JP2010151766A - Method for detecting position of tool of robot, method for detecting relative position of robot and object, their apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and highly accurately detect the position of a tool and the relative position of a robot and an object. <P>SOLUTION: In a tool position detection method, the tool 8 having a spherical surface part 8a is mounted to a tool mounting part 7e at the tip of an arm 7 of the robot 2. An unknown number is set as a component of a tool vector from the tool mounting part 7e to the center of the spherical surface part 8a. The spherical surface part 8a is brought into contact with a flat plate 16 as changing the attitude of the tool 8 by at least the same number of times as the unknown number. The positions of the tool mounting part 7e in contact are each determined on the basis of an joint angle of the arm 7 of the robot 2 in contact. Simultaneous equations which mean that the Z-position of the center of the spherical surface part 8a obtained from the sum of the Z-position of the plat plate 16 and a curvature radius Rc of the spherical surface part 8a is equal to the Z-position of the center of the spherical surface part 8a obtained from the sum of the Z-position of the tool mounting part 7e and a Z-component of the tool vector in a specific coordinate system are formed by at least the same number of times as the unknown number. By solving the simultaneous equations, the component of the tool vector is determined. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for detecting a tool position of a robot, a method for detecting a relative position between a robot and an object, and devices thereof.

  2. Description of the Related Art Conventionally, industrial robots are known that are used at production sites and the like by attaching a tool (for example, a welding torch or end mill) to the tip of an arm having a plurality of joints. In this industrial robot, an operator teaches a work operation in advance using a teaching pendant, and the robot reproduces the work operation in the main work, thereby automating the work. (For example, refer patent document 1 etc.).

  When a robot works on a workpiece with a tool, it is necessary to accurately grasp the tip position and posture of the tool. However, there are cases where the tool has a dimensional error or the tool is deformed. For this reason, the operator teaches the tool tip position and posture in advance. Specifically, in the case of a tool with a sharp tip, change the posture of the tool tip with respect to the tip of the needle-shaped jig to accurately make point contact, and the tool tip position from the teaching point at the time of the contact And the attitude is requested. In addition, there is a method of accurately measuring the dimensions of the tool using a three-dimensional measuring instrument.

Furthermore, when the robot works on a workpiece with a tool, it is necessary to accurately grasp the relative positional relationship between the robot and the workpiece. Therefore, the tool that the operator has attached to the robot in advance is brought into precise contact with a plurality of feature points on the workpiece (such as markings, cusps, corners, etc.), and the robot and workpiece are determined from the teaching points at the time of contact. The relative positional relationship is obtained. In addition, there is a method in which a visual sensor is attached to a robot, and a feature point on the workpiece is measured by the visual sensor to obtain a relative positional relationship between the robot and the workpiece.
Japanese Patent Publication No. 6-8730

  However, when the operator teaches the tool tip position and posture, it is necessary to accurately position the tool tip on the tip of the jig, which is very time consuming. In addition, when an unskilled worker performs the work, the tool may be bent too much due to the tool being bent, or a gap may be formed between the tool and the jig, resulting in inaccurate positioning. There are variations in teaching accuracy. Furthermore, when using a three-dimensional measuring instrument, the measurement work must be done once the tool is removed, and it is difficult to bring it to the work site if the device is large. There is also.

  Similarly, when an operator teaches feature points on a workpiece, it takes a very long time, and if an unskilled worker performs it, the teaching accuracy varies. Furthermore, when a visual sensor is used, there is a problem that the measurement accuracy is easily affected by light and the like, and it cannot be used in a poor working environment, and the sensor is expensive.

  Therefore, an object of the present invention is to make it possible to easily and accurately detect the tool position and the relative position between the robot and the object.

  The present invention has been made in view of the above circumstances, and a robot tool position detection method according to the present invention attaches a tool having a tip portion made of a spherical surface or a point to a tool mounting portion at the tip of a robot arm. Setting an unknown to the component of the tool vector from the tool mounting portion to the center of the tip, and changing the posture of the tool with respect to a plane at least as many times as the number of unknowns, Based on the joint angle of the arm of the robot at the time of contact, the position of the tool mounting portion at the time of contact is obtained, and in a specific coordinate system, the Z position of the plane and the radius of curvature of the tip portion The center Z position of the tip obtained from the sum is equal to the center Z position of the tip obtained from the sum of the Z position of the tool mounting portion and the Z component of the tool vector. The meaning simultaneous equations is the same number of simultaneous and at least the number of the unknowns, and obtains the components of the tool vector by solving the simultaneous equations.

  According to this, even if only focusing on the Z position that is one direction, the tool vector component can be obtained by solving the simultaneous equations by changing the posture of the tool and contacting the plane. Then, by focusing only on the Z position, the tip of the tool may be brought into contact with any position on the plane (the X and Y positions may be deviated from the previous contact position), and teaching work Can be performed roughly. Therefore, the teaching work can be simplified, the working time can be shortened, and the detection accuracy can be improved. In addition, when the front-end | tip part of a tool is a pointed part, it is good to treat the said curvature radius as zero.

  A flat plate that can be displaced in a substantially normal direction and a displacement sensor that can detect the displacement of the flat plate are used. The flat surface is a contact surface of the flat plate, and the Z position of the flat surface is used as an output of the displacement sensor. You may ask based on.

  According to this, when the tip of the tool is brought into contact with the contact surface of the flat plate, the flat plate can be displaced, so that the contact pressure is absorbed. Therefore, the tool can be accurately detected without being bent, and deformation of the jig (a flat plate or the like in the present invention) can be prevented. Further, since the abutment is performed between the tip portion formed of the spherical surface portion or the tip portion and the flat surface, the flat plate and the displacement sensor can be made inexpensive with one degree of freedom.

  An optical area sensor may be used, and the flat surface may be a sensing surface of the optical area sensor, and the joint angle of the robot arm may be detected when the tip of the tool contacts the sensing surface.

  According to this, since it is only necessary to detect that the tip of the tool is in contact with the optically formed plane (sensing surface), it is not necessary to mechanically contact the tip of the tool with the plane. It is possible to prevent the sensor from being loaded.

  The Z position of the plane when the tip is not in contact with the plane and the radius of curvature of the tip are further unknown, and at least all unknowns are obtained by changing the attitude of the tool with respect to the tip. The simultaneous equations may be contacted at the same number of times as at least as many as the number of all unknowns.

  According to this, it is not necessary to know the Z position of the plane and the radius of curvature of the tip in advance by simply increasing the number of simultaneous equations by increasing the number of times that the tip is brought into contact with the plane by changing the posture of the tool, Teaching work can be further simplified.

  A reference tool having a known dimensional shape is attached to the tool attachment portion, the reference tool is moved in the plane, and the reference tool is brought into contact with a plurality of locations on the plane, whereby X and Y positions on the plane are obtained. And the Z position are obtained in advance, the tool is attached to the tool mounting portion instead of the reference tool, the tool is brought into contact with the plane, and the X and Y positions in the plane of the contact location are determined. The Z position corresponding to the X and Y positions is obtained from the correlation, and the obtained Z position is determined from the plane of the simultaneous equations. It may be substituted for the Z position.

  According to this, the correlation between the X, Y position on the plane and the Z position is obtained in advance, and the Z position is corrected using the correlation from the X, Y position on the plane with which the tip of the tool abuts. Therefore, even if the normal direction of the plane does not coincide with the Z direction in the specific coordinate system, the component of the tool vector can be obtained correctly.

  In the relative position detection method between the robot and the object according to the present invention, a member having a flat surface is attached to the tool attachment part at the tip of the robot arm, and a target having an abutting part consisting of a spherical surface or a point is attached to the object. , Setting an unknown to the component of the target vector indicating the position and direction of the abutting part, changing the attitude of the member to the abutting part at least as many times as the number of unknowns, Based on the joint angle of the arm of the robot at the time of contact, the position of the tool mounting portion at the time of contact is obtained, and in a specific coordinate system, the position of the contact portion obtained from the Z component of the target vector Meaning that the center Z position is equal to the center Z position of the contact portion obtained from the sum of the Z position of the tool mounting portion, the Z position of the plane, and the radius of curvature of the contact portion. That simultaneous equations is the same number of simultaneous as the number of at least the unknowns, and obtains the component of the target vector by solving the simultaneous equations.

  According to this, even if paying attention only to the Z position which is one direction, the component of the target vector can be obtained by changing the posture of the member and bringing the plane into contact with the contact portion of the target and solving the simultaneous equations. it can. Then, by paying attention only to the Z position, the contact portion of the target may be brought into contact with any position on the plane (the X and Y positions may be deviated from the previous contact position). The work can be performed roughly. Therefore, the teaching work can be simplified, the working time can be shortened, and the detection accuracy can be improved. In addition, when the contact part of a target is a point part, it is good to treat the said curvature radius as zero.

  A flat plate displaceable in a substantially normal direction and a displacement sensor for detecting the displacement of the flat plate are attached to the tool mounting portion, and the flat surface is formed by a contact surface of the flat plate, and the Z position of the flat surface is displaced. You may obtain | require based on the output of a sensor.

  According to this, when the flat plate is brought into contact with the contact portion of the target, the flat plate can be displaced, so that the contact pressure is absorbed. Therefore, accurate detection can be performed without bending the target, and destruction of the jig (a flat plate or the like in the present invention) can be prevented. Further, since the abutment is performed between the tip portion formed of the spherical surface portion or the tip portion and the flat surface, the flat plate and the displacement sensor can be made inexpensive with one degree of freedom.

  An optical area sensor may be attached to the tool attachment portion, and the plane may be a sensing surface of the optical area sensor, and when the sensing surface contacts the target, the joint angle of the robot arm may be detected. .

  According to this, since it is only necessary to detect that the contact portion of the target is in contact with the optically formed flat surface (sensing surface), it is not necessary to mechanically contact the target contact portion with the flat surface. It is possible to prevent the sensor and the target from being loaded.

  The Z position of the plane when the plane is not in contact with the target and the radius of curvature of the target are further unknown, and at least all unknowns are obtained by changing the attitude of the member with respect to the contact portion. The simultaneous equations may be contacted at the same number of times as at least as many as the number of all unknowns.

  According to this, it is necessary to know in advance the Z position of the plane and the radius of curvature of the tip by merely increasing the number of simultaneous equations by changing the posture of the member and bringing the target abutting portion into contact with the plane. The teaching work can be simplified.

  The object may be a workpiece.

  According to this, the relative positional relationship between the robot and the workpiece can be obtained, and the workpiece can be handled accurately by the robot.

  Further, the robot tool position detection apparatus of the present invention comprises a robot to which a tool having a tip portion made of a spherical surface or a tip is attached to a tool attachment portion at the tip of an arm, and a control means for controlling the robot, The control means sets an unknown number for a component of the tool vector from the tool mounting portion to the center of the tip portion, and changes the posture of the tool with respect to the plane with respect to the plane, and applies at least as many times as the number of unknowns. The robot is driven to contact, and the position of the tool mounting portion at the time of contact is determined based on the joint angle of the arm of the robot at the time of contact, and the Z position of the plane in a specific coordinate system And the center Z position of the tip obtained from the sum of the radius of curvature of the tip and the sum of the Z position of the tool mounting portion and the Z component of the tool vector. The simultaneous equations means is the same number of simultaneous and at least the number of the unknowns is equal to the Z position of the center of the tip portion, and obtains the components of the tool vector by solving the simultaneous equations to be.

  According to this, as in the tool position detection method described above, the component of the tool vector can be obtained by solving the simultaneous equations by changing the posture of the tool and bringing it into contact with a plane even if only focusing on the Z position in one direction. Can be requested. Then, by focusing only on the Z position, the tip of the tool may be brought into contact with any position on the plane (the X and Y positions may be deviated from the previous contact position), and teaching work Can be performed roughly. Therefore, the teaching work can be simplified, the working time can be shortened, and the detection accuracy can be improved.

  Further, the relative position detection apparatus for a robot and an object of the present invention includes a robot in which a member having a flat surface is attached to a tool attachment portion at the tip of an arm, and a control means for controlling the robot, An unknown value is set for the component of the target vector indicating the position and direction of the abutting portion of the target having the abutting portion consisting of a spherical surface or a pointed portion attached to the object, and the plane is Change the posture of the member to contact at least as many times as the number of unknowns, and determine the position of the tool attachment part at the time of contact based on the joint angle of the robot arm at the time of contact, respectively In the coordinate system, the Z position of the center of the contact portion obtained from the Z component of the target vector is the Z position of the tool mounting portion, the Z position of the plane, and the contact portion. Obtaining a target vector component by solving a simultaneous equation for the number of detection times and solving the simultaneous equation, which means that it is equal to the Z position of the center of the contact portion obtained from the sum of the radius of curvature. Features.

  According to this, as in the relative position detection method described above, even if only focusing on the Z position that is one direction, the simultaneous equations are solved by changing the posture of the member and bringing the plane into contact with the contact portion of the target. Thus, the component of the target vector can be obtained. Then, by paying attention only to the Z position, the contact portion of the target may be brought into contact with any position on the plane (the X and Y positions may be deviated from the previous contact position). The work can be performed roughly. Therefore, the teaching work can be simplified, the working time can be shortened, and the detection accuracy can be improved.

  As is apparent from the above description, according to the present invention, the tool position and the relative position between the robot and the object can be detected easily and with high accuracy.

  Embodiments according to the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic view showing a tool position detecting device for a robot according to a first embodiment of the present invention. As shown in FIG. 1, the robot tool position detection apparatus 1 includes an industrial robot 2 and a control unit 3 that controls the robot 2. The control means 3 has a controller 4 connected to the robot 2 and a personal computer 5 which is a computer connected to the controller 4. The robot 2 has a base 6 installed on an installation surface G such as the ground, and an arm 7 protruding from the base 6, and is based on a coordinate system based on the installation surface G on which the base 6 is installed. The coordinate system is set. The arm 7 is provided with a plurality of joints 7a to 7d that are driven so as to change the angle in response to a command from the controller 4, and a flange-like tool attachment portion 7e is provided at the tip thereof.

  The robot 2 incorporates an encoder (not shown) capable of detecting the angles of the joints 7a to 7d, and the like, and a tool mounting portion is determined depending on the angles of the joints 7a to 7d and the dimensions of the links constituting the arm 7. The position and orientation in the base coordinate system of 7e can be understood. A tool 8 having a tip portion made of a spherical surface or a point is attached and fixed to the tool mounting portion 7e. Specifically, for the tool 8, a welding torch having a spherical portion at the tip, an end mill having a tip at the tip, or the like is used. In the present embodiment, description will be made using a tool 8 having a tip portion composed of a spherical portion 8a. A coordinate system based on the tool attachment portion 7e is set as the tool coordinate system.

  A touch sensor 10 is installed on the installation surface G of the robot 2. The touch sensor 10 includes a housing 11, a spring receiving plate 12 housed in the housing 11, a spring 13 that biases the spring receiving plate 12 upward, and protrudes upward from the spring receiving plate 12 through the housing 11. Rod 14 and a displacement sensor 15 capable of detecting the amount of displacement of the rod 14 in the vertical direction. As a specific example of the touch sensor 10, for example, a contact type digital sensor (model number: GT2-H12L) manufactured by Keyence Corporation can be used. A flat plate 16 whose upper surface is a contact surface is fixed to the tip of the rod 14 of the touch sensor 10. The output of the displacement sensor 15 is configured to be input to the personal computer 5.

  In this embodiment, the displacement detection direction of the touch sensor 10 and the normal direction of the contact surface 16a (upper surface) of the flat plate 16 are provided so as to coincide with the Z direction of the base coordinate system. There is no need to let them. For example, when the displacement detection direction of the touch sensor does not coincide with the Z direction of the base coordinate system, a matrix for matching it is measured in advance, and the coordinate system of the touch sensor 10 is determined using the matrix. It is preferable to set the personal computer 5 so as to convert to the base coordinate system.

  Next, the tool position detection procedure by the tool position detection apparatus 1 will be described. FIG. 2 is a view for explaining a tool position detecting method by the apparatus 1 shown in FIG. As shown in FIGS. 1 and 2, first, the robot 4 is operated by the controller 4 to bring the spherical surface portion 8 a of the tool 8 into contact with the contact surface 16 a of the flat plate 16 of the touch sensor 10. At the time of contact, the rod 14 of the touch sensor 10 can be displaced up and down by the elastic force of the spring 13, and the flat plate 16 moves downward. Therefore, the force applied to the tool 8 at the time of contact is relieved. Furthermore, since the contact is performed between the spherical surface portion 8a and the flat plate 16, the flat plate 16 and the touch sensor 10 can be made inexpensive with one degree of freedom.

  Further, as shown in FIG. 3A, the contact force between the flat plate 16 and the spherical surface portion 8a always acts only in the expansion / contraction direction of the spring 13, which is the normal direction of the flat plate 16, so that the deformation of the tool 8 is prevented. Can be measured accurately. That is, as in the comparative example of FIG. 3B, when the spheres (spherical portion 8a and sphere B) are in contact with each other, a force toward the center of the spherical portion 8a is generated, and the contact force is a spring. Since the tool does not necessarily act in the 13 expansion / contraction directions, the tool may be deformed, but according to the present embodiment, this is prevented.

  Next, returning to FIG. 2, when the spherical surface portion 8 a of the tool 8 is brought into contact with the contact surface 16 a of the flat plate 16, the position and posture of the tool mounting portion 7 d are based on the angles of the joints 7 a to 7 d of the robot 2. While measuring, the output of the displacement sensor 15 is also measured. Then, the position and orientation of the tool mounting portion 7 d and the output of the displacement sensor 15 are recorded in the personal computer 5. Next, the posture of the tool 8 is changed by the robot 2, and measurement and recording of the position and posture of the tool mounting portion 7d and the output of the displacement sensor 15 are performed a plurality of times (the number of times more than the number of unknowns in the simultaneous equation (3) described later). )repeat. At that time, as long as the spherical surface portion 8a of the tool 8 contacts the contact surface 16a of the flat plate 16, the contact position in the contact surface 16a may be shifted every time. Further, the posture of the tool 8 at each turn when the spherical surface portion 8a is repeatedly brought into contact with the flat plate 16 is selected so as not to rotate around the same axis (for example, the tool 8 is directed downward in the vertical direction and around the X axis). ± 45 degrees, 5 postures of ± 45 degrees around the Y axis, etc.).

  Next, the position and orientation of the tool mounting portion 7d obtained by the number of repetitions and the output data of the displacement sensor 15 are used to solve the simultaneous equations (3) described later, whereby the position of the center of the spherical portion 8a of the tool 8 is obtained. Then, the component of the tool vector tXtc from the tool attachment portion 7d to the center of the spherical portion 8a is obtained. As can be seen from FIG. 2, when each vector is projected onto a line segment in the Z direction in the base coordinate system, the following formula 1 is always established regardless of the posture of the tool 8.

Here, the symbols and variables in Equation 1 are defined as follows.
“・”: Inner product of vector “*”: product of matrix and vector
Nbz: Unit vector parallel to the Z direction of the base coordinate system, that is, a transposed vector of (0,0,1)
bXbt: Vector to the tool attachment (known for each measurement data)
Rbt: Coordinate transformation matrix between base coordinate system and tool coordinate system (known for each measurement data)
tXtc: Tool vector (each component is unknown)
L0: Natural length of touch sensor (length when output is 0: either unknown or known)
δL: Touch sensor output (Positive shrinking direction, known for each measurement data)
Rc: radius of curvature of the spherical surface (either unknown or known)
Equation 1 shows that the Z position of the center of the spherical surface portion obtained from the sum of the Z position of the contact surface 16a of the flat plate 16 and the radius of curvature Rc of the spherical surface portion 8a in the base coordinate system is the Z position of the tool mounting portion 7e. And the Z position of the center of the spherical surface portion 8a obtained from the sum of the Z component of the tool vector tXtc.

  Since the inner product is the same value even if the vector to be expressed is changed, the equation 1 is rewritten to the equation 2 converted into the tool coordinate system so that the simultaneous equations (3) described later can be easily combined into the equation 4 described later.

  Here, Rtb is an inverse matrix of Rbt (known for each measurement data).

  FIG. 4 is a view for explaining that the tool 8 is brought into contact with the flat plate 16 by changing its posture in the apparatus 1 shown in FIG. As shown in FIG. 4, when the robot 2 is operated and the posture of the tool 8 is changed a plurality of times and measured, Equation 2 can obtain the following simultaneous equations (3) in which the same number as the number of times N is measured. (N is an unknown number).

  This simultaneous equation (3) can be generally organized as follows.

  X, A, and B are expressed by the following equations 5 to 7 when the natural length L0 of the touch sensor 10 (that is, the initial Z position of the flat plate 16) and the radius of curvature Rc of the spherical surface portion 8a are set as unknowns. Is done.

  On the other hand, when both the natural length L0 of the touch sensor 10 and the radius of curvature Rc of the spherical surface portion 8a are set as known, X, A, and B are expressed by the following formulas 8 to 10.

  When the matrix A is regular (N = the number of unknowns), the unknown vector X is expressed by the following Equation 11.

  On the other hand, when the matrix A is irregular (N> the number of unknowns), the vector X of unknowns is expressed by Equation 12 below.

A ⁺ is a pseudo inverse matrix of A as shown in Equation 13 below, and thus a highly accurate solution can be obtained in the same manner as that obtained by the method of least squares.

  Then, each component of the tool vector tXtc is obtained by Expression 11 or Expression 12.

  As described above, each component of the tool vector tXtc can be obtained by solving the simultaneous equations by changing the posture of the tool 8 and contacting the flat plate 16 only by paying attention to only the Z position in one direction. Then, by focusing only on the Z position, the spherical portion 8a of the tool 8 may be brought into contact with any position on the contact surface 16a of the flat plate 16 (X and Y positions relative to the previous contact position). The teaching work can be performed roughly. Therefore, the teaching work can be simplified, the working time can be shortened, and the detection accuracy can be improved. Further, if the natural length L0 of the touch sensor 10 (that is, the initial Z position of the flat plate 16) and the radius of curvature Rc of the spherical surface portion 8a are set as unknowns, the number of simultaneous equations can be increased by increasing the number of contact, There is no need to know L0 and Rc in advance, and the teaching work can be further simplified.

  In the present embodiment, the tip portion of the tool 8 is the spherical surface portion 8a, but the tip portion of the tool may be a pointed portion (for example, when the tool is an end mill). In that case, if the above-described curvature radius Rc is treated as zero, the other tool position detection procedures are the same as described above. In this embodiment, simultaneous equations (3) are solved in the tool coordinate system, but may be solved in the base coordinate system.

(Second Embodiment)
FIGS. 5A and 5B are views for explaining a contact state of a tool according to a second embodiment of the present invention with a flat plate. As shown in FIGS. 5A and 5B, the present embodiment is a case where the normal direction of the flat plate 16 is fixed to the rod 14 of the touch sensor 10 in a state where the normal direction is inclined with respect to the Z direction of the base coordinate system. Assumed. In this case, even when the spherical portion 8a at the tip of the tool 8 is moved so that the height is constant, the flat plate 16 is displaced up and down, and the output value of the displacement sensor 15 changes by Lb. (The value of δL obtained as a sensor value is detected by increasing by Lb in the right-hand diagram (b).) Therefore, in order to correct this influence, Equation 2 as a basic equation is expressed as Equation 14 below. To correct.

  Then, a correction table or a correction function that uses the X and Y positions of the center of the spherical portion 8a of the tool 8 as input and outputs the correction value Lb of the output value of the displacement sensor 15 is obtained in advance as follows.

  First, a reference tool (not shown) having a known dimensional shape is attached to the tool attachment portion 7e of the robot 2. Next, the reference tool is brought into contact with the flat plate 16 by the robot 2, and the position (bXbc, bYbc, bZbc) of the tip of the reference tool at the time of contact and the output value δL of the displacement sensor 15 are recorded (FIG. 5). (See (a)). Note that the position of the tip portion of the reference tool can be obtained from the position and orientation of the tool attachment portion 7e of the robot 2 as shown in the following Equation 15 because the approximate size and shape of the reference tool are known.

  Note that tXtc0 is a reference tool vector from the tool attachment portion 7e to the center of the tip end portion of the reference tool, and is obtained from the size and shape of the reference tool and the posture of the tool attachment portion 7e.

  Then, the reference tool is moved in the XY plane (base coordinate system) so as not to change the Z position of the tip portion of the reference tool, and the reference tool is brought into contact with a plurality of locations on the contact surface 16a of the flat plate 16, and the contact is made. The position (bXbc, bYbc, bZbc) of the tip of the reference tool at the time of contact and the output value δL of the displacement sensor 15 are recorded (see FIG. 5B). Actually, without moving the reference tool parallel to the XY plane, the reference tool is once moved away from the flat plate and then moved parallel to return to the same height, thereby preventing the tool from being deformed. By repeating this operation, the number of times equal to or greater than the number of unknowns in Equation 4 is measured. Based on the measurement result thus obtained, a correlation between the X and Y positions on the flat plate 16 and the Z position for correcting the inclination of the flat plate 16 is obtained.

  Specifically, since the tool tip position and the sensor values corresponding to the tool tip position can be obtained, the correction amount of the output value of the displacement sensor 15 using the X and Y positions (bXbc, bYbc) of the tool tip part as input. Find the linear interpolation table that outputs Lb. Alternatively, instead of a table, a plane equation as shown in Formula 16 may be obtained.

  A, B, and Z0 are coefficients, and these three values are a vector (X, Y, Z) = determined from the tip position X, Y of the reference tool and the sensor output value δL obtained as many times as measured. It can be obtained by solving simultaneous equations obtained by substituting (bXbc, bYbc, δL + bZbc) into Equation 16.

  Next, the reference tool attached to the tool attachment portion 7e of the robot 2 is replaced with the tool 8 to be measured, and the spherical portion 8a of the tool 8 is set to at least an unknown number with respect to the flat plate 16 as in the first embodiment. After contacting the same number of times, Formula 2 in the first embodiment is replaced with Formula 8 (that is, δL in Formula 2 is replaced with δL−Lb), and then Formula 4 is obtained. As for the value of Lb at that time, Lb corresponding to the X and Y positions at the time of contact is obtained using the linear interpolation table or Expression 16. Then, a temporary value of the tool vector is calculated by solving the simultaneous equations. After that, if the same measurement is repeated using the obtained tool vector value, the accuracy of calculating the tool vector can be further improved. Other configurations, procedures, and the like are the same as those of the first embodiment described above, and thus detailed description thereof is omitted.

(Third embodiment)
FIG. 6 is a perspective view showing an optical area sensor according to the third embodiment of the present invention. As shown in FIG. 6, in this embodiment, a non-contact optical area sensor 20 is used instead of the touch sensor 10 to which the flat plate 16 is attached. Specifically, the optical area sensor 20 is a photoelectric switch including a light emitting device 21 having a plurality of light emitting units that irradiate a plurality of light beams in parallel and a light receiving device 22 having a plurality of light receiving units that receive the light beams. A virtual plane including a plurality of rays is the sensing surface 23. The light receiving portion that does not receive the light beam is generated, so that it can be detected that the spherical surface portion 8a of the tool 8 is in contact with the sensing surface 23.

  The optical area sensor 20 is installed at an arbitrary height so that the sensing surface 23 is parallel to the XY plane of the base coordinate system. Next, the tool 8 to be measured is attached to the tool attachment portion 7e of the robot 2, and slowly approached from above the optical area sensor 20. Then, when the light receiving device 22 detects that the spherical portion 8a of the tool 8 blocks the light beam, the position and posture of the tool attachment portion 7e are recorded by detecting the joint angle of the robot 2. This measurement is performed at least three times (or at least four times when L0 and Rc are unknown) by changing the posture. Then, the simultaneous equation (4) is calculated by substituting the position and orientation information of the tool attachment portion 7e into Equation 2. At this time, the sensor output value ΔL is calculated as zero. Thereafter, a tool vector is obtained by solving simultaneous equations according to the procedure described in the first embodiment. Other configurations, procedures, and the like are the same as those of the first embodiment described above, and thus detailed description thereof is omitted.

(Fourth embodiment)
FIG. 7 is a schematic diagram showing a relative position detection device 30 between the robot 2 and the workpiece W according to the fourth embodiment of the present invention. In addition, the same code | symbol is attached | subjected about the structure which is common in 1st Embodiment. As shown in FIG. 7, the relative position detection device 30 includes an industrial robot 2 and a control unit 103 that controls the robot 2. The control means 103 includes a controller 4 connected to the robot 2 and a personal computer 105 that is a computer connected to the controller 4. A touch sensor 10 is attached and fixed to the tool attachment portion 7e of the robot 2. A flat plate 16 is fixed to the tip of the rod 14 of the touch sensor 10. The output of the displacement sensor 15 of the touch sensor 10 is configured to be input to the personal computer 105.

  In this embodiment, the displacement detection direction of the touch sensor 10 and the normal direction of the contact surface 16a of the flat plate 16 are provided so as to coincide with the Z direction of the tool coordinate system. Absent. For example, if the displacement detection direction of the touch sensor 10 does not coincide with the Z direction of the tool coordinate system, a matrix for matching it is measured in advance, and the coordinate system of the touch sensor 10 is used using the matrix. It is preferable to set the personal computer 105 so as to convert to the tool coordinate system.

  A work W is provided in the work range of the robot 2. Three or more targets T each having a contact portion made up of a spherical surface or a cusp are attached to the workpiece W. Specifically, the target T is made of a metal member having a spherical surface portion Ta and a shaft portion Tb protruding downward from the spherical surface portion Ta, and the shaft portion is inserted into three or more reference holes H formed in the workpiece W. Each target T is positioned by inserting Tb. Then, the position of the spherical surface Ta with respect to the workpiece coordinate system with respect to the workpiece W is measured in advance with a three-dimensional measuring instrument or the like.

  Next, a procedure for detecting the relative position between the robot 2 and the workpiece W by the relative position detection device 30 will be described. FIG. 8 is a diagram for explaining a relative position detection method by the apparatus 30 shown in FIG. As shown in FIG. 8, first, the robot 2 is operated by the controller 4 to bring the flat plate 16 into contact with the spherical surface Ta of the target T. At the time of the contact, the rod 14 of the touch sensor 10 can be displaced by the elastic force of the spring 13, and the flat plate 16 moves in the normal direction. Furthermore, since the contact is performed between the spherical surface portion Ta and the flat plate 16, the flat plate 16 and the touch sensor 10 can be made inexpensive with one degree of freedom.

  When the contact surface 16a of the flat plate 16 is brought into contact with the spherical portion Ta of the target T, the position and posture of the tool mounting portion 7d are measured based on the angles of the joints 7a to 7d of the robot 2, and the displacement sensor 15 is used. The output of is also measured. Then, the position and orientation of the tool attachment portion 7 d and the output of the displacement sensor 15 are recorded in the personal computer 105. Next, the posture of the tool 8 is changed by the robot 2, and the measurement and recording of the position and posture of the tool mounting portion 7d and the output of the displacement sensor 15 are performed a plurality of times (the number of times more than the number of unknowns in the simultaneous equation (18) described later). )repeat. At that time, as long as the contact surface 16a of the flat plate 16 contacts the spherical surface portion Ta of the target T, the contact position in the contact surface 16a may be shifted every time. Further, the posture of the flat plate 16 at each time when the flat plate 16 is repeatedly brought into contact with the spherical surface portion Ta is selected so as not to rotate around the same axis.

  Next, the position and orientation of the tool mounting portion 7d obtained for the number of repetitions and the output data of the displacement sensor 15 are used to solve the simultaneous equations (18) described later, whereby the position of the center of the spherical portion Ta of the target T, that is, Then, a component of the target vector bXbc indicating the position and direction of the center of the spherical surface portion Ta in the base coordinate system is obtained. As can be seen from FIG. 8, when each vector is projected onto a line segment in the Z direction in the tool coordinate system, the following Expression 17 is always established regardless of the orientation of the flat plate 16.

Here, symbols and variables in Expression 17 are defined as follows.
“・”: Inner product of vectors
Ntz: Unit vector parallel to the Z direction of the tool coordinate system
bXbc: Target vector (each component is unknown)
bXbt: Vector to the tool attachment (known for each measurement data)
L0: Natural length of touch sensor (length at output 0: either unknown or known)
δL: Touch sensor output (Positive shrinking direction, known for each measurement data)
Rc: radius of curvature of the spherical surface (either unknown or known)
In the tool coordinate system, Equation 17 indicates that the Z position of the center of the spherical surface Ta obtained from the Z component of the target vector bXbt is the Z position of the tool mounting portion 7a, the Z position of the contact surface 16a of the flat plate 16, and the spherical surface portion. It means that it is equal to the Z position of the center of the spherical surface portion Ta obtained from the sum of the curvature radius Rc of Ta.

  FIG. 9 is a view for explaining that the flat plate 16 is brought into contact with the target T in the apparatus 30 shown in FIG. As shown in FIG. 9, when the robot 2 is operated and the posture of the flat plate 16 is changed a plurality of times and measured, Equation 17 can obtain the following simultaneous equations (18) in which the same number as the number of times N is measured. (N is an unknown number).

  The simultaneous equations (18) can be generally arranged as follows.

  X, A, and B are expressed by the following equations 20 to 22 when the natural length L0 of the touch sensor 10 (that is, the initial Z position of the flat plate 16) and the curvature radius Rc of the spherical surface portion Ta are set as unknowns. Is done.

  On the other hand, when both the natural length L0 of the touch sensor 10 and the radius of curvature Rc of the spherical surface portion 8a are set as known, X, A, and B are expressed by the following equations 23 to 25.

 Then, each component of the target vector bXbc is obtained by solving Equation 19.

  According to the above, even if attention is paid only to the Z position that is one direction, the orientation of the touch sensor 10 is changed, the flat plate 16 is brought into contact with the spherical surface Ta of the target T, and the simultaneous equations are solved to solve the components of the target vector. Can be requested. Then, by focusing only on the Z position, the spherical portion Ta of the target T may be brought into contact with any position on the flat plate 16 (the X and Y positions may be deviated from the previous contact position). , Teaching work can be performed roughly. Therefore, the teaching work can be simplified, the working time can be shortened, and the detection accuracy can be improved. Further, if the natural length L0 of the touch sensor 10 (that is, the initial Z position of the flat plate 16) and the radius of curvature Rc of the spherical surface portion Ta are set as unknown numbers, the number of simultaneous equations can be increased by increasing the number of contact, There is no need to know L0 and Rc in advance, and the teaching work can be further simplified.

  In the present embodiment, the contact portion of the target T is the spherical surface portion Ta, but it may be a pointed portion. In this case, if the radius of curvature Rc is treated as zero, the other procedures are the same as described above. In the present embodiment, the touch sensor 10 and the flat plate 16 are used. Instead, the optical area sensor 20 as in the third embodiment may be attached to the tool attachment portion 7e.

(Fifth embodiment)
FIGS. 10A to 10D are diagrams for explaining a relative position detection method according to the fifth embodiment of the present invention. As shown in FIGS. 10A to 10D, in the present embodiment, a positioner 40 that supports a table 41 on which a work is placed with a rotatable drive shaft 42 is used as a measurement object. Then, the target T is attached to the table 41, the table 41 is rotated to move the target T to at least three positions, and the components of the target vectors a1, a2, and a3 at the three positions are obtained. In this way, the movement direction of the positioner 40 (such as the rotation center of the drive shaft 42 and the axial center vector) can be obtained from the components of the target vectors a1, a2, and a3 at the three positions. Since other configurations are the same as those of the fourth embodiment described above, description thereof is omitted.

(Sixth embodiment)
FIGS. 11A to 11C are diagrams for explaining a relative position detection method according to the sixth embodiment of the present invention. As shown in FIGS. 11A to 11C, in this embodiment, the robot 2 is provided so as to be able to travel on a traveling rail 50 installed on the floor surface. The measurement object is the floor on which the traveling rail 50 is installed. The robot 2 is moved to at least two positions on the traveling rail 50, and the components of the target vectors b1 and b2 at the two positions are obtained. In this way, the position and vector of the traveling axis of the robot 2 can be obtained from the components of the target vectors b1 and b2 at the two positions. Since other configurations are the same as those of the fourth embodiment described above, description thereof is omitted.

  As described above, the robot tool position detection method, the robot-to-target relative position detection method, and the devices thereof according to the present invention can easily and accurately determine the tool position and the relative position between the robot and the target. It has an excellent effect that it can be detected, and is useful when applied widely to fields such as industrial robots used in production sites.

It is a mimetic diagram showing the tool position detecting device of the robot concerning a 1st embodiment of the present invention. It is drawing explaining the tool position detection method by the apparatus shown in FIG. (A) shows the contact state to the flat plate of the tool in this invention, (b) is drawing which shows the contact state to the touch sensor of the tool in a comparative example. It is drawing explaining changing a attitude | position with respect to a flat plate in the apparatus shown in FIG. (A) (b) is drawing explaining the contact state to the flat plate of the tool of 2nd Embodiment of this invention. It is a perspective view which shows the optical area sensor of 3rd Embodiment of this invention. It is a schematic diagram which shows the relative position detection apparatus of the robot and workpiece | work of 4th Embodiment of this invention. It is drawing explaining the relative position detection method by the apparatus shown in FIG. It is drawing explaining changing a attitude | position with respect to a target in the apparatus shown in FIG. 7, and making it contact | abut. (A)-(d) is drawing explaining the relative position detection method of 5th Embodiment of this invention. (A)-(c) is drawing explaining the relative position detection method of 6th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tool position detection apparatus 2 Robot 3,103 Control means 7 Arm 7a-7d Joint 7e Tool mounting part 8 Tool 8a Spherical part (tip part)
DESCRIPTION OF SYMBOLS 10 Touch sensor 13 Spring 16 Flat plate 16a Contact surface 20 Optical area sensor 23 Sensing surface 30 Relative position detection apparatus T Target Ta Spherical surface part (contact part)
W Work (object)

Claims (12)

Attach a tool with a tip part consisting of a spherical part or a point to the tool attachment part at the tip of the robot arm,
Set an unknown to the component of the tool vector from the tool attachment to the center of the tip,
Changing the posture of the tool with respect to the plane with respect to the plane, and abutting at least as many times as the number of unknowns,
Based on the joint angle of the arm of the robot at the time of contact, the position of the tool attachment portion at the time of contact is determined,
In a specific coordinate system, the center Z position of the tip obtained from the sum of the Z position of the plane and the radius of curvature of the tip is the Z position of the tool mounting portion and the Z component of the tool vector. A simultaneous equation that means equal to the Z position of the center of the tip obtained from the sum is made at least as many times as the number of unknowns;
A tool position detection method for a robot, wherein the tool vector component is obtained by solving the simultaneous equations. Using a flat plate displaceable in a substantially normal direction and a displacement sensor capable of detecting the displacement of the flat plate,
The plane is composed of a contact surface of the flat plate,
2. The robot tool position detection method according to claim 1, wherein the Z position of the plane is obtained based on an output of the displacement sensor. Using an optical area sensor,
The plane consists of a sensing surface of the optical area sensor,
The robot tool position detection method according to claim 1, wherein the joint angle of the robot arm is detected when the tip of the tool comes into contact with the sensing surface. The Z position of the plane when the tip is not in contact with the plane and the radius of curvature of the tip are further unknowns,
2. The tip is brought into contact with a plane at least as many times as the number of all unknowns by changing the attitude of the tool, and the simultaneous equations are set as many times as at least as many as all unknowns. 4. The robot tool position detection method according to any one of 3 above. A reference tool having a known dimensional shape is attached to the tool attachment portion, the reference tool is moved in the plane, and the reference tool is brought into contact with a plurality of locations on the plane, whereby X and Y positions on the plane are obtained. The correlation between the Z position and the Z position in advance,
Instead of the reference tool, the tool is attached to the tool attachment portion, the tool is brought into contact with the plane, and the X and Y positions in the plane of the contact portion are determined by the position of the detected tool attachment portion and Obtained from the approximate size and shape of the tool,
5. The Z position corresponding to the X and Y positions is obtained from the correlation, and the obtained Z position is substituted into the Z position of the plane in the simultaneous equations. 6. Tool position detection method for robots. Attach a flat member to the tool attachment part at the tip of the robot arm,
Attach a target having an abutting part consisting of a spherical part or a point to a target,
Set an unknown to the component of the target vector indicating the position and direction of the abutment,
Changing the posture of the member with respect to the abutting portion and abutting at least as many times as the number of unknowns;
Based on the joint angle of the arm of the robot at the time of contact, the position of the tool attachment portion at the time of contact is determined,
In a specific coordinate system, the Z position of the center of the contact portion obtained from the Z component of the target vector is the sum of the Z position of the tool mounting portion, the Z position of the plane, and the radius of curvature of the contact portion. A simultaneous equation that means that it is equal to the Z position of the center of the contact portion obtained from
A method for detecting a relative position between a robot and an object, wherein the component of the target vector is obtained by solving the simultaneous equations. A flat plate displaceable in a substantially normal direction and a displacement sensor for detecting the displacement of the flat plate are attached to the tool mounting portion,
The plane is composed of a contact surface of the flat plate,
The method for detecting a relative position between a robot and an object according to claim 6, wherein the Z position of the plane is obtained based on an output of the displacement sensor. Attach an optical area sensor to the tool mounting part,
The plane consists of a sensing surface of the optical area sensor,
The method according to claim 6, wherein the joint angle of the arm of the robot is detected when the sensing surface comes into contact with the target. The Z position of the plane when the plane is not in contact with the target and the radius of curvature of the target are further unknowns,
The surface of the member is changed with respect to the contact portion by changing the posture of the member at least as many times as the number of all unknowns, and the simultaneous equations are set at least as many times as the number of all unknowns. The relative position detection method of the robot and target object in any one of 6 thru | or 8.   The method for detecting a relative position between a robot and an object according to claim 6, wherein the object is a workpiece. A robot to which a tool having a tip portion composed of a spherical surface or a cusp is attached to the tool attachment portion at the tip of the arm;
Control means for controlling the robot,
The control means includes
Set an unknown to the component of the tool vector from the tool attachment to the center of the tip,
Driving the robot to bring the tip into contact with the plane at least as many times as the number of unknowns by changing the attitude of the tool;
Based on the joint angle of the arm of the robot at the time of contact, the position of the tool attachment portion at the time of contact is determined,
In a specific coordinate system, the center Z position of the tip obtained from the sum of the Z position of the plane and the radius of curvature of the tip is the Z position of the tool mounting portion and the Z component of the tool vector. A simultaneous equation that means equal to the Z position of the center of the tip obtained from the sum is made at least as many times as the number of unknowns;
A tool position detecting device for a robot, wherein the tool vector component is obtained by solving the simultaneous equations. A robot to which a member having a flat surface is attached to the tool attachment portion at the end of the arm;
Control means for controlling the robot,
The control means includes
Setting an unknown to the component of the target vector indicating the position and direction of the contact portion of the target having a contact portion comprising a spherical surface or a cusp attached to the object;
Changing the posture of the member with respect to the abutting portion and abutting at least as many times as the number of unknowns;
Based on the joint angle of the arm of the robot at the time of contact, the position of the tool attachment portion at the time of contact is determined,
In a specific coordinate system, the Z position of the center of the contact portion obtained from the Z component of the target vector is the sum of the Z position of the tool mounting portion, the Z position of the plane, and the radius of curvature of the contact portion. A simultaneous equation that means equal to the Z position of the center of the contact portion obtained from
An apparatus for detecting a relative position between a robot and an object, wherein a component of the target vector is obtained by solving the simultaneous equations.

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