JP4389980B2 - Control method for articulated robot - Google Patents

Description

  The present invention relates to a control method for an articulated robot in position control of a robot driven by a motor via a speed reducer.

  In recent years, there has been a demand for improved work accuracy in vertical articulated robots used for welding and handling. However, vertical articulated robots generally have a combined arm length of 1 m or more and 6 or more axes, and the tip of the arm is bent due to the bending of the arm and the spring component of the speed reducer mounted on each axis. The structure is easy to vibrate. In particular, the vibration due to the spring component of the speed reducer has a low frequency of 10 Hz or less in a large robot, and greatly affects the position control performance.

  FIG. 2 shows a model of a motor and a speed reducer in a robot. A motor (2), a speed reducer (3), and a bearing (4) are fixed to a first arm (1) as a motor mounting base, and the speed is reduced. The second arm (9), which is a load coupled to the rotating part of the machine secondary side (7), is driven.

  The reduction gear primary side (6) is coupled to the rotor in the motor by the motor rotation shaft (10), and rotates at the motor rotation speed ωM (11). The reduction gear (3) reduces the motor rotation speed ωM (11) to the load rotation speed ωL (12) at a reduction ratio Rg.

  However, since the speed reducer (3) has a spring component between the speed reducer primary side (6) and the speed reducer secondary side (7), the expression (Equation 1) is satisfied because of the extension of the spring. It is only the steady state where becomes constant. FIG. 3 shows a block diagram of the model of FIG. 2 where the spring constant of the spring component is Ks.

  In FIG. 3, a current command icom (13) is a motor current command for driving the motor (2), Kt (14) is a torque constant of the motor (2), 1 / Rg (15, 16) is a reciprocal of the reduction ratio, ( 17) is the motor transfer function, (18) is the load transfer function, spring constant Ks (19) is the spring constant of the reducer (3), and θs (20) is the reducer primary side (6) and the reducer secondary side. The torsion angle generated between (7), (21) is an integral element, and Td (22) is an external force applied to the load (second arm (9)).

  In the motor transfer function (17), JM is the moment of inertia around the rotating shaft (10) that combines the motor rotor (5) and the primary side of the speed reducer (6), and DM is the viscous friction coefficient. In the load transfer function (18), JL is the moment of inertia around the rotating shaft (10) that combines the load (second arm (9)) and the reduction gear secondary side (7), and DL is the viscous friction coefficient. is there.

  FIG. 4 shows a normally used positioning control loop for the load shown in FIG.

  In FIG. 4, the position control block (27) outputs a motor position feedback θM (24) obtained by integrating the motor rotation speed ωM detected by an encoder or the like connected to the motor with an integration element (25), and a motor position command θcom ( 23) and is multiplied by the position proportional gain KPP (26) to generate the motor speed command ωcom (28).

  The speed control block (31) generates a motor current command icom0 (32) from the speed command ωcom (28) and the motor rotation speed ωM by the following formula.

ただし、

However,

  In the normal position control loop shown in FIG. 4, the load speed ωL (12) and the reducer torsion angle θs (20) are ignored, and only the motor speed ωM (11) is observed for position control. The vibration of the load speed ωL (12) due to the spring component could not be suppressed.

  Accordingly, the load speed ωL (12) and the reducer torsion angle θs (20) are measured, and feedback (hereinafter abbreviated as FB) control is performed using the measured values, thereby suppressing vibration due to the spring component of the reducer. A method is conceivable. However, the addition of the measurement function of the load speed ωL (12) and the reducer torsion angle θs (20) causes an increase in apparatus cost and load mass.

  In order to solve the above problem, in FIG. 5, a state FB block (39) is added to the normal position control loop shown in FIG.

  In the state FB block (39), using the values of the current command icom (13) and the motor speed ωM (11), the state observer (33) causes the load speed estimated value ωLo (34) and the reducer torsion angle estimated value. Estimate θso (35). These estimated values and motor rotation speed ωM (11) are multiplied by gains (36) to (38), subtracted from the current command icom0 (32) generated from the speed control block, and a new current command icom (13) is obtained. Generate.

  With this configuration, it is possible to realize control characteristics that suppress the vibration of the load speed ωL (12) due to the spring component of the speed reducer by adjusting the state FB gains (36) to (38).

  FIG. 6 shows an internal structure in the case where the state observer (33) in FIG. 5 is configured by a minimum dimension observer, and is configured by calculating the state observer parameters 61 to 70 by the following equations.

  In (Expression 5), k1 and k2 (69 and 70 in FIG. 6) are gains that determine the responsiveness and stability of the observer, and the poles that determine the responsiveness and stability of the observer are designated as α1 and α2. It is calculated by the following formula.

ただし、

On the other hand, there are various methods for determining the state FB gains Kf1 to 3 (36) to (38), such as an optimum regulator, but a method for designating the pole of the transfer function from the speed command ωcom (23) to the motor speed ωM (11). When employed in the control system of FIG.
If the designated pole is β1-4

However,

  By the way, in the vertical multi-indirect robot, when the posture of the robot itself and the load attached to the arm change, the load inertia JL changes. Therefore, it is only necessary to calculate the load inertia JL and recalculate the parameters of the state observer and the state FB represented by the equations (6) to (9) of (Equation 5) to (Equation 7) based on the value. It is known as a known technique.

  However, in recent robots that require high responsiveness, it is necessary to perform calculations for all the axes of the position loop control shown in FIG. 5 with sampling within a few milliseconds, and a digital signal processor (hereinafter referred to as fast numerical calculation). Even if DSP is abbreviated), it is difficult to process the calculation of the load inertia JL and the expressions (6) to (9) of (Equation 5) to (Equation 7) with the remaining time of the position control loop sampling. It is. In addition, the equations (6) to (9) in (Equation 5) to (Equation 7) include many divisions that the DSP is not good at.

  To solve the above problem, there has been conventionally shown a method of shortening the computation time by terminating discretization of the state equation in the first order (see, for example, Patent Document 1).

  However, although shortened in the conventional observer control arithmetic device, if changes occur in the posture of the robot itself or the load attached to the arm, it is still necessary to calculate the load inertia JL, the state observer, and the state FB parameters. The division that the DSP is not good at is included.

  In recent robots, computation time must be allocated to control that is suitable for welding and force control applications, and control that improves safety represented by sensorless collision detection. It is coming.

  Therefore, focusing on the fact that the vibration of the robot tip due to the spring component of the reducer increases in the posture where the robot arm is extended, the parameters of the state observer and state FB in this posture are applied to a plurality of loads attached to the arm. A method is disclosed in which a plurality of state observers and states FB corresponding to the numbers prepared in advance are calculated simultaneously, and the amount of addition of each state FB value to the motor current command is adjusted (for example, Patent Document 2). reference.).

  FIG. 7A shows a vertical articulated robot to be controlled. A normal vertical articulated robot is composed of three basic axes and three wrist axes, and FIG. 7A shows only the three basic axes.

  An equation for converting the load speed ωL (12) of each axis into the linear speed vL of the arm tip shown in FIG. 5 and the like is as follows.

ただし、
回転半径ｒ：各軸の回転中心軸とアーム先端までの距離
手首３軸はアーム長が基本３軸に比べ短いため、回転半径ｒが小さく、軸回りの速度ωＬに振動成分が乗っていても、アーム先端速度ｖＬへの影響は少ないので無視することができる。

However,
Rotational radius r: Distance between the rotation center axis of each axis and the tip of the arm The wrist three axes have a shorter arm length than the basic three axes, so the rotational radius r is small and even if the vibration component is on the speed ωL around the axis. Since the influence on the arm tip speed vL is small, it can be ignored.

  In FIG. 7A, (101) is a first axis that rotates on a horizontal plane, (102) is a second axis that is attached to the first axis and rotates on a vertical plane, and (103) is a vertical plane that is attached to the second axis. It is the 3rd axis | shaft which rotates by. (104) is the angular velocity ωL1 of the first axis, (105) is the angular velocity ωL2 of the second axis, and (106) is the angular velocity ωL3 of the third axis.

  FIG. 7B shows a posture in which Expression (10) of (Equation 8) is maximized. However, for the third axis, the distance between the rotation center axis and the arm tip is constant regardless of the posture if the wrist axis is ignored.

  (107) and (108) are the rotation radii r1 and r2 of the first axis and the second axis, respectively, and coincide with each other unless the rotation centers of the first axis and the second axis are offset, and FIG. It becomes the maximum in the posture.

  Further, in this posture, the load inertia JL including the arm is maximized, so that the vibration frequency is the lowest and adversely affects the control performance. Furthermore, since the load ahead from the speed reducer spring (8) of the speed reducer (3) shown in FIG. 2 becomes large, it becomes difficult to stop when vibration is started.

  On the other hand, FIGS. 7C and 7D show the posture in which the arm is folded. FIG. 7C shows the rotation radius r1 (107) of the first axis, and FIG. 7D shows the rotation radius of the second axis. r2 (108) is shown.

  In any case, since the rotation radius r is smaller than that in FIG. 7B and the load inertia JL including the arm is also smaller, the vibration frequency becomes higher and the vibration can be easily suppressed.

  That is, it is considered that the vicinity of the posture shown in FIG. 7B has the largest vibration and is difficult to stop, so the parameters of the state observer and the state FB are adjusted in advance in the vicinity of FIG. 7B.

  However, the load attached to the arm is not constant, and changes during the operation of the robot during transfer work or the like. Therefore, the parameters corresponding to several kinds of loads are adjusted in advance near the state observer and the state FB in the vicinity of FIG.

  FIG. 8 shows a position control loop corresponding to two types of loads.

  8 includes state FB blocks 1 and 2 (47, 57) corresponding to two types of loads and state FB ratio gains RK1 and RK2 (48, 58).

  The state FB blocks 1 and 2 (47, 57) are configured only by the product-sum operation that the DSP is good at.

  The state observer and state FB parameters in the state FB blocks 1 and 2 (47, 57) correspond to the respective loads, and values adjusted in advance in the vicinity of the posture of FIG. 7B are used.

  When the robot operation program informs that the load attached to the arm is switched from the load adjusted in the state FB block 1 (47) to the load adjusted in the state FB block 2 (57), the state FB in FIG. The ratio gains RK1, RK2 (48, 58) are changed in the graph shown in FIG.

  The relationship between the state FB ratio gains RK1 and RK2 (48, 58) is determined by the following equation.

  In FIG. 9, the state FB ratio gain that was RK1 = 1 and RK2 = 0 at time 0 decreases RK1 until it becomes 0 when load switching is notified at time 0.2. Since RK2 maintains the relationship of Equation (11) in (Equation 9), it increases to RK2 = 1 at time 0.7, and the load switching correspondence is completed.

In this method, it is not necessary to perform the parameter calculation of the load inertia, the state observer, and the state FB in real time, and it is only necessary to calculate the plurality of state observers and the state FB constituted by the product-sum operation that the DSP is good at. In a state where a sufficient vibration suppressing effect is obtained, the calculation time can be reduced.
JP-A-8-123508 JP 2006-116631 A

  However, in the method shown in the second example of the conventional example, the parameters of the state observer and the state FB are calculated with the load inertia in the arm extension posture shown in FIG. 7B as JL, and are fixed values regardless of the arm posture. Is used.

  7 (c) and 7 (d) with the arm folded, the rotation radius r is small and the load inertia JL including the arm is also small, so that the vibration frequency is high, and the vibration suppression control by the state FB is Although it is originally unnecessary, the vibration suppression control based on the state FB is performed with the inconsistent parameters adjusted in the extended posture of FIG.

  That is, there is a possibility that the vibration due to the parameter mismatch may increase as compared with the case where the vibration suppression control based on the state FB is not performed.

  The present invention solves the above-described problem, and it is possible to achieve both suppression of vibration due to a reduction gear spring component that increases in a posture in which the robot arm is extended and prevention of increase in vibration due to parameter mismatch when the arm retracts. An object of the present invention is to provide a robot control method that can be performed within a calculation time within a control cycle.

In order to solve the above-described problems, the articulated robot control method of the present invention has a plurality of arms that are driven by a motor via a speed reducer and rotate around a rotation axis, and operate according to a pre-stored operation program. Then, a feedback control loop of the motor is configured based on the current and rotational position information of the motor , the state observer parameters and the state feedback gain are calculated in advance with the posture of the arm rotation radius maximum value, and the rotation of the motor By multiplying the estimated value of the rotational speed of the arm connected to the motor estimated by the speed and the state observer and the estimated value of the torsion of the reducer estimated by the state observer by multiplying the state feedback gain, respectively. outputs the resulting state feedback value, Ru state is added to the feedback control loop A method of controlling an articulated robot which controls the operation of the motor with the I over-back block, with respect to the said arm rotation radius maximum arm rotation radius around the rotation axis in the orientation of the articulated robot The state feedback value multiplied by the posture gain as a function of the ratio is subtracted from the motor current command to obtain a new motor current command, thereby multiplying the posture gain subtracted from the motor current command as the arm rotation radius decreases. it is to small fence the effect of state feedback by reducing the state feedback value.

  In the articulated robot control method of the present invention, in addition to the above, the posture gain is determined as a linear function of the square ratio of the arm rotation radius around the rotation axis to the maximum value of the arm rotation radius. Is.

  In addition to the above, the control method for the articulated robot of the present invention has a posture gain of 1 or less, and the square ratio of the arm rotation radius to the maximum value of the arm rotation radius in each posture of the articulated robot is 0. The first predetermined value is 0, the first predetermined value to the second predetermined value is a linear function that increases linearly, and the second predetermined value to 1 is 1 Is.

  In addition to the above, the articulated robot control method of the present invention can load and unload loads on the arm, and load and unload loads on the arm are included in the operation program. A plurality of corresponding state feedback blocks are provided, and the state feedback block is switched according to the load when the load fluctuates when the load is attached to or detached from the arm during the operation according to the operation program.

  As described above, in the articulated robot control method of the present invention, vibration suppression due to a reduction gear spring component that increases in a posture in which the robot arm is extended, and prevention of vibration increase due to parameter mismatch when the arm retracts Can be realized.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described mainly with reference to FIG. 1, FIG. 10, and FIG. In addition, the same code | symbol is attached | subjected about the location similar to FIGS. 2-9 demonstrated by the problem which the background art and invention which the invention is going to solve, and detailed description is abbreviate | omitted.

  FIG. 1 is a diagram showing a position control loop for one axis in a control method for an articulated robot. The main difference from FIG. 8 described in the background art is that the outputs of the state FB ratio gains RK1 (48) and RK2 (58) are multiplied by posture gains J1_KL1 (71) and J1_KL2 (72). It is.

  In FIG. 1, the outputs of the state FB ratio gains RK1 (48) and RK2 (58) are multiplied by posture gains J1_KL1 (71) and J1_KL2 (72), respectively, and the current command icom0 generated from the speed control block 31 is obtained. Subtracting from (32), a new current command icom (13) is generated.

  The posture gains J1_KL1 (71) and J1_KL2 (72) are determined by the following procedure.

  The parameters of the state observer and the state FB are obtained from (Equation 4) to (Equation 7) described in the background art above, and the load inertia JL used here is in the vicinity of the extended posture as shown in FIG. The value of is used.

  On the other hand, when the arm is retracted, the load inertia JL is reduced, and the error of the parameter of the state observer and state FB obtained in the extended posture is increased. However, the necessity of vibration suppression by the state FB is reduced, so the load inertia JL It is only necessary that the state FB is not effective as becomes smaller.

  The posture gains J1_KL1 (71) and J1_KL2 (72) are the inertia of the load inertia JL in each posture with respect to the maximum value JLMAX of the load inertia JL used for the parameter calculation of the state observer and the state FB according to the load attached to the arm. It is defined as a linear function of the ratio.

  However, if it is attempted to accurately obtain the load inertia JL by dynamic calculation or the like, the calculation time becomes long. Accordingly, since the magnitude of the load inertia JL is generally proportional to the square of the mass or the distance from the center of rotation, the ratio of the square of the arm rotation radius to the maximum value of the arm rotation radius Px (x = 1, 2, 3) As a substitute for inertia ratio.

  FIG. 10 is a diagram for illustrating the concept for obtaining the inertia ratio, and mainly shows the basic three axes of the three basic axes and the three wrist axes in the six-axis articulated robot. In FIG. 10, the first axis is the rotation axis on which the first arm (1) rotates, the second axis is the rotation axis on which the second arm (9) rotates, and the third axis is rotated by the third arm (73). A rotating shaft that moves. L1 is the horizontal distance from the first axis to the second axis, L2 is the distance from the second axis to the third axis, and L3 is the distance from the third axis to the tip of the third arm (73). It is. R1 is the horizontal distance from the first axis to the tip of the third arm (73) when the multi-joint robot is in a certain posture, that is, the rotation radius of the first axis, and is the maximum value of R1. R1MAX becomes L1 + L2 + L3. R2 is the distance from the second axis to the tip of the third arm (73), that is, the radius of rotation of the second axis, and R2MAX, which is the maximum value of R2, is L2 + L3. R3 is the distance from the third axis to the tip of the third arm (73), that is, the radius of rotation of the third axis, and R3MAX, which is the maximum value of R3, is L3. For each axis, the square ratio Px (x = 1, 2, 3) of the arm rotation radius to the maximum value of the arm rotation radius based on FIG. 10 is expressed as (Equation 10).

  FIG. 11 is an example showing the relationship between the linear function of the radius-of-rotation ratio P1 and the posture gain J1_KL1 (71) on the first axis.

ただし、

However,

  The posture gain J1_KL1 (71) is calculated using (Expression 13) of the above (Equation 11), and is multiplied by the feedback from the state observer.

  The posture gain J1_KL2 (72) is the same as the posture gain J1_KL1 (71), and is expressed as (Equation 12) below.

ただし、

However,

  Further, the posture gains of the second axis and the third axis are the same as the first axis expressed by (Equation 11) and (Equation 12), and the following (Equation 13) and (Equation 14) for the second axis. The third axis is expressed as (Equation 15) and (Equation 16) below.

ただし、

However,

ただし、

However,

ただし、

However,

ただし、

However,

  Here, a11, b11, c11, a21, b21, c21, a21, b21, c21, a22, b22, c22, and a31, b31, c31, a32, b32, c32 are, for example, experimentally determined. It can be obtained in advance.

  Further, R1 and R2 in each posture of the articulated robot can be obtained from an operation program of the articulated robot, or the first arm (1), the second arm (9), and the third arm (73). Is already known in advance, and can be obtained from the shape information of these arms and the angle information θ2 and θ3 shown in FIG.

  By adopting the above-described configuration, the posture gain KLx becomes 0 and the state observer feedback becomes invalid when the arm is retracted without the need for vibration suppression. The current command icom0 (32) generated from the speed control block is used as it is as the current command icom (13). As a result, adverse effects due to parameter errors can be prevented.

  By the way, when the movement of the wrist 3 axis with a small turning radius and little influence on vibration is ignored, the turning radius R3 of the third axis is constant regardless of the posture, there is no inertia variation, and the turning radius square ratio P3 is also constant. (= 1). Even when the rotation radius square ratio P2 of the second axis approaches 0 in the arm contraction posture, P3 = 1. That is, even when the posture gain J2_KL1 of the second axis approaches 0, the posture gain J3_KL1 of the third axis. = 1, and a large difference occurs in the state FB amount.

  The center of rotation of the third axis is at the tip of the second arm (9), and when the second arm (9) is operated, the center of rotation of the third axis moves. I want to let you. FIG. 12 is a welding torch (110) in which a rectangular parallelepiped work (111) placed horizontally on the robot installation surface is attached to the robot tip, and the robot moves from the posture of FIG. 12 (a) to the posture of FIG. 12 (b). Shows an example in which welding is performed at a constant speed in a direction (114) in which the angle is reduced. At this time, the second axis (102) rotates clockwise (112), and the third axis (103) rotates counterclockwise (113). By the operation of the second axis (102), the center of rotation of the third axis (103) is moved in the arm tip movement direction (114) and simultaneously moved upward. In order to operate the welding torch (110) at a constant speed in parallel on the workpiece (111), it is necessary to control the second axis (102) and the third axis (103) in synchronization. However, even if the angle commands θcom of the second axis (102) and the third axis (103) are correctly output so as to draw the locus, the actual position is obtained when the responsiveness of the position control loop differs for each axis. A difference also occurs in the follow-up delay of θM, and the locus is shifted. For example, if the response of the second axis (102) is faster than the third axis (103), the rotational movement of the second axis (102) moves faster in the direction of lifting the entire arm (the direction of lifting the third axis). The locus of the tip of the welding torch (110) is shifted upward (115).

  As an example of means for matching the responsiveness between the axes as much as possible in order to suppress the above-mentioned locus deviation due to the response difference between the axes, the speed command ωcom ( In the background art, a method for designating the pole of the transfer function from 23) to the motor speed ωM (11) is shown in the background art. However, only the state FB amount of the second axis (102) approaches 0 and there is no state FB. When returning to the function, there is a possibility that the response difference with the third axis (103) may widen, so that the second axis J2_KL1 may be used as the posture gain of the third axis (103).

  As described above, according to the control method of the articulated robot of the present embodiment, parameters adjusted in advance corresponding to a plurality of loads attached to the arm in a posture in which vibration due to the spring component of the speed reducer is likely to occur. A plurality of state observers and state FB are simultaneously calculated, and based on load information attached to the arm, the adjustment of the addition amount of each state FB value to the motor current command is performed. It is characterized in that it is multiplied by a posture gain defined as a linear function of a square ratio with respect to the value. As a result, the posture gain approaches 1 when decompressing and approaches 0 when retracted, so that the optimum amount of state FB can be obtained for each posture, and there is no need to perform parameter calculations for load inertia, state observer, and state FB in real time. The calculation time can be reduced in a state where a sufficient vibration suppression effect corresponding to the robot posture change can be obtained.

  In the articulated robot control method of the present invention, the time required for the parameter calculation of the load inertia, the state observer, and the state FB, which the conventional observer control arithmetic device method has, can obtain a sufficient vibration suppressing effect. Therefore, the calculation time can be devoted to control adapted to welding and force control applications, and control such as sensorless collision detection to increase safety, which is industrially useful.

The block diagram which shows the position control loop in embodiment of this invention Schematic configuration diagram showing the spring component of the reducer of the robot A block diagram modeling the spring component of a robot reducer The block diagram which shows the position control loop in the 1st prior art Block diagram showing a position control loop using observer control in the first prior art Block diagram showing the configuration of the state observer Schematic showing the relationship between robot posture and arm tip vibration The block diagram which shows the position control loop in the 2nd prior art The figure which shows the switching method of the state FB ratio gain in the 2nd prior art Schematic showing the arm turning radius in the embodiment of the present invention The figure which shows the relationship between the rotation radius square ratio P1 and attitude | position gain J1_KL1 in embodiment of this invention. Schematic for explaining locus deviation due to response difference between second axis and third axis

Explanation of symbols

1 First arm (Motor mounting base)
2 Motor 3 Reduction gear 4 Bearing 5 Motor rotor 6 Reduction gear primary side 7 Reduction gear secondary side 8 Reduction gear spring 9 Second arm (load)
10 Motor rotation shaft 11 Motor rotation speed ωM
12 Load rotation speed ωL
13 Current command icom
14 Kt (motor torque constant)
15 Inverse reduction ratio (1 / Rg)
16 Inverse reduction ratio (1 / Rg)
17 Motor transfer function 18 Load transfer function 19 Spring constant Ks
20 Reducer twist angle θs
21 integration element 22 Td (external force applied to load (second arm))
23 Motor position command θcom
24 Motor position feedback θM
25 integral element 26 position proportional gain KPP
27 Position control block 28 Motor speed command ωcom
29 Speed proportional gain KP
30 Speed integral gain KI
31 Speed control block 32 Motor current command icom0 (speed control block output)
33 State observer 34 Load speed estimate ωLO
35 Estimated value of reducer twist angle θso
36 gain (status FB gain 1 Kf1)
37 gain (status FB gain 2 Kf2)
38 gain (status FB gain 3 Kf3)
39 State FB block 40 State FB amount SFB
41 State Observer Block 1
42 Estimated value of motor rotation speed ωMO 1
43 Reducer torsion angle estimate θso1
44 State FB gain 1 Kf11
45 State FB gain 2 Kf21
46 State FB gain 3 Kf31
47 State FB block 1
48 state FB ratio gain RK1
49 State FB amount SFB1
51 State Observer Block 2
52 Estimated value of motor rotation speed ωMO 2
53 Estimated value of reducer twist angle θso2
54 State FB gain 1 Kf12
55 State FB gain 2 Kf22
56 State FB gain 3 Kf32
57 State FB block 2
58 State FB ratio gain RK2
59 State FB amount SFB2
61-70 State observer parameters 71 J1_KL1 (Attitude gain)
72 J1_KL2 (Attitude gain)
73 3rd arm

Claims (4)

It has a plurality of arms that are driven by a motor via a speed reducer and rotate around a rotation axis, operate according to a pre-stored operation program, and perform a feedback control loop of the motor based on the motor current and rotational position information The state observer parameter and the state feedback gain are calculated in advance with the arm rotation radius maximum posture, and the rotational speed of the motor and the rotational speed of the arm connected to the motor estimated by the state observer are estimated. value and the output state feedback value obtained by adding after having multiplied the state feedback gain to twist estimate each estimated the reduction gear in a state observer, the Ru state feedback is added to the feedback control loop Articulated type for controlling the operation of the motor having a block A method of controlling a bot,
New by subtracting the articulated state feedback value obtained by multiplying a position gain as a function of the ratio of the arm rotation radius maximum arm rotation radius around the rotation axis in the posture of the robot from the motor current command A control method for an articulated robot that reduces the effect of state feedback by reducing the state feedback value multiplied by the posture gain subtracted from the motor current command as the arm rotation radius is reduced by using the motor current command . 2. The articulated robot control method according to claim 1, wherein the posture gain is determined as a linear function of a square ratio of the arm rotation radius about the rotation axis to the maximum value of the arm rotation radius. The posture gain is 1 or less, and the square ratio of the arm rotation radius to the maximum value of the arm rotation radius in each posture of the articulated robot is 0 from the first predetermined value to 0. From the first predetermined value, 3. The articulated robot control method according to claim 2, wherein a linear function that increases linearly up to a second predetermined value is represented, and 1 from the second predetermined value to 1. A load can be attached to and detached from the arm, and the loading and unloading of the load to and from the arm are also included in the operation program. The method of controlling an articulated robot according to any one of claims 1 to 3, wherein the state feedback block is switched according to the load when the load fluctuates when the load is attached or detached and the load fluctuates.

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