JP2001022417A - Position controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position controller which appropriately compensates for torque and can reduce a quadrant projection much more since the quadrant projection occurs when a motor is reversed in a conventional position controller. SOLUTION: In a position controller, a torque feed forward control part 15 stores a torque command value when a speed command value is inverted and a torque command value when a position feed back signal is inverted in a register at an adjusting mode and the difference is operated. When a system becomes a compensation mode, the average value of or the minimum value of the operated difference is selectively outputted at timing when the speed command value is inverted as torque addition quantity. A torque command value adder 16 adds it to the torque command value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position control device used for a machine tool or the like and for controlling a position, a rotation speed, and the like of a tool, and more particularly to an improvement in control when switching a quadrant for reversing a motor.

[0002]

2. Description of the Related Art When machining a circular arc with a machine tool, generally a reversing control of a motor is involved. At the time of reversing, a control signal is output and then a tool reaches a specified position or speed. Due to the “control delay” of the time required until, for example, the so-called “quadrant projection” in which inversion control is performed and a part that is not processed remains even though the tool has not actually reached the predetermined position. appear. In order to prevent the quadrant protrusion, control for compensating for the torque of the motor has been conventionally performed.

[0003] The torque T output by the motor is generally expressed by the following equation (1).

[0004]

T = J × (dω / dt) + Kω + D where ω is the number of rotations of the motor, and J is the rotor speed.
It is the sum of the inertia and the motor shaft converted load inertia.
K is the coefficient of viscous friction and D is the friction torque.

As shown in [Equation 1], the torque T output from the motor is an acceleration torque proportional to the acceleration of the motor, a viscous torque proportional to the speed of the motor, and a friction torque determined by dynamic friction and static friction of the sliding surface. The sum of

FIG. 4 is a block diagram showing an example of a torque feedforward control device in a conventional position control device. The NC device 1 calculates and outputs a position command value (CON) of the drive system from an input program. The position controller 2 receives an input of a tracking delay (DIFF) which is a deviation between the CON and an actual position (APA) input from the outside, and calculates and outputs a speed command value (VEL1).

The speed control unit 3 has a speed command value (VEL)
And a torque command value (TO2) is calculated from the deviation from the actual speed input from the outside and output. The speed feedforward controller 4 calculates a speed feedforward amount to be differentiated from the position command value (CON) of the drive system and to be added to the speed command value (VEL1). The speed command value inversion detecting unit 6 detects that the polarity of the motor speed command value (VEL) has been inverted. When the speed command value inversion detecting unit 6 detects the inversion of the polarity, the torque feedforward control unit 7 outputs the torque addition ΔT in consideration of the influence of the control delay and the like.

[0008] The first adder 8 is a follow-up lag (deviation) between a position command value (CON) of the drive system input from the NC device 1 and an actual position (position feedback; APA) input from the outside. DIFF) and outputs the result.

The second adder 9 calculates the motor speed command value (VEL) by adding the output of the speed feedforward control unit 4 and the speed command value (VEL1) input from the position control unit 2. And output. The third adder 10
A deviation between a motor speed command value (VEL) and an actual speed input from the outside is calculated and output. Fourth adder 11
Is the acceleration torque feedforward amount input from the acceleration torque feedforward control unit 5 and the speed control unit 3
Is added to the torque command value (TO2) input from the controller to calculate and output the torque command value (TO1). The fifth adder 12 calculates the torque command value (TO1) and the torque addition Δ input from the torque feedforward control unit 7.
T is added to calculate and output a torque command value (TO) given to the motor.

FIG. 5 shows the operation of the position control device by a signal change when the NC device 1 outputs a position command to reverse the motor. In FIG. 5, (a) shows the magnitude of the motor speed command value (VEL) over time,
(B) shows the magnitude of the torque command value (TO) with respect to a change in time, and (c) shows the relationship between the position command value (CON) of the drive system and the actual position (APA) of the drive system with time. (D) shows the operation of the drive system following delay (DIFF) over time.

In FIG. 5B to FIG. 5D, the torque command value (TO), the actual position of the drive system (APA), and the follow-up delay of the drive system (DIFF) are drawn by broken lines. Indicates a case in which the torque addition ΔT output from the torque feedforward control unit 7 is not added, and the solid line indicates the torque feedforward control unit 7.
Represents a case in which the torque addition ΔT output from is added.

That is, the torque command value (TO) indicated by the solid line is added with the torque addition ΔT by the torque feedforward control at the time of motor reversal, so that the follow-up delay (DIFF) of the drive system does not execute the torque feedforward control. It becomes smaller than the case.

From equation (1), it can be seen that the difference between the torque command values (TO) immediately before and immediately after the reversal of the motor is a change 2D of the friction torque caused by the reversal of the sign of the dynamic friction force. This is as shown in FIG. Conventionally, torque feedforward control is performed to compensate for the change 2D of the friction torque. However, the friction torque changes due to component tolerances in machines having the same structure and aging even in the same machine. Therefore, when a predetermined fixed value is used as the torque addition ΔT, it is not always appropriate.

For this reason, when the motor includes a reversing operation as in an arc command program, the degree of compensation for the quadrant projection may be insufficient (uncompensated) or overcompensated. FIGS. 5B to 5D show an example in which the torque feedforward control is not compensated.

[0015]

As described above, in the above-described conventional position control device, the influence of a control delay or the like on the torque command value immediately after the motor reversal is used in order to reduce the quadrant protrusion generated when the quadrant is switched during the motor reversal. Torque feed forward control that adds torque taking into account
Since the torque addition ΔT applied to this control is not always appropriate, there is a problem that the quadrant projection is uncompensated or overcompensated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a position control device capable of appropriately compensating for a change in friction torque by a torque feedforward control and further reducing quadrant protrusions.

[0017]

According to a first aspect of the present invention, there is provided a servomotor for controlling a servomotor based on a torque command value calculated from a difference between a position command signal and a position feedback signal. In the position control device to be driven, a speed command value inversion detecting unit that detects that the polarity of the speed command value of the motor is inverted, and an axis inversion that detects the inversion of the position feedback signal corresponding to the inversion of the polarity of the speed command value. A first storage unit for storing the torque command value when the speed command value inversion detection unit detects the inversion of the speed command value of the motor when the operation mode is in the adjustment mode;
And a second register for storing the torque command value when the axis reversal detection unit detects the reversal of the position feedback signal, and the torque command value stored in the first register. Calculating a difference between the corresponding torque command value stored in the second register, and calculating an average value and a minimum value of the difference. When the operation mode becomes the compensation mode, the speed command When the value inversion detection unit detects that the polarity of the speed command value of the motor has been inverted, a torque that selectively outputs one of the calculated average value and the minimum value as a torque addition when the value is inverted. A feedforward control unit, a torque command value adder that adds a torque addition output by the torque feedforward control unit to the torque command value, and outputs a torque command value. Position control device characterized in that it comprises.

[0018]

Embodiments of the present invention will be described with reference to the drawings. In the following description, portions having the same configuration as the conventional one are denoted by the same reference numerals, and detailed description is omitted.

The position control device according to the embodiment of the present invention can switch the operation mode of the machine between learning (adjustment mode) and machining (compensation mode). In other words, initially drive in the adjustment mode, when switching quadrants,
The average value and the minimum value of the difference between the torque command values from when the polarity of the motor speed command value is inverted to when the position feedback signal is inverted are calculated and stored. Then, the mode is switched to the compensation mode during machining, and either the stored average value or the minimum value is selectively added to the torque command value when the polarity of the motor speed command value is reversed. Hereinafter, the position control device according to the present embodiment will be specifically described.

FIG. 1 is a configuration block diagram of a position control device according to an embodiment of the present invention. The position control device of the present embodiment and the conventional position control device
And a torque command value detector 14 and a mode changeover switch. Further, the operation of the NC device 1 to output the designated operation mode and the operation of the torque feedforward controller 15 are different. The axis reversal detection unit 13
It detects that the position feedback signal (APA) has been inverted. The torque command value detector 14 detects a torque command value TO1 based on a command from the speed command value reversal detector 6. Torque feed forward control unit 1 in the present invention
Reference numeral 5 is composed of two blocks, an operation unit and an output unit.

The torque command value adder 16 calculates and outputs a torque command value (TO) to be given to the motor by adding the torque command value (TO1) and the torque addition ΔT.

Here, the torque feed forward control unit 1
Operation 5 will be described with reference to FIG. FIG.
FIG. 2 is a configuration block diagram of a torque feedforward control unit 15; When the operation mode of the machine is set to the adjustment mode, the NC device 1
, And the torque feedforward control unit 15 takes in the output from the torque command value detection unit 14. When the polarity of the motor speed command value (VEL) is reversed, the torque command value (TO1) detected by the torque command value detection unit 14 is changed to the first registers A1 to An of the torque feedforward control unit 15 shown in FIG. Are sequentially stored. When the position feedback signal (APA) is inverted with a delay from the time when the speed command value is inverted, the torque command value (TO1) detected by the torque command value detection unit 14 is changed to the second register B1 to B2 of the torque feedforward control unit 15. B
n. Then, the torque feedforward control unit 15 calculates and stores the difference between the value of the first register An and the value of the second register Bn in the third register Cn, and further stores the difference in the fourth registers D1 and D2. An average value and a minimum value of the third registers C1 to Cn are calculated and stored, and any one of the average value and the minimum value is selectively output. This selection is performed at the same time as setting the operation mode to the compensation mode, and is performed by a user's experience-based instruction in consideration of the finish state of the workpiece to be processed. Select the average value if you want to prevent uncompensated uncut parts and digging in the work.If you want to avoid uncut parts, etc., you can select the average value.If you want to avoid overcompensation, select the minimum value. It is common to select

The mode changeover switch is turned off when the operation mode is the adjustment mode, so that the average value or the minimum value output from the torque feedforward control unit 15 is not transmitted to the torque command value adder 16 and when the operation mode is the compensation mode, O
At N, the average value or the minimum value output from the torque feedforward control unit 15 is transmitted to the torque command value adder 16.

When the operation mode of the machine is set to the compensation mode, the NC device 1 outputs a compensation mode command to the torque feed forward control unit 15, and the torque feed forward control unit 15 Stops capturing output. In addition, the motor speed command value (VE
When the polarity of L) is inverted, either the average value or the minimum value is output to the torque command value adder 16 as the torque addition ΔT, and the torque command value adder 16 outputs the torque output by the fourth adder 11. Command value (TO1) and torque addition ΔT
Are added and output as a torque command value (TO).

Next, the operation of the position control device according to the present embodiment will be described with reference to FIGS. First, the operation mode of the machine is set to the adjustment mode in the NC apparatus 1, and an operation program and the number of repetitions n of the operation program are input. After the operation is started, when the polarity of the speed command value (VEL) of the motor is reversed, the speed command value reversal detecting unit 6 sends the torque command value (TO) to the torque command value detecting unit 14.
A command for detecting 1) is output. Then, the torque command value detection unit 14 calculates the torque command value (TO1) at that time.
And outputs a torque command value (TO1) to the torque feedforward control unit 15. The torque feedforward control unit 15 stores the torque command value (TO1) in the first register A1. After the polarity of the motor speed command value is inverted and the corresponding inversion of the position feedback signal (APA) is detected by the axis inversion detection unit 13, the axis inversion detection unit 13 sends the torque instruction value detection unit 14. A command for detecting the torque command value (TO1) is output.
Then, the torque command value detecting section 14 detects the torque command value (TO1) at that time and outputs it to the torque feedforward control section 15. The torque feedforward control unit 15 stores the torque command value (TO1) in the register B1. Further, the torque feed forward control unit 15
Calculates the difference between the torque command values (TO1) stored in the first register A1 and the second register B1, and stores the result in the corresponding third register C1. These series of operations are repeated n times set in advance, and the values are sequentially stored in the registers A1 to An, B1 to Bn, and C1 to Cn, and then the torque feedforward control unit 15 sets the third registers C1 to C1. An average value and a minimum value with respect to the difference between the torque command values (TO1) stored in the register Cn are calculated, and the fourth register D1 and the fourth register D2 are respectively calculated.
To be stored. Here, since the operation mode is the adjustment mode, the average value and the minimum value are not output by the operation of the mode changeover switch. Therefore, the torque command value (TO1) is
It is output as a torque command value (TO) given to the motor as it is.

Thereafter, when the NC unit 1 sets the machine operation mode to the compensation mode for enabling the torque addition ΔT, the operation mode is stored in the fourth registers D1 and D2 of the torque feedforward control unit 15 when the operation program is executed. In addition, either the average value or the minimum value is selected by the instruction,
As the torque addition ΔT, the motor speed command value (VE
L) is output at a timing when the polarity of L) is inverted, added to the torque command value (TO1) by the torque command value adder 16, and output as a torque command value (TO) to be given to the motor.

FIG. 2 shows a state of a signal output from each unit of the position control device according to the present embodiment. Here, the torque command value (TO), the torque addition ΔT, the actual position of the drive system (APA), and the follow-up delay (DIFF) of the drive system, which are drawn by broken lines, are obtained by using a conventional position control device. Is shown for reference, and those drawn with solid lines are:
According to the invention. As shown in FIG. 2B, the torque addition ΔT is properly output, and as shown in FIG. 2D, the follow-up delay of the driving system becomes close to “0”. Will not occur.

According to the present embodiment, since appropriate torque feed-forward control is performed with a little learning, quadrant projections generated at the time of quadrant switching can be improved.

Here, the fourth registers D1 and D2
Although the average value and the minimum value are held, it is also possible to specify in advance whether to use the average value or the minimum value and store only the specified value in the fourth register D. is there.

Further, in addition to the minimum value and the average value, a value statistically calculated from the differences stored in the third registers C1 to Cn may be used instead of the minimum value and the average value. By doing so, it is possible to appropriately change the calculation method empirically and output a more appropriate torque addition ΔT.

[0031]

According to the present invention, the difference between the torque command value when the speed command value is inverted in the adjustment mode and the torque command value when the position feedback signal is actually inverted in the adjustment mode is determined in advance. After detecting and calculating and entering the compensation mode, either the average value or the minimum value of the difference calculated at the timing when the speed command value is inverted is selectively output according to the instruction and added to the torque command value. Thus, the quadrature projection can be reduced by appropriately compensating the torque command value.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing a position control device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a change in a signal when the motor is reversed in the position control device according to the embodiment of the present invention.

FIG. 3 is a configuration block diagram illustrating a torque feedforward control unit 15 of the position control device according to the embodiment of the present invention.

FIG. 4 is a configuration block diagram of a conventional position control device.

FIG. 5 is an explanatory diagram showing a change in a signal when the motor is reversed in a conventional position control device.

[Explanation of symbols]

1 NC device, 2 position control unit, 3 speed control unit, 4
Speed feedforward control unit, 5 acceleration torque feedforward control unit, 6 speed command value inversion detection unit, 7,
15 Torque feed forward control unit, 8 First adder, 9 Second adder, 10 Third adder, 11
Fourth adder, 12 fifth adder, 13 axis reversal detector, 14 torque command value detector, 16 torque command value adder.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3C001 KA08 KB04 TA02 TA05 TB02 TB05 TB07 TC01 TC02 TD01 5H004 GA05 GA12 GB15 HA07 HB07 HB08 JA04 KA61 KA69 KB13 KB31 KB32 KB34 KB39 KD63 LB04 MA04 5H269 AB05 BB03 GG01 AGG01 CC05 FF03 JJ01 KK14 KK16 KK18 KK28 KK29 KK33 KK37 MM05

Claims (1)

[Claims] A position control device for driving a servomotor based on a torque command value calculated from a difference between a position command signal and a position feedback signal, wherein a speed command for detecting that the polarity of the speed command value of the motor has been reversed. A value inversion detection unit, an axis inversion detection unit that detects inversion of a position feedback signal corresponding to the inversion of the polarity of the speed command value, and the speed instruction value inversion detection unit is a motor when the operation mode is in the adjustment mode. A first register that stores the torque command value when the inversion of the speed command value is detected, and a second register that stores the torque command value when the axis inversion detection unit detects the inversion of the position feedback signal. And a difference between a torque command value stored in the first register and a corresponding torque command value stored in the second register. When the operation mode is set to the compensation mode, the speed command value inversion detecting unit detects that the polarity of the speed command value of the motor is inverted when the operation mode is set to the compensation mode. Among the calculated average value and minimum value, a torque feed-forward control unit that selectively outputs one of the designated ones as a torque addition amount, and a torque addition amount output by the torque feed-forward control unit. A torque command value adder for adding the torque command value to the torque command value and outputting the torque command value as a torque command value.