CN-121986309-A - Machine tool control device

Abstract

A machine tool control device according to one embodiment of the present disclosure is a machine tool control device for controlling a machine tool having a spindle driven by an induction motor according to a machining program, and includes a load estimating unit for estimating whether a load state of the spindle includes no idling of a load due to machining or includes actual operation of the load due to machining by prereading the machining program, and a current control unit for controlling a d-axis current and a q-axis current of a spindle current supplied to the induction motor so that a rotational speed of the spindle matches a rotational speed according to the machining program, and setting the d-axis current to a value larger than that estimated as the idling when the actual operation is estimated.

Inventors

• Changlong Rengui
• IKAI SATOSHI

Assignees

• 发那科株式会社

Dates

Publication Date

20260505

Application Date

20231109

Claims (6)

1. 1. A machine tool control device for controlling a machine tool having a spindle driven by an induction motor according to a machining program, characterized in that, The machine tool control device is provided with: A load estimating unit for estimating whether the load state of the spindle includes idling of the load due to machining or actual operation of the load due to machining by pre-reading the machining program, and And a current control unit that controls a d-axis current and a q-axis current of a spindle current supplied to the induction motor so that a rotational speed of the spindle matches a rotational speed according to the machining program, and sets the d-axis current to a value larger than that estimated to be the idling when the actual operation is estimated.
2. 2. The machine tool control device according to claim 1, wherein, When the slip is estimated, the current control unit controls the d-axis current and the q-axis current to be equal to or less than a minimum value of norms of currents on a constant torque curve corresponding to friction torque of the main shaft at the time of the slip.
3. 3. A machine tool control device according to claim 1 or 2, wherein, When it is estimated that the motor is idling, the current control unit controls the spindle current so that the slip frequency of the induction motor coincides with the inverse of the second time constant of the induction motor.
4. 4. A machine tool control device according to claim 1 or 2, wherein, When the idling is estimated, the current control unit controls the d-axis current and the q-axis current to be equal to each other.
5. 5. The machine tool control device according to any one of claim 1 to 4, wherein, When it is estimated that the actual operation is shifted from the idling operation, the current control unit sets the d-axis current to a value larger than that at the idling operation before the shift to the actual operation.
6. 6. The machine tool control device according to claim 5, wherein, The preceding time from the time when the d-axis current is set to a value greater than the idling time to the time when the d-axis current is estimated to be shifted to the actual operation is 4 times or more and 10 times or less of the secondary magnetic flux time constant of the induction motor.

Description

Machine tool control device Technical Field The present invention relates to a machine tool control device. Background Induction motors are utilized as various power sources. The speed of the induction motor is also controlled by supplying electric power from the inverter to the induction motor (for example, refer to patent document 1). As a specific method of controlling the speed of the induction motor, V/f control, vector control, and the like are known, for example. Prior art literature Patent literature Patent document 1 Japanese patent application laid-open No. 2018-57161 Disclosure of Invention Problems to be solved by the invention In a machine tool, accurate control of the rotational speed of a motor is required. However, the load of the spindle of the machine tool abruptly changes according to the state of machining, for example, according to whether or not the workpiece is cut by the tool. For example, when the state of idling in which the tool is not in contact with the workpiece is shifted to the state of actual operation in which the tool cuts the workpiece, the output torque of the induction motor needs to be increased rapidly, but the rise of the secondary magnetic flux of the induction motor needs to take time, so that in the control based on the feedback of the rotation speed detection value, the deviation from the target speed may become large. Therefore, a technique capable of accurately controlling the rotational speed of a main shaft driven by an induction motor is desired. Means for solving the problems A machine tool control device according to one embodiment of the present disclosure is a machine tool control device for controlling a machine tool having a spindle driven by an induction motor according to a machining program, and includes a load estimating unit for estimating whether a load state of the spindle includes no idling of a load due to machining or includes actual operation of the load due to machining by prereading the machining program, and a current control unit for controlling a d-axis current and a q-axis current of a spindle current supplied to the induction motor so that a rotational speed of the spindle matches a rotational speed according to the machining program, and setting the d-axis current to a value larger than that estimated as the idling when the actual operation is estimated. Drawings Fig. 1 is a block diagram showing a structure of a machine tool provided with a machine tool control device according to an embodiment of the present disclosure. Fig. 2 is a graph showing a constant torque curve in the dq current coordinate system of the induction motor. Fig. 3 is a timing chart showing changes in the load of the spindle, the command value of the current control unit, and the state of the induction motor. Detailed Description Embodiments of the present disclosure will be described below with reference to the drawings. Fig. 1 is a block diagram showing the structure of a machine tool 1 according to a first embodiment of the present disclosure. The machine tool 1 includes a machine tool control device 10, a spindle 20 for rotating a workpiece or a tool, an induction motor 30 for driving the spindle 20, a spindle amplifier 40 for supplying a spindle current to the induction motor 30 in accordance with a command of the machine tool control device 10, a positioning mechanism 50 for determining a relative position between the workpiece and the tool, a plurality of servo motors 60 for driving the positioning mechanism, and a plurality of servo amplifiers 70 for supplying power to the servo motors 60 in accordance with a command of the machine tool control device 10. In the machine tool 1, the induction motor 30, the spindle amplifier 40, the positioning mechanism 50, the servo motor 60, and the servo amplifier 70 are well known structures, and therefore, detailed description thereof is omitted. The machine tool control device 10 is one embodiment of the machine tool control device of the present invention. The machine tool control device 10 has, for example, a memory, a processor, an input/output interface, and the like, and can be realized by one or more computer devices executing an appropriate control program. Typically, the machine tool control device 10 is configured as a numerical control device. The machine tool control device 10 includes a machining program storage unit 11, a load estimating unit 12, a current control unit 13, and a positioning control unit 14. These components are classified into functions of the machine tool control device 10, and may not be clearly distinguishable from the physical structure or the program structure. The machining program storage unit 11 stores a machining program describing a relative movement path of a tool with respect to a workpiece for cutting the workpiece to obtain a desired product, for example, in a predetermined language such as G-code. The load estimating unit 12 estimates the load state of the spindle 20 by a