JP2009226520A - Positioning control apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positioning control apparatus which suppresses low frequency vibration of a leading end position of a loading machine and high frequency vibration of a command torque to enable positioning control having reduced noise even when a position command being made discrete and having a waveform changing step-wise is input. <P>SOLUTION: An optional discrete position command generation part 7 of the positioning control device generates a position command x<SB>zr</SB>having a waveform with an optional shape. A discrete position compensation device 8 and a discrete correction secondary filter 9 output the position command x<SB>zr</SB>input from the optional discrete position command generation part 7 as a position command x<SB>zrf</SB>using a transfer function F<SB>d</SB>(z) and a transfer function F<SB>f</SB>(z), respectively. A discrete feedback control device 4 carries out the feedback control of the leading end position of the loading machine by inputting the position command x<SB>zrf</SB>and a signal x<SB>m</SB>for feedbacking a position of a motor which drives the loading machine. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a positioning control device that performs positioning using a driving device such as a motor, and more particularly to a positioning control device that suppresses vibration of an arm tip of an industrial machine having a flexible arm.

A conventional positioning control device that performs positioning control of an industrial machine having a flexible arm is disclosed in Patent Document 1, for example.
FIG. 5 is a block diagram of a positioning control device according to an embodiment of the invention disclosed in Patent Document 1. This conventional positioning control device includes an S-shaped position command generator 101, a secondary filter 102, a subtractor 103, and a feedback controller 104. The transfer function 105 is a transfer function P _M (s) from the torque command, which is an output of the feedback controller 104, to the motor position, and the transfer function 106 is a transfer function P _L (s) from the torque command to the flexible arm tip position. It is.

In this conventional positioning control device, the original position command x _r generated by the S-shaped position command generation unit 101 passes through the secondary filter 102, and the position command x _rf of the feedback control system is generated. The subtractor 103 calculates a deviation between the fed back motor position x _m and the position command x _rf, and the feedback controller 104 generates a torque command so that the deviation is minimized.

FIG. 6 shows the time function of the S pattern command X _r and the speed pattern V _r (t) of the S pattern command X _r (t). The original S-shaped position command X _r (t) generated by the S-shaped position command generator 101 is shown in FIG. 6A, and the speed pattern V _r (t) is shown in FIG. 6B. In FIG. 6, t _a is the acceleration time, t _d is the time to start decelerating from the acceleration start, t _e is the instruction time, and deceleration time (t _e -t _d) and acceleration time t _a is equal Yes.
Here, when the natural frequency of the flexible arm is ω _z and the natural vibration damping coefficient of the flexible arm is ζ _z , the transfer function of the secondary filter 102 is used.

におけるパラメータを
ω₁＝ω_z （２）
および
ζ₁＝ζ_z （３）
および

The parameter at ω ₁ = ω _z (2)
And ζ ₁ = ζ _z (3)
and

を満たすように設定する。
図７には、２次フィルタ１０２を用いずに位置決め制御装置を駆動した場合のシミュレーション結果を示し、図８には、（２）〜（４）式の設定にて図５に示す従来の位置決め制御装置を駆動した場合のシミュレーション結果を示す。２次フィルタ１０２を用いない場合は、図７に示すように、モータの位置が目標の位置に到達しても負荷先端の位置は固有振動数ω_zで大きく振動し続ける。しかし、（１）式に示した２次フィルタ１０２を用いることで、図８に示すように、負荷先端の残留振動が抑制されていることがわかる。
特開２００４−２７２７４９号公報

Set to satisfy.
FIG. 7 shows a simulation result when the positioning control device is driven without using the secondary filter 102, and FIG. 8 shows the conventional positioning shown in FIG. 5 by setting the equations (2) to (4). The simulation result at the time of driving a control apparatus is shown. Without the second-order filter 102, as shown in FIG. 7, the position of the even load tip position of the motor has reached the position of the target continues to vibrate largely the natural frequency omega _z. However, it can be seen that residual vibration at the tip of the load is suppressed by using the secondary filter 102 shown in the equation (1), as shown in FIG.
JP 2004-272749 A

In recent years, servo systems are digitally controlled, and the above-described positioning control device is generally digitally controlled. Here, if the positioning control device shown in FIG. 5 is represented as a discrete positioning control device of a digital control system, it is as shown in FIG. That is, the integral element 1 / s is converted to T _s / (1-z ⁻¹ ), and the differential element s is converted to (1−z ⁻¹ ) / T _s . However, z is a z conversion operator and T _s is a sample period.

This discretized positioning control device is composed of a discretized S-shaped position command generator 1, a discretized secondary filter 2, a discretized subtractor 3, and a discretized feedback controller 4. The transfer function 5 is a transfer function P _M (s) from the torque command that is the output of the discretization feedback controller 4 to the motor position, and the transfer function 6 is a transfer function P _L (s) from the torque command to the flexible arm tip position. ).

In this discretization positioning control device, position command x _ZrF the feedback control system by discretizing S-position command generating section original position command x _zr generated by 1 passes through the discrete secondary filter 2 is generated The The subtractor 103 calculates the deviation between the fed back motor position x _m and the position command x _rf, and the discretization feedback controller 4 generates a torque command so that the deviation is minimized.
In particular, the discretized secondary filter 2 is expressed by the following equation.

The simulation results are shown in FIGS. FIG. 10 shows the results when the discretized secondary filter 2 is not used, and FIG. 11 shows the results when the discretized secondary filter 2 is used.
The position of the load tip is suppressed to the same level as in the case of simulation in the continuous system by using the secondary filter 2, but it is confirmed that high-frequency vibration appears in the command torque waveform as shown in FIG. it can. This is because the secondary filter shown in equation (5) includes two differential operations. In a digital control system in which the waveform of the position command changes discretely (stepped), the change becomes the command torque. It is because it appears until.
Generally, when the encoder pulse amount is fed back as the motor position, the pulse amount is input as the position command. If the amount of change per sample period of the position command outputted from the discretization S-position command generating unit 1 and a [Delta] x _zr, the position command which has passed through the discrete secondary filter 2 1 sample periods per variation [Delta] x _ZrF Is as follows.

Therefore, if the response of the discretization feedback controller 4 is sufficiently fast, the command torque change Δτ with respect to the position command change amount Δx _zr is expressed by the following equation. However, X _R is the encoder resolution per one rotation of the motor.

That is, it can be seen that the amplitude Δτ of the torque slight vibration increases in proportion to the change amount Δx _zr per sample period of the position command x _zr . Furthermore, the lower the natural frequency ω _z of the arm and the shorter the sample period T _s , the higher the amplitude of the high frequency vibration that appears in the command torque.
Here, the torque ripple per sample period can be reduced by setting the value of ω ₂ small in the equation (7). However, if the value of ω ₂ is determined by a setting value other than the equation (4), the discretization 2 Since the output of F (z) of the secondary filter 2 vibrates at the frequency ω ₂ , it is limited to the case of k = 1 in the equation (4) at the minimum, and the high-frequency vibration cannot be sufficiently suppressed.

When expressed in a discrete system in this way, the torque command value becomes oscillating, causing problems such as the generation of loud operating noise from the mechanical system. In particular, since the sampling period tends to be shortened due to the recent high performance of microcomputers, this problem becomes prominent.
The present invention has been made in order to solve such a conventional problem, and an object of the present invention is to provide a tip of a load machine to be positioned even when a position command whose waveform is changed in a staircase pattern is input. An object of the present invention is to provide a positioning control device capable of performing low-noise positioning control while suppressing low-frequency vibration of a position and suppressing high-frequency vibration of a command torque.

  In order to solve the above-described problem, a positioning control device according to claim 1 is a digitally controlled positioning control device that drives a load machine connected by a relatively low-rigidity coupling body with a motor. A position command generating unit capable of generating a position command, a position command compensating unit that compensates the position command so as to cancel the natural vibration of the load machine and outputs the position command as a first position command, and A smoothing filter that smoothes the vibration waveform and outputs it as a second position command; and a feedback control unit that performs feedback control by inputting the second position command and a signal that feeds back the position of the motor that drives the load machine. And having the tip position of the load machine follow the second position command.

The positioning control device configured as described above suppresses low-frequency vibration at the tip position of the load machine and suppresses high-frequency vibration of the command torque even when a position command whose waveform is changed in a stepped manner is input. Therefore, positioning control with less noise can be performed.
Further, the positioning control device according to claim 2 is the positioning control device according to claim 1, wherein the transfer function F _d (z) of the filter of the position command compensation unit is

により表され、伝達関数Ｆ_d（ｚ）におけるω₁を負荷機械の固有振動数ω_zとし、ζ₁を負荷機械の固有振動減衰係数ζ_zとし、Ｔ_sをサンプル周期とすることを特徴とする。

Ω ₁ in the transfer function F _d (z) is the natural frequency ω _z of the load machine, ζ ₁ is the natural vibration damping coefficient ζ _z of the load machine, and T _s is the sample period. To do.

Since the positioning control device configured as described above can freely control the amount of change per one sample period of the second position command input to the feedback control unit by a second-order or higher filter, it is discretized and has a staircase. Even when a position command whose waveform changes in a shape is input, it is possible to suppress low-frequency vibration at the tip of the load machine while suppressing high-frequency vibration appearing in the command torque.
The positioning control device according to claim 3 is the positioning control device according to claim 1 or claim 2, wherein the transfer function F _f (z) of the smoothing filter is:

により表され、伝達関数Ｆ_f（ｚ）におけるω₃を次式で決定する事を特徴とする。

And ω ₃ in the transfer function F _f (z) is determined by the following equation.

In the positioning control device configured as described above, since the filter time constant changes according to the natural frequency of the load machine, it is possible to stably suppress high-frequency torque vibration regardless of the natural frequency of the load machine. .
A positioning control device according to a fourth aspect is the positioning control device according to the first or second aspect, wherein the transfer function F _f (z) of the smoothing filter is

により表され、前記伝達関数Ｆ_f（ｚ）におけるＮを次式で計算される値に最も近い整数とする事を特徴とする。
Ｎ＝ｎ・ω_z・Ｔ_s （１≦ｎ：ｎは整数） （１２）
上記のように構成された位置決め制御装置は、請求項３に記載の平滑フィルタよりも小さい時定数でトルクの高周波振動を抑制することができる。

And N in the transfer function F _f (z) is an integer closest to the value calculated by the following equation.
N = n · ω _z · T _s (1 ≦ n: n is an integer) (12)
The positioning control device configured as described above can suppress high-frequency vibrations of torque with a time constant smaller than that of the smoothing filter according to claim 3.

  A positioning control device according to the present invention includes a position command generation unit capable of generating a position command having a waveform of an arbitrary shape, and compensates the position command so as to cancel the natural vibration of the load machine as a first position command. A position command compensation unit for outputting, a smoothing filter for smoothing the vibration waveform of the first position command and outputting it as a second position command, and a signal for feeding back the second position command and the position of the motor driving the load machine And a feedback control unit for performing feedback control, and a position command having a discrete and stepped waveform is input to cause the tip position of the load machine to follow the second position command. Even in this case, low-frequency vibration at the tip of the load machine can be suppressed, and high-frequency vibration of the command torque can be suppressed, enabling positioning control with less noise. To become.

(First embodiment)
Hereinafter, a first embodiment of a positioning control device according to the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a positioning control device according to a first embodiment of the present invention. In FIG. 1, the same components as those in FIG. 9 are denoted by the same reference numerals, and description thereof is omitted.
The positioning control device according to the present embodiment can vibrate the tip of a load machine such as a flexible arm tip of an industrial machine even when a position command having an arbitrary waveform is used as well as a position command having an S-shaped waveform. In addition, it is possible to suppress high-frequency vibrations appearing in the command torque even when the waveform of the position command changes discretely.

The configuration different from the conventional positioning control device in the positioning control device of the present embodiment is that the discretized S-position command generation unit 1 in FIG. This is replaced with a discretized position compensator 8 and a discretized modified secondary filter 9 corresponding to the numerator of (z).
Transmission of discrete positions compensator 8 in FIG. 1 function F _d (z) and the transfer function F _f discretization modified secondary filter 9 (z) is expressed by the following equation.

The amount of change Δx _zrf during one sampling period of the position command x _zrf when it passes through the discretized modified secondary filter 9 is expressed by the following equation.

In the above equation, it can be _seen that if ω ₃ is set small, Δx _zrf can be reduced, and the magnitude of Δx _zrf can be arbitrarily controlled. For example, to the following vibration amplitude [Delta] x _zr appearing vibration amplitude [Delta] x _ZrF passing through the discrete corrected secondary filter 9 to an output of the discretization arbitrary position command generator section 7, omega ₃ may be determined by the following equation.

If in the above formula with n = 1, it can be the same [Delta] x _ZrF and [Delta] x _zr.
In the equation (13), ω ₁ and ζ ₁ are set so as to satisfy the following equation in the same manner as in the conventional method.
ω ₁ = ω ₂ (17)
ζ ₁ = ζ ₂ (18)
FIG. 2 shows a simulation result when the parameters of F _d (z) and F _f (z) are determined by the equations (16) to (18) in the positioning control device shown in FIG. As compared with the result of the conventional positioning control device shown in FIG. 11, it can be confirmed that the amplitude of the fine torque vibration appearing in the command torque is suppressed, and the vibration at the arm tip is suppressed equally. It can also be confirmed that the amplitude Δx _zrf of the torque slight vibration is equivalent to the case where the discretized position compensator 8 and the discretized modified secondary filter 9 are not used (see FIG. 10).

As described above, the positioning control apparatus according to the present embodiment can freely control the change amount Δx _zrf per one sample period of the position command input to the discretization feedback controller 4, so that it is discretized and stepped. Even when a changing position command is input, it is possible to suppress low-frequency vibration at the tip of the load machine while suppressing high-frequency vibration appearing in the command torque.

(Second Embodiment)
Hereinafter, a second embodiment of a positioning control device according to the present invention will be described with reference to the drawings. FIG. 3 is a block diagram showing a positioning control apparatus according to the second embodiment of the present invention. In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
The configuration in which the positioning control device of this embodiment is different from the conventional positioning control device is that the discretized modified secondary filter 9 in FIG. The transfer function F _ma (z) of the moving average filter 10 is as follows.

In the equation (19), N is the number of moving average stages. The amplitude Δx _zrf of the fine vibration of the position command waveform that appears after passing through the moving average filter 10 is expressed by the following equation.

Following the above equation, the smaller the change amount [Delta] x _ZrF position command after passing through the moving average filter to discretization arbitrary position command generator section 7 variation [Delta] x _zr per sample of the output to the position command x _zr of The number N of moving average filter stages may be determined as follows.
N = n · ω _z · T _s (1 ≦ n: n is an integer) (21)
If in the above formula with n = 1, it can be the same [Delta] x _ZrF and [Delta] x _zr.

FIG. 4 shows a simulation result in the configuration of FIG. Both the minute vibration of the command torque and the vibration of the arm tip are suppressed. Further, the time for the arm tip to reach the target position is shorter than the simulation result (see FIG. 2) shown in the first embodiment. This is because the discretized modified secondary filter 9 shown in FIG. 1 and the moving average filter 10 shown in FIG. The overall delay has been reduced accordingly.
As described above, even when a position command having an arbitrary-shaped waveform that is discretized and changes stepwise is input, the positioning control device suppresses low-frequency vibrations at the tip of the flexible arm and generates a high-frequency command torque. Vibration can be suppressed and positioning control with less noise can be performed.

  When positioning using a driving device such as a motor such as positioning of an arm tip of an industrial machine, positioning control with less noise can be performed while suppressing vibration.

It is a block diagram which shows the positioning control apparatus of the 1st Embodiment of this invention. It is a figure which shows the simulation result at the time of using the positioning control apparatus of the embodiment. It is a block diagram which shows the positioning control apparatus of the 2nd Embodiment of this invention. It is a figure which shows the simulation result at the time of using the positioning control apparatus of the embodiment. It is a block diagram which shows the structure of the conventional positioning control apparatus. It is a figure which shows the time function of the speed pattern of S character position command and this S character position command. It is a figure which shows the simulation result when not using a secondary filter in the conventional positioning control apparatus shown in FIG. It is a figure which shows the simulation result at the time of using a secondary filter in the conventional positioning control apparatus shown in FIG. It is a block diagram which shows the structure of the conventional discretization positioning control apparatus represented with a discrete system. It is a figure which shows the simulation result when not using a discretization secondary filter in the conventional discretization positioning control apparatus shown in FIG. It is a figure which shows the simulation result at the time of using the discretization secondary filter in the conventional discretization positioning control apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Discrete S-shaped position command generation part 2 Discrete secondary filter 3 Discretization subtractor 4 Discrete feedback controller 5 Transfer function from torque command to motor position 6 Transfer function from torque command to load tip 7 Discretization arbitrary Position command generator 8 Discretized position compensator 9 Discretized modified secondary filter 10 Moving average filter 101 S-shaped position command generator 102 Secondary filter 103 Subtractor 104 Feedback controller 105 Transfer function 106 from torque command to motor position Transfer function from torque command to load tip

Claims (4)

In a digitally controlled positioning control device for driving a load machine connected by a relatively low rigidity connecting body by a motor,
A position command generating unit capable of generating a position command having a waveform of an arbitrary shape, a position command compensating unit for compensating the position command so as to cancel the natural vibration of the load machine and outputting as a first position command; Feedback control is performed by inputting a smoothing filter that smoothes the vibration waveform of the first position command and outputs it as a second position command, and a signal that feeds back the second position command and the position of the motor that drives the load machine. A positioning control device that includes a feedback control unit and causes the tip position of the load machine to follow the second position command. The transfer function F _d (z) of the position command compensation unit is

Ω ₁ in the transfer function F _d (z) is the natural frequency ω _z of the load machine, ζ ₁ is the natural vibration damping coefficient ζ _{z of the} load machine, and T _s is the sample period. The positioning control device according to claim 1. The transfer function F _f (z) of the smoothing filter is

The positioning control apparatus according to claim 1, wherein ω ₃ in the transfer function F _f (z) is determined by the following equation.

The transfer function F _f (z) of the smoothing filter is

The positioning control device according to claim 1, wherein N in the transfer function F _f (z) is an integer closest to a value calculated by the following equation.
N = n · ω _z · T _s (1 ≦ n: n is an integer)

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