JP2012143842A - Locating device, automatic assembling device, locating method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a locating device capable of accurately finding a position for assembling a component to a workpiece.SOLUTION: The workpiece has a loose hole and a threaded hole formed at a bottom face of the loose hole. The locating device moves a screw bolt in positive and negative directions on a u-axis and in positive and negative directions on a v-axis while contacting the screw bolt with the bottom face. The locating device determines positions Pα, Pβ, Pγ, Pδ where a reaction force is not smaller than a threshold value Th1 when the screw bolt is moved in the positive and negative directions on the u-axis and in the positive and the negative directions on the v-axis. When a distance between the position Pα and the position Pβ is smaller than a threshold value Th2, the locating device performs movement in a v-axis direction starting from a middle position between the position Pα and the position Pβ and the determination of the position Pγ and the position Pδ. When a distance between the position Pγ and the position Pδ is smaller than the threshold value Th2, the locating device determines a middle position between the position Pγ and the position Pδ as an assembling position for the screw bolt.

Description

  The present invention relates to a search device that searches for an assembly position of a part such as a screw or a resin pin to a workpiece, an automatic assembly device that includes the search device, a search method, and a program.

  Conventionally, in screw tightening, which is a typical process of assembly, an automatic screw tightening machine that combines an automatic screw tightening driver and a direct-acting robot has been commercialized and used. However, in these automatic screw tightening machines, when the position of the screw hole is deviated from the design position due to workpiece variation or the like, the screw position cannot be properly corrected to tighten the screw. Specifically, the conventional automatic screw tightening machine cannot be tightened correctly if there is a displacement that exceeds approximately 1/10 of the screw diameter, and may cause incomplete screw tightening such as oblique biting, or an error. Stop. For this reason, manual correction is required.

  In order to solve such problems, Patent Document 1 uses a force control type robot and corrects the position of the driver based on the reaction force received through the screw, thereby eliminating the deviation between the screw and the hole. It has been corrected. Accordingly, in Patent Document 1, highly reliable automatic screw tightening is realized by the correction. In the correction method of Patent Document 1, when the screw tip is about to enter the hole, the screw can be correctly tightened by detecting the direction of deviation and correcting the position of the screw.

  Patent Document 2 discloses a method for positioning an ideal screwing position of a large-sized bolt, particularly a method for tightening a lid of a container having a screw hole.

  Patent Document 3 discloses a position control device for a locate pin. When the locating pin cannot be detected when the locating pin is positioned at a predetermined position, the position control device reads information on the shape of the locating hole from the machining data storage unit, and causes the locating pin to scroll. If the position control device can find the locate hole during the operation, the position control device performs the operation of inserting the locate pin.

  Patent Document 4 discloses an assembling apparatus for small parts. In the assembling apparatus, an end effector whose position can be adjusted in the XY directions and a force sensor for detecting a load in the Z direction are interposed between the robot arm and the robot hand of the assembling robot. The assembly apparatus controls the end effector based on the rate of change in weight in the Z direction detected by the force sensor, and adjusts the position of the robot hand in the XY direction. Thereby, the said assembly apparatus enables the insertion to the assembly hole of a fastener.

  Patent Document 5 discloses an assembling method for searching for an insertion position where a workpiece is inserted while pressing the workpiece against an object with a robot, and inserting and assembling the workpiece. In the assembling method, a search range of the reciprocating operation is set for each of a plurality of search directions, and a difference is provided in the magnitude of the reciprocating operation cycle. In the assembling method, the reciprocating motion in a certain search direction moves the search range in that direction once, and the reciprocating motion in the search direction having the next short cycle allows the workpiece to be inserted into the object in that direction. The workpiece is moved relative to the object by the robot so as to move by the amount or less. In the assembling method, the insertion position is searched by the relative movement.

JP 2002-331428 A Japanese Patent Laid-Open No. 62-102928 JP-A-7-160336 Japanese Patent Laid-Open No. 5-200638 JP 2004-167651 A

  However, even if it is patent documents 1-5, with respect to the workpiece | work which has the 1st recessed part for inserting components, and the 2nd recessed part for assembling the components formed in the bottom face of the 1st recessed part When assembling the parts, the parts may come into contact with the side surfaces of the first recess when searching for the second recess, and it is difficult to search for the assembly position of the parts with high accuracy.

  The present invention has been made in view of the above-described problems, and its object is to assemble a part even when the work has variations in position and / or dimensions in the process of assembling the part into the work. Is to provide a search device, an automatic assembly device, a search method, and a program.

  According to an aspect of the present invention, the search device is a search device that searches for an assembly position of a part with respect to a workpiece. The workpiece has a first recess for inserting a component and a second recess for assembling the component formed on the bottom surface of the first recess. The searching device has one direction and the other direction in the predetermined first movement direction in a state where the component and the bottom surface are brought into contact with each other by a pressing force in the insertion direction with respect to the component, and a predetermined second direction. Detects reaction force applied to parts caused by movement means for moving a part or workpiece in one direction and the other direction in the movement direction, and movement in the first movement direction and movement in the second movement direction A reaction force detecting means, a first position at which the reaction force is equal to or greater than a first threshold when the component or workpiece is moved in one direction in the first movement direction, and a first position from the first position. A first specifying means for specifying a second position at which the reaction force is equal to or greater than the first threshold when the component or workpiece is moved in the other direction in the moving direction; and one direction in the second moving direction To parts or workpiece When the component or workpiece is moved from the third position to the other direction in the second movement direction from the third position, the reaction force is first when the reaction force is greater than or equal to the first threshold when moved. And a second specifying means for specifying a fourth position that is equal to or greater than the threshold value. When the first distance between the first position and the second position is less than the second threshold, the search device performs the first series of processes as the first position and the second position. The movement in the second movement direction starting from the intermediate position of the first position and the identification of the third position and the fourth position by the second identification means are performed, and the third position and the fourth position are determined. When the second distance between them is less than the second threshold value, an intermediate position between the third position and the fourth position is determined as the assembly position.

  Preferably, the search device further includes changing means for changing the first movement direction and the second movement direction by a certain amount in a certain direction. When the first distance is greater than or equal to the second threshold, the search device changes the first movement direction and the second movement direction by the changing means until the first distance becomes less than the second threshold. , Movement by the moving means in the first moving direction after the change starting from an intermediate position between the first position and the second position, detection of reaction force by the reaction force detecting means, and first specifying means The second series of processing including the identification of the first position and the second position is repeated. When the first distance is less than the second threshold value by the second series of processes, the search device executes the first series of processes. When the second distance between the third position and the fourth position specified by the first series of processing is less than the second threshold, the search device determines whether the third position and the fourth position The intermediate position is determined as the assembly position.

  Preferably, when the second distance is equal to or larger than the second threshold, the search device repeats the second series of processes until the first distance becomes less than the second threshold again. When the first distance becomes less than the second threshold again, the search device executes the first series of processes again. When the second distance between the third position and the fourth position specified by the first series of processing is less than the second threshold, the search device 4 is determined as an assembly position.

  Preferably, when the movement distance in one direction in the first movement direction is equal to or greater than a predetermined distance, the search device stops the movement and changes the first movement direction and the second movement direction by the changing unit. The change, the movement by the moving means in the first moving direction after the change starting from the start position of the movement, the detection of the reaction force by the reaction force detection means, the first position by the first specifying means, The second position is identified.

  Preferably, the searching device includes an adsorbing unit that adsorbs the component by negative pressure, a detecting unit that detects air inflow into the sealed space formed by the adsorbing, a counting unit that counts the number of air inflows, Pressure control means for increasing the pressing force when the number of times reaches a predetermined number.

  When the other situation of this invention is followed, a search device is a search device which searches the assembly | attachment position of the components with respect to a workpiece | work. The workpiece has a first recess for inserting a component and a second recess for assembling the component formed on the bottom surface of the first recess. In the state where the component and the bottom surface are brought into contact with each other by the pressing force in the insertion direction with respect to the component, the search device is configured to move the component or the component in one direction in the predetermined moving direction and the other direction opposite to the one direction. A moving means for moving the workpiece, a reaction force detecting means for detecting a reaction force applied to the component caused by the movement, and a first that the reaction force is equal to or greater than a first threshold when the component or the workpiece is moved in one direction. And means for specifying the second position where the reaction force is equal to or greater than the first threshold when the part or workpiece is moved in the other direction from the first position, and the moving direction is constant. And changing means for changing the direction by a certain amount. When the distance between the first position and the second position is less than the second threshold, the search device determines an intermediate position between the first position and the second position as the assembly position. When the distance is equal to or greater than the second threshold, the search device changes the movement direction by the changing means and the moving means starting from the intermediate position in the changed movement direction until the distance becomes less than the second threshold. A series of processes including the movement by the above, detection of the reaction force by the reaction force detection means, and identification of the first position and the second position by the identification means are repeated. The search device determines an intermediate position between the first position and the second position when the distance is less than the second threshold as an assembly position.

  Preferably, the part is a screw. The workpiece has a first workpiece and a second workpiece. The first work is arranged so as to overlap the second work. The first workpiece has a hole as a first recess. The second workpiece has a screw hole as the second recess. The bottom surface is the surface of the second workpiece.

  According to still another aspect of the present invention, an automatic assembling apparatus includes the above-described searching device and an assembling unit that assembles a component into the second recess at the assembling position.

  If the further another situation of this invention is followed, a search method is a search method in the search device which searches the assembly | attachment position of the components with respect to a workpiece | work. The workpiece has a first recess for inserting a component and a second recess for assembling the component formed on the bottom surface of the first recess. In the search method, the processor of the search device is in a state in which the component and the bottom surface are brought into contact with each other by the pressing force in the insertion direction with respect to the component, A step of moving the part or the workpiece in one direction and the other direction in the determined second movement direction, and a sensor of the search device moves in the first movement direction and in the second movement direction. A step of detecting a reaction force applied to the component caused by the movement, and a first when the processor moves the component or the workpiece in one direction in the first movement direction, the reaction force is equal to or greater than a first threshold value. Identifying a position and a second position at which a reaction force is greater than or equal to a first threshold when the part or workpiece is moved from the first position to the other direction in the first movement direction; A third position where the reaction force is equal to or greater than the first threshold when the processor moves the part or the workpiece in one direction in the second movement direction, and the third position in the second movement direction from the third position; A step of identifying a fourth position at which the reaction force is equal to or greater than a first threshold when the part or workpiece is moved in the other direction; and a first position between the first position and the second position If the distance is less than the second threshold, the processor moves in the second movement direction starting from an intermediate position between the first position and the second position, and the third position and the fourth position If the second distance between the third position and the fourth position is less than the second threshold, the processor is configured to execute the position identification and the third position and the fourth position. And determining an intermediate position as an assembly position.

  If the further another situation of this invention is followed, a search method is a search method in the search device which searches the assembly | attachment position of the components with respect to a workpiece | work. The workpiece has a first recess for inserting a component and a second recess for assembling the component formed on the bottom surface of the first recess. In the search method, the processor of the search device makes one direction in a predetermined moving direction and the other opposite to the one direction in a state where the component and the bottom surface are brought into contact with each other by a pressing force in the insertion direction with respect to the component. Moving the part or workpiece in the direction of the movement, detecting the reaction force applied to the part caused by the movement of the sensor of the searching device, and counteracting when the processor moves the part or the work in one direction. A first position where the force is greater than or equal to the first threshold, and a second position where the reaction force is greater than or equal to the first threshold when the part or workpiece is moved from the first position to the other direction. The step of identifying, the step of changing the direction of movement by a fixed amount in a fixed direction, and the distance between the first position and the second position is less than a second threshold, the process. Determining that the intermediate position between the first position and the second position is the assembly position; and if the distance is greater than or equal to the second threshold, the processor until the distance is less than the second threshold A step of repeating a series of processes including a change in the movement direction, a movement starting from the intermediate position in the movement direction after the change, a reaction force detection, and the identification of the first position and the second position; Determining an intermediate position between the first position and the second position when the distance is less than the second threshold as an assembly position.

  If the further another situation of this invention is followed, a program is a program for controlling the search device which searches the assembly | attachment position of the components with respect to a workpiece | work. The search device includes a processor and a force sensor. The workpiece has a first recess for inserting a component and a second recess for assembling the component formed on the bottom surface of the first recess. The program has one direction and the other direction in a predetermined first movement direction and a predetermined second movement in a state where the part and the bottom surface are brought into contact with each other by a pressing force in the insertion direction with respect to the part. The force sensor detects a reaction force applied to the part caused by the step of moving the part or the workpiece in one direction and the other direction in the direction, the movement in the first movement direction, and the movement in the second movement direction. A first position at which the reaction force is equal to or greater than a first threshold when the part or workpiece is moved in one direction in the first movement direction, and the first movement from the first position. Identifying a second position where the reaction force is greater than or equal to the first threshold when the part or workpiece is moved in the other direction in the direction, and the part in one direction in the second movement direction. Is the third position where the reaction force is greater than or equal to the first threshold when the workpiece is moved, and the reaction when the component or workpiece is moved from the third position to the other direction in the second movement direction. The step of identifying the fourth position where the force is equal to or greater than the first threshold, and the first distance between the first position and the second position is less than the second threshold, the first Performing a movement in the second movement direction starting from an intermediate position between the first position and the second position, and the identification of the third position and the fourth position, and the third position and the fourth position. If the second distance between the first position and the second position is less than the second threshold value, the processor is caused to execute a step of determining an intermediate position between the third position and the fourth position as the assembly position.

  According to still another aspect of the present invention, the program is a program for controlling a search device that searches for an assembly position of a part with respect to a workpiece. The search device includes a processor and a force sensor. The workpiece has a first recess for inserting a component and a second recess for assembling the component formed on the bottom surface of the first recess. In the state where the part and the bottom surface are brought into contact with each other by the pressing force in the insertion direction with respect to the part, the program moves the part or workpiece in one direction in the predetermined moving direction and the other direction opposite to the one direction. A step of receiving the reaction force applied to the component caused by the movement from the force sensor, and a first position where the reaction force is equal to or greater than a first threshold when the component or workpiece is moved in one direction. And a step of identifying a second position where the reaction force is equal to or greater than the first threshold when the part or workpiece is moved from the first position to the other direction, and the moving direction is constant in a certain direction When the step of changing by the amount and the distance between the first position and the second position is less than the second threshold value, the intermediate position between the first position and the second position is determined as the assembly position. Step to do When the distance is greater than or equal to the second threshold, the movement direction is changed until the distance becomes less than the second threshold, the movement starting from the intermediate position in the changed movement direction, and the reaction force detection A step of repeating a series of processes including identification of the first position and the second position, and an intermediate position between the first position and the second position when the distance is less than the second threshold. The step of determining the attachment position is executed by the processor.

  According to the above invention, in the process of assembling a part to a workpiece, the assembly position of the component can be accurately searched even when the workpiece has variations in position and / or dimensions.

It is the figure which showed schematic structure of the automatic assembly apparatus. It is sectional drawing which showed the cross section of the front-end | tip part of a screw fastening driver, a screw adsorption | suction mechanism, and a workpiece | work. It is a top view of a workpiece. It is the figure which showed the structure of the control system of an automatic assembly | attachment apparatus. It is the functional block diagram which showed the functional structure of the automatic assembly | attachment apparatus. It is a transition diagram for demonstrating search of a screw hole. It is a transition diagram for demonstrating the search performed following FIG.6 (d). It is a transition diagram for demonstrating the search performed following FIG.7 (d). It is the flowchart which showed the flow of the process in an automatic assembly apparatus. 10 is a flowchart for explaining details of a process in step S4 in FIG. 9. It is a block diagram showing the hardware constitutions of the computer system which functions as a control part. It is the flowchart which showed the flow of the process in the case of performing the search method which considered only u-axis. It is a figure for demonstrating the process which inserts a resin pin in a workpiece | work.

  Hereinafter, an automatic assembly apparatus according to an embodiment of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

<Outline configuration>
FIG. 1 is a diagram showing a schematic configuration of an automatic assembly apparatus 1 according to the present embodiment. Referring to FIG. 1, an automatic assembly apparatus 1 is an apparatus for assembling a part to a workpiece. The automatic assembling apparatus 1 includes a searching device that searches for an assembling position of a component and an assembling device that assembles the component to a workpiece at the searched assembling position. In the automatic assembly apparatus 1, the search apparatus and the assembly apparatus are integrally configured. Specifically, the automatic assembly device 1 is an automatic screw fastening device for fastening a screw 800 to a screw hole of a workpiece 900.

  The automatic assembly apparatus 1 includes a base 11, a SCARA robot 12, an assembly unit 13, and a screw supply mechanism 14. The SCARA robot 12 includes a link 121, a joint 128, a link 122, a joint 129, and a link 123 in this order. The assembling unit 13 includes a linear motion shaft 131, a linear motion shaft 132, a linear motion shaft 133, a force sensor 134, a screw tightening driver 135, a screw suction mechanism 136, and an impact relaxation mechanism (not shown). Is provided.

  The base 11 is a metal base. The base 11 has a rectangular parallelepiped shape. The base 11 has an upper surface dimension of about 1500 mm × about 1500 mm.

  The SCARA robot 12 is a SCARA (Selective Compliance Assembly Robot Arm) type robot. The SCARA robot 12 has a rotation axis in the vertical direction and can move its tip in a horizontal plane. The link 121 is fixed to the base 11. The link 121 and the link 122 are connected by a joint 128. The link 122 and the link 123 are connected by a joint 129. The SCARA robot 12 moves the tip to a predetermined position by controlling the angles of the joints 128 and 129 by a robot controller 21 (not shown) (see FIG. 4).

  The distance between the joints 128 and 129 is 450 mm. The distance between the joint 129 and the axis of the screw tightening driver 135 when the linear motion axes 131 and 132 are set to the origin position is 550 mm. The SCARA robot 12 can move the screw tightening driver 135 within a radius of 1000 mm around the joint 128.

  The assembling unit 13 is a mechanism for performing an assembling process described later and a screw tightening operation. The assembly unit 13 is fixed to the tip of the link 123 of the SCARA robot 12 and is moved by the SCARA robot 12.

  The linear motion shafts 131, 132, 133 move the screw 800. The linear motion shafts 131, 132, 133 are linear motion actuators. The linear motion shafts 131, 132, 133 are composed of a motor and a ball screw.

  The base of the linear motion shaft 133 is fixed to the link 123. The linear motion shaft 133 drives the tip side in the vertical direction (z-axis direction) in FIG. The base of the linear motion shaft 132 is fixed to the distal end side of the linear motion shaft 133. The linear motion shaft 132 drives the tip side in the left-right direction (y-axis direction) in FIG. The base portion of the linear motion shaft 131 is fixed to the distal end side of the linear motion shaft 132. The linear motion shaft 131 drives the tip side in a direction perpendicular to the paper surface of FIG. 1 (a direction perpendicular to the z axis and the y axis (hereinafter referred to as “x direction”)).

  The linear motion shaft 131 and the linear motion shaft 132 have a stroke of 20 mm and operate with the center of the stroke as the origin. The linear motion shaft 133 has a stroke of 50 mm and operates with the upper end of the stroke as the origin. The linear motion shafts 131, 132, and 133 each move on the tip side to a designated position under the control of an assembly control unit 22 (see FIG. 4) (not shown).

  The force sensor 134 detects the contact pressure of the screw 800 against the workpiece 900. The force sensor 134 is a triaxial force sensor that detects the magnitude of the force applied in the three axial directions of the x axis, the y axis, and the z axis. In the following, the magnitude of the force applied to the x axis is “force FX”, the magnitude of the force applied to the y axis is “force FY”, and the magnitude of the force applied to the z axis is “force”. FZ ".

  A base portion of the force sensor 134 is fixed to the distal end side of the linear motion shaft 131. The three axes x, y, z of the force sensor 134 are attached so as to be parallel to the driving directions of the linear motion axes 131, 132, 133, respectively. The force measurement range of the force sensor 134 is ± 100 N in the x, y, and z directions. The force sensor 134 measures forces FX, FY, and FZ every 1 ms and outputs them to the control unit 20 in accordance with a reading process from the control unit 20 (see FIG. 4) described later. The output of the force sensor 134 is offset-adjusted so that the forces FX, FY, and FZ become zero in the state shown in FIG. 1 (that is, a state where the screw tightening driver 135 is mounted at the tip).

  The screw tightening driver 135 is a driver capable of automatic screw tightening by torque management. The screw tightening driver 135 is attached to the distal end side of the force sensor 134. When the screw tightening driver 135 receives an instruction to start screw tightening, the screw tightening driver 135 rotates the bit 1351 at the tip (see FIG. 2) to tighten the screw. When the counter torque from the bit 1351 reaches a predetermined completion torque, the screw tightening driver 135 stops the rotation of the bit 1351 and outputs a completion signal indicating that the screw tightening is completed to the control unit 20.

  The base of the bit 1351 has a built-in spring cushioning mechanism. The impact mitigating mechanism shortens the protruding amount of the bit 1351 according to the force in the pushing direction of the screw. Thereby, the shock absorbing mechanism alleviates the shock when the linear motion shaft 133 is driven and the bit 1351 contacts the workpiece 900. In addition, the impact mitigating mechanism mitigates the reaction force change when the Z-axis position fluctuates, and the control for keeping the force FZ, which is a pressing force during the search movement described later, is easily stabilized.

  The screw tightening driver 135 has a torque-up detection function. In addition, the control part 20 (refer FIG. 4) which is not illustrated has an abnormality determination function. The control unit 20 stops the rotation of the bit 1351 when the torque increases with a rotation less than a predetermined fastening rotation angle during screw tightening. The control unit 20 stops the rotation of the bit 1351 when the torque does not increase even after a predetermined time has elapsed after the start of screw tightening.

  FIG. 2 is a cross-sectional view illustrating a cross section of the tip of the screw tightening driver 135, the screw suction mechanism 136, and the workpiece 900. Referring to FIG. 2, the screw suction mechanism 136 functions as a gripping unit that grips the screw 800. Specifically, the screw suction mechanism 136 is a mechanism that sucks the screw 800 to the bit 1351 by negative pressure. The screw suction mechanism 136 is attached to the base of the bit 1351. The screw suction mechanism 136 is connected to an external negative pressure source by a pneumatic pipe (not shown). The screw suction mechanism 136 includes a rubber member 1361 at the tip. When the rubber member 1361 contacts the head portion 801 of the screw 800, the screw adsorption mechanism 136 causes the rubber member 1361 to be in close contact with the head portion 801 by a suction process using a pneumatic pipe. Thereby, the sealed space by a negative pressure is formed.

  Even when the screw 800 is inclined with respect to the bit 1351, the rubber member 1361 is deformed and followed by the elasticity of the rubber member 1361, so that the sealing is maintained. Therefore, the adsorption power is maintained. Further, when the screw 800 is inclined with respect to the bit 1351, a reaction force for eliminating the inclination is generated from the rubber member 1361.

  The screw supply mechanism 14 is a general automatic screw supply machine. The screw supply mechanism 14 takes out a single screw after aligning a plurality of screws stocked therein in advance. Further, the screw supply mechanism 14 moves the screw to a predetermined supply position on the upper surface of the screw supply mechanism 14 with the head 801 of the extracted screw facing upward with respect to the tip end surface 890 of the screw.

  The screw supply mechanism 14 has a substantially rectangular parallelepiped shape. The screw supply mechanism 14 is installed adjacent to the installation range of the workpiece 900 on the base 11. The screw supply mechanism 14 can move the screw tightening driver 135 onto the supply position of the screw supply mechanism 14 by driving the SCARA robot 12. The screw supply mechanism 14 has a sensor that detects whether there is a screw at the supply position. When the screw is removed, the screw supply mechanism 14 drives the internal mechanism to move the next screw to the supply position.

  The screw 800 is, for example, M3, a screw length of 6 mm, and a bind-head metric screw. The size and type of the screw 800 are not limited to this.

  The workpiece 900 is a member fastened by a screw 800. The workpiece 900 has an upper hole 911 (first recess) for inserting the screw 800 and a screw hole 921 (second recess) for assembling the screw 800 formed on the bottom surface 908 of the upper hole 911. Have.

  More specifically, the workpiece 900 includes a rectangular flat plate-shaped workpiece 901 and a workpiece 902. The work 901 is placed on the work 902 so as to cover the upper surface and the outer periphery, and is positioned within a certain error range in the lateral direction. The work 901 and the work 902 are provided with fastening holes at a plurality of locations along the outer periphery of the upper surface. The workpiece 901 has a thickness of 1.0 mm, and the workpiece 900 has an overall thickness of 40 mm. The hole of the work 901 is a fool hole with a constant diameter. The hole of the work 902 is an M3 female screw. The bottom surface 908 is also an exposed surface of the workpiece 902. Hereinafter, for convenience of explanation, the bottom surface 908 is also referred to as an “exposed surface 908”.

  The workpiece 900 is installed at a predetermined position on the base 11 by an external transfer device (not shown). When the screw tightening by the automatic assembling apparatus 1 is finished, the workpiece 900 is carried out by an external transfer device. The position of the hole of the workpiece 900 installed at a predetermined position on the base 11 has an error due to the following factors.

・ Variation in the operation of setting the workpiece 900 by the external transfer device ・ Backlash of the workpiece 901 relative to the workpiece 902 ・ Dimensional tolerance of the workpiece 901 and the workpiece 902 As the above accumulation, the workpiece 901 installed at a predetermined position on the base 11 and The position of the hole in the workpiece 902 has a variation in a range of ± 1.5 mm, for example, centering on the design reference position.

  FIG. 3 is a top view of the workpiece 900. Referring to FIG. 3, upper hole 911 and screw hole 921 have a circular opening. The center of the upper hole 911 and the center of the screw hole 921 are shifted. The automatic assembling apparatus 1 starts searching for the screw hole 921 after bringing the tip surface 890 (see FIG. 2) of the screw 800 into contact with the exposed surface 908.

<Control system configuration>
FIG. 4 is a diagram showing the configuration of the control system of the automatic assembly apparatus 1. The automatic assembly apparatus 1 includes a control unit 20, a robot control unit 21, an assembly control unit 22, a screw supply mechanism 14, a screw tightening driver 135, a force sensor 134, a screw adsorption mechanism 136, and a joint 128. A joint 129, a linear motion shaft 131, a linear motion shaft 132, and a linear motion shaft 133.

  The control unit 20 is a computer for setting a moving amount, generating a noise μ, evaluating the progress of assembly, storing various parameters, and updating the parameters, which will be described later. Specifically, the control unit 20 is a general PC (Personal Computer) (see FIG. 11).

  The control unit 20 stores an algorithm for executing a control flow (FIGS. 9 and 10) of the automatic assembly apparatus 1 described later in a storage unit (not shown) in advance. The storage unit is a non-volatile memory such as an HDD (Hard Disc Drive) or a flash memory.

  The control unit 20 is connected to the robot control unit 21, the assembly control unit 22, the screw tightening driver 135, and the force sensor 134 through communication lines, and reads and controls the state of each device. Specifically, the control unit 20 instructs the robot control unit 21 to read the angles of the joints 128 and 129 of the SCARA robot 12 and the target angle. The control unit 20 instructs the assembly control unit 22 to acquire the positions of the linear motion shafts 131, 132, and 133 and to set the target position. The control unit 20 instructs the screw tightening driver 135 to read the abnormal state and the completed state and to instruct the fastening start. The control unit 20 reads the latest forces FX, FY, and FZ from the force sensor 134. The control unit 20 stores the target positions PX, PY, and PZ of the linear motion axes 131, 132, and 133 and the movement amounts MX, MY, and MZ as calculation parameters, and updates them by control calculation.

<Functional block>
FIG. 5 is a functional block diagram showing a functional configuration of the automatic assembly apparatus 1. Referring to FIG. 5, the automatic assembly apparatus 1 includes a control unit 20, a reaction force detection unit 250, a moving unit 260, an adsorption unit 270, an air inflow detection unit 280, a contact pressure detection unit 291, A torque detector 292. The control unit 20 includes a specifying unit 210, a distance calculating unit 220, a changing unit 230, a counting unit 240, and a pressing force control unit 245. The specifying unit 210 includes a first specifying unit 211 and a second specifying unit 212.

  The contact pressure detection unit 291 corresponds to the force sensor 134. The contact pressure detection unit 291 detects the contact pressure of the screw 800 against the workpiece 900 and sends the detection result to the control unit 20.

  The torque detection unit 292 corresponds to the screw tightening driver 135. The torque detection unit 292 detects the tightening torque when the screw 800 is tightened, and sends the detection result to the control unit 20. The moving unit 260 corresponds to the linear motion shafts 131, 132, and 133.

  The moving unit 260 operates based on an instruction from the control unit 20. Specifically, the moving unit 260 has a predetermined first moving direction in a state where the screw 800 and the exposed surface 908 of the workpiece 902 are brought into contact with each other by a pressing force in the insertion direction (z direction) with respect to the screw 800. The screw 800 is moved in a positive direction (+ direction) and a negative direction (− direction) in the following (hereinafter referred to as “u-axis direction”). In addition, the moving unit 260 moves the screw 800 in a positive direction and a negative direction in a predetermined second moving direction (hereinafter referred to as “v-axis direction”) in the above-described contact state.

  The reaction force detector 250 detects a reaction force applied to the screw 800 caused by the movement in the u-axis direction and the movement in the v-axis direction. Specifically, the reaction force detection unit 250 has a frictional force with the exposed surface 908 generated by the movement, and a contact pressure generated when the side surface of the screw 800 (near the tip 802 of the screw) hits the side surface of the upper hole 911. The contact pressure generated when the side surface of the screw 800 hits the inlet side surface of the screw hole 921 is detected.

  The specifying unit 210 specifies the position of the screw in the xy coordinate system when the reaction force detected by the reaction force detection unit 250 satisfies a predetermined condition. Specifically, the specifying unit 210 performs a specifying process by the first specifying unit 211 and a specifying process by the second specifying unit 212 described below.

  The first specifying unit 211 specifies a position Pα (first position) at which the reaction force is equal to or greater than the threshold Th1 when the screw 800 is moved in the positive direction in the u-axis direction. The first specifying unit 211 further determines a position Pβ (second position) at which the reaction force becomes equal to or greater than the threshold Th1 when the screw 800 is further moved from the first position in the negative direction in the u-axis direction. Identify.

  The second specifying unit 212 specifies a position Pγ (third position) at which the reaction force is equal to or greater than the threshold Th1 when the screw 800 is moved in the positive direction in the v-axis direction. Further, the second specifying unit 212 specifies a position Pδ (fourth position) where the reaction force is equal to or greater than the threshold Th1 when the screw 800 is moved in the negative direction in the v-axis direction from the third position. To do.

  The distance calculation unit 220 calculates a distance L1 (first distance) between the position Pα and the position Pβ. Further, the distance calculation unit 220 calculates a distance L2 (second distance) between the position Pγ and the position Pδ.

  The details will be described based on the flowchart shown in FIG. 10. However, when the distance L1 between the position Pα and the position Pβ is less than the threshold Th2, the control unit 20 performs a series of processing Sα (first series). As a process of (2), the movement in the v-axis direction starting from the intermediate position Pm between the position Pα and the position Pβ and the specification of the position Pγ and the position Pδ by the second specifying unit 212 are executed. When the distance L2 between the position Pγ and the position Pδ is less than the threshold Th2, the control unit 20 determines an intermediate position Pn between the position Pγ and the position δ as an assembly position.

  The threshold value Th2 is a value sufficiently smaller than the diameters of the screw 800 and the screw hole 921. For example, when the screw diameter is 3 mm, the threshold Th2 is, for example, 1 mm. The threshold value Th2 is set in advance to a value based on the diameter of the screw and / or the diameter of the upper hole 911 or the like.

  The changing unit 230 changes the u-axis direction and the v-axis direction by a certain amount in a certain direction. Details of the direction and amount will be described later.

  Although details will be described based on the flowchart shown in FIG. 10, when the distance L1 is greater than or equal to the threshold Th2, the automatic assembling apparatus 1 uses the changing unit 230 until the distance L1 becomes less than the threshold Th2. The change in the u-axis direction and the v-axis direction, the movement by the moving unit 260 in the u-axis direction after the change from the intermediate position Pm between the position Pα and the position Pβ, and the reaction force by the reaction force detection unit 250 A series of processes Sβ (second series of processes) including detection and identification of the position Pα and the position Pβ by the first identification unit 211 are repeated. When the distance L1 becomes less than the threshold Th2 by the series of processes Sβ, the automatic assembly apparatus 1 executes the series of processes Sα. When the distance L2 between the position Pγ and the position Pδ specified by the series of processes Sα is less than the threshold Th2, the automatic assembly apparatus 1 sets the intermediate position Pn between the position Pγ and the position Pδ as the assembly position. to decide.

  Further, when the distance L2 is greater than or equal to the threshold Th2, the automatic assembling apparatus 1 repeats a series of processes Sβ until the distance L1 becomes less than the threshold Th2 again. When the distance L1 becomes less than the threshold Th2 again, the automatic assembling apparatus 1 executes the series of processing Sα again. When the distance L2 between the position Pγ and the position Pδ specified by the series of processes Sα is less than the threshold Th2, the automatic assembly apparatus 1 assembles an intermediate position Pn between the position Pγ and the position Pδ. Judge as position.

  The adsorbing part 270 adsorbs the screw 800 with a negative pressure. The air inflow detection unit 280 detects air inflow during adsorption. That is, the air inflow detection unit 280 detects the inflow of external air into the sealed space formed by the negative pressure. Note that the combination of the suction unit 270 and the air inflow detection unit 280 corresponds to the screw suction mechanism 136 shown in FIG.

  The count unit 240 counts the number of air inflows. The pressing force control unit 245 increases the pressing force (force in the z direction applied to the screw 800) when the number of air inflows reaches a predetermined number. As a result, the head 801 of the screw 800 further contacts the rubber member 1361. Therefore, the inflow of air into the sealed space can be prevented.

Other functions of the control unit 20 will be described later.
<Search example>
Next, the movement of the screw 800 when searching for the screw hole 921 will be described with reference to FIGS. That is, the process for searching for the fastening position of the screw 800 will be described.

  FIG. 6 is a transition diagram for explaining the search for the screw hole 921. FIG. 6A is a diagram showing a state in which the screw 800 is moved in the z direction and the tip end surface 890 of the screw 800 is brought into contact with the exposed surface 908. That is, FIG. 6A is a diagram illustrating a state where the insertion of the screw 800 into the upper hole 911 is completed. With reference to FIG. 6A, the control unit 20 moves the screw 800 in the positive direction of the u-axis (the direction of the arrow 701). The position P0 represents the center position of the tip surface 890. In other words, the position P0 represents the position of the axis of the screw 800.

  FIG. 6B is a diagram illustrating a state after the screw 800 is moved in the positive direction of the u-axis from the state of FIG. Referring to FIG. 6B, the screw 800 hits the side surface of the upper hole 911 and stops. Thereafter, the control unit 20 moves the screw 800 in the negative direction of the u-axis (the direction of the arrow 702). The center position P1 of the front end surface 890 corresponds to the position Pα (first position) described above.

  FIG. 6C is a diagram illustrating a state after the screw 800 is moved in the negative direction of the u-axis from the state of FIG. Referring to FIG. 6C, the screw 800 hits the side surface of the upper hole 911 and stops. Thereafter, the control unit 20 moves the screw 800 in the positive direction of the u-axis (the direction of the arrow 703). The center position P2 of the front end surface 890 corresponds to the position Pβ (second position) described above.

  FIG. 6D is a diagram illustrating a state after the screw 800 is moved in the positive direction of the u-axis from the state of FIG. Referring to FIG. 6D, the control unit 20 moves the screw 800 along the u-axis to a position P3 intermediate between the position P1 and the position P2. The position P3 corresponds to the intermediate position Pm described above.

  After the state shown in FIG. 6D, the distance calculation unit 220 calculates the distance between the position P1 and the position P2 (that is, the distance L1). The control unit 20 compares the distance L1 with the threshold Th2. Since the distance L1 is larger than the threshold Th2, the control unit 20 proceeds to a process of rotating the u axis.

  FIG. 7 is a transition diagram for explaining a search performed subsequent to FIG. FIG. 7A is a diagram for explaining the movement of the screw 800 starting from the position P3 shown in FIG. 6D. With reference to FIG. 7A, the changing unit 230 rotates the u-axis counterclockwise by 78.75 degrees in FIG. 7A with the position P3 as the rotation center. Thereafter, the control unit 20 moves the screw 800 in the positive direction of the u-axis after rotation (the direction of the arrow 704).

  Note that the rotation angle of the u-axis is not limited to 78.75 degrees. However, an angle other than 90 degrees is preferable. Moreover, although mentioned later for details, the control part 20 rotates the v-axis mentioned later according to rotation of the u-axis. The angle formed by the v-axis and the u-axis is constant (78.75 degrees in the present embodiment).

  FIG. 7B is a diagram showing a state after the screw 800 is moved in the positive direction of the u-axis from the state of FIG. Referring to FIG. 7B, the screw 800 hits the side surface of the screw hole 921 and stops. Thereafter, the control unit 20 moves the screw 800 in the negative direction of the u-axis (the direction of the arrow 705). The center position P4 of the front end surface 890 corresponds to the position Pα (first position) described above.

  FIG. 7C is a view showing a state after the screw 800 is moved in the negative direction of the u-axis from the state of FIG. 7B. Referring to FIG. 7C, the screw 800 hits the side surface of the screw hole 921 and stops. Thereafter, the control unit 20 moves the screw 800 in the positive direction of the u-axis (the direction of the arrow 706). The center position P5 of the front end surface 890 corresponds to the position Pβ (second position) described above.

  FIG. 7D is a diagram showing a state after the screw 800 is moved in the positive direction of the u-axis from the state of FIG. Referring to FIG. 7D, the control unit 20 moves the screw 800 along the u-axis to a position P6 that is intermediate between the position P4 and the position P5. The position P6 corresponds to the above-described intermediate position Pm.

  After the state shown in FIG. 7D, the distance calculation unit 220 calculates the distance between the position P4 and the position P5 (that is, the distance L1). The control unit 20 compares the distance L1 with the threshold Th2. Since the distance L1 is smaller than the threshold value Th2, the control unit 20 proceeds to a process of moving the screw 800 in the v-axis direction.

  FIG. 8 is a transition diagram for explaining the search performed subsequent to FIG. FIG. 8A is a diagram for explaining the movement of the screw 800 starting from the position P6 shown in FIG. 7D. With reference to FIG. 8A, the control unit 20 moves the screw 800 in the positive direction of the v-axis (the direction of the arrow 707). As described above, the angle formed between the v-axis and the u-axis is 78.75 degrees.

  FIG. 8B is a diagram illustrating a state after the screw 800 is moved in the positive direction of the v-axis from the state of FIG. Referring to FIG. 8B, the screw 800 hits the side surface of the screw hole 921 and stops. Thereafter, the control unit 20 moves the screw 800 in the negative direction of the v-axis (the direction of the arrow 708). The center position P7 of the tip surface 890 corresponds to the position Pγ (third position) described above.

  FIG. 8C is a view showing a state after the screw 800 is moved in the negative direction of the v-axis from the state of FIG. Referring to FIG. 8C, the screw 800 hits the side surface of the screw hole 921 and stops. Thereafter, the control unit 20 moves the screw 800 in the positive direction of the v-axis (the direction of the arrow 709). A position P8 at the center of the distal end surface 890 corresponds to the position Pδ (fourth position) described above.

  FIG. 8D is a diagram illustrating a state after the screw 800 is moved in the positive direction of the v-axis from the state of FIG. Referring to FIG. 8D, the control unit 20 moves the screw 800 along the v-axis to a position P9 that is intermediate between the position P7 and the position P8. The position P9 corresponds to the intermediate position Pn described above.

  After the state shown in FIG. 8D, the distance calculation unit 220 calculates the distance between the position P7 and the position P8 (that is, the distance L2). The control unit 20 compares the distance L2 with the threshold Th2. Since the distance L2 is smaller than the threshold Th2, the control unit 20 determines a position P9 intermediate between the position P7 and the position P8 as the fastening position of the screw 800.

The automatic assembly apparatus 1 executes the fastening process of the screw 800 at the position P9.
<Control structure>
FIG. 9 is a flowchart showing the flow of processing in the automatic assembly apparatus 1. With reference to FIG. 9, in step S <b> 2, the automatic assembling apparatus 1 inserts the screw 800 into the upper hole 911 of the work 900 and brings the screw 800 into contact with the exposed surface 908. In step S42 included in step S4, the automatic assembling apparatus 1 starts searching for the screw hole 921. In step S44, the automatic assembly apparatus 1 determines whether or not air inflow to the above-described sealed space has occurred.

  If automatic assembly apparatus 1 determines that air inflow has occurred (YES in step S44), the process proceeds to step S12. If automatic assembly apparatus 1 determines that no air inflow has occurred (NO in step S44), it determines in step S46 whether or not screw 800 has been moved 3 mm or more from the search start position. The reason why the automatic assembling apparatus 1 makes the determination is to prevent unnecessary movement of the screw 800 and shorten the time required for the search.

  If automatic assembly apparatus 1 determines that it has moved 3 mm or more (YES in step S46), the process proceeds to step S20. If it is determined that the automatic assembling apparatus 1 has not moved by 3 mm or more (NO in step S46), it is determined in step S48 whether the screw hole 921 has been successfully searched.

  When automatic assembly apparatus 1 determines that the search for screw hole 921 has been successful (YES in step S48), it starts screw tightening in step S6. If automatic assembly apparatus 1 determines that the search for screw hole 921 has failed (NO in step S48), the process proceeds to step S44.

  In step S8, the automatic assembly apparatus 1 determines whether or not an error has occurred in the screw tightening process. The automatic assembling apparatus 1 determines that an error has occurred, for example, if the torque does not increase even after 1500 msec has elapsed since the start of screw tightening.

  If the automatic assembling apparatus 1 determines that no error has occurred (NO in step S8), it determines whether or not the screw tightening has been successful in step S10. For example, when the torque rises to a predetermined value or more within 1500 msec after starting the screw tightening, the automatic assembling apparatus 1 determines that the screw tightening is successful.

  When the automatic assembling apparatus 1 determines that an error has occurred (YES in step S8), in step S26, the screw tightening driver 135 is reversely rotated for a certain time (for example, 1500 msec) to remove the screw 800 from the screw hole 902, The bit 1351 is pulled up by 5 mm. Specifically, the automatic assembling apparatus 1 reverses the screw tightening driver 135 and collects the screw 800 stuck in the workpiece 900 and then lifts the bit 1351. In step S28, the automatic assembling apparatus 1 moves the bit 1351 to the screw tightening position and the point target position with respect to the search start origin (for example, the position P0 in FIG. 6). When the screw 800 remains on the workpiece 900 and is detached from the bit 1351, the assembly process of the screw 800 is stopped.

  In step S12, the automatic assembly apparatus 1 determines whether or not the previous lifting distance is less than 3 mm and the number of air inflows is less than 3. Note that if the screw 800 cannot be attracted even when the bit 1351 is pulled up, the automatic assembling apparatus 1 enters the air leakage ignoring mode. When automatic assembly apparatus 1 determines that the distance is less than 3 mm and the number of inflows is less than 3 (YES in step S12), the process proceeds to step S14. When the automatic assembling apparatus 1 determines that the distance is 3 mm or more or the number of inflows is 3 times or more, in step S22, it is determined whether or not the previous lifting distance is less than 3 mm and the number of air inflows is less than 5 times. To do.

  When the automatic assembling apparatus 1 determines that the distance is less than 3 mm and less than 5 times (YES in step S22), the setting value of the pressing force is changed from the default 6N to 8N in step S24. This is because if the pressing force is increased, the attachment state of the screw 800 to the bit 1351 can be improved and air inflow can be reduced. Note that the pressing force is actually set to 8N based on the set value before returning the process to step S2. When automatic assembly apparatus 1 determines that the distance is 3 mm or more or the number of inflows is 5 or more (NO in step S22), the process proceeds to step S46. The reason why the automatic assembling apparatus 1 advances the process to step S46 is to avoid an infinite loop in the assembling process.

  In step S <b> 14, the automatic assembling apparatus 1 starts pulling up the bit 1351 to return the posture of the screw 800. In step S16, the automatic assembly apparatus 1 determines whether or not the air inflow has stopped. If automatic assembly apparatus 1 determines that it has stopped (YES in step S16), it moves bit 1351 to the immediately preceding search start position in step S20. The automatic assembly apparatus 1 advances the process to step S2 after step S20. That is, when an air leak occurs, the automatic assembling apparatus 1 starts over from the contact determination even if it recovers in the middle.

  If it is determined that the automatic assembling apparatus 1 is not stopped (NO in step S16), it is determined in step S18 whether or not the lifting distance is 3 mm or more. If automatic assembly apparatus 1 determines that it has been lifted by 3 mm or more (YES in step S18), the process proceeds to step S2. If automatic assembly apparatus 1 determines that it has not been pulled up by 3 mm or more (NO in step S18), the process proceeds to step S16.

  FIG. 10 is a flowchart for explaining details of the process in step S4 in FIG. With reference to FIG. 10, in step S102, the automatic assembling apparatus 1 sets the angle of the u axis to 0 degree with respect to the y axis of the xy coordinate system (see FIG. 6A), and sets the angle of the v axis to y. Set to 78.75 degrees to the axis. In step S104, the automatic assembly apparatus 1 advances the bit 1351 in the positive direction of the u axis. In step S106, the automatic assembling apparatus 1 determines whether or not the reaction force is equal to or greater than the threshold value Th1. This is to determine whether or not the screw 800 hits the side surface of the upper hole 911.

  If automatic assembly apparatus 1 determines that it is equal to or greater than threshold value Th1 (YES in step S106), it advances bit 1351 in the negative direction of the u-axis in step S108. When automatic assembly apparatus 1 determines that it is less than threshold value Th1 (NO in step S106), the process proceeds to step S104.

  In step S110, the automatic assembly apparatus 1 determines whether or not the reaction force is greater than or equal to a threshold value Th1. If automatic assembling apparatus 1 determines that it is equal to or greater than threshold value Th1 (YES in step S110), it advances bit 1351 to the center position in step S112. The “center position” refers to a position where the reaction force is equal to or greater than the threshold Th1 in step S106 (the position Pα described above) and a position where the reaction force is equal to or greater than the threshold Th1 in step S110 (the position Pβ described above). Intermediate position (intermediate position Pm described above). If automatic assembly apparatus 1 determines that it is less than threshold value Th1 (NO in step S110), the process proceeds to step S108.

  In step S114, the automatic assembling apparatus 1 determines whether or not the distance between both end points in the u-axis direction is equal to or less than the threshold Th2. That is, the automatic assembling apparatus 1 determines the distance between the position (position Pα) where the reaction force is equal to or greater than the threshold Th1 in step S106 and the position (position Pβ) where the reaction force is equal to or greater than the threshold Th1 in step S110. It is determined whether (the above-described distance L1) is equal to or less than the threshold value Th2.

  If automatic assembly apparatus 1 determines that it is equal to or less than threshold value Th2 (YES in step S114), in step S116, automatic assembly apparatus 1 advances bit 1351 in the positive direction of the v-axis. If automatic assembly apparatus 1 determines that the value is larger than threshold value Th2 (NO in step S114), the process proceeds to step S128.

  In step S118, the automatic assembling apparatus 1 determines whether or not the reaction force is equal to or greater than the threshold value Th1. If automatic assembly apparatus 1 determines that it is equal to or greater than threshold value Th1 (YES in step S118), it advances bit 1351 in the negative direction of the v-axis in step S120. If automatic assembly apparatus 1 determines that it is less than threshold value Th1 (NO in step S118), the process proceeds to step S116.

  In step S122, the automatic assembling apparatus 1 determines whether or not the reaction force is equal to or greater than the threshold value Th1. If automatic assembling apparatus 1 determines that it is equal to or greater than threshold value Th1 (YES in step S122), it advances bit 1351 to the center position in step S124. The “center position” refers to a position where the reaction force is equal to or greater than the threshold Th1 in step S118 (the position Pγ described above) and a position where the reaction force is equal to or greater than the threshold Th1 in step S122 (the position Pδ described above). Intermediate position (intermediate position Pn described above). If automatic assembly apparatus 1 determines that it is less than threshold value Th1 (NO in step S122), the process proceeds to step S120.

  In step S126, the automatic assembling apparatus 1 determines whether or not the distance between both end points in the v-axis direction is equal to or less than the threshold value Th2. In other words, the automatic assembling apparatus 1 determines the distance between the position (position Pγ) where the reaction force is equal to or greater than the threshold Th1 in step S118 and the position (position Pδ) where the reaction force is equal to or greater than the threshold Th1 in step S122. It is determined whether (distance L2 described above) is equal to or less than a threshold value Th2.

  If automatic assembly apparatus 1 determines that threshold value Th2 is equal to or smaller than threshold value Th2 (YES in step S126), the process proceeds to step S6 in FIG. 9 assuming that the screw hole 921 has been successfully searched. If automatic assembly apparatus 1 determines that it is greater than threshold value Th2 (NO in step S126), in step S129, both u-axis and v-axis are constant in a fixed direction (counterclockwise in the xy coordinate system). Then, in step S128, the u axis and the v axis are both rotated in a fixed direction (counterclockwise in the xy coordinate system) by a fixed amount (78.75 degrees). Rotate (see FIG. 7A). The automatic assembling apparatus 1 advances the process to step S104 after step S128.

<Summary of automatic assembly device 1>
(1) As described above, the automatic assembly apparatus 1 is an apparatus that searches for an assembly position of the screw 800 with respect to the workpiece 900. The workpiece 900 has an upper hole 911 for inserting the screw 800 and a screw hole 921 for assembling the screw 800 formed on the bottom surface 908 of the upper hole 911. The automatic assembly apparatus 1 includes a moving unit 260, a reaction force detecting unit 250, a first specifying unit 211, and a second specifying unit 212.

  The moving part 260 is in a state where the screw 800 and the bottom surface 908 are brought into contact with each other by a pressing force in the insertion direction (z direction) with respect to the screw 800, and a positive direction and a negative direction in the u-axis direction and a positive direction in the v-axis direction. The screw 800 is moved in the negative direction and the negative direction. The reaction force detector 250 detects a reaction force applied to the screw 800 caused by the movement in the u-axis direction and the movement in the v-axis direction. The first specifying unit 211 moves the screw 800 in a negative direction in the u-axis direction from the position Pα where the reaction force is equal to or greater than the threshold Th1 when the screw 800 is moved in the positive direction in the u-axis direction. The position Pβ at which the reaction force is equal to or greater than the threshold Th1 when it is set is specified. The second specifying unit 212 moves the screw 800 in a negative direction in the v-axis direction from the position Pγ and a position Pγ where the reaction force is equal to or greater than the threshold Th1 when the screw 800 is moved in the positive direction in the v-axis direction. The position Pδ at which the reaction force is equal to or greater than the threshold value Th1 is determined.

  When the distance L1 between the position Pα and the position Pβ is less than the threshold Th2, the automatic assembling apparatus 1 performs a series of processes Sα in the v-axis direction starting from an intermediate position Pm between the position Pα and the position Pβ. And the specification of the position Pγ and the position Pδ by the second specifying unit 212 are executed. When the distance L2 between the position Pγ and the position Pδ is less than the threshold Th2, the automatic assembly apparatus 1 determines that the intermediate position Pn between the position Pγ and the position Pδ is the assembly position.

  According to the above configuration, the automatic assembling apparatus 1 detects the reaction force equal to or greater than the threshold value Th1 when moving in the u-axis direction, and the screw is placed on the side surface of the upper hole 911 when searching for the screw hole 921. Can detect contact. Moreover, the automatic assembly apparatus 1 can detect the distance L1 in the u-axis direction using the position at the time of the contact. When the distance L1 is less than the threshold Th2, the automatic assembling apparatus 1 detects a reaction force equal to or greater than the threshold Th1 when moving in the v-axis direction. It is possible to detect contact with the side surface of 911. Moreover, the automatic assembly apparatus 1 can detect the distance L2 in the v-axis direction using the position at the time of the contact.

  When both the distance L1 and the distance L2 are smaller than the threshold value Th2, the tip of the screw 800 is in a state where the screw hole 921 is engaged. For this reason, an intermediate position Pn between the position Pγ and the position Pδ may be determined as the assembly position of the screw 800.

  Therefore, the automatic assembly apparatus 1 can search the assembly position of the screw 800 with high accuracy even when the workpiece has variations in position and / or dimensions when the upper hole 911 and the screw hole 921 are provided.

  (2) The automatic assembling apparatus 1 further includes a changing unit 230 that changes the u-axis direction and the v-axis direction by a certain amount in a certain direction. When the distance L1 is greater than or equal to the threshold Th2, the automatic assembling apparatus 1 changes the u-axis direction and the v-axis direction by the changing unit 230 until the distance L1 becomes less than the threshold Th2, and the position Pα and the position Pβ. This includes the movement by the moving unit 260 in the u-axis direction after the change starting from the intermediate position Pm, the detection of the reaction force by the reaction force detection unit 250, and the specification of the position Pα and the position Pβ by the first specifying unit 211. A series of processing Sβ is repeated. When the distance L1 becomes less than the threshold Th2 by the series of processes Sβ, the automatic assembly apparatus 1 executes the series of processes Sα. When the distance L2 between the position Pγ and the position Pδ specified by the series of processes Sα is less than the threshold Th2, the automatic assembly apparatus 1 sets the intermediate position Pn between the position Pγ and the position Pδ as the assembly position. to decide.

  Therefore, the automatic assembly apparatus 1 can make the distance L1 less than the threshold value Th2 by repeating a series of processes Sβ.

  (3) When the distance L2 is equal to or greater than the threshold Th2, the automatic assembly apparatus 1 repeats a series of processes Sβ until the distance L1 becomes less than the threshold Th2 again. When the distance L1 becomes less than the threshold Th2 again, the automatic assembling apparatus 1 executes the series of processing Sα again. When the distance L2 between the position Pγ and the position Pδ specified by the series of processes Sα is less than the threshold Th2, the automatic assembly apparatus 1 assembles an intermediate position Pn between the position Pγ and the position Pδ. Judge as position.

  Therefore, even when the distance L2 is greater than or equal to the threshold Th2, the automatic assembly apparatus 1 can make the distance L1 less than the threshold Th2 again by repeating a series of processes Sβ.

  (4) Further, the automatic assembling apparatus 1 cancels the movement when the movement distance in the positive direction in the u-axis direction is a predetermined distance (eg, 3 mm) or more (YES in step S46 in FIG. 9). , The change in the u-axis direction and the v-axis direction by the change unit 230, the movement by the moving unit 260 in the u-axis direction after the change starting from the start position of the movement, and the detection of the reaction force by the reaction force detection unit 250 And the specification of the position Pα and the position Pβ by the first specifying unit 211 is executed.

  Therefore, the automatic assembling apparatus 1 can shorten the time required for searching by avoiding unnecessary movement of the screw 800.

  (5) Moreover, the automatic assembly apparatus 1 includes an adsorption unit 270 that adsorbs the screw 800 by negative pressure, an air inflow detection unit 280 that detects air inflow into a sealed space formed by adsorption, and the number of air inflows. And a pressing force control unit 245 for increasing the pressing force when the number of air inflows reaches a predetermined number.

  Therefore, the automatic assembly apparatus 1 can return to the reference posture even when the posture of the screw 800 deviates from the reference posture.

<Hardware Configuration of Control Unit 20>
FIG. 11 is a block diagram illustrating a hardware configuration of a computer system 300 that functions as the control unit 20.

  The computer system 300 includes, as main components, a CPU 310 that executes a program, a mouse 320 and a keyboard 330 that receive input of instructions from a user of the computer system 300, data generated by execution of the program by the CPU 310, or a mouse 320. Alternatively, it includes a RAM 340 that stores data input via the keyboard 330 in a volatile manner, a hard disk 350 that stores data in a nonvolatile manner, a DVD-ROM drive device 360, a monitor 370, and a communication IF 380. Each component is connected to each other by a data bus. A DVD-ROM 361 is attached to the DVD-ROM drive device 360.

  The processing in the computer system 300 is realized by each hardware and software executed by the CPU 310. Such software may be stored in the hard disk 350 in advance. The software may be stored in a DVD-ROM 361 or other storage medium and distributed as a program product. Alternatively, the software may be provided as a program product that can be downloaded by an information provider connected to the so-called Internet. Such software is read from the storage medium by the DVD-ROM driving device 360 or other reading device, or downloaded via the communication IF 380 and then temporarily stored in the hard disk 350. The software is read from the hard disk 350 by the CPU 310 and stored in the RAM 340 in the form of an executable program. CPU 310 executes the program.

  Each component constituting the computer system 300 shown in the figure is general. Therefore, it can be said that the essential part of the present invention is the software stored in the RAM 340, the hard disk 350, the DVD-ROM 361 or other storage medium, or the software downloadable via the network. Since the operation of each hardware of computer system 300 is well known, detailed description will not be repeated.

  The recording media are not limited to DVD-ROM, CD-ROM, FD (Flexible Disk), and hard disk, but are magnetic tape, cassette tape, optical disk (MO (Magnetic Optical Disc) / MD (Mini Disc) / DVD (Digital Versatile Disc), IC (Integrated Circuit) card (including memory card), optical card, mask ROM, EPROM (Electronically Programmable Read-Only Memory), EEPROM (Electronically Erasable Programmable Read-Only Memory), flash ROM, and other semiconductors It may be a medium that carries a fixed program such as a memory. The recording medium is a non-temporary medium that can be read by the computer.

  The program here includes not only a program directly executable by the CPU but also a program in a source program format, a compressed program, an encrypted program, and the like.

<Modification>
(1) In the above description, the method for searching for the screw hole 921 using the u-axis and the v-axis has been described. However, when the upper hole 911 is close to a perfect circle (as shown in FIG. 3), u You may perform the search which considered only the axis | shaft. With this configuration, the processing can be simplified as compared with the configuration in which the u axis and the v axis are searched.

  FIG. 12 is a flowchart showing the flow of processing when performing a search method considering only the u-axis. Referring to FIG. 12, in step S102A, automatic assembly apparatus 1 sets the angle of u-axis to 0 degrees with respect to the y-axis of the xy coordinate system. After step S102A, the automatic assembling apparatus 1 performs the processes of steps S104 to S114 shown in FIG.

  When the automatic assembling apparatus 1 determines that the distance between the two end points in the u-axis direction is equal to or smaller than the threshold Th2 (YES in step S114), the automatic assembly apparatus 1 determines that the search for the screw hole 921 is successful, and the process is as shown in FIG. The process proceeds to step S6. If the automatic assembling apparatus 1 determines that the threshold value Th2 is greater than the threshold value Th2 (NO in step S114), in step S128A, the u-axis is set in a fixed direction (counterclockwise in the xy coordinate system) by a fixed amount (78.75). Rotate only degrees. The automatic assembling apparatus 1 advances the process to step S104 after step S128A.

  (2) In the above description, the automatic assembly apparatus 1 has been described by taking the process of attaching the screw 800 to the workpiece 900 as an example. Hereinafter, a process in which the automatic assembly apparatus inserts an insertion type resin pin into a workpiece will be described. For convenience of explanation, an automatic assembly apparatus for inserting an insertion type resin pin into a workpiece is referred to as “automatic assembly apparatus 1A”.

  FIG. 13 is a diagram for explaining a process of inserting the resin pin 600 into the workpiece 900A. Referring to FIG. 13, automatic assembly apparatus 1 </ b> A has gripping mechanism 139 instead of screw tightening driver 135. The screw supply mechanism 14 is a mechanism for supplying the resin pin 600 instead of the screw 800. The workpiece 900A is composed of two layers of plate-like workpieces 930 and 940. The workpiece 900A includes an upper hole 931 (first recess) for inserting the resin pin 600 and a screw hole 941 (second recess) for assembling the resin pin 600 formed on the bottom surface 909 of the upper hole 931. And have.

  The resin pin 600 is a resin fixed pin having a shape in which a fixing claw protrudes downward from a plate-shaped upper portion. When the resin pin 600 is inserted into the hole of the workpiece 900A, the workpiece 930 and the workpiece 940 are fixed by the hook of the claw. The gripping mechanism 139 is a vacuum suction type component gripping mechanism. A concave shape is formed on the lower surface of the gripping mechanism 139 to engage with the upper portion of the resin pin 600. A hole connected to a vacuum source for suction is provided inside the concave shape.

  The control operation of the automatic assembling apparatus 1A is the same as that of the automatic assembling apparatus 1 except that the process of starting the rotation of the screw by operating the screw tightening driver 135 is not executed in the flow shown in FIG. With such an automatic assembly apparatus 1A, the insertion type resin pin can be automatically inserted with high reliability under the installation condition having a positional deviation.

  (3) In FIG. 10, the threshold value in step S106 and the threshold value in step S110 do not necessarily match. Further, the threshold value in step S118 and the threshold value in step S122 do not necessarily match. Furthermore, the threshold values in steps S106 and S110 and the threshold values in steps S118 and S122 do not necessarily match. In addition, the threshold value in step S114 and the threshold value in step S126 do not necessarily match.

(4) The rotation directions of the u axis and the v axis may be clockwise in the xy coordinate system.
(5) The numerical value “3 mm” shown in step S46 and step S18 in FIG. 9 is an example, and the present invention is not limited to this. The numerical value “5 mm” in step S26 is also an example, and the present invention is not limited to this. The number of inflows shown in steps S12 and S22 is also an example, and is not limited to this. The change in the pressing force in step S24 is not limited to this.

  (6) The shape of the opening of the upper hole 911 is not limited to a perfect circle. The shape may be a shape of a region through which the perfect circle passes when the ellipse, rectangle, or perfect circle is moved in a certain direction (a shape surrounded by an opposing straight line and an opposing semicircle).

  (7) The automatic assembling apparatuses 1 and 1 </ b> A may be configured such that the moving unit 260 moves the workpiece in place of the component while the component and the workpiece are in contact with each other.

  The embodiment disclosed this time is an exemplification, and the present invention is not limited to the above contents. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be used for all automatic assembling apparatuses for assembling parts of inserted parts.

  1,1A Automatic assembly device, 11 base, 12 SCARA robot, 13 assembly unit, 14 screw supply mechanism, 20 control unit, 21 robot control unit, 22 assembly control unit, 121, 122, 123 link, 128, 129 Joint, 131, 132, 133 linear motion axis, 134 force sensor, 135 screw tightening driver, 136 screw suction mechanism, 139 gripping mechanism, 210 specifying unit, 211 first specifying unit, 212 second specifying unit, 220 distance calculating unit, 230 changing unit, 240 counting unit, 245 pressing force control unit, 250 reaction force detecting unit, 260 moving unit, 270 adsorbing unit, 280 air inflow detecting unit, 291 contact pressure detecting unit, 292 torque detecting unit, 310 CPU, 600 resin Pin, 800 screw, 801 head, 802 tip, 890 tip, 900, 900A, 01,902,930,940 workpiece 908 bottom 909 bottom 911 above the hole, 921,941 screw holes, 931 holes, 1351 bits, 1361 rubber member.

Claims (12)

A search device for searching for an assembly position of a part with respect to a workpiece,
The workpiece has a first recess for inserting the component, and a second recess for assembling the component formed on the bottom surface of the first recess,
The search device includes:
One direction and the other direction in a predetermined first movement direction and a predetermined second movement in a state where the component and the bottom surface are brought into contact with each other by a pressing force in an insertion direction with respect to the component. Moving means for moving the component or the workpiece in one direction and the other direction in a direction;
Reaction force detection means for detecting a reaction force applied to the component caused by the movement in the first movement direction and the movement in the second movement direction;
A first position at which the reaction force is equal to or greater than a first threshold when the component or the workpiece is moved in the one direction in the first movement direction; and the first position from the first position. First identifying means for identifying a second position at which the reaction force is equal to or greater than the first threshold when the component or the workpiece is moved in the other direction in the movement direction;
A third position where the reaction force is equal to or greater than a first threshold when the component or the workpiece is moved in the one direction in the second movement direction; and the second position from the third position. Second specifying means for specifying a fourth position at which the reaction force is equal to or greater than the first threshold when the part or the workpiece is moved in the other direction in the moving direction;
The search device includes:
When the first distance between the first position and the second position is less than the second threshold, as the first series of processes, the first position and the second position The movement in the second movement direction starting from the intermediate position of the first position and the identification of the third position and the fourth position by the second identification means,
If the second distance between the third position and the fourth position is less than the second threshold value, an intermediate position between the third position and the fourth position is assembled. A search device that determines a position. The search device includes:
The first moving direction and the second moving direction are each further provided with changing means for changing the first moving direction and the second moving direction in a fixed direction by a fixed amount,
When the first distance is equal to or greater than the second threshold, the first moving direction and the second moving direction by the changing unit until the first distance becomes less than the second threshold. Change, the movement by the moving means in the first moving direction after the change starting from an intermediate position between the first position and the second position, and the reaction by the reaction force detecting means. Repeating a second series of processes including detection of force and identification of the first position and the second position by the first identification means;
When the first distance is less than the second threshold by the second series of processes, the first series of processes is executed,
When the second distance between the third position and the fourth position specified by the first series of processing is less than the second threshold, the third position and the The search device according to claim 1, wherein an intermediate position with respect to a fourth position is determined as the assembly position. When the second distance is equal to or greater than the second threshold, the second series of processes is repeated until the first distance is less than the second threshold again.
When the first distance becomes less than the second threshold again, the first series of processes is executed again,
When the second distance between the third position and the fourth position specified by the first series of processing is less than the second threshold, the third position The search device according to claim 2, wherein an intermediate position between the first position and the fourth position is determined as the assembly position.   When the movement distance in the one direction in the first movement direction is equal to or greater than a predetermined distance, the movement is stopped, and the first movement direction and the second movement direction are changed by the changing means. The movement by the moving means in the changed first movement direction starting from the start position of the movement, the detection of the reaction force by the reaction force detecting means, and the first specifying means. The search device according to claim 3, wherein the first position and the second position are specified. The search device includes:
An adsorbing means for adsorbing the component by negative pressure;
Detecting means for detecting air inflow into the sealed space formed by the adsorption;
Counting means for counting the number of times of air inflow;
The search device according to claim 3, further comprising a pressure control unit that increases the pressing force when the number of times of air inflow is a predetermined number. A search device for searching for an assembly position of a part with respect to a workpiece,
The workpiece has a first recess for inserting the component, and a second recess for assembling the component formed on the bottom surface of the first recess,
The search device includes:
In a state where the component and the bottom surface are brought into contact with each other by a pressing force in the insertion direction with respect to the component, the component or the other direction opposite to the one direction in the predetermined moving direction Moving means for moving the workpiece;
A reaction force detecting means for detecting a reaction force applied to the component caused by the movement;
A first position where the reaction force is equal to or greater than a first threshold when the part or the work is moved in the one direction; and the part or the work is moved from the first position to the other direction. A specifying means for specifying a second position at which the reaction force is equal to or greater than the first threshold when moved;
Changing means for changing the moving direction in a certain direction by a certain amount;
The search device includes:
If the distance between the first position and the second position is less than a second threshold, determine an intermediate position between the first position and the second position as the assembly position;
If the distance is greater than or equal to the second threshold,
Until the distance becomes less than the second threshold, the change of the moving direction by the changing means, the movement by the moving means starting from the intermediate position in the changed moving direction, and the reaction force detection A series of processes including detection of the reaction force by means and specification of the first position and the second position by the specifying means,
A search device that determines an intermediate position between the first position and the second position when the distance is less than the second threshold as the assembly position. The part is a screw,
The workpiece has a first workpiece and a second workpiece,
The first work is arranged to overlap the second work,
The first workpiece has a hole as the first recess,
The second workpiece has a screw hole as the second recess,
The search device according to claim 1, wherein the bottom surface is a surface of the second workpiece. The search device according to any one of claims 1 to 7,
An automatic assembling apparatus comprising: an assembling unit that assembles the component into the second recess at the assembling position. A search method in a search device for searching for an assembly position of a part with respect to a workpiece,
The workpiece has a first recess for inserting the component, and a second recess for assembling the component formed on the bottom surface of the first recess,
The search method includes:
The processor of the search device, in a state in which the component and the bottom surface are brought into contact with each other by a pressing force in the insertion direction with respect to the component, the one direction and the other direction in a predetermined first movement direction, Moving the component or the workpiece in one direction and the other direction in the determined second movement direction;
A sensor of the search device detects a reaction force applied to the component caused by movement in the first movement direction and movement in the second movement direction;
A first position at which the reaction force is equal to or greater than a first threshold when the processor moves the component or the workpiece in the one direction in the first movement direction; and from the first position Identifying the second position at which the reaction force is greater than or equal to the first threshold when the component or the workpiece is moved in the other direction in the first movement direction;
When the processor moves the part or the workpiece in the one direction in the second movement direction, the third position where the reaction force is equal to or greater than a first threshold value, and the third position Identifying the fourth position at which the reaction force is greater than or equal to the first threshold when the part or the workpiece is moved in the other direction in the second movement direction;
If the first distance between the first position and the second position is less than a second threshold, the processor determines an intermediate position between the first position and the second position. Executing the movement in the second movement direction as a starting point and the identification of the third position and the fourth position;
If the second distance between the third position and the fourth position is less than the second threshold, the processor is an intermediate position between the third position and the fourth position. And a step of determining the position as the assembly position. A search method in a search device for searching for an assembly position of a part with respect to a workpiece,
The workpiece has a first recess for inserting the component, and a second recess for assembling the component formed on the bottom surface of the first recess,
The search method includes:
One direction in the predetermined moving direction and the other opposite to the one direction in a state in which the processor of the search device makes the part and the bottom face contact by a pressing force in the insertion direction with respect to the part Moving the part or the workpiece in the direction of
A sensor of the search device detects a reaction force applied to the component caused by the movement;
A first position at which the reaction force is equal to or greater than a first threshold when the processor moves the part or the workpiece in the one direction; and the part from the first position to the other direction. Or specifying a second position at which the reaction force is greater than or equal to the first threshold when the workpiece is moved;
The processor changing the direction of movement in a certain direction by a certain amount;
When the distance between the first position and the second position is less than a second threshold, the processor determines an intermediate position between the first position and the second position as the assembly position. A step of judging,
If the distance is greater than or equal to the second threshold, the processor
Until the distance becomes less than the second threshold, the change in the movement direction, the movement starting from the intermediate position in the movement direction after the change, the detection of the reaction force, and the first position And repeating a series of processes including identification of the second position;
And a step of determining an intermediate position between the first position and the second position when the distance is less than the second threshold as the assembly position. A program for controlling a search device that searches for an assembly position of a part with respect to a workpiece,
The search device includes a processor and a force sensor,
The workpiece has a first recess for inserting the component, and a second recess for assembling the component formed on the bottom surface of the first recess,
The program is
One direction and the other direction in a predetermined first movement direction and a predetermined second movement in a state where the component and the bottom surface are brought into contact with each other by a pressing force in an insertion direction with respect to the component. Moving the part or the workpiece in one direction and the other direction in a direction;
Receiving, from the force sensor, a reaction force applied to the component caused by movement in the first movement direction and movement in the second movement direction;
A first position at which the reaction force is equal to or greater than a first threshold when the component or the workpiece is moved in the one direction in the first movement direction; and the first position from the first position. Identifying the second position at which the reaction force is greater than or equal to the first threshold when the component or the workpiece is moved in the other direction in the movement direction;
A third position where the reaction force is equal to or greater than a first threshold when the component or the workpiece is moved in the one direction in the second movement direction; and the second position from the third position. Identifying the fourth position at which the reaction force is greater than or equal to the first threshold when the part or the workpiece is moved in the other direction in the movement direction;
When the first distance between the first position and the second position is less than a second threshold, the intermediate position between the first position and the second position is the starting point. Performing a movement in a second movement direction and identification of the third position and the fourth position;
If the second distance between the third position and the fourth position is less than the second threshold value, an intermediate position between the third position and the fourth position is assembled. A program for causing the processor to execute a step of determining a position. A program for controlling a search device that searches for an assembly position of a part with respect to a workpiece,
The search device includes a processor and a force sensor,
The workpiece has a first recess for inserting the component, and a second recess for assembling the component formed on the bottom surface of the first recess,
The program is
In a state where the component and the bottom surface are brought into contact with each other by a pressing force in the insertion direction with respect to the component, the component or the other direction opposite to the one direction in the predetermined moving direction Moving the workpiece;
Receiving a reaction force applied to the component caused by the movement from the force sensor;
A first position where the reaction force is equal to or greater than a first threshold when the part or the work is moved in the one direction; and the part or the work is moved from the first position to the other direction. Identifying a second position at which the reaction force is greater than or equal to the first threshold when moved;
Changing the moving direction in a certain direction by a certain amount;
A step of determining an intermediate position between the first position and the second position as the assembly position when a distance between the first position and the second position is less than a second threshold value; When,
If the distance is greater than or equal to the second threshold,
Until the distance becomes less than the second threshold, the change in the movement direction, the movement starting from the intermediate position in the movement direction after the change, the detection of the reaction force, and the first position And repeating a series of processes including identification of the second position;
A program for causing the processor to execute a step of determining an intermediate position between the first position and the second position when the distance is less than the second threshold as the assembly position.

Images