JP2009066733A - Robot hand for assembling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a robot hand for assembling in which a center position of a compliance action and magnitude of a compliance can be optionally changed, and a complicated calculation is not required at a passive movement. <P>SOLUTION: The robot hand for assembling is provided with: a plurality of chuck jaws 13 arranged in a line symmetry against one centerline 12, and being oscillatory on a plurality of plane surfaces overlapped with the center line around an oscillating a plurality of axes orthogonal to the center line; a means for moving the center position of the plurality of oscillating axes in the direction approximately orthogonal to the center line; and a plurality of means for loading force on the ends of the plurality of chuck jaws. The center position of the compliance action of a shaft-like member and the magnitude of the compliance is adjusted by changing the magnitude of the force loaded on positions and the ends of the plurality of oscillating axes. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a robot hand for assembling machine parts.

  In the assembly work of mechanical parts, when the robot is to perform the assembly for inserting the shaft-shaped part into the hole, it is required to match the position and the posture of the hole and the shaft-shaped part. If this does not match, there may occur a case where the shaft-like component is jammed in the hole during insertion work and cannot be inserted. Several methods have been devised in order to perform this insertion operation smoothly, that is, to perform insertion smoothly even if there is some position error or posture error.

  FIG. 11 shows an example of an assembly robot hand according to the prior art for solving this problem. It is an attempt to eliminate position and posture errors passively by mechanical means, and is generally called a remote center compliance hand. In the figure, the shaft 3 is held by a chuck 4 for the purpose of inserting the shaft 3 into a component 2 having a hole 1.

  Three parallel piano wires 8 are fixed to the base plate 5 at equal intervals. An intermediate plate 6 is fixed to the other end of the parallel piano wire, and three inclined piano wires 9 arranged so that the extension line coincides with the tip end of the shaft 3 are fixed to the intermediate plate 6. Yes. A swing plate 7 is fixed to the other end of the three inclined piano wires 9, and a chuck 4 is fixed to the swing plate 7. By adopting such a structure, the center position of the compliance action can be arranged at the tip of the shaft 3, and the insertion operation can be performed by absorbing the position and posture errors between the hole 1 and the shaft 3. .

  In recent years, patents for various compliance hands have been filed, including those that apply the principle of the above-mentioned remote center compliance hand and further improve the degree of compliance, that is, the flexibility of insertion work. Examples thereof include Patent Document 1 and Patent Document 2.

In addition, as an example according to the prior art that attempts to solve this problem by an electrically active means, a force sensor that can detect a three-dimensional force and moment is provided between a robot that grips a shaft to be inserted and a robot. The force sensor detects the force generated between the hole and the shaft during insertion work, and controls the position and posture of the robot so that this force becomes the minimum value. There is something. Examples thereof include Patent Document 3 and Patent Document 4.
JP 61-27490 JP 2004-66363 A JP 05-38637 A JP 09-16228

  In the mechanical passive means that inserts with the center position of the compliance action arranged at the tip of the shaft, it is necessary to change the arrangement of the three inclined piano wires according to the shape of the shaft to be inserted. There is. Moreover, since the magnitude of the compliance is determined by the elastic coefficient of the parallel piano wire and the tilted piano, it cannot be easily changed.

  Recent inventions that have been improved so that the amount of compliance can be varied can cope with position errors in the direction parallel to the center line of the axis to be inserted. Absent.

  In addition, the method of controlling the position and posture by detecting the force generated between the hole and the shaft during the insertion operation using an electrically active means requires complicated calculations for detecting the force and controlling the robot. It is necessary and difficult to work at high speed.

  An object of the present invention is to provide a means which can arbitrarily change the center position of the compliance action and the magnitude of the compliance, and is a passive operation and does not require a complicated calculation.

  In the present invention, a plurality of planes that are arranged symmetrically with respect to one center line and that overlap with the one center line are arranged around a plurality of swing axes that are perpendicular to the one center line. A plurality of chuck claws capable of swinging, a means for moving the center positions of the plurality of swing shafts in a direction substantially perpendicular to one center line, and a force is applied to the tips of the plurality of chuck claws. The shaft comprises a plurality of means, grips the shaft-like member by a plurality of chuck claws, and changes the position of the plurality of swing shafts and the force applied to the tip of the chuck claws to The assembly robot hand is characterized in that the center position of the compliance action of the shaped member and the magnitude of the compliance can be adjusted.

  Further, the present invention controls the position of one position control plate in the vertical direction by one motor, and causes a plurality of swing members to move by a plurality of links connected to the position control plate. The swing center position of the nail is moved simultaneously and at an equal distance in a direction substantially perpendicular to one center line.

  The present invention also provides control of the positions of the tip portions of the plurality of chuck claws that move in a swaying manner by the plurality of motors provided corresponding to the plurality of chuck claws, and the tip portions of the plurality of chuck claws. The force applied to the chuck is controlled, and the command value of the position of the tip of the plurality of chuck claws and the command value of the force applied to the tip of the plurality of chuck claws are set to the same value. Features.

  The present invention also controls the force applied to the tip of the plurality of chuck claws by controlling the impedance of a plurality of motors corresponding to the plurality of chuck claws, The absolute value of the applied force, spring constant, and vibration damping force can be changed.

  Further, according to the present invention, a linear portion that coincides with a straight line connecting the tip of the chuck claw and the swing center is provided in a part of the chuck claw, and the shaft-like member is gripped by this linear portion, thereby acting on the shaft-like member. The compliance effect is eliminated, and the shaft-like member is firmly held.

  According to the present invention, by changing the position of the swing shaft of the plurality of chuck claws and the magnitude of the force applied to the tip of the chuck claws, the center position of the compliance action of the shaft member and the magnitude of the compliance are changed. Since the height can be adjusted arbitrarily, it is possible to select appropriate compliance characteristics corresponding to the shape of the shaft-shaped member, the shape of the hole to be inserted, etc., and to smoothly respond to the force generated during the insertion operation. Can make a quick insertion.

  Further, according to the present invention, one position control plate is vertically controlled by one motor, and a plurality of swing members are moved by a plurality of links connected to the position control plate. The center position of the shaft-shaped member held by a plurality of chuck claws can be changed by moving the swing center positions of the chuck claws simultaneously and equidistantly in a direction substantially perpendicular to one center line. In addition, the center position of the chuck pawl can be easily changed.

  In addition, the present invention controls the position of a plurality of chuck claw tip portions that oscillate and control the force applied to the tip portion by a plurality of motors provided corresponding to the plurality of chuck claws. And the position and force of the plurality of chuck claws are set to the same value, the resultant force acting on the shaft-shaped member is zero, and the center line of the shaft-shaped member gripped by the plurality of chuck claws is The compliance force can be generated while maintaining the state substantially coincident with the center line. That is, depending on the force generated during the insertion operation, each chuck claw can passively change its position slightly and passively change the attitude of the shaft-like member according to the spring constant of force control. It becomes possible.

  According to the present invention, the force applied to the tips of the plurality of chuck claws is controlled by impedance control of a plurality of sets of motors corresponding to the plurality of chuck claws. By changing the absolute value of the force applied to the part, the spring constant of the force, and the vibration damping force, the shaft posture can be changed with an appropriate compliance force while maintaining a strong gripping force against the shaft-like member. And vibration generated during insertion can be attenuated.

  Further, according to the present invention, a linear member that coincides with a straight line connecting the tip of the chuck claw and the swing center is provided on a part of the chuck claw, and the shaft-shaped member is gripped by the linear member. It is possible to eliminate the compliance effect acting on the shaft, and to transport the shaft-shaped member with a quick operation.

  FIG. 1 is a diagram for explaining the basic principle of an assembly robot hand according to an embodiment of the present invention. The structure and operation of the shaft-like member 11 will be described by taking the case where the shaft-like member 11 is inserted into the hole 58 of the block 57 as an example. As shown in the figure, when inserting the shaft-like member 11 into the hole 58, if the center lines of the two do not coincide with each other, the insertion force causes a horizontal force acting in a direction perpendicular to the center line of the insertion member 11. A bending moment is generated. The purpose is to passively change the position and posture of the shaft-like member 11 and to smoothly insert it into the hole 58 in response to this horizontal force and bending moment.

  The shaft-like member 11 is held by a plurality of (three to four) chuck claws 13 arranged in a line object with respect to one center line 12. The chuck claw 13 is mounted so as to be rotatable around a pin 15 mounted on the lower end of the swing member 14. A pin 16 is fixed to the other end of the chuck claw 13, and a link 17 is attached to the pin 16 in a rotatable manner to control the position and force of the chuck claw 13.

  On the other hand, the swing member 14 is attached to the upper end of the movable base 18 through a pin 19 so as to be rotatable. A link 21 is rotatably mounted on the other end of the swing member 14 via a pin 20 to control the position of the swing member 14. Here, the linear portion 22 of the chuck claw 13 is arranged in a straight line connecting the tip 23 of the chuck claw and the pin 15. The movable base 18 is fixed to the fixed base 24 through a plurality of (3 to 4) parallel piano wires 25 (not shown in FIG. 1 but shown in FIG. 8).

  FIG. 1 shows the case where there are four chuck claws for easy understanding of the operation principle, and the chuck claws 13 are arranged symmetrically with respect to one center line 12. When there are three chuck claws, they are arranged at an interval of 120 degrees with respect to one center line 12, so the positional relationship does not become as shown in the figure, but it is clear that the operation is based on the same principle mechanically. is there.

  When performing the insertion operation, the positions of the link 17 and the link 21 are controlled so that the extended line intersection of the linear portion 22 of the chuck claw 13 substantially coincides with the tip of the shaft-like member in the downward direction of the drawing. When the insertion operation is started, the movement of the link 17 is switched to force control, and the chuck claw 13 holds the shaft-like member 11 with an appropriate force by the tip portion 23 thereof.

  FIG. 2 is a diagram for explaining the operation of the chuck claw 13 when a force is applied in the vicinity of the distal end portion of the shaft-shaped member 11 in the insertion step. The shaft-like member 11 behaves with its tip portion as the center of compliance action. That is, in the illustrated case, the horizontal force 31 applied to the tip of the shaft-shaped member in the direction perpendicular to the axis acts as two component forces 32 and 33 on the pin 15 which is the center of swinging, and the force is It is received by the link 21 and does not act on the link 17.

  The bending moment 34 applied to the shaft member 11 acts on the tip 23 of the chuck claw 13 as a force 35 in a direction perpendicular to the central shaft 12 of the shaft member, and this force is received by the link 17. As described above, the force of the link 17 is controlled. However, the force of the plurality of chuck claws is uniformly applied in the center direction of the shaft-like member, and the resultant force is zero. In the illustrated case, the bending moment 34 acts in the direction opposite to the force applied to the link 17 by the right chuck claw and the force applied to the link 17 in the forward direction by the left chuck claw. Thereby, the attitude | position of the shaft-shaped member 11 is inclined rightward, and stops in balance with the restoring force of force control.

  Next, a method for controlling the force of the link 17 will be described. When the amount of movement of the tip 23 of the chuck claw 13 in the direction substantially perpendicular to the one center line 12 is expressed as follows, a force represented by the expression (a) in FIG. In the equation (a) in FIG. 10, is a target position, is a viscosity coefficient, and is a spring constant. In addition, the characters with the symbol “•” indicate the differential value of each. This method is one of known force control methods generally called impedance control, and is a control method called stiffness control in which force feedback is not performed.

  By adopting this force control method for the force control of the link 17 of the present invention, and setting the value to an appropriate value, the force with which the chuck claw 13 grips the shaft member 11 can be adjusted. The compliance with respect to the bending moment can be adjusted. Moreover, the vibration which generate | occur | produces at the time of insertion work can be suppressed by making these into an appropriate value. In the case of the present invention, when force control is performed by an insertion operation, since the target position is a constant value, the differential value of becomes zero, and equation (a) becomes equation (b) in the figure.

  Next, a series of operations when performing the insertion work will be described with reference to FIG. Here, it is assumed that chamfering is performed on the tip of the shaft-shaped member 11 or the end of the hole 58.

  First, the tip of the shaft-shaped member is aligned with the position of the hole 58 of the block 57, and insertion of the shaft-shaped member 11 into the hole 58 is started. At this time, when there is a slight misalignment of the hole position, a force in a direction perpendicular to the center line acts on the tip portion of the shaft-like member by the chamfering process, and this force is the pin 15 which is the center of the swing. And is received by the link 21 via the swing member 14. Since the link 21 is fixed at a fixed position, this force acts as a force for moving the movable base in the lateral direction in the figure. Since the movable base is supported by the action of the elastic piano wire 25 (shown in FIG. 8), the entire movable base moves in the lateral direction, so that the center of the shaft-like member and the hole center coincide.

  When the insertion work is further advanced and the shaft member is inserted into the hole, if there is a slight difference in posture between the center line of the hole and the center line of the shaft member, the center line of the shaft member is The bending moment that tries to fit the line works. Due to this bending moment, the attitude of the shaft-like member 11 changes so as to coincide with the center line of the hole according to the principle described above.

  When the shaft member changes its posture with respect to a bending moment generated in a certain direction, the relative position between the chuck claw 13 and the shaft member changes, but the tip 23 of the chuck claw 13 and the shaft member 11 change. Since it is a point contact, no force is generated between the two to prevent relative movement for posture change.

  FIG. 3 is a cross-sectional view illustrating the overall configuration of the assembly robot hand according to the embodiment. FIG. 4 is a top view of the assembling robot hand shown in FIG. FIG. 5 is a bottom view of the same. In FIG. 5, the shaft-shaped member 11 is gripped by three chuck claws 13a, 13b, and 13c. When the three chuck claws 13a, 13b, 13c rotate around the pins 15a, 15b (not shown) and 15c (not shown) shown in FIG. When the pins 15a, 15b, and 15c are swayed by swaying movements of 14a, 14b (not shown) and 14c (not shown), they slide in the grooves 53a, 53b, and 53c provided in the swaying base 18. To do.

  In FIG. 3, the link 21a connected to the swing member 14a via the pin 20a is connected to a bearing 27a fixed to the lower portion of the position control plate 28 in a rotatable manner via the pin 26a. The position control plate 28 is fixed to a nut 29 of a ball screw 30 that is rotationally driven by a motor 34, and the position of the position control plate 28 is vertically controlled by the rotation of the motor. The rotational position of the motor at this time is detected by the position detector 53.

  Although not shown, other links 21b and 21c are connected to the position control plate via bearings 27b and 27c and pins 26b and 26c. FIG. 6 is a top view of the position control plate 28. A ball screw 30 and a nut 29 are provided at the center, and three bearings 27a, 27b, and 27c are fixedly attached to a point object around the center.

  Thus, when the position of the position control plate 28 is controlled in the vertical direction by rotationally driving the motor 34, the position of the pin 15, which is the swing center of the chuck claw 13, is controlled in the substantially horizontal direction, and the chuck claw 13. The position of the wobble center is determined.

  Next, a mechanism for controlling the force of the link 17 will be described with reference to FIGS. Here, FIG. 3 represents a cross-sectional view taken along the line A-O-A in FIG. The upper end of the link 17a that is rotatably connected to the other end of the chuck claw 13a via a pin 16a is connected to a bearing 37a fixed to the lower portion of the force control plate 38a in a rotatable manner via the pin 36a. Yes. The force control plate 38a is fixed to a nut 40a of a ball screw 41a that is rotationally driven by a motor 45a. In addition, the force control plate is prevented from rotating by being slidably connected to a guide shaft 39a whose both ends are fixed to the swing base 24 and the intermediate base 50. Thereby, when the motor 54a is rotationally driven, the force control plate 38a is moved in the vertical direction. The rotational position of the motor is detected by the position detector 54.

  FIG. 7 is a top view of the force control plate, including force control plates 38a, 38b, 38c and ball screws 41a, 41b, 41c, nuts 40a, 40b, 40c, bearings 37a, 37b, 37c, guide shafts 39a, 39b, 39c. Represents the arrangement. The guides 46a, 46b, and 46c serve to cause the force control plates 38a, 38b, and 38c to slide smoothly on the guide shafts 39a, 39b, and 39c.

  Thus, when the motors 45a, 45b, 45c are rotationally driven, the positions of the force control plates 38a, 38b, 38c are vertically controlled, and the positions of the tip portions 23a, 23b, 23c of the chuck claws 13a, 13b, 13c are controlled. Is controlled, and is held in contact with the shaft-shaped member 11. Here, since the motors 45a, 45b, and 45c are simultaneously controlled by being given the same position command value, the chuck claws 13a, 13b, and 13c maintain the target shape with respect to one center line 12 of the shaft-like member 11. Position controlled.

  When the insertion operation is started after the tip portions 23a, 23b, and 23c of the chuck claws 13a, 13b, and 13c are in contact with and grip the shaft-like member 11, the motors 45a, 45b, and 45c are switched to the force control mode, as described above. The force for gripping the shaft-like member by the method and the spring constant of the gripping force are selectively controlled, and the generated vibration is suppressed. Thus, a plurality of means for applying a force to the tips of the plurality of chuck claws are provided.

  At this time, the resultant force of the plurality of chuck claws applied to the shaft-shaped member 11 becomes zero, and the posture of the shaft-shaped member 11 changes according to the magnitude of the spring constant of the gripping force. That is, the magnitude of compliance can be changed by changing the spring constant of the gripping force.

  As shown in FIG. 6, the guide shafts 39 b and 39 c penetrate through the holes 56 b and 56 c provided in the position control plate 28 without contacting them. The guide shaft 39a penetrates the anti-rotation guide 47a fixed to the position control plate so as to be slidable. This prevents the position control plate 28 from rotating when the ball screw 30 rotates.

  FIG. 8 is a diagram illustrating a relative position between the chuck claw 13 and the shaft-shaped member 11 when the shaft-shaped member is firmly held. For example, when transporting from a material supply station to a predetermined assembly station, it is necessary to firmly grip the shaft-like member. By making the distance between the center line 12 of the shaft-like member and the swing center coincide with the radius of the shaft-like member, the shaft-like member comes into contact with the straight portion 22 of the chuck claw 13 and prevents the posture change of the shaft-like member 11. The shaft-like member 11 can be firmly held.

  FIG. 9 is a block diagram showing an embodiment of a control device for realizing the position and force control of the motor 45. The mode selection command 101 commands the value of s in the position control selector 102 and the force control selector 103 to either “1” or “0”. A value “0” is commanded in the position control mode, and a value “1” is commanded in the force control mode.

  The position command 104 commands a target value “” in the position control mode. The target value “” is compared with the output signal of the position detector 54 and a deviation signal “” is calculated. When the value of the mode command 101 is “0”, the output of the position selector 102 is in the “ON” state, and the deviation signal is sent from the motor via the path of the position control unit 106, the speed control unit 107 and the current control unit 108. Be controlled. At this time, the rotational position signal of the motor 45 detected by the position detector 54 is differentiated by the differentiation element 109 to become a speed signal and fed back to the speed control loop.

  The force command value 105 commands the target “” in the force control mode. This target position “” is compared with the output signal of the position detector 54 to calculate a deviation signal “”. When the value of the mode command 101 is “1”, the output of the force control selector 103 is set to “ON”, the deviation signal “” is multiplied by the spring constant “k” by the spring constant selector 111, and the position A value obtained by multiplying the value obtained by converting the rotational position signal of the detector 54 into the speed signal by the differential element 110 and the viscosity coefficient “d” of the viscosity coefficient selector 112 is subtracted, and the motor is controlled via the current control unit 108. To do.

  In this way, the motor 54 can be controlled by switching between the position control mode and the force control mode as necessary, and the force can be controlled according to the calculation formula shown in FIG.

  The fixed base plate 24 and the intermediate base plate 50 are firmly fixed by a main body case 49, and the motor base plate 51 and the intermediate base plate 50 to which the motor 34 and the motor 54 are fixed are firmly fixed by a main body auxiliary case 48. ing. The movable case 52 is fixed to the movable base plate 18.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used when a robot performs an assembly operation for inserting a shaft-like member into a hole at a manufacturing site such as an automobile and a precision machine.

It is a figure explaining the basic principle of the robot hand 10 for an assembly which concerns on embodiment of this invention. It is a figure explaining operation | movement of the chuck | zipper claw 13 when inserting a shaft-shaped member in a hole using the assembly robot hand 10 which concerns on embodiment of this invention. It is a figure explaining the whole structure of the robot hand for an assembly which concerns on embodiment of this invention. 1 is a top view of an assembly robot hand 10 according to an embodiment of the present invention. 1 is a bottom view of an assembly robot hand 10 according to an embodiment of the present invention. It is a top view of the position control plate 28 of the robot hand 10 for assembly which concerns on embodiment of this invention. It is a top view of the force control plate 38 of the robot hand 10 for assembly which concerns on embodiment of this invention. It is a figure explaining the state where chuck claw 13 of gripping robot hand 10 concerning an embodiment of the present invention held a shaft-like member firmly. It is a block diagram of the Example of the control apparatus which implement | achieves position and force control of the assembly robot hand 10 which concerns on embodiment of this invention. It is a figure explaining the example of the calculation formula which impedance-controls the motor which controls the position and force of the front-end | tip part 23 of a chuck | zipper nail | claw of the assembly robot hand 10 which concerns on embodiment of this invention. It is a figure explaining the operation | movement principle of the example implemented by the mechanical passive means in the assembly robot hand based on a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Assembly robot hand 11 Shaft-shaped member 12 One center line 13 Chuck claw 14 Shaking member 15 Pin 16 Pin 17 Link 18 Movable base plate 19 Pin 20 Pin 21 Link 22 Linear part 23 Chuck claw tip 24 Fixed base plate 25 Parallel Piano wire 26 Pin 27 Bearing 28 Force control plate 29 Nut 30 Ball screw 31 Horizontal force 32 Component force 33 Component force 34 Bending moment 35 Force in perpendicular direction 36 Pin 37 Bearing 38 Force control plate 39 Guide shaft 40 Nut 41 Ball screw 42 Bearing 43 Coupling 44 Motor output shaft 45 Motor 46 Guide 47 Anti-rotation bead 48 Main body auxiliary case 49 Main body case 50 Intermediate base plate 51 Motor base plate 52 Movable case 53 Position detector 54 Position detector 55 Groove 56 Buff hole 7 block 58 holes
101 mode selection command 102 position control selector 103 force control selector 104 position command value 105 force command value 106 position control unit 107 speed control unit 108 current control unit 109 differential element 110 differential element 111 spring constant selector 112 viscosity coefficient selector

Claims (5)

  It is arranged symmetrically with respect to one center line, and can swing on a plurality of planes overlapping with the one center line around a plurality of swing axes perpendicular to the one center line. A plurality of chuck claws, a means for moving the center positions of the plurality of swing shafts in a direction substantially perpendicular to one center line, and a plurality of means for applying a force to the tips of the plurality of chuck claws The gripping of the shaft-shaped member by gripping the shaft-shaped member with a plurality of chuck claws and changing the position of the plurality of swing shafts and the force applied to the tip of the chuck claw An assembly robot hand characterized in that the center position of action and the magnitude of compliance can be adjusted.   By controlling the position of one position control plate in the vertical direction by one motor and moving the plurality of swing members by a plurality of links connected to the position control plate, 2. The assembly robot hand according to claim 1, wherein the moving center positions are moved simultaneously and at equal distances in a direction substantially perpendicular to one center line.   Control of the positions of the tip portions of the plurality of chuck claws that are moved swayingly by a plurality of motors provided corresponding to the plurality of chuck claws, and the force applied to the tip portions of the plurality of chuck claws 2. The position command value of the tip portions of the plurality of chuck claws and the force command value applied to the tip portions of the plurality of chuck claws are set to the same value. Robot hand for assembly.   The force applied to the tip of the plurality of chuck claws is controlled by impedance control of a plurality of motors corresponding to the plurality of chuck claws, and the force applied to the tip of the plurality of chuck claws is controlled. 4. The assembly robot hand according to claim 3, wherein the absolute value, the spring constant of the force, and the vibration damping force can be changed.   A part of the chuck claw is provided with a straight line portion that matches the straight line connecting the tip of the chuck claw and the swing center, and the shaft member is gripped by this straight line portion, thereby eliminating the compliance effect acting on the shaft member. The assembly robot hand according to claim 1, wherein the shaft-shaped member is firmly held.