JP4888374B2 - Robot motion control apparatus and motion control method thereof - Google Patents

Description

  The present invention relates to a robot motion control apparatus and a motion control method for controlling a robot motion by performing coordinate transformation by applying a parameter to a target point.

In order to improve the static accuracy of the robot, a method for correcting the parameter error is used. As a method for correcting the parameter error, the robot performs various operations and the error of the tip (hand) is corrected. A multi-point positioning method for deriving parameters so that is minimized is used (see, for example, Patent Documents 1 and 2).
JP-A-6-304893 JP 60-218108 A

  By the way, since the multipoint positioning method described above derives parameters so that the error is minimized at the measurement point, the static accuracy of the robot is improved for the operation at the measurement point. The robot's static accuracy is reduced with respect to movement. Therefore, it is only necessary to derive parameters by setting measurement points over the entire robot motion space (motion region), but the accuracy of the entire robot motion space is high due to errors and non-linearities other than mechanical factors. It is difficult to derive parameters. As a result, there is a problem that the static accuracy of the robot is lowered and the time required for teaching is prolonged.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to improve the static accuracy of the robot and shorten the time required for teaching and the operation of the robot. It is to provide a control method.

  According to the first and sixth aspects of the invention, instead of setting the measurement points over the entire robot motion space and deriving the parameters, the robot motion space is divided into a plurality of regions, and the divided motions are divided. Set the measurement point for each space to derive the parameter, select the parameter of the motion space to which the target point belongs from the parameters of the derived motion space, and apply the selected parameter to the target point to coordinate Since the robot movement is controlled by conversion, every time the motion space to which the target point belongs changes, the coordinate transformation is performed by switching the parameters derived at the measurement points set for each divided motion space. The static accuracy of the robot can be improved without being affected by errors other than mechanical factors and non-linearity, and the time required for teaching can be shortened. It is possible.

  According to the second and seventh aspects of the invention, when the parameter derivation accuracy for each derived motion space is determined, and it is determined that the parameter derivation accuracy for each derived motion space is less than a certain value, the robot Since the operation space is subdivided into multiple regions and the parameters are re-derived by resetting the measurement points for each sub-division operation space, the parameter derivation accuracy can be kept above a certain value. The static accuracy of the robot can be improved reliably.

  According to the third and eighth aspects of the present invention, the robot motion space is a six-dimensional region in which the yaw angle, the pitch angle, and the roll angle representing the posture of each tip are added to the x axis, the y axis, and the z axis. Since the robot is divided into a plurality of regions, the static accuracy of the robot is improved in a six-dimensional region in which the yaw angle, the pitch angle, and the roll angle representing the posture of each tip are added to the x-axis, y-axis, and z-axis. Can be improved.

  According to the fourth and ninth aspects of the invention, since the robot operation space is divided into a plurality of regions in the polar coordinate system, the static accuracy of the robot can be improved in the polar coordinate system.

  Hereinafter, an embodiment in which the present invention is applied to a control device for controlling the operation of a vertical articulated robot will be described with reference to the drawings. As shown in FIG. 2, a robot apparatus 1 as an industrial robot apparatus includes a vertical articulated robot (hereinafter referred to as a robot) 2 and a control device 3 for controlling the operation of the robot 2 (operation control in the present invention). Means, motion space dividing means, parameter derivation means, parameter selection means, derivation accuracy determination means) and a teaching pendant 4 connected to the control device 3.

  The robot 2 is a robot having, for example, a six-axis vertical articulated joint, and is supported by the base 5, a shoulder portion 6 supported by the base 5 so as to be able to turn in the horizontal direction, and supported by the shoulder portion 6 so as to be able to turn in the vertical direction. The lower arm 7, the first upper arm 8 supported by the lower arm 7 so as to be pivotable in the vertical direction, and the second upper arm 8 supported by the tip portion of the first upper arm 8 so as to be able to rotate. An upper arm 9, a wrist 10 supported by the second upper arm 9 so as to be rotatable in the vertical direction, and a flange 11 supported so as to be rotatable (twisted) by the wrist 10. Yes.

  The shoulder portion 6, the lower arm 7, the first upper arm 8, the second upper arm 9, the wrist 10, and the flange 11 including the base 5 described above function as links in the robot 2, and each link excluding the base 5 Is rotatably connected to the lower link by a rotary joint. A flange (not shown) for gripping a workpiece can be attached to the flange 11 which is the most advanced link. In addition, the rotary joint that connects the links is provided with a reduction gear that reduces the rotation of the motor fixed to the previous link and transmits it to the next link.

  In this embodiment, the joint axis of the rotary joint that connects the base 5 that is the first link and the shoulder portion 6 that is the second link is the first axis, and the shoulder portion 6 that is the second link. The joint axis of the rotary joint that connects between the first link and the lower arm 7 that is the third link is the second axis, and the lower arm 7 that is the third link and the first upper arm 8 that is the fourth link The joint axis of the rotary joint that connects between the first upper arm 8 that is the fourth link and the second upper arm 9 that is the fifth link is the third axis. The fourth axis, the fifth link as the fifth link, and the wrist 10 as the sixth link as the joint axis of the rotary joint that connects the second upper arm 9 as the fifth link and the wrist 10 as the sixth link. And the joint 11 of the rotary joint that connects the flange 11 that is the seventh link is shown as a sixth axis.

  As illustrated in FIG. 3, the control device 3 that controls the operation of the robot 2 includes a CPU 12, a drive circuit 13, and a position detection circuit 14. The CPU 12 is connected with a ROM 15 for storing a robot language for creating a system program and an operation program for the entire robot 2 and a RAM 16 for storing an operation program for the robot 2 and used for teaching work. Teaching pendant 4 is connected. As shown in FIG. 2, the teaching pendant 4 includes various operation units 4a and a display 4b.

  The position detection circuit 14 is for detecting the positions of the shoulder unit 6, the arms 7 to 9, the wrist 10 and the flange 11. The position detection circuit 14 is a drive source for the shoulder unit 6, the arms 7 to 9, the wrist 10 and the flange 11. A rotary encoder 18 provided in a certain motor 17 is connected. Based on the detection signal input from the rotary encoder 18, the position detection circuit 14 rotates the shoulder portion 6 with respect to the base 5, the lower arm 7 with respect to the shoulder 6, and the first upper arm 8 with respect to the lower arm 7. The angle, the rotation angle of the second upper arm 9 relative to the first upper arm 8, the rotation angle of the wrist 10 relative to the second upper arm 9, and the rotation angle of the flange 11 relative to the wrist 10 are detected, and the detected position detection information Is output to the CPU 12. The CPU 12 controls the operation of the shoulder unit 6, the arms 7 to 9, the wrist 10 and the flange 11 based on the operation program using the position detection information input from the position detection circuit 14 as a feedback signal. To do.

  As shown in FIG. 2, three-dimensional coordinates are defined for each link. Among these, the coordinate system of the base 5 installed on the floor surface is a reference coordinate of the robot 2 as a stationary coordinate system, and the horizontal coordinate axes Xb and Yb are set with the center of the lower end of the base 5 as the origin. And one coordinate axis Zb in the vertical direction is defined. In the coordinate system of the other links, the position and orientation on the reference coordinates change due to the rotation of each rotary joint, and the CPU 12 receives the shoulder 6, the arms 7 to 9, the wrist 10, and the flange input from the position detection circuit 14. 11 based on the position detection information of each rotary joint and the length information of each joint stored in advance, the position and orientation of the coordinates of each joint are converted to the position and orientation on the reference coordinates by the coordinate conversion calculation function. Convert to and recognize.

  Of the coordinate systems of the joints described above, the coordinate system of the flange 11 has the rotation center of the tip surface of the flange 11 as the origin, the two coordinate axes Xm and Ym on the tip surface of the flange 11 and the rotation axis of the flange 11. Defines one coordinate axis Zm. Note that the rotation angles with respect to the coordinate axes Xm, Ym, and Zm are represented by a yaw angle RX, a pitch angle RY, and a roll angle RZ.

Next, the effect | action of an above-described structure is demonstrated with reference to FIG.1 and FIG.4.
The teaching operation of the robot 2 is defined by the position of the measurement point, the posture at the measurement point, the speed, and the acceleration. The position of the measurement point and the posture at the measurement point are performed by actually moving the robot 2 with the teaching pendant 4 and moving the flange 11 which is the tip of the robot 2 to the measurement point to take a desired posture. The CPU 12 calculates the positions of the links 6 to 11 on the reference coordinates based on the detection signal of the rotary encoder 18 that detects the rotational position of each motor 17 to calculate the positions of the measurement points of the links 6 to 11. At the same time, the directions of the unit vectors of the two coordinate axes are calculated for the coordinates of the links 6 to 11 to calculate the postures of the links 6 to 11 at the measurement points. Further, the speed and acceleration at the measurement point are set by inputting numerical values from the teaching pendant 4, and the CPU 12 calculates the speed and acceleration of each link 6 to 10 based on the speed and acceleration input from the teaching pendant 4. .

  Now, in the control device 3, the CPU 12 divides the operation space of the robot 2 into a plurality of regions (step S1). Here, in the present embodiment, as shown in FIG. 1, an example is shown in which the motion space of the robot 2 is divided into S1 (a space indicated by a dashed line) and S2 (a space indicated by a two-dot chain line). Next, the CPU 12 sets measurement points (P1 in the operation space S1 and P2 in the operation space S2) for each of the divided operation spaces (step S2), and the robot 2 is actually moved by the teaching pendant 4 to move the tip of the robot 2 The three-dimensional position data at each measurement point is acquired by moving the (flange 11) to the measurement point and taking a desired posture (step S3). Note that the number of divisions of the motion space and the number of measurement points in the divided motion space may be determined in consideration of various factors such as the content of the motion command and the motion range.

  Next, the CPU 12 calculates an error between the acquired three-dimensional position data and the measurement point (step S4), and derives a DH parameter from the error at each measurement point (step S5). In this case, the CPU 12 uses ai, bi, di, which are relative positions of the rotation axis i + 1 viewed from the rotation axis i with reference to the x axis, the y axis, and the z axis of the rotation axis i as DH parameters, and the rotation αi in each axis direction. , Βi, and γi are derived.

  Then, the CPU 12 determines whether or not the derived accuracy of the DH parameter is equal to or higher than a predetermined value (step S6). If the CPU 12 determines that the derivation accuracy of the derived DH parameter is not equal to or greater than a certain value (less than a certain value) (“NO” in step S6), the CPU 12 returns to the above step S1 and performs steps S1 to S6. Repeat. In other words, the CPU 12 subdivides the motion space of the robot 2 into a plurality of regions until the derivation accuracy of the derived DH parameter becomes a certain value or more, and resets the measurement points for each of the subdivided motion spaces. By re-deriving the parameters, DH parameters having derivation accuracy of a certain value or more are derived for each divided motion space.

  On the other hand, if the CPU 12 determines that the derivation accuracy of the derived DH parameter is equal to or greater than a certain value (“YES” in step S6), after inputting an operation command from the teaching pendant 4 (step S7), the input operation A DH parameter corresponding to the operation space of the command is selected (step S8), and the operation of the robot 2 is controlled by performing coordinate conversion by applying the selected DH parameter (step S9). That is, if the target point in the input motion command belongs to the motion space S1, the CPU 12 performs coordinate conversion by applying a DH parameter having a derivation accuracy equal to or greater than a certain value derived at the measurement point in the motion space S1. If the target point in the input motion command belongs to the motion space S2, the DH parameter having a derivation accuracy equal to or greater than a certain value derived at the measurement point in the motion space S2 is controlled. The operation of the robot 2 is controlled by applying the coordinate transformation by application. Note that the CPU 12 switches the DH parameter with hysteresis so that the DH parameter does not continuously vary within a series of operations when the operation command is over a plurality of operation spaces.

  As described above, according to the present embodiment, the motion space of the robot 2 is divided into a plurality of regions, measurement points are set for each of the divided motion spaces, DH parameters are derived, and the derived motion space. Since the DH parameter of the motion space to which the target point belongs is selected from each DH parameter, and the coordinate conversion is performed by applying the selected DH parameter to the target point, the operation of the robot 2 is controlled. Every time the operation space to which the target point belongs changes, coordinate conversion is performed by switching the DH parameter derived at the measurement point set for each operation space, which is affected by errors other than mechanical factors and non-linearity. In addition, the static accuracy of the robot 2 can be improved, and the time required for teaching can be shortened.

  Further, the accuracy of deriving the DH parameter for each derived motion space is determined, and if the accuracy of deriving the DH parameter for each derived motion space is determined to be less than a certain value, the motion space of the robot 2 is re-divided into a plurality of regions. Since the DH parameters are re-derived by dividing and re-determining the measurement points for each sub-division operation space, the DH parameter derivation accuracy can be kept above a certain value, and the static accuracy can be ensured. Can be improved.

The present invention is not limited to the above-described embodiment, and can be modified or expanded as follows.
The vertical articulated robot is not limited to the six-axis robot.
The robot motion space is not limited to a configuration in which a robot is divided into a plurality of regions in a six-dimensional region in which the yaw angle, pitch angle, and roll angle representing the posture of each tip are added to the x-axis, y-axis, and z-axis. The motion space may be divided into a plurality of regions in the polar coordinate system. In this case, the static accuracy of the robot can be improved in the polar coordinate system.

The figure which shows one Embodiment of this invention and shows the divided | segmented operation | movement space roughly Perspective view of industrial robot device Functional block diagram flowchart

Explanation of symbols

  In the drawing, 2 is a vertical articulated robot (robot), and 3 is a control device (motion control means, motion space dividing means, parameter derivation means, parameter selection means, derivation accuracy determination means).

Claims (10)

In a robot motion control device comprising motion control means for controlling the motion of the robot by applying a coordinate transformation by applying parameters to the target point,
Motion space dividing means for dividing the robot's motion space into a plurality of regions;
Parameter derivation means for deriving parameters by setting measurement points for each of the operation spaces divided by the operation space division means;
Parameter selection means for selecting a parameter of the motion space to which the target point belongs among the parameters for each motion space derived by the parameter derivation means;
The operation control means, to the target point in the operation command input, the parameter selection means by controlling the operation of the robot by performing coordinate transformation by applying the parameters of the operating space in which the target point belongs in the operation instruction A motion control apparatus for a robot. The robot motion control apparatus according to claim 1,
Derivation accuracy determination means for determining the derivation accuracy of the parameter for each motion space derived by the parameter derivation means,
When the derivation accuracy determination unit determines that the derivation accuracy of the parameter for each operation space derived by the parameter derivation unit is less than a predetermined value, the operation space dividing unit determines that the operation space of the robot is a plurality of operation spaces. The robot motion control apparatus according to claim 1, wherein the parameter derivation unit re-divides the region into regions, and resets the measurement points for each of the motion spaces subdivided by the motion space division unit to re-derived the parameters. In the robot motion control apparatus according to claim 1 or 2,
The movement space dividing means divides the movement space of the robot into a plurality of areas in a six-dimensional area obtained by adding a yaw angle, a pitch angle, and a roll angle representing the posture of each tip to the x axis, the y axis, and the z axis. A motion control apparatus for a robot. In the robot motion control apparatus according to claim 1 or 2,
The robot motion control device, wherein the motion space dividing means divides the robot motion space into a plurality of regions in a polar coordinate system. The robot motion control apparatus according to any one of claims 1 to 4,
The parameter deriving means includes ai, bi, di that are relative positions of the rotation axis i + 1 viewed from the rotation axis i with respect to the x axis, the y axis, and the z axis of the rotation axis i as the parameters, and the rotation αi in each axis direction. , Βi, γi, all or part of them is derived. In a method for controlling robot movement by applying coordinate transformation to a target point and performing coordinate transformation,
The robot's motion space is divided into a plurality of regions, parameters are derived by setting measurement points for each of the divided motion spaces, and the target points in the input motion command among the parameters for the derived motion spaces are A robot motion control method comprising : selecting a parameter of a motion space to which the robot belongs and applying the selected parameter to a target point in the motion command to perform coordinate transformation to control the robot motion. The robot operation control method according to claim 6,
Determining the derivation accuracy of the parameters for each derived motion space, and subdividing the robot's motion space into multiple regions when it is determined that the derivation accuracy of the parameters for each derived motion space is less than a certain value Then, the robot motion control method is characterized in that the measurement points are reset for each of the subdivided motion spaces and the parameters are derived again. The robot motion control method according to claim 6 or 7,
A robot characterized in that an operation space of the robot is divided into a plurality of regions by a six-dimensional region obtained by adding a yaw angle, a pitch angle, and a roll angle representing the posture of each tip to the x-axis, y-axis, and z-axis. Operation control method. The robot motion control method according to claim 6 or 7,
A robot motion control method, wherein the robot motion space is divided into a plurality of regions in a polar coordinate system. The robot motion control method according to any one of claims 6 to 9,
Among the parameters, ai, bi, di that are relative positions of the rotation axis i + 1 viewed from the rotation axis i with respect to the x axis, the y axis, and the z axis of the rotation axis i, and rotations αi, βi, γi in the respective axis directions A robot motion control method characterized by deriving all or part of the above.

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