JP6750707B1 - Motor drive device and method of controlling motor drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the stability of current control in a motor drive device by being able to converge on a torque command input from a higher-level control in a steady state, easily mounting a low-order model. SOLUTION: A speed control unit 1 outputs a torque command T * based on a detected motor angular velocity ωM and a speed command ω *. The vibration suppression control unit 2 extracts the vibration component by subtracting the detected motor angular velocity ωM from the estimated motor angular velocity ωest, feeds back the compensation torque TFB through the filter 22 that does not compensate the low frequency component and the high frequency component, and compensates the vibration component. The torque TFB is added to the torque command T * to calculate the vibration suppression torque command T **. The current control unit 3 outputs a gate signal based on the detection motor phase, the detection current, and the vibration suppression torque command. In the inverter 4, the switching element is controlled based on the gate signal, and the voltage is output to the motor M. [Selection diagram] Figure 2

Description

The present invention relates to a system in which a motor drives a two-inertia system or a multi-inertia system having two or more inertia systems, and particularly relates to vibration suppression.

A mechanism that generates a DC voltage composed of a battery or an AC power supply and a rectifier (AC-DC converter), an inverter that converts the DC voltage into an AC voltage and applies it to a motor (electric motor), and the applied electrical energy. Consider a two-inertia drive system composed of a motor that is converted into mechanical energy and rotates, one load connected to the motor by a shaft or the like, or a multi-inertia drive system in which a plurality of loads are connected.

Here, it is assumed that the inverter generates an AC voltage having an amplitude and a frequency that allows the motor to operate with an appropriate torque based on a torque command generated by operating the accelerator or the operation panel and applies the AC voltage to the motor. Systems having such a drive system include, for example, elevators and machine tools.

In a drive system via such a shaft, when a load is driven, a reaction force against torsion may be generated in the shaft, and resonance may be excited. Further, the inertial system may vibrate due to the disturbance component applied to the load. There is known a method of improving the control to take measures against the vibration of the inertial system.

For example, in the vibration suppression control for automobiles disclosed in Patent Document 1, the target response by the motor shaft-converted total inertia is compared with the detected motor angular velocity, and the vibration component is fed back to suppress the vibration.

In the vibration suppression control for a test device such as a transmission of Patent Document 2, the output torque is detected and fed back to suppress the vibration independent of the motor rotation speed.

In the vibration suppression control for machine tools of Patent Document 3, vibrations are suppressed by comparing the speeds of the motor and the driven part and feeding back the vibration component.

In the vibration suppression control of the multi-inertia system of Patent Document 4, the disturbance observer and the resonance ratio control are both achieved to achieve simple vibration suppression control.

Patent No. 6243279 Patent No. 5037024 Patent No. 6412071 Patent No. 5329203

In the vibration suppression control of Patent Document 1, the discussion is limited to automobiles, and the influence of the vibration suppression control on the current control system when a high frequency disturbance is input to the inertial system is not considered.

The vibration suppression control of Patent Document 2 requires an output torque detecting means. Many electric motor drive systems do not have output torque detection means, and there is a risk that design changes and parts procurement costs may occur when applied to general electric motor drive systems.

The vibration suppression control of Patent Document 3 requires a speed detector for both the motor and the driven part. When the number of detectors is two, problems such as an increase in component cost and an increase in failure risk occur as compared with the case of using one detector.

In the vibration suppression control of Patent Document 4, since the low frequency component is fed back, the torque command after the vibration suppression compensation does not converge to the torque command from the speed control in a steady state. This is not suitable when you want to control the motor torque to a specific value regardless of the magnitude of the command value and the presence or absence of disturbance.

From the above, in the motor drive device, it is possible to converge to the torque command input from the upper-level control in a steady state, a low-order model can be easily implemented, and it is necessary to improve the stability of current control. Become.

The present invention has been devised in view of the above conventional problems, and one aspect thereof is a motor drive device that drives one or a plurality of loads by a motor connected to an inverter, A speed control unit that outputs a torque command based on the motor angular speed and the speed command, and a filter that does not compensate the low-frequency component and the high-frequency component for the vibration component by subtracting the detected motor angular speed from the estimated motor angular speed to extract the vibration component. Based on the vibration suppression control unit that feeds back the compensation torque through and calculates the vibration suppression torque command by adding the compensation torque to the torque command, based on the detected motor phase, the detected current, and the vibration suppression torque command. A current control unit that outputs a gate signal, and an inverter that controls a switching element based on the gate signal and outputs a voltage to the motor are provided.

In addition, as one mode thereof, the vibration suppression control unit calculates the estimated motor angular velocity from an inertial system model block that calculates the estimated motor angular velocity by multiplying the vibration suppression torque command by an inertial system model, and the detected motor angular velocity from the estimated motor angular velocity. A subtraction unit that subtracts, a filter that inputs the output of the subtraction unit and outputs the compensation torque, and an addition unit that adds the compensation torque to the torque command and outputs the addition as the vibration suppression torque command. It is characterized by that.

Further, as one mode thereof, the transfer coefficient of the filter is expressed by the following equation (9).

G _FB : Transfer function Jr: Internal model inertia ζ _H : Suppression compensation strength ω _H : Frequency band s: Laplace operator.

According to the present invention, in the motor drive device, the torque command input from the upper control can be converged in a steady state, a low-order model can be easily mounted, and the stability of current control can be improved.

The connection block diagram of a motor and a load. The control system block diagram of the motor drive device in embodiment. The inertial system block diagram in embodiment. The block diagram of the vibration suppression control part in embodiment. The step response diagram in embodiment. The Bode diagram in the embodiment.

Hereinafter, an embodiment of a motor drive device according to the present invention will be described in detail with reference to FIGS.

[Embodiment]
FIG. 1 shows a connection configuration diagram of a motor and a load in this embodiment. FIG. 1 shows a four-inertia drive system in which a motor M drives three loads A, B, C via a shaft. The 4-inertia drive system is used for the purpose of explanation as an example of multi-inertia system control, and the embodiment is not limited to the 4-inertia system. That is, the number of loads is not limited to three, and may be any number of one or more. The motor torque T _M is a torque generated by controlling the current flowing through the motor M with an inverter, and drives the motor M and the loads A, B, C by the motor torque T _M. Below, the drive system of FIG. 1 is called a plant.

FIG. 2 shows a block diagram of the control system in this embodiment. A speed command ω ^* is input to the control system according to the amount of operation of the accelerator or operation panel. There may be a configuration in which there is position control before the speed command ω ^* and the speed command ω ^* is generated there. The speed control unit 1 outputs a torque command T ^* for following the speed command ω ^* based on the input speed command ω ^* and the detected motor angular speed ω _M.

The vibration suppression control unit 2 is a target control unit of the present embodiment, and a torque command (hereinafter, referred to as a vibration suppression torque command) for suppressing the vibration from the input torque command T ^* and the detected motor angular velocity ω _M. Output T ^** .

The vibration control torque command T ^** , the detected motor phase, and the detected current are input to the current control unit 3, a current control calculation for realizing the vibration control torque command T ^** is performed, and a gate signal is given to the inverter 4.

In the inverter 4, switching is performed according to the gate signal, and a voltage is applied to the motor M. When a voltage is applied to the motor M, a current flows and a motor torque T _M corresponding to the speed and the current is generated.

Here, although the detected motor angular velocity ω _M and the detected motor phase are used in FIG. 2, the estimated motor phase may be calculated by current control or the like, that is, the speed sensor may be omitted. In that case, the estimated motor angular velocity is input to the speed control unit 1 and the vibration suppression control unit 2 instead of the detected motor angular velocity ω _M. In this specification, the detected motor angular velocity ω _M includes the estimated motor angular velocity, and the detected motor phase includes the estimated motor phase.

Further, regarding the following vibration suppression control, it is assumed that the current control is sufficiently accurate and is regarded as a first-order lag transfer function with the same time constant as the current control response.

FIG. 3 is a block diagram of FIG. J _M , J _A , J _B , and J _C are inertias of the motor M, the load A, the load B, and the load C, respectively. Further, D _MA , D _AB , and D _BC are damping constants expressing the loss of the shaft connecting the motor M and the load A, the load A and the load B, and the load B and the load C, and K _MA , K _AB , and K _BC are the motors. It is the rigidity of the shaft that connects M and load A, load A and load B, and load B and load C. The shaft loss indicates a component such as friction generated according to the angular velocity of the shaft twist.

Blocks 7, 11, 15, and 18 using inertia such as 1/J _M s show a transfer function from torque to angular velocity. Blocks 9, 13, 17 using shaft coefficients such as D _MA s+K _MA /s show the transfer function from angular velocity to torque.

Subtractors 8, 12, 16 by feedback before the blocks 9, 13, 17 using the transfer function of the shaft coefficient are for deriving the angular velocity at which the shaft is twisted from the difference between the two angular velocities. Subtractors 6, 10, 14 by feedback before the blocks 7, 11, 15, 18 using the transfer function of the inertia of the motor M or the loads A, B, C represent the reaction force from the shaft.

A specific description will be given based on FIG. The subtraction unit 5 subtracts the disturbance torque T _dis from the motor torque T _M. The subtraction unit 6 subtracts the output of the first shaft block 9 from the output of the subtraction unit 5.

In the motor inertia block 7, the output of the subtraction unit 6 is multiplied by the motor inertia transfer function 1/J _M s to calculate the detected motor angular velocity ω _M. The subtraction unit 8 subtracts the output of the first load inertia block 11 from the detected motor angular velocity ω _M. In the first shaft block 9, the output of the subtraction unit 8 is multiplied by the first shaft transfer function D _MA s+K _MA /s.

The subtractor 10 subtracts the output of the second shaft block 13 from the output of the first shaft block 9. In the first load inertia block 11, the output of the subtraction unit 10 is multiplied by the first load transfer function 1/J _A s. The subtractor 12 subtracts the output of the second load inertia block 15 from the output of the first load inertia block 11.

In the second shaft block 13, the output of the subtraction unit 12 is multiplied by the second shaft transfer function D _AB s+K _AB /s. The subtraction unit 14 subtracts the output of the third shaft block 17 from the output of the second shaft block 13. In the second load inertia block 15, the output of the subtraction unit 14 is multiplied by the second load transfer function 1/J _B s. The subtraction unit 16 subtracts the output of the third load inertia block 18 from the output of the second load inertia block 15.

In the third shaft block 17, the output of the subtraction unit 16 is multiplied by the third shaft transfer function D _BC s+K _BC /s. In the third load inertia block 18, the output of the third shaft block 17 is multiplied by the third load transfer function 1/J _C s.

Although FIG. 3 shows the case where there are three loads, the number of loads may be one or more. When the load is one, the plant transfer function G _P is a block from the subtracting unit 6 to the first load inertia block 11 (however, there is no subtracting unit 10). When there are two loads, the blocks are the subtraction unit 6 to the second load inertia block 15 (however, there is no subtraction unit 14). When the load is four or more, necessary blocks may be added to FIG.

When the motor torque T _M and the disturbance torque T _dis are input, the motor M and the loads A, B and C are driven based on FIG. The motor angular velocity is detected and used as the detected motor angular velocity ω _{M in} the control system of FIG. The subtraction of the motor torque T _M and the disturbance torque T _dis is called the plant transfer function G _P from the plant input torque to the detected motor angular velocity ω _M. However, the plant does not need to have a combination of linear transfer functions as shown in FIG. 3, that is, a configuration in which one plant transfer function G _P is put together, and a plant having nonlinear elements such as gear backlash. Also, this embodiment is applicable.

FIG. 4 shows a configuration diagram of the vibration suppression control unit 2. G _P is the plant transfer function shown in FIG. The plant transfer function G _P is an external term of the vibration suppression control unit 2 in FIG. 2, but is shown for the sake of clarity of the entire vibration suppression control.

In the present embodiment, detection means is provided for a resonating model, and the result is compared with an in-control calculation result having a component other than resonance and is fed back to the output. This is the basic idea of control. A model that expresses components other than resonance is a model that roughly represents the entire inertial system, and this is a first-order lag whose time constant is the sum of all inertias of the inertial system.

A torque command T ^* is input to the vibration suppression control unit 2. The adder 19 adds the torque command T ^* and the fed back compensation torque T _FB to calculate the vibration suppression torque command T ^** .

The inertial system model block 20 calculates the estimated motor angular velocity ω _est by multiplying the vibration suppression torque command T ^** by the inertial system model (1/J _rs ) inside the control. Here, J _r is the internal model inertia. Further, the vibration suppression torque command T ^** becomes the motor torque T _M via a current control system (here, it is regarded as a primary delay having a small time constant and omitted). The subtractor 5 subtracts the disturbance torque T _dis from the motor torque T _M , and inputs the disturbance torque T _dis to the plant transfer function G _P. The output of the plant transfer function G _P is the detected motor angular velocity ω _M.

The subtraction unit 21 subtracts the detected motor angular velocity ω _M from the estimated motor angular velocity ω _est . That is, the internal model and the detected value from the plant are compared. The result of the subtraction is added to the torque command T ^* as the vibration suppression compensation torque T _FB via the filter 22 (transfer function G _FB ).

Here, only the vibration suppression control is considered, assuming that the speed control and the current control in FIG. 2 operate without any special problem.

The basic idea of the vibration suppression control (FIG. 4) of this embodiment will be described. The detected motor angular velocity ω _M from the plant oscillates due to the rigidity of the plant. On the other hand, the internal model is expressed only by integration considering the inertia, and the estimated motor angular velocity ω _est obtained from it has no vibration component. That is, if the internal model is appropriate, only the vibration component of the detected motor angular velocity ω _M can be extracted by comparing the detected motor angular velocity ω _M and the estimated motor angular velocity ω _est . Then, the obtained vibration component is passed through an appropriate filter (transfer function G _FB ) and fed back to the torque command T ^* , whereby the vibration of the detected motor angular velocity ω _M can be suppressed. The above is the basic idea of vibration suppression.

Vibration suppression control by the configuration of FIG. 4 will be described using mathematical expressions. Here, the current control system can be regarded as a first-order lag with a small time constant, and it is assumed that the vibration suppression torque command T ^** and the motor torque T _M are equal. In addition, the motor angular velocity of the plant is assumed to be accurately detected without delay.

First, the inertial system model inside the control will be described. Since it is desired to compare the detected motor angular velocity ω _M and the estimated motor angular velocity ω _est to extract the vibration component as described above, the estimated motor angular velocity ω _est may be a simulation of a rough movement of the motor angular velocity.

Therefore, in order to simulate that the loads A, B, and C are connected to the motor M, the internal model inertia J _r is adjusted to a value equal to or greater than the inertia J _M so that vibration can be easily suppressed. When the information on the inertia is known in advance, the internal model inertia Jr is the sum of the inertias of the motor M and the full loads A, B, C as shown in the following equation (1).

It should be noted here that when transmitting a force through a gear or the like, and when converting a rotational force such as a wheel into a back-and-forth motion, the inertia of each load A, B, C seen from the motor M is the inertia measured by a single measurement. Therefore, the estimated motor angular velocity ω _est deviates from the detected motor angular velocity ω _M with the equation (1) as it is. In such a case, the inertia of each load may be converted to the motor shaft using the gear ratio and the radius of gyration, and the sum may be calculated.

Next, the design of the filter (transfer function G _FB ) will be described. The transfer function from the torque command T ^* and the disturbance torque T _dis to the motor torque T _M is given by the following expression (2). The transfer function from the torque command T ^* and the disturbance torque T _dis to the detected motor angular velocity ω _M is given by the following expression (3).

Here, the plant transfer function G _P is represented by the numerator G _PN and the denominator G _PD . Further, considering the suppression of the vibration of the detected motor angular velocity ω _M , the coefficient part of the torque command T ^{* in} the equation (3) is set as G _X. Then, the following expressions (4) and (5) are obtained.

_Paying attention to the _designable transfer function 1/J _rs , G _FB , replacing it with the following equation (6), and rearranging the equation (5), the following equation (7) is obtained.

Focusing on the denominator of equation (7), it can be seen that the resonance caused by the denominator G _PD of the plant transfer function G _P can be suppressed by G _H.

Here, in the vibration suppression of the present embodiment, the following two points are emphasized, and the low frequency component and the high frequency component are not compensated.
-If there is no vibration, the value of the torque command T ^* is not changed, that is, steady compensation is not performed.
-No compensation is required, which requires consideration of the balance with the current control response.

Based on the expressions (3) and (6) that the response of the detected motor angular velocity ω _M to the disturbance torque T _dis is G _X ·G _H , G _H is set to the notch filter as shown in the expression (8). .. ω _H determines the frequency band and ζ _H determines the strength of suppression compensation.

The frequency band ω _H and the suppression compensation strength ζ _H are adjusted so that the vibration can be suppressed in accordance with the plant. Generally, the frequency band ω _H is from the anti-resonance point of the plant transfer function G _P. If the suppression compensation strength ζ _H is set low, the vibration suppression performance is weak if it is small, and if it is large, a steep compensation torque T _FB is generated. Therefore, it is preferable to set 0.2<ζ _H <0.8.

Regarding the filter (transfer function G _FB ) used for the vibration suppression control, the following expression (9) is derived from the expression (8).

The above is the description of the vibration suppression control of the present embodiment. The effect of this embodiment was confirmed by simulation. FIG. 5 shows the simulation result for the step response. The left side of FIG. 5 shows the case where the torque command T ^* is changed, and the right side shows the case where the disturbance torque T _dis is changed. It can be seen that the vibration of the detected motor angular velocity ω _M is suppressed regardless of whether the torque command T ^* or the disturbance torque T _dis is changed. Both results show that the torque command T ^* and the vibration suppression torque command T ^** , that is, the motor torque T _M here finally converge to the same value.

Therefore, it can be seen that the vibration of the multi-inertia system can be suppressed while achieving the target "to suppress the value of the torque command T ^* when there is no vibration", which is the object of the vibration suppression of the present embodiment. The deviation in the degree of increase in the angular velocity in the disturbance torque response results from the fact that the torque that cancels the disturbance is generated by the amount of vibration suppression only when control is performed.

FIG. 6 shows a Bode diagram. Because of the 4-inertia system, there are three resonance points without vibration suppression control. When vibration is suppressed, the gain at the resonance point can be suppressed for both the response to the torque command T ^* and the response to the disturbance torque T _dis .

Consider the features of this embodiment.

The first feature is steady characteristics. In the steady state after performing the vibration suppression, the vibration suppression torque command T ^** becomes equal to the torque command T ^* . This is advantageous when it is desired to output a specific motor torque T _M regardless of the presence or absence of disturbance.

The second feature is the order of the internal model. Usually, when the resonance of a multi-inertia system is reproduced by an internal model, the order of the transfer function becomes high, and the coefficient also greatly differs depending on the term. Therefore, it is necessary to pay attention to the decimal point position and calculation error at the time of mounting. However, the internal model 1/J _r s of the present embodiment has a low order and can reduce mounting difficulties.

The third feature is the consideration of high frequency disturbances. If the vibration suppression control is designed to compensate for high-frequency disturbances, the compensating torque may fluctuate at high frequencies and there is a risk of destabilizing the current control. On the other hand, in the present embodiment, G _H that contributes to the disturbance response is set as in equation (8), and compensation is not performed for high frequencies to ensure stability.
The above is the feature of this embodiment.

The effects of this embodiment will be described below.

After subtracting the estimated motor angular velocity ω _est that does not have a vibration component from the oscillating detected motor angular velocity ω _M , feedback is performed through a filter that does not compensate for low and high frequencies. Can converge to T ^* ,
It can be easily implemented with a low-order model, and it is possible to perform vibration suppression control of a multi-inertia system that does not make current control unstable.

Conventionally, vibration control of an automobile may be performed by expressing a resonance due to shaft rigidity by a model. Although this can be controlled by feedforward without overshoot, model accuracy is important instead.

The expression term of resonance (rigidity) when the vehicle model is a discrete transfer function is considerably smaller than the other terms, and if it is regarded as 0 and approximated, the expression of resonance disappears and the damping Cannot be done. Therefore, conventionally, measures are taken specifically for damping control in order to express resonance.

In the control of the present embodiment, the resonance is not expressed, and the vibration suppression control can be performed by a simple transfer function expression.

Regarding Patent Documents 1 to 4, considering the influence on the current control system when a high-frequency disturbance is input to the inertial system, no output torque detecting means is required, and the speed detector is at most the motor. On the other hand, there is an advantage that the torque command after vibration suppression converges to the torque command from the speed control in the steady state, only one of which is required.

In the above, the present invention has been described in detail only for the specific examples described, but it is obvious to those skilled in the art that various variations and modifications are possible within the scope of the technical idea of the present invention, Of course, such variations and modifications are within the scope of the claims.

1 ... speed control unit 2 ... vibration suppression control unit 3 ... current control unit 4 ... inverter M ... motor omega ^* ... speed command T ^* ... torque command omega _M ... detected motor angular velocity T ^** ... vibration suppression torque command omega _est ... estimate Motor angular velocity T _FB ... Compensation torque

Claims (3)

A motor drive device for driving a plurality of loads by a motor connected to an inverter,
A speed control unit that outputs a torque command based on the detected motor angular velocity and the speed command;
A vibration component is extracted by subtracting the detected motor angular velocity from the estimated motor angular velocity, the vibration component is passed through a filter that does not compensate for the low frequency component and the high frequency component, and the compensation torque is fed back, and the compensation torque is added to the torque command. And a vibration suppression control unit that calculates a vibration suppression torque command,
A current control unit that outputs a gate signal, based on the detected motor phase, the detected current, and the vibration suppression torque command,
An inverter that controls a switching element based on the gate signal and outputs a voltage to the motor,
Equipped with
The vibration suppression control unit,
The estimated motor angular velocity is calculated by multiplying the vibration suppression torque command by the inertia system model that is the sum of the inertia of the motor and the value obtained by converting the inertia of each load into the motor shaft using the gear ratio and the radius of gyration. Inertial model block to
A subtraction unit that subtracts the detected motor angular velocity from the estimated motor angular velocity,
The filter which inputs the output of the subtraction unit and outputs the compensation torque,
And a compensation unit that adds the compensation torque to the torque command and outputs the vibration suppression torque command. The motor drive device according to claim 1 , wherein the transfer coefficient of the filter is expressed by the following equation (9).

G _FB : Transfer function Jr: Internal model inertia ζ _H : Suppression compensation strength ω _H : Frequency band s: Laplace operator A method for controlling a motor drive device for driving a plurality of loads by a motor connected to an inverter,
In the speed control unit, based on the detected motor angular speed and the speed command, output a torque command,
In the vibration suppression control unit, the detected motor angular velocity is subtracted from the estimated motor angular velocity to extract a vibration component, the compensation torque is fed back through a filter that does not compensate for the low frequency component and the high frequency component, and the compensation torque is set to the torque. Add to the command to calculate the vibration suppression torque command,
In the current control unit, based on the detected motor phase, the detected current and the vibration suppression torque command, outputs a gate signal,
In the inverter, controlling the switching element based on the gate signal, outputs a voltage to the motor,
The vibration suppression control unit,
In the inertial system model block, the vibration suppression torque command is multiplied by the inertial model, which is the sum of the inertia of the motor and the value obtained by converting the inertia of each load into the motor shaft using the gear ratio and the radius of gyration. Calculating the estimated motor angular velocity,
In the subtraction unit, the detected motor angular velocity is subtracted from the estimated motor angular velocity,
In the filter, the output of the subtraction unit is input to output the compensation torque,
A method of controlling a motor drive device, wherein the adding unit adds the compensation torque to the torque command and outputs the addition as the vibration suppression torque command .

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