JPH06195118A - Fixed position stop controller - Google Patents

Abstract

PURPOSE:To execute fixed position stop control by prescribed torque by a simple processing or constitution, and to realize the control of a high speed by using a fixed position stop speed command being proportional to a square root of a position deviation. CONSTITUTION:In a subtracting means 15, a present position theta detected by a position detector 14 is subtracted from a target position theta* inputted to a fixed position stop speed command arithmetic part 2, and a position deviation 106 is outputted. In a multiplying means 16, the position deviation 106 is multiplied by a constant 2A, and by a square root arithmetic means 18, an output of the multiplying means 16 is outputted by a square root. In a comparing means 21, when a code of the deviation position 106 is positive, the output becomes an active state. A speed command switching means 22 outputs an output 109 of the square root arithmetic means 18, when the output of the comparing means 21 is in an active state, and outputs an output 110 of a multiplying means 19, in other case. In such a way, the fixed position stop speed command arithmetic part 2 generates a value being proportional to the square root of the position deviation as a fixed position stop speed command 113.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixed position stop device used for spindle control of machine tools.

[0002]

2. Description of the Related Art An example of the configuration of a conventional fixed position stop control device is shown in FIG. 3 for the case of being applied to spindle control of a machine tool. In FIG. 3, reference numeral 1 denotes a speed controller, which detects a current speed 10 from a speed detector 13 that outputs a current speed detection value 101 and a speed command 100 input to the speed controller 1.
Subtracting means 10 for subtracting 1, a driving device 11 for driving a motor 12 according to the output of the subtracting means 10, and a driving device 1
A motor 12 that drives a spindle of a machine tool according to the output of 1
The present speed is feedback-controlled according to the input speed command 100. A position detector 14 detects the position of the main shaft driven by the motor 12.

A fixed position stop speed command calculation unit 2 subtracts the current position θ detected by the position detector 14 from the target position θ ^* input to the fixed position stop speed command calculation unit 2 to obtain a position deviation 106. Subtraction means 15 for outputting and position deviation 106
Is provided with a multiplication means 33 for multiplying a preset constant V ₂ / Δθ ₂ and a value proportional to the position deviation 106 between the target position θ ^* and the current position θ is generated as the fixed position stop speed command 113. Note that V ₂ is a preset fixed position stop start speed command, and Δθ ₂ is a preset deceleration start position deviation.

Reference numeral 3 denotes a fixed position stop speed command switching section, which is a preset fixed position stop start speed command 114.
Constant position stop start speed command generating means 23 for generating
The deceleration start position deviation generating means 24 for generating a preset deceleration start position deviation 115 is compared with the fixed position stop start speed command 114 and the current speed 101, and the current speed 101 is compared.
Of the constant position stop start speed command 114 or less, the comparison means 25 for setting the output to the active state and the deceleration start position deviation 115 and the position deviation 106 are compared with each other to detect the position deviation 106.
AND when the deceleration start position deviation becomes 115 or less, the comparison means 26 that makes the output active, and the AND operation means 27 that makes the outputs active when the outputs of the comparison means 25 and 26 simultaneously become active, and There is provided a fixed position stop speed command switching unit 28 which outputs the fixed position stop speed command 113 when the output of the calculation unit 27 is in the active state and outputs the fixed position stop start speed command 114 otherwise. By these means, the fixed position stop speed command switching unit 3 stops the output when the current speed 101 matches the fixed position stop start speed command 114 and the position deviation 106 matches the deceleration start position deviation 115. From the start speed command 114 to the fixed position stop speed command 113
Switch to.

Reference numeral 4 denotes a speed command switching means, which gives a speed command 120 from the outside as a speed command 100 to the speed control unit 1 at the time of speed control according to a control switching command 121 from the outside, and at a fixed position stop control. The output 119 of the position stop speed command switching unit 3 is given to the speed control unit 1 as the speed command 100.

The operation of the fixed position stop control device will be described with reference to an example of changes in the current speed v and the output torque tq of the motor when the fixed position stop control is started during the high speed rotation of the spindle shown in FIG. First, when the fixed position stop control is started at time t1, thereafter, the speed command switching means 4 outputs the output 119 of the fixed position stop speed command switching unit 3 to the speed command v ^*.
Is given to the speed controller 1. On the other hand, the fixed-position stop speed command switching unit 3, until the current speed v is equal to the fixed-position stop start speed command V ₂ that is set in advance, and outputs a fixed-position stop start speed command V _2. At this time, the speed control unit 1 starts deceleration at the maximum output torque of the motor based on the received speed command V ₂ .

Next, when the current speed v coincides with the fixed position stop start speed command V ₂ at time t2, the position deviation Δθ between the target position and the current position becomes a preset deceleration start position deviation Δθ ₂ . Until they match, the constant position stop speed command switching unit 3 continues to output the constant position stop start speed command V ₂ . From time t2 to t3, since the main shaft is simply rotated, the output torque tq of the motor is hardly required.

Next, when the position deviation Δθ coincides with the deceleration start position deviation Δθ ₂ at time t3, the fixed position stop speed command switching unit 3 outputs the fixed position stop start speed command V ₂ to the fixed position stop speed command. Switch to. After time t3,
Position control is performed by the constant position stop speed command, the current speed v is decelerated as the position deviation Δθ decreases, and the spindle stops at the target position.

Position deviation Δθ and current speed v after time t3
The relationship is expressed as a mathematical expression where θ ^* is the target position and θ is the current position.

First, the relationship between the target position θ ^* , the current position θ, and the position deviation Δθ is expressed by equation 1.

[Equation 1] Next, it is assumed that the current speed v matches the fixed position stop speed command v ^* . In addition, in order for the current speed v to match the fixed position stop speed command v ^* , it is necessary to satisfy the condition described later, but it is assumed here that the condition is satisfied. Further, in the fixed position stop speed command calculation unit 2, the value obtained by multiplying the position deviation Δθ by V ₂ / Δθ ₂ is used as the fixed position stop speed command v ^*, and therefore the current speed v is as shown in Formula 2.

[Equation 2] Differentiating both sides of Equation 2 with respect to time t gives Equation 3.

[Equation 3] Differentiating the present position θ with respect to the time t gives the present velocity v, and since the target position θ ^* is a constant value, the following equation 4 is obtained.

[Equation 4] With the current speed V ₂ at time t3 as the initial value of t = 0, the differential equation of Equation 4 is solved, and the current speed v is represented by time t, then Equation 5 is obtained.

[Equation 5] Further, since the current speed v is differentiated by the time t to obtain the current acceleration, the current acceleration dv / dt becomes the expression 6 from the expression 5.

[Equation 6] From Equation 6, the current acceleration has a maximum value of −V ₂ ² / when t = 0.
It becomes Δθ ₂ and then decreases with an exponential function.

Here, assuming that the inertia of the main shaft system is J, inertia × acceleration becomes torque, so the motor output torque tq at t = 0 is −JV ₂ ² / Δθ ₂ and this −JV ₂ ² / Δθ ₂ is the maximum value required for the motor output torque tq. Because of the above relationship, the maximum output torque of the motor is -JV ₂ ² / Δθ ₂
If the deceleration start position deviation Δθ ₂ and the constant position stop start speed command V ₂ are set to values that increase the current speed v, the current speed v cannot match the constant position stop speed command v ^* Control is impossible and it cannot stop at a fixed position. Therefore, the condition that the current speed v matches the fixed position stop speed command v ^* is -JV ₂ rather than the maximum output torque of the motor.
² / [Delta] [theta] ₂ deceleration start position deviation Δ a value such decreases
θ ₂ and the fixed position stop start speed command V ₂ .

By the way, the motor output torque tq during the position control period by the constant position stop speed command exponentially decreases with the passage of time, and the motor output torque tq is not fully utilized. Further, since the current speed v also decreases exponentially with time, v does not become 0 for a finite time, and v≈0, that is, it takes a long time until the fixed position stop can be handled.

On the other hand, in some high-level position control devices using a servomotor, there is a high-level position control device which performs acceleration / deceleration operation by uniform acceleration motion to control a constant motor output torque. FIG. 4 shows an example of a block diagram of a high-level position control device using a servo motor. In FIG. 4, reference numeral 1 denotes a speed control unit, which is a speed detector 36 that outputs a current speed detection value 101.
And a subtracting means 10 for subtracting the current speed 101 from the speed command 100 input to the speed controller 1, and a driving device 34 for driving the servo motor 35 in accordance with the output of the subtracting means 10.
And a servo motor 35 that operates according to the output of the drive device 34, and feedback-controls the current speed according to the input speed command 100.

Reference numeral 37 is a position detector for detecting the current position. Reference numeral 38 denotes a movement amount generating means, which receives a target position 127 and generates a time function of the movement amount such that the acceleration becomes equal to or less than a preset acceleration, and the movement amount at each time is based on the time function of the movement amount. 128 is output. 39 is a subtraction means, which subtracts the current position 126 detected by the position detector 37 from the output 128 of the movement amount generation means 38,
The position deviation 129 for the movement amount 128 at each time is output. Reference numeral 40 denotes a speed command calculation means, which is a position deviation 1
A speed command 100 proportional to 29 is output.

The operation of this position control device will be described with reference to an example of changes in the current speed v and the output torque tq of the servo motor during deceleration shown in FIG. By decelerating at a preset acceleration, the deceleration is started when the position that can be positioned at the target position is reached. This time is set to t1. After the time t1, the movement amount generation means 38 outputs the movement amount 128 at each time processed so that the speed changes with the preset acceleration. Therefore, the vehicle is decelerated by the uniform acceleration motion from the time t1 to the stop point.

As described above, in the high-level position control device using the servomotor, a time function of the movement amount is generated so that the acceleration becomes equal to or less than the preset acceleration, and each time is calculated based on the time function of the movement amount. The acceleration / deceleration operation is performed by uniform acceleration motion by using the displacement amount generating means that outputs the displacement amount in. This movement amount generating means is usually realized by complicated processing using a microprocessor, but a complicated circuit is required to realize it by a hard circuit. Therefore, in a high-level position control device using a servomotor, the processing or configuration is more complicated than the conventional fixed position stop control device.

[0017]

Recently, in machine tools, it has been required to improve the efficiency by shortening the non-cutting time such as the tool changing time, and it is necessary to speed up the fixed position stop control. However, as described above, in the fixed position stop control device applied to the spindle control of the machine tool in the prior art, the motor output torque tq during the position control period by the fixed position stop speed command is exponential. It decreases with the passage of time and has a drawback that the motor output torque tq cannot be fully utilized. Further, since the current speed v also decreases exponentially with time, v = 0 does not occur in a finite time, and v≈0, that is, it takes a long time to reach a state where fixed position stop is completed. is there. On the other hand, in a high-level position control device using a servo motor, a time function of the movement amount is generated so that the acceleration is equal to or lower than a preset acceleration, and the movement amount at each time is output based on the time function of the movement amount. The moving amount generating means is used. Therefore, in order to fully utilize the motor output torque tq,
The use of a high-level position control device using a servo motor has a drawback that the processing or configuration is complicated as compared with the conventional fixed position stop control device.

For this reason, there is a problem in that it is not possible to sufficiently respond to the speedup of the fixed position stop control with the same processing or configuration as the current one.

The present invention has been made in view of the above problems, and an object of the present invention is to speed up fixed position stop control with the same simple processing or configuration as the fixed position stop control device in the prior art. It is to provide a fixed position stop control device that realizes the above.

[0020]

The above object of the present invention is to provide a speed control unit for feedback controlling the current speed according to an input speed command, and a constant proportional to the square root of the position deviation between the target position and the current position. The fixed position stop speed command calculation unit that outputs the position stop speed command, and the fixed position stop start speed command or the fixed position stop speed command calculation unit whose output is preset according to the current speed and the current position are input. Fixed position stop speed command switching unit for switching to a command, and a speed command from the outside is given to the speed control unit during speed control,
This is achieved by using a fixed position stop control device characterized by comprising speed command switching means for giving the output of the fixed position stop speed command switching unit as a speed command to the speed control unit during fixed position stop control.

[0021]

Since the present invention uses a simple function of a speed command proportional to the square root of the position deviation as the constant position stop speed command, it can be processed within a capability range of the fixed position stop control device by a simple process or configuration. The fixed position stop control can be performed so that the motion is uniform acceleration motion, and a constant output torque can be constantly output to the motor until the fixed position stop is completed.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of a fixed position stop control device according to the present invention applied to spindle control of a machine tool. Reference numeral 2 denotes a fixed position stop speed command calculation unit, which subtracts the current position θ detected by the position detector 14 from the target position θ ^* input to the fixed position stop speed command calculation unit 2 and outputs a position deviation 106. Means 15, a multiplying means 16 for multiplying the position deviation 106 by a preset constant 2A, an absolute value converting means 17 for converting the output of the multiplying means 16 into an absolute value, and a square root of the output of the absolute value converting means 17. Square root calculating means 18 for outputting and output 1 of the square root calculating means 18
The multiplication means 19 for multiplying 09 by -1 and the position deviation 106
When the sign of is positive, the comparing means 21 which makes the output active, and when the output of the comparing means 21 is active, the output 109 of the square root calculating means 18 is outputted, otherwise, the output 110 of the multiplying means 19 is outputted. A speed command switching means 22 for outputting is provided. By each of these means, the fixed position stop speed command calculation unit 2 generates a value proportional to the square root of the position deviation as the fixed position stop speed command 113.
A speed control unit 1 other than the fixed position stop speed command calculation unit 2, a fixed position stop speed command switching unit 3, and a speed command switching unit 4
Is the same as the example of the configuration diagram in the prior art of FIG. 3, and the same reference numerals have the same functions.

Next, FIG. 7 shows an example of changes in the current speed v and the motor output torque tq when the fixed position stop control is started during high speed rotation of the spindle in the fixed position stop control device shown in FIG. Is. In the present invention, since the fixed position stop control is performed by the fixed position stop speed command proportional to the square root of the position deviation, as shown below, from the position control start time t3 to the fixed position stop completion time, the constant output torque is constant. They are exercising at constant acceleration.

Here, it will be shown below that the speed command when performing position control by uniform acceleration motion is proportional to the square root of the position deviation. First, since the motion is uniform acceleration, the acceleration d
v / dt is shown by equation 7.

[Equation 7] Here, A is an arbitrary constant that satisfies the conditions described later.

The current speed v and the current position θ are obtained by integrating the equation 7 at time t.

[Equation 8]

[Equation 9] Here, B and C are arbitrary constants.

The current speed v is the fixed position stop start speed command V ₂
And the position deviation Δθ coincides with the deceleration start position deviation Δθ ₂ , the position control is started in the conventional manner. When the position control start time is t = 0, the current speed at time t = 0 is V ₂ , and thus the expression 8 becomes the expression 10.

[Equation 10] Further, since the position deviation at time t = 0 is Δθ ₂ , Formula 11 is established from Formula 1 and Formula 9.

[Equation 11] When Equation 11 is transformed, Equation 12 is obtained.

[Equation 12] Therefore, by rewriting Equations 8 and 9 using Equations 10 and 12, and obtaining the current velocity v and the current position θ when the position control operation start time is t = 0, Equations 13 and 14 are obtained.

[Equation 13]

[Equation 14] Next, the equation 13 is transformed and the time t is represented by the current speed v, and the equation 15 is obtained.

[Equation 15] Here, by substituting the equation 15 into the equation 14, the equation 16 is obtained.

[Equation 16] By the way, when the current speed v = 0, it means that the fixed position stop is completed, and therefore θ = θ ^* . Substituting this condition into Equation 16 gives Equation 17.

[Equation 17] Equation 17 is transformed into Equation 18.

[Equation 18] Substituting this equation 18 into the equation 16 yields the equation 19.

[Formula 19] When Formula 19 is arranged, Formula 20 is obtained.

[Equation 20] Since the target position θ ^* , the current position θ, and the positional deviation Δθ have the relationship of Expression 1, Expression 20 becomes Expression 21.

[Equation 21] Equation 21 is transformed into Equation 22.

[Equation 22] Here, in order to control the position deviation Δθ to decrease, if the value of the target position θ ^* is larger than the current position θ, that is, if the value of the position deviation Δθ is positive, the current position θ is the time t. Since it is necessary to increase with the passage of, the current velocity v and the acceleration A take positive values. On the other hand, when the value of the target position θ ^* is smaller than the current position θ, that is, the position deviation Δθ
When the value of is negative, the current position θ needs to decrease with the lapse of time t, so the current speed v and the acceleration A have negative values.

When the torque for generating an acceleration that can respond to a change in the speed command v ^* , such as the period from time t1 to t2 in FIG. 5, exceeds the maximum output torque of the motor, the motor outputs a constant output. Since the torque, that is, the maximum output torque is continuously output, the uniform acceleration motion is performed at the acceleration determined by the maximum output torque of the motor. However, even with the same uniform acceleration motion, the current speed v at this time cannot match the speed command v ^* , so position control is impossible.

From the above results, it is shown that the fixed position stop speed command when the fixed position stop control is performed by the uniform acceleration motion by the acceleration within the capability range of the control device is proportional to the square root of the position deviation Δθ. Was done.

In the present invention, since the fixed position stop control is performed by the fixed position stop speed command proportional to the square root of the position deviation, the constant acceleration motion is performed with a constant output torque from the time t3 to the fixed position stop completion time point. Further, since a simple function that is proportional to the square root of the position deviation is used for the fixed position stop speed command, the fixed position stop speed command calculation unit for generating the fixed position stop speed command includes subtraction means, square root calculation means, etc. It can be configured by a simple arithmetic means that can be easily realized by a hardware circuit. Therefore, in a high-level position control device using a servo motor, there is no movement amount generating means that requires complicated processing using a microprocessor,
Can perform uniform acceleration motion.

Therefore, by using the fixed position stop control device according to the present invention, which is provided with the fixed position stop speed command calculation unit for generating the fixed position stop speed command proportional to the square root of the position deviation, a simple process or configuration can be performed. , Perform constant position stop control by uniform acceleration motion by acceleration within the capability of the fixed position stop control device, and always output a constant output torque selected within the range that can be output until the fixed position stop is completed. You can

FIG. 2 is a block diagram showing another embodiment of the fixed position stop control apparatus according to the present invention applied to the spindle control of a machine tool. In FIG. 2, the functions of the speed control unit 1, the fixed position stop speed command switching unit 3, and the speed command switching unit 4 other than the fixed position stop speed command calculation unit 2 are the same as the example of the configuration diagram in the prior art of FIG. , The same code has the same function. The fixed position stop speed command calculation unit 2 in FIG. 2 is a preset unit for multiplying the fixed position stop speed command calculation unit 2 in FIG. 1 by the position deviation 106 and a preset constant D. The fixed position stop completion position deviation Δθ ₄ and the fixed position stop completion position deviation Δθ ₄ and the position deviation 10 are generated.
6 is compared and the position deviation 106 is the fixed position stop completion position deviation Δ
theta ₄ output when it becomes less than the comparison means 31 to the active state, the output of the comparison means 31 outputs the output 123 of the multiplying means 29 when in the active state, the output of the speed command switching means 22 at all other times Speed command switching means 32 for outputting 122 is added. For this reason,
The fixed position stop speed command calculation unit 2 in FIG. 2 generates a value proportional to the square root of the position deviation as the fixed position stop speed command 113 until the position deviation 106 becomes equal to or smaller than the fixed position stop completion position deviation Δθ ₄ . Further, when the position deviation 106 becomes equal to or less than the fixed position stop completion position deviation Δθ ₄ , a value proportional to the position deviation is generated as the fixed position stop speed command 113.

As described above, the function of the fixed position stop speed command is switched in the embodiment of FIG. 2 in proportion to the square root of the position deviation when the current position is moved due to the disturbance torque after the fixed position stop is completed. This is because if the fixed position stop speed command is used to hold the current position, the position control becomes unstable because the fixed position stop speed command is non-linear. Therefore,
After the fixed position stop is completed, the current position is held by using the linear fixed position stop speed command.

[0033]

As described above, according to the fixed position stop control device of the present invention, by using the fixed position stop speed command calculation unit which generates the fixed position stop speed command proportional to the square root of the position deviation, With uniform processing or configuration, uniform acceleration motion by acceleration within the capability range of the fixed position stop control device, that is,
The constant position stop control can be performed with a constant torque, and it is possible to maximize the use of the motor output torque after the start of the position control, which cannot be fully utilized in the conventional fixed position stop control device applied to the spindle control of machine tools. Becomes possible,
It is possible to realize high-speed fixed position stop control with a simple process or configuration equivalent to that of the fixed position stop control device in the prior art.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a fixed position stop control device according to the present invention applied to spindle control of a machine tool.

FIG. 2 is a configuration diagram showing another embodiment of a fixed position stop control device according to the present invention applied to spindle control of a machine tool.

FIG. 3 is an example of a configuration diagram of a conventional fixed position stop control device applied to spindle control of a machine tool.

FIG. 4 is an example of a configuration diagram of a high-grade position control device using a conventional servo motor.

5 is a diagram showing an example of changes in current speed and motor output torque when the fixed position stop control is started during high speed rotation of the main shaft in the conventional fixed position stop control device shown in FIG.

FIG. 6 is a diagram showing an example of changes in current speed and motor output torque during deceleration in a high-grade position control device using the conventional servo motor shown in FIG.

7 is a diagram showing an example of changes in the current speed and the output torque of the motor when the fixed position stop control is started during the high speed rotation of the spindle in the fixed position stop control device according to the present invention shown in FIG. is there.

[Explanation of symbols]

 1 speed control unit 2 fixed position stop speed command calculation unit 3 fixed position stop speed command switching unit 4 speed command switching means

Claims (2)

[Claims] 1. A control device for feedback-controlling a current speed according to a speed command from the outside, a speed control unit for feedback-controlling the current speed according to an input speed command, and a position between a target position and a current position. A fixed position stop speed command calculation unit that outputs a fixed position stop speed command that is proportional to the square root of the deviation, and a fixed position stop start speed command or the fixed position stop output that is preset according to the current speed and the current position. A fixed position stop speed command switching unit that switches to a command input from the speed command calculation unit, and an external speed command is given to the speed control unit during speed control, and a fixed position stop speed command switching unit is provided during fixed position stop control. A fixed position stop control device comprising speed command switching means for giving an output to the speed control unit as a speed command. 2. The constant position stop speed command calculation unit, after the position deviation becomes equal to or less than a preset fixed position stop completion position deviation, a fixed position proportional to the position deviation as a fixed position stop speed command. The fixed position stop control device according to claim 1, wherein a stop speed command is output.