JPH09136279A - Phase-adjusting fitting method using force control robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly carry out fitting operations requiring a series of operations performed under the condition where different force controls are performed, by utilizing a force control robot capable of specifying some parameters of force control out of operation instructions. SOLUTION: When the phase of a wave generator 41 falls within a range (a) of suitable phase immediately following the start of phase-alignment, the wave generator 41 immediately enters an opening part 53. At this time, a flake spline is gradually, elastically deformed into an elliptical shape, and the tooth of the flake spline and the tooth of a circular spline are engaged with each other on the major axis part. The inserting operation is a core part of the fitting operations, by which the tip point of a tool of a force control robot 1 is allowed to further enter the opening part 53 depending on the length previously instructed by means of parameters.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology of an industrial robot (hereinafter, simply referred to as "robot"), and more specifically, a force control robot for a fitting operation that requires phase matching when assembling parts. On how to get it to run.

[0002]

2. Description of the Related Art In the process of assembling parts in a factory,
In many cases, the work of fitting the works together is included. When fitting work using a robot, the fitting work should be gripped by the robot and part (convex part, etc.) or all of it should be accommodated in the accommodation part (concave part, opening part, etc.) of the work to be fitted. Become. A force control method can be applied to the robot during the fitting operation to give the robot softness. As a result, even if the posture of the mating work with respect to the mated work deviates from the optimum one to some extent,
In many cases, it is possible to achieve smooth fitting by utilizing the external force that acts between the works.

However, depending on the type of the assembled work, it may be difficult to perform the fitting work unless the posture of the fitting side work with respect to the work to be fitted around the insertion axis is within a specific angle range. It is considered that such a case can be dealt with by accurately teaching the fitting operation, but there is variation in the attitude of the work to be fitted (in particular, the attitude around the insertion axis of the accommodating portion). In some cases, even if the posture of the robot is determined, the posture of the gripped work (especially, the posture around the insertion axis of the accommodated portion) is not determined, which cannot be dealt with.

Therefore, it is necessary to adjust the attitude around the insertion axis so that the relative attitude within the allowable angular range can be obtained for each work pair. Such adjustments
This is called "phase matching", and the relative posture or angle around the insertion axis is called "phase".

By the way, for a fitting work in which it is difficult to supply a work in a state in which the phases are aligned, the robot approaching the work to be fitted is caused to perform an appropriate phase matching operation before inserting the work. It is said that it is difficult for the conventional robot control technology to smoothly execute a series of sequences to be performed or a sequence in which an operation of returning the phase to the original state (phase return) is added between the phase matching operation and the inserting operation. Was there. For this reason, manual work is unavoidably introduced into the fitting work involving such phase matching.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to perform an operation after approaching a work to be fitted, that is, a phase adjusting operation, for a fitting work in which it is difficult to supply a work in a phase aligned state. The robot is allowed to smoothly execute a series of sequences leading to the work inserting operation through the above, or a sequence in which the original phase returning operation for returning the phase is further added between the phase aligning operation and the work inserting operation.
Further, the present invention aims to improve the application capability of the robot to applications including fitting work through this.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a force control robot holding a fitted work is caused to execute a series of operation sequences, thereby performing a work of fitting between works which requires phase matching at the time of fitting. In this case, the above problem can be solved by advancing the operation sequence while selecting the force control condition so as to be suitable for each operation included in the operation sequence.

In the operation sequence of the phase matching and fitting, at least (1) an approach operation for moving the fitted work to the fitted work and moving it to a position where the phase matching can be started, and (2) the fitting work Includes a phase matching operation that rotates around the insertion axis while pressing it against the work to be fitted, and (3) an insertion operation that moves the work along the insertion axis while pressing it against the work to be fitted. There is.

The approaching operation, the phase adjusting operation, and the inserting operation are set by the parameters in the operation program, and the operation program is performed under the force control condition suitable for each operation as the operation sequence progresses. Contains a data array that describes the force control conditions associated with the commands associated with each motion in the motion sequence.

When the original phase restoration is necessary depending on the type of the work, the operation sequence must include at least
(1) An approach operation of moving the fitted work closer to the fitted work and moving it to a position where phase matching can be started,
(2) Phase matching operation of rotating the fitted work against the fitted work while rotating it around the insertion axis, and (3)
Original phase return operation for rotating the fitting work around the insertion axis to return the posture of the fitting work to the state before the phase alignment, and (4) pressing the fitting work against the fitted work. While including the insertion operation of moving along the insertion axis.

Then, the approach operation, the phase matching operation, the original phase restoring operation and the inserting operation are set by parameters in the operation program. The motion program includes a data array describing the force control conditions attached to the commands associated with each motion included in the motion sequence so that the motion program is performed under the force control conditions adapted to each motion as the motion sequence progresses. There is.

In the preferred embodiment, the control condition for keeping the force constant in the insertion axis direction is described in the data array describing the force control condition, and
According to the description, the magnitude of the force kept constant is switched at least once as the operation sequence progresses.

Impedance control can be used as the force control method. In that case, parameters for executing impedance control are described in the data array that describes the force control conditions. An example of an application in which the method of the present invention may be advantageously applied is in phased fitting for the assembly of harmonic drives.

[0014]

In the present invention, the force control parameter is prepared in the motion program in the form of an array structure, and is selectively designated as an argument in the motion command of each robot. That is, the force control conditions suitable for each operation mode are automatically set for the approach operation, the phase adjustment operation, the original phase return operation, the insertion operation, etc., which are sequentially executed according to the progress of the operation sequence for the phase adjustment fitting. Will be realized.

For example, in the data array describing the force control condition, the control condition for keeping the force constant in the insertion axis direction is described in association with each operation. , The phase matching operation, the original phase restoring operation, and the inserting operation are controlled so as to achieve a desired target force.

When impedance control is adopted as the force control method, smooth phase matching and fitting can be performed automatically by appropriately setting the parameters for executing impedance control in the data array describing the force control conditions. Will be achieved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sketch drawing outlining an overall arrangement in one embodiment of the present invention. The application will be described assuming a fitting operation included in the assembly process of the main part assembly of the harmonic drive device. In FIG. 1, reference numeral 1 denotes a force control robot body, which is connected to a robot controller 2 via a cable 11. The structure itself of the robot (main body) 1 is not particularly different from the conventional structure. Further, the robot controller 2 may be the same as the one conventionally used, except for software means for executing the processing described later.

A 6-axis force sensor 3 capable of detecting translational forces in the directions of three orthogonal axes and moments about the axes (collectively referred to as six-axis forces) is attached to the tip of the wrist of the force control robot 1. There is. Reference numeral 31 represents a cable connecting the force sensor 3 and the robot controller 2.

Workpieces to be fitted are indicated by reference numerals 4 and 5. The fitting work 4 in this example is a component (motor assembly) having the wave generator 41 attached to its tip. On the other hand, the work 5 to be fitted is a flexspline / circular spline assembly. The fitting work 4 is attached to the robot 1 via the 6-axis force sensor 3. Tool tip is wave generator 4
It is assumed that it is set at the center of the tip end surface of 1 (elliptical shape as described later).

Further, the work coordinate system (user coordinate system) is set so that the direction of the insertion axis (the moving direction of the robot 1 when inserting the wave generator 41 into the opening of the fitted work 5) coincides with the Y-axis direction. ) It is assumed that Σw is set. Then, the fitted work 5 supplied onto the work table 6 is assumed to be positioned in a posture aligned with the direction of the insertion axis (Y-axis direction).

FIG. 2 shows a harmonic drive device (CS type) which is a target work 4 and 5 for the fitting work in this embodiment.
FIG. 3 is a diagram illustrating a phase relationship at the time of fitting and a state after the fitting of the assembled component of FIG. Referring to FIG. 2 together with FIG. 1, the wave generator 41 forming the tip of the fitting work 4 gripped by the robot 1 is an element in which a bearing is mounted around an elliptic cam 411 made of a rigid body, and generally,
It is attached to the input shaft of the harmonic drive unit that constitutes the transmission. The inner ring 412 of the bearing is the elliptical cam 41.
The outer ring 4 fixed to the outer periphery of the outer ring 1 is made of an elastic material
13 is elastically deformed via balls 414 of a large number of bearings.

The flexspline / circular spline assembly 5 paired with the wave generator 41 is
The assembly includes a flex spline 51 and a circular spline 52. The flex spline 51 is an element formed of a thin cup-shaped metal elastic body, and has an opening 53.
A predetermined number of teeth are engraved on the outer periphery of the. The bottom of the flexspline 51 (bottom of the cup member) is called a diaphragm and is generally attached to the output shaft of a harmonic drive device.

On the other hand, the circular spline 52
Is an element consisting of a ring-shaped rigid body with more teeth than the number of teeth of the flexspline 51 engraved on the inner circumference, and the inner diameter of the flexspline 51 is in a neutral state (no elastic deformation).
Is slightly larger than the outer diameter in. Generally, the circular spline 52 is fixed to the casing 54.

From the above-mentioned relationship between the respective elements, when the wave generator 41 (abbreviated as a simple elliptical plate) is inserted into the opening 53 as shown in the leftmost diagram of FIG. If the major axis is in the phase range (angle range) indicated by the symbol (a), the insertion can be smoothly performed. If not, it is necessary to adjust the phase of the wave generator 41 so that the major axis direction of the wave generator 41 falls within the phase range (a), and then shift to the inserting operation.

When the wave generator 41 suitable for the phase range (a) is inserted, the flexspline 51 bends into an ellipse according to the shape of the wave generator 41, as shown in the rightmost part of FIG. Therefore, at the portion corresponding to the long axis of the wave generator 41, the flexspline 5
One tooth meshes with the tooth of the circular spline 52, and is separated from the tooth of the flex spline 51 and the tooth of the circular spline 52 at the portion corresponding to the short axis.

When the wave generator 41 is rotated clockwise through the input shaft while the circular spline 52 is fixed, the flex spline 51 is correspondingly rotated.
Elastically deforms, and the meshing positions of the teeth of the flex spline 51 and the circular spline 52 move sequentially. As a result, the flexspline 51 rotates counterclockwise as opposed to the wave generator 41. The flexspline 51 rotates and moves by one tooth of the flexspline 51 when the wave generator 41 rotates by 180 degrees. Since the number of teeth of the flex spline 51 is two less than the number of teeth of the circular spline 52, when the wave generator 41 makes one clockwise rotation (360 ° rotation), the flex spline 51 is counterclockwise. Rotate counterclockwise by a difference of two. Generally, the rotation of the flex plane 51 is taken out as the output of the harmonic drive device.

Next, on the premise of the above matters, in addition to the reference diagram of FIG. 3, an operation required for fitting the work 4 (wave generator 41) held by the robot 1 into the opening 53 of the work 5. The outline of the procedure will be described. It should be noted that the symbols of the respective elements are not shown except for the explanatory diagram of the approach operation start. As shown by the flow with arrows in FIG. 3, the entire process is composed of the following four operation sequences.

(1) Approach operation The force control robot 1 gripping the work 4 via the 6-axis force sensor 3 is almost in front of the opening 53 of the work 5 (just above in the figure).
To move along the insertion axis direction (the Y-axis direction of the work coordinate system Σw). This approach operation is a preparatory operation for starting the subsequent sequence of phase adjustment and thereafter, but the movement of the force control robot 1 is usually performed by enabling the force control. The force control during the approach operation is such that when the tip end surface of the wave generator 41 contacts the flexspline 51, the pressing force in the insertion axis direction (Y-axis direction) is maintained by the constant force specified by the parameter. Force control. In the present embodiment, the force control is validated from the approach starting point under such conditions. The impedance control method is applied as the force control method.

The outline of the control in each direction of the six degrees of freedom in the orthogonal space during the approach operation period is as follows. 1. Insertion axis (Y-axis): The approaching point advances in the inserting direction at a specified speed, and when the contact reaction force reaches a set value, the phase shift operation starts.

2. Axis orthogonal to the insertion axis (X axis, Z axis);
Control that does not output movement commands. That is, the X-axis and the Z-axis are controlled to maintain a constant position. The force control for the X axis and the Z axis is invalidated (the output of the force sensor 3 is not used). However, it is also possible to validate the constant pressing force as zero. 3. Around the insertion axis (around the Y axis): As with the translational movement of the X axis and Z axis, the control is such that no movement command is output. That is, X
Control is performed to maintain a constant posture about the axis and the Z axis.
The force control about the X axis and the Z axis is invalidated (the output of the force sensor 3 is not used). However, it is also possible to validate the constant moment as zero. 4. Around an axis orthogonal to the insertion axis (around the X-axis, around the Z-axis); similar to the rotation operation around the Y-axis, control is performed without outputting a movement command. That is, control is performed to maintain a constant posture about the X axis and the Z axis. The force control about the X axis and the Z axis is invalidated (the output of the force sensor 3 is not used). However, it is also possible to validate the constant moment as zero.

(2) Phase matching operation The approaching operation is followed by the phase matching operation. The phase matching operation is an operation equivalent to crank rotation, and the wave generator 41 rotates around the Y axis until the tool tip point of the force control robot 1 is inserted into the opening 53 by the length taught by the parameter in advance. Let it rotate. During this time,
Wave generator 41 is in the Y-axis direction (insertion axis direction)
Pressed to.

If the phase of the wave generator 41 is already within the compatible phase range (a) described with reference to FIG. 2 immediately after the start of phase matching, the wave generator 4
1 immediately enters the opening 53. If the phase of the wave generator 41 is not within the compatible phase range (a) at the start of phase matching, the phase of the wave generator 41 is within the compatible phase range (a) due to rotation around the insertion axis. The entry into the opening 53 is started from the time of entering.

As described above with reference to FIG. 2, the flexspline 51 gradually elastically deforms into an elliptical shape, and the teeth of the flexspline 51 and the teeth of the circular spline 52 engage with each other at the major axis portion.

When the translational movement amount in the insertion axis direction reaches the set amount (length), the phase adjustment sequence is ended. During this period, the engagement positions of the teeth of the flex spline 51 and the teeth of the circular spline 52 are slightly moved. The parameter that defines the insertion length during phase matching is set so as to represent the insertion length that does not exceed the total insertion length (insertion length until the insertion is completed) (for example, the number of total insertion lengths). 1).

In this way, the tool tip point position of the force control robot 1 moves to the position where it has entered the inside of the opening 53 by the insertion length (combination of rotation and translation). The operation up to this point is phase matching. Hereinafter, the final target position or the final position for phase matching will be referred to as the “middle point”.

The outline of the control in each direction of the six degrees of freedom in the orthogonal space during the phase matching operation period is as follows. It should be noted that, unless an operation error or the like occurs, the tool tip point actually reaches the intermediate point by the time the phase alignment is completed. 1. Insertion axis (Y-axis): Force control with constant force pressing until the intermediate point is the movement target point and the movement is over a predetermined length. The insertion length up to the intermediate point and the force of constant force pressing are set by parameters having appropriate values. 2. Axis orthogonal to the insertion axis (X axis, Z axis); Control that does not output movement commands. That is, the X-axis and the Z-axis are controlled to maintain a constant position. The force control for the X axis and the Z axis is invalidated (the output of the force sensor 3 is not used). However, it is also possible to validate the constant pressing force as zero. 3. Around the insertion axis (around the Y axis); control to rotate at a specified angular velocity. The force control around the Y axis is invalidated (the output of the force sensor 3 is not used). However, when there is friction around the rotation axis, it is possible to set the target moment and validate the force control.

4. Around an axis orthogonal to the insertion axis (around the X-axis, around the Z-axis); as with the translational movement of the X-axis and the Z-axis, control that does not output a movement command is performed. That is, control is performed to maintain a constant posture about the X axis and the Z axis. X axis, Z
The force control about the axis is invalidated (the output of the force sensor 3 is not used). However, it is also possible to validate the constant moment as zero. (3) Original phase return operation After the approach operation is completed, the posture of the component is adjusted according to the needs of the assembly process (here, the posture of the wave generator 41).
Is an operation that restores the original, and is performed prior to the insertion operation. The original phase restoring operation is an operation equivalent to crank turning, like the phase matching operation, but the direction of rotation is opposite to that of the phase matching operation. Further, the tool control point of the force control robot 1 is not translated. When the phase of the wave generator 41 returns to the phase at the start of phase matching, the original phase restoring operation is completed.

The outline of the control in each direction of the six degrees of freedom in the orthogonal space during the original phase adjusting operation is as follows. It should be noted that, unless an operation error or the like occurs, the attitude of the tool tip point returns to that at the time of starting the phase alignment. 1. Insertion axis (Y axis): Control that does not output movement commands. That is, the Y-axis is controlled so as to maintain a constant position.
Force control for Y-axis and Z-axis is invalidated (force sensor 3
Output is not used). However, it is also possible to validate the constant pressing force as zero. 2. Axis orthogonal to the insertion axis (X axis, Z axis); control that does not output a movement command, like the Y axis. That is, the X-axis and the Z-axis are controlled to maintain a constant position. The force control for the X axis and the Z axis is invalidated (the output of the force sensor 3 is not used). However, it is also possible to validate the constant pressing force as zero. 3. Around the insertion axis (around the Y axis); control is performed to rotate at the specified angular velocity (the sign opposite to that at the time of phase matching). The force control around the Y axis is invalidated (the output of the force sensor 3 is not used). However, when there is friction around the rotation axis, it is possible to set the target moment and validate the force control.

4. Around an axis orthogonal to the insertion axis (around the X-axis, around the Z-axis); as with the translational movement of the X-axis and the Z-axis, control that does not output a movement command is performed. That is, control is performed to maintain a constant posture about the X axis and the Z axis. X axis, Z
The force control about the axis is invalidated (the output of the force sensor 3 is not used). However, it is also possible to validate the constant moment as zero. (4) Inserting operation After the original phase returning operation (in some cases, after omitting this and after phase matching), the operation shifts to the inserting operation. The inserting operation is an operation that forms the center of the fitting operation, and is an operation of further advancing the tool tip point of the force control robot 1 into the opening 53 according to the length taught by the parameter in advance. By this insertion operation, the tool tip point position of the force control robot 1 leaves the intermediate point, and further translates toward the position advanced by the insertion length in the Y-axis direction.

The pressing state during the inserting operation can be realized by setting the target value of force. The pressing state shifts from the time when the insertion length set to be shorter than the insertable length is moved. Further, the upper limit value of the duration of the inserting operation is set by a parameter (generally, the time actually consumed by the inserting operation is different for each operation). Then, when the pressed state is released, the inserting operation is completed.

After the insertion operation is completed, the grip of the work 4 is released, and the force control robot 1 retracts to the department store point set outside the opening 53. For the evacuation operation,
The details are omitted because they are not particularly related to the features of the present invention.

The outline of the control in each direction of the six degrees of freedom in the orthogonal space during the insertion operation period is as follows.

1. Insertion axis (Y-axis): Force control with constant force pressing until a predetermined time elapses after advancing by more than the length specified by the parameter in the insertion direction. The insertion length, the magnitude and duration of the constant force pressing force are set by parameters having appropriate values. 2. Axes (X-axis, Z-axis) orthogonal to the insertion axis; force control for zeroing constant pressing force is performed. 3. Around the insertion axis (around the Y axis): As with the translational movement of the X axis and Z axis, the control is such that no movement command is output. That is, control is performed to maintain a constant posture about the insertion axis.

4. Around the axis orthogonal to the insertion axis (around the X axis, around the Z axis); force control is performed to make the constant moment zero.

Next, the robot control for realizing the above-described series of operations will be described with reference to FIG. 4 and subsequent drawings. First, FIG. 4 is a schematic block diagram of a main part of a control system including the robot controller 2 and the 6-axis force sensor 3 shown in FIG. Referring to the figure, the entire system is composed of the robot controller 2,
The robot controller 2 comprises a robot (main body mechanism section) 1 whose force is controlled, a 6-axis force sensor 3 supported by an arm tip portion of the robot body, and a signal processing device 30 which processes detection signals of the 6-axis force sensor 3. To be done.

The robot controller 2 has a central processing unit (hereinafter referred to as CPU) 21. CPU
Reference numeral 21 denotes a teaching operation panel having a memory 22 including a ROM, a memory 23 including a RAM, a non-volatile memory 24, and a keyboard for inputting various commands or setting values for teaching of the robot and the operation of other system parts. 25, an input / output device 26 that performs an interface function with the signal processing device 30, and a robot axis control unit 27 that controls the operation of each axis of the robot body 1 via a servo circuit 28. It is connected.

The 6-axis force sensor 3 may be of a known structure having a plurality of bridge circuits which are composed of, for example, strain gauges and are AC-driven by an oscillator. The 6-axis force sensor 3 outputs a detection signal representing each component of the 6-axis force to the signal processing device 30.

An outline of the signal processing in the signal processing device 30 will be described below. Each detection signal output from the 6-axis force sensor 3 is amplified by a differential amplifier, synchronously rectified and converted into a DC signal, and then input to a multiplexer in the signal processing device. The multiplexer sequentially sends out the detection signal representing each component to the input / output device 26 via the sample hold circuit and the A / D converter in accordance with the control signal received from the CPU 21 of the robot controller 2 via the input / output device 26.

The CPU 21 sequentially stores this in a predetermined area in the non-volatile memory 24. The stored detection data of the 6-axis force sensor 3 is used for force control (impedance control) of the robot performed in a manner described later.

The ROM 22, the RAM 23, and the non-volatile memory 24 store the detection data of the 6-axis force sensor 3 as well as a system program for controlling the operation of the robot controller 2 itself, a process for impedance control described later, and a signal. It is used for storing programs for executing control of signal exchange with the processing device 30 and storage of related set values for each processing.

In addition to the data of the conversion matrix between the sensor coordinate system set in the 6-axis force sensor 3 and the Cartesian coordinate system set in the robot, various force control (impedance control) data are included in this set value. Contains parameters. As described below,
These force control parameters are prepared with an array structure,
It is selectively specified as an argument in the motion command of each robot.

Next, an outline of an operation program and related data for sequentially executing the above series of operations (see FIG. 3 and its description) while switching the force control conditions will be described using a concrete example. In order to make the following description easy to understand, only the main parts relating to the method of the present invention regarding the program data and the like are extracted and expressed (the omitted parts are expressed as appropriate).

FIG. 5 shows an example of the operation program. Here, the position [1] represents the starting point of the approach motion, and the position [2] is the department store point (retraction position after the completion of the insertion motion).
Is represented. The first line represents an operation command to move to the approach operation start point in each axis movement form and perform 100% positioning. Similarly, the third line represents an operation command to move to the department store point in each axis movement form and perform 100% positioning.

The main part of the operation command for the fitting operation is the second line and is described as the "force fitting arrangement command". The content of the "force fitting arrangement command" is described in the "fitting data arrangement" described below. "Mating data array"
Has a multi-layered data structure.

FIG. 6 shows the basic structure (uppermost structure) of the "fitting data array". In the figure, the first line is a fitting data array relating to the above "force fitting array command", and indicates that two pieces of data are attached. The comment indicating the content of the first data indicating the fitting data 1 described later is “Souawase”, and the comment indicating the content of the second data indicating the fitting data 2 described below is
It's "Genso &Sonew".

FIG. 7 shows the skeleton of the fitting data structure attached to the fitting data array shown in FIG. The entire data array is divided into fitting data 1 and fitting data 2. The former is basic data 1 including impedance data 1.
And basic data 3 including impedance data 2,
The latter has basic data 3 including impedance data 3 and basic data 4 including impedance data 4.

These data are selectively used in each phase matching and fitting sequence as follows. (1) Approach operation Fitting data 1, basic data 1, impedance data 1 (2) Phase matching operation Fitting data 1, basic data 2, impedance data 2 (3) Original phase return operation Fitting data 2, basic data 3, Impedance Data 3 (4) Insertion Operation Fitting Data 2, Basic Data 4, Impedance Data 4 FIGS. 8 to 13 show an example of each fitting data and an essential part of the basic data. The following is a brief description of these data items itemized. The impedance data will be mentioned later in the description of impedance control.

[Fitting data 1 (FIG. 8)] The fitting data 1 used in the approach operation and the phase matching operation includes the following items regarding the phase matching fitting. 1st line; comment that it is fitting data mainly related to phase matching operation 2nd line; make insertion direction + Y axis direction 6th line; follow fitting method for harmonic drive device 7th line; The mating force during phase alignment (force-pressing force in the insertion axis direction) should be 10.000 kg weight. 10th line; Moving speed during approach movement is 2.000 m.
m / s Line 11; Basic conditions during approach operation follow basic data 1 Line 12; Basic conditions during phase matching operation follow basic data 2 Line 13; End of phase matching operation Judgment should be made based on the insertion depth, line 32;
000 mm Line 33: At the taught approach starting point, the distance between the fitted work and the work to be fitted is 2.000 mm Line 52: The rotation angle limit associated with the phase matching operation is
140.000 degrees The 53rd line; The acceleration / deceleration time of the rotational movement associated with the phase matching operation is 1.000 seconds 55th row; The direction of the rotational movement associated with the phase matching operation is positive (rotation around the Y axis [Basic data 1 (FIG. 9)] Basic data 1 used during the approach operation includes the following data.

1st line; comment indicating that it is basic data 1 used in the approach operation. 5th to 7th lines: data specifying the target force of force control for 6 axes. Each data is for the axis with activated force control (second
(See lines 9-31). Here, in order to push in the insertion axis direction when approaching, Y
A target force of 1.000 kg is set for the shaft. 8th to 10th lines: data for designating a target moving speed during the approach operation. Since the movement of the approach operation is only translation in the insertion axis direction, 2.000 mm / s is set for the Y axis and 0.000 mm / s or 0.000 deg / s is set for the other axes. Line 11: Data indicating that parameters representing spring strength, mass (inertia) magnitude, and damper strength are used as impedance control parameters. The set numerical value of each parameter is impedance data 1. included. Line 12: Mating work 4 (wave generator 41)
Is data that specifies a threshold value when it is determined that the workpiece 5 has come into contact with the work 5, and here, 1.000 kg weight is set.

Fifteenth line: Data for designating a determination method of approach operation completion. Here, it is specified that the contact determination using the above threshold value is used to determine the approach operation completion.

29th to 31st lines: data specifying whether or not force control by the impedance control method is validated for 6 axes. Here, it is specified that the force control is enabled only for the Y axis in order to perform the pressing in the insertion axis direction during the approach.

32nd to 34th lines: data specifying whether or not to output a movement command for 6 axes. Here, since the movement of the approach motion is only translation in the insertion axis direction, Y
Only the axis is designated as "valid", other axes are "invalid"
It has been. That is, the translational position about the X and Z axes, W,
Regarding the rotational position (posture) about the P and R axes, no movement command is output (force control is invalid and normal control for maintaining a constant position).

[Basic data 2 (FIG. 10)] The basic data 2 used in the phase matching operation includes the following data.

First line; comment that rotation is performed until the phases match. Lines 5 to 7: Data specifying the target force of force control for 6 axes. Each data is for the axis with activated force control (second
(See lines 9-31). Here, in order to push in the insertion axis direction at the time of phase matching, Y
A target force of 10.000 kg is set for the shaft (note that it is larger than during approach movement). 8th to 10th lines: data for designating a target moving speed during the phase matching operation. Since the movement of the phase matching operation is rotation around the insertion axis and translation in the insertion axis direction, 2.0 for the Y axis
00 mm / s and 5.000 deg / s are set for the P axis. The set value for other axes that do not move is 0.0
It is 00 mm / s or 0.000 deg / s. Line 11: Data indicating that parameters representing spring strength, mass (inertia) magnitude, and damper strength are used as impedance control parameters. The set values for each parameter are impedance data 2. included. Fifteenth line: data designating a determination method of completion of the phase matching operation. Here, the insertion length (the 32nd fitting data 1
Judgment at 10.000 mm specified in the row is specified.

29th to 31st lines: data specifying whether or not force control by the impedance control method is validated for 6 axes. Here, it is specified that the force control is validated in the insertion axis direction and the Y axis at the time of phase matching. Although invalidation is set for the P axis,
It is also possible to set a target moment and activate force control. In addition, X-axis and Z that have been set to invalid
Regarding the shafts, the W-axis, and the R-axis, it may be possible to enable all or part of them in order to make the insertion and the rotation smoother.

Lines 32 to 34: Data specifying whether or not to output a movement command for the 6 axes. Here, the movement of the phase matching operation is only translation in the insertion axis direction, so Y
Only the axis is designated as "valid", other axes are "invalid"
It has been. That is, the translational position about the X and Z axes, W,
Regarding the rotational position (orientation) about the P and R axes, no movement command is output (force control is invalid and normal control for maintaining the current position).

[Fitting Data 2 (FIG. 11)] The fitting data 2 used in the original phase restoring operation and the inserting operation include the following description regarding the phase matching fitting. 1st line; comment that it is mainly fitting data relating to the original phase return operation and insertion operation. 2nd line; the insertion direction is the + Y axis direction. 6th line; follows the fitting method for harmonic drive device. Line 7: Set the mating force during phase matching (pressing force in the insertion axis direction of force control) to 20.000 kg weight (note that it is set larger than the mating force during phase matching) Line 11: Original The basic condition at the time of the phase return operation is to follow the basic data 3 12th line; The basic condition at the time of the inserting operation is to follow the basic data 4th line 13; The end of the inserting operation is determined by the insertion depth. Line 32: Fitting depth after insertion is 15.000 m
m 56th line; enabling the original phase return operation for the harmonic drive [Basic data 3 (FIG. 12)] The basic data 3 used during the original phase return operation is the following. Contains data.

First line: comment indicating that the data is basic data used during the original phase return operation. Lines 5 to 7: data specifying the target force for force control on the six axes. Each data is for the axis with activated force control (second
(See lines 9-31). Here, in order to maintain the current position in the insertion axis direction when returning to the original phase,
A target force of 0.000 kg weight is set for the Y axis. 8th to 10th lines: data for designating a target moving speed at the time of original phase returning operation. Since the movement of the original phase returning operation is the rotation around the insertion axis, 0.000 mm / s is set for the Y axis and −5.000 mm / s is set for the P axis.
The set value of the other axis that does not move is 0.000 mm / s. Line 11: Data indicating that parameters representing spring strength, mass (inertia) magnitude, and damper strength are used as impedance control parameters. included. 13th line: Data designating the upper limit of the control time for performing the original phase return operation. Here, 60 sec is designated.

Fifteenth line: data for designating the operation completion determination method. Although the determination based on the control time is designated here, this is ignored in the phase matching fitting, and the operation ends when the original phase is restored. The thirteenth
If the original phase return is not made within the time specified by the row, an error signal is output. 29th to 31st lines: data specifying whether or not to enable force control by the impedance control method for 6 axes. The X-axis, Z-axis, W-axis and R-axis are invalid, but it is conceivable to enable all or a part of them in order to make insertion and rotation smoother.

Lines 32 to 34: Data specifying whether or not to output a movement command for the 6 axes. Here, since the movement of the original phase return operation is only the rotation around the insertion axis, P
Only the axis is designated as "valid", other axes are "invalid"
It has been. That is, the translational positions about the X, Y, and Z axes,
Regarding the rotational position (orientation) about the W and R axes, no movement command is output (force control is invalid and control for maintaining the current position).

[Basic data 4 (FIG. 13)] The basic data 4 used in the inserting operation includes the following data. 1st line; comment that it is basic data used at the time of insertion operation. 5th to 7th lines; data specifying target force of force control for 6 axes. Each data has a meaning for the axis for which force control is enabled (see lines 29 to 31). Here, in order to push in the insertion axis direction at the time of insertion,
A target force of 20.000 kg is set for the Y-axis (note that the maximum value is set for approach operation, phase adjustment, and original phase return). 8th to 10th lines: data for designating a target moving speed at the time of inserting operation. Since the movement of the insertion operation is only translation in the insertion axis direction, 2.000 mm / s is set for the Y axis. The set value of the other axis that does not move is 0.000 mm / s. Line 11: Data indicating that parameters representing spring strength, mass (inertia) magnitude, and damper strength are used as impedance control parameters. included. Line 13: Data designating the upper limit of the control time for performing the inserting operation. Here, 50 sec is designated.

Fifteenth line: Data for designating the determination method of completion of the phase matching operation. Here, the determination based on the moving distance is designated. 29th to 31st lines: data specifying whether or not to enable force control by the impedance control method for 6 axes. Here, only the P axis is invalid, and the other axes (X, Y,
All Z, W, and R axes) are valid.

Lines 32 to 34: Data specifying whether or not to output a movement command for the 6 axes. Here, the movement of the insertion operation is only translation in the insertion axis direction, but the X, Z, W, and R axes along with the Y axis are designated as "valid", and only the P axis is designated as "invalid". . That is, the movement command regarding the P-axis is not output (force control is also invalid and control for maintaining a constant position).

The outline of the processing executed by the reproduction operation of the operation program including the fitting arrangement command having the above data arrangement structure is shown in the flowchart of FIG. First, the first one block of the operation program shown in FIG. 5 is read (step S1). Ichi [1] as specified in the statement
A process for moving the robot 1 to the (starting point of the approach operation) in each axis movement form is performed (step S2).
As a result, the robot 1 is positioned at the starting point of the approach motion. It is not necessary to perform force control (impedance control) up to this point.

Then, the next one block of the operation program is read (step S3). What is read here is a "force fitting arrangement command". The processing for phase matching fitting is started according to the designation by the data having the above-described arrangement structure. First, in step 4, processing for the approach operation is executed according to the fitting data 1 and the basic data 1 described above. Hereinafter, a process for the phase matching operation according to the fitting data 1 and the basic data 2 (step S5), a process for the original phase returning operation according to the fitting data 2 and the basic data 3 (step S6), The process (step S7) for the insertion operation according to the fitting data 2 and the basic data 4 is sequentially executed.

As a result, the above-described operation sequence is realized and the fitting operation of the wave generator 41 is performed.

When the inserting operation is completed, one block of the next operation program is read (step S8), and the step [2]
The processing for moving the robot 1 to the (department point) in each axis movement form is performed (step S9), and the processing for one cycle of phase matching fitting is completed. Note that the description of the processing for releasing the grip of the work 4 prior to step S9 is omitted.

Finally, the impedance control used as the force control method in this embodiment will be described with reference to FIG. Since this control method itself is known, only an outline will be 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. . When a robot is modeled in such a system, the system is described by parameters that represent 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 by equation (11) described below using these parameters.

When applying the impedance control method,
Parameters for expressing inertia, damper and spring are properly set, and target position, velocity, acceleration (including posture) and target force are given. In the present embodiment, the impedance data 1 to 4 of the basic data 1 to 4 include these setting data. In general, the proper values of the parameters related to inertia, damper and spring are different in each operation (approach, phase adjustment, original phase return, insertion). These values are calculated individually according to theoretical calculation and empirical rule.
It is set in 4.

For the target trajectory, the approach starting point,
It is calculated from the insertion depth specified for each operation.
The target force at each operation is set in the fitting data and the basic data as described above. In this embodiment, the target for the position is given by the speed in the insertion direction.

Further, the target force ^D F _{d is set} to ^D F _d = [ ^D f _d
^T , ^D τ _d ^T ] ^T. Where ^D f _d
Is the target force and ^D τ _d is the target torque. As described above, these are set in the fitting data 1 and 2 and the basic data 1 to 4.

Hereinafter, the insertion operation for pressing in the Y-axis direction will be described as an example. In this case, ^D f _d =
_{^{[0, D f y, 0}} ] T, D τ d = [0,0,0] T and expressed (described figures ^D f _y is omitted. Hereinafter, the same). When the tool tip point moves along the insertion axis and the fitting is completed and the state shown in FIG. 16 is reached, the tip end surface of the wave generator 41 abuts on the bottom of the opening 53, and the robot causes the target force ^D F _d. The equilibrium state set for is reached and the movement is stopped.

Now, assuming that the coordinate system Σt is represented by a 6-dimensional vector of position and orientation as ^D r _C , the equation of motion described by the set impedance becomes the following equation (1).

[0084]

(Equation 1) In the above formula (1), the number of dots added on the variable r represents the differentiation by that number. ^D F _c is the force detected by the 6-axis force sensor 3, and the right side is the deviation from the target force ^D F _d multiplied by the force gain κ _F (hereinafter, κ _F = 1 for convenience). In the above formula (1), M is a target inertia matrix of 6 rows and 6 columns, D is a target viscosity matrix of 6 rows and 6 columns, and K is a target stiffness matrix of 6 rows and 6 columns. 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) ... (2) and K = 0 ... (3). 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.

With the above impedance setting and target force setting, the robot operates by force control so that the position / orientation is aligned with the insertion axis according to the force applied to the tool tip point, and smooth fitting work is possible. . From the above formula (1),
The target acceleration of the hand of the robot is obtained by the following equation (4).

[0086]

(Equation 2) When the joint variable of the robot is θ and the Jacobi matrix representing the relation between the one-time derivative of this joint variable and the one-time derivative of the vector ^D r _C is J, the following equation (5) is established.

[0087]

(Equation 3) As one of the methods for directly realizing the target acceleration (2 dots of θ _d ) in the above expression (3), the equation u of the robot motion is defined as the following expression (6), and the value u obtained by the expression (7) is obtained.
Command value to actuator (torque command to motor)
There is a method of using u.

[0088]

(Equation 4)

[0089]

(Equation 5) In the above equations (6) and (7), τ: torque of each joint of the robot I (θ): robot inertia matrix h (1 dot of θ, θ): nonlinear force such as Coriolis force or centrifugal force .

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

[0091]

(Equation 6)

[0092]

(Equation 7) The position θ _d after the time Δt and the target value of the speed (θ
(1 dot of _d ). Next, the outline of the impedance control calculation process is shown in the flowchart of FIG. In this process, the 6-dimensional vector ^D r _c and its differential value are obtained from each axis value of the robot and the velocity based on the teaching path along the insertion axis. Further, the target acceleration (2 dots of ^D r _c ) is obtained by calculating the equation (4) using the set target force ^D F _d and the force ^D F _c detected by the 6-axis force sensor 3. Further, the equation (5) is calculated from the obtained target acceleration and the velocity of each axis,
A target acceleration (2 dots of θ _d ) for each axis is obtained (step T1).

Then, for each axis, the target acceleration and the target position are obtained by calculating the equations (8) and (9) from the target acceleration and the detected speed obtained in step T1 and output to each axis servo system (step T2, T3).

When one cycle of the impedance control calculation is completed, the current robot hand position ri is calculated, the robot advancing direction vector Δi is calculated from the position and the position ri-1 immediately before, and the next impedance control calculation is performed. Prepare for processing.

As described above, the impedance control method is applied as the force control in the present embodiment, but other force control methods can be adopted.

Further, in the present embodiment, the case (assembly of the harmonic drive device) in which the insertable phase has a spread and the original phase restoration is necessary has been described. But,
It will be apparent from the above description that the method of the present invention can be applied to the case where the insertable phase has no spread or the case where the original phase restoration is unnecessary. FIG. 18 shows an example of a shaft with a key as such a work. In the example of the figure, the work 60 having the concave streak portion 61 is
The shaft with a key is assembled by fitting the work 70 having the ridges 71. The work gripped by the force control robot may be either the work 60 or 70.

[0097]

According to the present invention, a series of operations performed under mutually different force control conditions by utilizing a force control robot capable of designating several force control parameters in operation commands ( Mating work that requires phase matching, original phase restoration, insertion, etc. can be performed smoothly. Therefore, it has become possible to automate the type of assembly work that was difficult to automate in the past.

[Brief description of the drawings]

FIG. 1 is a sketch drawing outlining an overall arrangement in one embodiment of the present invention.

FIG. 2 is a diagram illustrating a phase relationship at the time of fitting and a state after the fitting of the assembly parts of the harmonic drive device (CS type) that is the target work of the fitting work in the present embodiment.

FIG. 3 is a diagram for explaining an outline of an operation procedure required for fitting a work (wave generator) gripped by the robot 1 into an opening of a work to be fitted.

FIG. 4 is a block diagram showing a schematic configuration of a control system used in the embodiment.

FIG. 5 shows an operation program in the embodiment.

FIG. 6 shows a basic structure (uppermost structure) of a fitting data array in the embodiment.

FIG. 7 shows a skeleton of a fitting data structure attached to the fitting data array shown in FIG.

FIG. 8 is a diagram illustrating a main part of fitting data 1 in the embodiment.

FIG. 9 is a diagram illustrating a main part of basic data 1 according to the embodiment.

FIG. 10 is a diagram illustrating a main part of basic data 2 according to the embodiment.

FIG. 11 is a diagram illustrating a main part of fitting data 2 in the embodiment.

FIG. 12 is a diagram illustrating a main part of basic data 3 according to the embodiment.

FIG. 13 is a diagram illustrating a main part of basic data 4 according to the embodiment.

FIG. 14 is a flowchart outlining a process executed by a reproduction operation of an operation program.

FIG. 15 is a diagram illustrating a position control target of impedance control in the embodiment.

FIG. 16 is a diagram illustrating a state in which fitting is completed in the embodiment.

FIG. 17 is a flowchart outlining an impedance control calculation process according to the embodiment.

FIG. 18 is a diagram illustrating fitting of a shaft with a key.

[Explanation of symbols]

 1 Force control robot (main body) 2 Robot controller 3 6-axis force sensor 4 Fitting work (harmonic drive device part) 5 Fitted work (harmonic drive device part) 6 Fitting work (key shaft part) 7 Work to be fitted (part of shaft with key) 11, 31 Cable 21 Central processing unit (CPU) 22 ROM 23 RAM 24 Non-volatile memory 25 Teaching operation panel 26 Input / output device 27 Robot axis control unit 28 Servo circuit 29 Bus 30 Signal processing device 41 Wave generator 51 Flexspline 52 Circular spline 53 Opening 54 Casing 61 Recessed ridge 71 Convex ridge 411 Elliptical cam 412 Bearing inner ring 413 Bearing ball 414 Bearing outer ring

Claims (6)

[Claims] 1. A force control robot for performing a fitting operation between works, which requires phase matching at the time of fitting, by causing a force control robot holding a fitted work to execute a series of operation sequences. In the above operation sequence, at least (1) an approach operation for moving the fitted work closer to the fitted work and moving it to a position where the phase matching can be started; The phase aligning operation of rotating the insertion work around the insertion axis while pressing it against the mating work, and (3) the insertion operation of moving the fitting work against the mating work while moving along the insertion axis. The approach motion, the phase matching motion, and the insertion motion are set by parameters in a motion program. The motion program includes a data array describing the force control conditions attached to the commands associated with each motion included in the motion sequence so that the motion program is performed under the force control conditions adapted to each motion according to the progress of the can. A phase matching mating method using a force control robot. 2. A force control robot for causing a force control robot holding a fitted work to execute a series of operation sequences so as to perform a fitting work between works that requires phase matching at the time of fitting. In the above operation sequence, at least (1) an approach operation for moving the fitted work closer to the fitted work and moving it to a position where the phase matching can be started; The phase aligning operation of pressing the combined work against the mating work while rotating it around the insertion axis, and (3) the inserting operation of moving the mating work along the insertion axis while pressing it against the mating work. The approach motion, the phase matching motion, and the insertion motion are set by parameters in a motion program. The motion program includes a data array describing the force control conditions attached to the commands associated with each motion included in the motion sequence so that the motion program is performed under the force control conditions adapted to each motion according to the progress of the can. In the data array describing the force control conditions, control conditions for keeping the force constant in the insertion axis direction are described, and the description indicates that the magnitude of the force kept constant is The phase matching fitting method using the force control robot, wherein the switching is performed at least once according to the progress of the operation sequence. 3. A force control robot for performing a fitting operation between works, which requires phase matching at the time of fitting, by causing a force control robot holding a fitted work to execute a series of operation sequences. In the above operation sequence, at least (1) an approach operation for moving the fitted work closer to the fitted work and moving it to a position where the phase matching can be started; Phase matching operation of rotating the fitting work against the work to be fitted while rotating it around the insertion axis, and (3) rotating the fitting work around the insertion axis to adjust the posture of the fitting work before phase matching. The original phase return operation to return to the state of (4) and (4) the insertion operation to move the fitting work against the fitted work while moving it along the insertion axis are included. The approach operation, the phase matching operation, the original phase return operation, and the insertion operation are set by parameters in the operation program, and are performed under force control conditions suitable for each operation as the operation sequence progresses. The phase matching fitting method using a force control robot, wherein the motion program includes a data array describing a force control condition attached to a command associated with each motion included in the motion sequence. 4. A force control robot adapted to execute a fitting operation between works that requires phase matching at the time of fitting by causing a force control robot holding a fitted work to execute a series of operation sequences. In the above operation sequence, at least (1) an approach operation for moving the fitted work closer to the fitted work and moving it to a position where the phase matching can be started; Phase matching operation of rotating the fitting work against the work to be fitted while rotating it around the insertion axis, and (3) rotating the fitting work around the insertion axis to adjust the posture of the fitting work before phase matching. The original phase returning operation to return to the state of (4) and (4) the insertion operation of moving the fitting work against the work to be fitted along the insertion axis while pressing it are included. The approach operation, the phase matching operation, the original phase return operation, and the insertion operation are set by parameters in the operation program, and are performed under force control conditions suitable for each operation as the operation sequence progresses. In the operation program, the operation program includes a data array describing a force control condition attached to an instruction associated with each operation included in the operation sequence, and the insertion axis is included in the data array describing the force control condition. With respect to the direction, a control condition for keeping the force constant is described, and the description is such that the magnitude of the force kept constant is switched at least once as the operation sequence proceeds. A phase matching fitting method using the force control robot. 5. The force control is impedance control, and the data array describing the force control condition describes parameters for executing impedance control. The described phase matching fitting method using a force control robot. 6. The work according to claim 1, wherein the fitted work and the fitted work are assembly parts of a harmonic drive device.
The phase-matching fitting method using a force control robot according to any one of 1.