JPS6248284A - Control for motor - Google Patents

Abstract

PURPOSE:To improve control response delay due to speed-detection time delay by using a speed information obtained by integrating a current command value for a motor as a speed feedback signal. CONSTITUTION:A speed detecting signal acquired from a phase feedback signal by a speed detecting circuit 16 is made to pass through a low-pass filter 25 and high-frequency components are erased, and the speed detecting signal is added to an adder 26. A current command value outputted from a PiD compensator 19 is made to pass through an integrator 27 and integrated, and amplified by an amplifier 28, and low-frequency components are erased from the amplified signal by a high-pass filter 29 and the signal is added to the adder 26. An output signal from the adder 26 is inputted to the subtraction side of a subtracter 18 as a speed feedback signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of controlling an electric motor, and more particularly to a control method suitable for improving the speed control performance of an electric motor.

Background of the Invention As a method of controlling an electric motor, the output of the electric motor is measured,
A feedback control method is known in which the drive power of an electric motor is controlled so that the deviation between the measured value and the target value becomes zero. For example, measure the rotational speed of an electric motor with a speed detector such as a tacho generator;
This is a double feedback control method in which the rotor position of the electric motor is further detected by a position detector such as a pulse generator to obtain a position feedback signal. There is also a feedback control method in which the second speed detector is omitted, the speed of the motor is calculated from the amount of change in the signal from the first position detector per fixed time, and a speed feedback signal is obtained from this. This will be explained with reference to FIG.

In FIG. 2, each of the three-phase currents of, for example, a brushless three-phase AC motor 1 is derived from a current command output from a multiplier 2, 3.4, and a current feedback signal, which is a detection signal of a current detector 5, 6.7. is subtracted by subtracters 8, 9 and 10, and further subtracted by amplifier 1
1, 12, and 13, the power is amplified and supplied to the electric motor.

A position detector 14 is mechanically connected to the electric motor 1.
The device feedback signal composed of this position detector 14 is transmitted to a subtracter 15, a speed detection circuit 16 and a three-phase sine wave generator 1.
7 respectively. 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 this subtracter 18 is PiD
A sine wave whose phase differs by 173 is amplified by the compensator 19 and output from the three-phase sine wave generator 17, and the PiD compensator 1
9 and the current command value output from each multiplier 2, 3.
．． 4 is entered.

FIG. 3 is an explanatory diagram of a resolver, which is an example of a position detector. The resolver is 1. It has a two-phase primary winding 20, 21 and a one-phase secondary winding 22 in which the same winding is electrically arranged at the position 90'. Then, the instantaneous voltage value of the primary winding 20 where the angular frequency is ω and the maximum voltage value is vl = V, sin
An AC sine wave of ωt is applied to the primary winding 21, and a 90'
When an alternating current cosine wave with a phase-shifted instantaneous voltage value = VICosωt is applied, the output signal induced in the secondary winding 22 is as follows.If the maximum voltage value is ■2° and the rotation angle of the resolver is θ, then V2sinω is referred to as cosθ+V2cosωt−. 5in(
−〇)=V2sin(ωt−θ)−(1) A sine wave signal is obtained. This is 1 for the excitation signal of primary winding 1.
This is a signal whose phase is shifted by "θ".

Therefore, the rotation angle of the resolver, that is, the rotor position of the electric 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 of the electric motor 1 is determined as shown in FIG. The rotation angles of the resolver at timings T1 and T2 are respectively θ1. If θ2, the speed detection circuit 16 of FIG. 2 calculates y=02-01 (2) based on the calculation formula 2-T1.

In this manner, in conventional feedback control, speed information is obtained from the output side of the electric motor, so the speed information is past information relative to the current actual speed. For this reason, feedback control inevitably causes a response delay. 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 above-mentioned prior art, and to suitably solve the problems.
The purpose is to provide a novel electric motor control method with excellent speed control performance.

Structure of the Invention The present invention focuses on the fact that the current command value (torque command value) of the motor to be controlled is a factor that determines the acceleration of the motor, and uses the current command value to detect sudden changes in motor speed in advance. The content is to estimate the current command value and use the signal obtained by calculating the current command value as the speed feedback signal.

Effects 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.

Note that the control method of the present invention may be applied to an open-loop control system, or may be used in combination with a feedback control system.

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

In this embodiment, the speed detector FIf! 11G, the speed detection signal obtained from the position feedback signal is passed through a low-pass filter (LPF).
) 25 to filter out the high frequency components, and add this to the adder 26.
In addition to Then, the current command value (torque command value) output from the PiD compensator 19 is integrated through an integrator 27, and then amplified by an amplifier 28, and then a low frequency component is extracted from this amplified signal by a bypass filter (HPF) 29. The output signal of the adder 26 is also input to the subtraction side of the subtracter 18 as a speed feedback signal. Note that a bandpass filter may be used instead of the bypass filter 29.

In general, the output torque T of the electric motor and the rotational angular speed ω of the electric motor
The following relational expression holds true between .

T=J chaos+D・ω+K...(3)t Here, J: Inertia of motor rotor and load D: Viscous resistance: Ii Friction torque Second and third terms on the right side of equation (3) Since the viscous resistance and frictional resistance appearing in are generally small values, the output torque T is .

T; Jdω...(4) Approximately as follows. Further, the output torque T is expressed as 1 = A·I (5) using the electric motor 1, the torque constant, 7, and the electric current. From these equations (4) and (5), the angular velocity ω is expressed as: Jdω~ in A·■ dt·°·ω: Kddt (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 controller in equation (6) can be substituted for the current command value.

Therefore, the signal obtained by integrating the current command value by the integrator 27 and further amplifying by the amplifier 28 with the amplification factor KT/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 ■ based on equation (6), but if a value that can be considered as real-time speed information is obtained, an integral equivalent process can be used. Alternatively, speed information may be obtained by subjecting the current command value I to other arithmetic processing. In addition, in an electric motor in which the viscous resistance, etc. of 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), to obtain a speed feedback signal. At this time, the output signal from the amplifier 28 is passed through a bypass 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, which is indirectly detected from the position detection value, is passed through a low-pass filter 25 with a gain of 1 to exclude the influence of the delay time that occurs when detecting the speed detection signal, and after adding It is possible to obtain a speed feedback signal with a gain of 1 for an actual motor rotor.

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 (rise) time delay of the speed detection signal is reduced. Furthermore, even when the control method of the present invention is applied to a feedback control system that uses a pulse generator as a position detector and is configured with an F/V converter or the like as a speed detection circuit, there is a delay in the probability of the output pulse frequency of the pulse generator. The time delay in speed detection caused by time and 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 tacho generator is mechanically connected to the motor, and the output signal of this speed detector is used as the output signal of the circuit 16 in FIG. Even when used in place of the present invention, the speed detection time delay of a tachometer generator, etc. that uses the control method of the present invention can be corrected.

In the description of the embodiments described above, the case where the control method of the present invention is applied to a brushless three-phase motor is described, but the present invention is not limited to this, and can also be applied to the control of other motors such as a DC motor. Needless to say, it can be applied.

In addition, we have explained an example in which a speed detection circuit is used to obtain a speed detection signal from a position feedback signal, and an integrator circuit is used to perform integral calculation processing. It may also be configured to do so.

Effects of the Invention According to the electric motor control method according to the present invention, a signal obtained by calculating a current command value is used as a speed feedback signal.
Improves speed control performance. In particular, by using the present invention in combination with a feedback control system, it is possible to improve the control response delay due to the speed detection time delay, which is a drawback of the feedback control system.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a configuration diagram of a three-phase motor control device as an example to which the motor control method according to the present invention can be suitably applied, and FIG. 2 is a conventional three-phase motor control device. Figure 3 is an explanatory diagram of a resolver, which is an example of a position detector, and Figure 4 is a diagram of the resolver.
FIG. 3 is a waveform diagram of input signals and output signals of the resolver shown in the figure. 1...Brushless 3-phase motor 14...Position detector 15.18...Subtractor 16
...Speed detection circuit 19...PiD compensator 25.
...Low pass filter 26... Heater 27... Integrator 28...
・Amplifier 29...Bypass filter FIG
, 3 2;zu insult, tt3 I guest number FIG, 4

Claims (5)

[Claims] (1) A method of controlling an electric motor, characterized in that a signal obtained by processing a torque command value of the electric motor is used as a speed feedback signal. (2) The method for controlling an electric motor according to claim 1, wherein the arithmetic processing is time integration or processing equivalent to time integration of the torque command value. (3) The amount of change per fixed time in the position feedback signal obtained from the position detector provided in the motor, or the signal obtained by adding the above-mentioned arithmetic processed signal to the output signal of the speed detector provided in the motor, is calculated as the speed. A method for controlling an electric motor according to claim 1 or 2, characterized in that the feedback signal is used as a feedback signal. (4) A method for controlling an electric motor according to any one of claims 1 to 3, characterized in that the arithmetic-processed signal is processed by a bypass filter or a bandpass filter before use. (5) The amount of change in the position feedback signal per fixed time or the output signal of the speed detector is processed by a low-pass filter and used. How to control an electric motor.