JP2003211376A - Robot control device and control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide flexible control of a working coordinate system that can cope with displacement of large stroke without using a sensor or the like, flexibly operate in a specific direction of a working coordinate system with simple operation and operate with high locus accuracy in directions other than the specific direction. <P>SOLUTION: This robot control device has a first forward conversion means for converting a measured joint angle into the position data of a working coordinate system; a second forward conversion means for converting a joint command into the position command data of the working coordinate system; a deviation correcting means for limiting computed position deviation data on the basis of the position data and position command data; an adding means for computing the position data of a second working coordinate system from the position command data and the position deviation data computed by the deviation correcting means; and a reverse conversion means for computing a second joint angle from the position data of the second working coordinate system. The second joint angle is used for state feed-back. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a robot controller, and more particularly to a robot controller and control for controlling the generated force of a servomotor for driving a joint based on a force and a torque set value in a work coordinate system. Regarding the method.

[0002]

2. Description of the Related Art A conventional robot is controlled by a position / speed state feedback system as shown in FIG. 6 for each joint axis of the robot. When performing spot welding or seam welding work that involves contact with the work with such a control system, if there is a work position deviation or work gripping position deviation, it is set to a large value to increase rigidity. Due to the action of the gain and the integrator, a large torque is generated, which makes it difficult to carry out the work due to the occurrence of welding defects, welding, etc., and sometimes there is a risk of damage to the tool or the robot. To solve such a problem, as disclosed in Japanese Patent Laid-Open No. 9-314347, there is a method of using a device which allows an action force due to a positional deviation of a work or the like to be caused by a coil spring and a leg portion provided on a jig base.

As a method of using force information, Japanese Patent Laid-Open No.
As shown in 2000-061645 publication, a method of measuring the pressing force of the upper and lower roller electrodes at the time of seam welding with a load cell and performing feedback control of the robot based on the difference in the pressing force, and disclosed in JP 2000-042752 A As described above, there is a method of detecting an abnormality when the rotational torque or the pressure applied by the torque detector exceeds the limit. Further, as a method of using the distance information, there is a method of using a distance sensor at the time of seam welding and correcting the position with a template having the same shape as the work in advance, as shown in Japanese Patent Laid-Open No. 9-314351. Also,
In recent years, as a method of performing flexible control in a work coordinate system without adding a special device to a robot, each coordinate system of the work coordinate system is disclosed in JP-A-8-227320 and JP-A-2000-005881. There is a method that can set the flexibility (spring constant) with respect to the direction and specify the degree of adaptability to external force for each direction in the space.

[0004]

[Patent Document 1] Japanese Patent Application Laid-Open No. 9-31
The method shown in Japanese Patent No. 4347 lacks versatility because it is necessary to remake the device itself according to the work when the work is changed, and the direction of the acting force is known in advance and the contraction direction of the spring is adjusted. There was a need. In addition, JP 2000-0
As described in Japanese Patent No. 61645 and Japanese Patent Laid-Open No. 2000-042752, a method in which a force sensor or a load cell is added to acquire sensor information has a problem of increased cost. Further, as shown in Japanese Patent Laid-Open No. 9-314351, the method using the distance sensor cannot cope with the positional deviation other than the direction of the distance sensor, and when changing the work, it is necessary to change the peripheral device such as the template. there were. Further, as shown in Japanese Patent Laid-Open No. 8-227320 and Japanese Patent Laid-Open No. 2000-005881, the flexibility (spring constant) is set in the working coordinate system to specify the degree of adaptability to external force for each direction in space. With this method, when the position deviation increases, the torque generated by the servomotor increases proportionally, so it cannot handle large strokes, and the calculation of the relational expression that makes the force in the work coordinate system correspond to the torque in the joint coordinate system is complicated. There is a problem that the load is heavy and it is difficult to control in real time. Therefore, the present invention has general versatility that can be used even when changing a workpiece without using a sensor or the like, and is inexpensive because it does not use a sensor or the like, can cope with a large stroke displacement, and has a work coordinate system with a simple calculation. It is an object of the present invention to perform flexible control of a work coordinate system that can be flexibly operated in a specific direction and that can be operated with high trajectory accuracy in a direction other than the specific direction.

[0005]

In order to solve the above-mentioned problems, a robot controller according to a first aspect of the present invention provides a robot for driving each joint by providing position / speed state feedback based on a joint command. In the control device, an angle measuring device for measuring a first joint angle with respect to the joint coordinate system of the robot, a first forward conversion means for converting the first joint angle into position data of the working coordinate system, and the joint command. To a work coordinate system position command data, and a first forward conversion means for calculating the work coordinate system position deviation data by subtracting the work coordinate system position command data from the work coordinate system position data. The subtraction means, the deviation correction means for correcting the position deviation data of the working coordinate system, the position deviation data calculated by the deviation correcting means, and the position command data of the working coordinate system are added. The second joint angle has an adding means for calculating position data of the work coordinate system and an inverse transforming means for calculating a second joint angle of the joint coordinate system from the position data of the second work coordinate system. Is used for the state feedback. According to the robot control device of claim 1, when the force is applied from the outside to the robot due to the positional deviation of the work during the handling work, the joint angle and the joint command obtained by the angle measuring device are respectively forward-converted. The position and orientation deviation in the work coordinate system generated by the external force is obtained by performing the forward conversion with the subtracting means, and the work coordinate is flexibly set in the work coordinate system (hereinafter, the flexible setting axis). The position and orientation deviation in the system is corrected to a smaller value by the deviation correcting means, and the deviation limited by the adding means is added to the position command and the attitude command of the working coordinate system to create the second position feedback value and the attitude feedback value. Then, the inverse transformation means inversely transforms the second position feedback and the posture feedback into the joint angle, and the obtained joint angle is converted into the position. By using it for state feedback, each joint angle is not updated at all or not fully updated, and the position deviation is small or no even if external force acts, so position deviation is allowed only in the flexible setting axis direction. It becomes possible to absorb the external force. Similarly, for an axis that is not flexibly set in the work coordinate system (hereinafter referred to as a non-flexible setting axis), the position and posture deviation in the work coordinate system is not limited by the deviation correction means, and the position and posture deviation is added by the addition means. A second position feedback and a posture feedback are created by adding them to the position command and the posture command of the work coordinate system, and the second position feedback and the posture feedback are inversely converted into the joint angle by the inverse conversion means, and the position state feedback is performed. , The joint angles are updated in the same manner as in a normal position control system, so that it is possible to operate with high trajectory accuracy as before.

According to a second aspect of the robot controller of the present invention, the second joint angle is used for the position feedback or the velocity, or both of them for the status feedback.
According to the robot control device of the second aspect, by using the differential of the second joint angle only in the soft setting axis direction for speed state feedback, even when a position deviation occurs in the soft setting direction. Since the component of the velocity integral term in the flexible setting axis direction becomes small, it is possible to suppress the generation of a large torque by the velocity integral term even when the positional deviation occurs in the flexible axis direction.

In the robot controller according to a third aspect of the present invention, the deviation correction means limits the positional deviation data of the working coordinate system to a threshold value, or gains the positional deviation data of the working coordinate system with a gain. Means to multiply by, or
It is a means of combining them. According to the robot control device of the third aspect, similarly to the first aspect, the joint angle obtained by the angle measuring device when the force is applied from the outside to the robot due to the positional deviation of the work during the handling work. And the joint command are respectively forward-converted by the forward-conversion means and subtracted by the subtraction means to obtain the position and posture deviation in the work coordinate system generated by the external force, and the axis is set flexibly in the work coordinate system (hereinafter, flexible setting). For the (axis) direction, the position and orientation deviations in the working coordinate system are multiplied by a gain that is sufficiently smaller than 1 preset by the deviation correcting means, and the deviation multiplied by the gains by the adding means is used as the position command of the working coordinate system. The second position feedback and the attitude feedback are created by adding to the attitude command, and the second position feedback and the attitude feedback are generated by the inverse conversion means. By inversely converting the back to a joint angle and using the obtained joint angle for position state feedback, each joint angle is not updated at all or is not sufficiently updated, and the positional deviation is small even if an external force acts. Since there is no such state, it is possible to allow the positional deviation only in the direction of the soft setting axis and absorb the acting force from the outside. Similarly, for the direction of the axis that is not flexibly set in the work coordinate system (hereinafter referred to as the non-flexible setting axis), the position and attitude deviation in the work coordinate system is not multiplied by the deviation correcting means, but the position and attitude deviation is calculated by the adding means. A second position feedback and a posture feedback are created by adding them to the position command and the posture command of the work coordinate system, and the second position feedback and the posture feedback are inversely converted into the joint angle by the inverse conversion means, and the position state feedback is performed. , The joint angles are updated in the same manner as in a normal position control system, so that it is possible to operate with high trajectory accuracy as before.

According to a fourth aspect of the present invention, there is provided a robot control device, wherein a gravity torque calculating means for calculating a gravity torque acting on each joint of the robot based on the joint angle from the angle measuring device, and the gravity torque. It has a gravity compensation calculation means for compensating the control system of the motor. According to the robot control device of claim 4, by separately compensating for the gravity component,
Since the value integrated in the velocity integral term of each joint coordinate system can be kept small, it is possible to suppress the generation of a large torque due to the velocity integral term even when a positional deviation occurs in the flexible axis direction.

According to a fifth aspect of the present invention, there is provided a robot control device for driving each joint by performing position feedback of a position / speed on the basis of a joint command, wherein the first joint relating to the joint coordinate system of the robot. The angle is measured, the position data of the working coordinate system is calculated based on the first joint angle, the position command data of the working coordinate system is calculated based on the joint command, and the position data and the position command data are calculated. Position deviation data is calculated, position deviation correction data obtained by correcting the position deviation data is calculated, and a second joint angle is calculated from the position deviation correction data and the position command data. Used for status feedback. According to the robot control device of the fifth aspect, when the force is applied from the outside to the robot due to the positional deviation of the work during the handling work, the joint angle and the joint command obtained by the angle measuring device are respectively forward-converted. The position and orientation deviation in the work coordinate system generated by the external force is obtained by performing the forward conversion with the subtracting means, and the work coordinate is flexibly set in the work coordinate system (hereinafter, the flexible setting axis). The position and orientation deviation in the system is corrected to a smaller value by the deviation correcting means, and the deviation limited by the adding means is added to the position command and the attitude command of the working coordinate system to create the second position feedback value and the attitude feedback value. Then, the inverse transformation means inversely transforms the second position feedback and the posture feedback into the joint angle, and the obtained joint angle is converted into the position. By using it for state feedback, each joint angle is not updated at all or not fully updated, and the position deviation is small or no even if external force acts, so position deviation is allowed only in the flexible setting axis direction. It becomes possible to absorb the external force. Similarly, for an axis that is not flexibly set in the work coordinate system (hereinafter referred to as a non-flexible setting axis), the position and posture deviation in the work coordinate system is not limited by the deviation correction means, and the position and posture deviation is added by the addition means. A second position feedback and a posture feedback are created by adding them to the position command and the posture command of the work coordinate system, and the second position feedback and the posture feedback are inversely converted into the joint angle by the inverse conversion means, and the position state feedback is performed. , The joint angles are updated in the same manner as in a normal position control system, so that it is possible to operate with high trajectory accuracy as before.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in the conventional example of FIG. 6, in a position / speed control state in a normal joint coordinate system, work coordinates are applied to a force externally applied by the action of the position control loop and the speed control loop. It is difficult to flexibly follow the working position of the tip only in a specific direction on the system. This depends on the reduction ratio of each joint axis, the magnitude of gain, and the posture of the robot. Therefore, by using only the position deviation component in a specific direction (non-flexible setting axis direction) of the work coordinate system for controlling the position state feedback, and not updating the position deviation component in the flexible setting axis direction sufficiently, It is possible to shift the position, and it is possible to perform an operation that keeps the trajectory with high accuracy in the non-flexible set axis direction. A first specific example of the present invention will be described below with reference to FIG. 1, and an example applied to a robot having n degrees of freedom will be described (n ≧
3). First, a control block diagram in which the flexible control of the present invention is applied to a position / speed control system in a normal joint coordinate system is shown.

(1) Forward conversion As described in claim 1, in the position feedback system of position and velocity in the joint coordinate system, the first joint angle obtained by the angle measuring device 1 is converted into the first forward conversion means. Convert to position data in the work coordinate system by 2. The working coordinate system is a three-dimensional coordinate system composed of three orthogonal axes,
The position data is data including a position and a posture. Here, the conversion means is an arithmetic expression generally called forward kinematics for obtaining the hand position of the robot from the angle of each joint axis of the robot. The first joint angle of the joint coordinate system is θfb = θFB1 to θFBn (1) where θfb is the joint angle vector of the joint coordinate system θFBn is the joint angle of the nth axis. Xfb = XFB, YFB, ZFB, αFB, βFB, γFB (2) where Xfb is the position / orientation feedback vector of the work coordinate system XFB: X-axis position feedback of the work coordinate system αFB: Putting it as attitude feedback around the X axis of the work coordinate system, Xfb = F (θfb) (3) where F: forward conversion formula.

Similarly, the joint command of the robot is obtained by the second forward conversion means 3 into a position command and a posture command of the work coordinate system. Θref = θREF1 to θREFn (4) where θref is a joint command vector in the joint coordinate system θREFn is a joint command for the nth axis. Xref = XREF, YREF, ZREF, αREF, βREF, γREF (5) where Xref: position / orientation command vector of work coordinate system XREF: X-axis position command of work coordinate system αREF: Putting it as a posture command around the X axis of the working coordinate system, Xref = F (θref) (6) where F: forward conversion formula.

(2) Subtracting means Next, the subtracting means 4 subtracts the position command and the attitude command from the position feedback and the attitude feedback of the working coordinate system to calculate the position deviation and the attitude deviation ΔX of the working coordinate system. ΔX = Xfb-Xref (7)

(3) Deviation correction means With respect to the flexible setting axis direction, the deviation correction means 5 sets the position deviation and the attitude deviation ΔX of the working coordinate system to a preset threshold value, for example, a value set to 0 or a value smaller than usual. Limit with. With respect to the non-flexible set axis direction, the deviation correction means does not limit the position deviation and the attitude deviation ΔX of the work coordinate system, or limits them with normal values. The position deviation and the attitude deviation after the limitation are represented by ΔXLLIMIT.

(4) Position deviation and posture deviation ΔXLLIMIT after addition means deviation correction means
Is added to the position command and attitude command Xref of the work coordinate system by the adding means 6 to become Xfb2 in the expression (8) which is the second position feedback and attitude feedback of the work coordinate system. Xfb2 = ΔXLLIMIT + Xref (8)

(5) Inverse transforming means The inverse transforming means 7 inversely transforms the second position feedback and posture feedback into joint angles, and the joint angles θfb2 thus obtained are used for position state feedback. The second joint angle of the joint coordinate system is θfb2 = θFB21 to θFB2n (9) where θfb2: second joint angle vector θFB2n of the joint coordinate system θfb2 = B (Xfb2 ) ... (10) Here, it becomes B: Inverse conversion type. By performing the position control by using the obtained second joint angle of the joint coordinate system for the state feedback of the position,
Non-flexible setting Only the position deviation component in the axial direction is used for position feedback control, and the position deviation component in the flexible setting axis direction is not updated sufficiently. It is possible to perform an operation that keeps the locus with high accuracy in the axial direction.

An example of using this control for an actual robot is shown in FIG.
The operation will be described with reference to a schematic diagram. In this example, a two-axis horizontal articulated robot is used for simplicity of description, but the same applies to a three-axis or more vertical articulated robot. Consider a case where an external force F acts on the tip of the robot as shown in FIG. At this time, the Y-axis direction of the work coordinate system is set to the flexible setting axis direction, and the X-axis direction is set to the non-flexible setting axis direction. Normally, the robot position command and the position feedback have the same value. However, the external force F causes the robot to move to the position shown by the solid line in FIG. 5 (b), which causes a slight deviation ΔX and ΔY in the position command and position feedback. At this point, the action of the high loop gain of the position and the velocity normally tries to return to the original position (the position shown by the dotted line),
The limit of the deviation correction means 5 works in the Y-axis direction. For example, when the threshold value of the limit is 0, ΔY becomes 0, and in the Y-axis direction, the deviation between the position command and the position feedback becomes ΔY = 0. . Since the limit of the deviation correcting means 5 does not work in the X-axis direction, ΔX does not become 0, and the deviation between the position command and the position feedback remains ΔX in the X-axis direction. Therefore, the obtained ΔX and ΔY are added to the position command by the addition unit 6, the second joint angle of the joint coordinate system is obtained by the inverse transformation unit 7, and the position control is performed by using the position feedback of the position. As shown by the solid line in FIG. 5 (c), since the position control works in the X-axis direction, the tip of the robot returns to the original value,
Since the position control does not work in the Y-axis direction, the tip of the robot does not return to the original value. That is, even if the external force F acts, the position is displaced in the Y-axis direction, but the locus can be maintained without being displaced in the X-axis direction.

Next, a second specific embodiment of the present invention will be described with reference to FIG.
Will be described. In the position / speed control state in a normal joint coordinate system, when the position deviation occurs due to the force acting from the outside due to the action of the velocity integration term of the velocity control loop, the velocity deviation increases and the torque is integrated and excessive torque is generated. I will end up. Therefore, in this embodiment, as described in claim 2,
In the first specific example, the joint angular velocity is obtained by differentiating the joint angle and is used for velocity state feedback. As a result, even if the position shift occurs due to the force applied from the outside, the position shift is limited to 0 or small in the direction in which the position shift is allowed, and the velocity component is relatively small, so that it is stored in the velocity integral term. The value can be small, and the generation of large torque can be suppressed. Here, since the component of the velocity integration term regarding the non-flexible set axis direction is the same as that of a normal position / velocity control system, it is possible to configure a control system capable of maintaining locus accuracy without displacement.

Next, a third specific embodiment of the present invention is shown in FIG.
Will be described. In the present embodiment, as described in claim 3, the deviation correcting means 5 in the first specific embodiment (the flexible setting axial direction is limited by a preset threshold value, and the non-flexible setting axial direction is restricted). (Means without restrictions)
Instead of, perform gain multiplication. This is because the position deviation and the attitude deviation ΔX are multiplied by a gain which is sufficiently smaller than 1 which is set in advance for the flexible setting axis direction of the work coordinate system, and the position deviation and the attitude deviation ΔX are 1 for the non-flexible setting axis direction. A means for multiplying by or not multiplying by anything is used. The addition means 6 is used for the post-multiplication position deviation and attitude deviation ΔXGAIN as in the first specific example, and the second position feedback and attitude feedback Xfb2 of the working coordinate system are obtained. Xfb2 = ΔXGAIN + Xref ··· (11)

Next, the inverse transformation means 7 is used, and the second joint angle θfb2 of the joint coordinate system is used for position state feedback according to the equations (9) and (10). As a result, by performing the position control by using the obtained second joint angle of the joint coordinate system for the position state feedback, only the position deviation component in the non-flexible set axis direction is used for the position state feedback control, By not sufficiently updating the position deviation component in the direction of the flexible setting axis, it is possible to perform a position shift in the direction of the flexible setting axis while maintaining a highly accurate trajectory in the direction of the non-flexible setting axis.

Next, a fourth concrete embodiment of the present invention will be described with reference to FIG.
Will be described. In the present embodiment, as described in claim 4, by separately compensating for a force such as gravity that constantly acts on the first specific embodiment, a positional deviation occurs in the vertical direction due to the influence of gravity. It is something that suppresses doing. As a method for calculating this gravity, for example, the gravity torque calculating means 8 calculates the gravity compensation torque from the weight of each link of the robot, the position of the center of gravity, and each joint angle, and the gravity integral calculation means 9 calculates the velocity integral value and There is a method of adding to the torque command obtained by adding the speed proportional value. This makes it possible to prevent the torque of the gravity component from being integrated into the velocity integral term of each joint coordinate system when the flexible set axis direction of the work coordinate system is the same as the vertical direction, and the velocity integral value itself is It can be made smaller than that at the time of position / speed control, and it is possible to suppress generation of a large torque due to the speed integral term even when a position deviation occurs.

[0022]

As described above, according to the robot control apparatus of the first aspect, the axis that is flexibly set in the working coordinate system with respect to the force exerted on the robot from the outside due to the positional deviation of the work or the like. The velocity and angular velocity are limited only in the (hereinafter, flexible setting axis) direction, and then converted into a joint angle, and the joint angle that is the integrated value is used for position state feedback. Therefore, since the positions of the components of the joint angles in the flexible setting axis direction are not updated, it is possible to allow the positional deviation only in the flexible setting axis direction and absorb the external force. Further, since the position of the component of each joint angle relating to the direction that is not the flexible setting axis is not updated, it is possible to operate with high trajectory accuracy as in the past.
According to the robot control device of claim 2, the component related to the flexible set axis direction of the velocity integral term is obtained by using the second joint angular velocity whose current speed is changed only in the flexible set axis direction for velocity state feedback. Is smaller, it is possible to suppress the generation of a large torque by the velocity integral term even when the positional deviation occurs in the flexible axis direction.
According to the robot control device of claim 3,
Similar to the description, after multiplying the velocity and angular velocity by a small gain only for the direction of the axis that is flexibly set in the work coordinate system (hereinafter, flexible setting axis) against the force that acts on the robot from the outside due to the work position deviation, etc. Convert to joint angle with
The joint angle, which is the integral value, is used for position state feedback. Therefore, since the positions of the components of the joint angles in the flexible setting axis direction are not updated, it is possible to allow the positional deviation only in the flexible setting axis direction and absorb the external force. Further, since the position of the component of each joint angle relating to the direction that is not the flexible setting axis is not updated, it is possible to operate with high trajectory accuracy as in the past. According to the robot control device of the fourth aspect, by separately compensating for the gravitational component, the value integrated in the velocity integral term of each joint coordinate system can be suppressed to a small value. Even if it occurs, it is possible to suppress the generation of a large torque due to the speed integral term. According to the robot control device of claim 5, the speed is only in the direction of the axis flexibly set in the work coordinate system (hereinafter, the soft setting axis) with respect to the force externally acting on the robot due to the position shift of the work. After the angular velocity is limited, it is converted into a joint angle, and the joint angle which is the integrated value is used for position state feedback. Therefore, since the positions of the components of the joint angles in the flexible setting axis direction are not updated, it is possible to allow the positional deviation only in the flexible setting axis direction and absorb the external force. Also,
Since the position of the component of each joint angle related to the direction that is not the flexible setting axis is not updated, it is possible to operate with high trajectory accuracy as in the past.

[Brief description of drawings]

FIG. 1 is a first specific example of the present invention.

FIG. 2 is a second specific example of the present invention.

FIG. 3 is a third specific example of the present invention.

FIG. 4 is a fourth specific example of the present invention.

FIG. 5 is a schematic diagram showing the operation of the present invention.

FIG. 6 is a diagram showing a conventional control method.

[Explanation of symbols]

1: Angle measuring device 2: First forward conversion means 3: Second forward conversion means 4: Subtraction means 5: Deviation correction means 6: Addition means 7: Inverse conversion means 8: Gravity torque calculation means 9: Gravity compensation calculation means

Claims (5)

[Claims] 1. A controller for a robot for driving each joint by performing position feedback of a position / velocity based on a joint command, and an angle measuring device for measuring a first joint angle with respect to a joint coordinate system of the robot, First forward conversion means for converting the first joint angle into position data of the working coordinate system; second forward conversion means for converting the joint command into position command data of the working coordinate system; First subtraction means for subtracting position command data of the working coordinate system from position data to calculate position deviation data of the working coordinate system; deviation correcting means for correcting position deviation data of the working coordinate system; Adding means for adding the position deviation data calculated by the means and the position command data of the working coordinate system to calculate the position data of the second working coordinate system; and the position data of the second working coordinate system. And a reverse conversion means for calculating a second joint angle Luo joint coordinate system, the robot control device characterized by using said second joint angle in the state feedback. 2. The robot controller according to claim 1, wherein the controller uses the second joint angle for position and / or velocity for the state feedback. 3. The deviation correcting means limits the positional deviation data of the working coordinate system to a threshold value, or means for multiplying the positional deviation data of the working coordinate system by a gain, or a combination thereof. The robot controller according to claim 1 or 2, which is means. 4. A gravity torque calculation means for calculating a gravity torque acting on each joint of the robot based on a joint angle from the angle measuring device, and a gravity compensation calculation for compensating the gravity torque to a control system of a motor. 4. The robot controller according to claim 1, further comprising means. 5. A robot controller for driving each joint by providing position / velocity state feedback on the basis of a joint command, measures a first joint angle with respect to the joint coordinate system of the robot, and determines the first joint. The position data of the working coordinate system is calculated based on the angle, the position command data of the working coordinate system is calculated based on the joint command, and the position deviation data is calculated from the position data and the position command data. The position deviation correction data is calculated by correcting the deviation data, and a second value is calculated from the position deviation correction data and the position command data.
A method for controlling a robot, characterized in that the joint angle is calculated, and the second joint angle is used for the state feedback.