JPS62242151A - Vibration damping equipment for speed reducer - Google Patents

Abstract

PURPOSE:To enable the phase shift of vibration due to a load fluctuation or the like to be followed up and aim at constant damping of the rotational vibration appearing in an output shaft by inputting the phase-difference signals from a phase corrector to a correction signal generator, and then causing the phase of correction signals to be adjusted. CONSTITUTION:The output of a filter 27, which is obtained from ripple signals appearing on both ends of a resistance 25 for detecting the ripple of current supplied from a servo amplifier 3 to a motor 1, is transmitted to a phase corrector 28. While, there is inputted a position signal from a position transducer 21 in the phase corrector 28, and then, a phase difference signal, which indicates the phase difference between a signal from the position transducer 21 and a signal from the filter 27, is output. Said phase difference signal is inputted to a correction signal generator 22 so that the phase of a correction signal is corrected. Thereby, the output signal from the correction signal generator 22 becomes such a correction signal that has no phase shift against the rotational vibration appearing in an output shaft 5, and then, the rotational vibration can be suppressed properly.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a device for damping rotational vibrations appearing on the output shaft of a speed reducer.

Conventional technology Regarding devices that dampen the rotational vibrations that appear on the output shaft of a reducer, a presentation was given at the 14th Technical Conference of the Japan Society of Mechanical Engineers (January 23 and 24, 1986) titled ``The latest technology in FA and robots''. A research presentation was made titled ``Applications''. The disclosed device includes a position detector connected to the rotating shaft of the motor, and a position detector connected to the rotating shaft of the motor, in order to damp rotational vibration appearing on the output shaft of a reducer driven by a servo control motor and having a controlled member connected to the output shaft. and a correction signal generator that receives the signal from the detector and outputs a correction signal that has the same synchronization as the rotational vibration.
The correction signal from the generator is input to the servo control system of the motor. This device converts the rotational vibration appearing on the output shaft of the speed reducer into the input shaft, drives the motor so as to suppress the rotational vibration, and attempts to attenuate the rotational vibration.

This device uses a motor as a drive source to suppress vibrations generated in the output system, and is characterized by eliminating the need for any data from the output system.

Therefore, with respect to the resonance vibration phenomenon at the tip of the Roboso l-arm, the troublesome work of extracting vibration data from the tip of the arm is eliminated, which is preferable.

Problems to be Solved by the Invention However, in the above device, the phase of the correction signal input to the motor is fixed in advance with an optimal value assumed, so the phase relationship may not be optimal due to load fluctuations, etc. This makes it difficult to adjust the vibration damping to all changes caused by load fluctuations. Of course, it is possible to measure the phase using, for example, an FFT (fast Fourier transform) analyzer to maintain the optimum state at all times, but this requires expensive and complicated equipment and also causes a delay in response to phase changes. There is a risk.

Therefore, it is an object of the present invention to improve known vibration damping devices, and in particular to provide a vibration damping device with a simple configuration that can follow the phase shift of vibrations due to load fluctuations, etc. There is a particular thing.

Means for Solving the Problems To achieve this object, the present invention provides a method for damping rotational vibrations appearing on the output shaft of a reducer driven by a servo-controlled motor and having a controlled member connected to the output shaft. , comprising a position detector connected to the rotating shaft of the motor, and a correction signal generator that receives a signal from the detector and outputs a correction signal having the same synchronization as the rotational vibration, and the correction signal from the generator. A vibration damping device for a speed reducer, which inputs a signal into a servo control system of a motor, and includes a means for detecting ripple in the current supplied to the motor, and a signal having a component N times the rotational frequency of the motor from this ripple signal. and a phase shift adjuster that inputs a signal from the filter and a signal from the position detector and outputs a phase difference signal, the phase difference signal from the phase adjuster being corrected by the phase difference signal. A vibration damping device for a speed reducer is provided, which is configured to adjust the phase of a correction signal by inputting it to a signal generator.

Operation With the above configuration, the current supplied to the motor is constantly monitored, changes due to motor load fluctuations, etc. are detected in real time, and this is input to the correction signal generator to adjust the phase of the correction signal. Therefore, the correction signal is sent to the servo control system at the optimum phase, and the rotational vibration appearing on the output shaft of the reducer is constantly damped.

Example 1 Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of a power system equipped with the vibration damping device of the present invention. The power system is provided with a motor 1 as a power source, and a tacho generator 2 and a servo amplifier 3 are provided on the rotating shaft of this motor and are servo-controlled.

Further, a speed reducer 4 is connected to the rotating shaft of the motor 1 to reduce the speed and drive the output shaft 5. A power system with a speed reducer equipped with such a servo control system is used, for example, to drive an arm of an industrial robot that requires high precision.

Further, the reducer may be of a normal gear type, but a harmonic gear device is often used in a place where space is narrow, such as in a robot arm. Also in this example, it is assumed that a harmonic gear device is used as the reducer 4 in the following explanation. However, the purpose of the present invention is to suppress rotational vibrations appearing on the output shaft of a reduction gear, and it goes without saying that it can be applied to other reduction gears in which such rotational vibrations occur.

First, a general explanation will be given of the principle of a harmonic gear system. As shown in FIG. 2, the harmonic gear device includes a rigid circular spline 11 and a flexible spline 12 that meshes with the circular spline 11.
is bent into an elliptical shape by the wave generator 13. The wave generator 13 is a flexible spline 1
2 is not only bent into an elliptical shape, but also rotated, and a ball bearing 14 is provided to prevent the flexible spline from rotating when the ellipse is rotated.

Since the flexible spline 12 is bent into an ellipse, its teeth mesh with the circular spline only at two points, arrows A and B. Note that the number of teeth of the circular spline 11 is different from the number of teeth of the flexible spline; for example, the circular spline 11 has two more teeth than the flexible spline 12.

In FIGS. 3(al to d), the circular spline 11 when the wave generator 13 is rotated clockwise.
The relationship between the flexible spline 12 and the flexible spline 12 is shown. When the wave generator 13 is in the position of FIG. 3 (al), one tooth 15 of the circular spline 11 meshes with one tooth 16 of the flexible spline 12. The wave generator 13 is shown in FIG. When the flexible spline 12 is rotated by 90 degrees as shown in FIG. As shown in C1, when the wave generator 13 rotates 180 degrees, the teeth 15 and 16
are engaged again, but their position is shifted by one tooth in the opposite direction to the direction of rotation. Then, as shown in FIG. 3(d), when the wave generator 13 rotates 360 degrees, the teeth 15 and 16 are shifted by two teeth in the opposite direction to the rotation direction.

In this way, if the movement in which the meshing positions are sequentially shifted is extracted as an output, a large reduction ratio can be obtained.

Therefore, this harmonic gear system has a small number of parts, is extremely compact, and can obtain a large reduction ratio, and is used, for example, to move the arm of an industrial robot that requires high precision. However, even in a speed reducer using this harmonic gear device, rotational vibration appears on the output shaft due to non-uniformity of output torque, as in other speed reducers.

In order to detect this rotational vibration, referring to FIG. 1, a position detector 21 is connected to the rotating shaft of the motor 1, which serves as the input shaft of the reducer 4. A shaft encoder is a typical example of the position detector 21, but it goes without saying that other rotational position detectors may also be used. The position detector 21 outputs a position signal indicating the rotational position of the motor 1, and this position signal includes:
The rotational position of the output shaft of reducer 4 is set to the input shaft, that is, motor 1.
Contains information converted to the axis of rotation.

The output of the position detector 21 is input to a correction signal generator 22, and in order to suppress the rotational vibration appearing on the output shaft 5, a correction signal having the same synchronization as the rotational vibration is generated. This correction signal is applied to the servo amplifier 3 together with the speed command signal and the speed signal from the tacho generator 2.
The servo amplifier 3 supplies a drive current to the motor 1 according to these signals to rotate the motor 1 at a predetermined speed.

As mentioned above, a configuration in which the above-mentioned position detector 22 and correction signal generator 22 are provided to suppress rotational vibration appearing on the output shaft 5 has already been published. However, in this published device, no consideration is given to fluctuations due to load fluctuations, etc., as described above. Therefore, it was not possible to respond to phase shifts due to load fluctuations and the like.

In the present invention, fluctuations due to such load fluctuations are monitored and this fluctuation information is included in the correction signal. Referring again to FIG. 1, a resistor 25 is provided in series with the supply line 26 to detect ripples in the current supplied from the servo amplifier 3 to the motor 1. A ripple signal appears across the resistor 25. It is known that this ripple signal has a proportional relationship to the rotational vibration of the output shaft 5, and when converted to the input shaft of the reducer 4, the phase relationship is the same and the amplitude is also proportional.

The ripple signal is input to the bandpass filter 27, which filters the current ripple that appears due to load fluctuations of the motor l, and extracts a component that is N times the rotational frequency of the motor (
N=1.2,...). In the case of harmonic gearing, the input shaft -
It fluctuates twice by rotation. This is because the wave generator is shaped like an ellipse and the flexible spline is interlocked with the circular spline at two points.

Therefore, when using a harmonic gear device as a reducer,
A component twice the rotational frequency of the motor 1 is extracted from the ripple signal by a filter 27.

The output of filter 26 is sent to phase adjuster 28. The position signal from the phase detector is also input to the phase adjuster 28, and a phase difference signal indicating the phase difference between the signal from the position detector 21 and the signal from the filter 27 is output. This phase difference signal is input to the correction signal generator 22, which corrects the phase of the correction signal. Therefore, the output signal of the correction signal generator 22 becomes a correction signal with no phase shift with respect to the rotational vibration appearing on the output shaft 5, and the rotational vibration can be appropriately suppressed.

As already mentioned, the output of the filter 26 is obtained from a ripple signal, and this signal includes not only phase information but also amplitude information associated with load fluctuations and the like. In the present invention, this can be used to adjust the amplitude of the correction signal output from the correction signal generator 22. Therefore, the correction signal is input to the amplitude adjuster 29, where its amplitude is adjusted. For this adjustment, amplitude adjuster 2
9, the signal from the filter 27 is input to its control terminal 30, and the amplitude of the correction signal is adjusted in response to fluctuations such as load fluctuations. Therefore, the phase and amplitude of the correction signal input to the servo amplifier 3 correspond to the phase and amplitude of the rotational vibration that appears on the actual output shaft, and no matter how much the rotational vibration changes due to load fluctuations, etc., this signal is always maintained. can be suppressed to a minimum.

FIG. 4 is a circuit diagram showing a typical detailed example of the power system of FIG. 1. In the example shown in FIG. 4, a shaft encoder type pulse encoder 31 is used as a position detector, which is connected to the rotating shaft of the motor 1 and outputs a rotational position signal. The encoder 31 has a Z terminal that outputs one pulse per revolution and a Z terminal that outputs one pulse per revolution.
There are A and B terminals that output as many as ~1000 pulses, and the output of the A terminal is 90" compared to the output of the B terminal.
Out of phase.

The correction signal generator 22' includes a direction discriminator 32, an up/down counter 33, a read-only memory (ROM>34) storing sine wave data, and a digital/analog converter (
DA converter) 35. The direction discriminator 32 receives the A signal and the B signal from the pulse encoder 31 and determines the rotational direction of the motor l, and determines whether to output a pulse in the up direction (U) or a pulse in the down direction (D). Establish. The up/down counter 33 receives an up pulse (U) or a down pulse (D) to count up or count down.

The output of this counter 33 is input to the address line of the ROM 34, and sine wave data corresponding to the address is output. This sine wave data is input to the DA converter 35, which outputs a sine wave.

Therefore, the correction signal generator 22' outputs a correction signal that changes according to the rotational position signal from the encoder 31 as a sine wave. This sine wave is formed as a sine wave having the same period as the rotational vibration of the output shaft 5, and data is stored in the ROM 34 so as to output the data according to the address signal from the counter 33. counter 33
counts up or down according to the position pulse signal that indicates the rotational speed of the motor 1, so the correction signal output from the correction signal generator 22' is based on the rotational vibration appearing on the output shaft 5 of the reducer 4 (and thus the input of the reducer). This corresponds to the rotational vibration of the shaft, that is, the motor 1. Therefore, if this correction signal has an appropriate phase (and amplitude), the correction signal is input to the servo amplifier 3 so as to cancel out the rotational vibration, and the rotational vibration is effectively suppressed.

However, as described above, the phase (and amplitude) of rotational vibration changes due to load fluctuations and the like.

A bandpass filter for detecting the phase (and amplitude) of rotational vibration is constituted by an IC-based digital filter 37 in FIG. Of course, this bandpass filter may be of any type as long as a predetermined frequency component can be obtained; for example, it may be a normal LC filter or RC filter, or it may be a mechanical filter. The digital filter used is convenient because it is easy to set the frequency band and occupies a small area, but it requires a clock pulse for operation. Therefore, in the example shown in FIG. 4, the pulse signal from the encoder 31 is appropriately stepped down by the counter 38 and used. This clock pulse is necessary for the operation of the filter 37, and
No temporal synchronization is required.

The signal output from the filter 37 is a sine wave, and in the case of wood, has a frequency twice the rotational frequency of the motor 1. This is because when the speed reducer is a harmonic gear device, the wave generator fluctuates greatly twice when it makes one rotation, and in the case of other speed reducers, it is sufficient to extract frequency components that are multiples of the wave generator. The output signal of filter 37 is input to phase adjuster 28'.

The phase adjuster 28' includes a zero cross comparator 39 and a counter 40. Zero cross comparator 3
9 detects the zero point crossing position of the sine wave output from the filter 37 and outputs a pulse (rectangular wave) corresponding thereto. Pulses from comparator 39 are input to counter 40 and counted. The Z signal from the encoder 31 is input to this counter 40, and the difference from the rotational position of the motor 1 is calculated. Therefore, the counter 40 outputs data on the phase difference between the rotational position of the motor 1 and the ripple, that is, the fluctuation. This phase difference data is input to the preset data terminal of the up/down counter 33 of the correction signal generator 22', and the counter 33 is preset in accordance with this phase difference data. Therefore, the contents of the counter 33 are shifted corresponding to the actual phase shift and D
The phase of the correction signal output from the /A converter 35 corresponds to the rotational vibration.

The output signal of the filter 37 is also used to adjust the amplitude of the correction signal. Therefore, the signal from the filter 37 is input to the rectifier 42 as an amplitude detection means, and the signal from the filter 37
Detect the level of amplitude from. The rectifier 42 is sent to the amplitude adjuster 29 to adjust the amplitude of the correction signal. This amplitude adjuster 29 may be any arbitrary device such as an analog multiplier or an automatic gain control amplifier (AGC). Thereby, the correction signal can suppress rotational vibration to a minimum.

Effects of the Invention According to the present invention, phase changes in rotational vibration due to load fluctuations, etc. are monitored in real time, and by adding this phase change to a correction signal for rotational vibration, rotational vibration can be effectively suppressed. As a result, rotational vibrations appearing in the reduction gear are suppressed regardless of load fluctuations, etc. Moreover, since this phase correction is performed only on the data on the input shaft side of the speed reducer, there is no need for any troublesome data on the output shaft side. Moreover, its configuration is extremely simple, and the space it occupies is extremely small.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the device according to the present invention, FIG. 2 is a schematic front view of a known harmonic gear device, and FIG.
l~(d+ is an explanatory diagram of the operation of the harmonic gear device, and FIG. 4 is a circuit diagram showing a detailed example of the device according to the present invention. 1...Motor, 2...Tachogenerator, 3゛...Servo Amplifier, 4...Reducer, 5...
・Output shaft, 11...Circular spline, 12...
Flexible spline, 13...Wave generator, 21...Position detector, 22.22'...Correction signal generator, 25...Ripple detection resistor, 27.37...Vani/dobas filler , 28.28'
... Phase adjuster, 29 ... Amplitude adjuster, 31 ... Pulse encoder.

Claims (1)

[Claims] 1. In order to damp rotational vibration appearing on the output shaft of a reducer driven by a servo control motor and having a controlled member connected to the output shaft, a position detector and a position detector connected to the rotating shaft of the motor are used. and a correction signal generator that receives the signal from this detector and outputs a correction signal having the same synchronization as the rotational vibration, and the correction signal from the generator is input to the servo control system of the motor. A vibration damping device comprising: means for detecting ripples in the current supplied to the motor; filter means for extracting a signal of a component N times the rotational frequency of the motor from the ripple signal; and a signal from the filter and the position. and a phase shift adjuster that inputs a signal from the detector and outputs a phase difference signal, and inputs the phase difference signal from the phase adjuster to the correction signal generator to adjust the phase of the correction signal. A vibration damping device for a speed reducer, characterized in that it is configured as follows. 2. An amplitude adjuster is provided between the waveform generator and the servo system, and the signal from the filter means is input to the control terminal of the amplitude adjuster via the amplitude adjuster. 2. The device as claimed in claim 1, wherein the gain of the regulator is varied according to the magnitude.