JP2002325472A - Inverter controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an asynchronous PWM inverter controller which can reduce the influence in a system of superposition of beat frequency over a motor current, without increase in an inverter capacity and the deterioration of control performance. SOLUTION: In this inverter controller, a PWM control unit 5 outputs a carrier frequency C2 different from an ordinary carrier frequency C1, when a motor revolution speed given by a resolver 9 is 0, and a clamp signal outputted by a clamp control unit 11 is in a high-pressure clamp state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an asynchronous PWM inverter control device used for a machine tool, a robot, or the like, which controls a motor at a variable speed, and more particularly to control when the motor is clamped by an external mechanism.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional asynchronous PWM (pulse width modulation) inverter control device. The conventional asynchronous PWM inverter control device is connected to, for example, the NC device 1, and includes a position control unit 2, a speed control unit 3, a current control unit 4, a PWM control unit 5, an inverter unit 6, and a motor current detection. Unit 7, a motor 8, a resolver 9 for detecting the speed of the motor 8, a pulse generator 10 for detecting the rotational position of the motor 8, a high-pressure clamp,
Or a clamp control unit 11 that outputs a command for a low-pressure clamp, a clamp device 12, and a rotating body 13 attached to a shaft of the motor 8. Further, a chuck or the like (not shown) is directly or indirectly attached to the motor 8 via a gear or a belt. As for the method of controlling the motor by PWM, see "Motor control mechanism and concept", Fumio Harashima et al.,
A detailed description is given on pages 70 to 71 of Ohmsha, 1981, and will not be repeated here.

The command position for the motor 8 output from the NC unit 1 is input to the position control unit 2. The position detection result of the motor 8 is fed back to the position control unit 2 from the pulse generator 10, and the command speed input to the speed control unit 3 is calculated based on the deviation from the command position. The speed controller 3 compares the command speed with the speed detection result of the motor 8 from the resolver 9 and calculates a command current to be input to the current controller 4. The current control unit 4 compares the command current with the detection current fed back from the motor current detection unit 7 and calculates a command voltage to be input to the PWM control unit 5. In the PWM control unit 5, the inverter unit 6
, A gate signal for an IGBT (not shown) to be input is calculated. Inverter section 6 outputs a current that flows through motor 8. The motor 8 has a rotating body 13
Is attached, and the clamp 12 is attached to the rotating body 13. When a high pressure clamp, unclamping, or low pressure clamp signal is input from the NC device 1 to the lamp control unit 11, the clamp control unit 11
The clamp device 12 is set to one of a high pressure clamp, an unclamping, and a low pressure clamp. As a result, the motor 8 to which the rotating body 13 is attached becomes a high pressure clamp,
Either unclamped or low pressure clamped.

[0004] The motor 8 is set in a high pressure clamp or a low pressure clamp state, for example, by attaching a chuck and a work (not shown) to the motor 8 in a lathe and performing drilling on the work or creation with another shaft. It's time to do it. When performing normal lathe processing, the motor 8 is in an unclamped state.

[0005] The PWM control section 5 generates a gate signal to be output to the inverter section 6 from a predetermined fixed carrier frequency and a command voltage output from the current control section 4, and supplies a current to the motor 8. . FIG. 5 shows the relationship between the command speed, the command torque, and the carrier frequency given to the motor 8. In FIG. 5, section A is when the motor 8 is stopped and the clamp device 12 is in the unclamped state, section B is when the motor 8 is rotating and the clamp device 12 is in the unclamped state, and section C is when the clamp device 12 is in the unclamped state. Stops the motor 8,
When the clamping device 12 is in the high pressure clamping state, the motor D rotates in the section D and the clamping device 12
In the low pressure clamp state respectively.

The speed of the motor 8 in the section D is generally several tens min-1 or less because the clamp device 12 is in the low pressure clamping state. Here, the carrier frequency is always C1 (H) regardless of the state of the clamp device 12, as shown in FIG.
z). For example, when the motor 8 is clamped at a high pressure and the rotation speed of the motor 8 is set to “0”, a driving signal is not output, but a carrier signal is always output. Leave it fixed at the frequency.

If the carrier frequency of the PWM control unit 5 is different from the current detection cycle for detecting the current supplied to the motor 8, the current supplied to the motor 8 corresponds to the difference between the carrier frequency and the current detection cycle. The beat frequency is superimposed as a beat frequency, and a beat phenomenon occurs. This beat phenomenon, depending on its magnitude, may cause abnormal noise, vibration, and the like, and may make the operation of the motor 8 unstable.

For example, when the natural frequency of the system including the motor 8 and the beat frequency coincide with each other when the clamp device 12 is in the high pressure clamping state, a resonance phenomenon occurs in the system. Further, even when the motor 8 is in the low pressure clamp state, the same phenomenon may occur. In order to prevent this phenomenon from occurring, the carrier frequency of the PWM control unit 5 may be set so as not to match the natural frequency of the system. However, when the carrier frequency is increased, the switching loss in the inverter unit 6 increases. When the switching loss increases, the inverter unit 6
Needs to be larger than the capacity of the motor 8. Also, when the carrier frequency is lowered, the control accuracy of the motor 8 is reduced, and the motor 8 generates magnetic noise.

[0009]

As described above, in the conventional asynchronous PWM inverter control device, in order to reduce the influence on the system due to the superposition of the beat frequency on the current supplied to the motor, it is fixed in the PWM control. Either a higher or lower carrier frequency was to be selected. As a result, there is a problem that the inverter capacity increases if the setting is made higher than usual, and the control performance deteriorates if the setting is made lower than usual.

The present invention has been made in view of the above circumstances, and can reduce the influence on the system due to the superposition of the beat frequency on the motor current without causing an increase in the inverter capacity and a deterioration in the control performance. An object of the present invention is to provide an asynchronous PWM inverter control device.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, the present invention relates to an asynchronous PWM inverter control device for controlling a motor at a variable speed. A detecting unit that detects a two-phase current; a control unit that compares the rotational position and the rotational speed with a commanded position and speed to calculate a command current to be output to the motor; And a PWM control unit for controlling an inverter unit by comparing the command current and the command current, wherein the carrier frequency of the PWM control unit is changed when the motor is in a clamped state by an external mechanism. I have.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. 1 corresponding to FIG. As shown in FIG. 1, a PWM inverter control device according to an embodiment of the present invention differs from a conventional inverter control device in that a motor 8
The detection signal of the resolver 9 that detects the speed of the motor and the output signal of the clamp control unit 11 that outputs a high pressure clamp, low pressure clamp or unclamping command to the clamp device 12 are input to the PWM control unit 5. The PWM control unit 5 changes the carrier frequency based on these signals.

That is, the PWM control unit 5 refers to the output signal of the clamp control unit 11 and, if it is in the unclamped state, performs PWM control of the motor 8 at a preset carrier frequency as in the conventional case. I do. Further, in the present embodiment, the clamp control unit 11 outputs a clamp signal to the clamp device 12 and also outputs a clamp signal to the PWM control unit 5 according to a clamp command input from the NC device 1. I do. The PWM control unit 5 detects that a high pressure or low pressure clamp state has been established based on the clamp signal. Further, the PWM control unit 5
A signal representing the detection result of the speed of the motor 8 is also input from the resolver 9.

The PWM control unit 5 adjusts the carrier frequency based on these clamp signals and the signal of the detection result of the speed of the motor 8. Specifically, FIG. 2 shows a command speed, a command torque, and a carrier frequency of the motor 8 in the present embodiment. The motor 8
And the relationship with the clamp device 12 is the same as that of the conventional device, and a detailed description thereof will be omitted.

FIG. 2 is different from the conventional one (FIG. 5) in the section C, that is, when the motor 8 is stopped and the clamping device 12 is in the high pressure clamping state, the carrier frequency is set to the normal value. That is, the state (C1 (Hz)) is changed to C2 (Hz). The value of the carrier frequency C2 is arbitrarily set by the user so that the beat frequency superimposed on the current supplied to the motor 8 does not resonate with the natural frequency of the system. Further, it is preferable that the magnetic noise of the motor 8 is set so as not to be bothersome according to the use situation.

In the section D, that is, when the motor 8 is rotating and the clamp device 12 is in the low pressure clamping state, if abnormal noise or vibration is generated without resonance, the carrier frequency is changed to the normal frequency. State (C1)
May be set to a different value (for example, an arbitrary frequency between C1 and C2) (broken line in FIG. 2). It is also preferable that the carrier frequency is arbitrarily set by using hardware logic using hardware or software logic using software.

According to the present embodiment, for example, as shown in FIG. 3, whether the motor 8 is stopped (speed is "0")
(S1), and if "0", it is further determined whether or not the clamp control unit 11 is outputting a high pressure clamp signal (S2). If it is a high pressure clamp, the carrier frequency is set to C2. (S3). Further, when the speed is not “0” in the process S1, or when the clamp control unit 11 does not output the high pressure clamp signal in the process S2, the carrier frequency is set to the normal C1 (S1).
4).

This process can be applied to a case where the carrier frequency is changed in the low pressure clamping state. In this case, the process S1 is not necessary, and the carrier frequency is changed and set merely depending on whether or not the clamp control unit 11 outputs a low pressure clamp signal.

[0019]

According to the present invention, when an object rotationally driven by a motor is in a clamped state, the carrier frequency is changed from the initial value in accordance with the clamped state and set to an arbitrary predetermined value. Therefore, the carrier frequency after the change can be set so that the beat frequency superimposed on the motor current and the natural frequency of the system do not resonate, and the influence on the system such as preventing the resonance phenomenon can be reduced. Can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an inverter control device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a signal change in the inverter control device according to the embodiment of the present invention.

FIG. 3 is a flowchart illustrating an example of an operation of the inverter control device according to the embodiment of the present invention.

FIG. 4 is a circuit diagram of a conventional inverter control device.

FIG. 5 is an explanatory diagram showing signal changes in a conventional inverter control device.

[Explanation of symbols]

1 NC device, 2 position control unit, 3 speed control unit, 4
Current control unit, 5 PWM control unit, 6 inverter unit, 7
Motor current detector, 8 motors, 9 resolver, 10
Pulse generator, 11 Clamp control unit, 12
Clamping device, 13 rotating body.

Claims (1)

[Claims] 1. An asynchronous PWM that controls a motor at a variable speed.
In the inverter control device, a rotation position of the motor, a rotation number, a detection unit that detects at least two-phase current, and a comparison between the rotation position and the rotation number, and a commanded position and speed, A control unit that calculates a command current to be output to the motor; and a PWM control unit that compares the detected current with the command current to control an inverter unit, wherein the motor is in a clamped state by an external mechanism. An asynchronous PWM inverter control device, wherein a carrier frequency of the PWM control unit is changed.