JP2013244540A - Gravity slope correcting method and device of industrial robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate a deflection correction by the aging of a joint axis without measuring an actual angle.SOLUTION: With respect to a multi-jointed robot 1 equipped with a position command section 81 that outputs position command values θn of gravity axes 20, 30, 50 to which loads in a direction of gravity are applied, a load torque calculation section 85 that computes load torque τ(θn), a slope correction calculation section 86 that multiplies load torque by spring constant K (n) to obtain a correction amount dθn by deflection, and a command value correction section 87 that adds the correction amount to the position command value for outputting to a servomotor, an angle confirmation position set at a predetermined angle is installed on the gravity axis, while positioning is performed so that the gravity axis comes to be identical with the angle confirmation position, whereas a difference dθ(n, i) between a confirmation position command value θ(n, i) and a theoretical position command value θtn is divided by a confirmation position negative torque τn to obtain a value as a spring constant K (n) for storage, then a negative torque is calculated from the position command value of the gravity axis at a negative torque calculation section, and the negative torque is multiplied by the spring constant so as to correct the slope in the direction of gravity.

Description

  The present invention relates to a gravitational deflection angle correction method and apparatus for an industrial robot system capable of accurately correcting a position shift caused by joint deflection in an industrial robot even when aged deterioration occurs.

  As shown in FIG. 1, in the vertical articulated robot 1, gravity acts in the rotation direction of each joint (axis) 20, 30, 50, so the joints are caused by the weight of the arms (links) 21-61 and the end effector 70. Even if the deflection occurs in the part and the position (angle) command value θn (n = 20, 30, 50) to the servo motor is the target (two-dot chain line in FIG. 1), the position of the movable arm is the target. Θ (n, i) deviated from the position (dotted line in FIG. 1). Therefore, the positional deviation dθn due to the influence of the reduction gear of the joint portion of the robot or the deflection of the arm is corrected.

  However, when it has been operating for many years, the joints of robots composed of mechanical elements such as gears and bearings undergo secular changes such as an increase in gaps in the mechanical elements due to wear, etc., and the flexure is as shown by the solid line in FIG. The quantity θ (n, i) increases. For this reason, it is necessary to correct the deflection amount dθ (n, i) according to the secular change. Therefore, in Patent Document 1, the deflection angle due to secular change is estimated and calculated from the load torque applied during operation of each robot or joint, the servo torque command value, the integrated value of the operation time, and the like. By adding the deflection angle due to the estimated aging change to the position command value of the servo motor, the displacement of the position due to the deflection considering the aging change is corrected.

  However, this represents the secular change of the correction value of the joint as a function of any one of the integrated value of torque and servo torque and the operating time. For this reason, it is not suitable for industrial robots used under various conditions, and in some cases, there is a problem that deviation from the target position increases according to the number of years elapsed. For example, when the secular change is determined by the operating time, the correction amount is simply estimated according to the operating time. However, in a program in which the movement of a certain axis and the load torque are extremely small, there is a case where the progress of aging deterioration does not coincide with the aging deflection estimation formula obtained in advance. In this case, the correction amount becomes excessive or excessive, and the deviation from the target position increases. Also, when aged deterioration is estimated by torque integration, generally, wear of mechanical elements such as gears and bearings does not proceed with only applied torque, and the amount of rotation also has a large effect. For this reason, secular deflection cannot be accurately estimated only by the integrated value of torque and servo torque, so if the operating years become long, the difference between the estimation formulas of the actual machine's secular deflection and the secular deflection will occur, and the reverse In addition, there is a problem that the work quality of the robot is deteriorated by increasing the deviation from the target position.

  Therefore, in Patent Document 2, a deflection angle is calculated by multiplying a load torque corresponding to a position (angle) command value of each joint by a spring constant determined for each joint, and the calculated deflection angle is calculated as a servo motor. The deflection angle is corrected in addition to the position command value input to. The spring constant used at this time is the actual position (angle) of the joint to which the position (angle) command value is given from the control unit, and the deviation between the position (angle) command value and the actual position (angle) of the joint. A load (joint) torque applied to the joint at the amount and position (angle) command value is obtained, and the calculated deviation amount is divided by the joint torque and used as the spring constant. Then, by periodically calculating the spring constant of each joint, deflection correction is performed in accordance with the aging (time) change of the joint.

JP 2004-154879 A JP 2010-058256 A

  However, in Patent Document 2, in order to obtain a deviation amount, it is necessary to acquire (measure or detect) an actual position (angle) with respect to a position (angle) command value from the control unit to the servomotor of the joint. is there. This requires a position (angle) detector and is expensive. Furthermore, since it is not necessary to always calculate the spring constant, it is useless because it interferes with wiring and the like when there is no other use for the detector. Moreover, errors such as detector failure and wear occur due to aging. In the embodiment, measurement is performed at two positions, a vertical position and a horizontal position. For this reason, it is necessary to make the measurement place wide. Further, in the vertical position, there is a problem that measurement may be difficult due to the influence of backlash of mechanical elements such as gears. Moreover, although the spring constant is updated corresponding to the secular change, it does not touch on judging the life or abnormality of the mechanical element from the state of the spring constant.

  In view of the above-mentioned problems, the problem of the present invention is that it is not necessary to measure the actual position (angle), and it is easy to deflect even if the position shift due to the joint deflection in an industrial robot occurs over time. It is intended to provide a gravity deflection angle correction method and apparatus that can maintain the accuracy of correction and that can easily determine abnormality or the like.

In the present invention, a drive-side shaft, a servomotor attached to the drive-side shaft, and a driven-side shaft that is rotatable or swingable with respect to the drive-side shaft via the speed reducer. And a plurality of control units for driving the servo motor, one or more sets of gravity axes that are loaded in the direction of gravity in the axial rotation direction of the drive side and driven side axes, and the position (angle) of the gravity axis ) A position command unit that outputs a command value, a load torque calculation unit that calculates a load torque applied to the gravity axis from the position (angle) command value, and a position (angle) by deflection obtained by multiplying the load torque by a spring constant. A multi-joint robot comprising: a deflection angle correction calculation unit that sets a correction amount; and a command value correction unit that adds the position (angle) correction amount to the position command value and outputs the correction value to a servo motor of the gravity axis. ,
The gravitational axis is provided with an angle confirmation position set in advance at a predetermined angle, and the control unit aligns the gravitational axis to the angle confirmation position, and the confirmation position (angle) command value and the angle The value obtained by dividing the difference from the theoretical confirmation position (angle) command value at the confirmation position by the confirmation position load torque at the angle confirmation position is stored as a spring constant, and then the position (angle) command value of the gravity axis is stored. The load torque calculation unit calculates the load torque, and multiplies the load torque by the spring constant to provide a gravity deflection angle correction method for an articulated robot that corrects the deflection angle in the gravity direction. .

  That is, an angle confirmation position set in advance at a predetermined angle is provided on the gravity axis, which is a joint axis to which a gravity load is applied, and the control unit performs alignment so that the gravity axis becomes the angle confirmation position. The difference between the confirmation position (angle) command value from the control unit at this time and the theoretical confirmation position (angle) command value when there is no deflection can be used as the deflection correction amount. Therefore, the value obtained by dividing the deflection correction amount by the check position load torque is used as a spring constant, so that the deflection amount of each gravity axis (joint) is corrected by the same calculation as in the prior art. Whereas in Patent Document 2, the position based on the position command value is measured with a measuring instrument in order to obtain the spring constant, whereas in the present invention, the confirmation position is aligned and the measured value is used to measure the position. The spring constant can be calculated without any work.

  The predetermined angle confirmation position may be a position where gravity load is applied to some extent and the spring constant becomes an average value. In addition, the angle confirmation position is adjusted so that the alignment mark on the drive shaft side and the driven shaft side and pin holes are provided on both sides so that the pin holes match, and a pin that fits into the pin hole with a small gap is inserted The position where it can slide may be set as the confirmation position. Further, an alignment mark may be provided and further confirmed with a magnifying glass. Further, the mark may be measured from the outside of the robot with a laser measuring device or the like. Further, a plurality of confirmation positions may be provided in order to increase reliability.

  According to a second aspect of the present invention, the control unit according to the first aspect positions the gravity axis so as to be the angle confirmation position, and the load torque calculation unit determines the angle confirmation position of the gravity axis. The confirmation position load torque applied to the gravitational axis is calculated from the confirmation position (angle) command value at, or the gravitational axis is positioned at the angle confirmation position by the control unit, and the angle confirmation position of the gravitational axis is determined. The confirmation position load torque applied to the gravity axis is calculated from the theoretical confirmation position (angle) command value in FIG.

  The check position load torque is within the error range between the calculated load torque for the check position (angle) command value and the calculated load torque for the theoretical check position (angle) command value at the angle check position. May be used.

  According to a third aspect of the present invention, the confirmation position load torque is the load torque of the servo motor when the controller is positioned so that the gravity axis is at the angle confirmation position. The confirmation position load torque can be obtained from the calculated value, but can also be obtained from the servo motor current. When the load condition is changed by exchanging the end effector or the like, the confirmation position load torque can be directly obtained without setting the recalculation condition or the like.

  According to this correction method, the deflection of the gravity axis (joint) of the robot can be corrected using the latest spring constant by resetting (resetting) the spring constant at the confirmation position. On the other hand, replacement of the end effector is not frequently performed. Moreover, the secular change such as the gravity axis does not change in a short time, but spans several months to several years. In this case, in the correction method described above, the spring constant can be obtained, but the change state of the spring constant cannot be captured. In addition, when the end effector is replaced, the spring constant becomes a completely new value, so that the influence due to secular change cannot be determined.

Therefore, in the invention according to claim 4, the position of the gravitational axis is set to the angle confirmation position by the control unit at the time of alignment for obtaining the Nth (N is 0 or a positive integer) spring constant. The difference between the Nth confirmation position (angle) command value, which is the position command value when rotated in this manner, and the theoretical confirmation position (angle) command value at the angle confirmation position is divided by the confirmation position load torque. N-th spring constant, at least the N-th confirmation position command value and the N-th spring constant are stored,
After the Nth alignment, the N + 1 confirmed position (angle) command value, which is a position command when the control unit turns the shaft to the angle confirmed position, and the Nth position command A position difference is obtained from the value, and the position difference is divided by the confirmation position load torque to obtain an N + 1 spring constant difference,
Storing the sum of the Nth spring constant and the N + 1 spring constant difference as a new N + 1th spring constant;
Further, after the (N + 1) th alignment, an N + 2 confirmation position (angle) command value that is a position command when the shaft is rotated so as to be the angle confirmation position by the control unit; Find the position difference from the position command value,
Divide the position difference by the confirmation position load torque to obtain an N + 2 spring constant difference,
Storing the sum of the N + 1 spring constant and the N + 2 spring constant difference as a new N + 2 spring constant;
In the control of the articulated robot after the Nth alignment and before the N + 1 alignment, a spring constant of a deflection angle correction calculating unit that corrects a deflection angle in the gravity direction is set as the Nth spring constant.
In the control of the articulated robot after the N + 1th alignment and before the N + 2 alignment, a spring constant of a deflection angle correction calculating unit that corrects a deflection angle in the gravity direction is set as the N + 1th spring constant.
In the control of the articulated robot after the N + 2 alignment, the spring constant of the deflection angle correction calculation unit that corrects the deflection angle in the gravity direction is the N + 2 spring constant,
After that, the gravitational deflection angle correction method for the articulated robot, which is obtained from the position difference between the previous and current positioning and the spring constant difference, is used.

  In other words, the position difference between the confirmation position command values at the past and current confirmation positions is obtained, the position difference is divided by the confirmation position load torque to obtain the spring constant difference, and the spring constant difference is added to the previous spring constant. Find a new spring constant.

  In the invention described in claim 5, the initial value (N = 0) of the N-th alignment is set at the time of shipment or initial operation of the articulated robot. Thereby, an initial value in an actual operating state can be set and can be regarded as a secular change. Moreover, even after the operation, the subsequent secular change can be measured.

  According to a sixth aspect of the present invention, the initial value (N = 0) of the N-th alignment is theoretically rotated by the control unit so that the gravity axis is at the angle confirmation position. A value obtained by dividing the deflection amount theoretically obtained from the confirmation position (angle) command value and the confirmation position load torque by the confirmation position load torque is stored as a spring constant. Thereby, even if the end effector is exchanged, the secular change and the like can be obtained from the theoretical (calculated) spring constant.

  Furthermore, in the invention according to claim 7, when the operation time between the N-th and N + 1-th alignment is stored, and the value obtained by dividing the spring constant difference by the operation time exceeds a predetermined value The gravity deflection angle correction method for articulated robots is output as a signal. It is possible to detect when the difference in spring constant becomes large due to aging abnormality or failure.

In performing the gravity deflection correction method for such an articulated robot, in the invention according to claim 8, the drive side shaft, the servo motor attached to the drive side shaft, and the servo motor via the speed reducer A plurality of driven side shafts that are rotatable or swingable with respect to the driving side shafts, and a controller that drives the servo motor;
One or more pairs of gravitational axes that are loaded in the gravitational direction in the axial rotation direction of the drive side and driven side axes, a position command unit that outputs a position (angle) command value of the gravitational axis, and the position (angle) command A load torque calculation unit that calculates a load torque applied to the gravity axis from a value; a deflection angle correction calculation unit that multiplies the load torque by a spring constant to obtain a position (angle) correction amount by deflection; and the position (angle) correction. A command value correction unit that adds an amount to the position command value and outputs to the servo motor of the gravity axis, and an articulated robot comprising:
An angle confirmation position set in advance at a predetermined angle is provided on the gravity axis,
The control unit aligns the gravity axis so as to be at the angle confirmation position, and a confirmation position (angle) command value at the angle confirmation position of the gravity axis and a theoretical confirmation position (angle) at the angle confirmation position. A spring constant calculation unit having a value obtained by dividing a difference from a command value by a check position load torque at the angle check position as a spring constant; and a spring constant storage unit for storing the spring constant;
The load torque calculation unit calculates the load torque from the position (angle) command value of the gravity axis and multiplies the load torque by the spring constant of the spring constant storage unit to correct the deflection angle in the gravity direction. Provided is a gravity deflection angle correction device for an articulated robot having a section.

  In the invention described in claim 9, the confirmation position load torque is positioned by the control unit according to claim 1 so that the gravity axis is at the angle confirmation position, and the load torque calculation unit The confirmation position load torque applied to the gravity axis is calculated from the confirmation position (angle) command value at the angle confirmation position of the gravity axis, or from the theoretical confirmation position (angle) command value at the angle confirmation position of the gravity axis. A gravity deflection angle correction device for an articulated robot that calculates a check position load torque applied to the gravity axis.

  Furthermore, in the invention described in claim 10, the confirmation position load torque is set to the load torque of the servo motor when the controller is positioned so that the gravity axis is at the angle confirmation position.

In the invention according to claim 11, at the time of alignment for obtaining the Nth (N is 0 or a positive integer) th spring constant, the gravity axis is set to the angle confirmation position by the control unit. The difference between the Nth confirmation position (angle) command value, which is the position command value when rotated in this manner, and the theoretical confirmation position (angle) command value at the angle confirmation position is divided by the confirmation position load torque. A command storage unit that stores at least the Nth confirmation position command value, a spring constant storage unit that stores the Nth spring constant,
After the Nth alignment, the N + 1 confirmed position (angle) command value, which is a position command when the control unit turns the shaft to the angle confirmed position, and the Nth position command Find the position difference from the value,
Divide the position difference by the check position load torque to obtain an N + 1 spring constant difference,
A spring constant difference calculation unit that stores the sum of the Nth spring constant and the N + 1 spring constant difference in the storage unit as a new N + 1 spring constant;
Further, the spring constant difference calculating unit is an N + 2 confirmation position (angle) that is a position command when the control unit rotates the shaft to be the angle confirmation position after the N + 1th alignment. A position difference is obtained from the command value and the (N + 1) th position command value,
Divide the position difference by the confirmation position load torque to calculate an N + 2 spring constant difference;
The sum of the (N + 1) th spring constant and the (N + 2) spring constant difference is stored as a new (N + 2) spring constant in the spring constant storage unit. This is a gravitational deflection angle correction device for an articulated robot.

  Furthermore, in the invention described in claim 12, the gravitational deflection angle of the articulated robot in which the initial value (N = 0) of the N-th alignment is at the time of shipment or initial operation of the articulated robot. A correction device was used.

  According to a thirteenth aspect of the present invention, the initial value (N = 0) of the N-th alignment is theoretically rotated by the control unit so that the gravity axis is at the angle confirmation position. A value obtained by dividing the deflection amount theoretically obtained from the confirmation position (angle) command value and the confirmation position load torque by the confirmation position load torque is stored as a spring constant.

  In a fourteenth aspect of the present invention, an operation time storage unit that stores an operation time between the Nth and N + 1th alignment, and a value obtained by dividing the spring constant difference by the operation time is a predetermined value ( A gravity deflection angle correction device for an articulated robot having a signal output unit that outputs a signal when a threshold value) is exceeded.

  In the present invention, the gravitational axis is provided with an angle confirmation position set in advance at a predetermined angle, and the control unit aligns the gravitational axis to be the angle confirmation position, and the confirmation position command value and the theoretical confirmation position command value are Since the spring constant is obtained from the confirmation position load torque, the structure is simple and the secular error is not so great. Further, there is no need to always provide a position measuring device, and there is no need to consider the arrangement of wiring, detectors, and the like. Furthermore, it has an effect that the influence of the detector over time is small (claims 1 and 8).

  In the second and ninth aspects of the invention, the confirmation position load torque uses the load torque obtained from the confirmation position command value by the load torque calculation unit at the angle confirmation position or the theoretical confirmation position command value. It is sufficient to store the data in a table or the like without calculating each time, and the procedure can be simplified.

  Furthermore, in the inventions according to claims 3 and 10, since the confirmation position load torque at the angle confirmation position of the power shaft is the load torque of the servo motor, it is not necessary to input a recalculation condition or the like when the load condition is changed. This makes it easier to set the spring constant.

  In the inventions according to claims 4 and 11, since the difference between the spring constants is obtained by comparing the past and present confirmation position command values at the confirmation position, the secular change of the spring constant is captured. Can do. In addition, the latest spring constant can be obtained at the same time as obtaining the difference.

  Furthermore, in the inventions according to claims 5 and 12, the initial value of the confirmation position alignment can be taken as the time of shipment or the initial operation of the articulated robot, and can be regarded as a secular change from the start of the operation state. Judgment can be made according to driving.

  In the inventions described in claims 6 and 13, the deflection amount obtained from the confirmation position command value rotated so as to be the confirmation position and the theoretical confirmation position command value is calculated as the confirmation position load torque. The theoretical spring constant divided is taken as the spring constant. As described above, the secular change and the like can be obtained from the theoretical spring constant, so that the secular change can be evaluated even if the end effector is replaced.

  Further, in the inventions according to claims 7 and 14, the operation time during alignment is stored, and when the value obtained by dividing the spring constant difference by the operation time exceeds a predetermined value, a signal is output, Since the state of the difference can be determined, it is possible to detect an abnormality or failure due to secular change by the difference of the spring constant.

FIG. 5 is a schematic diagram showing a simplified state in which the position and posture of the vertical articulated industrial robot in the embodiment of the present invention has changed due to secular change. It is a fragmentary sectional view which simplifies and shows the joint structure of the industrial robot in embodiment of this invention. It is a partial side view which simplifies and shows the state which the bending | flexion generate | occur | produced in the joint part by the vertical articulated type industrial robot in embodiment of this invention by secular change. It is a partial side view which simplifies and shows position alignment of the movable side arm of a joint structure in embodiment of this invention, and a fixed side arm. It is a fragmentary sectional view which simplifies and shows the state which made the positioning operation | movement of the movable arm and fixed arm of the vertical articulated industrial robot in embodiment of this invention correspond using the positioning hole and the pin. It is a block diagram which simplifies and shows the function structure of the control part in 1st embodiment of this invention. It is a block diagram which simplifies and shows the function structure of the control part in 2nd embodiment of this invention. It is a block diagram which simplifies and shows the function structure of the control part in 3rd embodiment of this invention. It is a flowchart which shows the procedure which calculates | requires the spring constant which changed with age in 3rd embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As an example, an example applied to a 6-axis articulated industrial robot having a gravity axis will be described. As shown in FIG. 1, the articulated robot 1 has a turning shaft 3 perpendicular to the base 2, and a turning shaft 10, an arm (link) 11, and an arm 11 axis that rotate around the turning shaft 3. An oscillating shaft 20 and an arm 21 that oscillate in a right angle direction are provided. Further, an oscillating shaft 30 and an arm 31 oscillating in a direction perpendicular to the axis of the arm 21 are provided. Also, the pivot axis 40 and the arm 41 that rotate about the axis with respect to the arm 31 axis, the swing axis 50 and the arm 51 that swings in a direction perpendicular to the axis of the arm 41, and the axis about the axis of the arm 51 rotate. A turning shaft 60 and an arm 61 are provided. An end effector 70 such as a gripping device or a measuring device is attached to the tip of the arm 61.

  The arms 11, 21, 31, 41, 51, 61 are movable side (driven side shaft 20 b) arms that are rotatably supported by the respective axes (joints) 10, 20, 30, 40, 50, 60. Further, the turning shaft 3 is fixed to the arm 11 via the shaft 10 (the driving side shaft 20a), the arm 11 is fixed to the arm 21 via the shaft 20, and the arm 21 is arm 31 via the arm 30. The arm 31 is the fixed side of the arm 41 via the shaft 40, the arm 41 is the fixed side of the arm 51 via the arm 50, and the arm 51 is the fixed side of the arm 61 via the arm 60.

  As shown in FIG. 2, for example, the swing shaft 20 (30, 50) includes a drive side shaft 20a (30a, 50a) fixed to the arm 11 (21, 41) and a drive side shaft. And a follower connected to a movable arm 21 (31, 51) that is swingable with respect to the drive side shaft via a speed reducer 23. It consists of the side shaft 20b (30b, 50b). Furthermore, as shown in FIG. 1, each servo motor is connected to a control device 71 in which an arm control unit 80 that drives each servo motor 24 is incorporated. Here, the shafts 20, 30, and 50 are gravity axes on which a load in the direction of gravity is applied in the axial rotation direction of the driving side and driven side shafts.

  If the axes 10, 40, 60 are arranged on a straight line as shown in FIG. 1, they do not need to be gravity axes. However, depending on the posture of the robot, a load in the gravitational direction is applied to the axial rotation direction of the driving side and the driven side axis, and bending may not be ignored. In this case, it may be handled as a gravity axis.

  In the gravity axis of the present invention, angle confirmation positions 12 and 22 are set in advance at a predetermined angle. For example, as shown in FIGS. 2 and 3, the angle confirmation positions are provided with alignment holes 12 and 22 that can match each other's positions. As shown in FIGS. 4 and 5, the gravity axis 20 (30, 50) is rotated by the control unit 80, the pin 13 is inserted into the holes 12, 22, and the pins are aligned so as to be slidable. The position can be accurately aligned. The positioning means may be such a mechanical device or an electrical device such as a touch sensor or a proximity sensor. Further, a scale or the like may be provided.

  On the other hand, as shown in FIG. 6, the control unit 80 for controlling each gravity axis includes a position command unit 81 that outputs a position (angle) command value θn of the gravity axis, and a gravity axis from the position (angle) command value. A load torque calculation unit 85 is provided for calculating the load torque τ (θn) applied to the. A deflection angle correction calculation unit 86 that calculates a position (angle) correction amount dθn by deflection by multiplying the obtained load torque τ (θn) by a spring constant K (n), and a position (angle) correction amount dθn as a position command value. In addition to θn, a command value correction unit 87 is provided for outputting θ to the servo motor of the gravity axis. The spring constant K (n) is stored in the spring constant storage unit 88. General servo motor control is performed from the command value correction unit 87 to the servo motor 24, and a position loop 82, a speed loop 83, and a current loop 84 circuit are provided. The position loop 82 differentiates the signal from the servomotor position detector 25, the speed loop 83 differentiates the signal from the position detector 25, and the current loop 84 feeds back the signal from the current detector 84b.

  Furthermore, in the first embodiment of the present invention, a spring constant calculation unit 89 for calculating a spring constant K (n) to be stored in the spring constant storage unit 88 is provided. Further, the theoretical confirmation position command value θtn at the angle confirmation position is stored (96). The load torque calculation unit 85 can output the check position load torque τn in a state where the target gravity axis is aligned with the angle check position according to the command. A theoretical value indicated by a dotted line in FIG. 6 may be used as the confirmation position load torque. In the spring constant calculation unit 89, the difference between the confirmation position (angle) command value θ (n, i) at the angle confirmation position and the theoretical confirmation position (angle) command value θtn at the angle confirmation position dθ (n, i) = A value K (n) = dθ (n, i) / τn obtained by dividing θ (n, i) −θtn by the confirmation position load torque τn is output as a spring constant and stored in the spring constant storage unit 88. Yes.

  In the first embodiment, the spring constant K (n) can be easily obtained by positioning so as to be the angle confirmation position. The spring constant may be stored in the spring constant storage unit 88 until the next angle confirmation position is aligned, and the same deflection correction as that of the prior art may be performed.

  Next, a second embodiment of the present invention will be described. Parts similar to those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. As shown in FIG. 7, in the first embodiment, the confirmation position load torque τn is converted from the servo motor current value I into the load torque by the actual load torque calculation unit 97 and stored as the confirmation position load torque (98). .

  Next, a third embodiment of the present invention will be described. The feature of the third embodiment is that the aging time and the change situation are taken into consideration. Parts similar to those described above are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 8, in the third embodiment, the angle confirmation position command value θ (n, N at the previous angle confirmation position is further added to the above-described spring constant storage unit 88 and spring constant calculation unit 89 ′. ) Is stored, and a spring constant difference calculation unit 91 is provided. The spring constant difference calculation unit 91 calculates the command value θ (n, N) in the command storage unit 90 from the position command value θ (n, N + 1) when the shaft is turned to the angle confirmation position after the confirmation position alignment. ) Is obtained as a position difference Δθ (n, N + 1), and the position difference is divided by the confirmed position load torque τn to obtain a spring constant difference ΔK (n, N + 1). ) Is added to the spring constant difference ΔK (n, N + 1) and stored in the spring constant storage unit 88 as a new spring constant K (n).

  In addition, an operation time storage unit 92 that stores an operation time T from the previous time to the next angle confirmation position alignment is provided. This may be provided for each power shaft, or the entire operation time may be a common operation time. Further, a signal output unit 94 that outputs the signal 95 when the determined spring constant difference ΔK (n, N + 1) is divided by the operating time T and exceeds a predetermined value (threshold value) U recorded in the threshold value recording unit 93. Is provided.

  The third embodiment will be described. As described above, the deflection angle θ (n, i) to be corrected (where n is the axis number and i is the number of corrections) can be approximated by the spring constant multiplied by the confirmation position load torque τn. θ (n, i) = K (n, i) × τ (n), where the load torque is considered to be almost constant for simplicity. n corresponds to the gravity axes 20, 30, and 50, respectively.

  In order to determine the spring constant based on the difference of the present invention, first, as an initial value, confirmation positioning is performed as shown in FIG. 5 at the time of shipment or at the beginning of operation, and the deflection angle θ (n, i) is corrected, and the angle command value θ (n, i) is recorded in the command storage unit 90 as an initial value θ (n, N). The spring constant K (n) is stored in the spring constant storage unit 88 as an initial value, which is a value K (n, N) obtained by dividing the theoretical deflection angle θtn by the confirmation position load torque τn. When the angle confirmation position is reproduced at the time of shipment or at the beginning of operation, the alignment positions coincide as shown in FIG.

  However, due to the secular change due to operation, as shown by the solid line in FIG. 1, the rigidity of the joint portion decreases, the deflection angle increases, and becomes θ (n, i + 1). As shown in FIG. 4, a deviation occurs in the confirmation positioning means. A method for obtaining the spring constant of the actual joint (gravity axis) that has changed over time in this case will be described with reference to the flowchart of FIG.

As shown in FIG. 9, in the first step (S1), alignment similar to that described above is performed using alignment means provided in the indirect portion (axis). In the second step (S2), a confirmation position command value θ (n, N + 1) is acquired. Further, in the third step (S3), the difference between the confirmation position command value θ (n, N) at the time of the previous alignment recorded in the instruction storage unit 90 and the current confirmation position command value θ (n, N + 1). , And the deflection angle change amount Δθ (n, N + 1) is obtained.
Δθ (n, N + 1) = θ (n, N + 1) −θ (n, N) (Formula 1)
The deflection angle difference (amount of change) Δθ (n, N + 1) obtained here means a deflection angle that has increased due to secular change since the previous axis confirmation alignment.

  In the fourth step (S4), the load torque calculation unit 85 calculates the load torque τ (n) applied to the axis n at the confirmation position alignment from the confirmation position command value. Note that the load torque may be substantially constant and stored as a constant value without being calculated each time.

In the fifth step (S5), the deflection angle change amount Δθ (n, N + 1) with the load torque T (n).
To obtain a spring constant difference (amount of change) ΔK (n, N + 1).
ΔK (n, N + 1) = Δθ (n, N + 1) / T (n) (Formula 2)

In the sixth step (S6), the spring constant difference ΔK (n, N + 1) is added to the spring constant K (n, N) recorded in the spring constant storage unit 88;
The current spring constant K (n, N + 1) that has changed over time is used.
K (n, N + 1) = K (n, N) + ΔK (n, N + 1) (Equation 3)

  In the seventh step (S7), in order to set the current spring constant K (n, N + 1) obtained in the equations (3) and (S7) as a new spring constant, it is recorded in the spring constant storage unit 88 as N = N + 1. Used to calculate the deflection angle correction amount according to the change. This spring constant is used until the next update. Further, in order to set the confirmation position command value θ (n, N + 1) as a new confirmation position command value, N = N + 1 is recorded in the command storage unit 90. At the next (N + 2) alignment, the process returns to step 1 and is repeated.

  As described above, after the initial value is determined, the previous confirmation position command value stored in the command storage unit 90, the spring constant stored in the spring constant storage unit 88, and the subsequent confirmation position command value are expressed by Formulas 1 to 1. A new spring constant can be obtained by substituting into Equation 3.

Here, it will be described that in the sixth step, the current spring constant at which the secular change has progressed becomes K (n, N + 1) = K (n, N) + ΔK (n, N + 1) in (Expression 3). First, the initial state N =
The deflection angle θ (n, 0) of the zero axis can be expressed as (Equation 4) using the joint spring constant K (n, 0) in the initial state and the load torque T (n) applied to the shaft. .
θ (n, 0) = K (n, 0) × T (n) (Formula 4)

Next, the deflection angle θ (n, 1) increased as a result of secular change is an increment Δθ (n, 1) of the deflection angle to the deflection angle θ (n, 0) of the joint in the initial state as shown in (Equation 5). Can be represented.
θ (n, 1) = θ (n, 0) + Δθ (n, 1) (Formula 5)

Here, θ (n, 1) and Δθ (n, 1) are expressed by respective spring constants K (n, 1) and spring constant differences ΔK (n, 1), respectively (Equation 6) and (Equation 7). It becomes like this.
θ (n, 1) = K (n, 1) × T (n) (Expression 6)
Δθ (n, 1) = ΔK (n, 1) × T (n) (Expression 7)

Substituting these (Equation 4), (Equation 6), and (Equation 7) into (Equation 5) yields (Equation 8).
K (n, 1) × T (n) = K (n, 0) × T (n) + ΔK (n, 1) × T (n) (Equation 8)
By dividing both sides of (Expression 8) by the load torque T (n), (Expression 3) in the case of N = 0 is obtained. Therefore, the current spring constant K (n, N + 1) whose secular change has progressed by adding the change amount ΔK (n, N + 1) of the spring constant to the current spring constant K (n, N) as shown in (Equation 3). become.

  Furthermore, when the confirmation position is adjusted, the spring constant difference ΔK (n, N + 1) obtained by Equation 3 is divided by the operating time T stored in the operating time storage unit 92, and when a predetermined value U is exceeded, a signal is output. Maintenance and inspection are facilitated by outputting a signal 95 from the unit 94 and performing an alarm or emergency stop. Alternatively, it is possible to detect a confirmation failure of the confirmation position operation.

1 Articulated robot 12, 22 Angle confirmation position 20, 30, 50 Gravity axis (indirect)
20a, 30a, 50a Drive side shaft 20b, 30b, 50b Drive side shaft 23 Reducer 24 Servo motor 71 Controller 80 Control unit 86 Deflection angle correction calculation unit 81 Position command unit 85 Load torque calculation unit 86 Deflection angle correction calculation unit 87 Command value correction unit 88 Spring constant storage unit 89, 89 ′ Spring constant calculation unit 90 Command storage unit 91 Spring constant difference calculation unit 92 Operating time storage unit 93 Threshold recording unit 94 Signal output unit 95 Signal θn Position (angle) command value K (N), K (n, i) Spring constant ΔK (n, i) Spring constant difference θ (n, i) Confirmation position (angle) command value θtn Theoretical confirmation position (angle) command value dθn, dθ (n , I) Position (angle) correction amount Δθ (n, i) Position difference T Operating time τn Confirmed position load torque τ (θn) Load torque U Threshold

Claims (14)

A drive-side shaft, a servomotor attached to the drive-side shaft, a driven-side shaft that is rotatable or swingable with respect to the drive-side shaft via the reduction gear to the servomotor, and the servomotor A plurality of control units for driving the one or more gravitational axes that apply a load in the gravitational direction in the axial rotation direction of the driving side and driven side shafts, and a position (angle) command value of the gravitational axis is output. A position command unit that performs a load, a load torque calculation unit that calculates a load torque applied to the gravity axis from the position (angle) command value, and a deflection that is obtained by multiplying the load torque by a spring constant to obtain a position (angle) correction amount. An articulated robot comprising: an angle correction calculation unit; and a command value correction unit that outputs the position (angle) correction amount to the position command value and outputs it to the servo motor of the gravity axis,
The gravitational axis is provided with an angle confirmation position set in advance at a predetermined angle, and the control unit aligns the gravitational axis to the angle confirmation position, and the confirmation position (angle) command value and the angle The value obtained by dividing the difference from the theoretical confirmation position (angle) command value at the confirmation position by the confirmation position load torque at the angle confirmation position is stored as a spring constant, and then the position (angle) command value of the gravity axis is stored. A gravity deflection angle correction method for an articulated robot, wherein the load torque calculation unit calculates a load torque and multiplies the load torque by the spring constant to correct a deflection angle in the gravity direction.   The position of the gravity axis is set to the angle confirmation position by the control unit according to claim 1, and the gravity axis is determined from a confirmation position (angle) command value at the angle confirmation position of the gravity axis by the load torque calculation unit. The confirmation position load torque applied to the gravity axis is calculated or positioned so that the gravity axis becomes the angle confirmation position by the control unit, and the theoretical confirmation position (angle) command value at the angle confirmation position of the gravity axis is calculated. 2. The method of correcting a gravitational deflection angle of an articulated robot according to claim 1, wherein a confirmation position load torque applied to the gravity axis is calculated.   The method of correcting a gravitational deflection angle of an articulated robot according to claim 1, wherein the confirmation position load torque is a load torque of the servo motor when the control unit is positioned so that the gravity axis is at the angle confirmation position. A position command value when the gravity axis is rotated to be the angle confirmation position by the control unit at the time of alignment for obtaining the Nth (N is 0 or positive integer) spring constant. A difference between a certain Nth confirmation position (angle) command value and a theoretical confirmation position (angle) command value at the angle confirmation position is divided by the confirmation position load torque to obtain an Nth spring constant, and at least the Nth The confirmation position command value and the Nth spring constant are stored,
After the Nth alignment, the N + 1 confirmed position (angle) command value, which is a position command when the control unit turns the shaft to the angle confirmed position, and the Nth position command A position difference is obtained from the value, and the position difference is divided by the confirmation position load torque to obtain an N + 1 spring constant difference,
Storing the sum of the Nth spring constant and the N + 1 spring constant difference as a new N + 1th spring constant;
Further, after the (N + 1) th alignment, an N + 2 confirmation position (angle) command value that is a position command when the shaft is rotated so as to be the angle confirmation position by the control unit; Find the position difference from the position command value,
Divide the position difference by the confirmation position load torque to obtain an N + 2 spring constant difference,
Storing the sum of the N + 1 spring constant and the N + 2 spring constant difference as a new N + 2 spring constant;
In the control of the articulated robot after the Nth alignment and before the N + 1 alignment, a spring constant of a deflection angle correction calculating unit that corrects a deflection angle in the gravity direction is set as the Nth spring constant.
In the control of the articulated robot after the N + 1th alignment and before the N + 2 alignment, a spring constant of a deflection angle correction calculating unit that corrects a deflection angle in the gravity direction is set as the N + 1th spring constant.
In the control of the articulated robot after the N + 2 alignment, the spring constant of the deflection angle correction calculation unit that corrects the deflection angle in the gravity direction is the N + 2 spring constant,
4. The method of correcting a gravitational deflection angle of an articulated robot according to claim 1, wherein the spring constant is obtained from the position difference between the previous and current positioning and the spring constant difference.   5. The method of correcting a gravitational deflection angle of an articulated robot according to claim 4, wherein the initial value (N = 0) of the N-th alignment is a shipment time or an initial operation time of the articulated robot.   The theoretical confirmation position (angle) command value and the confirmation position where the initial value (N = 0) of the N-th alignment is rotated by the control unit so that the gravity axis becomes the angle confirmation position. The gravity deflection angle correction method for an articulated robot according to claim 4 or 5, wherein a value obtained by dividing a deflection amount theoretically obtained from a load torque by the confirmation position load torque is stored as a spring constant.   5. An operation time between the N-th and N + 1-th alignments is stored, and is output as a signal when a value obtained by dividing the spring constant difference by the operation time exceeds a predetermined value. The gravity deflection angle correction method for the articulated robot according to claim 6. A drive-side shaft, a servomotor attached to the drive-side shaft, a driven-side shaft that is rotatable or swingable with respect to the drive-side shaft via the reduction gear to the servomotor, and the servomotor A plurality of control units for driving the
One or more pairs of gravitational axes that are loaded in the gravitational direction in the axial rotation direction of the drive side and driven side axes, a position command unit that outputs a position (angle) command value of the gravitational axis, and the position (angle) command A load torque calculation unit that calculates a load torque applied to the gravity axis from a value; a deflection angle correction calculation unit that multiplies the load torque by a spring constant to obtain a position (angle) correction amount by deflection; and the position (angle) correction. A command value correction unit that adds an amount to the position command value and outputs to the servo motor of the gravity axis, and an articulated robot comprising:
An angle confirmation position set in advance at a predetermined angle is provided on the gravity axis,
The control unit aligns the gravity axis so as to be at the angle confirmation position, and a confirmation position (angle) command value at the angle confirmation position of the gravity axis and a theoretical confirmation position (angle) at the angle confirmation position. A spring constant calculation unit having a value obtained by dividing a difference from a command value by a check position load torque at the angle check position as a spring constant; and a spring constant storage unit for storing the spring constant;
The load torque calculation unit calculates the load torque from the position (angle) command value of the gravity axis and multiplies the load torque by the spring constant of the spring constant storage unit to correct the deflection angle in the gravity direction. Gravity angle correction device for articulated robot having a part.   The confirmation position load torque is determined by the control unit according to claim 1 so that the gravity axis is at the angle confirmation position, and the load torque calculation unit is configured to confirm a position (angle) of the gravity axis at the angle confirmation position. ) Calculate the confirmation position load torque applied to the gravity axis from the command value, or calculate the confirmation position load torque applied to the gravity axis from the theoretical confirmation position (angle) command value at the angle confirmation position of the gravity axis. The apparatus for correcting a gravitational deflection angle of an articulated robot according to claim 8.   9. The gravity deflection angle correction device for an articulated robot according to claim 8, wherein the confirmation position load torque is set as the load torque of the servo motor when the control unit is positioned so that the gravity axis is at the angle confirmation position. A position command value when the gravity axis is rotated to be the angle confirmation position by the control unit at the time of alignment for obtaining the Nth (N is 0 or positive integer) spring constant. A difference between a certain Nth confirmation position (angle) command value and a theoretical confirmation position (angle) command value at the angle confirmation position is divided by the confirmation position load torque to obtain an Nth spring constant, and at least the Nth A command storage unit for storing a confirmation position command value, a spring constant storage unit for storing the Nth spring constant;
After the Nth alignment, the N + 1 confirmed position (angle) command value, which is a position command when the control unit turns the shaft to the angle confirmed position, and the Nth position command Find the position difference from the value,
Divide the position difference by the check position load torque to obtain an N + 1 spring constant difference,
A spring constant difference calculation unit that stores the sum of the Nth spring constant and the N + 1 spring constant difference in the storage unit as a new N + 1 spring constant;
Further, the spring constant difference calculating unit is an N + 2 confirmation position (angle) that is a position command when the control unit rotates the shaft to be the angle confirmation position after the N + 1th alignment. A position difference is obtained from the command value and the (N + 1) th position command value,
Divide the position difference by the confirmation position load torque to calculate an N + 2 spring constant difference;
The sum of the (N + 1) th spring constant and the (N + 2) spring constant difference is stored as a new (N + 2) spring constant in the spring constant storage unit. The gravity deflection angle correction device for an articulated robot according to any one of claims 8 to 10, wherein the correction is made from:   12. The gravity deflection angle correction device for an articulated robot according to claim 11, wherein the initial value (N = 0) of the N-th alignment is a shipment time or an initial operation time of the articulated robot.   The theoretical confirmation position (angle) command value and the confirmation position in which the initial value (N = 0) of the N-th alignment is rotated by the control unit so that the gravity axis becomes the angle confirmation position. The gravity deflection angle correction apparatus for an articulated robot according to claim 11 or 12, wherein a value obtained by dividing a deflection amount theoretically obtained from a load torque by the confirmation position load torque is stored as a spring constant.   An operation time storage unit that stores an operation time between the Nth and N + 1th alignment, and a signal output when a value obtained by dividing the spring constant difference by the operation time exceeds a predetermined value (threshold value) The gravity deflection angle correction device for an articulated robot according to any one of claims 11 to 13, further comprising a signal output unit for performing the operation.

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