Mobile robot comprising manipulator

Abstract

To provide a mobile robot configured to be enhanced in safety by reducing possibilities or frequencies of contact and collision.SOLUTION: A controller 6 that controls movement of leg corresponding parts 4 and of manipulators 3 has a posture control part 6A that makes a posture that is a relative position of the manipulators 3 with respect to a trunk part 2, different between a moving-time posture at the time when the leg corresponding parts 4 are operated to move and a stop-time posture at the time when the operation of the leg corresponding parts 4 are stopped to stop moving and when a gripping part 9 grips a predetermined object or releases the gripping. The posture control part 6A is configured to control the manipulators 3 so that the manipulators take a posture in which a separation quantity of the gripping part 9 from the trunk part 2 at the time when the leg corresponding parts 4 are operated to move is smaller than a separation quantity of the gripping part 9 from the trunk part 2 in the stop-time posture at the time when the gripping part 9 grips the predetermined object or releases the gripping.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mobile robot equipped with a manipulator or an articulated arm capable of movements that mimic those of a human arm. [Background technology]

[0002] This type of robot is expected to work alongside humans. In such cases, collisions or contact with humans or equipment in the work environment are expected. Therefore, the robot must operate in a way that avoids damage from such collisions. In other words, this type of robot must be safe. Patent Document 1 proposes a robot with enhanced safety. The robot has an arm attached to its body with a multi-joint structure, with shaft torque detection sensors incorporated into each joint. When the arm receives an external force, such as contact with a human, the contact or collision is detected based on the signal output by the shaft torque detection sensor, and each part of the robot is controlled based on the detection result. Patent Document 1 also describes servo-locking the arm while the robot is moving. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-229800 Summary of the Invention [Problem to be solved by the invention]

[0004] In the robot described in Patent Document 1, when the arm contacts or collides with a person or equipment in the work environment, an external force acts on each axial torque detection sensor, which outputs a signal, allowing for reliable and accurate detection of arm contact or collision. However, incorporating an axial torque detection sensor into each joint of the arm increases the size of the arm, increases its weight (inertial mass), and requires complex control. Furthermore, the robot described in Patent Document 1 is designed to reliably and accurately detect arm contact or collision. In other words, it is a robot that assumes arm contact or collision and improves subsequent control. Therefore, if the arm's inertial mass is large, the impact force upon contact or collision will be large, potentially reducing safety. Furthermore, if the arm is servo-locked during movement, the robot's inertial force will directly act on the object it contacts or collides with, resulting in a greater impact force.

[0005] The impact force when the arm comes into contact or collides can be reduced by slowing the robot's movement speed (traveling speed), but doing so reduces the robot's work speed or work efficiency. In contrast, a robot with enhanced backdrivability will move in a direction that reduces the impact force, such as by moving backward in the direction of the external force, either the robot itself or its arm. Therefore, by increasing backdrivability, the robot's movement speed can be maintained at a relatively high speed without compromising its safety. However, depending on the robot's posture while moving, the frequency of arm contact or collision may increase. While this may avoid damage to people and peripheral equipment in the work environment, it may also increase the frequency of the robot stopping or deceleration, potentially reducing the robot's work efficiency.

[0006] The present invention has been made in view of the above technical problems, and has as its object to provide a mobile robot that is safer against contact or collision during movement. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a mobile robot having leg equivalents provided at the bottom of a body for moving on a floor surface, and a manipulator attached to the body that is capable of bending, stretching, and rotating, the manipulator including at least an upper arm equivalent connected to the body by a shoulder joint, a forearm equivalent connected to the tip of the upper arm equivalent by an elbow joint, and a gripping part connected to the tip of the forearm equivalent by a wrist joint, the mobile robot further comprising a controller for controlling the movement of the leg equivalents and the manipulator, the controller controlling the movement of the manipulator relative to the body. The manipulator has a posture control unit that changes the posture, which is the relative position, between a moving posture when the leg equivalents are moving by operating the leg equivalents and a stopped posture when the operation of the leg equivalents is stopped and a predetermined object is being grasped or released by the gripping unit, and the posture control unit is configured to control the manipulator to change the moving posture to a posture in which the distance between the gripping unit and the torso when the leg equivalents are moving by operating the leg equivalents is smaller than the distance between the gripping unit and the torso in the stopped posture when the gripping unit is grasping or releasing the predetermined object.

[0008] In the present invention, the moving posture includes a first moving posture in which the gripping portion is moving without gripping the specified object, and a second moving posture in which the gripping portion is moving while gripping the specified object, and the first moving posture may be a folded posture in which the angle formed between the upper arm equivalent portion and the forearm equivalent portion is smaller than the angle formed between the upper arm equivalent portion and the forearm equivalent portion in the second moving posture.

[0009] In the present invention, the posture control unit may be configured to differentiate between backdrivability, which is the ease of movement of the upper arm equivalent part due to an external force, and backdrivability, which is the ease of movement of the forearm equivalent part due to an external force, in the moving posture.

[0010] In the present invention, the posture control unit may be configured to perform posture restriction control to limit the approach distance of the manipulator to the torso unit to a predetermined distance by the external force when the leg equivalent unit is operated to move. [Effects of the Invention]

[0011] According to the present invention, when moving, the gripping portion is positioned close to the body portion, thereby reducing the so-called outward protruding portion or protruding amount, thereby reducing the possibility and frequency of contact or collision with coexisting objects in the mobile robot's moving environment and increasing safety.

[0012] In particular, when the gripping portion is not gripping a specified object, the manipulator is put into a so-called folded state, so that it protrudes as little as possible from the body portion, thereby increasing safety and enabling faster movement speed.

[0013] Furthermore, if the ease of movement due to external forces is made different between the upper arm equivalent part and the forearm equivalent part, the movement of the manipulator due to external forces can be made appropriate for the object being grasped, and it is possible to avoid or suppress, for example, the object coming loose from the grasp or being dropped.

[0014] Furthermore, by limiting the manipulator's approach distance to the torso section during movement to a predetermined distance, even if the manipulator's posture changes due to an external force, it is possible to avoid or suppress the manipulator coming into contact with or colliding with the torso section, and resulting damage to the torso section. [Brief explanation of the drawings]

[0015] [Figure 1] 1A and 1B are schematic diagrams illustrating a mobile robot and movements at each joint in an embodiment of the present invention. [Figure 2] FIG. 10 is a schematic perspective view showing an example of the posture of the manipulator when it is moving without grasping an object. [Figure 3] FIG. 10 is a schematic perspective view showing an example of the posture of the manipulator when gripping and moving an object. [Figure 4] FIG. 10 is a schematic perspective view showing an example of the posture of the manipulator when moving while gripping the handle of the dolly. DETAILED DESCRIPTION OF THE INVENTION

[0016] Next, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the embodiment described below is merely an example of how the present invention can be implemented, and is not intended to limit the present invention.

[0017] A robot according to the present invention is capable of moving, such as by self-propelling, in order to carry objects, and is also equipped with the ability to grasp objects. Fig. 1(a) schematically shows a mobile robot (hereinafter sometimes simply referred to as a robot) 1 according to an embodiment of the present invention. The mobile robot 1 shown here has an appearance simulating a human, with a body 2 equipped with left and right manipulators 3 corresponding to the left and right arms, leg equivalents 4 corresponding to the feet, and a head equivalent 5 equipped with a camera (not shown) corresponding to the eyes. The body 2 is equipped with a motor for movement, a battery (not shown) that serves as the energy source for the motor, and a controller 6 that controls these.

[0018] The manipulators 3 are provided on both the left and right sides of the torso 2, and each includes an upper arm equivalent 7, a forearm equivalent 8, and a gripping portion 9 corresponding to the fingers of a hand. The upper arm equivalent 7 is attached to the torso 2 by a shoulder joint 10. The shoulder joint 10 is a so-called joint configured to change the posture of the upper arm equivalent 7 relative to the torso 2, and as shown in FIG. 1(b), it is configured to rotate about a Y-axis along the lateral (horizontal) direction of the torso 2, allowing rotation within a range of approximately 180 degrees between downward and upward directions along the torso 2 (vertical movement), and to rotate about a Z-axis along the vertical direction of the torso 2 (direction perpendicular to the Y-axis), allowing rotation within a range of approximately 90 degrees in a direction away from the torso 2 (horizontal swing).

[0019] The forearm equivalent portion 8 is attached to the tip of the upper arm equivalent portion 7 by an elbow joint portion 11. The elbow joint portion 11 is a so-called joint portion configured to change the angle and orientation of the forearm equivalent portion 8 relative to the upper arm equivalent portion 7, and as illustrated in FIG. 1(c), when the longitudinal direction of the upper arm equivalent portion 7 (the direction of the line connecting the shoulder joint portion 10 and the elbow joint portion 11) is taken as the Z axis, the elbow joint portion 11 is configured to be able to rotate (swing sideways) about the Z axis in a range of approximately 90 degrees from the front direction of the torso portion 2 to the side, and to rotate (movement up and down) in an angle range of less than 180 degrees in the up and down direction about the Y axis perpendicular to the Z axis and the X axis direction, which is the longitudinal direction of the forearm equivalent portion 8.

[0020] The gripping unit 9 has a portion corresponding to a hand or fingers for grasping a predetermined object, and is attached to the tip of the forearm portion 8 by a wrist joint 12. The wrist joint 12 is a so-called joint configured to change the angle and orientation of the gripping unit 9 relative to the forearm portion 8, and as shown in Fig. 1(d), is configured to allow rotation (twisting) within a range of approximately 180 degrees around an X-axis along the longitudinal direction of the forearm portion 8, rotation (up and down movement) within a range of approximately 90 degrees around a Y-axis perpendicular to the X-axis in a plane including the X-axis, and rotation in the left and right direction (horizontal swing) around a Z-axis perpendicular to the X-axis and Y-axis.

[0021] A servo motor 13 is provided as a driving force source for bending, stretching, and rotating the manipulator 3 by bending and rotating the joints 10, 11, and 12. This servo motor 13 may be provided at each of the joints 10, 11, and 12, or may be mounted on the body 2 and configured to drive the upper arm portion 7, the forearm portion 8, and the grip portion 9 via links, wires, or the like.

[0022] The manipulator 3 has a so-called flexible structure so that, when subjected to an external force, it moves (changes its posture) in response to the external force to absorb the external force. In other words, it has backdrivability. This flexible structure may be a structure in which the overall mechanical rigidity including the joints 10, 11, and 12 is reduced, or a structure in which the lock strength (reaction force against an external force) of the servo lock is reduced. This backdrivability can be made different between the upper arm portion 7, the forearm portion 8, and the gripper 9 while the robot 1 is moving. For example, the backdrivability can be made lower or different by making the strength of the servo lock of each joint 10, 11, and 12 different, or by fixing each joint with a stopper (not shown). Furthermore, when reduction mechanisms are used in each joint 10, 11, and 12, the reduction ratio of one of the reduction mechanisms may be made smaller than the reduction ratio of the other reduction mechanisms to increase the backdrivability.

[0023] Because the manipulator 3 is provided with backdrivability, it is anticipated that the manipulator 3 will be moved by an external force and will move beyond the controlled operating range. In such a case, an interference area (minimum approach distance) is set so that the manipulator 3 will not come into contact with or collide with the body 2. This interference area may be set by a protrusion functioning as a stopper provided on either the body or the manipulator 3, or may be set by incorporating a routine that limits the position and movement of the manipulator 3 into the program that controls the servo motor 13. Control that limits the position and movement of the manipulator 3 in this way corresponds to attitude restriction control in the embodiments of the present invention.

[0024] The leg equivalents 4 are parts that carry the torso 2 and allow it to move on the floor within the work environment, and can be configured as needed, such as a configuration that mimics a human leg, with ankle joints that allow it to move forward by bending and stretching and moving back and forth, or a configuration similar to a cart that moves forward by rotating wheels or rollers.

[0025] A controller 6 for controlling the manipulator 3, leg equivalents 4, etc. is provided on the torso 2. The controller 6 is an electronic control unit (ECU) mainly composed of a microcomputer, and outputs control command signals to the robot 1 so that the robot 1 completes a predetermined task. Various control programs, map data for identifying the robot's own position, data on the object to be grasped, etc. are pre-stored in the controller 6. Data on the surrounding environment obtained by the aforementioned camera, distance data from surrounding people or equipment obtained by an infrared sensor or LIDAR, etc. are input as data from time to time. In this embodiment of the present invention, an attitude control unit 6A is particularly provided in the controller 6.

[0026] The posture control unit 6A controls the overall shape of the manipulator 3, i.e., the bending, extension, and rotation states, as the posture of the robot 1. In particular, the posture of the robot 1 while it is moving and the backdrivability of the joints 10, 11, and 12 while maintaining that posture are controlled according to a pre-prepared program. That is, when attempting to grasp a specific object, or when the object is to be lowered and released from the grip at the destination, the posture of the manipulator 3, which is determined by the bending, extension, and rotation, is determined by the position, posture, or shape of the object. When the robot 1 is moving, there are posture constraints to the extent that the grasped object can be stably held, but there are almost no constraints on bending or extension. Furthermore, when the robot 1 is not grasping an object, so-called empty-hand, there are almost no constraints on the posture that the manipulator 3 should adopt. Therefore, in the robot 1 according to the embodiment of the present invention, the posture of the robot 1 (manipulator 3) while moving is controlled as described below, taking into consideration safety in the working environment.

[0027] FIG. 2 schematically shows the posture when moving with empty hands. Note that the gripper 9 and wrist joint 12 are omitted from FIG. 2. This posture is the so-called folded posture in which the manipulator 3 is folded. The upper arm 7 hangs down along the side of the torso 2, and the forearm 8 approaches the upper arm 7 and is bent at the elbow joint 11 so that the angle between them is approximately the minimum angle allowed by the mechanism. The gripper 9 is maintained in a direction extending forward from the forearm 8 in the longitudinal direction. This folded posture is a posture in which the manipulator 3 is so-called contained within the torso 2; in other words, a posture in which the projected shape of the manipulator 3 is completely or almost contained within the projected shape of the torso 2 from the side (lateral direction). Therefore, the portion protruding from the body 2 is reduced, which reduces the possibility or frequency of contact or collision with people or equipment in the working environment while the robot 1 is moving, thereby improving safety.

[0028] In the folded posture, the backdrivability, in which the forearm equivalent portion 8 rotates at the elbow joint portion 11, may be lowered relative to the backdrivability, in which the upper arm equivalent portion 7 rotates at the shoulder joint portion 10 relative to the torso portion 2. By doing so, when an external force acts on the manipulator 3, the entire manipulator 3, with the forearm equivalent portion 8 folded toward the upper arm equivalent portion 7, can rotate relatively easily around the shoulder joint portion 10. In other words, the external force can be released, and the reaction force against the external force, i.e., the pressing force on people or equipment that the manipulator 3 comes into contact with, can be reduced, thereby improving safety.

[0029] Furthermore, because the upper arm portion 7 can rotate around the X-axis along the front-rear direction of the torso portion 2, depending on the direction of the external force, the distal end portion of the upper arm portion 7 or the forearm portion 8 connected thereto may approach the torso portion 2 and come into contact with or collide with it. To avoid such contact or collision, it is preferable to set the aforementioned interference region between the upper arm portion 7 and the torso portion 2 in the folded position. As described above, the interference region can be set by operating a stopper or by controlling the servo motor 13. This folded position corresponds to the first moving position in this embodiment of the present invention.

[0030] FIG. 3 schematically illustrates the posture when the gripper 9 grasps and moves a predetermined object W. Note that the gripper 9 and wrist joint 12 are omitted from FIG. 3 as well. In this case, the manipulator 3 is extended to a certain extent so that the object W does not come into contact with the torso 2. Therefore, the distance between the gripper 9 and the torso 2 is greater than in the first movement posture described above, in which the manipulator 3 is folded. For example, as shown in FIG. 3, the forearm 8 is bent at approximately 90 degrees relative to the hanging upper arm 7, resulting in the upper arm 7, gripper 9, and object W protruding forward from the torso 2. When the robot 1 attempts to grasp the object W or when it lowers the grasped object W at the destination and releases the grasp, the manipulator 3 is extended forward from the torso 2 to perform the grasping or release operation. This is to avoid interference with the torso 2 and to prevent the torso 2 from interfering with a platform on which the object W is placed. Therefore, the posture of the manipulator 3 when gripping and moving the object W is different from the posture of the manipulator 3 when the robot 1 stops and grips or releases the object W (stationary posture) in that the upper arm equivalent 7 is pulled back toward the body 2 and hangs down, and the forearm equivalent 8 is bent relative to the upper arm equivalent 7. Also, compared to the folded posture (first moving posture) when moving without gripping the object W, this is a posture in which the angle formed between the upper arm equivalent 7 and the forearm equivalent 8 is larger. The posture when gripping and moving the object W described here corresponds to the second moving posture in this embodiment of the present invention.

[0031] It is preferable that the ease of movement of the manipulator 3 due to an external force when gripping and moving an object W, i.e., backdrivability, be different between the upper arm equivalent 7 side and the forearm equivalent 8 side. In this case, the level of backdrivability may be selected according to the characteristics of the object W being gripped.

[0032] For example, if the object W being grasped is not allowed to tilt from a horizontal state or the range of allowable tilt is narrow, the backdrivability in which the forearm equivalent portion 8 rotates about the elbow joint 11 is set lower than the backdrivability in which the upper arm equivalent portion 7 rotates about the shoulder joint 10. By doing so, when an external force is applied, the entire manipulator 3 rotates about the shoulder joint 10 while maintaining a posture in which the forearm equivalent portion 8 side is bent almost horizontally with respect to the hanging upper arm equivalent portion 7, thereby absorbing the external force, and the gripping portion 9 and the object W grasped by the gripping portion 9 are maintained in a nearly horizontal state. In other words, dropping the object W and spilling its contents can be avoided or suppressed without compromising safety.

[0033] On the other hand, if the gripping state does not change even when the orientation of the gripped object W or the gripper 9 is changed, or if it is preferable to increase the gripper 9's ability to follow external forces, the backdrivability of the upper arm 7 in the direction of rotation about the shoulder joint 10 or the backdrivability of the upper arm 7 is reduced to make it difficult to move the upper arm 7, and the backdrivability of the forearm 8 is increased to facilitate rotation about the elbow joint 11 or the wrist joint 12. An example of this is when the robot 1 pushes and moves a cart C, as shown in FIG. 4 . If the cart C, which is the object W, comes into contact with some environmental equipment during its movement and the orientation of the so-called handle that is gripping it changes, the gripper 9 quickly and smoothly follows the change in orientation of the object W. As a result, it is possible to avoid or suppress the application of excessive loads to the gripper 9 or the forearm 8, or the resulting increase in reaction force against a person or environmental equipment that comes into contact or collides with it. It is also possible to prevent the object W from coming off the gripping unit 9. In this case, the manipulator 3 is bent at its elbow joint 11 and the gripping unit 9 is pulled back to the body 2, thereby reducing the area occupied by the robot 1 including the object W. As a result, the possibility or frequency of contact or collision with people or equipment in the work environment can be reduced, and at the same time, the posture of the manipulator 3 changes due to an external force, thereby improving safety.

[0034] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and the number of manipulators is not limited to two on each side, but may be one, and the upper arm equivalent or forearm equivalent may be configured to be flexible in the twisting direction, so that rotation at the joint is generated by replacing the upper arm equivalent or forearm equivalent. Furthermore, the structure of each joint may be selected appropriately as needed, and therefore the direction of rotation, range of motion, etc. may be determined appropriately according to the specifications required of the robot. [Explanation of symbols]

[0035] 1. Mobile robot 2. Torso 3 Manipulator 4 Leg equivalent part 5 Head equivalent part 6 Controller 6A Attitude control unit 7 Upper arm equivalent 8 Forearm equivalent 9 Gripping part 10 Shoulder joint 11 Elbow joint 12 Wrist joint 13 Servo motor C dolly W Object

Claims

1. A mobile robot having leg equivalents provided at the bottom of a body for moving on a floor surface, and a manipulator that can bend, stretch, and rotate attached to the body, the manipulator including at least an upper arm equivalent connected to the body by a shoulder joint, a forearm equivalent connected to the tip of the upper arm equivalent by an elbow joint, and a gripping part connected to the tip of the forearm equivalent by a wrist joint, a controller for controlling the movement of the leg equivalent portion and the manipulator; The controller a posture control unit that changes a posture, which is a relative position of the manipulator with respect to the trunk unit, between a moving posture when the manipulator is moving by operating the leg equivalent units and a resting posture when the leg equivalent units have stopped operating and are holding or releasing a predetermined object by the holding unit, The attitude control unit is configured to control the manipulator to change the moving attitude to an attitude in which the distance of the gripping unit from the trunk unit when moving by operating the leg equivalent units is smaller than the distance of the gripping unit from the trunk unit in a stopped attitude when the gripping unit is gripping or releasing a predetermined object. A mobile robot equipped with a manipulator characterized by:

2. A mobile robot equipped with the manipulator according to claim 1, the moving posture includes a first moving posture in which the gripping unit is moving without gripping the predetermined object, and a second moving posture in which the gripping unit is moving while gripping the predetermined object, The first moving posture is a folded posture in which an angle formed between the upper arm equivalent portion and the forearm equivalent portion is smaller than an angle formed between the upper arm equivalent portion and the forearm equivalent portion in the second moving posture. A mobile robot equipped with a manipulator characterized by:

3. A mobile robot equipped with the manipulator according to claim 1 or 2, The posture control unit is configured to differentiate backdrivability, which is the ease of movement of the upper arm equivalent portion due to an external force, from backdrivability, which is the ease of movement of the forearm equivalent portion due to an external force, in the moving posture. A mobile robot equipped with a manipulator characterized by:

4. A mobile robot equipped with the manipulator according to claim 3, The attitude control unit is configured to perform attitude limiting control to limit an approach distance to the trunk unit by the external force of the manipulator to a predetermined distance when the leg equivalent unit is moving by operating the leg equivalent unit. A mobile robot equipped with a manipulator characterized by:

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