JP3491018B2 - Flexible jig - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to holding and fixing a part (hereinafter referred to as a work) to be assembled, such as a relatively small part, at a predetermined position and posture. It relates to a flexible jig that can be made. 2. Description of the Related Art A jig holds and fixes the position and orientation of a work in operations such as machining and assembly. Even when an external force is applied to the work, the position and orientation of the jig are maintained. The function to fix is required. As a jig,
A simple one is a vise, and a general one is a chuck mechanism of a processing machine such as a lathe. Many of the conventional jigs have a frame structure according to the shape of the outer periphery of the work, and maintain the position and posture by fitting or sandwiching the work. However, in this case, it is necessary to manufacture a jig corresponding to the shape of each work, and in a recent multi-product small-lot production mode, there are many problems in terms of cost and production efficiency particularly in an assembling process. In order to solve this problem, a jig capable of holding a work of an arbitrary shape by one unit is desired. [0003] In an assembling operation, a robot hand is one of devices having a function of holding a work of an arbitrary shape, and many hand mechanisms having various shapes have been devised. However, in the conventional hand, (1) In many cases, the hand is lowered from the upper surface of the work and the side is grasped by a finger, and the assembling surface is closed with the hand. (2) Corresponding to a variety of work shapes. The hand has a mechanism with a high degree of freedom like a multi-fingered hand, so the number of actuators increases and control tends to be complicated. (3) In many hands, gripping flexibility and work damage prevention are required. There is a problem that the function of fixing against external force cannot be expected due to the mechanism having elasticity. In other words, it can be said that even if it has a holding function for a work of an arbitrary shape, it lacks a function of fixing external force. On the other hand, as a device having a jig function separately from the hand, a plurality of pedestals are equipped with a rotating pedestal and thin rod-shaped fingers capable of translating vertically to the pedestal, and a plurality of fingers are fitted according to the shape of the lower surface of the work. A jig device that raises and lowers a workpiece to support it from below has been considered. However, in this jig device, (1) the control is complicated due to the large number of actuators, and (2) the work is supported from below, so there is concern about the ability to fix external lateral forces. There is a problem. For holding a work of an arbitrary shape, a mechanism for holding the work with a plurality of fingers, such as a multi-fingered hand, particularly a mechanism for reducing the degree of freedom of the hand and holding the side surface of the work on a flat surface, is operated. It is considered to be suitable for ease of control without impairing the function. In this case, in order to have a function of fixing an external force, it is desired that the finger is a driving mechanism without back drivability. However, a drive mechanism without back drivability has a drawback that the operating speed is slow and the working efficiency is poor. Therefore, in order to increase work efficiency, it is necessary to use a drive unit that can operate at high speed. The present invention has been made in consideration of the above-mentioned matters, and has as its object to provide a flexible jig which can reliably hold and fix the positions and postures of variously shaped workpieces during an assembling operation or the like. To provide tools. [0007] In order to achieve the above object, a flexible jig of the present invention comprises: a rotary driving section around a horizontal base on which a work is placed ;
Provided above, and a base for rotation along a foundation in above said base, a translation drive unit, a probe for translation along the base through rotation vital translation drive unit together with the base, the translation direction of the probe Check the holding power of
A force detection sensor that outputs a force and a sensor that detects a rotational force acting on the probe are provided with three or more unspecified tentacles, and a detection value of a holding force output from the force detection sensor
And the sensor that detects the rotational force acting on the probe
The retention force detection value output from the
When the specified holding force is obtained by comparing with the
A value is output to secure the holding position of the probe, and the work is held and fixed at the tip of each probe. The flexible jig having the above-described structure is composed of a plurality of touch fingers having both high-speed translational driving and high-rigidity (without back drivability) rotational driving. In addition to having the function of positioning the work to be held in an arbitrary direction, it is possible to hold and fix a variety of versatile works in a predetermined position and posture, as well as a quick operation. It can be carried out. Therefore, the work efficiency at the time of assembly can be improved. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 to FIG. 5 show an embodiment of the present invention. First, FIG. 1 shows an example of the flexible jig of the present invention. In this figure, reference numeral 1 denotes a horizontal base on which a work W is placed, which is, for example, square in plan view. Reference numeral 2 denotes a touch finger provided at an appropriate position on each side of the base 1. That is, the flexible jig of the present invention includes three or more (four in the illustrated example) touch fingers 2. The contact finger 2 includes one translation drive unit 3, one probe 4, and one rotation drive unit 5. The translation drive unit 3 is located above the xy plane of the base 1 and is mounted on the base 1. Holding of placed work W
Perform fixing. Note that the work W may have any shape as long as it can be stably mounted on the base 1, and therefore, needless to say, the shape in plan view is not limited to a square. The translation drive unit 3 is an element that moves the probe 4 linearly on the xy plane, and the rotation drive unit 5 is an element that rotates the probe 4 on the xy plane. The probe 4 is an element that comes into contact with the workpiece W. Translation drive 3
And the force generated by the rotation drive unit 5 is moved to a position where it comes into contact with the work W, and the probes 4 provided on the respective touch fingers 2 come into contact with the work W, and the translation drive unit 3 and the rotation drive unit 5 The workpiece W is held and fixed on the xy plane by the generated force. The interval between the touch fingers 2 provided along the side of the base 1 may be unspecified. Next, details of the configuration of each part will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 2 is a view showing an example of the touch finger 2, and the translation drive unit 3 is configured as follows. That is, in this figure, reference numeral 6 denotes a base provided above the rotation drive unit 5 (described later).
As shown in FIG. 2, the base 1 is located slightly above the xy plane, and is horizontally arranged so as to slightly overlap with the xy plane. Reference numeral 7 denotes a voice coil motor (hereinafter, referred to as VCM) as a drive source of the translation drive unit 3, which comprises a stator 8, a coil 9, and a bobbin 10 for fixing the coil 9 together. The VCM 7 constitutes a force detection sensor. A linear guide 11 is provided on the base 6 in the y direction, and a slider 12 is slidably provided on the upper surface in the y direction. The bobbin 10 is attached to the slider 12. Further, a shaft 13 of the probe 4 (the configuration thereof will be described later) and a sensor shaft 14 are attached to the slider 12. Reference numeral 15 denotes a sensor stand erected on the base 6. The sensor stand 15 holds a translation position detecting sensor 16 so as to cover the sensor shaft 14. Therefore, when a current (direct current) is applied to the coil 9, a force is generated in the positive and negative directions in the y direction in accordance with the direction of the current, and the coil 9 and the bobbin 10 move in the direction of the force. The slider 12 moves in the same direction along with the linear movement, whereby the probe shaft 13 and the sensor shaft 14 move in the same direction. The movement amount at this time is detected by the translation position detection sensor 16. Next, the details of the probe 4, described with reference to FIGS. The slider 12 has, for example, a square probe shaft 13 attached in the y direction, and a base plate 18 for attaching a strain gauge 17 to the tip thereof.
Are provided on a surface of the probe shaft 13 parallel to the yz plane. A probe tip shaft 19 is attached to the other end of the strain gauge base plate 18, and the other end of the probe tip shaft 19 is fixed to a rotation shaft 21 of a contact angle detection sensor 20. The rotating shaft 21 is rotatable around the z-axis by bearings 23 incorporated above and below a contact plate bearing 22, and the contact plate bearing 22 is attached to a contact plate 24 that contacts the work W. Accordingly, the contact plate 24 is rotatable around the rotation axis 21 of the contact angle detecting sensor 20, and the rotation angle is detected by the contact angle detecting sensor 20. The force generated in the contact plate 24 in the rotational tangential direction of the probe 4 is detected by the strain gauge 17 as a sensor for detecting the force acting on the probe 4. Next, the details of the rotary drive unit 5 will be described with reference to FIG. 4. In FIG. 4, reference numeral 25 denotes a servomotor with an encoder, which is mounted via a mounting plate 27 so that its output shaft 26 is horizontal. It is attached to the outside of the side plate 29 of the case 28. A gear box 30 is provided inside the case 28. The output shaft 26 of the servo motor 25 and the coupling 3
A worm gear 36 composed of a worm 33 provided at the tip of an input shaft 32 and a worm wheel 35 provided at a tip of a vertical output shaft 34 connected via the first shaft 1 is disposed. The other end of the output shaft 36 is attached to the bottom of the base 6 via an appropriate bracket (not shown) via a coupling 37 and a bearing 39 incorporated in a top plate 38 of the case 28. It is connected to the rotating shaft 40. Accordingly, when the servo motor 25 rotates forward or backward, the entire translation drive unit 3 provided above the rotation drive unit 5 rotates on the base 1. In the gear box 30, the worm gear 36 is used as a power transmission mechanism. Instead, for example, a bevel gear can be used. And, by selecting the gears inside the gearbox 30,
The characteristics of the rotation drive unit 5 differ. That is, in order to realize the function of holding and fixing the external force on the work W by a simple control system, it is necessary to reduce the speed by the worm gear. Since the worm gear has no back drivability, the rigidity of the drive system can be regarded as infinite. On the other hand, in the case of deceleration by, for example, a bevel gear other than the worm gear, the drive system has a large output and high rigidity, and a holding / fixing function can be realized depending on control. By the way, when the gear ratio is 1: 1, direct drive is performed by the servomotor 25, and large output and high rigidity cannot be expected, but a drive system excellent in controllability is obtained. Next, the configuration of the control system of the flexible jig of the present invention and the control method for holding the workpiece W will be described.
This will be described with reference to FIG. This figure shows one touch finger 2
41 is a block diagram showing an input / output relationship between the controller and a computer as a control device, where 41 is a computer, 42 is a driver of the VCM 7, 43 is its control circuit, 44 is a driver of the servo motor 25, and 45 is an encoder of the servo motor 25. It is. [0020] Now, when the workpiece W is held (grasped) by the m Sawayubi 2, translation drive force of the i-th Sawayubi 2, the rotational driving force respectively f _i, When n _i, the workpiece W Can be expressed as T = JF. Here, F is the driving force f _i , n _i of the individual touch finger 2
Is a 2m × 1 dimensional vector consisting of
A 3 × 1 dimensional vector composed of three elements of the y direction and the rotational force (θ), and J indicates a 3 × 2 m dimensional matrix determined by the position of the contact point between each touch finger 2 and the work W. When the workpiece W is placed and held at a predetermined position, T = 0 is substituted in the above equation, and the probe 4 of each touch finger 2 is determined based on 0 = JF from the previously determined contact position. The values of the amount of movement and the grasping force (holding force) are determined, and the values are given from the computer 41 to the translation drive unit 3 and the rotation drive unit 5. At this time, the movement amount by the translation drive from the translation position detection sensor 16 and the movement amount by the rotation drive from the encoder 45 attached to the servo motor 25 are fed back to the computer 41. The holding force applied to the workpiece W by the translation drive is determined by detecting the amount of current output by the driver 42 of the VCM 7 by utilizing the fact that the translation drive is a direct drive by the VCM 7, and holding the output in proportion to the current. Detect force. Then, the holding force due to the rotation drive is detected from the amount of strain of the strain gauge base plate 18 obtained from the strain gauge 17 and is taken into the computer 41. The detected value of the holding force is compared with a command value of the holding force obtained in advance, and when a predetermined holding force is obtained, the computer 41 instructs each of the driving units 3 and 5 at the time. Is output, and the probe 4 of the touch finger 2 is fixed at the holding position. Note that an error in the holding posture generated when the workpiece W is grasped is clarified by a detection value from the contact angle detection sensor 20. The resultant force received by the work W and the touch finger 2 already shown
As is apparent from the relational expression T = JF with respect to the driving force, the driving force of the touch finger 2 can be three elements in order to hold the workpiece W in a plane. Is redundant. Since the flexible jig of the present invention includes three or more touch fingers 2, it has three translational driving force elements and three rotational driving force elements. That is, the flexible jig is redundant with respect to holding in a plane, and the translational driving force and the rotational driving force of each of the touch fingers 2 can be considered separately.
This can be said to be the most characteristic feature of the flexible jig of the present invention. That is, the relational expression T = JF becomes T = J _A
Can be rewritten as F _A + J _L F _L. Here, F _A is the finger touch 2
Of represents m × 1-dimensional vector of the rotational driving force n _i, F _L represents a m × 1 dimensional vector of translation drive force f _i for each finger touch 2. Since at least three driving force elements are present, if the touch finger 2 is arranged at an appropriate position, the work W can be grasped only by the translational driving force, and the work W can be grasped only by the rotational driving force. It is clear from the above equation that it is also possible to grasp. As described above, in the conventional jig, to hold and fix the work W, the work W
Although a jig corresponding to the above shape is required, the flexible jig having the above configuration can grip (hold) a work W having various planar shapes with one apparatus. In the above embodiment, since the worm gear 36 is used as the transmission mechanism for applying the rotational force of the servo motor 25 to the touch finger 2 in the rotary drive unit 5, only the rotational drive force of the rotary drive unit 5 is used. Therefore, when the work W is held, the worm gear 36 can hold the work W with infinite rigidity. That is, even when some external force is applied to the work W, the work W is held and fixed without changing its position and posture. However, this holds under the condition that the contact point between the workpiece W and the probe 4 does not slip. However, by taking the force in the rotational tangent direction detected by the strain gauge 17 into the computer 41 and controlling the translation driving force by the translation drive unit 3, the contact point can be prevented from slipping. At this time,
There is no need to control the rotational drive. That is, by controlling only the translation driving force, the work W can be fixed even when an external force is generated. Further, while holding the work W,
If the desired position / posture of the work W is obtained, the trajectory of the tip (contact portion) of the probe 4 can be obtained correspondingly. From the target trajectory, target inputs of the translation drive unit 3 and the rotation drive unit 5 of each touch finger 2 are obtained in the computer 41 and output. At the same time, the translation and rotation forces are detected from the sensors and taken into the computer 41 so that the internal force for holding the workpiece W continues to be generated, and are taken into the computer 41 so that the internal force does not become zero or less during the movement. , 5. Thereby, the workpiece W is arbitrarily positioned in the xy plane. [0028] The present invention is not limited to the above embodiments, Ru out be implemented with various modifications. For example , the drive source of the translation drive unit 3 may be a servomotor or an air cylinder instead of the VCM 7. That is, FIG.
An example in which a servo motor is used as a drive source is shown. In this figure, reference numeral 46 denotes a gear box mounted on the base 6, a servo motor 47 with an encoder is provided on the input shaft side, and y is provided on the output shaft side. Ball screw 48 is base 6 in the direction
It is provided so as to be held by a support table 49 placed on the base. Reference numeral 50 denotes a table in which a force detection sensor is incorporated at an upper portion. The table 50 engages with a ball screw 48, and moves forward or backward along a guide member 51 extending in the y direction by forward or reverse rotation of the ball screw 48. A probe shaft 13 is attached to the force detection sensor portion of the table 50 so as to extend in the y direction. Although not shown, the tip of the probe shaft 13 has a strain gauge 17 and its mounting plate 1 as shown in FIG.
8, furthermore, probe tip shaft 19, contact angle detecting sensor 2
Needless to say, there are provided a rotary shaft 21 and its rotating shaft 21, a contact plate bearing 22, bearings 23 installed above and below the contact plate bearing 22, and a contact plate 24 for mounting the contact plate bearing 22. Therefore, when the servo motor 47 rotates,
The ball screw 48 rotates around the y-axis via the gear box 46, and the table 50 moves in the y-direction with this rotation, whereby the probe shaft 13 moves in the y-direction. The force received by the probe 4 in the translation direction is equal to
Is detected by a force detection sensor incorporated in the
The detection of the position of the probe 4 is performed by an encoder attached to the servomotor 47. FIG. 7 shows an example in which air pressure is used as a driving source.
In this figure, reference numeral 52 denotes an air cylinder, which is held by a holding member 54 erected on the base 6 so that the cylinder shaft 53 is parallel to the y-axis. A translation position detection sensor 16 is provided on one end of the cylinder shaft 53, and a coupling 55 incorporating a force detection sensor is provided on the other end of the cylinder shaft 53. The probe shaft 13 is attached so as to extend in the y direction. In this case as well, similarly to the embodiment shown in FIG.
7, its mounting plate 18, and further the probe tip shaft 19,
Needless to say, a contact angle detecting sensor 20 and its rotary shaft 21, a contact plate bearing 22, bearings 23 installed above and below the contact plate bearing 22, and a contact plate 24 for mounting the contact plate bearing 22 are provided. Therefore, by sending air into the air cylinder 52, the cylinder shaft 53 moves in the y direction along the guide 56, and the probe shaft 13 moves in the y direction with this movement. The force received by the probe 4 in the translation direction is detected by a force detection sensor incorporated in the coupling 55, and the position of the probe 4 is detected by a translation position detection sensor 16. In the rotary drive unit 5, a bevel gear may be provided in the gear box 30. In this case, the gear ratio can be 1: N or 1: 1. The VCM 7 (illustrated in FIG. 2), the servomotor 47 (illustrated in FIG. 6), and the air cylinder 52 (illustrated in FIG. 7) are used. And worm gear 3
6 and the servomotor 25 and the bevel gear. In the case of the servomotor 25 and the bevel gear, there are a case of 1: N and a case of 1: 1. In the translation drive mechanism, the VCM
7 and the air cylinder 52, the force is small but the operation is quick, and with the servo motor 47, the force is large but the operation is slow. In the case of the rotary drive mechanism, when the servo motor 25 and the worm gear 36 and the servo motor 25 and the 1: N bevel gear are used, the force is large but the operation is slow.
In the case of using one bevel gear, the operation is quick although the force is small. Accordingly, flexible jigs having various characteristics can be obtained by appropriately combining the various translation driving mechanisms and the rotation driving mechanisms.
In the case of the configuration shown in the embodiment shown in FIG. 5, the work W can be quickly and reliably held and fixed at a predetermined position and posture, and an optimum jig used for assembling or the like can be obtained. As described above, according to the present invention,
As well as the conventional multi-fingered hand, it can not only have a function of positioning the holding component in any direction, but also can reliably hold and fix a versatile work having various planar shapes at a predetermined position and posture. . Therefore, the working efficiency at the time of assembly can be improved. Further, the configuration of the entire apparatus is simple, and the control is also simple.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an overall configuration of a flexible jig according to one embodiment of the present invention. FIG. 2 is a perspective view showing a touch finger of the flexible jig and a translation drive unit thereof. FIG. 3 is a partially enlarged view of a part of a configuration of a tip portion of the touch finger, showing a part thereof. FIG. 4 is a partial cross-sectional perspective view showing a rotation drive unit of the touch finger. FIG. 5 is a block diagram showing a control relationship of the touch finger. FIG. 6 is a perspective view showing a translation driving unit according to another embodiment of the present invention. FIG. 7 is a perspective view showing a translation driving unit according to still another embodiment of the present invention. [Description of Signs] 1 ... base, 4 ... probe, 6 ... base, 20 ... contact angle detection sensor, W ... workpiece.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B23Q 3/06 303 B23Q 3/06 304 B23Q 3/18 B23P 19/00 304

Claims (1)

(57) [Claim 1] A rotary drive unit is provided around a horizontal base on which a work is placed , and provided above the rotary drive unit,
And a base for rotation along a foundation in above said base, a translation drive unit, a probe for translation along the base through rotation vital translation drive unit together with the base,
A force detection sensor for detecting a holding force of the probe in the translation direction;
And a sensor to detect the rotational force acting on the probe.
The force detecting device is provided with three or more tentacles,
Acts on the holding force detection value output from the sensor and the probe
Holding output from the sensor that detects the rotating force
The detected force value is compared with a previously determined holding force command value.
When a constant holding force is obtained, the position command value is output and the
A flexible jig configured to secure a lobe holding position and hold and fix the work at the tip of each probe.