Patent Application
20140277720
The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2013-053306, filed Mar. 15, 2013. The contents of this application are incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates to a robot system, a method for controlling a robot, and a method for producing a to-be-processed material.
2. Discussion of the Background
In recent years, there has been an increasing demand for automating human manual work using a robot. For example, Japanese Unexamined Patent Application Publication No. 2011-230245 discloses a robot system that uses an inner force sensor to fit a fitting member held by a hand mounted to a distal end of the robot into a receiver member.
According to one aspect of the present disclosure, a robot system includes a robot, a fitting member holder, a receiver member, a position determination member, and a robot controller. The fitting member holder is mounted to a distal end of the robot to hold a fitting member. The receiver member is configured to receive the fitting member. The position determination member is disposed at a fixed position relative to the receiver member. The robot controller is configured to control the robot. The robot controller includes a position identifying device and a fitting control device. The position identifying device is configured to bring at least one of the robot, the fitting member, and the fitting member holder into contact with the position determination member with the fitting member holder holding the fitting member. The position identifying device is configured to identify a fitting position based on a position of the contact as a reference position. The fitting control device is configured to control the robot to fit the fitting member into the receiver member at the fitting position.
According to another aspect of the present disclosure, a method for controlling a robot includes, with a fitting member holder mounted to a distal end of the robot being holding a fitting member, bringing at least one of the robot, the fitting member, and the fitting member holder into contact with a position determination member, so as to identify a fitting position based on a position of the contact as a reference position. The position determination member is disposed at a fixed position relative to a receiver member. The receiver member is configured to receive the fitting member. The robot is controlled to fit the fitting member into the receiver member at the fitting position.
According to the other aspect of the present disclosure, a method for producing a to-be-processed material includes holding a fitting member as the to-be-processed material using a fitting member holder. With the fitting member holder holding the fitting member, at least one of a robot, the fitting member, and the fitting member holder is brought into contact with a position determination member, so as to identify a fitting position based on a position of the contact as a reference position. The position determination member is disposed at a fixed position relative to a receiver member. The receiver member is configured to receive the fitting member. The robot is controlled to fit the fitting member into the receiver member at the fitting position.
A more complete appreciation of the present disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
The embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings.
In a robot system according to this embodiment, a robot performs various kinds of work such as processing and assembly on a workpiece (to-be-processed material). The workpiece may be a single part, or a product or a semi-processed product formed of a combination of a plurality of parts. In particular, the robot fits/inserts (hereinafter simply referred to as “fits”, “fit”, “fitted”, or “fitting”) a fitting member (which is a workpiece) into a receiver member. The robot system according to this embodiment utilizes inner force sensor technology to perform impedance control, described later, in an attempt to improve fitting work quality. The workpiece may be any kind of item subject to work in the robot system.
The robot 10 will be described in detail below by referring to
The robot arm 101 is made up of first to sixth arms 106 to 111 coupled to each other, in the order from the base end (base portion 105) side. Each of these arms accommodates an actuator to drive the arm into rotation as indicated by the two-headed arrows shown in
The hand 102 is mounted to the distal end of the robot arm 101. The sixth arm 111, which is at the distal end of the robot arm 101, incorporates an actuator to drive the hand 102 into rotation. The hand 102 incorporates an actuator to drive a pair of holding claws 102a mounted to the distal end of the hand 102.
Between the hand 102 and the sixth arm 111, which is at the distal end of the robot arm 101, an inner force sensor 103 is disposed. The inner force sensor 103 is what is called a 6-axis inner force sensor, which is capable of simultaneously detecting a total of six components, namely, force components in translational three axial directions to act on a detection portion and moment components about rotational three axes.
Under the control of the controller 11, the robot 10 operates the first to the sixth arms 106 to 111, the hand 102, and the holding claws 102a to hold the fitting member 20 at the holding claws 102a and fit the held fitting member 20 into the receiver member 30.
Referring back to
The operation command is a command as a program to activate the robot 10 or a combination job of programs to activate the robot 10. For example, a command to hold the fitting member 20 on the holding claws 102a, a command to fit the held fitting member 20 into the receiver member 30, and other commands are set in advance as the operation command. This ensures that normally, the robot 10 automatically performs its fitting work according to the operation command However, for unexpected reasons such as when the fitting member 20 held by the robot 10 is significantly heavy, the position of the robot 10 may change after the robot 10 has held the fitting member 20, or the position of the receiver member 30 may change. This can make it difficult for the robot 10 to perform accurate fitting work. For accurate fitting work, the controller 11 has the following function.
The function of the controller 11 will be described below by referring to
The controller 11 sets operation commands into the robot 10 in advance. The operation commands include a command to control the holding claws 102a (the hand 102) to hold the fitting member 20, and a command to, while the holding claws 102a (the hand 102) are holding the fitting member 20, control the robot arm 101 to move by a predetermined section from the position at which the holding claws 102a have held the fitting member 20. As shown in
The position determination member 50 has a shape corresponding to the outer shape of at least one of the robot 10, the fitting member 20, and the hand 102. Here, the position determination member 50 has a cubic shape corresponding to the fitting member 20, which has a cubic shape. The position determination member 50 may be formed integrally with the receiver member 30, or may be formed separately from the receiver member 30 insofar as the position determination member 50 has a fixed relative positional relationship with the receiver member 30. The relative positional relationship between the receiver member 30 and the position determination member 50 is stored in advance in the position identifying device 112 as position-determination-member position information. Specifically, the position-determination-member position information includes information on a spaced-apart distance between the receiver member 30 and the position determination member 50, and information on a direction in which the receiver member 30 is positioned as viewed from the position determination member 50.
Then, the robot 10 moves the robot arm 101 according to the operation command. When this results in a contact of the robot 10, the fitting member 20, or the hand 102 (including the holding claws 102a) with the position determination member 50, the inner force sensor 103 detects the contact. The inner force sensor 103 detects the position of the contact at the robot 10 or another element, as well as detecting a force component involved in the contact. An exemplary manner of the inner force sensor 103's detection of the position of the contact is as follows. Based on the force and moment detected by the inner force sensor 103, a line of action of force is calculated. Then, the intersection between the line of action of force and the surface of the robot 10 or another element is derived as the position of the contact.
The information on the contact detected by the inner force sensor 103 is input into the position identifying device 112 of the controller 11 from the inner force sensor 103 through the cable harness 13. When the position identifying device 112 receives the information on the contact from the inner force sensor 103, the position identifying device 112 sets the position of the contact as the reference position. Then, based on the position-determination-member position information, the position identifying device 112 identifies, as a fitting position 40, a position apart from the reference position by the spaced-apart distance between the receiver member 30 and the position determination member 50 in the direction in which the receiver member 30 is positioned. The fitting position 40 is identified based on positions in three directions (namely, a position in a first direction, a position in a second direction, and a position in a third direction). Here, the third direction is a direction in which the fitting member 20 is fitted into the receiver member 30 (that is, a Z direction). The first direction is a direction orthogonal to the third direction (that is, an X direction). The second direction is a direction orthogonal to the first direction and the third direction (that is, a Y direction). In
By referring to
Then, the controller 11 generates a command as an operation command to the robot 10 holding the fitting member 20. The command is to the effect that the robot arm 101 moves by a predetermined section. As shown in
In this case, the inner force sensor 103 detects the contact and inputs information on the detected contact into the position identifying device 112 of the controller 11. The position identifying device 112 stores in advance the position-determination-member position information, and thus uses the position-determination-member position information to identify, as the fitting position 40 shown in
Based on the position of the contact, the position identifying device 112 detects a position displacement of the fitting member 20 relative to the receiver member 30, and identifies the fitting position 40 based on the degree of the detected position displacement. The position identifying device 112 identifies the degree of the position displacement based on the position of the contact of at least one of the robot 10, the fitting member 20, and the hand 102 with the position determination member 50 (hereinafter referred to as the position of the contact at the robot 10 or another element), based on the position of the contact of the position determination member 50 with at least one of the robot 10, the fitting member 20, and the hand 102 (hereinafter referred to as the position of the contact at the position determination member 50), and based on the position-determination-member position information.
The inner force sensor 103 detects the position of the contact at the robot 10 or another element as described above. Specifically, the position identifying device 112 identifies the position of the contact at the robot 10 or another element based on the information on the contact input from the inner force sensor 103. Also, the position of the contact at the position determination member 50 is identified in such a manner that the robot 10 or another element is brought into contact with the position determination member 50 from the X direction, or from the X direction and the Y direction, or from the X direction, the Y direction, and the Z direction. That is, the position identifying device 112 identifies the position of the contact at the position determination member 50 in the X direction by bringing the robot 10 or another element into contact with the position determination member 50 from the X direction. The position identifying device 112 identifies the position of the contact at the position determination member 50 in the Y direction by bringing the robot 10 or another element into contact with the position determination member 50 from the Y direction. The position identifying device 112 identifies the position of the contact at the position determination member 50 in the Z direction by bringing the robot 10 or another element into contact with the position determination member 50 from the Z direction.
The position identifying device 112 stores in advance the position-determination-member position information for each of positions on the position determination member 50. Specifically, for each of the positions on the position determination member 50, the position identifying device 112 stores the spaced-apart distance between the position determination member 50 and the receiver member 30 in each of the directions.
The position identifying device 112 identifies the degree of the position displacement in the following manner. First, the position of the contact at the position determination member 50 is identified, and based on the position-determination-member position information, the spaced-apart distance relative to the receiver member 30 at the position of the contact at the position determination member 50 is identified for each of the directions. Next, the degree of the position displacement is identified based on the identified spaced-apart distance and another parameter in consideration of the position of the contact at the robot 10 or another element. Thus, the fitting position 40 is identified.
Specifically, for example, it is assumed that the spaced-apart distance relative to the receiver member 30 at the position of the contact at the position determination member 50 is identified as 20 centimeters (cm) in the X direction, 30 cm in the Y direction, and 0 cm in the Z direction. Then, it is assumed that the position of the contact at the robot 10 or another element is identified as a position at 10 cm toward the holding claws 102a in the Z direction from the distal end of the fitting member 20. In this case, the degree of the position displacement is identified as 20 cm in the X direction, 30 cm in the Y direction, and 10 cm in the Z direction.
It is also possible to make the shape of the position determination member 50 correspond to the shape of at least one of the robot 10, the fitting member 20, and the hand 102, to identify the position of the contact at the robot 10 or another element and the position of the contact at the position determination member 50, and thus to identify the fitting position 40. Specifically, for example, to identify the position of the contact at the position determination member 50 in the X direction and in the Y direction, instead of bringing the robot 10 or another element into contact with the position determination member 50 from the X direction and the Y direction as describe above, it is possible to bring the robot 10 or another element into contact with the position determination member 50 from the X direction, and to move the robot 10 or another element in the Y direction with the robot 10 keeping contact with the position determination member 50. Then, the position at which the robot 10 or another element is stabilized in accordance with the shape of the position determination member 50 may be identified as the position of the contact in the X direction and the Y direction. In this case, the position at which the robot 10 or another element is stabilized is determined as a single portion. This ensures that the position of the contact at the robot 10 or another element can be identified at the same time. The robot 10 or another element may be stabilized in accordance with the shape of the position determination member 50 by the use of an impedance control technique, described later.
By referring to
First, the controller 11 generates a command as an operation command to the robot 10 holding the fitting member 20x. The command is to the effect that the robot arm 101 moves by a predetermined section in the X direction, which is the first direction. This causes the fitting member 20x to be brought into contact with the position determination member 50x, as shown in
When the robot 10 moves the robot arm 101 in the Y direction, which is the second direction, in accordance with the operation command from the controller 11, then the side surface of the fitting member 20x reaches a position at which the shape of the side surface of the fitting member 20x matches the shape of the depressed portion 51x of the position determination member 50x (see
Then, based on the position at which the robot 10 is stabilized, the position identifying device 112 identifies the position of the contact at the position determination member 50x in the X direction and in the Y direction and identifies the position of the contact at the fitting member 20x. Based on the identified contact positions and the position-determination-member position information, the position identifying device 112 identifies the fitting position 40x.
Referring back to
The fitting processing by the use of the impedance control will be described in detail below. The impedance control is a manner of control by which mechanical impedance (such as inertia, attenuation coefficient, and rigidity) generated when external force acts on the hand of the robot is set at a value convenient for desired work, and the position and force are controlled based on the value. As described above, a prerequisite for the fitting processing is a state in which the fitting member 20 is positioned at the fitting position 40. At the fitting position 40, the fitting control device 113 starts force control and generates an operation command to the robot 10. The operation command is to the effect that the fitting member 20 comes into contact with the receiver member 30 (this command is referred to as a TOUCH command).
When the fitting control device 113 receives information on the contact from the inner force sensor 103, the fitting control device 113 generates an operation command to the robot 10. The operation command is to the effect that the robot 10 performs a hole position search operation. In the hole position search operation, the robot 10 searches for the depression of the fitting position 40 by swinging the robot arm 101 to the right and left. During the hole position search operation, the fitting member 20 keeps contact with the receiver member 30. A position determination pin is provided on the depression of the receiver member 30. The position determination pin helps the fitting member 20 to be fitted into the receiver member 30 in an appropriate orientation. When the hole position search operation is successful, the fitting control device 113 generates another operation command to the robot 10. The operation command is to the effect that the robot 10 performs a position determination pin search operation. In the position determination pin search operation, the robot 10 rotates along the shape of the depression.
When the robot 10 succeeds in the position determination pin search operation, the fitting control device 113 generates an operation command to the robot 10. The operation command is to the effect that the robot 10 inserts the fitting member 20 into the depression of the receiver member 30 (this command is referred to as an INSERT command). Then, in accordance with the operation command, the robot 10 inserts the fitting member 20 into the depression of the receiver member 30. Thus, the force control by the fitting control device 113 ends. After the fitting processing, the robot 10 releases the fitting member 20 in accordance with the operation command of the controller 11 and withdraws. Thus, the functions of the controller 11 have been described above.
Referring back to
Next, a flow of the series of the fitting work will be described by referring to
In the robot system 1 according to this embodiment, with the hand 102 holding the fitting member 20, at least one of the robot 10, the fitting member 20, and the hand 102 is brought into contact with the position determination member 50, which is disposed at a fixed position relative to the receiver member 30. In this manner, the position identifying device 112 identifies the position of the fitting position 40 for the fitting member 20 and the receiver member 30.
During the robot's fitting work, the relative positions of the fitting member and the receiver member may turn into an unmatched relationship in some cases before the fitting member and the receiver member are fitted to each other (that is, the relative positions of the fitting member and the receiver member can be displaced from each other). A conventional way to accommodate to the position displacement is to set an operation of searching for the receiver member (more specifically, its depression) in the fitting operation during the fitting work. However, if the position displacement is beyond the searchable range of the search operation, accurate fitting work may not be possible, and thus it may be difficult to maintain a constant level of work quality.
In this respect, in the robot system 1 according to this embodiment, the robot 10 or another element is brought into contact with the position determination member 50, which is disposed at a fixed position relative to the receiver member 30, and the fitting position 40 is identified based on the position of the contact as a reference position, as described above. This ensures accurate fitting work even if the position displacement is beyond the searchable range within which (the depression of) the receiver member 30 is searchable. Thus, the fitting work is maintained at a constant level of quality.
The inner force sensor 103 is disposed between the distal end of the robot 10 (that is, the sixth arm 111) and the hand 102. This ensures detection of the force component involved in the contact between the robot 10 or another element and the position determination member 50, and ensures detection of the position of the contact at the robot 10 or another element.
Also, the position identifying device 112 detects the position displacement of the fitting member 20 relative to the receiver member 30 based on the position of the contact, and identifies the fitting position 40 based on the degree of the detected position displacement. This ensures appropriate identification of the fitting position 40 for each contact position. This, in turn, further improves the quality of fitting work.
The position identifying device 112 brings at least one of the robot 10, the fitting member 20, and the hand 102 into contact with the position determination member 50 from the X direction, from the X direction and the Y direction, or from the X direction, the Y direction, and the Z direction so as to identify the position displacement. This ensures appropriate identification of the fitting position 40 for each of the portions where the fitting member 20 and the receiver member 30 are disposed. Specifically, when the displacement of the relative positions of the fitting member 20 and the receiver member 30 is one-dimensional, the robot 10 or another element is brought into contact with the position determination member 50 from the X direction. When the displacement of the relative positions of the fitting member 20 and the receiver member 30 is two-dimensional, the robot 10 or another element is brought into contact with the position determination member 50 from the X direction and the Y direction. When the displacement of the relative positions of the fitting member 20 and the receiver member 30 is three-dimensional, the robot 10 or another element is brought into contact with the position determination member 50 from the X direction, the Y direction, and the Z direction. This ensures appropriate identification of the fitting position 40 for each of the portions where the fitting member 20 and the receiver member 30 are disposed.
The position determination member 50 has a shape corresponding to the shape of at least one of the robot 10, the fitting member 20, and the hand 102. The fitting position 40 is identified based on the position at which the robot 10 or another element is stabilized in accordance with the shape of the position determination member 50. Thus, the robot 10 or another element is brought into contact with the position determination member 50 from one direction. This ensures identification of the fitting position 40 even when the displacement is in two directions or in three directions. That is, this facilitates identification processing of the fitting position 40.
While in this embodiment the fitting member 20 is fitted into the depression of the receiver member 30, the receiver member may not necessarily have a depression. The fitting member itself may have a depression and the receiver member may have a protrusion, so that the depression of the fitting member may receive the protrusion of the receiver member. While in this embodiment the fitting control device 113 performs the fitting processing by the use of impedance control, any other kind of control is also possible for the fitting processing insofar as the fitting member can be fitted into the receiver member.
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-053306 | Mar 2013 | JP | national |
