JP3639487B2 - Motor control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor control device for controlling a motor, and more particularly to improving the accuracy of a current command value.
[0002]
[Prior art]
In order to control the operation of the motor, various detection means (position detection means, speed detection means, current detection means, etc.) for detecting the state of the motor are provided, and detection values (position detection values and speed detection corresponding to the control) are provided. In general, a value, a current detection value, or the like) is sampled at predetermined intervals and fed back to a motor control unit (position control unit, speed control unit, or current control unit) for control.
[0003]
An example of a general motor controller that performs such feedback control is shown in FIG. As shown in FIG. 8, the general motor control device includes a current command calculation unit 3, a current control unit 4, an inverter circuit 5, a current detector 6, a motor 7, and a position detector 8. Has been.
[0004]
Here, the current command calculation unit 3 calculates the magnetic pole position of the rotor of the motor 7 from the position detection value θ detected by the position detector 8 and fed back. The current command calculation unit 3 receives the torque command value T *, generates a current command value I * from the torque command value T * and the calculated magnetic pole position of the rotor, and outputs the current command value I *.
[0005]
The current control unit 4 receives an input of the current command value I * and further receives an input of the current detection value I from the current detector 6 to calculate and output a current control value. The inverter circuit 5 is driven based on the output value (current control value) of the current control unit 4 input from the current control unit 4 to control the operation of the motor 7.
[0006]
Thus, the current command value I * is calculated from the torque command value T * and the rotor magnetic pole position of the motor. Here, the operation in which the current command calculation unit 3 calculates the magnetic pole position of the rotor of the motor 7 will be described. The rotor magnetic pole position of the motor 7 is calculated based on the position detection value θ and the rotation angle offset. If the rotor magnetic pole position of the motor 7 and the output of the position detector 8 are respectively Pe and Pm, for example, 6 poles (number of pole pairs) In the case of the motor 3), if the rotation angle offset is “0”, the relational expression Pe = 3Pm is established.
[0007]
In other words, when calculating the magnetic pole position of the motor, the relational expression between the magnetic pole position of the motor and the output of the position detecting means according to the number of pole pairs of the motor, and the actual magnetic pole position (electrical angle) and position of the motor rotor. Since the rotational angle offset, which is a deviation amount from the rotational position (mechanical angle) of the rotor detected by the detecting means, is taken into consideration, when the rotational angle offset is not an appropriate value, the calculated magnetic pole position of the motor is The current command value I * calculated is not appropriate and the controllability is affected.
[0008]
[Problems to be solved by the invention]
As described above, in the conventional motor control device described above, if there is no deviation between the phase calculated from the position detection value detected by the position detection means and the rotation angle offset and the optimum phase for control, However, in reality, the position detector mounting position cannot avoid an error with respect to the theoretical rotation angle offset. In other words, the magnetic pole position of the rotor calculated in consideration of the rotation angle offset is usually not an optimal value in terms of control, and thus there is a problem that high-precision control cannot be performed.
[0009]
Further, as shown in FIG. 5, the relationship between the rotation angle offset and the motor output torque is that the rotation angle offset is not set to the optimum rotation angle offset value in terms of control , and the rotation angle offset and the optimum rotation in terms of control. If the difference in angular offset is not “0”, the motor output is also affected. That is, when the rotation angle offsets are different, the output torque is different even with the same torque command value for the same load. As a result, the followability of the control is also different, and there is a problem that the torque command value itself becomes a different value due to the position or speed feedback control.
[0010]
Therefore, as shown in FIG. 6, a calculation unit 9 is provided, and this calculation unit 9 outputs a specific step-like current command value i * as shown in FIG. 7, at which time the position detector 8 detects it. Based on the position detection value, processing corresponding to the number of pole pairs of the motor 7 can be performed, and the rotation angle offset can be calculated in advance. In this case, the vehicle stops at a specific position depending on the current command value i *. In FIG. 7, iu *, iv *, and iw * indicate current command values for the U phase, the V phase, and the W phase, respectively, and satisfy the relational expression iu * + iv * + iw * = 0. However, in this case, if the motor 7 is in a no-load state, an optimal rotation angle offset can be calculated from the stop position of the motor 7. However, if the motor 7 is installed in the machine and put in a load state, the current command value i * is obtained. The motor 7 stops in a state where the output torque of the motor 7 and the load are balanced, and the optimum rotation angle offset cannot be calculated.
[0011]
The present invention has been made in view of the above circumstances, and by sampling the torque command value while varying the rotation angle offset at a predetermined frequency within a predetermined threshold range according to the rotation state of the motor. An object of the present invention is to provide a motor control device capable of performing highly efficient and highly accurate control by calculating an optimal rotation angle offset and calculating a motor current conduction phase optimal for control based on the calculated rotation angle offset And
[0012]
[Means for Solving the Problems]
The present invention according to claim 1 for solving the problems of the conventional example described above, in a motor control device, detects a rotor detector rotational position and a current value for driving the motor. In the motor control device, comprising: a current detection unit; and a current control unit that receives a current command value and controls the current value supplied to the motor while monitoring the detected current value. The speed of the motor is detected on the basis of this, and when the speed is constant, the rotation angle offset is changed and the relationship between the torque command value and the rotation angle offset is sampled a plurality of times, and the torque command value is minimized. Based on the torque command value, the rotation angle offset, and the rotor rotation position upon receiving the input of the torque command value, the offset setting unit that calculates and outputs the rotation angle offset It is characterized by having a current calculation unit for outputting a flow command value.
[0013]
The invention according to claim 2 for solving the problems of the conventional example described above is that in the motor control device according to claim 1, the offset setting unit preliminarily calculates the rotation angle offset estimated value with a predetermined amplitude and frequency. The rotation angle offset is calculated and held based on the rotor rotation position detected by the position detector, and the held rotation angle offset is output during operation. .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. In addition, about the thing which has the same structure as a conventional thing, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted. As shown in FIG. 1, the motor control circuit according to the present invention includes a current command calculation unit 1, an offset setting unit 2, a current control unit 4, an inverter circuit 5, a current detector 6, a motor 7, And a position detector 8.
[0015]
The offset setting unit 2 generates a difference Δθ between the position detection value θ output as the rotor rotation position output from the position detector 8 and the immediately preceding measurement value , grasps the operating state of the motor 7 , The optimum rotation angle offset in the invention is calculated. The specific operation of the offset setting unit 2 will be described in detail later. The current command calculation unit 1 calculates a phase value from the torque command value T * input from the outside, the position detection value θ detected by the position detector 8 and the optimum rotation angle offset, and this phase value and the motor 7 The current command value I * is calculated and output according to the number of pole pairs.
[0016]
Further, the current control unit 4 calculates a command for driving the inverter circuit from the current command value I * input from the current command calculation unit 1 and the current detection value I input from the current detector 6, and the inverter circuit 5 Based on the command, the operation of the motor 7 is controlled.
[0017]
Here, the process of calculating the optimum rotation angle offset of the offset setting unit 2 will be specifically described with reference to FIG. As a process for calculating the optimum rotation angle offset , the offset setting unit 2 first calculates the difference value Δθ of the position detection value θ, detects the operation state of the motor 7 from this, and determines the rotation angle offset based on this operation state. It is checked whether the change is possible (S1). Specifically, this determination corresponds to checking whether there is no problem even if the load fluctuation is small and the output torque of the motor 7 fluctuates. That is, for example, in the case of a machine tool in which a cutting tool is attached to the motor 7, if the output torque is varied during cutting, the influence appears on the cutting surface. In addition, since the load fluctuation increases during acceleration / deceleration, it is inappropriate to change the rotation angle offset during cutting or acceleration / deceleration. Therefore, in the machine tool, it is determined that the process angle S1 can change the rotation angle offset when the machine tool is operated at a constant speed during fast-forwarding. Note that if the change is not possible in the process S1 (if NO), the process S1 is repeatedly executed.
[0018]
When the rotation angle offset can be changed in step S1 (if YES), the offset setting unit 2 determines a range set in advance from the rotation angle offset value At calculated from the position detector mounting position. Within (± A), estimated rotation angle offset values (A1, A2,... An) that change at a preset frequency f are sequentially set based on the following [Equation 1] (S2).
[0019]
[Expression 1]
An = At + Asin (2πftn) (n = 1, 2,...)
[0020]
Then, the offset setting unit 2 outputs the estimated rotation angle offset value to the current command calculation unit 1 (S3). Then, the current command calculation unit 1 calculates the current command value (T * sinΦ) from the energization phase Φ for the motor 7 calculated using the estimated rotation angle offset and the torque command value T * to control the operation of the motor 7. It will be. Further, the offset setting unit 2 waits until the torque command value T * is stabilized, and then samples the torque command value T * m times (T * 1,..., T * m), and calculates the torque calculated as a result. The command value Tn and the estimated rotation angle offset An are stored in association with each other (S4). Here, as a calculation method of the torque command value Tn, for example, the sampled values may be simply averaged or may be averaged after removing the maximum value and the minimum value. That is, for example, the torque command value Tn may be calculated using the following [Equation 2] (when simply averaging) and [Equation 3] (when averaging except for the maximum and minimum).
[0021]
[Expression 2]
Tn = (T * 1 +... + T * m) / m
[0022]
[Equation 3]
Tn = {(T * 1 + ... + T * m) -max (T * 1, ..., T * m) -min (T * 1, ..., T * m)} / (m-2)
[0023]
In [Equation 3], max (T * 1,..., T * m) and min (T * 1,..., T * m) are the largest of T * 1,. Represents the smallest and the smallest.
[0024]
By using [Equation 2] and [Equation 3], the torque command value T * is constant when the torque command value T * is constant, and if there is a variation, the average value is adopted as the torque command value Tn. Accurate values can be obtained.
[0025]
The offset setting unit 2 examines whether or not it is necessary to determine an optimal rotation angle offset more finely (whether it is necessary to change the estimated rotation angle offset) (S5), and it is necessary to change the rotation angle offset. If YES (if YES), the process returns to the process S1 to continue the process. In this case, if it is found from Tn calculated in steps S2 to S4 that the optimum rotation angle offset is within a predetermined range (for example, between Ai and Aj for Ai <Aj, Ai to Aj), The processing from the processing S1 may be performed by setting At and A to (Ai + Aj) / 2 and Ai / 2, respectively.
[0026]
If it is not necessary to change the estimated rotation angle offset in the process S5, the offset setting unit 2 calculates an optimum rotation angle offset from the relationship between the rotation angle offset finally obtained in the process S4 and the torque command value. Calculation is performed, and feedback control is performed using the energization phase of the motor current optimum for control (S6). Here, for example, when the relationship shown in FIG. 3 is obtained when operating at a constant speed during fast-forwarding , the motor efficiency is maximized when the torque command value is minimized . The rotation angle offset Aa is output as the optimum rotation angle offset in the present invention.
[0027]
Here, if the rotation angle offset is changed in order to determine the optimum rotation angle offset , it is considered that the torque command value T * also changes, but the rotation angle offset is attached to the position detector as shown in FIG. By changing at a predetermined frequency within a predetermined range (± A) from the rotation angle offset value At calculated from the position, the change of the rotation angle offset becomes smooth, and the torque command accompanying the change of the rotation angle offset The fluctuation of the value T * can be kept low. As a result, the time until the torque command value T * is stabilized is shortened, and the calculation time of the optimum rotation angle offset can be shortened.
[0028]
The motor control device according to the present embodiment includes an offset setting unit that receives an input of a torque command value and an operating state of the motor, calculates and sets a rotation angle offset, and outputs it. The optimum rotation angle offset can be calculated, and the motor current conduction phase optimum for control can be calculated.
[0029]
For this reason, according to the motor control device according to the present embodiment, highly efficient motor control can be realized. Furthermore, since the optimum rotation angle offset is determined by changing the rotation angle offset at a predetermined frequency, even if the torque command value changes in frequency due to other disturbance torque, it can be separated by using a technique such as FFT. Thus, the optimum rotation angle offset can be calculated with higher accuracy.
[0030]
【The invention's effect】
According to the first aspect of the present invention, the offset setting unit that receives the input of the torque command value and the operating state of the motor, calculates and sets the rotation angle offset, and outputs it is provided. Therefore, it is possible to calculate a rotation angle offset that is optimal for the motor current in terms of control.
[0031]
According to the second aspect of the present invention, since the optimum rotation angle offset is determined by changing the rotation angle offset at a predetermined frequency, even if the frequency change of the torque command value occurs due to other disturbance torque, Separation is possible by using a technique such as FFT, and an optimal rotation angle offset can be calculated with higher accuracy.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration of a motor control device according to an embodiment of the present invention.
FIG. 2 is a flowchart showing processing contents of an offset setting unit 2;
FIG. 3 is an explanatory diagram showing a relationship between a rotation angle offset and a torque command value.
FIG. 4 is an explanatory diagram illustrating a control state of a rotation angle offset.
FIG. 5 is an explanatory diagram showing a relationship between a rotation angle offset and a motor output torque.
FIG. 6 is a configuration block diagram showing an example of a conventional motor control device.
FIG. 7 is an explanatory diagram showing a state of a current command value.
FIG. 8 is a configuration block diagram illustrating an example of a conventional motor control device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Current command calculating part, 2 Offset setting part, 3 Current command calculating part, 4 Current control part, 5 Inverter circuit, 6 Current detector, 7 Motor, 8 Position detector, 9 Calculation part.

Claims (2)

A position detector for detecting the rotor rotational position of the motor;
A current detection unit for detecting a current value for driving the motor;
In a motor control device including a current control unit that receives an input of a current command value and controls the current value supplied to the motor while monitoring the detected current value,
The motor speed is detected based on the rotor rotation position, and when the speed is constant, the rotation angle offset is changed, and the relationship between the torque command value and the rotation angle offset is sampled a plurality of times. An offset setting unit that calculates and outputs the rotation angle offset that minimizes
A current command calculation unit that receives the torque command value and outputs a current command value based on the torque command value, the rotation angle offset, and the rotor rotation position;
A motor control device comprising: The motor control device according to claim 1,
The offset setting unit calculates and holds the rotation angle offset in advance based on the rotor rotation position detected by the position detector while changing the rotation angle offset estimated value at a predetermined amplitude and frequency,
A motor control device that outputs the held rotation angle offset during operation.

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