JP2002350184A - Failure detection method for encoder for ac servo - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a failure diagnostic method for an encoder for an AC servo in which the failure of the encoder can be diagnosed surely by checking a counter value. SOLUTION: The failure detection method for the encoder for the AC servo comprises three pole sensor signals U, V, W synchronized with a phase A, a phase B and three-phase magnetic poles of a motor. When one phase from among the phase A and the phase B or both are out of order, a phase-A counter value and a phase-B counter value 11 which are latched 1 whenever the pole sensor signals U, V, W are changed are read out so as to be compared with previous values, the rotation of the motor is judged, and the failure at the phase A and the phase B is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for diagnosing an encoder failure of an AC servo controller.

[0002]

2. Description of the Related Art A conventional AC servo controller is shown in FIG.
As shown in FIG. 5, the A and B phases (for example, 1000 P / R, 2000 P / R, etc.) referred to as resolution pulses are synchronized with the three-phase magnetic poles U, V, and W of the respective motors whose detailed time chart is shown in FIG. It has output signals U, V, W of three pole sensors. Normally, the AC servomotor forms a speed / position control loop by using this detected value as fb data as shown in the control block diagram of FIG. 6 by raising and lowering the position counter 11 by the A and B phase resolution pulses. Is controlling the servo motor. Here, considering the case where one of the phases A and B fails and the pulse is fixed to the low level and the pulse is not output, the counter value which increases from 1 to 13 in the normal state as shown in FIG. As shown in FIG. 8, no matter how the motor rotates, the counter value repeats ± 1, and there is no more count-up or count-down. When this happens A
Even if the C servo controller 10 applies a current to rotate the motor, the AC servo controller determines that the position of the motor has not changed, and further supplies the current, which is different from the original command position. In the worst case, the motor runs out of control.

[0003]

However, in the above-mentioned conventional example, there is no method for avoiding runaway when a failure occurs due to an element failure, external noise, or the like.
There is a problem that a large machine such as a device may lead to destruction of the device or personal injury. Therefore, according to the present invention, A and B latch each time the pole sensor signal changes.
An object of the present invention is to provide a method for detecting a failure of an AC servo encoder capable of accurately detecting a failure of an encoder and preventing runaway by determining a rotation of a motor by reading a phase counter value and comparing with a previous value. .

[0004]

In order to achieve the above object, an invention according to claim 1 is an AC servo encoder having three pole sensor signals synchronized with A, B phases and three phase magnetic poles of a motor. When one or both of the phases A and B fail, the latched A and B phase counter values are read each time the pole sensor signal changes, and compared with the previous values, Judging rotation, A,
It is characterized by detecting a B-phase failure. The invention according to claim 2 is characterized in that when the first latch A and B phase counter values X1 are compared with the next A and B phase counter values X2 to determine the rotation of the motor, X = X2-X1 , -1 ≦ X
In the case of ≤ + 1, it is characterized that a failure is determined. According to the failure detection method of the AC servo encoder, when the encoder is normal, the counter value increases (increments) from 1 to 13 as shown in FIG. 7. Therefore, when the failure is shown in FIG. Just moving between 1 will not increase. Therefore, the comparison value between the current counter value X2 and the previous count value X1 is within ± 1, that is, X = X2−X1, and −
If 1 ≦ X ≦ + 1, it can be determined that a failure has occurred.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a failure detection method for an AC servo encoder according to an embodiment of the present invention. FIG. 2 is a time chart of the signals of the encoder shown in FIG. FIG. 3 is a flowchart of the encoder failure detection method shown in FIG. In FIG. 1, the configuration different from the conventional diagram shown in FIG. 4 is that a differentiating circuit 2 for detecting an edge of a pole sensor signal and a latch circuit 1 for latching a counter value by an edge of the pole sensor signal.
Is added. The other components of the microcomputer 10 and the position counter 11 constituting the AC servo controller are the same. Next, the operation will be described. Now, it is assumed that the AC servo controller gives a rotation command to the motor, passes a current to the motor, and the motor starts to rotate. When the pole sensor edge (a) shown in FIG. 2 comes, the microcomputer 10 determines the state of the pole sensors U, V, W (U = Hi, V = Lo).
w, W = Low), and the values of the A and B phase counters latched by the latch circuit 1 in (a) are stored as X1. Then, at the next pole sensor edge (b), the state of the pole sensors U, V, W (U = Hi, V = Hi, W = L)
ow), and the values of the A and B phase counters latched in (b) are stored as X2. X1 is compared with X2. If it is larger than ± 1, it is regarded as normal, the value of X2 is stored as X1, the original value of X1 is discarded, and the next pole sensor edge is awaited. If the comparison value is within ± 1, it will be an alarm. In this case, since the phase B is faulty, the counter value is smaller than ± 1 as shown in FIG. 8, so that an alarm always occurs and a fault can be detected. Next, after the power is turned on, the microcomputer 10
About the failure detection routine executed as monitoring processing by
This will be described in detail with reference to FIG. First, an edge interruption of the pole sensor signals U, V, W is performed (S100). Check the number of interrupts. It is determined whether the interrupt is the first interrupt after the power is turned on (S101). If it is the first time, the A and B latch counters are read (S102), and the counter value is stored as X1 (S103). This is the process at point (a). S
If the interruption is the second or later in the judgment of 101, it is judged whether or not the point (a) has moved to the point (b) (S10).
4). If it has moved to (b), the A and B latch counters are read, and the counter value is stored as X2 (S105). Next, as a comparison of the counter values, X = X
2−X1, and it is determined whether X is within −1 ≦ X ≦ + 1 (S106). If −1 ≦ X ≦ + 1, a warning is issued by alarm processing. If −1 ≦ X ≦ + 1 or more, it is regarded as normal, and X2 is replaced with new X1 and stored.
107). When the failure diagnosis routine is completed, the encoder determines that the encoder is normal, and starts a steady operation based on the position command as shown in FIG. Feedback count value of motor rotation detected by encoder (Pfb)
Then, the position controller outputs a speed command Va based on the deviation from the position command Pa. The speed controller differentiates the speed feedback value from the encoder value to obtain a deviation from the speed command Va, and outputs a current command Ia. The current control unit outputs a voltage command to be applied to the inverter to drive the motor. Thus, the servo control is performed by configuring the position control loop and the speed control loop with the encoder output.

[0006]

As described above, according to the present invention,
Whenever the pole sensor signal changes, the AC servo controller reads the latched value of the A and B phase counters X2 and compares it with the previous counter value X1 to determine the rotation of the motor, thereby detecting the failure of the A and B phases. There is an effect that the motor can be prevented from running away by reliably detecting.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a failure diagnosis method for an AC servo encoder according to an embodiment of the present invention.

FIG. 2 is a time chart of signals of the encoder shown in FIG. 1;

FIG. 3 is a flowchart of the encoder failure diagnosis method shown in FIG. 1;

FIG. 4 is a configuration diagram of a conventional AC servo encoder.

FIG. 5 is a time chart of signals of the encoder shown in FIG. 4;

FIG. 6 is a servo control block diagram using the encoder shown in FIG. 4;

7 is a diagram showing an AB phase counter value when the encoder shown in FIG. 4 is normal.

8 is a diagram showing a counter value at the time of failure of the encoder shown in FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Latch circuit 2 Differentiator circuit 10 Microcomputer 11 Counter

Claims (2)

[Claims] 1. A method of detecting a failure of an AC servo encoder having three pole sensor signals synchronized with the A and B phases and a three-phase magnetic pole of a motor, the method comprising the steps of: The AC servo servo is characterized by reading the latched values of the A and B phases each time the pole sensor signal changes, comparing the value with the previous value to determine the rotation of the motor, and detecting a failure in the A and B phases. Encoder failure detection method. 2. The first latch A, B phase counter value X
When determining the rotation of the motor by comparing 1 with the next A and B phase counter values X2, X = X2-X1, -1 ≦ X ≦ ± 1,
2. The failure detection method for an AC servo encoder according to claim 1, wherein the failure is determined in the case of (1).