JP2518297B2 - Spindle rotation position control method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a position control method for stopping a spindle of a machine tool at a predetermined stop position.

[Conventional technology]

In a machine tool such as a machining center having a function of automatically changing tools, the tool cannot be changed unless the rotational position of the spindle key for fixing the tool and the position of the key groove of the tool are accurately aligned.

Therefore, in this type of machine tool, the position detector 9 including the magnetic generator 7 such as a permanent magnet attached to the spindle 5 and the magnetic sensor 8 attached to the spindle fixing portion shown in FIG.
As shown in FIG. 5, fixed position stop control is performed using a position detection signal generated once per rotation.

FIG. 6 shows an example of the fixed position stop control system, and FIG. 7 shows its time chart.

In FIG. 6, during the normal speed control, the fixed position stop command device 14 does not operate, and the speed command selection switch 16a opens, 16b.
Is closed and the motor control device 1 with speed control function is NC
The speed command N _COM of the speed commander 15 and the speed detection signal N _FB of the pulse encoder 3 that detects the speed of the motor 2 are used to control the speed of the motor 2, and the transmission 4 using belts, gears, etc. , Drive the spindle 5 at the commanded speed.

With the above speed control, the work such as cutting is completed, and the tool 6
When the replacement is performed, the fixed position stop command device 14 is operated to close the speed command selection switch 16a and open the speed command selection switch 16b. Of FIG.
At this time t ₀ , the speed command is switched to _NORT of the speed command device 20 during the fixed position stop control. The motor control device 1 is
The time at which the motor 2 accelerates or decelerates rapidly so as to match the speed command _NORT , and the speed command and the actual speed almost match.
The speed matching signal AGR is output at t ₁ .

After the speed matching signal AGR is output, the position controller 19
When the signal from the position detector 9 including the magnetic generator 7 attached to the main shaft 5 and the magnetic sensor 8 attached to the main shaft fixing portion is output at time t ₂ , the speed command of the speed command device 20 is changed to _NORT.
To N _CRP, which is a level sufficiently lower than N _ORT . Therefore, the speed command input to the motor control device 1 decreases at a constant rate through the soft starter 21 that generates the ramp function and reaches N _CRP at time t ₃ , so the motor speed also follows this speed command and decelerate. To do. When the deceleration is completed, the deceleration rate of the soft starter 21 is adjusted so that the spindle 5 makes one revolution and reaches the vicinity of the spindle stop. Therefore, when the motor 2, that is, the main shaft 5 follows the speed command N _CRT and rotates for a short time until the time t ₄ and reaches the detection range of the position detector 9, the position controller 19 causes the magnetic sensor 8 to move. With the position detection signal, the position control loop changeover switch 18a is closed and 18b is opened, and the signal N _POS of the position controller 19 is instructed to the motor control device 1 to form a position control loop to form the spindle 5
To a fixed position.

In this way, after the fixed position stopping operation is completed, the tool is replaced and the operation such as the next cutting is performed.

[Problems to be solved by the invention]

As described above, in the conventional control method, the spindle 5
The fixed position stop is performed by the position detection signals of the magnetic generator 7 attached to the main body and the magnetic sensor 8 attached to the main shaft fixing portion. However, in this case, the detection range of the position detector 9 that detects the stop position is one revolution of the main shaft, that is, 360
Since the angle is 20 to 30 °, it is necessary to reach the _NORT speed once, and then it will stop in one rotation.

Therefore, when the fixed position is stopped from the normal stop state, the speed is accelerated up to the speed command _NORT. Therefore, the fixed position must be stopped at least 2 revolutions of the spindle, and the time until the fixed position cannot be shortened. become. That is,
In the magnetic sensor method, there is no position information outside the sensor detection range, so when stopping from a fixed position to a fixed position, first, accelerate to the speed of the speed command _NORT , and after reaching that speed, the sensor signal is sent. Detecting and decelerating without position control,
The sensor signal after one rotation must be used to control the position and stop at a fixed position.

As another method, it is possible to rotate the main shaft at a very low speed and control the position when the sensor detection range is reached.
In this case, there is a problem that it takes a long time to stop.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to stop the fixed position within one rotation of the spindle from an arbitrary stop position to shorten the fixed position stop time. To do.

[Means for solving problems]

In order to achieve this object, a spindle rotational position control method of the present invention is directed to a position detector attached to the spindle for use in fixed position stop control, a motor for driving the spindle via a transmission, and a motor for driving the spindle. In a spindle rotational position control device comprising a pulse encoder for detecting speed and rotational position, and a position controller and a motor control device having a speed control function, a spindle stop position signal from the position detector and setting in the position controller By using the main shaft rotational position signal calculated from the gear ratio of the motor shaft to the main shaft and the motor rotational position based on the pulse encoder signal, the first position control loop based on the calculated main shaft rotational position signal and the position detector. After configuring the second position control loop by the spindle stop position signal, inputting the positioning command, and after detecting the spindle origin signal by the magnetic sensor The position control is performed by the first position control loop, and the detection range of the position detector is stopped at a fixed position by performing the position control by the second position control loop. The feature is that it stops at a fixed position within one rotation of the main shaft.

〔Example〕

Hereinafter, the present invention will be specifically described based on the embodiments shown in the drawings.

As described in the section of the related art, when the fixed position stop control is performed only by the position detector using the magnetic sensor, there are problems such as the inability to stop within one rotation and the long stop time. Therefore, in the present invention, attention is paid to a pulse encoder with a built-in motor, and the main shaft rotational position is calculated as shown in FIG. 2 using the position signal from this pulse encoder, the gear ratio, and the magnetic sensor signal. The example of FIG. 2 is for a gear ratio of 1: 1.5. First, the fixed position stop position is set as the spindle origin. The spindle rotation angle signal is reset to 0 by this spindle origin pulse signal. Next, the pulse output from the pulse encoder of the motor is counted, and the motor shaft rotation angle is calculated by the following formula.

θ _M = (360 ° / N _R ) × N _θ However, N _θ : Number of count pulses N _R : Number of pulses per rotation Further, using the gear ratio R _S , the spindle rotation angle is θ _S = (1 / R _S ) × θ _M = (360 ° / N _R × R _S ) × N _θ . For example, N _R = 4096P / R, N _θ = 1024 pulses, R _S = 1.
When it is set to 5, θ _S = 60 °.

As described above, by having an accurate gear ratio, the pulse encoder of the motor has the same function as the spindle pulse encoder, and the spindle rotation position can be obtained.
Therefore, the fixed position stop from any position is quickly performed.

FIG. 3 shows the spindle angle and speed from the arbitrary stop position θ _x to the fixed position stop by the conventional method and the method of the present invention.

FIG. 1 is a block diagram of an embodiment of a spindle position control method to which the control method of the present invention is applied. In FIG. 1, the sixth
Those having the same functions as those of the conventional configuration shown in the figure are designated by the same reference numerals and the description thereof will be omitted.

As described above, during normal speed control, since the speed command selection switch 16a is open and 16b is closed, the motor control device 1
Controls the speed of the motor 2 based on the constant position command of the speed command unit 15.

Next, when stopping at the fixed position, the fixed position stop command device 14 operates to close the selection switch 16a and open 16b to switch to the position control loop. The position control loop includes a first position control loop that controls up to near the stop position and a second position control loop that stops at a fixed position. First, the first position control loop will be described.

The transmission 4 that transmits the force of the motor 2 to the main shaft 5 has two or three types of gear ratios, and the optimum gear ratio is selected by the gear ratio selection commander 13 from the main shaft speed. The gear ratio constant setting device 12 receives the signal from the command device 13 as an input and preliminarily sets the transmission 4
The spindle rotation position controller 11 is instructed with the same constant as the gear ratio selected from the constants for which the gear ratio is set. The spindle rotational position controller 11 uses a signal from a spindle position detector 9 composed of a magnetic generator 7 attached to the spindle 5 and a magnetic sensor 8 attached to a fixed portion of the spindle 5 as a spindle origin signal through a position controller 10. It receives and multiplies this by the motor shaft rotation signal of the speed detection pulse encoder 3 of the motor 2 and the aforementioned gear ratio constant to generate a spindle rotation position signal, and based on this signal, the position control loop selection switch 17b, The position control of the first position control loop including the speed command selection switch 16a, the motor control device 1, the motor 2, and the pulse encoder 3 is performed.

When reaching the vicinity of the stop position, the position controller 10 closes the position control loop selection switch 17a and opens 17b to switch to the second position control loop based on the signal from the position detector 9 to perform the fixed position stop control. I do.

As described above, by adding the first position control loop to the spindle rotational position control, the spindle rotational position can be estimated and the fixed position can be stopped within one rotation from any stop position.

In this embodiment, in order to improve the stop position accuracy with respect to all the gear ratios, the position detector 9 stops at a fixed position near the stop position. It is also possible to use the first position control loop until position stop.

〔The invention's effect〕

As described above, in the present invention, the spindle rotational position is estimated using the motor shaft rotational position signal and the motor / spindle gear ratio, and position control is performed up to the vicinity of the stop position. Thereby, the fixed position stop control can be performed within one rotation of the spindle even from an arbitrary stop position. Therefore, even when stopping at a fixed position during operation at an arbitrary speed, it is possible to quickly decelerate and stop while performing position control,
It becomes possible to shorten the fixed position stop time.

[Brief description of drawings]

FIG. 1 is a block diagram of a spindle position control method according to the present invention, and FIG.
FIG. 3 is a waveform diagram for explaining the position control method according to the present invention.
FIG. 4 is an explanatory view showing the effects of the method of the present invention and the conventional method in comparison, FIG. 4 is a general spindle position detector configuration diagram, FIG. 5 is a position detection signal characteristic with respect to the spindle rotation position, and FIG. Is a conventional example of a spindle position stop control system, and FIG. 7 is a time chart thereof. 1: Motor control device, 2: Motor 3: Pulse encoder, 4: Transmission 5: Spindle, 6: Tool 7: Magnetizer, 8: Magnetic sensor 9: Position detector, 10: Position controller 11: Spindle rotation position Controller 12: Gear ratio constant setter, 13: Gear ratio selection commander 14: Fixed position stop commander, 15: Speed commander 16a, 16b: Speed command selection switch 17a, 17b: Position control loop selection switch

Claims (1)

(57) [Claims] 1. A position detector mounted on a spindle for use in fixed position stop control, a motor for driving the spindle via a transmission, a pulse encoder for detecting the speed and rotational position of the motor, and position control. In the spindle rotation position control device consisting of a motor control device having a controller and a speed control function,
The main shaft stop position signal from the position detector, the main shaft rotational position signal calculated from the motor rotational position based on the gear ratio and the pulse encoder signal of the motor shaft with respect to the main shaft set in the position controller, are calculated. A first position control loop based on the main shaft rotation position signal and a second position control loop based on the main shaft stop position signal from the position detector are configured, and after inputting a positioning command, the main axis origin signal from the timing sensor is detected. The position control is performed by one position control loop, and the detection range of the position detector is controlled by the second position control loop to stop at a fixed position. A spindle rotational position control method characterized by stopping at a fixed position within one rotation.