JP6729084B2 - Correction device, correction method, and correction program - Google Patents

Description

The present invention relates to a correction device, a correction method, and a correction program.

Articulated robots are used as industrial robots. The industrial robot is used after the tip positions of articles such as tools and parts are determined with high accuracy. However, during operation, the link part may thermally expand due to its own heat generation, environmental heat, and the like. In this case, the positioned tip of the article is displaced. Therefore, a technique for correcting the positional deviation of the tip of the article is disclosed.

For example, a technique of sensing a temperature and calculating a correction amount has been disclosed (for example, see Patent Document 1). In addition, a technique for calibrating each time a displacement occurs is disclosed (for example, see Patent Document 2).

JP-A-63-144980 JP-A-5-261686

However, it is costly to provide a temperature sensor for an industrial robot. In addition, it is troublesome to try to calibrate each time a displacement occurs.

In one aspect, an object of the present invention is to provide a correction device, a correction method, and a correction program capable of correcting the positional deviation with simple processing.

In one aspect, the correction device includes a sensor that detects time series data of a predetermined position of the arm robot in a predetermined posture, or time series data of a predetermined position of an article held by the arm robot in the predetermined posture, and the sensor. using the time series data that is detected, the an estimation unit for estimating a positional deviation amount at a predetermined position, based on the positional deviation amount in which the estimating unit has estimated to correct the positional displacement of the arm robot correcting unit And the estimation unit does not use time-series data in which the deviation between the reference position and the position detected by the sensor is less than a first threshold value when estimating the positional deviation amount . In another aspect, the correction device includes a sensor that detects time series data of a predetermined position of the arm robot in a predetermined posture, or time series data of a predetermined position of an article held by the arm robot in the predetermined posture, and the sensor. An estimation unit that estimates the amount of positional deviation in the predetermined posture using the detected time series data, and a correction unit that corrects the positional deviation of the arm robot based on the amount of positional deviation estimated by the estimation unit. And the correction unit corrects the positional deviation of the arm robot when the deviation between the reference position and the position detected by the sensor is equal to or more than a second threshold value.

The positional deviation can be corrected by a simple process.

(A) is a figure which illustrates the whole structure of a robot system, (b) is a functional block diagram of a calculating part, (c) is a figure which illustrates the flow of a process in a robot system. It is a figure which illustrates an arm robot. It is a figure which illustrates the time series data stored in the calculating part. (A)-(c) is a figure which illustrates operation|movement of an arm robot. It is a flowchart which illustrates the process which a robot system performs. (A) is a block diagram for explaining the hardware constitutions of a computing part, and (b) is a figure which illustrates a work system concerning a modification.

Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1A is a diagram illustrating an overall configuration of the robot system 100. As illustrated in FIG. 1A, the robot system 100 includes an arm robot 10, a control unit 20, a sensor 30, a calculation unit 40, and the like. FIG. 1B is a functional block diagram of the calculation unit 40. As illustrated in FIG. 1B, the calculation unit 40 functions as a storage unit 41, an estimation unit 42, and a correction value calculation unit 43.

The arm robot 10 is a robot including at least one link. In the present embodiment, as an example, the arm robot 10 is a robot in which a plurality of links are connected by one or more joints. The control unit 20 controls the posture, movement, and the like of the arm robot 10. The sensor 30 is a sensor that detects a predetermined position of the arm robot 10 in a predetermined posture or a predetermined position of the article 50 held by the arm robot 10 in the predetermined posture, and is, for example, a camera. The article 50 is a tool, a part, or the like. In the present embodiment, as an example, the sensor 30 detects the tip position of the article 50 held by the arm robot 10 at the tip. The calculation unit 40 performs a calculation for correcting the displacement of the arm robot.

FIG. 1C is a diagram illustrating a flow of processing in the robot system 100. As illustrated in FIG. 1C, the control unit 20 controls the operation of the arm robot 10 by transmitting control data to the arm robot 10. The sensor 30 detects the tip position of the article 50 held by the arm robot 10 in a predetermined posture as a sensor value. For example, a Time of Flight method, a stereo vision method, or the like can be used. The detected sensor value is transmitted to the calculation unit 40.

The storage unit 41 stores the received sensor value. The estimation unit 42 estimates the position shift amount of the arm robot 10 based on the stored sensor value. The correction value calculation unit 43 calculates a correction value for suppressing the positional deviation based on the estimated positional deviation amount, and transmits the correction value to the control unit 20. The control unit 20 transmits control data for correcting the positional deviation of the arm robot 10 to the arm robot 10 based on the received correction value.

FIG. 2 is a diagram illustrating the arm robot 10. As illustrated in FIG. 2, the arm robot 10 according to the present embodiment is a multi-joint robot having a structure in which a plurality of links 11 are connected by joints 12. The arm robot 10 is fixed to a fixed place (base) such as a ceiling, a floor, or a wall. The link is a non-deformable portion forming the arm robot 10. The link length of the link connected to the base is the length from the base to the joint. The link length of a link connected between joints is the length from joint to joint. The link length of the tip link is the length from the joint to the tip. When the link at the tip holds the article 50, the link length of the link at the tip may be from the joint to a predetermined position (for example, the tip) of the article 50.

As illustrated in FIG. 2, the tip position p _E,0 of the arm robot 10 can be represented by the sum of the vectors p _i+1,i having the base as the origin and having the link length and the link direction. In the present embodiment, the tip position P _E,0 is the tip position of the article 50. i is the number of the link allocated from the base side. That is, the tip position p _E,0 can be expressed by the following equation (1).

When the temperature of the arm robot 10 changes according to heat generation of the arm robot 10 itself, environmental heat, or the like, the link length changes. For example, if the temperature change value is ΔT and the linear expansion coefficient of the i-th link is α _i , the vector p _i+1,i of the i-th link changes as in the following equation (2).

In this way, when the temperature of the arm robot 10 changes, the tip position shifts. In this case, a problem may occur in the work by the arm robot 10. Therefore, it is preferable to correct the positional deviation of the arm robot 10. According to the above formula (2), if the expansion rate Δa _i (=α _i ΔT _i ) can be estimated, the positional deviation amount can be estimated. Therefore, in the present embodiment, the displacement of the arm robot 10 is corrected by estimating the expansion rate Δa _i .

Specifically, the sensor 30 detects the tip position of the article 50 in a predetermined posture before fitting the article 50 to the work 60. The sensor 30 detects the tip position of the article 50 each time the arm robot 10 takes the posture. The calculation unit 40 stores time-series data of the detected tip position of the article 50. FIG. 3 is a diagram exemplifying time-series data stored in the calculation unit 40. As illustrated in FIG. 3, in the time series data, the tip position of the article 50 is associated with time (t_1, t_2,... ).

Next, the calculation unit 40 estimates the expansion rate Δa _i from the stored time series data and estimates the link length of each link. Next, the calculation unit 40 calculates a correction value for the tip position of the article 50 from the estimated link length. Next, the control unit 20 corrects the positional deviation by correcting the operation and posture of the arm robot 10 based on the calculated correction value. The details will be described below.

4A to 4C are diagrams illustrating the operation of the arm robot 10. As illustrated in FIG. 4A, the gripping portion provided at the tip of the arm robot 10 grips the article 50 (operation 1). Next, as illustrated in FIG. 4B, the arm robot 10 moves the article 50 in front of the sensor 30 and takes a predetermined posture (operation 2). The sensor 30 detects the tip position of the article 50 after the arm robot stops in the predetermined posture. Next, as illustrated in FIG. 4C, the arm robot 10 fits the article 50 into the work 60 (operation 3). By repeating FIG. 4A to FIG. 4C, it is possible to acquire time-series data of the tip position of the article 50.

Here, when the sensor 30 detects the tip position p _E,0 of the article 50, the control unit 20 controls the arm robot 10 so that the attitude of the arm robot 10 is the predetermined attitude. That is, when detecting the tip position _{p E, 0} of the article 50 by the sensor 30, tip position _{p E, 0} represented by the above formula (1) should not change. However, when the temperature of the arm robot 10 changes, the tip position p _E,0 is displaced. The positional deviation amount Δp _{E,0 in} this case can be expressed by the following equation (3).

Elongation .DELTA.a _i is a function of time t, the time of occurrence of heat in the i-th link _{t i,} coefficients _{A i,} and the heat transfer coefficient tau _i. That is, the elongation rate Δa _i is a function of the parameter related to heat generation. The extension rate Δa _i can be expressed by the following equation (4). Since the time t is an explanatory variable, to be estimated value, the heat generation time t _i, the coefficient A _i, and the heat transfer coefficient tau _i. Since the until heat is generated no change in elongation Δa _i, t <t _i In .DELTA.a _i is zero.

The residual sum of squares E of the positional deviation amount Δp _E,0 with respect to the time-series data can be expressed by the following equation (5). The non-linear least squares method for the residual sum of squares E makes it possible to estimate the heat generation time t _i , the coefficient A _i , and the heat transfer coefficient τ _i . In addition, "n" represents the number of links. “N” is the number of time series data.

When the above-mentioned nonlinear least squares method is naively executed, in order to determine the heat generation time t _i , the coefficient A _i , and the heat transfer coefficient τ _i (i=0, 1, 2,..., N), A sufficient number of time series data is required. Since it may be necessary to correct the positional deviation before the sufficient number of time-series data is obtained, the heat generation time t _i , the coefficient A _i , and the heat transfer coefficient τ _i are estimated according to the number of time-series data. The method may be divided depending on cases.

For example, when the number of time-series data is 1 to 2, A _i may be common to all i and τ _i may be infinite. Specifically, Δa _i =A may be set. In this case, the estimated value is limited to the coefficient A only. That is, only one parameter needs to be estimated. Thereby, the estimation error can be suppressed even if a sufficient number of time series data is not obtained.

Then, when the when the sequence number of data is 3-5, all i in heat generation time t _i, the coefficient A _i, and the heat transfer coefficient tau _i may be common. Although there are three estimated values, it is premised that each estimated value does not change, so that the estimation error can be suppressed.

Next, when the number of time-series data is 6 to 8, the heat generation time t _i , the coefficient A _i , and the heat transfer coefficient τ _i may be common to each of i and odd. Next, when the number of time-series data is 9 to 11, i may be divided into three modes, and the heat generation time t _i , the coefficient A _i , and the heat transfer coefficient τ _i may be common in each mode. .. Hereinafter, similarly, if the number of time-series data is 12 to 14, it may be divided into 4 and if 3n to 3n+2, it may be divided into n. When the number of time-series data is 3n+3 or more, the heat generation time t _i , the coefficient A _i , and the heat transfer coefficient τ _i (i=0, 1, 2,..., N) may be estimated.

Thus, the smaller the number of time-series data, the less parameters need to be estimated, and the larger the number of time-series data, the more parameters need to be estimated. In this case, the parameter estimation error can be suppressed even if sufficient time series data is not stored.

Next, the time-series data is obtained each time the tip position p _E,0 of the article 50 is confirmed by the sensor 30, but it is necessary to correct the positional deviation only when the positional deviation occurs. Therefore, it is preferable to detect the positional deviation. For example, as a method of defining the positional deviation, the initial positional data is used as a reference, and the subsequent time-series data whose distance from the reference is equal to or greater than a threshold value (for example, a predetermined number of times the error of the sensor 30 or more) is displaced. May be defined as data. As the predetermined multiple, for example, double or the like can be used. Further, the positional deviation may be corrected when the positional deviation reaches a predetermined magnitude larger than the predetermined multiple times. The predetermined size depends on the size of the arm robot 10 and required accuracy, but is, for example, 0.1 mm. The above-mentioned estimation may be executed according to the number of time-series data when the position shift occurs. After the correction, all the time-series data may be erased, the initial position data may be set again as a reference, and the process may be repeated thereafter.

Next, when a monocular camera is used as the sensor 30, only position data projected on a two-dimensional plane can be obtained. On the other hand, if the direction of the positional deviation is known in advance, it is possible to restore the ternary positional deviation data from the two-dimensional positional deviation data, and even the one-dimensional positional deviation data. Is possible. Therefore, before executing the estimation calculation, the displacement data may be three-dimensionally restored by using the displacement direction obtained from the immediately preceding estimation.

For example, when the number of time-series data when the position shift occurs is 1 to 6, since Δa _i is common to all i when the number of time-series data is 1 to 5, the position shift direction is expressed by the following formula ( It can be defined as parallel to p obtained in 6). Note that “p” is a vector extending from the base of the arm robot 10 to the tip. Since the immediately preceding estimated value Δa _i is not necessary, it can be applied even if the number of time series data is 1.

When the number of time-series data when the positional deviation occurs is 1 to 7, it may be defined as parallel to Δp _E,0 obtained by the following equation (7) calculated from Δa _i obtained in the previous estimation. it can.

FIG. 5 is a flowchart illustrating a process executed by the robot system 100. As illustrated in FIG. 5, the control unit 20 controls the arm robot 10 to perform the operation 1 of FIG. 4A (step S1). Next, the control unit 20 controls the arm robot 10 to perform the operation 2 of FIG. 4B (step S2). Next, the calculation unit 40 uses the detection result of the sensor 30 to acquire the tip position p _E,0 according to the above equation (1) (step S3).

Next, the calculation unit 40 determines whether or not the acquisition of the tip position p _E,0 is the first time (step S4). When it determines with "Yes" in step S4, the calculating part 40 sets the said tip position pE _,0 to a reference value (step S5). Next, the control unit 20 controls the arm robot 10 to perform the operation 3 in FIG. 4C (step S6). Next, the control unit 20 determines whether or not a predetermined number has looped (step S7). When it is determined as "No" in step S7, the process is repeated from step S1. When it is determined to be “Yes” in step S7, the execution of the flowchart ends.

When it is determined to be “No” in step S4, the calculation unit 40 determines whether or not the sensor 30 is a monocular camera (step S8). When it is determined to be “Yes” in step S8, the calculation unit 40 performs three-dimensionalization according to the number of acquired time series data (step S9). After execution of step S9 or when it is determined to be "No" in step S8, the calculation unit 40 calculates the distance Δp _E,0 from the reference value of the tip position acquired in step S3 (step S10).

Next, the calculation unit 40 determines whether or not the distance Δp _E,0 calculated in step S10 is larger than a predetermined number times (for example, twice) the measurement error of the sensor 30 (step S11). When it is determined as "No" in step S11, step S6 is executed. When it is determined to be “Yes” in step S11, it is determined whether or not the distance Δp _E,0 calculated in step S10 is equal to or larger than a predetermined size larger than the predetermined multiple (step S12). When it is determined to be “No” in step S12, the calculation unit 40 stores the distance Δp _E,0 calculated in step S10 (step S13). Then, step S6 is executed. When it is determined to be “Yes” in step S12, the calculation unit 40 calculates the correction value according to the number of stored time-series data. The control unit 20 corrects the positional deviation of the arm robot 10 according to the correction value (step S14). After the execution of step S14, the arithmetic unit 40 performs initialization by deleting the stored time-series data. Then, the execution of the flowchart ends.

According to the present embodiment, in order to estimate the positional deviation amount in the predetermined posture by using the time series data of the predetermined position of the arm robot or the predetermined position of the gripped article detected by the sensor when the predetermined posture is taken The positional deviation can be corrected by simple processing. Since it is not necessary to use the temperature sensor, the cost can be reduced. Further, since it is not necessary to perform the calibration every time the position shift occurs, it does not take time and effort. Further, normally, the position of the article is confirmed by a camera or the like in order to confirm the position of the gripped tool. Since the sensor value in this case can be used for the estimation of the positional deviation amount, it is not necessary to newly acquire the sensor value for application of the present embodiment.

Also, the number of parameters that need to be estimated may be changed according to the number of time-series data. For example, the smaller the number of time-series data, the less parameters need to be estimated, and the larger the number of time-series data, the more parameters need to be estimated. In this case, the parameter estimation error can be suppressed even if sufficient time series data is not stored.

In addition, the capacity can be reduced by not using the time-series data in which the deviation between the tip position p _E,0 detected by the sensor 30 and the reference position is less than the threshold value. Moreover, the amount of calculation can be reduced. When the deviation between the tip position p _E,0 detected by the sensor 30 and the reference position is equal to or greater than the threshold value, the amount of calculation can be reduced by correcting the positional deviation.

In the above example, the sensor 30 detects the tip position of the article 50, but the invention is not limited to this. For example, another position of the article 50 may be detected, or any position of the link of the arm robot 10 may be detected. However, it is preferable to detect the tip position of the arm robot 10 or the tip position of the article 50 because the positional deviation amount of the tip position of the arm robot 10 or the tip position of the article 50 becomes large. Further, when the links are extended in a straight line, the expansion and contraction of the links are added without canceling each other, and the positional deviation becomes the largest. Therefore, it is more preferable to detect the tip position of the arm robot 10 when each link is straightened and the tip position of the article 50. Also from the viewpoint of length measurement theory (Abbe's principle), it is preferable to detect the tip position or the tip position of the article 50 in a state where each link is extended in a straight line.

In the above example, the sensor 30 functions as an example of a sensor that detects the predetermined position of the arm robot in the predetermined posture or the predetermined position of the article held by the arm robot in the predetermined posture. The estimation unit 42 functions as an example of an estimation unit that estimates the amount of positional deviation in the predetermined posture by using the time-series data of the position detected by the sensor when the arm robot takes the predetermined posture. The correction value calculation unit 43 and the control unit 20 function as an example of a correction unit that corrects the positional deviation of the arm robot based on the positional deviation amount estimated by the estimation unit.

FIG. 6A is a block diagram for explaining the hardware configuration of the arithmetic unit 40. With reference to FIG. 6A, the calculation unit 40 includes a CPU 101, a RAM 102, a storage device 103, a display device 104, and the like. A CPU (Central Processing Unit) 101 is a central processing unit.

The CPU 101 includes one or more cores. A RAM (Random Access Memory) 102 is a volatile memory that temporarily stores a program executed by the CPU 101, data processed by the CPU 101, and the like. The storage device 103 is a non-volatile storage device. As the storage device 103, for example, a ROM (Read Only Memory), a solid state drive (SSD) such as a flash memory, a hard disk driven by a hard disk drive, or the like can be used. The storage device 103 stores a correction program. The display device 104 is a liquid crystal display, an electroluminescence panel, or the like, and displays the determination result. In the present embodiment, each unit of the arithmetic unit 40 is realized by executing a program, but hardware such as a dedicated circuit may be used.

(Modification 1)
FIG. 6B is a diagram illustrating a work system according to a modification. In each of the above examples, the calculation unit 40 acquires the time series data from the sensor 30. On the other hand, the server 202 having the function of the calculation unit 40 may acquire the data from the sensor 30 through the telecommunication line 201 such as the Internet. In this case, the calculation unit 40 transmits the calculated correction value to the control unit 20 via the telecommunication line 201.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and alterations are possible within the scope of the gist of the present invention described in the claims. It can be changed.

10 arm robot 11 link 12 joint 20 control unit 30 sensor 40 arithmetic unit 50 article 60 work 100 robot system

Claims (9)

A sensor that detects time-series data of a predetermined position of the arm robot in a predetermined posture, or time-series data of a predetermined position of an article held by the arm robot in the predetermined posture,
Using the time series data detected by the sensor, an estimation unit for estimating a positional deviation amount in the predetermined position,
A correction unit that corrects the positional displacement of the arm robot based on the positional displacement amount estimated by the estimation unit ,
The correction device is characterized in that the estimation unit does not use time-series data in which a displacement between a reference position and a position detected by the sensor is less than a first threshold when estimating the displacement amount . A sensor that detects time-series data of a predetermined position of the arm robot in a predetermined posture, or time-series data of a predetermined position of an article held by the arm robot in the predetermined posture,
Using the time-series data detected by the sensor, an estimation unit that estimates the amount of positional deviation in the predetermined posture,
A correction unit that corrects the positional displacement of the arm robot based on the positional displacement amount estimated by the estimation unit,
The correcting device corrects the positional deviation of the arm robot when the deviation between the reference position and the position detected by the sensor is equal to or more than a second threshold value. The correction apparatus according to claim 1 , wherein the estimation unit estimates the positional deviation amount by estimating a parameter related to heat generation and an extension rate of the arm robot. The correction device according to claim 1 , wherein the estimation unit changes the number of parameters used for estimating the positional deviation amount according to the number of the time-series data. The correction apparatus according to claim 1 , wherein the arm robot includes a plurality of links connected by one or more joints. The sensor is used to detect time series data of a predetermined position of the arm robot in a predetermined posture, or time series data of a predetermined position of an article held by the arm robot in the predetermined posture,
Estimation unit, using the time series data detected by the pre-Symbol sensor, estimates the positional displacement amount in the predetermined position,
The correction unit corrects the position shift of the arm robot based on the position shift amount estimated by the estimation unit ,
The correction method is characterized in that the estimation unit does not use time-series data in which a displacement between a reference position and a position detected by the sensor is less than a first threshold when estimating the displacement amount . The sensor is used to detect time-series data of a predetermined position of the arm robot in a predetermined posture, or time-series data of a predetermined position of an article held by the arm robot in the predetermined posture,
The estimating unit estimates the amount of positional deviation in the predetermined posture by using the time-series data detected by the sensor,
The correction unit corrects the position shift of the arm robot based on the position shift amount estimated by the estimation unit,
The correcting method corrects the positional deviation of the arm robot when the deviation between the reference position and the position detected by the sensor is equal to or more than a second threshold value. On the computer,
Using the time-series data of a predetermined position of the article the arm robot grips the time-series data or the predetermined posture at a predetermined position of the arm robot in a predetermined posture is detected by the sensor, estimates the positional displacement amount in the predetermined posture Processing and
A process of correcting the position shift of the arm robot based on the position shift amount estimated in the estimating process ;
A correction program , wherein time series data in which a deviation between a reference position and a position detected by the sensor is less than a first threshold value is not used when estimating the position deviation amount . On the computer,
Using the time-series data of the predetermined position of the arm robot in the predetermined posture detected by the sensor or the time-series data of the predetermined position of the article held by the arm robot in the predetermined posture, the amount of positional deviation in the predetermined posture is estimated. Processing and
A process of correcting the position shift of the arm robot based on the position shift amount estimated in the estimating process;
In the correction process, when the deviation between the reference position and the position detected by the sensor is equal to or more than a second threshold value, the position deviation of the arm robot is corrected.

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