JPH04331489A - Motor controller - Google Patents

Abstract

PURPOSE:To make the stepped interval of phase command as short as possible and to obtain a sine wave output current from an inverter as quick as possible. CONSTITUTION:Upon turn ON of power, an absolute position detecting means 15 produces a rough phase command at first. At a time point when the detection output of the absolute position detecting means 15 makes an initial variation, a relative position detecting means 16 outputs a correct phase command. Consequently, output current of an inverter 23 immediately becomes sinusoidal for each phase resulting in suppression of ripple and the like.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device for improving torque ripple at the initial stage of operation.

0003

2. Description of the Related Art FIG. 4 shows a general AC servo motor control device. As is well known, the AC servo motor 1 has three-phase stator windings 2u, 2v, and 2w on the stator side and permanent magnets 3 on the rotor side, and is a type of synchronous motor. A rotational position sensor, such as a rotary encoder 4, for detecting the rotational position of the rotor, that is, the magnetic pole position of the permanent magnet 3, is directly connected to the rotor. This rotary encoder 4 generates the signals shown in FIG. That is, the U signal, V signal, and W signal as absolute position detection signals having one period per rotation of the rotor are generated with a phase shift of 120 degrees from each other, and a large number of relative positions are detected at a minute pitch per rotation. Detection signal A
, B, and further generates a reference position detection signal Z of one pulse per rotation near the rising edge of the U signal.

The relative position detection signals A and B actually have several thousand pulses per rotation of the rotor, but since it is difficult to show them on the drawing, the number of cycles is omitted as appropriate. Furthermore, these relative position detection signals A and B are out of phase by 90 degrees in order to detect the rotational direction of the rotor.

Each output of the rotary encoder 4 is applied to a magnetic pole position detection circuit 5. As shown in FIG. 5, the magnetic pole position detection circuit 5 includes an absolute position detection circuit 5a, a relative position detection circuit 5b, and a switching control circuit 5c. The signal current is given to the absolute position detection circuit 5a, the relative position detection signals A and B are given to the relative position detection circuit 5b, and,
The reference position detection signal Z is provided to the relative position detection circuit 5b and the switching control circuit 5c. Based on these signals, this magnetic pole detection circuit 5 generates phase commands to flow sine wave currents iu*, iv*, iw* whose phases are shifted by 120 degrees to each phase of the AC servo motor 1, as will become clear from the description below. A current phase command θr is generated to drive the current control type inverter 6. As a result, sine wave currents having a phase shift of 120° are applied to each phase of the AC servo motor 1, and the driving of the AC servo motor 1 is controlled.

In the above configuration, when starting the AC servo motor 1, it is necessary to detect the position of the rotor (the magnetic pole position of the permanent magnet 3) as an absolute position when the power is first turned on. Therefore, the magnetic pole detection circuit 5 detects the position of the rotor by a combination of the U signal, the V signal, and the W signal when the power is turned on. That is, the position detection signal is a combination code of the U signal, V signal, and W signal, and for example, the combination code of the UVW signal is "101".
A detection signal of
1" means 210° detection, "011" means 270° detection, and "001" means 330° detection.

[0007] However, when the power is turned on, the switching control circuit 5
c, the output terminal is switched to the absolute position detection device 5a. When the power is turned on, the position of the rotor is detected by the absolute position detection device 5a, a current phase command θr corresponding to this detected position is generated, the AC servo motor 1 is started by the inverter 6, and the position of the rotor is set to 60°. Each time the unit is detected, the current phase command θr is set according to the position detection signal.
is generated to drive and control the AC servo motor 1 via the inverter 6.

Thereafter, when the reference position detection signal Z is applied, the switching control circuit 5c changes the output terminal to the relative position detection circuit 5.
At the same time, the relative position detection circuit 5b starts counting operation based on the relative position detection signals A and B, detects the rotor position almost linearly based on the count value, and detects a continuous current phase with good resolution. A command θr is generated. Note that when this current phase command θr becomes stepwise, each phase current iu*, iv*, iw* becomes stepwise, and when it becomes a straight line with a predetermined slope, each phase current iu*, iv*, iw* becomes a sine waveform. Become.

[0009]

[Problems to be Solved by the Invention] However, in the above conventional configuration, the first reference position detection signal Z after power is turned on is
During the period until input is input, the phase currents iu*, iv*, iw* change in a stepwise manner as shown in FIG. 5, which causes problems such as torque ripples and vibrations. In particular, when rotating at a very slow speed from when the power is turned on, the period until the first reference position detection signal is input may be extremely long, so this problem cannot be ignored.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a motor control device that can minimize the period during which the phase command is stepped and can quickly change the output current of the inverter to a sinusoidal waveform.

[Configuration of the invention]

0012

[Means for Solving the Problems] The motor control device of the present invention generates a plurality of absolute position detection signals per revolution of a motor rotor, and also generates a large number of relative position detection signals at minute angular pitches. a sensor, an absolute position detection means for detecting the rotational angular position of the rotor based on the absolute position detection signal and generating a phase command; Relative position detection means that detects the angular position and generates a phase command; calculation means that calculates a temporary reference position based on the detection result by the absolute position detection means at the time of power-on; and a phase command that switches when the power is turned on. a switching control means for outputting
and an inverter that fires any switching element at a phase according to a phase command output from the switching control means, and the switching control means is configured to turn on an arbitrary switching element at a phase according to a detection result of the absolute position detection means when the power is turned on. A command is output, and then, when the position detection output of this absolute position detection means changes for the first time, the relative position detection means is operated based on the calculation result of the calculation means, and the phase command by this relative position detection means is output. The feature is that it is configured to switch and output.

[0013]

[Operation] When the power is turned on, the position of the rotor is detected by the absolute position detection device. Further, the calculation means calculates a temporary reference position by adding, for example, a predetermined angle to this detected position. Furthermore, the switching control means outputs a phase command according to the detected position result by the absolute position detecting means when the power is turned on, and thereafter, when the detection output of the absolute position detecting means changes for the first time, the switching control means outputs a phase command according to the detected position result of the absolute position detecting means, and thereafter, when the detected output of the absolute position detecting means changes for the first time, the switching control means outputs a phase command according to the detected position result of the absolute position detecting means. It operates based on the calculation result of the calculation means, and also switches and outputs the phase command by the relative position detection means. Therefore, the phase command is fixed only until the detection output of the absolute position detection means changes for the first time, but after that it changes continuously. This causes a sinusoidal phase current to be applied to the motor.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. In FIG. 1, a motor, for example, an AC servo motor 11, has three-phase stator windings 12u, 12v, and 12w on the stator side, and has a permanent magnet 13 on the rotor side. A rotational position sensor such as a rotary encoder 14 is directly connected to the rotor to detect the rotational position of the rotor, that is, the magnetic pole position of the permanent magnet 13. This rotary encoder 14 generates the signals shown in FIG. The details are shown in FIG. 3. This rotary encoder 14 outputs U as an absolute position detection signal that has one period per rotation of the rotor.
The phase of the signal, V signal, and W signal is 120° with respect to each other.
A large number of relative position detection signals A and B are generated at minute pitches per rotation, and a reference position detection signal Z of one pulse per rotation is generated near the rising edge of the U signal.

The relative position detection signals A and B are actually several thousand pulses per rotation of the rotor, but as shown in FIGS.
In the following, the number of cycles is omitted as appropriate. In addition, these relative position detection signals A and B are 90° in order to detect the rotational direction of the rotor.
°Out of phase.

Among the outputs of the rotary encoder 14, the U signal, the V signal, and the W signal are given to an absolute position detection circuit 15 as absolute position detection means, and relative position detection signals A and B are used to detect the relative position. The reference position detection signal Z is applied to a count input terminal of a relative position detection circuit 16 as a detection means, and is also applied to a temporary reference position switching circuit 21 to be described later, and a reference position detection signal Z is applied to a clear input terminal of the relative position detection circuit 16. It has become.

The absolute position detection circuit 15 detects the position of the rotor by a combination of the U signal, the V signal, and the W signal. For example, the combination code of U, V, and W signals is "1".
A detection result of ``01'' is considered an absolute position detection of 30 degrees, and hereinafter, ``100'' is 90 degrees, ``110'' is 150 degrees,
“101” is 210°, “011” is 270°, “00
1" means 330° detection. The absolute position detection circuit 15 is configured to output a current phase command as a phase command according to the detection result. Note that each detection result is an intermediate value. That is, for example, U, V, W
When the combination of the respective signals becomes the logical value "101", the angular position of the rotor is in the range from 0° to 60°, so the intermediate value of 30° is taken as the detected value.

Further, the relative position detection circuit 16 usually detects the relative position using the rotor angular position corresponding to the reference position detection signal Z as a reference position each time the reference position detection signal Z is applied to its clear input terminal. The position of the rotor is continuously detected by counting up or down the signals A and B, and outputs a current phase command according to the detection result.

The calculation means 17 calculates the position detection results (30°, 90°, . . . ) of the absolute position detection circuit 15 when the power is turned on.
330°) and an angle of 30°, a temporary reference position is calculated and stored. Further, the calculating means 18 calculates a temporary reference position by subtracting an angle of 30° from the position detection result (any of 30°, 90°, ...330°) of the absolute position detecting circuit 15 when the power is turned on, and stores it. do.

The switching control circuit 19 serving as switching control means includes a change detection circuit 20, a temporary reference position switching circuit 21, and a command switching circuit 22. Change detection circuit 2
0 generates a change detection signal when the detection output of the absolute position detection circuit 15 changes for the first time after the power is turned on. The temporary reference position switching circuit 21 switches A after the power is turned on.
When the rotation direction of the C servo motor 11 is forward rotation, the calculation result of the calculation means 17 is given to the relative position detection circuit 16, and when the rotation direction of the AC servo motor 11 is reverse rotation, the calculation result of the calculation means 18 is given to the relative position detection circuit 16.
The calculation result is switched to be applied to the relative position detection circuit 16. The command switching circuit 22 has an output terminal connected to the absolute position detection circuit 15 when the power is turned on, and connected to the relative position detection circuit 16 when a change detection signal is applied.

The current phase command θr, which is the output of this switching control circuit 19, is given to a current control type inverter 23, and this inverter 23 generates each phase current iu*, iv*, iw* based on the current phase command θr. Thus, the AC servo motor 11 is driven and controlled.

The operation of the above configuration will be described. Before the power is turned on, the command switching circuit 22 is in a state where its output terminal is switched to the absolute position detection circuit 15 side. Further, the temporary reference position switching circuit 21 is in a state connected to the calculation means 17 side.

Now, when the power is turned on, the absolute position detection circuit 15 detects the position of the rotor based on the combination of the U signal, V signal, and W signal from the rotary encoder 14. The following explanation will be given assuming that the combination code of the U signal, V signal, and W signal is "101". In this case, an absolute position of 30° is detected. Then, the calculating means 17 calculates a temporary reference position by adding an angle of 30° to this position detection result, and calculates the temporary reference position (60° in this case).
). Further, another calculating means 18 calculates a temporary reference position by subtracting an angle of 30° from this position detection result, and stores this calculation result (0° in this case).

The absolute position detection circuit 15 outputs a current phase command according to the position detection result (30°) at this point. In this case, since the output terminal of the command switching circuit 22 is connected to the absolute position detection circuit 15 side, the current phase command of the absolute position detection circuit 15 is outputted as the current phase command θr. The inverter 23 generates each phase current iu*, iv*, iw* according to this current phase command θr, and
The C servo motor 11 is driven. At this time, the temporary reference position switching circuit 21 determines the rotation direction according to the relative position detection signals A and B, and connects the calculation means 17 to the relative position detection circuit 16 when the rotation is forward rotation, and connects the calculation means 17 to the relative position detection circuit 16 when the rotation is reverse rotation. The calculating means 18 of is connected to the relative position detection circuit 16.

Thereafter, when the absolute position detection circuit 15 changes the combination code of the U signal, V signal, and W signal to "100" due to the rotation of the rotor, this is detected by the change detection circuit 20. The change detection circuit 20 gives the change detection output to the calculation means 17 and 18. At this time, since the calculation means 17 side is connected to the relative position detection circuit 16, the calculation result in the calculation means 17 (temporary reference position 60°) is applied to the preset input terminal of the relative position detection circuit 16. The relative position detection circuit 16 starts an up-count operation based on the relative position detection signals A and B from the count value corresponding to this temporary reference position of 60°, and sequentially detects the position of the rotor. Then, it outputs a current phase command signal according to the detection result.

At the same time, the change detection output from the change detection circuit 20 is given to the command switching circuit 22, which switches the output terminal from the absolute position detection circuit 15 to the relative position detection circuit 16. . Therefore, the current phase command output of this relative position detection circuit 16 is outputted as a current phase command θr and given to the inverter 23. With this, the inverter 23 operates based on the current phase command θr having a predetermined slope rather than a step-like shape, and generates each phase current iu* of the sine wave.
, iv*, and iw* to drive and control the AC servo motor 11.

After that, when the relative position detection circuit 16 is given the reference position detection signal Z, it performs an up-count operation based on the relative position detection signals A and B, using this reference position detection signal Z as a reference position, and performs position detection. At the same time, a current phase command is output.

Note that when the rotational direction of the rotor is reverse rotation, the stored contents of the other calculation means 18 are given to the relative position detection circuit 16, and the relative position detection circuit 16 counts down. However, if the AC servo motor is always rotated in only one direction, only one calculation means is required, and in this case, the temporary reference position switching circuit 21 is not necessary.

As described above, according to this embodiment, the current phase command θr is fixed only until the detection output of the absolute position detection circuit 15 changes for the first time when the power is turned on, but after that, the current phase command θr is fixed. Since the continuous current phase command from 16 is output as the current phase command θr, the inverter 2
In case 3, even if each phase current becomes stepwise at the beginning of power-on, it is only up to a maximum rotation angle of 60°, and a sinusoidal phase current with no phase shift is immediately applied to the AC servo motor. become. Therefore, the occurrence of torque ripples, vibrations, etc. can be suppressed as much as possible.

[0030]

As is clear from the above description, the present invention outputs a phase command according to the detection result by the absolute position detection means after the power is turned on. When the phase change occurs, the relative position detecting means is operated and an appropriate phase command is output by the relative position detecting means, so that the inverter immediately provides a sinusoidal phase current with no phase shift to the motor.
As a result, the excellent effect of suppressing the occurrence of torque ripples, vibrations, etc. as much as possible is achieved.

[Brief explanation of drawings]

[Fig. 1] Block diagram showing one embodiment of the present invention

[Figure 2] Diagram showing each output signal of the rotary encoder, current phase command, and each phase current waveform

[Figure 3] Diagram showing each output signal of the rotary encoder

[Figure 4] Block diagram showing a conventional example

[Figure 5] Diagram equivalent to Figure 2

[Explanation of symbols]

11 is an AC servo motor (motor), 14 is a rotary encoder (rotary position sensor), 15 is an absolute position detection circuit, 16 is a relative position detection circuit, 17 and 18 are calculation means, and 19 is a switching control circuit (switching control means). It is.

Claims (1)

[Claims] 1. A rotational position sensor that generates a plurality of absolute position detection signals per rotation of a rotor of a motor and also generates a large number of relative position detection signals at minute angular pitches; an absolute position detection means that detects the rotational angular position of the rotor and generates a phase command; and an absolute position detection means that detects the relative angular position of the rotor from a predetermined reference position based on the relative position detection signal and generates a phase command. a position detection means, a calculation means for calculating a temporary reference position based on a detection result by the absolute position detection means at the time of power-on, a switching control means for switching and outputting a phase command at the time of power-on, and this switching control means. and an inverter that fires any switching element with a phase according to a phase command output from the switching control means, and the switching control means outputs a phase command according to the detection result of the absolute position detection means when the power is turned on. Then, when the position detection output of this absolute position detection means changes for the first time, the relative position detection means is operated based on the calculation result of the calculation means, and the phase command by this relative position detection means is switched and outputted. A motor control device characterized by having the following configuration.