JPS60219915A - Speed malfunction detecting circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a speed abnormality detection circuit for detecting abnormality in the rotational speed of a servo motor, and relates to an AC servo motor suitable for abnormality detection in the speed detection system of a special counterfeit AC servo system. This invention relates to a speed abnormality detection circuit.

[Background of the invention]

Conventionally, direct current (DC) servo motors have been most widely used as power actuators in fields such as robots. When viewed as a servo system, this
This is because a DC motor is most suitable from the viewpoint of control.

The first item is a block mouth that exemplifies a DC servo system using the conventional most common motor. In Fig. 1, 1 is a speed command voltage, 2 is an actual speed signal, 3 is a speed error amplifier, 4 is a current error amplifier, and 5 is a main circuit (generally consisting of a power element such as a thyristor or transistor).
power circuit), 6 is current transformer (OT), 7 is Domo-ri,
8 is generally a tacho generator (DC speed generator) or a speed detector (speed generator) such as an encoder or resolver, 9 is an armature current signal, and 10 is a speed deviation signal.

With this configuration, the difference between the speed command voltage 1 and the actual speed signal 2 detected by the speed generator 8 is amplified by the speed error amplifier 3, and the current error amplifier 4 amplifies the difference between the speed command voltage 1 and the actual speed signal 2 detected by the speed generator 8.
The difference between the speed deviation signal 10 from the DC motor 7 and the armature current signal 9 from the current transformer 6 which detects the armature current of the DC motor 7 is amplified.

The output of this current error amplifier 4 causes a D
The armature voltage of the C motor 7 is controlled, thereby controlling the speed of the DC motor 7. Note that the same reference numerals or symbols indicate the same or corresponding parts throughout the drawings.

FIG. 2 is a wiring diagram showing a typical example of the main circuit 50 shown in FIG. In Fig. 2, 11 is a DC power supply, TR, ~TR
4 is a transistor (power element), and D1 to D4 are diodes. With this configuration, the current error amplifier 4 shown in FIG.
The speed of C motor 7 is controlled. Generally, the speed of a DC motor is given by the following equation (1).

Va-ARa Ka (1°Kφ Kφ Here, N is the rotation speed, Va is the armature voltage, Ka is the induced voltage, Ia is the armature current, Ra is the armature resistance, and Kφ is the voltage constant.

Generally, when this DC servo motor is applied to fields such as robots, due to its usage and characteristics, it is necessary to pay sufficient attention to safety. % Extreme care must be taken to prevent the KDO motor from running out of control. If the DC motor, which is the actuator of the robot, runs out of control, the robot will make unexpected movements and there is a risk of personal injury.

For this reason, various elements that cause runaway have been protected from abnormalities by shutting them out. For example, a disconnection between the speed generator 8 and the control system (controller) naturally leads to runaway, so this disconnection is detected and the system protect However, 1
Since the speed generator 8 itself has become abnormal, even if there is no disconnection, if the output voltage (speed signal 2) is not output or is lower than the normal value, it will still lead to runaway. In addition, the speed error amplifier 6 of the control system outputs a voltage (speed deviation signal 10).
If the current error amplifier 4 is destroyed in a state where the current error amplifier 4 is output, or if the current error amplifier 4 is broken, a runaway may occur.

Furthermore, in the case of an abnormal state in which, for example, transistors TR and TR4 of the main circuit 5 remain on and become K, the armature voltage Va applied to the DC motor reaches its maximum value, so (1
)Two[,,! : The rotational speed N given by the motor becomes an abnormally large value, leading to runaway. In general, the armature's forging pressure Va is designed to be below the maximum value even at the rated state by switching the transistors TR, ~TR4, etc., in order to have a margin for voltage variations, etc., or a margin for obtaining sufficient transient characteristics. . As described above, in a DC servo system using a DC motor, there is a risk of speed abnormalities such as runaway in each component part, so it is necessary to ensure that no matter where an abnormality occurs, it will be caught. The safest method is to detect an abnormality and protect by detecting the armature voltage Va on the main circuit side of the final stage in accordance with equation (1).

FIG. 3 is a circuit diagram illustrating a conventional speed abnormality detection circuit of this type of DC servo motor. In Figure 3, 12
is armature voltage Va or induced voltage Ea [proportional signal,
13 is a reference voltage signal (source), 14 is a comparator, and 15 is an abnormal signal. With this configuration, the armature voltage Va or induced voltage E across both ends of the DC motor 7 in FIG. 2 corresponds to equation (1).
a=(Va-IaR) is detected, and the armature voltage Va or induced voltage Ea [proportional signal 12
is compared with the reference voltage signal 13 to detect whether the armature voltage Va or the induced voltage F1a0 value each exceeds the reference value, and if they exceed the reference value, an abnormality signal 15 is issued, thereby protecting the system. In this circuit, since the armature voltage Va across the DC motor 7 shown in FIG. 1
Speed command voltage 1, speed signal 2 and speed deviation signal 1 in the figure
0 and the armature current signal 9 are often handled insulated, and for this reason, in most cases, on-on control is performed in which an abnormality occurs when the busy armature voltage Va exceeds a reference value as shown in FIG.

On the other hand, recently, the application of alternating current (AO) servo motors has been attracting attention in fields such as FA equipment and robots. Systems are increasingly being oriented towards AC.

However, in an AC servo system using a conventional AC servo motor, when trying to detect an abnormal rotation speed of the AC servo motor on the main circuit side in the same way as with a DC servo motor, it is difficult to detect the abnormal rotation speed of the AC servo motor because the AC servo motor is an AC motor. Furthermore, it has the drawback that it is difficult to detect because it is a three-phase motor, for example, and its terminal voltage waveform is a PWM waveform. In other words, the basic operation is to rectify the AC for each of the above special conditions, make the 5-phase correspond to 3 (B) paths, and pass the PWM wave through a filter circuit. 1) It should be possible to detect the armature voltage in accordance with equation 1, and thereby detect speed abnormalities and protect them.However, the speed abnormality detection circuit is more complex and expensive than in the case of a DC motor, and the accuracy is also low. Therefore, there has been a demand for an abnormality detection circuit that can be used overnight (DO-I).

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a speed abnormality detection circuit for an AC servo motor that is simple, low cost, highly accurate, and suitable for detecting abnormalities in the speed detection system of a servo system. .

[Summary of the invention]

The present invention solves the problem of abnormal speed of AC servo motor.

Similar to a motor, if you try to detect it on the main circuit side, the detection circuit will be more complicated and expensive than that of a DC motor because the AC is, for example, 3-phase and the terminal voltage waveform is a PWM waveform. In contrast, the speed principle equation is given by the above equation (1) as with DC motors, but in other KAC motors, the speed is proportional to the primary frequency, and unlike DC motors, a high voltage is applied to both ends of the motor. However, we focused on the fact that the speed does not increase unless there is an alternating current, and based on this result, we found that an AC servo motor with a speed detector and a magnetic pole position detector (in an AC servo system using DC brushless motor power, the magnetic pole position detection The amplitude-foot reference sine wave magnetic pole position signal obtained from the sensor is time-differentiated using a differentiating circuit, and this differentiated signal proportional to the primary frequency, that is, the speed, is compared with the speed signal from the speed detector using a comparator. This is a speed abnormality detection circuit that outputs an abnormality signal when the difference exceeds a predetermined value, thereby enabling speed abnormality to be detected simply and inexpensively on the control circuit side.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 4(9) to 11.

FIG. 4 is a block diagram showing an embodiment of an AC servo system using an AC servo motor, which is the object of the present invention. In FIG. 4, 1 is the speed command (voltage) of the motor as in 1-, 2 is the speed signal detected from the speed detector,
3 is a speed error amplifier that compares and amplifies the difference between speed command 1 and speed signal 2 and outputs a speed deviation signal proportional to the motor torque; 20 is a speed deviation signal 10 and a reference sine wave magnetic pole position from the magnetic pole position detection circuit; Multiply signal 19 to obtain current command 21
4 is a current error amplifier (current control) that amplifies the difference between the current command 21 and the motor armature current signal 9 and outputs a control signal 22 that controls the motor's primary current through the main circuit. circuit), 5 is the main circuit (power circuit) generally consisting of power elements such as thyristors or transistors.
, 6 detects the armature current of the motor and outputs an armature current signal 9
16 is an AC servo motor (
17 is a magnetic pole position detector that detects the magnetic pole position of the motor and outputs a magnetic pole position signal; 18 is a reference sine wave magnetic pole position signal 19 that receives a magnetic pole position signal from the magnetic pole position detector 17 and has a constant amplitude; This is a magnetic pole position detection circuit that outputs .

FIG. 5 is a wiring diagram showing one embodiment of the main circuit 5 of FIG. 4. In Fig. 2, 11 is the same DC power supply as in Fig. 2;
TR, ~TR6 are transistors (power elements), D1~
D6 is a diode. With this configuration, the control signal 22 from the current error amplifier (current control circuit) 4 shown in FIG. The speed of the AC servo motor 16 may also be controlled. Note that the speed (rotation speed) of the AC motor is also given by equation (1) in the same way as for the DC motor, but if you want to detect the speed abnormality of this AO motor on the main circuit side as with the DC motor, the AC servo The motor 16 is an AC motor,
In addition, in this implementation, a 6-phase motor is used, and the terminal voltage waveform is also P.
As mentioned above, since the waveform is a WM waveform, a speed abnormality detection circuit similar to that of a DC motor cannot be realized.

FIG. 6 is a waveform diagram of the reference sine wave magnetic pole position signal 19 of the fourth magnetic pole position detection circuit 18. The main signal 19 is a sine wave signal synchronized with the magnetic pole position of each phase of the AC servo motor 16, and its amplitude is constant regardless of the rotation speed and primary frequency of the motor.

Note that the magnetic pole position detector 17 and the magnetic pole position detection circuit 18 are
For example, if the magnetic pole position detector 17 uses a Hall element, there is no magnetic pole position detection circuit 18, and the reference sine wave magnetic pole position signal 18 is directly generated from the magnetic pole position detector 17. Further, if the magnetic pole position detector 17 is a resolver, the reference sine wave magnetic pole position signal 1 is obtained from this magnetic pole position signal.
A magnetic pole position detection circuit 18 is required to obtain 8. In addition, the magnetic pole position detector 17 acts as an encoder such as U, V,
If the W signal (square wave) is generated, the magnetic pole position detection circuit 18 will be a circuit configured with a counter, a ROM, etc., and receives the encoder pulses p and B phase as inputs. In addition, the speed detector 8 is generally a resolver or encoder in the case of an AC servo motor, and a D
C tacho generators are rarely used.

With this configuration, the speed error amplifier 6 compares and amplifies the difference between the speed command voltage 1 of the motor and the actual speed signal 2 detected by the speed detector 8 of the motor.9 The motor torque output from the speed error amplifier 3 Speed deviation signal 1 proportional to
0 and the magnetic pole position detection circuit 18 based on the magnetic pole position signal detected by the magnetic pole position detector 17 of the AC servo motor 16.
Reference sinusoidal magnetic pole position signal 1 with constant amplitude obtained via
9 is multiplied by a multiplier 20, and the difference between the small current command 21 of this multiplier 20 and the armature current signal 9 detected by the current transformer 6 is amplified by the current error amplifier 4, and this current error The primary current of the AC servo motor 160 is controlled by the control signal output from the amplifier 4 through the main circuit 5 consisting of power elements such as transistors TR, .about.TR, and the speed of the AC servo motor is controlled by this K.

FIG. 7 is a block diagram showing an embodiment of an AC servo motor speed abnormality detection circuit according to the present invention intended for the AC servo system shown in FIG.
inputs the standard sine wave magnetic pole position signal 19 with constant amplitude output from the magnetic pole position detection circuit 18 in FIG.
25 is a rectifier circuit that rectifies the output signal 24 of the differentiator circuit 23 and converts it into a DC value, 27
is a comparator which takes in and compares the DC value 26 of the rectifier circuit 25 and the speed signal 2 from the speed detector 8 shown in FIG. 4, and outputs a speed abnormality signal 28 when the difference therebetween exceeds a predetermined value.

With this configuration, the reference sine wave magnetic pole position signal 19 (Uu
) is given by the following equation.

Uu=Vsinω, t (2) This signal 19 (Uu) is a sine wave signal synchronized with the magnetic pole position tc of each phase of the AC servo motor 16, where ω1 is the primary frequency, and ■ is the amplitude and the rotation speed N. and one missing frequency ω1
is constant regardless of

Then, the output signal 24 of the differentiating circuit 23 is expressed by the following equation by time-differentiating equation (2).

U'u = Vω, sinω, t (3) Therefore, the output signal 24 (U'u) becomes a signal proportional to the one-off frequency ω1, that is, the speed (rotational speed N).

Therefore, the output signal 24 (U'u) of the differentiating circuit 23 is rectified by the rectifier circuit 25 to obtain (3) a DC value 2 proportional to 2.
6, this DC value 26 and the speed signal 2 from the speed detector 8 are compared by a comparator 27, and when the difference exceeds a predetermined value, a speed abnormality signal 28 is output.

FIG. 8 is a circuit diagram showing an embodiment of the differentiating circuit 23 of FIG. 7. In FIG. 8, C1 is a capacitor, R1 is a resistor, and this circuit is the most basic circuit. With this configuration,
The input reference sinusoidal magnetic pole position signal 19 (Uu) is time differentiated to obtain an output signal 24 (U'u). Note that the differentiating circuit 23 may be a general differentiating circuit using an operational amplifier.

FIG. 9 is a circuit diagram showing an embodiment of the rectifier circuit 25 shown in FIG. 7. In FIG. 9, OF,,OF.

is an operational amplifier, R1-R8 are resistors, and D, , D are diodes. With this configuration, the input differentiated output signal 24 (U'u) is applied to the rectifier tongue with a direct current value 26 proportional to it.
is converted to Note that the rectifier circuit 25 may be an ideal absolute value circuit. Furthermore, when the comparator 27 at the subsequent stage compares the DC value 26 and the speed signal 2, if the set value of the difference between them is set to be large, simple diode rectification may be used. Further, in order to further reduce the ripple of the DC value 26, this circuit may be provided for six phases to produce a filter effect.

FIG. 10 is a circuit diagram showing one embodiment of the comparator 27 of FIG. 7. 1 [In the figure, Re −IR+t is the resistance,
C1 is a capacitor, OP is an operational amplifier with a filter of the timer number R1t x C1 of resistor (value) R11 and capacitor (value) Ot, 29 is an operational amplifier OF, and the absolute value is obtained by rectifying the output of the output. A circuit 30 is a comparator that compares the absolute value output Vr of the absolute value circuit 29 with a predetermined reference voltage Vr and outputs the result. Absolute value circuit 29 is generally similar to rectifier circuit 26 of FIG. DC value 2 from rectifier circuit 25
6 is generally inputted as a DC voltage with ripples, and the speed signal 2 from the speed detector 8 is inputted to this circuit as a signal having a polarity different from that of the DC value 26. In addition, the operational amplifier op is adjusted so that its output is approximately 0 during normal operation when the difference between the input DC value 26 and the speed signal 2 is small, and the output of the comparator 60 is at a low level in this circuit during normal operation. be. With this configuration, the difference between the DC value 26 from the rectifier circuit 25 and the speed signal 2 from the speed detector 8 is determined by the operational amplifier op.

The amplified output is rectified by an absolute value circuit 29, and the absolute value output Vr is a predetermined reference voltage Vr.

When the absolute value output Vr exceeds the reference voltage Vr, the output becomes a high level, and when the difference between the input DC value 26 and the speed signal 2 exceeds a predetermined value, an abnormality signal 28 is generated. According to the AC servo motor speed abnormality detection circuit of this embodiment, it is possible to detect and protect speed abnormalities and runaway caused by various abnormality factors in the speed detection system of the AC servo system. For example, in the case of an abnormal drop in the output of the speed detector 8, that is, if there is no disconnection but the output is not output or is lower than the normal output, the speed signal 2 will drop, and the comparator 27 will detect this. Since the abnormality signal 28 is issued by the engine, it is possible to prevent the risk of runaway. Abnormalities in the outputs of one of the magnetic pole position detectors 17 and the magnetic pole position detection circuit 18 can also be similarly detected by the comparator 27. Furthermore, if the speed detector 8 is a speed detector using encoder pulses A and B phases, the button cannot be detected by the conventional circuit, for example, if the encoder is affected by temperature and its pulses are missing. However, this circuit is advantageous in that it can sufficiently detect abnormalities.

FIG. 11 is a block diagram showing another embodiment of the speed abnormality detection circuit for an AC servo motor according to the present invention. In FIG. 11, 61 is a comparator that compares the DC value 26 of the output of the rectifier circuit 25 with a predetermined reference voltage Vr, and the other components are the same as in FIG. That is, in this circuit, the speed signal 2 and comparator 27 in FIG. 7 are replaced with the reference voltage Vr2 and comparator 31.

With this configuration, the reference sinusoidal magnetic pole position signal 19 from the magnetic pole position detector path 18 is differentiated by the differentiating circuit 23, the differentiated output signal 24 is rectified by the rectifying circuit 25, and the rectified DC value 26 is set to a predetermined value. It is compared with the reference voltage Vr by the comparator 31, and if the DC value 26 exceeds the reference voltage Vr, an abnormality signal 2 is generated.
Roll an 8.

According to the abnormal speed detection circuit of the AC servo motor of this embodiment, when the peak value of the DC value 26 exceeds the reference voltage Vr even instantaneously, the abnormal signal 28 is outputted. It is possible to detect when the speed error amplifier 3 is abnormal.

〔Effect of the invention〕

As described above, according to the present invention, a simplified, low-cost, and high-precision speed abnormality detection circuit for an AO servo motor is provided. It is possible to detect abnormalities such as the following, and it is also possible to detect abnormalities at low speeds or medium speeds. Moreover, since the abnormalities can be detected on the control circuit side rather than on the main circuit side, various effects such as easier signal processing can be obtained.

[Brief explanation of the drawing]

Figure 1 is a block diagram illustrating a conventional DC servo system, Figure 2 is a wiring diagram of the main circuit example in Figure 1, Figure 6 is a conventional DC servo motor speed abnormality detection circuit, and Figure 4 is a diagram of the main circuit shown in Figure 1. A block diagram showing an embodiment of the AO servo system of the subject of the invention, FIG. 5 is a wiring diagram of the main circuit example of Section 4, Section 1, and FIG. 6 is a waveform diagram of the reference sine wave magnetic pole position signal of FIG. FIG. 7 is a block diagram showing an embodiment of the AC servo motor speed abnormality detection circuit according to the present invention, FIG. 8 is a circuit diagram of a 74th differential circuit example, and FIG. 9 is a 7th example of a rectifier circuit. Circuit diagram, No. 10
This figure is a circuit diagram of the comparator example shown in FIG. 7, and FIG. 11 is a block diagram showing another embodiment of the speed abnormality detection circuit for an AC servo motor according to the present invention. 1... Speed command voltage, 2... Speed signal, 3... Speed error amplifier, 4... Current error amplifier (current control circuit), 5... Main circuit (power circuit), 6... ·Current transformer,
8... Speed detector, 9... Armature current signal, 10.
...Speed deviation (1,16...AC servo motor (D
C brushless motor), 17... magnetic pole position detector, 1
8... Magnetic pole position detector path, 19... Reference sine wave magnetic pole position signal, 2°... Multiplier, 23... Differentiation circuit, 2
5... Rectifier circuit, 27... Comparator, 28... Abnormal signal, 31... Comparator 1-+ mouth $2121 R3 rRz TR4 easy 3 day 4 4th figure $ 5 defense $61211 book ? t21 s8 day

Claims (1)

[Claims] 1. An AC servo motor having a speed detector and a magnetic pole position detector, and comparing and amplifying the speed command of the motor and the speed signal from the speed detector to generate a signal proportional to the torque of the motor. an amplifier for outputting, a magnetic pole position detection circuit that obtains a reference sine wave magnetic pole position signal which is a sine wave signal with a constant machine width from the magnetic pole position signal from the magnetic pole position detector, and the reference sine wave magnetic pole position signal and the output of the amplifier. In an AC servo system consisting of a power circuit and a current control circuit that controls a motor primary current using the output of the multiplier as a current command, a differentiation circuit that differentiates the reference sine wave magnetic pole position signal; A speed abnormality detection circuit comprising a comparator that compares the output of the differentiating circuit with the speed signal from the speed detector and outputs a speed abnormality signal when the difference exceeds a predetermined value. 2. An AC servo motor having a speed detector and a magnetic pole position detector, an amplifier that compares and amplifies the speed command of the motor and the speed signal from the speed detector and outputs a signal proportional to the torque of the motor; a magnetic pole position detection circuit that obtains a reference sine wave magnetic pole position signal that is a sine wave signal with a constant amplitude from a magnetic pole position signal from a magnetic pole position detector; a multiplier that multiplies the reference sine wave magnetic pole position signal by the output of the amplifier; In an AC servo system consisting of a current control circuit and a power circuit that control the motor primary current using the multiplier output as a current command, there is a differentiating circuit that differentiates the reference sine wave magnetic pole position signal, and the output of the differentiating circuit is set to a predetermined standard. A speed abnormality detection circuit comprising a comparator that compares the output with the voltage and outputs a speed abnormality signal when the output exceeds a reference snow pressure.