JP2008036733A - Trajectory control device for articulated link mechanism - Google Patents

Abstract

[PROBLEMS] To easily determine the accuracy of the trajectory of an articulated mechanism by measuring the amount of deviation from the ideal position on the Cartesian coordinate axis and converting the amount of deviation on the Cartesian coordinate axis into the amount of deviation for each axis of the rotating link. To improve.
A jig positioning unit 1 configured by a four-axis multi-joint mechanism that holds a jig 5 to be machined and holds it in a necessary position and posture, and a machining tool for burr machining of the workpiece 5 4 includes a tool operation unit 2 configured by a two-axis multi-joint mechanism that operates 4 and a control device 3 that operates these units 1 and 2.
[Selection] Figure 1

Description

    The present invention relates to a trajectory control device for an articulated link mechanism used for casting deburring of a casting, and in particular, measures a deviation amount with respect to an ideal position on an orthogonal coordinate axis, and rotates each deviation amount on the orthogonal coordinate axis. The present invention relates to a trajectory control device that easily improves the trajectory accuracy of an articulated link mechanism by converting and holding the shift amount for each axis.

  Articulated link mechanisms such as robots have been widely used because they are more versatile and have a smaller installation area than orthogonal motion mechanisms. However, this has a poor motion trajectory accuracy and cannot be used in fields where trajectory accuracy is required.

  When performing a linear motion or circular arc motion by interpolation operation with an articulated link mechanism, the actual articulated link mechanism has an assembly error or link length error, and the connecting portion of the rotating shaft is bent by a gap or an external force. There are elastically deformed parts. When the rotation of the servo motor is decelerated with a speed reducer, an angle transmission error inherent to the speed reducer and an elastic deformation error deflected by a gap or an external force are added, so that the linear accuracy and the arc accuracy are lowered.

  As an improvement measure, for example, as disclosed in Japanese Patent Application Laid-Open No. 2005-59102, there is a method of correcting an error for only one axis using a deviation amount for one axis. In this case, only one axis is corrected. There is a drawback that it cannot be applied to the multi-joint link mechanism.

When the displacement correction amount is held for each of the multi-joint rotation shafts, the amount of deformation of the reduction gear is changed by changing the load torque generated by its own weight according to the rotation angle of the shaft related to the shaft. Therefore, a huge amount of displacement data for each axis is required, and it was virtually impossible to hold the displacement data.
JP 2005-59102 A Japanese Patent Laid-Open No. 7-204952 Registered Utility Model No. 3085828

  Therefore, the problem to be solved by the present invention is a trajectory control device for an articulated link mechanism used for casting deburring of a casting, and in particular, an amount of deviation from an ideal position is measured on an orthogonal coordinate axis. A trajectory control device that easily improves the trajectory accuracy of the articulated link mechanism by converting the shift amount into a shift amount for each axis of the rotating link, and improves the above-mentioned drawbacks of the known technology. There is to do.

In order to solve the above-described problem, according to the trajectory control device of the present invention, in the trajectory control device for a casting deburring multi-joint link mechanism that performs linear motion or arc motion by interpolation control of a plurality of axes, a jig to be processed is provided. Tool operation composed of a jig positioning unit composed of a four-axis multi-joint mechanism that holds and holds the necessary position and posture, and a three-axis multi-joint mechanism that operates a processing tool for burr processing of the jig. Each unit of the articulated link constituent axis at the lattice point position on the Cartesian coordinate axis, and the amount of deviation between the actual trajectory of the articulated link mechanism and the ideal trajectory. This is characterized in that it is approximated to an ideal trajectory by correcting the error amount of this error list during actual articulated link mechanism operation.

  The present invention measures the amount of deviation from the ideal position on the Cartesian coordinate axis, converts the amount of deviation on the Cartesian coordinate axis into the amount of deviation for each axis of the rotating link, and maintains the trajectory accuracy of the articulated link mechanism. The multi-joint link mechanism can be used even in a field that cannot be dealt with simply by improving the conventional linear guide method.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view of a specific example of an articulated link mechanism according to the present invention. FIG. 2 is an explanatory diagram showing the amount of deviation between the ideal trajectory and the actual motion trajectory. FIG. 3 is a graph showing the trajectory accuracy when correction is not performed. FIG. 4 is a graph showing the trajectory accuracy when corrected.

  As shown in FIG. 1, the trajectory control device of the present invention is a cast deburring multi-joint link mechanism that performs linear motion or arc motion by multi-axis interpolation control, and includes a jig positioning unit 1 and a tool operation unit 2. And the control device 3 basically.

  The jig positioning unit 1 is a jig to be processed, that is, a one-axis turning 7, a two-axis swing 8, a three-axis swing 9, which holds the work 5 with a work clamp jig 6 and holds it in a required position and posture. It is composed of a 4-axis articulated link mechanism with 4-axis swing 10.

  Further, the tool operating unit 2 is provided with a 5-axis swing 11, a 6-axis swing 12, and a 7-axis swing 13 for operating various processing tools 4 such as an end mill, a tip saw, and a chipper for burr processing of the workpiece 5. It consists of a three-axis multijoint mechanism.

  The control device 3 includes a jig side NC mechanism and a tool side NC mechanism, and operates the jig positioning unit 1 and the tool operation unit 2 described above.

Generally, in the casting finishing process, particularly in the casting deburring process, burrs are generated in any direction on each surface of the workpiece. Therefore, a 6-axis vertical articulated robot capable of setting an arbitrary position and posture is very effective. . However, casting sand, casting burrs, and pouring gates for casting are attached to the casting workpiece, and since this deposit has a different shape, the casting workpiece is misaligned when it is transported by a robot. Interference collisions with other components frequently occur. In this case, since a general 6-axis vertical articulated robot has weak joint strength, the joint axis is displaced, the production line is stopped for a long time, and the operation rate of the production line cannot be increased.

  As a method for increasing the joint strength, it is only necessary to use a large speed reducer for each joint so as to have strength that can overcome the force acting on the joint at the time of collision. However, if the required strength is provided, the size of each joint will be large, the size of the device will be very large, the weight will increase, and it will not be possible to move at high speed, so the finishing time will be short. become longer. As a result, the installation space is large, the cost is high, and the production capacity is low.

  The present invention divides a 6-axis vertical multi-joint configuration into two to make a compact size even when using a speed reducer with a required joint strength, and a 4-axis that positions a workpiece at a required position and posture. A jig unit with a vertical multi-joint configuration is combined with a tool unit with a 3-axis vertical multi-joint configuration that moves the trajectory necessary for machining to the tool, and both the jig side unit and the tool side unit are controlled by a single controller. The problem of solving the problem was made possible by interpolating the workpiece.

  Such an apparatus according to the present invention is a deburring facility for cast aluminum, and includes a jig positioning unit 1 composed of a four-axis multi-joint mechanism that holds a workpiece 5 to be processed and holds it in a required position and posture, It comprises a tool operation unit 2 composed of a three-axis articulated mechanism that operates a processing tool 4 such as an end mill cutter, which is a tool for machining, and a control device 3 that operates each unit.

  After the multi-joint link mechanism is operated based on the command (ideal) position of the program using the above-described device of the present invention, the actual position of the movement locus is measured with a digital scale, and the amount of deviation on the orthogonal coordinate axis is calculated The trajectory accuracy is improved by converting to the amount of deviation of each axis angle of the multi-joint link mechanism by reverse calculation and correcting according to the amount of deviation of each axis angle. The most important feature of the present invention is that the amount of deviation from the ideal position is measured on the orthogonal coordinate axis, and the amount of deviation on the orthogonal coordinate axis is converted into the amount of deviation for each axis of the rotating link and held. .

  FIG. 2 shows an example of the operation trajectory of the tool unit when the amount of deviation is not corrected. The deviation from the ideal state occurs in a form in which a large undulation deviation and a small deviation overlap. The machining accuracy is deteriorated by the amount of deviation. The amount of deviation for making the motion locus close to the ideal state is corrected.

  The actual position ZP11 is displaced by DY11 in the Y-axis direction and ZD11 in the Z-axis direction with respect to the command position (ideal position) point P11 on the program for machining. This is a difference between the command (ideal) position Pij and the actual movement position ZPij over a whole range of movement of the tool movement unit composed of a two-axis multi-joint mechanism that moves in parallel with the Y and Z orthogonal axes. The Y-direction misalignment amount DYij and the Z-direction misalignment amount DZij are measured with a digital scale (not shown). At this time, the lattice pitch to be measured needs to be measured with a width that can reproduce a small deviation. This time, both Y direction 600 mm and Z direction 450 mm were measured at a pitch of 3 mm, and Y direction deviation amount DYij and Z direction deviation amount DZij were measured at 30000 points.

  Based on the measured shift amount, a correction position HPij = (Pij−DYij, Pij−DZij) on the orthogonal coordinate axis is calculated, and corrected joint axis angles (Hθ1ij) and (Hθ2ij) are obtained by inverse calculation, and the command The difference between the (ideal) angle (θ1ij) and (θ2ij) is used as the correction angle at the point Pij, and the correction angle of the entire operation area is obtained in the same manner to create a correction angle list. In this list, there is a correction angle at the grid intersection point, but since there is no data in the middle part of the grid intersection point, the correction angle is calculated and applied by linear interpolation during this period. Since the formula for the inverse calculation from the orthogonal coordinates to each axis angle is known, it will be omitted.

  If the accuracy of the trajectory after the linear motion is not corrected, a deviation of about 0.35 mm with a large undulation and about 0.05 mm with a small undulation occurs as shown in FIG. When corrected, the large waviness as shown in FIG. 4 can be reduced to 0.0 mm and the small waviness can be reduced to about 0.02 mm.

  Thus, in the case of the embodiment, it is possible to correct the operation range of 600 mm, 450 mm, and rectangle with 60000 pieces of correction angle data.

  The amount of deviation from the ideal position is measured on the Cartesian coordinate axis, and the amount of deviation on the Cartesian coordinate axis is converted to the amount of deviation for each axis of the rotating link, and the trajectory accuracy of the articulated link mechanism is easily improved. Let For this reason, this invention is used for casting deburring of a casting, and has high industrial applicability.

It is a perspective view of an example of the articulated link mechanism concerning the present invention. It is explanatory drawing which showed the deviation | shift amount of an ideal locus | trajectory and an actual motion locus | trajectory. It is a graph showing the locus | trajectory precision when not correct | amending. It is a graph showing the locus | trajectory precision when correct | amending.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Jig positioning unit 2 Tool operation unit 3 Control device 4 Processing tool 5 Work piece 6 Work clamp jig 7 1 axis rotation 8 2 axis oscillation 9 3 axis oscillation 10 4 axis oscillation 11 5 axis oscillation 12 6 axis oscillation 13 7-axis swing P11 Target position on program ZP11 Actual operating position of NC HP11 Corrected target position on program DZ11 Amount of deviation in Z direction from target position DY11 Amount of deviation in Y direction from target position -DZ11 Target Correction amount in the Z direction from the position -DY11 Correction amount in the Y direction from the target position

Claims (7)

  A multi-joint multi-joint mechanism that holds a jig to be machined and holds it in the required position and orientation in a trajectory control device for a casting deburring multi-joint link mechanism that performs linear motion or arc motion by multi-axis interpolation control A tool positioning unit composed of a multi-axis multi-joint mechanism that operates a machining tool for burr machining of the jig, and a control device that operates these units. The amount of deviation between the motion trajectory of the multi-joint link mechanism and the ideal trajectory is provided as a transmission error list for each axis of the multi-joint link constituent axes at the grid point positions on the Cartesian coordinate axes, and during actual multi-joint link mechanism operation A trajectory control device for an articulated link mechanism characterized in that it approximates an ideal trajectory by correcting the error amount of the error list.   The shift amount between the motion trajectory and the ideal trajectory is measured on the orthogonal coordinate axis, and the shift amount on the orthogonal coordinate axis is converted into a shift amount for each axis of the rotating link and held. The trajectory control device according to claim 1.   2. The multi-joint link mechanism is operated according to the command position of the program, the actual position of the operation locus is measured with a digital kale, the amount of deviation on the orthogonal coordinate axes is calculated, and then the multi-joint is calculated by inverse calculation. The trajectory control device according to claim 1, wherein the trajectory accuracy is improved by converting into a shift amount of each axis angle of the link mechanism and correcting according to the shift amount of each axis angle.   2. The trajectory control device according to claim 1, wherein the articulated link mechanism is driven by a servo motor.   2. The trajectory control device according to claim 1, wherein the control device for operating the unit is an NC mechanism.     The trajectory control device according to claim 1, wherein the processing tool is an end mill, a tip saw, or a chipper. 2. The trajectory control device according to claim 1, wherein the jig to be processed is a work to which burrs are attached.

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