JP2015120221A - Component fitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To absorb excessive force to mate each other if the excessive force arises when components that are complicated in shape and relatively large in dimension error are fitted together.SOLUTION: A component fitting device comprises: a plurality of gripping pawls 11, 12 that move in a predetermined direction, thereby gripping a target object; drive motors 16, 18 provided in combination with the corresponding gripping pawls 11, 12 to form pairs, and used to move the corresponding gripping pawls 11, 12 independently; and a control part 22 that controls the drive motors 16, 18. The control part 22 controls the gripping forces of the gripping pawls 11, 12 such that an addition value of a thrust force generated by each gripping pawl 11, 12 is constant and such that respective moving directions of the gripping pawls 11, 12 are controlled on the basis of the difference between thrusts generated by the gripping pawls 11, 12.

Description

  The present invention relates to a component assembling apparatus using, for example, a robot.

In recent years, automation and efficiency have been actively promoted by introducing industrial robots in production sites such as electronic component assembly.
Industrial robots greatly exceed human capabilities in terms of speed, power, and (position) accuracy, and are suitable for high-speed and large-scale assembly of parts with simple shapes and small dimensional errors.
On the other hand, in human manual work, even for parts that are complicated in shape and have relatively large dimensional errors, and flexible objects such as cables, component fitting is performed by comprehensively using the information from the eyes and the sense of the hand. Can locate and assemble the position.

JP 2005-59118 A JP 2006-310216 A

Here, the following methods have been used in the past to safely assemble parts that are large, heavy, and highly rigid industrial robots that are as complex as humans and that have a relatively large dimensional error or severe precision. Yes.
(1) An impact absorbing mechanism and a component position error absorbing mechanism that do not cause a problem even if the robot contacts at a predetermined speed are installed for each jig of the assembled component.
(2) A force sensor is installed between the robot and an end effector such as a hand, and the position is controlled so that excessive force is not generated during assembly.
(3) A passive compliance such as RCC (Remote Compliance) is installed between the robot and an end effector such as a hand.

In the above method (1), since the jig is specialized for an assembly part, it can be assembled at a relatively high speed. However, since an impact absorbing mechanism and a position error absorbing mechanism are required for each part, the apparatus itself becomes large and expensive, and it cannot flexibly cope with changes in the type of assembled parts.
On the other hand, in the method (2), a jig for absorbing shock is not necessary, and it is possible to cope with changes in assembly parts by a program. However, the assembly operation requiring force control by the force sensor is slow and the force sensor is also expensive.
The method (3) can absorb position error. However, when the type of assembly parts changes, there remains a problem that adjustment is required each time.

  In order to solve the above problems, a device that can change characteristics such as contact speed, contact force, and compliance according to the type of assembly parts and the assembly method between the robot and the end effector such as a hand. Should be installed to absorb shocks and position errors.

Control of contact speed, contact force, compliance, etc. for absorbing the impact and position error can be realized by a single robot equipped with a force sensor. However, in order to allow parts to come into contact with each other without being damaged safely with a large, heavy, and highly rigid robot, consider the worst case of dimensional errors and gripping errors and reduce the speed sufficiently before the part where the parts come into contact. There is a problem that it is necessary.
In addition, after the components come into contact with each other, it is necessary to assemble with an optimum working force for the type of component and the assembling method while absorbing and imitating the position error. However, there is a problem that even if a force sensor is installed, it is difficult to control delicate force and compliance at high speed with a single robot having a deceleration mechanism with much friction.

Therefore, in assembly that does not require too much force, control of contact speed, contact force, compliance, etc. for absorbing impacts and position errors is greater than with a robot that is large, heavy, rigid, and has a lot of friction. It is more advantageous to use a direct drive actuator that is small, light, rigid, and has little friction.
Further, it is advantageous that the actuator is near the end factor because the weight supported by the actuator is small and the size can be reduced, and it is better if the end effector itself, for example, the gripping claw of the hand has the above-mentioned compliance function.

  The present invention has been made to solve the above-described problems. When a part having a complicated shape and a relatively large dimensional error is assembled, even if an excessive force is generated, it is absorbed and copied. An object of the present invention is to provide a component assembling apparatus capable of performing the above.

  A component assembly device according to the present invention includes a plurality of gripping claws that grip an object by moving in a predetermined direction, and a drive unit that is provided in pairs with each gripping nail and moves the corresponding gripping nails independently. A control unit that controls the drive unit, and the control unit controls the gripping force of each gripping nail so that the added value of the thrust generated by each gripping nail is constant, and each gripping nail The moving direction of the gripping claw is controlled based on the difference in generated thrust.

  According to the present invention, since it is configured as described above, when assembling a component having a complicated shape and a relatively large dimensional error, even if an excessive force is generated, it can be absorbed and copied.

It is a figure which shows an example of the conventional electric hand, (a) It is a front view which shows the state which opened the nail | claw, (b) It is a front view which shows the state which closed the nail | claw, (c) It is a perspective view which shows the relationship between a drive motor and a cam. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the outline | summary of the electric hand to which the component assembly apparatus which concerns on Embodiment 1 of this invention is applied, (a) It is a front view which shows the state which opened the nail | claw, (b) The state which closed the nail | claw (C) is a perspective view showing a relationship between a gripping claw, a driving motor, and a cam. It is a figure which shows the structural example of the control block of the electric hand to which the component assembly apparatus which concerns on Embodiment 1 of this invention is applied. It is a figure which shows holding | grip of the round bar by the electric hand to which the component assembly apparatus which concerns on Embodiment 2 of this invention is applied, (a) It is a figure which shows the state in which the center position of a round bar corresponds with a holding claw central axis. (B) It is a figure which shows the state which the center position of the round bar shifted | deviated from the holding claw central axis. It is a figure which shows the structural example of the control block of the electric hand to which the component assembly apparatus which concerns on Embodiment 2 of this invention is applied.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
First, an example of a conventional electric hand will be described with reference to FIG. In FIG. 1, in order to show the relationship between the pins 4 and 5 and the drive motor 6 and the cam 7, the positions thereof are changed and the claw tips of the gripping claws 1 and 2 are omitted.

As shown in FIG. 1, the conventional electric hand is provided with gripping claws 1 and 2 for gripping an object by moving in a predetermined direction. The gripping claws 1 and 2 are supported by the linear guide 3 and can be independently moved in the axial direction of the linear guide 3 (the left-right direction shown in FIGS. 1A and 1B).
Further, pins 4 and 5 are erected on the gripping claws 1 and 2 in a direction substantially perpendicular to the respective moving surfaces. As shown in FIG. 1, the pins 4 and 5 are guided by a cam 7 having a cam groove 71 that is symmetrical and spirally arranged around the rotation axis of the drive motor 6.

  Here, as shown in FIG. 1A, when the gripping claws 1 and 2 are in the most open state, the pins 4 and 5 of the gripping claws 1 and 2 are guided near the outer periphery of the cam groove 71. On the other hand, when the driving motor 6 starts to rotate counterclockwise, the pins 4 and 5 are guided by the cam groove 71, so that the gripping claws 1 and 2 move along the linear guide 3 toward the gripping center. To do. As shown in FIG. 1B, the gripping claws 1 and 2 are closed when the pins 4 and 5 are guided to the vicinity of the inner periphery of the cam groove 71.

The conventional configuration as described above is also disclosed in Patent Document 1 and the like, and the grip center position can be accurately obtained with a simple configuration, and the gripping force can be controlled by changing the rotational torque of the driving motor 6. There is.
However, as described in the problem to be solved by the invention, in order to assemble a part having a complicated shape and a relatively large dimensional error, a function for absorbing and copying the relative position error between the parts is necessary. Such a conventional electric hand has a problem that it is difficult to absorb and imitate even if an excessive force is generated during assembly.

  Next, an outline of an electric hand to which the component assembling apparatus of the present invention is applied will be described. 2 is a diagram showing an outline of an electric hand to which the component assembling apparatus according to Embodiment 1 of the present invention is applied, and FIG. 3 is a diagram showing a configuration example of a control block of the electric hand. In FIG. 2, in order to show the relationship between the pins 14 and 15 and the drive motors 16 and 18 and the cams 17 and 19, their positions are changed, and the claw tips of the gripping claws 11 and 12 are not shown. doing.

As shown in FIG. 2, the electric hand of the present invention is provided with gripping claws 11 and 12 for gripping an object by moving in a predetermined direction. The grip claws 11 and 12 are supported by a linear guide 13 and can be independently moved in the axial direction of the linear guide 13 (the left-right direction shown in FIGS. 2A and 2B).
Further, pins 14 and 15 are erected on the gripping claws 11 and 12 in a direction substantially perpendicular to the respective moving surfaces. As shown in FIG. 2, the pin 14 is driven by a cam 17 having a cam groove 171 spirally arranged around the rotation axis of a drive motor (drive unit) 16, and the pin 15 is driven by a drive motor (drive unit). ) The guides 19 are independently guided by the cams 19 having cam grooves 191 arranged spirally around the 18 rotation axes.

  Here, as shown in FIG. 2A, when the gripping claws 11 and 12 are in the most open state, the pins 14 and 15 of the gripping claws 11 and 12 are guided near the outer periphery of the cam grooves 171 and 191. Yes. On the other hand, when the driving motor 16 starts to rotate counterclockwise and the driving motor 18 starts to rotate clockwise, the pins 14 and 15 are guided by the cam grooves 171 and 191 so that the gripping claws 11 and 12 are moved. Each moves along the linear guide 13 toward the grip center. 2B, the gripping claws 11 and 12 are closed when the pins 14 and 15 are guided to the vicinity of the inner periphery of the cam grooves 171 and 191.

Since the cam grooves 171 and 191 are formed in a spiral shape, even if the rotational torque of the drive motors 16 and 18 is constant, the pins 14 and 15 are directed toward the outer periphery of the cams 17 and 19, that is, the gripping claws 11 and 11. As 12 opens, the gripping force decreases.
The linear guide 13 and the cams 17 and 19 constitute a torque conversion mechanism that converts the rotational torque of the drive motors 16 and 18 into the thrust of the gripping claws 10 and 11.

  Further, as shown in FIG. 3, rotational position detectors 20 and 21 such as a rotary encoder capable of detecting the rotational positions of the driving motors 16 and 18 are attached to the driving motors 16 and 18, respectively. And the control part 22 controls the drive motors 16 and 18 by acquiring the rotation position of the drive motors 16 and 18 by acquiring the pulse number output from the rotational position detectors 20 and 21. At this time, the control unit 22 controls the gripping force of the gripping claws 11 and 12 so that the added value of the thrust generated by the gripping claws 11 and 12 is constant, and also controls the gripping claws 11 and 12. The movement direction of the grip claws 11 and 12 is controlled based on the difference in thrust generated.

The mechanical difference between the electric hand of the present invention and the conventional electric hand is that the configuration of the cam grooves 171 and 191 and the gripping claws 11 and 12 are controlled by independent drive motors 16 and 18. On the other hand, Patent Document 2 also discloses a configuration in which each gripping claw is controlled by an independent drive motor.
However, in Patent Document 2, the shape of the cam groove is devised to increase the shape that can be gripped and accurate centering, and a means for absorbing and copying the relative position error between components is mentioned. It does not solve the problem to be solved by the invention.

Next, the configuration of the control unit 22 will be described with reference to FIG.
As shown in FIG. 3, the control unit 22 includes up / down counters 221, 222, gripping claw position conversion units 223, 224, thrust calculation unit 225, target thrust conversion units 226, 227, speed detection units 228, 229, and subtraction. , And motor driving drivers 232 and 233.

The up / down counter 221 detects the rotational position of the drive motor 16 by counting the number of pulses output by the rotational position detector 20.
The up / down counter 222 detects the rotational position of the drive motor 18 by counting the number of pulses output by the rotational position detector 21.
The drive motors 16 and 18 rotate in opposite directions, and the outputs from the up / down counters 221 and 222 increase as the gripping claws 11 and 12 open.

The gripping claw position conversion unit 223 is detected by the up / down counter 221 based on reference data determined in advance regarding the relationship between the rotational position of the driving motor 16 and the position of the gripping claw 11 on the linear guide 13 axis. The rotational position of the driving motor 16 is converted into the position of the gripping claw 11 on the linear guide 13 axis (the gripping claw position P1).
The grip claw position conversion unit 224 is detected by the up / down counter 222 based on reference data determined in advance regarding the relationship between the rotational position of the driving motor 18 and the position of the grip claw 12 on the linear guide 13 axis. The rotational position of the driving motor 18 is converted into the position of the gripping claw 12 on the linear guide 13 axis (the gripping claw position P2).

  Based on the gripping claw positions P1 and P2 converted by the gripping claw position conversion units 223 and 224 and the input target gripping force fr / 2 and the gripping claw center target position Pr, the thrust calculation unit 225 , 12 thrust command values f1, f2 are calculated. The thrust calculation unit 225 includes a subtracter 234, a comparator 235, an amplifier 236, an adder 237, and a subtractor 238.

  The subtractor 234 subtracts the grip claw position P2 converted by the grip claw position conversion unit 224 from the grip claw position P1 converted by the grip claw position conversion unit 223. Here, the value obtained by subtracting the position P2 of the gripping claw 12 from the position P1 of the gripping claw 11 represents a gripping center shift amount (gripping center position shift Pd), and the actual shift amount is obtained by dividing P1-P2 by 2. Value. Note that a value obtained by adding the position P1 of the gripping claws 11 and the position P2 of the gripping claws 12 represents an open interval between the gripping claws 11 and 12.

The comparator 235 adds the gripping center position shift Pd input from the subtractor 234 from the inverted value of the input gripping claw center target position Pr (the target position Pr is positive or negative with the center of the linear guide 13 being zero). Value).
The amplifier 236 amplifies the value obtained by the comparator 235 with a predetermined gain G.

The adder 237 adds the input target gripping force fr / 2 and the value obtained by the amplifier 236 to obtain a thrust command value f1 of the gripping claw 11.
The subtractor 238 subtracts the value obtained by the amplifier 236 from the input target gripping force fr / 2 to obtain a thrust command value f2 of the gripping claw 12.

The target thrust converting unit 226 calculates the thrust calculated by the thrust calculating unit 225 based on reference data determined in advance regarding the relationship between the rotational torque of the driving motor 16 and the generated thrust of the gripping claws 11 on the linear guide 13 axis. From the command value f1 and the gripping claw position P1 converted by the gripping claw position conversion unit 223, the rotational torque necessary to generate the target thrust of the gripping claw 11 is obtained.
The target thrust conversion unit 227 calculates the thrust calculated by the thrust calculation unit 225 based on reference data determined in advance regarding the relationship between the rotational torque of the drive motor 18 and the generated thrust of the gripping claws 12 on the linear guide 13 axis. From the command value f2 and the gripping claw position P2 converted by the gripping claw position conversion unit 224, the rotational torque necessary for generating the target thrust of the gripping claw 12 is obtained.

The speed detector 228 calculates the moving speed of the gripping claw 11 by differentiating the rotational position of the driving motor 16 detected by the up / down counter 221.
The speed detection unit 229 calculates the moving speed of the gripping claws 12 by differentiating the rotational position of the driving motor 18 detected by the up / down counter 222.

  The subtracter 230 subtracts the value obtained by the speed detector 228 from the rotational torque obtained by the target thrust converter 226, and the subtracter 231 calculates the speed from the rotational torque obtained by the target thrust converter 227. The value obtained by the detection unit 229 is subtracted, and the speed component is fed back to each of the motor driving drivers 232 and 233. Thereby, stabilization of the grip claw position control can be performed.

The motor driving driver 232 controls the driving motor 16 so as to generate the same rotational torque based on the rotational torque input from the target thrust converter 226 via the subtractor 230.
The motor driving driver 231 controls the driving motor 18 so as to generate a rotational torque having the same value based on the rotational torque input from the target thrust converting unit 227 via the subtractor 231.

  Next, in the electric hand configured as described above, a method for realizing the position and compliance adjustment function while keeping the gripping force constant will be described in detail. Note that the position of the gripping claws 11 and 12 on the linear guide 13 axis in a state where the gripping claws 11 and 12 are closed is the origin, and the rotational position of the rotational position detectors 20 and 21 at that time is zero.

First, a case where the gripping force is simply kept constant will be described (when the gripping center position deviation Pd and the gripping claw center target position Pr are zero).
In this case, the value of ½ of the target gripping force fr is given as the thrust command values f1 and f2 of the gripping claws 11 and 12 to the inputs of the target thrust conversion units 226 and 227 via the adders / subtracters 238 and 239.
When the thrust command values f1 and f2 are given, the driving motors 16 and 18 rotate in opposite directions and the gripping claws 11 and 12 start to move in the closing direction. Thereafter, the gripping operation is completed when the gripping claws 11 and 12 come into contact with the gripping object and stop.

  The gripping force at this time is f1 + f2, and is always equal to the target gripping force fr regardless of the center positions of the gripping claws 11 and 12. However, in this state, when a force is applied from the outside, the position of the gripping claw center moves.

Next, a method for providing a compliance function while keeping the gripping force constant will be described (when the gripping claw center target position Pr is zero).
In FIG. 3, the value obtained by subtracting the position P2 of the gripping claws 12 from the position P1 of the gripping claws 11 by the subtractor 234 represents the gripping center shift amount (grip center position shift Pd), and the actual shift amount is P1-P2. The value obtained by dividing by 2 was explained before.

  Then, the gripping center position deviation Pd is added to the target gripping force fr / 2 of the gripping claw 11 by the adder 237 via the comparator 235 and the amplifier 236, and at the same time, the subtractor 238 adds the target gripping force fr / Subtract from 2.

Here, consider a case where the grip center position shift Pd is not zero. At this time, the thrust command value f1 of the gripping claw 11 and the thrust command value f2 of the gripping claw 12 are expressed by Expression (1) and Expression (2), where G is the gain of the amplifier 236.
f1 = fr / 2 + G · Pd (1)
f2 = fr / 2−G · Pd (2)

In addition, since the generated thrust of the gripping claw 11 and the generated thrust of the gripping claw 12 in Formula (1) and Formula (2) are opposite to each other, the gripping force is proportional to Formula (3) and the grip center position deviation Pd. The misregistration stress generated in this way is expressed by equation (4).
Gripping force = f1 + f2 = (fr / 2 + G · Pd) + (fr / 2−G · Pd) = fr
(3)
Misalignment stress = f1−f2 = (fr / 2 + G · Pd) − (fr / 2−G · Pd) = 2G · Pd (4)

From the above equation, the gripping force is not affected by the gripping center position shift Pd and is a constant value fr. The displacement stress generated according to the gripping center position shift Pd is proportional to the gripping center position shift Pd. It can be seen that the orientation is the grip center position direction.
This means that the electric hand having the compliance function can be realized without changing the gripping force by the configuration of the present invention.

Next, a method for transferring a gripping object to an arbitrary position while keeping the gripping force constant will be described.
In FIG. 3, the gripping center position deviation Pd is added to the target gripping force fr / 2 of the gripping claw 11 by the adder 237 via the comparator 235 and the amplifier 236, and at the same time, the target gripping force fr of the gripping claw 12 by the subtractor 238 is added. As described above, by subtracting from / 2, the compliance function can be provided without changing the gripping force.

Here, consider a case where the gripping claw center target position Pr input to the comparator 235 is not zero. At this time, the thrust command value f1 of the gripping claw 11 and the thrust command value f2 of the gripping claw 12 are expressed by Expression (5) and Expression (6), where G is the gain of the amplifier 236.
f1 = fr / 2 + G · (Pd−Pr) (5)
f2 = fr / 2−G · (Pd−Pr) (6)

Accordingly, the displacement stress generated due to the gripping force and the gripping center position shift Pd with respect to the gripping claw center target position Pr is expressed by Expression (7) and Expression (8).
Gripping force = f1 + f2 = (fr / 2 + G · (Pd−Pr)) + (fr / 2−G · (Pd−Pr)) = fr (7)
Misalignment stress = f1-f2 = (fr / 2 + G · (Pd−Pr)) − (fr / 2−G · (Pd−Pr)) = 2G · (Pd−Pr) (8)

  From the above equation, the gripping force is not affected by the gripping center position shift Pd and is a constant value fr, and the position shift stress generated according to the gripping center position shift Pd with respect to the gripping claw center target position Pr has a magnitude of gripping It can be seen that the direction is in the direction of the gripping claw center target position Pr in proportion to the value (Pr−Pd) obtained by subtracting the gripping center position deviation Pd from the claw center target position Pr. Accordingly, the gripping claws 11 and 12 can transfer the gripping object to the gripping claw center target position Pr while keeping the gripping force constant.

  In the first embodiment, the electric hand has been described in which the rotational movements of the drive motors 16 and 18 are converted into linear movements by the cams 17 and 19 and the linear guide 13, but the drive motors 16 and 18 are linear. An electric hand using a linear motor that performs various operations may be used. In the latter case, the thrust generated by the drive motors 16 and 18 becomes the thrust of the gripping claws 11 and 12 as they are, so that the input and output values of the target thrust conversion units 226 and 227 in the control unit 22 of FIG.

  In the present invention, the number of drive motors 16 and 18 is increased with respect to the conventional configuration. In this regard, for example, when two drive motors with the same rating are used, the gripping force is doubled, so that there is no disadvantage in terms of space compared to the case where the thrust is doubled in the conventional configuration.

  As described above, according to the first embodiment, a plurality of gripping claws 11 and 12 that grip an object by moving in a predetermined direction and the gripping claws 11 and 12 are provided in pairs. The gripping claws 11 and 12 are independently moved, and the control unit 22 is configured to control the driving motors 16 and 18. The control unit 22 is a thrust generated by the gripping claws 11 and 12. The gripping force of each of the gripping claws 11 and 12 is controlled so that the added value becomes constant, and the moving direction of the gripping claws 11 and 12 is determined based on the difference in thrust generated by the gripping claws 11 and 12. Since it is configured to control, when assembling a component having a complicated shape and a relatively large dimensional error, even if an excessive force is generated, it can be absorbed and copied.

That is, since the control is made so that the added value of the thrust generated by the plurality of gripping claws 11 and 12 transferred in a predetermined direction by the independent drive motors 16 and 18 is constant, the object is gripped. Even if the claws 11 and 12 are gripped at any position, the gripping force is always constant.
In addition, the moving direction of the gripping claws 11 and 12 is controlled based on the difference in thrust generated by the plurality of gripping claws 11 and 12 that are moved in a predetermined direction by the independent drive motors 16 and 18, respectively. The object can be transferred to an arbitrary position while keeping the force constant.
Further, the difference in thrust generated by the plurality of gripping claws 11 and 12 transferred in a predetermined direction by the independent drive motors 16 and 18 is configured to be proportional to the amount of deviation from the predetermined reference position at the center of the gripping claws. Therefore, it is possible to provide a compliance function while keeping the gripping force constant.

Embodiment 2. FIG.
In the first embodiment, the case where the number of the gripping claws 11 and 12 and the drive motors 16 and 18 is two and the electric hand in which the movement direction of the gripping claws 11 and 12 is uniaxial has been described. However, the present invention is not limited to this. For example, the number of gripping claws and drive motors may be three, and an electric hand in which the gripping claws move in two or three axes may be used. Hereinafter, a case where the component assembling apparatus of the present invention is applied to a three-axis electric hand will be described.

  An outline of an electric hand to which the component assembling apparatus of the second embodiment is applied will be described. FIG. 4 is a diagram showing gripping of a round bar by an electric hand to which a component assembling apparatus according to Embodiment 2 of the present invention is applied, and FIG. 5 is a diagram showing a configuration example of a control block of the electric hand. In addition, description of the holding claws 23-25 is abbreviate | omitted in FIG.

As shown in FIGS. 4 and 5, the electric hand of the second embodiment is provided with gripping claws 23 to 25 for gripping an object by moving in a predetermined direction. The three gripping claws 23 to 25 are arranged equidistantly at intervals of 120 ° in the radial direction around a predetermined point. The gripping claws 23 to 25 are supported by a linear guide (not shown) and can be moved independently in the axial direction of the linear guide.
In addition, the gripping claws 23 to 25 are provided with pins (not shown) in a direction substantially perpendicular to the respective moving surfaces. As in the first embodiment, the pins are independent of each other by cams 29 to 31 having cam grooves spirally arranged around the rotation shafts of the independent drive motors (drive units) 26 to 28. Will be guided.

  Here, as in the first embodiment, when the gripping claws 23 to 25 are in the most open state, the pins of the gripping claws 23 to 25 are guided near the outer periphery of the cam groove. On the other hand, when the driving motors 26 to 28 start to rotate in a specific direction, the gripping claws 23 to 25 move in the direction of the gripping center along the linear guides by the pins being guided by the cam grooves. And when the pin is guided to the inner periphery vicinity of the cam groove, the grip claws 23 to 25 are closed.

In addition, since the cam groove is formed in a spiral shape, even when the rotational torque of the driving motors 26 to 28 is constant, as the pin moves toward the outer periphery of the cams 29 to 31, that is, as the gripping claws 23 to 25 are opened, The power drops.
The linear guides and cams 29 to 31 constitute a torque conversion mechanism that converts the rotational torque of the drive motors 26 to 28 into the thrust of the gripping claws 23 to 25.

  Further, as shown in FIG. 5, rotational position detectors 32 to 34 such as a rotary encoder capable of detecting rotational positions of the driving motors 26 to 28 are attached to the driving motors 26 to 28, respectively. And the control part 35 controls the drive motors 26-28 by acquiring the rotation position of the drive motors 26-28 by acquiring the pulse number output from the rotational position detectors 32-34. At this time, the control unit 35 controls the gripping force of the gripping claws 23 to 25 so that the added values of the thrusts f1, f2, and f3 generated by the gripping claws 23 to 25 are constant, and The moving direction of the gripping claws 23 to 25 is controlled based on the difference in thrust generated by the gripping claws 23 to 25.

Next, the configuration of the control unit 35 will be described with reference to FIG.
As shown in FIG. 5, the control unit 35 includes up / down counters 351 to 353, gripping claw position conversion units 354 to 356, thrust calculation unit 357, target thrust conversion units 358 to 360, speed detection units 361 to 363, subtraction 364 to 366 and motor drivers 367 to 369.

The up / down counter 351 detects the rotational position of the drive motor 26 by counting the number of pulses output by the rotational position detector 32.
The up / down counter 352 detects the rotational position of the drive motor 27 by counting the number of pulses output by the rotational position detector 33.
The up / down counter 353 detects the rotational position of the drive motor 28 by counting the number of pulses output by the rotational position detector 34.
It is assumed that the output by the up / down counters 351 to 353 increases as the gripping claws 23 to 25 open.

The gripping claw position converting unit 354 detects the drive detected by the up / down counter 351 based on reference data predetermined for the relationship between the rotational position of the driving motor 26 and the position of the gripping claw 23 on the linear guide shaft. The rotational position of the motor 26 is converted into the position of the gripping claw 23 on the linear guide shaft (the gripping claw position P1).
The gripping claw position conversion unit 355 detects the drive detected by the up / down counter 352 based on reference data predetermined for the relationship between the rotational position of the driving motor 27 and the position of the gripping claw 24 on the linear guide shaft. The rotation position of the motor 27 is converted into the position of the gripping claw 24 on the linear guide shaft (the gripping claw position P2).
The gripping claw position conversion unit 356 detects the drive detected by the up / down counter 353 based on reference data predetermined for the relationship between the rotational position of the driving motor 28 and the position of the gripping claw 25 on the linear guide shaft. The rotational position of the motor 28 is converted into the position of the gripping claw 25 on the linear guide shaft (the gripping claw position P3).

  The thrust calculation unit 357 performs gripping based on the gripping claw positions P1 to P3 converted by the gripping claw position conversion units 354 to 356 and the input target gripping force fr / 3, the X direction target position, and the Y direction target position. Thrust command values f1 to f3 for the claws 23 to 25 are calculated. The thrust calculation unit 357 includes a subtractor 370, an amplifier 371, comparators 372 and 373, amplifiers 374 to 376, an adder / subtractor 377, an adder 378 and a subtractor 379.

The subtractor 370 subtracts the gripping claw position P2 converted by the gripping claw position conversion unit 355 from the gripping claw position P1 converted by the gripping claw position conversion unit 354.
The amplifier 371 multiplies the value obtained by the subtractor 370 by a predetermined gain (1 / √3).

The comparator 372 adds the value input from the amplifier 371 from the input inverted value of the X direction target position (the target position takes a positive or negative value with the linear guide center as zero).
The comparator 373 adds the gripping claw position P3 input from the gripping claw position conversion unit 356 from the input reversal value of the Y-direction target position (the target position is a positive or negative value with the linear guide center set to zero. ).
The amplifier 374 amplifies the value obtained by the comparator 372 with a predetermined gain Gx.
The amplifier 375 amplifies the value obtained by the comparator 373 with a predetermined gain Gy.
The amplifier 376 amplifies the value obtained by the amplifier 375 with a predetermined gain (1/2).

The adder / subtractor 377 subtracts the value obtained by the amplifier 374 from the input target gripping force fr / 3, and adds the value obtained by the amplifier 376 to obtain the thrust command value f1 of the gripping claw 23. It is.
The adder 378 adds the input target gripping force fr / 3, the value obtained by the amplifier 374, and the value obtained by the amplifier 376 to obtain the thrust command value f2 of the gripping claw 24. is there.
The subtracter 379 subtracts the value obtained by the amplifier 375 from the input target gripping force fr / 3 to obtain a thrust command value f3 of the gripping claw 25.

The target thrust converting unit 358 is a thrust command calculated by the thrust calculating unit 357 based on reference data determined in advance regarding the relationship between the rotational torque of the driving motor 26 and the generated thrust of the gripping claws 23 on the linear guide shaft. From the value f1 and the gripping claw position P1 converted by the gripping claw position conversion unit 354, the rotational torque necessary for generating the target thrust of the gripping claw 23 is obtained.
The target thrust conversion unit 359 is a thrust command calculated by the thrust calculation unit 357 based on reference data that is predetermined for the relationship between the rotational torque of the drive motor 27 and the generated thrust of the gripping claws 24 on the linear guide shaft. From the value f2 and the gripping claw position P2 converted by the gripping claw position conversion unit 355, the rotational torque necessary for generating the target thrust of the gripping claw 24 is obtained.
The target thrust conversion unit 360 is a thrust command calculated by the thrust calculation unit 357 on the basis of reference data determined in advance regarding the relationship between the rotational torque of the drive motor 28 and the generated thrust of the gripping claws 25 on the linear guide shaft. From the value f3 and the gripping claw position P3 converted by the gripping claw position conversion unit 356, the rotational torque necessary for generating the target thrust of the gripping claw 25 is obtained.

The speed detection unit 361 calculates the moving speed of the gripping claws 23 by differentiating the rotational position of the driving motor 26 detected by the up / down counter 351.
The speed detector 362 calculates the moving speed of the gripping claws 24 by differentiating the rotational position of the driving motor 27 detected by the up / down counter 352.
The speed detector 363 differentiates the rotational position of the driving motor 28 detected by the up / down counter 353 to calculate the moving speed of the gripping claws 25.

  The subtractor 364 subtracts the value obtained by the speed detection unit 361 from the rotational torque obtained by the target thrust conversion unit 358, and the subtractor 365 calculates the speed from the rotational torque obtained by the target thrust conversion unit 359. The value obtained by the detecting unit 362 is subtracted, and the subtractor 366 subtracts the value obtained by the speed detecting unit 363 from the rotational torque obtained by the target thrust converting unit 360, and each motor driving driver. The speed component is fed back to 367 to 369. Thereby, stabilization of the grip claw position control can be performed.

The motor driving driver 367 controls the driving motor 26 so as to generate a rotational torque having the same value based on the rotational torque input from the target thrust converting unit 358 via the subtractor 364.
The motor driving driver 368 controls the driving motor 27 to generate the same value of rotational torque based on the rotational torque input from the target thrust conversion unit 359 via the subtractor 365.
The motor drive driver 369 controls the drive motor 28 to generate the same value of rotational torque based on the rotational torque input from the target thrust converter 360 via the subtractor 366.

  Next, in the electric hand configured as described above, as shown in FIG. 4A, consider a case where a round bar having a radius r is gripped with the individual gripping claw thrusts f1 to f3 being equal. . At this time, the center position of the round bar coincides with the point where the center axes of the individual grip claws intersect.

  Next, a method for independently controlling the compliance in the individual axial directions in the XY plane will be described. Here, the state where the center position of the round bar coincides with the point where the center axes of the individual gripping claws intersect (FIG. 4A) is shifted by ΔX in the horizontal direction and ΔY in the vertical direction (FIG. 4B). ))think of.

At this time, the position of the gripping claw 23 is P1, the position of the gripping claw 24 is P2, the position of the gripping claw 25 is P3, the amount of movement of the gripping claw 23 from the reference position is Δp1, and the amount of movement of the gripping claw 24 from the reference position Is Δp2 and the amount of movement of the gripping claw 25 from the reference position is Δp3, the relationship between the horizontal displacement amount ΔX and the vertical displacement amount ΔY of the round bar is geometrically expressed by the following equation.
ΔX = 1 / √3 (P1−P2) = 1 / √3 (Δp1 + Δp2) (9)
ΔY = P1 + P2 = Δp1−Δp2 = Δp3 (10)

Further, when the thrust generated by the gripping claw 23 is f1, the thrust generated by the gripping claw 24 is f2, and the thrust generated by the gripping claw 25 is f3, the horizontal component fx and the vertical component fy of the force applied to the round bar This relationship can also be expressed geometrically by the following equation.
fx = √3 / 2 (f1-f2) (11)
fy = 1/2 (f1 + f2) −f3 (12)

Next, a specific description will be given of a method for independently controlling the compliance in the individual axial directions in the XY plane with the electric hand having the gripping claws 23 to 25 that can be transferred in the three axial directions based on the above formula.
In FIG. 5, when the gripping claw position P2 is subtracted from the gripping claw position P1 and multiplied by a coefficient 1 / √3, ΔX shown in Expression (9) is obtained.
ΔY is the deviation Δp3 itself from the reference position of the grip claw position P3.

  Next, the obtained ΔX is compared with the target position in the X direction shown in FIG. 4B, but the three gripping claws 23 to 25 are arranged equidistantly at 120 ° intervals in the radial direction around a predetermined point. The target position when gripping in the applied state is set to zero, and after multiplying by a coefficient Gx that determines the strength of compliance in the X-axis direction, the thrust command of the drive motor 27 is increased and simultaneously the thrust of the drive motor 26 Add or subtract to the thrust command to reduce the command.

  With the above configuration, since the value added to the thrust command of the drive motor 26 and the value subtracted from the thrust command of the drive motor 27 are the same value and in the opposite direction, there is a deviation of ΔX in the X-axis direction. When it occurs, a force to return to the original position is generated even if it is proportional to the amount of deviation, so that a compliance operation in the X-axis direction can be realized.

  The compliance operation in the X-axis direction is realized only by the drive motor 26 and the drive motor 27, and the drive motor 28 is not involved.

  Further, the obtained ΔY is compared with the Y-direction target position shown in FIG. 4B, but the three gripping claws 23 to 25 are arranged equidistantly at intervals of 120 ° in the radial direction around a predetermined point. The target position when gripping in the state of gripping is set to zero and multiplied by a coefficient Gy that determines the strength of compliance in the Y-axis direction. After that, the thrust command for the drive motor 26 and the drive motor 27 is increased, and at the same time Addition / subtraction to the thrust command is performed so as to reduce the thrust command of the motor 28.

  At this time, the value added to the thrust command of the drive motor 26 and the drive motor 27 is ½ of the value subtracted from the thrust command of the drive motor 28.

  With the above configuration, the value added to the thrust command of the drive motor 26 and the drive motor 27 and the value to be subtracted from the thrust command of the drive motor 28 are the same value and in the opposite direction. When a deviation of ΔY occurs, a force to return to the original position is generated even in proportion to the deviation amount, and a compliance operation in the Y-axis direction can be realized.

  The compliance operation in the Y-axis direction is realized by the drive motor 26, the drive motor 27, and the drive motor 28.

Here, the thrust command values f1 to f3 of the individual gripping claws in FIG. 5 are expressed by the following equations.
Thrust command value f1 = fr / 3−GxΔX + Gy / 2ΔY (13)
Thrust command value f2 = fr / 3 + GxΔX + Gy / 2ΔY (14)
Thrust command value f3 = fr / 3−GyΔY (15)

The gripping force is expressed by the following equation.
Gripping force f1 + f2 + f3 = (fr / 3 + fr / 3 + fr / 3) + (− GxΔX + Gy / 2ΔY + GxΔX + Gy / 2ΔY) −GyΔY = fr + GyΔY−GyΔY = fr (16)

  From the above formula, the present invention is an electric hand having gripping claws 23 to 25 that can be transferred in three axial directions, and the gripping force is always constant while independently controlling the compliance in the individual axial directions in the XY plane. It can be seen that this is possible with the configuration.

  In the present invention, any constituent element of the embodiment can be modified or any constituent element of the embodiment can be omitted within the scope of the invention.

1, 2, 11, 12, 23 to 25 Holding claws 3, 13 Linear guides 4, 5, 14, 15 Pins 6, 16, 18, 26 to 28 Driving motor (driving unit)
7, 17, 19, 29-31 Cam 20, 21, 32-34 Rotation position detector 22, 35 Control unit 71, 171, 191 Cam grooves 221, 222, 351-353 Up / down counters 223, 224, 354- 356 Grasping claw position conversion unit 225,357 Thrust calculation unit 226,227,358-360 Target thrust conversion unit 228,229,361-363 Speed detection unit 230,231,234,238,364-366,366,370,379 Subtractor 237,378 Adders 232, 233, 367 to 369 Motor drive drivers 236, 371, 374 to 376 Amplifiers 235, 372, 373 Comparator 377 Adder / Subtractor

Claims (6)

A plurality of gripping claws for gripping an object by moving in a predetermined direction;
A drive unit that is provided in pairs with each gripping claw and moves the corresponding gripping claw independently;
A control unit for controlling the drive unit,
The controller is
The gripping force of each gripping claw is controlled so that the added value of the thrust generated by each gripping claw is constant, and the moving direction of the gripping claw is controlled based on the difference of the thrust generated by each gripping claw A component assembly apparatus characterized by: The component assembling apparatus according to claim 1, wherein a difference in thrust generated by the gripping claws is proportional to a deviation amount from a predetermined reference position between the gripping claws. The number of the said gripping claws and the said drive part is two, and the moving direction of the said gripping claws is 1 axis | shaft. The component assembly apparatus of Claim 1 or Claim 2 characterized by the above-mentioned. The number of the said gripping claws and the said drive part is three, The moving direction of the said gripping claws is biaxial. The component assembly apparatus of Claim 1 or Claim 2 characterized by the above-mentioned. The number of the said gripping claws and the said drive part is three, and the moving direction of the said gripping claws is a 3 axis | shaft. The component assembly apparatus of Claim 1 or Claim 2 characterized by the above-mentioned. The drive unit generates a rotational torque,
The component assembly apparatus according to claim 1, further comprising: a torque conversion mechanism that converts a rotational torque generated by the drive unit into a thrust generated by the gripping claws.

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