JP2009068950A - Machine diagnostic system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that a frequency characteristic is occasionally examined from a motor torque instruction to a motor speed as a means to comprehend a dynamic characteristic of a machine connected to a motor, however, the comprehended dynamic characteristic is currently used only as a servo adjustment support function and thus the machine cannot be diagnosed with respect to its abnormality (increase of frictional force due to increased viscosity at support sections). <P>SOLUTION: A plurality of speed instructions are transmitted from a personal computer 101 to a servo amplifier 102 pattern-by-pattern, a torque instruction and a motor speed are loaded from a motor 103 in use, the loaded data undergo an averaging treatment, and the result is displayed as a graph, consequently, increase or decrease of viscous or static friction can be simply confirmed and problems of the machine can be diagnosed based on the result. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a machine diagnostic apparatus for diagnosing the breakage status and grease life of a machine driven by an electric motor.

As a conventional machine diagnostic apparatus, a machine diagnostic apparatus as shown in FIG. 8 is disclosed (see Patent Document 1). In the figure, 801 is a program analysis unit, 802 is a command value generation unit, 803 is a motor control unit, 804 is a state quantity calculation unit, 805 is a temperature estimation unit, 806 is an evaluation data calculation unit, and 807 is an evaluation data storage unit. , 808 is a current life evaluation unit. The grease life is evaluated in consideration of the temperature of the grease estimated by the temperature estimation unit 805 from the state quantity of the speed reducer calculated by the state quantity calculation unit 804.
In addition, the friction coefficient of the speed reducer is identified from the motor state quantity, and the temperature is estimated from the friction coefficient. This makes it possible to accurately evaluate the life of the grease without adding a temperature sensor or the like even when the temperature condition is unknown or the temperature condition changes.
Further, as a diagnostic device capable of monitoring the arrival of a real replacement time for parts of an industrial robot and detecting and notifying the maintenance inspection time, a diagnostic device as shown in FIG. 9 is disclosed (see Patent Document 2). In the figure, 901 is a display unit, 902 is a calculation unit, 903 is a drive unit, 904 is a monitor unit, M1 to Mn are motors, and Jn is a joint.
The calculation unit 902 is a monitor unit 904 that monitors the operation state of the motors M1 to Mn, detects the torque of the motor shaft and the rotation speed of the motor shaft, calculates the damage degree per unit time of the joint Jn from these, and The maintenance time or the remaining durability time or the replacement time of the joint Jn can be detected on the basis of the accumulated damage degree obtained by accumulating the degree and can be notified by the display 901.
Further, Patent Document 3 is disclosed as an apparatus that can manage the life of parts of a robot. After the servo power is turned on to the robot controller, the life of the reducer and grease is cumulatively calculated using the motor torque commanded to the servo motor and the number of revolutions every sampling time. This cumulative calculation value is compared with a preset reference value, and if this reference value is exceeded, the necessity for parts replacement and inspection is displayed and a warning is issued.

JP 2004-309221 A Japanese Patent Laid-Open No. 9-81215 Japanese Unexamined Patent Publication No. 7-124889

In conventional machine diagnostic equipment, it is said that the life of the reducer and grease can be accurately grasped. Actually, the friction coefficient is identified using the motor current, motor speed, torque command, etc., and the temperature is estimated from the friction coefficient. If so. Regarding the life of grease, not only temperature but also humidity is related, and it is difficult to separate the relationship between aging and temperature change, so it is difficult to accurately measure the life of grease. Further, the degree of damage was determined using the rotational speed of the joint Jn, the sampling time, and the limit number of repetitions, and the time when the cumulative value of the degree of damage exceeded a certain threshold was set as the grease injection timing. In this case, there is a problem that the grease injection timing is known, but the breakage timing is unknown.
The present invention has been made in view of such problems, and an object of the present invention is to provide a machine diagnostic apparatus that diagnoses a grease injection timing based on a failure point of a machine and an increase / decrease in a friction coefficient.

In order to solve the above problem, the present invention is configured as follows.
The invention of the machine diagnostic device according to claim 1 is a machine diagnostic device for diagnosing the life of a machine by measuring friction of a machine driven by a motor, wherein an input unit for inputting a speed command to the motor control unit, a storage unit, and a display In the machine diagnostic device comprising a unit and a calculation unit, a torque command or a thrust command during driving of the motor driven by the motor control device and a motor speed are stored in the storage unit, and the calculation unit is stored in the storage unit. The torque command or the thrust command and the motor speed during initial operation, and the torque command or the thrust command and the motor speed after a predetermined period of time are read out and simultaneously displayed on the display screen of the display unit, respectively. It is characterized by.
According to a second aspect of the present invention, in the machine diagnostic apparatus according to the first aspect, the torque command or the thrust command corresponding to the plurality of motor speeds stored by the arithmetic unit is read, and these are subjected to Fourier transform. A power spectrum of the torque command or the thrust command is obtained and displayed on a display screen of the display unit.
According to a third aspect of the present invention, in the machine diagnostic apparatus according to the first aspect, the torque command or the thrust command data is stored in one cycle from the start of acceleration to the completion of acceleration during motor acceleration, and the arithmetic unit stores the data. The torque command or the thrust command is read and Fourier transformed to obtain a power spectrum of the torque command or the thrust command, and this is displayed on the display screen of the display unit.
According to a fourth aspect of the present invention, there is provided a machine diagnostic apparatus for diagnosing the life of a machine by measuring friction of a machine driven by a motor, wherein an input unit, a storage unit, and a display for inputting a position command to the motor control unit are provided. In the machine diagnostic device comprising a unit and a calculation unit, a torque command or a thrust command during driving of the motor driven by the motor control device and a motor position are stored in the storage unit, and the calculation unit is stored in the storage unit. The torque command or the thrust command and the motor position at the time of initial operation, and the torque command or the thrust command and the motor position after a predetermined time have elapsed are read and simultaneously displayed on the display screen of the display unit, respectively. It is characterized by.

According to the first aspect of the present invention, since the torque command and the motor speed during the initial operation, and the torque command and the motor speed after a predetermined time have been simultaneously displayed on the display screen of the display unit, Changes in static friction force and coefficient of friction after time can be observed.
According to the second aspect of the present invention, the torque command corresponding to the motor speed is Fourier-transformed, and the power spectrum of the torque command is displayed on the display screen, so that periodic torque fluctuations around one rotation of the motor are observed. As a result, the machine breakage status can be confirmed in detail.
According to the invention described in claim 3, the torque command is Fourier-transformed with one cycle from the start of acceleration to the completion of acceleration during motor acceleration, and the power spectrum of the torque command is obtained and displayed. Since the torque command in the speed change state can be observed, the machine breakage status can be confirmed in a short time.
According to the fourth aspect of the invention, the torque command and the motor position at the time of initial operation, and the torque command and the motor position after a predetermined time have been simultaneously displayed on the display screen of the display unit. The torque change depending on can be observed, so that the machine breakage point can be specified.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of the machine diagnostic apparatus of the present invention.
In the figure, 101 is an external display device (for example, a personal computer), 102 is a servo amplifier that drives a motor, 103 is a motor, 104 is a load machine (for example, a single-axis slider), and 105 is a command from the external display device 101 to the servo amplifier 102. And a communication cable for transferring data to be transmitted from the servo amplifier 102 to the external display device 101, a power cable 106 for transmitting a drive current from the servo amplifier 102 to the motor 103, and an encoder signal (107) from the motor 103 to the servo amplifier 102. Encoder cable to transmit (sine, cosine wave, serial data, etc.). In the external display device 101, for example, a speed trapezoidal wave command is created in advance and transferred to the servo amplifier 102. Based on this speed command, the motor 103 rotates and the machine 104 coupled to the motor 103 moves. Motor information (motor position, motor speed, motor torque command) when the motor 103 is driven is transferred to the external display device 101. Before displaying on the external display device 101, the motor speed and torque command at the maximum motor speed with respect to the command are stored. After the motor speed and torque command are stored in a plurality of speed trapezoidal waves, the external display device 101 plots and displays the motor speed and motor torque in FIG. 2 using the motor speed and torque command. When this is displayed and linear interpolation is performed for the portions 201 and 202 in the figure, Equation (1) is obtained.

T represents a torque command, v represents a motor speed, A represents a viscous friction coefficient, and B represents static friction.
For example, the viscous friction coefficient (A) of the 201 portion shown in FIG. 2 is 10.2e-5 (Nms / rad), the static friction (B) is 0.0125 Nm, and the viscous friction coefficient (A) of the 202 portion is 8 .46e-5 (Nms / rad) and static friction (B) is -0.00549 Nm. It can be seen that the average value of the positive and negative static friction (B) is a steady torque disturbance and is 0.0035 Nm. The viscous friction coefficient and the static friction are recorded after the initial continuous operation, and the motor information when the motor is operated with the speed trapezoidal wave pattern for one week or one month is used for the external display device 101 to When the motor torque is plotted, a waveform as shown in FIG. 3 is obtained.
In FIG. 3, the horizontal axis is the motor speed (rad / s), the vertical axis is the motor torque (Nm), the solid line in the diagram is the friction characteristic of the new slider, the thick line is the friction characteristic of the slider two years after the start of use, and the dotted line Is the friction characteristics of the slider that is about to be replaced.
It can be confirmed that both the friction coefficient (gradient) and static friction (intercept) of the slider friction characteristics (thick line) two years after the start of use increase compared to the friction characteristics (solid line) of the new slider. . Therefore, if the viscous friction coefficient (gradient) exceeds the value specified by the grease manufacturer (gradient of the friction characteristics of the dotted slider that is about to be replaced) over time, the grease is replaced and static friction is applied. If the (intercept) is larger than the value specified by the machine manufacturer (intercept of the dotted slider frictional characteristic), there may be factors such as machine wear. Check the wear of machine parts (mainly bearings). .

In the first embodiment, the machine diagnostic apparatus that gives an instruction to replace grease is described. In the second embodiment, a flowchart of the machine diagnostic apparatus for checking the wear state of the machine will be described with reference to FIG.
First, in step S41, the external display device 101 (FIG. 1, for example, a personal computer) creates a speed trapezoidal wave command and transmits it to the servo amplifier 102 (FIG. 1). For example, the speed trapezoidal wave has a constant speed of 100 (1 / min) at an acceleration time and a deceleration time of 100 ms. The servo amplifier 102 gives a speed command to the motor 103 (FIG. 1), and the motor 103 is driven according to the speed command. Information on the motor speed, motor torque, and motor position at that time is acquired and stored in the memory of the servo amplifier 102 for each control cycle of the servo amplifier 102 via the encoder cable 107 (FIG. 1) (S42). Motor information is transferred from the servo amplifier 102 to the external display device 101 using the motor difference position of 0 as a trigger condition (S43).
If the motor information has not been acquired with two or more commands in step S44, the process returns to step S41, and another speed trapezoidal wave command (for example, constant speed 300 (1 / min) with acceleration time and deceleration time 100 ms) Is transmitted to the servo amplifier (S41). The motor is driven according to the speed command. The motor speed, motor torque, and motor position at that time are stored in the memory of the servo amplifier (S42). Similarly to the previous time, motor information is transferred from the servo amplifier 102 to the external display device 101 with the motor difference position being 0 as a trigger condition (S43).
When motor information is acquired by two or more instructions at Step S44, it progresses to Step S45. In step S45, the external display apparatus 101 performs a Fourier transform (FFT) on the torque command in the obtained motor information, and calculates a power spectrum. In step S46, the power spectrum is displayed on the display screen of the external display device 101 with the vertical axis representing the power spectrum of the torque command and the horizontal axis representing the frequency.
The motor speed is Fourier transformed to calculate the power spectrum. The vertical axis represents the motor speed power spectrum and the horizontal axis represents the frequency.
FIG. 5 shows the power spectrum-frequency diagram obtained in this manner, where (a) shows the power spectrum-frequency diagram of the torque command, and (b) shows the power spectrum-frequency diagram of the motor speed. Show. The horizontal axis is frequency (Hz).
Thus, the torque command synchronized with the speed can be confirmed by displaying the power spectrum of the torque command (a) and the speed command (b) and checking the correlation. The power spectrum when the motor is rotating is the largest, and higher-order modes due to the number of rotations also appear. In the figure, the dotted line is the power spectrum at the time of abnormality, and the thick line represents the power spectrum at the time of normal. When abnormal, the power spectrum of the torque command and motor speed is larger than when normal. This is because a power loss occurs at an abnormal time (for example, a wear scar), so that more torque commands are required.
If there are wear marks on the machine, large torque fluctuations depending on the number of rotations can be observed as indicated by the broken line in both figures, but if normal, these are indicated by the thick line at normal. Does not occur. Machine diagnosis is performed by looking at these two power spectra.
Further, in order to increase the measurement accuracy, the torque command and the motor speed when the command condition is changed are acquired, and the same evaluation as described above is performed. This makes machine diagnosis easy and accurate.

In the third embodiment, the location of the wear mark of the machine can be specified.
A machine diagnostic apparatus according to Embodiment 3 will be described with reference to the flowchart of FIG. Similar to the second embodiment, the external display device 101 generates a speed command (for example, acceleration time and deceleration time 10 ms, constant speed 100 (1 / min)), and transmits the generated speed command to the servo amplifier 102 (S61). . The servo amplifier 102 is driven by generating a current for driving the motor 103 in accordance with the speed command and passing the current through the motor 103. The motor information is acquired on condition that the motor speed is “constant speed + α speed” (S62), and the motor information is acquired and stored in the memory area of the servo amplifier 102 (S63). Using the motor difference position of 0 as a trigger condition (S64), the motor information is transferred to the external display device 101 (S65). The external display device 101 displays the motor position on the horizontal axis and the torque command on the vertical axis (S66). Locations where there is a change in torque can be identified as locations of wear marks on the machine.
7A and 7B are diagrams for explaining the third embodiment, where FIG. 7A is a torque command differential-motor position diagram, and FIG. 7B is a conceptual diagram of an apparatus for driving a table of a uniaxial slider with a motor.
Although the horizontal axis is the motor position, since the converted value of the machine axis unit (m) is known with respect to the motor position pulse, the wear part of the machine can be specified. In addition, in order to make the change in torque easy to understand, the first order time differential value of the torque command value (hereinafter referred to as the torque command differential value) is calculated, and the motor position is represented on the horizontal axis and the torque command differential value is represented on the vertical axis. This makes it easier to limit the wear scar location of the machine. The wear mark is generated, for example, when dust adheres to the table guide of the slider and the slider is driven without removing the dust. If there is a wear scar, the frictional force changes (thrust or torque change).
In FIG. 7B, 71 is a motor, 72 is a ball screw, 73 is a coupling for connecting the motor 71 and the ball screw 72, and 74 is a table that moves in the direction of the arrow in the drawing by rotation of the ball screw 72. Therefore, the torque command and the motor position when the position of the table 74 is moved by rotating the motor 71 at a constant speed are acquired and plotted as shown in FIG. At this time, in the portion where the ball screw 72 has no wear mark (sections La and Lc in FIG. 7A), the torque command varies little and becomes a substantially constant value. The reason why it becomes a constant value instead of 0 is that a torque is generated against the friction. Therefore, if time differentiation is taken, the constant friction becomes zero.
However, a large fluctuation occurs in the acquired torque command at a portion where the ball screw 72 has a wear mark (section Lb in FIG. 7A). When time differentiation is taken, a large amplitude change is emphasized as shown by a diagram indicated by “abnormal part” in the section Lb of FIG.
As described above, according to the third embodiment, the wear mark of the machine is present at the site where the change is emphasized, and the location of the wear mark of the machine becomes extremely easy and accurate.

It is a schematic diagram of a machine diagnostic device of the present invention. It is a diagnostic result (relationship between a motor speed and a motor torque) at the time of using this invention. It is a diagnostic result at the time of using this invention (comparison after initial operation and time passage). 10 is a flowchart illustrating a second embodiment. FIG. 5 is a diagram for explaining a second embodiment, where (a) shows a power spectrum-frequency diagram of a torque command, and (b) shows a power spectrum-frequency diagram of a motor speed. 10 is a flowchart illustrating a third embodiment. FIG. 6 is a diagram for explaining a third embodiment, where (a) is a differential torque-motor position diagram of a torque command, and (b) is a conceptual diagram of a mechanical wear trace identifying device that implements the third embodiment. It is a block diagram showing the prior art example 1 of a diagnostic apparatus. It is a block diagram showing the prior art example 2 of a diagnostic apparatus.

Explanation of symbols

101 External display device 102 Servo amplifier 103 Motor 104 Load machine 105 Communication cable 106 Power cable 107 Encoder cable

Claims (4)

A machine diagnostic apparatus for diagnosing the life of a machine by measuring the friction of a machine driven by a motor, the machine diagnostic apparatus comprising an input unit for inputting a speed command to the motor control device, a storage unit, a display unit, and a calculation unit In
A torque command or thrust command during motor driving driven by the motor control device and a motor speed are stored in the storage unit, and the calculation unit stores the torque command or thrust command and the motor during initial operation from the storage unit. A machine diagnostic apparatus, wherein the speed, the torque command or the thrust command and the motor speed after a predetermined time have passed are read out and simultaneously displayed on the display screen of the display unit.   The calculation unit reads the torque command or the thrust command corresponding to the plurality of stored motor speeds, Fourier transforms them, obtains a power spectrum of the torque command or the thrust command, and obtains the power spectrum of the display unit The machine diagnosis apparatus according to claim 1, wherein the machine diagnosis apparatus is displayed on the display screen.   The torque command or the thrust command data is stored in one cycle from the start of acceleration to the completion of acceleration during motor acceleration, the torque command or the thrust command stored in the arithmetic unit is read and Fourier transformed, and the torque The machine diagnostic apparatus according to claim 1, wherein a power spectrum of the command or the thrust command is obtained and displayed on a display screen of the display unit. A machine diagnostic apparatus for diagnosing the life of a machine by measuring friction of a machine driven by a motor, the machine diagnostic apparatus comprising an input unit, a storage unit, a display unit, and a calculation unit for inputting a position command to the motor control device In
The torque command or thrust command during motor driving and the motor position driven by the motor control device are stored in the storage unit, and the calculation unit stores the torque command or thrust command and the motor during initial operation from the storage unit. A machine diagnostic apparatus, wherein a position, the torque command or the thrust command after a predetermined time has elapsed, and the motor position are read out and simultaneously displayed on a display screen of the display unit.

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