JPH0550238B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to a control method for an electric motor, and particularly to a control method suitable for improving the speed control performance of an electric motor.

Prior Art As a method for controlling an electric motor, a feedback control method is known in which the output of the electric motor is measured and the driving power of the electric motor is controlled so that the deviation between the measured value and a target value becomes zero. For example, a double feedback method is used in which the rotational speed of the motor is measured with a speed detector such as a tachogenerator to obtain a speed feedback signal, and the rotor position of the motor is further detected with a position detector such as a pulse generator to obtain a position feedback signal. This is the control method. There is also a feedback control method in which the speed detector is omitted, the speed of the motor is calculated from the amount of change in the signal from the position detector per fixed time, and a speed feedback signal is obtained from this. This is the second
This will be explained with reference to the figures.

In FIG. 2, for example, each of the three-phase currents of the brushless three-phase AC motor 1 is determined from the current command output from the multipliers 2, 3, 4 by the current detectors 5, 6,
The current feedback which is the detection signal of 7 is sent to subtracters 8, 9, 1
The power is subtracted by 0, the power is amplified by amplifiers 11, 12, and 13, and the power is supplied to the motor 1.

A position detector 14 is mechanically connected to the electric motor 1, and a position feedback signal output from the position detector 14 is input to a subtracter 15, a speed detection circuit 16, and a three-phase sine wave generator 17, respectively. Ru. The subtracter 15 subtracts the position feedback from the rotor position command and outputs a speed command, and the subtracter 18 subtracts the speed feedback output from the speed detection circuit 16 based on this speed command. The output of the subtracter 18 is amplified by the PiD compensator 19, and the sine waves output from the three-phase sine wave generator 17 whose phases differ by 1/3 are combined with the current command value output from the PiD compensator 19. It is input to each of the multipliers 2, 3, and 4 mentioned above.

FIG. 3 is an explanatory diagram of a resolver, which is an example of a position detector. The resolver consists of two-phase primary windings 20 and 21 with the same windings placed electrically at 90 degrees.
and a one-phase secondary winding 22. Then, the angular frequency is ω and the maximum voltage is V ₁ in the primary winding 20.
When an AC sine wave with an instantaneous voltage value = V ₁ sinωt is applied to the primary winding 21, and an AC cosine wave with an instantaneous voltage value = V ₁ cosωt that is phase shifted by 90 degrees from this is applied to the primary winding 21, the secondary winding 22 The induced output signal has a voltage maximum of V ₂ ,
If the rotation angle of the resolver is θ, then V ₂ sinωt・cosθ＋V ₂ cosωt・sin(−θ)=V ₂ si
A sine wave signal of n(ωt−θ)……(1) is obtained. This is a signal whose phase is shifted by "θ" with respect to the excitation signal for the primary winding.

Therefore, the rotation angle of the resolver, that is, the rotor position of the motor 1, is detected by the phase difference between the excitation signal of the primary winding and the output signal of the secondary winding, and the speed ν of the motor 1 is shown in FIG. When the rotation angles of the resolver at timings T ₁ and T ₂ shown in FIG. 2 are θ _{1 and θ 2} respectively, the speed detection circuit 16 of _{FIG .} ) is calculated based on the calculation formula.

Problems to be Solved by the Invention As described above, in conventional feedback control, speed information is obtained from the output side of the motor, so that speed information is past information relative to the current actual speed. Therefore, in feedback control,
This inevitably causes a delay in response. In particular, when speed information is detected indirectly from a position detector, factors such as calculation time are added, which has the disadvantage of deteriorating speed control performance.

Purpose of the Invention The present invention has been proposed in view of the drawbacks inherent in the prior art described above, and has been proposed to suitably solve the problems. The present invention provides a method for controlling an electric motor.

Means for Solving the Problems In order to overcome the above problems and suitably achieve the intended purpose, the present invention provides a position detector for an electric motor as a controlled object, and a position feedback signal output from the position detector. is branched into a speed detection circuit and a subtracter, and the speed feedback signal from this speed detection circuit is subtracted by the speed command signal output from the subtracter.
In the motor control circuit configured to obtain a torque command value for the electric motor, the torque command value is subjected to time integration processing to obtain the motor speed, and is further subjected to high-pass filter processing to obtain an estimated motor speed consisting only of high frequency components. Obtaining a speed signal; On the other hand, low-pass filtering the speed feedback signal from the speed detection circuit to obtain a speed feedback signal consisting only of low frequency components, and generating an estimated motor speed signal consisting only of the high frequency components and the low frequency component. The speed feedback signal of the motor is characterized in that the output obtained by adding the speed feedback signal consisting of only the components is used as the speed feedback signal of the electric motor.

Effect With the above configuration, it is possible to estimate the speed change of the electric motor in advance and appropriately control the current command value according to the speed change, and the speed control performance of the control system is favorably improved.

Embodiment Next, a method for controlling an electric motor according to the present invention will be described with reference to FIG. 1, using an embodiment thereof. In FIG. 1, devices that are the same as those already shown in connection with FIG. 2 are given the same reference numerals, and their explanation will be omitted, and only the different parts will be explained.

In this embodiment, the speed detection signal obtained from the position feedback signal by the speed detection circuit 16 is passed through a low pass filter (LDF) 25 to remove high frequency components, and is added to an adder 26. and PiD compensator 1
The current command value (torque command value) output from 9 is integrated through an integrator 27, and then amplified by an amplifier 28, and then low frequency components are filtered out from this amplified signal by a high pass filter (HPF) 29. It is added to the adder 26. Further, the output signal of the adder 26 is inputted to the subtraction side of the subtracter 18 as a speed feedback signal. Note that a band pass filter may be used instead of the high pass filter 29.

Generally, the following relational expression holds between the output torque T of the electric motor and the rotational angular velocity ω of the electric motor.

T=Jdω/dt+D・ω+K...(3) Here, J: Inertia of the motor rotor and load D: Viscous resistance K: Friction torque The viscous resistance that appears in the second and third terms on the right side of equation (3) Since D and frictional resistance K are generally small values, the output torque T is approximated as T≈Jdω/dt (4). Further, the output torque T is expressed by the motor torque constant K _T and the current I as T=K _T ·I (5). From these equations (4) and (5), the angular velocity ω is expressed as Jdω/dt≒K _T ·I ∴ω≒K _T /J∫Idt (6).

In FIG. 1, if the current control system after the output (current command value) of the PiD compensator 19 can perform highly accurate current control, the current I in equation (6) can be substituted for the current command value. Therefore, the current command value is
The signal which is integrated by , and further amplified by the amplifier 28 with the amplification factor K _T /J becomes speed information of the electric motor 1 without time delay (real time). In this example,
Speed information is obtained by integrating the current command value I based on equation (6), but if a value that can be considered as real-time speed information is obtained, an integral equivalent process or other arithmetic processing is performed. The current command value I may be subjected to speed information. In addition, for electric motors in which the viscous resistance D, etc. in equation (3) cannot be ignored, it is necessary to obtain speed information using a corresponding arithmetic circuit.

In this embodiment, the adder 26 adds this real-time speed information to the output signal of the speed detection circuit 16, that is, the speed detection signal obtained by the above-mentioned equation (2).
is added as a speed feedback signal. At this time,
The output signal from the amplifier 28 is passed through a high-pass filter 29 with a gain of 1, and high frequency components, that is, steep changes, of the real-time speed information are extracted and used. In addition, the speed detection signal of the speed detection circuit 16 indirectly detected from the position detection value is
pass through a low-pass filter 25 to exclude the influence of delay time that occurs when detecting the speed detection signal,
Moreover, the speed feedback signal after the addition can be obtained with a gain of 1 according to the actual motor speed.

By using the speed information obtained by integrating the current command value (torque command value) of the electric motor as the speed feedback signal in this way, speed detection delay time is eliminated and speed control performance is improved. In addition, as in this embodiment, a signal obtained by supplementarily adding speed information obtained by integrating the current command value to a speed detection signal indirectly obtained by a position feedback signal from a position detector is used as a speed feedback signal. By using this, the detection (calculation) time delay of the speed detection signal is reduced. Furthermore, the control method of the present invention may be implemented by using a pulse generator as a position detector and using an F/F as a speed detection circuit.
Even when applied to a feedback control system configured with a V converter, etc., the delay time until the pulse frequency that is the output of the pulse generator is established,
The time delay in speed detection caused by the response delay of the F/V converter itself is reduced.

Note that instead of obtaining the speed detection signal indirectly from the position feedback signal, a speed detector such as a tachogenerator is mechanically connected to the motor, and the output signal of this speed detector is converted into the output signal of the circuit 16 in FIG. Even when used instead, if the control method of the present invention is used in combination, the speed detection time delay of the tachogenerator, etc. can be corrected.

In the description of the embodiments described above, a case has been described in which the control method of the present invention is applied to a brushless three-phase motor, but the present invention is not limited to this, and can also be applied to control of other motors such as a DC motor. Needless to say, it can be applied. In addition, an example has been explained in which a speed detection circuit is used to obtain a speed detection signal from a position feedback signal, and an integration circuit is used to perform integral calculation processing, but a microprocessor can be used to perform these calculation processing. It may be configured to be performed by software.

Effects of the Invention According to the method for controlling an electric motor according to the present invention, the speed detection delay time is reduced, and therefore speed control performance is improved.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a three-phase motor control device as an example to which the electric motor control method according to the present invention can be suitably applied, FIG. 2 is a configuration diagram of a conventional three-phase motor control device, and FIG. 4 is an explanatory diagram of a resolver which is an example of a position detector, and FIG. 4 is a waveform diagram of an input signal and an output signal of the resolver shown in FIG. 3. 1... Brushless 3-phase motor, 14... Position detector, 15, 18... Subtractor, 16... Speed detection circuit, 19... PiD compensator, 25... Low pass filter, 26... Adder, 27 ...integrator, 28
...Amplifier, 29...High-pass filter.

Claims (1)

[Claims] 1. A position detector 14 is provided on the electric motor 1 as a controlled object.
The position feedback signal output from the position detector 14 is branched into the speed detection circuit 16 and the subtracter 15, and the speed feedback signal from the speed detection circuit 16 is used as the speed command output from the subtracter 15. In the motor control circuit that obtains the torque command value for the electric motor 1 by subtracting the signal, the torque command value is subjected to time integration processing to obtain the motor speed, and is further subjected to high-pass filter processing to obtain the high frequency signal. Obtain an estimated motor speed signal consisting only of components, and process the speed feedback signal from the speed detection circuit 16 with a low-pass filter to obtain a speed feedback signal consisting only of low frequency components, and obtain an estimated motor speed signal consisting only of the high frequency components. A method for controlling an electric motor, characterized in that an output obtained by adding a motor speed signal and the speed feedback signal consisting only of low frequency components is used as a speed feedback signal for the electric motor 1.