JP2019055456A - Robot controller - Google Patents

Abstract

To provide a robot controller capable of suppressing vibration of a robot without using an acceleration sensor.SOLUTION: A trajectory generation section 21 generates a speed pattern for moving a hand of an arm to a final target position when the final target position of the hand moved is given, and calculates an angle command value θn given to a servo mechanism 23 so that the hand is moved to the target position for each sampling period. A command value correction part 22 calculates a spring constant K of the arm according to a current position of the hand, calculates inertia I for a workpiece held by the arm and the hand, and calculates an acceleration ω (dot) when a command value changes for each of the sampling periods. When calculating a correction amount {Iω(dot)/K} of the command value from these values, the command value correction part corrects the command value θn based on the correction amount and outputs the corrected command value to the servo mechanism 23.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus for controlling the operation of a robot.

  Conventionally, an acceleration sensor that detects the acceleration amount is attached near the tip of the arm of the robot, and based on the acceleration amount detected by the acceleration sensor, the drive unit of each joint unit is controlled so as to suppress vibration generated at the tip of the arm. There is one that compensates a command value to be controlled (see Patent Document 1).

Japanese Patent Laid-Open No. 10-100085

  By the way, in the method using the acceleration amount detected by the acceleration sensor in this way, it is necessary to attach the acceleration sensor in the vicinity of the tip of the arm that actually generates vibration. However, when applied to an actual robot, the space for mounting the acceleration sensor in the vicinity of the tip of the arm, the wiring of the wiring to the acceleration sensor, and the like are problematic and difficult to realize.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a robot control apparatus that can suppress vibration of the robot without using an acceleration sensor.

  According to the robot control apparatus of the first aspect, the first axis that is perpendicular to the installation surface, the second axis that is perpendicular to the first axis, and a plurality of parts that are coupled to the second axis and thereafter. Of these axes, a robot having four or more axes including at least one axis parallel to the second axis is a control target. When a final target position for moving the hand of the arm is given, the speed pattern generation unit generates a speed pattern for moving the hand to the final target position. The command value calculation unit calculates a command value to be given to the servo mechanism so as to move the hand to the passing target position for each control cycle.

For a robot having an arm configured as described above, the entire arm is regarded as one spring,
A model in which “arm inertia” − “arm spring” − “work inertia” is connected can be assumed. In this case, “arm inertia” and “arm spring” change according to the position of the hand. When the arm is accelerated to move the work held by the hand, the movement of the tip side of the arm is delayed by inertial force, and when the arm is decelerated, the movement of the tip side is advanced. Thereby, vibration is generated.

  Therefore, the spring constant calculation unit calculates the spring constant of the arm according to the current position of the hand, and the inertia calculation also calculates the inertia for the arm and the work held by the hand according to the current position of the hand. To do. And an acceleration calculation part calculates the acceleration at the time of a command value changing for every control period. When the correction amount calculation unit calculates the correction amount of the command value from the spring constant, inertia, and acceleration, the command value correction unit corrects the command value based on the correction amount and outputs it to the servo mechanism.

  As a result, when the arm is accelerated, the command value is corrected so that the base side of the arm moves forward by the amount delayed, and when the arm is decelerated, the command value is corrected so that the base side of the arm is delayed by the amount advanced. Vibration is suppressed. Therefore, even if an acceleration sensor or the like is not attached to the tip of the arm, it is possible to suppress vibrations that occur when the work held by the arm is moved.

  According to the robot control device of the second aspect, the spring constant calculation unit calculates the spring constant of the entire arm, and the inertia calculation unit calculates the inertia including the entire arm and the workpiece. Thereby, the amount of calculation can be reduced and correction processing can be executed at high speed.

According to the robot control apparatus of the third aspect, the spring constant calculation unit uses the distance from the third axis to the hand as L ₃ , the distance from the first axis to the hand as L _f , and the first axis as a reference. Assuming that the spring constant up to the third axis is K ₁₂ and the spring constant up to the hand with respect to the third axis is K ₃ , the spring constant K used for obtaining the correction amount is expressed by the following equation 1 / K = {1 / K ₁₂ + L ₃ ² / (K ₃ L _f ² )}
Ask for. As a result, the spring constant K when the arm is integrally regarded as a spring can be quickly obtained.

  According to the robot control apparatus of the fourth aspect, the spring constant calculation unit calculates a spring constant based on each axis of the arm, and the inertia calculation unit calculates inertia based on each axis. Then, the correction amount calculation unit obtains a correction coefficient corresponding to each axis by dividing the inertia corresponding to each axis by the spring constant corresponding to each axis, and uses the one that indicates the maximum value among the correction coefficients. To determine the amount of correction applied to each axis. That is, the physical characteristics of each axis of the arm vary depending on the position in the rotational direction. However, if the correction coefficient corresponding to each axis is applied individually, the delay amount of each axis is greatly different, and there is a possibility that the initially planned movement trajectory of the hand cannot be maintained. Therefore, the correction amount calculation unit determines the correction amount to be applied to each axis using the correction coefficient that indicates the maximum value, thereby suppressing vibration within a range in which the movement locus can be maintained.

According to the robot control apparatus of the fifth aspect, the correction amount calculation unit calculates the spring constant by a linear approximation formula. For example, the spring constant K obtained by calculating as claimed in claim 3, a curve with respect to the square of the distance L _f. A first-order approximation can be performed without increasing the error for the section in which the range of values is divided into a plurality of ranges for the curve. Therefore, the spring constant K used for correction can be obtained more easily.

  According to the robot control apparatus of the sixth aspect, the command value correction unit performs a low-pass filter process on the corrected command value. Since the correction value includes acceleration as a parameter, there may be a case where a wide-range noise component is superimposed on the acceleration or the torque is saturated when the rise is steep. Therefore, it is possible to prevent the torque from being saturated by performing low-pass filter processing on the corrected command value.

  According to the robot control apparatus of the seventh aspect, the command value correction unit variably sets the cutoff frequency of the low-pass filter in accordance with a correction coefficient obtained by dividing the inertia by the spring constant. Thereby, the cutoff frequency can be appropriately set in consideration of the inertia and the spring constant.

Functional block diagram showing the configuration of the controller in the robot system according to the first embodiment Diagram showing the configuration of the robot system Diagram explaining robot model used for vibration suppression control The figure explaining the structure of the robot which applies this embodiment (the 1) The figure explaining the structure of the robot which applies this embodiment (the 2) The figure explaining the structure of the robot which applies this embodiment (the 3) Diagram explaining the principle of vibration suppression control The figure explaining derivation | leading-out of the formula which calculates | requires the spring constant K Flow chart showing details of vibration suppression control Time chart showing an angular velocity pattern to which the vibration damping control of the comparative example and this embodiment is applied Time chart showing an error between the target position and the actual hand position in the comparative example and this embodiment The flowchart which is 2nd Embodiment and shows the content of damping control The figure which is 3rd Embodiment and shows the curve which calculated | required the spring constant K by (7) Formula The figure which shows an example which carried out the primary approximation of the spring constant K shown in FIG.

(First embodiment)
Hereinafter, the first embodiment will be described with reference to FIGS. 1 to 11. As shown in FIG. 2, the robot system 1 includes a vertical articulated robot 2, a controller 3 that controls the robot 2, and a pendant 4 that is connected to the controller 3. The robot system 1 is used for general industrial purposes.

  The robot 2 has a well-known configuration as a so-called 6-axis vertical articulated robot, and the shoulder 6 rotates on the base 5 in the horizontal direction via a first axis (J1) having an axis in the Z direction. Connected as possible. A lower end portion of a lower arm 7 extending upward is connected to the shoulder 6 via a second shaft (J2) having an axis in the Y direction so as to be rotatable in the vertical direction. A first upper arm 8 is connected to the tip of the lower arm 7 via a third axis (J3) having an axis in the Y direction so as to be rotatable in the vertical direction.

  The second upper arm 9 is connected to the tip of the first upper arm 8 via a fourth axis (J4) having an X-axis axis so as to be able to rotate. A wrist 10 is connected to the tip of the second upper arm 9 via a fifth axis (J5) having an axis in the Y direction so as to be rotatable in the vertical direction. A flange 11 is connected to the wrist 10 via a sixth shaft (J6) having an X-direction axis so as to be able to rotate.

  The base 5, shoulder 6, lower arm 7, first upper arm 8, second upper arm 9, wrist 10 and flange 11 function as the arm of the robot 2. As shown, a tool (not shown) for holding the workpiece 13 is attached. Each axis (J1 to J6) provided in the robot 2 is provided with a motor (not shown) serving as a drive source corresponding to each axis.

  The controller 3 is a control device for the robot 2 and controls the robot 2 by executing a computer program in a control means including a computer (not shown) including a CPU, ROM, RAM, and the like. Specifically, the controller 3 includes a drive unit configured by an inverter circuit or the like, and based on the rotational position of the motor detected by an encoder provided corresponding to each motor, for example, by feedback control. Drive the motor.

  The controller 3 includes a CPU, a ROM, a RAM, a drive circuit, a position detection circuit, and the like. The ROM stores system programs and operation programs for the robot 2. The RAM stores parameter values and the like when executing these programs. Detection signals from encoders (not shown) provided at the joints of the robot 2 are input to the position detection circuit. The position detection circuit detects the rotation angle position of the motor provided at each joint based on the detection signal of each encoder. As shown in FIG. 1, the controller 3 includes a trajectory generation unit 21, a command value correction unit 22, and a servo mechanism 23.

  The controller 3 calculates the target stop position of the hand, which is the tip of the sixth axis, based on the operation program of the robot 2 and the like. Then, the controller 3 calculates the target stop angle position of each axis based on the target stop position. The trajectory generation unit 21 generates an angular velocity pattern of each axis when changing the angular position of each axis to the target stop angle position based on the target stop angle position of each axis. The trajectory generation unit 21 calculates a command value θn that is the nearest target angular position of each axis based on the angular velocity pattern of each axis. The servo mechanism 23 corresponding to the drive control unit sets each motor to each drive torque so that the angle of each axis is set to the command value θn based on the angle θen of each axis detected by each encoder and the command value θn. Control by Tn. The command value correction unit 22 outputs a command value θn ′ obtained by correcting the command value θn to the servo mechanism 23. Details of the correction will be described later.

  In the present embodiment, the controller 3 regards the robot 2 as an operation model shown in FIG. 3 and executes vibration suppression control that suppresses hand vibration. As shown in the figure, a 6-axis robot 2 has a 6-axis arm connected to a first-axis motor at the base, and a work 13 is held at the tip of the arm. In this case, when the six-axis arm is viewed as one spring, it can be viewed as a model in which the inertia of the arm and the load inertia which is the work 13 are connected to the spring.

  Next, a robot arm structure to which this model can be applied will be described with reference to FIGS. FIG. 4 corresponds to the vertical 6-axis robot shown in FIG. 2, and includes a first axis perpendicular to the installation surface, a second axis perpendicular to the first axis, and the second and subsequent axes. Among the plurality of axes connected to each other, at least one of the axes is a robot having four or more axes including a third axis that is parallel to the second axis. FIG. 5 shows a vertical five-axis robot having a fifth axis corresponding to the sixth axis except for the fifth axis having the configuration shown in FIG. FIG. 6 shows a vertical seven-axis robot in which a seventh axis orthogonal to the second axis is added between the second axis and the third axis configured as shown in FIG. For these, the model shown in FIG. 2 can be similarly applied.

  FIG. 7 illustrates the principle of vibration suppression control according to the present embodiment, and shows control according to the present embodiment and a comparative example. In the drawing, the upper point corresponds to the base side of the arm and the motor side of the first shaft, and the lower point corresponds to the tip side and the load side, and the arm is simplified to only one link. The case where the base side moves linearly in the right direction in the figure by this model will be described. The upper diagram is a comparative example when the base side is simply moved, and the lower diagram is a case where the control principle of the present embodiment is applied.

  In the comparative example, when the base portion starts moving from the stopped state and accelerates in the right direction, an inertial force acts on the tip portion, and thus the movement is delayed by that amount. Conversely, when the base portion decelerates to stop from the moving state, the moving position advances by the amount of inertial force acting on the tip portion. And when a base part stops, the position of a front-end | tip part will return to the left direction from the position which advanced previously. Such movement causes vibrations in the arm.

  When the control principle of this embodiment is applied to the movement of this comparative example, when the base portion accelerates, the base portion is accelerated so that the movement of the tip portion is delayed. Further, when the base is decelerated, the base is decelerated so as to be delayed by the amount of advancement of the position of the tip. And when stopping a base, a base is moved according to the restoring force which a front-end | tip part tends to return to the left direction. By controlling in this way, the vibration of the arm is suppressed.

  Next, a method of obtaining the spring constant K used for actual control will be described with reference to FIG. The right point in the figure indicates the positions of the first axis and the second axis (J1, J2) of the 6-axis robot 2, the left point in the figure indicates the position of the hand, and the point between them is the third point. The position of the axis (J3) is shown.

In the XZ plane when the arm is viewed from the side, the distance from the first axis and the second axis to the third axis is L ₁ , the distance from the third axis to the hand is L ₃ , the first axis and the second axis _Let L _f be the distance from the hand to the hand. Further, in the XY plane of a state seen from above the arm, the angular deviation of the Y-axis direction of the third axis relative to the X-axis and [Delta] [theta] _12, of the hand relative to the X axis in the Y-axis direction the angle deviation and Δθ _3.

When inertial force F (= M · a) due to mass M and acceleration a acts on the hand, torque τ ₁₂ acting on the first axis and second axis, and torque τ ₃ acting on the third axis are respectively τ ₁₂ = L _f × F, τ ₃ = L ₃ × F (1)
It becomes.

Assuming that the spring coefficient of the hand with respect to the first axis and the second axis is K ₁₂ and the spring coefficient of the hand with respect to the third axis is K ₃ , the angle deviations Δθ ₁₂ and Δθ ₃ are
Δθ ₁₂ = τ ₁₂ / K ₁₂ , Δθ ₃ = τ ₃ / K ₃ (2)
The positional displacements ΔY ₁₂ and ΔY ₃ in the Y-axis direction are
ΔY ₁₂ = L _f × τ ₁₂ / K ₁₂ = L _f ² × F / K ₁₂
ΔY ₃ = L ₃ × τ ₃ / K ₃ = L ₃ ² × F / K ₃ (3)
It becomes.

The total position displacement ΔY _f is
ΔY _f = ΔY ₁₂ + ΔY ₃ = L _f ² × F / K ₁₂ + L ₃ ² × F / K ₃
= (L _f ² / K ₁₂ + L ₃ ² / K ₃ ) F (4)
It is. Further, from the equation (1), F = τ ₁₂ / L _f .
ΔY _f = (L _f ² / K ₁₂ + L ₃ ² / K ₃ ) τ ₁₂ / L _f (5)
It becomes.

Here, the total angle deviation Δθ _f is the angle deviation for each sampling period,
Since Δθ _f ≈0,
_{Δθ f ≒ tanΔθ f = ΔY f} / L f
= (L _f ² / K ₁₂ + L ₃ ² / K ₃ ) τ ₁₂ / L _f ²
= (1 / K ₁₂ + 1 / K ₃ × L ₃ ² / L _f ² ) τ ₁₂ (6)
It becomes. And since the inside of the parenthesis of the equation (6) is the reciprocal of the spring constant K,
1 / K = (1 / K ₁₂ + 1 / K ₃ × L ₃ ² / L _f ² ) (7)
It is. Thus, the spring constant K becomes a function depending on the rigidity of each axis, that is, the spring constants K ₁₂ and K ₃ and the reciprocal of the hand distance L _f . For the spring constants K ₁₂ and K ₃ , the rigidity values of the cross roller bearings used for the second and third axes are used, or values measured in advance are used. In the present embodiment, the spring constant K expressed by the equation (7) is used for vibration suppression control.

  FIG. 9 is a flowchart showing a procedure of vibration suppression control in the present embodiment. When the trajectory generating unit 21 acquires the angular position at the time of stopping the hand, which is the target position of each axis (S1), the trajectory generating unit 21 generates an angular velocity pattern of each axis based on the target position of each axis (S2). For example, a trapezoidal angular velocity pattern is generated like a commanded angular velocity indicated by a broken line in FIG. The “velocity” shown in each figure is an “angular velocity”. Further, the target position in step S1 corresponds to the final target position.

  Subsequently, the trajectory generation unit 21 calculates a target angle θ (n = 1 to 6) of each axis, which is a command value, based on the generated angular velocity pattern (S3). The target angle θn here corresponds to the target angle of the nth axis in the current control cycle, that is, the cycle of sampling the angle θen detected by each axis encoder. The trajectory generator 21 corresponds to a speed pattern generator and a command value generator.

Next, when the command value correction unit 22 obtains the target position P of the hand from the target angle of each axis (S4), it obtains the spring constant K corresponding to the target position P by the equation (7) and calculates the inertia I. Obtain (S5). Incidentally, when obtaining the target position P, is also required distance L ₃ and L _f is an operation parameter of equation (7). Inertia I is the product of the workpiece 13 and the mass and the distance L ₃ of the arm. The target position P corresponds to the passing target position. Subsequently, the angular acceleration ω (dot) during which each axis reaches the target angle is calculated from the velocity pattern of each axis (S6).

  Next, the command value correction unit 22 calculates an angle correction amount {Iω (dot) / K} (S7). That is, Δθ = T / K = I · dω / dt / K. When the correction command value θn ′ obtained by adding the correction amount {Iω (dot) / K} to the angle command value θn of each axis is calculated (S8), the correction command value θn ′ is subjected to low-pass filter processing ( S9) Transfer to the servo mechanism 23 (S10). Then, the process returns to step S3. The command value correction unit 22 corresponds to a spring constant calculation unit, an inertia calculation unit, an acceleration calculation unit, and a correction amount calculation unit.

  The reason why the low pass filter process is performed in step S9 is as follows. Since the angular acceleration ω (dot) is included as a parameter in the correction amount, the torque may be saturated when a wide-range noise component is superimposed on the angular acceleration or when the rise is steep. Therefore, the torque is prevented from being saturated by performing low-pass filter processing on the corrected command value. The cutoff frequency is, for example, about several Hz to several tens Hz.

  FIG. 10 is a time chart showing normal control as a comparative example and an angular velocity pattern according to the present embodiment. The broken line corresponds to the angular velocity pattern generated in step S2, and indicates the command angular velocity. The alternate long and short dash line indicates the angular velocity when the command value θ calculated in step S3 based on the generated angular velocity pattern is transferred to the servo mechanism 23 as it is. A solid line indicates an angular velocity when the vibration suppression control of the present embodiment is executed.

  As shown in the figure, at the time of starting acceleration from the stop state, the control of the present embodiment has an earlier timing for increasing the angular velocity than in the comparative example. This corresponds to (2) movement during acceleration shown in FIG. At this time, since the correction command value θ ′ is low-pass filtered in step S9, a rapid change in the correction command value θ ′ is suppressed. As a result, when the motors of the respective axes are controlled based on the correction command value θ ′, it is possible to prevent the angular velocity of the respective axes from changing suddenly.

  Further, at the time of transition from acceleration to constant speed, the timing at which the angular velocity becomes constant in the control of this embodiment is slower than in the comparative example. This corresponds to (3) movement during deceleration shown in FIG.

  Even at the time of transition from the next constant speed to deceleration, the control of the present embodiment allows the angular velocity to be lowered earlier than the comparative example, and even at the time of transition from the next deceleration to the end of movement. In the embodiment control, the timing at which the angular velocity decreases is slower than in the comparative example. This corresponds to the movement at (3) deceleration and (4) stop shown in FIG.

  FIG. 11 is a time chart simulating an error between the target position and the actual hand position in the comparative example and the present embodiment at the end of the movement. As indicated by the alternate long and short dash line in the figure, in the comparative example, the error from the target position is alternately changed between the negative side and the positive side, and the hand of the arm vibrates. On the other hand, as indicated by a solid line, in the control of this embodiment, the error with respect to the target position is close to zero. That is, the vibration of the hand is suppressed.

  As described above, according to the present embodiment, when the final target position for moving the hand of the arm is given, the trajectory generating unit 21 generates a speed pattern for moving the hand to the final target position, and the hand is sampled in the sampling period. An angle command value θn to be given to the servo mechanism 23 is calculated so as to move to each target position. The command value correction unit 22 calculates the spring constant K of the arm according to the current position of the hand, calculates the inertia I for the arm and the work held by the hand, and the command value changes every sampling cycle. The acceleration ω (dot) is calculated. When the command value correction amount {Iω (dot) / K} is calculated from these values, the command value θn is corrected based on the correction amount and output to the servo mechanism 23.

  As a result, when the arm is accelerated, the command value is corrected so that the base side of the arm moves forward by the amount delayed, and when the arm is decelerated, the command value is corrected so that the base side of the arm is delayed by the amount advanced. Vibration is suppressed. Therefore, it is possible to suppress vibration generated when the work 13 held by the arm is moved without attaching an acceleration sensor or the like to the tip of the arm.

  Further, since the command value correction unit 22 calculates the spring constant K of the entire arm and calculates the inertia I including the entire arm and the workpiece 13, the correction amount can be reduced and the correction process can be executed at high speed. Specifically, since the spring constant K is obtained by the equation (7), the spring constant K when the arm is integrally regarded as a spring can be quickly obtained. Thereby, the robot 2 can be operated at high speed.

  Further, the command value correction unit 22 performs a low-pass filter process on the corrected command value θn ′. As a result, it is possible to prevent the torque from being saturated even when a wide-range noise component is superimposed on the acceleration or the rise is steep.

(Second Embodiment)
Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, description thereof will be omitted, and different parts will be described. In the control of the second embodiment shown in FIG. 12, when step S4 is executed, the command value correction unit 22 obtains spring constants K1 to K6 and inertias I1 to I6 for each axis from the target position P (S11). . The spring constants K1 to K6 are calculated by applying equation (7) to each axis. Further, when the correction coefficients I1 / K1 to I6 / K6 of each axis are obtained based on them (S12), the correction coefficient max (I / K) having the maximum value is selected as MaxA (S13). Subsequently, when step S6 is executed, the correction amount Adj {= MaxA · ω (dot)} is calculated using the correction coefficient MaxA (S14), and the correction is performed by adding the correction amount Adj to the command value θ (S15).

  That is, the physical characteristics of each axis of the arm vary depending on the position in the rotational direction. However, if the correction coefficient corresponding to each axis is individually applied, the delay amount of each axis is greatly different, and there is a possibility that the initially planned movement trajectory of the hand cannot be maintained. Therefore, by determining the correction amount Adj to be applied to each axis using the maximum value MaxA of the correction coefficient, vibration is suppressed within a range in which the movement locus can be maintained. Subsequently, the low-pass filter process is performed on the correction command value θ ′ in the same manner as in step S9, but the band and cutoff frequency of the filter here are set as the square root of the reciprocal of the correction coefficient MaxA (S16). Then, the process proceeds to step S10.

  As described above, according to the second embodiment, the command value correction unit 22 calculates the spring constants K1 to K6 for each axis of the arm and calculates the inertias I1 to I6 for each axis of the arm. Then, the maximum correction coefficient I / K is selected as MaxA, and the command value θn of each axis is corrected by the correction amount Adj based on the maximum correction coefficient. Also by such control, the vibration of the hand can be suppressed as in the first embodiment. Further, since the cutoff frequency of the low-pass filter is variably set according to the correction coefficient obtained by dividing the inertia I by the spring constant K, the cutoff frequency can be appropriately set in consideration of these values.

(Third embodiment)
In the third embodiment, the spring constant K is obtained by using a first-order approximate expression instead of obtaining by the expression (7). Figure 13 is an example of a case of obtaining the spring constant K in equation (7), taking the square of the distance L _f in the horizontal axis, a curve. In FIG. 13, the range of the distance L _f is 300 mm to 1500 mm. As shown in FIG. 14, the region of 900 mm or more where the vibration of the hand becomes remarkable and the region of less than that are divided into primary regions. If approximation is applied, it can be approximated with few errors.

Then, by solving the simultaneous equations with the two spring constants K1 and K2 obtained by the primary approximation, the intersection of the two straight lines can be obtained. The application of the two spring constants K1 and K2 may be switched at the intersection. In the example shown in FIG. 14, the intersection is L _f = 767 mm.
As described above, according to the third embodiment, the command value correction unit 22 calculates the spring constant K using a first-order approximation formula, so that the spring constant K used for correcting the command value can be obtained more easily. .

The present invention is not limited to the embodiments described above or shown in the drawings, and the following modifications or expansions are possible.
The low-pass filter processing in steps S9 and S16 may be performed as necessary.
The spring constant K in the first embodiment may be obtained by an expression other than the expression (7).
The primary approximation in the third embodiment may be performed by dividing into three or more regions.

  In the drawings, 1 is a robot system, 2 is a robot, 3 is a controller, 13 is a workpiece, 21 is a trajectory generator, and 22 is a command value corrector.

Claims (7)

At least one of the first axis that is perpendicular to the installation surface, the second axis that is perpendicular to the first axis, and the plurality of axes that are connected after the second axis is the second axis. Four or more arms with axes parallel to each other;
A control device for a robot that drives and controls the arm via a servo mechanism,
Given a final target position for moving the hand of the arm, a speed pattern generation unit that generates a speed pattern for moving the hand to the final target position;
A command value calculation unit that calculates a command value to be given to the servo mechanism so as to move the hand to a passing target position for each control cycle;
A spring constant calculator for calculating a spring constant of the arm according to the current position of the hand;
An inertia calculation unit for calculating an inertia of the arm and a work held by the hand according to a current position of the hand;
An acceleration calculator that calculates an acceleration when the command value changes for each control cycle;
A correction amount calculation unit that calculates a correction amount of the command value from the spring constant, the inertia, and the acceleration;
A robot control apparatus comprising: a command value correction unit that corrects the command value based on the correction amount and outputs the corrected command value to the servo mechanism. The spring constant calculation unit calculates a spring constant of the entire arm,
The robot control apparatus according to claim 1, wherein the inertia calculation unit calculates an inertia including the entire arm and the workpiece. The spring constant calculation unit calculates a distance from the third axis to the hand as L ₃ ,
The distance from the first axis to the hand is expressed as L _f ,
The spring constant up to the third axis with respect to the first axis is expressed as K ₁₂ ,
When the spring constant up to the hand with respect to the third axis is K ₃ ,
The spring constant K used for obtaining the correction amount is expressed by the following equation: 1 / K = {1 / K ₁₂ + L ₃ ² / (K ₃ L _f ² )}
The robot control device according to claim 2, which is obtained by: The spring constant calculation unit calculates a spring constant based on each axis of the arm,
The inertia calculation unit calculates an inertia based on each axis of the arm,
The correction amount calculation unit obtains a correction coefficient corresponding to each axis by dividing the inertia corresponding to each axis by the spring constant corresponding to each axis, and uses a value indicating the maximum value among the correction coefficients. The robot control apparatus according to claim 1, wherein a correction amount applied to each axis is determined.   5. The robot control apparatus according to claim 1, wherein the correction amount calculation unit calculates the spring constant using a first-order approximation formula.   The robot control device according to claim 1, wherein the command value correction unit performs low-pass filter processing on the corrected command value.   The robot control device according to claim 6, wherein the command value correction unit variably sets a cutoff frequency of the low-pass filter according to a correction coefficient obtained by dividing the inertia by the spring constant.

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