Robot

Abstract

A pair of wheels (240) support a body part (100). A motor (210) rotates the pair of wheels (240). A weight member (220) is disposed such that a center of gravity B of the body part (100) is positioned vertically below a rotation axis A of the pair of wheels (240) when the body part (100) is in an upright state. The weight member (220) is fixed to a stator (211) of the motor (210), and is configured such that when torque is applied to the motor (210), torque required to rotate the pair of wheels (240) is generated around the rotation axis A.

Description

robot

[0001] The present disclosure relates to robots.

[0002] Research into domestic robots is underway to improve quality of life by providing practical assistance and enhancing emotional and social well-being. Examples of such robots include the bipedal robots disclosed in Non-Patent Document 1 and Non-Patent Document 2.

[0003] Robaczewski, A., Bouchard, J., Bouchard, K., & Gaboury, S.: “Socially assistive robots: The specific case of the NAO,” International Journal of Social Robotics, 13, 795-831, 2021. Ozeki, T., Mouri, T., Sugiura, H., Yano, Y., & Miyosawa, K.: “Use of communication robots to converse with people suffering from schizophrenia,” ROBOMECH Journal, 7, 1-14, 2020.

[0004] While these robots offer various benefits, they often lack essential characteristics necessary for seamless interaction with humans and their surroundings. For example, bipedal robots such as those disclosed in Non-Patent Document 1 or Non-Patent Document 2 tend to be unstable.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and one of its objectives is to provide a robot that can ensure posture stability in a robot that operates in harmony with humans.

[0006] In one aspect, the robot comprises a main body, a pair of wheels, and a motor. The main body includes a main member and a weight member. The pair of wheels support the main body. The motor rotates the pair of wheels. The weight member is positioned so that, when the main body is in an upright position, the center of gravity of the main body is located vertically below the rotation axis of the pair of wheels. The weight member is fixed to the stator of the motor and is configured so that, when torque is applied to the motor, the torque required to rotate the pair of wheels is generated around the rotation axis.

[0007] According to the robot of the above aspect, it is possible to ensure stability of posture in a robot that operates in harmony with humans.

[0008] 1 is a schematic diagram of a robot according to a first embodiment; FIG. 2 is a block diagram illustrating an example of the hardware configuration of the robot; FIG. 3 is a diagram illustrating a drive mechanism of the robot; FIG. 4 is a diagram illustrating a driving mechanism of the robot; FIG. 5 is a diagram illustrating a running state of the robot; FIG. 6 is a schematic diagram of a robot according to a second embodiment; FIG. 7 is a block diagram illustrating an example of the hardware configuration of the robot; FIG. 8 is a diagram illustrating a drive mechanism of the robot; FIG. 9 is a diagram illustrating a change in the pitch angle of the main body when the robot runs; FIG. 10 is a diagram illustrating a change in the position of the wheels when the robot rotates at a fixed position; FIG. 11 is a diagram illustrating a change in the pitch angle of the main body when the robot runs on a slope; FIG. 12 is a diagram illustrating an example of a counterweight connection; FIG. 13 is a diagram illustrating an example of a counterweight connection; FIG. 14 is a diagram illustrating a change in the pitch angle of the main body when a counterweight is connected; FIG. 15 is a diagram illustrating an example of a counterweight connection; FIG. 16 is a diagram illustrating an example of a counterweight connection; FIG. 17 is a diagram illustrating an example of a counterweight connection;

[0009] Hereinafter, the embodiments will be described in detail with reference to the drawings. Note that the same or corresponding parts are designated by the same reference characters and description thereof will not be repeated.

[0010] [First embodiment] Fig. 1 is a schematic diagram of a robot 1 according to the first embodiment. The robot 1 according to the first embodiment is a humanoid robot. The robot 1 is capable of coexisting harmoniously with humans in everyday spaces and is envisioned for use as a household robot suited to a home environment.

[0011] The robot 1 comprises a main member 101 that resembles a human body and a pair of wheels 240 for running. As shown in the photograph in Figure 1, the upper part of the main member 101 is covered with a soft member that resembles a human torso, taking into consideration safety in the event of a collision.

[0012] The robot 1 can move by driving a pair of wheels 240. The main member 101 is provided with a drivable head 170 that corresponds to a human head, and two drivable arm portions 180 that correspond to human arms. As shown in the photograph in Figure 1, a member that resembles a human face is attached to the head 170.

[0013] Fig. 2 is a block diagram showing an example of the hardware configuration of the robot 1. As shown in Fig. 2, the robot 1 includes a main body 100, a pair of wheels 240, and a motor 210. The main body 100 includes a main member 101 and a weight member 220. The two motors 210 drive (rotate) the pair of wheels 240. The pair of wheels 240 support the main body 100. The weight member 220 includes a third weight member 220a and a fourth weight member 220b.

[0014] The motors 210 include a first motor 210 a and a second motor 210 b. The third weight member 220 a includes a first battery 230 that supplies power to the first motor 210 a. The fourth weight member 220 b includes a first battery 230 that supplies power to the second motor 210 b. A single motor 210 may drive the pair of wheels 240.

[0015] The robot 1 further includes a first weight member 102. The first weight member 102 includes a control device 110, a second battery 120, and actuators 150 and 160. The control device 110 controls the driving of the motor 210 and the actuators 150 and 160.

[0016] The second battery 120 supplies power to the control device 110 and the actuators 150 and 160. The actuator 150 drives the head 170. The actuator 160 drives the arm 180.

[0017] The control device 110 is configured by a microcomputer including a processor 111, a memory 112, and a communication interface (IF) 113. The processor 111 is, for example, a CPU (Central Processing Unit). The memory 112 is, for example, configured by RAM (Random Access Memory) and a non-volatile memory. The non-volatile memory stores programs operated by the CPU.

[0018] The communication IF 113 is a device for communicating with an external device of the robot 1. For example, the robot 1 receives an operation command from the external device via the communication IF 113 and operates based on the operation command. For example, the robot 1 drives the motor 210 to run based on a running command from the external device. The robot 1 drives the actuators 150, 160 to drive the head 170 or the arm 180 based on a drive command from the external device. Alternatively, the control device 110 may be configured to autonomously control the motor 210 and the actuators 150, 160 in accordance with a program stored in the memory 112.

[0019] The control device 110 may be configured by a microcomputer including a CPU, RAM, and non-volatile memory, or may be configured by a field programmable gate array (FPGA), or may be configured by a dedicated circuit such as an application specific integrated circuit (ASIC). The control unit 20 may be configured by a combination of at least two of these.

[0020] Returning to the explanation of Figure 1, the first motor 210a is provided on the right side of the robot 1 (the left side when viewed from the front) and the second motor 210b is provided on the left side of the robot 1 (the right side when viewed from the front).

[0021] The first motor 210a rotates the wheel 240 (one of the pair of wheels 240) on the right side of the robot 1. The second motor 210b rotates the wheel 240 (the other of the pair of wheels 240) on the left side of the robot 1. A third weight member 220a is attached to the first motor 210a. A fourth weight member 220b is attached to the second motor 210b.

[0022] 1 shows the rotation axis A of the pair of wheels 240 and the center of gravity B of the main member 101. When the main body 100 (main member 101) is in an upright state, the first weight member 102 is arranged on the main member 101 so that the center of gravity B of the main member 101 is located vertically below the rotation axis A of the pair of wheels 240. Furthermore, when the robot 1 is stopped and the main body 100 (main member 101) is in an upright state, the weight members 220 (third weight member 220a, fourth weight member 220b) are arranged so that the center of gravity B of the main body 100 is located vertically below the rotation axis A of the pair of wheels 240.

[0023] As described above, the first weight member 102 includes the control device 110, the second battery 120, and the actuators 150 and 160. These devices are relatively heavy among the devices that make up the robot 1.

[0024] In the robot 1 of this embodiment, the second battery 120 is disposed at the bottom of the main member 101, and the control device 110 is disposed above that. In this manner, the heavy devices such as the second battery 120 and the control device 110 are configured to be below the rotation axis A, and further, the heavy devices such as the actuators 150 and 160 are also concentrated as low as possible, so that the center of gravity B of the main member 101 is positioned below the rotation axis A.

[0025] As a result, in the normal state, the robot 1 maintains a stable, upright state. Even if the robot 1 changes from the upright state (the pitch angle changes) due to running or stopping, the pitch angle is attenuated and the robot 1 returns to the stable, upright state.

[0026] As described above, the robot 1 of this embodiment is equipped with a passive self-balancing mechanism, and therefore the robot 1 can be stabilized in an upright state without performing complex control such as feedback control (e.g., PID control) for posture control.

[0027] If the robot 1 does not have the above-described self-balancing mechanism and needs to be stabilized in an upright state by feedback control, a sensor for measuring the pitch angle would be required, and the motor 210 would need to be constantly controlled by feedback control. On the other hand, the robot 1 according to this embodiment does not need the above-described sensor, and is stabilized in an upright state even when the power to the motor 210 is turned off. Therefore, the robot 1 according to this embodiment can be stabilized with a motor 210 that has a smaller torque output than one that uses the above-described feedback control, which allows the robot to be made smaller and more energy-efficient.

[0028] Furthermore, when the motor 210 is driven, the torque thereof changes the rotation angle of the weight member 220. On the other hand, when the motor 210 is not driven and the robot 1 is at a standstill, the center of gravity of the weight member 220 is located vertically below the rotation axis A (the pitch angle of the weight member 220 is 0°). Details will be described later using Figures 3A and 3B.

[0029] The head 170 has two degrees of freedom when driven, namely, rotation of the yaw angle and rotation of the pitch angle. The head 170 and two actuators 150 constitute a head drive device 179. The head 170 includes a head joint unit 175 having a gear 171. The actuator 150 located on the upper side controls the yaw angle of the head 170 in the range of -90° to +90°. The actuator 150 located on the upper side controls the pitch angle of the head 170 in the range of -25° to +25° via the gear 171.

[0030] Driving each of the two arms 180 provides three degrees of freedom: yaw angle rotation, roll angle rotation, and pitch angle rotation. The arms 180, belts 181, and three actuators 160 constitute an arm drive device 189. The arms 180 include arm joints 185 having gears 182. The actuators 160 located on the lower side control the yaw angle of the arms 180 in the range of -30° to +30°. The two actuators 160 located on the upper side rotate the gears 182 via the belts 181, thereby controlling the roll angle of the arms 180 in the range of 0° to +45° and controlling the pitch angle of the arms 180 to be rotatable 360°.

[0031] Thus, the head 170 and arms 180 have a total of eight degrees of freedom for driving, which allows the robot 1 to generate various social interaction modalities such as head movements and arm gestures, allowing the robot 1 to seamlessly fit into everyday home environments.

[0032] The footprint of the robot 1 is 0.3 m x 0.3 m. This allows the robot 1 to spin around in an arc with a diameter of 42.4 cm (the diagonal length of a 30 cm x 30 cm square = 42.4 cm (= 30 x √2) is the diameter of the arc traced by the robot 1). The width of a hallway in a typical Japanese house is less than 0.78 m, and considering the cross-section of an adult's lower back (approximately 0.3 m x 0.2 m), the footprint was designed to not exceed 0.3 m x 0.3 m. The robot 1 weighs 13.5 kg. To enhance safety in a home environment, the robot 1 was designed to weigh less than 15 kg, the average weight of a 3-year-old child. The eye level of the robot 1 is 0.9 m. Because the height of a desk in an office is often 0.7 m, the eye level of the robot 1 was designed to be 0.9 m, assuming the height at which the robot 1 can see objects on the desk. The diameter of the wheels 240 is 0.3 m, which allows it to easily overcome obstacles typically found in a domestic environment.

[0033] 3A and 3B are diagrams for explaining the drive mechanism of the robot 1. For simplicity, the explanations in Fig. 3A and 3B show a simplified version of the robot 1, omitting the actuators 150 and 160, the head 170, the arms 180, and the like.

[0034] 3A , the motors 210 (first motor 210a, second motor 210b) include a stator 211 and a rotor 212. The rotors 212 are fixed to the wheels 240. The weight members 220 (third weight member 220a, fourth weight member 220b) are fixed to the stators 211 of the motors 210, and are configured so that when torque is applied to the motors 210, a torque required to rotate the pair of wheels 240 is generated around the rotation axis A.

[0035] The third weight member 220a is fixed to the stator 211 of the first motor 210a. The fourth weight member 220b is fixed to the stator 211 of the second motor 210b. On the other hand, the main member 101 is not fixed to the stator 211 of the motor 210. Therefore, the main member 101 is configured to freely rotate around the rotation axis A regardless of the driving of the motor 210 and to be stabilized in an upright state.

[0036] This will be described in detail with reference to Figure 3B. As shown in Figure 3B, when no torque is applied to the motors 210 (first motor 210a, second motor 210b) (time t0), the fourth weight member 220b is positioned vertically below the rotation axis A. Similarly, the third weight member 220a is also positioned vertically below the rotation axis A.

[0037] Hereinafter, rotation of the motor 210 or the wheel 240 in the direction of travel of the robot 1 will be referred to as "positive rotation," and rotation in the direction opposite to the direction of travel will be referred to as "negative rotation." The first motor 210a and the second motor 210b can rotate independently of each other, and can each rotate in either the positive or negative direction.

[0038] In this example, equal torque is applied to the first motor 210a and the second motor 210b so that both wheels 240 rotate in the forward direction at the same speed. When torque is applied to the motor 210, the torque of the second motor 210b causes the fourth weight member 220b to rotate in the negative direction (similarly to the third weight member 220a). Meanwhile, at this point, the wheels 240 are not rotating. At this point, the torque of the second motor 210b is not sufficient to overcome the frictional force generated between the robot 1 and the ground.

[0039] At time t1, when the torque of the second motor 210b is generated enough to overcome the frictional force, the wheel 240 starts to rotate in the forward direction. At this time, the rotation angle of the fourth weight member 220b reaches a predetermined angle (for example, −60° in this example) (the same applies to the third weight member 220a).

[0040] When the rotation angle of the fourth weight member 220b is a predetermined angle (-60°), the force acting in the opposite direction to the rotation direction of the second motor 210b due to the gravity of the fourth weight member 220b and the force rotating the second motor 210b due to the torque of the second motor 210b (the torque required for the robot 1 to move) are balanced.

[0041] If the fourth weight member 220b is even heavier, a stronger force acts on the second motor 210b, and the predetermined angle becomes smaller. On the other hand, if the fourth weight member 220b is lighter, only a weak force acts on the second motor 210b, and the predetermined angle becomes larger. If the fourth weight member 220b is too light, a force sufficient to counteract the torque of the second motor 210b is not applied, and the fourth weight member 220b rotates around in the negative direction, preventing the robot 1 from starting to move. The same applies to the third weight member 220a.

[0042] Therefore, the fourth weight member 220b needs to be configured so that when torque is applied to the motor 210, the torque required to rotate the pair of wheels 240 (to start the robot 1 moving) is generated around the rotation axis A (i.e., the fourth weight member 220b needs to be installed with a weight sufficient to counteract the torque). The same applies to the third weight member 220a.

[0043] At time t2 when the robot 1 is in a running state, the wheels 240 continue to rotate. Meanwhile, the fourth weight member 220b maintains a rotation angle in the negative direction (near a predetermined angle). When the application of torque to the motor 210 is stopped, the robot 1 stops.

[0044] The experimental results are shown below. FIG. 4 is a diagram showing the running state of the robot 1. The robot 1 is stationary in an upright position. At time "0 seconds," torque is applied to the motor 210. As described with reference to FIG. 3B , thereafter, after the weight members 220 (the third weight member 220a and the fourth weight member 220b) have rotated a predetermined angle in the negative direction, the pair of wheels 240 start rotating in the positive direction.

[0045] At time "2 seconds", the robot 1 is in a running state. At this time, the robot 1 maintains a nearly upright position (the pitch angle remains close to 0%). At time "4 seconds", the robot 1 continues running. At time "6 seconds", the driving of the motor 210 is stopped, and at time "8 seconds", the robot 1 stops. During this time, the robot 1 maintains a nearly upright position.

[0046] When the robot 1 is caused to travel, for example, the control device 110 may control the driving of the motor 210 so that a constant torque is applied to the motor 210. For example, the control device 110 may output a travel ON command to the motor 210 when causing the robot 1 to travel, and output a travel OFF command to the motor 210 when stopping the robot 1. When the travel ON command is issued, the control device 110 issues a command to the motor 210 so that the motor 210 has a constant output (rotational speed), and when the travel OFF command is issued, the output of the motor 210 is turned OFF.

[0047] In this way, in this embodiment, no complex drive control is performed, but simple ON / OFF control is performed when the robot 1 is running or stopped. Alternatively, an output command may be given to the motor 210 so that the torque gradually increases when the robot 1 starts running, or so that the torque gradually decreases when the robot 1 is stopped.

[0048] However, the present invention is not limited to this, and various other methods may be used to control the drive of the motor 210. For example, a configuration may be adopted in which the rotation angle (pitch angle) of the main member 101 is detected by a sensor, and the output of the motor 210 is controlled by feedback control (such as PID control) so that the main member 101 is kept upright (the pitch angle is 0°). Furthermore, such feedback control may or may not be performed.

[0049] Furthermore, as described above, when the robot 1 is running, the rotation angle of the fourth weight member 220b (third weight member 220a) reaches a predetermined angle (for example, −60° in this example). Increasing the driving force of the motor 210 during running increases this rotation angle. For this reason, a configuration may be adopted in which the rotation angle of the fourth weight member 220b (third weight member 220a) is measured by a sensor, and this rotation angle is controlled by feedback control, thereby controlling the strength of the driving force of the motor 210 during running. Furthermore, such feedback control may or may not be performed.

[0050] As described above, in the first embodiment, the robot 1 includes the main body 100, the pair of wheels 240, and the motor 210. The main body 100 includes a main member 101 and a weight member 220. The pair of wheels 240 support the main body 100. The motor 210 rotates the pair of wheels 240. The weight member 220 is disposed so that, when the main body 100 is in an upright position, the center of gravity B of the main body 100 is positioned vertically below the rotation axis A of the pair of wheels 240. The weight member 220 is fixed to the stator 211 of the motor 210 and is configured so that, when torque is applied to the motor 210, the torque required to rotate the pair of wheels 240 is generated around the rotation axis A.

[0051] Because the robot 1 is equipped with a passive self-balancing mechanism, it can be stabilized in an upright position without performing complex control such as feedback control for posture control. Compared to a robot that performs the above-mentioned feedback control, the robot 1 requires only a motor 210 with a smaller torque output, which allows the robot 1 to be made smaller and consume less power. In this way, posture stability can be ensured in the robot 1 that operates in harmony with humans.

[0052] The robot 1 further includes a first weight member 102. The first weight member 102 is disposed on the main member 101 so that the center of gravity B of the main member 101 is positioned vertically below the rotation axis A when the main body 100 is in an upright position. The main member 101 is not fixed to the stator 211 of the motor 210. The weight member 220 is fixed to the stator 211 of the motor 210. In this manner, the pitch angle of the main body 100 does not fluctuate due to the torque of the motor 210, and the self-balancing mechanism can stabilize the robot 1 in an upright position.

[0053] The weight member 220 includes a first battery 230 that supplies power to the motor 210. This allows the weight member to be configured by utilizing existing equipment, without adding a new weight member.

[0054] The robot 1 further includes a control device 110. The control device 110 controls the driving of the motor 210. The first weight member 102 includes the control device 110 and a second battery 120. The second battery 120 supplies power to the control device 110. This makes it possible to configure the weight member by reusing existing equipment, without adding a new weight member.

[0055] The main member 101 is provided with a drivable head 170 and arm 180. The first weight member 102 includes actuators 150, 160 that drive the head 170 and arm 180. By arranging the heavy equipment as low as possible in this manner, the robot 1 can be stabilized in an upright position.

[0056] The motor 210 includes a first motor 210a and a second motor 210b. The first motor 210a rotates one of a pair of wheels 240. The second motor 210b rotates the other of the pair of wheels 240. The weight member 220 includes a third weight member 220a and a fourth weight member 220b. The third weight member 220a is fixed to the stator 211 of the first motor 210a. The fourth weight member 220b is fixed to the stator 211 of the second motor 210b. This allows the robot 1 to be stabilized in an upright state by the self-balancing mechanism while independently controlling the rotation of each wheel 240, enabling the robot 1 to change direction in a narrow space, such as by spinning on the spot.

[0057] The control device 110 controls the driving of the motor 210 so that a constant torque is applied to the motor 210. This eliminates the need for complex control such as feedback control for posture control, and allows the motor 210 to have a small torque output, thereby enabling the robot 1 to be made smaller and more energy-efficient.

[0058] Second Embodiment Next, a robot 1a according to the second embodiment will be described. Fig. 5 is a schematic diagram of the robot 1a according to the second embodiment. Unlike the robot 1 according to the first embodiment, the robot 1a according to the second embodiment does not include a weight member 220. The main member 101a is configured to be fixed to a stator 211 of a motor 210. The motor 210 includes a first motor 210a that rotates one of a pair of wheels 240 and a second motor 210b that rotates the other of the pair of wheels.

[0059] Furthermore, the weight member 220c is disposed so that, when the main body 100a (main member 101a) is in an upright state, the center of gravity B of the main body 100a is located vertically below the rotation axis A of the pair of wheels 240. The weight member 220c includes the control device 110, the second battery 120, and the actuators 150 and 160.

[0060] As described above, the robot 1a according to the second embodiment does not include the weight member 220 including the first battery 230, as compared with the robot 1 according to the first embodiment, and the power supply is concentrated in the second battery 120. In this respect, the mechanism of the robot 1 can be simplified, which has the effect of reducing manufacturing costs.

[0061] 6 is a block diagram showing an example of the hardware configuration of the robot 1a. The robot 1a includes a main body 100a, a pair of wheels 240, and a motor 210. The main body 100a includes a main member 101a and a weight member 220c. The pair of wheels 240 support the main body 100a. The motor 210 (first motor 210a, second motor 210b) rotates the pair of wheels 240.

[0062] The second battery 120 supplies power to the control device 110, the actuators 150 and 160, and the motors 210 (first motor 210a, second motor 210b). The actuator 150 drives the head 170. The actuator 160 drives the arm 180.

[0063] 7 is a diagram for explaining the drive mechanism of the robot 1a. For simplicity, the explanation of FIG. 7 shows a simplified version of the robot 1a, omitting the actuators 150 and 160, the head 170, the arms 180, etc.

[0064] The main member 101a is fixed to the stator 211 of the motor 210 (first motor 210a, second motor 210b). In other words, the weight member 220c is fixed to the stator 211 of the motor 210 by being disposed on the main member 101a.

[0065] The weight member 220c is fixed to the stator 211 of the motor 210 and is configured so that when torque is applied to the motor 210, the torque required to rotate the pair of wheels 240 (to cause the robot 1a to start moving) is generated around the rotation axis A (i.e., it is necessary to install the weight member 220c in the main member 101a so as to be heavy enough to counteract the torque).

[0066] An explanation will be given using experimental results. Figure 8 is a diagram showing the change in pitch angle of the main body 100a while the robot 1a is running. At time = 0 seconds, the robot 1a is stationary, and the pitch angle at this time is = 0°. When torque is applied to the motor 210 at time t1, the torque of the motor 210 causes the main body 100a to tilt backward, and the pitch angle becomes a negative value. Meanwhile, at this point, the wheels 240 are not rotating. At this point, the motor 210 is not generating enough torque to overcome the frictional force generated between the robot 1a and the ground.

[0067] At time t2, when the motor 210 generates enough torque to overcome the frictional force, the wheels 240 begin to rotate in the forward direction (the robot 1a begins to move). After that, the robot 1a continues to move with the main body 100a tilted backward (the pitch angle is a negative value). At time t3, the motor 210 stops driving, and the robot 1a stops. As a result, the main body 100a tilts forward significantly, and the pitch angle becomes a positive value. After that, the main body 100a sways back and forth, and the swaying gradually dampens, and the main body 100a eventually returns to an upright position (pitch angle = 0).

[0068] 9 is a diagram showing the change in wheel position when the robot 1a rotates at a fixed position. In this experiment, the first motor 210a that drives the right wheel 240 (also referred to as the "right wheel") of the robot 1a is rotated in the positive (or negative) direction, and the second motor 210b that drives the left wheel 240 (also referred to as the "left wheel") of the robot 1a is rotated in the negative (or positive) direction.

[0069] As a result, as shown in Figure 9, the right and left wheels of the robot 1a move in an arc while the center position of the robot 1a remains almost unchanged. In other words, the robot 1a spins around while remaining in its fixed position. This allows the robot 1a to change direction 360° using only an area of ​​30 cm x 30 cm.

[0070] 10 is a diagram showing the change in pitch angle of the main body 100a when the robot 1a travels on a slope. In this experiment, the robot 1a travels on a slope with a certain inclination (for example, about 30°). The first section of this slope has unevenness. In this experiment, the main body 100a of the robot 1a sways back and forth, but after passing the uneven section, the swaying dampens, and the main body 100a eventually returns to an upright position (pitch angle = 0).

[0071] As described above, in the second embodiment, the robot 1a includes the main body 100a, the pair of wheels 240, and the motor 210. The main body 100a includes a main member 101a and a weight member 220c. The pair of wheels 240 support the main body 100a. The motor 210 rotates the pair of wheels 240. The weight member 220c is disposed so that, when the main body 100a is in an upright position, the center of gravity B of the main body 100a is positioned vertically below the rotation axis A of the pair of wheels 240. The weight member 220c is fixed to the stator 211 of the motor 210 and is configured so that, when torque is applied to the motor 210, the torque required to rotate the pair of wheels 240 is generated around the rotation axis A.

[0072] Because the robot 1a is equipped with a passive self-balancing mechanism, it can be stabilized in an upright position without performing complex control such as feedback control for posture control. Compared to a robot that performs the above-mentioned feedback control, the robot 1a requires only a motor 210 with a smaller torque output, which allows the robot 1 to be made smaller and more energy-efficient. In this way, posture stability can be ensured in the robot 1a, which operates in harmony with humans.

[0073] The main member 101a is fixed to the stator 211 of the motor 210. The weight member 220c is disposed on the main member 101a and is thereby fixed to the stator 211 of the motor 210. This allows the robot 1a to be stabilized in an upright state by the self-balancing mechanism.

[0074] The motor 210 includes a first motor 210a that rotates one of a pair of wheels 240 and a second motor 210b that rotates the other of the pair of wheels 240. This allows the robot 1a to be stabilized in an upright state by the self-balancing mechanism, while the rotation of each wheel 240 can be controlled independently, enabling the robot 1a to change direction in a narrow space, such as by making a spin turn on the spot.

[0075] [Modification] Next, a modification of the robot 1a will be described. Fig. 11A is a diagram showing an example of connection of a counterweight 191. The robot 1a further includes a pendulum-type counterweight 191.

[0076] The main body 100a and the counterweight 191 are connected so that when the main body 100a tilts, the counterweight 191 exerts a force that restores the main body 100a to an upright position.

[0077] 11A, when the main body 100a is in an upright position, the connection position with the counterweight 191 is located vertically below the rotation axis A. The counterweight 191 is connected in a manner such that it is suspended from the connection position.

[0078] 11B is a diagram showing an example of connection of the counterweight 192. The robot 1a further includes a pendulum-type counterweight 192. The main body 100a and the counterweight 192 are connected so that when the main body 100a tilts, the counterweight 192 exerts a force that restores the main body 100a to an upright state.

[0079] 11B, when the main body 100a is in an upright state, the connection position with the counterweight 192 is located vertically above the rotation axis A. The counterweight 192 is connected in a manner such that it is suspended from the connection position.

[0080] 12 shows the experimental results of the change in the pitch angle of the main body 100a when the robot 1a is running. FIG. 12 is a diagram showing the change in the pitch angle of the main body 100a when the counterweight 191 is connected. When the counterweight 191 is not connected, the result is the same as the example shown in FIG. 8. As shown in FIG. 12, when the counterweight 191 is connected, the pitch angle damping effect is higher and recovery to the equilibrium position is faster than when the counterweight 191 is not connected.

[0081] In this way, the connection position between the main body 100a and the counterweight 191 should be designed so that when the pitch angle of the main body 100a swings in the positive direction, a force from the counterweight 191 acts to return the pitch angle to the negative direction, and when the pitch angle of the main body 100a swings in the negative direction, a force from the counterweight 191 acts to return the pitch angle to the positive direction (a force of the opposite phase acts without resonance).

[0082] The counterweight 191 may be connected to the main body 100a so as to swing back and forth relative to the direction of travel of the robot 1a, or may be connected to the main body 100a so as to swing in other directions. Two counterweights 191 may be connected to the main body 100a as a pair of pendulums, or a single counterweight 191 may be connected. The same applies to the counterweight 192.

[0083] As described above, the robot 1a further includes the counterweight 191 (192). The main body 100a and the counterweight 191 are connected so that when the main body 100a tilts, the counterweight 191 (192) applies a force that restores the main body 100a to an upright state. This makes it possible to more stably restore the robot 1a to an upright state.

[0084] Other examples of counterweight connections will be described below. Figures 13 to 18 are diagrams showing connection examples of counterweights 134, 134a, and 135. These counterweights are connected to the robot 1b. Hereinafter, the "counterweight" will also be referred to as the "pendulum."

[0085] As in the above-described modified example, these counterweights are connected so that when the main body 100a (main member 101a) tilts, the counterweights exert a force that restores the main body 100a to an upright state. Note that some of the counterweights may be connected to the main body 100a so as to inhibit the force that restores the main body 100a to an upright state.

[0086] First, a description will be given with reference to Figure 13. The basic configuration of the robot 1b is the same as that of the robot 1a, so a description of the common parts will be omitted. The robot 1b is equipped with counterweights 134 and 135. The counterweights 134 and 135 are connected to the main body 100a.

[0087] The robot 1b has the same drive mechanism as the robot 1a shown in Fig. 7. The main member 101a has a lower body part 131 at its lower part. The lower body part 131 includes a base part 132, a support part 133, and counterweights 134 and 135.

[0088] The base 132 is fixed to the stator 211. The support column 133 is attached to the base 132. The weight member 220c is installed inside the support column 133. Alternatively, a portion of the weight member 220c may be installed on the base 132.

[0089] A counterweight 134 is provided on the right side of the support column 133 of the robot 1b (on the left side of the support column 133 when viewed from the front of the robot 1b). A counterweight 135 is provided on the left side of the support column 133 of the robot 1b (on the right side of the support column 133 when viewed from the front of the robot 1b).

[0090] The rotation axis C of the counterweight 134 is provided at the upper part of the support part 133 and above the rotation axis A. The center of gravity E of the counterweight 134 is provided below the rotation axis A.

[0091] The rotation axis D of the counterweight 135 is located at the top of the support column 133 and above the rotation axis A. The center of gravity F of the counterweight 135 is located below the rotation axis A. The counterweights 134 and 135 are located evenly on the left and right sides of the support column 133. When the main body 100a is in an upright position, the heights of the rotation axes C and D are the same, and the heights of the centers of gravity E and F are also the same. The length and weight of the counterweights 134 and 135 are also the same.

[0092] Fig. 14 shows the lower body part 131 when the robot 1b is in an upright position. When the wheels 240 are rotating and the robot 1b is moving, the counterweights 134, 135 are a pair of pendulums 134, 135 connected to the main body part 100a (support part 133) so as to swing back and forth relative to the direction of travel of the robot 1b, as shown in Fig. 15. A pair of pendulums 134, 135, or a single pendulum 134 or pendulum 135 may be connected to the main body part 100a.

[0093] As described above, robot 1b is a humanoid robot (see FIG. 1). Robot 1b is expected to be used as a household robot that can coexist harmoniously with humans in everyday spaces and is suited to home environments. When robot 1b is in an upright position, the center of gravity B of main body 100a is positioned vertically below the rotation axis A of the pair of wheels 240. This allows robot 1b to maintain a stable posture.

[0094] On the other hand, in this embodiment, counterweights 134 and 135 are connected to the main body 100a. When the main body 100a rotates (sways) around the rotation axis A due to the movement of the robot 1b, the counterweights 134 and 135 rotate (sways) around the rotation axes C and D. The forces of the counterweights 134 and 135 act on the main body 100a, resulting in a characteristic movement (swing) of the main body 100a that is different from normal.

[0095] 13 to 15 are merely examples, and any counterweights 134, 135 may be connected in any manner. This increases the degree of freedom of movement of the robot 1b and broadens the range of expression while ensuring stability in the posture of the robot 1b.

[0096] If the posture of the robot 1b is controlled by active control such as feedback control, the posture is stabilized by efficient movement. Alternatively, if the robot 1b is about to collide with an object, image recognition processing using a camera image or object detection processing using a sensor can be performed, allowing for smooth and efficient movement that avoids collision with the object.

[0097] On the other hand, in this embodiment, the posture is stabilized solely by passive control without implementing the above-mentioned active control, etc. In addition, by providing the counterweight as described above, the degree of freedom of movement of the robot 1b is increased and the range of expression can be broadened.

[0098] As a result, the robot 1b moves randomly or irregularly and with fluctuations, which differs from normal robots that are actively controlled, etc., and can therefore achieve human-like movements (for example, suspicious movements, almost bumping into things, etc.) In this way, it is possible to provide a communication robot that can coexist harmoniously with people in everyday spaces.

[0099] Here is another example. The counterweights 134, 135 do not have to be provided evenly on the left and right. For example, as shown in Fig. 16, counterweights 134a, 135 that are unequal on the left and right are provided on the support 133 of the main body lower part 131a. The counterweights 134a, 135 are a pair of pendulums 134a, 135 connected to the main body 100a so as to swing back and forth relative to the direction of travel of the robot 1b.

[0100] The pair of pendulums 134a, 135 have different lengths. As a result, when the main body 100a is in an upright position, the heights of the centers of gravity (heights of the centers of gravity from the ground) of the pair of pendulums 134a, 135 are different. Specifically, the counterweight 135 is longer than the counterweight 134a, and the position of the center of gravity F of the counterweight 135 is lower than the position of the center of gravity E of the counterweight 134a.

[0101] Alternatively, the counterweights 134, 135 may be configured as shown in Fig. 17. The counterweights 134, 135 are a pair of pendulums 134, 135 connected to the main body 100a so as to swing back and forth relative to the direction of travel of the robot 1b.

[0102] The counterweights 134 and 135 have the same length, but the heights of the rotation axes C and D may be different to create imbalance. When the main body 100a is in an upright position, the heights of the connection positions of the pair of pendulums 134, 135 with the main body 100a (heights of the connection positions from the ground) are different. In the example of Fig. 17, the rotation axis C of the pair of pendulums 134 is installed at a higher position than the rotation axis D of the pair of pendulums 135.

[0103] In the above example, the counterweights 134, 134a, and 135 are configured to swing back and forth relative to the direction of travel of the robot 1b. However, this is not limiting, and the counterweights may be configured to swing left and right relative to the direction of travel of the robot 1b.

[0104] 18, a counterweight 135 may be installed in front of a support column 133 of the robot 1b, and a counterweight 134 may be installed behind the support column 133. The counterweights 134 and 135 are connected to the main body 100a so as to swing left and right relative to the direction of travel of the robot 1b.

[0105] Specifically, rotation axes C and D are provided above a position where rotation axis A of wheel 240 is rotated 90 degrees on a horizontal plane. When counterweights 134 and 135 swing left and right, robot 1b tends to swing left and right. For example, when robot 1b spins, counterweights 134 and 135 swing left and right. A pair of pendulums 134 and 135, or a single pendulum 134 or pendulum 135 may be connected to main body 100a.

[0106] As described above, the robot 1b further includes counterweights 134, 135 connected to the main body 100a. This increases the degree of freedom of movement of the robot 1b and broadens the range of expression while ensuring stability in the posture of the robot 1b. This allows the robot 1b to move in a human-like manner, making it possible to provide a communication robot that can coexist harmoniously with humans in everyday spaces.

[0107] 16, the counterweights 134a, 135 are a pair of pendulums 134a, 135 connected to the main body 100a so as to swing back and forth relative to the direction of travel of the robot 1b. The lengths of the pair of pendulums 134a, 135 are different. This makes the movements of the robot 1b more random, thereby increasing the degree of freedom of the robot 1b and broadening the range of expression.

[0108] 17, the counterweights 134, 135 are a pair of pendulums 134, 135 connected to the main body 100a so as to swing back and forth relative to the direction of travel of the robot 1b. When the main body 100a is in an upright position, the heights at which each of the pair of pendulums is connected to the main body 100a are different. This makes the movements of the robot 1b more random, thereby increasing the degree of freedom of the robot 1b and broadening the range of expression.

[0109] 18, the counterweights 134 and 135 are connected to the main body 100a so as to swing left and right relative to the direction of travel of the robot 1b. This allows the robot 1b to swing left and right more easily, just like a human walking with their shoulders swinging from side to side, thereby realizing more human-like movements.

[0110] As described above, the lengths of the counterweights (pendulums) 134, 134a, and 135, the connection positions to the main body 100a, and other connection methods may be designed arbitrarily. Changing the length of the pendulums changes the period of their swing. For example, as shown in FIG. 16 , changing the length of each of the pair of pendulums 134a and 135 can change the period of each swing. By devising a method for connecting the pendulums in this way, the movements of the robot 1b become more random, increasing the degree of freedom of the robot 1b and broadening the range of expression.

[0111] [Additional Notes] The above-described embodiment is a specific example of the following additional notes.

[0112] (Supplementary Note 1) A robot comprising: a main body including a main member and a weight member; a pair of wheels supporting the main body; and a motor for rotating the pair of wheels, wherein the weight member is positioned so that the center of gravity of the main body is located vertically below the axis of rotation of the pair of wheels when the main body is in an upright position; and the weight member is fixed to a stator of the motor, and is configured so that when torque is applied to the motor, the torque required to rotate the pair of wheels is generated around the axis of rotation.

[0113] (Appendix 2) The robot described in Appendix 1 further comprises a first weight member, the first weight member being arranged on the main member such that the center of gravity of the main member is positioned vertically below the rotation axis when the main body is in an upright position, the main member not being fixed to the stator of the motor, and the weight member being fixed to the stator of the motor.

[0114] (Supplementary Note 3) The robot according to Supplementary Note 1 or Supplementary Note 2, wherein the weight member includes a first battery that supplies power to the motor.

[0115] (Supplementary Note 4) The robot according to any one of Supplementary Notes 1 to 3, further comprising a control device that controls the driving of the motor, wherein the first weight member includes: the control device; and a second battery that supplies power to the control device.

[0116] (Supplementary Note 5) The robot according to any one of Supplementary Notes 1 to 4, wherein the main member is provided with a drivable head and arm portions, and the first weight member includes an actuator that drives the head and the arm portions.

[0117] (Supplementary Note 6) The robot according to any one of Supplementary Notes 1 to 5, wherein the motor includes a first motor that rotates one of the pair of wheels and a second motor that rotates the other of the pair of wheels, and the weight member includes a third weight member fixed to a stator of the first motor and a fourth weight member fixed to a stator of the second motor.

[0118] (Supplementary Note 7) The robot according to Supplementary Note 1, wherein the main member is fixed to a stator of the motor, and the weight member is fixed to the stator of the motor by being disposed on the main member.

[0119] (Appendix 8) The robot according to Appendix 7, further comprising a counterweight, wherein the main body and the counterweight are connected such that when the main body tilts, the counterweight exerts a force that restores the main body to an upright state.

[0120] (Supplementary Note 9) The robot according to Supplementary Note 7, further comprising a counterweight connected to the main body portion.

[0121] (Supplementary Note 10) The robot according to Supplementary Note 9, wherein the counterweight is a pair of pendulums connected to the main body so as to swing back and forth relative to the direction of travel of the robot, and the lengths of the pair of pendulums are different.

[0122] (Supplementary Note 11) The robot described in Supplementary Note 9 or Supplementary Note 10, wherein the counterweight is a pair of pendulums connected to the main body so as to swing back and forth relative to the direction of travel of the robot, and when the main body is in an upright position, the heights of the connection positions of each of the pair of pendulums with the main body are different.

[0123] (Supplementary Note 12) The robot according to Supplementary Note 9, wherein the counterweight is connected to the main body so as to swing left and right relative to a direction of travel of the robot.

[0124] (Supplementary Note 13) The robot according to any one of Supplementary Note 7 to Supplementary Note 13, wherein the motor includes: a first motor that rotates one of the pair of wheels; and a second motor that rotates the other of the pair of wheels.

[0125] (Supplementary Note 14) The robot according to any one of Supplementary Notes 1 to 13, further comprising a control device that controls driving of the motor, wherein the control device controls driving of the motor so that a torque applied to the motor is constant.

[0126] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of this application is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0127] 1, 1a, 1b Robot, 100, 100a Main body, 101, 101a Main member, 102, 102a First weight member, 110 Control device, 120 Second battery, 131, 131a, 131b Lower body, 132 Base, 133 Support, 134, 134a, 135 Counterweight, 150, 160 Actuator, 170 Head, 171 Gear, 175 Head joint, 179 Head drive device, 180 Arm, 181 Belt, 182 Gear, 185 Arm joint, 189 Arm drive device, 191, 192 Counterweight, 210 Motor, 210a First motor, 210b Second motor, 211 Stator, 212 Rotor, 220, 220c Weight member, 220a: Third weight member, 220b: Fourth weight member, 230: First battery, 240: Wheel, 241: Passive joint, A, C, D: Rotation axis, B, E, F: Center of gravity.

Claims

1. A robot comprising: a main body including a main member and a weight member; a pair of wheels supporting the main body; and a motor for rotating the pair of wheels, wherein the weight member is positioned so that the center of gravity of the main body is located vertically below the axis of rotation of the pair of wheels when the main body is in an upright position; and the weight member is fixed to the stator of the motor, and is configured so that when torque is applied to the motor, the torque required to rotate the pair of wheels is generated around the axis of rotation.

2. The robot according to claim 1, further comprising a first weight member, the first weight member being arranged on the main member so that the center of gravity of the main member is positioned vertically below the rotation axis when the main body is in an upright position, the main member not being fixed to the stator of the motor, and the weight member being fixed to the stator of the motor.

3. The robot of claim 2, wherein the weight member includes a first battery that supplies power to the motor.

4. The robot according to claim 2, further comprising a control device that controls the driving of the motor, wherein the first weight member includes the control device and a second battery that supplies power to the control device.

5. The robot according to claim 2, wherein the main member is provided with a drivable head and arm, and the first weight member includes an actuator for driving the head and arm.

6. The robot according to claim 2, wherein the motors include a first motor that rotates one of the pair of wheels and a second motor that rotates the other of the pair of wheels, and the weight members include a third weight member fixed to a stator of the first motor and a fourth weight member fixed to a stator of the second motor.

7. The robot according to claim 1, wherein the main member is fixed to a stator of the motor, and the weight member is fixed to the stator of the motor by being disposed on the main member.

8. The robot according to claim 7, further comprising a counterweight, wherein the main body and the counterweight are connected so that when the main body tilts, the counterweight exerts a force that restores the main body to an upright position.

9. The robot of claim 7, further comprising a counterweight connected to the body portion.

10. The robot according to claim 9, wherein the counterweight is a pair of pendulums connected to the main body so as to swing back and forth relative to the direction of travel of the robot, and the lengths of the pair of pendulums are different.

11. The robot described in claim 9, wherein the counterweight is a pair of pendulums connected to the main body so as to swing back and forth relative to the direction of travel of the robot, and when the main body is in an upright position, the heights of the connection positions of each of the pair of pendulums with the main body are different.

12. The robot according to claim 9, wherein the counterweight is connected to the main body so as to swing left and right relative to the direction of travel of the robot.

13. The robot according to claim 7, wherein the motors include a first motor that rotates one of the pair of wheels, and a second motor that rotates the other of the pair of wheels.

14. The robot according to any one of claims 1 to 13, further comprising a control device that controls the drive of the motor, wherein the control device controls the drive of the motor so that the torque applied to the motor is constant.

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