Control device and program

Abstract

Provided is a control device and program capable of easily outputting the state of mechanical loss in an induction motor. A control device that controls an industrial machine having an induction motor includes: a power cutoff section that cuts off power supply to the induction motor; a speed acquisition section that acquires the rotational speed of the induction motor; an acceleration calculation section that calculates acceleration based on the acquired rotational speed; a moment of inertia acquisition section that acquires the moment of inertia of the main shaft of the induction motor; a mechanical loss calculation section that calculates the mechanical loss of the induction motor based on the acquired rotational speed, the calculated acceleration, and the acquired moment of inertia; and an output section that outputs the calculated mechanical loss.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a control device and a program. BACKGROUND

[0002] Conventionally, a machine tool having an induction motor is known. The induction motor is used for rotation of a spindle, for example, in accordance with its relatively wide low output characteristics.

[0003] In addition, since the mechanical friction of the spindle is large, relatively large heat generation can occur at the time of no-load start of the induction motor. In addition, since the mechanical friction of the spindle is large, machining according to the output specifications of the induction motor can not be performed at times. In order to detect such a state, for example, a machine tool that checks the deterioration state of a motor is proposed (for example, refer to Patent Literature 1).

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2016-200523 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] In the machine tool described in Patent Literature 1, the time until the motor that rotates by inertia stops is measured after the power to the spindle motor is cut off. In addition, in the machine tool described in Patent Literature 1, it is determined whether the measured time deviates from a threshold time interval that is decided in advance. Thus, the deterioration of the motor can be easily detected. In particular, it is useful to easily output the state of mechanical loss in the induction motor.

[0009] SOLUTION TO PROBLEM

[0010] (1) The present disclosure relates to a control device that controls an induction motor, the control device including: a power cut-off section that cuts off power supply to the induction motor; a speed acquisition section that acquires a rotational speed of the induction motor; an acceleration calculation section that calculates an acceleration based on the acquired rotational speed; an inertia moment acquisition section that acquires an inertia moment of a spindle of the induction motor; a mechanical loss calculation section that calculates a mechanical loss of the induction motor based on the acquired rotational speed, the calculated acceleration, and the acquired inertia moment; and an output section that outputs the calculated mechanical loss.

[0011] (2) In addition, the present disclosure relates to a program that causes a computer to function as a control device that controls an induction motor, the program causing the computer to function as: a power cutoff section that cuts off power supply to the induction motor; a speed acquisition section that acquires a rotational speed of the induction motor; an acceleration calculation section that calculates an acceleration based on the acquired rotational speed; a moment of inertia acquisition section that acquires a moment of inertia of a main shaft of the induction motor; a mechanical loss calculation section that calculates a mechanical loss of the induction motor based on the acquired rotational speed, the calculated acceleration, and the acquired moment of inertia; and an output section that outputs the calculated mechanical loss.

[0012] Effects of the Invention

[0013] According to the present disclosure, it is possible to provide a control device and a program that can easily output a state of a mechanical loss in an induction motor. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a schematic configuration diagram illustrating a control system including a control device according to an embodiment of the present disclosure.

[0015] Figure 2 is a schematic diagram illustrating a relationship between input and output of an induction motor controlled by the control device according to an embodiment.

[0016] Figure 3 is a block diagram illustrating a structure of the control device according to an embodiment.

[0017] Figure 4 is a graph illustrating a relationship between a rotational speed of an induction motor acquired by a speed acquisition section of the control device according to an embodiment and a time.

[0018] Figure 5 is a graph illustrating a relationship between an acceleration of an induction motor calculated by an acceleration calculation section of the control device according to an embodiment and a time.

[0019] Figure 6 is a graph illustrating an example of a relationship between a rotational speed and a mechanical loss output by an output section of the control device according to an embodiment.

[0020] Figure 7 is a graph illustrating an example of a relationship between a rotational speed and a mechanical loss output by an output section of the control device according to an embodiment.

[0021] Figure 8 is a graph illustrating an example of a relationship between a rotational speed and a mechanical loss output by an output section of the control device according to an embodiment.

[0022] Figure 9 is a flowchart showing a flow of an action of the control device of one embodiment. DETAILED DESCRIPTION

[0023] Hereinafter, a control device 1 and a program according to one embodiment of the present disclosure will be described with reference to Figures 1 to 9

[0024] Before the control device 1 and the program of the present embodiment are described, a configuration of a control system 100 including the control device 1 will be described.

[0025] For example, as shown in Figure 1 , the control system 100 is provided with an industrial machine 10 and the control device 1. The control system 100 is, for example, a system that processes a workpiece W according to a machining program decided in advance.

[0026] The industrial machine 10 is, for example, a machine tool. The industrial machine 10 processes the workpiece W placed on a table T. The industrial machine 10 is provided with an induction motor 11 and a tool 12. Further, the industrial machine 10 refers to a machine including various machines such as a machine tool, an industrial robot, a service robot, a forging press, and an injection molding machine.

[0027] The induction motor 11 is, for example, a motor that drives a spindle (not shown). The induction motor 11 rotates the spindle around an axis by generating a rotating magnetic field at the time of energization. On the other hand, the induction motor 11 rotates the spindle around the axis by inertia until the induction motor 11 stops after the power is turned off (hereinafter, the rotation after the power is turned off is also referred to as "free rotation").

[0028] The tool 12 is, for example, an implement that actually processes the workpiece W by removal. The tool 12 is disposed to the spindle. The tool 12 is, for example, mounted to the spindle of the induction motor 11. Also, the tool 12 processes the workpiece W using the torque of the induction motor 11.

[0029] The control device 1 is a device that controls the industrial machine 10. The control device 1 is, for example, a device that servo-controls the action of the induction motor 11. The control device 1 processes the workpiece W into a desired shape by controlling the action (rotational speed) of the induction motor 11.

[0030] Next, the calculation method of the mechanical loss of the induction motor 11 will be described in more detail.

[0031] For example, as shown in Figure 2 , the induction motor 11 outputs power with respect to the input (supply) of electric power. At this time, the loss in the induction motor 11 can be found by the difference between the input and the output. That is, it can be found by (loss) = (input) - (output). ​

[0032] Further, the loss can be found by the sum of the copper loss, the iron loss, and the mechanical loss. That is, by (loss) = (copper loss) + (iron loss) + (mechanical loss).

[0033] Here, the copper loss is a loss generated by current. In addition, the iron loss is a loss generated by a change in magnetic flux.

[0034] The induction motor 11 does not have a permanent magnet. Therefore, in the induction motor 11, both the copper loss and the iron loss become 0 by power cut. That is, in the induction motor 11, it becomes (loss) = (mechanical loss), and it becomes (mechanical loss) = -(output). Further, the average loss P [W] in a certain range at the time of deceleration stop by power cut so as to be reduced only by the mechanical loss is expressed by using the moment of inertia J [kgm 2 ] of the main shaft.

[0035] [Equation 1]

[0036]

[0037] Here, N1 (1 / min) is a start speed at the start time t1 (sec) of the above certain range. In addition, N2 is an end speed at the end time t2 (sec) of the above certain range.

[0038] In addition, when an angular acceleration a [rad / s 2 ] at a certain angular velocity ω [rad / s] at the time of deceleration stop is used, the mechanical loss L [W] at the angular velocity ω [rad / s] can be found by calculating

[0039] L = J · a · ω

[0040] .

[0041] Next, the control device 1 and the program of the present embodiment will be described.

[0042] For example, as shown in Figure 3 , the control device 1 related to the present embodiment is provided with a power cut portion 101, a speed acquisition portion 102, an acceleration calculation portion 103, a moment of inertia acquisition portion 107, a mechanical loss calculation portion 104, a detection portion 105, and an output portion 106.

[0043] The power cut portion 101 is realized by, for example, the CPU acting. The power cut portion 101 is used to cut the power supply to the induction motor 11. The power cut portion 101 cuts the power supply from the power supply portion (not shown) to the induction motor 11 at a prescribed timing, for example. Specifically, the power cut portion 101 causes the industrial machine 10 to cut the power supply to the induction motor 11 by transmitting an instruction for cutting the power supply to the induction motor 11 to the industrial machine 10.

[0044] The speed acquisition unit 102 is implemented, for example, by a CPU. The speed acquisition unit 102 acquires the rotational speed of the induction motor 11. The speed acquisition unit 102 acquires, for example, the rotational speed of the induction motor 11 by acquiring an output signal representing angular velocity from a sensor (not shown) provided on the induction motor 11. The speed acquisition unit 102 acquires, for example, the rotational speed of the induction motor 11. Figure 4 The rotational speed of the induction motor 11 is shown when the power is cut off at time t0.

[0045] The acceleration calculation unit 103 is implemented, for example, by a CPU. The acceleration calculation unit 103 calculates acceleration based on the acquired rotational speed. For example, the acceleration calculation unit 103 calculates acceleration by differentiating the acquired rotational speed. The acceleration calculation unit 103 calculates, for example, as... Figure 5 The acceleration shown is caused by the mechanical losses of the induction motor 11 when the power is cut off at time t0.

[0046] The moment of inertia acquisition unit 107 is implemented, for example, by a CPU. The moment of inertia acquisition unit 107 acquires the moment of inertia of the main shaft of the induction motor 11 from an external source.

[0047] The mechanical loss calculation unit 104 is implemented, for example, by a CPU. Based on the acquired rotational speed, the calculated acceleration, and the acquired moment of inertia, the mechanical loss calculation unit 104 calculates the mechanical loss of the induction motor 11. For example, the mechanical loss calculation unit 104 calculates... Figure 6 The relationship between mechanical loss and rotational speed (frequency) is shown.

[0048] Furthermore, in the event of a sudden phenomenon that causes changes such as friction in the induction motor 11, the mechanical loss calculation unit 104 calculates, for example... Figure 7 The relationship between mechanical loss and rotational speed (frequency) is shown. In this example, the mechanical loss calculation unit 104 calculates a higher rate of change of mechanical loss compared to other rotational speeds at rotational speed v1. That is, regarding the rate of increase of mechanical loss relative to the increase of rotational speed, the mechanical loss calculation unit 104 calculates a relatively high rate of increase of mechanical loss at rotational speed v1.

[0049] Furthermore, in the event of improper lubrication of the bearings (not shown) of the induction motor 11, the mechanical loss calculation unit 104 calculates as follows: Figure 8The illustrated mechanical loss is a relationship with the rotational speed (frequency). In this example, the mechanical loss calculating section 104 calculates a change rate of the mechanical loss that is higher than that of the other rotational speeds at the rotational speed v2. That is, with respect to the increase rate of the mechanical loss with respect to the increase in the rotational speed, the mechanical loss calculating section 104 calculates a higher increase rate of the mechanical loss at the rotational speed v2.

[0050] The detecting section 105 is realized by, for example, the CPU acting. The detecting section 105 detects a change in which the increase rate of the mechanical loss with respect to the increase in the speed becomes greater than a prescribed value, with respect to the calculated mechanical loss. In addition, the detecting section 105 detects the rotational speed at which the increase rate becomes greater than the prescribed value. For example, in the example of Figure 6 , the detecting section 105 does not detect a change in which the increase rate becomes greater than the prescribed value. For example, in the example of Figure 7 , the detecting section 105 detects an increase in the mechanical loss at the rotational speed vl as a change in which the increase rate becomes greater than the prescribed value. For example, in the example of Figure 8 , the detecting section 105 detects an increase in the mechanical loss at the rotational speed v2 as a change in which the increase rate becomes greater than the prescribed value.

[0051] The output section 106 is realized by, for example, the CPU acting. The output section 106 outputs the calculated mechanical loss. The output section 106, for example, outputs the relationship between the rotational speed (frequency) and the mechanical loss calculated by the mechanical loss calculating section 104 as a signal displayed on a display device (not illustrated) such as a display. In addition, the output section 106 outputs a signal indicating that a change greater than a prescribed value is detected. The output section 106, for example, outputs a signal indicating that a change greater than a prescribed value is detected as a signal of display, sound, or the like. In addition, the output section 106 outputs a signal indicating the detected rotational speed. The output section 106, for example, outputs a signal indicating the detected rotational speed vl. In addition, the output section 106, for example, outputs a signal indicating the detected rotational speed v2.

[0052] Next, the operation of the control device 1 will be described.

[0053] First, the power cutoff section 101 cuts off the supply of electric power to the induction motor 11 (step S1). Next, the speed acquiring section 102 acquires the rotational speed of the induction motor 11 over time (step S2). Next, the acceleration calculating section 103 calculates the acceleration based on the acquired rotational speed (step S3). In addition, the moment of inertia acquiring section 107 acquires the moment of inertia of the main shaft of the induction motor 11 (step S4). Next, the mechanical loss calculating section 104 calculates the mechanical loss based on the acquired rotational speed, the calculated acceleration, and the acquired moment of inertia (step S5).

[0054] Next, the detection section 105 detects the rotational speed at which the rate of increase in the rotational speed in the relationship between the rotational speed and the mechanical loss forms an increase rate of a prescribed value or more (step S6). In a case where the increase rate of the prescribed value or more is detected (step S6: "Yes"), the processing proceeds to step S7. On the other hand, in a case where the increase rate of the prescribed value or more is not detected (step S6: "No"), the detection section 105 does not output a signal. Then, the processing proceeds to step S8.

[0055] In step S7, the detection section 105 sends a signal indicating the detected signal to the output section 106. In addition, the detection section 105 sends a signal indicating the detected rotational speed to the output section 106. Then, the processing proceeds to step S8.

[0056] In step S8, the output section 106 outputs the calculated mechanical loss. In addition, the output section 106 outputs a signal indicating that the increase rate of the prescribed value or more is detected and a signal indicating the detected rotational speed in a case where the signal from the detection section 105 is received.

[0057] Next, the program will be described.

[0058] Each structure included in the control device 1 can be realized by hardware, software, or a combination thereof, respectively. Here, the realization by software means the realization by reading and executing the program by a computer.

[0059] The program can be saved and provided to a computer using various types of non-transitory computer readable medium. The non-transitory computer readable medium includes various types of tangible storage media. Examples of the non-transitory computer readable medium include a magnetic recording medium (e.g., a floppy disk, a magnetic tape, a hard disk drive), a magneto-optical recording medium (e.g., a magneto-optical disk), a CD-ROM (Read Only Memory), a CD-R, a CD-R / W, a semiconductor memory (e.g., a mask ROM, a PROM (Programmable ROM), an EPROM (Erasable PROM), a flash ROM, a RAM (Random Access Memory)). In addition, the program can be supplied to the computer by various types of transitory computer readable medium. Examples of the transitory computer readable medium include an electrical signal, an optical signal, and an electromagnetic wave. The transitory computer readable medium can supply the program to the computer via a wired communication path such as an electrical wire and an optical fiber, or a wireless communication path.

[0060] According to the control device 1 and the program according to the above one embodiment, the following effects can be obtained.

[0061] (1) A control device 1 that controls an industrial machine 10 having an induction motor 11, the control device 1 including: a power cutoff section 101 that cuts off power supply to the induction motor 11; a speed acquisition section 102 that acquires a rotational speed of the induction motor 11; an acceleration calculation section 103 that calculates an acceleration based on the acquired rotational speed; an inertia moment acquisition section 107 that acquires an inertia moment of a main shaft of the induction motor 11; a mechanical loss calculation section 104 that calculates a mechanical loss of the induction motor 11 based on the acquired rotational speed, the calculated acceleration, and the acquired inertia moment; and an output section 106 that outputs the calculated mechanical loss. Thereby, it is possible to easily output the state of the mechanical loss in the induction motor 11. Thus, in a case where the vibration at the time of no-load operation of the induction motor 11 is large, it is possible to easily determine the presence or absence of a mechanical abnormality of the main shaft M. In addition, in a case where there is an abnormality in the main shaft M, it is possible to distinguish the main cause and thus easily perform analysis.

[0062] (2) The control device 1 further includes a detection section 105 that detects, with respect to the calculated mechanical loss, a change in which an increase rate of the mechanical loss with respect to an increase in the rotational speed becomes larger than a prescribed value, and the output section 106 outputs a signal indicating that the change larger than the prescribed value is detected. Thereby, it is possible to output the abnormality of the mechanical loss of the induction motor 11 together with the calculated mechanical loss.

[0063] (3) The detection section 105 detects a rotational speed at which the increase rate of the mechanical loss becomes larger than the prescribed value, and the output section 106 outputs a signal indicating the detected rotational speed. Thereby, it is also possible to output details of the abnormality. Thus, it is possible to provide information that can be predicted with respect to the kind of the assumed bad condition.

[0064] The above describes one embodiment of the control device and the program of the present disclosure, but the present disclosure is not limited to the above-described embodiment and can be appropriately changed.

[0065] For example, in the above-described embodiment, it is assumed that the speed acquisition section 102 operates after the power supply is cut off, but it is not limited thereto. The speed acquisition section 102 can acquire the rotational speed of the induction motor 11 at all times.

[0066] In addition, in the above-described embodiment, a main cause output section (not shown) that outputs a main cause of the assumed abnormality based on the increase rate of the mechanical loss can also be included. The main cause output section can also output, for example, a signal indicating that the rotational speed is high in a case where the rotational speed is high when the increase rate of the mechanical loss becomes larger than the prescribed value.Figure 7 In this case, the signal indicating that a sudden change in friction or the like is considered to have occurred is sent to the output section 106. In addition, for example, in Figure 8 In this case, the main cause output section can also send a signal to the output section 106 indicating that the state of the lubrication of the bearing is inappropriate, and thus the loss increases in the high speed region. The output section 106 can also output the signal acquired from the main cause output section.

[0067] In addition, in the above embodiment, the detection section 105 can also detect the rotational speed at which the increase rate of the mechanical loss becomes greater than a prescribed value in the form of a region. The output section 106 can also output a signal indicating the region of the detected rotational speed.

[0068] Explanation of Reference Signs

[0069] 1: control device; 10: industrial machine; 11: induction motor; 12: tool; 101: power cut-off section; 102: speed acquisition section; 103: acceleration calculation section; 104: mechanical loss calculation section; 105: detection section; 106: output section; 107: moment of inertia acquisition section.

Claims

1. A control device that controls an induction motor, the control device comprising: a power cut-off section that cuts off supply of electric power to the induction motor; a speed acquisition section that acquires a rotational speed of the induction motor; an acceleration calculation section that calculates an acceleration based on the acquired rotational speed; a moment of inertia acquisition section that acquires a moment of inertia of a main shaft of the induction motor; a mechanical loss calculation section that calculates a mechanical loss of the induction motor based on the acquired rotational speed after the supply of electric power to the induction motor is cut off by the power cut-off section, the calculated acceleration, and the acquired moment of inertia; and an output section that outputs the calculated mechanical loss.

2. The control device according to claim 1, further comprising a detection section that detects, with respect to the calculated mechanical loss, a change in which an increase rate of the mechanical loss with respect to an increase in rotational speed becomes greater than a prescribed value, wherein the output section outputs a signal indicating that the change in which the increase rate becomes greater than the prescribed value is detected.

3. The control device according to claim 2, wherein the detection section detects a rotational speed that causes the increase rate of the mechanical loss to become greater than the prescribed value, and the output section outputs a signal indicating the detected rotational speed.

4. A non-transitory computer-readable recording medium that stores a program that causes a computer to function as a control device that controls an induction motor, the program causing the computer to function as: a power cut-off section that cuts off supply of electric power to the induction motor; a speed acquisition section that acquires a rotational speed of the induction motor; an acceleration calculation section that calculates an acceleration based on the acquired rotational speed; a moment of inertia acquisition section that acquires a moment of inertia of a main shaft of the induction motor; a mechanical loss calculation section that calculates a mechanical loss of the induction motor based on the acquired rotational speed after the supply of electric power to the induction motor is cut off by the power cut-off section, the calculated acceleration, and the acquired moment of inertia; and an output section that outputs the calculated mechanical loss. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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