SERVO CONTROL

Abstract

Servo control (10) for controlling an electric motor that drives an axis of an industrial machine, the servo control comprising: a state value derivation unit (11) that derives chronological or event-dependent data of a state value of the electric motor or of a driven element operated by the electric motor from 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 velocity gain, a position gain, a feedforward gain, a filter frequency and an acceleration / deceleration time constant after interpolation based on the data derived in the state value derivation unit (11) either chronologically or event-dependently.

Description

BACKGROUND OF THE INVENTION Area of ​​the invention

[0001] The present invention relates to servo controls. State of the art

[0002] As is well known, CNC technology (Computerized Numerical Control) is used in the field of machine work; the amount of movement, the speed of movement, and the like are numerically controlled by a computer, thus automating the repetition of the same process, a complicated process, and the like to a high degree.

[0003] Design and drawing creation are carried out using CAD (Computer Aided Design), an operational program corresponding to the CAD data (for example, a machining program) is created using CAM (Computer Aided Manufacturing), the data created with the CAM is transferred to a CNC, for example, various data types such as options, parameters, an NC program, a macro program, a macro variable, an offset of the working origin, a tool offset, tool shape data and tool management data are entered and controlled, so that an NC machine tool such as an NC lathe and a machining center or similar is automated from design to manufacturing.

[0004] On the other hand, in a servomotor (electric motor) used to drive an axis or the like of an industrial machine such as a machine tool or robot, the amount of rotation, the speed, the drive torque and the like are controlled for the drive.

[0005] Here, patent document 1 discloses a “control for an electric motor comprising: a means that adds a sinusoidal command value to a torque command for the electric motor; a means that detects a current value flowing through the electric motor; a means that detects an acceleration value for the electric motor; and a means that estimates the inertia of an element driven by the electric motor from a typical current value and a typical acceleration value obtained from a plurality of current values ​​and a plurality of acceleration values ​​over a plurality of periods of the sinusoidal command in the same operating state and a torque constant for the electric motor”.

[0006] Patent document 2 discloses a "numerical control connected to a shared database that controls a machine tool, in which the shared database stores information about machining resources relating to the numerical control and the machine tool, information about the machining content generated with a CAD and CAM system and relating to the content of the machining, and information about machining commands, including information about machining requests for at least one request for machining, comprising a command decoding unit for decoding machining commands, which decodes the machining command information, and a command execution unit for executing machining commands, which performs the machining based on the result of the decoding by the command decoding unit for decoding machining commands."and in which the instruction decoding unit for decoding machining instructions performs at least one processing step which, based on the machining instruction information and the machining resource information stored in the shared database, determines whether the machining can be performed in the machine tool with the machining instruction information or not, one processing step which determines parameters for the machining, and one processing step which automatically selects functions of the numerical control and the machine tool used for the machining." Patent document 1: Japanese patent no. JP 4 565 034 B2. Patent document 2: Japanese unexamined patent application, Publication No. JP 2018 - 151 736 A. Patent document 3: DE 698 22 425 T2 SUMMARY OF THE INVENTION

[0007] For example, if the inertia and state of a machine position (state value) in a machine tool are changed by a machine operation such as machining, optimal parameters such as gains (e.g., position gain and velocity gain) and a filter band are also changed. Since the parameters are fixed, the most conservative settings are generally used so that they correspond to the machine's fluctuations. In particular, to reduce the occurrence of vibrations caused by a machine operation such as machining, settings are applied beforehand that include low gains, a filter with high damping (high delay), and a long time constant. This makes it difficult to reduce the cycle time.Alternatively, if the parameters are set to be optimal under certain conditions, when inertia and position are changed, the parameters are not optimal, and therefore vibrations are likely to occur during machining in a machine tool, resulting, for example, in a scratch being created on the surface of the machining.

[0008] Since fixed parameters are disadvantageous when variations occur as described above, a method for optimizing parameters that correspond to the state of a machine or similar device is highly desirable. Methods for optimizing parameters so that they correspond to a state include (1) an adaptive parameter change method and (2) a method for systematically changing parameters in advance. Of the methods described above, the adaptive parameter change method requires estimating the state and calculating the optimal values ​​in real time. This presents problems such as (A) an increased computational load (requiring an expensive computing device), (B) the use of real-time FB data from sensors for the estimation calculation, which introduces noise, and (C) difficulty in setting the hyperparameters used for the estimation calculation itself.

[0009] In (2) the systematic modification of parameters in advance, information within a CNC (numerical control) is often insufficient to create an optimal parameter plan.

[0010] The problem is solved by a servo control system with the features of claim 1.

[0011] A servo controller according to one aspect of the present disclosure is a servo controller for controlling an electric motor that drives the axis of an industrial machine and comprises: a state value derivation unit that derives the chronological or event-dependent data of the state value of the electric motor or of a driven element operated by the electric motor from an operation program and / or from operation plan information of the industrial machine; and a parameter change unit that changes at least one parameter of a velocity feed gain, a position feed gain, a feedforward gain, a filter frequency and an acceleration / deceleration time constant after interpolation based on the chronological or event-dependent data derived either chronologically or event-dependently in the state value derivation unit.

[0012] In servo control, according to the aspect of the present disclosure, the event-dependent or chronological schedule of the optimal parameter is determined based on the predicted event-dependent or chronological data of a machine. The parameter is then modified according to this schedule, thus making it possible to optimize the parameter according to the state of the machine, such as a driven element, an axis, and the like. In this way, it is possible to improve the working accuracy of the industrial machine, such as increasing the machining accuracy of a machine tool and achieving a reduction in machining time (increased yield). BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing a control system and servo control of a machine tool in a first aspect; Fig. 2 is a block diagram showing the servo control in the view; Fig. Figure 3 is a diagram used to illustrate the creation of the event-dependent or chronological schedule of the optimal parameter with servo control in aspect; Fig. Figure 4 is a diagram used to illustrate the generation of the event-dependent or chronological schedule of the optimal parameter with servo control in aspect; Fig. Figure 5 is a diagram used to illustrate the generation of the event-dependent or chronological sequence of the optimal parameter with servo control in aspect; Fig. Figure 6 is a diagram used to illustrate the generation of the event-dependent or chronological sequence of the optimal parameter with servo control in aspect; and Fig. Figure 7 is a diagram used to illustrate the creation of the event-dependent or chronological schedule of the optimal parameter with servo control in aspect. DETAILED DESCRIPTION OF THE INVENTION

[0013] A servo control according to one embodiment is described below with reference to Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. 7 described.

[0014] In the present embodiment, a description is first given assuming that an industrial machine is a machine tool and that an electric motor is a servo motor that drives the spindle (axis, driven element) or similar component of the machine tool. However, the industrial machine according to the present invention can, of course, also be a different type of industrial machine, such as a robot, a transport device, a measuring device, a testing device, a press machine, a press-fitting device, a printing press, a die-casting machine, an injection molding machine, a food processing machine, a packaging machine, a welding machine, a washing machine, a coating machine, an assembly device, an assembly machine, a woodworking machine, a sealing device, or a cutting machine.

[0015] As in Fig. 1 and Fig. As shown in Figure 2, the control system 1 of the machine tool of the present embodiment comprises: a CAD 2 for carrying out the design, drawing, and the like of a product; a machine program production unit (operation program production unit) 3, which generates a machine machining program (operation program) from the machining form data (product data) generated with the CAD 2; a CAM 5, which comprises a machine machining simulator simulator unit (operation simulator unit) 4, which performs a machining simulation (operation simulation); a CNC 6, a command unit, which outputs a command signal based on machining plan information (G-code, operation plan information) 9 supplied by the CAM 5; and a motor control unit 8, which initiates the drive of the servo motor (drive unit) 7 of the machine tool based on the command from the CNC 6.

[0016] The servomotor 7 of the drive unit is, for example, a servomotor (electric motor) for driving a spindle (axis) to which a feed axis (axis) for moving a table (driven element) that holds a workpiece (driven element), a tool (driven element) or similar is attached, and the motor control unit 8 is, for example, a servo amplifier.

[0017] On the other hand, the servo control 10 of the present embodiment comprises: the machine processing program production unit 3 described above; the machine processing simulator unit 4; a state value derivation unit 11, which acquires the machining plan information generated in the machine processing program production unit 3 and the machine processing simulator unit 4 in order to determine from the machining plan information chronological or event-dependent data of state values ​​of the driven elements, such as the workpiece and the table and the servo motor 7;and a parameter change unit 12 that changes at least one parameter of a velocity gain, a position gain, a feedforward gain, a filter frequency and an acceleration / deceleration time constant after interpolation based on the chronological or event-dependent data derived either chronologically or event-dependently in the state value derivation unit 11.

[0018] Specifically, how in Fig. 1 shows the machining plan information 9 generated in the CAD 2 and the CAM 5, which is recorded in the CNC 6. After interpolation, the CNC 6 of the command unit outputs a position command and an acceleration / deceleration command to the motor control unit 8 of the servo amplifier, and thus the drive of the servo motor 7 is controlled by the motor control unit 8.

[0019] Here, in the servo control 10 of the present embodiment, the state value derivation unit 11 acquires the machining plan information 9 from the CAM 5 and determines a relationship 13 of the chronology or event sequence of inertia from the machining plan information 9. The event sequence of inertia specifies a time that is continuously and chronologically required for each machining step (event) and represents, for example, the chronology of inertia, which reflects, for instance, a case in which a time independent of the steps results between a particular machining step and the subsequent machining step, for example, due to a contingency.

[0020] An example will be described in more detail.

[0021] As in Fig. Figure 3 shows that in a state where the workpiece is not held (placed) on a stage (table) 6, which is moved by the forward / reverse rotation of a feed axis (ball screw) 15 about a supply line by the drive of the servo motor 7, the inertia J = J0. J0 is the sum of the inertia values ​​of the rotor of the motor, the feed axis 15 and the stage 16.

[0022] As in Fig. Figure 4 shows that when the workpiece 17 of mass M is held on the level 6, the inertia J LOAD = J0 + MR 2 . R is a conversion coefficient of rotationally linear motion for a slope (distance of motion) L (m), and R = L / 2π (m / rad).

[0023] In this way, a speed gain FB and a speed gain FF are defined as J LOAD / J = 1 + (MR 2 / J0) times. If, for example, J0 = 0.01 kgm 2, M = 500 kg and L = 0.02 m, the amplification is 1.5 times that of J LOAD / J = 1 + (MR 2 / J0) set.

[0024] If, on the other hand, a transmission characteristic curve is shown from the torque of the servo motor 7 to the position (machine end) of stage 16, the transmission characteristic curve is, for example, as in Fig. 5 shown. As shown in Fig. As shown in Figure 6, changing the position of stage 16 changes the stiffness Kt of the machine in the axial direction and thus also its resonant frequency (natural frequency). Particularly with a large machine or a long ball screw (e.g., stroke), the stiffness changes significantly depending on its position.

[0025] Therefore, as in Fig. Figure 7 shows the damping center frequency (resulting from the change in the resonance frequency) of a filter 18, a time constant (since vibrations can occur when stiffness is reduced, the time constant is increased) and similar elements designed to correspond to the position.

[0026] Then, as in Fig. As shown in Figure 1, the state value derivation unit 11 acquires the machining plan information 9 from the CAM 5 to determine the relationship 13 of the chronology or event sequence of inertia from the machining plan information 9, and then the state value derivation unit 11 determines a gain plan (the speed feed unit, the position feed unit, the forward coupling gain and the like, which are chronological) 14 from the relationship 13 of the chronology or event sequence of inertia to synchronize the gain plan and the instruction unit of the CNC 6.

[0027] Then the parameter change unit 12 modifies the parameter of the speed control loop (and / or the position control loop) of the motor control unit 8 based on the gain scheme (chronological or event-dependent data) 14, which is derived either chronologically or event-dependently in the state value derivation unit 11. For example, as in Fig. Figure 1 shows that the parameters “β (coefficient)” and “Kv (gain)” of the speed control loop have been changed to correspond to the gain scheme. Here, “s” is in the speed loop or in the position loop of Fig. 1 is a derived value.

[0028] Then, based on the speed FF (or the position FF: forward coupling gain), which is changed to match the gain plan, the command, for example the torque command, is issued by the motor control unit 8, and thus the servo motor 7 is controlled to drive.

[0029] In this way, in the servo control 10 of the present embodiment, based on the event-dependent or chronological data of the predicted machine, the event-dependent or chronological schedule 14 of the optimal parameter is determined as described above, the parameter is changed according to the schedule 14, and thus it is possible to continuously optimize the parameter according to the state of the machine, such as the driven elements, the axis, and the like. It is not necessary to perform control with the FB.

[0030] Therefore, in the servo control 10 of the present embodiment it is possible to increase the accuracy of the machining of the machine tool (improvement of the working accuracy of the industrial machine) and to reduce the time (increase in yields).

[0031] Here, the state value derivation unit 11 preferably derives the chronological or event-dependent data of the inertia of the driven element or derives the chronological or event-dependent data of the position of the axis of the machine tool or the like. Although in Fig.1. The parameters “β (coefficient)” and “Kv (gain)” of the velocity control loop (velocity gain) can be changed to conform to the gain schedule. The parameter of the position control loop (position gain) can also be changed, and the parameters of the feedforward gain, filter frequency, and acceleration / deceleration time constant after interpolation can be changed based on the result of the derivation of the state value derivation unit 11. If the chronological or event-dependent data of the inertia of the driven element are derived, a schedule for changing the velocity gain parameter can be created, whereas if the chronological or event-dependent data of the axis position are derived, a schedule for changing the filter frequency and time constant can be created.Then, in the cases described above, it is also possible to achieve the same operational effects as described above.

[0032] Although the embodiment of the servo control has been described above, the present invention is not limited to the embodiment described above and can be modified as necessary without departing from its spirit. REFERENCE MARK 1 Control system of a machine tool (industrial machine) 2 CAD 3 Machine processing program production unit (Operation program production unit) 4 Machining simulator unit (operations simulator unit) 5 CAM 6 CNC 7 Servo motor (drive unit) 8 Engine control unit 9. Processing plan information (operations plan information) 10 Servo control 11 State Value Derivation Unit 12 parameter change unit

Claims

[1] Servo control (10) for controlling an electric motor that drives an axis of an industrial machine, the servo control comprising: a state value derivation unit (11) that derives chronological or event-dependent data of a state value of the electric motor or of a driven element operated by the electric motor from 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 velocity gain, a position gain, a feedforward gain, a filter frequency and an acceleration / deceleration time constant after interpolation based on the data derived in the state value derivation unit (11) either chronologically or event-dependently. [2] Servo control (10) according to claim 1, wherein the state value derivation unit (11) derives the chronological or event-dependent data of the inertia of the driven element. [3] Servo control (10) according to claim 1, wherein the state value derivation unit (11) derives the chronological or event-dependent data of a position of the axis.

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