JPS5972515A - Diagnosing system of position feedback loop function - Google Patents

Abstract

PURPOSE:To decide a fault of a feedback loop when the contents of an error register are not set at zero after a dummy pulse is applied to the error register from a numerical controller to actuate a servo mechanism and then the contents of the error register are checked. CONSTITUTION:When a power supply is applied to a numerical controller, a prescribed number of dummy pulses are supplied to an error register 3 via an adder 2. The output of the register 3 undergoes a D/A conversion through a servo unit 4 and is amplified. Thus a motor 5 is revolved to set the contents of the register 3 at 0. The controller 1 reads the contents of the register 3 after a fixed time elapses. When the contents show 0, it is decided that a position feedback loop is nondefective. While a fault is decided with the feedback loop when the contents of the register 3 are not 0. Thus the power supply of the motor 5 is turned off, and an alarm is delivered. This check is possible at an optional time point with operation of a keyboard 8. Thus an assured diagnosis is possible to the position feedback loop, and the runaway is prevented with a servo system.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a position feedback loop function diagnosis method for diagnosing the function of a position feedback loop.

Prior Art and Problems In numerically controlled machine tools (1), a position feedback loop is generally formed using a position detector that detects the rotation angle position of a servo motor or machine position, and the rotation angle or machine position and numerical value are The operation of the servo motor is controlled so that the difference from the command value from the control device is zero.By the way, in a numerically controlled machine tool equipped with such a position feedback loop, the position feedback loop(
If two failures occur, the servo motor will run out of control. In order to prevent such runaway of the servo motor, conventionally, the position detector is equipped with an abnormality diagnosis function that sends an abnormality detection signal to the numerical control device when an abnormality in the position feedback loop is detected. The numerical control device detects an abnormality in the position feedback loop and turns off the excitation of the servo motor based on the abnormality detection signal from the abnormality diagnosis function.

However, in this conventional method, the numerical control device indirectly detects an abnormality in the position feedback loop based on the abnormality detection signal (2) from the abnormality diagnosis function. If a failure occurs in the position tweed back loop and the operation C1 is not performed normally, the servo motor may run out of control if an abnormality occurs in the position tweed back loop.

OBJECTS OF THE INVENTION The present invention has been made to improve the above-mentioned drawbacks, and its purpose is to make it possible to reliably detect abnormalities in the position feedback loop. Examples will be explained in detail below.

Embodiment of the Invention FIG. 1 is a block diagram of an embodiment of the invention, in which 1 is a numerical control device, 2 is an adder, 6 is an error register, 4 is a servo unit, 5 is a motor, and 6 is an optical encoder. 7 is a table, and 8 is a keyboard. Further, FIG. 2 is a flowchart showing the processing contents of the numerical control device 1 when diagnosing the function of the position feedback loop.

The error register 3 stores the difference between the number of command pulses from the numerical control device 1 and the number of detected pulses from the position detector 6. and motor 5 (in addition to the motor 5)
The motor 5 is driven so that the difference between the rotational angular position and the command value given by the command pulse (2) becomes zero.The above-mentioned operation is already well known.

Next, the operation of the position feedback loop during functional diagnosis will be explained with reference to the flowchart shown in FIG.

When the numerical control device 1 is powered on, it sends out a predetermined number of dummy pulses.

After a certain period of time has elapsed after sending out the dummy pulse, the numerical control device 1 reads the contents of the error register 6 and determines whether the position feedback loop is normal based on the contents (2).In other words, the position feedback loop If it is operating normally, the detection pulse from the position detector 6 cancels the dummy pulse and the contents of the error register 3 become zero, so the numerical control device 1 makes sure that the read contents of the error register B are zero. In this case, it is determined that the position feedback loop is normal, and if there is an abnormality in the position feedback loop, the contents of the error register 6 will not be zero, so the numerical control device 1 will check that the contents of the error register B read are not zero. If so, it is determined that there is an abnormality in the position feedback loop (2), and the excitation of the motor 5 is cut off.

Take measures such as sounding an alarm.

In the embodiment (1), the function of the two-position feedback loop was diagnosed when the power was turned on, but this C1
The operation of the keyboard 8 (from the second,
Of course, the functional diagnosis may be performed at any arbitrary time. In addition, in the embodiment, when diagnosing the function of the position feedback loop formed using the position detector 6 that detects the rotational angular position of the motor 5 (although it has been explained with two Of course, the method of the present invention can be applied to functional diagnosis of a position feedback loop formed using a device.

As described in detail, the present invention applies a dummy pulse to the error register C2 from the numerical control device when diagnosing the function of the position feedback loop, and detects an abnormality in the position feedback loop based on the contents of the error register. Like,
Since the numerical control device directly detects abnormalities in the position feedback loop, the numerical control device indirectly detects the
Compared to the conventional method C1 which detects an abnormality in a two-position feedback loop, this method has the advantage of being able to reliably detect an abnormality in a position feedback loop.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a flowchart showing the processing contents of the numerical control device at the time of functional diagnosis. 1 is a numerical controller, 2 is an adder, 6 is an error register, 4
5 is a servo unit, 5 is a motor, 6 is a position detector, 7 is a table, and 8 is a keyboard. Patent applicant: Representative of FANUC Co., Ltd. Patent attorney: Gobe Tamamushi (6 others)

Claims (1)

[Claims] A position feedback system that determines the difference between the detection result of the position detector and the command pulse from the numerical control device, and diagnoses the function of the position feedback loop equipped with an error register that controls the operation of the servo motor based on the difference (2). In the loop function diagnosis method, during diagnosis, the numerical control device adds a dummy pulse to the error register and star, and diagnoses the function of the position feedback loop based on the contents of the error register. Feedback loop function diagnosis method.