JPH0834708B2 - Inverter control device - Google Patents

Description

The present invention relates to a drive device for a motor that drives a spindle of a machine tool.

[Conventional technology]

FIG. 3 is a block diagram showing a system in the case of synchronously operating a main shaft and a feed shaft in a conventional machine tool. In the figure, 1 is a numerical controller for giving a position command to a feed axis and a main axis, 2 is a feed axis amplifier for controlling a feed axis motor 3, 3 is a feed axis motor, and 4 is for detecting the position of the feed axis. A feed shaft position detector, 5 is a main shaft amplifier composed of an inverter controller for controlling the main shaft motor 6, 6 is a main shaft motor, and 7 is a main shaft position detector for detecting the rotational position of the main shaft.

FIG. 4 is a block diagram showing the configuration of a spindle amplifier composed of a conventional inverter controller common to the present invention. In the figure, 8 is a position loop calculation unit that calculates a speed command ▲ ω ^* _r ▼ from the deviation between the position command P _ref and the position feedback signal P _FB from the position detector 7 for the spindle, and 9 is a speed command ▲ ω ^* _r ▼. And the speed feedback signal ω _r to calculate the torque component current i _qs , a speed loop calculation unit, 10 is a weak excitation calculation unit that calculates the weak excitation ratio ▲ ψ ^′ ₂ ▼ of the excitation component current from the torque component current i _qs , and 11 is Weak excitation rate ▲ ψ ^' ₂ ▼ and speed feedback signal ω _r, which are the outputs of the weak excitation calculator 10.
Phi ₂ ^* calculator for calculating the secondary magnetic flux command phi ₂ ^* from 12 secondary magnetic flux command φ ₂ ^* φ ₂ calculator for calculating a secondary flux phi ₂ performs first-order lag calculation from 13 secondary An M calculation unit for calculating the mutual reactance M from the magnetic flux φ ₂ , 14 is an i _ds calculation unit for calculating the excitation flux current i _ds from the secondary magnetic flux command φ ₂ ^* and the mutual reactance M, and 15 is the torque current i _qs and the excitation Minute current i _ds
Calculate the peak value | I ₁ | of the primary current given to the motor from | I
₁ | Calculation unit, 16 is a Δθ calculation unit that calculates the phase angle Δθ of the primary current from the torque component current i _qs and the excitation component current i _ds , and 17 is the slip frequency ω _s from the torque component current i _qs and the secondary magnetic flux φ _2. Is a ω _s calculation unit that calculates

Next, the operation of the system in the case of synchronously operating the main shaft and the feed shaft in the conventional machine tool shown in FIG. 3 will be described with reference to the inverter control device shown in FIG. For example, in a machine tool, when a main shaft and a feed shaft are synchronously operated to thread a workpiece, an interpolation calculation is performed so that the main shaft makes one rotation when the feed shaft moves by one pitch of the screw. 1 is given to the feed shaft amplifier 2 and the main shaft amplifier 5 as a movement command for a position of reverse rotation at the screw hole bottom. The feed axis amplifier 2 matches the position feedback signal of the feed axis position detector 4 with the movement command, forms a position loop, and rotates the feed axis motor 3. Similarly,
The spindle amplifier 5 matches the position feedback signal from the spindle position detector 7 with the movement command, forms a position loop, and rotates the spindle motor 6. By the above-described method, the main shaft and the feed shaft are synchronously operated to move and rotate, thereby performing highly accurate thread cutting on the workpiece.

That is, as shown in FIG. 4, in the spindle amplifier 5 composed of an inverter control device, the given position command P _ref and the position feedback signal P _FB are made to match, and the position loop gain K _PP is multiplied in the position loop calculation unit 8. To obtain a speed command ▲ ω ^* _r ▼. Velocity loop in the speed command calculation unit 9 ▲ ω ^* _r ▼ and abutting the speed feedback signal omega _r, the speed loop gain K _SP, to obtain a torque current i _qs performs PI control calculation which the integral gain K _SI. The φ ₂ ^* calculation unit 11 calculates the secondary magnetic flux command φ ₂ ^* in the speed feedback signal ω _r from the electric constant of the motor, and the weak magnetic excitation ratio φ ₂ ′ calculated by the weak magnetic excitation calculation unit 10 is multiplied to obtain the secondary magnetic flux. Calculate the command φ ₂ ^* . The weakening excitation rate φ ₂ ′ controls the excitation rate to be reduced when the torque component current i _qs is small. When the load is not applied to the spindle motor 6, the excitation current of the spindle motor 6 is reduced to suppress vibration noise. There is. The φ ₂ calculator 12 uses the primary delay calculation to calculate the secondary magnetic flux φ
₂ is estimated. The M computing unit 13 estimates the mutual reactance M of the spindle motor 6 from the secondary magnetic flux φ ₂ by the electric constant of the spindle motor 6, and the i _ds computing unit 14 And the excitation current i _ds is obtained. | I ₁ | Operation unit 15
Then Is calculated to calculate the peak value | I ₁ | of the primary current of the spindle motor 6, and the Δθ calculation unit 16 calculates the phase angle Δθ of the primary current from tan ⁻¹ (i _qs / i _ds ). Further, the ω _s calculator 17 calculates the slip frequency ω _s from the secondary magnetic flux φ ₂ and the torque component current i _qs.
Is calculated and ω _o = ω _r + ω _s is calculated to obtain the primary current I ₁
The angular frequency ω _{o of} is calculated. The primary current I ₁ sin (ω _o t + Δθ) given to the spindle motor 6 by the above calculation
Is calculated. The above is the outline of the operation of the inverter control device based on the known vector operation.

[Problems to be solved by the invention]

Since the inverter control device of the system for synchronously operating the spindle and the feed axis in the conventional machine tool is configured as described above, when the spindle load is light and there is no speed fluctuation of the spindle due to the load, Synchronous operation of the spindle and the feed axis with high accuracy can be performed, but if the spindle load is heavy and the spindle speed changes due to that load,
There is a problem in that the main shaft and the feed shaft are out of sync with each other, and the tool is damaged especially in thread cutting of the work by the machine tool.

The present invention has been made to solve the above problems, and a spindle that can perform stable, highly accurate, and highly responsive control even during synchronous operation of the spindle and the feed axis or during other operations. It is intended to obtain an inverter control device for.

[Means for solving problems]

The inverter control device according to the present invention performs vector control by fixed excitation in which the excitation current supplied to the spindle motor is a constant value during the synchronous operation of the spindle and the feed shaft, and during the other operations, the excitation current is torqued. Vector control is performed by variable excitation that is variable according to the divided current.

[Action]

In the inverter control device of the present invention, depending on whether the main shaft and the feed shaft are in synchronous operation or in another operation, the vector control by fixed excitation in which the excitation component current given to the main spindle motor is a constant value Alternatively, the control is performed so as to switch to vector control by variable excitation that is variable according to the torque component current, so that stable, highly accurate and highly responsive operation can be performed.

〔Example〕

FIG. 1 is an explanatory diagram showing a weak magnetic excitation rate pattern in an inverter control device according to an embodiment of the present invention. In Fig. 1, the horizontal axis represents the torque component current i _qs , and the vertical axis represents the weakening excitation rate φ.
Shows the ₂ '. Further, (I) is a weak excitation rate pattern for performing synchronous control (a pattern showing fixed excitation according to the present invention),
(II) is a normal weak excitation rate pattern (a pattern showing variable excitation according to the present invention) in which synchronous control is not performed. Such weakening excitation rate patterns (I) and (II) are applied to the fourth
It is held in the weak excitation calculation unit 10 shown in the figure.

FIG. 2 is a flow chart for explaining the operation of switching the weak excitation rate pattern in the inverter control device of FIG.

Next, the operation of the inverter control device according to the present invention will be described. When the main shaft and the feed shaft are operated synchronously, the numerical control device 1 shown in FIG. 3 sends a synchronous signal to the main shaft amplifier 5 composed of the inverter control device shown in FIG. 4 as a switching signal. If the main axis amplifier 5 sees the switching signal and is in synchronous operation, if the weak magnetic excitation rate pattern (I) shown in FIG. 1 is selected, the weak magnetic excitation calculation unit 10 shown in FIG. 4 relates to the torque component current i _qs . Since the weak magnetic excitation rate φ ₂ ′ is set to a constant value of 100%, the secondary magnetic flux command φ ₂ ^* of the φ ₂ ^* calculation unit 11 is not affected by the torque component current i _qs . Here, according to the known vector operation, Therefore, the secondary magnetic flux φ ₂ has a primary delay. Therefore, in the weak excitation rate pattern (II) shown in FIG.
When a load is applied to the spindle motor 6, the rise of the secondary magnetic flux φ ₂ is delayed with respect to the rise of the torque current i _qs.
Although the rising be first-order delay of the output torque T _M, so selecting the excitation rate pattern (I) weakened in synchronous operation, the rise of the output torque T _M of the spindle motor 6 with respect to the rise of the torque current i _qs secondary Not affected by magnetic flux φ ₂ . Therefore, when a load is applied to the main spindle, the delay of the output torque T _M of the main spindle motor 6 is small, the speed fluctuation is suppressed, and the synchronous deviation can be reduced when the synchronous operation of the main spindle and the feed axis is performed. In addition, the conventional control can be performed during the normal operation other than the synchronous operation.

Next, the features of the inverter control device according to the present invention will be described. In the inverter control device of the present invention, as shown in FIG. 1, (1) the torque component current of the spindle motor 6
When i _qs is 0, that is, when there is no load, the weak excitation ratio φ ₂ ′ is 5
0%, (2) the weaker excitation rate φ ₂ ′ is increased as the torque component current i _qs increases, and (3) the torque component current i _qs is 100%, that is, the spindle motor 6 has a rated load. When applied, the weakening excitation rate φ ₂ ′ is also set to 100%. By performing such a control operation, (A) when the spindle motor 6 is unloaded or when the load is light, the excitation current of the spindle motor 6 is reduced to reduce the vibration and noise (excitation sound) of the spindle motor 6. Further, (B) when the spindle motor 6 is at the rated load, the excitation current of the spindle motor 6 is set to 100% excitation, and the spindle motor 6 can output a regular rated torque. As a result, the spindle motor 6 can exhibit the characteristics that vibration and noise are small and stable torque can be generated.

In the above embodiment, the case where the machine tool is used to thread the workpiece has been described. However, the C-axis control (rotating angle of the spindle axis (spindle) of the machine tool for controlling the rotational position of the workpiece to perform cutting is described. In the case of controlling), the same effect as that of the above embodiment is obtained.

〔The invention's effect〕

As described above, according to the present invention, in the inverter control device, during synchronous operation of the spindle and the feed axis, vector control is performed by fixed excitation with a constant value of the excitation rate current applied to the spindle motor, and during other operations, the excitation is performed. Since vector control is performed by variable excitation that makes the split current variable according to the torque split current, in all operating modes when the spindle and feed axis are in synchronous operation or in other operation, or Even when the load is light or heavy, the present invention has an excellent effect that stable, highly accurate and highly responsive operation can be performed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a weak excitation rate pattern in an inverter control device according to an embodiment of the present invention, and FIG. 2 is a flow chart for explaining an operation of switching the weak excitation rate pattern in the inverter control device of FIG. FIG. 3 is a block diagram showing a system for synchronously operating a spindle and a feed axis in a conventional machine tool, and FIG. 4 is a block showing a configuration of a spindle amplifier composed of a conventional inverter controller common to the present invention. It is a figure. In the figure, 1 ... Numerical control device, 2 ... Feed axis amplifier, 3 ... Feed axis motor, 4 ... Feed axis position detector,
5 ... Spindle amplifier, 6 ... Spindle motor, 7 ... Spindle position detector, 8 ... Position loop calculation unit, 9 ... Velocity loop calculation unit, 10 ... Weak excitation calculation unit, 11 ... φ ₂ ^* Calculator,
12 …… φ ₂ arithmetic unit, 13 …… M arithmetic unit, 14 …… _ids arithmetic unit, 15 …… | I ₁ | arithmetic unit, 16 …… Δθ arithmetic unit, 17 …… ω _s
It is a calculation unit. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An inverter control device for a spindle motor, wherein a spindle motor for driving a spindle of a machine tool is controlled in synchronization with a feed shaft motor for driving a feed shaft. Vector control is performed by fixed excitation with the excitation current supplied to the spindle motor as a constant value.In other operations, the weak excitation rate changes up to 100% in proportion to the change in the torque current, and the weak excitation rate of 10%.
An inverter control device comprising a control means for performing vector control by variable excitation, which is kept constant when 0% is reached.