Processing system and processing method

Abstract

To adjust a control parameter according to hardness of a tool to be used.SOLUTION: A processing system 100 includes a main shaft 11 supporting a tool T, and a control device 50 for controlling operation of the main shaft 11. The control device 50 is configured to execute pushing of the tool T against a workpiece 90, calculation of a coefficient of elasticity between the tool T and the workpiece 90, determination of a control parameter of force control for controlling pushing of the tool T against the workpiece 90 on the basis of the calculated coefficient elasticity, and processing of the workpiece 90 using a control parameter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to processing systems and methods. [Background technology]

[0002] In machining systems, force control is sometimes used to control tools. For example, the robot system of Patent Document 1 uses both position control and force control to control the end effector. In the robot system of Patent Document 1, position control is used to move the end effector along a target trajectory. Force control is also used to make the end effector contact an object with a target force. The virtual viscosity coefficient in force control is set according to the velocity coefficient in position control.

[0003] Furthermore, the robot control device of Patent Document 2 uses impedance control as force control to control a robot arm. In the robot control device of Patent Document 2, when the speed of the hand of the robot arm is a first speed, the viscosity parameter of the impedance control is adjusted to a first viscosity value. When the speed of the hand of the robot arm is a second speed that is slower than the first speed, the viscosity parameter is adjusted to a second viscosity value that is higher than the first viscosity value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-089747 [Patent Document 2] Japanese Patent Application Publication No. 2019-214105 Summary of the Invention [Problem to be solved by the invention]

[0005] A machining system may use various tools with different hardnesses. In this case, the control parameters used for force control may vary depending on the hardness of the tools. However, in the systems of Patent Documents 1 and 2, the control parameters are not adjusted depending on the hardness of the tools used.

[0006] The present disclosure aims to provide a machining system and machining method that can adjust control parameters depending on the hardness of the tool being used. [Means for solving the problem]

[0007] A machining system according to one aspect of the present disclosure includes a spindle that supports a tool. and an arm supporting the main shaft. and, robot A control device for controlling the operation of the tool pressing against the workpiece, Robot arm and a control device configured to calculate an elastic coefficient between a tool and a workpiece, determine a control parameter for force control for controlling pressing of the tool against the workpiece based on the calculated elastic coefficient, and machine the workpiece using the control parameter. , Pressing the tool against the workpiece involves rotating the tool. .

[0009] Calculating the elastic modulus may be performed while machining the workpiece, with the tool moving along the surface of the workpiece.

[0010] Calculating the modulus of elasticity may be performed before moving the tool along the surface of the workpiece.

[0011] Another aspect of the present disclosure is a method of processing, comprising: A robot including a spindle that supports a tool and an arm that supports the spindle, Pressing the tool against the workpiece; Robot arm and Calculating an elastic coefficient between a tool and a workpiece, determining a control parameter for force control for controlling pressing of the tool against the workpiece based on the calculated elastic coefficient, and machining the workpiece using the control parameter. Pressing the tool against the workpiece involves rotating the tool. . [Effects of the Invention]

[0012] According to the present disclosure, the control parameters can be adjusted depending on the hardness of the tool being used. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing a processing system according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the processing system of FIG. [Figure 3] FIG. 3 is a flowchart showing the operation of the machining system according to the embodiment. [Figure 4] FIG. 4 shows an example of calculation of the elastic modulus between the tool and the workpiece in another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Specific dimensions, materials, numerical values, etc. shown in the embodiments are merely examples for ease of understanding and do not limit the present disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present disclosure are not shown.

[0015] FIG. 1 is a schematic diagram showing a processing system 100 according to an embodiment. In the present disclosure, the processing system 100 may also be simply referred to as a system. In this embodiment, the system 100 is used for surface finishing of a workpiece 90. In other embodiments, for example, the system 100 may be used for other machining or removal processes. In this embodiment, the system 100 includes a processing apparatus 10 and a control device 50. The system 100 may further include other components.

[0016] In this embodiment, the processing apparatus 10 is a robot. For example, the processing apparatus 10 may be a multi-degree-of-freedom articulated robot. In other embodiments, the processing apparatus 10 may be another robot. In still other embodiments, the processing apparatus 10 may be, for example, a machine tool that moves a spindle 11 linearly in three axis directions. The processing apparatus 10 includes a spindle 11 and an arm 12. The processing apparatus 10 may further include other components.

[0017] The spindle 11 supports the tool T. The spindle 11 rotates the tool T around the central axis A. For example, the tool T can be various tools having different hardnesses, such as a brush or a grinding wheel. As described above, in this embodiment, the system 100 is used for surface finishing of the workpiece 90, so the tool T can be a soft tool. When the tool T is pressed against the workpiece 90, the tool T elastically deforms. Therefore, the contact model between the tool T and the workpiece 90 can be regarded as a spring having an elastic coefficient K.

[0018] The spindle 11 includes a force sensor 14. The force sensor 14 measures a load acting from the tool T on the workpiece 90 in at least a direction parallel to the central axis A. In the present disclosure, the load acting from the tool T on the workpiece 90 in a direction parallel to the central axis A is also referred to as a "pressing force." The force sensor 14 may also measure loads in other directions. For example, the force sensor 14 may be a sensor capable of measuring loads in multiple directions, or may be a sensor capable of measuring a load in a single direction. In other embodiments, for example, the force sensor 14 may be provided on a table (not shown) that supports the tool T. The force sensor 14 is communicatively connected to the control device 50 via wire or wirelessly and transmits measurement data to the control device 50.

[0019] The arm 12, for example, moves the spindle 11 with multiple degrees of freedom. For example, the arm 12 moves the spindle 11 in a direction parallel to the central axis A and in one or more directions perpendicular to the central axis A. The tool T is pressed against the workpiece 90 in a direction parallel to the central axis A. Therefore, in the present disclosure, the direction parallel to the central axis A is also referred to as the pressing direction A. The tool T is fed in a direction B perpendicular to the central axis A. In the present disclosure, this direction B is also referred to as the feed direction B.

[0020] The machining apparatus 10 includes a plurality of motors M for moving the arm 12. For example, the motors M may be servo motors and may include encoders. The motors M are connected to the control device 50 via wired or wireless communication. For example, the control device 50 can obtain the position and attitude of the tool T based on signals from the encoders. Therefore, in this embodiment, the motors M function as "position sensors" for measuring the position of the tool T. In other embodiments, for example, a contact or non-contact displacement sensor that measures the distance between the spindle 11 and the workpiece 90 may be used as the "position sensor." The control device 50 sends command signals to the motors M to control the movement of the tool T in the pressing direction A and the feed direction B.

[0021] The control device 50 can obtain the amount of pressing displacement of the tool T against the workpiece 90 based on the signal from the encoder. The amount of pressing displacement can be obtained by measuring the amount of displacement from a first position where contact between the tool T and the workpiece 90 is detected by the force sensor 14 to a second position where the tool T has further moved toward the workpiece 90. Note that in this embodiment, since the system 100 is used for surface finishing of the workpiece 90 and the tool T may be a soft tool, the removal depth of the workpiece 90 can be substantially ignored when calculating the amount of pressing displacement.

[0022] The surface 91 of the workpiece 90 may include surface textures such as roughness and waviness. Therefore, a position error may exist between the ideal surface L of the workpiece 90 based on, for example, a design drawing and the actual surface 91. When the tool T is pressed against the workpiece 90, a force error is input to the machining device 10 due to this position error. As will be described in detail later, in the system 100, tracking performance is improved by setting a position command taking this force error into consideration.

[0023] The control device 50 controls all or part of the system 100. The control device 50 includes components such as a processor 50a, a storage device 50b, and a connector 50c, which are connected to one another via a bus. For example, the processor 50a includes a central processing unit (CPU). For example, the storage device 50b includes a hard disk, a ROM for storing programs, and a RAM as a work area. The control device 50 communicates with each component of the machining system 100 via the connector 50c. For example, the control device 50 may further include other components, such as a display device such as an LCD display or a touch panel, and an input device such as a keyboard, buttons, or a touch panel. For example, the operation of the control device 50 described below may be realized by the processor 50a executing a program stored in the storage device 50b.

[0024] Fig. 2 is a block diagram showing the machining system 100 of Fig. 1. For example, the system 100 may be designed as a two-degree-of-freedom control system as shown in Fig. 2. The system 100 includes a force controller 51, a reference model 52, and a nominal model 53. For example, the force controller 51, the reference model 52, and the nominal model 53 may be realized by causing the processor 50a to execute a program stored in the storage device 50b. The symbols shown in Fig. 2 are as follows:

[0025] f d : target force value D C :Damper coefficient KC : Elastic modulus s : complex number u :Position command P: Robot model P H :Nominal robot model (assumed robot model) K: Elastic modulus between the tool and workpiece K H : Nominal elastic coefficient between the tool and workpiece (assumed elastic coefficient) Q: Reference model w: Force error y: force output

[0026] The force controller 51 controls the pressing of the tool T against the workpiece 90 by force control in the pressing direction A. Note that in the feed direction B, the tool T may be controlled by position control based on, for example, PID control or the like.

[0027] The reference model 52 shapes the position command u. The nominal model 53 estimates the position error from the force output y. The reference model Q is selected so that the nominal model 53 becomes proper. Subtracting the difference between the output of the reference model 52 and the output of the nominal model 53 from the position command u is equivalent to taking into account the error calculated back from the current force output y in the position command u of feedback control. This configuration improves the tracking ability of the system 100.

[0028] In the system 100 shown in FIG. 2, the position command u and the output y are expressed by the following equations (1) and (2), respectively.

[0029]

number

[0030]

number

[0031] The transfer function of the output y with respect to the error w is expressed by the following equation (3).

[0032]

number

[0033] As can be seen from equation (3), when the elastic coefficient K is increased by a factor of α, the damping coefficient D C , elastic modulus K C and the nominal elastic modulus K H By multiplying by α, y / w is maintained constant, i.e., the responsiveness to the error w is maintained constant. In other words, if the elastic coefficient K is multiplied by α, y / w is maintained constant by multiplying the force controller 51 by 1 / α. This relationship applies to the entire frequency domain because equation (3) is expressed in the frequency domain after the Laplace transform. Therefore, in the system 100, it is not necessary to adjust the control parameters depending on the frequency domain.

[0034] Next, a processing method according to the embodiment will be described.

[0035] 3 is a flowchart showing the operation of the machining system 100 according to the embodiment. For example, the operation shown in FIG. 3 may be performed when the control device 50 receives a command to start machining. Prior to the operation shown in FIG. 3, the damper coefficient D C , elastic modulus K C and initial values ​​of the elastic modulus K between the tool T and the workpiece 90 are set in advance in the control device 50. These initial values ​​can be set by a known method such as an experiment.

[0036] The processor 50a moves the tool T to an initial position above the workpiece 90 and away from the workpiece 90 (step S100).

[0037] Next, the processor 50a moves the tool T toward the workpiece 90 along the pressing direction A (step S102). For example, the tool T may be moved at a constant speed along the pressing direction A. During step S102, the processor 50a rotates the tool T at a predetermined rotation speed, for example, the rotation speed used in machining. Also during step S102, the processor 50a acquires measurement data from the force sensor 14.

[0038] Subsequently, the processor 50a determines whether or not contact between the tool T and the workpiece 90 is detected (step S104). If contact is not detected in step S104 (NO), the processor 50a repeats step S102.

[0039] If contact is detected in step S104 (YES), the processor 50a calculates the true elastic modulus K of the tool T (step S106). For example, after step S104, the processor 50a may press the tool T against the workpiece 90 along the pressing direction A until a predetermined pressing displacement amount is measured based on a signal from the encoder of the motor M, or until a predetermined pressing force is measured based on a signal from the force sensor 14. The processor 50a can calculate the true elastic modulus K by dividing the pressing force by the pressing displacement amount. The pressing force is measured by the force sensor 14. The pressing displacement amount is obtained by measuring, based on a signal from the encoder, the amount of displacement from a first position where contact between the tool T and the workpiece 90 is detected by the force sensor 14 to a second position where the tool T has further moved toward the workpiece 90.

[0040] Subsequently, the processor 50a adjusts the control parameters (step S108). Specifically, the processor 50a obtains a ratio α of the true elastic coefficient K to the initial value K0 of the elastic coefficient K (K=αK0). Subsequently, the processor 50a calculates the damper coefficient D C and the elastic modulus K C By multiplying the initial value of by the ratio α, the adjusted damper coefficient D C and the elastic modulus K CIn other words, the processor 50a divides the force controller 51 by the ratio α to obtain the adjusted force controller 51. The processor 50a also obtains the nominal elastic coefficient K H By multiplying the initial value of by the ratio α, the adjusted nominal elastic coefficient K H get.

[0041] Subsequently, the processor 50a uses the adjusted control parameters to machine the workpiece 90 (step S110), and ends the series of operations. Specifically, the processor 50a uses the adjusted control parameters to press the tool T against the workpiece 90 by force control in the pressing direction A, and moves the tool T along the surface 91 of the workpiece 90 by position control in the feed direction B.

[0042] The system 100 as described above includes a spindle 11 that supports a tool T, and a control device 50 that controls the operation of the spindle 11. In the system 100 and the machining method as described above, the control device 50 presses the tool T against a workpiece 90, calculates a true elastic modulus K between the tool T and the workpiece 90, and sets a control parameter D for force control for controlling the pressing of the tool T against the workpiece 90 based on the calculated true elastic modulus K. C ,K C and determining the control parameter D C ,K C According to this configuration, the true elastic modulus K is calculated according to the hardness of the tool T, and the control parameter D for force control is set based on the true elastic modulus K. C ,K C Therefore, the control parameter D is determined depending on the hardness of the tool T used. C ,K C can be adjusted

[0043] Furthermore, in the system 100, pressing the tool T against the workpiece 90 includes rotating the tool T. The elastic coefficient K between the tool T and the workpiece 90 may vary depending on the hardness of the tool T as well as the number of rotations of the tool T. Therefore, according to the above configuration, a more appropriate elastic coefficient K and control parameter D C ,K C can be determined.

[0044] In the system 100, the true elastic modulus K is calculated before the tool T is moved along the surface 91 of the workpiece 90, i.e., before machining. With this configuration, the adjusted control parameter D C ,K C can be used.

[0045] Although the embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to the above-described embodiments. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that such modifications also fall within the technical scope of the present disclosure.

[0046] For example, the force controller 51 is not limited to the one shown in FIG. 2, but may be a controller based on a general PID control.

[0047] Also, for example, in the above embodiment, the calculation of the elastic coefficient K (steps S100 to S106) is performed before the tool T is moved along the surface 91 of the workpiece 90, i.e., before machining begins. In another embodiment, the calculation of the elastic coefficient K may be performed while the tool T is being moved along the surface 91 of the workpiece 90 and machining the workpiece 90. With this configuration, the control parameters are adjusted during machining, so no additional time is required for adjustment. This configuration is also useful, for example, when the hardness of the tool T changes during machining. FIG. 4 shows an example of calculation of the elastic coefficient K between the tool T and the workpiece 90 in this other embodiment. In this embodiment, the pressing force is measured by the force sensor 14 as described above, and the elastic coefficient K can be calculated from the fluctuation of the force around the target value over a certain period of time and the fluctuation of the position deviation (the difference between the measured position and the target position) as shown, for example, by the least-squares approximation line y=KΔx-b in FIG. 4. [Explanation of symbols]

[0048] 11 Spindle 50 Control device 90 Work 91 Work surface 100 Processing System D C Damper coefficient (control parameter for force control) K is the elastic modulus between the tool and the workpiece K C Elasticity coefficient (control parameter for force control) T-tool

Claims

1. a robot including a spindle that supports a tool and an arm that supports the spindle; A control device for controlling the operation of the robot, The control device includes: pressing the tool against a workpiece; Calculating elastic coefficients between the arm of the robot, the tool, and the workpiece; determining a control parameter for force control for controlling pressing of the tool against the workpiece based on the calculated elastic coefficient; machining the workpiece using the control parameters; configured to perform a control device; Equipped with Pressing the tool against the workpiece includes rotating the tool. Processing system.

2. The machining system according to claim 1 , wherein the elastic modulus is calculated while machining the workpiece by moving the tool along the surface of the workpiece.

3. The machining system of claim 1 , wherein the elastic modulus is calculated before the tool is moved along the surface of the workpiece.

4. Pressing the tool against a workpiece by a robot including a spindle that supports the tool and an arm that supports the spindle; Calculating elastic coefficients between the arm of the robot, the tool, and the workpiece; determining a control parameter for force control for controlling pressing of the tool against the workpiece based on the calculated elastic coefficient; machining the workpiece using the control parameters; Including, Pressing the tool against the workpiece includes rotating the tool. Processing method.

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