WO2021145229A1 - Mobile body and control method - Google Patents

Abstract

This mobile body is an autonomous mobile type, and comprises: a body; two drive wheels that are driven by an electric motor and move the body; a differential mechanism that turns the body by giving a difference in the rotation angle velocity between the drive wheels; and a steering mechanism that changes the steering angle of the drive wheel for each drive wheel.

Description

Mobile and control method

The present invention relates to a moving body and a control method. This application claims priority based on US Provisional Patent Application No. 62/960699 filed in the United States on January 14, 2020, the contents of which are incorporated herein by reference.

In recent years, the development of autonomous mobile bodies such as unmanned vehicles (eg, autonomous mobile robots) has been active. In the case of unmanned vehicles driving on the road, there are fixed places and rules to operate, such as roads, lanes, and traffic lights. On the other hand, there are robots that have to move while avoiding static and dynamic obstacles in an environment where humans come and go without any special guidance. For example, it is a case of a security / guidance robot, a cleaning robot, a cargo carrying robot, a personal mobility (transporting one person), and the like. In the case of a robot that moves in such an environment where humans come and go, flexible movement control that can move in a more complicated environment without disturbing human activities is required.
Robots that move in an environment where humans come and go have size and shape restrictions. For example, indoors, it is better for robots to be able to use doors, elevators, etc. used by humans, so the width of the robot must be less than or equal to the width of the human body. In addition, since it runs in an environment where humans exist, it needs to have a certain height that is easily recognized by humans. Therefore, security / guidance robots and the like often have a vertically long shape having a size conforming to the human body shape.

For this reason, robots that move in an environment where humans come and go are often composed of a differential two-wheel mechanism that is not complicated and easy to miniaturize. The differential two-wheel mechanism changes the direction of the course by attaching two left and right wheels to the robot, driving each independently, and making a difference in the rotation speeds of the left and right wheels. For example, Patent Document 1 discloses a mobile system operated by a differential two-wheel mechanism.

Japanese Unexamined Patent Publication No. 2019-105901

In the environment where humans come and go, there are static obstacles such as desks, chairs, and walls, and dynamic obstacles such as walking humans. Therefore, the robot needs to quickly avoid dynamic obstacles and change the movement route. However, in the differential two-wheel mechanism, even if an attempt is made to change the wheel rotation speeds of the left and right two wheels while the motor is operating at high speed, the reaction is slow and the motor can only slowly turn around.
The present inventor states that when considering the operation of a robot in a space where people gather, it is difficult to avoid obstacles in the space where people gather, and as a result, the frequency of stopping of the mobile robot increases. I found a problem.
In addition, the problem is that the ability of a mobile robot equipped with two differential wheels to follow the target trajectory depends on the control by the motor, and due to the characteristics of the DC motor, the torque decreases at high speeds, so the target during running It was found that the factor was that it had a structural problem that the ability to follow the orbit deteriorated.
Due to these issues, robots have not yet been operated in a crowded space such as a city center.
The present invention has been made in view of the above points, and an object of the present invention is to provide a moving body and a control method capable of improving the ability to follow a target trajectory.

(1) One aspect of the present invention is an autonomously moving moving body, in which a main body, two driving wheels driven by an electric motor to move the main body, and a difference in rotational angular velocity between the driving wheels are given. It is a moving body including a differential mechanism for turning the main body and a steering mechanism for changing the steering angle of the driving wheels for each driving wheel.
(2) In one aspect of the present invention, in the moving body according to (1) above, the differential mechanism changes the steering angle with the position of the drive wheels in the contact patch as the turning center for each drive wheel. Let me.
(3) One aspect of the present invention further includes a control unit that simultaneously controls the differential mechanism and the steering mechanism along a target trajectory in the moving body according to the above (1) or (2).
(4) In one aspect of the present invention, in the moving body according to the above (3), the control unit has a course information indicating a target course of the moving body, a moving speed of the driving wheels, and a turning speed of the main body. The target rotation angular velocity of the drive wheels and the target steering angle of the drive wheels are calculated based on the steering angle of the drive wheels.
(5) In one aspect of the present invention, in the moving body according to the above (3), the control unit has the driving wheel so as to eliminate an orientation error between the first target point on the target orbit and the orientation of the main body. The target directional angle speed of the above is determined, and the target steering angle of the drive wheels is determined toward the second target point on the target orbit.
(6) In one aspect of the present invention, in the moving body according to the above (5), the control unit sets the orientation error, the target azimuth angular velocity and the target steering angle, the orientation error α, and the first target point. Was (xt1, yt1), the second target point was (xt2, yt2), Ψ was the yaw angle, wd was the target yaw rate, L was the tracking length, forward speed was v, and δ was the steering angle (steering angle). In some cases, 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.
(7) In one aspect of the present invention, in the moving body according to any one of (1) to (6) above, the projected area of the main body when viewed in the moving direction is the said when viewed vertically. It is larger than the projected area of the main body.
(8) In one aspect of the present invention, in the moving body according to any one of (1) to (7) above, the height is longer than the width of the shaft connecting the two drive wheels.
(9) One aspect of the present invention further includes an attitude control device for controlling the posture of the main body of the moving body according to any one of (1) to (8) above.
(10) One aspect of the present invention is an autonomous moving type moving body control method, in which the main body is rotated by giving a difference in the rotational angular velocities of the drive wheels based on the course information indicating the target course. This is a control method including changing the steering angle of the driving wheels for each driving wheel based on the course information.

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

It is a schematic diagram of the moving body which concerns on one Embodiment of this invention. It is a figure which shows an example of the driving method of the moving body which concerns on this embodiment. It is a block diagram which shows the moving body which concerns on this embodiment. It is a figure which shows an example of the operation of the moving 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 trajectory tracking performance of the moving body which concerns on this embodiment. It is a figure which shows an example of the steering angle control of the moving 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. It is a figure which shows an example of the locus of a moving body. It is a figure which shows an example of the locus of a moving body which concerns on this embodiment. It is a figure which shows another example of the moving body which concerns on this embodiment. It is external drawing of the moving body which concerns on the modification of 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 the operation of the moving body which concerns on the modification of embodiment. It is a figure for demonstrating Example 1 of the acceleration received by a moving body. It is a figure for demonstrating Example 2 of the acceleration received by a moving body. It is a figure for demonstrating Example 3 of the acceleration received by a moving body. It is a figure for demonstrating an example of the posture angle of a moving body.

Next, the moving body and the control method according to the present embodiment will be described with reference to the drawings. The embodiments described below are merely examples, and the embodiments to which the present invention is applied are not limited to the following embodiments.
In all the drawings for explaining the embodiment, the same reference numerals are used for those having the same function, and the repeated description will be omitted.
Further, "based on XX" in the present application means "based on at least XX", and includes a case where it is based on another element in addition to XX. Further, "based on XX" is not limited to the case where XX is used directly, but also includes the case where XX is calculated or processed. "XX" is an arbitrary element (for example, arbitrary information).

(Embodiment)
(Mobile)
FIG. 1 is a schematic view of a moving body according to an embodiment of the present invention. The moving body 100 according to the present embodiment autonomously travels on a preset route or an automatically generated route by following a preset speed profile or an automatically generated speed profile. An example of the mobile body 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 rotating body (prolate spheroid) obtained when an ellipse is placed on a horizontal plane (ground) with its long axis perpendicular to the horizontal plane (ground) and rotated with the long axis as the rotation axis. The main body 105 has an elliptical shape when viewed in the moving 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 the projected area when viewed vertically. With such a configuration, when traveling in an environment in which a human exists, it can be easily recognized by the human.

The drive mechanism 140 moves the main body 105. The drive mechanism 140 includes two drive wheels and a steering angle mechanism.
Each of the two drive wheels is driven by the power of different motors and the like. In the present embodiment, as an example, a case where each of the two drive wheels is driven by a different motor 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 case where the direction of the line connecting the two drive wheels is the Y-axis, the longitudinal direction of the moving body 100 is the Z-axis, and the Y-axis and the direction perpendicular to the Z-axis are the X-axis will be continued. The vertical upward direction in the longitudinal direction of the moving body 100 is defined as the positive direction of the Z axis.
The controller 130 controls each of the two drive wheels. The controller 130 gives a difference in the rotation speed between the drive wheels when the main body 105 is turned. That is, the controller 130 controls each of the two drive wheels to a different rotation speed when the main body 105 is rotated. The controller 130 changes the steering angle of the driving wheels for each driving wheel with respect to the steering angle mechanism. That is, when the main body 105 is turned, the controller 130 controls each of the two drive wheels to a different steering angle with respect to the steering angle mechanism.

FIG. 2 is a diagram showing an example of a method of driving a moving body according to the present embodiment.
FIG. 2 is a schematic view of the drive mechanism 140 of the moving body 100 as viewed from the positive side of the Z axis. As described above, the drive mechanism 140 includes two drive wheels (drive wheels A and drive wheels B) and a steering angle mechanism. The two drive wheels are driven by different motors. The length connecting the two drive wheels is, for example, within 1 m. With this configuration, the moving body 100 can also use the doors, elevators, and the like used by humans. The minimum turning radius of the moving body 100 is, for example, 0.5 m or less. Hereinafter, the angle will be described with clockwise as a plus.
The uppermost view of FIG. 2 is a diagram showing a state of drive wheels when the moving body 100 moves in the positive direction of the X-axis. In the uppermost view of FIG. 2, the main body 105, the drive wheel A, the drive wheel B, the axle γ, and the shaft α are shown. When the moving body 100 moves in the positive direction of the X-axis, the axle γ is in the same direction as the axis α. It is desirable that the axis α passes near the center of gravity of the main body 105.
The second figure from the top of FIG. 2 is a diagram showing the state of the drive wheels when the moving body 100 moves to the right, in other words, to the plus direction side of the Y axis. When the moving body 100 moves in the positive direction of the Y-axis, the controller 130 controls the angle formed by the X-axis and the direction perpendicular to the axis α in the drive wheel A to the angle a, and becomes the axis α in the drive wheel B. The angle formed by the vertical direction and the X-axis is controlled to the angle b. When moving the moving body 100 to the plus direction side of the Y axis, the controller 130 sets the angle a and the angle b individually. The angle a is set with the position in the surface where the drive wheels A are in contact with the ground (hereinafter referred to as "ground contact surface") as the turning center. The angle b is set with the position in the ground contact surface where the drive wheels B are in contact with the ground as the turning center. The ground contact surface is a place where the drive wheels come into contact with the horizontal plane when the moving body is placed on the horizontal plane, and means a ground contact point or its vicinity.

The third figure from the top of FIG. 2 is a diagram showing the state of the drive wheels when the moving body 100 moves to the left, in other words, to the minus direction side of the Y axis. When the moving body 100 moves to the minus direction side of the Y axis, the controller 130 controls the angle formed by the direction perpendicular to the axis α and the X axis in the drive wheel A to an angle −c, and the axis α in the drive wheel B. The angle between the direction perpendicular to the X-axis and the X-axis is controlled to the angle −d. When moving the moving body 100 to the minus direction side 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 contact surface where the drive wheels A are in contact with the ground as the turning center. The angle −d is set with the position in the ground contact surface where the drive wheels B are in contact with the ground as the turning center.
The bottom view of FIG. 2 is a diagram showing that the moving body 100 may further include wheels. The drive mechanism 140 includes one or more wheels C that can move in all directions in a direction perpendicular to the axis α. In the example shown in the lowermost figure of FIG. 2, a case is shown in which wheels C1 and wheels C2 that can move in all directions are provided at two locations sandwiching the Y axis in a direction perpendicular to the axis α. Here, the case where the wheels C1 and the wheels C2 are provided has been described, but either the wheels C1 and the wheels C2 may be provided. With this configuration, the traveling of the moving body 100 can be stabilized.

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

The traveling condition acquisition unit 132 is connected to the encoder 142-1, the encoder 142-2, the steering mechanism 143-1, the steering mechanism 143-2, and the control device 131. The traveling condition acquisition unit 132 acquires information indicating the rotation speed n1 of the electric motor 141-1 output by the encoder 142-1. The traveling condition acquisition unit 132 acquires information indicating the rotation speed n2 of the electric motor 141-2 output by the encoder 142-2. The traveling condition acquisition unit 132 acquires information indicating the steering angle (steering angle) δ1 of the drive wheels A output by the steering mechanism 143-1. The traveling condition acquisition unit 132 acquires information indicating the steering angle (steering angle) δ2 of the drive wheels B output by the steering mechanism 143-2.
The traveling condition acquisition unit 132 has a turning speed ω1 which is a speed at which the forward speed V1 of the drive wheel A of the moving body 100 and the moving body 100 are turned based on the acquired information indicating the rotation speed n1 of the electric motor 141-1. And derive. Based on the acquired information indicating the rotation speed n2 of the electric motor 141-2, the traveling condition acquisition unit 132 advances the forward speed V2 of the drive wheels B of the moving body 100 and the turning speed ω2 which is the speed at which the moving body 100 is turned. And derive.
The traveling condition acquisition unit 132 sends the derived information indicating the forward speed V1 of the drive wheel A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the drive wheel B, and the information indicating the turning speed ω2 to the control device 131. Output. The traveling condition acquisition unit 132 outputs the acquired information indicating the steering angle δ1 of the drive wheels A and the 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 unit 135 and a rotation angular velocity control unit 136.
The steering angle control unit 135 outputs information indicating the forward speed V1 of the drive wheel A, information indicating the turning speed ω1, information indicating the forward speed V2 of the drive wheel B, and information indicating the turning speed ω2 output by the traveling condition acquisition unit 132. And the information indicating the steering angle δ1 of the drive wheel A and the information indicating the steering angle δ2 of the drive wheel B are acquired. The rudder angle control unit 135 includes the acquired information indicating the forward speed V1 of the drive wheel A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the drive wheel B, the information indicating the turning speed ω2, and the rudder of the drive wheel 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 ”) and are derived. The steering angle control unit 135 outputs the derived information indicating the target steering angle A to the steering mechanism 143-1 and outputs the information indicating the target steering angle B to the steering mechanism 143-2.
The rotation angular velocity control unit 136 outputs information indicating the forward speed V1 of the drive wheel A, information indicating the turning speed ω1, information indicating the forward speed V2 of the drive wheel B, and information indicating the turning speed ω2 output by the traveling condition acquisition unit 132. And the information indicating the steering angle δ1 of the drive wheel A and the information indicating the steering angle δ2 of the drive wheel B are acquired. The rotation angular velocity control unit 136 includes the acquired information indicating the forward speed V1 of the drive wheel A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the drive wheel B, the information indicating the turning speed ω2, and the steering of the drive wheel A. Based on the information indicating the angle δ1 and the information indicating the steering angle δ2 of the drive wheel B, the rotation angular velocity of the drive wheel A (hereinafter referred to as “target rotation angular velocity A”) and the rotation angular velocity of the drive wheel B (hereinafter referred to as “target rotation angular velocity”). B ”) and are derived. The rotation angular velocity control unit 136 outputs the derived control information for controlling at the target rotation angular velocity A to the motor 141-1 and outputs the control information for controlling at the target rotation angular velocity B to the motor 141-2.
In the control device 131, the steering angle control unit 135 outputs the information indicating the target steering angle A to the steering mechanism 143-1 and the information indicating the target steering angle B to the steering mechanism 143-2, and the rotational angular velocity control. The control is performed simultaneously with the control in which the unit 136 outputs the control information for controlling at the target rotational angular velocity A 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.
In the control device 131, the steering angle control unit 135 outputs the information indicating the target steering angle A to the steering mechanism 143-1 and the information indicating the target steering angle B to the steering mechanism 143-2, and the rotational angular velocity control. The control in which the unit 136 outputs the control information for controlling at the target rotational angular velocity A 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 means that the moving body 100 outputs the control information. It is done at an arbitrary timing while driving.

(Movement of moving body)
FIG. 4 is a diagram showing an example of the operation of the moving body according to the present embodiment. A process when the moving body 100 follows the target trajectory will be described with reference to FIG.
(Step S1-1)
The traveling condition acquisition unit 132 acquires information indicating the rotation speed n1 of the electric motor 141-1 output by the encoder 142-1. The traveling condition acquisition unit 132 acquires information indicating the rotation speed n2 of the electric motor 141-2 output by the encoder 142-2.
(Step S2-1)
The traveling condition acquisition unit 132 acquires information indicating the steering angle (steering angle) δ1 of the drive wheels A output by the steering mechanism 143-1. The traveling condition acquisition unit 132 acquires information indicating the steering angle (steering angle) δ2 of the drive wheels B output by the steering mechanism 143-2.
(Step S3-1)
The traveling condition acquisition unit 132 has a turning speed ω1 which is a speed at which the forward speed V1 of the drive wheel A of the moving body 100 and the moving body 100 are turned based on the acquired information indicating the rotation speed n1 of the electric motor 141-1. And derive. Based on the acquired information indicating the rotation speed n2 of the electric motor 141-2, the traveling condition acquisition unit 132 advances the forward speed V2 of the drive wheels B of the moving body 100 and the turning speed ω2 which is the speed at which the moving body 100 is turned. And derive.
(Step S4-1)
The traveling condition acquisition unit 132 sends the derived information indicating the forward speed V1 of the drive wheel A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the drive wheel B, and the information indicating the turning speed ω2 to the control device 131. Output. The traveling condition acquisition unit 132 outputs the acquired information indicating the steering angle δ1 of the drive wheels A and the information indicating the steering angle δ2 of the drive wheels B to the control device 131.
The steering angle control unit 135 outputs information indicating the forward speed V1 of the drive wheel A, information indicating the turning speed ω1, information indicating the forward speed V2 of the drive wheel B, and information indicating the turning speed ω2 output by the traveling condition acquisition unit 132. And the information indicating the steering angle δ1 of the drive wheel A and the information indicating the steering angle δ2 of the drive wheel B are acquired. The steering angle control unit 135 includes the acquired 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 drive wheels B, the information indicating the turning speed ω2, and the steering of the drive 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 the derived information indicating the target steering angle A to the steering mechanism 143-1 and outputs the information indicating the 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. The steering mechanism 143-1 changes the steering angle of the steering actuator of the drive wheel A based on the acquired information indicating the target steering angle A.
The steering mechanism 143-2 acquires information indicating a target steering angle B of the drive wheels B output by the control device 131. The steering mechanism 143-2 changes the steering angle of the steering actuator of the drive wheel B based on the acquired information indicating the target steering angle B.
(Step S6-1)
The rotation angular velocity control unit 136 outputs information indicating the forward speed V1 of the drive wheel A, information indicating the turning speed ω1, information indicating the forward speed V2 of the drive wheel B, and information indicating the turning speed ω2 output by the traveling condition acquisition unit 132. And the information indicating the steering angle δ1 of the drive wheel A and the information indicating the steering angle δ2 of the drive wheel B are acquired. The rotation angular velocity control unit 136 includes the acquired information indicating the forward speed V1 of the drive wheel A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the drive wheel B, the information indicating the turning speed ω2, and the steering of the drive wheel A. Based on the information indicating the angle δ1 and the information indicating the steering angle δ2 of the drive wheel B, the target rotation angular velocity A of the drive wheel A and the target rotation angular velocity B of the drive wheel B are derived. The rotation angular velocity control unit 136 outputs the derived control information for controlling at the target rotation angular velocity A to the motor 141-1 and outputs the control information for controlling at the target rotation angular velocity B to the motor 141-2.
(Step S7-1)
The electric motor 141-1 acquires the control information output by the control device 131. The electric motor 141-1 drives the drive wheels A based on the acquired control information.
The electric motor 141-2 acquires the control information output by the control device 131. The electric motor 141-2 drives the drive wheels B based on the acquired control information.

(Performance of mobile body)
The trajectory tracking performance of the moving body 100 will be described. In order to compare the trajectory tracking performance of the conventional moving body (differential two-wheeled trolley with steering) and the moving body 100, a simulation based on a model formula was performed. Here, as an example, the track tracking result of the differential two-wheeled bogie according to the Pure Pursuit rule is shown. Tracking the trajectory of a differential two-wheeled trolley according to the Pure Pursuit law is commonly used in the field of robots. The Pure Pursuit law is a method of chasing a target (carrot) in 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-wheeled trolley, and the distance to the target (carrot) is set to 2 [m]. The target speed was 3 [m / s] (about 11 [km / h]), which was considerably faster than the general walking speed, and was set to a speed sufficient for a short run.
FIG. 5 is a diagram showing an example of the trajectory tracking performance of the moving body. In FIG. 5, the horizontal axis is the x-coordinate and the vertical axis is the y-coordinate. In FIG. 5, the target trajectory (hereinafter referred to as “target trajectory”) is indicated by a thick line, and the trajectory of a conventional moving body is indicated by a thin line. The target orbit includes a small avoidance behavior with an amplitude of 1 [m] and a period of about 6 [m]. By assuming such an orbit, it can be assumed that crowds will be avoided. The target trajectory is determined by the future position of the dynamic obstacle (person), which changes from moment to moment. 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 orbit at all, and in some cases, the phase is reversed. The fact that the phase is reversed means that the person has passed the place where it is assumed that there is a person to avoid, and thus it corresponds to the failure to avoid.
FIG. 6 is a diagram showing an example of the trajectory tracking performance of the moving body according to the present embodiment. In FIG. 6, in addition to the track tracking according to the Pure Pursuit rule, a dolly (CCV) capable of turning the steering wheel 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 is shown by a thick line, and the trajectory of the moving body 100 is shown by a thin line. The target trajectory includes a small avoidance behavior having an amplitude of 1 [m] and a period of about 6 [m] as in FIG. The tracking parameters of the first carrot have the same settings as in FIG. The distance to the second carrot was set to 0.5 [m], and the maximum value of the steer angle was set to 24 [deg] (= 0.42 [rad]).
According to FIG. 6, it can be seen that the trajectory can be tracked without a phase delay.
FIG. 7 is a diagram showing an example of steering angle control of the moving body according to the present embodiment. In FIG. 7, the horizontal axis is time and the vertical axis is the rudder angle. According to FIG. 7, it can be seen that the moving body 100 is actively steering 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 the model formula. Here, a unicycle model will be described as an example.
In FIG. 8, the moving body 100 located at the coordinates (x, y) with respect to the target trajectory TT sets a point at a predetermined distance as a target point (carrot 1 (first target point), carrot 2 (second target point)). A state in which turning control is performed in order to reach that point is shown.
A method in which the control device 131 sets the carrot 1 in the mobile body 100 will be described.
When the speed of the robot is V [m / s], the distance that can be reached after the elapse of T [s] is V × T [m]. Therefore, the control device 131 is generally set so that L1 [m] ≈VT. Here, the azimuth angle change amount α that can be turned differentially during the time T is represented by α = ωmax × T, where the maximum turning speed is ωmax. If α is larger than the maximum curvature ρmax of the target trajectory (α> ρmax), the target trajectory can be traced.
When the forward speed V of the robot (moving body 100) is small, there is a solution that satisfies this, but when V is large, there may be no solution that satisfies this. Therefore, carrot2 is set in order to improve traceability.
A method in which the control device 131 sets the carrot 2 in the mobile 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 a relatively high speed. Therefore, the distance L2 to this target can be placed relatively close. That is, L2 << L1 holds. However, when L2 is too close (when L2 is equal to or less than a predetermined threshold value), the rudder is turned too violently (larger), so that the acceleration received by the robot (moving body 100) also increases. Therefore, the control device 131 sets the carrot 2 to an appropriate place (position) that satisfies 0 << L2 << L1.
In the Pure pursuit, as shown in FIG. 8, carrot1 (xt1, yt1) and carrot2 (xt2, yt2) are set for an arbitrary point cx of the target orbit TT. The mobile 100 tracks carrot 1 and carrot 2 at the same time. 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 (steering angle).

The update formula is 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 + dat (4)
With respect to carrot 1, the rotation angular velocity control unit 136 sets the target directional angular velocity of the drive wheels so as to eliminate the directional error between the first target point on the target orbit and the directional of the main body 105, and is based on the set target directional angular velocity. The attitude and direction are controlled by differential. That is, the rotation angular velocity control unit 136 sets the target directional angular velocity of the drive wheel that reduces the directional error between the first target point on the target orbit and the orientation of the main body 105, and differentially performs based on the set target directional angular velocity. Attitude Direction control is performed.
The orientation error α with respect to the moving body 100 with respect to carrot 1 is expressed by the equation (4).
α = arctan ((yt1-y) / (xt1-x))-Ψ (4)
When the carrot 1 and the center of the moving body 100 are connected by a circle, the turning radius R is represented by R = L / (2 sin α).
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)
With respect to carrot2, the steering angle control unit 135 sets the target steering angle of the drive wheels toward the second target point on the target trajectory, and adjusts the steering based on the set target steering angle to obtain the speed vector. Control the direction.
The turning angle δ of the rudder is expressed by the equation (6). However, δ ≦ δmax.
δ = arctan ((yt2-y) / (xt2-x))-Ψ (6)
The moving body 100 simultaneously performs two types of control, that is, the attitude and direction control by differential (slow and large movement) and the direction control of the velocity vector by steering (high speed and small movement). With this configuration, higher trajectory tracking performance can be exhibited as compared with the case where the attitude / direction control and the direction control of the velocity vector do not coexist.

In FIG. 8, a case where the model is replaced with a unicycle model has been described. The unicycle model corresponds to the bicycle model in a four-wheeled vehicle. In reality, since the moving body 100 has drive wheels on the left and right, it is necessary to determine the steering angle for each of the two drive wheels. Next, a case where the steering angles of the two drive wheels are determined will be described.
FIG. 9 is a diagram for explaining an example of the model formula.
When a general differential two-wheeled trolley without a rudder turns while traveling, its rotation (turning) center is always on an extension of the line connecting the centers of the left and right wheels. However, since the moving body 100 includes a rudder, the turning center is within the range shown by the diagonal line in FIG. 9, depending on the limit value that the actual rudder angle can take. When it is −δmax or more and δmax or less, the center of rotation can be placed in the range indicated by the diagonal line. In FIG. 9, the rudder turning angle δi and the rudder turning angle δ0 are represented by the 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)
Further, the equation (9) and the equation (10) are established.
ω = (1 / L1) vα (9)
r = v / ω (10)
The steering angle is determined so that the axles of each wheel penetrate the turning center placed in the range indicated by the diagonal line. With this configuration, the moving body 100 can simultaneously determine the traveling direction (at that moment) by the steering angle and generate the directional angular velocity (yaw rate) around a certain rotation center.

FIG. 10 is a diagram showing an example of a locus of a moving body. FIG. 10 shows an example of the locus of a moving body such as a commonly used differential two-wheeled trolley. In FIG. 10, the horizontal axis is the velocity of the moving body and the vertical axis is the locus of the moving body in the Y-axis direction. The solid black line is the locus of the moving body, and the light black broken line is the locus of the moving body whose speed is 1.5 times that of the moving body shown in black.
A commonly used moving body controls its direction by the difference in traveling speed between the left and right wheels. For this reason, in a commonly used moving body, the speed of directional change is determined by how fast the speed difference can be applied. In other words, in a commonly used moving body, the speed of directional change is determined by the magnitude of torque.
A DC motor is used to drive the moving body. The torque of the DC motor decreases linearly as the speed increases. As shown in FIG. 10, when the speed is increased by 1.5 times, the region of the locus of the moving body 100 decreases. Therefore, it can be seen that the higher the moving speed of the moving body, the more difficult it is to follow the target trajectory.

FIG. 11 is a diagram showing an example of the locus of the moving body according to the present embodiment. FIG. 11 also shows an example of the locus of a moving body such as a differential two-wheeled trolley that is generally used for comparison. In FIG. 11, the horizontal axis is the velocity of the moving body and the vertical axis is the locus of the moving body in the Y-axis direction. The light black broken line is the locus of the moving body whose speed is 1.5 times that of the moving body shown by the black solid line in FIG. 10, and the black solid line in FIG. 11 is the locus of the moving body 100. The moving body 100 includes a mechanism for adjusting steering (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 region of the locus of the moving body 100 increases. Compared with the differential two wheels, the mobile body 100 has a significantly increased area in which it can penetrate. That is, 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 in the direction perpendicular to the axis α has been described, but the present invention is not limited to this example. For example, one or more support mechanisms may be provided instead of the wheel C.
In the above-described embodiment, the case where the axle γ is in the same direction as the axis α when the direction of the drive wheels is changed has been described, but the present invention is not limited to this example. For example, when changing the direction of the drive wheels, the direction of the wheels γ connected to the axle γ may be changed.
In the above-described embodiment, the moving body 100 may include training wheels in addition to the two drive wheels (drive wheels A and drive wheels B).
FIG. 12 is a diagram showing another example of the moving body according to the present embodiment. FIG. 12 shows a moving body 100 provided with training wheels 150. By providing the auxiliary wheels 150 in addition to the two drive wheels, the moving body 100 can be stably moved as compared with the case where the two drive wheels are provided. Therefore, it is possible to reduce the possibility that the moving body 100 falls over.
In the above-described embodiment, the track tracking result of the differential two-wheeled trolley controlled by using the Pure Pursuit law has been described as an example, but the present invention is not limited to this example. For example, it is also possible to control the moving body 100 by using LQR (Linear Quadratic Regulator), model prediction control, or the like.
According to the moving body 100 according to the present embodiment, the moving body 100 is an autonomous moving type, and is driven by a main body 105 and an electric motor (electric motor 141-1, electric motor 141-2) to move the main body 105. The wheels (drive wheels A, drive wheels B), the rotational angular velocity control unit 136 as a differential mechanism that turns the main body 105 by giving a difference in the rotational angular velocities between the drive wheels, and the steering angle of the drive wheels for each drive wheel. It is provided with a steering angle control unit 135 as a steering mechanism that changes the steering angle to. With this configuration, the main body 105 can be turned by giving a difference in the rotational angular velocities of the drive wheels, and the steering angle of the drive wheels can be changed for each drive wheel. Therefore, the target trajectory of the moving body 100 can be changed. Can improve the ability to follow.
Further, the differential mechanism changes the steering angle with the position of the drive wheels in the contact patch as the turning center for each drive wheel. With such a configuration, the energy efficiency of the moving body 100 can be improved because the steering can be quickly turned with a small torque as compared with the case where the position of the drive wheel in the contact patch is not set as 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 wheels A and drive wheels B) at different target steering angles, and the steering mechanism controls the two drive wheels (drive wheels A and drive wheels B). Each of the drive wheels A and the drive wheels B) is controlled at different target rotational angular velocities. Therefore, the moving body 100 can avoid obstacles quickly and in a small turn.
Further, the control unit sets the target directional angle velocity of the drive wheels so as to eliminate the directional error between the first target point on the target orbit and the orientation of the main body 105, and the drive wheels are directed toward the second target point on the target orbit. Set the target steering angle of. With this configuration, at two different target points, the first target point and the second target point, the target azimuth angular velocity is set with respect to the first target point, and the target rudder is set with respect to the second target point. Since the angle can be set, the differential mechanism and the steering mechanism can be controlled at the same time.
Further, the control unit sets the azimuth error, the target azimuth angular velocity and the target rudder angle, the azimuth error is α, the first target point is (xt1, yt1), the second target point is (xt2, yt2), and Ψ is the yaw angle. Equations (1) to (3), where wd is the target yaw rate, L is the tracking length, forward speed is v, and δ is the steering angle (steering angle).
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 wheel with the rudder turned δ runs. 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. With such a configuration, when traveling in an environment in which a human exists, it can be easily recognized by the human.

(Modified example of the embodiment)
(Mobile)
FIG. 13 is an external view of a moving body according to a modified example of the embodiment. The moving body 100a according to the modified example of the embodiment receives the course information transmitted by the server 200, and autonomously travels so that the received course information follows a speed profile given in advance or an automatically generated speed profile. conduct.
The mobile body 100a is connected to the server 200 via the 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 100a includes a main body 105, a distance measuring unit 110, a communication unit 120, a controller 130, a drive mechanism 140, training wheels 150, an inertial measurement unit 160, a communication unit 170, an imaging unit 180, and a depth detection unit 190.
The main body 105 is a housing of the moving body 100, and stores a distance measuring unit 110, a communication unit 120, a controller 130, a drive mechanism 140, an inertial measurement unit 160, a communication unit 170, an imaging unit 180, and a depth detection unit 190. ..

The distance measuring unit 110 measures the distance between an obstacle such as a person or an object existing around the moving body 100a. An example of the ranging unit 110 is a three-dimensional LiDAR (Light Detection and Ranging). Three-dimensional LiDAR measures scattered light with respect to laser irradiation that emits pulsed light, and analyzes the distance to an object at a long distance and the properties of the object.
The 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 by a wireless communication method such as LTE (registered trademark). 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 speed, moving distance, and position of the moving body 100a. An example of the inertial measurement unit 160 includes a three-axis gyro and a three-direction accelerometer. The inertial measurement unit 160 derives a three-dimensional angular velocity and acceleration by using a three-axis gyro and a three-direction accelerometer. The inertial measurement unit 160 derives the velocity, moving distance, and position of the moving body 100a based on the derived three-dimensional angular velocity and acceleration.
The 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 by 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 periphery of the moving body 100a. An example of the image pickup 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 body 100a. An example of the depth detection unit 190 is a 360 ° depth camera.

FIG. 14 is a diagram showing a moving body according to a modified example of the embodiment. As described above, the moving body 100a according to the embodiment includes the main body 105, the distance measuring unit 110, the communication unit 120, the controller 130, the drive mechanism 140, the training wheels 150, the inertial measurement unit 160, the communication unit 170, and the imaging unit 180. It is provided with a depth detection unit 190.
The controller 130 includes a control device 131a, a traveling condition acquisition unit 132a, a reception unit 133, a processing unit 134, and a position / orientation estimation unit 137.
The position / posture estimation unit 137 measures the distance between the distance measuring unit 110 and static obstacles such as desks, chairs, and walls existing around the moving body 100a, and dynamic obstacles such as walking humans. Obtain the measurement result of the distance between and. The position / orientation estimation unit 137 acquires the result of deriving the velocity, the moving distance, and the position of the moving body 100a from the inertial measurement unit 160. The position / orientation estimation unit 137 acquires the detection result of the depth of an obstacle such as a person or an object existing around the moving body 100a from the depth detection unit 190. The position / posture estimation unit 137 measures the distance between the acquired moving body 100a and the static obstacle, the measurement result of the distance between the moving body and the dynamic obstacle, and the speed of the moving body 100a. The position and posture of the moving body 100a are estimated based on the result of deriving the moving distance and the position and the detection result of the depth of the obstacle existing around the moving body 100a.
The reception 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 unit 135a and a rotation angular velocity control unit 136a.
The steering angle control unit 135a outputs information indicating the forward speed V1 of the drive wheel A, information indicating the turning speed ω1, information indicating the forward speed V2 of the drive wheel B, and information indicating the turning speed ω2 output by the traveling condition acquisition unit 132. And the information indicating the steering angle δ1 of the drive wheel A and the information indicating the steering angle δ2 of the drive wheel B are acquired.
The steering angle control unit 135a acquires the result of estimating the position and attitude of the moving body 100a from the position / attitude estimation unit 137. The steering angle control unit 135a acquires the course information notification from the reception unit 133. The steering angle control unit 135a acquires the course information included in the acquired course information notification.
The steering angle control unit 135a includes the acquired information indicating the forward speed V1 of the drive wheel A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the drive wheel B, the information indicating the turning speed ω2, and the steering of the drive wheel A. Based on the information indicating the angle δ1, the information indicating the steering angle δ2 of the driving wheel B, the result of estimating the position and orientation of the moving body 100a, and the course information, the target steering angle A of the driving wheel A and the driving wheel B The target rudder angle B is derived. The steering angle control unit 135 outputs the derived information indicating the target steering angle A to the steering mechanism 143-1 and outputs the information indicating the target steering angle B to the steering mechanism 143-2.

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

(Movement of moving body)
FIG. 15 is a diagram showing an example of the operation of the moving body according to the modified example of the embodiment. Here, a case where the mobile body 100a is located in an environment where a wireless LAN can be used will be described.
(Step S1-2)
The server 200 acquires the course information of the mobile body 100a.
(Step S2-2)
The server 200 creates a course information notification destined for the mobile body 100a, including the acquired course information of the mobile body 100a.
(Step S3-2)
The server 200 transmits the created route information notification to the mobile body 100a.
(Step S4-2)
In the mobile body 100a, the communication unit 170 receives the route information notification transmitted by the server 200.
(Step S5-2)
In the mobile body 100a, the reception unit 133 receives the route information notification received by the communication unit 170. The control device 131a acquires the course information notification received by the reception unit 133. The control device 131a acquires the course information included in the acquired course information notification.
(Step S6-2)
In the moving body 100a, the position / orientation estimation unit 137 measures the distance measurement result between the distance measuring unit 110 and the static obstacle existing around the moving body 100a and the distance between the dynamic obstacle and the moving body 100a. Get the result and. The position / orientation estimation unit 137 acquires the result of deriving the velocity, the moving distance, and the position of the moving body 100a from the inertial measurement unit 160. The position / orientation estimation unit 137 acquires the detection result of the depth of an obstacle such as a person or an object existing around the moving body 100a from the depth detection unit 190. The position / posture estimation unit 137 measures the distance between the acquired moving body 100a and the static obstacle, the measurement result of the distance between the moving body and the dynamic obstacle, and the speed of the moving body 100a. The position and posture of the moving body 100a are estimated based on the result of deriving the moving distance and the position and the detection result of the depth of the obstacle existing around the moving body 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 by the encoder 142-1. The traveling condition acquisition unit 132 acquires information indicating the rotation speed n2 of the electric motor 141-2 output by the encoder 142-2.
(Step S8-2)
In the moving body 100a, the traveling condition acquisition unit 132 acquires information indicating the steering angle (steering angle) δ1 of the drive wheels A output by the steering mechanism 143-1. The traveling condition acquisition unit 132 acquires information indicating the steering angle (steering angle) δ2 of the drive wheels B output by the steering mechanism 143-2.
(Step S9-2)
In the moving body 100a, the traveling condition acquisition unit 132 rotates the forward speed V1 of the drive wheel A of the moving body 100 and the moving body 100 based on the acquired information indicating the rotation speed n1 of the electric motor 141-1. The turning speed ω1 is derived. Based on the acquired information indicating the rotation speed n2 of the electric motor 141-2, the traveling condition acquisition unit 132 advances the forward speed V2 of the drive wheels B of the moving body 100 and the turning speed ω2 which is the speed at which the moving body 100 is turned. And derive.
(Step S10-2)
In the moving body 100a, the traveling condition acquisition unit 132 includes the derived information indicating the forward speed V1 of the drive wheel A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the drive wheel B, and the information indicating the turning speed ω2. Is output to the control device 131a. The traveling condition acquisition unit 132 outputs the acquired information indicating the steering angle δ1 of the drive wheels A and the information indicating the steering angle δ2 of the drive wheels B to the control device 131a.
The steering angle control unit 135a outputs information indicating the forward speed V1 of the drive wheel A, information indicating the turning speed ω1, information indicating the forward speed V2 of the drive wheel B, and information indicating the turning speed ω2 output by the traveling condition acquisition unit 132. And the information indicating the steering angle δ1 of the drive wheel A and the information indicating the steering angle δ2 of the drive wheel B are acquired. The steering angle control unit 135a acquires the result of estimating the position and attitude of the moving body 100a from the position / attitude estimation unit 137. The steering angle control unit 135a acquires course information.
The steering angle control unit 135a includes the acquired information indicating the forward speed V1 of the drive wheel A, the information indicating the turning speed ω1, the information indicating the forward speed V2 of the drive wheel B, the information indicating the turning speed ω2, and the steering of the drive wheel A. Based on the information indicating the angle δ1, the information indicating the steering angle δ2 of the driving wheel B, the result of estimating the position and orientation of the moving body 100a, and the course information, the target steering angle A of the driving wheel A and the driving wheel B The target rudder angle B is derived.

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

Here, the acceleration received by the moving body 100a and the posture angle control will be described. The moving body 100a receives translational acceleration by controlling changes in traveling speed, turning, and steering. The moving body 100a has a function of adjusting the posture angle in the front-rear and left-right directions. The mobile body 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 the acceleration received by the moving body. In FIG. 16, the direction in which the moving body 100a is facing is Nose, the steering angle of the drive wheels is δ, 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 front-back shaking direction of the moving body 100a, is expressed by the equation (11), and the acceleration ay in the Way direction, which is the left-right shaking direction of the moving body 100a, is expressed by the equation (12). NS.
ax = a × cosδ-ac × sinδ (11)
ay = a × sinδ ＋ ac × cosδ (12)
FIG. 17 is a diagram for explaining Example 2 of the acceleration received by the moving body. 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 the equation (13).
ac = v × ω (13)

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

In the modified example of the above-described embodiment, the case where the mobile body 100a autonomously travels so as to follow the course information transmitted by the server 200 has been described, but the present invention is not limited to this example. For example, the moving body 100a may be configured to autonomously travel on a preset route or an automatically generated route so as to follow a preset speed profile or an automatically generated speed profile.
In the modified example of the above-described embodiment, the moment as a reaction 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 moment as a reaction is generated. When the posture is changed at high speed, a large moment that cannot be ignored may be generated, and the moving body 100a may become unstable.
In the modified example of the above-described embodiment, the Coriolis force when changing the posture of the moving body 100a is not considered, but it may be considered. When the moving body 100a suddenly changes its posture while turning, a moment is generated in the direction perpendicular to each rotation axis (= Coriolis force). For example, when pitching while turning, a roll moment is generated, and when rolling while turning, a pitching moment is generated. As a result, if the posture is suddenly changed, the effect of the moving body 100a seems to be relatively minor, but it may become unstable.
According to the moving body 100a according to the modified example of the embodiment, in the moving body 100 of the embodiment, the control unit includes the course information indicating the target course of the moving body 100a, the moving speed of the driving wheels, and the turning speed of the main body 105. And the target rotation angular velocity of the drive wheels and the target steering angle of the drive wheels are calculated based on the steering angle of the drive wheels. With this configuration, the target rotation angular velocity of the driving wheels and the target steering angle of the driving wheels can be calculated based on the course information indicating the target course of the moving body 100a. Therefore, the target course of the moving body 100a can be calculated. Can be taken.
Further, 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. With this configuration, the posture of the moving body 100a can be stabilized.

Although the 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 variations thereof are included in the scope and gist of the invention, and at the same time, are included in the scope of the invention described in the claims and the equivalent scope thereof.
In addition, a part of each device included in the mobile body 100 in the above-described embodiment and the mobile body 100a in the modified example of the embodiment may be realized by a computer. In that case, the program for realizing this control function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by the computer system and executed. The "computer system" referred to 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 "computer-readable recording medium" refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, or a CD-ROM, or a storage device such as a hard disk built in a computer system. Furthermore, a "computer-readable recording medium" is a medium that dynamically holds a program for a short period of time, such as a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In that case, a program may be held for a certain period of time, such as a volatile memory inside a computer system serving as a server or a client. Further, the above-mentioned program may be a program for realizing a part of the above-mentioned functions, and may be a program capable of realizing the above-mentioned functions in combination with a program already recorded in the computer system. .. Further, a part or all of each functional block of each device included in the visit management system in the above-described embodiment may be realized as an integrated circuit such as an LSI. Each functional block of each device included in the visit management system may be made into a processor individually, or a part or all of them may be integrated into a processor. Further, the method of making an integrated circuit is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. Further, when an integrated circuit technology that replaces an LSI appears due to advances in semiconductor technology, an integrated circuit based on this technology may be used.

100, 100a ... moving body, 105 ... main body, 110 ... ranging unit, 120 ... communication unit, 130 ... controller, 131, 131a ... control device, 132 ... traveling condition acquisition unit, 133 ... reception unit, 134 ... processing unit, 135, 135a ... Steering angle control unit, 136, 136a ... Rotation angular velocity control unit, 137 ... Position and orientation estimation unit, 140 ... Drive mechanism, 141-1, 141-2 ... Electric motor, 142-1, 142-2 ... Encoder, 143-1, 143-2 ... Steering mechanism, 150 ... Auxiliary wheels, 160 ... Inertial measurement unit, 170 ... Communication unit, 180 ... Imaging unit, 190 ... Depth detection unit, 200 ... Server

Claims (10)

1. It is an autonomous mobile type mobile body
   With the main body
   Two drive wheels that are driven by an electric motor to move the main body,
   A differential mechanism that rotates the main body by giving a difference in rotational angular velocity between the drive wheels, and
   A steering mechanism that changes the steering angle of the drive wheels for each drive wheel,
   A mobile body equipped with.
2. The moving body according to claim 1, wherein the differential mechanism changes the steering angle with the position of the drive wheels in the contact patch as the turning center for each drive wheel.
3. The moving body according to claim 1 or 2, further comprising a control unit that simultaneously controls the differential mechanism and the steering mechanism along a target trajectory.
4. The control unit determines the target rotation angular velocity of the driving wheels based on the course information indicating the target course of the moving body, the moving speed of the driving wheels, the turning speed of the main body, and the steering angle of the driving wheels. The moving body according to claim 3, wherein the target steering angle of the drive wheels is calculated.
5. The control unit determines the target directional angular velocity of the drive wheels so as to eliminate the directional error between the first target point on the target trajectory and the directional of the main body.
   The moving body according to claim 3, wherein a target steering angle of the drive wheels is determined toward a second target point on the target trajectory.
6. The control unit sets the azimuth error, the target azimuth angular velocity and the target rudder angle, the azimuth error as α, the first target point as (xt1, yt1), the second target point as (xt2, yt2), and Ψ as yaw. When the angle and wd are the target yaw rate, L is the tracking length, the forward speed is v, and δ is the steering angle (steering angle), the determination is made according to 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)
   The mobile body according to claim 5.
7. The moving body according to any one of claims 1 to 6, 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.
8. The moving body according to any one of claims 1 to 7, wherein the height is longer than the width of the shaft connecting the two drive wheels.
9. The moving body according to any one of claims 1 to 8, further comprising an attitude control device for controlling the posture of the main body.
10. It is a control method for autonomous mobile objects.
    Based on the course information indicating the target course, turning the main body by giving a difference in the rotational angular velocity between the drive wheels, and
    To change the steering angle of the drive wheels for each drive wheel based on the course information.
    Control method having.

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