Servo control device

Abstract

The present invention provides a servo control device, which continuously optimizes parameters according to the state of a machine. A servo control device (10) is used to control a motor that drives an axis of an industrial machine, and the servo control device comprises: a state value derivation unit (11) that derives a time series or event sequence of state values ​​of the motor or a driven body that moves through the motor according to an operation program and / or operation plan information of the industrial machine; and a parameter change unit (12) that changes at least one parameter of a speed gain, a position gain, a feedforward gain, a filter frequency, and an acceleration / deceleration time constant after interpolation along the time series or event sequence based on the time series or event sequence data derived by the state value derivation unit (11).

Description

Technical Field

[0001] The invention relates to a servo control device. Background Art

[0002] As is known to all, in the field of mechanical work, CNC (Computerized Numerical Control) technology is applied to numerically control the movement amount, movement speed, etc. using a computer, thereby highly automating the repetition of the same action, complex actions, etc.

[0003] In addition, design and drawing are performed through CAD (Computer Aided Design), and action programs (machining programs, etc.) that match CAD data are produced through CAM (Computer Aided Manufacturing). The data produced by CAM is acquired into CNC, and various data such as input options, parameters, NC programs, macro programs, macro variables, workpiece origin offset, tool offset, tool shape data, tool management data, etc. are used for control. In this way, NC machine tools such as NC lathes and machining centers are consistently automated from design to manufacturing.

[0004] On the other hand, servomotors (electric motors) for driving shafts and the like of industrial machines such as machine tools and robots are driven and controlled in terms of rotation amount, speed, torque, and the like.

[0005] Here, Patent Document 1 discloses "a control device for an electric motor, characterized in that it comprises the following units: adding a sinusoidal wave instruction to a torque instruction for the electric motor; obtaining a current value flowing to the electric motor; obtaining an acceleration value of the electric motor; and estimating the inertia of a driven body driven by the electric motor based on a torque constant of the electric motor and a current representative value and an acceleration representative value obtained from a plurality of the current values ​​and a plurality of the acceleration values ​​in the same action state in a plurality of cycles of the sinusoidal wave instruction."

[0006] Patent document 2 discloses "a numerical control device connected to a shared database for controlling a machine tool, wherein processing instruction information and processing resource information related to the numerical control device and the machine tool are stored in the shared database, the processing instruction information includes processing content information about processing content produced by CAD and CAM and processing requirement information about at least one requirement required for processing, the numerical control device has a processing instruction interpretation unit for interpreting the processing instruction information and a processing instruction execution unit for executing processing based on the result interpreted by the processing instruction interpretation unit, the processing instruction interpretation unit executes at least one of the following processes: judging whether the machine tool can be used for processing according to the processing instruction information based on the processing instruction information and the processing resource information stored in the shared database; determining processing parameters; and automatically selecting the functions of the numerical control device and the machine tool used in the processing."

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent No. 4565034

[0010] Patent Document 2: Japanese Patent Application Publication No. 2018-151736 Summary of the invention

[0011] Problem that the invention aims to solve

[0012] For example, in a machine tool, when the state (state value) of inertia or machine position changes due to a machine operation such as machining, optimal parameters such as gain (position gain, speed gain, etc.) and filter band also change.

[0013] Generally, since the parameters are fixed, the most conservative settings are made to match the mechanical changes. That is, low gain, large attenuation (large delay) filters, and long time constants are pre-set to prevent oscillation due to mechanical movements such as processing. As a result, it is difficult to shorten the cycle time.

[0014] Alternatively, when parameters are set to be optimal under certain conditions, there is a concern that the parameters may become non-optimal when inertia or position changes occur, and vibration may occur during machining using a machine tool, leaving scratches on the machined surface.

[0015] If the parameters are fixed as described above, it is not convenient to change them, and therefore a method of changing the parameters to the optimum according to the state of the machine is strongly desired.

[0016] In addition, as methods for optimizing parameters according to the state, consider (1) a method of adaptively changing parameters and (2) a method of changing parameters in a pre-planned manner. In the adaptive parameter change method among them, state estimation and optimal value calculation need to be performed in real time, so there are the following problems: (A) the calculation load increases (i.e., an expensive arithmetic device is required); (B) the estimation calculation uses FB data obtained from sensors in real time, so it is affected by noise; and (C) it is difficult to adjust the hyperparameters used in the estimation calculation itself.

[0017] In addition, regarding the case of (2) changing parameters in a pre-planned manner, if only relying on the information within the CNC (numerical control device), in most cases, the information sufficient to create an optimal parameter schedule is insufficient.

[0018] Solutions for solving problems

[0019] One aspect of the servo control device of the present disclosure is a servo control device for controlling a motor that drives a shaft of an industrial machine. The servo control device includes: a state value derivation unit that derives data of a time series or an event sequence of a state value of the motor or a driven body that operates by the motor according to the operation program and / or operation plan information of the industrial machine; and a parameter change unit that changes at least one parameter among a speed gain, a position gain, a feedforward gain, a filter frequency, and an interpolation acceleration / deceleration time constant along the time series or the event sequence based on the data of the time series or the event sequence derived by the state value derivation unit.

[0020] Effects of the Invention

[0021] According to one aspect of the servo control device of the present disclosure, based on the predicted event sequence data or time series data of the machine, an optimal parameter schedule according to the event sequence or the time series is obtained, and the parameters are changed along this schedule, thereby enabling optimization of the parameters according to the state of the machine such as the driven body and the shaft. As a result, for example, it is possible to improve the operation accuracy of industrial machines such as the machining accuracy of machine tools and shorten the time (improve the productivity (in Japanese: fukari)). BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a diagram showing a control system and a servo control device of a machine tool according to one aspect.

[0023] Figure 2 It is a block diagram showing a servo control device according to one aspect.

[0024] Figure 3This is a diagram used to explain the event-sequence or time-series scheduling in which an optimal parameter is created by a servo control device of one embodiment.

[0025] Figure 4 This is a diagram used to explain the event-sequence or time-series scheduling in which an optimal parameter is created by a servo control device of one embodiment.

[0026] Figure 5 This is a diagram used to explain the event-sequence or time-series scheduling in which an optimal parameter is created by a servo control device of one embodiment.

[0027] Figure 6 This is a diagram used to explain the event-sequence or time-series scheduling in which an optimal parameter is created by a servo control device of one embodiment.

[0028] Figure 7 This is a diagram used to explain the event-sequence or time-series scheduling in which an optimal parameter is created by a servo control device of one embodiment.

[0029] Description of Reference Numerals

[0030] 1: Control system of machine tool (industrial machinery); 2: CAD; 3: Machining program creation unit (operation program creation unit); 4: Machining simulator unit (operation simulator unit); 5: CAM; 6: CNC; 7: Servo motor (drive unit); 8: Motor control unit; 9: Machining plan information (operation plan information); 10: Servo control device; 11: Status value export unit; 12: Parameter change unit. DETAILED DESCRIPTION

[0031] Below, refer to Figures 1 to 7 A servo control device according to one embodiment will be described.

[0032] First, in the present embodiment, the description will be given assuming that the industrial machine is a machine tool and the electric motor is a servo motor that drives a main shaft (shaft, driven body) and the like of the machine tool.

[0033] However, the industrial machinery involved in the present invention can of course also be other industrial machinery such as robots, conveyors, measuring instruments, testing equipment, punches, presses, printers, die-casting machines, injection molding machines, food machinery, packaging machines, welding machines, cleaning machines, coating machines, assembly devices, installation machines, woodworking machines, sealing devices, cutting machines, etc.

[0034] First, if Figure 1 and Figure 2As shown, the control system 1 of the machine tool of the present embodiment comprises: CAD 2, which is used for designing and drawing products, etc.; CAM 5, which has a processing program creation unit (operation program creation unit) 3 for creating a processing program (operation program) based on processing shape data (product data) created by CAD 2 and a processing simulator unit (operation simulator unit) 4 for performing processing simulation (operation simulation); CNC 6 as an instruction unit, which sends instruction signals based on processing plan information (G code, operation plan information) 9 sent from CAM 5; and a motor control unit 8, which controls the drive of the servo motor (drive unit) 7 of the machine tool based on the instruction of CNC 6.

[0035] The servo motor 7 serving as a driving unit is, for example, a servo motor (electric motor) for driving a feed shaft (axis), a spindle (axis) of an assembly tool (driven body), etc. The feed shaft is used to move a worktable (driven body) holding a workpiece (driven body), and the motor control unit 8 is, for example, a servo amplifier.

[0036] On the other hand, the servo control device 10 of the present embodiment comprises: the above-mentioned machining program creation unit 3; a machining simulator unit 4; a state value export unit 11, which obtains the machining plan information produced by the machining program creation unit 3 and the machining simulator unit 4, and obtains the time series or event sequence data of the state values ​​of the workpiece, the worktable and other driven bodies, and the servo motor 7 based on the machining plan information; and a parameter changing unit 12, which changes at least one parameter of the velocity gain, position gain, feedforward gain, filter frequency, and acceleration / deceleration time constant after interpolation along the time series or event sequence based on the time series or event sequence data exported by the state value export unit 11.

[0037] Specifically, if Figure 1 As shown, after CNC 6 obtains the processing plan information 9 produced by CAD 2 and CAM 5, CNC 6 as the instruction unit issues interpolated position instructions and acceleration and deceleration instructions to the servo amplifier, namely the motor control unit 8, and the motor control unit 8 controls the drive of the servo motor 7.

[0038] At this time, in the servo control device 10 of the present embodiment, the state value derivation unit 11 obtains the processing plan information 9 from the CAM 5, and obtains the relationship 13 of the inertial time series or event series based on the processing plan information 9. In addition, the inertial event series is formed by continuously showing the time required for each processing process (event) in a time series, for example, it refers to the inertial time series that reflects the situation that time irrelevant to the process is generated between a certain processing process and the next processing process due to unpredictable events, etc.

[0039] An example will be described more specifically.

[0040] In such Figure 3 As shown, in a state where no workpiece is held (mounted) on the stage (workbench) 6, the inertia J is J=J0, and the stage 6 is moved by rotating the feed shaft (ball screw) 15 in the forward and reverse directions around the axis by the drive of the servo motor 7. J0 is the sum of the inertia values ​​of the motor rotor, the feed shaft 15, and the stage 16.

[0041] In such Figure 4 As shown in the figure, when the workpiece 17 with a mass M is held on the mounting table 6, the inertia is J LOAD =J0+MR 2 In addition, R is a conversion coefficient of rotation-linear motion with respect to the lead (movement distance) L (m), and is represented by R=L / 2π (m / rad).

[0042] Therefore, the speed FB gain and speed FF gain are scheduled as J LOAD / J=1+(MR 2 / J0) times. For example, when J0 = 0.01kgm 2 , M = 500kg, L = 0.02m, according to J LOAD / J=1+(MR 2 / J0) and set the gain to 1.5 times.

[0043] On the other hand, when the transmission characteristics from the torque of the servo motor 7 to the position (mechanical end) of the mounting table 16 are shown, for example Figure 5 In addition, if Figure 6 As shown, when the position of the mounting table 16 changes, the axial rigidity Kt of the machine changes, and the resonance frequency (natural vibration frequency) also changes. In particular, in the case of a large machine or a long ball screw (stroke, etc.), the rigidity changes greatly depending on the position.

[0044] Therefore, if Figure 7 As shown, the attenuation center frequency (due to the change in resonance frequency), the time constant (due to the increase in time constant due to the decrease in rigidity, vibration is more likely to occur) and the like of the filter 18 are scheduled according to the position.

[0045] Then, if Figure 1 As shown, the state value export unit 11 obtains the processing plan information 9 from the CAM 5, and obtains the relationship 13 of the time series or event sequence of inertia based on the processing plan information 9. Then, the state value export unit 11 obtains the gain scheduling (speed gain, position gain, feedforward gain, etc. in time series) 14 based on the relationship 13 of the time series or event sequence of inertia, and synchronizes the gain scheduling with the instructions of the CNC 6.

[0046] Next, the parameter changing unit 12 changes the parameters of the speed loop (and / or position loop) of the motor control unit 8 along the time sequence or event sequence based on the gain schedule (data of the time sequence or event sequence) 14 derived by the state value deriving unit 11. For example, Figure 1 As shown, the speed loop parameters "β (coefficient)" and "Kν (gain)" are changed to match the gain scheduling. Figure 1 The "s" of the speed loop and position loop is the differential value.

[0047] Then, based on the speed FF (or position FF: feedforward) changed in accordance with the gain scheduling, a torque command or other command is issued from the motor control unit 8 to drive and control the servo motor 7 .

[0048] Thus, in the servo control device 10 of the present embodiment, the above-mentioned optimal parameter schedule 14 according to the event sequence or time series is obtained based on the predicted event sequence data or time series data of the machine, and the parameters are changed according to the schedule 14, thereby being able to continuously optimize the parameters according to the state of the machine such as the drive body and the axis. In addition, it is no longer necessary to use FB for control.

[0049] Therefore, according to the servo control device 10 of the present embodiment, it is possible to improve the machining accuracy of the machine tool (improve the operating accuracy of the industrial machine) and shorten the time (improve the productivity).

[0050] Here, it is preferable that the state value deriving unit 11 derives the time series or event series data of the inertia of the driven body, or derives the time series or event series data of the position of the axis of the machine tool or the like. Figure 1 In the example, the parameters "β (coefficient)" and "Kν (gain)" of the speed loop (speed gain) are changed to match the gain scheduling, and the parameters of the position loop (position gain) can also be changed based on the export result of the state value export unit 11, or the parameters of the feedforward gain, filter frequency, and acceleration / deceleration time constant after interpolation can be changed.

[0051] When deriving the time series or event series data of the inertia of the driven body, a schedule for changing the speed gain of the parameter can be created. When deriving the time series or event series data of the position of the axis, a schedule for changing the filter frequency and time constant can be created.

[0052] Furthermore, even in the case described above, the same effects as described above can be obtained.

[0053] As mentioned above, although one embodiment of the servo control device was described, the present invention is not limited to the above-mentioned embodiment, and can be appropriately modified within the scope not departing from the gist of the present invention.

Claims

1. A servo control device for controlling a motor driving a shaft of an industrial machine, the servo control device comprising: a state value deriving unit that derives time series or event series data of state values ​​of the motor or a driven object operated by the motor based on an operation program and / or operation plan information of the industrial machine; and a parameter changing unit that changes at least one parameter of a speed gain, a position gain, a feedforward gain, a filter frequency, and a post-interpolation acceleration / deceleration time constant along the time series or the event series based on the data of the time series or the event series derived by the state value deriving unit, in, The state value deriving unit derives time series or event series data of the inertia of the driven body.

2. The servo control device according to claim 1, characterized in that: The state value deriving unit derives time series or event series data of the position of the axis.

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