JP6042124B2 - 2-inertia speed controller - Google Patents

Description

  The present invention relates to an improved two-inertia disturbance observer and a speed control apparatus using the same.

  In a speed control device for an industrial electric motor that drives a rolling mill or the like of a steel plant, it is known that torsional vibration is generated in a drive shaft that mechanically connects the rotor of the electric motor and the rolling mill. This is a torsional vibration of a two-inertia system that occurs when the rotor and rolling roll of the electric motor each have a moment of inertia and the drive shaft has insufficient rigidity.

  In order to suppress such torsional vibration of the two-inertia system, for example, it is conceivable to attach a rotation sensor to the rolling mill and perform control using this signal, but in reality, a rotation sensor is attached to the rolling roll. Is extremely difficult in terms of structure and maintenance.

  In such a situation, as a technique for suppressing the torsional vibration of the two-inertia system, the state quantity such as the rotation speed of the rolling roll is estimated from the constant of the two-inertia system and the detectable state quantity using the state observer. Some use this estimated value. This typical one is a state observer of the same dimension as the controlled object, and incorporates feedback control so that both outputs are the same when the same input is given to the controlled object and the state observer. It is configured to estimate a desired state quantity. (For example, refer nonpatent literature 1.).

“Modern Control Theory Note”, Chapter 3 Basic Stabilization Theory, 3.2.2 Same-Dimensional Observer, March 1, 2000 1st Edition, Shimane University Faculty of Science and Engineering, Department of Electronic Control System Engineering, Yoshida Kazunobu, [2012 June 11, 2011], Internet <URL: http://www.ecs.shimane-u.ac.jp/~kyoshida/note2000.pdf

  The state observer shown in Non-Patent Document 1 can accurately estimate the state quantity when there is no disturbance or there is little fluctuation even when there is a disturbance. However, when a so-called load disturbance occurs such that the rolling material is caught in the rolling roll of the rolling mill, it is difficult to estimate the state quantity correctly due to the influence.

  The present invention has been made in view of the above problems, and a two-inertia disturbance observer capable of accurately estimating a state quantity even when there is a load disturbance, and a state quantity estimated using the same. It is an object of the present invention to provide a two-inertia speed control device capable of suppressing torsional vibrations.

In order to achieve the above object, the present invention is characterized by the following .

The two-inertia speed control device according to the present invention comprises a two-inertia system comprising a power converter and a control device for controlling a controlled object in which a rotor and a load of an electric motor driven by the power converter are coupled by a drive shaft. A speed control device of the system, wherein the control device has the same control block as that represented by the control block diagram in which the motor torque and the disturbance torque are input and the motor speed and the load speed are output. A state observer, a disturbance observer for applying an estimated disturbance torque to the state observer, an integration controller for feedback control so that the estimated load speed matches a speed command, a state obtained from the motor torque and the state observer Proportional control that outputs a current reference by feedback control so that the feedback amount obtained by weighting and adding the amount matches the output of the integral controller If, comprising a current controller output current of the power converter to output a voltage reference of the power converter with a feedback control so as to coincide with said current reference, said disturbance observer, first the motor torque 1 is obtained by multiplying the result of multiplication by 1 and subtracting the value obtained by multiplying the rotational speed of the motor by the second transfer function from the multiplication result, and filtering the result of the subtraction with a third-order or higher filter to obtain the estimated disturbance torque. And the first and second transfer functions are obtained by back-calculating the disturbance torque from a transfer function of a two-inertia system that obtains the motor speed from the motor torque and the disturbance torque. An estimated rotational speed, an estimated torsion angle of the drive shaft, and an estimated rotational speed of the load. These state quantity weighting gains, motor torque weighting gains, and integral speeds It is characterized in that the gain of the controller and the seek by the ILQ design method.

  According to the present invention, it is possible to suppress a torsional vibration based on a two-inertia disturbance observer capable of accurately estimating a state quantity even when there is a load disturbance, and a state quantity estimated using the two-inertia disturbance observer. A possible two-inertia speed control device can be provided.

The block block diagram of the speed control apparatus of 2 inertia systems of this invention. FIG. 3 is an internal configuration diagram of a disturbance observer and a state observer of the two-inertia speed control device of the present invention. The simulation result of the state quantity estimation using the disturbance observer of 2 inertia systems of this invention. The simulation result of the control characteristic of the speed control apparatus of 2 inertia systems of this invention.

  Hereinafter, embodiments of a two-inertia disturbance observer and a two-inertia speed controller according to the present invention will be described with reference to FIGS.

  FIG. 1 is an example of a block diagram of a two-inertia speed control device according to the present invention.

In FIG. 1, a control object 1 is a control object of a two-inertia system, and includes a rotor of an electric motor and a load that is mechanically coupled with a drive shaft. The control object 1 rotates when a motor torque T _M is applied from a drive device 2 including a power converter and a motor, and a motor rotation speed ω _M and a load rotation speed ω _L are obtained. The rotational speed ω _M of the electric motor is detected by a speed detector (not shown) provided in the control target 1. Further, a disturbance torque _TL acts on the load.

  The drive device 2 includes, for example, a power converter 21 that converts a DC voltage of a DC power source (not shown) into AC, an electric motor 22 that is driven by the output of the power converter 21, and a current that detects an output current of the power converter 2. And a detector 23.

A voltage command V _M ^* is given to the drive device 2 from the control device 3, and the electric motor torque T _M is output from the electric motor 22 when the power converter 21 outputs a voltage corresponding to the voltage command V _M ^*. .

  Hereinafter, the internal configuration of the control device 3 will be described.

Normally, a difference between a speed command ω _L ^* given from the outside and an estimated load speed ω _L ^ obtained from a state observer 7 to be described later is given to the integral speed controller 4. The integral speed controller 4 integrates and amplifies this deviation, and gives a difference between this output and a state signal which is an output of a weighting adder 9 described later to the proportional speed controller 5. The proportional speed controller 5 proportionally amplifies this difference, and outputs a current command I _M ^* that minimizes the input difference as a result. The difference between the current command I _M ^* and the feedback current I _M by the current detector 23 described above is given to the current controller 6 having the first-order lag characteristic. The current controller 6 controls the power converter 21 by outputting a voltage command V _M ^* that minimizes the difference input as a result. Here, since the command value of the current command I _M ^* or feedback current I _M motor torque T _M from the torque component of is required, the following motor torque T _M and those using this command value. Incidentally, it is also possible to use the torque component of the feedback current I _M as a feedback current.

The state observer 7 is an observer of the same dimension as the object to be controlled. As will be described later, when the motor torque T _M and the motor rotational speed ω _M are given, the estimated motor rotational speed ω _M ^ is converted into the motor rotational speed ω. _It has a feedback loop that matches _M. Further, an estimated disturbance torque T _L ^ obtained from a disturbance observer 8 described later is given to the state observer 7.

The weighted adder 9 calculates the estimated rotational speed ω _M ^ of the motor obtained from the state observer 7, the estimated torsion angle θ _Δ ^ of the drive shaft, the estimated rotational speed ω _L ^ of the load, and the motor torque T _M that is input to the state observer 7. To give. In the weighted adder 9, the optimum gains K _F1 ⁰ and K _F2 ^{0 for} the estimated rotational speed ω _M ^ of the motor, the estimated twist angle θ _Δ ^ of the drive shaft, the estimated rotational speed ω _L ^ of the load, and the motor torque T _M , respectively. , K _F3 ⁰ and K _F4 ⁰ are added to obtain a status signal. A method for obtaining these optimum gains will be described later. Here, the motor torque T _M, but not the state quantity state observer 7 is estimated by the value also feedback controlled as the quantity of state, robust control system is achieved than the response delay of the current controller 6 has been compensated It becomes possible.

  FIG. 2 shows the internal configuration of the control target 1, the state observer 7, and the disturbance observer 8. Here, the codes used in each block have the following meanings.

J _M : Motor rotor inertia moment J _M0 : Motor rotor inertia moment nominal (nominal) value J _L : Load inertia moment J _L0 : Load inertia moment nominal value K _SP : Drive shaft spring constant K _SP0 : nominal value of the spring constant of the drive shaft ω _c : cutoff frequency K: feedback gain in the state observer First, the internal configuration of the controlled object 1 will be described. When the disturbance torque T _L of the load is integrated by the integrator 11, the rotation speed omega _L of the load is obtained by equations of motion. Similarly, when the motor torque T _M is integrated by the integrator 12, the rotation speed ω _M of the motor is obtained by the equation of motion. Rotational speed of the electric motor omega _M and the load torsion angle theta _delta of the drive shaft a difference of the rotation speed omega _L to integrated by the integrator 13 is obtained. Multiplying the spring constant 14 in helix angle theta _delta of the drive shaft to obtain an output torque of the spring, the torque acting on the disturbance torque T _L and the motor torque T _M of the load.

  The internal structure modeling the control target 1 does not include the load or the motor friction torque. However, these friction torques act in a direction to further increase the damping, so that the torsional vibration that is the object of the present application is suppressed. It works effectively against suppression. Therefore, it is sufficient for the control target 1 not to consider these friction torques.

Next, the internal configuration of the state observer 7 will be described. Estimated disturbance torque T _L ^, which will be described later, is given from a disturbance observer, and when this is integrated by the integrator 71, an estimated rotational speed ω _L ^ of the load is obtained from the equation of motion. Similarly, when the motor torque T _M is integrated by the integrator 72, the estimated rotational speed ω _M ^ of the motor is obtained from the equation of motion. When the difference between the estimated rotational speed ω _M ^ of the electric motor and the estimated rotational speed ω _L ^ of the load is integrated by the integrator 73, the estimated twist angle θ _Δ ^ of the drive shaft is obtained. When the estimated torsion angle θ _Δ ^ of the drive shaft is multiplied by a spring constant (nominal value) 74, an estimated output torque of the spring is obtained, and this torque acts on the estimated disturbance torque T _L ^ and the motor torque T _M of the load.

The above is basically the same block configuration as the control target 1. Then, to match the estimated rotational speed of the motor omega _{M ^} to the rotational speed omega _M of measurable electric motor, both the difference is multiplied by a proportional gain 75 and the coefficient 76 is fed back to the part of the motor torque T _M. By performing such feedback control, the estimated rotational speed ω _M ^ of the electric motor can be matched with the rotational speed ω _M of the electric motor. In FIG. 2, this feedback control is performed by a proportional system. However, if an integral system incorporating an integral is used instead of the proportional gain 75, the offset error can be further reduced.

Next, the internal configuration of the disturbance observer 8 will be described. The disturbance observer 8 multiplies the motor torque T _M by the transfer function 82, subtracts the value obtained by multiplying the motor rotational speed ω _M by the transfer function 83 from this multiplication result, and obtains this result as a fourth-order Bessel filter 83. To estimate the estimated disturbance torque T _L ^. The reason why the estimated disturbance torque T _L ^ can be obtained by such calculation will be described below.

The transfer function of the two-inertia system shown in FIG.

When this equation (1) is solved for the disturbance torque _TL , equation (2) is obtained.

Therefore, the estimated disturbance torque T _L ^ can be obtained from the motor torque T _M and the rotation speed ω _{M of} the motor from the equation (2). That is, the transfer function 81 is expressed by equation (3), and the transfer function 82 is expressed by equation (4).

Of these transfer functions, equation (3) is a second-order differential system, and equation (4) is a third-order differential system. Therefore, in order to remove the influence of noise and the like, it is necessary to pass at least a third-order filter. In consideration of practicality such as response characteristics, it is preferable to pass a fourth-order filter. As a result of comparing and examining the Patterworth filter and the Bessel filter as the fourth-order filter, it is possible to multiply the output of the expression (2) by a fourth-order Bessel filter 83 having excellent responsiveness and less overshoot. It turned out to be preferable. The estimation accuracy of the estimated disturbance torque T _L ^ can be improved by appropriately selecting the cutoff frequency ω _c in the transfer function of the filter shown in the fourth-order Bessel filter 83 in FIG.

  Next, the configuration of the weighted adder 9 in FIG. 1 and the ILQ control method will be described.

The ILQ (Inverse Linear Quadratic) design method is an optimal servo design method using the inverse problem of the optimal regulator (LQ) problem based on the modern control theory, and the solution of the LQ problem can be obtained from a simple pole arrangement without giving a weight. Can be derived. According to this ILQ control, it is possible to achieve a control that is low in sensitivity and robust to parameter variations. Since the speed control system shown in FIG. 1 is a typical type 1 servo control system based on the optimal control theory, the gain K _I ⁰ of the integral speed controller 4 in FIG. Optimal gains K _F1 ⁰ , K _F2 ⁰ , K _F3 ⁰ , K _F4 ⁰ can be obtained. Here, these gains are determined as follows based on the solution process of the inverse LQ design method that can be derived analytically.

However, _TC : Time constant s ₁ of the current controller 6: Designated pole in ILQ control. Equation (6) is a determinant notation, and indicates K _F1 ⁰ , K _F2 ⁰ , K _F3 ⁰ , K _F4 ⁰ in order from the left term.

  Next, a simulation result of state quantity estimation using the disturbance observer 8 will be described.

3 (a) is, at the time 1sec in the presence of periodic disturbance torque by changing the motor torque T _M in steps, twist angle when the disturbance torque T _L is increased stepwise at the time 1.5sec θ _Δ is shown. The estimated twist angle θ _Δ ^ estimated by the state observer 7 is shown in FIG. Thus, both agree well. FIG. 3C shows the estimated twist angle θ _Δ ^ when the disturbance observer 8 is not provided. In this case, it can be seen that there is a phase error in the estimation and a large error in the estimation.

  FIG. 4 shows a simulation result of the control characteristics of the two-inertia speed control device of the present invention. The simulation conditions are as follows.

J _M = 0.004016 (kgm ² )
J _L = 0.002921 (kgm ² )
K _SP = 39.21 (Nm / rad)
ω _c = 2000π (rad / sec)
T _C = 0,0025 (sec)
G _Σ = 1000
s ₁ = −120 (rad / sec)
As shown in FIG. 4A, the speed command ω _L ^* is given stepwise at time Time = 0 sec, and the disturbance torque _TL is given stepwise at time Time = 0.5 sec. The time responses of the motor rotational speed ω _M and the load rotational speed ω _L in this case are shown in FIGS. 4A and 4B, respectively. As can be seen from these figures, torsional vibration, which is the initial purpose, is suppressed, and stable control characteristics are obtained.

  Although the embodiment of the present invention has been described above, this embodiment is presented as an example and is not intended to limit the scope of the invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

For example, in FIG. 1, the gain K _I ⁰ and the optimum gains K _F1 ⁰ , K _F2 ⁰ , K _F3 ⁰ , K _F4 ⁰ of the weighting adder 9 do not necessarily have to be obtained by the ILQ design method. Moreover, it is not always necessary to use the feedback of the motor torque T _M in the case of slow system response, there are cases where using only the state quantity estimated by the state observer be effective even if the feedback control, the According to the ILQ design method, robust control can be realized even in a fast response system, and a large number of gains can be determined simultaneously, and the time required for parameter adjustment is greatly reduced.

  Also, so-called sensorless vector control in which the speed is not detected by the speed detector can be applied. In this case, a speed estimator that estimates the speed from the voltage and current signals of the power converter may be used.

DESCRIPTION OF SYMBOLS 1 Control object 2 Drive apparatus 3 Control apparatus 4 Integral speed controller 5 Proportional speed controller 6 Current controller 7 State observer 8 Disturbance observer 9 Weighted adder 11 Integrator 12 Integrator 13 Integrator 14 Spring constant 21 Power converter 22 Electric motor 23 Current detector 71 Integrator 72 Integrator 73 Integrator 74 Spring constant (nominal value)
75 proportional gain 76 coefficient 81 transfer function 82 transfer function 83 4th order Bessel filter

Claims (3)

A speed control device of a two-inertia system comprising a power converter, and a control device that controls a controlled object in which a rotor and a load of an electric motor driven by the power converter are coupled by a drive shaft,
The controller is
A state observer composed of the same control block as the control block represented by the control block diagram in which the motor torque and the disturbance torque are input and the motor speed and the load speed are output;
A disturbance observer for applying an estimated disturbance torque to the state observer;
An integral controller that performs feedback control so that the estimated load speed matches a speed command;
A proportional controller that outputs a current reference by performing feedback control so that a feedback amount obtained by weighting and adding the state amount obtained from the motor torque and the state observer matches the output of the integral controller;
A current controller that performs feedback control so that an output current of the power converter matches the current reference and outputs a voltage reference of the power converter;
The disturbance observer is
The motor torque is multiplied by a first transfer function, and a value obtained by multiplying the rotation speed of the motor by a second transfer function is subtracted from the multiplication result, and the subtraction result is filtered by a third-order or higher filter to perform the estimation. The configuration is such that the disturbance torque is obtained, and the first and second transfer functions are obtained by back-calculating the disturbance torque from a transfer function of a two-inertia system that obtains the motor speed from the motor torque and the disturbance torque,
The state quantity is
The estimated rotational speed of the motor, the estimated torsion angle of the drive shaft, and the estimated rotational speed of the load. The weight gain of these state quantities, the weight gain of the motor torque, and the gain of the integral speed controller are obtained by the ILQ design method. 2-inertia system speed control apparatus, characterized in that the. The moment of inertia of the rotor of the motor is J _M , The moment of inertia of the load is J _L , The spring constant of the drive shaft is K _SP , The time constant of the current controller is T _C S designated pole in ILQ control ₁ When
The gain of the integral speed controller is obtained by the following (Equation 5),
The estimated rotational speed of the motor, the estimated torsion angle of the drive shaft, the estimated rotational speed of the load, and the weighting gain of the motor torque are each obtained by the following (Equation 6) in order from the left term in determinant notation. The speed control device for a two-inertia system according to claim 1.
3. The two-inertia speed control device according to claim 1, wherein the filter is a fourth-order Bessel filter .