JP5451219B2 - Parts assembly method - Google Patents

Description

  The present invention relates to a component assembling method for assembling components using a robot.

  In assembly work using a robot, a process of instructing the robot which part to be assembled is to be moved from which position to which position and in which precise trajectory is required. Such a precise trajectory is generated by creating a teaching point group including a starting point and an ending point for a linear trajectory and further including an intermediate point for a bending trajectory, and interpolating between the teaching points.

  For example, Patent Document 1 discloses a method of obtaining a precise teaching point from a relatively rough teaching point when a linear workpiece is linearly inserted into a hole. This is manually taught as a relatively rough point at a level that does not contact the side wall of the inlet of the insertion hole in advance and that can reliably capture the insertion hole as a starting point of assembly. After that, it goes straight in the insertion direction, and the point where the detection value Sz in the Z direction of the force sensor exceeds the threshold value Tz, that is, the point where it hits is set as the Z coordinate of the insertion end point.

  Next, it is finely moved individually in the ± X direction and the ± Y direction and brought into contact with the side wall of the insertion hole, so that the detected value Sx in the X direction and the detected value Sy in the Y direction of the force sensor are below the threshold value. Stop. This point is a point where contact with the side wall of the insertion hole does not become excessive, and by using these as the X coordinate and Y coordinate of the insertion end point, automatic teaching is automatically performed in comparison with the rough teaching point. You get points. According to this method, it is possible to correct the difference between the drawing error due to off-line teaching and the error of the robot body.

  Patent Document 2 discloses a method of inserting a pin straight into a hole without being affected by variations in teaching points. This is a method in which a pin is brought into contact with the periphery of the hole and a hole is searched for from a change in force applied to the pin, and after the start of insertion, the insertion is continued in a direction in which the moment decreases, and a reaction force is received from the insertion direction.

  As another idea, an attempt is made to decompose the contact state of the fitting into a mathematical local model, extract the teaching information of the time series data, and realize the transition of the contact as a collection of local models (Patent Document 3). reference).

JP 63-162180 A JP-A-7-314262 JP-A-9-198121

  The above prior art has the following unsolved problems. The first problem is that it is difficult to assemble with a robot because the assembling trajectory covers a wide range such as bending and arcing in addition to a straight line. For example, the method disclosed in Patent Document 1 is limited to specific conditions for straight line insertion. That is, after the abutting of the linear movement of the reference axis (Z axis), control is performed so that the contact of the other axis (XY axis) is minimized. For this reason, in the case of a bent part or an arc-shaped part, the assembly cannot be completed by interfering with the insertion object in the middle, and the applications that can adopt this method are limited.

  The second problem is that there are scenes where an operator who starts up the apparatus needs special skills and familiarity with teaching. For example, in the method disclosed in Patent Document 3, a trajectory is generated using a mathematical model, so that an operator needs skill. Therefore, this method may not be adopted for consumer products such as digital cameras whose product cycle is about six months at the shortest because human resources and time are required for changeover.

  Further, as an incidental problem, there is a case where it is not possible to cope with a change in the absolute coordinates of the teaching point. According to the experiment of the present inventor, an absolute coordinate variation of 200 μm was measured 30 minutes after the operation at the tip of a 7-axis vertical articulated robot having an arm length of 600 mm. However, in this case, it cannot be introduced as it is to precision assembly requiring accuracy of less than 200 μm. As a countermeasure, for example, as disclosed in Patent Document 2, there is a method of searching the state of the force sensor at the time of assembly without giving importance to absolute coordinates. However, since a long tact is required for each assembly, this method is not suitable when mass productivity is required.

  FIG. 12 explains the necessary accuracy with respect to the teaching point. As shown in FIG. 12A, a rectangular column 101 having a width W, a height H, and a length D is gripped by a robot hand, and a width W + Δw and a height H + Δh. Assume that an assembling process of inserting into an insertion object 102 having a square hole of depth Ze-Zi.

  Here, for easy understanding, the entrance of the square hole exists on the XY plane, the insertion direction and the Z-axis direction are the same, and the insertion position and posture of the prism 101 in the Y and Z axial directions at the time of insertion The error is zero. Accordingly, the success rate of the insertion start in this case is roughly governed by the error in the X-axis direction between the insertion start point Pi and the end point Pe of the prism 101.

  As shown in FIG. 12 (b), if the vertical axis is the success rate of insertion and assembly, and the horizontal axis is the X-axis coordinate, the probability is almost 100% in the range of the accuracy Δw in the X-axis direction with respect to the center value Xo. The assembly succeeds. However, if this is exceeded, the success rate drops sharply, and if it exceeds a certain point, insertion becomes impossible and contact interference (collision) occurs at every insertion. Alternatively, the interference force becomes excessive during insertion, and scratches and overload of the drive system occur. Therefore, precise teaching work is required for the start point Pi and the end point Pe. In this case, Δw may be required to be around 20 μm when taking small parts constituting consumer products such as home appliances as an example.

  The present invention provides a part assembling method capable of efficiently generating a wide variety of precise trajectories by straight lines, bending, arcs, etc. in assembly using a robot and automatically responding to environmental fluctuations and machine differences. It is for the purpose.

The component assembling method of the present invention assembles a first component grasped by a robot hand having a force sensor for detecting at least moment force and pushing force into a second component based on an image photographed by a coordinate measuring machine . A part assembly method for attaching, wherein the trajectory range from the start point to the end point of the assembly is limited based on images of the first part and the second part photographed by the coordinate measuring machine . A first step of setting a divergent track limiting cylinder with respect to the moving direction of one component, and driving the robot hand, the first component moves in a three-axis linear direction from a reference point in the divergent track limiting cylinder Then, the teaching point at which the detection value of the force sensor is minimum due to the first part contacting the second part is searched for by turning in a turning and turning direction, and the first part is set at the teaching point. And a third step of moving the first part to the end point of the assembly by repeating the second step with the teaching point as a reference point. To do.

  The self-study of the teaching points of the assembly route by the apparatus is possible, and the labor of teaching by the operator can be reduced. The teaching method does not necessarily require specialized knowledge because it requires only a combination of setting of the approximate trajectory, shooting of the workpiece by the camera, or simple coordinate designation.

  Furthermore, the assembly path can be automatically corrected even when the absolute coordinates of the teaching point need to be changed due to changes over time or various machine differences. For this reason, expansion of the range of application to precision assembly of articulated robots and improvement of robustness can be expected. In addition, the on-site work at the time of on-site introduction after offline teaching is almost unnecessary.

It is a perspective view which shows the vertical articulated robot which concerns on one Embodiment. It is a figure explaining the component assembly method by Example 1. FIG. It is a figure explaining the track | orbit production | generation method by Example 1. FIG. It is a figure explaining the method of recognizing the advancing direction of an assembly by the image processing using a pointing stick, and the generated orbit It is a figure which shows the example of a shape of a track | orbit limit cylinder. It is a figure explaining the fine movement direction for searching an orbit. It is a flowchart which shows the main routine of component assembly. It is a flowchart explaining the subroutine of the 1st assembly | attachment accompanying a track generation. It is a flowchart which shows the subroutine of the assembly after the 2nd including the fine adjustment of a track | orbit. It is a figure explaining the components assembly method by Example 2. FIG. It is a figure explaining the track | orbit production | generation method by Example 2. FIG. It is a figure explaining a prior art example.

  Using the vertical articulated robot shown in FIG. 1, the trajectory is automatically generated as shown in FIGS. 2 to 9, and the L-shaped first part 1 is assembled to the second part 2. Similarly, as shown in FIG. 10, the first part 3 curved in an arc shape can be inserted into the second part 4.

  The robot hand 5 that holds the component 1 is attached to the tip of an arm 8 on which a stereo camera (camera) 7 is mounted via a force sensor 6. The component 2 is fixed and the arm 8 has seven axes, but the five axes other than the pivot axis 9 and the bending axis 10 are omitted and not shown.

  The image processing unit 11 and the robot controller 12 serving as the control unit control the seven axes of the vertical articulated robot using information from the force sensor 6 and the stereo camera 7.

  The stereo camera 7 is a part of a three-dimensional stereo system that acquires three-dimensional coordinates by triangulation using a parallax at an arbitrary specific point by the left and right cameras. Here, the stereo method using the left and right binocular cameras has been described as a three-dimensional measurement method, but other methods such as the light cutting method using laser projection and the moire method using contour projection can be substituted as well as the trinocular stereo method. Is possible.

  In order to make the explanation easy to understand, it is assumed that the robot coordinates (X, Y, Z, Xθ, Yθ, Zθ) of the six axes of the arm 8 are equal to the assembly coordinates (world coordinates). In the assembly coordinates here, the long side of the work platform on which the robot is installed is defined as the X-axis direction, and the short side is defined as the Y-axis direction. Xθ, Yθ, and Zθ mean the directions of rotation about the X, Y, and Z axes.

  The robot coordinates (X, Y, Z, Xθ, Yθ, Zθ) described above and the camera coordinates (Xc, Yc, Zc, Xcθ, Ycθ, Zcθ) that are the three-dimensional imaging space of the stereo camera 7 mounted on the arm 8. It is assumed that the robot controller 12 has grasped the relative position to). Therefore, the description relating to the relative coordinate calibration of the fixed robot coordinates and the camera coordinates moving with the arm 8 is omitted, and the coordinates unless otherwise specified are the robot coordinates. From the camera coordinates of the part 1 and the part 2 measured by the stereo camera 7, the assembly coordinates of the part 1 with respect to the part 2 can be obtained. For ease of explanation, it is assumed that the camera coordinate Zc and the center line of the arm 8 are coaxial.

  In the image processing unit 11, it is possible to acquire three-dimensional information of camera coordinates for arbitrary designated points of the parts 1 and 2. The arbitrary designated points are, for example, the points T11, T12, and T13 in FIG. 2A for the component 1, and the points T21, T22, and T23 for the component 2. From the three-dimensional coordinates of the parts 1 and 2, the relative posture between the parts can be acquired.

  Although the stereo camera 7 is mounted on the arm 8 to be movable, it may be fixed to a robot base (not shown). When mounted on a robot arm, the movable type tends to have a relatively narrow field of view, a shallow depth of field, high accuracy, and a large amount of calculation for calibration between camera coordinates and robot coordinates. Also, when fixed to the mounting base, there is a tendency to have a relatively wide field of view, deep depth of field, high accuracy, and easy alignment with robot coordinates. Is appropriately selected according to the application.

  For example, a strain gauge type sensor can be used as the force sensor 6, but is not particularly limited. A total of six axes of force can be detected by the linearly moving force and moment force of each axis of the camera coordinates (Xc, Yc, Zc). The detected force can be replaced with robot coordinates as described above. However, since the force sensor 6 and the force point of the component 1 are generally at a suitable distance (for example, 50 mm), the moment force and the pushing force Zc are dominant in practical use, and the rectilinear force in the Xc and Yc axis directions is relatively small. Since it is a value, it may be ignored. Instead of the vertical articulated robot, a robot having another structure such as an orthogonal coordinate type, a horizontal articulated type, or a cylindrical coordinate type may be used.

  The L-shaped part 1 is assembled to the part 2 using the robot shown in FIG. FIG. 2 shows the assembly process, (a) to (c) are perspective views, (d) to (h) are cross-sectional views, and (i) is a continuous view in which (d) to (h) are overwritten. It is. 2 (a) and 2 (d) show the starting point of assembly, (b) and (e) to (g) show intermediate points of the assembly, and (c) and (h) show the end point of the assembly. FIG. 3 shows the same assembly start point as in FIGS. 2 (a) and 2 (d).

  There are three main items of pre-assembly preparation (first step) as initial settings.

  In the first preparation, as shown in FIG. 2 (a), the assembly track starting from the vicinity of the point B which is the center of the insertion surface of the part 2 is an L-shape from the hole cross-sectional shape of the part 2 (d). I understand that Therefore, as shown in FIG. 3, a track limiting cylinder for limiting the track range of a sufficiently large size that can include the track 16 of the point A of the component 1 (see FIG. 1) is a cylinder arranged in an L shape. 21 and body 22 are set. A method for setting the barrels 21 and 22 will be described later.

  In the second preparation, in order for the component 1 held by the distant hand 5 (not shown) to obtain the traveling direction with reference to FIGS. Coordinate I is registered. The image I is obtained by, for example, photographing the insertion slot including T21 to T23 in FIG.

  The coordinate I indicates, for example, a point B in the vicinity of the insertion opening of the component 2 with the pointing rod 20 shown in FIG. 4A and is photographed with the stereo camera 7, and the tip shape of the pointing rod 20 includes pattern matching and area characteristics. Camera coordinates are obtained by an image processing method, and converted into robot coordinates. Alternatively, the center of the insertion slot is simply calculated by image processing without using the pointer 20. The coordinates I may be directly input from the teaching unit 13 shown in FIG.

  Further, the image W in the state shown in FIGS. 2B and 2E, which is an intermediate point of assembly, the coordinates W, and the like may be stored to increase information on the determination element.

  As a third preparation, the relative positions of the parts 1 and 2 including the robot hand 5 are included in each of the images in FIG. 2A in the actual assembly start state and FIG. 2C in the assembly end state. Take a picture with the stereo camera 7. The coordinates of the part 1 are acquired at the start point and the end point of the assembly and stored in the control unit, and are set as the start point image S, the end point image E, the start point coordinate S, and the end point coordinate E, respectively. By the way, the speed limit and the generated torque limit are controlled to control the arm 8 of the robot to prevent mechanical damage due to unnecessary interference during trajectory search. The pre-preparation for assembly (first step) is thus completed.

  Aiming at the state of FIGS. 2A and 2D, that is, the starting point 31 of the assembly shown in FIG. The image I of the insertion opening is searched with the stereo camera 7 or the arm 8 is moved in the direction of the coordinate I.

  Whether the current image of the stereo camera 7 is in the vicinity of the pre-registered image S, for example, within ± 1 mm, or whether the current coordinate is in the vicinity of the pre-registered coordinate S, for example, within ± 1 mm, is determined for reaching the start point 31. Implement either.

  When contact interference is detected by the force sensor 6 without reaching the starting point 31 and the point is in the vicinity of the image W and the coordinate W, stop at that point. Then, this is treated as the starting point 31, and the process proceeds to the next step in the same manner as when the original starting point 31 is reached.

  As shown in FIG. 4B, the arbitrary reference point 17 is advanced from the starting point 31 while searching for the direction in which the detection value of the force sensor 6 is minimized within the trajectory limiting cylinder (second step). In this search (search), a fine movement in the three-axis straight direction, a turning around each axis, and a fine movement in the turning direction are performed and returned once, and among them, the detection value of the force sensor 6 is the smallest. Make a slight movement (movement) in a certain direction to confirm the progress. This is repeated until the end point 33 is reached (third step). In addition, when the comparison result of a detected value is equivalent, it progresses to the same direction as the last movement.

  Each time fine movement progress is determined, the position coordinates of the stop point (teaching point) of the component 1 and the detection value of the force sensor 6 are stored and converted into table data to create a precise trajectory (fourth step). Such a movable space for searching is limited to a trajectory range by the cylinder 21 and the cylinder 22.

  When the situation where the detection value of the force sensor 6 is excessively small continues, it is determined that the assembly is deviated and is stopped abnormally, and the width of fine movement or the weighting coefficient of the passive force calculation formula of the force sensor 6 to be described later Review and restart assembly.

  The determination of arrival at the end point 33 in FIG. 3 is performed by either comparing the current image of the stereo camera 7 with the image E of the assembly end point, comparing the current coordinate with the coordinate E of the assembly end point, or Implement in both to complete the table data. Then, a precise trajectory is obtained by interpolating between the coordinate points of the table data. The above is the direction of assembly, that is, the trajectory generation in the forward direction, but the direction of disassembly from the end of the assembly, that is, the generation of the trajectory in the backward direction is also possible, and the reverse procedure is performed. The method of searching for the trajectory by fine movement is the same as when moving forward. In this case, the image E2 in the state of FIG. 2B, which is the end point of decomposition, and the coordinate E2 are used for comparison determination of the end point of decomposition.

  Although the precise orbit is established by the first assembly described above, the absolute position of the arm 8 may change over time due to a thermal change, which may be an obstacle to precise assembly. Therefore, in the second and subsequent (next and subsequent) assembly, the current coordinates being assembled and the detection value of the force sensor 6 are compared with the table data stored in the previous assembly. If there is a difference between the detected values of the force sensor 6 at the coordinates and the table data, finely move the coordinates so that there is no difference in the forces at the coordinates, rewrite the coordinates of the table data, and perform the interpolation calculation again. carry out. In this way, the precise trajectory is corrected as needed based on the detection value of the force sensor 6.

  From here, the part assembling method according to the present embodiment will be described in the order of steps in a manner that supplements the above description. FIG. 7 is a flowchart showing a main routine starting from F1000. After initial setting, in the first assembly, the assembly destination is searched like a human hand to generate the coordinate data of the assembly trajectory (precision trajectory), and at the same time, the detection value of the force sensor 6 corresponding to the coordinate group And create a table. The second and subsequent assembling is performed along the generated trajectory, and the trajectory is corrected when the detection value of the force sensor 6 at the time of assembling the coordinate fluctuates based on the above table.

  Each step (process) will be described below in order. First, in F1010, the following seven items need to be registered in the image processing unit 11 and the robot controller 12 as various initial settings.

  (1) The part 1 held by the hand 5 located at a distant position (not shown) within a range in which the image I or the coordinates I: B point for assembling the traveling direction can be seen is shown in FIGS. The stereo camera 7 captures an image I of the assembly hole including the point B as an index for determining the direction toward the position). And it goes to there as a direction of assembling by a search method such as pattern matching and area feature. Or the coordinate I of B point is set and it goes to there.

  (2) Image S for determining assembling start: used for determining reaching the assembling start position 31. For this purpose, the state shown in FIGS. 2A and 2D is captured as an image S by the stereo camera 7 and stored. Further, the image W in FIG. 2B, which is an intermediate point of assembly, the coordinates W, and the like may be stored to increase the number of determination elements.

  (3) Image E or coordinates E at the end of assembly for determining the end of assembly: The image E at the end of assembly in FIG. Alternatively, the coordinate E is taught in the state shown in FIGS. 2C and 2H as a precise point at the end of assembly. The image E and the coordinates E are used for determining whether to reach the assembly end portion.

  (4) Trajectory creation direction D: When creating a trajectory, it is determined whether to advance in the direction of assembly (forward) or advance in the direction of disassembly from the end of assembly (reverse). In the case of disassembly, the above-described image W and coordinates W are useful for determining the contact / leaving point.

  (5) Setting of trajectory limiting cylinder for limiting trajectory search range and traveling direction: A cylinder for limiting the trajectory searching range for assembling part 1 to part 2 is registered. In the actual assembly track, the point A of the component 1 shown in FIG. 1 passes through the track 16 of FIG. However, at the time before assembly, the imagination is limited to the L-shaped trajectory from the center line 14 in FIG. 3 to the center line 15 through the intersection with the center line 15. Therefore, two orbital limiting cylinders including the point A are virtually set as a cylinder 21 and a cylinder 22 with this L-shape as an axis.

  Here is a description of the trunk. In order to advance the search for a precise trajectory by blindness, if the position of the search range is not limited, there is a possibility that the trajectory may be deviated and head in the direction of travel. Therefore, the accuracy of trajectory acquisition is increased by limiting the search range.

  As shown in FIGS. 5A to 5D, various shapes such as a megaphone, a cylinder, a cone, and a pyramid can be assumed as the shape of the trunk. In general, the diameter of the trunk can be reduced as the accuracy of the set coordinates increases in a trajectory close to a straight line. The diameter reduction means, for example, reducing the diameters of the start point plane 30a and the end point plane 30b in the megaphone form 30 shown in FIG. By reducing the diameter, the trajectory search space is narrowed, so the search speed can be increased.

  In FIG. 3, in assembling the part 1, it can be easily predicted that the trajectory on the way includes a bent portion or a non-linear portion, but the accuracy is difficult to define, and a search range for the portion is desired. Accordingly, the megaphone form 30 shown in FIG. In FIG. 3, as described above, the cylinder 21 and the cylinder 22 having the L-shape as an axis are set. The lengths DL1 and DL2, the bottom surface radii DD1b and DD2b, the top surface radii DD1t and DD2t of each of the cylinders are estimated using the dimensions W1 to W5 of the component 2. The dimensional accuracy of the cylinder setting is not particularly required, but if the cylinder dimension is too small, the target trajectory cannot be searched, and if it is too large, tact will be required or discrete, so the maximum value among W1 to W5 may not be exceeded. desirable.

  That is, at least the following settings are required. Coarse dimensions constituting the cylinders 21 and 22, coarse coordinates of points 31 and 32 centered on the bottom surfaces of the cylinders 21 and 22, an image or precise coordinates of the assembly end point 33. The term “coarse” as used herein may be a value that is about 10 times or more as large as the assembly accuracy because of the characteristic of “searching” for the assembly track. Each cylinder 21, 22 suggests the direction of assembly along with the scope of the search. The outline of the direction is an assembly completion direction (traveling direction) that is divided into two by the normal line of the current position of the orbit every time assembly progresses, as shown by the two-dot chain line surface in FIG. Of course, when the direction D of trajectory creation is disassembly, it is the opposite direction.

  (6) Robot-driven interlock: In order to prevent mechanical damage due to interference when the robot hand 5 is finely moved in multiple directions in order to search for a trajectory, the upper limit is set on the operating speed and generated torque of the arm 8 as an interlock. Set.

  (7) Various constants: ΔSs, θs1, θs2, ΔSr, θr, ΔSf, θf, which are numerical values such as the width of fine movement, which will be described later, and numerical constants mainly including Kv, Ki, which are weighting coefficients for force comparison. Configuration. In addition, counter zero memory zero clear will be implemented.

  The above are the seven default items.

  Next, an outline of F2000 in FIG. 7 will be described. This is the first time that the part 1 is assembled to the part 2, and the trajectory is automatically generated. Here, the main part of trajectory generation will be described. To the end point of assembly, multiple points of stop points (teaching points) that moved slightly in the direction in which the detection value (passive force) of the force sensor 6 is the smallest in small steps like a groping are tabulated, A trajectory is generated by interpolation calculation. Further, the passive force corresponding to the extracted teaching point is also tabulated. A track can also be generated in the disassembling direction from the state in which the part 1 has been assembled to the part 2, but in the flow diagram, the “assembled” direction is used for convenience of explanation. Details of F2000 are shown in FIG. 8 and will be described later.

  Next, in F1020 in FIG. 7, it is determined whether or not an abnormality has occurred during assembly track generation. When an abnormality is detected, the process returns by resetting the parameters in F1030. In resetting the parameters of F1030, ΔSs, θs1, θs2, ΔSr, θr, ΔSf, and θf, which are set in F1010, and Kv and Ki that are weighting coefficients for force comparison are adjusted. . Basically, the search movement amount is subdivided, and the weighting balance of calculation coefficients is changed.

  Next, since the generation of the trajectory is completed at the time of F1040 in FIG. 7, the interlock of the robot performed in F1010 is released here.

  Next, F3000 in FIG. 7 is the second and subsequent assembly steps performed following the assembly track automatically generated in F2000. In the process of assembly, when the current position corresponds to the table coordinates created by F2000, the detected value (passive force) of the current force sensor 6 is compared with the table passive force created by F2000. As a result, if a difference occurs, the coordinate is stopped at that coordinate, and the table coordinate is replaced with the current position by fine movement so that the difference in passive force disappears. An abnormality occurs when the passive force is too low or too high. Details of F3000 have been described in detail with reference to FIG. 9, and will be described later.

  Next, in F1050 of FIG. 7, the process is terminated when there is an abnormality in F3000. In F1060, the loop is repeated until the number of assembling of the component 1 reaches a value desired by the user. The main routine ends at F1070.

  This is the end of the description of FIG.

  FIG. 8 is a flowchart for explaining F2000. This flow is a method for automatically generating a precise trajectory based on the table data described above. In F2010, the counter of the coordinate and passive force data table described later is reset to zero. In F2020, as a method of generating a trajectory, there are two types of methods: a method of assembling the part 1 to the part 2 (forward) and a method of disassembling the part 1 from the state assembled to the part 2 (retreat). The user chooses any method. First, the case of forward movement will be described.

  Next, in F2025, aiming at the starting point 31 of the assembly shown in FIG. Search with the camera 7 or move the arm 8 in the direction of the coordinate I.

  Next, in F2030, the current position is stored as coordinates Pn (where n = 0) of the starting point of the trajectory. In F2040, it goes straight in the direction of the assembly inlet, and in F2050, it stops once it comes into contact.

  The next F2060 is the main part of trajectory generation. Using the current coordinates as a reference point, the actuator moves slightly in various directions (six axis directions) and returns to the reference point. Among them, the fine movement is made again in the direction where the detection value of the force sensor 6 is the smallest, and the coordinates of the stop position are acquired as the teaching points, and the arrival of the final point, which is the completion of the acquisition of the coordinates Pn, is determined. The various directions referred to here are the three types shown in FIGS. 6A, 6B, and 6C. That is, the reference point 17 (Xp1, Yp1, Zp1, Xt1, Yt1, Zt1), which is the current coordinates during the trajectory, is combined with fine movements of straight advancement, turning, and turning. As a result, all directions and postures toward the traveling direction surface side are created, and the traveling direction with the smallest assembly and disassembly force is searched. The search of the traveling direction by this fine movement is referred to as “search” here.

  6A, the amount of movement of magnitude ΔSs is swung by θs1 in the turning direction and θs2 in the turning direction, and the amount of fine movement ΔP is changed to movement command vectors ΔVs1, 2, 3,.・ ・ Give as N and shift.

  6 (b), the amount of movement of magnitude ΔSr is swung left and right by θr in the turning direction, and the amount of fine movement ΔP in the direction covering the turning circle is moved to movement command vectors ΔVr1, 2, 3,. Give it as N and shift.

  6 (c), the movement amount of magnitude ΔSf is swung in the turning direction by θf, and the amount of movement ΔP is changed to a movement command vector ΔVf1, 2, 3,. , Give as N and shift. The above-mentioned straight movement, turning, and rolling, and individual tremors are performed once each with the body that restricts the trajectory as the upper limit of the movement range. The determination of the completion of the fine movement is made based on the fact that the deviation pulse between the command position and the current position is almost zero, and the detection value of the force sensor 6 is not excessive as in a collision.

  After the fine movement is completed, the coordinates of the point and the detection value of the force sensor 6 are stored, and then the coordinates return to the coordinates before the fine movement. Thereafter, the detected value of the force sensor 6 is compared between the straight direction, the turning direction, and the turning direction, and the teaching point in the fine movement direction that becomes the minimum is finely moved again as the final movement destination, and the coordinate Pn of the teaching point and the force sensor 6 The passive force Qn that is the detected value is stored and tabulated.

Here, the comparison of the detection values of the force sensor 6 is performed by setting the weighting coefficient Kv such as the combined vector Vsa of the XYZ linear force and the weighting coefficient Ki such as the moment force Vsm with respect to the items to be regarded as important. The magnitudes of the passive forces Vs, Vr, and Vf that depend are compared.
Passive force for linear fine movement Vs = Kv x Vsa + Ki x Vsm
Passive force of fine turning tremor Vr = Kv × Vra + Ki × Vrm
Passive force of swaying tremor Vf = Kv × Vfa + Ki × Vfm

  At this time, when the state where these numerical values are too small continues, there is a possibility that the assembly has moved in a direction away from the assembly, so the direction of fine movement may be changed, or it may be stopped abnormally.

  Next, in F2070, it is stopped as an error when F2060 is abnormal. Next, in F2080, the determination of the arrival of the final point of the trajectory is performed by comparing the current image of the stereo camera 7 with the pre-registered image E of the assembly end part or the current coordinate of the arm 8 and the pre-registered coordinate E. In F2110, the assembling trajectory Cvg is completed by interpolating between the points from the table data of the coordinates Pn.

  Next, the procedure for creating the assembly track Cvg in the backward direction described in the description of F2020 will be described only with respect to the difference from the forward direction. First, in F2120, the component 1 assembled to the component 2 is gripped by the arm 8 via the robot hand 5 based on the pre-registered image E of the assembly end part or the data of the coordinates E. The gripped coordinates are stored as teaching points Pn (n = 0).

  Next, after fine movement in F2060, in F2080, it is determined whether or not the final point of the track viewed from the backward direction is reached. This is performed by comparing the current image of the stereo camera 7 with the pre-registered image S of the assembling start section, or the current coordinates of the arm 8 and the pre-registered coordinates S. In F2140, the table data direction is changed. In other words, this is because the table arrangement of the coordinates Pn and the passive force Qn obtained by “retreat” is opposite to that at the time of “forward”. The process ends at F2150.

  FIG. 9 is a flowchart for explaining F3000, which is the second and subsequent assembling steps, on the premise that the assembling track Cvg has been completed. In F3010, assembly is started following the assembly track Cvg. In F3020, it is confirmed whether the current coordinates correspond to any neighborhood of the coordinates Pn in the storage table. If so, the process proceeds to next F3030. As the approximate allowable value, an arbitrary numerical value such as ± 1 mm is set in advance. At this time, when the occurrence of malfunction is predicted due to the noise of the force sensor 6 or a transient timing shift, it may be compared with a moving average in the storage table. Alternatively, if the absolute coordinates of the arm 8 change slowly due to temperature changes and the like, and the degree of component assembly hit also changes slowly, it is effective to increase the period of comparison between the stored coordinates and the current coordinates.

  In F3030, it is confirmed whether or not the current passive force by the force sensor 6 corresponding to the coordinates corresponds to the vicinity of the passive force Qn in the storage table (for example, ± 10%). If not, it is determined that orbit adjustment is necessary and the process proceeds to F3050. If no trajectory adjustment is required, the process proceeds to F3040 to determine whether the assembly trajectory Cvg has reached the end point. If not, the process returns to F3010 above to continue driving the robot following the trajectory until the end point is reached. To do.

  In F3050, the arm 8 is stopped as soon as possible on the spot and returned to the coordinate Pn. In F3060, the fine movement described in F2060 is performed so that the current passive force corresponds to the passive force Qn in the storage table, and the trajectory is finely adjusted (corrected) by rewriting the table coordinates of the coordinates Pn. In F3070, excessive or small force is continuously detected during fine movement of F3060, and if it cannot be recovered, it is stopped as an error. The process ends at F3080.

  In F1010 of FIG. 7, the coordinates I of the point B of FIG. 2A are registered, but in order to simplify the work, a pointer 20 held by the operator is used as shown in FIG. 4A. There is a way. The stereo camera 7 is made to recognize the tip shape from the registered image (template) of the tip shape by a method such as pattern matching or area feature extraction, and the pointing position is recognized as the three-dimensional coordinate I. The tip shape of the pointer 20 was a three-dimensional cone. Although it may be a flat plate, pay attention to the difference in shooting shape depending on the camera angle. If the recognition points are any two or more rectangular points (for example, diagonal), the posture of the component 2 can also be extracted. As described above, since the assembly is performed like a human groping, the teaching accuracy of the coordinates I is not necessarily required. The standard of teaching accuracy may be a low level such that about half of the inserted parts are captured with respect to the insertion opening.

  Using the robot shown in FIG. 1, as shown in FIGS. 10 and 11, the part 3 having a portion that is curved in an arc shape is assembled to the part 4 in an arc-shaped path. The state before assembly is shown in FIGS. 10A and 10C in perspective and sectional views, and the state after assembly is shown in perspective views and sectional views in FIGS. 10B and 10H.

  As shown in FIG. 11, the trajectory limiting cylinder virtually sets a drum 51 and a cylinder 52 in the form of a megaphone, but it is possible to use only a cylinder 53 including both cylinders. The cylinder 51 has an upper surface diameter DD3 and a length DL3, the cylinder 52 has an upper surface diameter DD4 and a length DL4, and the cylinder 53 has an upper surface diameter DD5 and a length DL5. The assembly process is shown in cross-sectional views in FIGS. Although the collision occurs from the position shown in FIG. 10C to the position shown in FIG. 10D, the process proceeds from the assembling start point 61 to the end point 63 via the intermediate point 62 and the like in accordance with the searching method in F2060 described above.

1, 2, 3, 4 Parts 5 Robot hand 6 Force sensor 7 Stereo camera 8 Arm 11 Image processing unit 12 Robot controller 21, 22, 51, 52, 53 Body

Claims (3)

A component assembly method for assembling a first component gripped by a robot hand having a force sensor for detecting at least moment force and pushing force based on an image photographed by a three-dimensional measuring machine to a second component,
Based on the images of the first part and the second part taken by the CMM , the traveling direction of the first part for limiting the trajectory range from the start point to the end point of the assembly A first step of setting a divergent trajectory limiting cylinder;
By driving the robot hand, the first part is finely moved in the three-axis linearly moving direction, turning, and turning direction from the reference point in the divergent trajectory limiting cylinder, and the first part contacts the second part. A second step of searching for a teaching point at which the detection value of the force sensor is minimum and moving a first part to the teaching point;
And a third step of moving the first part to the end point of the assembly by repeating the second step using the teaching point as a reference point. Storing a position coordinate of the teaching point in the control unit of the robot hand and creating a precise trajectory by performing interpolation calculation between the points;
2. The component assembling method according to claim 1, wherein in the subsequent assembly, the first component is moved along the precise trajectory by driving the robot hand. 3.   3. The precise trajectory is corrected based on a detection value of the force sensor when the first component is moved along the precise trajectory in the subsequent assembly. 4. Parts assembly method.

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