JP2020027366A - Motor controller - Google Patents

Abstract

To provide a motor controller adapted to operate a control object part such as a machine tip point according to a command by optimizing a parameter of a machine model.SOLUTION: A motor controller optimizes a parameter of a machine model using an acceleration signal detected by attaching an acceleration sensor for detecting an acceleration signal on a machine tip point and an output signal of a machine model from a control input to a machine tip point. The acceleration signal and a machine-model output signal are FFT-operated to extract a peak frequency and amplitude of a power spectrum and update/optimize the resonance frequency and gain of the machine model. By designing a feedforward compensator using the optimized parameter, feed-forward control is enabled corresponding to a characteristic variation of a control object such as aging or tool exchange, allowing a position command and a machine tip point position to follow up.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a control device that controls a machine with a motor.

  Position feedback control and speed feedback control are used to control the driven body driven by the servo motor in the machine tool, and the position and speed of the driven body are controlled so as to follow the position command and the speed command. are doing.

  In a machine tool, the operation of a driven body driven by a servomotor and the operation of a machine tip point to which a tool or the like is attached basically match. Therefore, by controlling the motor position and the speed detected by the encoder attached to the servomotor so as to match the command value, the operation in which the machine tip point follows the command can be realized.

  However, when the mechanical rigidity between the motor and the machine tip point is low, or in the case of machining operation with high acceleration, mechanical resonance at a resonance frequency not found in the motor occurs only at the machine tip point. The operation of the motor and the tip of the machine may not match.

  In order to solve the above problem, in a control system described in Patent Document 1 below, acceleration feedback control is used in which an acceleration signal of a machine tip point is detected by an acceleration sensor, integrated, and fed back. However, in this technique, when integrating the machine tip point acceleration signal detected by the acceleration sensor, the DC offset amount included in the signal is integrated, so that an error occurs in the calculation result.

  Further, in the control system described in Patent Document 2 below, prior to the machining operation, a sine wave command value is input to the control target to obtain the frequency characteristic of the control target, and the inverse characteristic is transmitted to a filter expressing a transfer function by a transfer function. By inputting a value, a command signal for trajectory control of a tip of a machine such as a tool is generated. However, this technology needs to input a sine wave command value to the control target before the machining operation to acquire the frequency characteristics of the control target, and cannot respond to the characteristic fluctuation of the control target such as aging. There is also.

  Further, in the control system described in Patent Document 3 below, a real machine is modeled by a transfer function, an actual output is compared with an output of the model, parameters of the model are identified by a least square method, and the identified parameter and the transfer function are identified. Positioning accuracy is improved by feedforward control using a model. However, in this technique, the number of parameters to be identified is determined by the model order. Therefore, when the model order is high, the number of parameters increases and the amount of processing calculation also increases, but a model that matches well with the actual machine can be obtained. On the other hand, when the model order is low, the number of parameters decreases and the amount of processing calculation also decreases, but the model does not match the actual machine, and improvement in machining accuracy cannot be expected. For this reason, when determining the model order, it is necessary to consider a trade-off between the amount of processing operation and the processing accuracy.

Patent No. 5648870 JP 2010-186461 A JP 2003-272328 A

  An object of the present invention is to develop a new method for achieving both optimization of a machine model used for controlling a machine and reduction in the amount of computation.

  The motor control device of the present invention is a control unit that drives a motor according to a position command to control a control target portion of a machine, an acceleration detection unit that detects acceleration of the control target portion, and the position command is given. A mechanical model represented by a transfer function up to the control target part in the case where the control target frequency analysis unit performs frequency analysis of the acceleration of the control target part detected by the acceleration detection unit, and the position command is given. In the case, a machine model frequency analysis unit for frequency-analyzing the acceleration of the control target part obtained by the machine model, and a parameter of the machine model is updated and optimized based on a frequency analysis result by the two frequency analysis units. And a parameter updating unit that controls the control target part based on the parameters of the machine model. Parameter updating unit further corresponding to the updating of the parameters of the machine model, and updates the parameters of the control unit, characterized in that.

  ADVANTAGE OF THE INVENTION According to this invention, optimization of a machine model can be implemented with a small amount of calculation, and it is possible to achieve both high-precision machine control and quick control.

FIG. 2 is a control device block diagram of the positioning device according to the first embodiment of the present invention. FIG. 2 is a detailed block diagram of a control device according to the first embodiment of the present invention. It is a flowchart figure of the machine model optimization procedure in a 1st embodiment of the present invention. It is a control device block diagram of a positioning device of a 2nd embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram of a control device of the positioning device according to the first embodiment of the present invention. As shown in FIG. 1, in the present embodiment, an acceleration detection unit 7 is installed at a machine tip point 6 where a workpiece and a tool to be machined are attached, and a position detection unit 5 is installed on a motor 4. Based on the detected position signal, the displacement of the tool tip, which is the machine tip point 6, is corrected, and control is performed to follow the command.

  In the control target 8 of the motor control device shown in FIG. 1, the motor 4 for driving the driven body is provided with a position detecting unit 5 for detecting the moving amount of the driven body from the number of rotations of the motor. Is provided with an acceleration detection unit 7 for detecting the acceleration of the machine tip point 6. An encoder is used for the position detection unit 5 and an acceleration sensor is used for the acceleration detection unit 7, respectively.

The motor control device in FIG. 1 includes a control unit including a position control unit 1 and a speed control unit 2, and controls the motor 4 and the machine end point 6 by controlling the position and speed of the motor. . Further, a machine model 9 that expresses from the control input τ to the machine tip point acceleration α _L by a transfer function is provided, and the machine tip point acceleration α _L detected by the acceleration detection unit 7 is subjected to FFT calculation to calculate a power spectrum. a control target frequency analysis unit 10 for extracting a peak frequency and amplitude, and FFT computing machinery model output y _m generated by inputting the position command Pr on the machine model 9 calculates the power spectrum, peak frequency and amplitude , A change rate is calculated from the peak frequency and the amplitude extracted by the control target frequency analysis unit 10 and the machine model frequency analysis unit 11, and the resonance frequency and the gain of the machine model 9 are used as conditions. And a parameter updating unit 16 that updates the parameters according to the machine model and the control unit.

A commonly used motor positioning device can be treated as a two inertial system in which a motor and a load are connected by an elastic shaft. Thus, the control target 8 in FIG. 1 can be represented by a block diagram shown in FIG. In FIG. 2, J is the moment of inertia, theta is angle of rotation, tau is the control input, K _s is the spring coefficient, K _t is a torque constant, D is a viscosity coefficient, subscript M is the motor, L is load (machine effecting end) Show.

The motor control apparatus of the first embodiment of the present invention in FIG. 1, the first subtraction unit 12, from the position command Pr, calculates the deviation by subtracting the motor position theta _M detected by the position detection unit 5. The speed command Vr is calculated by multiplying the deviation by the transfer function Cp (s) of the position control unit 1 and output to the second addition / subtraction unit 13.

The second subtraction unit 13 is obtained by the speed command Vr input from the position controller 1, for differential processing of the motor position theta _M is detected from the position detecting unit 5 at a rate calculating unit 3 of the differentiator motor to calculate the deviation by subtracting the speed ω _M. The deviation is multiplied by the transfer function Cv (s) of the speed control unit 2 to calculate a control input τ, which is output to the control target 8.

In a first embodiment of the present invention, more detailed block diagram of the controlled object 8 in FIG. 2, the transfer function from the control input τ to machine effecting end position theta _L has the formula (1), the motor position theta _M from the control input τ the transfer function to the formula (2), the transfer function from the motor position theta _M to machine effecting end position theta _L can be expressed by equation (3).

Here, if the inertia ratio of the two inertial system is R, the anti-resonance angular frequency is ω _a , and the resonance angular frequency is ω _b , they can be expressed by the following equations.

When Expressions (1) and (2) are expressed using R, ω _a and ω _b , Expressions (7) and (8) are obtained.

Resonance angular frequency omega _b of the controlled object 8 using the resonance frequency f _b, it is possible to express the ω _{b =} 2π · f _b, antiresonance angular frequency omega _a can be expressed by Equation (9).

In the first embodiment of the present invention, the transfer function G _f (s) from the control input τ to the machine tip point acceleration α _L in the machine model 9 can be defined by the equation (10) from the equation (7).

It is assumed that the initial values of the parameters of the machine model 9 in the equation (10) are set in advance. In this case, the machine model 9 from the control input τ to the machine tip point acceleration α _L is defined by the equation (10) based on the two-inertia system. It may be defined by a machine model that has been set.

Next, an optimization method of the machine model 9 defined by the equation (10) will be described. FIG. 3 shows a flowchart of the procedure for optimizing the machine model parameters. By inputting the machine tip point acceleration α _L detected from the acceleration detection unit 7 attached to the machine tip point 6 to the control target frequency analysis unit 10, FFT calculation is performed to calculate the power spectrum of the machine tip point acceleration α _L. I do. From the calculated power spectrum to extract amplitude and it becomes frequency (peak frequency) f _p and the maximum amplitude A _p at that time. Similarly, the machine model output y _m generated by inputting the position command Pr to machine model 9 which is defined by equation (10), and FFT calculation by inputting the machine model the frequency analyzing unit 11, the machine model It calculates the power spectrum of the output y _m. From the calculated power spectrum to extract the amplitude A _m when the peak frequency f _m.

At parameter updating unit 16, the first divider 14, divided by the peak frequency f _m which is extracted peak frequency f _p extracted from the machine effecting end acceleration alpha _L from the machine model output y _m, the resonance frequency change rate Calculate Δf _pm . If the rate of change than the reference value f _s of the resonance frequency change rate Delta] f _pm is set large, equation (11), the resonance angular frequency omega _b of the machine model 9 as shown in Equation _(12), the anti-resonant angular frequency omega _a Update. If the resonance frequency change rate Delta] f _pm is smaller than the reference value f _s, it is not reflected in the machine model 9.

Here, ω _a ′, ω _b ′, and f _b ′ are the anti-resonance angular frequency, the resonance angular frequency, and the resonance frequency after updating the parameters, respectively.

In the second divider 15, divided by the peak amplitude A _m extracted peak amplitude A _p extracted from the machine effecting end acceleration alpha _L from the machine model output y _m, to calculate the amplitude change rate .DELTA.A _pm. If the amplitude change rate .DELTA.A _pm sets the reference value A _s than the change rate is high, to be reflected in the machine model 9 as shown in equation (13). If the amplitude change rate .DELTA.A _pm is less than the reference value A _s, not reflected in the machine model 9.

Resonance frequency change rate Delta] f _pm and amplitude change rate .DELTA.A _pm reference value _f s, and repeats the optimization procedure until the following _{A s.}

  Further, the parameter update unit 16 updates the parameters of the control units (the position control unit 1 and the speed control unit 2) in accordance with the update of the parameters of the machine model 9. As a result, control corresponding to the optimized machine model 9 is performed.

In the positioning device of the first embodiment of the present invention, the machine effecting end acceleration alpha _L and machine model output y _m frequency analysis, mechanically so that the error of the resonance frequency and the gain of the controlled object 8 and the machine model 9 is reduced By updating the parameters of the model 9, the resonance frequency and the gain of the machine model 9 can be optimized. In the first embodiment, the machine model 9 is represented by a transfer function from the control input τ to the machine tip point as shown in FIG. However, the machine model only needs to express the behavior of the machine tip point according to the position command. For example, the machine model may be expressed using a transfer function from the position command Pr to the machine tip point.

  Subsequently, a block diagram of a control device of the positioning device according to the second embodiment of the present invention is shown in FIG. The difference from the first embodiment of the present invention lies in the feedforward control unit. That is, in the positioning device of FIG. 1, a feedforward control unit is newly added to the control unit to perform feedforward control. In FIG. 4, the resonance frequency and the gain of the machine model 9 are optimized by the same method as in the first embodiment so that the error between the resonance frequency and the gain of the control target 8 and the machine model 9 is reduced. Feed-forward control is performed using feed-forward control units 18, 19, and 20 designed based on the optimized machine model 9.

In the positioning control system of FIG. 4, shown in equation (14) to a transfer function of a machine effecting end position theta _L from the position command Pr.

In the equation (14), G _f1 (s) is a transfer function of the first feedforward control unit 18, G _f2 (s) is a transfer function of the second feedforward control unit 19, and G _f3 (s) is a transfer function of the third feedforward control unit 20. , G _M (s) is the motor position θ _M from the control input τ, _GL (s) is the machine tip point position θ _L from the motor position θ _M , and G _ML (s) is the machine tip point position θ _L from the control input τ. Represents the transfer function up to

In equation (14), if the transfer functions of the three feedforward control units are designed as in the following equation, the transfer characteristic from the position command Pr to the machine tip point position θ _L becomes 1, and the position command Pr and the machine tip point position Control in which θ _L matches can be performed.

  Expressions (15), (16), and (17) use the transfer functions (3) and (7), which are transfer functions when the controlled object 8 is treated as a two-inertia system. By using an optimized value for the gain, highly accurate feedforward control can be performed.

  In the positioning apparatus according to the second embodiment of the present invention, by performing feedforward control using a feedforward controller to which optimized parameters are applied, control for following a position command and a machine tip point position can be performed. .

  In the first and second embodiments of the present invention, the acceleration at the tip of the machine is detected by the acceleration sensor, and the FFT operation is performed, so that the resonance frequency and the gain of the machine model can be optimized. Using the parameters, the machine tip point can be operated as instructed. In particular, by performing feedforward control using the optimized parameters, it can be expected that the control accuracy of the machine tip point is improved. In these embodiments, even if the characteristics of the control target change due to aging, individual variation, or the like, robust positioning control by feedforward control that optimizes the parameters of the machine model and reflects the changes can be realized.

  In the above description, the transfer function is not limited to the embodiment. For example, it is possible to construct a mechanical model by using a transfer function using another parameter such as a damping constant and optimize the parameter. is there.

  In the above description, control of the machine tip point of a machine tool for processing a workpiece is described as an example. However, the present invention is applicable to all machines that perform motor control. For example, control can be performed with the position of the motor itself or another part moved by the motor as a control target.

  1 position control unit, 2 speed control unit, 3 speed calculation unit (differentiator), 4 motor, 5 position detection unit, 6 machine tip point, 7 acceleration detection unit, 8 control target, 9 machine model, 10 control target frequency analysis Unit, 11 mechanical model frequency analysis unit, 12 first addition / subtraction unit, 13 second addition / subtraction unit, 14 first division unit, 15 second division unit, 16 parameter update unit, 17 third addition / subtraction unit, 18 first feedforward control Unit, 19 second feedforward control unit, 20 third feedforward control unit.

Claims (6)

A control unit that drives a motor according to a position command to control a control target portion of the machine,
An acceleration detection unit that detects the acceleration of the control target portion,
A machine model represented by a transfer function up to the control target part when the position command is given,
A control target frequency analysis unit that performs frequency analysis of the acceleration of the control target part detected by the acceleration detection unit,
A machine model frequency analysis unit for frequency-analyzing the acceleration of the control target part obtained by the machine model when the position command is given,
A parameter updating unit that updates and optimizes parameters of the machine model based on a frequency analysis result by the two frequency analyzing units;
With
The control unit is controlling the control target part based on the parameters of the machine model,
The motor control device, wherein the parameter update unit further updates a parameter of the control unit in response to an update of a parameter of the machine model. The motor control device according to claim 1,
The control unit includes a feedforward control unit that performs feedforward control based on the parameters of the machine model,
The motor control device, wherein the parameter updating unit updates a parameter of the feedforward control unit. The motor control device according to claim 1,
The control target portion controlled by the control unit is a tip of the machine,
The motor control device, wherein the acceleration detection unit detects acceleration of the tip of the machine. The motor control device according to claim 1,
The motor control device, wherein the transfer function in the machine model is expressed by treating a control target as a two-inertia system. The motor control device according to claim 1,
The control target frequency analysis unit receives the acceleration of the control target portion, calculates a power spectrum by performing an FFT operation, and extracts a peak frequency and an amplitude from the calculated power spectrum.
The machine model frequency analysis unit inputs the acceleration of the control target portion by the machine model, calculates a power spectrum by performing an FFT operation, and extracts a peak frequency and an amplitude from the calculated power spectrum,
The motor control device, wherein the parameter update unit compares the peak frequency and the amplitude obtained from the two frequency analysis units to update the parameters of the mechanical model and the control unit. The motor control unit according to claim 5,
The parameter updating unit calculates a peak frequency and a change rate of a gain with respect to the acceleration of the machine and the acceleration based on the machine model extracted by the two frequency analysis units, and calculates the calculated change rate and a preset reference value. Optimizing the resonance frequency and gain of the mechanical model and the control unit by comparing