JPH06315882A - Weight/center of gravity position correcting device for force control working machine - Google Patents

Abstract

PURPOSE:To simplify the tool attitude setting action for a force control working machine, surely attain the necessary tool attitude, and calculate the weight and the center of gravity position of the tool with good precision. CONSTITUTION:The first Cartesian coordinate system corresponding to the installation position of a mechanism section 1 and the second Cartesian coordinate system corresponding to a force sensor 4 are set. The weight/center of gravity position correcting device for a force control working machine is provided with the means 11, 12 measuring the force data and attitude data by utilizing the first and second Cartesian coordinate systems, an attitude setting means 17 guiding and setting the mechanism section 1 to a plurality of attitudes, a weight/center of gravity position calculating means 13 calculating the weight and the center of gravity position of the working tools from the attitude data and force data, an attitude judging means 16 calculating the force data and attitude data on the working tool at individual attitudes when a plurality of attitudes are to be taken and judging whether the attitude data used in calculating the weight and the center of gravity position satisfy the condition or not, and an attitude judgment informing means 18 informing an operator of the judged result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
Regarding the center-of-gravity position correction device, particularly for a work tool that is mounted on a force-controlled work machine via a force sensor, determine the weight and center-of-gravity position parameters of this work tool, and use these parameters to detect the values detected by the force sensor during work. The present invention relates to a weight / center-of-gravity position correction device.

[0002]

2. Description of the Related Art A work tool is attached to an arm tip of a mechanism unit (robot body) through a force sensor such as a grinder, deburring device, fitting device, etc. In a force-controlled work machine that is configured to change its posture and force the work tool to perform force work, the weight and center of gravity of the work tool and its holder (hereinafter referred to as tool) fixed to the force sensor are used as parameters (gravity force). It is necessary for control to set it as a correction value). The reason is as follows.

When the tool performs a predetermined force work on the work, the force data detected by the force sensor is the force applied to the detection center position of the force sensor. On the other hand, originally,
The force information to be known is the force acting on the tool from the work at the location where the tool and the work contact each other. Assuming that the tool exists in the air and is not subjected to any external force, the tool has a weight due to gravity applied to its center of gravity. Therefore, a combined force of the acting force at the contact point and the force due to the weight of the tool itself is applied to the tool which is in contact with the work and is working. The force detected by the force sensor is such a combined force. Therefore, in order to detect only the force information related to the work at the contact point of the tool, the values related to the weight and center of gravity of the tool are prepared in advance as gravity correction values, and the force data detected by the force sensor is used using this. I have to compensate. Therefore, it is necessary to set the weight and center of gravity of the tool as parameters for gravity correction.

As a conventional method for calculating the parameters of the weight and the position of the center of gravity of the tool, there is a method disclosed in Japanese Patent Laid-Open No. 62-74594. In the force sensor calibration method for a robot device disclosed in this prior art document, a simple example is shown about how to take three postures required when obtaining the weight / center of gravity position of a tool.

[0005]

According to the method shown in the above-mentioned prior art, it is not so easy for the operator to make the three postures described based on the guidance. That is, there are cases where the weight / center of gravity position of the tool cannot be calculated depending on how the posture is taken. In other words, the operator guides the tool and the arm, and the operator himself
Even if it is considered that the entire mechanical unit has three postures designated by a manual or the like, there are cases where two postures are substantially the same in terms of coordinates. In such a case, since the three postures necessary for calculating the weight / center of gravity position have not been taken, the weight / center of gravity position of the tool cannot be calculated. Thus, in spite of the way of taking the posture of the tool such that the weight / center of gravity position of the tool cannot be actually calculated, in the above-mentioned conventional apparatus, the operator avoids this. There was a problem in that it did not provide.

An object of the present invention is to easily operate the tool posture setting and reliably obtain a necessary tool posture when obtaining the values of the weight / center of gravity position of the tool in the force control work machine, and to obtain the weight of the tool. -To provide a weight / center-of-gravity position correction device for a force control work machine capable of calculating the center-of-gravity position with good accuracy.

[0007]

A weight / center-of-gravity position correcting device for a force control work machine according to the present invention has a structure in which an arbitrary posture is taken during operation. A force-controlled work machine in which a work tool is attached via a force sensor that detects a moment around a point, and the mechanism section is operated based on the force control executed by the control means to cause the work tool to perform a predetermined force work. , A first Cartesian coordinate system (base coordinate system) corresponding to the installation location of the mechanical section,
A second Cartesian coordinate system (for example, a sensor coordinate system) corresponding to the force sensor is set, and the force data applied to the work tool and the posture data of the work tool are measured using the first and second Cartesian coordinate systems. Means, a posture setting means for guiding and setting the posture of the mechanism part to which the work tool is attached to a plurality of postures, and the weight of the work tool from the posture data and force data of the work tool measured by using these coordinate systems. -A weight / center-of-gravity position calculation means for calculating the center-of-gravity position is further provided, and further, when the operator is guided to operate so that the mechanism section has a plurality of postures, force data and posture data regarding the work tool in each posture. Attitude determination means for determining whether or not the attitude data obtained by the measurement in each attitude satisfies the condition for calculating the weight / center of gravity position, and the determination result It provided with a posture determination notification means to notify the author. In the above configuration, the plurality of postures are preferably at least three postures. Further, the attitude determination means preferably determines based on the relative attitude relationship of the second Cartesian coordinate system with respect to the first Cartesian coordinate system.
Further, with respect to this relative posture relationship, a conical guiding area having an origin set on one axis of the first Cartesian coordinate system is set, and the origin of the second Cartesian coordinate system is made to coincide with the apex. In this state, each axis of the second Cartesian coordinate system is included in the conical guiding area.

[0008]

According to the present invention, when the operator guides and sets a plurality of postures of the work tool necessary in the process of calculating the weight / center of gravity position of the work tool, the posture is the weight when the operator takes the posture. -Determine whether or not the posture is sufficient to satisfy the conditions that can be calculated when calculating the position of the center of gravity.
Notify the determination result. As a result, the operator can immediately know whether or not the position of the mechanism portion can be calculated for the position of the weight and the center of gravity, so that the calculation accuracy will not be insufficient due to an incorrect attitude input, and the accuracy is high. Since the weight parameter and the center-of-gravity position parameter can be obtained, accurate force feedback required for the force control work machine can be performed.

[0009]

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

FIG. 2 is a block diagram showing the entire system of a force control work machine to which the weight / center of gravity position correcting apparatus according to the present invention is applied. The force control work machine includes a robot main body (mechanical unit) 1 as a work machine that operates based on position and force control, a control device 2 for controlling the operation of the robot main body 1, and a predetermined force work such as grinding. The work tool 3 for carrying out the work, a force sensor 4 for detecting a force and a moment applied to the work tool 3, and a teaching box 5 as a teaching device. As a matter of course, the robot body 1 is subjected to position control in performing its operation, and in addition, force control is also performed based on work necessity, and therefore the robot body 1 is recognized as a force control work machine due to its characteristics. The work tool 3 includes a tool holder and is hereinafter referred to as a tool 3.

The robot main body 1 is provided with an arm 6 on the upper side, and the tool 3 is attached to the wrist of the arm 6 via the force sensor 4, and the tool 3 is structurally provided with 6 degrees of freedom for performing the operation, so that the tool 3 can be mounted. It can be moved to any position in any posture. The robot main body 1, the control operation of convenience FIG 2 shows such base 7 in a fixed Cartesian coordinate system (base coordinate system B: 3 three orthogonal axes X _B, Y _B, Z
_B ) is set. Also, the arm 6 of the robot body 1
The force sensor 4 attached to the wrist of the device measures the forces of the three orthogonal axes (X _S , Y _S , Z _S ) in the respective axial directions and the moments around the respective axes, that is, the forces in the six axial directions. Force sensor 4
For convenience of control calculation, a Cartesian coordinate system (sensor coordinate system S) unique to the force sensor is set with the center of force detection (reference point of moment) as the origin, as shown in FIG.

The controller 2 is an arithmetic processing unit composed of a computer, and controls the operation of the robot body 1 (controls the position and force) and the weight / center of gravity position of the tool 4 according to the present invention. And correction processing. The teaching box 5 is provided with a plurality of various command push buttons 8 necessary for teaching and guiding work operations of the robot body 1 and a display device 9 having, for example, a liquid crystal screen for displaying various information. By operating the teaching box 5, the operator can input data or a command program for instructing the robot body 1 to perform an arbitrary operation required for manual work, and the input teaching content is
It is stored in the storage device of the control device 2.

Next, referring to FIG. 1, the internal structures of the control device 2 and the teaching box 5 will be described in detail.

The robot operation control device 10 generates signals for controlling the operation of the motors attached to the joints (movable shafts) of the robot body 1 and gives the control signals to the motors to cause the robot body 1 to move. Take the necessary posture,
The tool 3 is made to perform the necessary work operation. The control executed by the robot motion control apparatus 10 handles position and force as control information, and includes so-called force control. In the force control, the force applied to the tool 3 from the work is detected by the force sensor 4 described above, the detected force data is fed back and compared with a preset desired force reference value, and the desired force is determined based on the difference. Controls are made to occur. The principle of basic control of the robot main body 1 that operates based on position and force control, and the basic configuration of the robot operation control device 10 for performing this control are known. In force control,
It is necessary to use correct force information obtained by compensating for the gravity value of the tool 3 attached to the force sensor 4 and its holder. In order to perform the compensation calculation of the gravity value of the tool 3, it is necessary to obtain the respective values of the weight and the position of the center of gravity of the tool as parameters (gravity correction values) in advance. The gravity value of the tool 3 is different for each tool. In actual grinding work etc.,
Since the tools are exchanged according to the contents of the work, it is necessary to relatively frequently perform the work for obtaining the parameters of the weight and the center of gravity of the tool.

The force input device 11, the posture input device 12, the weight / center of gravity position calculation device 13, and the parameters of the weight and center of gravity position are stored as functional elements constituting the device for obtaining the parameters of the weight and center of gravity position of the tool 3. A storage device 14 is provided. The storage device 14 is a storage device which is originally provided in the control device 2 and is composed of a RAM and a ROM. The storage device 14 stores programs used for operation control of the robot body 1 and various control parameters. It is also used as a means for storing the parameters of the weight and the center of gravity position calculated by the center of gravity position calculation device 13. Various control parameters and programs stored in the storage device 14 are read into the robot operation control device 10 at appropriate timings as needed.

The force input device 11 inputs force data detected by a force sensor 4 provided in the robot body 1. The force data detected by the force sensor 4 is represented by the sensor coordinate system S described above. The force data detected by the force sensor 4 is the weight of the tool itself when the tool 3 is not performing the force work, and the force applied to the tool 3 from the work and the tool itself when the tool 3 is in contact with the work to perform the force work. Is the combined weight of. Further, the posture input device 12 inputs posture data detected by a position displacement sensor provided in each joint of the robot body 1. The position displacement sensor is, for example, an encoder mounted in the motor of each joint of the robot body 1, and the posture of the robot body 1 generally calculates the direction cosine of each axis using the detection output of the position displacement sensor. Based on this, it is represented by the base coordinate system B.

The weight / center-of-gravity position calculation device 13 includes force data and attitude input device 12 loaded by the force input device 11.
It has a calculation function of obtaining the weight parameter and the center-of-gravity position parameter of the tool 3 mounted on the wrist portion of the arm 6 of the robot body 1 via the force sensor 4 by using the posture data captured in step 2. As the weight / center-of-gravity position calculation device 13, any device can be used as long as it has such a calculation function. For example, as one calculation method for obtaining the weight parameter and the center-of-gravity position parameter, the present inventors A weight / center-of-gravity position correction device that first calculates weight parameters in vector format (Japanese Patent Application No. 3-279).
No. 774) is proposed. In this weight / center-of-gravity position correction device, the weight parameter of the tool used for gravity correction is determined by the vector amount expressed in the base coordinate system, etc., so it was calculated by the scalar amount like the previous calculation method. In comparison, the installation state of the force-controlled work machine can be necessarily included in the weight representation of the work tool, which has the advantage that no adjustment means or adjustment process is required. In any case, in the weight / center-of-gravity position correction device according to the present invention, the force input device 11 that captures the force data output from the force sensor 4, the posture input device 12 that captures the posture data output from the position displacement sensor, the force data and the posture data The condition is to include a weight / center-of-gravity position calculation device 13 for calculating the weight parameter and the center-of-gravity position parameter using, and to use force data and position data regarding at least three postures in calculating the weight parameter and the center-of-gravity position parameter. As long as this condition is satisfied, an arbitrary weight / center-of-gravity position correction device can be used for the construction of the means for obtaining each parameter of the weight and center-of-gravity position.

The operator guides the robot body 1 to sequentially adopt, for example, a first posture, a second posture, and a third posture, and the weight / center of gravity position is calculated using all the force data and posture data obtained in each posture. The arithmetic unit 13 calculates the weight parameter and the center-of-gravity position parameter regarding the tool 3. weight·
The weight parameter and the center of gravity position parameter regarding the tool 3 obtained by the center of gravity position correcting device 13 are stored in the storage device 14.
Stored in. The weight parameter and the center-of-gravity position parameter stored in the storage device 14 are read by the robot operation control device 10 when the tool 3 is actually used to perform force work, and the force data detected by the force sensor 4 is weight-compensated. Used as data.

A feature of the present invention is whether the operator correctly takes three different postures when the robot body 1 is guided to take the first posture, the second posture, and the third posture. It is possible to provide information to the operator at an appropriate timing, and it is determined whether the posture of the robot body 1 taken while the operator is guiding and operating the robot body 1 is appropriate or inappropriate. That is, it has a configuration that can be accurately recognized. Therefore, in order to enable the operator to accurately recognize whether the posture of the robot body 1 that is taken by the guiding operation is proper or inappropriate, the control device 2 is provided with the posture calculation device 15 and the posture determination device 16. At the same time, a posture guidance instruction device 17 and a posture determination device 18 are provided in the teaching box 5. The posture guidance instruction device 17 in the teaching box 5 is for giving a command for a guidance operation input by the operator to the robot operation control device 10.

The operator operates the teaching box 5, that is, the posture guidance instructing device 17 and the posture determination notifying device 18 in the teaching box 5 to calculate an appropriate posture necessary for calculating the weight parameter and the gravity center position parameter. To the robot body 1. Regarding the posture guidance instructing device 17 and the posture determination notifying device 18, specifically, the posture guidance instructing device 17 is configured to include the plurality of push buttons 8 for guidance described above, and the posture determination notifying device 1
8 includes a screen of the display device 9.

In order to calculate each parameter of the weight / center of gravity position, the robot body 2 is operated based on the robot operation control device 10 in accordance with a command signal output from the posture guidance instruction device 17 by the operator, and the posture calculation device 15
Then, the posture of the robot body 1 is calculated, and the posture determination device 16 determines whether or not the posture at that time is sufficient to calculate each parameter of the weight / center of gravity position. Posture determination device 1
As a result of the judgment in 6, if the posture satisfies the condition, the force data (force value) detected by the force sensor 4 at that time is taken in via the force input device 11 and the posture data output from the position displacement sensor. The force input device 11 and the posture input device 1.
2. The weight / center-of-gravity position calculation device is given, and a message to take the next posture is given to the operator through the posture determination / notification device 18. By repeating such operation, data sufficient for calculating the weight parameter and the center-of-gravity position parameter are prepared based on at least three postures, the weight / center-of-gravity position calculating device 13 calculates the weight / center-of-gravity position, and the calculation result is calculated. It can be stored in the storage device 14. It should be noted that the posture determination device 16 makes the determination based on, for example, the relative posture relationship of the sensor coordinate system (second Cartesian coordinate system) with respect to the base coordinate system (first Cartesian coordinate system).

How to take the posture of the robot body 1 for calculating the weight / center of gravity position will be described with reference to FIGS. 3 and 4. It is necessary to take at least three types of postures to calculate the weight / center of gravity position. In this example, the Z _S axis of the sensor coordinate system enters an angle within θ with respect to the Z _B axis of the base coordinate system shown in FIG. 4 in the first posture (FIG. 3A), and
In the posture of, the X _S axis of the sensor coordinate system enters an angle within θ (FIG. 3B), and in the third posture, the Y _S axis of the sensor coordinate system enters an angle within θ (FIG. 3C). ) Try it. In the above guidance, each axis of the sensor coordinate system may be guided in the conical guidance region 19 shown in FIG. 4 in a state where the origin of the base coordinate system B and the origin of the sensor coordinate system S are matched. If the robot body 1 is installed vertically, the operator may visually check each axis to be substantially vertical.
The above θ is preferably in the range of 0 ° ≦ θ <25 °.

The flow of the whole process will be described with reference to FIG.
First, the posture No. (posture number) is set to 1 (first posture setting: step S1), and the teaching box 5
A guidance instruction message for guiding the operator to the first posture is displayed on the screen of the display device 9 (step S2). The operator manually operates the robot body 1 while pushing down the guide button (step S3) to take the first posture (step S4). Then, when the operator determines that he / she can take the first posture, the operator releases the depression of the guidance button (step S3) and depresses the posture determination button (step S5). When the posture determination button is pushed down, the posture of the robot body 1 at this time is measured and calculated (step S6). Next, attitude determination is performed (step S7). The first attitude is determined by the Z _S axis of the sensor coordinate system. A unit vector indicating the direction of the Z _S axis is calculated based on the base coordinate system, and this is calculated as (za _x , za
_y , za _z ), the determination is performed by the following equation.

[0024]

[Formula 1] za _z > cos θ

If the first attitude does not satisfy the condition of (Equation 1), an error message is displayed using the attitude determination notification device 18 (step S8). When the first posture satisfies (Equation 1), the force sensor 4 detects the force and outputs it to the force input device 11 (step S9). Further, the posture data obtained by the position displacement sensor is output to the posture input device 12 (step S10). Next determination step S11
Then, if the posture No. is less than 3, the next posture (second posture) is set (step S12), and the above processing contents are repeated for the second posture. However, in the determination of the position, since the posture No2 (second posture) is determined by X _S axis, a unit vector indicating the direction of the X _S axis (xn _x, xn _y, xn
_z ) is determined by the following equation.

[0026]

[Formula 2] xn _z > cos θ

Similarly, the posture No. 3 (third posture) is Y.
Since the determination is made based on the _s axis, when the unit vector indicating the direction of the Y _s axis is (yo _x , yo _y , yo _z ), the determination is performed according to the following equation.

[0028]

[Equation 3] yo _z > cos θ

When the force data and the posture data up to posture No. 3 have been obtained, the weight / center of gravity position calculating device 13 calculates the weight / center of gravity position using these data (step S13), and stores this in the storage device 14. It is stored (step S14). As an example of the calculation of the weight / center of gravity position, there is the method described in Japanese Patent Application No. 3-279774, as described above.

In the above description of the embodiment, a method has been described in which the operator uses the guidance push button 8 of the posture guidance instruction device 17 of the teaching box 5 to guide the robot body 1 automatically. In addition, the robot main body 1 may be moved to a desired posture, or the robot main body 1 may automatically take three postures to calculate each parameter of the weight / center of gravity position.

Although the determination of the posture has been described with reference to the sensor coordinate system, any coordinate system can be used as long as it is conveniently provided after the wrist of the robot body 1.

[0032]

As is apparent from the above description, according to the present invention, when the operator takes at least three postures suitable for guiding the robot body and calculating the weight / center of gravity position for weight compensation. Since the robot informs the operator whether or not the posture set by guidance is appropriate, the robot can be set to the correct posture accurately, the operability is good, the accuracy of the calculation result can be guaranteed, and it can be used for force control. If so, the control performance is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an internal configuration of a weight / center-of-gravity position correction device for a force control work machine according to the present invention.

FIG. 2 is a diagram showing an overall system configuration of a force control work machine.

FIG. 3 is a diagram showing each of three guided postures.

FIG. 4 is a diagram showing a guidance allowable range in a base coordinate system.

FIG. 5 is a flowchart showing a flow of overall processing in posture guidance.

[Explanation of symbols]

 1 Robot Main Body 2 Control Device 3 Work Tool 4 Force Sensor 5 Teaching Box 6 Arm 8 Push Button 9 Display Device 10 Robot Motion Control Device 11 Force Input Device 12 Posture Input Device 13 Weight / Center of Gravity Calculator 14 Storage Device 15 Posture Calculator 16 Attitude determination device 17 Attitude guidance instruction device 18 Attitude determination notification device 19 Conical guidance area

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shoji Yaginuma 7-1-1 Higashi Narashino, Narashino-shi, Chiba Hitachi Keiyo Engineering Co., Ltd. (72) Inventor Masafumi Suzuki 7-1-1 Higashi Narashino, Narashino, Chiba Hitachi Inside Keiyo Engineering Co., Ltd. (72) Inventor Shinichi Sarugaku 7-1-1 Higashi Narashino, Narashino City, Chiba Prefecture Inside Hitachi Keiyo Engineering Co., Ltd.

Claims (4)

[Claims] 1. A work tool is attached to a mechanism unit via force detection means, and the mechanism unit is operated by force control by a control unit to cause the work tool to perform a force work, and the installation location of the mechanism unit is supported. In a force-controlled work machine in which a first Cartesian coordinate system and a second Cartesian coordinate system corresponding to the force sensor are set, a force applied to the work tool using the first and second Cartesian coordinate systems. Means for measuring data and posture data of the work tool; posture setting means for guiding and setting the posture of the mechanism part to which the work tool is attached to a plurality of postures; and the work tool obtained in each posture. Weight / center-of-gravity position calculation means for obtaining a weight / center-of-gravity position for correction of the work tool using force data and the posture data, and each of the plurality of postures has the weight Weight of a force control work machine characterized by including posture determination means for determining whether or not the posture satisfies a condition for obtaining a heart position, and posture determination notification means for notifying an operator of the determination result. Center of gravity position correction device. 2. The weight of the force control work machine according to claim 1.
In the center-of-gravity position correction device, the plurality of postures are at least three postures, the weight-center-of-gravity position correction device of the force control work machine. 3. The weight of the force control work machine according to claim 1.
In the center-of-gravity position correction device, the posture determination means makes a determination based on a relative posture relationship of the second Cartesian coordinate system with respect to the first Cartesian coordinate system. Position correction device. 4. The weight of the force control work machine according to claim 3.
In the center-of-gravity position correction device, the posture relationship is the first
Of the second Cartesian coordinate system in a state where a conical guiding region having an origin set at one axis of the Cartesian coordinate system is set, and the origin of the second Cartesian coordinate system coincides with the vertex. A weight / center-of-gravity position correcting device for a force control work machine, wherein each axis has a relationship included in the conical guiding region.