JPH09121579A - Motor speed controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a speed controller in which the saturation of an amplifier is avoided and which is hardly influenced by a noise. SOLUTION: A difference between a value which is obtained by multiplying the estimated value of a motor torque which is the product of a detected motor armature current value IM and the nominal value KTn , of a motor torque constant by a factor β/α and a value which is obtained by multiplying the estimated value of a motor torque which is obtained by differentiating the detected motor speed value by a differentiator 31 which is the simulation of an inverse model of the integral characteristic of the moment of inertia of a motor rotor by a factor 1/α and a difference between a value which is obtained by multiplying the value which is obtained by multiplying the estimated value of a motor torque which is the product of a detected motor armature current value IM and the nominal value KTn by a factor (β-1) /α and the above mentioned latter value are respectively obtained by an external disturbance torque observer 2. Then a difference between both the differences is calculated and the calculated value is multiplied by a factor αand the obtained value is used as the estimated value Td0 of an external disturbance torque. With this constitution, the saturation of an amplifier 21 of which the external disturbance torque observer 2 is composed can be avoided and the influence of the noise can be almost eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor speed control device for estimating a disturbance torque applied to a motor and correcting a command value to the motor by the estimated value.

[0002]

2. Description of the Related Art A method for improving the robustness of a servo system in consideration of external forces such as gravity, inertial force and frictional force in order to realize highly accurate positioning control and force control of machine tools and robot systems. As such, an acceleration control system using a disturbance observer has been proposed ("Robust high-speed servo control technology" by Trikeps Corporation (September 27, 1991).
(Sun), pp. 154 to 163), ("Motion Control", Corona (March 25, 1993), 154.
Pages to 163).

The configuration of the above-mentioned conventional example will be described with reference to FIGS. The speed command value ω _ref output from the control device (not shown) is added to the motor speed feedback output ω by the adder 5.
After being added to _fb , it is input to the proportional integrator 3. The output of the proportional integrator 3 is added to the current compensation value ΔIc by the adder 6,
It becomes the current command value Ic.

The current command value Ic is added by the adder 7 to a value obtained by inverting the sign of the motor armature current detection value, and then input to the current amplifier 8 and amplified to a predetermined power by the current amplifier 8. The output of the amplifier 8 drives the motor 1.

The motor 1 has an armature inductance L, an impedance element 13 having an armature resistance value R, a torque element 11 having a torque constant K _T , a feedback element 12 having a counter electromotive force constant K _{E, and} a moment of inertia of the rotor. It consists of a moment of inertia element 14 designated J _M and is shown in the block diagram shown in FIG.

From the motor 1, the armature current I _M and the motor speed ω _M are output as detection outputs, and the disturbance torque Td is input. The speed output ω _M of the motor 1 is amplified to a predetermined value by the speed feedback amplifier 4 and subtracted from the speed command value ω _ref in the adder 5.

In the disturbance torque observer 52, the armature current I _M amplified by the amplifier 42 is converted into a nominal value K _Tn of the torque constant K _T (subscript n is a nominal value nomina).
l. The same shall apply hereinafter) and the estimated value of the generated torque of the motor 1 and the detected speed ω _M are detected by the differentiator 43 which simulates an inverse model of the integral characteristic of the inertia moment of the motor rotor. The estimated value of the generated torque of the motor obtained by differentiating is input to the adder 44, and the difference between the estimated values of the two torques is calculated as the estimated value Td1 of the disturbance torque by the following mathematical expression 1. In the differentiator 43, the nominal value J _Mn of the inertia moment J _M of the motor rotor is used.
Incidentally, in the equation 1, S is a Laplace operator (hereinafter the same).

[0008]

(Equation 1)

Then, the estimated value Td1 of the disturbance torque is canceled so that the estimated value Td1 of the obtained disturbance torque is canceled.
Reciprocal 1 / K of the nominal value K _Tn of the torque constant in the amplifier 9
_The current command value is compensated by adding _Tn and the current compensation value ΔIc which is the output of the amplifier 9 with the current command value Iref by the adder 6, and outputs the compensated current command value Ic.

Determined by the disturbance torque observer 52,
The transfer function from the current command value Iref and the disturbance Td to the motor speed output ω _M when the current command value Iref is not compensated by the current compensation value ΔIc can be expressed by the following mathematical expression 2.

[0011]

(Equation 2)

Further, the transfer function from the current command Iref and the disturbance Td to the motor speed output ω _M in the case of compensation is
It can be expressed by the following expression 3.

[0013]

(Equation 3)

The transfer function from the current command value Iref to the speed output ω _{M in the} case where the current command value is not compensated by the current compensation value ΔIc is the second term of the equation (2), and the current command value Iref in the case of compensation is calculated from the speed output ω. The transfer function up to _M is the first term of Equation 3.

If the torque constant K _T and its nominal value K _Tn , and the rotor inertia moment J _M and its nominal value J _Mn are set to be substantially equal to each other, then δ in Equation 3 becomes approximately 1 and Equations 2 and 3 The denominators are also approximately equal, and the speed output ω is calculated from the current command value Iref.
_It may be considered that the transfer functions up to _M are also substantially equal.

Similarly, the velocity output ω _M from the disturbance Td when the current command value Iref is not compensated by the current compensation value ΔIc.
Is the second term of the equation 2 and the transfer function from the disturbance Td to the velocity output ω _M in the case of compensation is the second term of the equation 3 and the denominator is considered to be substantially equal.

When the current compensation value ΔIc is not used for compensation, since the gain Ka of the current amplifier 8 introduced to increase the stability of the control system is in the numerator of the second term of the equation 2, the disturbance torque Td has an influence Ka. It is multiplied and appears in the motor speed ω _M.

On the other hand, since the gain Ka of the current amplifier 8 does not appear in the numerator of the second term of the equation 3 which is the transfer function from the disturbance Td to the velocity output ω _M when compensated by the current compensation value ΔIc, the disturbance torque Td. Has less effect on the motor speed ω _M.

Therefore, by compensating the current command value Iref with the current compensation value ΔIc obtained by the disturbance torque observer 52, the current control enhances the stability of the control system, and at the same time, the influence of the disturbance torque on the motor speed. There are two effects of reducing the.

However, if the speed output ω _{M of the} motor is purely differentiated, noise becomes large in a high frequency range. Therefore, in practice, a low-pass filter 47 having an integral characteristic as shown in FIG. Then, the disturbance torque is estimated and the estimated value Td1 is obtained.

Refer to FIG. 4 for the method of obtaining this estimated value Td1.
I will explain. Detected armature current I_MThe torque
Nominal number K_TnInput to the amplifier 42 with the gain of K_Tn
Multiplied value and detected motor speed ω_MThe rotor
Nominal value of moment of inertia J of _MnAnd low pass filter 4
7 cutoff frequency ω_FThe gain with the gain obtained by multiplying by
Input to width device 55_FJ_MnThe value obtained by multiplying is added by the adder 44.
And the output of the adder 44 is added to the cutoff frequency ω_FTo
Input to the low pass filter 47 that has
The adder 48 calculates the difference between the output of 47 and the output of the amplifier 55.
The calculation is performed, and the output is estimated as the disturbance torque Td1. Push
The determined disturbance torque Td1 can be expressed by the following equation 4.

[0022]

(Equation 4)

As shown in the equation 4, the disturbance torque observer 52 constituted by the low pass filter 47 having the integral characteristic.
Is equivalent to the case where the estimated value Td1 shown in the equation 1 which is the disturbance torque obtained by using the differentiator 43 is passed through the low pass filter 47. The estimated value Td1 of the disturbance torque is multiplied by 1 / K _Tn by an amplifier 9 having a gain that is the reciprocal 1 / K _Tn of the nominal value K _Tn of the torque constant, and the current compensation value ΔIc is calculated.

The current compensation value ΔIc is added to the current command value Iref by the adder 6 to compensate the current command value and output as the compensated current command value Ic.

The cutoff frequency ω _F of the low-pass filter 47 is larger than the natural frequency of the controlled object, and if it is set as large as possible so as not to be affected by noise, the delay of the estimated value Td1 of the disturbance torque Td will be very large. The disturbance torque observer 52 is small and practically negligible of lag, and is not affected by noise because a differentiator is not used.
Can be configured.

[0026]

As shown in the conventional example, the control system in which the current command value Iref is compensated by the current compensation value ΔIc obtained by the disturbance torque observer 52 is as follows.
Although it has excellent characteristics, it has the following problems when applied to an actual motor.

As an example, a motor having a rated torque of 0.2 Nm, a rated rotation speed of 3000 rpm (314 rad / sec), a rotor inertia moment of 2 × 10 ^-5 kgm ^{2 and a} torque constant of 0.2 Nm / A, a rotation speed of 3000 rpm and an electric machine Consider the case of operating with a child current of 0.1 A.

The cutoff frequency ω _F of the low-pass filter 47 is set to 1 × 10 ⁴ rad / sec, the nominal value of the rotor inertia moment J _Mn is set to 2 × 10 ^-5 kgm ^2, and the nominal value of the torque constant K _{Tn is set.} Is 0.2 Nm / A.

A value obtained by multiplying the detected speed ω _M , the nominal value J _{Mn of the} rotor inertia moment J _M and the cutoff frequency ω _F of the low pass filter 47 is 62.8.

In converting the torque value into voltage, 1N
When m is 1 V, the output of the amplifier 55 is 62.8 V, and the output is saturated with a commonly used operational amplifier. Further, the estimated value of the generated torque of the motor obtained by multiplying the detected armature current I _M by the nominal value K _Tn of the torque constant is 0.02 Nm, and assuming that 1 Nm is 1 V, the output of the amplifier 42 is 0.02 V. Become.

Further, in order to prevent the amplifier 55 from being saturated, when 1 Nm is set to 0.1 V, the output of the amplifier 42 must be set to a small value of 0.002 V and becomes unstable due to the influence of noise. .

In view of the above problems, the present invention provides a speed control device using a disturbance torque observer that prevents the saturation of an amplifier and is not easily affected by noise.

[0033]

According to the first aspect of the present invention,
For a speed control loop that controls the motor speed, in a motor control device that has a current control loop that controls the motor armature current as a minor loop, multiply the motor armature current detection value by the nominal value of the motor torque constant. A differentiator that simulates a value obtained by multiplying the obtained estimated value of the motor torque by a coefficient β / α (α and β are arbitrary numbers) and an inverse model of the integral characteristic of the inertia moment of the motor rotor. According to, the difference between the estimated value of the motor torque obtained by differentiating the detected motor speed value and the value obtained by multiplying the coefficient 1 / α, the detected motor armature current value, and the nominal value of the motor torque constant The estimated value of the motor torque obtained by multiplying by
1) / α and the value obtained by multiplying the difference, the difference between the two values is calculated, and the value obtained by multiplying the calculated value by the coefficient α is It is characterized in that it has a disturbance torque observer as an estimated value.

According to a second aspect of the present invention, in a motor control device having a current control loop for controlling a motor armature current as a minor loop in contrast to a speed control loop for controlling a motor speed, a motor armature current detection value and , A value obtained by multiplying the estimated value of the motor torque obtained by multiplying the motor torque constant by the coefficient β / α, the detected rotation speed, and the nominal value of the inertia moment of the rotor, input to low-pass filter having a sum cutoff frequency omega _F of a value obtained by multiplying the coefficient 1 / alpha to a value obtained by multiplying the cutoff frequency omega _F of the low-pass filter, passes through the low-pass From the output of the filter, subtract the value obtained by multiplying the nominal value of the rotation speed and the inertia moment of the rotor by the cutoff frequency ω _F of the low pass filter, and from the value of this subtraction result, the motor armature current detection value and Motor torque constant The value obtained by multiplying the estimated value of the motor torque obtained by multiplying the nominal value by the coefficient (β-1) / α is subtracted, and the value obtained by multiplying the obtained value by the coefficient α is the disturbance torque. It is characterized by having a disturbance torque observer for estimating

The operation of the invention described in claim 1 is as follows. That is, the disturbance torque observer multiplies the estimated value of the motor torque obtained by multiplying the motor armature current detection value and the nominal value of the motor torque constant by the coefficient β / α (α and β are arbitrary numbers). The estimated value of the motor torque obtained by differentiating the detected motor speed is multiplied by a coefficient 1 / α by a differentiator that simulates an inverse model of the obtained value and the integral characteristic of the inertia moment of the motor rotor. The estimated value of the motor torque obtained by multiplying the difference between the obtained value, the detected value of the motor armature current, and the nominal value of the motor torque constant is a coefficient (β-
1) / α and the difference from the value obtained.

Further, the disturbance torque observer calculates the difference between the values of the above two differences, and multiplies the value of the calculation result by the coefficient α to obtain the estimated value of the disturbance torque.

As a result, it is possible to prevent the amplifier constituting the disturbance torque observer from being saturated and to be less susceptible to the influence of noise.

The operation of the invention according to claim 2 is as follows. That is, the disturbance torque observer is a value obtained by multiplying the estimated value of the motor torque obtained by multiplying the motor armature current detection value and the nominal value of the motor torque constant by the coefficient β / α, and the detected rotation. The sum of the value obtained by multiplying the nominal value of the speed and the inertia moment of the rotor by the cutoff frequency ω _F of the low-pass filter and the value obtained by multiplying the coefficient 1 / α by the low cutoff frequency ω _F Input to the pass filter.

Further, the disturbance torque observer uses the output of the low-pass filter to determine the nominal values of the rotational speed and the rotor inertia moment and the cut-off frequency ω _{F of the} low-pass filter.
And the coefficient 1 / α are subtracted, and the estimated value of the motor torque obtained by multiplying the detected value of the motor armature current by the nominal value of the motor torque constant from the value of the subtraction coefficient (β -1) / α, then input to a low-pass filter having a cutoff frequency ω _F , the output of this low-pass filter is subtracted to obtain a value, and the obtained value is multiplied by a coefficient α. The value is the estimated value of the disturbance torque.

As a result, as in the case of the first aspect of the present invention, it is possible to prevent the amplifier constituting the disturbance torque observer from being saturated and to be less susceptible to noise.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIG.

[First Embodiment] FIG. 1 is a block diagram of a motor degree control device according to a first embodiment. The same elements as those in the conventional example shown in FIG. Detailed description is omitted.

The motor degree control device of the first embodiment is characterized in that the disturbance torque observer 52 shown in FIG. 1 is used in place of the disturbance torque observer 52 of the conventional example.

[0044] The disturbance torque observer 2, an amplifier 21 with a gain value obtained by multiplying the nominal value K _Tn and arbitrary coefficient beta / alpha torque constant, nominal value K _Tn and any coefficient of the torque constant (beta An amplifier 26 having a gain of a value obtained by multiplying -1) / α, a differentiator 31 simulating an inverse model of an integral characteristic of α times the inertia moment J _Mn of the motor rotor, and the amplifier 21 and the differential The adder 22 performs arithmetic processing of each output with the adder 31, the adder 29 performs arithmetic processing of the output of the adder 22 and the output of the amplifier 26, and the amplifier 30 having a gain α. .

In the first embodiment, the generated torque of the motor 1 is calculated by differentiating the detected motor speed, which is the same as in the conventional example, but it is α times the inertia moment J _Mn of the motor rotor. The output of the differentiator 31 becomes 1 / α and the output of the differentiator 31 becomes J _Mn s / α by differentiating the motor speed detection value by the differentiator 31 simulating the inverse model of the integral characteristic.

That is, the armature current I _M from the motor 1 is
It is amplified by an amplifier 21 having a gain of a value obtained by multiplying the nominal value K _Tn of the torque constant and an arbitrary coefficient β / α.
Output is βK _Tn I _M / α.

The armature current I _M is amplified by an amplifier 26 having a gain of a value obtained by multiplying the nominal value K _Tn of the torque constant by an arbitrary coefficient (β-1) / α, and the output of this amplifier 26. Is (β-1) K _Tn I _M / α.

The output of the differentiator 31 is subtracted from the output of the amplifier 21 by the adder 22. This adder 22
After the output of the amplifier 26 is subtracted from the output of the above, the estimated value Td0 of the disturbance torque becomes the following Expression 5 by amplifying the subtraction result by the amplifier 30 having the gain α, which is the same as the case of Expression 1 of the conventional example. become.

[0049]

(Equation 5)

According to the first embodiment, by differentiating the motor speed detection value by the differentiator 31 simulating the inverse model of the integral characteristic of α times the inertia moment J _Mn of the motor rotor, the motor speed detection value is differentiated. The output of the device 31 becomes 1 / α, and the operation can be performed at the level of the signal with the best characteristics without saturating the differentiator 31.

That is, multiplication of the detected armature current I _M and the nominal value of the torque constant K _Tn is performed by multiplying by an arbitrary coefficient β / α so that the amplifier 21 does not saturate and is not affected by noise. The signal level with the best characteristics can be used. Further, the multiplication of the detected armature current I _M and the nominal value of the torque constant K _Tn is also multiplied by an arbitrary coefficient (β-1) / α so that the amplifier is not saturated and is not affected by noise. 26 can be performed at the signal level having the best characteristics. In this case, the value of β is a value of β >> 1.

Further, as shown in Equation 5, the basic characteristics of the disturbance torque observer 2 are not changed at all, and the design and use of the differentiator 31, the amplifiers 21 and 26 for realizing the disturbance torque observer 2 are performed. The state can be optimized, and a motor speed control device having a wide range of applications and excellent characteristics can be provided.

[Second Embodiment] FIG. 2 is a block diagram of a speed control device according to a second embodiment. In the speed control device according to the second embodiment, in addition to the configuration of the disturbance torque observer 2 in the speed control device according to the first embodiment,
Cutoff frequency ω _F for low pass processing of output of adder 22
A low-pass filter 24a having a cut-off frequency ω _F for performing low-pass processing of the output of the amplifier 26, and a nominal value J of the rotor inertia moment.
_An amplifier 23 having a gain of a value obtained by multiplying _{Mn by} a cutoff frequency ω _F of the low pass filter 24a and a coefficient 1 / α, and by subtracting the output of the amplifier 23 from the output of the low pass filter 24a, The disturbance torque observer 2A including the adder 25 to be sent to the adder 29 is used.

In the speed controller of the second embodiment, the detected armature current I _M has an amplifier 21 having a gain of a value obtained by multiplying the nominal value K _Tn of the torque constant and an arbitrary coefficient β / α.
And the nominal value of the torque constant K _Tn and an arbitrary coefficient (β-1) /
It is simultaneously input to the amplifier 26 having a gain of a value multiplied by α. The output of the amplifier 21 becomes βK _Tn I _M / α,
The output of the amplifier 26 is (β-1) K _Tn I _M / α.

Further, the detected speed ω _M is supplied to the amplifier 23 having a gain of a value obtained by multiplying the nominal value J _Mn of the inertia moment of the rotor by the cutoff frequency ω _F of the low pass filter and the coefficient 1 / α. Is entered. The output of this amplifier 23 is J _Mn ω
It becomes _F ω _M / α.

Then, the output of the amplifier 21 and the output of the amplifier 23 are input to the adder 22, where they are added and sent to the low-pass filter 24a for low-pass processing, and then to the adder 25. Is entered. In addition, the gain (ω _F J _Mn
The output of the amplifier 23 having / α) is also input to the adder 25.

The adder 25 subtracts the output of the amplifier 23 from the output of the low pass filter 24a, and the result ω
_{F · (βK Tn I M -J} Mn ω M s) / {α (s + ω F)}
Is input to the adder 29.

The output of the amplifier 26 is sent to the low-pass filter 24b and low-pass processed, and then the adder 2
9 The output of the low-pass filter 24b is (β
−1) ω _F K _Tn I _M / {α (s + ω _F )}.

The adder 29 subtracts the output of the low pass filter 24b from the output of the adder 25, and inputs the subtraction result to the amplifier 30 having the gain α. The amplifier 30 performs amplification processing with a gain α, and inputs the result to the amplifier 9 as an estimated value Td0 of the disturbance torque shown in Expression 6. The estimated value Td0 of the disturbance torque shown in Expression 6 is the same as the estimated value Td0 of the disturbance torque shown in Expression 5 that has passed through the low-pass filter 24a.

[0060]

(Equation 6)

The amplifier 9 performs amplification processing with a gain of the reciprocal 1 / K _Tn of the nominal value K _Tn of the torque constant, and the current compensation value ΔI
It is input to the adder 6 as c. The current compensation value ΔIc is added to the current command value I _ref by the adder 6.

According to the second embodiment, without changing the basic characteristics of the disturbance torque observer 2A,
It is possible to optimize the design and use condition of the amplifier 23, the amplifiers 21 and 26 for realizing the disturbance torque observer 2A, and it is possible to provide a speed control device having a wide range of applications and excellent characteristics.

Further, the detected speed ω _M is equal to the nominal value J _Mn of the inertia moment of the rotor and the low pass filter 24.
By amplifying with the amplifier 23 having a gain of a value obtained by multiplying the cutoff frequency ω _F of a and 24b by the coefficient 1 / α, the amplifier 2
The output of 3 becomes 1 / α, and the amplifier 23 can be operated at the signal level with the best characteristics of the amplifier 23 without making saturation a problem.

Further, the cutoff frequency ω _{F of} the low pass filters 24a and 24b can be set to a sufficiently large value. Further, the multiplication of the detected armature current I _M and the nominal value of the torque constant K _Tn can be performed at the level of the signal with the best characteristics of the amplifier 21 by multiplying it by an arbitrary coefficient β / α.

[0065]

According to the present invention, the saturation of the amplifier is prevented and the influence of noise is prevented, without impairing the basic characteristics of the disturbance torque observer having the feature of improving the robustness of the servo system. It is possible to provide a high-performance and high-performance motor speed control device.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a motor speed control device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a motor speed control device according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional motor speed control device.

FIG. 4 is a block diagram showing a disturbance torque observer in a conventional motor speed control device.

[Explanation of symbols]

 1 Motor 2 Disturbance Torque Observer 2A Disturbance Torque Observer 3 Proportional Integrator 4 Speed Feedback Amplifier 5 Adder 6 Adder 7 Adder 8 Current Amplifier 9 Amplifier 21 Amplifier 22 Adder 24a Low Pass Filter 24b Low Pass Filter 26 Amplifier 29 Adder 30 Amplifier 31 Differentiator

Claims (2)

[Claims] 1. A motor control device having, as a minor loop, a current control loop for controlling a motor armature current, as opposed to a speed control loop for controlling a motor speed, in a motor armature current detection value and a nominal value of a motor torque constant. The estimated value of the motor torque obtained by multiplying
It is obtained by differentiating the detected motor speed value with a value obtained by multiplying (α and β are arbitrary numbers) and a differentiator that simulates an inverse model of the integral characteristic of the moment of inertia of the motor rotor. The difference between the estimated value of the motor torque and the value obtained by multiplying by the coefficient 1 / α, the detected value of the motor armature current, and the estimated value of the motor torque obtained by multiplying the estimated value of the motor torque by the coefficient (Β-
1) / α, the difference between the value and the value obtained is multiplied, and the difference between the two values is calculated.
A motor speed control device comprising a disturbance torque observer, wherein a value obtained by multiplying by is used as an estimated value of the disturbance torque. 2. A motor control device having, as a minor loop, a current control loop for controlling a motor armature current, as opposed to a speed control loop for controlling a motor speed, in a motor armature current detection value and a nominal value of a motor torque constant. The estimated value of the motor torque obtained by multiplying
Multiply the value obtained by multiplying by, the detected rotational speed, the nominal value of the rotor's moment of inertia, and the cutoff frequency ω _F of the low pass filter by the coefficient 1 / α. The sum of the obtained value is input to the low-pass filter with cut-off frequency ω _F, and from the output of this low-pass filter, the nominal value of the rotation speed and the rotor inertia moment and the cut-off frequency of the low-pass filter are input. The value obtained by multiplying by ω _F is subtracted, and from the value of this subtraction result, the estimated value of the motor torque obtained by multiplying the detected motor armature current value and the nominal value of the motor torque constant by the coefficient (β-1 ) / Α is subtracted, a value obtained by multiplying the obtained value by a coefficient α is used as an estimated value of the disturbance torque, and a motor speed control is provided which is provided with a disturbance torque observer. apparatus.