JPH09105644A - Method and apparatus for detection of failure of position detection circuit of ac servomotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a failure detection method and a detection apparatus by which the failure of a position detection circuit of an AC servomotor with an incremental encoder can be detected without having a coarse-density-type angular position detection means and which can prevent a secondary trouble from being generated. SOLUTION: Position data are counted by a position-data counting circuit 14 on the basis of a position detection signal 31 from an incremental encoder 3. A CPU 10 estimates a present magnetic-pole position on the basis of the counted position data, on the basis of reference position data and reference magnetic-pole-position data which are stored in a memory 11 in advance, on the basis of the number of poles of an AC servomotor 2 and on the basis of the number of encoder pulses of the incremental encoder 3. The estimated present magnetic-pole position is compared with present magnetic-pole position data which has been fetched by a magnetic-pole detection circuit 13 on the basis of a magnetic-pole signal 33 from the incremental encoder 3. When the difference in a position is not within a predetermined tolerance, the failure of a position detection circuit is judged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for detecting a failure of a position detection circuit of an AC servo motor, and more particularly to a method and a device for detecting a failure of an AC servo motor having an incremental encoder.

[0002]

2. Description of the Related Art For speed detection of an AC servo motor,
Position detection signal PA phase, PB as feedback signal
Phase, 1 rotation detection signal PZ phase, electrical angle signal PU phase, PV
Phase and PW phase are generally used. If the PA phase, the PB phase, or both the PA and PB phases are not input to the control side due to a cable disconnection, an output circuit failure, or the like, position detection becomes impossible and the motor may run away.

A conventional fault detection method and detection device for a position detection circuit of an AC servomotor of this type is disclosed in Japanese Patent Laid-Open No. 63-136989.
C servo motor monitoring device "and JP-A-5-282046.
There is an “AC servomotor control method” disclosed in the publication.

The "AC servo motor monitoring device" disclosed in Japanese Patent Laid-Open No. 63-136989 discloses a conventional control system in which the output of the incremental feedback means (encoder) of the AC servo motor is not normally supplied. As a method for preventing runaway, monitoring was performed using a combination signal of the output of the coarse density angular position detection means and its inverted output, but it may not operate if the pulse coder itself fails. Therefore, it has been proposed as a means for solving the drawback.

That is, as the failure detecting means, a coarse density type angular position detecting means, for example, an absolute pulse encoder and a high density type angular position detecting means, for example, a coarse density detecting unit angle and a high density detecting respectively, which are sequentially detected respectively. The number of high-density detection unit angles that occur during each step period when the unit angle is memorized and each step period in which the value obtained by successively subtracting the coarse density detection unit angle that is sequentially detected is less than or equal to a specific value is detected Is counted and the case where this value is less than a predetermined value is determined to be a failure.

The "AC servomotor control method" disclosed in Japanese Unexamined Patent Publication No. 5-282046 is a robot or machine tool in which the distance between the drive unit and the control circuit is long and the electric wire itself often slides. , Noise on the wire,
It has been proposed as a means for solving the hindrance of accurate detection of the magnetic pole position that occurs when a wire breakage occurs.

That is, after the initialization by the absolute position data, the magnetic pole position detection counter for inputting the position detection signal, the electrical angle 0 degree vicinity determination circuit for inputting the output of the counter, and the output of the determination circuit. And an origin position signal, the origin position of the magnetic pole position data detected by the counter is compared with the origin position detected by the origin position detection signal, and origin detection is performed outside the origin. If it is, it is judged as abnormal.

[0008]

The first problem is that in the prior art, when the position detection signal cannot be detected due to the position detection circuit failure of the incremental encoder, high speed failure detection becomes impossible. At Z
This means that if the axis moves vertically like the axis, it will fall.

The reason is that, if either or both of the position detection signals PA and PB are fixed to a certain voltage level due to a failure of the detection circuit of the incremental encoder, the motor control is performed even if the axis moving in the vertical direction falls. This is because it is very difficult for the unit to judge that the position data counted from the position detection signal is abnormal.

Here, according to the prior art shown in the above-mentioned "AC servomotor monitoring device", this problem can be solved, but in the case of a device having no coarse density type angular position detecting means, There is a problem that it is not applied.

Further, in the conventional technique shown in the "AC servo motor control method", the maximum of the motor is 1 before the abnormality is detected.
For example, when the machining tool attached to the Z-axis and the work on the XY table are very close to each other, the tool and the work collide with each other because of the rotation.

An object of the present invention is to provide an AC having an incremental encoder without a coarse density type angular position detecting means.
Detects failure of servo motor position detection circuit at high speed and
It is an object of the present invention to provide a failure detection method and a detection device capable of preventing the occurrence of a subsequent failure.

[0013]

A method of detecting a failure of a position detection circuit of an AC servo motor according to the present invention is a method of detecting a failure of a position detection circuit of an AC servo motor having an incremental encoder, in which a position is detected from a position detection signal of the incremental encoder. The data is counted, and the current magnetic pole position is estimated from the counted position data, the previously stored reference position data, the reference magnetic pole position data, the number of poles of the AC servo motor, and the number of encoder pulses of the incremental encoder. The current magnetic pole position is compared with the current magnetic pole position data fetched from the magnetic pole signal of the incremental encoder, and if the difference between the positions is not within a predetermined allowable range, it is determined that the position detection circuit has failed.

Further, the number of poles of the AC servo motor used for estimating the current magnetic pole position and the number of encoder pulses of the incremental encoder correspond to the AC servo motor to be controlled and the incremental encoder, and are arbitrarily notified by an external notice. May be configurable.

A failure detection device for a position detection circuit of an AC servo motor according to the present invention is a failure detection device for a position detection circuit of an AC servo motor having an incremental encoder, which represents a magnetic pole state by inputting a magnetic pole signal from the incremental encoder. A magnetic pole detection circuit that outputs magnetic pole position data; a position data counting circuit that counts the position detection signal and the one-rotation detection signal from the incremental encoder as inputs and outputs the position data as position data;
A magnetic pole change detection circuit that detects a change in the magnetic pole signal and outputs it as a magnetic pole change detection signal, a magnetic pole data latch circuit that holds the output of the magnetic pole detection circuit as a reference value by inputting the magnetic pole change detection signal, and a magnetic pole change detection signal A position data latch circuit that holds the output of the position data counting circuit as a reference value by input, a reference value output from the magnetic pole data latch circuit and the position data latch circuit, the number of input AC servo motor poles, and an encoder for an incremental encoder. The number of pulses is stored in the memory means, the counted position data, the reference position data and the reference magnetic pole position data stored in advance in the memory means, the number of poles of the AC servo motor, and the number of encoder pulses of the incremental encoder are used to obtain the current value. The magnetic pole position is estimated, and the estimated current magnetic pole position and A calculation that compares the current magnetic pole position data output from the detection circuit and, if the position difference is not within a predetermined allowable range, determines that the position detection circuit has failed and outputs it to the control unit of the AC servo motor. And means.

In the AC servo motor position detection circuit failure detection method and apparatus of the present invention, the position detection signals PA and P are detected due to the failure of the detection circuit of the incremental encoder.
Even if either or both of B is fixed to a certain voltage level, the AC servo motor will not exceed maximum 60 ° +
It is possible to determine that the position data counted from the position detection signal is abnormal by rotating the position by a preset allowable range ".

[0017]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block configuration diagram of an AC servo motor failure detection device according to an embodiment of the present invention, and FIG. 2 is a graph for explaining magnetic pole position data output from a magnetic pole detection circuit of a three-phase AC servo motor.

In the figure, reference numeral 1 is a motor control unit of an AC servo motor, 2 is an AC servo motor to be controlled, 3 is an incremental encoder, 31 to 33 are signals output from the incremental encoder 3, and 31 is a position detection signal PA. , PB, 32 are one-rotation detection signals PZ, 33 are magnetic pole signals PU, PV, PW, and 4 is a main control unit for controlling the entire apparatus by communicating command data and alarm data with the motor control unit 1.

Reference numerals 10 to 17 are respective circuits constituting the motor control unit 1, 10 is a CPU which controls various positions such as the position, speed, current and alarm of the AC servomotor, and 11 is a CP.
U10 is a memory, 12 is a drive circuit for exchanging data by communication with the CPU 10, and a drive circuit for supplying drive power to the AC servomotor 2, 13 is a magnetic pole signal 33PU, PV, PW from the incremental encoder 3 As a magnetic pole detection circuit that indicates the state of the magnetic pole, 14 is a position data counting circuit that counts position data by inputting the position detection signals 31PA, PB and one rotation detection signal 32PZ, and 15 detects changes in the magnetic pole signals 33PU, PV, PW. A magnetic pole change detection circuit, 16 is a magnetic pole data latch circuit that holds the output of the magnetic pole detection circuit 13 by the output of the magnetic pole change detection circuit 15, and 17 is an output of the position data counting circuit 14 by the output of the magnetic pole change detection circuit 15. It is a position data latch circuit. The memory 11 stores the outputs of the magnetic pole data latch circuit 16 and the position data latch circuit 17.

Generally, when an AC servomotor is manufactured, the electrical angle of 0 ° generated in one reference phase and the origin position signal of the incremental encoder are set to substantially match. Further, due to the structure of the three-phase AC servomotor 2, the magnetic pole position data output from the magnetic pole detection circuit 15 is shown in FIG.
There are only 6 types, as shown in
It changes every 0 °. Further, the output of the position data counting circuit 14 is increased due to changes in the position detection circuits 31PA and PB.
Although the down is performed, the count value for one rotation of the AC servomotor 2 is expressed as E / (P / 2), where E (p / rev) is the encoder pulse number and P (pole) is the motor pole number. . That is, when the electrical angle changes by 360 °, the count number changes by E / (P / 2) = 2 × E / P.

In order to determine the reference point, the magnetic pole position data output from the magnetic pole detection circuit 13 and the position data output from the position data counting circuit 14 when the AC servomotor 2 rotates and the magnetic pole position data changes. Are stored as reference values. Next, the position data at any given time is detected regardless of the change in the magnetic pole position data, and is compared with the data stored as the reference value. If the count value is "reference position data + 2 x E / P", then A
The C servo motor 2 takes one rotation to obtain the same magnetic pole position data as when the reference position data was stored, and if the count value is “reference position data + E / (3 × P)”, the AC servo motor 2 has 60 °. Since it is rotating, it can be estimated that the electrical angle deviates from the reference value of the reference position data by 60 °.

That is, by detecting the position data at a certain time and comparing it with the position data stored as the reference value, the range in which the magnetic pole position of the AC servomotor 2 exists can be estimated. Therefore, from the relationship between the magnetic pole position data and the magnetic pole position estimated from the position data, if the magnetic pole position estimated from the position data is not within the predetermined allowable range, it can be determined that the position detection circuit has failed. .

Since the magnetic pole position data and the reference value of the position data only have to be detected and stored only once, generally, when the AC servomotor 2 is turned on and first rotated, it becomes 1 Detected only once.

Next, the operation of the embodiment of the present invention will be described in detail. The magnetic pole signal 3 from the incremental encoder 3 is generated by the rotation of the AC servo motor 2.
3PU, PV, PW and position detection signals 31PA, P
B, 1 rotation detection signal 32PZ is the magnetic pole detection circuit 1
3 and the position data counting circuit 14 and the signal P
The magnetic pole position data indicating the states of U, PV, and PW and the position data that is the count result of the signals PA and PB are output from the magnetic pole detection circuit 13 and the position data detection circuit 14, respectively. At this time, when the value of any of the signals PU, PV, PW changes at some point, the output of the magnetic pole change detection circuit 15 is input to the magnetic pole data latch circuit 16 and the position data latch circuit 17, and the magnetic pole data latch circuit 16 and The position data latch circuit 17 holds the outputs of the magnetic pole detection circuit 13 and the position data counter circuit 14 as a magnetic pole position data reference value and a position data reference value, respectively. C
The PU 10 internally takes in the magnetic pole position data reference value and the position data reference value held in the magnetic pole data latch circuit 16 and the position data latch circuit 17 only once at an arbitrary time and stores them in the memory 11.

Next, the CPU 10 internally takes in the outputs of the magnetic pole detection circuit 13 and the position data counting circuit 14 as magnetic pole position data and position data at arbitrary time intervals, and stores the magnetic pole position data stored in the memory 11. The current magnetic pole position is calculated using the reference value, position data reference value, and the position data acquired this time, and the calculated magnetic pole position is compared with the value of the magnetic pole position data acquired this time, and is included in the predetermined allowable range. If not, it is determined that the position detection circuit has failed.

Here, the encoder pulse number E (p / re
v), the count value for one revolution of the AC servomotor changes depending on the value of the number of motor poles P (poles), which is represented by 2 × E / P, but the encoder pulse is generated by the data transfer from the main control unit 4. The number E and the number of motor poles P are calculated by the CPU
Since it can be notified to 10 and stored in the memory 11, the present invention can be applied to an incremental encoder having an arbitrary encoder pulse number E and an AC servomotor having an arbitrary motor pole number P.

[0027]

As described above, according to the present invention, even if the position detection signal cannot be detected due to the failure of the position detection circuit of the incremental encoder, the high-speed operation without the coarse density type angular position detection means is required. Failure detection is possible,
For example, there is an effect that it is possible to prevent a fall accident of a vertically moving axis such as the Z axis of a machine tool.

The reason for this is that even if either or both of the position detection signals PA and PB are fixed to a certain voltage level due to a failure of the detection circuit of the incremental encoder, the AC servo motor sets a maximum of "60 ° + preset". This is because it is possible to determine that the position data counted from the position detection signal is abnormal if the rotation is performed by the "allowable range".

As a result, the device having the failure detection method of the present invention is very effective in ensuring the reliability for the normal AC servo motor drive.

[Brief description of the drawings]

FIG. 1 is a block configuration diagram of an AC servomotor failure detection device according to an embodiment of the present invention.

FIG. 2 is a graph illustrating magnetic pole position data output from a magnetic pole detection circuit of a three-phase AC servomotor.

[Explanation of symbols]

 1 Motor Control Unit 2 AC Servo Motor 3 Incremental Encoder 4 Main Control Unit 10 CPU 11 Memory 12 Drive Circuit 13 Magnetic Pole Detection Circuit 14 Position Data Counting Circuit 15 Magnetic Pole Change Detection Circuit 16 Magnetic Pole Data Latch Circuit 17 Position Data Latch Circuit 31 Position Detection Signal PA, PB 32 1 rotation detection signal PZ 33 Magnetic pole signal PU, PV, PW

Claims (3)

[Claims] 1. An A having an incremental encoder.
In a method of detecting a failure of a position detection circuit of a C servo motor, position data is counted from a position detection signal of the incremental encoder, and the counted position data and prestored reference position data and reference magnetic pole position data and the AC servo are stored. The current magnetic pole position is estimated from the number of poles of the motor and the encoder pulse number of the incremental encoder, and the estimated current magnetic pole position is compared with the current magnetic pole position data fetched from the magnetic pole signal of the incremental encoder. A method for detecting a failure of a position detection circuit of an AC servo motor, characterized in that if the position difference is not within a predetermined allowable range, it is determined that the position detection circuit has failed. 2. The AC servo motor position detection circuit failure detection method according to claim 1, wherein the number of poles of the AC servo motor used to estimate the current magnetic pole position and the number of encoder pulses of the incremental encoder are A method for detecting a failure of a position detection circuit of an AC servo motor, which can be arbitrarily set by a notification from the outside in correspondence with the AC servo motor and the incremental encoder to be controlled. 3. A having an incremental encoder
In a failure detection device for a position detection circuit of a C servo motor, a magnetic pole detection circuit that receives a magnetic pole signal from the incremental encoder and outputs it as magnetic pole position data indicating the state of the magnetic pole, a position detection signal from the incremental encoder, and one revolution A position data counting circuit that counts a detection signal as an input and outputs it as position data; a magnetic pole change detection circuit that detects a change in the magnetic pole signal and outputs it as a magnetic pole change detection signal; A magnetic pole data latch circuit for holding the output of the magnetic pole detection circuit as a reference value; a position data latch circuit for holding the output of the position data counting circuit as a reference value by inputting the magnetic pole change detection signal; and the magnetic pole data latch circuit. The reference value output from the position data latch circuit and Memory means for storing the number of applied poles of the AC servomotor and the number of encoder pulses of the incremental encoder; and the counted position data and reference position data and reference magnetic pole position data stored in advance in the memory means, The current magnetic pole position is estimated from the number of poles of the AC servo motor and the number of encoder pulses of the incremental encoder, and the estimated current magnetic pole position is compared with the current magnetic pole position data output from the magnetic pole detection circuit. , If the position difference is not within the predetermined tolerance,
A failure detection device for the position detection circuit of the AC servo motor, comprising: a calculating unit that determines that the position detection circuit has a failure and outputs it to the control unit of the AC servo motor.