JP2007216367A - Device and method for holding object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of gripping an object of an arbitrary shape by a natural operation such as that performed by a human using a robot hand including a plurality of fingers whose posture changes when a joint is rotated.
An apparatus of the present invention is an apparatus that grips an object using a robot hand including a plurality of fingers whose postures change when a joint rotates. The apparatus includes means for acquiring shape information of an object, means for selecting a finger to be used for gripping an object from the shape information of the object, and a position of a grip point on the object of the finger to be used for gripping the object from the shape information of the object. , A means for calculating a target joint angle of each joint, and a means for rotating each joint in accordance with the calculated target joint angle. In the apparatus, the means for calculating the target joint angle calculates the target joint angle from the position of the grip point for a finger used for gripping an object, and holds the finger for a finger not used for gripping the object. A target joint angle to be realized is set.
[Selection] Figure 1

Description

  The present invention relates to an apparatus and a method for gripping an object of an arbitrary shape using a robot hand including a plurality of fingers whose postures change when a joint rotates.

  Currently, humanoid robots are actively developed. These robots are expected to work on behalf of humans at home or office, or to assist humans in their work. In order to put the robot into practical use at home or in the office, it is necessary to let the robot perform the work of handling the tool. Tools used in homes and offices have specifications suitable for human handling, and many are suitable for handling with human hands having five fingers. Therefore, it is preferable that the humanoid robot as described above has five fingers in the hand, like a human being.

  Conventionally, a robot hand having five fingers like a human hand has been developed. Patent Documents 1 to 5 describe examples of robot hands having five fingers that have been conventionally developed.

Japanese Patent Laid-Open No. 2001-351057 JP 2004-355295 A JP-A-7-28891 JP-A-4-358277 JP 2003-228593 A

  In order to realize a natural motion like that performed by a human, as disclosed in Patent Document 1, a target joint angle is specified for each of the finger joints, and the target joint angle is realized. It is preferable that the joint be rotated as described above. For each finger joint, a target joint angle that realizes a natural motion is designated, and the joint is rotated to realize the target joint angle, whereby an object can be gripped with a natural motion.

However, depending on the shape of the object, not all fingers of the robot hand may be used when gripping the object. For example, when it is desired to grip a small object compared to a robot hand, if all the fingers are used for gripping, the fingers may interfere with each other and the object may not be gripped.
Also, if you try to grip an object using all your fingers without causing your fingers to interfere with each other, the posture of your fingers may be unnatural, and you may not be able to achieve natural movements that humans hold. .

  There is a need for a technology that can grip an object of an arbitrary shape with a natural motion like a human being.

  The present invention solves the above problems. The present invention provides a technique capable of gripping an object of an arbitrary shape with a natural motion such as that performed by a human using a robot hand including a plurality of fingers whose postures change when a joint is rotated.

  The present invention is embodied as a device. The apparatus of the present invention is an apparatus for gripping an object using a robot hand including a plurality of fingers whose postures change when a joint rotates. The apparatus includes means for acquiring shape information of an object, means for selecting a finger to be used for gripping an object from the shape information of the object, and a position of a grip point on the object of the finger to be used for gripping the object from the shape information of the object. , A means for calculating a target joint angle of each joint, and a means for rotating each joint in accordance with the calculated target joint angle. In the apparatus, the means for calculating the target joint angle calculates the target joint angle from the position of the grip point for a finger used for gripping an object, and holds the finger for a finger not used for gripping the object. A target joint angle to be realized is set.

  The above device acquires shape information of an object, selects a finger to be used for gripping the object based on the acquired shape information of the object, and makes the finger contact the object (gripping point) Calculate the position of. The shape information of the object can be acquired using, for example, a camera or a sensor. When a finger to be used for gripping an object is selected and a gripping point is calculated for each of the selected fingers, the above device calculates a target joint angle of each joint. For a finger used for gripping an object, a target joint angle of the joint of the finger is calculated based on the calculated position of the gripping point. For a finger that is not used for gripping an object, a target joint angle of the joint of the finger is set so as to realize a posture for gripping the finger. When the target joint angle of each joint is calculated, the above device rotates each joint according to the calculated target joint angle.

  In the above apparatus, a finger used for gripping is selected according to the shape of the object, and a gripping point of the finger used for gripping is calculated according to the shape of the object. For fingers used for gripping an object, rotate the joint so that it comes into contact with the object at the calculated gripping point, and for fingers not used for gripping the object, rotate the joint so as to realize a posture to grip the finger. To do. As a result, an object having an arbitrary shape can be gripped by a natural motion that is performed by a human.

  In the apparatus described above, the robot hand includes one finger and four fingers that can be bent toward the one finger and each has a unique possible range, and the means for selecting However, it is preferable to select a finger to be used for gripping an object depending on whether or not the possible range of each finger and the object overlap.

The human hand includes a thumb, an index finger, a middle finger, a ring finger, and a little finger that can be bent toward the thumb and each has a unique range of motion. The robot hand described above has a structure close to that of a human hand, and can realize a natural motion closer to that of a human when gripping an object.
When gripping an object using the robot hand as described above, each finger has a unique movable range. Depending on the position and shape of the object, some fingers overlap the movable range, and some fingers do not overlap the movable range. In the above device, a finger whose finger movable range overlaps with the object is selected as a finger used for gripping the object, and a finger whose finger movable range does not overlap with the object is selected as a finger not used for gripping the object. To do. Since such a finger selection is naturally performed when a human grips an object, according to the above-described apparatus, an object can be gripped by a natural motion closer to that of a human.

  The present invention is also embodied as a method. The method of the present invention is a method of gripping an object using a robot hand including a plurality of fingers whose postures change when a joint rotates. The method includes the steps of obtaining object shape information, selecting a finger to be used for gripping the object from the object shape information, and the position of the grip point on the object of the finger to be used for gripping the object from the object shape information. , Calculating a target joint angle of each joint, and rotating each joint according to the calculated target joint angle. In the method of calculating the target joint angle, the target joint angle is calculated from the position of the gripping point for a finger used for gripping an object, and the posture of grasping the finger for a finger not used for gripping the object is calculated. A target joint angle to be realized is set.

  According to the apparatus and method of the present invention, it is possible to grip an object of an arbitrary shape with a natural motion that a human performs, using a robot hand including a plurality of fingers whose postures are changed by driving a joint. Become.

The best mode for carrying out the invention is listed below.
(Form 1)
Means for calculating the shape center position of the object from the shape information of the object;
It further comprises means for adjusting the position of the robot hand,
The position of the robot hand is adjusted so that the center position of the shape of the object enters a region where the movable ranges of some fingers overlap each other.

  The gripping device 100 according to the present embodiment includes a robot hand 102, cameras 104a and 104b, and a control device 106. The gripping device 100 according to the present embodiment grips the object P using the robot hand 102.

  The robot hand 102 includes a palm part 108 and five fingers: a thumb 110 extending from the palm part 108, an index finger 124a, a middle finger 124b, a ring finger 124c, and a little finger 124d.

  The thumb 110 is a four-degree-of-freedom link system supported by the palm 108. The thumb 110 includes four joints 112, 114, 116, and 118, and a motor 152, 154, 156, and 158 is disposed for each joint. The joint 112 corresponds to an interphalangeal joint (IP joint) referred to as a human thumb, the joint 114 corresponds to a metacarpal joint (MP joint), and the joints 116 and 118 correspond to Ohishi metacarpal joint (TM joint). To do. The tip portion 122 of the thumb 110 is formed of a curved elastic body. A six-axis force sensor 120 is disposed at the base of the thumb 110. The six-axis force sensor 120 is a sensor that can independently detect forces in directions along three axis directions orthogonal to each other and moments around the respective axis directions. The six-axis force sensor 120 detects a gripping reaction force acting on the thumb 110. Encoders 172, 174, 176, and 178 for detecting the bending angles of the joints are arranged at the joints 112, 114, 116, and 118, respectively.

  The index finger 124a, the middle finger 124b, the ring finger 124c, and the little finger 124d are a three-degree-of-freedom link system supported by the palm portion 108. The index finger 124a includes four joints 126a, 128a, 130a, and 132a, and motors 160a, 162a, and 164a are disposed at the three joints 128a, 130a, and 132a, respectively, excluding the joint 126a at the most distal end side. . The joint 126a on the most distal side is an interlocking joint that interlocks with the adjacent joint 128a. The joint 126a corresponds to a distal interphalangeal joint (DIP joint) as a human index finger, the joint 128a corresponds to a proximal interphalangeal joint (PIP joint), and the joints 130a and 132a are metacarpal joints (MP joint). ). The tip portion 136a of the index finger 124a is formed of a curved elastic body. A six-axis force sensor 134a is disposed at the base of the index finger 124a. The six-axis force sensor 134a detects a gripping reaction force acting on the index finger 124a. In each of the joints 126a, 128a, 130a, and 132a, encoders 170a, 172a, 174a, and 176a for detecting the bending angle of the joint are arranged.

  The middle finger 124b, ring finger 124c, and little finger 124d have the same configuration as the index finger 124a. Hereinafter, the constituent elements of the middle finger 124b, the ring finger 124c, and the little finger 124d are given the same reference numerals as those of the corresponding constituent elements of the index finger 124a, but are different only in the subscript alphabet, and detailed description thereof will be omitted.

  The thumb 110, the index finger 124a, the middle finger 124b, the ring finger 124c, and the little finger 124d can each take a posture of being gripped by the palm 108 by bending the joint. As an example, FIG. 5 shows a posture in which the index finger 124a is gripped by the palm portion 108. The index finger 124a can realize a posture in which the index finger 124a is gripped by the palm 108 by rotating the joints 128a and 130a by 90 degrees. Similarly, by rotating the joints of the other fingers, it is possible to realize a posture of grasping the palm part 108. As will be described in detail later, in the gripping device 100 according to the present embodiment, a finger that is not used for gripping the object P realizes a posture in which the finger is gripped by the palm portion 108 as described above.

  The palm part 108 of the robot hand 102 is attached to a robot arm (not shown). By driving the robot arm, the robot hand 102 can be moved to a desired position.

  The cameras 104a and 104b are commonly used CCD cameras. The cameras 104 a and 104 b image the object P and transmit the obtained image data to the control device 106.

  The control device 106 includes a CPU, a ROM, a RAM, and the like. FIG. 2 shows a functional block diagram of the control device 106. The control device 106 recognizes the position and shape of the object P by image recognition from the image data of the cameras 104a and 104b, and grasps that calculate how the object P is grasped by the robot hand 102 based on the recognition result. A posture calculation unit 204, a hand control unit 206 that controls the movement of the robot hand 102, and a motor driver 208 that drives a motor group are provided.

  The control device 106 is not limited to such a configuration, and the image recognition unit 202, the gripping posture calculation unit 204, the hand control unit 206, and the motor driver 208 may be separate devices as hardware. Good. Alternatively, the image recognition unit 202, the gripping posture calculation unit 204, the hand control unit 206, and the motor driver 208 may be classified as software modules that operate on the same hardware.

  The image recognition unit 202 receives the image data transmitted from the cameras 104a and 104b, and specifies the position and shape of the object P through image recognition processing. The position and shape of the object P can be specified by extracting the image of the object P from the respective image data of the cameras 104a and 104b and using the principle of stereo vision from the extracted image of the object P. The image recognition unit 202 transmits the recognition result to the gripping posture calculation unit 204.

  The gripping posture calculation unit 204 determines the position of the robot hand 102 when gripping the object P, the finger used to grip the object P, and the finger used for gripping from the position and shape of the object P transmitted from the image recognition unit 202. The position of a contact point on the object P (hereinafter referred to as a gripping point) when the object P is brought into contact with the object P is set, and a target angle (target joint angle) of each joint of each finger when the object P is gripped is calculated. . Details of the processing by the gripping posture calculation unit 204 will be described later.

  The hand control unit 206 generates time-series joint angle command values corresponding to the target joint angles of the thumb 110, the index finger 124a, the middle finger 124b, the ring finger 124c, and the little finger 124d obtained by the grasping posture calculation unit 204. The command value is transmitted to the motor driver 208. At this time, the hand control unit 206 inputs the detection signal of the encoder group, and feedback-controls the angle of each joint (joint angle). Alternatively, a detection signal of the six-axis force sensor group may be input, and the gripping force by each finger may be feedback controlled.

  The motor driver 208 supplies a drive current corresponding to the joint angle command value generated by the hand control unit 206 to each motor, and rotates each motor. As each motor rotates, each joint realizes a joint angle corresponding to the joint angle command value, and the posture of the robot hand 102 changes.

  Hereinafter, the calculation processing of the target joint angle of each finger by the gripping posture calculation unit 204 will be described with reference to the flowchart of FIG.

  In step S <b> 302, the position and shape of the object P are acquired from the image recognition unit 202.

  In step S304, the shape center position PG of the object P is calculated from the position and shape of the object P. When the object P is made of a homogeneous material, the shape center position PG of the object P corresponds to the center of gravity position of the object P. In the gripping apparatus 100 of the present embodiment, assuming that the shape center position PG of the object P is substantially equal to the position of the center of gravity of the object P, selection of a finger used for gripping the object P and a gripping point on the object P Calculate the position of.

  In step S306, the target position of the palm part 108 of the robot hand 102 is set based on the shape center position PG of the object P. The target position of the palm part 108 of the robot hand 102 is set so that the shape center position PG of the object P falls within a region where the movable range of more fingertips overlaps based on the movable range of the fingertip of each finger. Is done.

  For example, if the shape center position PG of the object P is in an area where the movable ranges of the thumb 110 and the index finger 124a overlap, the fingertip of each finger is used when the object P is gripped using the thumb 110 and the index finger 124a. A gripping force toward the shape center position PG of the object P can be applied. By gripping in this way, the object P can be stably gripped. If the center position PG of the shape of the object P is in an area where the movable range of the fingertip of the middle finger 124b overlaps in addition to the thumb 110 and the index finger 124a, the object P is grasped using the thumb 110, the index finger 124a and the middle finger 124b. In doing so, it is possible to apply a gripping force from the respective fingertips toward the shape center position PG of the object P. As described above, when the shape center position PG of the object P enters the region where the movable ranges of the fingertips of more fingers overlap, the gripping force toward the shape center position PG of the object P from more fingertips. The object P can be stably gripped.

In the gripping device 110 of the present embodiment, the gripping posture calculation unit 204 stores in advance the movable range of the fingertip of each finger relative to the palm unit 108. Then, the gripping posture calculation unit 204 determines whether or not the shape center position PG of the object P can be placed in an area where the movable ranges of all five fingertips overlap by moving the palm unit 108. If it is possible to put the shape center position PG of the object P in a region where the movable ranges of all five fingers overlap, the gripping posture calculation unit 204 sets the position of the palm unit 108 at that time as the target position. If the shape center position PG of the object P cannot be put in an area where the movable ranges of all five fingertips overlap, the shape center position of the object P in an area where the movable ranges of the four fingertips including the thumb 110 overlap. It is determined whether or not PG can be inserted. If it is possible to put the shape center position PG of the object P in a region where the movable ranges of the four fingertips including the thumb 110 overlap, the gripping posture calculation unit 204 sets the position of the palm unit 108 at that time as the target position. Set. If the shape center position PG of the object P cannot be entered even in the region where the movable ranges of the four fingertips including the thumb 110 overlap, the object P is in the region where the movable ranges of the three fingertips including the thumb 110 overlap. It is determined whether or not the shape center position PG can be entered. If the shape center position PG of the object P cannot be entered even in the region where the movable ranges of the three fingertips including the thumb 110 overlap, the object P is in the region where the movable ranges of the two fingertips including the thumb 110 overlap. It is determined whether or not the shape center position PG can be entered. If the shape center position PG of the object P cannot be entered even in an area where the movable ranges of two fingertips including the thumb 110 overlap, it is determined that the object P cannot be gripped by the robot hand 102, and exception processing is performed. After that. If the shape center position PG of the object P can be put in a region where the movable range of the fingertip overlaps, the gripping posture calculation unit 204 sets the position of the palm unit 108 at that time as the target position.
When the target position of the palm unit 108 is set by the gripping posture calculation unit 204, the palm unit 108 moves to the set target position by driving a robot arm (not shown).

In step S308, a finger used to hold the object P is selected from the thumb 110, the index finger 124a, the middle finger 124b, the ring finger 124c, and the little finger 124d. In the present embodiment, a finger that can bring the fingertip into contact with the surface of the object P by rotating the joint is selected as a finger used for gripping the object P.
The gripping posture calculation unit 204 evaluates for each finger whether or not the movable range of the fingertip of the finger intersects the surface of the object P. The movable range of the fingertip of each finger is stored in advance. The surface of the object P can be obtained from the position and shape of the object P. When the movable range of the fingertip intersects the surface of the object P (that is, when the movable range of the fingertip and the object overlap), the gripping posture calculation unit 204 selects the finger as a finger used for gripping the object P. When the movable range of the fingertip does not intersect the surface of the object P (that is, when the movable range of the fingertip and the object do not overlap), the gripping posture calculation unit 204 selects the finger as a finger that is not used for gripping the object P.

  In step S310, the position of the grip point on the object P is calculated for each finger used to grip the object P. The position of the grip point on the object P of each finger is calculated as a position where the object P can be stably gripped within the range of the region where the movable range of the fingertip and the surface of the object P intersect. As an example, FIG. 4 schematically illustrates a method of calculating the position of the gripping point when the thumb 110, the index finger 124a, and the middle finger 124b are selected as the fingers used for gripping the object P. 4, the boundary of the movable range of the fingertip part 122 of the thumb 110 is indicated by reference numeral 402, the boundary of the movable range of the fingertip part 136a of the index finger 124a is indicated by reference numeral 404, and the boundary of the movable range of the fingertip part 136b of the middle finger 124b is indicated. This is indicated by reference numeral 406. In FIG. 4, the shape center position PG of the object P is in an area where the movable range of the fingertip portion 122 of the thumb 110, the movable range of the fingertip portion 136a of the index finger 124a, and the movable range of the fingertip portion 136b of the middle finger 124b overlap. ing. In this case, with respect to the fingertip portion 122 of the thumb 110, the gripping point can be set within the range of the region where the surface of the object P and the movable range intersect. The same applies to the index finger 124a and the middle finger 124b. The gripping posture calculation unit 204 calculates the gripping point of each finger under the condition that the fingertip part 122 of the thumb 110, the fingertip part 136a of the index finger 124a, and the fingertip part 136b of the middle finger 124b do not interfere with each other. The gripping posture calculation unit 204 is configured such that the average position of the gripping point 410 of the fingertip part 122 of the thumb 110, the gripping point 412 of the fingertip part 136a of the index finger 124a, and the gripping point 414 of the fingertip part 136b of the middle finger 124b is the shape of the object P. The gripping point of the fingertip of each finger is calculated so as to be closest to the center position PG.

  In step S312, it is determined whether or not the gripping point has been calculated for each finger used to grip the object P. If the gripping point cannot be calculated with any one of the fingers used to grip the object P (YES in step S312), the finger whose gripping point cannot be calculated is used for gripping the object P. The finger is selected again, and the position of the gripping point is calculated again in step S312. When the gripping points can be calculated for all the fingers used for gripping the object P (NO in step S312), the process proceeds to step S314, and the target joint angle is calculated.

  In step S314, a target joint angle is calculated for a finger that is used to grip the object P and for which the grip point is calculated on the object P. The gripping posture calculation unit 204 calculates a joint angle such that the fingertip is located at the gripping point on the object P by the inverse kinematics method, and sets the calculated joint angle as the target joint angle.

  In step S316, it is determined whether or not the target joint angle has been calculated for each finger used to grip the object P. If the target joint angle cannot be calculated by any one of the fingers used to grip the object P (YES in step S316), the finger that cannot calculate the target joint angle is gripped by the object P. The finger is not selected for use again, and the calculation of the position of the gripping point in step S312 and the calculation of the target joint angle in step S314 are performed again. When the target joint angle can be calculated for all the fingers used for gripping the object P (NO in step s316), the process proceeds to step S318, and the target joint angle of the finger not used for gripping the object P is set. Do.

  In step S318, a target joint angle is set for a finger that is not used to hold the object P. In the gripping device 100 of the present embodiment, for a finger that is not used for gripping the object P, the target joint angle is set so that the finger is held in the palm portion 108. For example, when the little finger 124d is a finger that is not used for gripping the object P, the target joint angle of each of the joint 130d and the joint 128d is set to 90 degrees. For the joint 132d, the target joint angle is set to 0 degree. As a result, when the robot hand 102 grips the object P, an operation of bending and gripping the little finger 124d is realized.

  As described above, when the target joint angle is calculated for each of the finger used for gripping the object P and the finger not used for gripping the object P, the gripping posture calculation unit 204 calculates the calculated target joint angle in step S320. Is output to the hand control unit 206, and the process ends.

  When the target joint angle is set for each finger by the gripping posture calculation unit 204, the hand control unit 206 generates a time-series joint angle command value, and the motor is driven by the motor driver 208. The joint of each finger rotates to the target joint angle, and the posture in which the finger used for gripping contacts the gripping point on the object P is realized, and the object P is gripped.

  In this embodiment, an example in which the object P is gripped using the robot hand 102 including the thumb 110, the index finger 124a, the middle finger 124b, the ring finger 124c, and the little finger 124d has been described. However, the robot hand 102 that can be handled by the gripping device 100 is described. The structure is not limited to this. The robot hand 102 may have a smaller number of fingers or a larger number of fingers. Further, the thumb 110, the index finger 124a, the middle finger 124b, the ring finger 124c, and the little finger 124d of the robot hand 102 may have more joints or fewer joints.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
In addition, the technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

FIG. 1 is a diagram schematically showing an overview of the gripping device 100. FIG. 2 is a diagram schematically showing the configuration of the control device 106. FIG. 3 is a flowchart for explaining processing performed by the gripping posture calculation unit 204. FIG. 4 is a diagram schematically showing a method for calculating the position of the gripping point. FIG. 5 is a diagram schematically showing a posture in which the index finger 124a is grasped.

Explanation of symbols

100: gripping device 102: robot hand 104a, 104b: camera 106: control device 108: palm 110: thumbs 112, 114, 116, 118: thumb joints 120, 134a, 134b, 134c, 134d: 6-axis force sensor 122 : Thumb tip 124a: index finger 124b: middle finger 124c: ring finger 124d: little finger 126a, 128a, 130a, 132a: index finger joint 136a: index finger tip 126b, 128b, 130b, 132b: middle finger joint 136b: middle finger tip Parts 126c, 128c, 130c, 132c: ring finger joint 136c: ring finger tip 126d, 128d, 130d, 132d: little finger joint 136d: little finger tip 202: image recognition unit 204: gripping posture calculation unit 206: hand control Part 208: Motor driver 4 2,404,406: the boundary 410, 412, 414: Gripping point

Claims (3)

An apparatus for gripping an object using a robot hand having a plurality of fingers whose posture changes when a joint rotates,
Means for obtaining shape information of the object;
Means for selecting a finger to be used for gripping the object from the shape information of the object;
Means for calculating the position of the gripping point on the object of the finger used for gripping the object from the shape information of the object;
Means for calculating a target joint angle of each joint;
Means for rotating each joint according to the calculated target joint angle;
The means for calculating the target joint angle calculates a target joint angle from the position of the grip point for a finger used for gripping an object, and realizes a posture for gripping the finger for a finger not used for gripping an object. An apparatus for gripping an object using a robot hand characterized by setting an angle. The robot hand includes one finger and four fingers that can be bent toward the one finger and each has a unique possible range;
2. The apparatus according to claim 1, wherein the selecting means selects a finger to be used for gripping an object depending on whether or not an object overlaps a possible range of each finger. A method of gripping an object using a robot hand having a plurality of fingers whose posture changes when a joint rotates,
Obtaining object shape information;
Selecting a finger to be used for gripping the object from the shape information of the object;
Calculating the position of the gripping point on the object of the finger used for gripping the object from the shape information of the object;
Calculating a target joint angle for each joint;
A step of rotating each joint according to the calculated target joint angle,
In the step of calculating the target joint angle, for a finger used for gripping an object, the target joint angle is calculated from the position of the grip point, and for a finger not used for gripping the object, a target joint that realizes a posture for gripping the finger A method of gripping an object using a robot hand characterized by setting an angle.

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