Multi-axis robot and control method therefor, and work tool

A multi-axis robot includes: a robot main body including a head and a movement mechanism that three-dimensionally moves the head; and a work tool attached to the head. The work tool includes: a first link pivotally supported on the head; a second link pivotally supported on a distal end of the first link; a first change mechanism that changes an angle of the first link to a central axis of the head; and a second change mechanism that changes an angle of the second link to the first link.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based on PCT filing PCT/JP2020/048923, filed Dec. 25, 2020, which claims priority to JP 2019-237748, filed Dec. 27, 2019, the entire contents of each are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a multi-axis robot that performs a predetermined work while moving along a shape of a workpiece and to a work tool for use in the multi-axis robot.

BACKGROUND ART

A work tool for use in a multi-axis robot as described in Patent Literature 1 has been known. The work tool described in Patent Literature 1 is intended for a work of applying sealant on a workpiece and is attached to a robot wrist at a distal end of the multi-axis robot or industrial robot having degrees of freedom of motion. The work tool includes: a housing fixedly attached to the robot wrist; a motor provided in the housing; a ball-screw mechanism protruding from a lower end of the housing in an advanceable and retractable manner in response to a rotation of the motor; and a tool arm coupled to a lower end of the ball-screw mechanism. The tool arm includes a short secondary arm coupled to the lower end of the ball-screw mechanism via a pin and a long primary arm extending downward from an end of the secondary arm, and has an L-shape entirely. A connection portion where the secondary arm and the primary arm are connected to each other is pivotally supported by an arm holder provided at the lower end of the housing via a pin.

The work tool having the structure described above according to Patent Literature 1 can swing the L-shaped tool arm over a predetermined angle by causing the ball-screw mechanism to move away from or toward the housing in response to the rotation of the motor. The swinging of the tool arm is considered to lead to an increase in the degrees of freedom of motion and be useful for prevention of contact between the workpiece and the work tool.

However, Patent Literature 1 directed to the mechanism of causing the tool arm having the L-shape or a given shape to swing about the robot wrist has a drawback of not high expectation for the prevention of the contact with the workpiece. Specifically, the work tool of Patent Literature 1 may avoid the contact in a work on a workpiece having a specific shape, but may fail to avoid the contact when used for another workpiece having a different shape even by swinging the tool arm to any position. This necessitates, for example, replacement of the tool arm itself with another one having a corresponding shape. The replacement needs an extra time and the work efficiency is reduced accordingly. In other words, the technique of Patent Literature 1 has a drawback of failure to efficiently perform a work on various kinds of workpieces with the same work tool.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

The present invention has been achieved in view of the aforementioned circumstances, and has an object to provide a work tool which can efficiently perform a work on various kinds of workpieces having different shapes while avoiding contact with the workpiece, and a multi-axis robot including the work tool.

To overcome the aforementioned drawback, a multi-axis robot according to an aspect of the present invention performs a predetermined work while moving along a shape of a workpiece. The multi-axis robot includes: a robot main body including a head and a movement mechanism that three-dimensionally moves the head; and a work tool attached to the head. The work tool includes: a first link pivotally supported on the head; a second link pivotally supported on a distal end of the first link; a first change mechanism that changes a first angle being an angle of the first link to a central axis of the head; and a second change mechanism that changes a second angle being an angle of the second link to the first link.

A work tool according to another aspect of the present invention is attached to a head of a multi-axis robot that moves along a shape of a workpiece. The work tool includes: a first link pivotally supported on the head; a second link pivotally supported on a distal end of the first link; a first change mechanism that changes a first angle being an angle of the first link to a central axis of the head; and a second change mechanism that changes a second angle being an angle of the second link to the first link.

A control method according to further another aspect is a method for controlling the multi-axis robot. The method includes: a first step of moving a tip of the second link to an initial working position of the workpiece; a second step of adjusting each of the first angle and the second angle to a predetermined angle before the tip of the second link reaches the initial working position; and a third step of moving the tip of the second link from the initial working position along the shape of the workpiece while keeping the first angle and second angle.

A multi-axis robot according to still another aspect of the present invention performs a predetermined work while moving along a shape of a workpiece. The multi-axis robot includes: a robot main body including a head and a movement mechanism that three-dimensionally moves the head; and a work tool attached to the head. The work tool includes: a first link pivotally supported on the head; a second link extending from a distal end of the first link in a direction different from a central axis of the first link; and a change mechanism that changes a first angle being an angle of the central axis of the first link to a central axis of the head. The change mechanism adjusts the first angle in such a manner that a center line of the first link and a center line of the second link intersect with an extension line of the central axis of the head, and that a tip of the second link is closer to the extension line.

A work tool according to still further another aspect of the present invention is attached to a head of a multi-axis robot that moves along a shape of a workpiece. The work tool includes: a first link pivotally supported on the head; a second link extending from a distal end of the first link in a direction different from a central axis of the first link; and a change mechanism that changes a first angle being an angle of the central axis of the first link to a central axis of the head. The change mechanism adjusts the first angle in such a manner that a center line of the first link and a center line of the second link intersect with an extension line of the central axis of the head, and that a tip of the second link is closer to the extension line.

DESCRIPTION OF EMBODIMENTS

Overall Configuration of Robot

FIG.1andFIG.2are respectively a perspective view and a side view showing a work robot1according to an embodiment of the present invention.FIG.3is a partly enlarged view ofFIG.2. The work robot1is an example of a multi-axis robot according to the present invention and applies sealant S (FIG.3) or smooths the sealant S having been applied. The work robot1includes: a robot main body2of six-axis type having six arm joints JT1to JT6; and a work tool3attached to a distal end of the robot main body2. The arm joints JT1to JT6correspond to the “movement mechanism” in the present invention.

The robot main body2includes: a base10; a first arm link11connected to the base10via the first arm joint JT1; a second arm link12connected to the first arm link11via the second arm joint JT2; a third arm link13connected to the second arm link12via the third arm joint JT3; a fourth arm link14connected to the third arm link13via the fourth arm joint JT4; a fifth arm link15connected to the fourth arm link14via the fifth arm joint JT5; and a head16serving as a sixth arm link and connected to the fifth arm link15via the sixth arm joint JT6.

As shown inFIG.2, the first arm joint JT1causes the first arm link11to rotate about a first arm axis X1extending in a vertical direction with respect to the base10, as denoted by arrow A1. The second arm joint JT2causes the second arm link12to swing about a second arm axis X2extending in a horizontal direction with respect to the first arm link11, as denoted by arrow A2. The third arm joint JT3causes the third arm link13to swing about a third arm axis X3extending in a horizontal direction with respect to the second arm link12, as denoted by arrow A3. The fourth arm joint JT4causes the fourth arm link14to rotate about a fourth arm axis X4serving as a central axis of a distal end of the third arm link13with respect to the third arm link13, as denoted by arrow A4. The fifth arm joint JT5causes the fifth arm link15to swing about a fifth arm axis X5extending in a horizontal direction with respect to the fourth arm link14, as denoted by arrow A5. The sixth arm joint JT6causes the head16to rotate about a sixth arm axis X6serving as a central axis of a distal end of the fifth arm link15with respect to the fifth arm link15, as denoted by arrow A6. The first to sixth arm joints JT1to JT6respectively have motors M1to M6(FIG.7) of electric type as their driving sources. The sixth arm link16and the fifth arm link15are coaxially provided, and the sixth arm axis X6serves as a central axis of each of the fifth and sixth arm links15,16. Therefore, hereinafter, the central axis of the sixth arm link16is called a “central axis X6of the sixth arm link16” by using the same reference sign as that of the sixth arm axis X6.

Details of Work Tool

FIG.4Ais a perspective view of the work tool3and the periphery therearound seen at an angle different from that inFIG.1, andFIG.4Bis a side view thereof. As shown in the drawing and the precedingFIG.1toFIG.3, the work tool3includes: a base part20; a first link21; a second link22; a first joint JT7; and a second joint JT8. The base part20is detachably attached to the head16of the robot main body2via a fastener. The first link21straightly extends from the base part20. The second link22straightly extends from a distal end of the first link21. The first joint JT7represents an example of the “first change mechanism” in the present invention, and connects the base part20and the first link21to each other in such a manner as to change an angle. The second joint JT8represents an example of the “second change mechanism”, and connects the first link21and the second link22to each other in such a manner as to change an angle. In the embodiment, a ratio between a length of the first link21and a length of the second link22is set to substantially 1:1.

The first link21includes, for example, a proximal end21ahaving a disc shape and a distal end21bhaving a disc shape with a diameter smaller than that of the proximal end21aas shown inFIG.4. The proximal end21ais rotatably attached to the base part20. In other words, the first link21is pivotally supported on the head16via the base part20.

The second link22includes a proximal end pivotally supported on the distal end21bof the first link21. The second link22includes a distal end tool section22aat a distal end thereof. As shown inFIG.5, the distal end tool section22amay be a nozzle22a1that applies the sealant S (FIG.3) on a workpiece being a work target, or a spatula22a2that smooths the sealant S applied on the workpiece. In the case where the distal end tool section22ais the nozzle22a1(FIG.5A), the work tool3additionally includes a syringe (not shown) that supplies the sealant S to the nozzle.

FIGS.6A and6Bschematically show an inner structure of the work tool3. As shown in the drawing, the first joint JT7is a mechanism causing the first link21to swing with respect to the base part20, and can change an angle θ1(FIG.4B) between a center line Y1of the first link21and a central axis X6of the head16owing to the swinging. The second joint JT8serves as the mechanism causing the second link22to swing with respect to the first link21and can change an angle θ2(FIG.4B) between a center line Y2of the second link22and the center line Y1of the first link21(FIG.4B) owing to the swinging. Hereinafter, the angle θ1is referred to as a first angle θ1and the angle θ2is referred to as a second angle θ2.

As shown inFIG.6, the first joint JT7includes the motor M7of the electric type, a driving gear31driven by the motor M7to rotate, and a driven gear32meshing with the driving gear31. The driven gear32has a ring shape with a hollow at the center thereof, and is integrally coupled to the proximal end21aof the first link21. The driven gear32accommodates inside a part of the structural elements of the second joint JT8, i.e., a driving gear41and a driven gear42to be described later. The motor M7, the driving gear31, and the driven gear32are disposed in the base part20.

The second joint JT8includes: the motor M8of the electric type; the driving gear41driven by the motor M8to rotate; the driven gear42meshing with the driving gear41; a driving pulley43connected to the driven gear42coaxially therewith; a driven pulley44located away from the driving pulley43; and a belt45looped over the driving pulley43and the driven pulley44. The driven pulley44is integrally coupled to a proximal end of the second link22. The driving gear41and the driven gear42are disposed in the base part20, specifically, accommodated inside the driven gear32of the first joint JT7. The driving pulley43, the driven pulley44, and the belt45are disposed in the first link21.

A rotation of the motor M7in the first joint JT7leads to an operation of causing the first link21to swing with respect to the base part20, i.e., an operation of changing the first angle θ1. Specifically, when the motor M7rotates, the rotation is transmitted to the driving gear31and the driven gear32. Accordingly, the driven gear32and the first link21integrated therewith rotate about a first tool axis X7serving as a central axis of the driven gear32. Consequently, the first link21swings with respect to the base part20, resulting in changing the first angle θ1between the central axis X6of the head16and the center line Y1of the first link21.

A rotation of the motor M8in the second joint JT8leads to an operation of causing the second link22to swing with respect to the first link21, i.e., an operation of changing the second angle θ2. Specifically, when the motor M8rotates, the rotation is transmitted to the driven pulley44via the driving gear41, the driven gear42, the driving pulley43, and the belt45. Accordingly, the driven pulley44and the second link22integrated therewith rotate about a second tool axis X8serving as a central axis of the driven pulley44. Consequently, the second link22swings with respect to the first link21, resulting in changing the second angle θ2between the center line Y1of the first link21and the center line Y22of the second link22.

Control System

FIG.7is a block diagram showing a control system of the work robot1according to the embodiment. A controller50shown in this drawing aims at totally controlling the work robot1, and includes a microprocessor having a CPU, an RAM, and a ROM each commonly known. Moreover, an external input device60receives an input of teaching data, such as shape data of the workpiece, and includes a versatile computer. The external input device60is electrically connected to the controller50for the input of the data if necessary. The controller50is electrically connected to the parts of the work robot1. Specifically, The controller50is electrically connected to the motors M1to M6to respectively move the arm joints JT1to JT6of the robot main body2, and further electrically connected to the motors M7, M8to respectively move the joints JT7, JT8of the work tool3.

The controller50functionally includes a calculation part51, a servo control part52, and a storage part53. The storage part53is a storage medium storing various data, set values, programs and the like required to control the work robot1. The servo control part52is a module that controls the motors M1to M6of the robot main body2and the motors M7, M8of the work tool3. The calculation part51is a module that calculates, based on given data (conditions), an instructive value to be output to the motors M1to M8.

Control Operation Example

Next, a specific operation of the work robot1under the control by the controller50will be described. Here, first, described is a case where a work target (workpiece) of the work robot1is represented by a structure70shown inFIG.1andFIG.2, and a work of applying the sealant S (FIG.3) on the structure70is performed by the work robot1.

The structure70includes a base plate71supported on a workbench100in a standing manner, and horizontal plates72, vertical plates73, and protrusions74, each attached to the base plate71. The horizontal plate72is a plate member longitudinally extending in the horizontal direction. The vertical plate73is a rectangular plate member extending in an up-down direction. The protrusion74is a rod member protruding from a main surface71afarther than the horizontal plate72and the vertical plate73.

The horizontal plates72are attached to the main surface71a(the surface facing the work robot1) of the base plate71at different height positions. Each horizontal plate72integrally has: a flange section72abeing in surface contact with the main surface71a; a flat section72bprotruding from an upper end of the flange section72ain a direction perpendicularly intersecting the main surface71a; and a bent section72cextending upward from an end edge of the flat section72bthat is opposite to the main surface71a. The horizontal plate72is fixedly attached to the base plate71with the flange section72athereof fastened to the base plate71with rivets (not shown).

The vertical plates73are attached to the main surface71aat regular intervals in the up-down direction and a left-right direction. Specifically, the vertical plates73are arranged in such a manner that the vertical plates73and the horizontal plates72are alternately arrayed from the top at associated positions in the left-right direction.

The protrusions74are attached to the main surface71aat pitches similar to those of vertical plates73. Specifically, each of the protrusions74is interposed between the horizontal plate72and the vertical plate73adjacent to each other in the up-down direction.

FIG.1toFIG.3show a state where the work tool3is used to apply the sealant S (FIG.3) on a corner C1where the main surface71aof the base plate71and the flat section72bof the horizontal plate72intersect with each other. As shown in these drawings, the distal end tool section22aapproaches the corner C1from an oblique outside (obliquely upper side) in applying the sealant S on the corner C1. The distal end tool section22ahere is the nozzle22a1shown inFIG.5A. In the application of the sealant S on the corner C1as shown inFIG.1toFIG.3, the main surface71aof the base plate71corresponds to the “base surface” in the present invention, and the flat section72bof the horizontal plate72, specifically, a top surface of the flat section72b, which defines the corner C1with the main surface71acorresponds to the “intersection surface” in the present invention.

The corner C1has a long dimension in the left-right direction along a back edge (an edge on the side farther from the work robot1) of the flat section72bof the horizontal plate72. Concerning the corner C1, a division enclosed between adjacent two vertical plates73in the left-right direction is defined as a work division R. The application of the sealant S on the corner C1is performed per work division R. For instance, the work robot1performs the application of the sealant S from one work division R to another work division R in the left-right direction along the corner C1while moving the work tool3in this order. Specifically, the aforementioned application work of the sealant S is performed in accordance with a control procedure to be described below.

FIG.8is a flowchart showing a procedure of controls to be executed by the controller50to apply the sealant S on the corner C1. When the controls shown in this drawing are started, the controller50causes the work tool3to move to a work division R (hereinafter, referred to as an initial work division R) where the sealant S is to be firstly applied on the corner C1(step S1). Specifically, the controller50causes the first to sixth arm links11to16to rotate or swing by driving the motors M1to M6of the robot main body2so that the distal end tool section22a(here, the nozzle22a1) of the work tool3moves to a position closer to the corner C1in the initial work division R.

In particular, in step S1, the position and orientation of the head16are adjusted so that an extension line Lx of the central axis X6of the head16substantially meets a tip of the second link22(tip of the distal end tool section22a) at a time when the work tool3reaches the work division R.

The controller50adjusts the first angle θ1and the second angle θ2of the work tool3(step S2) concurrently with executing the control in step S1. Specifically, the controller50adjusts each of the first angle θ1between the head16and the first link21and the second angle θ2between the first link21and the second link22to a predetermined angle by driving the motors M7, M8of the work tool3. Each of the first angle θ1and the second angle θ2having been adjusted, that is, the predetermined angle is defined to satisfy three Conditions (i) to (iii) to be described below. The predetermined angle here may be obtained in advance through calculation based on, for example, shape data of the structure70and a positional relation between the work robot1and the structure70.

(i) The work tool3avoids contact with the respective parts of the structure70in application of the sealant S within each work division R.

(ii) The distal end tool section22aof the second link22approaches the corner C1from an oblique outside. Specifically, arrangement of the second link22along a line obliquely extending upward from the corner C1makes the second link22located away from both the two surfaces, i.e., the main surface71aof the base plate71and the top surface of the flat surface section72bof the horizontal plate72, defining the corner C1therebetween.

(iii) The first link21is inclined from the second link22inward, i.e., toward a side of approaching the horizontal plate72. Specifically, when a line passing through an intersection (the second tool axis X8) of the center line Y1of the first link21and the center line Y2of the second link22and perpendicularly intersecting the main surface71is defined as a reference line L (FIG.3), the center line Y1of the first link21is closer to the flat section72bof the horizontal plate72than (here, on a lower side of) the reference line L. In this arrangement, the second angle θ2between the first link21and the second link22, that is, the second angle θ2being an intersection angle between the center line Y1of the first link21and the center line Y2of the second link22on the lower side, reaches less than 180° (approximately 90° in the drawing).

The angle adjustment (control in step S2) is performed before the work tool3reaches the initial work division R. Specifically, the controller50adjusts each of the first angle θ1and the second angle θ2to a predetermined angle satisfying Conditions (i) to (iii) before the distal end tool section22aof the work tool3reaches the initial work division R (initial working position).

The angle adjustment under Conditions (i) to (iii) achieves entire compactification of the work tool3in combination with the adjustment of the position and orientation of the head16in step S1, i.e., the adjustment of causing the extension line Lx of the central axis X6of the head16to substantially meet the tip of the second link22. Specifically, the respective adjustments establish such a positional relation as to form a substantially triangle (seeFIG.3) defined among the extension line Lx of the central axis X6of the head16, the center line Y1of the first link21, and the center line Y2of the second link22. In other words, the center line Y1of the first link21and the center line Y2of the second link22intersect with the extension line Lx of the central axis X6of the head16at an angle of less than 90°, and the center line Y1of the first link21and the center line Y2of the second link22intersect with each other at an angle of less than 180°. The establishment of the relation makes the entire dimension of the work tool3relatively small in a direction parallel to the central axis X6of the head16and in a direction perpendicularly intersecting the central axis X6.

Here, the position and orientation of the head16having moved to the work division R are adjusted so that the extension line Lx of the central axis X6substantially meets the tip of the second link22(tip of the distal end tool section22a) in principle as described above. However, Conditions (i) to (iii) may be dissatisfied depending on a shape of the workpiece in a state of keeping the positional relation between the head16and the distal end tool section22a. In this case, the extension line Lx of the central axis X6of the head16is permitted, in step S1, to deviate from a desired position (where the extension line substantially meets the tip of the distal end tool section22a). That is to say, Conditions (i) to (iii) are prioritized over the positional relation between the head16and the distal end tool section22a. In difficulty of establishing the positional relation between the head16and the distal end tool section22awhere the tip of the distal end tool section22asubstantially meets the extension line Lx, the position and orientation of the head16are adjusted to allow the distal end tool section22ato approach the extension line Lx as close as possible within a range satisfying Conditions (i) to (iii). In other words, a posture of the second link22is adjusted so that at least the tip thereof is closer to the extension line Lx.

Next, the controller50determines whether the distal end tool section22areaches a start point of the application work (position where the application of the sealant S is started) in the initial work division R (step S3). In the embodiment, the application work of the sealant S in the work division R is continuously performed from one end to another end (from the left end to the right end in the drawings) on the corner C1in the work division R in the left-right direction as shown inFIG.9. The start point in this case corresponds to the one end on the corner C1in the work division R and represents a position where the work tool3denoted by a solid line applies the sealant S. On the other hand, another end on the corner C1, that is, a position where the work tool3denoted by a chain double-dashed line applies the sealant S represents a finish point where the application work is finished.

When the determination is made YES in step S3and the distal end tool section22ais confirmed to reach the start point of the application work, the controller50executes the application of the sealant S on the corner C1while moving the distal end tool section22aalong the corner C1from the start point (step S4). Specifically, the controller50executes the application of the sealant S on the corner C1by ejecting the sealant S from the distal end tool section22a(here, the nozzle22a1) at a constant rate and moving the distal end tool section22afrom the one end (start point) to another end (finish point) along the corner C1at a given speed. At this time, each of the first angle θ1and the second angle θ2of the work tool3is not changed and kept at the adjusted angle (predetermined angle) in step S2. In other words, the controller50executes the application of the sealant S within the same work division R by moving the distal end tool section22aalong the corner C1while keeping the first angle θ1and the second angle θ2of the work tool3.

Then, the controller50determines whether the distal end tool section22areaches the finish point of the application work, that is, another end on the corner C1where the application of the sealant S is finished (step S5).

When the determination is made YES in step S5and the distal end tool section22ais confirmed to reach the finish point, the controller50moves the work tool3to a subsequent work division R and executes, after the movement, application of the sealant S on the corner C1in the subsequent work division R in the same order of steps S3to S5(step S6). At this time, the position and orientation of the head16is set, in the same manner as in step S1, so that the extension line Lx of the central axis X6of the head16substantially meets the tip of the second link22(tip of the distal end tool section22a) of the work tool3(seeFIG.3).

A destination of the work tool3to be moved in step S6is set to another work division R closest to the finish point of the current work division R. For instance, when the sealant S is applied while the distal end tool section22ais moved from the left to the right in the current work division R as shown inFIG.9, the destination of the work tool3is set to a work division R adjacent to the right of the current work division R in principle. When the current work division R indicates a rightmost work division R in the structure70, another work division R adjacent to the current work division R at an upper or lower position thereof is selected as the work division at the destination.

When the work tool3is moved in the adjacent work division R in the above-described manner, the work tool3is moved at a shortest distance within a range of avoiding contact with structural elements (in particular, the vertical plate73and the protrusion74located in the adjacent work division R) existing in the vicinity of a movement route of the tool. The movement between the work divisions R is performed while the first angle θ1and the second angle θ2of the work tool3are kept. In other words, the angles θ1, θ2of the work tool3are kept unchanged until the application of the sealant S in all the work divisions R is completed. Needless to say, this does not intend to exclude exceptional change of each angle that is inevitable in a specific situation in terms of a shape and a structure of the structure70.

Subsequently, the controller50determines whether the application work of the sealant S in all the work divisions R in the structure70is completed (step7). When the determination is made NO, the application work of the sealant S is performed in a remaining work division R in the same manner. When the determination is made YES, the series of controls is finished there.

Although omitted in the description above, the work divisions R are partitioned from each other by the vertical plates73. Therefore, each of the start point and the finish point on the corner C1in each work division R comes under the corresponding vertical plate73. The distal end tool section22aof the work tool3is required to enter a gap existing under the vertical plate73, that is, enter a gap G (FIG.9) between a lower end of the vertical plate73and the flat section72bof the horizontal plate72, to apply the sealant S on each point. However, this operation is basically attainable only by slightly rotating the head16about the central axis X6thereof. Specifically, in the embodiment, the robot main body2takes such a posture that the extension line Lx of the central axis X6of the head16substantially meets the tip of the distal end tool section22ain the application work of the sealant S within each work division R (seeFIG.3). Hence, the head16may be slightly rotated to tilt the second link22in a state of the work tool3having moved very close to the vertical plate73as shown inFIG.9so that the distal end tool section22aenters the gap G. In other words, the controller50permits the distal end tool section22aof the work tool3to enter the gap G by slightly rotating the head16at the start or finish of the application of the sealant in each work division R. In this manner, the sealant S can be applied over a whole range of the corner C1without any void.

Other Work Examples

Heretofore, described in detail is the example where the work robot1applies the sealant S on the corner C1in the structure70, that is, on the corner C1where the main surface71aof the base plate71and the flat section72bof the horizontal plate72intersect with each other. However, the sealant S can be applied on other portion demanding a sealing property. For example, in the embodiment where the flange section72aof the horizontal plate72is fastened to the base plate71with the rivets, there is a demand for applying the sealant S over a whole periphery of the flange section72ato prevent water from entering a gap between the flange section72aand the base plate71. To meet the demand, the sealant S is applied to portions on the periphery of the flange section72a, that is, a lower edge, and left and right end edges of the flange section72aas well as the corner C1. Moreover, in a case where the vertical plate73is fastened to the base plate71with rivets, the sealant S is applied on peripheries of facing surfaces thereof for the fastening.

A target (workpiece) to be subjected to the application of the sealant S is not limited to the above-described structure70. For instance, a structure80shown inFIG.10may subjected to the application of the sealant S. The structure80shown in this drawing includes a base plate81which is flat, and a disc-shaped member82fastened to a main surface81aof the base plate81with rivets (not shown). In this case, the work robot1applies the sealant S on a corner C2where a circumferential surface82aof the disc-shaped member82and the main surface81aof the base plate81intersect with each other. The main surface81acorresponds to the “base surface” in the present invention, and the circumferential surface82acorresponds to the “intersection surface” in the present invention.

The corner C2endlessly extends along the circumferential surface82aof the disc-shaped member82. For the application of the sealant S on the corner C2extending in this manner, the controller50first adjusts each of the first angle θ1and the second angle θ2of the work tool3to an angle as shown inFIG.10, and then executes the application of the sealant S on the corner C2by moving the distal end tool section22aof the work tool3in a circle along the corner C2, as denoted by arrow B1. Each of the first angle θ1and the second angle θ2at this time is set to a predetermined angle to allow the distal end tool section22ato approach the corner C2from an oblique outside and allow the first link21to be inclined (here, inclined radially inward) from the second link22toward the circumferential surface82a. The adjustment of the first and second angles θ1, θ2is performed before movement to an initial working position on the corner C2, and the first and second angles θ1, θ2are kept unchanged in principle during the application of the sealant S on the corner C2.

The work robot1having applied the sealant S on the structure70(or80) in the above-described manner may further perform a work of smoothing the sealant S having been applied. For the smoothing work, the spatula22a2shown inFIG.5Bis adopted as the distal end tool section22aof the work tool3. The spatula22a2is moved along the shape (e.g., the corner C1or C2) of the application target of the sealant S in the same manner as the distal end tool section22a(nozzle22a1) adopted in the application of the sealant. Consequently, unevenness on a surface of the sealant S having been applied is removed to smooth the sealant S.

Operational Effects

As described above, in the embodiment, the work tool3including the first link21and the second link22is attached to the head16of the robot main body2that can three dimensionally move, and each of the first angle θ1between the head16and the first link21and the second angle θ2between the first link21and the second link22is changeable. This configuration has an advantage of efficient performance of the work of applying (or smoothing) the sealant on various kinds of workpieces having different shapes while avoiding contact with each workpiece.

Specifically, in the embodiment, the work tool3having two degrees of freedom for changing the first angle θ1and the second angle θ2is attached to the head16of the robot main body2. Therefore, adjustment of both the first angle θ1and the second angle θ2in conformity with the shape of the workpiece, such as the structure70,80, succeeds in ensuring a maximally long division where the work is continuously performable without contact between the work tool3and the workpiece and increasing the work efficiency. For instance, although partition into work divisions is indispensable for the work of applying or smoothing the sealant S on the corner C1in the structure70to avoid contact with the vertical plate73, the continuity of the work in each work division R is favorable. Specifically, even if an obstruction Z denoted by a chain double-dashed line inFIG.1exists, preliminary adjustment of each of the first angle θ1and the second angle θ2to an angle (each angle shown inFIG.1toFIG.3) at which contact with the obstruction Z is avoidable leads to achievement of continuous performance of the work in each work division R with the angles θ1, θ2being kept. In other words, it is possible to avoid a decrease in a division length for the continuous performance of the work attributed to the existence of the obstruction Z, and accordingly, the work efficiency can be increased as great as possible. In contrast, use of a tool which cannot change an angle, like a work tool130shown inFIG.11for example, inevitably limits a posture of each of the work tool130and a robot main body2. This may impede, for example, continuous performance of the work on the corner C1in the structure70to avoid the contact with the obstruction Z (FIG.1), resulting in a possible reduction in the work efficiency. The embodiment contrarily achieves efficient performance of the work while avoiding the aforementioned reduction.

Moreover, in the embodiment, the robot main body2is controlled in such a manner that each of the first angle θ1and the second angle θ2is adjusted to a predetermined angle satisfying the conditions including avoidance of the contact with the workpiece, such as the structure70,80, before the work tool3(the distal end tool section22athereof) moves to the initial working position of the workpiece, and that the distal end tool section22amoves along the shape of the workpiece (e.g., the shape of the corner C1, C2) while keeping the angels θ1, θ2after the movement to the initial working position. This configuration only requires the head16to move along the shape of the workpiece under the drive control of the robot main body2without the necessity of changing the first angle θ1and the second angle θ2after the work tool3reaches the initial working position, and therefore can efficiently perform the work while favorably ensuring positional accuracy of the distal end tool section22a.

In the embodiment, in the work on the corner in the structure70(80), e.g., on the corner C1(C2) defined between the main surface71a(81a) facing the head16and the intersection surface (the flat section72bor the circumferential surface82a), the first angle θ1and the second angle θ2are adjusted to allow the distal end tool section22ato approach the corner C1(C2) from the oblique outside and allow the first link21to be inclined from the second link22toward the intersection surface (72b,82a). This configuration permits the center of the head16to approach the corner C1, C2serving as a working portion in a directional view along the central axis X6of the head16, and can enhance the controllability in moving the distal end tool section22aalong the corner C1, C2. Furthermore, in the work on a working portion having an arc-shape like the corner C2(FIG.10) of the structure80, this configuration can decrease a movement distance of the head16to move the distal end tool section22aalong the corner C2and increase the work efficiency more effectively than a provisional configuration where the first link21is inclined (here, inclined radially outward) from the second link22in an opposite direction to the direction shown in the drawings.

In particular, the embodiment where the work is performed in the state where the extension line Lx of the central axis X6of the head16substantially meets the tip of the distal end tool section22acan facilitate the positioning of the head16with respect to the corner C1(C2) in, for example, moving the distal end tool section22aalong the corner C1(C2), and accordingly can enhance the positional accuracy at the movement of the head16and the work tool3. Specifically, in the directional view along the central axis X6of the head16, the positioning of the head16to allow the center of the head16to substantially meet the corner C1(C2) leads to the facilitated positioning of the head16with respect to the corner C1(C2). In addition, moving the head16in such a manner as to maintain the positional relation leads to achievement of moving the distal end tool section22aexactly along the corner C1(C2) and enhancing the positional accuracy.

Modifications

Although used is the work tool3having the two degrees of freedom for changing the first angle θ1being an angle between the center line Y1of the first link21and the central axis X6of the head16and the second angle θ2between the center line Y2of the second link22and the center line Y1of the first link21in the embodiment, the work tool does not necessarily have two degrees of freedom and may have one degree of freedom. Specifically, only the first angle θ1may be changeable and the second angle θ2may be unchangeable by fixing the first link21and the second link22to each other in a state of intersecting with each other at a predetermined angle. However, in this case, on the condition that at least the first angle θ1falls within a specific angle range, the first link21and the second link22may be formed in such a manner that the center line Y1of the first link21and the center line Y2of the second link22intersect with the extension line Lx of the central axis X6of the head16, and that the tip of the second link22is closer to the extension line Lx. In this manner, the work tool3becomes entirely compact, and thus can avoid the contact with the workpiece owing to the adjustment of an intersection angle (first angle θ1) between the central axis of the head16and the first link21. Furthermore, the tip of the second link22substantially meets or approaches the extension line Lx, resulting in achievement of facilitated positioning of the head16to a working portion and enhancement of the positional accuracy at the time of moving the head16and the work tool3.

Although described is the example where the work robot1is used to perform the work of applying the sealant S on the workpiece or smoothing the sealant S having been applied in the embodiment, the usage of the multi-axis robot or the work tool according to the present invention is not limited thereto. The multi-axis robot or the work tool according to the present invention is adoptable for various works each demanding movement along a shape of a workpiece. For instance, the multi-axis robot or the work tool according to the present invention is favorably adoptable for a work of painting a workpiece and a burr removal work of removing burrs occurring in a certain portion of the workpiece.

Although described is the example where the work tool3is attached to the robot main body2of the six-axis type, a robot main body to which the work tool according to the present invention is attachable is not limited to the six-axis type, but may be a robot main body of another type as long as the robot main body can three-dimensionally move the head. For instance, the work tool according to the present invention may be attached to an articulated robot having fewer than six joints or more than six joints, or to a cartesian robot.

CONCLUSION

The embodiment covers each invention including the configuration to be described below.

A first invention relates to a multi-axis robot that performs a predetermined work while moving along a shape of a workpiece, the multi-axis robot including: a robot main body including a head and a movement mechanism that three-dimensionally moves the head; and a work tool attached to the head. The work tool includes: a first link pivotally supported on the head; a second link pivotally supported on a distal end of the first link; a first change mechanism that changes a first angle being an angle of the first link to a central axis of the head; and a second change mechanism that changes a second angle being an angle of the second link to the first link.

According to the first invention, the work tool having two degrees of freedom for changing the first angle and the second angle is attached to the head of the robot main body. Therefore, adjustment of both the first angle and the second angle in conformity with the shape of the workpiece succeeds in ensuring a maximally long division where the work is continuously performable without contact between the work tool and the workpiece and increasing the work efficiency for various kinds of workpieces.

Preferably, the multi-axis robot further includes a controller that controls the movement mechanism, the first change mechanism, and the second change mechanism. The controller executes: a first control of moving a tip of the second link to an initial working position of the workpiece; a second control of adjusting each of the first angle and the second angle to a predetermined angle before the tip of the second link reaches the initial working position; and a third control of moving the tip of the second link from the initial working position along the shape of the workpiece while keeping the first angle and second angle.

This configuration only requires the head to move along the shape of the workpiece under the drive control of the robot main body without the necessity of changing the first angle and the second angle after the work tool reaches the initial working position, and therefore can efficiently perform the work while favorably ensuring the positional accuracy of the tip of the second link.

The workpiece may include a corner defined between a base surface and an intersection surface intersecting with the base surface. In this case, the first angle and the second angle having been adjusted under the second control preferably allows the tip of the second link to approach the corner from an oblique outside and allow the first link to be inclined from the second link toward the intersection surface.

This configuration permits the center of the head to approach the corner serving as a working portion in a directional view along the central axis of the head, and can enhance the controllability in moving the tip of the second link along the corner. Furthermore, in the work on a corner having an arc-shape, this configuration can decrease a movement distance of the head to move the tip of the second link along the corner, and increase the work efficiency.

Preferably, the controller executes the third control in a state where an extension line of the central axis of the head meets the tip of the second link.

This configuration can facilitate positioning of the head with respect to the working portion, such as the corner, and enhance the positional accuracy at the time of moving the head and the work tool. Specifically, in the directional view along the central axis of the head, the positioning of the head to allow the center of the head to substantially meet the working portion leads to the facilitated positioning of the head with respect to the working portion. In addition, moving the head in such a manner as to maintain the positional relation leads to achievement of moving the tip of the second link exactly along the working portion and enhancing the positional accuracy.

The second link preferably includes a nozzle at a distal end thereof to apply sealant on the workpiece. Alternatively, the second link may include a spatula at the distal end thereof to smooth the sealant applied on the workpiece.

This configuration attains efficient performance of each of the work of applying the sealant on the workpiece and the work of smoothing the sealant having been applied.

A second invention relates to a work tool to be attached to a head of a multi-axis robot that moves along a shape of a workpiece, the work tool including: a first link pivotally supported on the head; a second link pivotally supported on a distal end of the first link; a first change mechanism that changes a first angle being an angle of the first link to a central axis of the head; and a second change mechanism that changes a second angle being an angle of the second link to the first link.

The work tool according to the second invention exerts the same effects as those of the above-described first invention when adopted in a multi-axis robot.

A third invention relates to a method for controlling the multi-axis robot, the method including: a first step of moving a tip of the second link to an initial working position of the workpiece; a second step of adjusting each of the first angle and the second angle to a predetermined angle before the tip of the second link reaches the initial working position; and a third step of moving the tip of the second link from the initial working position along the shape of the workpiece while keeping the first angle and second angle.

The third invention achieves efficient performance of the work while favorably ensuring the positional accuracy of the tip of the second link.

Preferably, the workpiece includes a corner defined between a base surface and an intersection surface intersecting with the base surface, and the first angle and the second angle are adjusted to allow the tip of the second link to approach the corner from an oblique outside and allow the first link to be inclined from the second link toward the intersection surface in the second step.

In this manner, the controllability in moving the tip of the second link along the corner can be enhanced.

The tip of the second link is preferably moved in a state where an extension line of the central axis of the head substantially meets the tip of the second link in the third step.

Accordingly, the positional accuracy at the time of moving the head and the work tool can be enhanced.

A fourth invention relates to a multi-axis robot that performs a predetermined work while moving along a shape of a workpiece, the multi-axis robot including: a robot main body including a head and a movement mechanism that three-dimensionally moves the head; and a work tool attached to the head. The work tool includes: a first link pivotally supported on the head; a second link extending from a distal end of the first link in a direction different from a central axis of the first link; and a change mechanism that changes a first angle being an angle of the central axis of the first link to a central axis of the head. The change mechanism adjusts the first angle in such a manner that a center line of the first link and a center line of the second link intersect with an extension line of the central axis of the head, and that a tip of the second link is closer to the extension line.

According to the fourth invention, established is such a positional relation as to form a substantially triangle shape among the extension line of the central axis of the head, the center line of the first link, and the center line of the second link. In this manner, the work tool becomes entirely compact, and thus can easily avoid the contact with the workpiece owing to the adjustment of an intersection angle between the central axis of the head and the first link. Furthermore, the tip of the second link substantially meets or approaches the extension line, resulting in achievement of facilitated positioning of the head to a working portion and enhancement of the positional accuracy at the time of moving the head and the work tool.

A fifth invention relates to a work tool to be attached to a head of a multi-axis robot that moves along a shape of a workpiece, the work tool including: a first link pivotally supported on the head; a second link extending from a distal end of the first link in a direction different from a central axis of the first link; and a change mechanism that changes a first angle being an angle of the central axis of the first link to a central axis of the head. The change mechanism adjusts the first angle in such a manner that a center line of the first link and a center line of the second link intersect with an extension line of the central axis of the head, and that a tip of the second link is closer to the extension line.

The work tool according to the fifth invention exerts the same effects as those of the above-described first invention when adopted in a multi-axis robot.