JPH089672A - Speed controller for motor - Google Patents

Abstract

PURPOSE:To suppress speed change and mechanical vibration due to a load torque by individually providing approximate differentiation compensating means of the primary delay of a motor torque current and and the motor speed. CONSTITUTION:A primary delay compensator 10 calculates the primary delay compensation for a torque current detected value It of a motor, outputs a compensation current Ic1. An approximate differentiation compensator 11 calculates to approximate differentiation compensate a motor speed detected value omegam, and outputs a compensation current ICE. When a speed command value omegaref is applied, a speed controller 12 proportionally integrates the deviation of the value omegaref and the value omegam detected by a speed detecting calculator 9, and calculates a torque current command value Iout. The current IC2 calculated by the compensator 11 and the current Ic1 calculated by the compensator 10 are added to or subtracted from the value Iout by adders 13, 14, and a motor torque current command value Iref is calculated for a current controller 5. As a result, its time constant can be independently set, and a shaft torque is fed-back for compensation to suppress its vibration.

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, and more particularly to a motor speed control device for driving a mechanical load.

[0002]

2. Description of the Related Art Conventionally, in a speed control device for a motor that drives a mechanical load, as a method for suppressing impact drop of speed, shaft torsional vibration, etc., which occurs when load torque is applied, it is described in Japanese Patent Application Laid-Open No. 1-259777. The method is known. In this method, the disturbance observer method asymptotically estimates the axial torque acting on the motor shaft as a component of the drive torque generated by the motor that is not used for the acceleration / deceleration torque of the motor. Here, the drive torque of the motor is calculated from the torque current of the motor, and the acceleration / deceleration torque of the motor is calculated from the motor speed. By compensating the motor torque current command value using the estimated shaft torque, the load torque acting on the mechanical load is compensated and the impact drop of the speed is reduced. Further, by compensating so as to suppress the shaft torsion torque component included in the shaft torque, excitation of shaft torsion vibration between the motor and the mechanical load is suppressed.

[0003]

In the conventional method using the disturbance observer, the shaft torque is asymptotically estimated by using two signals of the motor torque current and the motor speed as inputs. As the speed of shaft torque estimation is increased, the shaft torque estimated value can be calculated without delay with respect to changes in shaft torque. By compensating the influence of the load torque and the shaft torsion torque by using the estimated value with less delay, speed control with good characteristics can be achieved.
However, if the speed of shaft torque estimation is increased, the speed control system may become unstable due to the influence of noise included in the motor speed and motor current, the calculation time, and the like. In particular,
Since the acceleration / deceleration torque of the motor is calculated by the differential calculation of the detected motor speed value, the high frequency component of noise is easily amplified. Therefore, the shaft torque could not be estimated sufficiently fast. As a result, it has been difficult to satisfactorily respond to suppression of impact load and suppression of shaft torsional vibration. An object of the present invention is to control the speed of a motor, which is suitable for estimating and compensating the shaft torque with good response even when there is an influence of noise included in the detected value of the motor speed, and suppressing speed fluctuations and mechanical vibrations due to load torque. To provide a device.

[0004]

In order to achieve the above object, one output (shaft torque estimated value) for two inputs (motor torque current and motor speed) to a disturbance observer.
The characteristics from the motor torque current to the shaft torque estimated value are expressed by the first-order lag element, and the characteristics from the motor speed to the shaft torque estimated value are expressed by the differential and first-order lag elements (also called approximate differential elements). . Compensation means having these transfer characteristics are individually provided for the detected torque current value and the detected motor speed value of the motor, and the output of each compensation means is individually fed back to compensate the torque current command value.

[0005]

By separating the compensating means for the motor torque current and the compensating means for the motor speed, the time constants of the first-order lag compensation for the motor torque current and the time constants of the differential and the first-order lag compensation (approximate differential compensation) for the motor speed are obtained. Can be set individually. Here, since the compensation element for the motor speed includes the differential term, it is necessary to prevent the noise from being amplified in the high frequency region as in the case of the conventional disturbance observer. This can be achieved by setting the time constant of the approximate differential compensation for the motor speed to a relatively large value to suppress the differential function in the high frequency region. On the other hand, since the torque current of the motor is used for current control that requires a high control response, detection noise and detection delay are small. Further, since the compensation element does not include a differential term, there is no amplification of noise in the high frequency region. Therefore, the time constant of the first-order lag compensation for the motor torque current can be made sufficiently small without impairing the stability. As a result, the high-frequency component of the shaft torque component included in the motor torque current can be fed back and compensated, and the same effect as that of estimating and compensating the shaft torque with high response can be obtained.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a motor speed control system showing an embodiment of the present invention. In FIG. 1, a torque transmitting connecting shaft 2 is coupled to an output shaft of a motor 1, and a mechanical load 3 is driven by this. A load torque τ _d acts on the mechanical load 3. The motor 1 is an induction motor,
It is driven by the power converter 4. The speed controller 12 is
The torque current command value I _out is calculated by proportionally integrating the deviation between the speed command value ω _ref and the motor speed detection value ω _m . Motor current detected by the current detector 6 is Decomposition in current component detector calculator 7, and the torque current component I _t which is proportional to the motor driving torque tau _m, is detected as an exciting current component I _m orthogonal thereto . The current controller 5 executes vector control by using these detected current values, and outputs the torque current command value I _ref.
The motor drive torque τ _m is controlled according to the above. On the other hand, since the motor 1 detects the speed, an encoder 8 that outputs a pulse train having a frequency proportional to the rotation speed
Is attached. The speed detection calculator 9 detects the motor speed ω _m from this pulse train. The speed control system of the motor includes a first-order delay compensator 10, an approximate differential compensator 11, a speed controller 12, and adders 13 and 14. Here, the first-order lag compensator 10 executes a first-order lag compensation calculation on the detected torque current value I _{t of the} motor and outputs a compensation current I _c1 . On the other hand, the approximate differential compensator 11 executes an approximate differential compensation operation on the detected motor speed value ω _m ,
The compensation current I _c2 is output. Here, the two compensation currents I _c1 and I _c2 are calculated by the following equation.

[Equation 1] Here, s is a Laplace operator, k ₁ and T _d1 are first-order lag compensation gain and time constant, and k ₂ and T _d2 are approximate differential compensation gain and time constant, respectively.

Now, the speed command value ω _ref is equal to the speed controller 12
To the speed command value ω _ref
And the deviation of the motor speed detection value ω _m detected by the speed detection calculator 9 are proportionally integrated to calculate the torque current command value I _out . The compensation current I _c2 calculated by the approximate differential compensator 11 and the compensation current I _c1 calculated by the first-order lag compensator 10 are added to the torque current command value I _out in the adders 13 and 14, respectively.
Is added or subtracted to calculate the motor torque current command value I _ref for the current controller 5.

[Equation 2] On the other hand, the current detector detected motor current and component resolution at a current component detector calculator 7 with 6, a torque current component I _t and the current controller of the exciting current component I _m orthogonal thereto which is proportional to the motor driving torque tau _m Enter in 5. In the current controller 5,
Vector control is executed using these detected current values, the power converter 4 is operated so that the motor drive torque τ _m is generated according to the torque current command value I _ref , and the motor 1 is controlled.

Next, in explaining the operations of the first-order lag compensator 10 and the approximate differential compensator 11, the effect when the motor 1 and the mechanical load 3 exhibit axial torsional vibration will be described. First, a vibration model of the motor 1 and the mechanical load 3 is shown in FIG.
Shown in. In FIG. 2, the moments of inertia J _m and J _l of the motor 1 and the mechanical load 3 are coupled by a spring 201,
Represents the torsional rigidity of the connecting shaft 2. Here, the motor drive torque is τ _m , the motor speed is ω _m , the mechanical load speed is ω _l ,
The load torque acting on the mechanical load is τ _d . In the axial torsional vibration state, the motor 1 and the mechanical load 3 vibrate via the spring 201. The equivalent block diagram of this vibration model is 2
It is well known as an inertial vibration model and can be expressed as shown in FIG. Here, the motor torque current is I _t , the shaft torsion torque is τ _s , and the shaft torque acting on the motor shaft is τ _t ,
Other variables are the same as those in FIG. Further, K _t is the torque constant of the motor, J _m is the moment of inertia of the motor, J _l is the moment of inertia of the mechanical load, K _f is the torsional rigidity of the shaft, and c _f is its damping coefficient. From the two-inertia vibration model of FIG. 3, the mechanical load speed ω _l is accelerated and decelerated by the shaft torsion torque τ _s , and the reaction force becomes the shaft torque τ _t to the motor shaft. Here, the relationship between ω _m , ω _l and τ _s , τ _s and τ _t , and τ _t and ω _l is
It can be expressed by the following formula.

[Equation 3] Here, s represents a Laplace operator, and 1 / s represents integration. Further, τ _d represents the load torque that acts on the mechanical load. On the other hand, the axial torque τ _t due to the axial torsional vibration between the motor 1 and the mechanical load 3 corresponds to a component of the drive torque τ _m that is not used for acceleration / deceleration of the motor speed. That is, the relational expression on the motor side can be expressed by the following expression.

[Equation 4] From this, it can be seen that the shaft torque τ _t is calculated from the motor torque current I _t and the motor speed ω _m by the following equation.

[Equation 5] Here, s of the Laplace operator represents differentiation.

With respect to such a drive system, in this embodiment, the first-order delay compensator 10 and the approximate differentiator 1 shown in FIG. 1 are used.
1, and the gains k ₁ and k ₂ of each compensator are given by the following equations.

[Equation 6] The torque current command value I _{ref at} this time can be expressed by the following equation by substituting the equations (1) and (6) into the equation (2).

[Equation 7] Here, K _t is a torque constant, J _m is a motor inertia moment value, and g and ΔJ _m are adjustable parameters.
Expression (7) can be equivalently converted as in the following expression by dividing the denominator by (1 + T _d1 s) and substituting the relationship of expression (5).

[Equation 8] Here, α ₁ , α ₂ , and α ₃ can be expressed by the following equations.

[Equation 9] From this, the gain k ₁ of the first-order lag compensation G ₁ (s) with respect to the motor torque current I _t , the time constant T _d1 and the motor speed ω _m
To the approximate differential compensation G ₂ (s) gain k ₂ and time constant T _d2
By adjusting the coefficient α ₁ in the equation (9),
α ₂ and α ₃ can be adjusted independently. Thus, the main control loop, in addition to the control process by feeding back the motor speed omega _m, shaft torque tau _t acting on the motor drive system, and, first derivative Esuomega _m of the motor speed, further, the second derivative of the motor speed A control loop for feeding back s ² ω _m can be constructed. Here, the time constant T _d2 of the approximate differential compensation element G ₂ (s) for the motor speed is set to be larger than the time constant T _d1 of the first-order delay compensation G ₁ (s) for the motor torque current. At this time, as is clear from the relationship of the equation (8), the axial torque τ _t can be compensated by the delay time constant T _d1 of the torque current compensation element. On the other hand, since the time constant T _d2 of the approximate differentiation of the motor speed can be set as T _d2 ≧ T _d1 , the shaft torque component is compensated with good response without increasing the high frequency component of noise included in the detected motor speed value. it can.

Next, the simulation waveform of the speed control system according to the present invention will be described in comparison with the simulation waveform of the speed control system according to the conventional method (by the disturbance observer). First, FIG. 4 shows a configuration of a speed control system according to the present invention by a block diagram using a transfer function. here,
The transfer characteristics of the first-order delay compensator 10 and the approximate differential compensator 11 are represented by the gains k ₁ and k ₂ and the time constants T _d1 and T _d2 as shown in the equation (1). The integral gain of the speed controller 12 is k _i and the proportional gain is k _p . The characteristic of the current control system is _a first-order lag system whose response time constant is T _a . Further, the characteristics of the motor and mechanical system are vibration systems having resonance peaks at 15 Hz and 60 Hz. On the other hand, FIG. 5 shows a block diagram in which a speed control system of a conventional (disturbance observer) system is represented by a transfer function. Where disturbance observer 15
Is composed of an integrator 1531 / J _1e s, an adder 154, and an observer gain k _o 155. When the absolute value of the observer pole is k _d (k _d = k _o / J _1e ), 1 /
The shaft torque τ _t is estimated with the time constant of k _d . Multiplied by the gain k _f the estimated value from the disturbance observer, by subtracting from the torque current command value to suppress the axial torsional vibration. The simulation results of both are shown in FIG. When the motor speed command value is changed stepwise, the motor speed (ω
_m), machine load speed (ω _l), the motor torque current (I _t)
Shows the waveform of. Here, (a) shows the result of the conventional method using the disturbance observer, and (b) shows the result of the present invention. In the conventional method of FIG. 6A, in the configuration of FIG.
With k _i = 20000 and k _p = 800, T _a = 1.6 ms
And Also, the time constant of the disturbance observer T _d (T _d = 1 /
k _d ) was set to 3.3 ms, and the feedback gain k _f of the shaft torsion torque estimated value was set to 1.2. As is clear from the result of FIG. 6A, the shaft torsion vibration between the motor and the mechanical load is suppressed to some extent from the mechanical load speed, but unstable continuous vibration is excited in the motor speed and the motor torque current. There is. This is because such a unstable vibration occurs because the shaft torque estimation response cannot be made sufficiently high with the conventional method using the disturbance observer 15. In contrast, in the present invention in FIG. _{6 (b), k i,} k p, k of T _a same city as FIGS. 6 (a) and, k ₁ of the first-order lag compensator 10 and the approximate differentiation compensator 11 ₂ Was set so that the same shaft torque estimated value feedback as k _f = 1.2 was obtained. Here, constant T _d2 when approximate differentiation compensator 11, the same 3.3ms constant T _d time of the disturbance observer 15, and a 1ms constant T _d1 when first order delay compensator 10. As is apparent from the result of FIG. 6B, according to the speed control system of the present invention, the time constant T _d1 of the first-order delay compensator 10 can be set without decreasing the time constant T _d2 of the approximate differential compensator 11. By making it small, unstable vibration does not occur, and high response of shaft torque estimation can be achieved.

As described in detail above, according to this embodiment,
By providing a first-order lag compensator G ₁ (s) for the motor torque current I _t and an approximate differential compensator G ₂ (s) for the motor speed ω _m , respectively, the time constant of the first-order lag compensation for the motor torque current can be obtained. , The time constants of the derivative with respect to the motor speed and the first-order lag compensation (approximate differential compensation) can be set independently, which makes it possible to equivalently estimate the shaft torque with high response without increasing the high frequency component of the approximate derivative of the motor speed. Is controlled by feedback, without exciting the vibration of the mechanical system,
Speed control the motor with high response. That is, in the case of the approximate differential compensation for the motor speed, since the compensating element includes the differential term, it is necessary to prevent the noise from being amplified in the high frequency region as in the case of the conventional disturbance observer. The time constant of is set to be large to some extent to suppress the differentiation function in the high frequency region and prevent an increase in the high frequency component of noise included in the speed detection value. On the other hand, if the first-order lag compensator torque current I _t of the motor,
The motor torque current is used for current control that requires high control response, so detection noise and detection delay are small,
Further, since the compensation element does not include a differential term, there is no amplification of noise in the high frequency region. For this reason, the time constant of the first-order lag compensation for the motor torque current can be made sufficiently small without impairing the stability, so that the shaft torque is estimated to be highly responsive and compensated. Further, as shown in (Equation 8), not only the axial torque but also the first and second differentials of the motor speed can be fed back, so the stability of the closed loop control system can be improved by the effect of advancing the phase by the differential. There is also.

[0012]

According to the present invention, by providing the motor torque current first-order lag compensator and the motor speed approximate differential compensator individually, the time constant of the first-order lag compensation for the motor torque current can be made small. Since the time constants of the differential with respect to the speed and the first-order lag compensation (approximate differential compensation) can be set independently, the axial torque can be feedback-compensated with high response without increasing the high frequency component of noise contained in the speed detection value, and the disturbance The torque can be compensated with good response, and the speed of the motor can be controlled with high response without exciting the vibration of the mechanical system. Further, since the first and second differentials of the motor speed can be fed back and controlled to the speed control system, the phase delay of the closed loop speed control system can be improved and the stability can be improved by the effect of advancing the phase by the differential. .

[Brief description of drawings]

FIG. 1 is a block diagram of a motor speed control system showing an embodiment of the present invention.

[Fig.2] Vibration model of mechanical load drive system

FIG. 3 is a block diagram of a vibration model.

FIG. 4 is a block diagram showing a speed control system according to the present invention by a transfer function.

FIG. 5 is a block diagram showing a transfer function of a speed control system by a conventional method (disturbance observer).

FIG. 6 is a diagram showing a simulation result of a velocity step response.

[Explanation of symbols]

 1 Motor 2 Connected Shaft 3 Mechanical Load 4 Power Converter 5 Current Controller 6 Current Detector 7 Current Component Detection Calculator 8 Encoder 9 Speed Detection Calculator 10 Primary Delay Compensator 11 Approximate Differential Compensator 12 Speed Controller

Claims (4)

[Claims] 1. A motor for driving a mechanical load, a means for respectively detecting a motor current and a motor speed, a means for calculating a torque current command value from a speed command value and a motor speed, and a motor from a detected value of the motor current. In a motor speed control device having means for calculating the torque current of the motor and means for controlling the torque current of the motor in accordance with the torque current command value, a control loop for feeding back the torque current of the motor through the delay compensation means, and a motor speed Is separately provided with a control loop that feeds back through differential and delay compensation (approximate differential compensation) means, and the torque current command value is compensated by the output of these control loops. 2. A motor for driving a mechanical load, a means for respectively detecting a motor current and a motor speed, a means for calculating a torque current command value from a speed command value and a motor speed, and a motor from a detected value of the motor current. In the motor speed control device having a means for calculating the torque current and a means for controlling the motor torque current according to the torque current command value, a means for delay compensation using the detected torque current value as an input, and a motor speed detected value A means for applying differential and delay compensation (approximate differential compensation) is provided as an input, and the time constant of the approximate differential compensation for the motor speed is set to be larger than the time constant of the first-order delay compensation for the motor torque current.
A speed control device for a motor, wherein speed control is executed with a result obtained by adding and subtracting a calculation result of the delay compensation and a calculation result of the approximate differential compensation to the torque current command value as a torque current command value. 3. The transfer function for delay compensation with respect to a detected torque current according to claim 1 or 2, wherein G ₁ (s) is
When the transfer function of differential and delay compensation (approximate differential compensation) with respect to the detected motor speed is G ₂ (s), G ₁ (s) is the first-order delay compensation described by equation (a), G ₂ (s) (B)
A motor speed control device characterized by differential and first-order lag compensation (approximate differential compensation) described by equations. [Equation 10] [Equation 11] Here, s is a Laplace operator, k ₁ and T _d1 are gains and time constants for first-order lag compensation, and k ₂ and T _d2 are gains and time constants for differential and first-order lag compensation (approximate differential compensation), respectively. 4. The control according to claim 1 or 2, wherein the torque current command value calculated from the speed command value and the motor speed is fed back with the axial torque, the first differential and the second differential of the motor speed. A speed control device for a motor.