JP3350687B2 - Robot control method and robot control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a robot control method and a robot control apparatus for controlling the position and force of a multi-degree-of-freedom machine tool such as a robot or a machine tool having at least two degrees of freedom. Further, the present invention relates to a robot control method and a robot control device for causing a mechanism main body to perform a work operation involving a force such as deburring, curved surface polishing, and curved surface copying operation.

[0002]

2. Description of the Related Art Conventionally, a multi-degree-of-freedom work machine (generally an industrial robot or a work robot, hereinafter referred to as a "robot") that performs a grinder work using force control is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei.
As described in JP-A-222315, JP-A-1-222316, and JP-A-3-262009, when performing a work involving a force based on force control, the direction in which a work tool applies a force to the work and the work The direction in which the tool is moved is specified in a rectangular coordinate system, and the direction of the coordinate axis is rotated and changed in accordance with the shape of the workpiece, thereby performing a force work. In these robots, when moving the work tool while applying a force to the work based on the force control, the direction in which the force is applied is directed to the normal direction of each part of the work to improve the accuracy and performance of the force control. In a robot that performs force work by moving the work tool along the work while applying force to the work with the work tool using force control, the setting of the normal direction in the part to be processed that determines the direction to apply the force The manner is important for smooth work.

For example, in the multi-degree-of-freedom working machine disclosed in Japanese Patent Application Laid-Open No. 1-222315, the normal direction of each workpiece to be processed is determined in advance, and the determined normal direction is stored in a storage device provided in a control device. I remember. JP-A 1-222211
In the multi-degree-of-freedom work machine disclosed in Japanese Patent Application Laid-Open No. HEI 1-222316, the normal direction of each contact point is obtained based on the reaction force at the contact point of the work. Japanese Patent Application Laid-Open No. 3-26200
In the multi-degree-of-freedom robot No. 9, the normal direction is obtained by the Fresne equation based on the trajectory data relating to the movement of the work tool.

[0004]

The method of setting the normal direction according to the above-mentioned prior art has the following problems, respectively.

According to the setting method of Japanese Patent Application Laid-Open No. 1-222315, assuming a system using a microcomputer, a storage device having an enormous storage capacity is required, and there is a problem in the efficiency of the system. Also, considering a trial work for storing data for performing work in advance in the storage device of the control device in advance, it is extremely troublesome work to set and store a coordinate system according to the shape of the work. Become. According to the setting method of JP-A-1-222311 and JP-A-1-222316, measuring the reaction force at the contact point of the work tool on the work has a large error in practice, and therefore,
Each time the position changes, the direction of the coordinates changes greatly, resulting in poor stability and poor control.

In the method based on the Fresne's formula disclosed in Japanese Patent Application Laid-Open No. 3-262009, depending on how the trajectory is set, the coordinate axes are reversed, and the direction in which the force is applied is opposite to the direction in which the force is required. There is no case. This situation will be described with reference to FIGS.

In FIG. 11, target trajectories 103 for movement of a work tool 102 on a work 101 are represented by P001 to P0.
Assume that a sequence of 11 points is given. At this time, each axis direction of the coordinate system obtained by the calculation will be described focusing on, for example, P002 and P007. First, in P002, the x-axis direction is (Equation 1).

[0008]

(Equation 1)

Thus, if the unit vector in the x-axis direction is <n>, the following equation is obtained.

[0010]

(Equation 2)

Here, the symbol "<>" represents a vector. The y-axis direction is given by the following equation.

[0012]

(Equation 3)

If the unit vector in the y-axis direction is <o>, it is given by the following equation.

[0014]

(Equation 4)

If this is illustrated, it becomes a vector directed in the direction of the radius of curvature of the trajectory. Assuming that the unit vector is <a> in the z-axis direction, it is given by the following equation.

[0016]

(Equation 5)

FIG. 12A shows a coordinate system at P002 obtained by the above calculation.

Next, FIG. 12B shows the result of the same calculation for P007. In the case of P007, the y-axis direction is directed to the radius of curvature, so that the direction is opposite to that of the case of P002, whereby the z-axis direction is also reversed. Therefore, a large problem is posed in the force control when the force target value and the gain relating to the operation are set with reference to the axial direction of the coordinate system. More specifically, for example, as shown in FIG.
At -1.0 Kgf force in the y-axis direction (negative direction of y-axis)
When the setting is made such that the work tool 102 mounted on the wrist of the robot mechanism is pressed against the work 101 to perform the deburring work, as shown in FIG.
In this case, the direction of the y-axis is reversed, and the direction in which the force is applied is also reversed, so that the work tool 102 cannot be pressed against the work 101.

In addition, the method disclosed in Japanese Patent Application Laid-Open No. Hei 3-262009 has a problem that at least three position data are required to perform the operation because the second derivative of the position must be calculated. ing.

An object of the present invention is to provide a robot control method and a robot control device that allow a user to easily set a coordinate system without causing a problem in control stability and accuracy.

[0021]

A robot control method according to the present invention is a robot control method for controlling a position and a force of a work tool at a tip end of a working robot having multiple degrees of freedom,
The pressing direction that presses the work tool against the workpiece
Is set as general direction, optionally the determined pressing direction and one axial <br/> tentative workpiece coordinate system as general direction, for generating a target trajectory with respect to the processing unit of the power tool The direction calculated from the position parameter is the work coordinate system
The other main axis direction is assumed to be the temporary one axis direction.
In this method, the vector in each axis direction of the workpiece coordinate system is calculated by correcting the work tool so as to be orthogonal to the axis direction, and the position and force of the power tool are controlled using the vectors in each axis direction.

In the above method, preferably, the vector in one axial direction is specified in one axial direction from a coordinate system fixed in the installation space of the working robot.

In the above method, preferably, the vector in one axis direction is specified in one axis direction from a coordinate system calculated and generated by the control means in accordance with the operation of the robot mechanism .

In the above method, preferably, the position parameter is position data stored in the storage means according to a user's teaching to the work robot.

In the above method, preferably, the position parameter is data created by an arithmetic process based on the position data stored in the storage means in accordance with a user's teaching to the work robot.

In the above method, preferably, the calculation processing is an interpolation calculation.

A robot control device according to the present invention is a position and force robot control device for controlling a working robot having multiple degrees of freedom, and includes a position parameter, a user program, and various force control parameters in a preceding stage. A teaching / setting unit including a plurality of storage units for storing and a control execution unit including a force control calculation unit at a subsequent stage are provided, and a user program analysis unit of the control execution unit reads a user program set in the teaching / setting unit. In the robot controller that transfers the position parameters and the force control parameters from the respective storage units to the respective input units of the control execution unit in accordance with the contents of the instructions, the teaching / setting unit includes a coordinate system parameter for storing parameters related to the coordinate system. A storage unit and a work coordinate system arbitrarily determined as a general direction with respect to the work coordinate system from the above coordinate systems. And a work coordinate system axis storing section, the control execution unit, for each position to form a target track, the coordinate system parameter storage position parameter storage unit for which stores the specified pressing direction as one axial direction of the provisional And input each output of the work coordinate system axis direction storage unit, and use each position parameter, a parameter related to the coordinate system, and one axis direction arbitrarily determined as a rough direction with respect to the work coordinate system, to use each of the outputs in the work coordinate system It is characterized by including a work coordinate system calculation unit that calculates an axial vector and outputs this vector as a control command value.

In the above configuration, preferably, the work coordinate system calculation unit is configured to perform a calculation according to a command output from the user program analysis unit.

In the above configuration, preferably, instead of using the position parameter from the position parameter storage unit, data on a position obtained by performing a predetermined operation on the position parameter is used.

[0030]

According to the present invention, when a work is given and it is instructed to perform a force operation such as polishing on a work portion of the work, the work portion is formed of a grinder and a grindstone. When a target trajectory for pressing and moving the work tool is given as a point sequence including a plurality of pieces of position data with respect to the workpiece, a general direction (pressing) required to press the work tool with respect to the workpiece of the workpiece
Direction) is determined by the user himself, set as a vector in one axial direction in the teaching / setting unit, and for each position forming the target trajectory, the moving direction is obtained from the position data, and is calculated in the unit of one axial direction. Then, a unit vector for the other two orthogonal axes is obtained in accordance with a predetermined calculation using a vector in one axis direction set in the teaching / setting unit, and a coordinate system is thus generated.

The coordinate system of each position forming the target trajectory is set in order to set the approximate direction in which the work tool presses the workpiece by observing the workpiece by the user.
Even if the condition of the portion to be machined changes significantly, the direction of the force exerted by the power tool does not reverse, the pressing direction is always maintained in a desired state, and the power tool does not separate from the workpiece.
Also, the calculation for setting the coordinate system is simple, the data required for the calculation is small, and the calculation time is short.

[0032]

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

FIG. 1 is a block diagram conceptually showing the configuration of a robot control device according to the present invention which is realized by software. FIG. 1 also shows mechanical components and hardware components such as a sensor unit. . FIG. 2 is a block diagram illustrating an example of a specific configuration of the force control calculation unit, and FIG. 3 is a block diagram illustrating a configuration of a computer system for realizing the robot control device.

In FIG. 1, a robot mechanism 1 is a robot main body, and includes a mechanical mechanism, a driving device disposed at each movable part (joint) of the mechanical mechanism, and an arm of the mechanical mechanism. And a work tool (generally a hand effector) attached to the front end. The robot mechanism 1 is controlled as a whole by each driving device arranged in the movable part receiving various control signals for determining the attitude and the operation of the robot mechanism 1 given from the force control calculating section 20 through the servo circuit 2. It operates according to the signal and performs necessary work on a work (not shown) with a work tool. The work operation by the robot mechanism 1 and the work tool includes a force work operation by force control. Therefore, when the work tool performs a force work such as polishing on the work, the work tool receives a reaction force from the work. Since the power tool is fixed to the force sensor 3 due to its mounting structure, a force (including a moment) applied to the power tool is detected by the force sensor 3. Data relating to the force detected by the force sensor 3 is sent to the force control calculation unit 20, and is used as force data relating to the control situation in subsequent force control. Similarly, each movable part of the robot mechanism 1 is provided with a sensor for detecting the amount of movement, and when the movable part is operated by the corresponding driving device, each sensor measures the amount of movement, and a servo circuit is provided. 2 to the force control calculation unit 20 as operation amount data. These motion amount data are used as actual position data for subsequent force control and position control.

A block 5 indicated by a dashed line is a part of the robot controller. In a robot system to which the robot control device according to the present invention is applied, a teaching playback (teaching playback) method is employed. Therefore, FIG.
Is composed of a part (teaching / setting unit) relating to teaching and setting of a plurality of control parameters, and a part (control executing unit) for taking out the plurality of set control parameters and executing control. Is done. In the robot control device 5, regarding the transfer route of the taught program and data, the teaching / setting unit is located at the front stage on the left side of the figure, and the control execution unit is located at the rear stage on the right side. That is, the teaching / setting unit includes the force control parameter storage 14, the user program storage 13, and the position parameter storage 1.
0, a coordinate system parameter storage unit 11, and a work coordinate system axis direction storage unit 12. On the other hand, the control execution unit includes a user program analysis unit 16, a force control parameter transfer unit 17, a position parameter transfer unit 15, a work coordinate system calculation unit 18, a force control calculation preprocessing unit 19, and the above-described force control calculation unit 20. .

Force control parameter storage unit 14, user program storage unit 13, position parameter storage unit 10, coordinate system parameter storage unit 11, work coordinate system axis direction storage unit 12.
In each of the cases, when an operator of the user wants the robot mechanism 1 including the robot control device 5 to perform required work (work that requires position control and force control with respect to the operation of a work tool), By performing the teaching operation, data relating to each control parameter of force control and position control necessary for controlling the work and a necessary user program are stored. In the teaching operation by the operator, for example, a handy type teaching operation device 4 is used. The teaching operation device 4 includes an input function unit 4a for inputting a control command and a plurality of data using a program language.
A display function unit 4 having a predetermined display area and visually confirming the contents of control commands and the like input by the operator.
b. By using the teaching operation device 4, the robot mechanism 1 can imitate the work before the actual work.
Performs a trial operation, and stores data required for each section during the operation regarding a plurality of control parameters in the force control parameter storage unit 14 and the user program storage unit 1.
3, can be given to the position parameter storage unit 10, the coordinate system parameter storage unit 11, and the work coordinate system axis direction storage unit 12, respectively.

The position parameter transfer unit 15, the force control parameter transfer unit 17, the work coordinate system calculation unit 18 for calculating the work coordinate system, the force control calculation pre-processing unit 19, and the force control calculation unit 20 are used when executing control. The program is started based on the user program obtained by the user program analysis unit 16 which takes out the user program from the user program storage unit 13 and analyzes it.

Next, the configuration and operation of each section of the teaching / setting section will be described in detail.

The parameters stored in the force control parameter storage section 14 include, for example, set values of a plurality of various control parameters as shown in FIG. These control parameters are a force control coordinate system designation, a feed rate, a force target value, a virtual spring constant, a virtual viscosity coefficient, and a force dead zone. Set values a, b, c, d, and e are given to the feed speed, the target force value, the virtual spring constant, the virtual viscosity coefficient, and the dead zone of the force, respectively. These control parameters show an example where virtual compliance control described in, for example, JP-A-61-7905 is used as a force control method. FIG. 5 shows the relationship between the control parameters of the feed speed, the target force value, the virtual spring constant, and the virtual viscosity coefficient and the image of the control state. In FIG. 5, 21 is a work tool,
Reference numeral 22 denotes a robot wrist, which is an arm tip of the robot mechanism 1, and reference numeral 23 denotes a work.

Next, each force control parameter will be described. “Force control coordinate system designation” designates a reference coordinate system for performing force control. Each control parameter of the feed speed, the target force value, the virtual spring constant, the virtual viscosity coefficient, and the dead zone of the force is set for each axis direction of the reference coordinate system. As the force control coordinate system, a base coordinate system set on a base on which the main body of the robot mechanism 1 is installed, a tool coordinate system set on a work tool (also referred to as a work tool), set in advance corresponding to an arbitrary position Any one of the arbitrary coordinate system that can be performed and the work coordinate system according to the present invention is appropriately selected. “Feed speed” is a speed for moving the power tool 21 in the direction taught in advance. In this case, the “taught direction” is a moving direction determined by the position data stored in the position parameter storage unit 10. The “force target value” is a target value for pressing the power tool 21 against the work 23. The “virtual spring constant” and “virtual viscosity coefficient” are
These are characteristic parameters in virtual compliance control, and are a spring and a damper realized by software, respectively, as shown in FIG. "The dead zone of power"
Is for setting a dead zone for the force data from the force sensor 3 in order to secure the stability of the operation.

The coordinate system parameter storage section 11 stores data of several types of coordinate systems necessary for the operation of the robot mechanism 1. As described above, the coordinate system data includes the base coordinate system fixed to the base of the robot mechanism 1 and the work tool fixed to the arm tip (list section) of the robot mechanism 1 for controlling the operation of the robot mechanism 1. A tool coordinate system in which the position and orientation change accordingly, an arbitrary coordinate system that can be arbitrarily set by the user, and the like are included.

As shown in FIG. 6, the work coordinate system axis direction storage unit 12 stores the general direction of one of the coordinate axes x, y, and z of the work coordinate system as a vector <k>. . This <k> is arbitrarily set by the user. In the example of FIG. 6, the approximate direction of the z-axis of the work coordinate system is <k>. That is, as shown in FIG.
Although the direction of the z-axis of the system changes along the workpiece, this
Is given by <k>. <K> can be arbitrarily set by the user.
It is set, but to make teaching work even easier,
In the embodiment, the coordinates stored in the coordinate system parameter storage unit 11 are set.
One of the reference axis direction vectors is used. The work coordinate system axis direction storage unit 12 outputs <k> in consideration of convenience in calculating the work coordinate system. As described above, the work coordinate system axis direction storage unit 12 specifies the coordinate information of one of the x, y, and z axes of the work coordinate system and <k> in order to specify the coordinate system parameter storage unit 11. And which axis of which coordinate system among the coordinate systems stored in is designated as <k>. In the following description, for convenience of describing these set values, <k> for calculating the direction of the z-axis of the workpiece coordinate system will be described.
Assume that the vector is given by a vector in the z-axis direction of the base coordinate system.

The position parameter storage section 10 is a section for storing data such as the position or posture of each part of the mechanical part and the work tool required for the operation of the robot mechanism 1 during work. The position parameter storage unit 10 has the same configuration as the storage unit of the teaching position data provided in the conventional position control robot, and is known. The robot control device according to the present invention is applied to a robot system that performs work based on force control. However, since position control is required in addition to force control, the position parameter storage unit While preparing.

Next, the configuration and operation of each unit of the control execution unit will be described. The control execution unit has a function of performing a reproducing operation using a set value such as force and a program relating to the work taught and stored using the teaching / setting unit, and actually performing the work.

The user program analysis section 16 reads the user program stored in the user program storage section 13, decodes the user program, and starts necessary processing. For example,
When the decrypted user program includes a description about the position, the position parameter transfer unit 15 is started,
Necessary position data is extracted from the position parameter storage unit 10 and transferred to the force control calculation preprocessing unit 19. When the decoded user program includes a description related to the force control parameter, the control unit 17 activates the force control parameter transfer unit 17 and sends the necessary force control parameter to the force control calculation preprocessing unit 19. In this case, when the work coordinate system is designated in the force control coordinate system designation of the force control parameter, the work coordinate system calculation unit 18 is started.

Next, the flow of processing in the work coordinate system calculation unit 18 will be described with reference to the flowchart of FIG.

When the process is started, first, the work coordinate system axis direction storage unit 12 is referred to (step S1). Here, it is assumed that the set value has been instructed to set the z-axis direction of the work coordinate system to the z-axis direction of the base coordinate system. Based on the contents, a z-axis direction vector of the base coordinate system is acquired from the coordinate system parameter storage unit 11, and is set as <k> (step S2). Next, a position target value relating to the operation of the robot mechanism 1 is acquired from the position parameter storage unit 10 through the position parameter transfer unit 15, and is set as Pn (step S3). As the position parameters, there are target values of the position and the posture. In this case, only the position target values need to be acquired. Further, it is assumed here that the previously acquired position parameter is Pn-1 (step S3). At this time,
Immediately after the work coordinate system operation unit 18 is started, P
Since n-1 cannot be defined, Pn-1 may be used as the current position. Next, a unit vector <n> in the x-axis direction of the work coordinate system is calculated by the following equation using Pn and Pn-1 (step S4).

[0048]

(Equation 6)

Next, a unit vector <o> in the y-axis direction is calculated. At this time, if it is assumed that the <n> vector is parallel to the <k> vector, the calculation cannot be performed. Therefore, first, whether or not the vector is parallel is determined by the following equation (step S5).

[0050]

<N> · <k><α where the symbol “•” means an inner product and | α | <
It is one.

When the above condition is satisfied, <o>
And the unit vector <a> in the z-axis direction are calculated by the following equations (steps S6 and S7).

[0052]

[Expression 8] <o> = <k> × <n><a> = <n> × <o> Here, the symbol “x” means an outer product. The result of this operation
To explain, each axis direction of the workpiece coordinate system is as follows.
You. First, the moving direction from Pn-1 to Pn is the x-axis,
<k> given as the approximate direction of the z-axis and the x-axis direction
The direction perpendicular to the x-axis in the plane where the vector <n> extends is the z-axis
And the direction perpendicular to these x and z axes is the y axis.
You.

When the condition of the above (Equation 7) is not satisfied, an exception process is performed (step S8). Examples of exception processing include stopping the operation of the entire robot, notifying the user that the setting is inappropriate, and using the previously calculated <n>, <o>, and <a> unit vectors. A method using unit vectors in the x, y, and z directions of the coordinate system (the base coordinate system in this example) designated by the work coordinate system axis direction storage unit 12 can be used, and can be appropriately used. . The calculation is completed, and the resulting <n>, <o>, and <a> vectors are transferred to the force control calculation preprocessing unit 19 as coordinate data of the work coordinate system (step S9).

In the above example, the teaching data stored in the position parameter storage unit 10 is used as it is as the position parameter. However, the data created by the arithmetic processing based on the position data stored in the position parameter storage unit 10, Alternatively, it is possible to use data that has been subjected to interpolation processing, and data that is sent by communication from a workstation or the like from outside the robot control device 5. The above process is executed at regular sampling intervals after startup, and is repeated until an end command is received.

[0055] In the work 23 having a shape shown in FIG. 6, when the working tool 21 along a trajectory indicated by reference numeral 24 is performing, for example, grinding work while moving, the position P001~P0
In each of 10, the above-described calculation (the flowchart of FIG. 8) is executed using the position parameter of each position, and <n>,
<O> and <a> are obtained. As apparent from FIGS. 7A and 7B, according to the robot control method of the above embodiment,
For example, the coordinate system of the position P002 and the coordinate system of P007 face the same direction, and a force always acts on the work 23.

The force control calculation preprocessing unit 19 converts the given position parameters, force control parameters for executing force control, and control parameters related to the coordinate system into the force control calculation unit 2.
Perform processing to convert to a format that can be used with 0.

The configuration of the above-described force control calculation section 20 is a control device capable of executing virtual compliance control, and specifically has a configuration as shown in FIG. 2, for example. Each control parameter converted into a predetermined format by the force control calculation preprocessing unit 19 is set in each parameter input unit provided in the force control calculation unit 20. As shown in FIG. 2, as the parameter input unit, a force target value input unit 40 corresponding to the force control parameter, a force dead zone input unit 41, a virtual viscosity coefficient input unit 42, a virtual spring constant input unit 43, a coordinate system An input unit 44 and a position target value input unit 45 corresponding to the position parameter are provided. The parameter for specifying the force control coordinate system set in the coordinate system input unit 44 is given as a processing parameter to each of the coordinate conversion processing units 46, 47, and 48.

The configuration and operation of the force control calculation section 20 will be schematically described. The target force value of the target force input unit 40 is subtracted by a subtractor 49.
Where the difference between the actual force data and the actual force data from the force sensor 3 is determined. However, before reaching the subtractor 49, the force data detected by the force sensor 3 is:
Gravity compensation is performed by the force calculation unit 50, and the coordinate is converted into a force control coordinate system by the coordinate conversion processing unit 48. The difference signal obtained by the subtractor 49 is processed by the dead zone processing unit 51 in which the operating condition is set based on the dead zone width set in the dead zone input unit 41, and is input to the subtracter 52.

The position parameter set in the position target value input section 45 is given to a subtractor 53, where the difference from the current position of the work tool calculated by the position calculation section 54 is obtained. The position calculation unit 54 receives, as a position signal, angle data obtained by accumulating a signal from an encoder 55 attached to each movable unit, that is, each joint unit of the robot mechanism 1 by a counter 62, and calculates the current position by kinematics calculation. Calculate the position. The difference data obtained by the subtractor 53 is converted into a force control coordinate system by a coordinate conversion processing unit 46.
Based on the data of the difference between the positions, the virtual spring constant input unit 4
The spring force is calculated by the virtual spring force calculator 56 using the virtual spring constant set to 3. The obtained spring force is input to the subtractor 52. The output of the difference obtained by the subtractor 52 is processed by the virtual viscosity calculation unit 57 based on the virtual viscosity coefficient set in the virtual viscosity coefficient input unit 42. The output of the virtual viscosity calculation unit 57 is converted into a reference coordinate system by a coordinate conversion processing unit 47, and the rotation speed of a motor 59, which is a driving device disposed at each joint, is calculated by a motor speed calculation unit 58. Is done. The calculated control command value of the motor rotation speed is given to each motor 59 of the robot mechanism 1 via the servo amplifier 60, and its rotation operation is controlled. The configuration of the control execution unit of the robot control device 5 described above is configured to obtain a solution that satisfies an equation that defines a predetermined virtual compliance control. The solution obtained by this configuration is given to the drive device of the robot mechanism 1 as a control command for satisfying a control condition determined by a plurality of control parameters set in each control parameter input unit,
An operation is given to the robot mechanism 1. Thus, the robot mechanism 1 can be operated based on the plurality of control parameters specified by the user's teaching / setting operation.

When any one of the x, y, and z axes of the tool coordinate system as the workpiece coordinate system axis direction is designated, the current value of the tool coordinate system is required. As shown in FIG. 1, the tool coordinate system data output unit 61 updates the stored data in the coordinate system parameter storage unit 11 through the force control calculation preprocessing unit 19 as needed.

In the configuration shown in FIG. 2, as described above, the motor 59 and the encoder 55 for detecting the amount of operation are provided as driving devices disposed at each movable part (joint part) of the robot mechanism 1.
And the counter 62 are explicitly shown.

Referring to FIGS. 9 and 10, an example of generating a workpiece coordinate system by the robot control method according to the present invention will be described. In both figures, it is assumed that the user has designated the z-axis of the base coordinate system as the axial direction of the work coordinate system. In the case of FIG. 9, the z-axis changes in the normal direction of the work 23 while the y-axis direction faces the inside of the work 23 based on the position parameters given in P001 to P005 in the processed portion of the work 23. You can see that In the case of FIG. 10, the y-axis direction is oriented in the normal direction to the side surface 23a of the work 23 by the position parameters given by P001 to P007 in the work 23,
It can be seen that the z-axis direction is normal to the slope 12b of the work 23.

If force control is performed by setting the work coordinate system as described above, a constant force target value is set in the positive direction of the y-axis in the case of FIG. By simply setting a constant force target value in the negative direction of the y-axis, the work tool can always be pressed against each workpiece of the work, and highly accurate force control can be performed with simple settings.

In order to improve the accuracy of generating the work coordinate system, the work shape is finely taught by teaching, or an interpolation of a circular arc, a spline, a straight line, or the like is performed between the teaching data. What is necessary is just to generate.

Next, with reference to FIG. 3, a computer configuration for realizing the robot controller 5 and its operation will be described.

The detection value output by the force sensor 3 is input to the force input device 70. The force input device 70 is constituted by an A / D converter when the output of the force sensor 3 is an analog signal, and the output is a serial communication (RS422, RS232).
-C etc.), it is configured with a receiver suitable for communication. The data input to the force input device 70 is transmitted to the bus 7
1 and stored in the RAM 72. The angle data of each axis generated by the encoder 55 arranged corresponding to each joint is integrated by the counter 62,
Stored in M72. The parameter input device 73 is a device for inputting control parameters relating to force control. The input control parameters are stored in the RAM 72 via the bus 71. As for the position parameter, the parameter input device 73 is configured to store the position when instructed in the RAM 72. Thus, the RAM 72 has the position parameter storage unit 10 and the user program storage unit 1
3. A force control parameter storage unit 14, a coordinate system parameter storage unit 11, a work coordinate system axis direction storage unit 12, and the like are formed. Further, intermediate parameters required for arithmetic processing in the CPU 74 are stored. Various processing programs executed by the CPU 74 are stored in the ROM 75.

When causing the robot mechanism 1 to perform a force control operation using a plurality of taught and set control parameters, the CPU 74 executes a user program, control parameters determined corresponding to each work section, and position control. The parameters are read out and set in the control execution section, the detection signals of the force sensor 4 and the encoder 55 are taken in, the taken-in force data is compensated, and the operation command value is calculated while comparing with the set control target value. The operation command value is output from the operation command value output device 76 and supplied via the servo amplifier 60 to a required motor 59 disposed at a joint of the robot mechanism 1. Thus, the CPU 74 implements the function as the robot control device 5.

[0068]

As apparent from the above description, according to the present invention, a coordinate system expressing the shape of a workpiece to be machined can be automatically set by calculation based on simple settings by a user. In addition, this calculation is suitable for real-time processing because the number of necessary data and the amount of calculation are small, and in the work that requires force control, the actual control according to the shape of the work with respect to the control contents such as the direction of applying force This enables efficient control and highly accurate control.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a robot control device according to the present invention.

FIG. 2 is a block circuit diagram showing an internal configuration of a force control calculation unit.

FIG. 3 is a block diagram for realizing the robot control device according to the present invention by a computer system.

FIG. 4 is a table showing the contents of a plurality of force control parameters in a table.

FIG. 5 is a diagram showing a correspondence relationship between a work image and each control parameter.

FIG. 6 is a diagram showing a target trajectory on a workpiece and a coordinate system generated at each position.

FIG. 7 is a diagram showing a coordinate system generated at two positions on a target trajectory.

FIG. 8 is a flowchart illustrating a robot control method according to the present invention.

FIG. 9 is a diagram illustrating an example of a coordinate system generated by the coordinate system setting method according to the present invention.

FIG. 10 is a diagram showing another example of a coordinate system generated by the coordinate system setting method according to the present invention.

FIG. 11 is a diagram showing an example of a coordinate system generated by a conventional method on a target trajectory.

FIG. 12 is a diagram showing a coordinate system generated at two positions on a target trajectory based on a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Robot mechanism 3 Force sensor 4 Teach operating device 5 Robot control device 10 Position parameter storage unit 11 Coordinate system parameter storage unit 12 Work coordinate system axis direction storage unit 13 User program storage unit 14 Force control parameter storage unit 16 User program analysis unit 18 Work coordinate system calculation unit 19 Force control calculation preprocessing unit 20 Force control calculation unit 21 Work tool 23 Work

Continuation of the front page (72) Inventor: Shinichi Saruga 7-1-1, Higashi-Narashino, Narashino-shi, Chiba Hitachi Keiyo Engineering Co., Ltd. (56) References JP-A-3-104579 (JP, A) JP-A-1- 222315 (JP, A) JP-A-3-262009 (JP, A) JP-A-5-150837 (JP, A) JP-A-3-240105 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B25J 13/00 G05B 19/18 G05D 3/12 305

Claims (9)

(57) [Claims] 1. A method of controlling a position and a force of a work tool at a tip end of a work robot having a plurality of degrees of freedom, wherein the work tool is pressed against a workpiece to be processed.
Countercurrent is set as general direction, the pressing direction is arbitrarily determined as general direction as one axial direction of the temporary workpiece coordinate system, for generating a target trajectory for the processed portion of the work tool Calculated from position parameters
The direction is defined as the main other axis direction of the work coordinate system,
So that one axis direction is orthogonal to the other main axis direction.
A robot control method comprising: calculating a vector in each axis direction of a work coordinate system by correcting the position; and controlling the position and force of the power tool using the vector in each axis direction. 2. The robot control method according to claim 1, wherein the vector in one axis direction is specified in one axis direction from a coordinate system fixed in a space where the work robot is installed. Robot control method. 3. The robot control method according to claim 1, wherein the one axis direction vector is designated in one axis direction from a coordinate system calculated and generated by the control means in accordance with the operation of the robot mechanism. A robot control method characterized by the above-mentioned. 4. The robot control method according to claim 1, wherein the position parameter is position data stored in a storage unit in accordance with a user's teaching to the work robot. 5. The robot control method according to claim 1, wherein the position parameter is data created by an arithmetic process based on position data stored in a storage unit according to a user's teaching to the work robot. A robot control method characterized by the above-mentioned. 6. The robot control method according to claim 5, wherein the arithmetic processing is an interpolation operation. 7. A position and force robot control device for controlling a working robot having multiple degrees of freedom, comprising a plurality of storage units for storing a position parameter, a user program, and various force control parameters in a preceding stage. A control execution unit including a teaching / setting unit including and a control control unit including a force control calculation unit at a subsequent stage, and reading and analyzing the user program set in the teaching / setting unit by a user program analysis unit of the control execution unit, In a robot controller for transferring a position parameter and a force control parameter from each storage unit to each input unit of the control execution unit according to the contents of the command, the teaching / setting unit stores a parameter related to a coordinate system. Arbitrarily determined as an approximate direction with respect to the work coordinate system from among the coordinate systems.
Pressing and a work coordinate system axis storage unit for storing a direction as one axial direction of the temporary, the control execution unit, for each position to form a target track, the position parameter storing unit and the coordinate system parameter storage unit And input each output of the work coordinate system axis direction storage unit, using the position parameters, the parameters related to the coordinate system, and the one axis direction arbitrarily determined as the approximate direction with respect to the work coordinate system, A robot control device including a work coordinate system calculation unit that calculates each axis direction vector in a work coordinate system and outputs the vector as a control command value. 8. The robot control device according to claim 7, wherein the work coordinate system operation unit performs an operation in accordance with a command output from the user program analysis unit. 9. The robot control device according to claim 7, wherein, instead of using the position parameter from the position parameter storage unit, data on a position obtained by performing a predetermined operation on the position parameter is used. Robot control device.