JPH09309089A - Wrist mechanism for assembly robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform further pliable assembly work by a method wherein a force generated at a compliance mechanism is detected and based on a detecting force, feedback control is performed. SOLUTION: The arm mechanism having three sets of links 13 is formed such that the arm mechanism of an assembly robot comprises a cylinder member 15 and a rod member 16, and forms a direct acting mechanism having one degree of freedom, the end part of the cylinder member 15 is coupled in such a manner to be rotated integrally with the rotary shaft 14a of the rotation motor 14, and the end pat of the rod member 16 is rotatably coupled to a moving body 12. A torque sensor 22 to detect torque of a rotary motor 14 is provided. Based on the detecting torque, feedback control is effected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wrist mechanism of a robot, and more particularly to a wrist mechanism of a robot having a compliance mechanism that absorbs positional deviation between assembly members.

[0002]

2. Description of the Related Art Conventionally, in order to smoothly perform a fitting operation by a robot, an assembly robot having a compliance mechanism for connecting a hand to an arm in a displaceable manner and absorbing a positional deviation of a central axis line between assembly parts. A wrist mechanism is known. As a wrist mechanism of this type of robot, for example, the one described in Japanese Examined Patent Publication No. 4-20755 is reported. This mechanism is provided with a linear motor in which a yoke 30A, a coil plate 33A, a permanent magnet 34A, and a yoke 31A are layered on a pair of parallel leaf springs 23A facing each other for controlling the X direction, and a parallel plate spring 23A is provided. A linear motor in which a yoke 30B, a coil plate 33B, a permanent magnet 34B, and a yoke 31B are superposed on a pair of parallel leaf springs 23B opposed to each other for Y-direction control with a 90 ° phase shift is provided. By configuring 2, the X is adjusted according to the insertion pressure when the assembly part A is inserted into the mating part B.
The size and weight of the compliance mechanism that deforms in the Y direction and the Y direction are reduced.

As described above, the conventional wrist mechanism of a robot generally employs a compliance mechanism in which a stage displaceable in the X direction and a stage movable in the Y direction are multi-staged by using laminated rubber or coils. In addition, the compliance is variable in order to suppress shaking of the hand during movement. However, in the conventional wrist mechanism, since the stage displaceable in the X direction and the stage displaceable in the Y direction are configured in multiple stages, the thickness of the mechanism (direction orthogonal to the XY plane) is large. I was left with such a problem.

Further, in the conventional wrist mechanism, XY
Although excellent compliance was obtained with respect to the insertion pressure in the direction, it is not possible to cope with the positional deviation in the rotation direction (hereinafter, also referred to as the θ direction) with the direction orthogonal to the XY plane as the central axis. That left a problem. Therefore, the applicant of the present application previously proposed a wrist mechanism of an assembly robot described in Japanese Patent Application No. 7-196386 in order to solve the above problem. This wrist mechanism has a base member 1 at one end.
Two sets of links 12 having two 1-degree-of-freedom rotary joints and one-degree-of-freedom linear motion mechanism connected to the movable body 13 at the other end are provided, and each link 12 is servo-controlled. Driven by a possible rotary motor 14,
If a displacement occurs in the X direction, the Y direction, or the θ direction during the fitting work of the parts, the link 32 is expanded or contracted or rotated according to the displacement direction of the movable body 13 to absorb the displacement. There is. In addition, the P gain and D gain of the PD gain circuit 28 in the servo control circuit 9 are changed to change the compliance characteristic of the movable body 13, and the gravity compensation circuit 29 adds the gravity compensation value to the PD gain and Maintains compliance characteristics regardless of posture. For this reason, the wrist mechanism of the robot which can perform the insertion work more smoothly is provided.

[0005]

However, in the wrist mechanism of the assembly robot described in Japanese Patent Application No. 7-196386, PD control is performed for each joint of each link 12, and therefore the rotary motor 14 is used. If a speed reducer is interposed between the link 12 and the link 12, there is a problem that it is difficult to accurately set the compliance due to friction loss and viscous resistance of the speed reducer.

Further, since the compliance mechanism performs feedback control according to the displacement thereof, the work is stopped when a force exceeding a predetermined force is applied to the compliance mechanism, for example, a constant force is maintained regardless of the displacement. It did not reach the active control such as to perform, or regard it as the end of the assembly work. Therefore, an object of the present invention is to provide a wrist mechanism of a robot that can perform more flexible assembly work by detecting a force generated in a compliance mechanism and performing feedback control based on the detected force. I am trying.

[0007]

In order to achieve the above object, the invention according to claim 1 is a base member connected to the tip of a robot arm, a movable member to which a robot hand can be attached, and the base member. A first rotary joint rotatably connected to one surface of the movable member, a second rotary joint rotatably connected to one surface of the movable member, and a distance between the first and second rotary joints. At least three or more link means having a variable linear motion mechanism, and a first of the link means.
A robot wrist mechanism including an actuator that drives any one of a rotary joint, a second rotary joint, and a linear motion mechanism, and a control unit that outputs a control signal to the actuator. It is characterized in that a detecting means for detecting a force is provided, and the control means carries out a feedback control of the actuator based on a detection signal of the detecting means.

According to the first aspect of the invention, the feed back control of the actuator is performed by the control means based on the driving force of the actuator detected by the detection means. Therefore, the force generated in the compliance mechanism can be observed based on the driving force of the actuator detected by the detection means, and the feedback control of the actuator can be performed. Therefore, the assembly work is performed while setting the compliance to an appropriate value. be able to. For this reason, for example, when no force is applied between the parts, the occurrence of galling is prevented, the force generated in the compliance mechanism is kept constant, or the force exceeding the predetermined force is applied to the compliance mechanism. It is possible to perform active control such that the work is stopped immediately or the assembly work is regarded as the end. Therefore, it is possible to provide a wrist mechanism of a robot that can perform more flexible assembly work.

According to a second aspect of the present invention, a base member connected to the tip of the robot arm, a movable member to which a robot hand can be attached, and a first member rotatably connected to one surface of the base member. At least 3 having a rotary joint, a second rotary joint rotatably connected to one surface of the movable member, and a linear motion mechanism capable of varying a distance between the first and second rotary joints. One or more plurality of link means, an actuator that drives any one of the first rotary joint, the second rotary joint, and the linear motion mechanism of the link means, and control means that outputs a control signal to the actuator In a wrist mechanism of a robot comprising: a detecting means for detecting a force acting on the movable member via the robot hand, the control means based on a detection signal of the detecting means. The above And performing Fiddobakku control actuator.

According to a second aspect of the present invention, the movable member is provided with detection means for detecting a force acting between the robot hand and the link means, and the control means performs the feedback of the actuator based on the detection signal of the detection means. Control is performed. Therefore, the force generated in the compliance mechanism can be observed by the detection means and feedback control of the actuator can be performed, so that the assembly work can be performed while setting the compliance to an appropriate value.
For this reason, for example, when no force is applied between the parts, the occurrence of galling is prevented, the force generated in the compliance mechanism is kept constant, or the force exceeding the predetermined force is applied to the compliance mechanism. It is possible to perform active control such that the work is stopped immediately or the assembly work is regarded as the end. Therefore, it is possible to provide a wrist mechanism of a robot that can perform more flexible assembly work.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the invention described above, the actuator is a rotary motor. According to the third aspect of the invention, since the actuator is constituted by the rotary motor, the servo mechanism having the feedback control circuit together with the control means can be easily constituted.

According to a fourth aspect of the present invention, in the first aspect of the invention, the actuator comprises a rotary motor, and the detecting means comprises a torque sensor for detecting the torque of the rotary motor. . In the invention of claim 4, since the actuator is constituted by the rotary motor and the torque thereof is detected by the torque sensor, the servo mechanism having the feedback control circuit together with the control means can be easily constituted. .

According to a fifth aspect of the present invention, in the second aspect of the present invention, the detecting means has X-axis and Y-axis which are orthogonal to each other.
It is characterized in that each of at least two axial directions of the axes and the Z axis and the rotational force with the remaining one axis as a central axis are detected. In the invention according to claim 5, of the detecting means, the respective forces in at least two axial directions of the X axis, the Y axis, and the Z axis orthogonal to each other and the rotational force having the remaining one axis as the central axis are detected. With this configuration, for example, when an inserting pressure is generated in the X direction, the Y direction, or the θ direction during the fitting work of the parts, the link means is driven by the actuator according to the pressure in the displacement direction of the movable body. As a result, the pressure in the displacement direction can be absorbed. Therefore, a smoother insertion work can be performed.

The invention according to claim 6 is the invention according to claim 3 or 4.
In the invention described above, an encoder for detecting the rotation amount of the rotary motor is provided, and the control means performs feedback control of the actuator based on the rotation amount detected by the encoder. According to the sixth aspect of the invention, the feedback control of the actuator is performed by the control means based on the rotation amount of the rotary motor detected by the encoder. Therefore, since the feedback control system can be configured based on the rotation amount of the rotary motor detected by the encoder, the compliance effect in the position displacement space of the movable member due to the rotation of the link means can be reliably generated. .

[0015]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIGS. 1 to 5 are views showing a preferred embodiment of a wrist mechanism of a robot according to the present invention, and FIG. 1 is a view showing an overall configuration of a robot to which the wrist mechanism is applied. is there. As shown in FIG. 1, the robot 1 has a body 2,
Arm 3, arm 4, arm 5, wrist mechanism 6, hand 7
And a controller 8.

The body 2 comprises a fixed part 2a fixed to the installation surface and a swivel part 2b for swiveling the arm 3 in the horizontal direction. The arm 3 is provided so as to rotate in the vertical direction with respect to the body 2 with the rotating shaft 3a as a fulcrum, and the arm 4 is provided at the tip of the arm 3 so as to rotate in the vertical direction with the rotating shaft 4a as a fulcrum. The arm 5 is provided at the tip of the arm 4.
Are provided so as to be rotatable in the vertical direction with the pivot shaft 5a as a fulcrum, and each constitutes a rotary joint. The central axes of the arms 3, 4 and 5 are designed to rotate in substantially the same plane. A hand 7 is provided at the tip of the arm 5 via a wrist mechanism 6.

As shown in FIGS. 2 to 4, the wrist mechanism 6 is
A base body 11 fixed to the flange-shaped tip portion 5b of the arm 5 with a plurality of screws 10, a movable body 12 to which the hand 7 is attached, and one end of the base body 11 provided on one surface side of the base body 11. Three sets of links 13 which are connected to each other and the other end of which is connected to the movable body 12, and a rotary motor 1 which is provided on the other surface side of the base body 11 and drives each link 13 respectively.
4 is provided.

The link 13 is composed of a cylinder member 15 and a rod member 16 fitted in the cylinder member 15 so as to be able to move back and forth, and constitutes a linear motion mechanism having one degree of freedom. Further, the end portion of the cylinder member 15 is connected so as to rotate integrally with the shaft 17 around the shaft 17 that is integrally connected with the rotation shaft 14a of the rotary motor 14, and constitutes a rotary joint with one degree of freedom. are doing. The end of the rod member 16 is rotatably connected to the movable body 12 about a shaft 18 provided on the movable body 12 to form a rotary joint having one degree of freedom.

The rotary motor 14 is composed of, for example, a servo motor, and is fixed to the other surface side of the base body 11 via a support base 20 together with a rotary encoder 19 for detecting the rotation amount of the rotary motor 14. The shaft 17 is connected to the rotary shaft 14a of the rotary motor 14 and is axially supported by a bearing 21 inserted in the base body 11 so as to rotate integrally with the rotary shaft 14a. A torque sensor 22 for detecting the torque of the rotary motor 14 is provided on the rotary shaft 14a, and the detected torque is output to the servo control circuit 9 described later. As the torque sensor 22, for example, one using a strain gauge is small and lightweight and easy to use, but the present invention is not limited to this. The end of the cylinder member 15 is fitted to the shaft 17 via the spacer 23 and defined by the nut 24.

As shown in FIGS. 2 and 4, each link 13 has a center of the movable body 12 and the base body 1 in an initial state.
The center of the linear motion mechanism is aligned with the Z-axis direction, and the linear motion mechanisms are arranged at equal angles so that the linear motion mechanism moves toward the center of the base body 11. Returning to FIG. 1, the controller 8 controls each drive unit of the robot 1, and has a servo control circuit 9 inside which controls the compliance of the wrist mechanism 6. As shown in FIG. 5, the servo control circuit 9
Constitutes a torque control system for feeding back the torques T ₁ , T ₂ and T ₃ of the rotary motors 14 detected by the torque sensors 22.

Further, the servo control circuit 9 controls the rotation angle Δ of the rotary motor 14 detected by each encoder 19.
Based on θ ₁ , Δθ ₂ , Δθ ₃ Tr = K _T Δθ (1) where Tr = [T _r1 T _r2 T _r3 ] ^t , Δθ = [Δθ ₁ Δθ ₂ Δθ ₃ ] ^t , K _T It has a target value calculation circuit 31 for calculating a target value (torque) Tr represented by a diagonal matrix of 3 rows and 3 columns, and constitutes a position feedback control system.

_KT is obtained as follows. Here, as shown in FIG. 4, the base body 11 in the initial state is
In the XY space consisting of the X-axis and the Y-axis directions which are orthogonal to each other and whose center is the origin of the movable body 12, the displacement of the movable body 12 in the X-axis direction is Δx, the displacement in the Y-axis direction is Δy, The rotation angle of the movable body 12 is represented by Δθ ₀ , the X-axis component of the force acting on the movable body 12 is fx, and the Y-axis component is f.
y, and the moment acting on the movable body 12 is represented by M, Δθ = J ^-1 ΔX (2) Tr = J ^t F (3) where J: Jacobian matrix, ΔX = [Δx It is known that the relationship of Δy Δθ ₀ ] ^t and F = [fx fy M] ^t holds. The Jacobian matrix represents the geometrical properties of the wrist mechanism consisting of three links. Then, from the formulas (1) to (3), F = (J ^t ) ^-1 K _T J ^-1 ΔX (4) holds. Here, F = K _F ΔX (5) However, if KF: is defined as a diagonal matrix of 3 rows and 3 columns, then by the equations (4) and (5), KT = J ^t K _F J (6) becomes, and the compliance effect in the XY space can be provided.

Further, 32 is a target value Tr and the torque sensor 2
Error ΔT =
An arithmetic circuit for calculating Tr-T, 33 is proportional-integral control (PI control) according to the arithmetic result of the arithmetic circuit 32.
It is a PI gain circuit for performing. The P gain is calculated by the arithmetic circuit 32.
The error ΔT obtained in step 1 is fed back, and the I gain reduces the steady deviation of ΔT. Rotary motor 1
4 is driven by using the output of the PI gain circuit 33 as a control signal, and the wrist mechanism 6 is operated.

Next, the operation will be described. The operation of the wrist mechanism of this robot will be described by taking an insertion operation between two parts as an example.
In the initial state, in each link 13, the center of the movable body 12 and the center of the base body 11 coincide with each other in the Z-axis direction with the hand 7 holding one component, and the forward / backward direction of the linear motion mechanism is the base body. They are arranged at equal angles to each other so as to face the center of 11. At this time, Δθ ₁ = Δθ ₂ = Δθ ₃ = 0
It is.

During the inserting operation, the torque sensor 22 detects the torques T ₁ , T ₂ , and T ₃ of the rotary motors, and the encoder 19 rotates the rotation angles Δθ ₁ , Δθ ₂ , and Δθ of the rotary motors 14. ₃ is detected, the target value calculation circuit 31 calculates the target value Tr based on the above equation (1), the calculation circuit 32 calculates the error ΔT, and the PI gain circuit 33 performs PI control to perform rotation control of the rotary motor 14 Is activated. By the operation of each of the rotary motors 14, the link 13 rotates about the shaft 17, and the rod member 16 moves back and forth with respect to the cylinder member 15 to displace the movable body 12 in the direction of displacement, thereby generating compliance. To do.

Japanese Patent Application No. 7-19 described in the section of the prior art.
In the wrist mechanism of the assembly robot described in Japanese Patent No. 6386, since PD control is performed for each joint of each link 12, it is indirectly controlled by a model such as the voltage-torque characteristic of the motor. For example, the influence cannot be excluded unless the friction of the speed reducer is incorporated into the model, which makes it difficult to set accurate compliance.

On the other hand, in the robot wrist mechanism of the present embodiment, by feeding back the torque of the motor, the above influence is recognized as a disturbance, and the influence is suppressed by the disturbance suppressing operation of the feedback control system. be able to. Therefore, it becomes easy to set accurate compliance. Thus, in the present embodiment,
Based on the driving force of the rotary motor 14 detected by the torque sensor 22, the servo control circuit 9 causes the rotary motor 14 to rotate.
Feedback control is performed. Therefore, the force generated in the compliance mechanism is observed based on the driving force of the rotary motor 14 detected by the torque sensor 22,
Since the feedback control of the rotary motor 14 can be performed, the assembly work can be performed while setting the compliance to an appropriate value. For this reason, for example, when no force is applied between the parts, the occurrence of galling is prevented, the force generated in the compliance mechanism is kept constant, or the force exceeding the predetermined force is applied to the compliance mechanism. It is possible to perform active control such that the work is stopped immediately or the assembly work is regarded as the end. Therefore, it is possible to provide a wrist mechanism of a robot that can perform more flexible assembly work.

Since the actuator is constituted by the rotary motor 14 and the torque thereof is detected by the torque sensor 22, the servo mechanism having the feedback control circuit together with the servo control circuit 9 can be easily constructed. it can. Further, the servo control circuit 9 performs feedback control of the actuator based on the rotation amount of the rotary motor 14 detected by the encoder 19. Therefore, the feedback control system can be configured based on the rotation amount of the rotary motor 14 detected by the encoder 19, so that the compliance effect in the position displacement space (XY space) of the movable member due to the rotation of the link 13 is ensured. Can be caused to.

(Second Embodiment) FIGS. 6 to 7 are views showing a preferred embodiment of a wrist mechanism of a robot according to the present invention, and FIG. 6 is a view showing the wrist mechanism. In addition,
The same components as those of the wrist mechanism shown in FIGS. 2 to 4 are designated by the same reference numerals, and the description thereof will be omitted. As shown in FIG. 6, in the wrist mechanism, the movable body 40 is composed of a plate-shaped body 30a to which the rod members of the links 13 are connected and a hand 30b to which the hand 7 is attached, and a plate-shaped body 12a and a plate-shaped body 12b. The force sensor 31 is interposed between the two.

The force sensor 31 has a strain gauge inside, and applies a force acting in each axial direction of the X-axis, the Y-axis and the Z-axis, which are substantially orthogonal to each other, and a moment about each axial direction. It is something to detect. Force sensor 3
Three of these six components are used to provide the force 1 for detecting the forces fx, fy and the moment M in the θ direction acting in each of the X-axis and Y-axis directions shown in FIG. ing.

That is, the force sensor 31 is the torque sensor 2
In this case, the force acting on the movable body 40 can be observed without using the conversion formula (6) described above, so that the force control is easy. In addition, 32 is a coupling,
Is integrally connected to the rotating shaft 14a. FIG. 7 is a diagram showing the configuration of a servo control circuit that controls the operation of the rotary motor 14. As shown in FIG. 7, the servo control circuit constitutes a control system that feeds back fx, fy, and M detected by the force sensor 22.

Further, the servo control circuit is provided for each encoder 19
The rotation angles Δθ ₁ , Δ of the rotary motor 14 detected by
Fr = K _F ΔX based on θ ₂ and Δθ ₃ (7) However, the feedback control system includes target value calculation circuits 51 and 52 for calculating a target value Fr represented by ΔX = JΔθ. Are configured. The target value calculation circuit 52 is a circuit for calculating ΔX = [Δx Δy Δθ ₀ ] ^t based on the rotation angle Δθ = [Δθ ₁ Δθ ₂ Δθ ₃ ] ^t of the rotary motor 14, and the target value calculation circuit 51 is an equation. (7)
Is a circuit that executes. The calculation circuit 51 is a circuit that calculates the target value Fr = [fx _r fy _r M _r ] ^t by setting the gain K _F to a desired compliance.

Reference numeral 53 is a calculation circuit for calculating ΔF = Fr-F by adding / subtracting the target value Fr and the force F detected by the force sensor 41, and 54 is a circuit for calculating J ^t ΔF, Reference numeral 55 is a PI gain circuit that performs proportional-integral control (PI control) according to the result of this calculation. The rotary motor 14 is driven by using the output of the PI gain circuit 55 as a control signal, and the wrist mechanism 6 is operated.

Next, the operation will be described. Also in the wrist mechanism of this robot, similar to the wrist mechanism of the first embodiment,
Forces fx, fy, M acting on the movable body 40 via the hand 7 by the force sensor 41 during the insertion work between the two components.
Is detected, the rotation angles Δθ ₁ , Δθ ₂ , and Δθ _{3 of the} rotary motors 14 are detected by the encoder 19.
The target value Fr is calculated by the target value calculation circuits 52 and 51 based on the above equation (7), and the error ΔF is calculated by the calculation circuit 53.
Is calculated, PI control is performed by the J ^t circuit 54 and the PI gain circuit 55, and the rotary motor 14 is operated. By the operation of each of these rotary motors 14, the respective link 1
3 rotates about the shaft 17, and the rod member 16
Moves toward and away from the cylinder member 15, and the movable body 40 is displaced in the direction of displacement, generating compliance.

As described above, in the present embodiment, the movable body 4
0 is provided with a force sensor 41 for detecting a force acting on the link 13 via the hand 7, and a feed back control of the rotary motor 14 is performed by a servo control circuit based on a detection signal of the force sensor 41. Therefore, the force sensor directly detects the force generated in the compliance mechanism and the feedback control of the rotary motor 14 is performed, so that the assembly work can be performed while setting the compliance to an appropriate value. For this reason, for example, when no force is applied between the parts, the occurrence of galling is prevented, the force generated in the compliance mechanism is kept constant, or the force exceeding the predetermined force is applied to the compliance mechanism. It is possible to perform active control such that the work is stopped immediately or the assembly work is regarded as the end. Therefore, it is possible to provide a wrist mechanism of a robot that can perform more flexible assembly work.

Further, since the actuator is constituted by the rotary motor 14, the servo mechanism having the feedback control circuit together with the servo control circuit can be easily constructed. Further, the force sensor 41 is configured to detect the respective forces in at least two axis directions among the X axis, the Y axis, and the Z axis which are orthogonal to each other and the rotational force having the remaining one axis as the central axis. Therefore, when an inserting pressure is generated in the X direction, the Y direction, or the θ direction during the fitting work of the parts, the rotation mode is changed according to the pressure in the displacement direction of the movable body 40.
The link 14 can be driven by the motor 14 to absorb the pressure in the displacement direction. Therefore, a smoother insertion work can be performed.

Further, feedback control of the rotary motor 14 is performed by the control means based on the rotation amount of the rotary motor 14 detected by the encoder 19. Therefore, the feedback control system can be configured based on the rotation amount of the rotary motor 14 detected by the encoder 19, so that the compliance effect in the position displacement space (XY space) of the movable member due to the rotation of the link 13 is ensured. Can be caused to.

In the present embodiment, the servo control circuit is configured to feed back the detection signal of the force sensor 41 and the detection signal of the encoder 19, respectively. However, as shown in FIG. It is also possible to feed back only the detection signal of 41. In this case, X
The compliance effect in Y space cannot be generated. The control system shown in FIG. 8 matches the force F acting on the movable body 40 via the hand 7 with the target value Fr. For example, a work such as a grinder work that traces the work surface with a constant force. Suitable for Of course, whether or not the position feedback is performed by the encoder 19 can be easily switched according to the work contents of the robot, for example, by software switching means.

[0039]

According to the first aspect of the invention, the feed back control of the actuator is performed by the control means based on the driving force of the actuator detected by the detection means. Therefore, the force generated in the compliance mechanism can be observed based on the driving force of the actuator detected by the detection means, and the feedback control of the actuator can be performed. Therefore, the assembly work is performed while setting the compliance to an appropriate value. be able to. For this reason, for example, when no force is applied between the parts, the occurrence of galling is prevented, the force generated in the compliance mechanism is kept constant, or the force exceeding the predetermined force is applied to the compliance mechanism. It is possible to perform active control such that the work is stopped immediately or the assembly work is regarded as the end. Therefore, it is possible to provide a wrist mechanism of a robot that can perform more flexible assembly work.

According to the second aspect of the present invention, the movable member is provided with the detecting means for detecting the force acting on the movable member through the robot hand, and the control means detects the force of the actuator based on the detection signal of the detecting means. Performs feedback control. Therefore, the force generated in the compliance mechanism can be observed by the detection means and feedback control of the actuator can be performed, so that the assembly work can be performed while setting the compliance to an appropriate value. For this reason, for example, when no force is applied between the parts, the occurrence of galling is prevented, the force generated in the compliance mechanism is kept constant, or the force exceeding the predetermined force is applied to the compliance mechanism. It is possible to perform active control such that the work is stopped immediately or the assembly work is regarded as the end. Therefore, it is possible to provide a wrist mechanism of a robot that can perform more flexible assembly work.

According to the third aspect of the invention, since the actuator is constituted by the rotary motor, it is possible to easily construct the servo mechanism having the feedback control circuit together with the control means. According to the invention of claim 4, since the actuator is constituted by the rotary motor and the torque thereof is detected by the torque sensor, the servo mechanism having the feedback control circuit together with the control means can be easily constituted. You can

According to the fifth aspect of the present invention, the detecting means is rotated about the respective forces in at least two axial directions among the X axis, the Y axis and the Z axis which are orthogonal to each other and the remaining one axis as the central axis. Since the force is detected, if an inserting pressure is generated in the X direction, Y direction, or θ direction during the fitting work of the parts, the actuator is actuated according to the pressure in the displacement direction of the movable body. The link means can be driven to absorb the pressure in the displacement direction. Therefore, a smoother insertion work can be performed.

According to the sixth aspect of the invention, the feedback control of the actuator is performed by the control means based on the rotation amount of the rotary motor detected by the encoder.
Therefore, since the feedback control system can be configured based on the rotation amount of the rotary motor detected by the encoder, the compliance effect in the position displacement space of the movable member due to the rotation of the link means can be reliably generated. .

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a robot to which a wrist mechanism according to the present invention is applied.

FIG. 2 is a front view showing a wrist mechanism of the robot according to the first embodiment of the present invention.

FIG. 3 is a bottom view of the wrist mechanism shown in FIG. 2 seen from below.

FIG. 4 is an enlarged view showing a main part of the wrist mechanism shown in FIG.

5 is a block diagram showing a configuration of a servo control circuit in the controller 8 shown in FIG.

FIG. 6 is a front view showing a wrist mechanism of a robot according to a second embodiment of the present invention.

7 is a block diagram showing a configuration of a servo control circuit in the controller of the wrist mechanism shown in FIG.

8 is a block diagram showing a modified example of the servo control circuit shown in FIG. 7, showing a configuration of a control circuit in which only a detection signal of a force sensor is fed back.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 robot 2 body 3, 4, 5 arm 6 wrist mechanism 7 hand 8 controller 9 servo control circuit (control means) 11 base body (base member) 12 movable body (movable member) 13 link (link means) 14 rotary motor 14a rotation Axis 15 Cylinder member 16 Rod member 17, 18 Axis 19 Rotary encoder 20 Support base 21 Bearing 22 Torque sensor (detection means) 31, 51, 52 Target value calculation circuit 32, 53, 54 Calculation circuit 33, 55 PI gain circuit 40 Movable Body 41 Force sensor (Detection means) 42 Coupling

Claims (6)

[Claims] 1. A base member connected to the tip of a robot arm, a movable member to which a robot hand can be attached, a first rotating joint rotatably connected to one surface of the base member, At least three or more links having a second rotary joint rotatably connected to one surface side of the movable member and a linear mechanism capable of varying the distance between the first and second rotary joints. Means, an actuator for driving any one of the first rotary joint, the second rotary joint, and the linear motion mechanism of the link means, and a control means for outputting a control signal to the actuator. In the wrist mechanism, the detection means for detecting the driving force of the actuator is provided, and the control means performs the feedback control of the actuator based on the detection signal of the detection means. Bot of the wrist mechanism. 2. A base member connected to a tip end portion of a robot arm, a movable member to which a robot hand can be attached, a first rotating joint rotatably connected to one surface side of the base member, At least three or more links having a second rotary joint rotatably connected to one surface side of the movable member and a linear mechanism capable of varying the distance between the first and second rotary joints. Means, an actuator for driving any one of the first rotary joint, the second rotary joint, and the linear motion mechanism of the link means, and a control means for outputting a control signal to the actuator. In the wrist mechanism of the above, the movable member is provided with a detection unit that detects a force acting on the movable member via the robot hand, and the control unit is configured to detect the force of the actuator based on a detection signal of the detection unit. Robot wrist mechanism and performs Ddobakku control. 3. The wrist mechanism of the assembly robot according to claim 1, wherein the actuator comprises a rotary motor. 4. The wrist mechanism of an assembly robot according to claim 1, wherein the actuator comprises a rotary motor, and the detecting means comprises a torque sensor for detecting a torque of the rotary motor. 5. The X-axis, wherein the detecting means is substantially orthogonal to each other,
The wrist mechanism of the assembly robot according to claim 2, wherein each of the forces in at least two axis directions of the Y axis and the Z axis and the rotational force around the remaining one axis are detected. 6. An encoder for detecting the amount of rotation of the rotary motor is provided, and the control means performs feedback control of the actuator based on the amount of rotation detected by the encoder. The wrist mechanism of the described assembly robot.