JP6576824B2 - Robot controller - Google Patents

Description

  The present invention relates to a robot control apparatus.

  Conventionally, an articulated robot having a plurality of arms is known. In this type of articulated robot, the output shaft of a servo motor is drivingly connected to a speed reducer, and the arm is driven according to the rotation of the output shaft of the speed reducer. Thus, when a speed reducer is interposed between the servo motor and the arm, an angle transmission error may occur between the servo motor and the speed reducer. When an angle transmission error occurs, a deviation also occurs between the target rotation angle of the servo motor and the control position of the arm.

  In contrast, in the robot control system described in Patent Document 1, an actual position of the arm is grasped by attaching an LED to the arm of the articulated robot and photographing the position of the LED with a camera. . Then, a correction value for correcting the target rotation angle is calculated based on the deviation between the actual position of the arm and the target rotation angle of the servo motor at that time, and the correction value is stored in advance. Thereafter, when the arm of the articulated robot is operated, the target rotation angle of the servo motor is corrected with the correction value, so that a deviation between the target rotation angle of the servo motor and the control position of the arm can be suppressed.

JP 2010-120110 A

  The misalignment between the target rotation angle of the servo motor and the control position of the arm is not limited to the angle transmission error described above, but is also caused by deformation due to deterioration with time of the servo motor, reducer, arm, etc., and the servo motor and reducer. This can also occur by replacing parts. Therefore, in order to realize more accurate arm position control, it is preferable to grasp the deviation between the target rotation angle of the servo motor and the arm control position as frequently as possible.

  However, in the robot control system of Patent Document 1, it is necessary to prepare an external device unnecessary for the original operation of the articulated robot, such as an LED attached to the arm of the articulated robot and a camera for photographing the LED. There is. And every time it is going to grasp | ascertain the shift | offset | difference between the target rotation angle of a servomotor and the control position of an arm, it takes a considerable effort to install and install LED and a camera. For this reason, it is not realistic to frequently grasp the deviation between the target rotation angle of the servo motor and the arm control position with the technology of the robot control device described in Patent Document 1.

  In order to solve the above problems, the present invention provides a robot control apparatus for controlling a robot in which an output shaft of a servo motor is drivingly connected to a speed reducer and a movable member is driven in accordance with rotation of the output shaft of the speed reducer. A command generation unit configured to set a target rotation angle for rotating the output shaft of the servo motor and generate a position command based on the target rotation angle; and the servo motor rotated according to the position command A calculation unit that calculates a correction angle that indicates a deviation between a motor rotation angle that indicates a rotation angle of the output shaft and a reduction gear rotation angle that indicates a rotation angle of the output shaft in the speed reducer rotated according to the position command And a storage unit that associates and stores the calculated correction angle and the motor rotation angle when the correction angle is calculated, and the command generation unit newly sets a target rotation angle. If the motor rotation angle corresponding to the target rotation angle is stored in the storage unit, the target rotation angle is corrected with the correction angle associated with the motor rotation angle, and the corrected target The position command is generated based on a rotation angle.

  According to the present invention, it is possible to obtain a correction angle for correcting the target rotation angle more easily based on the deviation between the target rotation angle of the servo motor and the control position of the arm.

The side view of an articulated robot. The figure which shows the position of the welding torch when driving according to a teaching program. The block diagram of a robot control apparatus. The figure which shows the example of a 1st correction table. The figure which shows the example of a 2nd correction table. The flowchart of a 1st correction table creation process. The flowchart of a 2nd correction table creation process. The flowchart of the correction process of a target rotation angle.

(Robot control system configuration)
A schematic configuration of a robot control system to which the robot control apparatus of the present invention is applied will be described. First, an articulated robot R (hereinafter abbreviated as robot R) will be described.

  As shown in FIG. 1, a swivel base C2 is provided on an upper part of a base C1 of the robot R so as to be turnable about a first rotation axis J1. A first arm C3 is provided above the swivel base C2 so as to be pivotable about the second rotation axis J2. A second arm C4 is provided at the distal end of the first arm C3 so as to be rotatable about a third rotation axis J3 orthogonal to the second rotation axis J2. A third arm C5 is provided at the tip of the second arm C4 so as to be pivotable about a fourth rotation axis J4 orthogonal to the third rotation axis J3.

  As shown in FIG. 1, a fourth arm C6 is provided at the tip of the third arm C5 so as to be pivotable about a fifth rotation axis J5 orthogonal to the fourth rotation axis J4. A fifth arm C7 is provided at the tip of the fourth arm C6 so as to be rotatable about a sixth rotation axis J6 orthogonal to the fifth rotation axis J5. A tool fixing member C8 is provided at the tip of the fifth arm C7 so as to be pivotable about a seventh rotation axis J7 orthogonal to the sixth rotation axis J6. A welding torch C9 is fixed to the tool fixing member C8 as a work tool, and the welding torch C9 rotates integrally with the tool fixing member C8. The fourth arm C6, the fifth arm C7, and the tool fixing member C8 may be collectively referred to as a wrist assembly.

  As shown in FIG. 3, the robot R has a built-in servo motor 10 as a drive source for turning the first arm C3. The output shaft 10 a of the servo motor 10 is drivingly connected to the speed reducer 11. The output shaft 11a of the speed reducer 11 is fixed to the first arm C3. Therefore, when the output shaft 10a of the servo motor 10 rotates, the speed reducer 11 is decelerated at a predetermined reduction ratio, and the output shaft 11a of the speed reducer 11 rotates. And according to rotation of the output shaft 11a of the reduction gear 11, the 1st arm C3 turns.

  As shown in FIG. 3, the robot R has a built-in motor encoder 12 for detecting the rotation angle of the output shaft 10 a of the servo motor 10. The motor encoder 12 is, for example, an increment encoder, and outputs a pulse signal corresponding to the rotation angle of the output shaft 10a of the servo motor 10 as the motor rotation angle α. Further, the robot R has a built-in speed reducer encoder 13 for detecting the rotation angle of the output shaft 11a of the speed reducer 11. The reduction gear encoder 13 is, for example, an increment encoder, and outputs a pulse signal corresponding to the rotation angle of the output shaft 11a of the reduction gear 11 as the reduction gear rotation angle β1. The motor rotation angle α output from the motor encoder 12 and the reduction gear rotation angle β1 output from the reduction gear encoder 13 are input to the robot control device RC via a communication cable connected to the base C1. In the following description, it is assumed that one pulse (numerical value “1”) of the motor rotation angle α corresponds to the rotation angle 1 ° of the output shaft 10 a of the servo motor 10.

  The robot R is provided with a servo motor, a reducer, a motor encoder, and a reducer encoder corresponding to the swivel base C2, the second arm C4 to the fifth arm C7, and the tool fixing member C8. Since these configurations are the same as those of the servo motor 10, the speed reducer 11, the motor encoder 12, and the speed reducer encoder 13 described above, detailed description thereof is omitted. In this embodiment, the swivel base C2, the first arm C3 to the fifth arm C7, and the tool fixing member C8 all correspond to movable members that are driven according to the rotation of the output shaft of the speed reducer. In the following description, the swivel base C2, the second arm C4 to the fifth arm C7, and the tool fixing member C8 may be referred to as “movable members”.

Next, the robot controller RC will be described.
As shown in FIG. 3, the main control unit 20 of the robot controller RC includes a calculation unit 21 (CPU) that executes various applications, and a nonvolatile storage unit 25 that stores applications necessary for processing and various data. The computer includes a volatile memory 28 in which data is temporarily stored when each application is executed.

  As shown in FIG. 3, the calculation unit 21 in the main control unit 20 functions as a command generation unit 22 that generates a position command S <b> 1 for rotating the output shaft 10 a of the servo motor 10 to a target angular position. For example, when controlling the first arm C3, the command generation unit 22 sets the target rotation angle θ1 as the angular position of the output shaft 10a of the servomotor 10 necessary to drive the first arm C3 to a predetermined position. In addition, the command generation unit 22 corrects the target rotation angle θ1 with the correction angle Δ stored in the storage unit 25 as the first correction table T1 or the second correction table T2, and sets the correction target angle θ2. The command generator 22 generates and outputs a position command S1 based on the corrected target angle θ2. Similarly, the command generator 22 generates the position command S1 when controlling other movable members than the first arm C3.

  As shown in FIG. 3, the calculation unit 21 in the main control unit 20 functions as a calculation unit 23 that calculates the correction angle Δ. The calculation unit 23 receives the motor rotation angle α output from the motor encoder 12 and the reduction gear rotation angle β1 output from the reduction gear encoder 13. The calculation unit 23 calculates a conversion angle β2 obtained by converting the reduction gear rotation angle β1 into the motor rotation angle α. Based on the motor rotation angle α and the conversion angle β2 (reduction gear rotation angle β1), the calculation unit 23 calculates a correction angle Δ indicating a deviation between the two rotation angles, and stores this in the storage unit 25. The first correction table T1 or the second correction table T2 is stored. A specific calculation mode of the conversion angle β2 and the correction angle Δ will be described later.

  As shown in FIG. 3, the storage unit 25 in the main control unit 20 stores a teaching program P for driving the movable members C2 to C8. The teaching program P records, for example, the positions and postures of the movable members C2 to C8 necessary for moving the tip position of the welding torch C9 along a predetermined locus. As the movement trajectory of the tip position of the welding torch C9, for example, as shown in FIG. 2, it moves linearly from the point A to the point B and moves linearly from the point B to the point C.

  As illustrated in FIG. 3, the storage unit 25 stores a first correction table T1 in association with the teaching program P. As shown in FIG. 4, the name of the teaching program P and the name of the movable member to which the first correction table T1 is applied are stored in the first correction table T1. In the first correction table T1, the tip position of the welding torch C9, the motor rotation angle α when the tip position is reached, and the reduction gear rotation angle β1 when the tip position is reached are converted into the motor rotation angle α. The converted angle β2 and the correction angle Δ of the target rotation angle θ1 when the tip end position is reached are stored in association with each other. FIG. 4 shows the first correction table T1 applied to the first arm C3, but the storage unit 25 stores the first correction for each of the movable members C2 to C8 for one teaching program P. A table T1 (a total of seven first correction tables T1) is stored.

  As shown in FIG. 3, the storage unit 25 stores a second correction table T2 separately from the first correction table T1. The second correction table T2 is not associated with a specific teaching program P, but is a general-purpose correction table. As shown in FIG. 5, in the second correction table T2, the angular position of the movable member, the motor rotation angle α when the angular position is reached, and the speed reducer rotation angle β1 when the angular position is reached are rotated by the motor. The converted angle β2 converted to the angle α and the correction angle Δ of the target rotation angle θ1 when the angle is reached are stored in association with each other. In FIG. 5, the second correction table T2 applied to the first arm C3 is illustrated, but the storage unit 25 stores the second correction table T2 for each of the movable members C2 to C8 (a total of seven second correction tables T2). A correction table T2) is stored.

  As shown in FIG. 3, the robot controller RC has a built-in servo control unit 30 that supplies power to each servo motor built in the robot R. For example, when controlling the servo motor 10, the servo control unit 30 outputs to the servo motor 10 a motor control voltage Vx in which the pulse frequency, the pulse width, etc. are adjusted according to the position command S 1 output from the calculation unit 21. . Similarly, the servo control unit 30 outputs the motor control voltage Vx adjusted according to the position command S <b> 1 to the other servo motors 10.

(Calculation process of first correction table)
A calculation process of the first correction table T1 executed by the robot controller RC will be described. In the following description, it is assumed that the teaching program P is stored in advance in the storage unit 25 of the robot controller RC. Then, as shown in FIG. 2, the teaching program P linearly moves the tip position of the welding torch C9 from the start point A to the point B, and then from the point B to the end point C. The content is moved linearly. In addition, the calculation process of the first correction table T1 will be described by taking the first arm C3 as an example of the movable members C2 to C8, but the same applies to other movable members.

  For example, when the operator operates the robot control device RC or an operation device connected to the robot control device RC to instruct the calculation processing of the first correction table T1 for the teaching program P, the main control of the robot control device RC is performed. The control unit 20 executes a series of processes shown in FIG.

  In step ST10, the command generation unit 22 of the main control unit 20 generates a position command S1 for each servo motor so that the tip position of the welding torch C9 is located at the starting point A according to the teaching program P. In addition, the servo control unit 30 supplies a motor control voltage Vx corresponding to the position command S1 to each servo motor. As a result, each of the movable members C2 to C8 turns and the tip position of the welding torch C9 is located at the point A that is the starting point. Thereafter, the process of the main control unit 20 proceeds to step ST11.

  In step ST11, the calculation unit 23 of the main control unit 20 acquires the motor rotation angle α output by the motor encoder 12 corresponding to the first arm C3 in a state where the tip position of the welding torch C9 is located at the point A. Similarly, the calculation unit 23 acquires the reduction gear rotation angle β1 output by the reduction gear encoder 13 corresponding to the first arm C3 in a state where the tip position of the welding torch C9 is located at the point A. Thereafter, the process of the main control unit 20 proceeds to step ST12.

  In step ST12, the calculation unit 23 of the main control unit 20 calculates a conversion angle β2 obtained by converting the reduction gear rotation angle β1 into the motor rotation angle α. When the reduction ratio in the reduction gear 11 is “N”, the resolution of the motor encoder 12 is “P1”, and the resolution of the reduction gear encoder 13 is “P2”, the conversion angle β2 is obtained by the following equation 1.

(Formula 1) β2 = β1 × (P1 / P2) × N
Specifically, the reduction gear rotation angle β1 is 32 [pulse], the resolution of the motor encoder 12 is 10 [bit] (= 1024), the resolution of the reduction gear encoder 13 is 14 [bit] (= 16384), and the reduction ratio is When 100, the conversion angle β2 is 200 [pulses]. Thereby, the conversion angle β2 of the reduction gear rotation angle β1 in consideration of the reduction ratio and the difference in resolution between the motor encoder 12 and the reduction gear encoder 13 is obtained. After calculating the conversion angle β2, the process of the main control unit 20 proceeds to step ST13.

  In step ST13, the calculation unit 23 of the main control unit 20 calculates the correction angle Δ by subtracting the conversion angle β2 calculated in step ST12 from the motor rotation angle α. In subsequent step ST14, the calculation unit 23 outputs the calculated correction angle Δ and the motor rotation angle α and conversion angle β2 when the correction angle Δ is calculated to the storage unit 25. The storage unit 25 stores the correction angle Δ, the motor rotation angle α, and the conversion angle β2 in association with each other as parameters of the first correction table T1 when the tip position of the welding torch C9 is at the point A. Thereafter, the process of the main control unit 20 proceeds to step ST15.

  In step ST15, the command generation unit 22 of the main control unit 20 determines whether or not the tip position of the welding torch C9 has reached the end point C. At this time, since the tip position of welding torch C9 is located at point A, it is determined that the tip position of welding torch C9 has not reached point C (NO in step ST15). In this case, the process of the main control unit 20 moves to step ST16.

  In step ST16, the command generation unit 22 of the main control unit 20 generates a new position command S1, and the servo motor so that the tip position of the welding torch C9 moves linearly from point A to point B. The ten output shafts 10a are rotated by a unit angle. In this embodiment, the unit angle is set to an angle corresponding to one pulse of the motor encoder 12. As a result, the tip position of the welding torch C9 is located at the point X1. Thereafter, the process of the main control unit 20 returns to step ST11, and the processes of steps ST11 to ST16 are repeated for the point X1 that is the tip position of the new welding torch C9.

  When the above steps ST11 to ST16 are repeated, the tip position of the welding torch C9 passes from point A to point B and finally reaches point C which is the end point. Then, when the process of step ST15 is executed in a state where the tip position of the welding torch C9 has reached the point C, the command generation unit 22 of the main control unit 20 causes the point C where the tip position of the welding torch C9 is the end point. Is reached (YES in step ST15), and a series of processing ends.

  As shown in FIG. 4, the series of calculation processes of the first correction table T <b> 1 as described above is performed by using the output shaft 10 a as a unit in the rotation angle range of the output shaft 10 a of the servo motor 10 when the robot R is operated according to the teaching program. Each correction angle Δ when rotated by an angle is stored in the storage unit 25 as the first correction table T1.

(Calculation process of second correction table)
A calculation process of the second correction table T2 executed by the robot controller RC will be described. In the following description, the calculation process of the second correction table T2 will be described using the first arm C3 as an example of the movable members C2 to C8, but the same applies to the other movable members.

  For example, when the operator operates the robot control device RC or the operation device connected to the robot control device RC to instruct the calculation processing of the second correction table T2 for the first arm C3, the robot control device RC The command generation unit 22 of the main control unit 20 moves the position of the movable member other than the first arm C3 to a predetermined reference position. The reference position is set, for example, at a position where the center of gravity of each movable member is closest to the second rotation axis J2 that is the rotation axis of the first arm C3. When the positions of the movable members other than the first arm C3 are positioned at the reference positions, a series of processes shown in FIG. 7 are executed.

  In step ST20, the command generation unit 22 of the main control unit 20 generates a position command S1 for the servo motor 10 so that the position of the first arm C3 is located at a predetermined origin. In the present embodiment, a range of 120 ° in total is set as the turning range of the first arm C3 by 60 ° forward and backward with respect to the vertical direction. The range from the end of the 120 ° range to the end (120 °) is the origin (0 °) to the end point (120 °). After the first arm C3 is located at the origin, the processing of the main control unit 20 proceeds to step ST21.

  In step ST21, the calculation unit 23 of the main control unit 20 acquires the motor rotation angle α output by the motor encoder 12 with the first arm C3 positioned at the origin. Similarly, the calculation unit 23 acquires the reduction gear rotation angle β1 output from the reduction gear encoder 13 in a state where the first arm C3 is located at the origin. Thereafter, the process of the main control unit 20 proceeds to step ST22.

  In step ST22, the calculation unit 23 of the main control unit 20 calculates the conversion angle β2 obtained by converting the reduction gear rotation angle β1 into the motor rotation angle α according to the above-described (Equation 1). After calculating the conversion angle β2, the process of the main control unit 20 proceeds to step ST23.

  In step ST23, the calculation unit 23 of the main control unit 20 calculates the correction angle Δ by subtracting the conversion angle β2 calculated in step ST22 from the motor rotation angle α. In subsequent step ST24, the calculation unit 23 outputs the calculated correction angle Δ and the motor rotation angle α and conversion angle β2 when the correction angle Δ is calculated to the storage unit 25. The storage unit 25 stores the correction angle Δ, the motor rotation angle α, and the conversion angle β2 in association with each other as parameters of the second correction table T2 when the first arm C3 is located at the origin. Thereafter, the process of the main control unit 20 proceeds to step ST25.

  In step ST25, the command generation unit 22 of the main control unit 20 determines whether or not the position of the first arm C3 has reached the end point. At this time, since the position of the first arm C3 is 0 ° (origin), it is determined that the end point has not been reached (NO in step ST25). In this case, the process of the main control unit 20 moves to step ST26.

  In step ST26, the command generation unit 22 of the main control unit 20 generates a new position command S1, and rotates the output shaft 10a of the servo motor 10 by a unit angle. In this embodiment, the unit angle is set to 10 pulses of the motor encoder 12, that is, 10 °. As a result, the first arm C3 rotates 10 ° from the origin. Thereafter, the process of the main control unit 20 returns to step ST21, and the processes of steps ST21 to ST36 are repeated for the new position of the first arm C3.

  When the above steps ST21 to ST26 are repeated, the first arm C3 rotates 120 ° from the origin and reaches the end point. Then, when the process of step ST25 is executed in a state where the position of the first arm C3 has reached the end point, the command generation unit 22 of the main control unit 20 determines that the first arm C3 has reached the end point ( In step ST25, YES), a series of processing ends. By the calculation process of the second correction table T2, as shown in FIG. 5, each correction angle Δ when the output shaft 10a of the servo motor 10 is rotated by a unit angle within a predetermined turning range of the first arm C3 is changed to the first correction angle Δ. 2 stored in the storage unit 25 as a correction table T2.

(Target rotation angle correction process)
Next, processing for correcting the target rotation angle θ1 based on the first correction table T1 or the second correction table T2 will be described. First, the command generator 22 of the main controller 20 in the robot controller RC selects whether the correction table to be referred to is the first correction table T1 or the second correction table T2. When the command generating unit 22 drives each movable member according to the teaching program P, the command generating unit 22 selects the first correction table T1 as a correction table to be referred to. When each movable member is driven according to another teaching program not associated with the first correction table T1, and when each movable member is operated without following the teaching program, the second correction table is used as a correction table to be referred to. Select T2. After selecting the correction table to be referred to, the processing of the main control unit 20 proceeds to step ST30 shown in FIG. In the following description, correction processing of the target rotation angle θ1 in the output shaft 10a of the servomotor 10 that drives the first arm C3 will be described, but the same applies to other movable members.

  In step ST30, the command generation unit 22 of the main control unit 20 sets the target rotation angle θ1 of the output shaft 10a of the servomotor 10. Specifically, for example, when the first arm C3 is driven according to the teaching program P, the target rotation angle θ1 is set according to the teaching program P. Further, for example, when the first arm C3 is driven without following the teaching program P, the target rotation angle θ1 is set according to the information input by the operator on the robot control device RC or the operation device connected to the robot control device RC. Set. Thereafter, the process of the main control unit 20 proceeds to step ST31.

  In step ST31, the command generation unit 22 of the main control unit 20 sets the target rotation angle θ1 set in step ST30 in the motor rotation angle α stored in the first correction table T1 or the second correction table T2 to be referred to. It is determined whether there is an identical thing. Specifically, for example, as shown in FIG. 4, the motor correction angle α is stored for each pulse in the first correction table T1. Therefore, when referring to the first correction table T1, it is determined that there is the same motor rotation angle α regardless of what target rotation angle θ1 is set. On the other hand, for example, as shown in FIG. 5, the second correction table T2 stores the motor rotation angle α every 10 pulses. Therefore, when referring to the second correction table T2, it may be determined that there is the same motor rotation angle α, or it may be determined that there is no same motor rotation angle α.

  When it is determined that there is the same motor rotation angle α (YES in step ST31), the process of main control unit 20 proceeds to step ST32. In step ST32, the command generation unit 22 of the main control unit 20 reads from the storage unit 25 the correction angle Δ associated with the motor rotation angle α determined to be the same as the target rotation angle θ1. Then, the command generation unit 22 performs correction by adding the read correction angle Δ to the target rotation angle θ1 set in step ST30, and calculates the correction target angle θ2. Specifically, as shown in FIG. 4, when the motor rotation angle α determined to be the same as the target rotation angle θ1 is “33”, the command generation unit 22 sets “2” as the correction angle Δ. "Is read out. Then, the command generation unit 22 adds the correction angle “2” to the target rotation angle “33” to calculate the correction target angle “35”. In subsequent step ST34, the command generator 22 generates a position command S1 based on the corrected target angle θ2.

  On the other hand, when it is determined that there is no same motor rotation angle α (NO in step ST31), the process of main control unit 20 proceeds to step ST33. In step ST33, the command generation unit 22 of the main control unit 20 is closest to the motor rotation angle α corresponding to the target rotation angle θ1 within a predetermined range (for example, ± 10 °) centered on the target rotation angle θ1. The motor rotation angle α is determined. If there are two closest motor rotation angles α, the smaller motor rotation angle α is determined as the corresponding motor rotation angle α. When the closest motor rotation angle α can be determined, the motor rotation angle α corresponding to the target rotation angle θ1 is stored in the storage unit 25. Then, the correction angle Δ associated with the motor rotation angle α determined to be the closest is read from the storage unit 25. The command generation unit 22 corrects by adding the read correction angle Δ to the target rotation angle θ1 set in step ST30, and calculates the correction target angle θ2. Specifically, as shown in FIG. 5, when the target rotation angle θ1 is “19”, the closest motor rotation angle α stored in the second correction table T2 is the motor rotation angle “20”. It is. When the motor rotation angle α determined to be closest is “20”, the command generation unit 22 reads “2” as the correction angle Δ. Then, the command generation unit 22 adds the correction angle “2” to the target rotation angle “19” to calculate the correction target angle “21”. In subsequent step ST34, the command generator 22 generates a position command S1 based on the corrected target angle θ2. These series of processes are executed each time the command generation unit 22 of the main control unit 20 sets a new target rotation angle θ1. When the storage unit 25 does not store the motor rotation angle α corresponding to a predetermined range centered on the target rotation angle θ1, the command generation unit 22 does not correct the target rotation angle θ1. .

(Operation of robot controller)
The operation of the above embodiment will be described while comparing the robot control device RC that corrects the target rotation angle θ1 with the correction angle Δ as described above and the robot control device that does not correct the target rotation angle θ1. .

  For example, as shown in FIG. 2, it is assumed that the operator has created a teaching program P in which the tip position of the welding torch C9 reaches from point A to point C through point B. At this time, the operator operates the robot R while visually observing the tip of the welding torch C9 or detecting it with a sensor, and positions the tip of the welding torch C9 at points A, B, and C. Therefore, at each of the points A, B, and C, it is between the motor rotation angle α of the output shaft 10a of the servo motor 10 and the reduction gear rotation angle β1 (converted angle β2) of the output shaft 11a of the reduction gear 11. Regardless of whether or not there is a deviation, the tip position of the welding torch C9 coincides with the points A, B and C. On the other hand, the movement trajectory from point A to point B and the movement trajectory from point B to point C are automatically calculated by the main controller 20 of the robot controller RC. Therefore, even if there is a deviation between the motor rotation angle α and the reduction gear rotation angle β1 (converted angle β2) due to deformation of the servo motor 10, the reduction gear 11, and each movable member, etc. automatically The shift is not reflected in the calculated movement trajectory between the points. Therefore, ideally, the movement trajectory between the points becomes linear, but when the robot is actually driven by the robot control device that does not correct the target rotation angle θ1, as shown by the one-dot chain line in FIG. The movement trajectory between the points may be wavy or arcuate. In FIG. 2, the shift is exaggerated.

  In this regard, in the robot control device RC of the above-described embodiment, the robot R is actually driven to calculate the deviation between the motor rotation angle α and the reduction gear rotation angle β1 (converted angle β2). It is stored as the correction angle Δ in the correction table T1. By correcting the target rotation angle θ1 with this correction angle Δ, a deviation when the robot R is actually driven can be suppressed.

  Further, without following the teaching program P, for example, an operator may input coordinates with the robot controller RC or the operating device, and move the tip position of the welding torch C9 on the coordinates. Even in this case, when the robot R is actually driven, the tip position of the welding torch C9 is input due to the deviation between the motor rotation angle α and the reduction gear rotation angle β1 (converted angle β2). It may deviate from the coordinates. In this regard, in the above embodiment, the deviation between the motor rotation angle α and the reduction gear rotation angle β1 (converted angle β2) when the robot R is actually driven is stored as the correction angle Δ in the second correction table T2. is doing. By correcting the target rotation angle θ1 with this correction angle Δ, a deviation when the robot R is actually driven can be suppressed.

(Features and effects of the robot control device)
The characteristics of the robot control device RC of the above embodiment will be described together with the effects thereof.
(1) In the above embodiment, if the motor R 12 and the speed reducer encoder 13 are built in the robot R, the target rotational angle θ1 is set based on the deviation between the motor rotational angle α and the speed reducer rotational angle β1. The correction angle Δ can be calculated. In addition to the calculation of the correction angle Δ, the motor encoder 12 and the speed reducer encoder 13 can be used for position control of each movable member of the robot R. Therefore, it is not necessary to prepare an external device only for grasping the deviation between the motor rotation angle α and the reduction gear rotation angle β1, and the external device is attached or installed every time the deviation is to be grasped. There is no need to do. As a result, in the above embodiment, the deviation between the motor rotation angle α and the reduction gear rotation angle β1 can be grasped as the correction angle Δ more easily.

  (2) The deviation between the motor rotation angle α and the speed reducer rotation angle β1 can also occur, for example, when the weight of each movable member acts on the speed reducer 11 or the like and the speed reducer 11 is elastically deformed. The degree of elastic deformation of the speed reducer 11 varies depending on the posture of each movable member. In this regard, in the above embodiment, the correction angle Δ when the robot R is actually driven according to the teaching program P is stored as the first correction table T1. Therefore, the deviation between the motor rotation angle α and the reduction gear rotation angle β1 due to the action of the weight of each movable member can be reflected in the correction angle Δ, and more accurate correction of the target rotation angle θ1 can be performed. It becomes possible.

  (3) In the above embodiment, even when the robot R is not driven according to the teaching program P, the target rotation angle θ1 can be corrected using the correction angle Δ stored as the second correction table T2. That is, as long as it is within the angle range stored as the motor rotation angle α in the second correction table T2, the correction angle Δ stored as the second correction table T2 does not select the situation to be applied, and is generally used as a target. It can be used to correct the rotation angle θ1.

  (4) In the above embodiment, the correction angle Δ is stored for each pulse of the motor rotation angle α in the first correction table T1 corresponding to the teaching program P. By storing the correction angle Δ for each finer unit angle in this way, the accuracy of the correction of the target rotation angle θ1 can be ensured. On the other hand, since the driving range of the first arm C3 that operates according to the teaching program P is limited, the capacity of the storage unit 25 of the main control unit 20 is limited even if the correction angle Δ is stored for each fine unit angle. The possibility of doing is small.

  (5) In the above embodiment, for the general-purpose second correction table T2 that does not correspond to the teaching program P, the correction angle Δ is stored for every 10 pulses of the motor rotation angle α larger than the unit angle in the first correction table T1. To do. If the correction angle Δ is stored for each relatively large unit angle in this way, the second correction table T2 is stored even when the correction angle Δ is stored corresponding to a relatively wide range. It is possible to reduce the storage capacity required for the storage.

(Example of change)
The above embodiment can be modified as follows. In addition, it can also apply combining each modification example suitably.

  The aspect of the robot R is not limited to that of the above embodiments. For example, the number of movable members C2 to C8 is not limited to seven, and may be six or less or eight or more. Further, the movable members C2 to C8 are not limited to those that perform a turning operation, and may be those that slide, for example.

  The motor encoder 12 and the speed reducer encoder 13 are not limited to the increment encoder as long as the rotation angle of each output shaft can be detected. For example, an absolute encoder may be applied as the motor encoder 12 and the reduction gear encoder 13.

  A plurality of speed reducers may be connected in series to the output shaft 10a of the servo motor 10. For example, a first speed reducer may be connected to the output shaft 10a of the servo motor 10, and a second speed reducer may be connected to the output shaft of the first speed reducer. In this case, if the rotation of the output shaft of the second speed reducer is detected by the speed reducer encoder, a deviation between the rotation angle of the output shaft of the first and second speed reducers and the motor rotation angle α can be detected. it can.

  In the embodiment described above, one pulse of the motor rotation angle α (numerical value “1”) corresponds to the rotation angle 1 ° of the output shaft 10a of the servo motor 10. However, this is merely an illustrative example. It is. In general, for example, several tens to several hundreds of pulses of the motor rotation angle α often correspond to a rotation angle of 1 ° of the output shaft 10 a of the servo motor 10. Of course, as exemplified in the embodiment, one pulse (numerical value “1”) of the motor rotation angle α may correspond to the rotation angle 1 ° of the output shaft 10 a of the servo motor 10.

  The correction angle Δ (correction table) may not be stored corresponding to all the movable members C2 to C8. For example, depending on the positions of the movable members C2 to C8 and the configurations of the servo motor and the speed reducer, there may be a case where a deviation is not easily generated between the motor rotation angle α and the speed reducer rotation angle β1. For such a movable member, the correction angle Δ (correction table) may not be stored and the target rotation angle θ1 may not be corrected.

  Only one of the first correction table T1 and the second correction table T2 may be stored in the storage unit 25 in the robot control device RC. If the robot R is mostly operated according to the teaching program P, the second correction table T2 may not be stored. Conversely, if the robot R is rarely operated according to the teaching program P, the first correction table T1 is not necessary. May not be stored. That is, a correction table to be stored may be determined according to the operation mode of the robot R to be controlled.

  Even when the robot R is operated according to the teaching program P, the target rotation angle θ1 may be corrected using the correction angle Δ stored as the second correction table T2.

  When a plurality of teaching programs P are stored in the storage unit 25 in the robot controller RC, the first correction table T1 may be stored corresponding to each of all the teaching programs P, or a plurality of teaching programs The first correction table T1 may be stored corresponding to a part of P.

  In the case where the correction angle Δ is stored in the storage unit 25 of the robot controller RC, the storage mode is not limited to the correction table mode illustrated above. For example, if the relationship between the change in the motor rotation angle α and the change in the correction angle Δ has regularity, the regularity may be stored as an equation. Even when mathematical expressions are stored in this way, it can be said that the motor rotation angle α and the correction angle Δ are associated with each other.

  In the calculation process of the second correction table T2, the turning range of the first arm C3 can be changed as appropriate. If the first arm C3 is driven to turn, it can be set as appropriate as long as each movable member does not interfere with other devices, the ground, etc., and within a range in which excessive stress is not applied to the cables connected to the robot R. Good.

  In the calculation process of the second correction table T2, a reference position where a movable member other than the target movable member is moved can be set as appropriate. For example, when the first arm C3 is turned, a position where the movable member does not interfere with the ground or the like may be set as the reference position. It is also possible not to set the reference position. If the reference position is not set, the position and posture of each movable member may be different for each calculation process of the second correction table T2, but the reduction gear or the like is deformed due to the weight of each movable member. If it is difficult, there will be no problem.

  In the first correction table T1 and the second correction table T2 in the above embodiment, the unit angle of the motor rotation angle α can be changed as appropriate. For example, the motor rotation angle α and the correction angle Δ may be stored for every 10 pulses in the first correction table T1, or the motor rotation angle α and the correction angle Δ for each pulse may be stored in the second correction table T2. Also good. Further, the unit angle need not be constant and can be changed in the middle. For example, in the first correction table T1, the motor rotation angle α and the correction angle Δ are stored for each pulse when the tip position of the welding torch C9 is in the range from point A to point B, and in the range from point B to point C. The motor rotation angle α and the correction angle Δ may be stored every 10 pulses.

  In the above-described embodiment, the correction table calculation process and the target rotation angle correction process have been described separately, but these may be performed simultaneously. For example, when the robot R is operated according to the teaching program P, the target rotation angle θ1 is corrected using the first correction table T1 already stored in the storage unit 25 of the robot controller RC. At the same time, the difference between the motor rotation angle α and the reduction gear rotation angle β1 is calculated as the correction angle Δ, and a new first correction table T1 is stored. In this way, in the case where the robot R repeatedly performs the same operation according to the teaching program P, the robot R is operated after the next time while correcting the target rotation angle θ1 with the first correction table T1 stored in the previous operation. A new first correction table T1 that can be used when operating is stored.

(Addition of technical thought)
The technical ideas that can be derived from the above-described embodiments and modified examples are added below.
The command generation unit corrects the target rotation angle with the correction angle stored as the second correction data when setting the target rotation angle without being based on the teaching program.

  The robot has a plurality of movable members, and the first correction data and the second correction data are stored in the storage unit for each movable member.

  R ... Articulated robot, RC ... Robot control device, 20 ... Main control unit, 21 ... Calculation unit, 22 ... Command generation unit, 23 ... Calculation unit, 25 ... Storage unit, P ... Teaching program, T1 ... First correction Table, T2 ... second correction table, S1 ... position command, .alpha .... motor rotation angle, .beta.1 ... speed reducer rotation angle, .beta.2 ... converted angle, .DELTA.

Claims (2)

A robot control device for controlling a robot, in which an output shaft of a servo motor is drivingly connected to a speed reducer, and a movable member is driven in accordance with rotation of the output shaft of the speed reducer,
A command generation unit that sets a target rotation angle for rotating the output shaft of the servo motor and generates a position command based on the target rotation angle;
Between the motor rotation angle indicating the rotation angle of the output shaft in the servomotor rotated in response to the position command and the reduction gear rotation angle indicating the rotation angle of the output shaft in the reduction gear rotated in response to the position command A calculation unit for calculating a correction angle indicating a deviation of
A storage unit that associates and stores the calculated correction angle and the motor rotation angle when the correction angle is calculated;
The storage unit stores a teaching program for driving the movable member from the first operation position to the second operation position,
The calculation unit includes a first angle range from a motor rotation angle when the movable member is positioned at the first operation position according to the teaching program to a motor rotation angle when the movable member is positioned at the second operation position. And calculating the correction angle for each unit angle,
The storage unit stores the correction angle calculated for each unit angle in the first angle range as first correction data in association with the teaching program,
When the command generation unit newly sets a target rotation angle based on the teaching program , the command generation unit sets the target rotation angle at a correction angle corresponding to the target rotation angle stored as the first correction data in the storage unit. A robot control device that corrects and generates the position command based on the corrected target rotation angle. Comprising a plurality of the movable members;
The calculation unit rotates the motor while stopping other movable members in a second angle range that is a range of a motor rotation angle when a single movable member is driven over a predetermined movable range. Calculate the correction angle for each unit angle of the angle,
The storage unit stores a correction angle calculated for each unit angle in the second angle range as second correction data ,
When the command generation unit newly sets a target rotation angle, and the motor rotation angle corresponding to the target rotation angle is stored as the second correction data in the storage unit, the motor rotation angle 2. The robot control device according to claim 1 , wherein the target rotation angle is corrected with a correction angle associated with, and the position command is generated based on the corrected target rotation angle .

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