JP3193878B2 - Cooperative robot system for fitting work - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for automating a fitting operation required in a part assembling process and the like.
More specifically, the present invention relates to a cooperative robot system used for automating a fitting operation.

[0002]

2. Description of the Related Art A fitting operation is one of basic operations included in many assembling processes and the like, and automation of the fitting operation using a robot has already been performed. In a fitting operation using a robot, one work (fitted work) is gripped by the robot and inserted into a predetermined portion (usually a concave portion) of the other work (fitted work). In many cases, a force control robot is used as a robot for gripping a fitting work.

[0003] The force control robot is preferably used for the fitting operation because it absorbs the variation in the position / posture relationship between the fitted work and the work to be fitted and changes the force or moment during the insertion operation to a predetermined condition. This is because there is a function to control with.
However, even when the force control robot is used, the fitting operation may not be performed smoothly. For example, when the shape and size of the concave portion on the mating work side are in a tight relationship with the shape and size of the convex portion of the mating work, when the frictional force between the contact surfaces of both works is large, or when the mating work For example, when the insertion operation must be performed against the elasticity of the robot, the resistance force acting during the insertion operation becomes large, and a situation in which the pressing force of the robot against the fitted work is insufficient tends to occur.

In the conventional robot system used for the fitting operation, the force required for the insertion operation is required only by a single robot holding the fitted work.
It is necessary to prepare a robot capable of outputting a force that reliably exceeds the force expected to be required in the insertion operation, which has been a difficulty when introducing a robot system into the fitting operation.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a robot system which does not require a robot exclusively for gripping a fitting work for a force required for an insertion operation. To provide.

[0006]

According to the present invention, the above-mentioned technical problem is solved by a cooperative robot system including a supporting robot, which supports a fitting work, and a supporting robot for supporting the supporting work. The support robot supports an insertion operation support force acting means for supporting the insertion operation of the supported robot. The robot system control means for controlling both robots causes the support robot to approach the supported robot when the supported robot inserts the fitted work into the fitted work, and then the insertion operation assisting force acting means is operated. The support robot is operated to support the insertion operation in cooperation.
The insertion operation assisting force acting means is configured to
Pressing with a projection that applies a pressing force to the work
It is equipped with a tool.

[0007] Typically, the fitting work is gripped by a hand attached via a force sensor, and the insertion operation assisting force acting means is supported by the support robot with the force sensor. The robot system control means executes the insertion operation of the supported robot and the support operation thereof by force control using the outputs of these force sensors. A pressing tool having a projecting portion for applying a pressing force to the fitting work at the time of supporting the insertion operation can be used as the insertion operation supporting force acting means.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view illustrating the overall arrangement of a cooperative robot system according to the present invention. As shown in FIG. 1, the system includes two robots 1 and 2 and a robot controller 3 for controlling the robots 1 and 2. Force sensors 12 and 22 are attached to the hand portions 11 and 21 of the robots 1 and 2, respectively. As each of the force sensors 12 and 22, a known sensor including a plurality of bridge circuits and a signal processing unit which are constituted by, for example, strain gauges and are AC-driven by an oscillator can be used. Each force sensor 1
From the sensors 2 and 22, detection signals representing the components of the six-axis force acting on the force sensors are output to the robot controller 3 and used for force control of the robots 1 and 2.

The force sensor 11 of the robot 1 has a hand 13
Is attached to the force sensor 12 of the robot 2 as a pressing tool 6 as a force acting means for assisting the insertion operation.
Is installed. The fitting operation in this case is to insert the cylindrical fitting work 4 into the concave portion 51 of the work 5 to be fitted. At the time of the inserting operation, the pressing tool 6 enters from between the holding claws of the hand 13 and the robot moves. The work 4 is pressed against the top 41 of the fitting work 4 by the operation under the force control of 2. Reference numeral 61 denotes a projection that comes into contact with the top of the fitting work 4 at the time of pressing.

The work 5 to be fitted is positioned on the work table 7, and a work coordinate system Σw having the work mounting surface of the work table 7 on the XY plane is set for both robots 1 and 2. The fitting operation using the present system is executed by a method in which the robot 2 cooperates (supports) the insertion operation of the fitting work 4 by the robot 1. That is, in this case, the robot 2 supporting the pressing tool 6 is a support robot, and the robot 1 supporting the fitting work 4 is a supported robot. The details of the operation support at the time of insertion will be described later.

As shown in FIG. 2, the entire robot controller 3 includes a control unit 31 for the robot 1 which becomes the master robot during the cooperative operation and a control unit 32 for the robot 2 which also becomes the slave robot during the cooperative operation. Are connected by a communication line CL or a bus line BL. The control unit 31 is connected to the force sensor 12, the hand 13, and the teaching operation panel 104 in addition to the robot 1, and the control unit 32 is connected to the force sensor 22 in addition to the robot 2.

The hardware of the control units 31 and 32 can be of substantially the same configuration. Therefore, FIG. 3 shows a main configuration of the control unit 31 here. As shown in the figure,
The control unit 31 has a central processing unit (main CPU, hereinafter simply referred to as a CPU) 101. The CPU 101 has a memory 102 composed of a RAM and a ROM, and teaches operation and teaches coordinates and the like. Interface 103 for teaching operation panel connected to operation panel 104, general-purpose input / output interface 105 also serving as communication interface
And servo control units # 1 to # 7 are connected via a bus 106.

The servo controllers # 1 to # 6 are connected to respective axis motors M1 to M6 of the robot 1 via respective servo amplifiers. The servo control unit # 7 and the motor M7 are for an additional axis. When a servo hand is used as the hand 13, the motor M7 is a servo motor that drives the hand 13. When the servo hand is not used, the hand 13
(Not shown) are connected to a general-purpose signal interface.

The output of the force sensor 12 is taken into the control unit 31 via the general-purpose signal interface, and
1 sequentially stores them in a predetermined area in the memory 102. The stored output data of the force sensor 12 is used for force control (for example, impedance control) of the robot 1. The output of the force sensor 22 is similarly controlled by the control unit 32.
And is used for force control of the robot 2.

The ROM, RAM and non-volatile memory of the memory 102 store the output data of the force sensor 12 as well as a program for controlling the operation of the control unit 31 itself, operation program data for a fitting operation, and control. It is used for storing a program for controlling the transmission and reception of signals with the unit 32 and setting values related to each process. The set values include the set data of the sensor coordinate system set for the force sensor 12, the data of the work coordinate system Σw described above, and the set data for defining the conditions of the force control of the robot 1 and the like. The items corresponding to these are described in the control unit 3 on the robot 2 side.
Since the same applies to No. 2, the repeated description is omitted.

Next, an outline of the sequence of the fitting operation in the present embodiment will be described with reference to FIGS. The pre-teach data such as pre-approach position / posture data of the robot 1, approach position / posture data of the robots 1 and 2, and fitting length data need to be well-known methods (teaching / playback method, manual input method, etc.). It is assumed that the robot controller 3 has already been used for teaching.

4 to 7, the fitting work 4 and the work 5 to be fitted are schematically illustrated by cross sections of a stepped cylinder and a perforated cylinder, respectively, and the hand 13, the force sensors 12, 22 and the like are illustrated. The illustration is omitted. Tool tip point TCP for robots 1 and 2
Reference numerals 1 and 2 are set at the center point of the distal end surface of the fitting work 4 and the distal end of the projection of the pressing tool 61, respectively, with the orientation shown in FIG. FIG.
~ 9. Are collectively shown in a flowchart. The step numbers in parentheses refer to those in the flowchart of FIG.

1. Pre approach point waiting support robot 2 (step S1): pressing supporting the robot 2 a tool 6, allowed to stand by moving and positioning the teachings already pre approach point represented by a matrix ^W Q _P. Matrix ^W Q _P represents the position and orientation of the tool center point TCP2 in the pre approach point of the robot 2 on the work coordinate system? W. From the viewpoint of shortening the cycle time, it is preferable that the pre-approach point is the home position of the robot 2 (return position every time the paired work is completed). However, the pre-approach point of the robot 2 is set such that the tip of the pressing tool 6 approaches the top surface 41 of the fitting work 4 in the approach completed state in consideration of the position of the claw of the hand 13 not shown. Must be selected so that no interference occurs.

2. Approach Movement of Supported Robot 1 (Step M1): The robot 1 (TCP1) holding the fitting work 4 is moved from the preceding teaching point position to the approach point for starting the insertion operation and positioned.
Approach point of the robot 1 is taught in the data of the matrix ^W A _A representing the approach position and orientation on the work coordinate system? W.

FIG. 4 shows a state in which the pre-approach of the robot 2 and the approach of the robot 1 have been completed. As understood from the figure, the approach point of the robot 1 teaches the position / posture at the start of the insertion of the fitting work 4.

3. Transmission and reception of the approach operation completion signal of the supported robot 1 (step M2 / step S2):
The control unit 31 notifies the control unit 32 of the completion of the approach of the robot 1. 4. Approach movement of the support robot 2 (step S
3): Robot 2 (TCP) supporting pressing tool 6
2) is moved to the approach point of the robot 2 that has been taught.
Position and wait. The approach point of robot 2 is
Matrix representing approach position / posture on working coordinate system Σw
Taught by ^W Q _A data.

FIG. 5 shows a state in which the robots 1 and 2 have completed the approach movement. As can be seen, the approach point of the robot 2 is such that the TCP 2 set at the tip of the projection of the pressing tool 6 matches the center point of the top surface 41 of the fitting work 4 and the lower surface 62 of the pressing tool 6 It is taught to be parallel to the top surface 41 of the fitting work 4.

5. Transmission / reception of an approach operation completion / cooperative operation start synchronization signal of the support robot 2 (step S4 /
Step M3): The controller 32 notifies the controller 31 of the completion of the approach of the robot 2. This signal also serves as a synchronization signal for starting a cooperative operation.

6. Cooperative insertion operation / insertion support operation (Step M4 / Step S5): After the completion of the approach operation / cooperation operation start synchronization signal transmission / reception, the supported robot 1 immediately
And the support operation by the support robot 2 are started. For both the robots 1 and 2, the moving direction from the approach state is the direction of the insertion direction vector n which is taught in advance as the axial direction toward the bottom of the concave portion 51. The cooperative operation of the robots 1 and 2 in the force control state will be described later and supplemented.

FIG. 6 illustrates a state in which the insertion operation is in progress. Matrix ^W A _H, ^W Q _H are each represents an insertion operation in progress tool center point TCP1, the position and posture of the TCP2.

7. Insertion operation completion determination (step M5):
Whether the robot 1 advances by the insertion length L taught in advance,
It is determined that the insertion operation is completed when any of the set times T has elapsed after the start of the insertion operation. The insertion length L is the length of the fitting work 4
If you want to ensure that the tip of
Set slightly larger than the maximum possible insertion length. Otherwise, it is set slightly smaller than the maximum possible insertion length. The determination based on the elapse of the set time T may be omitted or employed for determining an error signal output (work insertion failure).

8. Transmission / Reception of Cooperative Insertion Operation Completion Signal (Step M6 / Step S6): When it is determined that the insertion operation is completed, the control unit 31 immediately transmits a cooperative insertion operation completion signal to the control unit 32.

9. Cooperative insertion operation / insertion support operation end (Step M7 / Step S7): Immediately after transmitting and receiving the cooperative insertion operation completion signal, the force control of the supported robot 1 and the support robot 2 is released, the operations are stopped, and both control units 3
The processing of steps 1 and 32 ends. FIG. 7 illustrates a state when the cooperative insertion operation is completed. ^W A _E, ^W Q _E are each insertion operation is completed at the time of the tool tip point TCP1, TCP2 position and of
This is a matrix representing the posture on the work coordinate system Σw.

The above is the outline of the sequence of the fitting operation in the present embodiment. The basic feature of the system of the present invention resides in that the support robot supports the insertion operation of the supported robot.It is not essential that the insertion operation and the insertion support operation of both robots are performed by force control. In order to smoothly perform the insertion operation and the insertion support operation, it is preferable to adopt a force control method as in the above sequence.

Various types of force control are known, and all of them are controlled so that the force acting on the hand of the robot is maintained in a desired state (typically, a predetermined constant value). Control method. Therefore, in the example of the present embodiment, the robots 1 and 2 have the following 6
Force control may be performed during the movement in steps M4 and S5 under the condition of the axial force. Note that, in this case, the insertion direction n coincides with the Z-axis direction of the coordinate system Σw.

[Conditions of Force in X-axis direction and Y-axis direction] Robot 1: Force control effective. Force control is performed under the condition of FX = FY = 0. 2. Robot 2: Force control disabled (no force sensor output) and X to maintain the X and Y coordinate values of the approach position
A movement command that commands movement in the axial direction and the Y-axis direction is not output.

[Condition of Force in Z-Axis Direction] Robots 1 and 2: Force control is performed by setting appropriate force conditions F1 and F2 for each force component FZ of robots 1 and 2. F1 and F2 are set so that the sum F1 + F2 of the two appropriately exceeds the minimum insertion force required to reliably perform the insertion operation. If F1 + F2 is too small, insertion failure may occur, and if F1 + F2 is too large, there is a risk of damage to the work and hand. Also, F1, F2
It is needless to say that consideration should be given so that the value of is not unreasonable in view of the capabilities (maximum force output) of the robots 1 and 2.

[Conditions of Moment around X-axis, around Y-axis and around Z-axis] Robot 1: Force control is performed under the condition that the moments around the XY axes are all 0, that is, μX = μY == 0. Z
No force control is performed around the axis, and no movement command that commands movement around the Z axis is output. 2. Robot 2: Force control invalid (no use of force sensor output) around the X axis, around the Y axis, and around the Z axis, and to maintain the approach posture, around the X axis, around the Y axis, and Z
It does not output a movement command that commands movement around the axis.

Finally, an impedance control method will be described as an example of the force control. Since the control method itself is known, an outline and a method of applying the present invention to the present embodiment will be briefly described. The impedance control method (also referred to as mechanical impedance control) is a control method in which a robot has a certain desired inertia and operates as if it were a single virtual rigid body suspended on a target trajectory by a damper and a spring. . To model a robot into such a system, the system is described with parameters describing inertia, dampers and springs. The set of parameters set to describe the system is called the set mechanical impedance. The equation of motion of the system can be expressed using these parameters.

In general, when applying the impedance control method, parameters representing inertia, damper, and spring are appropriately set, and a target position (including posture), speed, acceleration, and target force are given. The target force may be the one described in the above condition of the force. Also, for the target track, the position of the approach point, can be calculated from the posture ^W T _A, ^W Q _A and the insertion length L. In this embodiment, the target for the position is given by the speed in the insertion direction.

[0036] Now, a target force and ^D F _d, further ^D F this
_d = to be represented by _{^{[D f d T, D τ}} d T] T. Here, ^D f _d is a target force, and ^D τ _d is a target torque. If the above-mentioned force control conditions are applied to the robot 1, the force ^D f _d and the torque ^D τ _d are given by the following equations (1),
It is represented by (2). ^D f _d = [0,0, ^D f _z ] ^T = [0,0, F1] ^T ... (1), ^D τ _d = [0,0,0] ^T. If the conditions of the force control described above are applied to the robot 2, the force ^D f _d and the torque ^D τ _d are given by the following equations (3) and (4).
Is represented by ^D f _d = [0,0, ^D f _z ] ^T = [0,0, F2] ^T (3) ^D τ _d = [0,0,0] ^T (4) In the expressions (1) to (4), the target component for which the force control is invalid is set to 0.

When the TCP 1 or TCP 2 moves in the insertion direction n and the fitting is completed and the state shown in FIG. 7 is reached, the front end surface of the fitting work 4 hits the bottom of the concave portion 51 and the robots 1 and 2 move. reaches the equilibrium state set to each target force ^D F _d, movement stops.

Now, assuming that TCP1 or TCP2 is represented by a six-dimensional vector of position and posture as ^D r _C , the equation of motion described by the set impedance is given by the following equation (5).

[0039]

(Equation 1) In the above equation (5), the number of dots given on the variable r represents the differential of the number. ^D F _c is the force detected by the force sensor 12 or 22, the right side is multiplied by the gain κF force on the deviation between the target force ^D F _d (hereinafter, for convenience and kappa _F = 1 ). In the above equation (5), M is a 6 × 6 target inertia matrix D is a 6 × 6 target viscosity matrix K is a 6 × 6 target stiffness matrix When the force control direction and the position control direction are determined as in this embodiment, M = diag (m1, m2,... M6) D = diag (d1, d2,... D6) K = diag (K1, k2,... K6)... (6) and K = 0. Since the remaining parameters and the specific numerical values of the equation (9) depend on the control target, they are determined by tuning or the like and set in the impedance data.

By the above-described setting of the impedance and the setting of the target force, the robot 1 or the robot 2 operates by force control so as to match the position / posture with the insertion axis in accordance with the force applied to the tip of the tool. Becomes possible.
From the above equation (5), the target acceleration of the hand of the robot 1 or the robot 2 is obtained by the following equation (8).

[0041]

(Equation 2) The robot joint variables and theta, when the first derivative and the Jacobian matrix representing the first derivative of the relationship between the vector ^D r _C of the joint variables and J, the following equation (9) is satisfied.

[0042]

(Equation 3) As one of the methods for directly realizing the target acceleration (two dots of θ _d ) in the above equation (9), the equation of motion of the robot is expressed by the following equation (10), and the value u obtained by the equation (11) is calculated as follows. There is a method of setting a command value to the actuator (torque command to the motor) u.

[0043]

(Equation 4)

[0044]

(Equation 5) In the above equations (10) and (11), τ: torque of each joint of the robot I (θ): inertia matrix of the robot h (one dot of θ, θ): nonlinear force such as Coriolis force, centrifugal force, etc. .

When a position and speed servo system is provided for each actuator (motor),

[0046]

(Equation 6)

[0047]

(Equation 7) The position θ _d after the time Δt and the target value of the speed (θ
(1 dot of _d ). Next, an outline of the processing of the impedance control calculation is shown in the flowchart of FIG. In this process, based on the teaching path along the insertion axis, each axis value of the robot 1 or the robot 2 and 6-dimensional vector ^D r _c and its differential value than the rate is determined. The target force ^D F _d and the set force, the force ^D F _c detected by the six-axis force sensor 12 or 22 (8) target acceleration performs the operation of expression (2 dots ^D r _c)
Is required. Furthermore, by performing the determined target acceleration and the operation speed from (9) of each axis, obtaining the (2 dots theta _d) the target acceleration for each axis (step T1).

From the target acceleration and the detected speed obtained in step T1 for each axis, the above equations (12) and (13)
The target speed and the target position are obtained by calculating the equations and output to the respective axis servo systems (steps T2 and T3).

When one cycle of the above impedance control calculation is completed, the current robot hand position ri is obtained, and the robot's traveling direction vector Δi is obtained from this position and the position ri-1 immediately before. Prepare for processing.

As described above, in the present embodiment, the impedance control method is applied as the force control, but other force control methods can be adopted. Further, in the present embodiment, the force is applied to the top of the fitting work 4 using the rod-shaped pressing tool 6 as the force acting means for supporting the insertion operation. Points and the like can be appropriately changed according to the gripping form of the fitting work 4 and the like.

[0051]

According to the present invention, since the resultant force of the two robots can be used during the insertion operation, a robot having a relatively low force can be used for the fitting operation.
Therefore, the restriction that a particularly powerful robot must be prepared for the insertion operation is eliminated.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating the overall arrangement of a cooperative robot system according to the present invention.

FIG. 2 is a block diagram illustrating an overall configuration of a robot controller 3;

FIG. 3 is a main block diagram showing a schematic configuration of a control unit 31.

FIG. 4 is a diagram illustrating a state in which a pre-approach of the robot 2 and an approach of the robot 1 are completed in the embodiment.

FIG. 5 is a diagram illustrating a state where the approach of the robot 2 and the approach of the robot 1 are completed in the embodiment.

FIG. 6 is a diagram illustrating a state in which a cooperative insertion operation is in progress in the embodiment.

FIG. 7 is a diagram illustrating a completed state of the cooperative insertion operation in the embodiment.

FIG. 8 is a flowchart illustrating an outline of a sequence of a fitting operation according to the present embodiment.

FIG. 9 is a flowchart illustrating an outline of processing of impedance control calculation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Supported robot (master robot) 2 Supported robot (slave robot) 3 Robot controller 4 Fitted work 5 Fitted work 6 Press tool 7 Work table 7 11,21 Robot hand 12,22 Force sensor 13 Hand 31, 32 control unit 41 top surface of fitting work 4 51 recess 61 protrusion 101 central processing unit (CPU) 102 memory 103 teaching operation panel interface 104 teaching operation panel 105 input / output interface 106 bus

(56) References JP-A-63-260777 (JP, A) JP-A-63-312087 (JP, A) JP-A-6-297364 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) B25J 13/00 B25J 13/08 G05B 19/18 B23P 19/04

Claims (2)

(57) [Claims] 1. A supported robot that grips a fitted workpiece, a support robot that supports an insertion operation support force acting means for supporting an insertion operation of the supported robot, and controls the support robot and the supported robot. A robot system control means for performing a fitting operation, wherein the robot system control means performs an operation of inserting the fitted work into the fitted work by the supported robot. the support is brought close to the robot to the object support robot, and have the following, the said insertion operation assist force acting means are adapted to operate so as to cooperatively support the insertion operation by the support robot, the insertion movement supporting force acting Means for supporting the insertion operation.
A pusher with a projection for applying a pressing force to the fitting work
A cooperative robot system for performing the fitting operation , comprising a butting tool . 2. A supported robot for gripping a fitting work with a hand attached via a force sensor, and an insertion operation supporting force acting means for supporting an insertion operation of the supported robot via a force sensor. A cooperative robot system for performing a fitting operation, comprising: a supported support robot; and a robot system control unit configured to control the support robot and the supported robot, wherein the robot system control unit includes: At the time of the insertion operation of the fitting work into the fitting work by force control, the support robot approaches the supported robot, and then the insertion operation assisting force acting means coordinates the insertion operation by the supported robot. being adapted to be operated by a force controlled assist, the insertion operation援力effector means, said during insertion operation support
A pusher with a projection for applying a pressing force to the fitting work
A cooperative robot system for performing the fitting operation , comprising a butting tool .