JPS5810210A - Position controller - Google Patents

Abstract

PURPOSE:To detect and discriminate the stop state of a servomotor with high accuracy, by eliminating an oscillation of an output value of a deviation counter, through the storage of the output value once in a register, in detecting the stop state. CONSTITUTION:A register 26 and a subtractor 28 are connected to an output terminal of a deviation counter 12, an output value S2 of the counter 12 is stored in a register 26 and this storage value S3 and the output value S2 of the deviation counter 12 are subtracted at a subtractor 28. A subtraction value S4 of the subtractor 28 is compared with a set value through a setter 30 and a comparator 32. The output of the comparator 32 is inputted to the register 26 with the AND condition of a sampling clock CLK at an AND gate 34. Thus, the output of the comparator 32 is inputted to the register 26 under the AND condition with the sampling clock CLK via the AND gate 34 and the output value S2 of the deviation counter 12 is stored to the register 26.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital position control device for automatically positioning various types of control machines, and more particularly to a position control device for positioning a stop position of a control machine with high precision.

Conventionally, this type of position control device uses a servo motor to control a controlled object such as a controlled machine based on a command signal from a position command device, and also detects the speed and position of the servo motor and uses these detection signals. A method of feedback controlling a servo motor based on this is generally known.

FIG. 1 is a block diagram showing a conventional position control device. In FIG.
is a servo amplifier, /♂ is a control pair 45. a servo motor that controls zo; 22 is a speed detector for the servo motor/f;
11 is a servo motor/zip position j; J detector. The position control device configured in this way generates a command pulse 81 from the position command device io, and calculates the deviation between this command pulse S1 and the position No. 1 of the servo motor /1 detected by the position detector cog. Calculate with counter 7.2. The deviation ft4 S2 obtained by the deviation counter/co in this way is
)/A converter/l converts it into an analog signal and supplies it as a control signal to the servo motor/g via the servo amplifier/l.

What? , the servo motor/which speed signal f detected by the speed detector, 2.2, is fed back to the analog signal obtained by (1)/A converter l≠.

In the above-mentioned conventional position control device, in order to obtain a highly accurate stop F position, the servo gain is increased and the device is configured so that there is no pulse error.

However, in general, for the controlled object 20, it is common to perform sequence control at the same time as position control, and in this case, to determine the timing of position control and sequence control, it is necessary to determine which state of the servo motor is stopped. There is a need. As a means of determining the stopped state of this type of servo motor /l, for example, a method of determining based on the output value of the deviation counter /2 is extremely simple, but as shown in Fig. 2,
When stopped (deviation counter/deviation signal S2 in Al
Since there are minute vibrations, the above-mentioned discrimination becomes difficult.

Therefore, the inventor of the present invention conducted various studies to properly determine whether the servo motor is stopped in the conventional position control device described above, and as a result, connected a register and a subtracter to the output terminal of the deviation counter. , the output value of the deviation counter is stored and held in a register, and this stored value is subtracted from the output value of the deviation counter in a subtracter, and the obtained calculated value is used to remove all the effects that occur in the output value of the deviation counter. If there is a difference between the calculated value and the set value by comparing it with a sufficient set value, the stored value in the register is updated under the AND condition with the sampling clock, and the output value of the deviation counter is set until the operation stops. It has been found that when a vibration state occurs, the stored value of the VC register is held at a predetermined level, and the stopped state of the servo motor can be properly determined and detected.

Therefore, an object of the present invention is to provide a position control device that performs automatic positioning using a feedback control method and is capable of detecting and determining the stopped state of a servo motor with high precision from signals from the feedback control system accompanied by minute vibrations. is to provide.

In order to achieve the above object, the present invention includes a position command device and a servo motor, detects the position of the servo motor with a position detector, and uses this detection signal to compare the command signal from the position command device. The position control device, which is configured to calculate the deviation using a deviation counter and perform feedback control of the servo motor, sequentially stores and holds the output value of the deviation counter at a predetermined timing, and maintains the output value of the deviation counter in a constant vibration state. The present invention is characterized in that a stop state determination circuit is provided, which includes a register that outputs a signal at a predetermined level when .

In the above position control device, the stop state determination circuit includes a subtracter that inputs and subtracts the output value of the deviation counter from a value stored in a register that stores the entire output value of the deviation counter, and a calculated value of the subtracter. It is preferable to include a comparator that compares the output of the comparator with a set value determined by a setter, and an AND gate that determines an AND condition between the output of the comparator and a sampling clock and supplies a command signal to the register.

It is preferable that the setting device of the stop state discrimination circuit sets the level of the set value in response to the vibration value that occurs after the deviation counter generates the output value of the stop position.

Next, embodiments of a position control device according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 3 is a block diagram showing one embodiment of the device of the present invention. For convenience of explanation, the same reference numerals are given to the same components as those of the apparatus shown in FIG. 1, and detailed explanation thereof will be omitted.

That is, in this embodiment, the feedback control loop for controlling the servo motor /j by the position command device IQ is exactly the same as the device shown in FIG.

In this embodiment, a register 24 and a subtracter 2r are connected to the output terminal of the deviation counter /2, and a register 24 and a subtracter 2r are connected to the output terminal of the deviation counter
The output value st'1 of the deviation counter/2 is stored in &, and the stored value S, and the output value S2 of the deviation counter/2 are stored in the output value st'1.
and is subtracted by a subtracter, 2t. Further, a setter 30 and three comparators are provided to compare the calculated value S4f of the subtracter 21 with the set value. Then, the output of the comparator 32 is converted to the AND gate 3.
4! The configuration is such that it is input to the register 2B under an AND condition with the sampling clock OLK.

Next, the operation of the circuit configured as described above will be explained.

Now, let the setting values in the setting device 30 be "O" and "l",
The comparator 3.2 outputs the subtractor 1f4' when the calculated value S4 of the subtractor 2F and the set value [O/J, "/#I" differ. In this case, the comparator 32 outputs the subtractor 3.2. An output is generated when the calculated value 84 of the device 2r becomes equal to or greater than ",2" or equal to or less than r-/J. The output of the comparator 3.2 obtained in this way is inputted to the register 2B under the AND condition with the sampling clock OLK via the AND gate JIA, and the output value S2 of the deviation counter 12 at this time is input to the register 2B. register 2
6.

The time chart i of the above-mentioned operation is as shown in Figures 1 and 1. Note that FIG. 1 shows the normal rotation state of the servo motor/r.

FIG. 1 shows the reversed state of servo morley/r.

That is, in Fig. 1, when the output value St of the deviation counter/λ (Fig. 1 (1)) gradually decreases and becomes a vibration state, the deviation counter/λ is outputting a drive signal pulse for the servo motor IT. Sometimes the sampling clock [μth
The output value 82 of the deviation counter 12 is sequentially stored under the AND condition with [Figure (2)] [Figure (3)]. In addition, the calculated value S4 in the subtractor 2r in this case is shown in Fig. μ (
4). Therefore, when the output value 82 of the deviation counter /λ enters an oscillating state where it changes from N to N+/, the calculated value S4 at the subtractor 2r becomes "O", r/J
Since this is a change, it matches the setting value of the setting device 30, the comparator 3.2 becomes a non-output state, and the stored value 83 of this register 2B holds N. Therefore, before starting the drive of the servo motor it, the stored value S in the register 2B is read, and after driving the servo motor /l, the stored value S in the register t is read.

The stopped state can be determined at the point (A) where the value coincides with the value before the start of driving.

Moreover, in the case of the reverse rotation state of the servo motor /l shown in FIG. 1, the stored value of the register 2t is 8! during deceleration! changes by 2 for each odd or even value (Figure 1 (3)). However, in this case as well, the output value of the deviation counter/λ is 8. When it enters a vibration state in which it changes from N to N+/, the stored values S and N of the register 2t are held.

In addition, in the above-described embodiment, N as the stored value S held in the register 2t means that the system is balanced at a point where it is not O due to an offset or the like.

As is clear from the embodiments described above, according to the present invention,
When detecting the stop state of the position control device from the output value of the deviation counter in the control loop, by once holding the output value of the deviation counter in a register, vibrations in the output value can be removed, and the servo motor can be stopped. It is possible to appropriately detect the state and perform position control and sequence control for the controlled object in a timely manner.

Further, in the present invention, the functions of the register, subtracter, setter, and comparator can be programmed using a computer, and the device can also be made smaller.

Furthermore, in the above-mentioned embodiment, the application is applied to a deviation counter that calculates the deviation by inputting a position command pulse and a position detection signal, but if applied to a current position counter, the servo motor is stopped. It is also possible to remove the vibration of the current position counter. That is, in absolute position control, when the value of the origin is preset in the current position counter, the present invention is extremely convenient and has the advantage of stabilizing the current position display.

Although the preferred embodiments of the present invention have been described above, it goes without saying that various design changes can be made without departing from the spirit of the present invention.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional position control device, Fig. 1 (1) to (3) are time charts showing operating characteristics of the position control device shown in Fig. 1, and Fig. 3 is a diagram according to the present invention. Block wiring diagram showing one embodiment of the position control device, see Figure (1)
A time chart showing the operating characteristics of the servo motor in the circuit (4) when the servo motor rotates in the forward direction. FIGS. (1) to (4) are time charts showing operating characteristics when the servo motor reverses rotation in the circuit of FIG. 3. 10...Position command unit /2...Deviation counter/l...D/A converter/J °゛°Servo amplifier llr...Servo motor O°°°Controlled object 2.2...Speed Detector, 2≠...Position detector 26...Register -t・°・Subtractor 3
0...Setter 3.2...Comparator 3...And gate Sl...Command pulse S,...Output value of deviation counter S3...Memorized value of register S4...
・Calculated value of subtracter OLK...sampling clock

Claims (1)

[Claims] (1) A position command device and a servo motor are provided, the position of the servo motor is detected by a position detector, and the deviation from the command signal from the position command device is calculated by a deviation counter based on this detection signal. In a position control device configured to perform feedback control of a servo motor, the output value of a deviation counter is stored and held sequentially at a predetermined timing, and when the output value of the deviation counter reaches a certain vibration state, the output value of the deviation counter is stored at a predetermined level. A position control device comprising a stop state determination circuit equipped with a register that outputs a signal. (2. In the position control device according to claim 7, the stop state determination circuit inputs and subtracts the output value of the deviation counter from the stored value of the register that stores and holds the output value of the deviation counter. a comparator that compares the calculated value of the subtracter with the set value determined by the setter, and an AND gate that determines the AND condition between the output of the comparator and the sampling clock and supplies a command signal to the register. (3) In the position control device according to claim 2, the setting device of the stop state discrimination circuit is configured to detect a vibration value generated after the deviation counter generates the output value of the stop position. A position control device that sets the level of the set value in accordance with the