JPH0331912A - Servo controller - Google Patents

Abstract

PURPOSE:To obtain a servo controller to prevent a malfunction beforehand by providing a latch counter to execute a latch with the reference pulse of a free-run counter position detector and an abnormality detecting circuit. CONSTITUTION:A latch counter 9 latches the value of a free counter 7 at the time of inputting a Z phase pulse by a Z phase pulse, namely, reference pulse outputted from a position detector 6. An abnormality detecting circuit 10 discriminates whether the absolute value of the incremental pulse quantity of the latch counter 9 is within a prescribed permissible range or not to the number of pulses per one rotation of the position detector 6. When the difference exceeds the permissible range, the signal of a detection abnormality is transmitted to a pulse distributing circuit 2. Thus, the reliability can be improved, and the servo controller with high accuracy can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a servo control device that detects abnormalities in a position control system and prevents malfunctions.

[Prior Art] In a servo control device that controls position, a servo loop as shown in FIG. 2, for example, has conventionally been implemented. In the figure, (1) is a command decoding circuit that decodes a command from a numerical control device (not shown) to a position control device to determine speed, movement pulse amount, etc., (2> is a command decoding circuit (1)
), (3) is a position control circuit that controls the difference between the command pulse and position feedback to be O, and (4) is a position control circuit (3) that generates a predetermined command pulse according to the output of (5) is the servo motor, (6) is the position detector of the servo motor (5), (7) is the position detector (6)
) is a free-run counter with an up-down counter function that counts the positive and negative feedback pulses from the free-run counter (7), and (7a) is a subtraction circuit that calculates the difference between the current output value and the previous output value of the free-run counter (7). , (8) is an up-down counter similar to the free run counter (7), but it is preset by a two-phase pulse that is a reference pulse output from the position detector (6) at one reference position per rotation. This is a cycle counter.

Next, the operation of this servo loop will be explained. The command to the position control circuit (3) is decoded by the command decoding circuit (1), and the speed, movement pulse amount, etc. are determined. Based on this speed and the amount of movement pulses, the one-pulse distribution circuit (2) outputs the amount of movement pulses per predetermined unit time as a position command. The position control circuit (3) outputs a speed command so that the difference between this position command and position feedback described later becomes 0, and the servo motor (5)
) to drive. The position detector (6) is coupled to the servo motor and outputs a feedback pulse according to the rotation angle and direction of the servo motor (5). This feedback pulse is counted by a free run counter (7),
The difference from the previous value of the free run counter (7) is fed back to the position control circuit (3) by the subtraction circuit (7a) as the amount of movement pulse per unit time of the servo motor 5). Also, the cycle counter (8) counts the foot pulses from the position detector (6) at the same time as the free run counter (7), but the Z-phase pulses from the position detector (6) preset by
When the power is turned on, the position control circuit (3) performs reference point return to set the coordinate system, and detects the magnetic pole position when the servo motor (5) is an AC induction motor, and the output is sent to the Norculus distribution circuit. (Feed Pa Sok to 2).

[Problem to be solved by the invention] Since the conventional position control system is configured as described above,
There is a problem in that if the foot nozzles and nocturnals from the position detector (6) are erroneously counted, correct positioning to a commanded position in an NC processing machine cannot be performed, for example.

This invention was made in order to solve the above-mentioned problem, and when there is a miscount in the foot count from the position detector, the detection abnormality is detected and output at that point, and the malfunction can be prevented. The purpose is to obtain a servo control device that can prevent this.

[Means for Solving the Problems] A servo control device according to the present invention is provided with a latch counter that deceives or counters with a reference pulse of a free run counter position detector, and detects the difference from the previous value every time the reference pulse is input. An abnormality detection circuit is provided which compares the absolute value of 0 with the O value or the number of pulses per rotation of the position detector, and outputs a detected abnormality signal when the difference between the two exceeds a predetermined tolerance range.

[Function] The abnormality detection circuit according to the present invention compares the absolute value of the difference from the previous value of the latch counter with a predetermined value and determines V and lI every time the reference pulse is emitted. malfunctions are detected immediately.

[Embodiment] FIG. 1 is a control loop diagram showing an embodiment of the present invention, and (1) to (8) are the same parts as the conventional device described above. (
9) is a latch counter that latches the free run counter (7) by the Z-phase pulse output from the position detector (6), (9a) is a subtraction circuit that outputs the difference between the current value and the previous value; > determines whether the difference between the absolute value of the difference from the previous value of the latch counter (9) and the number of pulses per rotation of the position detector (6) is within a predetermined tolerance range. This is an abnormality detection circuit that outputs a detected abnormality signal when a predetermined allowable range is exceeded.

Next, the operation will be explained. U-Sochi counter (9) uses the Zt pulse (reference pulse) output from the position detector (6) to counter (7) when the Z-phase pulse is input.
The value of is latched and the difference between the current value and the previous value is set as the increment pulse of the counter (9) in the subtraction circuit (9a).The absolute value of the increment pulse of the counter (9) is It is clear that when the servo motor (5) is rotating in the - constant direction and a new Z control is manually applied, the number of pulses per revolution of the position detector (6) is equal to the number of pulses per rotation of the position detector (6). .

Further, if the servo motor rotates in the opposite direction and returns to its original position midway, the incremental nox becomes 0. Therefore, the abnormality detection circuit (10) detects whether the absolute value of the incremental pulse amount of the latch counter (9) is within a predetermined tolerance range with respect to the number of pulses per rotation of the position detector (6). A determination is made, and if this difference exceeds the allowable range, a detection abnormality signal is sent to the pulse distribution circuit (2). This makes it possible to take measures such as stopping the pulse distribution and displaying a message to that effect on the display of the position control circuit (3).

In addition, in the above embodiment, an example was shown regarding the erroneous count of the free run counter (7) in the position control system, but this invention is also applicable to the reference point return or the magnetic pole position when the servo motor (5) is an AC induction motor. It can also be used to detect an erroneous count of the cycle counter (8) used for detection, or to detect an erroneous count of a free run counter in a speed control system.

[Effects of the Invention] As described above, according to the present invention, there is provided a latch that latches the erroneous counting of feedback pulses from the position detector of the servo motor that is the controlled object in the position control system using the reference pulse from the position detector. By providing a counter and an abnormality detection circuit that determines the allowable value for miscounting based on this output, we have created a control system that can immediately respond to abnormal conditions in the servo motor, resulting in improved reliability and high precision. A servo control device is obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a servo control device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of the configuration of a conventional servo control device. In the figure, (5> is a servo motor, (6) is a position detector, (7) is a free run counter (up/down counter), (9) is a latch counter, (9a> is a compensator circuit,
(10) is an abnormality detection circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] an up/down counter that counts feedback pulses from a position detector of the servo motor; a latch counter that latches the up/down counter using a reference pulse output from the position detector for each rotation of the servo motor; It is equipped with an abnormality detection circuit that calculates the difference from the previous value, compares the absolute value of this difference with the reference pulse number from the position detector, and outputs an abnormal signal when a predetermined tolerance value is exceeded. A servo control device characterized by: