JP2002355782A - Working force estimation system and working force estimation method for robot tip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a working force estimation method that can estimate working force at a robot tip without the arrangement of a force sensor in a production line. SOLUTION: The working force estimation method estimates working force at a robot tip operating to bring into contact a first part 7 held at the tip of a robot 6 and a second part 8 placed on a worktable 9. A force sensor arranged in advance under the worktable computes a measured value when the first part 7 held by the robot 6 and the second part 8 are brought into contact. A parameter that satisfies a linear relation between the measurement and a difference between a target command position and a feedback position of the robot 6 is extracted, and the parameter is stored in advance in a material characteristic storing means 2 for each material of the first part 7 and second part 8. In an automatic operation, the difference between the target command position and feedback position of the robot 6, and the parameter corresponding to the material of the first part 7 and second part 8 are read out from the material characteristic storing means 2, and working force at the robot tip is estimated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device and method for estimating the acting force at the tip of a robot.

[0002]

2. Description of the Related Art In a conventional force estimating apparatus for estimating the acting force at the tip of a robot, there is a method and apparatus for estimating the force by installing a force sensor at the tip. In this method, since the force sensor is arranged at the robot tip, the load capacity of the robot is reduced by the weight of the force sensor, and the distance from the tool tip to the robot flange is increased, and the rigidity of the tool support mechanism is increased. There is a problem that resonance accompanying the decrease is likely to occur. Therefore, in order to solve the above two problems, a method and apparatus have been invented in which a force sensor is installed on the workbench side and the output is used to control the robot. Among them, Japanese Patent Application Laid-Open No. 09-216185 discloses a robot control system that performs force control by feeding back measurement data of a force sensor installed on a workbench. Hereinafter, this known robot control system will be described with reference to the drawings.

FIG. 6 is a diagram showing a basic configuration of a known robot control system. In FIG. 6, the robot S1
Is the coordinate system ΣR, and the robot tool S1a is the coordinate system Σ.
t, the coordinate system Σc on the surface of the workpiece W, and the force sensor S
3 is provided with a coordinate form ΔS. The robot system α includes a robot S1, a workbench S2, a force sensor S3 functioning as force recognizing means, and a robot control device S4 functioning as a control system of the robot motion. In the control device as described above, the tool S1a of the robot S1 is
, The force sensor S3 recognizes the interaction force generated when the tool S1a of the robot S1 comes into contact with the workpiece W through the workbench S2. Then, the measurement data of the force sensor S3 is transferred to the robot control device S4, and the robot control device S4 feeds back the adjustment operation data for comparison and output with the standard set target value based on the measurement data of the force sensor S3. The force control of S1 is performed. As described above, since the force sensor S3 is provided at the lower part of the work table S2 instead of the robot S1, the load capacity of the robot S1 is not reduced, and the rigidity of the tool support mechanism is not reduced. The occurrence of resonance at the time of contact with a rigid environment can be suppressed.

[0004]

However, even in the above-mentioned conventional robot control device, a force sensor must always be separately installed on the workbench side, resulting in cost and unexpected interference of parts on the production line. It is not practical due to problems such as failure due to overload on the force sensor. Accordingly, an object of the present invention is to provide a practical acting force estimating apparatus for estimating the acting force of a robot tip without installing a force sensor in an actual production line.

[0005]

In order to solve the above problem, an apparatus for estimating the acting force at the tip of a robot according to claim 1 is provided.
The working force estimating device for a robot tip for estimating the acting force of a robot tip for performing a contact work between a first component gripped by the robot tip and a second component installed on a worktable, the device being installed below the worktable A force sensor, a measurement value of the force sensor when the first component and the second component are in contact,
Material characteristic coefficient generating means for extracting the parameter for establishing a linear relationship between the target command position of the robot and the difference between the feedback position of the robot, and a target component setting for inputting the materials of the first component and the second component Means, and material property storage means for storing parameters output from the material property coefficient generation means for each material input by the target component setting means, thereby enabling teaching to the action force estimating apparatus. It is a feature. According to a second aspect of the present invention, in the apparatus for estimating the acting force of the robot tip for estimating the acting force of the robot tip which performs a contact work between the first component gripped by the robot tip and the second component installed on the worktable, A linear relationship between a measurement value of a force sensor installed below the work table when the first component and the second component come in contact with each other and a difference between a target command position of the robot and a feedback position of the robot. A material property storing means for storing the parameters to be established for each material of the first part and the second part; a difference between a target command position of the robot and a feedback position of the robot; and an output of the material property storing means. And an acting force estimating means for estimating the acting force of the robot tip, thereby enabling the same automatic driving as in the case where the force sensor is provided. .

Further, according to a third aspect of the present invention, the working force of the robot tip for estimating the working force of the robot tip for performing a contact work between the first component gripped by the robot tip and the second component installed on the worktable. In the estimating device, at the time of teaching of the acting force estimating device, a force sensor is installed under the work table to identify parameters necessary for the acting force estimation,
Establishing a linear relationship between a measured value of the force sensor when the first component and the second component gripped by the robot come into contact with each other and a difference between a target command position of the robot and a feedback position of the robot. Material characteristic coefficient generating means for extracting parameters, target part setting means for inputting the materials of the first part and the second part, and parameters output from the material characteristic coefficient generating means input by the target part setting means Material property storage means for storing for each material that has been performed, during automatic operation, the measured value of the force sensor when the first component and the second component gripped by the robot contact, The parameter for establishing a linear relationship between the target command position of the robot and the difference between the feedback position of the robot is set for each material of the first part and the second part. A material property storage means for storing, and an action force estimation means for estimating an action force of the robot tip from a difference between a target command position of the robot and a feedback position of the robot, and an output of the material property storage means. It is characterized by having. According to the apparatus for estimating the acting force at the robot tip having the above configuration, highly accurate estimation is possible because parameters for establishing a linear relationship for each material are previously stored. Since the acting force can be estimated from the target command position of the robot and the feedback position of the robot which are normally attached, a force sensor is not required, the load capacity of the robot is not reduced, and the rigidity of the tool support mechanism is reduced. The present invention can provide a practical device for estimating the acting force at the tip of a robot that does not reduce the force. According to a fourth aspect of the present invention, in the device for estimating the acting force of the robot tip according to the second or third aspect, the acting force estimating means comprises a difference between a target command position of the robot and a feedback position of the robot. The present invention is characterized in that the acting force of the robot tip is estimated from a linear polynomial. According to this acting force estimating device, since approximation is made by a linear polynomial, highly accurate estimation can be easily performed by increasing the order. According to a fifth aspect of the present invention, in the apparatus for estimating the acting force of the robot tip according to the first or third aspect, the material characteristic coefficient generating means outputs the output of the force sensor at time t to Sfi (t) (i =
x, y, z), and the difference between the command position and the feedback position of the robot is Ei (t) (i = x, y, z).
The coefficient is calculated so that the sum of the squares is minimized.

(Equation 2) According to this acting force estimating apparatus, the minimum 2
Since the coefficient is calculated by the multiplication method, the calculation can be easily and quickly obtained.

According to a sixth aspect of the present invention, there is provided a method for estimating the acting force of a robot tip, wherein the acting force of a robot tip for performing a contact work between a first component gripped by the robot tip and a second component mounted on a worktable is determined. In the method of estimating the acting force of the robot tip, the first part gripped by the robot and the first part grasped by the robot with a force sensor installed under the work table to identify parameters necessary for the acting force estimation. Second
Obtain a measurement value when a part comes into contact, extract a parameter that establishes a linear relationship between a target command position of the robot and a difference between a feedback position of the robot, and extract the extracted parameter with the first part and the first part. It is stored in advance for each material of the second part, and during automatic operation, the difference between the target command position of the robot and the feedback position of the robot and the material for the first part and the second part are stored in advance. The present invention is characterized in that the acting force of the robot tip is estimated from the certain parameter. According to the acting force estimating method having the above configuration, highly accurate estimation is possible because parameters for establishing a linear relationship for each material are stored in advance, and a force sensor is not required and the payload of the robot is not reduced. In addition, it is possible to provide a practical robot force acting estimating device that does not reduce the rigidity of the tool supporting mechanism.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 and FIG. 2 are views showing the configuration of an apparatus for estimating the acting force at the tip of a robot according to the present invention. FIG.
FIG. 2 is a diagram showing a configuration at the time of teaching of the acting force estimation device, and FIG.
FIG. 3 is a diagram showing a configuration during automatic driving. In FIG. 1, 1
Is a target part setting means, 2 is a material property storage means, 4 is a position control means, 5 is a joint drive amplifier, 6 is an articulated robot, 7 is a first part, 8 is a second part, 9 is a worktable, Reference numeral 10 denotes a force sensor, and 11 denotes a material characteristic coefficient generating unit. The position of the articulated robot 6 performing the work is controlled by the position control means 4 and the joint drive amplifier 5. The tip of the robot 6 holds the first component 7 and is pressed against the second component 8 installed on the workbench 9. As a coordinate system necessary for controlling the robot 6, a coordinate system Σw is installed at the base of the robot 6 and a coordinate system Σp is installed at the tip of the first part 7, and the position of the coordinate system Σp with respect to the coordinate system Σw is (x, y, z)
Notation.

In the acting force estimating apparatus according to the present invention, at the time of teaching, a force sensor 10 is installed between the second part 8 and the work table 9 as shown in FIG. When the gripped first component 7 contacts the second component 8, the force sensor 10 measures the acting force. The output measured by the force sensor 10 is input to the material characteristic coefficient generating means 11, and the difference between the target command position and the feedback position of the robot 6 is also input to the material characteristic coefficient generating means 11, where the output of the force sensor 10 is output. Then, parameters (coefficients (a0, a1, a2, a3)) for establishing a linear relationship between the target command position of the robot and the difference between the feedback positions are calculated. This calculation result is stored in the material property storage means 2. On the other hand, the target component setting means 1 sets various materials of the first component 7 and the second component 8,
The coefficients (a0, a1, a2, a3) for each material are stored in the material characteristic storage means 2. Note that the material characteristic coefficient generation means 11
The output of the force sensor 10 at the time t is Sfi (t) (i = x, y, z),
Assuming that the difference between the command position of the robot 6 and the feedback position of the robot 6 is Ei (t) (i = x, y, z), 2 of the following equation (1) is obtained.
The coefficients (a0, a1, a2, a3) are calculated so that the sum of the squares is minimized.

(Equation 3) FIG. 3 shows the material and the coefficients (a0, a1,
a2, a3) (iron, aluminum). The coefficients of iron are a0 = 0.2, a1 = 1.2, a2 = 0.1, a3 = 0.
01. Also, each coefficient of aluminum is a0 = 0.12,
a1 = 1.0, a2 = 0.03, and a3 = 0.02. Such coefficients are stored in the material characteristic storage means 2 together with the material. In this example, the order is approximated up to the third order.
If more accurate estimation is required, the order may be increased.

FIG. 2 is a diagram showing a configuration when the acting force estimating apparatus automatically operates using the material characteristics obtained as shown in FIG. In FIG. 2, reference numeral 1 denotes a target component setting unit;
Is a material characteristic storage means, 3 is an action force estimating means, 4 is a position control means, 5 is a joint drive amplifier, 6 is an articulated robot, 7 is a first part, 8 is a second part, and 9 is a work table. is there.
The position of the articulated robot 6 performing the work is controlled by the position control means 4 and the joint drive amplifier 5. As shown in FIG. 2, the apparatus for estimating the acting force at the time of automatic driving includes a target component setting unit 1, a material characteristic storage unit 2, a difference between a target command position of the robot 6 and a feedback position of the robot 6, and a material characteristic storage unit. And an action force estimating means 3 for estimating an action force from a linear polynomial, which will be described later, composed of the outputs of the two. Next, the operation during automatic driving will be described. When the first part 7 is gripped by the tip of the robot 6 and the first part 7 is pressed against the second part 8 on the work table 9, a large difference between the target command position of the robot 6 and the feedback position of the robot 6 is obtained. (A deviation Ei (i = x, y, z indicates each direction)) occurs. Therefore, the difference between the target command position of the robot 6 and the feedback position of the robot 6 is input to the acting force estimation means 3. The acting force estimating means 3 estimates the acting force Fi (indicating each direction by i = x, y, z) using a third-order linear polynomial of the following estimation formula (2).

(Equation 4) At this time, the coefficients (a0, a1, a2, a3) of the estimation formula (Equation 2) are transmitted from the material property storage means 2 to the acting force estimation means 3 according to the material set by the target component setting means 1 at the time of teaching. The input values are stored in the material property storage means 2 as shown in FIG. Therefore, the apparatus for estimating the acting force at the robot tip according to the present embodiment calculates the coefficient stored in the material property storage means 2 once, and thereafter calculates the coefficient stored in the material property storage means 2 and the coefficient. Since the force acting on the tip of the robot 6 is estimated via the acting force estimating means 3 from the difference between the target command position 6 and the feedback position of the robot 6, there is no need to install a force sensor in the actual production line.

[0011]

Here, there will be described an embodiment for estimating the acting force (contact force) when the robot grips the insulator and makes contact with the metal block by using the acting force estimating device of the robot tip of the present invention. Fig. 4 shows the bolt part 4 of the insulator gripped by the robot
FIG. 3 is an experimental view for estimating a contact force when the contact 1 comes into contact with the metal block 40, and estimates a contact force when the bolt portion 41 of the insulator contacts the metal block 40 from three directions of W, Y and Z. is there. In the impedance control, the following relational expression (A) is assumed between the contact force, the target position of the robot tip, and the current position of the robot tip.

(Equation 5) Here, assuming that the operating speed change is small and the influence of the terms of the inertia matrix and the damping coefficient matrix on the contact force is extremely small,
The following equations (3) to (8) hold.

(Equation 6) At this time, if the coefficients Kx, Ky, Kz, bx, by, and bz are known before the operation, the contact force at the time of contact can be estimated from the positional deviation. Coefficients Kx, Ky, K
z, bx, by, and bz were identified by the least squares method as shown in the following equations (9) to (17) from data measured using a force sensor in advance.

(Equation 7) [Experimental Results] FIG. 5 shows a comparison between the estimated contact force of the case shown in FIG. 4 and the measured contact force measured by the force sensor.
Is shown in FIG. 5A is a diagram of actual measured values (dotted line) showing the contact force in the X-axis direction and an estimated value (solid line) according to the present invention, and similarly, FIG. 5B is a diagram of the Y-axis direction, and FIG. c) is a diagram showing each contact force in the Z-axis direction. In each figure,
The vertical axis indicates the contact force (kgf (Note: 1 kgf @ 9.8 N))
The horizontal axis is time (seconds). In FIG. 5A, it can be seen that the measured value (approximately 7 kgf @ 69 N) up to about 5 seconds after contact and the estimated value almost overlap. FIG.
In (b), the measured value up to about 4 seconds after contact (about 4
kgf ≒ 39N) and the estimated value almost overlap. Also, in FIG. 5 (c), it can be seen that the measured value (about 5 kgf @ 49 N) and the estimated value almost up to about 6 seconds after contact are almost the same. As described above, as a result of the experiment, it can be seen that the error between the measured value and the estimated value is large when the contact force is large, but is relatively consistent when the contact force is small. For example, in a sleeve insertion operation such as an operation of inserting a sleeve from a wire end, 10 kgf (about 98 kgf) is used.
N) Since the insertion operation is possible if the following contact force can be detected, the estimation device and method of the present invention are effective for such a sleeve insertion operation.

[0012]

As described above, according to the apparatus for estimating the acting force at the tip of a robot of the present invention, it is possible to perform highly accurate estimation because parameters for establishing a linear relationship for each material are stored. Furthermore, once the parameters are identified, the acting force can be estimated from the target command position of the robot and the feedback position of the robot that are normally attached to the existing robot, so that a force sensor is not required and the robot can be used. A practical apparatus for estimating the acting force at the tip of a robot can be provided without reducing the carrying weight and without reducing the rigidity of the tool support mechanism. In addition, since the approximation is made by using a linear polynomial, it is possible to easily perform highly accurate estimation by increasing the order.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration at the time of teaching, out of a diagram showing a basic configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration at the time of automatic driving in a diagram showing a basic configuration of the embodiment of the present invention.

FIG. 3 is a diagram showing a storage example of a material property storage means of the present invention.

FIG. 4 is an experimental diagram for estimating a contact force when a bolt portion of an insulator gripped by a robot contacts a metal block.

5A and 5B are diagrams showing an estimated contact force value of the experimental result of FIG. 4 and an actual measured contact force value measured by a force sensor, wherein FIG. 5A is an X-axis direction, FIG. 5B is a Y-axis direction, FIG. 5C is a diagram showing each contact force in the Z-axis direction.

FIG. 6 is a diagram illustrating a configuration of a conventional acting force estimating device for estimating the acting force of a robot tip.

[Description of Signs] 1 target part setting means 2 material property storage means 3 acting force estimation means 4 position control means 5 joint drive amplifier 6 robot 7 first part 8 second part 9 work table 10 force sensor 11 material characteristic coefficient generation means S1 Robot S1a Tool S2 Work table S3 Force sensor S4 Robot controller

Continued on the front page F term (reference) 2F051 AA10 AC07 BA07 3C007 AS06 KS34 KV04 KW03 KX19 LU06 MT04

Claims (6)

[Claims] 1. An apparatus for estimating the acting force of a robot tip for performing a contact operation between a first component held on the tip of a robot and a second component installed on a worktable, wherein: A linear relationship between a force sensor installed below, a measurement value of the force sensor when the first component and the second component come into contact, and a difference between a target command position of the robot and a feedback position of the robot. Material characteristic coefficient generating means for extracting the parameters to be satisfied; target part setting means for inputting the materials of the first part and the second part; and parameter output from the material characteristic coefficient generating means for the target part setting. A material property storage means for storing for each material input by the means, whereby teaching to the acting force estimation device is enabled. Bet the tip of the acting force estimation device. 2. The apparatus for estimating the acting force of a robot tip for performing a contact work between a first component held on the tip of a robot and a second component installed on a worktable, wherein the first component is And the parameter that establishes a linear relationship between the measurement value of the force sensor installed below the work table when the second part comes into contact with the robot and the difference between the target command position of the robot and the feedback position of the robot. The first
A material property storage means for storing for each material of the part and the second part; a difference between a target command position of the robot and a feedback position of the robot; and an output of the material property storage means, the acting force of the robot tip. And a force estimating means for estimating the force, whereby the same automatic operation as in the case where the force sensor is provided is enabled. 3. The apparatus for estimating the acting force of a robot tip for performing a contact operation between a first component held on the tip of the robot and a second component installed on a worktable, wherein the acting force estimating device includes: At the time of teaching the device, a force sensor is installed under the work table to identify parameters necessary for the action force estimation, and when the first component and the second component gripped by the robot come into contact with each other. Material characteristic coefficient generating means for extracting the parameter that establishes a linear relationship between the measured value of the force sensor and the difference between the target command position of the robot and the feedback position of the robot; the first component and the second component A target component setting means for inputting the material of the component; and a material for storing a parameter output from the material characteristic coefficient generating means for each material input by the target component setting means. Material characteristic storage means, during automatic operation, the measured value of the force sensor when the first component and the second component gripped by the robot come into contact with each other, and a target command position of the robot Material property storage means for storing, for each material of the first part and the second part, the parameter for establishing a linear relationship with a difference between the feedback positions of the robot; a target command position of the robot and a feedback position of the robot A working force estimating means for estimating the working force of the robot tip from the difference between the two and the output of the material property storage means. 4. The operating force estimating means estimates the operating force of the robot tip from a linear polynomial consisting of a difference between a target command position of the robot and a feedback position of the robot. 4. The apparatus for estimating the acting force at the robot tip according to 3. 5. The method according to claim 1, wherein the material characteristic coefficient generation unit generates a time t
The output of the force sensor is Sfi (t) (i = x, y, z), and the difference between the command position and the feedback position of the robot is Ei (t).
4. The method according to claim 1, wherein when (i = x, y, z), a coefficient is calculated such that the sum of squares of the following equation (1) is minimized. apparatus. (Equation 1) 6. The method for estimating the acting force of a robot tip for estimating the acting force of a tip of a robot performing a contact operation between a first component held on the tip of the robot and a second component installed on a worktable, the method of estimating the acting force. With a force sensor installed under the work table to identify necessary parameters, a measurement value when the first part and the second part gripped by the robot come into contact with each other is obtained, A parameter that establishes a linear relationship between a target command position and a difference between a feedback position of the robot is extracted, and the extracted parameter is stored in advance for each material of the first part and the second part, and is automatically stored. During operation, the difference between the target command position of the robot and the feedback position of the robot, and the parameters stored in advance for each material of the first part and the second part are used. And estimating the acting force of the robot tip.