstacle (person).
According to FIG. 5, it can be seen that the turning radius cannot be reduced because the traveling speed of the moving body is high. As a result, the moving body does not follow the target trajectory at all, and in some places the phase is reversed. If the phase is reversed, it means that the vehicle is passing through a place where it is assumed that there is a person to be avoided, which corresponds to failure in avoidance.
FIG. 6 is a diagram showing an example of trajectory tracking performance of a moving object according to this embodiment. In FIG. 6, in addition to trajectory tracking based on the Pure Pursuit law, a steerable vehicle (CCV) was used, and the second carrot was simultaneously tracked by steering control. In FIG. 6, the horizontal axis is the x-coordinate and the vertical axis is the y-coordinate. In FIG. 6, the target trajectory (course) is indicated by a thick line, and the trajectory (trajectory) of the moving body 100 is indicated by a thin line. The target trajectory includes a small avoidance action with an amplitude of 1 [m] and a period of about 6 [m] as in FIG. The tracking parameters for the first carrot are the same settings as in FIG. The distance to the second carrot was set to 0.5 [m], and the maximum value of the steering angle was set to 24 [deg] (=0.42 [rad]).
As can be seen from FIG. 6, the trajectory can be tracked without any phase delay.
FIG. 7 is a diagram showing an example of steering angle control of a moving body according to the present embodiment. In FIG. 7, the horizontal axis is time and the vertical axis is steering angle. According to FIG. 7, it can be seen that the moving body 100 actively steers in accordance with the vibration of the target trajectory.

Here, an example of the model formula used for the simulation will be described.
FIG. 8 is a diagram for explaining an example of a model formula. Here, a unicycle model will be described as an example.
FIG. 8 shows that the moving body 100 positioned at the coordinates (x, y) with respect to the target trajectory TT moves a point at a predetermined distance to target points (carrot1 (first target point), carrot2 (second target point)). , shows how turning control is performed in order to reach that point.
A method for the control device 131 to set carrot1 in the mobile object 100 will be described.
When the speed of the robot is V [m/s], the reachable distance after T [s] has passed is V×T [m]. Therefore, the controller 131 generally sets L1[m]≈VT. Here, the amount of azimuth angle change α that can be differentially turned during time T is represented by α=ωmax×T, where ωmax is the maximum turning speed. If α is greater than the maximum curvature ρmax of the target trajectory (α>ρmax), the target trajectory can be traced.
If the forward speed V of the robot (moving body 100) is small, there is a solution that satisfies the requirement, but if V becomes large, there may be no solution that satisfies the requirement. Therefore, carrot2 is set to improve traceability.
A method of setting carrot2 by the control device 131 in the moving body 100 will be described.
Let L1 be the distance from the current position to carrot1, and L2 be the distance from the current position to carrot2. The steering angle of the robot (moving body 100) can be changed at relatively high speed. Therefore, the distance L2 to this target can be relatively short. That is, L2<<L1 holds. However, if L2 is set too close (L2 is equal to or less than a predetermined threshold value), the rudder is turned too violently (larger), and the robot (moving body 100) is also subjected to greater acceleration . Therefore, the controller 131 sets carrot2 to an appropriate location (position) that satisfies 0<<L2<<L1.
In Pure Pursuit, as shown in FIG. 8, carrot1 (xt1, yt1) and carrot2 (xt2, yt2) are set for an arbitrary point cx on the target trajectory TT. The moving body 100 simultaneously tracks carrot1 and carrot2. The target speed of the moving body 100 is the forward speed v. In FIG. 8, Ψ is the yaw angle and δ is the steering angle of the rudder.

The update formulas are represented by formulas (1) to (4). However, |δ|≦|δmax|.
x=x+vcos(Ψ+δ)dt (1)
y=y+vsin(Ψ+δ)dt (2)
Ψ = Ψ + (dΨ/dt) dt (3)
v=v+adt (4)
The rotational angular velocity control unit 136 sets the target azimuth angular velocity of the driving wheels so as to eliminate the azimuth error between the first target point on the target trajectory and the azimuth of the main body 105 for the carrot 1, and Attitude and heading control is performed by differential. That is, the rotational angular velocity control unit 136 sets a target azimuth angular velocity of the drive wheels that reduces the azimuth error between the first target point on the target trajectory and the azimuth of the main body 105, and based on the set target azimuth angular velocity, the differential Attitude and heading control is performed.
The orientation error α with respect to the moving object 100 for carrot1 is expressed by Equation (4).
α = arctan ((yt1-y)/(xt1-x))-Ψ (4)
When carrot1 and the center of the moving body 100 are connected by a circle, the turning radius R is represented by R=L/(2sinα).
Therefore, using the forward speed v, the target yaw rate ωd is expressed by equation (5). However, L is the pursuit length (tracking length), that is, the distance from the current position to the target value.
ωd=(1/L)vα (5)
For carrot2, the steering angle control unit 135 sets the target steering angle of the drive wheels toward the second target point on the target track, and adjusts the steering based on the set target steering angle to determine the speed vector. Direction control.
The steering angle δ of the rudder is expressed by Equation (6). However, δ≦δmax.
δ = arctan ((yt2-y)/(xt2-x))-Ψ (6)
The moving body 100 simultaneously performs two types of control, namely, differential attitude/orientation control (slow, large motion) and steering-based velocity vector direction control (high-speed, small motion). By configuring in this way, high trajectory following performance can be exhibited compared to the case where two controls, ie, attitude control and velocity vector direction control, do not coexist.

In FIG. 8, the case of replacing with a unicycle model has been described. A unicycle model corresponds to a bicycle model in a four-wheeled vehicle. In reality, the moving body 100 has left and right drive wheels, so the steering angle must be determined for each of the two drive wheels. Next, a case of determining steering angles for two drive wheels will be described.
FIG. 9 is a diagram for explaining an example of a model formula.
When a general differential two-wheeled bogie without a rudder turns while traveling, its center of rotation (turning) is always on the extension of the line connecting the centers of the left and right wheels. However, since the moving body 100 is equipped with a rudder, the turning center is within the shaded range in FIG. 9 according to the limit values that the actual steering angle can take. In the case of −δmax or more and δmax or less, the center of rotation can be placed in the hatched range. In FIG. 9, the steering angle δi of the rudder and the steering angle δ0 of the rudder are expressed by equations (7) and (8). However, |δi|<|δmax|.
δi=arctan(r×sin δ/(r×cos δ−(B/2)) (7)
δ0=arctan(r×sin δ/(r×cos δ+(B/2)) (8)
Also, equations (9) and (10) hold.
ω=(1/L1)vα (9)
r=v/ω (10)
The rudder angle is determined so that the axle of each wheel passes through the turning center placed in the hatched range. With this configuration, the moving body 100 can simultaneously determine the traveling direction (at that moment) based on the steering angle and generate the azimuth angular velocity (yaw rate) around a certain rotation center.

FIG. 10 is a diagram showing an example of a trajectory of a moving object. FIG. 10 shows an example of the trajectory of a moving body such as a commonly used differential two-wheel type trolley. In FIG. 10, the horizontal axis is the speed of the moving body, and the vertical axis is the trajectory of the moving body in the Y-axis direction. The solid black line is the trajectory of the moving body, and the thin black dashed line is the trajectory of the moving body whose speed is 1.5 times that of the moving body shown in black.
A moving body that is generally used controls its direction based on the running speed difference between the left and right wheels. For this reason, the speed of direction change of a generally used moving body is determined by how fast the speed difference can be made. In other words, in a generally used moving body, the direction change speed is determined by the magnitude of the torque.
Also, a DC motor is used to drive the moving body. DC motors linearly decrease torque as speed increases. As shown in FIG. 10, when the speed increases by 1.5 times, the area of the trajectory of the moving body 100 decreases. Therefore, it can be seen that following the target trajectory becomes more difficult as the moving speed of the moving object increases.

FIG. 11 is a diagram showing an example of a trajectory of a moving object according to this embodiment. For comparison, FIG. 11 also shows an example of the trajectory of a moving object such as a differential two-wheel type trolley generally used. In FIG. 11, the horizontal axis is the speed of the moving body, and the vertical axis is the trajectory of the moving body in the Y-axis direction. The thin black dashed line is the trajectory of the moving body whose speed is 1.5 times that of the moving body shown by the solid black line in FIG. 10, and the solid black line in FIG. 11 is the trajectory of the moving body 100. The moving body 100 includes a steering mechanism (steering mechanism 143-1 and steering mechanism 143-2). As shown in FIG. 11, when the traveling direction of the moving body 100 is arbitrarily changed by steering, the area of the trajectory of the moving body 100 increases. The moving body 100 has a significantly increased area that can be entered compared to a differential two-wheel vehicle. In other words, it can be seen that the moving body 100 can easily follow the target trajectory regardless of the moving speed of the moving body, although the steering angle is limited by the steering.

In the above-described embodiment, the case where the drive mechanism 140 includes one or more wheels C that can move in all directions perpendicular to the axis α has been described, but the present invention is not limited to this example. For example, instead of the wheels C, one or more support mechanisms may be provided.
In the above-described embodiment, the case where the axle γ is oriented in the same direction as the axle α when changing the direction of the drive wheels has been described, but the present invention is not limited to this example. For example, when changing the direction of the driving wheels, the direction of the wheels connected to the axle γ may be changed.
In the above-described embodiment, the moving body 100 may include auxiliary wheels in addition to the two drive wheels (drive wheel A and drive wheel B).
FIG. 12 is a diagram showing another example of the moving body according to this embodiment. FIG. 12 shows a moving body 100 equipped with training wheels 150 . By providing the auxiliary wheels 150 in addition to the two drive wheels, the moving body 100 can be moved more stably than when the two drive wheels are provided. Therefore, it is possible to reduce the overturning of the moving body 100 .
In the above-described embodiment, as an example, the trajectory tracking result of the differential two-wheeled vehicle controlled using the Pure Pursuit law has been described, but the present invention is not limited to this example. For example, it is possible to control the moving body 100 using LQR (Linear Quadratic Regulator), model predictive control, and the like.
According to the mobile body 100 according to the present embodiment, the mobile body 100 is an autonomous mobile type, and is driven by the main body 105 and the electric motors (the electric motors 141-1 and 141-2) to move the main body 105. A rotation angular velocity control unit 136 as a differential mechanism for turning the main body 105 by giving a difference in rotation angular velocity between the wheels (drive wheel A, drive wheel B) and a steering angle of the drive wheels for each drive wheel. and a steering angle control unit 135 as a steering mechanism for changing the With this configuration, it is possible to turn the main body 105 by giving a difference in rotational angular velocity between the drive wheels and to change the steering angle of the drive wheels for each drive wheel. can improve the ability to follow
In addition, the differential mechanism changes the rudder angle for each drive wheel with the position on the ground contact surface of the drive wheel as the turning center. By configuring in this way, the energy efficiency of the moving body 100 can be improved because the rudder can be quickly steered with a small torque as compared with the case where the position in the ground contact surface of the drive wheels is not the turning center.
Further, a control unit as a control device 131 that simultaneously controls the differential mechanism and the steering mechanism along the target trajectory is further provided. With this configuration, in the moving body 100, the differential mechanism controls each of the two drive wheels (drive wheel A, drive wheel B) at different target steering angles, and the steering mechanism controls the two drive wheels ( Driving wheels A and B) are controlled at different target rotational angular velocities. Therefore, the moving body 100 can avoid the obstacle quickly and in a small turning circle.
Further, the control unit sets the target azimuth angular velocity of the driving wheels so as to eliminate the azimuth error between the first target point on the target trajectory and the azimuth of the main body 105, and moves the driving wheels toward the second target point on the target trajectory. set the target rudder angle. With this configuration, at two different types of target points, the first target point and the second target point, the target azimuth angular velocity is set for the first target point, and the target rudder speed is set for the second target point. Since the angle can be set, the differential mechanism and the steering mechanism can be controlled simultaneously.
Also, the control unit controls the heading error, the target azimuth angular velocity, and the target rudder angle, with α as the azimuth error, (xt1, yt1) as the first target point, (xt2, yt2) as the second target point, Ψ as the yaw angle, When ω is the target yaw rate, L is the tracking length, v is the forward speed, and δ is the steering angle of the rudder, equations (1) to (3)
α = arctan ((yt1-y)/(xt1-x))-Ψ (1)
ωd=(1/L)vα (2)
δ = arctan ((yt2-y)/(xt2-x))-Ψ (3)
decide according to Here, when va is the forward speed of the vehicle body, va=v×cos δ using the speed v at which the wheels with the rudder turned δ are used. With this configuration, the target azimuth angular velocity can be set for the first target point, and the target steering angle can be set for the second target point.
Further, the projected area of the main body 105 when viewed in the moving direction is larger than the projected area of the main body 105 when viewed vertically.
Also, the height is longer than the width of the shaft connecting the two drive wheels. By configuring in this way, when traveling in an environment where humans are present, it can be easily recognized by humans.

(Modification of embodiment)
(moving object)
FIG. 13 is an external view of a moving body according to a modification of the embodiment; The moving object 100a according to the modification of the embodiment receives the route information transmitted by the server 200, and uses the received route information to autonomously travel so as to follow a speed profile given in advance or an automatically generated speed profile. conduct.
Mobile object 100a is connected to server 200 via network NW. The network NW includes, for example, the Internet, a WAN (Wide Area Network), a LAN (Local Area Network), a provider device, a radio base station, and the like.
The moving body 100 a includes a main body 105 , a distance measuring section 110 , a communication section 120 , a controller 130 , a drive mechanism 140 , a training wheel 150 , an inertial measurement section 160 , a communication section 170 , an imaging section 180 and a depth detection section 190 .
The main body 105 is a housing for the moving object 100a , and houses the distance measurement unit 110, the communication unit 120, the controller 130, the drive mechanism 140, the inertial measurement unit 160, the communication unit 170, the imaging unit 180, and the depth detection unit 190. do.

The distance measuring unit 110 measures the distance between obstacles such as people and objects existing around the moving object 100a. An example of the rangefinder 110 is a three-dimensional LiDAR (Light Detection and Ranging). Three-dimensional LiDAR measures the scattered light of pulsed laser radiation and analyzes the distance to a distant target and the properties of that target.
Communication unit 120 is realized by a communication module. The communication unit 120 communicates with an external communication device such as the server 200 via the network NW. The communication unit 120 communicates using a wireless communication method such as LTE (registered trademark), for example. The communication unit 120 holds communication information necessary for communicating with the server 200 via the network NW. The communication unit 120 receives the route information notification transmitted by the server 200 .
The inertial measurement unit 160 detects the angular velocity and acceleration of the moving body 100a, and derives the velocity, movement distance, and position of the moving body 100a. An example of the inertial measurement unit 160 includes a triaxial gyro and a tridirectional accelerometer. The inertial measurement unit 160 derives three-dimensional angular velocity and acceleration from a three-axis gyro and a three-directional accelerometer. The inertial measurement unit 160 derives the velocity, movement distance, and position of the moving body 100a based on the derived three-dimensional angular velocity and acceleration.
Communication unit 170 is realized by a communication module. The communication unit 170 communicates with an external communication device such as the server 200 via the network NW. The communication unit 170 communicates using a wireless communication method such as a wireless LAN or Bluetooth (registered trademark). The communication unit 170 holds communication information necessary for communicating with the server 200 via the network NW. The communication unit 170 receives the route information notification transmitted by the server 200 .
The imaging unit 180 images the surroundings of the moving body 100a. An example of the imaging unit 180 is a high-definition camera.
The depth detection unit 190 detects the depth of obstacles such as people and objects around the moving object 100a. An example of the depth detector 190 is a 360° depth camera.

FIG. 14 is a diagram illustrating a moving object according to a modification of the embodiment; As described above, the moving object 100a according to the embodiment includes the main body 105, the distance measurement unit 110, the communication unit 120, the controller 130, the driving mechanism 140, the auxiliary wheels 150, the inertial measurement unit 160, the communication unit 170, and the imaging unit 180. and a depth detection unit 190 .
The controller 130 includes a control device 131 a , a traveling condition acquisition section 132 , a reception section 133 , a processing section 134 and a position/orientation estimation section 137 .
The position/orientation estimating unit 137 obtains the measurement result of the distance from the distance measuring unit 110 to static obstacles such as desks, chairs, and walls existing around the moving object 100a, and the dynamic obstacles such as walking humans. Get the measurement result of the distance between The position/orientation estimation unit 137 acquires the result of deriving the speed, movement distance, and position of the moving body 100 a from the inertia measurement unit 160 . The position/orientation estimation unit 137 acquires the detection result of the depth of obstacles such as people and objects existing around the moving object 100 a from the depth detection unit 190 . The position/orientation estimating unit 137 obtains the measurement result of the distance to static obstacles existing around the moving body 100a, the measurement result of the distance to the dynamic obstacle, the speed of the moving body 100a, The position and posture of the moving object 100a are estimated based on the result of deriving the movement distance and position and the detection result of the depth of obstacles existing around the moving object 100a.
The receiving unit 133 acquires the route information notification received by the communication unit 120 or the communication unit 170, and receives the acquired route information notification.

The control device 131a includes a steering angle control section 135a and a rotational angular velocity control section 136a.
The steering angle control unit 135a receives the information indicating the forward speed V1 and the turning speed ω1 of the drive wheels A and the information indicating the forward speed V2 and the turning speed ω2 of the driving wheels B output by the driving condition acquisition unit 132. , the information indicating the steering angle .delta.1 of the driving wheel A and the information indicating the steering angle .delta.2 of the driving wheel B are obtained.
The steering angle control unit 135a acquires the result of estimating the position and orientation of the moving body 100a from the position and orientation estimation unit 137 . The steering angle control unit 135 a acquires the route information notification from the receiving unit 133 . The steering angle control unit 135a acquires the route information included in the acquired route information notification.
The steering angle control unit 135a uses the acquired information indicating the forward speed V1 of the driving wheels A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the driving wheels B, the information indicating the turning speed ω2, and the acquired information indicating the turning speed ω2 of the driving wheels A. Based on the information indicating the angle δ1, the information indicating the steering angle δ2 of the driving wheels B, the result of estimating the position and attitude of the moving body 100a, and the course information, the target steering angle A of the driving wheels A and the steering angle of the driving wheels B are determined. A target steering angle B is derived. The steering angle control unit 135 outputs information indicating the derived target steering angle A to the steering mechanism 143-1, and outputs information indicating the derived target steering angle B to the steering mechanism 143-2.

The rotational angular velocity control unit 136a acquires the result of estimating the position and orientation of the moving object 100a from the position/orientation estimating unit 137 . The steering angle control unit 135 a acquires the route information notification from the reception unit 133 . The rotation angular velocity control unit 136a receives the information indicating the forward speed V1 and the turning speed ω1 of the driving wheel A output by the driving condition acquiring unit 132, the information indicating the forward speed V2 of the driving wheel B, and the information indicating the turning speed ω2. , the information indicating the steering angle .delta.1 of the driving wheel A and the information indicating the steering angle .delta.2 of the driving wheel B are acquired.
The rotation angular velocity control unit 136a controls the obtained information indicating the forward speed V1 of the driving wheels A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the driving wheels B, the information indicating the turning speed ω2, and the acquired information indicating the turning speed ω2 of the driving wheels A. Based on the information indicating the angle δ1, the information indicating the steering angle δ2 of the driving wheels B, the result of estimating the position and attitude of the moving body 100a, and the course information, the target rotational angular velocity A of the driving wheels A and the steering angle of the driving wheels B are calculated. A target rotational angular velocity B is derived. The rotation angular velocity control unit 136a outputs control information for controlling at the derived target rotation angular velocity A to the electric motor 141-1, and outputs control information for controlling at the target rotation angular velocity B to the electric motor 141-2.

(movement of moving body)
FIG. 15 is a diagram illustrating an example of motion of a moving body according to a modification of the embodiment; Here, a case where the mobile object 100a is located in an environment where a wireless LAN can be used will be described.
(Step S1-2)
The server 200 acquires the route information of the moving object 100a.
(Step S2-2)
The server 200 creates a route information notification addressed to the mobile unit 100a, including the acquired route information of the mobile unit 100a.
(Step S3-2)
The server 200 transmits the created route information notification to the moving object 100a.
(Step S4-2)
In the mobile unit 100a, the communication unit 170 receives the route information notification transmitted by the server 200. FIG.
(Step S5-2)
In the moving body 100a, the reception unit 133 receives the route information notification received by the communication unit 170. FIG. The control device 131 a acquires the route information notification received by the receiving unit 133 . The control device 131a acquires the route information included in the acquired route information notification.
(Step S6-2)
In the moving object 100a, the position/orientation estimating unit 137 obtains the measurement result of the distance from the distance measuring unit 110 to static obstacles existing around the moving object 100a and the measurement of the distance to the dynamic obstacle. Get results and The position/orientation estimation unit 137 acquires the result of deriving the speed, movement distance, and position of the moving body 100 a from the inertia measurement unit 160 . The position/orientation estimation unit 137 acquires the detection result of the depth of obstacles such as people and objects existing around the moving object 100 a from the depth detection unit 190 . The position/orientation estimating unit 137 obtains the measurement result of the distance to static obstacles existing around the moving body 100a, the measurement result of the distance to the dynamic obstacle, the speed of the moving body 100a, The position and posture of the moving object 100a are estimated based on the result of deriving the movement distance and position and the detection result of the depth of obstacles existing around the moving object 100a.

(Step S7-2)
In the moving body 100a, the traveling condition acquisition unit 132 acquires information indicating the rotation speed n1 of the electric motor 141-1 output from the encoder 142-1. The traveling condition acquisition unit 132 acquires information indicating the rotation speed n2 of the electric motor 141-2 output from the encoder 142-2.
(Step S8-2)
In the moving object 100a, the traveling condition acquisition unit 132 acquires information indicating the steering angle (steer angle) δ1 of the drive wheels A output from the steering mechanism 143-1. The driving condition acquisition unit 132 acquires information indicating the steering angle (steer angle) δ2 of the drive wheels B output from the steering mechanism 143-2.
(Step S9-2)
In the mobile body 100a, the traveling condition acquisition unit 132 determines the forward speed V1 of the driving wheels A of the mobile body 100a and the turning speed of the mobile body 100a based on the acquired information indicating the rotation speed n1 of the electric motor 141-1. and the turning speed ω1, which is the speed of . Based on the acquired information indicating the rotation speed n2 of the electric motor 141-2, the traveling condition acquisition unit 132 determines the forward speed V2 of the driving wheel B of the moving body 100a and the turning speed, which is the speed at which the moving body 100a is turned. and the velocity ω2.
(Step S10-2)
In the moving body 100a, the traveling condition acquisition unit 132 obtains information indicating the forward speed V1 of the driving wheel A, information indicating the turning speed ω1, information indicating the forward speed V2 of the driving wheel B, and information indicating the turning speed ω2. is output to the control device 131a. The driving condition acquisition unit 132 outputs the acquired information indicating the steering angle δ1 of the drive wheels A and the acquired information indicating the steering angle δ2 of the drive wheels B to the control device 131a.
The steering angle control unit 135a receives the information indicating the forward speed V1 and the turning speed ω1 of the drive wheels A and the information indicating the forward speed V2 and the turning speed ω2 of the driving wheels B output by the driving condition acquisition unit 132. , the information indicating the steering angle .delta.1 of the driving wheel A and the information indicating the steering angle .delta.2 of the driving wheel B are obtained. The steering angle control unit 135a acquires the result of estimating the position and orientation of the moving body 100a from the position and orientation estimation unit 137 . The steering angle control unit 135a acquires course information.
The steering angle control unit 135a uses the acquired information indicating the forward speed V1 of the driving wheels A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the driving wheels B, the information indicating the turning speed ω2, and the acquired information indicating the turning speed ω2 of the driving wheels A. Based on the information indicating the angle δ1, the information indicating the steering angle δ2 of the driving wheels B, the result of estimating the position and attitude of the moving body 100a, and the course information, the target steering angle A of the driving wheels A and the steering angle of the driving wheels B are determined. A target steering angle B is derived.

(Step S11-2)
In the moving body 100a, the steering angle control section 135a outputs information indicating the derived target steering angle A to the steering mechanism 143-1, and outputs information indicating the derived target steering angle B to the steering mechanism 143-2.
The steering mechanism 143-1 acquires information indicating the target steering angle A of the driving wheels A output from the control device 131a. The steering mechanism 143-1 changes the steering angle of the steering actuator for the driving wheels A based on the acquired information indicating the target steering angle A. FIG.
The steering mechanism 143-2 acquires information indicating the target steering angle B of the drive wheels B output by the control device 131a. The steering mechanism 143-2 changes the steering angle of the steering actuator for the driving wheels B based on the acquired information indicating the target steering angle B. FIG.
(Step S12-2)
The rotation angular velocity control unit 136a receives the information indicating the forward speed V1 and the turning speed ω1 of the driving wheel A output by the driving condition acquiring unit 132, the information indicating the forward speed V2 of the driving wheel B, and the information indicating the turning speed ω2. , the information indicating the steering angle .delta.1 of the driving wheel A and the information indicating the steering angle .delta.2 of the driving wheel B are obtained. The steering angle control unit 135a acquires the result of estimating the position and orientation of the moving body 100a from the position and orientation estimation unit 137 . The steering angle control unit 135a acquires course information.
The rotation angular velocity control unit 136a controls the obtained information indicating the forward speed V1 of the driving wheels A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the driving wheels B, the information indicating the turning speed ω2, and the acquired information indicating the turning speed ω2 of the driving wheels A. Based on the information indicating the angle δ1, the information indicating the steering angle δ2 of the driving wheels B, the result of estimating the position and attitude of the moving body 100a, and the course information, the target rotational angular velocity A of the driving wheels A and the steering angle of the driving wheels B are calculated. A target rotational angular velocity B is derived. The rotation angular velocity control unit 136 outputs control information for controlling at the derived target rotation angular velocity A to the electric motor 141-1, and outputs control information for controlling at the target rotation angular velocity B to the electric motor 141-2.
(Step S13-2)
The electric motor 141-1 acquires the control information output by the control device 131a . The electric motor 141-1 drives the driving wheels A based on the acquired control information.
The electric motor 141-2 acquires the control information output by the control device 131a . The electric motor 141-2 drives the driving wheels B based on the obtained control information.

Here, the acceleration received by the moving body 100a and attitude angle control will be described. The moving body 100a receives translational acceleration due to changes in traveling speed, turning, and steering being controlled. The moving body 100a has a function of adjusting the posture angle in the front, rear, left, and right directions. The moving object 100a uses this function to perform ZMP (Zero Moment Point) control. The rotation angular velocity control unit 136a of the moving body 100a derives the x-direction component and the y-direction component of the acceleration.
FIG. 16 is a diagram for explaining Example 1 of acceleration that a moving body receives. In FIG. 16, the moving body 100a is facing in the direction of Nose, the steering angle of the driving wheels is .delta., and the moving body 100a is moving in the direction of c2 at the speed v and the traveling acceleration a. Let ac be the centripetal acceleration of the moving body 100a. In this case, the acceleration ax in the Surge direction, which is the direction in which the moving body 100a swings back and forth, is expressed by Equation (11), and the acceleration ay in the Sway direction, which is the direction in which the moving body 100a swings left and right, is expressed by Equation (12). be.
ax=a×cos δ−ac×sin δ (11)
ay=a×sin δ+ac×cos δ (12)
FIG. 17 is a diagram for explaining example 2 of the acceleration that the moving body receives. In FIG. 16, Ψ indicates the yaw angle of the moving body 100a, and ω is the turning speed of the moving body 100a. The centripetal angular velocity ac of the moving body 100a is represented by Equation (13).
ac=v×ω (13)

FIG. 18 is a diagram for explaining Example 3 of the acceleration received by the moving object. FIG. 18 shows the relationship between the change in steering angle and the acceleration received by the moving object 100a. In FIG. 18, the upper diagram shows the relationship between time and steering angle. In the upper diagram, the horizontal axis is time [s] and the vertical axis is steering angle (δ) [rad]. The figure below shows the relationship between time and acceleration. In the figure below, the horizontal axis is time [s] and the vertical axis is acceleration [m/s2]. For acceleration, a Surge component (accel-x) and a Sway component (accel-y) are shown. It can be seen from FIG. 18 that the Sway component follows the steering angle.
FIG. 19 is a diagram for explaining an example of an attitude angle of a moving body; FIG. 19 shows attitude angles when the ZMP coincides with the center of the moving body 100a. In FIG. 19, the upper diagram shows the relationship between time and pitch angle. In the above diagram, the horizontal axis is time [s] and the vertical axis is pitch angle [deg]. The figure below shows the relationship between time and rolling angle . In the figure below, the horizontal axis is time [s] and the vertical axis is rolling angle [deg]. FIG. 19 shows how the vehicle tilts forward when accelerating, tilts backward when decelerating, and tilts right when turning right. The simulation shows a state when the moving body 100a is traveling at a relatively high speed of 3 m/s. According to FIG. 19, it can be seen that a large attitude angle adjustment of about 10 degrees maximum for the pitch angle and about 20 degrees for the roll angle is required.

In the modified example of the embodiment described above, a case has been described in which the moving body 100a autonomously travels so as to follow the route information transmitted by the server 200, but the present invention is not limited to this example. For example, the moving body 100a may be configured to autonomously travel along a preset route or automatically generated route following a given speed profile or automatically generated speed profile.
In the modified example of the above-described embodiment, the reaction moment when changing the posture of the moving body 100a is not considered, but it may be considered. Actually, when the moving body 100a is tilted, a reaction moment is generated. When the posture is changed at high speed, an unignorably large moment is generated, and the moving body 100a may become unstable.
Although the Coriolis force when changing the posture of the moving body 100a is not taken into account in the modified example of the above-described embodiment, it may be taken into consideration. When the moving body 100a changes its attitude abruptly while turning, a moment is generated in a direction orthogonal to each rotation axis (=Coriolis force). For example, pitching while turning generates a roll moment , and rolling while turning generates a pitching moment . If the attitude of the moving body 100a is changed abruptly, the effect on the moving body 100a is considered to be relatively small, but there is a possibility that the moving body 100a will become unstable.
According to the mobile object 100a according to the modified example of the embodiment , the control unit obtains the route information indicating the target route of the mobile object 100a, the moving speed of the driving wheels, the turning speed of the main body 105, and the steering angle of the driving wheels. , the target rotational angular velocity of the drive wheels and the target steering angle of the drive wheels are calculated. With this configuration, it is possible to calculate the target rotational angular velocity of the driving wheels and the target steering angle of the driving wheels further based on the course information indicating the target course of the moving body 100a. can be taken.
Furthermore, a position/orientation estimation unit 137 and a control device 131a as an attitude control device for controlling the attitude of the main body 105 are further provided. By configuring in this way, the posture of the moving body 100a can be stabilized.

Although embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and equivalents thereof.
A part of each device included in the moving body 100 in the above-described embodiment and the moving body 100a in the modification of the embodiment may be realized by a computer. In that case, a program for realizing this control function may be recorded in a computer-readable recording medium, and the program recorded in this recording medium may be read into a computer system and executed. The "computer system" here is a computer system built into each device included in the visit management system, and includes hardware such as an OS and peripheral devices.

The term "computer-readable recording medium" refers to portable media such as flexible discs, magneto-optical discs, ROMs and CD-ROMs, and storage devices such as hard discs incorporated in computer systems. Furthermore, "computer-readable recording medium" means a medium that dynamically stores a program for a short period of time, such as a communication line for transmitting a program via a network such as the Internet or a communication line such as a telephone line. It may also include a volatile memory inside a computer system that serves as a server or client in that case, which holds the program for a certain period of time. Further, the above-mentioned program may be for realizing a part of the above-mentioned functions, or may be a program capable of realizing the above-mentioned functions in combination with a program already recorded in the computer system. . Also, part or all of each functional block of each device included in the visit management system in the above-described embodiments may be realized as an integrated circuit such as LSI. Each functional block of each device included in the visit management system may be individually processorized, or a part or all of them may be integrated and processorized. Also, the method of circuit integration is not limited to LSI, but may be realized by a dedicated circuit or a general-purpose processor. In addition, when an integration circuit technology that replaces LSI appears due to advances in semiconductor technology, an integrated circuit based on this technology may be used.

DESCRIPTION OF SYMBOLS 100, 100a... Mobile body 105... Main body 110... Distance measuring part 120... Communication part 130... Controller 131, 131a... Control device, 132... Driving condition acquisition part, 133... Receiving part, 134... Processing part, 135, 135a... Rudder angle control section 136, 136a... Rotational angular velocity control section 137... Position and attitude estimation section 140... Drive mechanism 141-1, 141-2... Electric motor 142-1, 142-2... Encoder, 143-1, 143-2... steering mechanism, 150... auxiliary wheel, 160... inertial measurement unit, 170... communication unit, 180... imaging unit, 190... depth detection unit, 200... server

Claims (7)

An autonomous mobile object,
the main body;
two drive wheels driven by electric motors to move the body;
a differential mechanism that rotates the main body by providing a difference in rotational angular velocity between the drive wheels;
a steering mechanism that changes the rudder angle of the drive wheels for each of the drive wheels;
a control unit that simultaneously controls the differential mechanism and the steering mechanism along a target trajectory;
with
The control unit determines a target azimuth angular velocity of the drive wheels so as to eliminate an azimuth error between a first target point on the target trajectory and an azimuth of the main body, and drives the vehicle toward a second target point on the target trajectory. Determine the target rudder angle of the wheels,
The azimuth error, the target azimuth angular velocity and the target rudder angle, where α is the azimuth error, (xt1, yt1) is the first target point, (xt2, yt2) is the second target point, Ψ is the yaw angle, and ωd is the target. Determined according to formulas (1) to (3), where yaw rate, L is the tracking length, v is the forward speed, and δ is the steering angle of the rudder,
α = arctan ((yt1-y)/(xt1-x))-Ψ (1)
ωd=(1/L)vα (2)
δ = arctan ((yt2-y)/(xt2-x))-Ψ (3)
Mobile. 2. The moving body according to claim 1, wherein the differential mechanism changes a rudder angle for each of the driving wheels with a position on the ground contact surface of the driving wheels as a turning center. The control unit calculates a target rotational angular velocity of the drive wheels based on track information indicating a target track of the moving body, a moving speed of the drive wheels, a turning speed of the main body, and a steering angle of the drive wheels. , and a target rudder angle of the driving wheels. The moving body according to any one of claims 1 to 3 , wherein the projected area of the main body when viewed in the moving direction is larger than the projected area of the main body when viewed vertically. The moving body according to any one of claims 1 to 4 , wherein the height is longer than the width of the shaft connecting the two drive wheels. The moving object according to any one of claims 1 to 5 , further comprising an attitude control device that controls the attitude of the main body. A method for controlling an autonomous mobile object,
The control unit causes the main body to turn by giving a difference between the rotational angular velocities of the two drive wheels based on the course information indicating the target course to the differential mechanism;
The control unit causes the steering mechanism to change the rudder angle of the drive wheels for each of the drive wheels based on the course information;
a control unit simultaneously controlling the differential mechanism and the steering mechanism along the target trajectory;
The control unit determines a target azimuth angular velocity of the drive wheels so as to eliminate an azimuth error between a first target point on the target trajectory and the azimuth of the main body, and drives the vehicle toward a second target point on the target trajectory. Determining a target steering angle of the wheels;
The controller controls the heading error, the target heading angular velocity and the target rudder angle, with α as the heading error, (xt1, yt1) as the first target point, (xt2, yt2) as the second target point, and Ψ as the yaw angle. where ωd is the target yaw rate, L is the tracking length, v is the forward speed, and δ is the rudder steering angle (steer angle);
α = arctan ((yt1-y)/(xt1-x))-Ψ (1)
ωd=(1/L)vα (2)
δ = arctan ((yt2-y)/(xt2-x))-Ψ (3)
A control method with

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