Robot control device

Abstract

The present invention provides a robot control device (1) comprising: a creep information storage unit (12) that stores the amount of deflection caused by creep deformation on the robot in relation to the accumulated time; a zero-point calibration data storage unit (13) that stores the zero-point calibration data of the robot; a timer (11) that counts the accumulated time; and a correction unit (14) that corrects the zero-point calibration data stored in the zero-point calibration data storage unit (13) based on the amount of deflection stored in the creep information storage unit (12) in relation to the accumulated time counted by the timer (11). Thus, even when deflection caused by creep deformation occurs on the robot, the robot can perform actions with high precision.

Description

Technical Field

[0001] The invention relates to a robot control device. Background Art

[0002] As robots become lighter, in order to reduce the impact of increased deflection of the robot's mechanism on the robot's accuracy, the following robot control device is known: the deflection generated on the connecting rod is calculated based on the robot's kinematics, and the deflection of the entire robot is corrected and positioned at the target posture (for example, refer to patent document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 3808321 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, when the arm of the robot is made of a light material such as resin, in addition to the deflection caused by elastic deformation, deflection caused by creep deformation is also likely to occur over time. Even when deflection caused by creep deformation occurs, it is desirable to make the robot move with high precision. It is known that creep deformation increases not only over time, but also with the increase of ambient temperature or humidity and the increase of load.

[0008] Solutions to Solve Problems

[0009] One embodiment of the present invention is a robot control device, comprising: a creep information storage unit, which stores the deflection amount caused by creep deformation generated on the robot corresponding to the accumulated time; a zero point calibration data storage unit, which stores the zero point calibration data of the robot; a timer, which counts the accumulated time; and a correction unit, which corrects the zero point calibration data stored in the zero point calibration data storage unit based on the deflection amount stored in the creep information storage unit corresponding to the accumulated time counted by the timer. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic diagram showing a robot system including a robot control device according to an embodiment of the present invention.

[0011] Figure 2 Yes means Figure 1 Block diagram of the robot control device.

[0012] Figure 3 It means that the corresponding storage Figure 2FIG. 1 is a diagram showing an example of a table of accumulated time and deflection amount in a creep information storage unit included in a robot control device.

[0013] Figure 4 It means in Figure 1 A schematic diagram of an example of creep deformation occurring in a robot included in a robot system.

[0014] Figure 5 It means by Figure 1 Schematic diagram of the posture of the robot at the origin position before and after the correction unit of the robot control device corrects the zero point calibration data.

[0015] Figure 6 Yes means Figure 3 FIG. 4 is a diagram of a modified example of a table of .

[0016] Figure 7 Yes means Figure 2 A block diagram of a modified example of a robot control device.

[0017] Figure 8 It means by Figure 2 A schematic diagram of an example of mechanism parameters before and after calibration by a calibration unit of a robot control device.

[0018] Fig. 9 It means in Figure 1 Schematic diagram of the movement of the robot in which only the inertial force acts on the arm of the robot system.

[0019] Fig.10 It means in Figure 1 Schematic diagram of the robot system in which gravity acts on the robot arm in addition to inertial force.

[0020] Fig.11 Yes means Fig. 9 A graph showing the relationship between the time in the motion and the amount of deflection caused by creep deformation.

[0021] Fig.12 Yes means Fig.10 A graph showing the relationship between the time in the motion and the amount of deflection caused by creep deformation.

[0022] Fig.13 Yes Fig. 9 and Fig.10 A graph showing the integration of the deflection amount at each duration in the action.

[0023] Description of reference numerals:

[0024] 1: Robot control device (control device)

[0025] 11: Timer

[0026] 12: Creep information storage unit

[0027] 13: Zero point calibration data storage unit

[0028] 14: Correction Department

[0029] 15: Parameter storage unit

[0030] 20: Robot DETAILED DESCRIPTION

[0031] Hereinafter, a robot control device 1 according to an embodiment of the present invention will be described with reference to the drawings.

[0032] The robot control device 1 of this embodiment includes Figure 1 In the robot system 100 shown in FIG. 1 , the robot system 100 includes, for example, a vertical articulated robot 20 and a robot control device 1 connected to the robot 20. The type of the robot 20 is not limited to this.

[0033] like Figure 4 As shown, the robot 20 includes a base 21, a rotating body 22, a first arm 23, a second arm 24, and a wrist unit 25. The base 21 is set on the ground (installation surface) F. The rotating body 22 is supported to be able to rotate relative to the base 21 around a vertical first axis. The first arm 23 is supported to be able to rotate relative to the rotating body 22 around a horizontal second axis. The second arm 24 is supported to be able to rotate relative to the first arm 23 around a horizontal third axis and has a long axis. The wrist unit 25 is supported at the front end of the second arm 24. The reference numeral S in the figure is a tool.

[0034] The wrist unit 25 includes a first wrist element 26, a second wrist element 27, and a third wrist element 28. The first wrist element 26 is supported at the front end of the second arm 24 in a manner that allows rotation around a fourth axis along the long axis of the second arm. The second wrist element 27 is supported in a manner that allows rotation around the first wrist element 26. The third wrist element 28 is supported in a manner that allows rotation around the second wrist element 27. The second wrist element 27 is supported in a manner that allows rotation around a fifth axis that is orthogonal to the fourth axis. The third wrist element 28 is supported in a manner that allows rotation around a sixth axis that is orthogonal to the fifth axis and passes through the intersection of the fourth axis and the fifth axis.

[0035] like Figure 2 As shown, the robot control device 1 includes a timer 11 , a creep information storage unit 12 that stores creep information, a zero point calibration data storage unit 13 that stores zero point calibration data of the robot 20 , and a calibration unit 14 .

[0036] The timer 11 is activated when the robot 20 is set up, counts the cumulative time after the setting up, and outputs the counted cumulative time to the correction unit 14 .

[0037] The zero point calibration data is a value of an encoder that detects the rotation angle of each axis of the robot 20 when the robot 20 is arranged at the origin position.

[0038] The zero point calibration data storage unit 13 stores, for example, zero point calibration data generated by a zero point calibration operation performed after the robot 20 is manufactured. By performing the zero point calibration operation on each robot 20, the front end point of the tool S can be configured at a desired position even if the components of the robot 20 have dimensional errors due to individual differences.

[0039] like Figure 3 As shown, the creep information storage unit 12 stores the deflection amount caused by creep deformation and the accumulated time (accumulated time) in correspondence. The relationship between the deflection amount and the accumulated time can be obtained by experiments performed in advance. The creep information storage unit 12 stores the deflection amount and the accumulated time in correspondence through a table. In addition, it can also be stored through a map or an approximate formula instead of a table.

[0040] like Figure 4 As shown, on the robot 20, especially on the arms 23 and 24 on which gravity acts, creep deformation will occur over time. Figure 4 , the case where creep deformation occurs only on the second arm 24 is shown. The solid line in the figure represents the posture of the robot 20 at the origin before creep deformation occurs, and the dashed line in the figure represents the posture of the robot 20 at the origin after creep deformation occurs. The deflection amount is the deflection vector shown by the arrow in the figure.

[0041] When the arms 23 and 24 are made of a lightweight material such as resin, deflection due to creep deformation is likely to occur.

[0042] according to Figure 4 Before and after the creep deformation, the front end point of the tool S moves from the position marked with reference numeral A to the position marked with reference numeral A'.

[0043] The correction unit 14 corrects the leading end point of the tool S moved to the position of the reference numeral A' due to creep deformation to the position of the reference numeral A by correcting the zero point calibration data. Figure 5 In FIG. 1 , the solid line represents the posture of the robot 20 at the origin after the zero-point calibration data is corrected, and the dashed-dotted line represents the posture of the robot 20 at the origin before the creep deformation occurs.

[0044] The correction unit 14 receives the accumulated time input from the timer 11, and reads the deflection amount stored in the creep information storage unit 12 corresponding to the accumulated time at a predetermined time interval or as needed. When the correspondence between the accumulated time and the deflection amount stored in the creep information storage unit 12 is discrete data, the deflection amount can be calculated by simply storing the data. The correction unit 14 is composed of a processor.

[0045] Then, the correction unit 14 corrects the zero calibration data using the deflection amount read from the creep information storage unit 12 , and updates the zero calibration data stored in the zero calibration data storage unit 13 .

[0046] For example, in Figure 5 In the example shown, the angle of the first arm 23 relative to the rotating body 22 and the angle of the second arm 24 relative to the first arm 23 are changed by the angle required to return the position of the intersection of the fourth axis and the fifth axis, i.e., the center of the wrist, after creep deformation to the position before creep deformation. In this state, the angle of the second wrist element 27 relative to the first wrist element 26 around the fifth axis is also changed by the angle required to make the front end point of the tool S before and after creep deformation consistent. That is, the zero point calibration data is corrected by the correction unit 14 so that the posture after the angle of each axis is changed relative to the posture before creep deformation as described above becomes the posture of the origin position after creep deformation.

[0047] Thus, according to the robot control device 1 of the present embodiment, even if the deflection amount caused by creep deformation increases with the time after setting, the correction unit 14 will promptly correct the zero point calibration data based on the deflection amount stored corresponding to the accumulated time. Thus, it is possible to maintain the position accuracy of the origin of the tool S for operation, that is, the front end point of the tool S, well without using a fixture or the like to perform zero point calibration again.

[0048] In addition, in the robot control device 1 of the present embodiment, the cumulative time and the deflection amount are stored in correspondence in the creep information storage unit 12, but instead, Figure 6 As shown, the accumulated time and the deflection amount are stored in correspondence with each other according to the operating environment temperature.

[0049] When the robot 20 continuously operates in an environment where the operating environment temperature does not change, such as a clean room, the deflection amount corresponding to the accumulated time can be read based on the relationship between the accumulated time corresponding to the input operating environment temperature of the robot 20 and the deflection amount. The operating environment temperature can be input by an operator or detected by a thermometer provided in the robot control device 1.

[0050] In this manner, the deflection amount due to creep deformation that also varies depending on the operating environment temperature of the robot 20 can be estimated with higher accuracy, and the zero point calibration data can be corrected with higher accuracy.

[0051] Instead of or in addition to the operating environment temperature, the operating environment humidity may be used.

[0052] In addition, when the robot 20 performs an action in an environment where the action environment conditions such as the action environment temperature, the action environment humidity or the load acting on the robot 20 change, the timer 11 counts the duration and cumulative time of the action under each action environment condition, and the correction unit 14 can calculate the cumulative deflection by integrating the time change of the deflection amount within the cumulative time counted by the timer 11 and the increment of the deflection amount calculated based on the duration counted by the timer 11, and based on the calculated cumulative deflection amount, correct at least one of the zero point calibration data and the mechanism parameters.

[0053] For example, assuming that other operating environment conditions except the load are constant, repeatedly implement the following Fig. 9 The gravity does not act on the arms 23, 24, but only the inertial force acts on the arms 23, 24, and the Fig.10 In addition to the inertial force, gravity also acts on the arms 23 and 24 in action B. In this case, Fig.11 The relationship between time and the deflection amount caused by creep deformation when only action A is performed is shown in FIG. Fig.12 The relationship between the time and the deflection amount caused by creep deformation when only the action B is performed is stored in advance in the creep information storage unit 12 .

[0054] Then, the timer 11 counts the duration t1 and the accumulated time T1 of the action A, and the duration t2 and the accumulated time T2 of the action B.

[0055] Then, when the action A continues for a duration t1 and the accumulated time of the action A reaches T1, the creep information storage unit 12 reads Fig.11 The time change (slope) of the deflection amount at the accumulated time T1 is multiplied by the duration t1. Thus, the deflection amount δ1 within the duration t1 of the action A is calculated.

[0056] When the action B continues for a duration of t2 and the accumulated time of the action B reaches T2, the creep information storage unit 12 reads the creep information. Fig.12 The time change (slope) of the deflection amount at the cumulative time T2 is multiplied by the duration t2. Thus, the deflection amount δ2 within the duration t2 of action B is calculated. Fig.13As shown, the current deflection amount δ can be calculated by integrating these deflection amounts. The reference symbol K in the figure represents the initial deflection amount.

[0057] As the operating environment condition, the case where only the load acting on the robot 20 changes is exemplified, but the present invention is not limited to this and can be applied to a case where other operating environment conditions change or a case where one or more operating environment conditions change.

[0058] In addition, since the deflection amount caused by creep deformation also changes according to the mass and center of gravity of the tool S mounted on the front end of the robot 20 or the workpiece held by the tool S, or the mass and center of gravity of the peripheral device mounted on the arms 23 and 24, the relationship between the accumulated time and the deflection amount may be stored in advance in correspondence with these load information. The load information may be input by the user, or may be measured by the current value of the motor driving the second arm 24, or may be measured by the output of the torque sensor when the second arm 24 is equipped with a torque sensor.

[0059] In addition, in the present embodiment, the zero point calibration data is corrected based on the deflection amount stored in the creep information storage unit 12, but instead of or in addition to this, it is also possible to correct the zero point calibration data as follows: Figure 7 As shown, a parameter storage unit 15 for storing mechanism parameters is provided, and the mechanism parameters are corrected based on the deflection amount.

[0060] As the mechanism parameter, for example, the DH parameter representing the geometric state of each link of the robot 20 can be cited. When all the action axes of the robot 20 are rotation axes that make the links rotate relatively, the DH parameter of each action axis can be used as the mechanism parameter. Here, the DH parameter includes the distance between the links, the distance between the action axes, the angle between the links, the torsion angle of the links, etc. In addition, the number of the mechanism parameters that are the main factors that increase the positioning error is set to be consistent with the number of the action axes of the robot 20.

[0061] More specifically, if Figure 4 As shown in FIG. 1 , when deflection caused by creep deformation occurs only on the second arm 24, as shown in FIG. Figure 8 As shown, it can be considered that the offset of the second arm 24 is from L a0 Change to L a1 , the length of the second arm 24 is L b0 Change to L b1 .

[0062] In this case, if the displacement amount of the intersection of the fourth axis and the fifth axis before and after creep deformation is set to D, and the displacement angle is set to θ, it can be approximated as:

[0063] θ=sin -1 (D / Lb0 )

[0064] L b1 =L b0 cosθ

[0065] L a1 =L a0 -D.

[0066] Therefore, the DH parameter can be corrected using the length L of the second arm 24 after creep deformation. b1 and offset L a1 Then, by using the corrected DH parameters to perform inverse kinematics calculations to obtain the angles of each action axis, the tip of the tool S can be placed at the same position as before the creep deformation even after the creep deformation. This has the following advantages: even if the creep deformation increases, there is no need to perform zero point calibration again using a fixture, etc., and the position accuracy of the tip of the tool S can be well maintained.

[0067] In addition, in the present embodiment, the case where the zero point calibration data or the mechanism parameter is corrected based on the deflection amount corresponding to the elapsed time is exemplified, but instead, both the mechanism parameter and the zero point calibration data may be corrected.

[0068] For example, the change in the length and offset of the second arm 24 can be dealt with by correcting the DH parameters as described above. Figure 5 The angle of the second wrist element 27 relative to the first wrist element 26 can be addressed by correcting the zero point calibration data.

[0069] In addition, in this embodiment, as a typical case where deflection caused by creep deformation occurs, the second arm 24 that is always subjected to bending moment caused by gravity is exemplified. In addition, when the first arm 23 is in an operating environment subjected to bending moment in one direction, deflection caused by creep deformation can also be corrected in the same manner.

[0070] In addition, when the acceleration and deceleration directions of the rotation of each action axis are offset by the action program, the various parts of the robot 20 are subjected to bending moments caused by the inertia of the robot 20 and the tool S by continuing to execute the action program. Therefore, with regard to the bending moments caused by inertia to which the various parts of the robot 20 are subjected, it is sufficient to store the deflection amount corresponding to the elapsed time in advance according to the magnitude of the acceleration and deceleration.

[0071] Furthermore, the time during which the first arm 23 and the second arm 24 are subjected to acceleration and deceleration is accumulated, and the deflection amount stored corresponding to the accumulated time is read from the creep information storage unit 12. Thus, similar to the creep deformation caused by gravity, even in the case where the creep deformation caused by the acceleration rate increases, at least one of the zero point calibration data and the mechanism parameter is corrected, so that the position accuracy of the front end point of the tool S can be well maintained without the need to perform zero point calibration again using a fixture or the like.

Claims

1. A robot control device, characterized in that: have: a creep information storage unit for storing the deflection amount caused by creep deformation generated in the robot in correspondence with the accumulated time and the operating environment conditions of the robot; A zero point calibration data storage unit, which stores the zero point calibration data of the robot; A parameter storage unit, which stores the mechanism parameters of the robot; A timer for counting the accumulated time; as well as a correction unit that corrects at least one of the zero point calibration data stored in the zero point calibration data storage unit and the mechanism parameters stored in the parameter storage unit based on the deflection amount stored in the creep information storage unit corresponding to the cumulative time counted by the timer and the operating environment condition, The timer counts the duration of the action and the accumulated time according to each of the action environment conditions. The correction unit calculates the cumulative deflection amount by integrating the time change of the deflection amount within the accumulated time counted by the timer and the deflection amount calculated based on the duration counted by the timer, and corrects at least one of the zero point calibration data and the mechanism parameters based on the calculated cumulative deflection amount.

2. A robot control device, characterized in that: have: a creep information storage unit for storing the deflection amount caused by creep deformation generated in the robot in correspondence with the accumulated time and the operating environment conditions of the robot; A zero point calibration data storage unit, which stores the zero point calibration data of the robot; A timer for counting the accumulated time; as well as a correction unit that corrects the zero point calibration data stored in the zero point calibration data storage unit based on the deflection amount stored in the creep information storage unit corresponding to the cumulative time counted by the timer and the operating environment condition, The operating environment condition is at least one of the operating environment temperature of the robot, the operating environment humidity, and the load information acting on the robot. The timer counts the duration of the action and the accumulated time according to each of the action environment conditions. The correction unit calculates a cumulative deflection amount by integrating the deflection amount calculated based on the time change of the deflection amount within the cumulative time counted by the timer and the duration counted by the timer, and corrects the zero point calibration data based on the calculated cumulative deflection amount.

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