JPH05346359A - Load inertia measuring device - Google Patents

Abstract

PURPOSE:To obtain a load inertial measuring device for accurately measuring a load inertial which is connected to the shaft of a servo electric motor in a machine system with the servo electric motor as a drive source. CONSTITUTION:The title device is provided with a servo electric motor 1, sensors 4 and 2 for measuring the rotary position and rotary speed of the servo electric motor, a position comparator 5 for detecting passage of a second rotary position, an acceleration data selection means 6, an acceleration sign inversion means 8, an acceleration integrator 10, a speed difference operator 14, a speed amplifier 15, and a current control amplifier 16 for controlling current command so that the rotary acceleration is equal to a positive or a negative constant value, and a zero speed detection means 13 for detecting the time when the rotary speed reaches 0. Further, it is provided with an electric motor current detection means 3 and an amplifier 12 for calculating the electric motor output torque by observing the current of the servo electric motor, a torque data selection means 7, a torque sign inversion means 9, a torque integrator 11 for measuring the result which is obtained by subtracting the electric motor output torque during rotation with a negative first acceleration from the integration value of the electric motor output torque during rotation with a positive first acceleration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load inertia measuring device for measuring a load inertia connected to a shaft of a servo motor in a mechanical system using a servo motor as a drive source such as a machine tool or an industrial robot. is there.

[0002]

2. Description of the Related Art In order to precisely and rapidly control a servomotor that drives a complex mechanical system, it is necessary to accurately grasp the load inertia connected to the shaft of the servomotor. This load inertia also includes the inertia of the rotor of the servomotor.

FIG. 5 shows a result of analyzing a load which is generally connected to a servomotor. FIG. 5A is a block diagram showing the load connected to the shaft of the servo motor by focusing on the change in the rotation speed with respect to the torque generated by the servo motor, and J is the load inertia.

A load having a loss torque 45 of 0 in FIG. 5A is called a full inertia load. The load inertia measuring device in this case can be constructed extremely simply, and can be calculated by measuring the torque generated by the servomotor and the rotational acceleration. When the loss torque 45 is not 0, it is difficult to separate the loss torque 45, which is the main cause of measurement error.

FIG. 5B is an analysis of the loss torque 45. The offset torque 46 is a constant component regardless of the rotation speed, and the viscous load torque 47 proportional to the rotation speed.
And other non-linear load torque 48 such as air resistance loss.

A conventional load inertia measuring device will be described below. FIG. 6 shows the configuration of a conventional load inertia measuring device. In FIG. 6, 1 is a servo motor, and 2 is a motor speed detecting means for detecting the rotation speed of the shaft of the servo motor 1 and outputting a speed feedback signal 18. Reference numeral 35 is a current command generating means for outputting the current command signal 32 of the servomotor 1, and reference numeral 16 is a current control amplifier for controlling the motor current 33 according to the current command signal 32.
Reference numeral 36 is a first speed comparator that detects the match between the speed feedback signal 18 and a preset first rotation speed 40 and outputs a first speed match signal 41. 37 detects a match between the speed feedback signal 18 and a preset second rotation speed 42, and outputs a second speed match signal 43.
Is a second speed comparator that outputs 38 is a time measuring means for measuring the output timing time difference between the first speed coincidence signal 41 and the second speed coincidence signal 43 and outputting the time difference data 44. Reference numeral 39 is an inertia calculation means for calculating the load inertia from the time difference data 44, the first rotation speed 40, the second rotation speed 42 and the current command signal 32.

The operation of the load inertia measuring device configured as described above will be described below.

Generally, a servomotor has a property of generating a torque proportional to a motor current, and the ratio of the motor current to the torque generated by the current is a torque constant KT.
Is a known value. Therefore, manipulating the motor current is manipulating the torque generated by the servomotor.

In FIG. 6, first, the current command signal 32 is 0.
In addition, the speed feedback signal 18 starts from the initial state of 0, the current command signal 32 is changed to a predetermined value, and the value is held. As a result, a current that matches the current command signal 32 flows in the servo motor 1 to generate a constant torque, the rotational speed of the shaft of the servo motor 1 is accelerated, and the speed feedback signal 18 increases.

For this speed feedback signal 18,
The first speed comparator 36 and the second speed comparator 37 judge whether or not they match the first rotation speed 40 and the second rotation speed 42, respectively. The coincidence signal 41 and the second speed coincidence signal 43 are output. The time measuring means 38 measures the time difference from the output of the first speed coincidence signal 41 to the output of the second speed coincidence signal 43, and outputs the result as time difference data 44.

Next, the inertia calculation means 39 calculates the load inertia based on the time difference data 44. At this time, when the load of the servomotor 1 is a complete inertia load, it is possible to completely calculate the load inertia from one measurement data. However, in reality, there is the loss torque 45, and in order to separate this influence, the value of the current command signal 32, the first rotation speed 40 and the second rotation speed 4
The load inertia is calculated by changing the setting value of 2 and repeating the measurement several times to calculate the result by solving a complicated simultaneous equation.

[0012]

However, the above-mentioned conventional configuration has a drawback in that it is necessary to repeat the measurement operation in order to improve the measurement accuracy, which requires a long measurement time. Moreover, it is difficult to completely grasp the loss torque 45, and therefore the accuracy of measuring the load inertia is low.

Further, it is not possible to know in advance how much the shaft of the servomotor 1 will rotate to measure the load inertia, and it depends on the size of the load. That is, the larger the load inertia and the loss torque, the more the servomotor 1
The axis of will rotate. Depending on the mechanical system,
Many of them only allow rotation of the axis of the servomotor 1 within a certain range, which has a problem that the application range is limited.

The present invention solves the above-mentioned conventional problems. The measurement accuracy is very high, the measurement time is short, and the rotation operation of the axis of the servomotor for measurement is performed within a predetermined range. An object of the present invention is to provide a load inertia measuring device that can perform the load inertia measurement.

[0015]

In order to achieve this object, a load inertia measuring apparatus of the present invention comprises a servomotor, a sensor for momentarily measuring a rotational position and a rotational speed of a shaft of the servomotor, and the sensor. Control means for controlling the current of the servomotor using the signal of
First, the servo motor is stopped at a predetermined first rotation position, and then the current of the servo motor is controlled so that the rotation acceleration of the axis of the servo motor becomes a predetermined first positive acceleration, and the current is controlled to a predetermined value. The control is changed so that the rotational acceleration becomes the predetermined negative first acceleration at the time of passing the second rotational position, and the rotational speed of the servomotor eventually becomes negative, and the second rotational speed is returned again. The control is changed so that the rotational acceleration becomes the positive first acceleration when passing through the position, and the operation is stopped when the rotational speed reaches 0, and the current of the servo motor during the operation is observed. Then, the motor output torque is calculated moment by moment, and the result is obtained by subtracting the integrated value of the rotating motor output torque with the negative first acceleration from the integrated value of the rotating motor output torque with the first positive acceleration. Determined The multiply has a configuration of calculating the load inertia.

[0016]

With this configuration, the effect of the loss torque 45 is obtained by obtaining the result of subtracting the integrated value of the rotating motor output torque with the negative rotating acceleration from the integrated value of the rotating motor output torque with the positive rotating acceleration. Can be canceled out completely, and the integral value of the motor output torque required for acceleration / deceleration as the load inertia can be obtained, and the load inertia can be calculated extremely accurately.

That is, the load inertia can be calculated by dividing the integral value of the electric motor output torque by the integral time to obtain the average value of the electric motor output torque during rotation, and dividing this by the rotational acceleration.

In this calculation, since the integration time and the rotational acceleration are known constants, they are multiplied in advance and the reciprocals thereof are collected as a constant, so that the load inertia can be obtained by one multiplication from the integrated value of the motor output torque. Can be calculated.

Further, it is possible to grasp in advance how much the shaft of the servo motor rotates for the load inertia measurement,
Rotate for load inertia measurement by twice the distance between the first and second rotational positions. Therefore, if the first rotation position and the second rotation position are appropriately set, they can be used for all purposes.

Further, if the distance between the first rotation position and the second rotation position is set to a multiple of 360 degrees in terms of the rotation angle of the axis of the servo motor, the influence of torque unevenness of the servo motor can be canceled out, so that the load can be more accurately measured. Inertia can be measured.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a servo motor, and 2 is a motor speed detecting means for detecting the rotational speed of the shaft of the servo motor 1 and outputting a speed feedback signal 18. Reference numeral 3 is a motor current detecting means for detecting the motor current 33 and outputting the current feedback signal 19. Reference numeral 12 is an amplifier that multiplies the current feedback signal 19 by a predetermined constant and outputs an output torque feedback signal 25. Reference numeral 4 is a motor position detecting means for detecting the rotational position of the shaft of the servo motor 1 and outputting a position feedback signal 20. Reference numeral 5 is a position comparator that compares the second rotational position 21 with the position feedback signal 20 and outputs a sign inversion command signal 22. Reference numeral 6 denotes an acceleration data selecting means for selecting either one of the acceleration constant 23 and "0" and outputting the result as acceleration data 24. Reference numeral 7 is a torque data selection means for selecting either one of the output torque feedback signal 25 and "0" and outputting the result as torque data 26. 8, the sign of the acceleration data 24 is inverted according to the sign inversion command signal 22, and the acceleration data 27
Is an acceleration sign reversing means for outputting. An acceleration integrator 10 integrates the acceleration data 27 and outputs a speed command signal 28. Reference numeral 9 is a torque sign reversing means for reversing the sign of the torque data 26 according to the sign reversal command signal 22 and outputting torque data 29. 11 is torque data 29
Is a torque integrator that outputs the torque integration data 30. Reference numeral 39 is an inertia calculation means for inputting the torque integrated data 30 and calculating the load inertia. Thirteen
Is a zero speed detecting means for detecting that the speed command signal 28 is 0 and outputting a zero speed detection signal 34. 14
Is a speed difference calculator that subtracts the speed feedback signal 18 from the speed command signal 28 and outputs a speed deviation signal 31. 15 receives the speed deviation signal 31 and inputs the current command signal 3
It is a speed amplifier that outputs 2. 16 is a current command signal 3
2 is a current control amplifier for controlling the motor current 33 as shown in FIG. Reference numeral 17 is generally called a speed minor loop, and the speed deviation can be maintained at almost 0 by using the speed amplifier 15 as a proportional-plus-integral amplifier.

The operation of the load inertia measuring device configured as described above will be described below.

First, in FIG. 1, it is assumed that the speed of the axis of the servomotor 1 is 0, the speed command signal 28 is 0, and the torque integral data 30 is 0.

At this point, both the acceleration data selecting means 6 and the torque data selecting means 7 select "0", and the sign inversion command signal 22 commands non-inversion. The rotational position of the shaft of the servo motor 1 in this initial state will be referred to as a first rotational position. In this state, the acceleration data selecting means 6 first selects the acceleration constant 23, and the torque data selecting means 7 selects the output torque feedback signal 25, respectively, to start the measurement.

FIG. 2 is a diagram showing the operation of the load inertia measuring apparatus shown in FIG. 1. The horizontal axis represents time, and the time t0 is the start timing. The load is assumed to be a complete inertial load for the sake of simplicity.

1 and 2, the acceleration integrator 10 integrates the acceleration constant 23 immediately after the measurement is started, and the speed command signal 28 linearly increases.
The axis of the servomotor 1 rotates substantially in the same way as the speed command signal 28 due to the movement of the speed minor loop 17, and the position feedback signal 20 increases. Eventually, when the position feedback signal 20 passes a predetermined second rotational position 21, the sign inversion signal 22 commands the inversion, and the acceleration sign inversion means 8 inverts the sign of the acceleration data 24 to obtain the acceleration data 27. Output. This time point is the timing of t1 in FIG.

As a result, the speed command signal 28 linearly decreases, and eventually the speed command signal 28 passes 0 and becomes a negative value. This time is the timing of t2 in FIG.

The rotation direction of the shaft of the servomotor 1 from t0 to t2 so far has been the direction moving away from the first position, but t2 to t4 is the direction approaching the first position.

When the position feedback signal 20 again passes through the second rotational position 21, the sign reversal command signal 22 commands non-reversal, and the acceleration sign reversing means 8 outputs the acceleration constant 23 as it is as the acceleration data 24. To do. This time point is the timing of t3 in FIG.

Next, when the speed command signal 28 becomes 0, the acceleration data selecting means 6 and the torque data selecting means 7 are selected.
Are switched to select "0" respectively. As a result, the speed command signal 28 becomes 0, and the torque integrated data 3
0 results in continuing to hold data on the verge of being switched.

Now, let us consider the movement of the torque integral data 30 during the above operation.

First, the torque required to rotate the shaft of the servomotor 1 according to the speed command signal 28 is detected as the torque data 26.

Since FIG. 2 is written assuming that the load is a completely inertial load, the waveforms of the acceleration data 27 and the torque data 26 are similar to each other. This torque data 26
Is the sign reversal command signal 22 by the torque sign reversing means 9.
The sign is inverted according to. As a result, the torque data 29 becomes a constant value, the torque integral data 30 increases linearly, and is held at the timing of t4. Here, the time from t0 to t4 is called the integration time. Also t0
The absolute value of the acceleration between t4 and t4 is a constant value,
This is called rotational acceleration.

By dividing the torque integration data 30 at the timing of t4 by the integration time, it is possible to obtain the average absolute value of the motor output torque required for accelerating and decelerating the load inertia. The load inertia can be obtained by dividing. However, since the integration time and the rotational acceleration are predetermined known values respectively, if they are multiplied in advance and the reciprocals thereof are collected as a constant, the torque integration data 30 can be easily multiplied by the constant. You can ask for inertia.

The above is the description in the case where the load inertia measuring device of FIG. 1 is applied to a complete inertia load.

Next, the operation when the load inertia measuring apparatus of FIG. 1 is applied to other than the complete inertia load will be described.

FIG. 3 is a view showing how the influence of the viscous load torque 47 is canceled in the operation of the load inertia measuring apparatus of FIG.

As shown in FIGS. 5 (a) and 5 (b), the viscous load torque 47 changes depending on the rotation speed. Therefore, as shown in FIG. 3, the output torque feedback signal 25
Is added with the viscous load torque 47 that changes under the influence of the rotation speed. The viscous load torque 4 is the shaded area
Equivalent to 7.

The influence of the viscous load torque 47 also appears in the torque integral data 30, and the shaded portion corresponds to it. However, it is understood that the influence of the viscous load torque 47 on the torque integral data 30 is completely 0 at the timing of t4.

FIG. 4 is a diagram showing how the influence of the offset torque 46 is canceled in the operation of the load inertia measuring apparatus of FIG.

In FIG. 4, the shaded portions of the output torque feedback signal 25 and the torque integrated data 30 show the influence of the offset torque 46. From the same consideration as in FIG. 3, it can be seen that the influence of the offset torque is zero at the timing of t4.

The same thing can be said for a non-linear load, and as a result, it can be seen that the load inertia measuring device of FIG. 1 is not affected by the loss torque.

The above is the consideration of the influence of the loss torque, but as another cause of the error in the load inertia measurement, there is the influence of the torque unevenness of the servo motor. In an actual servomotor, the torque constant KT changes periodically every 360 degrees depending on the rotation angle of the shaft. The influence of this torque unevenness can be eliminated by setting the distance between the first rotation position and the second rotation position in the load inertia measuring device of FIG. 1 to be a multiple of 360 degrees in terms of the rotation angle of the shaft of the servomotor 1. This is clear from the same considerations as in FIGS. 3 and 4.

As described above, the load inertia measuring apparatus of FIG. 1 can measure the load inertia extremely accurately.

Although the input signal of the amplifier 12 is the current feedback signal 19 in the load inertia measuring apparatus of FIG. 1, it may be a current command signal 32. This is because the current according to the current command signal 32 always flows through the servomotor 1 due to the operation of the current control amplifier 16, and the current feedback signal 19 and the current command signal 32 always match.

[0047]

As described above, according to the present invention, the servo motor and the sensor for momentarily measuring the rotational position and the rotational speed of the shaft of the servo motor, and the signal of the sensor are used to control the current of the servo motor. The control means for controlling the servomotor is first brought into a stopped state at a predetermined first rotational position, and then the current of the servomotor is adjusted so that the rotational acceleration of the axis of the servomotor becomes a predetermined positive first acceleration. The control is changed so that the rotational acceleration reaches the predetermined negative first acceleration at the time of passing the predetermined second rotational position, and eventually the rotational speed of the servomotor becomes negative. Then, the control is changed so that the rotational acceleration becomes the positive first acceleration when the second rotational position is passed again, and the operation is stopped when the rotational speed reaches 0. Servo motor The result of subtracting the integrated value of the rotating motor output torque with the negative first acceleration from the integrated value of the rotating motor output torque with the positive first acceleration, by observing the current With the configuration in which the load inertia is calculated by multiplying with a predetermined constant, the effect of the loss torque 45 can be completely offset, and the load inertia can be calculated extremely accurately.

Further, it is possible to grasp in advance how much the servomotor shaft rotates for the load inertia measurement, and it can be widely used for all purposes if the first rotational position and the second rotational position are appropriately set. ..

Further, by setting the distance between the first rotation position and the second rotation position to be a multiple of 360 degrees in terms of the rotation angle of the shaft of the servo motor, it is possible to cancel the influence of the torque unevenness of the servo motor more accurately. This has the effect of measuring the load inertia.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a load inertia measuring device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an operation of the load inertia measuring device in the embodiment of the present invention.

FIG. 3 is a diagram showing a state in which the influence of the viscous load torque is canceled by the operation of the load inertia measuring device in the embodiment of the present invention.

FIG. 4 is a diagram showing how the influence of the offset torque is canceled by the operation of the load inertia measuring apparatus in the embodiment of the present invention.

FIG. 5A is a block diagram in which a load connected to a servomotor is analyzed, and FIG. 5B is a diagram in which loss torque is analyzed.

FIG. 6 is a diagram showing a configuration of a conventional load inertia measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Servo electric motor 2 Electric motor speed detecting means 3 Electric motor current detecting means 4 Electric motor position detecting means 5 Position comparator 6 Acceleration data selecting means 7 Torque data selecting means 8 Acceleration sign reversing means 9 Torque sign reversing means 10 Acceleration integrator 11 Torque integrator 12 Amplifier 13 Zero Speed Detection Means 14 Speed Difference Calculator 15 Speed Amplifier 16 Current Control Amplifier 17 Speed Minor Loop 18 Speed Feedback Signal 19 Current Feedback Signal 20 Position Feedback Signal 21 Second Rotation Position 22 Sign Reversal Command Signal 23 Acceleration Constant 24 , 27 Acceleration data 25 Output torque feedback signal 26, 29 Torque data 28 Speed command signal 30 Torque integration data 31 Speed deviation signal 32 Current command signal 33 Motor current 34 Zero speed detection signal 35 Current command Raw means 36 First speed comparator 37 Second speed comparator 38 Time measuring means 39 Inertia calculation means 40 First rotation speed 41 First speed matching signal 42 Second rotation speed 43 Second speed matching signal 44 Time difference data 45 Loss torque 46 Offset torque 47 Viscous load torque 48 Non-linear load torque 49 Servo motor generated torque 50 Rotation speed 51 First rotation position

Claims (2)

[Claims] 1. A servo motor, a sensor for constantly measuring a rotational position and a rotational speed of a shaft of the servo motor, and a control means for controlling a current of the servo motor by using a signal of the sensor. At a predetermined first rotation position, and then the current of the servo motor is controlled so that the rotation acceleration of the axis of the servo motor becomes a predetermined positive first acceleration, and a predetermined second rotation position is set. Control is changed so that the rotational acceleration becomes a predetermined negative first acceleration when the rotational position of the servo motor is passed, and eventually the rotational speed of the servomotor becomes negative and the second rotational position is passed again. The control is changed so that the rotational acceleration becomes the positive first acceleration at that time, the operation is stopped at the time when the rotational speed reaches 0, and the electric current of the servo motor during the operation is observed to observe the current. Output Is calculated every second, and the result obtained by subtracting the integrated value of the rotating motor output torque with the negative first acceleration from the integrated value of the rotating motor output torque with the positive first acceleration is multiplied by a predetermined constant. A load inertia measuring device having a configuration for calculating the load inertia. 2. The load inertia measuring device according to claim 1, wherein the distance between the first rotational position and the second rotational position is a multiple of 360 degrees in terms of the rotational angle of the shaft of the servomotor.