JP6666126B2 - Control device with torque ripple correction function - Google Patents

Description

  The present invention relates to a control device having a torque ripple correction function.

  In the electric motor, torque pulsation called torque ripple occurs during rotation due to the interaction between the magnetic flux generated by energizing the winding and the magnetic flux generated from the magnet, and the influence of the stator teeth shape and the rotor pole shape.

  When an electric motor having a large torque ripple is used for a feed shaft of a machine tool, problems such as streaks appearing on a cutting surface occur. Therefore, in general, a torque ripple correction function is provided in the control device of the electric motor to correct the torque command so as to cancel the torque ripple, thereby suppressing an error in the actual speed and the position with respect to the operating speed and the position command.

  As a control device having a torque ripple correction function, for example, a device disclosed in Patent Document 1 or the like is known. Patent Literature 1 discloses an apparatus that corrects a torque command based on a torque command output from a speed loop controller when a motor is rotated by speed feedback control. A specific configuration will be described with reference to FIG. FIG. 3 is a diagram showing a schematic configuration of a control device 61 having a torque ripple correction function. The control device 61 includes a rotation angle detector 12, a speed loop controller 62, a torque command correction unit 63, a current control unit 65, and a differentiator 66. The torque command correction unit 63 stores, for each rotation angle, the pulsation of the torque command T * output from the speed loop controller 62 when the rotation speed command V * is input, and stores the pulsation of the stored torque command T *. Is added to the torque command T * for each rotation angle, thereby correcting the torque command T *.

JP-A-7-284286

  In the control device having a torque ripple correction function disclosed in Patent Document 1, the torque ripple correction amount is calculated based on a torque command of the same amplitude and cycle that cancels the torque ripple generated by the speed loop controller. Is done. Therefore, in order to accurately calculate the torque ripple correction amount, it is necessary for the speed loop controller to output a torque command having the same amplitude as the torque ripple.

  However, when the rotation speed of the motor is increased, the torque ripple frequency exceeds the frequency band of the speed loop controller, so that the speed loop controller cannot respond and the torque command output from the speed loop controller is higher than the torque ripple. The amplitude will be small. For this reason, there has been a problem that the correction amount is small and the correction amount cannot be accurately calculated at high speed. On the other hand, even at a low speed, it is necessary to determine the frequency of the torque ripple and the band of the speed loop controller in order to accurately calculate the correction amount by reducing the rotation speed.

  However, the frequency of the torque ripple differs for each electric motor, and the frequency band of the speed loop also differs depending on the rigidity of the machine on which the electric motor is mounted. Therefore, the rotational speed at the time of correction also differs for each type of electric motor and controller. For this reason, especially when handling various types of controllers and electric motors, the operator may instruct an incorrect rotation speed, and the correction amount may not be accurately calculated even at a low speed.

A control device for a motor having a torque ripple correction function according to the present invention includes a rotation angle detector for detecting a rotation angle of a motor, and a torque command calculated by inputting a constant rotation speed command to a speed loop controller. In the torque ripple correction amount calculation processing for controlling the angular acceleration, an angular acceleration calculation unit for calculating the angular acceleration of the electric motor by second-order differentiation of the rotation angle, and in the torque ripple correction amount calculation processing, the angular acceleration and the rotor of the electric motor. A torque calculating unit for multiplying the angular acceleration into torque by multiplying the torque command by an inertia moment, and an offset removing unit for removing an offset from the torque command and calculating a pulsation component included in the torque command in the torque ripple correction amount calculating process. and parts, in the torque ripple correction amount calculation processing, the torque calculated by the torque calculation unit, Oh Pulsation component of the torque command outputted from the set removal unit, and the torque ripple adder for calculating a torque ripple correction amount by subtracting, in the torque ripple correction amount calculation processing, the rotation angle detector rotation each angle detected by A correction amount calculation unit that stores the torque ripple correction amount calculated by the torque ripple addition unit as a torque ripple correction amount corresponding to the rotation angle; and after executing the torque ripple correction amount calculation process, A correction amount adding unit that adds the correction amount stored in the correction amount calculation unit to the torque command.

  According to the present invention, the torque ripple correction amount can be accurately calculated even at a high speed. Further, since the torque ripple correction amount can be calculated accurately regardless of the speed, it is possible to prevent the operator from instructing an incorrect rotation speed and calculating the correct correction amount.

FIG. 1 is a block diagram illustrating a configuration of a control device having a torque ripple correction function according to a first embodiment of the present invention. 5 is a flowchart of a control device having a torque ripple correction function according to the present invention. It is a schematic block diagram of the control apparatus provided with the conventional torque ripple correction function.

  An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of a control device 1 having a torque ripple correction function according to the present embodiment. The control device 1 having the torque ripple correction function is a device that controls the electric motor 11, and includes a rotation angle detector 12, a proportional amplifier 22, a current distributor 23, an integral amplifier 24, a current control unit 25, a differentiator 26, It includes a phase PWM inverter 28, a current detector 29, a torque ripple detection unit 30, a correction amount calculation unit 35, and a correction amount addition unit 36. The torque ripple detector 30 includes an angular acceleration calculator 31, a torque calculator 32, an offset remover 33, and a torque ripple adder 34.

In this control device, when a rotation speed command V * is input, the difference between the rotation speed of the motor 11 obtained by differentiating the detection value of the rotation angle detector 12 with the differentiator 26 is calculated by the proportional amplifier 22 and the integration amplifier. 24, a PI operation is performed to generate a torque command T *. Since the torque command T * includes an offset component such as friction torque of the rotating shaft and a pulsation component due to the torque ripple of the electric motor, the offset removing unit 33 removes the offset component of the torque command T * to remove the torque command T *. Take out only the pulsation of The angular acceleration calculation unit 31 calculates the angular acceleration by second-order differentiation of the rotation angle detected by the rotation angle detector 12, and the torque calculation unit 32 calculates the angular acceleration of the rotation axis known to the angular acceleration calculated by the angular acceleration calculation unit 31. Multiply the moment of inertia to calculate the torque. Note that the torque command T * and the rotation angle are temporarily stored in the storage unit 40. The torque ripple adding unit 34 adds the pulsating component of the torque command T * output from the offset removing unit 33 and the calculated torque value output from the torque calculating unit 32. However, the torque calculation value output from the torque calculation unit 32 has the same polarity as the torque ripple, and the reverse polarity of the torque ripple is used as the torque ripple correction amount. The torque ripple is added by the torque ripple adding unit 34. The output of the torque ripple adding unit 34 becomes the torque ripple correction amount.

  The correction amount calculation unit 35 includes a central processing unit (CPU) 37 and a memory 38. The memory 38 includes a ROM storing various programs, control parameters, and the like, and a RAM storing rewritable detection data and the like. The program stored in the memory 38 is, for example, a program for creating a torque ripple correction amount corresponding to the rotation angle based on the detection value of the rotation angle detector 12 and the torque ripple correction amount output from the torque ripple addition unit 34. There are a program for storing the generated torque ripple correction amount in the memory 38, a program for outputting the torque ripple correction amount corresponding to the detected value of the rotation angle detector 12, and the like. Further, the central processing unit 37 has a function of reading and executing various programs stored in the memory.

  The correction amount adding unit 36 adds the torque ripple correction amount corresponding to the rotation angle output from the correction amount calculation unit 35 to the torque command T *. In response to the input of the torque command T * 'obtained by adding the torque ripple correction amount, the current distributor 23 outputs the current commands Iu * and Iv * for two phases of the three-phase current commands Iu *, Iv * and Iw *. Is generated and output to the current control unit 25. At this time, the value detected by the rotation angle detector 12 is considered when generating the current command. The current controller 25 controls the three-phase voltage based on the current commands Iu * and Iv * input from the current distributor 23 and the current command Iw * derived from the relational expression of iu * + iv * + iw * = 0. Commands eu *, ev *, ew * are generated and output to the three-phase PWM inverter 28. The motor 11 is driven by applying a three-phase AC voltage obtained by converting a DC voltage supplied from a DC power supply 27 by a three-phase PWM inverter 28 based on the three-phase voltage commands eu *, ev *, ew *. The voltage actually applied to the electric motor 11 is determined by the current control unit 25 in the three-phase voltage command eu *, ev *, ew * obtained from the deviation from the current detection values iu, iv, iw detected by the current detector 29. It is.

  Next, a procedure for calculating the torque ripple correction amount will be described with reference to FIG. First, in step S10, a constant rotation speed command V * is input to the control device. Here, input rotation speed command V * is not limited to a low rotation speed, and may be any value within the rotation speed range of electric motor 11. When the rotation speed command V * is input, the electric motor 11 is controlled at a constant rotation speed as described above.

  Next, in step S11, the rotation angle of the electric motor 11 detected by the rotation angle detector 12 and the torque command T * are stored.

  Subsequently, in step S12, it is determined whether the electric motor 11 has made one rotation. Whether or not the electric motor 11 has made one rotation is determined by whether or not the difference between the initially stored rotation angle and the current rotation angle after the start of the calculation of the torque ripple correction amount exceeds 360 °. If the motor 11 has not made one rotation, the rotation angle of the motor 11 and the torque command T * are stored again in step S11. This operation is repeated until the electric motor 11 makes one rotation.

In order to measure the torque ripple in all cycles, it is desirable to collect the rotation angle and the torque command T * for one rotation of the electric motor 11, but it is not always necessary to collect one rotation. For example, the cycle of the torque ripple can be obtained. In this case, it is sufficient to collect data for at least (torque ripple cycle / 360 °) rotations .

  Then, when the motor 11 makes one rotation, in step S13, a torque ripple correction amount corresponding to the rotation angle is calculated based on the collected data.

  Next, the reason why the torque ripple correction amount can be accurately calculated at high speed in the present embodiment will be described. In the above-described problem, in the control device having the torque ripple correction function disclosed in Patent Document 1, when the frequency of the torque ripple exceeds the frequency band of the speed loop controller, the speed loop controller cannot react. Has explained that the torque command output from is smaller than the torque ripple and the torque ripple correction amount cannot be obtained accurately.

  In the present embodiment, the torque ripple correction amount is obtained by adding two values of the pulsation component of the torque command T * output by the speed loop controller and the torque ripple calculated by the fluctuation of the rotation speed of the electric motor 11. Is used to calculate the torque ripple correction amount. For this reason, at a high rotation speed where the frequency of the torque ripple exceeds the frequency band of the speed loop controller, the remaining torque ripple which is not canceled by the speed loop controller is considered in the torque ripple calculated from the fluctuation of the rotation speed. Therefore, the torque ripple correction amount can be accurately calculated.

  In the present embodiment, the torque ripple detecting unit 30 includes the angular acceleration calculating unit 31, the torque calculating unit 32, the offset removing unit 33, and the torque ripple adding unit 34. This solves the problem that the correction amount cannot be calculated. For example, when the torque ripple detection unit 30 includes only the angular acceleration calculation unit 31 and the torque calculation unit 32, the problem cannot be solved for the following reasons.

  First, considering the case where the correction amount is calculated in the speed control state as in the present embodiment, the torque ripple correction amount calculated by the torque calculation unit is rotated to a value obtained by second-order differentiation of the detection angle of the rotation angle detector 12. Since the calculation is made only by the value multiplied by the shaft inertia moment, the correction amount is reduced by the amount by which the speed loop controller cancels the speed fluctuation due to the torque ripple. For this reason, in this configuration, the correction amount is calculated not by the speed control but by the constant torque control so that the control for canceling the speed fluctuation is not performed. In the constant torque control, the motor 11 is accelerated at a constant angular acceleration. However, if the torque command value is increased to calculate the correction amount at a high speed, the angular acceleration of the motor 11 increases, whereby the rotation angle detector Many noises occur at the twelve detection positions. Therefore, the correction amount calculated by second-order differentiation of the detection position of the rotation angle detector 12 lacks accuracy due to noise. In the present embodiment, the correction amount can be calculated in the constant speed control state, so that the influence of noise is small, and the torque ripple correction amount can be accurately calculated even at high speed.

1. Control device with torque ripple correction function, 11 motor, 12 rotation angle detector, 21 proportional amplifier, 23 current distributor, 24 integrating amplifier, 25 current controller, 26 differentiator, 27 DC power supply, 28 3-phase PWM Inverter, 29 current detector, 30 torque ripple detector, 31 angular acceleration calculator, 32 torque calculator, 33 offset remover, 34 torque ripple adder, 35 correction amount calculator, 36 correction amount adder, 37 central operation Processing unit, 38 memory.

Claims (2)

A motor control device having a torque ripple correction function,
A rotation angle detector for detecting a rotation angle of the electric motor,
In a torque ripple correction amount calculation process for controlling a motor based on a torque command calculated by inputting a constant rotation speed command to a speed loop controller, an angular acceleration calculation for calculating the angular acceleration of the motor by second-order differentiation of the rotation angle Department and
In the torque ripple correction amount calculation process, a torque calculation unit that converts the angular acceleration into torque by multiplying the angular acceleration by a rotor inertia moment of the electric motor,
In the torque ripple correction amount calculation process, an offset removal unit that removes an offset from the torque command, and calculates a pulsation component included in the torque command.
In the torque ripple correction amount calculation processing, the torque calculated by the torque calculation unit, from the pulsation component of the torque command output from the offset removal unit, a torque ripple addition unit that calculates a torque ripple correction amount by subtracting,
In the torque ripple correction amount calculation process, for each rotation angle detected by the rotation angle detector , the torque ripple correction amount calculated by the torque ripple addition unit as a torque ripple correction amount corresponding to the rotation angle A correction amount calculating unit to be stored;
After the execution of the torque ripple correction amount calculation process, a correction amount addition unit that adds the correction amount stored in the correction amount calculation unit to the torque command,
A control device comprising: The control device according to claim 1,
The control device, wherein the torque ripple adding unit calculates the torque ripple for each rotation angle during a period in which the electric motor rotates at least (torque ripple cycle / 360 °).