JP2011101938A - Robot and control device for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joint robot and a control device for the same independently controlling an attitude angle of a joint and rigidity and capable of attaining both sufficient safety and excellent control performance. <P>SOLUTION: The robot includes: a base; four motors installed on the base; four roll-up devices mounted to of the four motors, respectively; a support pillar installed on a surface of the base so that an axis center line becomes vertical; a spherical surface joint mounted to an upper end of the support pillar; a movable plate mounted to the spherical surface joint; four universal joints installed on a bottom of the movable plate; four wires assembled with a non-linear spring for connecting the four roll-up devices to the four universal joints, respectively; and an output shaft fixed to an upper surface of the movable plate so that an axis center line becomes vertical. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a joint robot capable of changing drive rigidity and a three-degree-of-freedom posture via a wire and a non-linear spring, and a control device therefor.

  Recently, researches on service robots and human cooperative industrial robots have been actively conducted. Since these robots are in direct contact with humans, safety assurance is important. In order to maintain the safety of the entire robot, each joint of the robot is required to be flexible and lightweight. Therefore, in the conventional technique, the compression coil is arranged around the center rod and wire driving is used to make the apparatus flexible and light (see, for example, Patent Document 1).

JP 11-77577 A (page 5-8, FIG. 1)

Conventionally, the stiffness of the device is determined by the spring coefficient of the compression coil. If the spring coefficient is reduced, the rigidity is lowered and the safety is improved, but the position control accuracy of the end effector is lowered. On the other hand, when the spring coefficient is increased, the position control accuracy of the end effector can be improved, but the rigidity is increased and the safety is deteriorated. That is, there is a problem that it is difficult to achieve both safety and control performance.
The present invention has been made in view of such problems. A nonlinear spring element is incorporated in the wire, and a wire tension command is given according to a torque command and a stiffness target command necessary for posture feedback control. To provide a joint robot capable of controlling the wire tension, causing the posture angle and stiffness of the joint to follow the target command independently and accurately, and achieving both good safety and excellent control performance, and a control device thereof. With the goal.

In order to solve the above problem, the present invention is configured as follows.
In the first aspect of the present invention, the base, the four motors installed on the base, the four winding devices respectively attached to the four motors, and the axial center line perpendicular to the surface of the base A support column installed at the top, a spherical joint attached to the upper end of the support column, a movable plate attached to the spherical joint, four universal joints installed at the bottom of the movable plate, and four Four wires incorporating a non-linear spring for connecting the winding device and the four universal joints one-on-one, and an output shaft fixed so that an axial center line is perpendicular to the upper surface of the movable plate A spherical center point of the spherical portion of the spherical joint is defined as an origin O, an axial center line of the output shaft is defined as a Z axis, and a direction away from the upper surface of the movable plate is defined as a positive direction of the Z axis. A moving orthogonal coordinate system XYZO is provided, and the intersection of the axis of the support column and the surface of the base is the origin o, and the axis of the support column is the z-axis away from the surface of the base Fixed orthogonal coordinates so that the x axis and the y axis are parallel to the X axis and the Y axis, respectively, when the direction is the positive direction of the z axis and the axis center line of the output axis coincides with the axis center line of the support column The system xyz is provided, the four motors are arranged so that the four winding devices are in different quadrants of the xy coordinate system, and the four universal joints have four phases in the XOY coordinate system. The xoy coordinate system is arranged so as to have the same value as the phase in the xoy coordinate system, and the winding device in the first quadrant of the xoy coordinate system and the universal joint in the second quadrant of the XOY coordinate system are In the second quadrant of the system The winding device and the universal joint in the first quadrant of the XOY coordinate system, the winding device in the third quadrant of the xy coordinate system and the universal joint in the fourth quadrant of the XOY coordinate system, The winding device in the fourth quadrant of the xoy coordinate system and the universal joint in the third quadrant of the XOY coordinate system are respectively connected by four wires.
According to a second aspect of the present invention, there are provided a base portion, three winding motors in which the stator is fixed above the base portion, and the axial center line of the rotor is parallel to the surface of the base portion, and the axial center line of the rotor One swing motor perpendicular to the surface of the base 420, three winding devices respectively attached to the three winding motors, a swing transmission shaft connected to a mover of the swing motor, and the swing transmission A universal joint attached to the upper end of the shaft, a movable plate, a support fixed to the center of the upper surface of the movable plate, two or more thrust bearings, three universal joints, and three winding devices Three wires incorporating a nonlinear spring for connecting the three universal joints one-to-one and an output shaft attached to the universal joint, and the swing motor is provided at the center of the base. The three winding motors are installed at three equiangular positions on the circumference centered above the base, and the three universal joints are on the circumference centered on the lower surface of the movable plate. And are constrained by two or more thrust bearings between the output shaft and the support base.
According to a third aspect of the present invention, there is provided a target command generator for generating a posture angle target command and a stiffness target command, an encoder for detecting a rotation angle of each motor, and detecting a tension of each wire. The posture angle target command, the stiffness target command, and the rotation angle signal of each motor while controlling the tension based on the tension command of each wire and the tension signal of each wire. A posture that generates a tension command for each wire based on the control signal, controls a posture angle and rigidity of the joint robot, and calculates an estimated value of the posture angle based on a rotation angle signal of each motor and a tension signal of each wire An angle estimation unit; a posture angle control unit that inputs a deviation between the posture angle target command and the posture angle estimation value and outputs a torque command; and the torque command and the stiffness target. Based on the estimated value of decrees and the posture angle is obtained by a tension command calculation unit for calculating a tension instruction.

  Torque commands required for posture feedback control while configuring a joint robot having a redundant motor and a wire incorporating a non-linear spring that transmits force by connecting the motor and movable plate in terms of joint freedom By constructing a joint robot control device that controls the wire tension by giving a wire tension command according to the target command of rigidity and the machine, while making the posture angle of three degrees of freedom accurately follow the target command, the machine The rigidity of the can also be controlled. Further, by giving the rigidity target command to a small value at high speed displacement and a large value at high acceleration / deceleration and low speed displacement, both good safety and excellent control performance can be achieved.

The block diagram of the joint robot which shows 1st Example of this invention Block diagram showing joint robot controller The block diagram of the joint robot which shows 2nd Example

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of an articulated robot showing a first embodiment of the present invention. In the figure, the motors 101, 102, 103, and 104 have a stator installed above the base 121 so that the axial center line of the rotor is parallel to the surface of the base 121. Winding devices 105, 106, 107, and 108 are connected to the rotation shafts of motors 101, 102, 103, and 104, respectively, and wind the wire while rotating together with the rotor of the motor. The wires 111, 112, 113 and 114 incorporate non-linear springs 115, 116, 117 and 118, respectively. Here, the term “non-linear spring” means that the spring constant is not a constant value but changes according to displacement. For example, a coil spring whose pitch is changed stepwise is used. Not only this but the structure which combined the movable pulley between two motors and the two static pulleys connected with each motor with the wire can be taken. The support pillar 122 is installed on the upper surface of the base 121 so that the axis center line is perpendicular. The movable plate 124 has an output shaft 125 fixed vertically at the upper center. The spherical joint 123 has a spherical portion connected to the tip of the support column 122 and a receiving member connected to the movable plate 124. Fixed orthogonal coordinates so that the contact point between the axial center line of the support column 122 and the top surface of the base 121 is the origin o, the center line of the support column 122 is the z axis, and the direction away from the top surface of the base 121 is the positive direction of the z axis A system xyzo is provided. Further, the spherical center point of the spherical portion of the spherical joint 123 is the origin O, the axis center line of the output shaft 125 is the Z axis, and the direction away from the upper surface of the movable plate 124 is the positive direction of the Z axis. A moving orthogonal coordinate system XYZO is provided in which the Y axis and the Z axis are parallel to the x axis, the y axis, and the z axis, respectively, and move together with the movable plate 124. The motor 101 and the winding device 105 are in the first quadrant of the fixed plane coordinate system xoy, the motor 102 and the winding device 106 are in the second quadrant of the fixed plane coordinate system xoy, and the motor 103 and the winding device 107 are the fixed plane coordinate system. The motor 104 and the winding device 108 are installed in the third quadrant of the fixed plane coordinate system xoy in the fourth quadrant of xoy. A and B on the lower surface of the movable plate 124 whose phases in the moving plane coordinate system XOY are the same as the phases in the fixed plane coordinate system xoy at the wire entrances a, b, c and d of the winding devices 105, 106, 107 and 108, respectively. , C and D, universal joints 131, 132, 133 and 134 are installed. Further, the non-linear spring 115 is provided between the winding device 106 and the universal joint 131, between the winding device 105 and the universal joint 132, between the winding device 107 and the universal joint 133, and between the winding device 108 and the universal joint 134, respectively. The wire 111 into which the nonlinear spring 116 is incorporated, the wire 113 into which the nonlinear spring 117 is incorporated, and the wire 114 into which the nonlinear spring 118 is incorporated are attached.
FIG. 2 is a block diagram showing a control device for the joint robot. In the figure, a target command generation unit 201 generates target command values α ^* , β ^* , γ ^* and a stiffness target command value η ^* of the attitude angle of the output shaft. The encoders 141, 142, 143, and 144 detect the rotation angles θ ₁ , θ ₂ , θ _3, and θ ₄ of the motors 101, 102, 103, and 104, respectively. The tension sensors 151, 152, 153 and 154 detect the tensions F ₁ , F ₂ , F ₃ and F ₄ of the wires 111, 112, 113 and 114, respectively. The posture angle estimation unit 204 inputs the outputs of the encoders 141, 142, 143, and 144 and the outputs of the tension sensors 151, 152, 153, and 154, and estimates the posture angles α, β, and γ, α _s , β _s, and γ _s is output. The posture angle control unit 202 includes a deviation e _α between the target command value α ^* and the estimated value α _s of the posture angle _α , a deviation e β between the target command value β ^* and the estimated value β _s of the posture angle _β, and the posture angle. A deviation e _γ between the target command value γ ^* of γ and the estimated value γ _s is input, and torque commands T _Xc, T _Yc and T _Zc are output. Based on the torques T _Xc, T _Yc , T _Zc , the stiffness target command value η ^* and the posture angle estimation values α _s , β _s , γ _s , the tension command calculation unit 204 _generates tension commands F _1c , F _2c , Calculate F _3c and F _4c . The tension controllers 211, 212, 213, and 214 are respectively a deviation between the tension command F _1c and the tension F ₁ of the wire 111, a deviation between the tension command F _2c and the tension F ₂ of the wire 112, and a tension command F _{3c of the} wire 113. a tension _{F 3} and the deviation and the wire 114 of the tension instruction _{F 4c} and the tension _{F 4} and the deviation by inputting the motor 101, 102, 103 and 104 of the current command _{I 1c, I 2c,} outputs the _{I 3c} and _{I 4c} To do. The motor drive units 221, 222, 223, and 224 drive and control each motor based on the current commands I _1c , I _2c , I _3c, and I _4c of the motors 101, 102, 103, and 104, respectively.

Hereinafter, a method for realizing each compensation unit of the control device will be described.
First, a method for realizing the posture angle estimation unit 204 will be described.
The XYZ Euler angles (herein referred to as posture angles) of the movable plate 124 are α, β, and γ, and the corresponding posture conversion matrix R is expressed by Equation (1).

However, the element of R is represented by Formula (2)-Formula (10).

The absolute coordinates of the points a, b, c, and d are respectively (x _a , y _a , z _a ), (x _b , y _b , z _b ), (x _c , y _c , z _c ), (x _d , y _d , z _d ), and the absolute coordinates of point _O are (x _O , y _O , z _O ), the relative coordinates of points a, b, c, and d are expressed by equations (11) to (14). Is given as follows.
(X _a , Y _a , Z _a ) = {(x _a , y _a , z _a ) − (x _O , y _O , z _O )} R ⁻¹ (11)
(X _b , Y _b , Z _b ) = {(x _b , y _b , z _b ) − (x _O , y _O , z _O )} R ⁻¹ (12)
_{(X c, Y c, Z} c) = {(x c, y c, z c) - (x O, y O, z O)} R -1 (13)
(X _d , Y _d , Z _d ) = {(x _d , y _d , z _d ) − (x _O , y _O , z _O )} R ⁻¹ (14)
Then, the relative coordinates of points A, B, C, and D are respectively (X _A , Y _A , Z _A ), (X _B , Y _B , Z _B ), (X _C , Y _C , Z _C ), (X _{D, Y} D, When _{Z D),} the vector

However, I, J, and K are unit vectors facing the X-axis, Y-axis, and Z-axis directions, respectively.
Therefore, the distance L ₁ between the points A and b, the distance L ₂ between the points B and a, the distance L ₃ between the points C and d, and the distance between the points D and c. the distance _{L 4} are given by equation (19) to (22).

When the mechanism of the joint robot is determined, the absolute coordinates of the points a, b, c, d, and O and the relative coordinates of the points A, B, C, and D are known, and the equations are obtained from the equations (1) to (14). Expressions (19) to (22) are functions of the posture angles α, β, and γ.
On the other hand, the relationship between the force F generated by the non-linear spring and the corresponding expansion / contraction amount σ is expressed by Expression (53).
F = f (σ) (23)
Further, when the radius of the pulley of the winding device is r, Expressions (24) to (27) are established.
L ₁ = f ⁻¹ (F ₁ ) + θ ₁ r (24)
L ₂ = f ⁻¹ (F ₂ ) + θ ₂ r (25)
L ₃ = f ⁻¹ (F ₃ ) + θ ₃ r (26)
L ₄ = f ⁻¹ (F ₄ ) + θ ₄ r (27)
Where F ₁ , F ₂ , F ₃ and F ₄ are the tensions of the wires 111, 112, 113 and 114, respectively, and θ ₁ , θ ₂ , θ ₃ and θ ₄ are the rotation angles of the motors 101, 102, 103 and 104, respectively. (A value obtained by multiplying the rotation angle of the motor by the gear ratio when there is a gear between the motor and the winding device).
The values of the tensions F ₁ , F ₂ , F ₃ and F ₄ detected by the tension sensors 151, 152, 153 and 154, and the rotation angles θ ₁ , θ ₂ , θ ₃ and the encoders 141, 142, 143 and 144 detected Substituting the value of θ ₄ into the equations (24) to (27), L ₁ , L ₂ , L ₃ and L ₄ are calculated. Then, when the simultaneous equations are solved by substituting the values of L ₁ , L ₂ , L ₃ and L ₄ into the equations (19) to (22), the posture angles α, β and γ can be obtained. The values of the posture angles α, β, and γ thus determined are assumed to be estimated values α _s , β _s, and γ _s of the posture angles α, β, and γ.
Next, a method for realizing the posture angle control unit 202 will be described.
Torque by applying PID compensation to the deviations e _α , e _β and e _γ obtained by subtracting the estimated values α _s , β _s and γ _s of the posture angle from the posture angle command values α ^* , β ^* and γ ^* , respectively. _Commands T _Xc, T _Yc and T _Zc are obtained.
Next, a method for realizing the tension command calculation unit 204 will be described.
Assuming that all the wires are always fully extended (the wire tension is 0 or more), the force vector acting on the movable plate 124 by each wire is expressed by the equations (28) to (31). It is expressed as follows.

A vector using the relative coordinates of points A, B, C, and D

A vector of torque generated by is expressed by equations (36) to (39).

Therefore, the amount of the total torque T acting on the movable plate 124 in the X, Y, and Z directions is expressed as in Expression (40) to Expression (42).

However,

T _Xc, T _Yc , and T _Zc are substituted for T _X, T _Y , and T _Z , respectively, and F _1c , F _2c , F _3c , and F _4c are substituted for F ₁ , F ₂ , F ₃ , and F ₄ respectively. Substituting into (40) to (42) results in (55) to (57).

Instead of the posture angles α, β, and γ, the posture angle estimation values α _s , β _s, and γ _s calculated by the posture angle estimation unit 204 are substituted into the equations (2) to (10), and the posture conversion matrix R Each element is calculated, and the relative coordinates of points a, b, c, and d are calculated as in equations (11) to (14). Together with L ₁ , L ₂ , L ₃ and L ₄ obtained by substituting the relative coordinates of points a, b, c, d and points A, B, C, and D into equations (19) to (22) Substituting into equations (43) to (54), _kX1-4 , _kY1-4, and _kZ1-4 are calculated. Then, when the torque commands T _Xc, T _Yc, and T _Zc that have entered from the attitude angle control unit 202 are substituted into Expressions (55) to (57), Expressions (55) to (57) are expressed as F _1c , F It becomes a linear equation of _2c , _F3c , _F4c .
On the other hand, if the non-linear spring has a larger spring constant as the amount of deformation increases, the tension of each wire may be increased when high rigidity is required. Therefore, the command value F _s ^* of the sum of the tensions F _s of each wire corresponding to the stiffness target command value η ^* is given as shown in Expression (58).
F _s ^* = g (η ^* ) (58)
However, g (·) is a monotonically increasing function.
In general, when the simultaneous equations are solved by adding the formula (59) to the formulas (55) to (57), F _1c , F _2c , F _3c , and F _4c can be uniquely determined.
_{F 1c + F 2c + F 3c} + F 4c = F s * (59)
However, the simultaneous equations of equations (55) to (57) and (59) may be singular. In that case, each variable F _1c , F _2c , F _3c , F _4c is multiplied by an appropriate weighting factor k ₁ , k ₂ , k ₃ , k ₄ , respectively, and equation (59) is expressed as equation (60). You can rewrite to
_{k 1 F 1c + k 2 F} 2c + k 3 F 3c + k 4 F 4c = F s * (60)
Also, when the safety in a certain direction is more important, the weighting coefficient corresponding to the wire close to that direction may be set large in order to reduce the rigidity in that direction.
When the value of the tension command obtained by solving the simultaneous equations becomes negative, the function g (•) is corrected as shown in Equation (61).
g (η ^* ) = g (η ^* ) + F _a ^* (61)
However, F _a ^* is an appropriate positive number. When the equation (59) is incorporated in the simultaneous equations, F _a ^* may be given to a value slightly larger than twice the absolute value of the sum of the negative variables. Further, when there is still a negative solution for the modified simultaneous equations, the above correction method may be repeated until all the solutions of the simultaneous equations become positive.
Finally, a method for realizing the tension control unit will be described.
A PI compensator may be included in the tension control unit.

Hereinafter, the operation principle of the joint robot will be described.
In general, the tension control minor loop has a smaller phase delay than the main loop for posture control, so that the gain of the tension control unit can be increased greatly, and the response characteristic of the tension control minor closed loop is high. That is, the wire tension is controlled according to the tension command.
On the other hand, since the tension command is obtained based on the equations (55) to (57), the moving coordinate system is compared by comparing the equations (55) to (57) with the equations (40) to (42). It can be seen that the torques T _X, T _Y , and T _Z around the respective axes follow the commands T _Xc , T _Yc , and T _Zc . That is, the stiffness control does not affect the posture control, and the stiffness and the posture can be controlled independently and accurately.
The influence of the rigidity on the control performance is significant when the output shaft 125 is displaced at high acceleration / deceleration and at low speed. On the other hand, safety should be considered when the output shaft 125 is displaced at a high speed. Therefore, the rigidity target command may be given to a small value at high speed displacement and a large value at high acceleration / deceleration and low speed displacement.

  Thus, in view of the degree of freedom of the joint, a joint robot having a redundant motor and a wire incorporating a non-linear spring that transmits the force by connecting the motor and the movable plate is configured, and for posture feedback control. By constructing a joint robot controller that controls the wire tension by giving the wire tension command according to the required torque command and the stiffness target command, the posture angle of 3 degrees of freedom is accurately followed by the target command. In addition, the rigidity of the machine can be controlled. Further, by giving the rigidity target command to a small value at high speed displacement and a large value at high acceleration / deceleration and low speed displacement, both good safety and excellent control performance can be achieved.

FIG. 3 is a block diagram of the joint robot showing the second embodiment. In the figure, the turning motor 320 has a stator installed at the center of the base 321 so that the axial center line of the rotor is perpendicular to the surface of the base 321. The winding motors 301, 302, and 303 are installed at three positions that are equiangular with each other on the circumference with the stator as the center above the base 321. The winding devices 304, 305, and 306 wind the wire while rotating together with the rotor of the winding motor. The wires 311, 312, and 313 incorporate non-linear springs 314, 315, and 316, respectively. The turning transmission shaft 322 is connected to the rotor of the turning motor 320. The movable plate 324 is provided with a cylindrical support 326 at the center of the upper surface. The universal joint 323 connects the turning transmission shaft 322 and the output shaft 325. Thrust bearings 327 and 328 restrain the output shaft 325 to the support base 326. The fixed orthogonal coordinate system xyzo is provided so that the center o of the base 321 is the origin o, the center line of the swivel transmission shaft 322 is the z axis, and the direction away from the upper surface of the base 321 is the positive direction of the z axis. The center of the universal joint is the origin O, the axis center line of the output shaft 419 is the Z axis, the direction away from the upper surface of the movable plate 324 is the positive direction of the Z axis, and the lower surface of the movable plate 324 is parallel to the upper surface of the base 321. A moving orthogonal coordinate system XYZO that moves together with the movable plate 324 is provided so that the X axis and the Y axis are parallel to the x axis and the y axis, respectively. The phase in the moving plane coordinate system XOY is the same as the phase in the fixed plane coordinate system xoy where the wire entrances a, b, c of the winding devices 304, 305, 306 are on the circumference around the lower surface of the movable plate 324. Universal joints 317, 318, and 319 are installed at points A, B, and C that are equiangular with each other. Further, a wire 311 and a nonlinear spring 315 in which a nonlinear spring 314 is taken in between the winding device 304 and the universal joint 317, between the winding device 305 and the universal joint 318, and between the winding device 306 and the universal joint 319, respectively. The taken-in wire 312 and the wire 313 into which the non-linear spring 316 is taken in are attached.

Hereinafter, the operation principle will be described.
Since the turning transmission shaft 322 is fixed to the mover of the turning motor 320, the central position of the universal joint 323 connected to the tip of the turning transmission shaft 322 does not change. It can only be displaced around. In other words, the tip of the output shaft 325 performs a spherical motion with three degrees of freedom around the center point of the universal joint 323. Further, since the support base 326 and the output shaft 325 are constrained by the thrust bearings 327 and 328, the relative motion between them is only the rotational motion about the axis of the output shaft 325. Therefore, the support base 326 and the movable plate 324 to which the support base 326 is fixed can only be displaced around the center point of the universal joint 323.
When the frictional force of the thrust bearing is sufficiently small, the rotational motion around the Z axis between the output shaft 325 and the support base 326 does not affect each other. The posture of the output shaft 325 in the X-axis and Y-axis directions is determined by the posture of the movable plate 324, but the posture in the Z-axis direction is completely determined by the rotation angle of the turning motor 320. That is, the two-degree-of-freedom motion of the output shaft 325 is operated using three wires. Therefore, the posture and rigidity in the X-axis and Y-axis directions can be adjusted independently. On the other hand, although the rigidity around the Z-axis cannot be adjusted, a large torque is not output because the maximum radius of rotation around the Z-axis is small, so that no great damage is caused to the outside.

As described above, since the posture and rigidity in the direction in which the output torque increases are independently adjusted using three wires, it is possible to achieve both good safety and excellent control performance for the joint robot.
Compared with the first embodiment, when the technique of this embodiment is used, the structure is slightly complicated, but the movable range is widened.

100 Joint robot 101, 102, 103, 104 Motor 105, 106, 107, 108 Winding device 111, 112, 113, 114, 311, 312, 313 Wire 115, 116, 117, 118, 315, 316, 317 Non-linear spring 131, 132, 133, 134, 317, 318, 319 Universal joint 121, 321 Base 122 Support column 123 Spherical joint 124, 324 Movable plate 125, 325 Output shaft 141, 142, 143, 144 Encoder 151, 152, 153, 154 Tension sensor 201 Target command generation unit 202 Attitude angle control unit 203 Tension command calculation unit 204 Attitude angle estimation units 211, 212, 213, 214 Tension control units 221, 222, 223, 224 Motor drive units 301, 302, 303 Winding motor 04,305,306 retractor 320 pivot motor 322 turning the transmission shaft 323 universal joint
327, 328 Thrust bearing

Claims (3)

A base, four motors installed on the base, four winding devices respectively attached to the four motors, and a support column installed so that an axial center line is perpendicular to the surface of the base, A spherical joint attached to the upper end of the support column, a movable plate attached to the spherical joint, four universal joints installed at the bottom of the movable plate, four winding devices and four universal Four wires incorporating nonlinear springs that connect the joints one-to-one, and an output shaft fixed so that an axial center line is perpendicular to the upper surface of the movable plate, The spherical center point is the origin O, the axis center line of the output shaft is the Z axis, the direction away from the upper surface of the movable plate is the positive direction of the Z axis, and the moving straight line moves along with the movable plate. A cross coordinate system XYZO is provided,
The intersection point between the axis center line of the support column and the surface of the base is the origin o, the axis center line of the support column is the z axis, the direction away from the surface of the base is the positive direction of the z axis, and the output shaft A fixed orthogonal coordinate system xyzo is provided so that the x axis and the y axis are parallel to the X axis and the Y axis, respectively, when the axis center line coincides with the axis center line of the support column;
The four motors are arranged so that the four winding devices are in different quadrants of the xoy coordinate system, and the four universal joints have phases in the XOY coordinate system, respectively, in the xoy coordinate system of the four winding devices. The winding device in the first quadrant of the xoy coordinate system and the universal joint in the second quadrant of the XOY coordinate system are arranged so as to have the same value as the phase, and the second quadrant of the xoy coordinate system The winding device in the first quadrant of the XOY coordinate system and the universal joint in the third quadrant of the xy coordinate system and the universal joint in the fourth quadrant of the XOY coordinate system The robot is characterized in that the winding device in the fourth quadrant of the xoy coordinate system and the universal joint in the third quadrant of the XOY coordinate system are respectively connected by four wires.   A base, three winding motors in which the stator is fixed above the base, and the axial centerline of the rotor is parallel to the surface of the base, and one pivot in which the axial centerline of the rotor is perpendicular to the surface of the base 420 A motor, three winding devices respectively attached to the three winding motors, a turning transmission shaft connected to a mover of the turning motor, and a universal joint attached to an upper end of the turning transmission shaft; A movable plate, a support base fixed to the center of the upper surface of the movable plate, two or more thrust bearings, three universal joints, three winding devices and three universal joints on a one-to-one basis 3 wires incorporating nonlinear springs to be connected, and an output shaft attached to the universal joint, the swing motor is installed in the center of the base, and the three winding motors Installed at three equiangular positions on the circumference centered above the base, and the three universal joints at three equiangular positions on the circumference centered on the lower surface of the movable plate. A robot installed and restrained by two or more thrust bearings between the output shaft and the support base. A target command generation unit that generates a target command for posture angle and a target command for rigidity, an encoder that detects the rotation angle of each motor, and a tension sensor that detects the tension of each wire, and the tension of each wire While controlling the tension based on the command and the tension signal of each wire, the tension command for each wire is generated based on the posture angle target command, the rigidity target command, and the rotation angle signal of each motor. Control the posture angle and rigidity of the joint robot,
A posture angle estimator for calculating an estimated value of the posture angle based on the rotation angle signal of each motor and the tension signal of each wire;
A posture angle control unit that inputs a deviation between the posture angle target command and the estimated value of the posture angle and outputs a torque command;
A robot control device comprising: a tension command calculation unit that calculates a tension command based on the torque command, the stiffness target command, and the estimated value of the posture angle.

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